Hamstring vs. Patellar Tendon Grafts
Abstract & Commentary
Synopsis: There were no significant functional differences in patients treated with either graft at a minimum of 5 years. Hamstring grafts were slightly looser initially but equal at later time points, and patellar tendon grafts had more arthritic changes.
Source: Pinczewski LA, et al. Am J Sports Med. 2002;30: 523-536.
The debate over hamstring vs. patellar tendon grafts for ACL reconstruction continues to escalate. With improved fixation methods, hamstring grafts have seen resurgence in popularity. What has been lacking to this point are good prospective, comparative studies to help determine the differences in outcome with the 2 methods. Pinczewski and colleagues have provided us with an outstanding paper that follows 2 separate groups of 90 patients for a minimum of 5 years. The methods were prospective but not randomized. They began with all patellar grafts and then made a switch to hamstring grafts hoping to randomize patients. However, when patients heard from each other how much more rapid the recovery was with hamstring grafts they could no longer talk patients into randomization and went to hamstring grafts only. Strengths of this study include the long-term, prospective follow-up, single-surgeon team, consistent surgical technique, and exactly the same fixation for both grafts. Seven × 25 mm RCI soft-threaded titanium screws (Smith & Nephew Endoscopy, Andover, Mass) were used to fix all grafts proximally and distally regardless of graft size. Only isolated ACL tears were included, and meniscal pathology was comparable between groups. No patients were braced postoperatively. Evaluations at varying intervals by an independent examiner included Lachman and pivot shift testing, IKDC and Lysholm knee scores, KT 1000 arthrometry, assessment of thigh atrophy and weightbearing radiographs.
IKDC scores, Lysholm knee scores, level of activity, and range of motion were not statistically different. Hamstring grafts were slightly more loose at 1 year, with roughly 70% of patients having a stable exam and less than 3 mm of side-to-side difference on KT testing vs. 90% of patella tendon graft patients. Interestingly, over the 5 years of follow-up, the hamstring grafts appeared to gradually tighten so that the final laxity was very similar with a mean side-to-side difference of 1.7 mm with hamstrings and 1.3 mm for the patellar group. The subset of female patients with hamstrings seemed to be most responsible for the increased laxity at the early time points. This has been noted by other investigators and may be related to bone density and fixation strength. Patella patients were more likely to complain of donor site pain and difficulty with kneeling which persisted even to 5 years (41% vs 12%).
A notable finding is the difference in the rate of arthritic changes noted on weightbearing x-rays. The patella group at 5 years had mild arthritic changes in 18% compared to just 4% of the hamstring group. With this was seen a gradual loss of extension for the patella group. With the exception of differences in arthritic findings and extension, Pinczewski et al feel that both grafts are comparable and both are acceptable.
Comment by David R. Diduch, MS, MD
This paper, though lengthy, merits reading as it is packed with information. I think we can say with confidence that hamstring and patellar tendon grafts are both acceptable for our patients. What was fairly interesting to note was a difference in arthritic changes with the patellar tendon grafts. The only clue Pinczewski et al provide is that the native patella tendons shortened about 10% in the patients receiving that graft while the hamstring group did not see any patella tendon shortening. Patella baja is associated with increased joint contact pressures and arthritic changes so this may be the culprit. The patellar tendon defects were not closed in any of these patients.
It was notable that the hamstring grafts were looser in the first 1-2 years, especially for the women. Whether this is related to inherent tissue differences or bone fixation remains to be studied. What is even more remarkable is that the hamstring grafts appeared to tighten while the patellar grafts gradually loosened with time so that both ended in a comparable range. How the grafts could tighten is unclear. A recent study demonstrated myofibroblasts on sheep tendon grafts that may be responsible and should be an area of further research.1 This also may be the gradual remodeling of the graft and repopulation with host cells that allows the graft to function more like a native ACL. It is important to note that Pinczewski et al used aperture fixation with an interference fit screw that should result in a stiffer graft construct than suspensory fixation. The results are remarkably good with a single screw diameter and no attempt at tunnel compaction. Compared to other studies, this paper offers the longest follow-up with the largest numbers and the most carefully designed methodology to date. It is well worth reading and outlines very clearly the differences that do exist between the grafts and the long-term success that can be expected with each.
Dr. Diduch, Associate Professor, Department of Orthopaedic Surgery, University of Virginia School of Medicine, Charlottesville, VA, is Editor of Sports Medicine Reports.
Reference
1. Weiler A, et al. J Orthopaedic Res. 2002;20:310-317.
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