On the semitendinosus tendon in anterior cruciate ligament reconstructive surgery

University dissertation from Stockholm : Karolinska Institutet, Karolinska Institutet, Stockholm Söder Hospital

Abstract: The aim of this thesis was to address issues concerning the use of the semitendinosus tendon as an autologous transplant in anterior cruciate ligament reconstructive surgery. The specific objectives of the study concern the regenerative capability of the semitendinosus tendon following its harvest, the morphology and function of the semitendinosus muscle following harvesting of its tendon, the potential for ingrowth of the semitendinosus tendon graft into the bone tunnels, the early postoperative morbidity after anterior cruciate ligament reconstruction with a quadruple sernitendinosus graft as compared to the commonly used bone-patellar tendon-bone graft and, finally, the outcome at a minimum 2-year follow-up on comparing the sernitendinosus tendon graft with the bone-patellar tendon-bone graft. A prospective MRI study revealed regeneration of the harvested tendon in 8 out of 11 (73%) cases, 6-12 months after surgery. The regenerated tendons inserted below the knee joint line together with the gracilis tendon in a conjoined tendon at the pes anserinus. There was atrophy of the sernitendinosus muscle in all cases with a smaller cross-sectional area compared to the non-operated leg. The atrophy was, however, smaller when regeneration of the tendon was observed. To evaluate the regenerated tendons macro- and micromorphologically, 6 patients were selected, 5 with semitendinosus tendon regeneration and I without regeneration. Open surgical biopsy specimens of the regenerated tendons were taken and both macro- and micromorphology revealed regeneration of a tendon structure with parallel collagen arrangements. The morphology and function of the sernitendinosus muscle, 6-12 months postoperatively, were studied prospectively in 16 patients using MRI isokinetic strength performance test and muscle biopsies of the semitendinosus muscle. Neither histochemistry nor enzymatic evaluation of the muscle revealed signs of denervation or inactivity. In isokinetic strength rests, the quadriceps deficit was more marked than the hamstring deficit. The reduction of quadriceps cross-sectional area accounted for the main portion of the thigh atrophy. In cases where no regeneration of the semitendinosus tendon was present, the semimembranosus muscle showed compensatory hypertrophy. Tendon to bone healing of the semitendinosus tendon graft was investigated in 2 patients with different kinds of early graft failure. In patient no. 1, who sustained a traumatic graft rupture 7 months postoperatively, the graft was incorporated into the bone tunnel with Sharpey's fibres and chondroid differentiation resembling a normal ligament insertion. In patient no.2, who presented with early clinical signs of failure, the graft was degenerated and bone resorption around the graft was observed. Early postoperative morbidity (20-35 weeks), following reconstruction with a quadruple semitendinosus tendon graft with endobutton fixation and a bone-patellar tendon-bone graft with interference screw fixation, was assessed in a prospective and randomised study of 107 patients. The semitendinosus tendon group performed better in the one-leg-hop test, bad less patellofemoral problems and less donor site morbidity than the patellar tendon group. There were, however, no differences in activity levels or functional scores between die groups. In a prospective and randomised study of 164 patients, the quadruple semitendinosus tendon graft was compared with the bone-patellar tendon-bone graft 31(24-59) months after surgery. No differences were found in IKDC, Lysholm score, Tegner activity level, visual analogue scale and patellofemoral score. Apart from hampered kneeling ability (P< 0.001) and slightly impaired hyperextension (P<0.05), both parameters more prominent in the bone-patellar tendon-bone group, no clinical differences were found between the groups. Concomitant meniscus injury significantly reduced the recovery potential and early reconstruction (r) 5 months after the injury) was found to be beneficial. The 2-year results can be predicted with approximately 70% accuracy at the 6-moth follow-up. In conclusion, a quadruple semitendinosus tendon graft presents functional results equal to those of the bone-patellar tendon-bone graft in anterior cruciate ligament reconstructive surgery. There is less early postoperative morbidity with the semitendinosus tendon graft, which also has the potential for appropriate ingrowth in the bone tunnels. The semitendinosus tendon regenerates in 75% of the harvested cases to form a functional muscle tendon complex. In cases where no regeneration is present, the semimembranosus muscle compensates with hypertrophy and, in most cases, the morbidity following semitendinosus tendon harvesting is low.

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