Summary

ACL repair is associated with better isokinetic hamstring muscle strength and forgotten joint scores but higher rates of graft rupture than ACL reconstruction

Abstract

Introduction

Renewed interest in ACL repair is supported by promising early results from case series. However, comparative studies are currently lacking. The purpose of this study was to compare the clinical and functional outcomes of ACL repair versus ACL reconstruction, at a minimum follow-up of two years.

Methods

A retrospective analysis of prospectively collected data was undertaken. Patients who underwent ACL repair were propensity matched (based on variables including age, gender, BMI, time between injury and surgery, knee laxity parameters, the presence of meniscal lesions, pre-operative activity level and sports participation) in a 1:1 ratio, to those who underwent ACL reconstruction during the same period. Isokinetic testing was used to evaluate strength deficits compared to the contralateral limb at 6 months post-operatively. At final follow-up, knee laxity parameters, return to sport, and outcome measures including Lysholm, Tegner, IKDC, ACL-RSI, and the Forgotten Joint Score-12 (FJS) were recorded.

Results

75 matched pairs were evaluated. The ACL repair group had significantly better mean hamstring muscle strength (+1.7% ± 12.8, compared to contralateral limb) when compared to their counterparts who underwent ACL reconstruction (-10.0% ± 12.8, compared to contralateral limb) (p<0.0001). At a mean final follow-up of 30 ± 4.8 months, the ACL repair group had significantly better FJS (82.0 ± 15.1) compared to the reconstruction group (74.2 ± 21.7) (p=0.017). Non-inferiority criteria were met for ACL repair, when compared to reconstruction, with respect to the IKDC subjective score and knee laxity parameters (side to side antero-posterior laxity difference). No significant differences were found for other functional outcomes or clinical examination (pivot shift). There were no significant differences in the rate of return to the pre-injury level of sport (repair group 74.7% vs reconstruction group 60%, p=0.078). However, a significant difference was observed regarding the occurrence of ACL re-rupture (failure rates: ACL repair, 5,3%; ACL reconstruction, 0%; p=0.045). Patients experiencing failure of ACL repair were significantly younger than those that did not (26.8 years vs 40.7 years, p=0.013). There was no significant difference in rupture rates between groups when only patients aged over 21 years were considered (age >21, failure rates: ACL repair 2.8%; ACL reconstruction 0%, p=0.157). The MCID and PASS thresholds were defined for the ACL repair group. A significantly greater proportion of patients in the ACL repair group achieved PASS for FJS-12 when compared to their counterparts in the ACL reconstruction group (77.3% vs 60%, p=0.034).

Conclusion

ACL repair was associated with significantly better isokinetic strength tests at 6 months, better FJS at final follow-up, and non-inferior IKDC and antero-posterior laxity. However, the rate of re-rupture was significantly higher when compared to ACL reconstruction and younger patients were particularly at risk.