Twenty consecutive, chronic and isolated anterior cruciate ligament (ACL) lesions that underwent reconstruction with quadrupled semitendinosus (ST) and gracilis (G) were prospectively examined to compare tendon regeneration and muscle strength recovery. Twenty consecutive axial nuclear magnetic resonance (NMR) scans were done after 1 month, 6 months and 2 years from surgery. A CybexII was used to evaluate concentric strength deficits both in flexion and in internal tibia rotation at 6 months and 2 years. At 2 years, an NMR signal comparable to the contralateral was present in 14 (70%) cases and absent in 6 (30%). Semitendinosus tendon exceeded the meniscal plateau since the first month, while the G tendon crossed the joint line only after 6 months. However, the distal-end insertions of both tendons were always significantly more proximal than the contralateral normal side (ST: P = .002; G: P = .003). In case of tendon regeneration, flexion deficit was not significant after 6 months, while internal tibia rotation deficit became not significant only after 2 years. In case of non-regeneration, a flexion deficit was present after 6 months [15.5% (P = .05)] but not after 2 years, while internal tibial rotation deficit was significant both after 6 months [30.3% (P < .001)] and 2 years [24.3% (P = .03)]. In case of tendon regeneration, isokinetic evaluation showed a non-significant deficit in both flexion and internal rotation strength after ACL reconstruction with ST and G. At the 2-year follow-up, none of the 6 patients without tendon regeneration found any impairment in their sport activities despite the loss of internal rotation strength.
Keywords: ACL; hamstrings; muscle strength; tendon regrowth.