Hamstring Regeneration Following Harvest for Anterior Cruciate Ligament Reconstruction: A Review of the Current Literature

Abstract

The semitendinosus (ST) and gracillis (Gr) tendons are commonly used as a replacement graft during the anterior cruciate ligament (ACL) reconstruction. There are many advantages of using the hamstrings tendons, including the ease of harvesting, suitable morphology for use as a graft, lower donor site morbidity, early rehabilitation, and patient satisfaction. In most cases, the ST tendon can regenerate after harvesting, showing similar morphology to the native tendon. Although some researchers have demonstrated a loss of hamstring muscle strength in such patients, most investigators have found only slight differences between the operated and the controlateral side in the postoperative period. Recovery of the muscle strength after division of the ST and G tendons can be explained by a process of functional regeneration of the tendons or by compensatory hypertrophy of other knee flexors. Morphological changes including atrophy and shortening of the ST have been confirmed in patients with ACL reconstruction using the ST tendon. MRI analysis has indicated a surprising potential for the harvested tendons to regenerate, in particular when only the ST, and not the G, has been used for autologous transplant. Both in vitro and in vivo studies have illustrated "intrinsic" and "extrinsic" healing potential of the injured or surgically reconstructed tendon, although some have shown a regenerative process of the full-length tendon. The aim of this chapter was to present more information and morphologically document the regeneration ability of the semitendinosus after whole length and full thickness harvesting. The final question is if the quality of the regenerated tendons which resembled the normal ones would allow their use as a new graft. © 2018 Elsevier Inc. All rights reserved.