Purpose

To examine the long-term clinical outcomes of primary ACL repair combined with biologic healing augmentation in patients with symptomatic partial ACL tears.

Study Design: Case series; Level of evidence, 4.

Methods

50 patients (mean age, 29.5 years) with a partial ACL tear and symptomatic knee instability were treated with primary ligament repair in conjunction with marrow stimulation and followed prospectively for a mean duration of 10.2 years (range, 5.3- 14.3 years). Comparative analysis of preinjury, preoperative, and postoperative scores using patient-reported assessment instruments was performed to examine clinical outcomes. Correlation of final outcome scores with patient age, type of ACL tear, side-to-side difference in ligamentous laxity, and body mass index (BMI) was performed through use of Spearman rank analysis.

Results

44 patients were available for assessment at final follow-up. The median Tegner Activity Scale score of 7 at final followup
was the same as the preinjury median score of 7 (P = .128). The mean Marx Activity Scale, International Knee Documentation
Committee (IKDC) Subjective, and Lysholm Knee Questionnaire scores were 10.8, 90.4, and 96.2, respectively, at final follow-up.
Mean final Knee injury and Osteoarthritis Outcome Score (KOOS) subset assessments of Pain, Symptoms, Activities of Daily Living,
Sports, and Quality of Life were 98.6, 97.5, 99.7, 94.3, and 95.6, respectively. Secondary ACL insufficiency occurred in 27%
of patients. Clinical outcome scores were similar for all scoring instruments between patients treated for an associated diagnosis
of meniscal or articular cartilage injury. No significant correlations of age, BMI, ACL tear type, or laxity and final IKDC Subjective,
Lysholm, or KOOS scores were found. Analysis revealed a negative correlation of patient age and Tegner score at preinjury (rs =
20.333, P = .022) and at final follow-up (rs = 20.376, P = .013). The mean side-to-side difference in ligamentous laxity of 3.4 mm
at short-term follow-up in those patients who developed secondary ACL insufficiency over the duration of follow-up was significantly
greater than the mean of 0.9 mm in those who did not (P = .010).

Conclusion

Primary ACL repair combined with biologic healing augmentation to treat select cases of knee instability secondary to incomplete ACL rupture demonstrated good to excellent long-term outcomes in this cohort for those patients who did no experience secondary ACL insufficiency, with high rates of restoration of knee stability and return to preinjury athletic activities. The rate of secondary treatment for recurrent ACL insufficiency over the course of long-term follow-up was greater than would be
expected for primary ACL reconstruction. Greater side-to-side differences in objective findings of ligamentous laxity were identified at shorter term follow-up in the patients who later went on to experience symptomatic secondary ACL insufficiency, compared with those who maintained stability long term.

Keywords: anterior cruciate ligament (ACL); primary ligament repair; partial ligament tear; marrow stimulation; knee arthroscopy;
biologic healing