- Email: [email protected]
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Approximately, two-thirds to three-quarters of the way back on the superior medial aspect of the notch, the shaver/bur frequently becomes more erratic and is difficult to maintain on the surface of the wall of the notch. This is due to a change in slope that occurs within the notch and represents a change in the density and cortical thickness of the bone itself. This is the resident’s ridge.17 The change in slope occurs immediately anterior to the ACL insertion onto the femur. The resident’s ridge can be carefully flattened with the shaver/bur to match the entire flat surface of the wall of the notch. This allows for excellent visualization of the true over-theback position on the femur and confirmation of optimal tunnel placement using classic femoral over-the-back guides. Indeed, at the time of notchplasty, we will usually make a small prehole or concavity where we expect the tunnel placement to be. This concavity allows the over-the-back guide to slide more securely in place over the back of the lateral femoral condyle. We are careful to leave the cortical edge on the most posterior aspect of the notch as an important anatomic landmark for guide placement. Notchplasty that is too aggressive on the posterior wall of the notch can lead to a loss of visualization of this anatomic landmark, making proper positioning of the over-the-back guide difficult. Although notchplasties for primary reconstructions performed in a timely fashion are generally straightforward, notchplasties can be particularly challenging in cases of revisions, chronic reconstructions, and for patients who suffered postoperative loss of extension or arthrofibrosis. In revision cases, the previous surgeon may have débrided relative landmarks. In chronic cases, significant osteophytic overgrowth can virtually close off the entire entry into the notch or can leave spurs posteriorly that miss target over-theback guides. Ultimately the goal in these complex cases is the same: full extension, adequate space available for the ligament, and excellent visualization for anatomic placement of tunnels. Technically the surgeon must work stepwise from known to unknown, from front to back in the notch. Débridement of soft tissue is usually straightforward; however, care must be taken to avoid viable anatomical structures, including previous reconstructed ligaments. The anatomy may be distorted. If a Cyclops lesion is present (scar tissue anteriorly in the notch, frequently with an adherent fat pad), flexing and extending the knee under arthroscopic visualization may help identify the ACL so that the
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surgeon can target the scar tissue itself. In some cases it may be necessary to remove the previously reconstructed ligament to regain full extension, with plans for subsequent revision if instability recurs. Fortunately, débridement and notchplasty in post-ACL patients with arthrofibrosis are usually successful in regaining motion and normal gait, as well as returning to athletic activities.31,45 In patients with significant bony overgrowth, the surgeon should begin by carefully taking down obvious osteophytes under direct visualization and then working posteriorly. Osteophytes are usually softer than the native bone and are removed more easily by the bur/shaver. In revision cases in which osteophytes may be present posteriorly, we recommend obtaining intraoperative radiographs to confirm femoral tunnel placement prior to final selection to ensure optimal position. In conclusion, knowledge of notch anatomy is an essential part of optimal tunnel placement and successful ACLR. Regarding notchplasty, two key fundamentals are true. First, we must avoid postoperative graft impingement, and second we must have optimal visualization to ensure anatomic tunnel positioning. Beyond these two fundamentals, consideration regarding the extent of notchplasty is based on surgeon preference, specific technique, and preexisting pathology. Currently, only minimal notchplasty is usually necessary to ensure visualization of anatomic femoral tunnel placement and optimizing surgical outcomes. SELECTED READINGS
Koga H, Muneta T, Yagishita K, et al. Effect of notchplasty in anatomic double-bundle anterior cruciate ligament reconstruction. Am J Sports Med. 2014;42:1813–1821. Seo YJ, Yoo YS, Kim YS, et al. The effect of notchplasty on tunnel widening in anterior cruciate ligament reconstruction. Arthroscopy. 2014;30:739–746. Van Eck CF, Martins CA, Kopf S, Lertwanich P, Fu FH, Tashman S. Correlation between the 2-dimensional notch width and the 3-dimensional notch volume: a cadaveric study. Arthroscopy. 2011;27:207–212. Zeng C, Gao SG, Wei J, et al. The influence of the intercondylar notch dimensions on injury of the anterior cruciate ligament: a meta-analysis. Knee Surg Sports Traumatol Arthrosc. 2013;21:804–815.
A complete reference list can be found online at ExpertConsult.com.
Computer-Assisted Navigation for Anterior Cruciate Ligament Reconstruction Jason L. Koh, MD, Seung Jin Yi, MD
Computer-assisted navigation for anterior cruciate ligament (ACL) reconstruction can increase precision in tunnel placement and also provide valuable outcome information, such as rotational stability.1–10 This is accomplished by registering anatomical landmarks and tracking the location of instruments and the tibia and femur in virtual three-dimensional space on the computer. Values such as the location of instruments and measures of impingement and isometry, as well as the location of the femoral and tibial tunnels, are calculated and shown to the operating surgeon in real time. Computer-assisted navigation has been demonstrated in several studies to improve accuracy and decrease laxity of the ACL-reconstructed joint5;
the clinical outcomes at this time have not been dramatically different.11
RATIONALE Computer assistance for precision navigation has been increasingly common in everyday applications such as the global positioning system for drivers and has spread into surgical applications such as total knee replacement, pedicle screw placement, stereotactic brain surgery, and otolaryngology. In orthopaedic surgery, computer-assisted navigation has repeatedly been demonstrated to improve the accuracy of total knee replacement components,
CHAPTER 57 Computer-Assisted Navigation for Anterior Cruciate Ligament Reconstruction
not only in reducing outliers but also in correcting consistent repeated errors made by experienced surgeons.12,13 Similarly, improved accuracy in the placement of total hip components has also been demonstrated.14 Clinical outcomes have been shown to be comparable or superior for navigated groups.7,15
NEED FOR PRECISION IN TUNNEL PLACEMENT Clinical outcomes in ACL-reconstructed patients are significantly related to accurate tunnel placement. Ample evidence exists that certain tunnel positions will result in mechanical problems with the graft and/or produce inappropriate kinematics. Incorrect tunnel placement can result in pain, laxity, synovitis, loss of range of motion, graft impingement, and graft failure.16–27 Up to 70%–80% of the complications in ACL reconstruction surgery were a result of malpositioned tunnels.28 In longer-term follow-up, errors in tunnel placement result in an increased risk of arthritis.18,22
CURRENT ACCURACY WITHOUT NAVIGATION Multiple authors have recommended techniques for tunnel placement; however, the few published studies assessing surgeon accuracy have shown surprisingly poor results. Approximately 10%–20% of all cases are revised,28–30 typically related to tunnel placement. The most common error is excessive anterior femoral tunnel placement, which can decrease rotational stability and may result in a graft that is lax in extension and tight in flexion.26,28 Another common error is a posterior tibial tunnel,31 resulting in posterior cruciate ligament (PCL) impingement with the knee in flexion and subsequent loss of knee flexion or strain on the graft. In addition, the graft will tend to be more vertically oriented and contribute less rotational stability.28 The accuracy of ACL tunnel placement has been evaluated in knee models, cadavers, and patients. The researchers from the University of Pittsburgh evaluated tunnel placement by two experienced ACL surgeons in foam knee models using typical arthroscopic guides. Tibial tunnel placement was a mean of 4.9 mm from the ideal tunnel site, and the femoral tunnel was a mean of 4.2 mm from the ideal.8 This group repeated the study with fellows and experienced surgeons; the tibial tunnel had 2–3.4 mm of average error, and the femoral side 2–4.5 mm of average error.32 In a cadaver study performed at an advanced arthroscopy course, instructors placed tunnels in 24 specimens; 50% (12/24) of the femoral tunnels and 25% (6/24) of the tibial tunnels were “unacceptable”.33 Clinical studies have also shown variable placement when arthroscopically placed tunnels are analyzed radiographically. Cha et al. reported a series of 30 patients where arthroscopically
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placed tibial guide pins were evaluated by the use of intraoperative fluoroscopy.34 The pin had to be repositioned 43% of the time. Typically, the tendency was to place the tibial tunnel too posterior (13/14 cases). Interestingly, there was no improvement in accuracy over time; the pin was repositioned 50% of the time in the last 10 cases. Similar results were found for a series of 24 patients in which tunnel position was evaluated postoperatively by radiographs.35 Two experienced ACL surgeons performed ACL reconstructions, and tunnel placement was correlated with postoperative x-rays. Surgeons had poor (R2 = 0.14) correlation for mediolateral tibial tunnel position, and no correlation (R2 = 0.07, P = .36) to the true anteroposterior (AP) position of the tibial tunnel. The authors found that 12.5% of tunnels “were in very different positions than that expected by the surgeon.” Other authors have noted that radiographical analysis of tunnel placement demonstrated too-posterior placement of the tibial tunnel and a relatively vertically oriented (the 11- or 1-o’clock position) femoral tunnel using standard arthroscopic instrumentation.2–6 The evidence suggests that there is room for improvement in the accuracy of ACL tunnel placement, even among the more experienced surgeons who typically participated in these studies. Accuracy among less experienced surgeons would likely be lower.
TECHNIQUES OF COMPUTER-ASSISTED NAVIGATION Computer-assisted navigation for ACL reconstruction involves accurately tracking the relative positions of the tibia and femur, as well as the intra-articular landmarks that guide correct tunnel placement. Markers on rigid bodies attached to the tibia and femur are tracked intraoperatively by an infrared camera to less than 1 mm and less than 1 degree of error (Fig. 57.1). Some systems require the use of preoperative computed tomography scans or intraoperative fluoroscopy (Brainlab, Westchester, Illinois). Other systems are image free, such as the OrthoPilot (Aesculap, Center Valley, Pennsylvania). Most navigation protocols follow a similar progression of registration of intra-articular and extraarticular landmarks. The following description is of the workflow of the OrthoPilot (Aesculap), which functions to record kinematic and anatomical data and calculates critical values of concern to the surgeon. The navigation camera and display screen (Fig. 57.2) are set up opposite to the operative side of the patient, and next to the arthroscopy tower or screen. Before the placement of the trackers, the ACL stump is removed and a notchplasty is performed, if desired, and intra-articular pathologies, such as meniscal or chondral injuries, are addressed. The graft is harvested and prepared. The optical trackers for ACL reconstruction are then attached by either Kirschner wires (K wires; see Fig. 57.1) or threaded
Fig. 57.1. Trackers attached to femur and tibia with Kirschner wires.
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Extra-articular Landmarks
Fig. 57.3. Extra-articular landmarks.
Fig. 57.4. Knee stability testing.
Fig. 57.2. OrthoPilot (Aesculap) System. Copyright Aesculap.
pins to the tibia and femur. We prefer to use trackers that can be attached by K-wire fixation, avoiding the potential stress riser of a larger threaded pin. The K wires are placed through small stab incisions onto the anterior tibia and medial epicondyle of the femur, minimizing quadriceps morbidity and avoiding interference with instruments. A passive tracking system using light reflected from trackers is used because there is less weight and no cords, unlike an active LED system. After attachment of the trackers to the femur and tibia, tibial extra-articular landmarks are registered by palpation with a pointer (Fig. 57.3). Kinematic evaluation of knee motion is then performed by recording the relative positions of the femur and tibia in full extension and flexion. Registration and kinematic testing take approximately 90 seconds. Femorotibial laxity is then assessed by the surgeon at a chosen degree of flexion, usually 30, and also during a pivot-shift maneuver. Anterior/posterior translation in millimeters and degrees of internal and external rotation are recorded (Fig. 57.4). This quantitative rotational measurement is typically not possible without computer assistance.
Fig. 57.5. Intra-articular palpation of landmarks with pointer.
After the laxity measurement, arthroscopic intra-articular landmarks are registered with the pointer, similar to palpation with a probe (Fig. 57.5). These include the PCL, lateral meniscus, medial tibial spine, anterior and posterior margin of the intercondylar notch, and femoral ACL origin. Accurate measurements of
CHAPTER 57 Computer-Assisted Navigation for Anterior Cruciate Ligament Reconstruction
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Fig. 57.6. Double-bundle tibial tunnel navigation.
Fig. 57.7. Double-bundle femoral tunnel navigation.
the length of the Blumensaat line provide feedback to the surgeon about the true location of the posterior notch. At this point the system allows either the femoral or tibial side tunnels to be created first. A tibial guide with reflective markers is then used to place the tibial guide pin with respect to the PCL, the intracondylar notch, and other intra-articular and extra-articular landmarks (Fig. 57.6), to ensure selected tunnel angles and avoid impingement. Double-bundle tunnels can be placed to avoid overlap. The proposed femoral tunnel location is then palpated (Fig. 57.7) to provide the position of the tunnel with respect to the posterior femoral cortex and clockface orientation. Graft isometry and impingement are also displayed for each bundle. Finally, after securing the graft, the final measurements of AP translation and internal and external rotation are obtained under both fixed angle and pivot-shift tests (Fig. 57.8).
RESULTS Computer-assisted navigation has shown variable results for improvements in tunnel placement. Several authors have shown improvements for inexperienced and expert surgeons. The Pittsburgh group demonstrated improved accuracy in tunnel
Fig. 57.8. Pivot-shift testing results, preoperatively and postoperatively.
placement in foam knees when compared with standard manual instrumentation for both experienced surgeons and novices.8 Clinically, Koh et al. reported that navigation improved the accuracy of tibial tunnel placement.2 Forty-two navigated knees demonstrated a more anatomical, more anterior tibial tunnel without impingement compared with nonnavigated knees. The variability of tunnel placement was extremely low in both the navigated and nonnavigated knee groups. After an initial learning curve, minimal extra time was needed for the navigated knees. Similarly Eichorn reported better accuracy, decreased variability, and more anatomical placement for inexperienced surgeons3 and for his own4 tunnel placement. A French study of patients randomized to navigated or manual tunnels found manual tunnels had significant impingement versus none of the navigated knees.5 Knee laxity was also substantially less variable and less than 2 mm in 96.7% of navigated knees versus 83% of nonnavigated knees. Other studies have not demonstrated improved tunnel placement. Meuffels et al. using the Brainlab system performed a prospective randomized clinical trial that showed no difference in accuracy or precision of the tunnel placement between conventional and computer-assisted ACL reconstruction.36 Both manual and navigated tunnels had a considerable lack of precision. Clinical outcome studies and a 2014 Cochrane review show no significant improvement in clinical outcomes with navigation compared with manual guidance.11,37 No clinically noticeable differences have been found in the Lachman test, pivot-shift test, International Knee Documentation Committee score, Lysholm score, and Tegner score short-term clinical follow-up. However, these studies have typically been performed by experienced surgeons, who may have less benefit, compared with novices, from ACL navigation. A significant benefit from navigation systems may be related to double-bundle guidance and in providing objective rotational as well as A-P translation data.38 This has yet to be fully quantified.
DISCUSSION ACL reconstructions performed with computer-assisted navigation have demonstrated improved accuracy in tunnel placement and improved measurements of clinically assessed laxity in patients when compared with nonnavigated knees in several studies. After an initial learning curve, the additional time required for this increased precision is minimal. There is a cost associated with acquisition of the navigation system, but it is typically used for other procedures, such as joint replacement. Seventy percent
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of the cost was associated with increased operative time due to the learning curve of using a system. In specialty centers with surgeons experienced in navigation, there was only a 14% increase in cost.39 This cost may be offset if the high cost of revision surgery may be avoided with more accurate tunnel position. Navigation continues to become more useful in research as it better quantifies and describes knee kinematics and stability. Double-bundle ACL techniques and their bundle-specific differences in the knee are being widely studied. Since 2005 there has been a large number of articles on navigated ACL and on anatomical double-bundle reconstruction techniques.38,40–43 Most of them characterize the different contributions from each bundle and how it changes the kinematics. Navigation may become more useful in remnant-preserving ACL reconstruction. Some surgeons are applying the knowledge from double-bundle reconstructions and performing p artial- bundle reconstructions. Taketomi et al. used navigation in 47 ACL reconstructions while leaving the attached remnant in place to help with the healing of the ligament.44 Despite poor arthroscopic visualization of the femoral tunnel site due to the remnant ACL, navigation allowed them to place an anatomical femoral socket without any wall blowouts or shortened tunnels. Computer-assisted navigation for ACL reconstruction will provide a more precise method of accurately placing tunnels and will likely reduce the rate of ACL failures. These systems will be able to compare the operative knee with the normal knee and follow objectively the nuances of the kinematics in
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postoperative knees. These systems will provide valuable information to the surgeon for ligament, cartilage, and bony reconstruction. SELECTED READINGS
Eichorn J. Three years of experience with computer navigation-assisted positioning of drilling tunnels in anterior cruciate ligament replacement (SS-67). Arthroscopy. 2004;20:31–32. Klos TV. Computer-assisted anterior cruciate ligament reconstruction: four generations of development and usage. Sports Med Arthrosc Rev. 2014;22(4):229–236. Koh J. Computer-assisted navigation and anterior cruciate ligament reconstruction: accuracy and outcomes. Orthopedics. 2005;28:S1283–S1287. Koh JL, Koo S, Leonard J, Kodali P. ACL tunnel placement: a radiographic comparison between navigated versus manual ACL reconstruction. Orthopedics. 2006;10:S122–S124. Meuffels DE, Reijman M, Verhaar JA. Computer-assisted surgery is not more accurate or precise than conventional arthroscopic ACL reconstruction: a prospective randomized clinical trial. J Bone Joint Surg Am. 2012;94:1538–1545. Plaweski S, Cazal J, Rosell P, Merloz P. Anterior cruciate ligament reconstruction using navigation: a comparative study on 60 patients. Am J Sports Med. 2006;34:542–552. Taketomi S, Inui H, Sanada T, et al. Remnant-preserving anterior cruciate ligament reconstruction using a three-dimensional fluoroscopic navigation system. Knee Surg Relat Res. 2014;26:168–176.
A complete reference list can be found online at ExpertConsult.com.
Sparing the Anterior Cruciate Ligament Remnant: Is It Worth the Hassle? Rocco Papalia, MD, PhD, Sebastiano Vasta, MD, Andrea Tecame, MD, Nicola Maffuli, MD, PhD, FRCS, Vincenzo Denaro, MD
INTRODUCTION The anterior cruciate ligament (ACL) is composed of two bundles, the anteromedial bundle (AM) and the posterolateral bundle (PL), measuring on average 33 mm in length and 11 mm in diameter. The insertion on the tibial plateau is close to the medial tibial eminence, while the femoral attachment is located on the posteromedial aspect of the lateral femoral condyle.1 The function of the two ACL bundles has been investigated by several studies over the last 10 years. The PL is mainly tight in extension and has a central role in the rotational stability of the knee joint;2 AM is taut throughout the whole range of motion, with maximum tension between 45 degrees and 60 degrees of knee flexion.3,4 The annual incidence of ACL rupture in the United States is about 200,000, with at least 100,000 receiving arthroscopic reconstruction.5 ACL injuries mainly occur among athletes. Most of them are caused by a noncontact pivoting injury, related to a change of direction or deceleration maneuver.6,7 Often athletes are not able to keep playing because of instability.6 Patients frequently claim to feel a “pop” during the injury and successively develop an immediate or subacute effusion.7–9 Partial lesions of the ACL constitute about half of all ligamentous damages. In the general population, almost 1 in 3000 are injured per year; 70% are injured during sport activities.10
Although ACL complete injuries are more frequent than the partial ones, these kinds of injuries have also been widely described. Considering all the injuries of the ACL, almost 5%–15% involves only one of the two bundles of which it is composed.11–14 Women have a higher risk of developing injuries of the ACL than males; Messina et al.15 observed a sample of female basketball players of a high school in Texas and found out that the male to female ratio was 1:4. The same relationship was found by Lindenfeld et al.16 and Ferretti et al.17 between male and female players who played football and volleyball, respectively. Partial ACL injuries can show a negative Lachman test;18,19 therefore the pivot-shift test and magnetic resonance imaging (MRI)18,20 are necessary to improve the diagnosis.21 When clinical examinations and imaging studies do not yield to univocal diagnosis, an accurate arthroscopy may be advocated to obtain a definitive diagnosis of a single-bundle ACL lesion.2,22 Some authors, such as Dejour et al.,23 advocate the combination of clinical examinations and stress x-rays to help the surgeon identify partial ACL tears, these being diagnostic tools highly sensitive in discriminating between complete versus partial ACL tears. Preserving uninjured bundles has several advantages, though their effectiveness in the clinical setting is still to be proven. Some
REFERENCES
1. Koh J. Computer-assisted navigation and anterior cruciate ligament reconstruction: accuracy and outcomes. Orthopedics. 2005;28:S1283– S1287. 2. Koh J, Koo SS, Leonard J, Kodali P. Anterior cruciate ligament (ACL) tunnel placement: a radiographic comparison between navigated versus manual ACL reconstruction. Orthopedics. 2006;29:S122– S124. 3. Eichorn J. Three years of experience with computer navigationassisted positioning of drilling tunnels in anterior cruciate ligament replacement (SS-67). Arthroscopy. 2004;20:31–32. 4. Eichorn J. Three years of experience with computer-assisted navigation in anterior cruciate ligament replacement. ; 2004. 5. Plaweski S, Cazal J, Rosell P, Merloz P. Anterior cruciate ligament reconstruction using navigation: a comparative study on 60 patients. Am J Sports Med. 2006;34:542–552. 6. Plaweski S, Rossi J, Merloz P, Julliard R. Analysis of anatomic positioning in computer-assisted and conventional anterior cruciate ligament reconstruction. Orthop Traumatol Surg Res. 2011;97:S80–S85. 7. Plaweski S, Tchouda SD, Dumas J, et al. Evaluation of a computerassisted navigation system for anterior cruciate ligament reconstruction: prospective non-randomized cohort study versus conventional surgery. Orthop Traumatol Surg Res. 2012;98:S91–S97. 8. Picard F, DiGioia AM, Moody J, et al. Accuracy in tunnel placement for ACL reconstruction. Comparison of traditional arthroscopic and computer-assisted navigation techniques. Comput Aided Surg. 2001;6:279–289. 9. Klos TV, Habets RJ, Banks AZ, Banks SA, Devilee RJ, Cook FF. Computer assistance in arthroscopic anterior cruciate ligament reconstruction. Clin Orthop Relat Res. 1998;354:65–69. 10. Degenhart M. Computer-navigated ACL reconstruction with the OrthoPilot. Surg Technol Int. 2004;12:245–251. 11. Eggerding V, Reijman M, Scholten RJ, Meuffels DE. Computerassisted surgery for knee ligament reconstruction. Cochrane Database Syst Rev. 2014;(9):CD007601. 12. Stulberg SD, Loan P, Sarin V. Computer-assisted navigation in total knee replacement: results of an initial experience in thirty-five patients. J Bone Joint Surg Am. 2002;84-A(suppl 2):90–98. 13. Berry DJ. Computer-assisted knee arthroplasty is better than a conventional jig-based technique in terms of component alignment. J Bone Joint Surg Am. 2004;86-A:2573. 14. Parratte S, Argenson JN. Validation and usefulness of a computerassisted cup-positioning system in total hip arthroplasty. A prospective, randomized, controlled study. J Bone Joint Surg Am. 2007;89:494–499. 15. Hoffart HE, Langenstein E, Vasak N. A prospective study comparing the functional outcome of computer-assisted and conventional total knee replacement. J Bone Joint Surg Br. 2012;94:194–199. 16. Aglietti P, Buzzi R, Giron F, Simeone AJ, Zaccherotti G. Arthroscopic-assisted anterior cruciate ligament reconstruction with the central third patellar tendon. A 5-8-year follow-up. Knee Surg Sports Traumatol Arthrosc. 1997;5:138–144. 17. Howell SM, Clark JA. Tibial tunnel placement in anterior cruciate ligament reconstructions and graft impingement. Clin Orthop Relat Res. 1992;283:187–195. 18. Howell SM, Taylor MA. Failure of reconstruction of the anterior cruciate ligament due to impingement by the intercondylar roof. J Bone Joint Surg Am. 1993;75:1044–1055. 19. Howell SM, Wallace MP, Hull ML, Deutsch ML. Evaluation of the single-incision arthroscopic technique for anterior cruciate ligament replacement. A study of tibial tunnel placement, intraoperative graft tension, and stability. Am J Sports Med. 1999;27:284–293. 20. Howell SM, Gittins ME, Gottlieb JE, Traina SM, Zoellner TM. The relationship between the angle of the tibial tunnel in the coronal plane and loss of flexion and anterior laxity after anterior cruciate ligament reconstruction. Am J Sports Med. 2001;29:567–574. 21. Ikeda H, Muneta T, Niga S, Hoshino A, Asahina S, Yamamoto H. The long-term effects of tibial drill hole position on the outcome of anterior cruciate ligament reconstruction. Arthroscopy. 1999;15:287–291. 22. Jarvela T, Paakkala T, Jarvela K, Kannus P, Jarvinen M. Graft placement after the anterior cruciate ligament reconstruction: a new method to evaluate the femoral and tibial placements of the graft. Knee. 2001;8:219–227.
23. Khalfayan EE, Sharkey PF, Alexander AH, Bruckner JD, Bynum EB. The relationship between tunnel placement and clinical results after anterior cruciate ligament reconstruction. Am J Sports Med. 1996;24:335–341. 24. Romano VM, Graf BK, Keene JS, Lange RH. Anterior cruciate ligament reconstruction. The effect of tibial tunnel placement on range of motion. Am J Sports Med. 1993;21:415–418. 25. Muneta T, Yamamoto H, Ishibashi T, Asahina S, Murakami S, Furuya K. The effects of tibial tunnel placement and roofplasty on reconstructed anterior cruciate ligament knees. Arthroscopy. 1995;11:57–62. 26. Sommer C, Friederich NF, Muller W. Improperly placed anterior cruciate ligament grafts: correlation between radiological parameters and clinical results. Knee Surg Sports Traumatol Arthrosc. 2000;8:207– 213. 27. Yaru NC, Daniel DM, Penner D. The effect of tibial attachment site on graft impingement in an anterior cruciate ligament reconstruction. Am J Sports Med. 1992;20:217–220. 28. Allen CR, Giffin JR, Harner CD. Revision anterior cruciate ligament reconstruction. Orthop Clin North Am. 2003;34:79–98. 29. Getelman MH, Friedman MJ. Revision anterior cruciate ligament reconstruction surgery. J Am Acad Orthop Surg. 1999;7:189–198. 30. Matava MJ, Boden BP, Eds. AOSSM institutes multi-center revision ACL study”. AOSSM Sports Medicine Update. 2005;(5):5. 31. Howell SM, Hull ML. Checkpoints for judging tunnel and anterior cruciate ligament graft placement. J Knee Surg. 2009;22:161–170. 32. Burkart A, Debski RE, McMahon PJ, et al. Precision of ACL tunnel placement using traditional and robotic techniques. Comput Aided Surg. 2001;6:270–278. 33. Kohn D, Busche T, Carls J. Drill hole position in endoscopic anterior cruciate ligament reconstruction. Results of an advanced arthroscopy course. Knee Surg Sports Traumatol Arthrosc. 1998;6(suppl 1):S13– S15. 34. Cha PS, West RV, Harner CD. The results of using intraoperative fluoroscopy for ideal tibial tunnel position during anterior cruciate ligament reconstruction. 11th ESSKA Congress. May 8, 2004. 35. Sudhahar TA, Glasgow MM, Donell ST. Comparison of expected vs. actual tunnel position in anterior cruciate ligament reconstruction. Knee. 2004;11:15–18. 36. Meuffels DE, Reijman M, Verhaar JA. Computer-assisted surgery is not more accurate or precise than conventional arthroscopic ACL reconstruction: a prospective randomized clinical trial. J Bone Joint Surg Am. 2012;94:1538–1545. 37. Cheng T, Zhang GY, Zhang XL. Does computer navigation system really improve early clinical outcomes after anterior cruciate ligament reconstruction? A meta-analysis and systematic review of randomized controlled trials. Knee. 2012;19:73–77. 38. Zaffagnini S, Urrizola F, Signorelli C, et al. Current use of navigation system in ACL surgery: a historical review. Knee Surg Sports Traumatol Arthrosc. 2016;24:3396–3409. 39. Margier J, Tchouda SD, Banihachemi JJ, Bosson JL, Plaweski S. Computer-assisted navigation in ACL reconstruction is attractive but not yet cost efficient. Knee Surg Sports Traumatol Arthrosc. 2015;23:1026–1034. 40. Plaweski S, Grimaldi M, Courvoisier A, Wimsey S. Intraoperative comparisons of knee kinematics of double-bundle versus single-bundle anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc. 2011;19:1277–1286. 41. Verhelst L, Van Der Bracht H, Oosterlinck D, Bellemans J. ACL repair with a single or double tunnel: a comparative laboratory study of knee stability using computer navigation. Acta Orthop Belg. 2012;78:771–778. 42. Anthony CA, Duchman K, McCunniff P, et al. Double-bundle ACL reconstruction: novice surgeons utilizing computer-assisted navigation versus experienced surgeons. Comput Aided Surg. 2013;18:172– 180. 43. Luites JW, Wymenga AB, Blankevoort L, Eygendaal D, Verdonschot N. Accuracy of a computer-assisted planning and placement system for anatomical femoral tunnel positioning in anterior cruciate ligament reconstruction. Int J Med Robot. 2014;10:438–446. 44. Taketomi S, Inui H, Sanada T, et al. Remnant-preserving anterior cruciate ligament reconstruction using a three-dimensional fluoroscopic navigation system. Knee Surg Relat Res. 2014;26:168–176.
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Approximately, two-thirds to three-quarters of the way back on the superior medial aspect of the notch, the shaver/bur frequently becomes more erratic and is difficult to maintain on the surface of the wall of the notch. This is due to a change in slope that occurs within the notch and represents a change in the density and cortical thickness of the bone itself. This is the resident’s ridge.17 The change in slope occurs immediately anterior to the ACL insertion onto the femur. The resident’s ridge can be carefully flattened with the shaver/bur to match the entire flat surface of the wall of the notch. This allows for excellent visualization of the true over-theback position on the femur and confirmation of optimal tunnel placement using classic femoral over-the-back guides. Indeed, at the time of notchplasty, we will usually make a small prehole or concavity where we expect the tunnel placement to be. This concavity allows the over-the-back guide to slide more securely in place over the back of the lateral femoral condyle. We are careful to leave the cortical edge on the most posterior aspect of the notch as an important anatomic landmark for guide placement. Notchplasty that is too aggressive on the posterior wall of the notch can lead to a loss of visualization of this anatomic landmark, making proper positioning of the over-the-back guide difficult. Although notchplasties for primary reconstructions performed in a timely fashion are generally straightforward, notchplasties can be particularly challenging in cases of revisions, chronic reconstructions, and for patients who suffered postoperative loss of extension or arthrofibrosis. In revision cases, the previous surgeon may have débrided relative landmarks. In chronic cases, significant osteophytic overgrowth can virtually close off the entire entry into the notch or can leave spurs posteriorly that miss target over-theback guides. Ultimately the goal in these complex cases is the same: full extension, adequate space available for the ligament, and excellent visualization for anatomic placement of tunnels. Technically the surgeon must work stepwise from known to unknown, from front to back in the notch. Débridement of soft tissue is usually straightforward; however, care must be taken to avoid viable anatomical structures, including previous reconstructed ligaments. The anatomy may be distorted. If a Cyclops lesion is present (scar tissue anteriorly in the notch, frequently with an adherent fat pad), flexing and extending the knee under arthroscopic visualization may help identify the ACL so that the
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surgeon can target the scar tissue itself. In some cases it may be necessary to remove the previously reconstructed ligament to regain full extension, with plans for subsequent revision if instability recurs. Fortunately, débridement and notchplasty in post-ACL patients with arthrofibrosis are usually successful in regaining motion and normal gait, as well as returning to athletic activities.31,45 In patients with significant bony overgrowth, the surgeon should begin by carefully taking down obvious osteophytes under direct visualization and then working posteriorly. Osteophytes are usually softer than the native bone and are removed more easily by the bur/shaver. In revision cases in which osteophytes may be present posteriorly, we recommend obtaining intraoperative radiographs to confirm femoral tunnel placement prior to final selection to ensure optimal position. In conclusion, knowledge of notch anatomy is an essential part of optimal tunnel placement and successful ACLR. Regarding notchplasty, two key fundamentals are true. First, we must avoid postoperative graft impingement, and second we must have optimal visualization to ensure anatomic tunnel positioning. Beyond these two fundamentals, consideration regarding the extent of notchplasty is based on surgeon preference, specific technique, and preexisting pathology. Currently, only minimal notchplasty is usually necessary to ensure visualization of anatomic femoral tunnel placement and optimizing surgical outcomes. SELECTED READINGS
Koga H, Muneta T, Yagishita K, et al. Effect of notchplasty in anatomic double-bundle anterior cruciate ligament reconstruction. Am J Sports Med. 2014;42:1813–1821. Seo YJ, Yoo YS, Kim YS, et al. The effect of notchplasty on tunnel widening in anterior cruciate ligament reconstruction. Arthroscopy. 2014;30:739–746. Van Eck CF, Martins CA, Kopf S, Lertwanich P, Fu FH, Tashman S. Correlation between the 2-dimensional notch width and the 3-dimensional notch volume: a cadaveric study. Arthroscopy. 2011;27:207–212. Zeng C, Gao SG, Wei J, et al. The influence of the intercondylar notch dimensions on injury of the anterior cruciate ligament: a meta-analysis. Knee Surg Sports Traumatol Arthrosc. 2013;21:804–815.
A complete reference list can be found online at ExpertConsult.com.
Computer-Assisted Navigation for Anterior Cruciate Ligament Reconstruction Jason L. Koh, MD, Seung Jin Yi, MD
Computer-assisted navigation for anterior cruciate ligament (ACL) reconstruction can increase precision in tunnel placement and also provide valuable outcome information, such as rotational stability.1–10 This is accomplished by registering anatomical landmarks and tracking the location of instruments and the tibia and femur in virtual three-dimensional space on the computer. Values such as the location of instruments and measures of impingement and isometry, as well as the location of the femoral and tibial tunnels, are calculated and shown to the operating surgeon in real time. Computer-assisted navigation has been demonstrated in several studies to improve accuracy and decrease laxity of the ACL-reconstructed joint5;
the clinical outcomes at this time have not been dramatically different.11
RATIONALE Computer assistance for precision navigation has been increasingly common in everyday applications such as the global positioning system for drivers and has spread into surgical applications such as total knee replacement, pedicle screw placement, stereotactic brain surgery, and otolaryngology. In orthopaedic surgery, computer-assisted navigation has repeatedly been demonstrated to improve the accuracy of total knee replacement components,
CHAPTER 57 Computer-Assisted Navigation for Anterior Cruciate Ligament Reconstruction
not only in reducing outliers but also in correcting consistent repeated errors made by experienced surgeons.12,13 Similarly, improved accuracy in the placement of total hip components has also been demonstrated.14 Clinical outcomes have been shown to be comparable or superior for navigated groups.7,15
NEED FOR PRECISION IN TUNNEL PLACEMENT Clinical outcomes in ACL-reconstructed patients are significantly related to accurate tunnel placement. Ample evidence exists that certain tunnel positions will result in mechanical problems with the graft and/or produce inappropriate kinematics. Incorrect tunnel placement can result in pain, laxity, synovitis, loss of range of motion, graft impingement, and graft failure.16–27 Up to 70%–80% of the complications in ACL reconstruction surgery were a result of malpositioned tunnels.28 In longer-term follow-up, errors in tunnel placement result in an increased risk of arthritis.18,22
CURRENT ACCURACY WITHOUT NAVIGATION Multiple authors have recommended techniques for tunnel placement; however, the few published studies assessing surgeon accuracy have shown surprisingly poor results. Approximately 10%–20% of all cases are revised,28–30 typically related to tunnel placement. The most common error is excessive anterior femoral tunnel placement, which can decrease rotational stability and may result in a graft that is lax in extension and tight in flexion.26,28 Another common error is a posterior tibial tunnel,31 resulting in posterior cruciate ligament (PCL) impingement with the knee in flexion and subsequent loss of knee flexion or strain on the graft. In addition, the graft will tend to be more vertically oriented and contribute less rotational stability.28 The accuracy of ACL tunnel placement has been evaluated in knee models, cadavers, and patients. The researchers from the University of Pittsburgh evaluated tunnel placement by two experienced ACL surgeons in foam knee models using typical arthroscopic guides. Tibial tunnel placement was a mean of 4.9 mm from the ideal tunnel site, and the femoral tunnel was a mean of 4.2 mm from the ideal.8 This group repeated the study with fellows and experienced surgeons; the tibial tunnel had 2–3.4 mm of average error, and the femoral side 2–4.5 mm of average error.32 In a cadaver study performed at an advanced arthroscopy course, instructors placed tunnels in 24 specimens; 50% (12/24) of the femoral tunnels and 25% (6/24) of the tibial tunnels were “unacceptable”.33 Clinical studies have also shown variable placement when arthroscopically placed tunnels are analyzed radiographically. Cha et al. reported a series of 30 patients where arthroscopically
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placed tibial guide pins were evaluated by the use of intraoperative fluoroscopy.34 The pin had to be repositioned 43% of the time. Typically, the tendency was to place the tibial tunnel too posterior (13/14 cases). Interestingly, there was no improvement in accuracy over time; the pin was repositioned 50% of the time in the last 10 cases. Similar results were found for a series of 24 patients in which tunnel position was evaluated postoperatively by radiographs.35 Two experienced ACL surgeons performed ACL reconstructions, and tunnel placement was correlated with postoperative x-rays. Surgeons had poor (R2 = 0.14) correlation for mediolateral tibial tunnel position, and no correlation (R2 = 0.07, P = .36) to the true anteroposterior (AP) position of the tibial tunnel. The authors found that 12.5% of tunnels “were in very different positions than that expected by the surgeon.” Other authors have noted that radiographical analysis of tunnel placement demonstrated too-posterior placement of the tibial tunnel and a relatively vertically oriented (the 11- or 1-o’clock position) femoral tunnel using standard arthroscopic instrumentation.2–6 The evidence suggests that there is room for improvement in the accuracy of ACL tunnel placement, even among the more experienced surgeons who typically participated in these studies. Accuracy among less experienced surgeons would likely be lower.
TECHNIQUES OF COMPUTER-ASSISTED NAVIGATION Computer-assisted navigation for ACL reconstruction involves accurately tracking the relative positions of the tibia and femur, as well as the intra-articular landmarks that guide correct tunnel placement. Markers on rigid bodies attached to the tibia and femur are tracked intraoperatively by an infrared camera to less than 1 mm and less than 1 degree of error (Fig. 57.1). Some systems require the use of preoperative computed tomography scans or intraoperative fluoroscopy (Brainlab, Westchester, Illinois). Other systems are image free, such as the OrthoPilot (Aesculap, Center Valley, Pennsylvania). Most navigation protocols follow a similar progression of registration of intra-articular and extraarticular landmarks. The following description is of the workflow of the OrthoPilot (Aesculap), which functions to record kinematic and anatomical data and calculates critical values of concern to the surgeon. The navigation camera and display screen (Fig. 57.2) are set up opposite to the operative side of the patient, and next to the arthroscopy tower or screen. Before the placement of the trackers, the ACL stump is removed and a notchplasty is performed, if desired, and intra-articular pathologies, such as meniscal or chondral injuries, are addressed. The graft is harvested and prepared. The optical trackers for ACL reconstruction are then attached by either Kirschner wires (K wires; see Fig. 57.1) or threaded
Fig. 57.1. Trackers attached to femur and tibia with Kirschner wires.
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Extra-articular Landmarks
Fig. 57.3. Extra-articular landmarks.
Fig. 57.4. Knee stability testing.
Fig. 57.2. OrthoPilot (Aesculap) System. Copyright Aesculap.
pins to the tibia and femur. We prefer to use trackers that can be attached by K-wire fixation, avoiding the potential stress riser of a larger threaded pin. The K wires are placed through small stab incisions onto the anterior tibia and medial epicondyle of the femur, minimizing quadriceps morbidity and avoiding interference with instruments. A passive tracking system using light reflected from trackers is used because there is less weight and no cords, unlike an active LED system. After attachment of the trackers to the femur and tibia, tibial extra-articular landmarks are registered by palpation with a pointer (Fig. 57.3). Kinematic evaluation of knee motion is then performed by recording the relative positions of the femur and tibia in full extension and flexion. Registration and kinematic testing take approximately 90 seconds. Femorotibial laxity is then assessed by the surgeon at a chosen degree of flexion, usually 30, and also during a pivot-shift maneuver. Anterior/posterior translation in millimeters and degrees of internal and external rotation are recorded (Fig. 57.4). This quantitative rotational measurement is typically not possible without computer assistance.
Fig. 57.5. Intra-articular palpation of landmarks with pointer.
After the laxity measurement, arthroscopic intra-articular landmarks are registered with the pointer, similar to palpation with a probe (Fig. 57.5). These include the PCL, lateral meniscus, medial tibial spine, anterior and posterior margin of the intercondylar notch, and femoral ACL origin. Accurate measurements of
CHAPTER 57 Computer-Assisted Navigation for Anterior Cruciate Ligament Reconstruction
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Fig. 57.6. Double-bundle tibial tunnel navigation.
Fig. 57.7. Double-bundle femoral tunnel navigation.
the length of the Blumensaat line provide feedback to the surgeon about the true location of the posterior notch. At this point the system allows either the femoral or tibial side tunnels to be created first. A tibial guide with reflective markers is then used to place the tibial guide pin with respect to the PCL, the intracondylar notch, and other intra-articular and extra-articular landmarks (Fig. 57.6), to ensure selected tunnel angles and avoid impingement. Double-bundle tunnels can be placed to avoid overlap. The proposed femoral tunnel location is then palpated (Fig. 57.7) to provide the position of the tunnel with respect to the posterior femoral cortex and clockface orientation. Graft isometry and impingement are also displayed for each bundle. Finally, after securing the graft, the final measurements of AP translation and internal and external rotation are obtained under both fixed angle and pivot-shift tests (Fig. 57.8).
RESULTS Computer-assisted navigation has shown variable results for improvements in tunnel placement. Several authors have shown improvements for inexperienced and expert surgeons. The Pittsburgh group demonstrated improved accuracy in tunnel
Fig. 57.8. Pivot-shift testing results, preoperatively and postoperatively.
placement in foam knees when compared with standard manual instrumentation for both experienced surgeons and novices.8 Clinically, Koh et al. reported that navigation improved the accuracy of tibial tunnel placement.2 Forty-two navigated knees demonstrated a more anatomical, more anterior tibial tunnel without impingement compared with nonnavigated knees. The variability of tunnel placement was extremely low in both the navigated and nonnavigated knee groups. After an initial learning curve, minimal extra time was needed for the navigated knees. Similarly Eichorn reported better accuracy, decreased variability, and more anatomical placement for inexperienced surgeons3 and for his own4 tunnel placement. A French study of patients randomized to navigated or manual tunnels found manual tunnels had significant impingement versus none of the navigated knees.5 Knee laxity was also substantially less variable and less than 2 mm in 96.7% of navigated knees versus 83% of nonnavigated knees. Other studies have not demonstrated improved tunnel placement. Meuffels et al. using the Brainlab system performed a prospective randomized clinical trial that showed no difference in accuracy or precision of the tunnel placement between conventional and computer-assisted ACL reconstruction.36 Both manual and navigated tunnels had a considerable lack of precision. Clinical outcome studies and a 2014 Cochrane review show no significant improvement in clinical outcomes with navigation compared with manual guidance.11,37 No clinically noticeable differences have been found in the Lachman test, pivot-shift test, International Knee Documentation Committee score, Lysholm score, and Tegner score short-term clinical follow-up. However, these studies have typically been performed by experienced surgeons, who may have less benefit, compared with novices, from ACL navigation. A significant benefit from navigation systems may be related to double-bundle guidance and in providing objective rotational as well as A-P translation data.38 This has yet to be fully quantified.
DISCUSSION ACL reconstructions performed with computer-assisted navigation have demonstrated improved accuracy in tunnel placement and improved measurements of clinically assessed laxity in patients when compared with nonnavigated knees in several studies. After an initial learning curve, the additional time required for this increased precision is minimal. There is a cost associated with acquisition of the navigation system, but it is typically used for other procedures, such as joint replacement. Seventy percent
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of the cost was associated with increased operative time due to the learning curve of using a system. In specialty centers with surgeons experienced in navigation, there was only a 14% increase in cost.39 This cost may be offset if the high cost of revision surgery may be avoided with more accurate tunnel position. Navigation continues to become more useful in research as it better quantifies and describes knee kinematics and stability. Double-bundle ACL techniques and their bundle-specific differences in the knee are being widely studied. Since 2005 there has been a large number of articles on navigated ACL and on anatomical double-bundle reconstruction techniques.38,40–43 Most of them characterize the different contributions from each bundle and how it changes the kinematics. Navigation may become more useful in remnant-preserving ACL reconstruction. Some surgeons are applying the knowledge from double-bundle reconstructions and performing p artial- bundle reconstructions. Taketomi et al. used navigation in 47 ACL reconstructions while leaving the attached remnant in place to help with the healing of the ligament.44 Despite poor arthroscopic visualization of the femoral tunnel site due to the remnant ACL, navigation allowed them to place an anatomical femoral socket without any wall blowouts or shortened tunnels. Computer-assisted navigation for ACL reconstruction will provide a more precise method of accurately placing tunnels and will likely reduce the rate of ACL failures. These systems will be able to compare the operative knee with the normal knee and follow objectively the nuances of the kinematics in
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postoperative knees. These systems will provide valuable information to the surgeon for ligament, cartilage, and bony reconstruction. SELECTED READINGS
Eichorn J. Three years of experience with computer navigation-assisted positioning of drilling tunnels in anterior cruciate ligament replacement (SS-67). Arthroscopy. 2004;20:31–32. Klos TV. Computer-assisted anterior cruciate ligament reconstruction: four generations of development and usage. Sports Med Arthrosc Rev. 2014;22(4):229–236. Koh J. Computer-assisted navigation and anterior cruciate ligament reconstruction: accuracy and outcomes. Orthopedics. 2005;28:S1283–S1287. Koh JL, Koo S, Leonard J, Kodali P. ACL tunnel placement: a radiographic comparison between navigated versus manual ACL reconstruction. Orthopedics. 2006;10:S122–S124. Meuffels DE, Reijman M, Verhaar JA. Computer-assisted surgery is not more accurate or precise than conventional arthroscopic ACL reconstruction: a prospective randomized clinical trial. J Bone Joint Surg Am. 2012;94:1538–1545. Plaweski S, Cazal J, Rosell P, Merloz P. Anterior cruciate ligament reconstruction using navigation: a comparative study on 60 patients. Am J Sports Med. 2006;34:542–552. Taketomi S, Inui H, Sanada T, et al. Remnant-preserving anterior cruciate ligament reconstruction using a three-dimensional fluoroscopic navigation system. Knee Surg Relat Res. 2014;26:168–176.
A complete reference list can be found online at ExpertConsult.com.
Sparing the Anterior Cruciate Ligament Remnant: Is It Worth the Hassle? Rocco Papalia, MD, PhD, Sebastiano Vasta, MD, Andrea Tecame, MD, Nicola Maffuli, MD, PhD, FRCS, Vincenzo Denaro, MD
INTRODUCTION The anterior cruciate ligament (ACL) is composed of two bundles, the anteromedial bundle (AM) and the posterolateral bundle (PL), measuring on average 33 mm in length and 11 mm in diameter. The insertion on the tibial plateau is close to the medial tibial eminence, while the femoral attachment is located on the posteromedial aspect of the lateral femoral condyle.1 The function of the two ACL bundles has been investigated by several studies over the last 10 years. The PL is mainly tight in extension and has a central role in the rotational stability of the knee joint;2 AM is taut throughout the whole range of motion, with maximum tension between 45 degrees and 60 degrees of knee flexion.3,4 The annual incidence of ACL rupture in the United States is about 200,000, with at least 100,000 receiving arthroscopic reconstruction.5 ACL injuries mainly occur among athletes. Most of them are caused by a noncontact pivoting injury, related to a change of direction or deceleration maneuver.6,7 Often athletes are not able to keep playing because of instability.6 Patients frequently claim to feel a “pop” during the injury and successively develop an immediate or subacute effusion.7–9 Partial lesions of the ACL constitute about half of all ligamentous damages. In the general population, almost 1 in 3000 are injured per year; 70% are injured during sport activities.10
Although ACL complete injuries are more frequent than the partial ones, these kinds of injuries have also been widely described. Considering all the injuries of the ACL, almost 5%–15% involves only one of the two bundles of which it is composed.11–14 Women have a higher risk of developing injuries of the ACL than males; Messina et al.15 observed a sample of female basketball players of a high school in Texas and found out that the male to female ratio was 1:4. The same relationship was found by Lindenfeld et al.16 and Ferretti et al.17 between male and female players who played football and volleyball, respectively. Partial ACL injuries can show a negative Lachman test;18,19 therefore the pivot-shift test and magnetic resonance imaging (MRI)18,20 are necessary to improve the diagnosis.21 When clinical examinations and imaging studies do not yield to univocal diagnosis, an accurate arthroscopy may be advocated to obtain a definitive diagnosis of a single-bundle ACL lesion.2,22 Some authors, such as Dejour et al.,23 advocate the combination of clinical examinations and stress x-rays to help the surgeon identify partial ACL tears, these being diagnostic tools highly sensitive in discriminating between complete versus partial ACL tears. Preserving uninjured bundles has several advantages, though their effectiveness in the clinical setting is still to be proven. Some
REFERENCES
1. Koh J. Computer-assisted navigation and anterior cruciate ligament reconstruction: accuracy and outcomes. Orthopedics. 2005;28:S1283– S1287. 2. Koh J, Koo SS, Leonard J, Kodali P. Anterior cruciate ligament (ACL) tunnel placement: a radiographic comparison between navigated versus manual ACL reconstruction. Orthopedics. 2006;29:S122– S124. 3. Eichorn J. Three years of experience with computer navigationassisted positioning of drilling tunnels in anterior cruciate ligament replacement (SS-67). Arthroscopy. 2004;20:31–32. 4. Eichorn J. Three years of experience with computer-assisted navigation in anterior cruciate ligament replacement.
23. Khalfayan EE, Sharkey PF, Alexander AH, Bruckner JD, Bynum EB. The relationship between tunnel placement and clinical results after anterior cruciate ligament reconstruction. Am J Sports Med. 1996;24:335–341. 24. Romano VM, Graf BK, Keene JS, Lange RH. Anterior cruciate ligament reconstruction. The effect of tibial tunnel placement on range of motion. Am J Sports Med. 1993;21:415–418. 25. Muneta T, Yamamoto H, Ishibashi T, Asahina S, Murakami S, Furuya K. The effects of tibial tunnel placement and roofplasty on reconstructed anterior cruciate ligament knees. Arthroscopy. 1995;11:57–62. 26. Sommer C, Friederich NF, Muller W. Improperly placed anterior cruciate ligament grafts: correlation between radiological parameters and clinical results. Knee Surg Sports Traumatol Arthrosc. 2000;8:207– 213. 27. Yaru NC, Daniel DM, Penner D. The effect of tibial attachment site on graft impingement in an anterior cruciate ligament reconstruction. Am J Sports Med. 1992;20:217–220. 28. Allen CR, Giffin JR, Harner CD. Revision anterior cruciate ligament reconstruction. Orthop Clin North Am. 2003;34:79–98. 29. Getelman MH, Friedman MJ. Revision anterior cruciate ligament reconstruction surgery. J Am Acad Orthop Surg. 1999;7:189–198. 30. Matava MJ, Boden BP, Eds. AOSSM institutes multi-center revision ACL study”. AOSSM Sports Medicine Update. 2005;(5):5. 31. Howell SM, Hull ML. Checkpoints for judging tunnel and anterior cruciate ligament graft placement. J Knee Surg. 2009;22:161–170. 32. Burkart A, Debski RE, McMahon PJ, et al. Precision of ACL tunnel placement using traditional and robotic techniques. Comput Aided Surg. 2001;6:270–278. 33. Kohn D, Busche T, Carls J. Drill hole position in endoscopic anterior cruciate ligament reconstruction. Results of an advanced arthroscopy course. Knee Surg Sports Traumatol Arthrosc. 1998;6(suppl 1):S13– S15. 34. Cha PS, West RV, Harner CD. The results of using intraoperative fluoroscopy for ideal tibial tunnel position during anterior cruciate ligament reconstruction. 11th ESSKA Congress. May 8, 2004. 35. Sudhahar TA, Glasgow MM, Donell ST. Comparison of expected vs. actual tunnel position in anterior cruciate ligament reconstruction. Knee. 2004;11:15–18. 36. Meuffels DE, Reijman M, Verhaar JA. Computer-assisted surgery is not more accurate or precise than conventional arthroscopic ACL reconstruction: a prospective randomized clinical trial. J Bone Joint Surg Am. 2012;94:1538–1545. 37. Cheng T, Zhang GY, Zhang XL. Does computer navigation system really improve early clinical outcomes after anterior cruciate ligament reconstruction? A meta-analysis and systematic review of randomized controlled trials. Knee. 2012;19:73–77. 38. Zaffagnini S, Urrizola F, Signorelli C, et al. Current use of navigation system in ACL surgery: a historical review. Knee Surg Sports Traumatol Arthrosc. 2016;24:3396–3409. 39. Margier J, Tchouda SD, Banihachemi JJ, Bosson JL, Plaweski S. Computer-assisted navigation in ACL reconstruction is attractive but not yet cost efficient. Knee Surg Sports Traumatol Arthrosc. 2015;23:1026–1034. 40. Plaweski S, Grimaldi M, Courvoisier A, Wimsey S. Intraoperative comparisons of knee kinematics of double-bundle versus single-bundle anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc. 2011;19:1277–1286. 41. Verhelst L, Van Der Bracht H, Oosterlinck D, Bellemans J. ACL repair with a single or double tunnel: a comparative laboratory study of knee stability using computer navigation. Acta Orthop Belg. 2012;78:771–778. 42. Anthony CA, Duchman K, McCunniff P, et al. Double-bundle ACL reconstruction: novice surgeons utilizing computer-assisted navigation versus experienced surgeons. Comput Aided Surg. 2013;18:172– 180. 43. Luites JW, Wymenga AB, Blankevoort L, Eygendaal D, Verdonschot N. Accuracy of a computer-assisted planning and placement system for anatomical femoral tunnel positioning in anterior cruciate ligament reconstruction. Int J Med Robot. 2014;10:438–446. 44. Taketomi S, Inui H, Sanada T, et al. Remnant-preserving anterior cruciate ligament reconstruction using a three-dimensional fluoroscopic navigation system. Knee Surg Relat Res. 2014;26:168–176.
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