Loosening of Transtibial Pullout Meniscal Root Repairs due to Simulated Rehabilitation Is Unrecoverable: A Biomechanical Study.

PURPOSE: To determine whether meniscal root repairs recover from displacement due to rehabilitative loading.

METHODS: Transtibial pullout repairs of the posteromedial meniscal root were performed in 16 cadaveric ovine knees. Single- and double-tunnel repairs using the 2-simple suture technique were cyclically loaded in tension to 10,000 cycles, allowed to rest, and loaded in tension again. Paired differences in displacement with rest were recorded to evaluate recoverability. Displacement of repairs at cycles of interest was recorded, and the response of repairs to 10,000 cycles was assessed.

RESULTS: All outcomes were not significantly different between the single- and double-tunnel techniques; therefore, the results were pooled. The difference in displacement between the first cycle and the first cycle after rest was 1.59 ± 0.69 mm. Repair displacement did not reach an equilibrium within 10,000 cycles and instead resulted in a steady increase in displacement of 0.05 ± 0.02 mm per additional 1,000 cycles. Sutures macroscopically began to cut out of the meniscus in both single- and double-tunnel repairs.

CONCLUSIONS: This study showed that significant, unrecoverable loosening from rehabilitative loading occurred in single- and double-tunnel meniscal root repairs. Root repairs also gradually displaced with continued loading instead of reaching an equilibrium displacement after 10,000 cycles. This progressive, unrecoverable loosening needs to be studied further to better understand the resultant impact on knee mechanics. In addition, the quality and quantity of meniscal root repair healing at the time of rehabilitation should be studied to determine how susceptible patients are to repair loosening.

CLINICAL RELEVANCE: Rehabilitative loading caused unrecoverable and progressive loosening of root repairs, showing the importance of healing before loading. Investigations on the effects of loosening on mechanics and the quality of repair healing at weight bearing are necessary to better understand the clinical implications.