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Letter to the Editor Zachary Mark Working, Leo Pinczewski, Carola F. van Eck and Freddie H. Fu Am J Sports Med 2011 39: NP2 DOI: 10.1177/0363546511407163 The online version of this article can be found at: http://ajs.sagepub.com/content/39/5/NP2
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American Orthopaedic Society for Sports Medicine
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Letter to the Editor Dear Editor: With great interest we read ‘‘Fifteen-Year Outcome of Endoscopic Anterior Cruciate Ligament Reconstruction With Patellar Tendon Autograft for ‘Isolated’ Anterior Cruciate Ligament Tear’’ by Hui et al.1 In this article, the authors present the long-term follow-up after anterior cruciate ligament (ACL) reconstruction for isolated ACL injury. Patientreported outcome measures and evaluation of knee stability showed good results. However, 8% of the cohort reruptured their graft, while 24% injured their contralateral ACL. Fifty-one percent of patients had osteoarthritic changes at the 15-year follow-up by radiographic assessment. The work done by Dr Hui and associates should be commended. Fifteen years of follow-up is outstanding and reflects tremendous effort by the research team. Additionally, this cohort has been followed by the researchers and clinicians throughout the postoperative period as reflected by data points at 2, 5, 7, 10, and 15 years, which allows for an understanding of trends that is very informative and robust. This type of analysis is rare in the literature and truly enhances our collective understanding of patient performance. We agree that evaluation of the placement of the graft should consider the anatomic, native ACL. The method used to evaluate tunnel position, as described by Pinczewski et al,4 has limitations in this regard. Tunnel position is measured by this method relative to bony anatomic structures on radiographs, but not to the insertion site of the ACL. Additionally, no arthroscopic pictures, postoperative radiographs, MRI scans, or 3-dimensional CT scans (Figure 1) are shown in the article, which makes it difficult to assess tunnel location and whether anatomic reconstruction was performed. Nonanatomic ACL reconstruction can lead to non-native forces in the reconstructed ACL graft. Because of the nonanatomic position, the graft sees less force than the normal ACL,2 making it less prone to rupture. The authors mention that the ‘‘reconstructed knee is more resilient than the contralateral ACL.’’ We would challenge this statement and clarify that the high graft position redirects knee forces through the articular surface instead of on the ACL fibers. Not only could the lower force experienced by the fibers explain the authors’ findings of significantly more contralateral ruptures than ipsilateral ruptures, but our hypothesis is that this restructuring cannot be ruled out as a significant contribution to the high rate of osteoarthritis still seen after ACL reconstruction.3 The reconstructed knee has not become more resilient, but perhaps instead has experienced a trade-off from one kind of injury to another. Additionally, the authors found that a graft inclination angle of less than 17° was associated with an increased
Figure 1. A, radiograph after single-bundle anterior cruciate ligament (ACL) reconstruction showing a graft inclination angle of 19.3°. B, the corresponding 3-dimensional CT scan shows the tunnel located outside of the native ACL insertion site in a nonanatomic position. chance of rupture. The authors should be specific that this refers to reconstructed knees only; otherwise, this statement contradicts the previously discussed finding that the more vertical graft would have a decreased chance of rupture. These findings of increased rupture with higher grafts are difficult to extrapolate beyond this cohort because of the narrow range of inclination angles in the analysis; all procedures were performed by a single surgeon with a similar technique in a narrow time frame and are unlikely to vary in surgical construct. The mean graft inclination of this group is 19°, further illustrating that this analysis should be confined in its applicability to relatively vertically oriented grafts. A beneficial analysis may be to define an anatomic range of the graft inclination angle, which would help to illustrate the degree of anatomicness of this cohort. Again, we cannot stress enough how excellent the duration of follow-up and degree of analysis are within this cohort. This article discusses a large variety of very interesting data regarding ACL reconstruction and is the result of careful follow-up of patients. The authors’ work should be exemplary to all of us. Zachary Mark Working, BSEng Carola F. van Eck, MD Freddie H. Fu, MD, DSc (Hon), DPs (Hon) Pittsburgh, Pennsylvania Address correspondence to Freddie H. Fu, MD, DSc (Hon), DPs (Hon) (e-mail:
[email protected]) One or more of the authors has declared the following potential conflict of interest or source of funding: Our institution receives funding from Smith & Nephew for research on ACL reconstruction; it is not related to the research presented in this contribution.
REFERENCES The American Journal of Sports Medicine, Vol. 39, No. 5 DOI: 10.1177/0363546511407163 Ó 2011 The Author(s)
1. Hui C, Salmon LJ, Kok A, Maeno S, Linklater J, Pinczewski LA. Fifteen-year outcome of endoscopic anterior cruciate ligament
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Vol. 39, No. 5, 2011
Letter to the Editor
reconstruction with patellar tendon autograft for ‘‘isolated’’ anterior cruciate ligament tear. Am J Sports Med. 2011;39(1):89-98. 2. Kato Y, Ingham SJ, Kramer S, Smolinski P, Saito A, Fu FH. Effect of tunnel position for anatomic single-bundle ACL reconstruction on knee biomechanics in a porcine model. Knee Surg Sports Traumatol Arthrosc. 2010;18(1):2-10. 3. Lohmander LS, Ostenberg A, Englund M, Roos H. High prevalence of knee osteoarthritis, pain, and functional limitations in female soccer players twelve years after anterior cruciate ligament injury. Arthritis Rheum. 2004;50(10):3145-3152. 4. Pinczewski LA, Salmon LJ, Jackson WF, von Bormann RB, Haslam PG, Tashiro S. Radiological landmarks for placement of the tunnels in single-bundle reconstruction of the anterior cruciate ligament. J Bone Joint Surg Br. 2008;90(2):172-179.
Author’s Response: We thank Working, Eck, and Fu for their interest and commendations on our recent publication on the ‘‘Fifteen-Year Outcome Of Endoscopic Anterior Cruciate Ligament Reconstruction With Patellar Tendon Autograft for ‘Isolated’ Anterior Cruciate Ligament Tear.’’4 Their major concern is that tunnel position is nonanatomic, leading to laxity, decreased graft tension, a high incidence of osteoarthritis, and a lower rate of graft failure. They use the work of Kato et al,6 a biomechanical porcine model study, as the basis of this concern. Kato et al6 consider that the widely performed singleincision endoscopic transtibial approach to ACL reconstruction results in nonanatomic tunnel placement, and we are in complete agreement. For this reason, we have drilled the femoral tunnel before the tibial tunnel through a low anteromedial portal, with the knee in maximal flexion, since 1989. This makes it extremely difficult to drill a femoral tunnel into the roof of the intercondylar notch and the surgical technique is described in detail by Webb et al.9 While we acknowledge that tunnel assessment based on postoperative radiographs has its limitations, it has been previously reported in the literature with validated clinical outcomes.7 Arthroscopic pictures, MRI, and 3-dimensional CT scans may more accurately demonstrate tunnel position; however, we based our tunnel placement measurements on plain radiographs, which are readily available and more practical to the surgeon. Working et al challenge the statement that the ‘‘reconstructed knee is more resilient than the contralateral ACL,’’ and again we are in agreement. This was presented in the article as 1 of 3 possible reasons for patients sustaining contralateral native ACL rupture. Their clarification, based on Kato’s work, where nonanatomic grafts are shown to experience lower forces upon instrumented testing, and their conclusion that these lower forces seen by the graft are the reason for a lower reinjury rate, are not borne out by our experience or other clinical studies. Multiple previous studies have shown that the most common reason for failure leading to revision ACL surgery is technical error resulting in nonanatomic placement of, most commonly, the femoral tunnel, but also the tibial tunnel.1,3,5,8 Nonanatomically placed grafts result in joint laxity, instability, and impingement and are more prone to rupture.2 The letter writers request that the authors of the article be specific that the term ‘‘graft inclination angle’’ refers to
reconstructed knee only. We believe that use of the word ‘‘graft’’ makes this self-evident. The writers further suggest that a graft inclination angle of 19° is nonanatomic and vertical. It is difficult to garner any useful information regarding tunnel placement based on the image provided by the writers showing a single PA radiograph of a knee that was taken in internal rotation. Professor Fu has previously suggested a ‘‘correlation between a tunnel angle of less than 20° on AP radiographs and a non-anatomical tunnel position on 3D CT scan’’ in an ongoing study. This statement concurs with the findings of our report, which found a mean coronal graft angle of 19° with a critical graft angle of 17° between the graft rupture and nonrupture groups. These numbers are certainly within measurement error of the 20° suggested by Fu and colleagues. Our previous studies have demonstrated that a coronal graft angle of 19° restores rotation stability on the pivot-shift test and is correlated with a decreased radiographic evidence of osteoarthritis and excellent long-term clinical outcome following ACL reconstructive surgery.7 Leo Pinczewski, MBBS, FRACS Wollstonecraft, Australia Address correspondence to Leo A Pinczewski, MBBS, FRACS (e-mail:
[email protected]). The author has declared the following potential conflict of interest or source of funding: Dr Pinczewski has received research funds and consultancy fees from Smith & Nephew.
REFERENCES 1. Carson EW, Anisko EM, Restrepo C, Panariello RA, O’Brien SJ, Warren RF. Revision anterior cruciate ligament reconstruction: etiology of failures and clinical results. J Knee Surg. 2004;17(3):127-132. 2. Colvin AC, Shen W, Musahl V, Fu FH. Avoiding pitfalls in anatomic ACL reconstruction. Knee Surg Sports Traumatol Arthrosc. 2009;17: 956-963. 3. Diamantopoulos AP, Lorbach O, Paessler HH. Anterior cruciate ligament revision reconstruction: results in 107 patients. Am J Sports Med. 2008;36(5):851-860. 4. Hui C, Salmon LJ, Kok A, Maeno S, Linklater J, Pinczewski LA. Fifteen-year outcome of endoscopic anterior cruciate ligament reconstruction with patellar tendon autograft for ‘‘isolated’’ anterior cruciate ligament tear. Am J Sports Med. 2011;39(1):89-98. 5. Johnson DL, Swenson TM, Irrgang JJ, Fu FH, Harner CD. Revision anterior cruciate ligament surgery: experience from Pittsburgh. Clin Orthop Relat Res. 1996;325:100-109. 6. Kato Y, Ingham SJ, Kramer S, Smolinski P, Saito A, Fu FH. Effect of tunnel position for anatomic single-bundle ACL reconstruction on knee biomechanics in a porcine model. Knee Surg Sports Traumatol Arthrosc. 2010;18(1):2-10. 7. Pinczewski LA, Salmon LJ, Jackson WF, von Bormann RB, Haslam PG, Tashiro S. Radiological landmarks for placement of the tunnels in single-bundle reconstruction of the anterior cruciate ligament. J Bone Joint Surg Br. 2008;90(2):172-179. 8. Uribe JW, Hechtman KS, Zvijac JE, Tjin-A-Tsoi EW. Revision anterior cruciate ligament surgery: experience from Miami. Clin Orthop Relat Res. 1996;325:91-99. 9. Webb JM, Corry IS, Clingeleffer AJ, Pinczewski LA. Endoscopic reconstruction for isolated anterior cruciate ligament rupture. J Bone Joint Surg Br. 1998;80(2):228-294.
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