Evaluation of Muscle Size and Fatty Infiltration with MRI Nine to Eleven Years Following Hamstring Harvest for ACL Reconstruction
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.
Available from: Toran D MacLeod
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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.
Available from: Gregory P Boivin
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ABSTRACT: The hamstring tendon autograft is one of the most commonly used graft choices in Anterior cruciate ligament (ACL) reconstruction. There are conflicting results regarding postoperative hamstring strength deficits in patients who have had a hamstring graft. The semitendinosus tendon has been shown to regenerate after harvesting for ACL autograft, suggesting that the muscle has the potential to regain normal function. However, no studies have been performed to define the microstructural changes that occur in the semitendinosus muscle after tendon resection. In this study, we hypothesized that fatty infiltration of the semitendinosus muscle after tendon harvest in New Zealand White rabbits increases postoperatively and remains constant or increases during the first year of repair. The semitendinosus tendon was unilaterally detached and harvested from 15 rabbits. Five rabbits were sacrificed at 3-, 6-, and 12-month intervals, and the semitendinosus muscle-tendon units were analyzed. The contralateral unoperated limb served as the control. The gross tendon and muscle dimensions and histologic percentage of fatty infiltration were measured. We found no significant difference in fatty infiltration at any time point between the control muscle and test specimens and that there was no progression of fatty infiltration over time. If these results hold true in humans, natural repair of the hamstring muscle following tendon harvest during ACL autograft reconstruction is not inhibited by fatty infiltration. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res XX:XXX-XXX, 2013.
Available from: Kristin Briem
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ABSTRACT: Although changes in hamstring muscle morphology after anterior cruciate ligament reconstruction (ACLR) using a semitendinosus autograft hamstrings-gracilis (HG) of the ipsilateral limb are recognized, alterations in muscle activation patterns have not been extensively studied. The purpose of this controlled laboratory trial was therefore to monitor muscle activation levels of the medial (MH) and lateral (LH) hamstring muscles in athletes who had undergone ACLR using a HG autograft and to contrast these to activation levels demonstrated by healthy controls.
Surface electromyography (EMG) was sampled from bilateral hamstring muscles of 18 athletes 1-6 years after ACLR and 18 matched controls (CTRL) during the performance of two dissimilar exercises, both involving eccentric knee flexor activity. Peak normalized muscle activation levels were identified for MH and LH of both limbs during the performance of the Nordic Hamstring (NH) exercise and TRX(®) hamstring curl (TRX) exercise.
A statistically significant limb by exercise interaction was found for peak activation levels of LH, due to significant interlimb differences in activation during the performance of the TRX exercise compared to more symmetrical activation during the NH (p < 0.001). A three-way interaction was found for peak activation levels of MH, due to group differences in peak muscle activation between limbs and exercise type (p = 0.025). Whereas CTRL group participants consistently favoured one limb over the other during the performance of both exercises, ACLR participants demonstrated dissimilar peak MH activation patterns between limbs during the performance of the NH exercise compared to the TRX.
In light of these results and considering the surgical procedure, patients who undergo ACLR using a HG autograft from the ipsilateral limb may benefit from post-operative rehabilitation that involves muscle activation and strengthening specifically targeting the MH component.
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