Evaluation of Muscle Size and Fatty Infiltration with MRI Nine to Eleven Years Following Hamstring Harvest for ACL Reconstruction

University of Utah, Salt Lake City, Utah, USA.
The Journal of Bone and Joint Surgery (Impact Factor: 5.28). 07/2012; 94(14):1274-82. DOI: 10.2106/JBJS.K.00692
Source: PubMed


The long-term effect of hamstring tendon harvest for anterior cruciate ligament (ACL) reconstruction on muscle morphology is not well documented. Our hypothesis was that harvest of the hamstring tendons for ACL reconstruction would result in persistent loss of volume and cross-sectional area of the gracilis and semitendinosus muscles.
Magnetic resonance images were made of both limbs of ten patients nine to eleven years after they had ACL reconstruction with ipsilateral hamstring autograft. The volume of the individual thigh muscles bilaterally was calculated. The peak cross-sectional area and the cross-sectional area 7 cm proximal to the joint line was measured for the gracilis and semitendinosus muscles. Data were evaluated with use of the paired t test and Wilcoxon signed-rank test. The gracilis and semitendinosus muscles on the operatively treated side were evaluated for fatty infiltration and tendon regeneration.
The mean volume on the operatively treated side was 54.2% of that on the noninvolved side for the gracilis muscle and 58.5% for the semitendinosus muscle. A 7% decrease in quadriceps volume and an 8% increase in the volume of the long head of the biceps on the operatively treated extremity were noted. The semimembranosus muscle and short head of the biceps muscle showed no difference in volume. The gracilis and semitendinosus muscles also showed a decrease in peak cross-sectional area, a decrease in the cross-sectional area 7 cm proximal to the joint line, and evidence of fatty infiltration. There was variable evidence of tendon or scar formation within the tendon bed, with most patients having some tissue that blended into either the sartorius muscle or medial gastrocnemius fascia at a level proximal to the joint line.
At nine to eleven years after ACL reconstruction with ipsilateral hamstring autograft, the gracilis and semitendinosus muscles showed persistent atrophy on the operatively treated side with evidence of fatty infiltration and variability in tendon regeneration. There was also persistent atrophy of the quadriceps muscles and compensatory hypertrophy of the long head of the biceps.
Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

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    ABSTRACT: The semitendinosus-gracilis tendon autograft is often used to reconstruct the anterior cruciate ligament. Tendon regeneration appears to occur for most individuals in the short term, but little is known about the long-term effects of graft harvest. The purpose of this study was to describe the effect of semitendinosis-gracilis tendon graft harvest on muscle and tendon morphology at least five years following reconstruction in a case series. Magnetic resonance images were taken of the knees of three subjects at least five years following anterior cruciate ligament reconstruction. These subjects represented the different regeneration patterns at the time of return-to-sport. Muscle and tendon morphology were analyzed by calculating the volume, peak cross-sectional area, and length of the knee flexors. Muscle and tendon morphological changes were analyzed individually, and then in combination as defined as a knee flexor group. Muscle and tendon regeneration continued in those tendons that had begun regeneration at the time of return-to-sports in two subjects. There was significant additional muscle degeneration in those muscles whose tendons had not regenerated at the time of return-to-sports, in the remaining subject. Compensatory hypertrophy of the remaining knee flexors restored the knee flexor group to near preoperative peak cross-sectional area and volume across the each of the three case subjects. Knee flexor morphology at the time of return-to-sports foreshadowed the long-term outcome in the three studied subjects. Preservation of the tendon sheath in situ may play a role in tendon regeneration. When tendon regeneration did not occur, fatty infiltration of the muscle may be a worst-case outcome. Semitendinosus-gracilis muscle synergists demonstrated hypertrophy, perhaps in an effort to compensate for knee flexor group morphology deficits that existed after Semitendinosus gracilis tendon graft harvest. Semitendinosus and gracilis tendon harvest technique may play a role in regeneration. Additionally, knee flexor morphology at the time of return-to-sports may foreshadow the long-term outcome. prospective (longitudinal) cohort - level II.
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