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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. 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, 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, 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. 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 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.