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Primer on Minimally Invasive Subvastus Total Knee Arthroplasty
GETTING STARTED
Primer on Minimally Invasive Subvastus Total Knee Arthroplasty Russell G. Cohen, MD Minimally invasive total knee arthroplasty is an excellent alternative to a standard approach in knee arthroplasty. The technique can be learned at one’s own pace and progress to a true muscle-sparing technique. A continuum of decreasing exposure and wound size, along with specialized instuments, facilitate the learning curve and ultimately allow the operation to succeed. Benefits include preservation of the extensor mechanism, a tighter soft tissue envelope with greater ease of ligament balancing, and faster recovery to independent ambulation. Implant positioning remains reliable and should not affect the ultimate longterm success of total knee arthroplasty. Oper Tech Orthop 16:136-144 © 2006 Elsevier Inc. All rights reserved. KEYWORDS minimally invasive surgery, knee replacement, subvastus approach
M
inimally invasive knee replacement surgery can have several definitions and iterations. It can range from either a smaller incision through the same median parapatellar arthrotomy as a standard total knee arthroplasty (TKA), to a minimally invasive (MIS) quad-sparing TKA with innovative side-cutting instrumentation. However, the smaller incision alone generally does not allow the same benefits as those procedures whereby injury or invasion to the quadriceps mechanism are avoided. MIS surgery should fulfill certain requirements to be considered truly minimally invasive. However, first and foremost, the procedure should in no way compromise the ultimate outcome by poor implant placement or by introducing an unacceptable complication rate compared with a standard TKA. To be considered MIS, the procedure should greatly reduce the muscle trauma necessary to expose the joint and maintain the soft-tissue envelope, thereby allowing the patient a faster recovery, decreased perioperative pain, greater early limb control, and ultimately a happier and more satisfied patient. Herein is one version of a MIS TKA that through a relatively short learning curve can be mastered to allow patients
Tucson Orthopedic Institute, Tucson, AZ. Address reprint requests to Russell G. Cohen, MD, Tucson Orthopedic Institute, 2424 N Wyatt, Suite 260, Tucson, AZ 85712. E-mail: RussGC@ aol.com
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1048-6666/06/$-see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1053/j.oto.2006.06.006
greater potential for a rapid and relatively easier convalescence. This soft-tissue envelope is remarkably stable postoperatively, with complete quadriceps control returning very rapidly. This “primer” is written to help those surgeons who are otherwise comfortable with a standard TKA procedure get started with a continuum of less-invasive techniques and ultimately glean enough knowledge and experience to perform a MIS TKA through a subvastus approach. It is my opinion that this procedure can be mastered by many surgeons in their own practice over a reasonable period of time.
Patient Selection Initial selection of patients, as in any new procedure, should be those with relatively straight forward anatomy. Generally, patients with less developed quadriceps and with reasonable thigh girth are easier patients on which to initially learn this procedure. However, once mastered, this can be done on most everyone. The exceptions to this rule are those patients with previous incisions that would compromise incision placement, valgus deformities greater than 25°, and those patients whose thigh size or implant size would not accommodate this procedure. The real benefit to this operation is the ability to include most patients without narrow inclusion criteria.
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Figure 1 Slightly medialized incision for MIS subvastus TKA. (Color version of figure is available online.)
Getting Started As with most MIS techniques, familiarity with the implants and instrumentation before changing the surgical approach is crucial. This will make the transition to a more limited approach less stressful. I recommend the Zimmer CR Flex (Warsaw, IN) or LPS Flex TKA system using the 4-in-1 MIS instruments that has specially designed instrumentation to facilitate this less-invasive approach. I would also advise initially selecting patients with straightforward arthritis who are not excessively muscular or obese. Sizing the knee for smaller implants also will make the initial learning process a little easier. Trying to correct larger deformities might be saved for cases later in the learning process. As the procedure becomes more familiar and as surgeons learn the nuances with experience, they will be able to expand the inclusion criteria to the vast majority of knee arthroplasty patients. For those surgeons not yet comfortable with operating through a small incision and the concept of a mobile window, I suggest by starting with a standard median parapatellar arthrotomy performed through a reduced incision
Figure 2 Subvastus arthrotomy line. (Color version of figure is available online.)
with the instruments that will be ultimately used for a minimally invasive approach. This will help visualize the anatomy through the beginnings of a MIS approach. Once comfortable with this, performing the TKA through a midvastus approach will help preserve the quadriceps tendon and a portion of the medial muscular attachment. By simply making an oblique incision through the VMO and retracting the patella laterally will give the initial concept of muscle sparing yet still allow relatively easy exposure of the joint. A key aspect to any minimally invasive approach is not everting the patella, which avoids tearing of the muscle fibers and maintenance of muscle contraction soon after surgery. As the surgeon becomes comfortable with the midvastus approach, the level of the midvastus incision is lowered to maintain more muscle attachment. Eventually, the point of oblique incision takeoff is kept below the vastus medialis
Figure 3 Subvastus arthrotomy line. (Color version of figure is available online.)
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Figure 6 Distal intramedullary cutting guide with wand. (Color version of figure is available online.) Figure 4 Capsule to be excised at junction of the longitudinal and oblique arthrotomy line. (Color version of figure is available online.)
Figure 5 Retractor is placed into the lateral gutter and moves patella laterally to visualize the joint. (Color version of figure is available online.)
obliquus (VMO) attachment all together and will now preserve all the medial muscle attachment including the retinacular attachment to the medial patella. The longitudinal incision should not continue all the way to the proximal pole but rather to the point of insertion of the VMO inferiorly, usually about at 10- or 11-o’clock position in a left knee and 1- to 2-o’clock position in a right knee. The incision is placed along medial third of patella (Fig. 1) starting at medial edge of the tibial tubercle and extending about 1 cm above proximal pole of patella. The knee should be flexed to outline the incision and then complete the incision. Arthrotomy extends from the medial edge of tubercle along the retinaculum-tendon border to a point on the patella corresponding with 10-o’clock position on a left knee and
Figure 7 Cutting guide secured with pins and wand removed. (Color version of figure is available online.)
Primer on MIS subvastus TKA
Figure 8 Retractor placement for tibial resection. (Color version of figure is available online.)
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Figure 10 Femoral sizing guide with external rotation guide. (Color version of figure is available online.)
Releases 2-o’clock positon on a right knee (Fig. 2). A 1- to 2-cm oblique incision just below and in line with the VMO fibers is then used to create the “subvastus” extension (Fig. 3). This should not be split beyond this point because it is not necessary and creates further muscle invasion that does not provide a benefit to the exposure.
The medial release is performed as deemed necessary based on the degree of varus or valgus deformity. This is easiest to do with the knee in extension with a rake placed medially providing tension to assist in developing this plane. In patients with a valgus deformity, I find it better to do less of a medial release to avoid over releasing an already attenuated tissue complex.
Figure 9 Extramedullary cutting guide used to resect tibia. (Color version of figure is available online.)
Figure 11 Femoral finishing guide secured with screws. (Color version of figure is available online.)
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Figure 12 Patella held 90º during resection. (Color version of figure is available online.)
The retro-patella fat pad is also removed at this stage with tension placed on the patella with a skin rake and the knee in extension. A small piece of the capsule at the junction of the longitudinal and oblique retinacular incisions is now excised (Fig. 4). This is also seen best with the knee extended and tension placed on the patella. This release allows the patella to retract laterally. I also find it useful to undermine the supra-patella fat pad but not excise it. This will ensure the femoral sizing stylus is placed directly on bone rather than inadvertently referencing off soft tissue and potentially increase the apparent femoral size.
Retractor Placement
Figure 14 Trial components in place. (Color version of figure is available online.)
Femoral Preparation Knee is flexed to approximately 70° to start femoral preparation. This includes drilling the pilot hole, placing the distal cutting guide beneath the quadriceps, and pinning the guide to the anterior femur (Fig. 6). A right angle retractor to pull up the quads and allow the guide to seat directly on bone makes a more accurate cut. The IM wand can be removed to make the cut (Fig. 7).
Placement of a lateral retractor is very important for adequate retraction of the patella. It is placed with the knee extended and slips into the lateral gutter and levers on the retinaculum at the superomedial border of the patella. As the knee is flexed, the patella is retracted laterally giving good visualization of the joint (Fig. 5).
Figure 13 Patella should not be everted past 90º. (Color version of figure is available online.)
Figure 15 Range of motion assessment. (Color version of figure is available online.)
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141
Figure 18 Cement placed on prosthesis and bone. (Color version of figure is available online.)
Tibial Preparation
Figure 16 Patella tracking evaluation. (Color version of figure is available online.)
The distal femoral cut is made as the initial bony resection. It is then easier to proceed with the tibial resection before completing the femur. This makes the accuracy of femoral sizing and placement of the guide easier to do. The extramedullary cutting guide is used to resect the tibia with the lateral retractor now placed anterolaterally to protect the patella tendon and facilitate exposure (Fig. 8). The medial retractor is placed along the joint line to protect the MCL. A posterior retractor can be used to deliver the tibia anteriorly but generally is not
Figure 17 Tibia delivered anteriorly. (Color version of figure is available online.)
Figure 19 Tibial impaction facilitated with a posterior retractor. (Color version of figure is available online.)
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Figure 22 Nonabsorbable suture to repair arthrotomy. (Color version of figure is available online.) Figure 20 Patella cemented and held with a clamp. (Color version of figure is available online.)
Figure 21 Apex on longitudinal incision closed first. (Color version of figure is available online.)
possible, at this stage, to fully expose the tibia. A cutting stylus can be used to measure the depth of resection, be it off the medial or lateral side of the tibia (Fig. 9). Once the tibial cut is removed, the available space expands significantly. This is done by extending the knee to approximately 30° of full extension and using a Lahey or Kocher clamp to pull the tibial fragment and a bovie to release the posterior and lateral soft tissue attachments. It is now easier to size the femur, retract tissues laterally and hold the patella on end for patella resurfacing. The femoral sizing guide is placed below the posterior femoral condyles and the stylus should reference off the highest point on the distal femur, located laterally (Fig. 10). The
Figure 23 Ability to straight leg raise in recovery room. (Color version of figure is available online.)
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Figure 24 Radiographs should reveal desired orientation of implants and cement interfaces.
femur is pinned in the appropriate degree of external rotation, usually 3°, and the finishing guide is then secured with screws or pins (Fig. 11). Once the femoral cuts are completed, the menisci are removed and posterior chamfer cuts made with a curved osteotome. A bone hook placed in the notch can help expose these posterior structures. The tibia is now sized to achieve maximum coverage without overhanging of the component. It is also advisable to use a drop rod to check for tibial cut accuracy. The rod should follow the anterior border of the tibia. The patella is held on end (90°) with a towel clip at the proximal and distal poles and the wide saw blade used to resect the patella articular surface (Fig. 12). It is then sized and drilled for placement of the patella trial component (Fig. 13).
Trial Reduction Trial components are assembled starting with the femoral component followed by the tibial tray (Fig. 14). With the knee flexed 30°, the trial poly is then inserted and finally the patella button. All planes are checked for stability, including medial and lateral tension, femoral rollback, and posterior cruciate ligament competence (Fig. 15). Patella tracking is then evaluated and, typically, with this approach, the patella tracks centrally without need for lateral release (Fig. 16). Once the stability and sizes are confirmed, the tibial tray is marked for rotation and final preparation is made.
Implantation Visualization of the tibial surface is facilitated by placing a posterior retractor and deep flexion of the knee. A lateral
retractor is placed laterally to prevent soft-tissue overhang and a third retractor adjacent to the MCL provides excellent exposure for final implantation (Fig. 17). Cement is placed on the tibial component as well as the posterior and anterior portions of the femoral component (Fig. 18). The tibia is placed first to allow removal of cement posteriorly followed by placement of the femoral component (Fig. 19). After all excess cement is removed, the trial or final polyethylene is inserted and finally the patella component is cemented in place (Fig. 20).
Closure Wounds are closed over a hemovac drain placed in the lateral gutter. I prefer to flex the knee to 90° and use nonabsorbable suture for the retinacular closure (Fig. 21). Two sutures are used along the short oblique portion of the arthrotomy and the remaining sutures placed along the patella tendon (Fig. 22). Subcutaneous and skin closure is per surgeons’ preference.
Postoperative Protocol Patients are encouraged to move their knee as soon as regional anesthesia permits. I prefer active leg extension and flexion while in bed rather than continuous passive motion (Fig. 23). However, a continuous passive motion can be used if desired. Patients are mobilized out of bed the day of surgery, ambulating when possible, and performing a “drop and dangle ” as tolerated. Drains are removed on postoperative day 1, and patients are released when able to mobilize independently, hemodynamically
144 stable, and tolerating a normal diet, which typically occurs on postoperative 1 or 2. Deep vein thrombosis prophylaxis should be administered according to the surgeon’s preference and either home or outpatient therapy is necessary for gait, range of motion, and edema
R.G. Cohen control. Use of assistive devices is progressed according to patient need but typically with excellent quadriceps control the use of walker or cane is minimized and usually not necessary beyond the first week or two. Radiographs at 6 weeks reveal excellent alignment and good cement interfaces (Fig. 24).
Primer on Minimally Invasive Subvastus Total Knee Arthroplasty Russell G. Cohen, MD Minimally invasive total knee arthroplasty is an excellent alternative to a standard approach in knee arthroplasty. The technique can be learned at one’s own pace and progress to a true muscle-sparing technique. A continuum of decreasing exposure and wound size, along with specialized instuments, facilitate the learning curve and ultimately allow the operation to succeed. Benefits include preservation of the extensor mechanism, a tighter soft tissue envelope with greater ease of ligament balancing, and faster recovery to independent ambulation. Implant positioning remains reliable and should not affect the ultimate longterm success of total knee arthroplasty. Oper Tech Orthop 16:136-144 © 2006 Elsevier Inc. All rights reserved. KEYWORDS minimally invasive surgery, knee replacement, subvastus approach
M
inimally invasive knee replacement surgery can have several definitions and iterations. It can range from either a smaller incision through the same median parapatellar arthrotomy as a standard total knee arthroplasty (TKA), to a minimally invasive (MIS) quad-sparing TKA with innovative side-cutting instrumentation. However, the smaller incision alone generally does not allow the same benefits as those procedures whereby injury or invasion to the quadriceps mechanism are avoided. MIS surgery should fulfill certain requirements to be considered truly minimally invasive. However, first and foremost, the procedure should in no way compromise the ultimate outcome by poor implant placement or by introducing an unacceptable complication rate compared with a standard TKA. To be considered MIS, the procedure should greatly reduce the muscle trauma necessary to expose the joint and maintain the soft-tissue envelope, thereby allowing the patient a faster recovery, decreased perioperative pain, greater early limb control, and ultimately a happier and more satisfied patient. Herein is one version of a MIS TKA that through a relatively short learning curve can be mastered to allow patients
Tucson Orthopedic Institute, Tucson, AZ. Address reprint requests to Russell G. Cohen, MD, Tucson Orthopedic Institute, 2424 N Wyatt, Suite 260, Tucson, AZ 85712. E-mail: RussGC@ aol.com
136
1048-6666/06/$-see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1053/j.oto.2006.06.006
greater potential for a rapid and relatively easier convalescence. This soft-tissue envelope is remarkably stable postoperatively, with complete quadriceps control returning very rapidly. This “primer” is written to help those surgeons who are otherwise comfortable with a standard TKA procedure get started with a continuum of less-invasive techniques and ultimately glean enough knowledge and experience to perform a MIS TKA through a subvastus approach. It is my opinion that this procedure can be mastered by many surgeons in their own practice over a reasonable period of time.
Patient Selection Initial selection of patients, as in any new procedure, should be those with relatively straight forward anatomy. Generally, patients with less developed quadriceps and with reasonable thigh girth are easier patients on which to initially learn this procedure. However, once mastered, this can be done on most everyone. The exceptions to this rule are those patients with previous incisions that would compromise incision placement, valgus deformities greater than 25°, and those patients whose thigh size or implant size would not accommodate this procedure. The real benefit to this operation is the ability to include most patients without narrow inclusion criteria.
Primer on MIS subvastus TKA
137
Figure 1 Slightly medialized incision for MIS subvastus TKA. (Color version of figure is available online.)
Getting Started As with most MIS techniques, familiarity with the implants and instrumentation before changing the surgical approach is crucial. This will make the transition to a more limited approach less stressful. I recommend the Zimmer CR Flex (Warsaw, IN) or LPS Flex TKA system using the 4-in-1 MIS instruments that has specially designed instrumentation to facilitate this less-invasive approach. I would also advise initially selecting patients with straightforward arthritis who are not excessively muscular or obese. Sizing the knee for smaller implants also will make the initial learning process a little easier. Trying to correct larger deformities might be saved for cases later in the learning process. As the procedure becomes more familiar and as surgeons learn the nuances with experience, they will be able to expand the inclusion criteria to the vast majority of knee arthroplasty patients. For those surgeons not yet comfortable with operating through a small incision and the concept of a mobile window, I suggest by starting with a standard median parapatellar arthrotomy performed through a reduced incision
Figure 2 Subvastus arthrotomy line. (Color version of figure is available online.)
with the instruments that will be ultimately used for a minimally invasive approach. This will help visualize the anatomy through the beginnings of a MIS approach. Once comfortable with this, performing the TKA through a midvastus approach will help preserve the quadriceps tendon and a portion of the medial muscular attachment. By simply making an oblique incision through the VMO and retracting the patella laterally will give the initial concept of muscle sparing yet still allow relatively easy exposure of the joint. A key aspect to any minimally invasive approach is not everting the patella, which avoids tearing of the muscle fibers and maintenance of muscle contraction soon after surgery. As the surgeon becomes comfortable with the midvastus approach, the level of the midvastus incision is lowered to maintain more muscle attachment. Eventually, the point of oblique incision takeoff is kept below the vastus medialis
Figure 3 Subvastus arthrotomy line. (Color version of figure is available online.)
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R.G. Cohen
Figure 6 Distal intramedullary cutting guide with wand. (Color version of figure is available online.) Figure 4 Capsule to be excised at junction of the longitudinal and oblique arthrotomy line. (Color version of figure is available online.)
Figure 5 Retractor is placed into the lateral gutter and moves patella laterally to visualize the joint. (Color version of figure is available online.)
obliquus (VMO) attachment all together and will now preserve all the medial muscle attachment including the retinacular attachment to the medial patella. The longitudinal incision should not continue all the way to the proximal pole but rather to the point of insertion of the VMO inferiorly, usually about at 10- or 11-o’clock position in a left knee and 1- to 2-o’clock position in a right knee. The incision is placed along medial third of patella (Fig. 1) starting at medial edge of the tibial tubercle and extending about 1 cm above proximal pole of patella. The knee should be flexed to outline the incision and then complete the incision. Arthrotomy extends from the medial edge of tubercle along the retinaculum-tendon border to a point on the patella corresponding with 10-o’clock position on a left knee and
Figure 7 Cutting guide secured with pins and wand removed. (Color version of figure is available online.)
Primer on MIS subvastus TKA
Figure 8 Retractor placement for tibial resection. (Color version of figure is available online.)
139
Figure 10 Femoral sizing guide with external rotation guide. (Color version of figure is available online.)
Releases 2-o’clock positon on a right knee (Fig. 2). A 1- to 2-cm oblique incision just below and in line with the VMO fibers is then used to create the “subvastus” extension (Fig. 3). This should not be split beyond this point because it is not necessary and creates further muscle invasion that does not provide a benefit to the exposure.
The medial release is performed as deemed necessary based on the degree of varus or valgus deformity. This is easiest to do with the knee in extension with a rake placed medially providing tension to assist in developing this plane. In patients with a valgus deformity, I find it better to do less of a medial release to avoid over releasing an already attenuated tissue complex.
Figure 9 Extramedullary cutting guide used to resect tibia. (Color version of figure is available online.)
Figure 11 Femoral finishing guide secured with screws. (Color version of figure is available online.)
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140
Figure 12 Patella held 90º during resection. (Color version of figure is available online.)
The retro-patella fat pad is also removed at this stage with tension placed on the patella with a skin rake and the knee in extension. A small piece of the capsule at the junction of the longitudinal and oblique retinacular incisions is now excised (Fig. 4). This is also seen best with the knee extended and tension placed on the patella. This release allows the patella to retract laterally. I also find it useful to undermine the supra-patella fat pad but not excise it. This will ensure the femoral sizing stylus is placed directly on bone rather than inadvertently referencing off soft tissue and potentially increase the apparent femoral size.
Retractor Placement
Figure 14 Trial components in place. (Color version of figure is available online.)
Femoral Preparation Knee is flexed to approximately 70° to start femoral preparation. This includes drilling the pilot hole, placing the distal cutting guide beneath the quadriceps, and pinning the guide to the anterior femur (Fig. 6). A right angle retractor to pull up the quads and allow the guide to seat directly on bone makes a more accurate cut. The IM wand can be removed to make the cut (Fig. 7).
Placement of a lateral retractor is very important for adequate retraction of the patella. It is placed with the knee extended and slips into the lateral gutter and levers on the retinaculum at the superomedial border of the patella. As the knee is flexed, the patella is retracted laterally giving good visualization of the joint (Fig. 5).
Figure 13 Patella should not be everted past 90º. (Color version of figure is available online.)
Figure 15 Range of motion assessment. (Color version of figure is available online.)
Primer on MIS subvastus TKA
141
Figure 18 Cement placed on prosthesis and bone. (Color version of figure is available online.)
Tibial Preparation
Figure 16 Patella tracking evaluation. (Color version of figure is available online.)
The distal femoral cut is made as the initial bony resection. It is then easier to proceed with the tibial resection before completing the femur. This makes the accuracy of femoral sizing and placement of the guide easier to do. The extramedullary cutting guide is used to resect the tibia with the lateral retractor now placed anterolaterally to protect the patella tendon and facilitate exposure (Fig. 8). The medial retractor is placed along the joint line to protect the MCL. A posterior retractor can be used to deliver the tibia anteriorly but generally is not
Figure 17 Tibia delivered anteriorly. (Color version of figure is available online.)
Figure 19 Tibial impaction facilitated with a posterior retractor. (Color version of figure is available online.)
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R.G. Cohen
Figure 22 Nonabsorbable suture to repair arthrotomy. (Color version of figure is available online.) Figure 20 Patella cemented and held with a clamp. (Color version of figure is available online.)
Figure 21 Apex on longitudinal incision closed first. (Color version of figure is available online.)
possible, at this stage, to fully expose the tibia. A cutting stylus can be used to measure the depth of resection, be it off the medial or lateral side of the tibia (Fig. 9). Once the tibial cut is removed, the available space expands significantly. This is done by extending the knee to approximately 30° of full extension and using a Lahey or Kocher clamp to pull the tibial fragment and a bovie to release the posterior and lateral soft tissue attachments. It is now easier to size the femur, retract tissues laterally and hold the patella on end for patella resurfacing. The femoral sizing guide is placed below the posterior femoral condyles and the stylus should reference off the highest point on the distal femur, located laterally (Fig. 10). The
Figure 23 Ability to straight leg raise in recovery room. (Color version of figure is available online.)
Primer on MIS subvastus TKA
143
Figure 24 Radiographs should reveal desired orientation of implants and cement interfaces.
femur is pinned in the appropriate degree of external rotation, usually 3°, and the finishing guide is then secured with screws or pins (Fig. 11). Once the femoral cuts are completed, the menisci are removed and posterior chamfer cuts made with a curved osteotome. A bone hook placed in the notch can help expose these posterior structures. The tibia is now sized to achieve maximum coverage without overhanging of the component. It is also advisable to use a drop rod to check for tibial cut accuracy. The rod should follow the anterior border of the tibia. The patella is held on end (90°) with a towel clip at the proximal and distal poles and the wide saw blade used to resect the patella articular surface (Fig. 12). It is then sized and drilled for placement of the patella trial component (Fig. 13).
Trial Reduction Trial components are assembled starting with the femoral component followed by the tibial tray (Fig. 14). With the knee flexed 30°, the trial poly is then inserted and finally the patella button. All planes are checked for stability, including medial and lateral tension, femoral rollback, and posterior cruciate ligament competence (Fig. 15). Patella tracking is then evaluated and, typically, with this approach, the patella tracks centrally without need for lateral release (Fig. 16). Once the stability and sizes are confirmed, the tibial tray is marked for rotation and final preparation is made.
Implantation Visualization of the tibial surface is facilitated by placing a posterior retractor and deep flexion of the knee. A lateral
retractor is placed laterally to prevent soft-tissue overhang and a third retractor adjacent to the MCL provides excellent exposure for final implantation (Fig. 17). Cement is placed on the tibial component as well as the posterior and anterior portions of the femoral component (Fig. 18). The tibia is placed first to allow removal of cement posteriorly followed by placement of the femoral component (Fig. 19). After all excess cement is removed, the trial or final polyethylene is inserted and finally the patella component is cemented in place (Fig. 20).
Closure Wounds are closed over a hemovac drain placed in the lateral gutter. I prefer to flex the knee to 90° and use nonabsorbable suture for the retinacular closure (Fig. 21). Two sutures are used along the short oblique portion of the arthrotomy and the remaining sutures placed along the patella tendon (Fig. 22). Subcutaneous and skin closure is per surgeons’ preference.
Postoperative Protocol Patients are encouraged to move their knee as soon as regional anesthesia permits. I prefer active leg extension and flexion while in bed rather than continuous passive motion (Fig. 23). However, a continuous passive motion can be used if desired. Patients are mobilized out of bed the day of surgery, ambulating when possible, and performing a “drop and dangle ” as tolerated. Drains are removed on postoperative day 1, and patients are released when able to mobilize independently, hemodynamically
144 stable, and tolerating a normal diet, which typically occurs on postoperative 1 or 2. Deep vein thrombosis prophylaxis should be administered according to the surgeon’s preference and either home or outpatient therapy is necessary for gait, range of motion, and edema
R.G. Cohen control. Use of assistive devices is progressed according to patient need but typically with excellent quadriceps control the use of walker or cane is minimized and usually not necessary beyond the first week or two. Radiographs at 6 weeks reveal excellent alignment and good cement interfaces (Fig. 24).