The Fate of the Semitendinosus Muscle Following Harvest
The Fate of the Semitendinosus Muscle Following Harvest
Abstract & Commentary
Synopsis: The semitendinosus was re-evaluated with clinical examination, isokinetic strength performance, MRI, and ultrasound-guided muscle biopsy at a median of 8 months postoperatively. Regeneration of the semitendinosus occurred in 75% of patients.
Source: Eriksson K. Arthroscopy. 2001;17(8):808-817.
Hamstring grafts have become a popular alternative to bone-patellar tendon-bone (BPTB) grafts for ACL reconstruction. Although the potential for graft site morbidity is widely recognized for BPTB graft harvest, hamstring grafts are believed to have less donor site morbidity. Conflicting studies have been reported regarding hamstring strength return following hamstring graft harvest, but the potential for actual tendon regrowth has only recently been recognized.
In this study, 16 patients were evaluated at a median of 8 months (range, 3-24 months) following semitendinosus harvesting for ACL reconstruction. At the time of the initial surgery, muscle specimens from the musculotendinous junction were prepared and used for controls. At the time of follow-up, MRI, clinical examination, an isokinetic muscle performance test, and a percutaneous ultrasound-guided needle biopsy of the semitendinosus was accomplished. Eight of the patients also had biopsies of their opposite leg done for a second control. Eriksson and colleagues reported that 12 of 16 tendons demonstrated regeneration on MRI. The cross-sectional area of the neotendon was bigger than the opposite side, but the difference was not statistically different. Most of the clinical findings were not significantly different between the operative and nonoperative leg. Eriksson et al, with a deficit of approximately 15-20%, noted a statistically significant difference in isokinetic strength. Muscle biopsies demonstrated no significant differences in citrate synthase activity, muscle fibers, and other parameters between regenerate and control specimens.
Comment by Mark D. Miller, MD
This is an interesting paper that adds to the growing body of literature on this important subject. Erikkson et al refer to an earlier MRI study that also reported regrowth of 75% of harvested semitendinosus tendons.1 Also, in an article published earlier this year in Arthroscopy (and reviewed in the April 2001 issue of Sports Medicine Reports), we reported regrowth in all 20 of our patients and characterized the progression from proximal to distal.2
The present paper attempts to look at the biology of the semitendinosus muscle. The most amazing aspect of this paper was that patients actually volunteered to have biopsies of their thigh taken at follow-up and that half of the patients allowed biopsies to be harvested from both of their thighs! Although these biopsies studied the semitendinosus muscle, it is the tendon that is of even more interest. In order to investigate this issue, we recently completed a preliminary study in the rabbit model, and have another study underway.3 In our preliminary study we showed that the regenerate neotendon is indeed tendon, with all of the histologic characteristics of tendon. Further research may yield even more information of this process, which has been termed "the lizard tail phenomenon."
References
1. Eriksson K, et al. Knee Surg Sports Traumatol Arthrosc. 1999;7:220-225.
2. Rispoli DM, et al. Arthroscopy. 2001;17(1):2-8.
3. Miller MD, et al. Hamstring regrowth following ACL regeneration: An experimental study in the rabbit. American Orthopaedic Society for Sports Medicine Speciality Day. San Francisco Calif, March 2001.
Dr. Miller, Associate Professor, UVA Health System, Department of Orthopaedic Surgery, Charlottesville, VA, is Associate Editor of Sports Medicine Reports.
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