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More Than 20 Years Navigation of Knee Surgery With the Orthopilot Device
25 G
More Than 20 Years Navigation of Knee Surgery With the Orthopilot Device Dominique Saragaglia CHU Grenoble-Alpes, South Teaching Hospital, Grenoble, France
ABSTRACT Navigation of knee surgery was born in Grenoble (France) in the mid-1990s. The first total knee arthroplasty (TKA) was implanted on a human being on January 1997 and a prospective randomized study comparing computer-assisted TKA and conventional technique finished in March 1999. The results were published, leading to marketing of the Orthopilot device. In March 2001 we carried out the first high tibial osteotomy for genu varum deformity and in January 2008 we implanted for the first time a UniKA with a “light” software. The aim of this chapter is first to present the Orthopilot device and the operative technique, then the evolution of the software in order to use it for osteotomies around the knee, UniKA, and revision of Uni to TKA. Second, results of these techniques are presented, and finally, the usefulness of navigation is discussed. Handbook of Robotic and Image-Guided Surgery. DOI: https://doi.org/10.1016/B978-0-12-814245-5.00025-6 © 2020 Elsevier Inc. All rights reserved.
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25.1
Introduction
Computer-assisted surgery began with stereotactic neurosurgery [1] toward the end of the 1980s. This new technique aimed to improve the precision of operations, reduce surgical invasiveness, and improve the traceability of interventions. The history of computer-assisted implantation of total knee prostheses dates back to 1993 when we set up a work group including two surgeons (D. Saragaglia and F. Picard), one medical doctor/computer scientist (P. Cinquin), two computer scientists (S. Lavalle´e and F. Leitner), and an industry partner, which was at the time I.C.P. France (boughtover by Aesculap-AG, Tuttlingen, Germany, in 1994). In our first meeting, the senior surgeon drew up the specifications defining computer assistance for total knee replacement. A preoperative scan was not needed to guide surgical navigation for several reasons, this was first because, at the time, this examination was not part of the preoperative check-up required for a knee prosthesis, second, we felt that an examination of this sort could only complicate the operative procedure, and last, this would have added additional cost and a considerable amount of radiation exposure for the patient. We needed to have a reference to the mechanical leg axis throughout the whole operation so that the cutting guides could be placed perpendicular to this axis in a frontal and sagittal plane. The cutting guides needed to be placed freehand without any centromedullary or extramedullary rods. Finally, the operation was not supposed to last more than 2 hours (maximum tourniquet time) and the procedure was to be accessible to all surgeons, whatever their computing skills. The project was assigned to F. Picard, as part of his Postgraduate Diploma in Medical and Biological Engineering, and to F. Leitner a computer scientist who was completing his training. After 2 years of research, the system was validated by the implantation of 10 knee prostheses on 10 cadaver knees, and the results were published in 1997 [2,3] in several national and international publications, including CAOS, SOFCOT, and SOBCOT. After obtaining the consent of the local ethics committee on December 4, 1996, the first computer-assisted prosthesis was implanted in a patient, on January 21, 1997 (D. Saragaglia, F. Picard, T. Lebredonchel). The operation lasted 2 hours and 15 minutes and was uneventful. A prospective randomized study comparing this technique to the conventional technique began in January 1998 and was completed in March 1999. The results (Table 25.1) were published in several national and international meetings and in a lead article in the French Journal of Orthopaedic Surgery [4]. In March 1999, the prototype that we had used in this study evolved to a final model called Orthopilot (B-Braun-Aesculap, Tuttlingen, Germany). Since that time, numerous papers have been published confirming that this technique was well founded and more than 360,000 prostheses have been implanted worldwide with Orthopilot. The software packages have evolved (versions 3.0, 3.2, 4.0, 4.2, TABLE 25.1 Results of the prospective randomized study published in 2001. Conventional surgery
Navigation
Patients (n)
25
25
Preoperative goal
180 6 3 degrees
180 6 3 degrees
Genu varum (%)
80
76
Genu valgum (%)
16
24
Neutral
4
0
P value
Preop HKA angle
175 degrees (162 210 degrees)
175 degrees (162 210 degrees)
Postop HKA angle
181.2 6 2.7 degrees
179 6 2.5 degrees
Goal achievement
75%
84%
P 5 .35 NS
MFMA
91 6 2 degrees
89.5 6 1.6 degrees
P 5 .048 S
Goal achievement for MFMA (90 degrees)
16.5%
48%
S
MTMA
90.2 6 1.6 degrees
89.5 6 1.4 degrees
P 5 .11 NS
Posterior slope
90.8 6 2.2 degrees
89.5 6 2 degrees
P 5 .18 NS
Goal achievement for postslope
41%
76%
S
HKA, Hip knee ankle; MFMA, medial femoral mechanical angle; MTMA, medial tibial mechanical angle; S, significant.
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5.0, 5.1) but the basic principle has remained the same since the system was created. Today, the operative procedure lasts between 1 and 1.5 hours, depending on the difficulty of the case, and almost 4000 total knee arthroplasties (TKAs) have been implanted in our department, using navigation. In March 2001 we did the first high tibial osteotomy (HTO) for genu varum deformity and in January 2008 we implanted for the first time a UniKA with a “light” Software. The aim of this chapter is first to present the Orthopilot device and the operative technique, then the evolution of the software in order to use it for osteotomies around the knee, UniKA, and revision of Uni to TKA. Second, to present the results of these techniques, and last, to discuss the usefulness of navigation.
25.2
The Orthopilot device
FIGURE 25.1 The Orthopilot device.
25. The Orthopilott Device
The Orthopilot device is an image-free navigation system based on intraoperative data acquisition. The equipment includes a navigation station (Fig. 25.1), which allows the markers to be spatially located in real time, as well as an ancillary device adapted to this navigation. The navigation station is made up of a personal computer, an infrared Spectra localizer (Northern Digital Inc.), and a dual-command foot-pedal. The progress of the operative protocol is defined in the software and the surgeon controls this via the pedal and a dedicated graphic interface. The computer-navigation system is placed 1.8 2.2 m from the knee on the patient’s opposite side, closer to the patient’s head. This navigation station also includes ancillary devices, which are the wireless markers and their tightening system. Markers, also called “rigid bodies,” are a collection of four reflective spheres rigidly held together (Fig. 25.2). An embedded localizer infrared source illuminates these spheres whose positions are detected thanks to an image triangulation computation. The attitude (position and orientation) of each marker is therefore computed from sphere positions and the marker’s own shape. All the objects that need to be tracked can have markers attached to them. It is also possible to mark out specific points in space using a metallic pointer linked to a marker whose accurate extremity coordinates are prerecorded. The markers are rigidly attached to the bone using special bicortical screws. For TKA, the ancillary device is made up of cutting guides equipped with markers that are firmly attached to the bone by four threaded pins. These guide the tibial cut (height of cut, valgus varus, tibial slope) and the femoral cut (height of cut, valgus varus, flexum, recurvatum). The chamfer cutting guide allows the anterior and posterior cuts to be made. A distractor can be used to guide the ligament balance in flexion and extension.
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FIGURE 25.2 Marker with four reflecting balls (passive marker). FIGURE 25.3 Tibial and femoral markers fixed percutaneously to the bone.
25.3
Operative procedures: total knee arthroplasty
A tourniquet is placed at the root of the thigh and the patient is put in a supine position without any particular setup. In the majority of cases a medial parapatellar approach is used but all kind of approaches can be used. The patella is everted and the markers are inserted. To reduce the length of the incision, the femoral and tibial markers are inserted percutaneously (Fig. 25.3) and are positioned so that they can be seen throughout the whole operation without the need to move the localizer. The femoral marker is placed 15 cm above the joint line in an oblique position with respect to the frontal plan and the tibial marker is placed 10 cm below the joint, parallel to the frontal plan.
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25.3.1
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Navigation of the femoro-tibial mechanical angle
The navigation step begins with the palpation of the anterior cortex of the femur just above the upper margin of the trochlea and the posterior side of the medial and lateral condyles. Then, the middle of the tibial spines is palpated as well as the middle of the medial or lateral tibial plateau. When the tibial mechanical axis is in varus, as is almost always the case in genu varum deformities, the lateral plateau is palpated. When the tibial mechanical axis is in valgus, the medial plateau must be palpated in order to avoid too much resection on the medial side. At the end of this step, the center of the knee has been located and the size of the femoral implant is registered in the computer. The acquisition of the center of the ankle is obtained by palpation of the medial and lateral malleoli as well as the middle of the tibiotarsal joint. Finally, the center of the femoral head is located by moving the leg in a small circular motion, slowly and progressively, with the knee in extension or in flexion. This lets the localizer track to follow the infrared diodes of the femoral “rigid body” and locate the center of the femoral head. At this step of the procedure, we know the hip knee ankle (HKA) angle which can be compared to the radiological preoperative axis, and the size of the femoral implant. Before inserting the cutting guides, it is very important to check the reducibility of the deformity [5], above all in extension (10 degrees of flexion), in order to predict any release. In the case of genu varum, a lateral manual stress of the knee is applied, and the HKA angle is checked on the computer. In the case of hyperreducibility (varus going into valgus) or hyporeducibility less than 3 degrees, there is no need to do a release of the medial collateral ligament (MCL). In the case of hyporeducibility from 3 to 6 degrees a release of the MCL is needed (pie-crusting) and in case of hyporeducibility above 6 degrees a major release is needed (release of the MCL at its femoral insertion). Otherwise, the laxity of the convexity of the knee is noted.
25.3.2
Navigation of the bone cuts
FIGURE 25.4 Measurement of the resection height of the tibial plateau, the varus valgus alignment, and the posterior slope.
25. The Orthopilott Device
The tibial cutting guide is mounted on a support, which allows the valgus varus, the height of the cut, and the posterior tibial slope to be measured (Fig. 25.4). We currently prefer to position this cutting guide freehand, without any support, which means shorter cutaneous incisions can be made. This cutting guide is positioned in front of the tibia with its “rigid body” (Fig. 25.2) and it is fixed to the bone by four threaded pins once the correct measurements are displayed on the screen, which for us are a valgus varus at 0 degree, a posterior tibial slope from 0 to 2 degrees, and a cutting height of 8 or 10 mm, which corresponds to the thickness of the tibial plateau implant. Once the cutting guide is fixed into position, an oscillating saw is used to make the cut. The femoral cutting guide equipped with its “rigid body” is then placed against the anterior side of the distal end of the femur, with the knee flexed at 90 degrees after the overhang of the femoral trochlea has been resected. This step is very important to determine the femoral mechanical axis and to compare it with the radiological preoperative measurements (Fig. 25.5). The surgeon then adjusts the valgus varus of the distal femoral cutting guide (0 degree for us), the posterior slope (between 0 and 2 degrees flexum to avoid notching the anterior cortex), and the height of the resection
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FIGURE 25.5 Radiological measurement of the varus deformity: HKA angle, medial femoral mechanical angle, medial tibial mechanical angle. HKA, Hip knee ankle.
(minimal resection in the convex side of the deformity to reduce ligament imbalance) corresponding to the thickness of the prosthesis. At this stage of the operation, the computer has carried out a “bone” alignment of the leg and the prosthesis is then implanted using the classic ancillary equipment, especially when making the anterior, posterior, and chamfer cuts.
25.3.3
Implanting the trial prosthesis
The implantation of the trial prosthesis uses computer assistance to check the mechanical leg axis in extension, in the walking position, and in flexion at 90 degrees. Ligament balance is also controlled by taking stress valgus or varus measurements, and assessing any medial or lateral gaping. The mechanical leg axis can also be checked when the prosthesis is permanently implanted. This will allow the detection of any excess medial or lateral cement that is liable to change the axis by 1 or 2 degrees (1 mm of cement 5 1 degree).
25.3.4
Rotation of the femoral implant
We never systematically apply external rotation to the femoral implant, at least in genu varum. We only apply rotation according to the femoral valgus or varus (Fig. 25.6). If, in the case of genu varum, the femur is in a valgus of 3 degrees or more, we believe it is logical to apply external rotation, because it will be necessary to resect more of the distal medial condyle and as a result more of the posterior condyle if one wants the ligament to be balanced in flexion. This rotation does not need to be navigated since the ancillary makes it easy to perform. If the femur is in varus, and if the genu varum is overreducible, it is equally logical to apply internal rotation, since less distal medial condyle will be resected and therefore less posterior medial condyle. In the case of genu valgum, external rotation is almost systematic since the femoral valgus is almost constant. We usually apply 1 degree of rotation for 1 degree of femoral valgus and do not exceed 5 6 degrees of rotation, to limit the cut in the anterolateral cortex of the femur.
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FIGURE 25.6 Measurement of the femoral mechanical angle with the computer.
25.3.5
Ligament balance
25.3.6
Implanting the final prosthesis
The final prosthesis is cemented (or not, in the case of cementless prostheses) when the HKA angle is at 180 6 3 degrees, the ligaments are well balanced, the tracking of the patella is optimal as well as the range of motion. At last, the approach is closed step by step according the habits of each.
25. The Orthopilott Device
There are two ways to proceed: either by working from reducibility of the deformity tests (valgus and varus stress near extension) or by following ligament balance management software. We prefer to use the first method, which allows the surgeon to consider and remain master of his/her decisions. We proceed in the following way: when the mechanical leg axis appears on the computer screen, before any ablation of osteophytes, we apply manual force in varus and valgus, with the knee at 5 10 degrees of flexion, to assess the reducibility of the deformity and the gap in convexity. If the deformity is completely reducible, or even hyperreducible, we are certain that the ligaments will be balanced in extension and that it will not be necessary to release soft tissue in the concavity. The same is true if reducibility gives a hypocorrection of 2 3 degrees. If hypocorrection is greater than this, it will be necessary to allow for the progressive release of soft tissue with trial implants, after removing the osteophytes. However, it should be stated that a perfect balance does not necessarily mean that there is a symmetrical gap between the medial and the lateral side, since it is known that, in a normal knee, the lateral compartment is more lax than the medial compartment. We therefore readily accept, in genu varum, a difference of 3 or 4 degrees more for the lateral compartment of the knee. As far as the management of gaps between extension and flexion is concerned, we never have an imbalance since, on one hand we commonly use a posterior cruciate ligament (PCL) retaining prosthesis which is a good “keeper” of the gaps, and on the other hand the bone resection thickness is identical to the thickness of the implants. Thus, there is no reason for the balance which was adequate before the implantation of the prosthesis to change afterwards. Finally, the medial lateral balance in flexion can be controlled without any distractor, since we believe that this is an artificial procedure which does not guarantee an adequate balance; indeed, creating tension between the two sides is subjective and difficult to reproduce from one surgeon to the next. To check this balance, it is sufficient, once the cutting guide for the chamfers has been applied at the distal femur level, to raise the thigh through the use of this supporting point, to manually pull into the axis of the knee flexed at 90 degrees, and to check the parallelism of the cutting guide with the cut of the tibial plateau (Fig. 25.7). In genu varum, parallelism is perfect in most cases and it is not necessary to release soft tissue. Otherwise, especially in genu valgum, it is necessary to release the medial or lateral collateral ligaments progressively.
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FIGURE 25.7 Checking of the ligaments balancing in flexion at 90 degrees.
FIGURE 25.8 HKA angle displayed on the screen of the computer. HKA, Hip knee ankle.
25.4 25.4.1
Osteotomies for genu varum deformity High tibial opening wedge osteotomy
The same principles of real-time acquisition of the rotation center of the HKA centers and of the anatomical landmarks at the level of the knee joint line (palpation of medial and lateral epicondyles and the tip of the patella) and ankle is applied. They allow the mechanical axis of the lower limb to be shown dynamically on the computer screen (Fig. 25.8), that is, the axis of the lower limb to be seen both pre- and postosteotomy and to check if the preplanned correction has been established [6 8]. Generally, the procedure follows this sequence: The rigid body markers are fixed percutaneously at the level of the distal femur and proximal tibia allowing acquisition of the centers of hip, knee and ankle. The lower limb mechanical axis then appears on the screen and can be compared with the preoperative radiological goniometry. The HTO is performed 3 cm below the level of the medial joint line, the level confirmed by placing an intraarticular needle. The osteotomy is directed at the fibula head, keeping the saw as horizontal as possible to avoid fracturing the lateral tibial plateau.
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FIGURE 25.9 Opening wedge high tibial osteotomy filled by a tricalcium phosphate wedge (Biosorb) and fixed by a locking screw plate.
25.4.2
Double-level osteotomy
The first stage is essentially the same as for that of an HTO: percutaneous insertion of the rigid body markers (high enough not to hamper the femoral osteotomy and low enough on the other level to avoid interfering with the tibial osteotomy), followed by acquisition of the hip center, middle of the knee, and tibio-tarsal joints in order to find the mechanical axis of the lower limb. The second stage consists of making the femoral closing osteotomy in the distal femur (in general a 5 6 degrees alteration is made, although sometimes more in congenital femoral varus) and fixing it in position with a plate. A lateral approach with elevation of the vastus lateralis is chosen, the lateral arthrotomy allowing the tip of the trochlea to be located. The track of the osteotomy lies above the trochlea and is directed obliquely from above laterally to below on the medial femoral cortex. A wedge of bone is then excised from the distal femur with a 4 5 mm lateral base, corresponding to a 5 6 degrees correction. The osteotomy is fixed with the plate after placing the femur into valgus manually. Once this stage is reached the mechanical axis is rechecked so that the required correction at the level of the tibia can be calculated in order to achieve the preoperative objectives. The last stage is to perform the HTO exactly in the fashion described above (Fig. 25.10A and B). The definitive axis is then displayed on the computer screen.
25.5
Osteotomy for genu valgum deformity
The technique used is similar to that used in varus knees as described above [9]. After intraoperative acquisition of the mechanical axis of the lower limb, the appropriate femoral varus osteotomy is carried out: or medial closing or lateral
25. The Orthopilott Device
With the aid of two Pauwels osteotomes inserted along the track of the saw cut, the tibia is placed into valgus. These are then replaced by a metal spacer which is inherently stable and allows the amount of correction to be checked. If there was 8 degrees of varus one would try a 10 11 mm spacer and make sure that an appropriate hypercorrection is produced real time on the computer screen. If this is insufficient we try a thicker spacer, and the reverse if the correction is too great. The metallic spacer is then replaced with a bio-absorbable tricalcium phosphate wedge (Biosorb, B. Braun Aesculap, Boulogne, France) of the desired thickness, and the intervention is completed by plating the proximal tibia (Fig. 25.9) with a locking screw plate.
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FIGURE 25.10 (A) Double-level osteotomy performed for severe genu varum deformity: AP view. (B) Doublelevel osteotomy performed for severe genu varum deformity: lateral view. AP, antero-posterior view.
opening wedge. In some cases of excessively tight fascia lata where the required lateral opening osteotomy exceeded 6 8 degrees, piecrust lengthening is performed on the iliotibial band; this contributes to easier recovery of knee flexion. Medial closing osteotomies were performed in our earliest cases and were secured with an AO T-shaped plate. Lateral opening osteotomy is performed currently; the opening is filled with bio-absorbable tricalcium phosphate wedge (Biosorb, SBM, Lourdes, France) and secured with an AO locking plate or an OTIS-F locking plate (SBM, Lourdes, France) (Fig. 25.11). A double varus osteotomy of the femur and tibia due to valgus medial distal femoral mechanical axis and medial proximal tibial mechanical axis is performed to avoid an oblique joint line (Fig. 25.12A). In these cases, a medial closing-wedge osteotomy of the tibia is performed first and fixed with an OTIS locking plate (SBM, Lourdes, France) and then a lateral opening-wedge varus osteotomy of the femur is carried out (Fig. 25.12B and C).
25.6
Uni knee arthroplasty
The rigid body markers are set as for TKA. A 7 9-cm medial parapatellar skin incision is performed, its length dependent on the patient’s BMI and soft-tissue elasticity. Then a subvastus or midvastus intraarticular approach is done to access the knee [10,11]. The next step involves data collection of the knee: middle of the intercondylar notch, the middle of the tibial spines (Fig. 25.13), the middle of the medial tibial plateau, the more distal point of the femoral condyle, and finally, the medial, lateral malleoli, and the middle of the ankle joint. The second step is the registration of the hip kinematic center using hip circumduction movement and the knee kinematic center using flexion extension and rotation axis of the knee in 90 degrees flexion. At the end of the registration, the femoro-tibial mechanical axis (FTMA) is displayed on the monitor screen and the surgeon then starts to navigate the tibial bone cut resection. Before proceeding to tibial cutting guide navigation, one checks the correlation between FTMA displayed on the computer monitor screen and the measured preoperative HKA X-ray angle and also assesses reducibility of the leg deformity. If the deformity is hypercorrectable (too much valgus), it is a contraindication for mobile uni knee arthroplasty (UKA) due to the risk of hypercorrection. Indeed, if the leg
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FIGURE 25.11 Opening wedge distal femoral osteotomy for genu valgum deformity filled by a tricalcium phosphate wedge and fixed by an AO locking screw plate.
25. The Orthopilott Device FIGURE 25.12 (A) Genu valgum with femoral mechanical axis in valgus as well as proximal tibial mechanical axis. (B) Double-level osteotomy to correct the deformity (tibial closing wedge and femoral opening wedge): AP view. (C) Double-level osteotomy to correct the deformity (tibial closing wedge and femoral opening wedge): lateral view. AP, antero-posterior view.
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FIGURE 25.13 Palpating of the intercondylar eminence for UKA. UKA, Uni knee arthroplasty.
stays in varus, the MCL will remain slack and the mobile bearing surface is at risk of dislocation. In order to avoid this, a larger polyethylene would fill the gap but this would then increase the load-stress on the other side of the joint. The tracked tibial cutting jig is positioned in front of the medial tibial plateau, then navigated and fixed using three to four threaded pins (Fig. 25.14). Using the graphic user interface, the tibial jig is placed between 2 and 3 degrees varus and between 3 and 5 degrees slope with a bone resection ranging between 4 and 8 mm (never more than 8 mm in order to avoid any subsidence of the tibial plateau implant related to weak cancellous bone). However, the less varus the more bone resection, and vice versa according to the indications for UKA [12]. Once these three parameters (coronal, sagittal, and height) are satisfactory, the tibial cut is performed using an oscillating saw for the horizontal cut and a reciprocating saw for the vertical cut. At this stage, the navigation is finished, and the femoral cut is performed using a tibial spacer placed between the resected tibial plateau bony surface and the distal medial femoral condyle with the knee in extension. The distal femoral jig is slotted onto the tibial spacer until it reaches the femur, ensuring that the tibial plateau fits perfectly well onto the resected bony surface (Fig. 25.15). Two threaded pins are used to stabilize the femoral jig and the distal femoral cut is performed using an oscillating saw. Then the knee is flexed to 90 degrees and with the use of several templates, the best-size fit is chosen for the femoral condyle. Posterior and chamfrain cuts are performed using the suitable template. The tibial and femoral trial implants are tested. The surgeon verifies leg alignment which should be within 177 6 2 degrees that is a slight hypocorrection. When using a mobile bearing tibial plateau, a “safe laxity” is tolerated at around 1 degree. If the “safe laxity” is more than 2 degrees, the choice will then be to use a fixed bearing tibial plateau. Once satisfactory alignment and position are obtained, the final implants are cemented and postimplant FTMA is controlled and recorded before closing.
25.7
Uni knee arthroplasty to total knee arthroplasty revision
In cases of UKA to TKA revisions, the navigation is the same as in primary TKAs. The implants are not removed and the images are taken with the implants in place even when there is loosening or sinking of the implants (Fig. 25.16). This works because the navigation system is not based on bone morphing but on palpation of several critical points, especially the lateral tibial plateau in the case of revision of medial UKA or the medial plateau in the case of revision
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FIGURE 25.15 Insertion of the distal cutting guide for UKA. UKA, Uni knee arthroplasty.
25. The Orthopilott Device
FIGURE 25.14 Fixation of the tibial cutting guide for UKA. UKA, Uni knee arthroplasty.
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FIGURE 25.16 Loosening of UKA revised by computer-assisted TKA. TKA, Total knee arthroplasty; UKA, uni knee arthroplasty.
of the lateral one. Once the lower limb angle is obtained, the various cuts are made using the cutting guides, positioned with the help of the navigator. The tibial cut rarely presents problems, except where there is major bone loss under the tibial component, which requires either a bone graft or the use of metal wedges. Loss of bone substance after removal of the implant is rarely a problem in the femur, except in rare cases where the femoral component has subsided into the cancellous bone of the condyle (Fig. 25.17). After removing the implant, it is important to ensure that the posterior cut is compensated for when implanting the primary prosthesis, by adjusting the external rotation of the femoral implant, using the navigation system. The rest is carried out in the same way as a primary TKA [11].
25.8 25.8.1
Results Total knee arthroplasty
The first results were published in 2001 to validate the device [4]. Two other papers were published in 2017 to present the results after more than 10 years follow-up [13,14]. These results are very interesting regarding the HKA angle because this angle was at 180 6 3 degrees in more than 90% of cases (n 5 208) for severe preoperative varus deformities [13] and 92.3% (n 5 243) for all types of osteoarthritis [14]. The mean IKS scores were, respectively, 180 and 189.5 points. Moreover, the survival rate of the prostheses at more than 10 years of follow-up was 99.2% for all types of osteoarthritis and 99.3% for severe genu varum deformities.
25.8.2
Uni knee arthroplasty and revision to total knee arthroplasty
The results were published in 2017 [11]. In cases of genu varum (n 5 79), preoperative objectives were attained in 88.5% of cases for the HKA angle, with four cases (5.1%) under 175 degrees and five cases (6.1%) over 179 degrees; in 92.4% of cases for the mechanical tibial axis with three cases over 90 degrees and three cases under 84 degrees; and in 95% of cases for the tibial slope. In cases of genu valgum (n 5 19), preoperative objectives were attained in 84% of cases for the HKA angle and in 92% of cases for posterior tibial slope.
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FIGURE 25.17 Navigated TKA for the case of Fig. 25.16. Note the screws to fill femoral bone loss. TKA, Total knee arthroplasty.
25.8.3
Osteotomies
25.8.3.1 High tibial osteotomy In a comparative study comparing navigation to conventional technique [6], two groups of 28 patients were included. The preoperative aim (184 6 2 degrees) was attained in 27 of 28 cases in the navigated group (96%), compared to 20/28 in the conventional group (71%). This difference was statistically significant in favor of the computer-navigated cases. Not only was the objective achieved but also a wide dispersion of results was avoided (especially in overcorrection).
25.8.3.2 Double-level osteotomy In an article published in 2011 [8], based on 42 cases, we found that not only did the patients had very good functional results but also that the preoperative goal was reached in 92.7% of the cases.
25.8.3.3 Osteotomies for genu valgum These results were published in 2014 [9]. No complications other than a transient paralysis of the common fibular nerve were observed. Twenty-three patients (25 knees out of 29) were reviewed at a mean follow-up of 51 months. Twentytwo patients were satisfied or very satisfied. The preoperative goal was achieved in 86.2% of cases (25/29) for the HKA angle.
25.9
Discussion
Computer navigation in knee replacement surgery has reached maturity, but it should be recognized that it has not achieved the degree of development it deserves. The reasons for this lack of enthusiasm are multiple: the complexity of
25. The Orthopilott Device
In the revision series, preoperative objectives were achieved in 92.4% of cases for the HKA angle. In another article where we compared computer-assisted revision to conventional revision [15], we found that this rate for revision with conventional technique was 87.5%. This slight difference in favor of the computer-assisted group was not statistically significant.
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FIGURE 25.18 Osteoarthritis post malunion of the right femur (plate in place for more than 20 years in an 82-year-old female patient). (A) Preoperative X-ray: AP view. (B) Preoperative X-ray: lateral view. (C) Postoperative long leg X-ray. (D) Postoperative lateral view. AP, antero-posterior view.
certain navigation systems which emerged in the early 2000s [16] which added over 30 minutes to the operating time; the cost of the equipment at the time, when it had to be bought or rented; the lack of long-term studies proving increased survival of navigated implants; a certain confusion regarding the objectives of navigation, which is not just a tool for implanting prostheses at 180 6 3 degrees, but according to the axis chosen, whether anatomical or kinematic [17], with increased precision and greater reproducibility. It is important to recognize that there are close to zero complications linked to navigation—far fewer than with traditional techniques—in terms of fat embolism and postoperative bleeding [18,19]. Also, the learning curve is fast and it is a remarkable tool for teaching knee replacement surgery [20]. The major advantage of navigation is its usefulness in major knee deformities, whether varus or valgus. In this context, it allows preoperative objectives to be met in over 90% of cases [13], and thanks to its evaluation of the reducibility of the deformity [5], it considerably reduces the major release rate, which was only 9.5% in a recent series [13]. It is also of particular interest for evaluating sagittal ligament balance in the knee, as it is always difficult intraoperatively, to evaluate visually the degree of flexum or residual recurvatum, which navigation can quantify precisely, in degrees. Finally—and this is certainly one of its major benefits—navigation allows knee replacement to be carried out in excellent conditions in cases of gonarthrosis with femoral or tibial bone malunion, and especially where nonremovable osteosyntheses hardware (particularly femoral) are in place [21 23]. The presence of this type of hardware (plates or nails) makes it impossible to use an intramedullary rod, which makes surgery riskier (Fig. 25.18A D). Regarding UKA navigation and osteotomies, these are probably the best indications for navigation. Indeed, the long-term results are related to the accurate coronal alignment. For UKA, the best coronal alignment is to leave 2 5 degrees of undercorrection that is not easy to reach when using a conventional technique. In the case of overcorrection or too much undercorrection, the risk of failure is much more important. It is the same for osteotomies when there is a varus or valgus deformity. For genu varum, the best results are obtained when there is an overcorrection from 3 to 6 degrees. Without navigation it is not easy to reach this goal and in cases of too much under- or overcorrection, the risk of poor results is not negligible. It is probably the major reason explaining the lack of acceptance of this technique.
25.10
Conclusion
Computer-assisted knee surgery is a fantastic tool allowing to reach the preoperative goal in a large majority of cases. When the goal is well defined the superiority of navigation to conventional techniques has been demonstrated over more than 20 years of experience with Orthopilot. Navigation allows knee replacement to be carried out in excellent conditions in cases of gonarthrosis with femoral or tibial bone malunion, and especially where nonremovable
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osteosyntheses hardware (particularly femoral) is in place. Regarding UKA navigation and osteotomies, these are probably the best indications for navigation since the long-term results are related to the accurate coronal alignment.
References
25. The Orthopilott Device
[1] Lavalle´e S. Geste me´dico-chirurgicaux assiste´s par ordinateur: application a` la neurochirurgie ste´re´otaxique [The`se, ge´nie biologique et me´dical]. Grenoble, France; 1989. [2] Leitner F, Picard F, Minfelde R, Schultz HJ, Cinquin P, Saragaglia D. Computer-assisted knee surgical total replacement. In: “lecture note in computer science”: CURMed-MRCAS’97. Berlin-Heidelberg: Springer Verlag; 1997. p. 629 38. [3] Picard F, Leitner F, Saragaglia D, Cinquin P. Mise en place d’une prothe`se totale du genou assiste´e par ordinateur: a propos de 7 implantations sur cadavre. Rev Chir Orthop Reparatrice Appar Mot 1997;83(Suppl. II):31. [4] Saragaglia D, Picard F, Chaussard C, Montbarbon E, Leitner F, Cinquin P. Computer-assisted knee arthroplasty: comparison with a conventional procedure. Results of 50 cases in a prospective randomized study. Rev Chir Orthop Reparatrice Appar Mot 2001;87:18 28. [5] Saragaglia D, Chaussard C, Rubens-Duval B. Navigation as a predictor of soft tissue release during 90 cases of computer-assisted total knee arthroplasty. Orthopedics 2006;29:S137 8. [6] Saragaglia D, Roberts J. Navigated osteotomies around the knee in 170 patients with osteoarthritis secondary to genu varum. Orthopaedics 2005;28(Suppl 10):S1269 74. [7] Saragaglia D, Mercier N, Colle PE. Computer-assisted osteotomies for genu varum deformity: which osteotomy for which varus? Int Orthop 2010;34:185 90. [8] Saragaglia D, Blaysat M, Mercier N, Grimaldi M. Results of forty two computer-assisted double level osteotomies for severe genu varum deformity. Int Orthop 2012;36:999 1003. Available from: https://doi.org/10.1007/s00264-011-1363-y. [9] Saragaglia D, Chedal-Bornu B. Computer-assisted osteotomy for valgus knees: medium-term results of 29 cases. Orthop Traumatol Surg Res 2014;100:527 30. Available from: https://doi.org/10.1016/j.otsr.2014.04.002 Epub 2014 Jul 30. [10] Saragaglia D, Picard F, Refaie R. Navigation of the tibial plateau alone appears to be sufficient in computer-assisted unicompartmental knee arthroplasty. Int Orthop 2012;36:2479 83. Available from: https://doi.org/10.1007/s00264-012-1679-2. [11] Saragaglia D, Marques Da Silva B, Dijoux P, Cognault J, Gaillot J, Pailhe´ R. Computerised navigation of unicondylar knee prostheses: from primary implantation to revision to total knee arthroplasty. Int Orthop 2017;41:293 9. Available from: https://doi.org/10.1007/s00264-0163293-1 Epub 2016 Sep 28. [12] Hernigou P, Deschamps G. Alignment influences wear in the knee after medial unicompartmental arthroplasty. Clin Orthop Relat Res 2004;423:161 5. [13] Saragaglia D, Sigwalt L, Gaillot J, Morin V, Rubens-Duval B, Pailhe´ R. Results with eight and a half years average follow-up on two hundred and eight e-Motion FPs knee prostheses, fitted using computer navigation for knee osteoarthritis in patients with over ten degrees genu varum. Int Orthop 2017. Available from: https://doi.org/10.1007/s00264-017-3618-8. [14] Saragaglia D, Seurat O, Pailhe´ R, Rubens Duval B. Computer-assisted TKA: long-term outcomes at a minimum follow-up of 10 years of 129 emotion FP mobile bearing prostheses. EPiC Ser Health Sci 2017;1:322 4. [15] Saragaglia D, Cognault J, Refaie R, Rubens-Duval B, Mader R, Rouchy RC, et al. Computer navigation for revision of unicompartmental knee replacements to total knee replacements: the results of a case-control study of forty six knees comparing computer navigated and conventional surgery. Int Orthop 2015;39:1779 84. Available from: https://doi.org/10.1007/s00264-015-2838-z Epub2015 Jul 2. [16] Stindel E, Briard JL, Merloz P, Plaweski S, Dubrana F, Lefevre C, et al. Bone morphing: 3D morphological data for total knee arthroplasty. Comput Aided Surg 2002;7:156 68. [17] Howell SM, Papadopoulos S, Kuznik K, Ghaly LR, Hull ML. Does varus alignment adversely affect implant survival and function six years after kinematically aligned total knee arthroplasty? Int Orthop 2015;39:2117 24. Available from: https://doi.org/10.1007/s00264-015-2743-5. [18] Kalairajah Y, Cossey AJ, Verrall GM, Ludbrook G, Spriggins AJ. Are systemic emboli reduced in computer-assisted knee surgery? A prospective, randomised, clinical trial. J Bone Joint Surg Br 2006;88:198 202. [19] McConnell J, Dillon J, Kinninmonth A, Sarungi M, Picard F. Blood loss following total knee replacement is reduced when using computerassisted versus standard methods. Acta Orthop Belg 2012;78:75 8. [20] Jenny J-Y, Picard F. Learning navigation Learning with navigation. A review. SICOT J 2017;3:39. Available from: https://doi.org/10.1051/ sicotj/2017025. [21] Mullaji A, Shetty GM. Computer-assisted total knee arthroplasty for arthritis with extra-articular deformity. J Arthroplasty 2009;24:1164 9. [22] Kim KK, Heo YM, Won YY, Lee WS. Navigation-assisted total knee arthroplasty for the knee retaining femoral intramedullary nail, and distal femoral plate and screws. Clin Orthop Surg 2011;3:77 80. Available from: https://doi.org/10.4055/cios.2011.3.1.77. [23] Tigani D, Masetti G, Sabbioni G, Ben Ayad R, Filanti M, Fosco M. Computer-assisted surgery as indication of choice: total knee arthroplasty in case of retained hardware or extra-articular deformity. Int Orthop 2012;36:1379 85. Available from: https://doi.org/10.1007/s00264-0111476-3.
More Than 20 Years Navigation of Knee Surgery With the Orthopilot Device Dominique Saragaglia CHU Grenoble-Alpes, South Teaching Hospital, Grenoble, France
ABSTRACT Navigation of knee surgery was born in Grenoble (France) in the mid-1990s. The first total knee arthroplasty (TKA) was implanted on a human being on January 1997 and a prospective randomized study comparing computer-assisted TKA and conventional technique finished in March 1999. The results were published, leading to marketing of the Orthopilot device. In March 2001 we carried out the first high tibial osteotomy for genu varum deformity and in January 2008 we implanted for the first time a UniKA with a “light” software. The aim of this chapter is first to present the Orthopilot device and the operative technique, then the evolution of the software in order to use it for osteotomies around the knee, UniKA, and revision of Uni to TKA. Second, results of these techniques are presented, and finally, the usefulness of navigation is discussed. Handbook of Robotic and Image-Guided Surgery. DOI: https://doi.org/10.1016/B978-0-12-814245-5.00025-6 © 2020 Elsevier Inc. All rights reserved.
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25.1
Introduction
Computer-assisted surgery began with stereotactic neurosurgery [1] toward the end of the 1980s. This new technique aimed to improve the precision of operations, reduce surgical invasiveness, and improve the traceability of interventions. The history of computer-assisted implantation of total knee prostheses dates back to 1993 when we set up a work group including two surgeons (D. Saragaglia and F. Picard), one medical doctor/computer scientist (P. Cinquin), two computer scientists (S. Lavalle´e and F. Leitner), and an industry partner, which was at the time I.C.P. France (boughtover by Aesculap-AG, Tuttlingen, Germany, in 1994). In our first meeting, the senior surgeon drew up the specifications defining computer assistance for total knee replacement. A preoperative scan was not needed to guide surgical navigation for several reasons, this was first because, at the time, this examination was not part of the preoperative check-up required for a knee prosthesis, second, we felt that an examination of this sort could only complicate the operative procedure, and last, this would have added additional cost and a considerable amount of radiation exposure for the patient. We needed to have a reference to the mechanical leg axis throughout the whole operation so that the cutting guides could be placed perpendicular to this axis in a frontal and sagittal plane. The cutting guides needed to be placed freehand without any centromedullary or extramedullary rods. Finally, the operation was not supposed to last more than 2 hours (maximum tourniquet time) and the procedure was to be accessible to all surgeons, whatever their computing skills. The project was assigned to F. Picard, as part of his Postgraduate Diploma in Medical and Biological Engineering, and to F. Leitner a computer scientist who was completing his training. After 2 years of research, the system was validated by the implantation of 10 knee prostheses on 10 cadaver knees, and the results were published in 1997 [2,3] in several national and international publications, including CAOS, SOFCOT, and SOBCOT. After obtaining the consent of the local ethics committee on December 4, 1996, the first computer-assisted prosthesis was implanted in a patient, on January 21, 1997 (D. Saragaglia, F. Picard, T. Lebredonchel). The operation lasted 2 hours and 15 minutes and was uneventful. A prospective randomized study comparing this technique to the conventional technique began in January 1998 and was completed in March 1999. The results (Table 25.1) were published in several national and international meetings and in a lead article in the French Journal of Orthopaedic Surgery [4]. In March 1999, the prototype that we had used in this study evolved to a final model called Orthopilot (B-Braun-Aesculap, Tuttlingen, Germany). Since that time, numerous papers have been published confirming that this technique was well founded and more than 360,000 prostheses have been implanted worldwide with Orthopilot. The software packages have evolved (versions 3.0, 3.2, 4.0, 4.2, TABLE 25.1 Results of the prospective randomized study published in 2001. Conventional surgery
Navigation
Patients (n)
25
25
Preoperative goal
180 6 3 degrees
180 6 3 degrees
Genu varum (%)
80
76
Genu valgum (%)
16
24
Neutral
4
0
P value
Preop HKA angle
175 degrees (162 210 degrees)
175 degrees (162 210 degrees)
Postop HKA angle
181.2 6 2.7 degrees
179 6 2.5 degrees
Goal achievement
75%
84%
P 5 .35 NS
MFMA
91 6 2 degrees
89.5 6 1.6 degrees
P 5 .048 S
Goal achievement for MFMA (90 degrees)
16.5%
48%
S
MTMA
90.2 6 1.6 degrees
89.5 6 1.4 degrees
P 5 .11 NS
Posterior slope
90.8 6 2.2 degrees
89.5 6 2 degrees
P 5 .18 NS
Goal achievement for postslope
41%
76%
S
HKA, Hip knee ankle; MFMA, medial femoral mechanical angle; MTMA, medial tibial mechanical angle; S, significant.
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5.0, 5.1) but the basic principle has remained the same since the system was created. Today, the operative procedure lasts between 1 and 1.5 hours, depending on the difficulty of the case, and almost 4000 total knee arthroplasties (TKAs) have been implanted in our department, using navigation. In March 2001 we did the first high tibial osteotomy (HTO) for genu varum deformity and in January 2008 we implanted for the first time a UniKA with a “light” Software. The aim of this chapter is first to present the Orthopilot device and the operative technique, then the evolution of the software in order to use it for osteotomies around the knee, UniKA, and revision of Uni to TKA. Second, to present the results of these techniques, and last, to discuss the usefulness of navigation.
25.2
The Orthopilot device
FIGURE 25.1 The Orthopilot device.
25. The Orthopilott Device
The Orthopilot device is an image-free navigation system based on intraoperative data acquisition. The equipment includes a navigation station (Fig. 25.1), which allows the markers to be spatially located in real time, as well as an ancillary device adapted to this navigation. The navigation station is made up of a personal computer, an infrared Spectra localizer (Northern Digital Inc.), and a dual-command foot-pedal. The progress of the operative protocol is defined in the software and the surgeon controls this via the pedal and a dedicated graphic interface. The computer-navigation system is placed 1.8 2.2 m from the knee on the patient’s opposite side, closer to the patient’s head. This navigation station also includes ancillary devices, which are the wireless markers and their tightening system. Markers, also called “rigid bodies,” are a collection of four reflective spheres rigidly held together (Fig. 25.2). An embedded localizer infrared source illuminates these spheres whose positions are detected thanks to an image triangulation computation. The attitude (position and orientation) of each marker is therefore computed from sphere positions and the marker’s own shape. All the objects that need to be tracked can have markers attached to them. It is also possible to mark out specific points in space using a metallic pointer linked to a marker whose accurate extremity coordinates are prerecorded. The markers are rigidly attached to the bone using special bicortical screws. For TKA, the ancillary device is made up of cutting guides equipped with markers that are firmly attached to the bone by four threaded pins. These guide the tibial cut (height of cut, valgus varus, tibial slope) and the femoral cut (height of cut, valgus varus, flexum, recurvatum). The chamfer cutting guide allows the anterior and posterior cuts to be made. A distractor can be used to guide the ligament balance in flexion and extension.
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FIGURE 25.2 Marker with four reflecting balls (passive marker). FIGURE 25.3 Tibial and femoral markers fixed percutaneously to the bone.
25.3
Operative procedures: total knee arthroplasty
A tourniquet is placed at the root of the thigh and the patient is put in a supine position without any particular setup. In the majority of cases a medial parapatellar approach is used but all kind of approaches can be used. The patella is everted and the markers are inserted. To reduce the length of the incision, the femoral and tibial markers are inserted percutaneously (Fig. 25.3) and are positioned so that they can be seen throughout the whole operation without the need to move the localizer. The femoral marker is placed 15 cm above the joint line in an oblique position with respect to the frontal plan and the tibial marker is placed 10 cm below the joint, parallel to the frontal plan.
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25.3.1
429
Navigation of the femoro-tibial mechanical angle
The navigation step begins with the palpation of the anterior cortex of the femur just above the upper margin of the trochlea and the posterior side of the medial and lateral condyles. Then, the middle of the tibial spines is palpated as well as the middle of the medial or lateral tibial plateau. When the tibial mechanical axis is in varus, as is almost always the case in genu varum deformities, the lateral plateau is palpated. When the tibial mechanical axis is in valgus, the medial plateau must be palpated in order to avoid too much resection on the medial side. At the end of this step, the center of the knee has been located and the size of the femoral implant is registered in the computer. The acquisition of the center of the ankle is obtained by palpation of the medial and lateral malleoli as well as the middle of the tibiotarsal joint. Finally, the center of the femoral head is located by moving the leg in a small circular motion, slowly and progressively, with the knee in extension or in flexion. This lets the localizer track to follow the infrared diodes of the femoral “rigid body” and locate the center of the femoral head. At this step of the procedure, we know the hip knee ankle (HKA) angle which can be compared to the radiological preoperative axis, and the size of the femoral implant. Before inserting the cutting guides, it is very important to check the reducibility of the deformity [5], above all in extension (10 degrees of flexion), in order to predict any release. In the case of genu varum, a lateral manual stress of the knee is applied, and the HKA angle is checked on the computer. In the case of hyperreducibility (varus going into valgus) or hyporeducibility less than 3 degrees, there is no need to do a release of the medial collateral ligament (MCL). In the case of hyporeducibility from 3 to 6 degrees a release of the MCL is needed (pie-crusting) and in case of hyporeducibility above 6 degrees a major release is needed (release of the MCL at its femoral insertion). Otherwise, the laxity of the convexity of the knee is noted.
25.3.2
Navigation of the bone cuts
FIGURE 25.4 Measurement of the resection height of the tibial plateau, the varus valgus alignment, and the posterior slope.
25. The Orthopilott Device
The tibial cutting guide is mounted on a support, which allows the valgus varus, the height of the cut, and the posterior tibial slope to be measured (Fig. 25.4). We currently prefer to position this cutting guide freehand, without any support, which means shorter cutaneous incisions can be made. This cutting guide is positioned in front of the tibia with its “rigid body” (Fig. 25.2) and it is fixed to the bone by four threaded pins once the correct measurements are displayed on the screen, which for us are a valgus varus at 0 degree, a posterior tibial slope from 0 to 2 degrees, and a cutting height of 8 or 10 mm, which corresponds to the thickness of the tibial plateau implant. Once the cutting guide is fixed into position, an oscillating saw is used to make the cut. The femoral cutting guide equipped with its “rigid body” is then placed against the anterior side of the distal end of the femur, with the knee flexed at 90 degrees after the overhang of the femoral trochlea has been resected. This step is very important to determine the femoral mechanical axis and to compare it with the radiological preoperative measurements (Fig. 25.5). The surgeon then adjusts the valgus varus of the distal femoral cutting guide (0 degree for us), the posterior slope (between 0 and 2 degrees flexum to avoid notching the anterior cortex), and the height of the resection
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FIGURE 25.5 Radiological measurement of the varus deformity: HKA angle, medial femoral mechanical angle, medial tibial mechanical angle. HKA, Hip knee ankle.
(minimal resection in the convex side of the deformity to reduce ligament imbalance) corresponding to the thickness of the prosthesis. At this stage of the operation, the computer has carried out a “bone” alignment of the leg and the prosthesis is then implanted using the classic ancillary equipment, especially when making the anterior, posterior, and chamfer cuts.
25.3.3
Implanting the trial prosthesis
The implantation of the trial prosthesis uses computer assistance to check the mechanical leg axis in extension, in the walking position, and in flexion at 90 degrees. Ligament balance is also controlled by taking stress valgus or varus measurements, and assessing any medial or lateral gaping. The mechanical leg axis can also be checked when the prosthesis is permanently implanted. This will allow the detection of any excess medial or lateral cement that is liable to change the axis by 1 or 2 degrees (1 mm of cement 5 1 degree).
25.3.4
Rotation of the femoral implant
We never systematically apply external rotation to the femoral implant, at least in genu varum. We only apply rotation according to the femoral valgus or varus (Fig. 25.6). If, in the case of genu varum, the femur is in a valgus of 3 degrees or more, we believe it is logical to apply external rotation, because it will be necessary to resect more of the distal medial condyle and as a result more of the posterior condyle if one wants the ligament to be balanced in flexion. This rotation does not need to be navigated since the ancillary makes it easy to perform. If the femur is in varus, and if the genu varum is overreducible, it is equally logical to apply internal rotation, since less distal medial condyle will be resected and therefore less posterior medial condyle. In the case of genu valgum, external rotation is almost systematic since the femoral valgus is almost constant. We usually apply 1 degree of rotation for 1 degree of femoral valgus and do not exceed 5 6 degrees of rotation, to limit the cut in the anterolateral cortex of the femur.
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FIGURE 25.6 Measurement of the femoral mechanical angle with the computer.
25.3.5
Ligament balance
25.3.6
Implanting the final prosthesis
The final prosthesis is cemented (or not, in the case of cementless prostheses) when the HKA angle is at 180 6 3 degrees, the ligaments are well balanced, the tracking of the patella is optimal as well as the range of motion. At last, the approach is closed step by step according the habits of each.
25. The Orthopilott Device
There are two ways to proceed: either by working from reducibility of the deformity tests (valgus and varus stress near extension) or by following ligament balance management software. We prefer to use the first method, which allows the surgeon to consider and remain master of his/her decisions. We proceed in the following way: when the mechanical leg axis appears on the computer screen, before any ablation of osteophytes, we apply manual force in varus and valgus, with the knee at 5 10 degrees of flexion, to assess the reducibility of the deformity and the gap in convexity. If the deformity is completely reducible, or even hyperreducible, we are certain that the ligaments will be balanced in extension and that it will not be necessary to release soft tissue in the concavity. The same is true if reducibility gives a hypocorrection of 2 3 degrees. If hypocorrection is greater than this, it will be necessary to allow for the progressive release of soft tissue with trial implants, after removing the osteophytes. However, it should be stated that a perfect balance does not necessarily mean that there is a symmetrical gap between the medial and the lateral side, since it is known that, in a normal knee, the lateral compartment is more lax than the medial compartment. We therefore readily accept, in genu varum, a difference of 3 or 4 degrees more for the lateral compartment of the knee. As far as the management of gaps between extension and flexion is concerned, we never have an imbalance since, on one hand we commonly use a posterior cruciate ligament (PCL) retaining prosthesis which is a good “keeper” of the gaps, and on the other hand the bone resection thickness is identical to the thickness of the implants. Thus, there is no reason for the balance which was adequate before the implantation of the prosthesis to change afterwards. Finally, the medial lateral balance in flexion can be controlled without any distractor, since we believe that this is an artificial procedure which does not guarantee an adequate balance; indeed, creating tension between the two sides is subjective and difficult to reproduce from one surgeon to the next. To check this balance, it is sufficient, once the cutting guide for the chamfers has been applied at the distal femur level, to raise the thigh through the use of this supporting point, to manually pull into the axis of the knee flexed at 90 degrees, and to check the parallelism of the cutting guide with the cut of the tibial plateau (Fig. 25.7). In genu varum, parallelism is perfect in most cases and it is not necessary to release soft tissue. Otherwise, especially in genu valgum, it is necessary to release the medial or lateral collateral ligaments progressively.
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FIGURE 25.7 Checking of the ligaments balancing in flexion at 90 degrees.
FIGURE 25.8 HKA angle displayed on the screen of the computer. HKA, Hip knee ankle.
25.4 25.4.1
Osteotomies for genu varum deformity High tibial opening wedge osteotomy
The same principles of real-time acquisition of the rotation center of the HKA centers and of the anatomical landmarks at the level of the knee joint line (palpation of medial and lateral epicondyles and the tip of the patella) and ankle is applied. They allow the mechanical axis of the lower limb to be shown dynamically on the computer screen (Fig. 25.8), that is, the axis of the lower limb to be seen both pre- and postosteotomy and to check if the preplanned correction has been established [6 8]. Generally, the procedure follows this sequence: The rigid body markers are fixed percutaneously at the level of the distal femur and proximal tibia allowing acquisition of the centers of hip, knee and ankle. The lower limb mechanical axis then appears on the screen and can be compared with the preoperative radiological goniometry. The HTO is performed 3 cm below the level of the medial joint line, the level confirmed by placing an intraarticular needle. The osteotomy is directed at the fibula head, keeping the saw as horizontal as possible to avoid fracturing the lateral tibial plateau.
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FIGURE 25.9 Opening wedge high tibial osteotomy filled by a tricalcium phosphate wedge (Biosorb) and fixed by a locking screw plate.
25.4.2
Double-level osteotomy
The first stage is essentially the same as for that of an HTO: percutaneous insertion of the rigid body markers (high enough not to hamper the femoral osteotomy and low enough on the other level to avoid interfering with the tibial osteotomy), followed by acquisition of the hip center, middle of the knee, and tibio-tarsal joints in order to find the mechanical axis of the lower limb. The second stage consists of making the femoral closing osteotomy in the distal femur (in general a 5 6 degrees alteration is made, although sometimes more in congenital femoral varus) and fixing it in position with a plate. A lateral approach with elevation of the vastus lateralis is chosen, the lateral arthrotomy allowing the tip of the trochlea to be located. The track of the osteotomy lies above the trochlea and is directed obliquely from above laterally to below on the medial femoral cortex. A wedge of bone is then excised from the distal femur with a 4 5 mm lateral base, corresponding to a 5 6 degrees correction. The osteotomy is fixed with the plate after placing the femur into valgus manually. Once this stage is reached the mechanical axis is rechecked so that the required correction at the level of the tibia can be calculated in order to achieve the preoperative objectives. The last stage is to perform the HTO exactly in the fashion described above (Fig. 25.10A and B). The definitive axis is then displayed on the computer screen.
25.5
Osteotomy for genu valgum deformity
The technique used is similar to that used in varus knees as described above [9]. After intraoperative acquisition of the mechanical axis of the lower limb, the appropriate femoral varus osteotomy is carried out: or medial closing or lateral
25. The Orthopilott Device
With the aid of two Pauwels osteotomes inserted along the track of the saw cut, the tibia is placed into valgus. These are then replaced by a metal spacer which is inherently stable and allows the amount of correction to be checked. If there was 8 degrees of varus one would try a 10 11 mm spacer and make sure that an appropriate hypercorrection is produced real time on the computer screen. If this is insufficient we try a thicker spacer, and the reverse if the correction is too great. The metallic spacer is then replaced with a bio-absorbable tricalcium phosphate wedge (Biosorb, B. Braun Aesculap, Boulogne, France) of the desired thickness, and the intervention is completed by plating the proximal tibia (Fig. 25.9) with a locking screw plate.
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FIGURE 25.10 (A) Double-level osteotomy performed for severe genu varum deformity: AP view. (B) Doublelevel osteotomy performed for severe genu varum deformity: lateral view. AP, antero-posterior view.
opening wedge. In some cases of excessively tight fascia lata where the required lateral opening osteotomy exceeded 6 8 degrees, piecrust lengthening is performed on the iliotibial band; this contributes to easier recovery of knee flexion. Medial closing osteotomies were performed in our earliest cases and were secured with an AO T-shaped plate. Lateral opening osteotomy is performed currently; the opening is filled with bio-absorbable tricalcium phosphate wedge (Biosorb, SBM, Lourdes, France) and secured with an AO locking plate or an OTIS-F locking plate (SBM, Lourdes, France) (Fig. 25.11). A double varus osteotomy of the femur and tibia due to valgus medial distal femoral mechanical axis and medial proximal tibial mechanical axis is performed to avoid an oblique joint line (Fig. 25.12A). In these cases, a medial closing-wedge osteotomy of the tibia is performed first and fixed with an OTIS locking plate (SBM, Lourdes, France) and then a lateral opening-wedge varus osteotomy of the femur is carried out (Fig. 25.12B and C).
25.6
Uni knee arthroplasty
The rigid body markers are set as for TKA. A 7 9-cm medial parapatellar skin incision is performed, its length dependent on the patient’s BMI and soft-tissue elasticity. Then a subvastus or midvastus intraarticular approach is done to access the knee [10,11]. The next step involves data collection of the knee: middle of the intercondylar notch, the middle of the tibial spines (Fig. 25.13), the middle of the medial tibial plateau, the more distal point of the femoral condyle, and finally, the medial, lateral malleoli, and the middle of the ankle joint. The second step is the registration of the hip kinematic center using hip circumduction movement and the knee kinematic center using flexion extension and rotation axis of the knee in 90 degrees flexion. At the end of the registration, the femoro-tibial mechanical axis (FTMA) is displayed on the monitor screen and the surgeon then starts to navigate the tibial bone cut resection. Before proceeding to tibial cutting guide navigation, one checks the correlation between FTMA displayed on the computer monitor screen and the measured preoperative HKA X-ray angle and also assesses reducibility of the leg deformity. If the deformity is hypercorrectable (too much valgus), it is a contraindication for mobile uni knee arthroplasty (UKA) due to the risk of hypercorrection. Indeed, if the leg
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FIGURE 25.11 Opening wedge distal femoral osteotomy for genu valgum deformity filled by a tricalcium phosphate wedge and fixed by an AO locking screw plate.
25. The Orthopilott Device FIGURE 25.12 (A) Genu valgum with femoral mechanical axis in valgus as well as proximal tibial mechanical axis. (B) Double-level osteotomy to correct the deformity (tibial closing wedge and femoral opening wedge): AP view. (C) Double-level osteotomy to correct the deformity (tibial closing wedge and femoral opening wedge): lateral view. AP, antero-posterior view.
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FIGURE 25.13 Palpating of the intercondylar eminence for UKA. UKA, Uni knee arthroplasty.
stays in varus, the MCL will remain slack and the mobile bearing surface is at risk of dislocation. In order to avoid this, a larger polyethylene would fill the gap but this would then increase the load-stress on the other side of the joint. The tracked tibial cutting jig is positioned in front of the medial tibial plateau, then navigated and fixed using three to four threaded pins (Fig. 25.14). Using the graphic user interface, the tibial jig is placed between 2 and 3 degrees varus and between 3 and 5 degrees slope with a bone resection ranging between 4 and 8 mm (never more than 8 mm in order to avoid any subsidence of the tibial plateau implant related to weak cancellous bone). However, the less varus the more bone resection, and vice versa according to the indications for UKA [12]. Once these three parameters (coronal, sagittal, and height) are satisfactory, the tibial cut is performed using an oscillating saw for the horizontal cut and a reciprocating saw for the vertical cut. At this stage, the navigation is finished, and the femoral cut is performed using a tibial spacer placed between the resected tibial plateau bony surface and the distal medial femoral condyle with the knee in extension. The distal femoral jig is slotted onto the tibial spacer until it reaches the femur, ensuring that the tibial plateau fits perfectly well onto the resected bony surface (Fig. 25.15). Two threaded pins are used to stabilize the femoral jig and the distal femoral cut is performed using an oscillating saw. Then the knee is flexed to 90 degrees and with the use of several templates, the best-size fit is chosen for the femoral condyle. Posterior and chamfrain cuts are performed using the suitable template. The tibial and femoral trial implants are tested. The surgeon verifies leg alignment which should be within 177 6 2 degrees that is a slight hypocorrection. When using a mobile bearing tibial plateau, a “safe laxity” is tolerated at around 1 degree. If the “safe laxity” is more than 2 degrees, the choice will then be to use a fixed bearing tibial plateau. Once satisfactory alignment and position are obtained, the final implants are cemented and postimplant FTMA is controlled and recorded before closing.
25.7
Uni knee arthroplasty to total knee arthroplasty revision
In cases of UKA to TKA revisions, the navigation is the same as in primary TKAs. The implants are not removed and the images are taken with the implants in place even when there is loosening or sinking of the implants (Fig. 25.16). This works because the navigation system is not based on bone morphing but on palpation of several critical points, especially the lateral tibial plateau in the case of revision of medial UKA or the medial plateau in the case of revision
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FIGURE 25.15 Insertion of the distal cutting guide for UKA. UKA, Uni knee arthroplasty.
25. The Orthopilott Device
FIGURE 25.14 Fixation of the tibial cutting guide for UKA. UKA, Uni knee arthroplasty.
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FIGURE 25.16 Loosening of UKA revised by computer-assisted TKA. TKA, Total knee arthroplasty; UKA, uni knee arthroplasty.
of the lateral one. Once the lower limb angle is obtained, the various cuts are made using the cutting guides, positioned with the help of the navigator. The tibial cut rarely presents problems, except where there is major bone loss under the tibial component, which requires either a bone graft or the use of metal wedges. Loss of bone substance after removal of the implant is rarely a problem in the femur, except in rare cases where the femoral component has subsided into the cancellous bone of the condyle (Fig. 25.17). After removing the implant, it is important to ensure that the posterior cut is compensated for when implanting the primary prosthesis, by adjusting the external rotation of the femoral implant, using the navigation system. The rest is carried out in the same way as a primary TKA [11].
25.8 25.8.1
Results Total knee arthroplasty
The first results were published in 2001 to validate the device [4]. Two other papers were published in 2017 to present the results after more than 10 years follow-up [13,14]. These results are very interesting regarding the HKA angle because this angle was at 180 6 3 degrees in more than 90% of cases (n 5 208) for severe preoperative varus deformities [13] and 92.3% (n 5 243) for all types of osteoarthritis [14]. The mean IKS scores were, respectively, 180 and 189.5 points. Moreover, the survival rate of the prostheses at more than 10 years of follow-up was 99.2% for all types of osteoarthritis and 99.3% for severe genu varum deformities.
25.8.2
Uni knee arthroplasty and revision to total knee arthroplasty
The results were published in 2017 [11]. In cases of genu varum (n 5 79), preoperative objectives were attained in 88.5% of cases for the HKA angle, with four cases (5.1%) under 175 degrees and five cases (6.1%) over 179 degrees; in 92.4% of cases for the mechanical tibial axis with three cases over 90 degrees and three cases under 84 degrees; and in 95% of cases for the tibial slope. In cases of genu valgum (n 5 19), preoperative objectives were attained in 84% of cases for the HKA angle and in 92% of cases for posterior tibial slope.
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FIGURE 25.17 Navigated TKA for the case of Fig. 25.16. Note the screws to fill femoral bone loss. TKA, Total knee arthroplasty.
25.8.3
Osteotomies
25.8.3.1 High tibial osteotomy In a comparative study comparing navigation to conventional technique [6], two groups of 28 patients were included. The preoperative aim (184 6 2 degrees) was attained in 27 of 28 cases in the navigated group (96%), compared to 20/28 in the conventional group (71%). This difference was statistically significant in favor of the computer-navigated cases. Not only was the objective achieved but also a wide dispersion of results was avoided (especially in overcorrection).
25.8.3.2 Double-level osteotomy In an article published in 2011 [8], based on 42 cases, we found that not only did the patients had very good functional results but also that the preoperative goal was reached in 92.7% of the cases.
25.8.3.3 Osteotomies for genu valgum These results were published in 2014 [9]. No complications other than a transient paralysis of the common fibular nerve were observed. Twenty-three patients (25 knees out of 29) were reviewed at a mean follow-up of 51 months. Twentytwo patients were satisfied or very satisfied. The preoperative goal was achieved in 86.2% of cases (25/29) for the HKA angle.
25.9
Discussion
Computer navigation in knee replacement surgery has reached maturity, but it should be recognized that it has not achieved the degree of development it deserves. The reasons for this lack of enthusiasm are multiple: the complexity of
25. The Orthopilott Device
In the revision series, preoperative objectives were achieved in 92.4% of cases for the HKA angle. In another article where we compared computer-assisted revision to conventional revision [15], we found that this rate for revision with conventional technique was 87.5%. This slight difference in favor of the computer-assisted group was not statistically significant.
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FIGURE 25.18 Osteoarthritis post malunion of the right femur (plate in place for more than 20 years in an 82-year-old female patient). (A) Preoperative X-ray: AP view. (B) Preoperative X-ray: lateral view. (C) Postoperative long leg X-ray. (D) Postoperative lateral view. AP, antero-posterior view.
certain navigation systems which emerged in the early 2000s [16] which added over 30 minutes to the operating time; the cost of the equipment at the time, when it had to be bought or rented; the lack of long-term studies proving increased survival of navigated implants; a certain confusion regarding the objectives of navigation, which is not just a tool for implanting prostheses at 180 6 3 degrees, but according to the axis chosen, whether anatomical or kinematic [17], with increased precision and greater reproducibility. It is important to recognize that there are close to zero complications linked to navigation—far fewer than with traditional techniques—in terms of fat embolism and postoperative bleeding [18,19]. Also, the learning curve is fast and it is a remarkable tool for teaching knee replacement surgery [20]. The major advantage of navigation is its usefulness in major knee deformities, whether varus or valgus. In this context, it allows preoperative objectives to be met in over 90% of cases [13], and thanks to its evaluation of the reducibility of the deformity [5], it considerably reduces the major release rate, which was only 9.5% in a recent series [13]. It is also of particular interest for evaluating sagittal ligament balance in the knee, as it is always difficult intraoperatively, to evaluate visually the degree of flexum or residual recurvatum, which navigation can quantify precisely, in degrees. Finally—and this is certainly one of its major benefits—navigation allows knee replacement to be carried out in excellent conditions in cases of gonarthrosis with femoral or tibial bone malunion, and especially where nonremovable osteosyntheses hardware (particularly femoral) are in place [21 23]. The presence of this type of hardware (plates or nails) makes it impossible to use an intramedullary rod, which makes surgery riskier (Fig. 25.18A D). Regarding UKA navigation and osteotomies, these are probably the best indications for navigation. Indeed, the long-term results are related to the accurate coronal alignment. For UKA, the best coronal alignment is to leave 2 5 degrees of undercorrection that is not easy to reach when using a conventional technique. In the case of overcorrection or too much undercorrection, the risk of failure is much more important. It is the same for osteotomies when there is a varus or valgus deformity. For genu varum, the best results are obtained when there is an overcorrection from 3 to 6 degrees. Without navigation it is not easy to reach this goal and in cases of too much under- or overcorrection, the risk of poor results is not negligible. It is probably the major reason explaining the lack of acceptance of this technique.
25.10
Conclusion
Computer-assisted knee surgery is a fantastic tool allowing to reach the preoperative goal in a large majority of cases. When the goal is well defined the superiority of navigation to conventional techniques has been demonstrated over more than 20 years of experience with Orthopilot. Navigation allows knee replacement to be carried out in excellent conditions in cases of gonarthrosis with femoral or tibial bone malunion, and especially where nonremovable
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osteosyntheses hardware (particularly femoral) is in place. Regarding UKA navigation and osteotomies, these are probably the best indications for navigation since the long-term results are related to the accurate coronal alignment.
References
25. The Orthopilott Device
[1] Lavalle´e S. Geste me´dico-chirurgicaux assiste´s par ordinateur: application a` la neurochirurgie ste´re´otaxique [The`se, ge´nie biologique et me´dical]. Grenoble, France; 1989. [2] Leitner F, Picard F, Minfelde R, Schultz HJ, Cinquin P, Saragaglia D. Computer-assisted knee surgical total replacement. In: “lecture note in computer science”: CURMed-MRCAS’97. Berlin-Heidelberg: Springer Verlag; 1997. p. 629 38. [3] Picard F, Leitner F, Saragaglia D, Cinquin P. Mise en place d’une prothe`se totale du genou assiste´e par ordinateur: a propos de 7 implantations sur cadavre. Rev Chir Orthop Reparatrice Appar Mot 1997;83(Suppl. II):31. [4] Saragaglia D, Picard F, Chaussard C, Montbarbon E, Leitner F, Cinquin P. Computer-assisted knee arthroplasty: comparison with a conventional procedure. Results of 50 cases in a prospective randomized study. Rev Chir Orthop Reparatrice Appar Mot 2001;87:18 28. [5] Saragaglia D, Chaussard C, Rubens-Duval B. Navigation as a predictor of soft tissue release during 90 cases of computer-assisted total knee arthroplasty. Orthopedics 2006;29:S137 8. [6] Saragaglia D, Roberts J. Navigated osteotomies around the knee in 170 patients with osteoarthritis secondary to genu varum. Orthopaedics 2005;28(Suppl 10):S1269 74. [7] Saragaglia D, Mercier N, Colle PE. Computer-assisted osteotomies for genu varum deformity: which osteotomy for which varus? Int Orthop 2010;34:185 90. [8] Saragaglia D, Blaysat M, Mercier N, Grimaldi M. Results of forty two computer-assisted double level osteotomies for severe genu varum deformity. Int Orthop 2012;36:999 1003. Available from: https://doi.org/10.1007/s00264-011-1363-y. [9] Saragaglia D, Chedal-Bornu B. Computer-assisted osteotomy for valgus knees: medium-term results of 29 cases. Orthop Traumatol Surg Res 2014;100:527 30. Available from: https://doi.org/10.1016/j.otsr.2014.04.002 Epub 2014 Jul 30. [10] Saragaglia D, Picard F, Refaie R. Navigation of the tibial plateau alone appears to be sufficient in computer-assisted unicompartmental knee arthroplasty. Int Orthop 2012;36:2479 83. Available from: https://doi.org/10.1007/s00264-012-1679-2. [11] Saragaglia D, Marques Da Silva B, Dijoux P, Cognault J, Gaillot J, Pailhe´ R. Computerised navigation of unicondylar knee prostheses: from primary implantation to revision to total knee arthroplasty. Int Orthop 2017;41:293 9. Available from: https://doi.org/10.1007/s00264-0163293-1 Epub 2016 Sep 28. [12] Hernigou P, Deschamps G. Alignment influences wear in the knee after medial unicompartmental arthroplasty. Clin Orthop Relat Res 2004;423:161 5. [13] Saragaglia D, Sigwalt L, Gaillot J, Morin V, Rubens-Duval B, Pailhe´ R. Results with eight and a half years average follow-up on two hundred and eight e-Motion FPs knee prostheses, fitted using computer navigation for knee osteoarthritis in patients with over ten degrees genu varum. Int Orthop 2017. Available from: https://doi.org/10.1007/s00264-017-3618-8. [14] Saragaglia D, Seurat O, Pailhe´ R, Rubens Duval B. Computer-assisted TKA: long-term outcomes at a minimum follow-up of 10 years of 129 emotion FP mobile bearing prostheses. EPiC Ser Health Sci 2017;1:322 4. [15] Saragaglia D, Cognault J, Refaie R, Rubens-Duval B, Mader R, Rouchy RC, et al. Computer navigation for revision of unicompartmental knee replacements to total knee replacements: the results of a case-control study of forty six knees comparing computer navigated and conventional surgery. Int Orthop 2015;39:1779 84. Available from: https://doi.org/10.1007/s00264-015-2838-z Epub2015 Jul 2. [16] Stindel E, Briard JL, Merloz P, Plaweski S, Dubrana F, Lefevre C, et al. Bone morphing: 3D morphological data for total knee arthroplasty. Comput Aided Surg 2002;7:156 68. [17] Howell SM, Papadopoulos S, Kuznik K, Ghaly LR, Hull ML. Does varus alignment adversely affect implant survival and function six years after kinematically aligned total knee arthroplasty? Int Orthop 2015;39:2117 24. Available from: https://doi.org/10.1007/s00264-015-2743-5. [18] Kalairajah Y, Cossey AJ, Verrall GM, Ludbrook G, Spriggins AJ. Are systemic emboli reduced in computer-assisted knee surgery? A prospective, randomised, clinical trial. J Bone Joint Surg Br 2006;88:198 202. [19] McConnell J, Dillon J, Kinninmonth A, Sarungi M, Picard F. Blood loss following total knee replacement is reduced when using computerassisted versus standard methods. Acta Orthop Belg 2012;78:75 8. [20] Jenny J-Y, Picard F. Learning navigation Learning with navigation. A review. SICOT J 2017;3:39. Available from: https://doi.org/10.1051/ sicotj/2017025. [21] Mullaji A, Shetty GM. Computer-assisted total knee arthroplasty for arthritis with extra-articular deformity. J Arthroplasty 2009;24:1164 9. [22] Kim KK, Heo YM, Won YY, Lee WS. Navigation-assisted total knee arthroplasty for the knee retaining femoral intramedullary nail, and distal femoral plate and screws. Clin Orthop Surg 2011;3:77 80. Available from: https://doi.org/10.4055/cios.2011.3.1.77. [23] Tigani D, Masetti G, Sabbioni G, Ben Ayad R, Filanti M, Fosco M. Computer-assisted surgery as indication of choice: total knee arthroplasty in case of retained hardware or extra-articular deformity. Int Orthop 2012;36:1379 85. Available from: https://doi.org/10.1007/s00264-0111476-3.