Hamstring Muscle Atrophy Following Tendon Harvesting
Abstract & Commentary
Synopsis: This study shows variable atrophy of the hamstring tendons when they were evaluated by CT over 1 year postoperatively. It also suggests that functional deficits may occur in athletes who require knee flexion strength at higher degrees of knee flexion.
Source: Irie K, Tomatsu T. Orthopedics. 2002;25(5):491-495.
The semitendinosus and gracilis tendons are commonly used in ACL reconstruction. There has been a great deal of controversy regarding the effect of hamstring harvesting on hamstring function. Recent reports have suggested that the tendons may actually regrow following harvesting—but what happens to the muscles? The present report suggests that they may atrophy; at least in some cases.
Thirteen patients were followed 12-16 months following hamstring ACL reconstruction. Of these patients, 5 had gracilis harvest alone; the other 8 had semintendinosus harvest as well. CT scan sections taken 10 cm above the superior pole of the patella were studied and cross-sectional areas of the muscles were evaluated using special computer software. Strength testing (mean peak torque and > 75° knee flexion) was accomplished using Cybex measurements. The average cross-sectional area of the harvested semitendinosus muscles was 52.9%; the average cross-sectional area of the harvested gracilis muscles was 48.9%; both compared to the opposite side. These values fell roughly into 2 groups—one group (3/8 semitendinosus and 5/12 gracilis) had > 70% cross sectional area and the other group had < 50% of the cross sectional area of the opposite side. The mean peak torque of the harvested side was 97.8% of the opposite side and the total work of knee flexion was 88.4% of the opposite side. The mean > 75° work of the operated side was 75.5% of the nonoperative side. Irie and Tomatsu attribute the minimal morbidity of peak torque to hypertrophy of the other knee flexors. They did find a significant strength deficit in maximum degrees of flexion, and, therefore, recommended that alternate graft sources be considered for athletes who participate in sports such as judo, wrestling, and gymnastics.
Comment by Mark D. Miller, MD
Although this study suffers from low numbers (only 8 semitendinosus muscles were evaluated), Irie and Tomatsu offer some new insight into this controversial problem. Their strength evaluations considered > 75 degree work—this may be an important measurement that has not been considered in prior studies. Numerous studies have suggested that strength and functional results are not affected by hamstring harvest, and other studies have challenged these results. This study suggests that these differences may be related to how each individual responds to the harvest—that is, whether they fall into the > 70% or the < 50% groups. We have seen this same phenomenon in our evaluation of hamstring tendon regrowth in animals. Some of these tendons are robust on late evaluation, and others are thin and atrophic. We have found the same finding in our clinical patients, with some recovering nicely following hamstring harvest, and others never regaining the performance that they had preoperatively. Perhaps future research will focus on factors to enhance muscle and tendon regrowth following hamstring harvest.
Dr. Miller, Associate Professor, UVA Health System, Department of Orthopaedic Surgery, Charlottesville, VA, is Associate Editor of Sports Medicine Reports.
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