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Older age, smoking decreased chance of hamstring tendon regeneration
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Results published in The American Journal of Sports Medicine showed regeneration of the hamstring tendon following ACL reconstruction was less likely to occur among older patients and patients who smoked. However, loss of function may not occur among tendons that do not regenerate.
Among 154 patients included in the Knee Osteoarthritis Anterior Cruciate Ligament Lesion study, researchers identified 79 patients between 18 and 45 years of age with ACL rupture who underwent ACL reconstruction entailing the hamstring tendons, had MRI within 6 months after trauma and 2-year follow-up MRI data. Researchers defined hamstring tendon regeneration as complete if patients had a tendon-like structure at the level of the joint line or more cranially. To determine predictive factors for tendon regeneration or examine functional recovery of hamstring tendon regeneration, researchers evaluated patient characteristics preoperatively and at 2 years.
Results showed 67.1%, 81% and 59.5% of patients had regeneration of semitendinosus tendons, gracilis tendons and both tendons, respectively, at 2-year follow-up. Older age and smoking significantly decreased the likelihood of semitendinosus tendon regeneration. Although researchers found no predictive factor for gracilis tendon regeneration, smoking was negatively related with regeneration of the semitendinosus and gracilis tendons. Postoperative VAS scores during physical activity and Tegner scores were similar to preoperative scores among patients without regeneration. Results also showed patients without regeneration had a significant decrease of upper leg circumference postoperatively vs. preoperatively. Researchers found a significant increase in one-legged hop test results at 2-year follow-up, regardless of regeneration status. – by Casey Tingle
Disclosure: The Dutch Osteoarthritis Society financially supported the Knee Osteoarthritis Anterior Cruciate Ligament Lesion study.
Perspective
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James H. Lubowitz, MD
Suijkerbuijk and colleagues show hamstring tendons may regenerate after harvest but do so less frequently in older patients and smokers. This is intuitive and as also reported, absence of regeneration does not result in adverse outcome. "Regeneration” is an MRI finding. There is no evidence the neo-tendons provide a dynamic strong attachment from muscle to bone. This study should not change clinical practice. Autograft choice is not the primary determinant of knee reconstruction outcome. Autograft is preferred for young, active patients. Small-diameter hamstring grafts have a higher failure rate. Bone-patellar tendon-bone grafts are an alternative, and for patients with open growth plates and to avoid the morbidity of bone plug harvest, quadriceps soft tissue autografts could continue to gain in popularity.
Suijkerbuijk and colleagues suggest that if a patient asks, “Will my hamstrings grow back?” we can tell young non-smokers, “probably," and we can tell old smokers, “probably not." We might add, “It doesn’t matter — regeneration does not determine outcome.”
My experience is that patients want to know when they can return to sport and what the risk of reinjury is; I do not recall patients asking about regrowth, nor do I think hamstring tendon regeneration after harvest is of clinical significance.
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