Abstract
BACKGROUND: Previous systematic reviews have reported the incidence of anterior knee pain (AKP) and extension deficit (ED) after anterior cruciate ligament reconstruction (ACLR); however, both outcomes are estimated separately and thus are assumed to be uncorrelated. PURPOSE: To estimate whether there is a clinically relevant association between the population effects of ED and AKP after ACLR. STUDY DESIGN: Systematic review; Level of evidence, 2. METHODS: Under PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, a systematic review was conducted by searching PubMed, EMBASE, and the Cochrane Library electronic databases for published articles reporting incidence of both AKP and ED after ACLR with either bone-patellar tendon-bone (BPTB) or hamstring (HS) graft that returned 298 studies after the initial search. A Bayesian hierarchical measurement error model estimated the population effect of ED and AKP. RESULTS: Twelve publications involving 976 patients (mean follow-up, 77.9 months; range, 24-180 months) were included in the systematic review. There was a clear, moderate correlation between population ED and population AKP for the BPTB (r = 0.40; 95% CI, 0.39-0.42) and the HS grafts (r = 0.35; 95% CI, 0.33-0.36). Model expected estimates for the population effects of AKP and ED were 24.1% (95% CI, 17.4%-31.9%) and 17.5% (95% CI, 10.6%-25.0%), respectively, for the BPTB graft and 16.1% (95% CI, 9.2%-23.9%) and 13.1% ED (95% CI, 6.0%-20.8%) for the HS graft, respectively. The posterior mean difference in AKP between BPTB and HS grafts was clear and substantial (8.3% [95% CI, 0.3% to 16.1%]); there was no substantial difference in the posterior mean difference of ED between BPTB and HS grafts (4.3% [95% CI, -3.8% to 13.0%). CONCLUSION: Our systematic review demonstrated a moderate but clear correlation between ED and AKP irrespective of graft type. From a clinical perspective, this association emphasizes the need for intraoperative achievement of full extension and avoidance of situations that may cause ED. The higher incidence of AKP in patients with BPTB graft may also be attributed to factors related to the graft harvest site. Future metaregression analyses could investigate whether additional factors such as follow-up duration or rehabilitation protocols can moderate the association between AKP and ED after ACLR with either BPTB or HS graft.