Background: Previous clinical studies have reported that conservatively managed medial collateral ligament (MCL) injuries remained unstable 9 years post injury with subjective complaints of muscle weakness, reinjuries, and post-traumatic osteoarthritis. Animal studies have also reported that healing MCLs were weaker and more lax than controls. Therefore, our purpose was to study the early effects of ligament repair on scar laxity, creep, and creep recovery in a rabbit model of bilateral medial collateral ligament (MCL) injury.
Methods: Each rabbit had one MCL cut in midsubstance which was not repaired, while the other MCL had a sagittal Z-plasty repair. Six weeks after surgery, isolated bone-MCL-bone complexes were biomechanically tested for MCL laxity, cyclic creep, creep recovery, and then loaded to ultimate failure.
Results: Nonrepaired scars were significantly more lax than both repaired Z-plasty scars and normal controls. In contrast, there was no significant difference in MCL laxity between repaired scars and normal controls. There were no significant differences between nonrepaired or repaired scars for either cyclic creep and creep recovery. Both crept significantly more and recovered significantly less than normal controls after the same load history. There were no significant differences in the failure load, stiffness, and tensile strength between gap scars and Z-plasty scars. All healing ligaments had significantly lower failure load, stiffness, and tensile strength than normal controls.
Conclusions: The present study demonstrates that ligament repair is effective in decreasing short-term laxity of ligament scars. These 6-week scars would be prone to abnormal creep if loaded excessively.