Objective

The goal of this study was to assess ACL grafts compliance (equal inverse of stiffness) after surgery (D-1, 30, 90, 180, 1Y).

Material/patients and methods

Fifty-three patients (15F, 38 M) were tested with GNRB laximeter (Genourob company, France) during 1 year. We analysed the slope of the curves during the first year of ligamentisation (It’s a more objective parameter than just the laxity at one force): operated side/healthy side (O/H). It was the same surgeon and the same surgery (hamstrings tendon transplant) for all patients. A retrospective study has shown without any adaptation protocol and with high divergence of compliance curves early after surgery (> 1 month) a high risk of re-surgery (between 2 or 5 years after the first ACL surgery).

Results

More than 80% (patients) had an operated curve under the healthy one (it means less laxity of ACL graft O/H) and none were divergent (equal same stiffness) at day one (D-1). More than 80% (patients) had an operated curve above the healthy one but parallel (it means more laxity of ACL graft O/H) and more than 10% were divergent (more compliance, less stiffness) thirty days after surgery (D-30). This group (> 10%) had rigorous recommendations and less dynamic exercises in rehabilitation protocols to avoid high strains on ACL graft. After these recommendations, operated curves were going parallel month after month and after one year (1Y) curves were parallel with a little laxity (no divergence and no clinical knee instability for these patients). A retrospective study (> 300 patients) has shown high-risk cases of re-surgery (ACL) between 2 to 5 years after the first ACL reconstruction surgery: patients with severe divergent curves (O/H) the first months (> 1 month and after 1Y).

Discussion – conclusion

The link with aggressive strains on ACL grafts and divergence of compliance curves is important and it was validated high correlation between divergence (high compliance) and clinical knee instability ( P = 0.0001 ; 1500 cases). It’s important to see how to avoid bad evolution of the healing (ligamentisation) with ACL graft controls (GNRB tests) the first months after surgery.