Poor Synovial Sheath Integrity Is Associated With an Increased Failure Rate After Anterior Cruciate Ligament Primary Repair.

PURPOSE: To evaluate the impact of anterior cruciate ligament (ACL) synovial sheath integrity, tear location and rupture pattern on failure rates and clinical outcomes after ACL primary repair (ACLPR). METHODS: A retrospective analysis was performed of all patients with complete, modified Sherman type I or II ACL tears who underwent selective, anatomic, dual-suture anchor ACLPR by a single surgeon between 2008 and 2021 and follow-up between 2 and 5 years. Inclusion criteria were proximal ACL tears with good to excellent tissue quality and available arthroscopic images. Synovial sheath integrity (grade I, completely intact; grade II, >50% intact; and grade III, <50% intact), tear location (modified Sherman types I-II), and tear pattern (1-strand, 2-strands, and complex tear pattern) were graded retrospectively in a blinded fashion from arthroscopic images. Univariate and multivariate logistic regression identified predictors of failure. The Spearman correlation assessed relations of tear characteristics as well as baseline and injury characteristics regarding failure rates and patient-reported outcome measures. RESULTS: A total of 281 patients (50.7% women; mean age 39.1 ± 10 years) underwent ACLPR. Of these, 234 patients (92%) completed a minimum 2-year follow-up and were included in the final outcome analysis, with 24 failures observed (10%). Multivariate analysis identified synovial sheath integrity <50% (odds ratio, 3.31; P = .049) and younger age (6% increased failure risk per year younger; P < .001) as independent significant predictors of ACLPR failure. A significant correlation was observed between lower synovial sheath grade integrity and more complex ACL tear patterns (P < .001). Complex rupture patterns were associated with inferior patient-reported outcome measures at the 2-year follow-up. The mean time to last physical examination was 3.4 months (range, 0-15.6 months). Interobserver reliability was good to excellent in all grading parameters (κ = 0.734-0.956); intraobserver reliability ranged from moderate to excellent. CONCLUSIONS: Reduced synovial sheath integrity (<50%) was associated with an increased risk of failure after ACLPR, whereas younger age was independently associated with a higher failure risk. In addition, lower synovial sheath integrity was significantly correlated with more complex ACL rupture patterns, which were associated with inferior patient-reported outcome measures at 2-year follow-up. LEVEL OF EVIDENCE: Level III, retrospective prognostic comparative case series.