Semitendinosus tendon regeneration after anterior cruciate ligament reconstruction: can we use it twice?

Abstract

Purpose: It has been demonstrated that the semitendinosus tendon can regenerate after being harvested in its whole length and thickness for anterior cruciate ligament (ACL) reconstruction. Ultrasound studies and guided biopsies of the regenerated tendon have shown compatibility and resembling features of the normal tendon. The question is if this neo-tendon is biologically and functionally adequate for re-use?

Methods: Two randomised groups of 150 volunteers were followed up for two years after harvesting the semitendinosus only (25) or the semitendinosus and gracilis tendons (25) in ACL reconstruction. The patients were followed up with clinical and ultrasound examinations, biopsies and histological tests. Surgical exploration was done in three patients for macroscopic verification. The injected arteries of four lower limbs were dissected and the tendon's arterial supplies were examined.

Results: Seventy-two percent of the cases showed regeneration of the semitendinosus tendons. The neotendons were inserted mostly below the knee joint (83.3%) where they had fused with the gracilis tendon, and above the joint (60%) when the gracilis was harvested as well. The isokinetic strength of the hamstrings and quadriceps was not significantly diminished on the operated side. A macroscopic and histological analysis of the regenerated tendons demonstrates close resemblance to normal anatomy, with focal areas of fibrosis. In one patient the regenerated tendon was used for medial patellofemoral ligament reconstruction.

Conclusion: The semitendinosus muscle can recover and the tendon has great potential to regenerate after harvesting for ACL reconstruction. Our data suggest that the regenerated tendons could be used for iterative ligament reconstruction.

Fig. 1

Longitudinal sonogram of a preoperative semitendinosus (ST) tendon (a, outlined by arrows), one month after tendon resection (b), after six months (c), and two years after harvesting (d)

Fig. 2

The histological appearance of the control semitendinosus (ST) tendon (a), and the regenerated ST tendon (b) (H&E, original magnification x10)

Fig. 3

Medial patellofemoral ligament (MPFL) reconstruction with regenerated semitendinosus (ST) tendon in a patient with traumatic patellar luxation

Fig. 4

Medial view of the right knee. G tendon (1) is supplied by two small branches (large arrows) which originate from the femoral artery, and from the saphenous branch (2) (which follows and supplies the saphenous nerve (3, elevated) of the descending genicular artery (4); its tibial attaching pes anserinus part (1′) has small branches (small white arrows) from the inferior medial genicular artery. ST tendon (5) (retracted) receives large branches (6) from the popliteal artery, and from the saphenous artery (small black arrows) for its pes anserinus part (5′). Small arteries (small red arrows), from surrounding loose connective tissue and adjacent muscle tissue, branching and anastomosing freely, form a complex arterial network, a vascular bed of the tendons (arteries injected with India ink and gelatin solution). Sartorius muscle (7) is cut and reflected, and great saphenous vein cat and removed (8)