Evaluation of Factors Associated With Short-term Failure After Primary Isolated PCL Reconstruction: A Study of Patients From the Swedish and Norwegian Knee Ligament Registries

Background: The rate of subjective failure after isolated primary posterior cruciate ligament reconstruction (PCL-R) is relatively high, requiring an improved understanding of factors associated with inferior outcomes.

Purpose: To determine the association between patient and injury-related factors and total (surgical and clinical) failure at 2 years after PCL-R based on data from the Swedish National Knee Ligament Registry (SNKLR) and the Norwegian Knee Ligament Registry (NKLR).

Study design: Cohort study; Level of evidence, 3.

Methods: Patients with primary isolated PCL-R registered between January 1, 2004 (NKLR), or January 1, 2005 (SNKLR), and December 31, 2020, were included. The primary study outcome was the risk of PCL-R failure at the 2-year follow-up, either surgical (≤2 years of index surgery) or clinical (Knee injury and Osteoarthritis Outcome Score [KOOS] Quality of Life subscale [QoL] <44) failure. Risk factors for failure were estimated utilizing univariable and multivariable logistic regression analyses.

Results: Among the 189 included patients (36.0% from the SNKLR and 64.0% from the NKLR), the rate of 2-year surgical failure was 5.8%, while the rate of clinical failure was 45.0%. Multivariable analysis showed a negative association between the baseline KOOS QoL and the risk of PCL-R failure (OR, 0.74; 95% CI, 0.57-0.97; P = .027). Univariable analysis indicated a positive association between traffic-related injury mechanism and PCL-R failure risk (OR, 3.11; 95% CI, 1.48-6.50; P = .0026), with a further positive association shown in the adjusted (OR, 6.08; 95% CI, 2.00-18.50; P = .0015) and multivariable (OR, 6.11; 95% CI, 2.01-18.55; P = .0014) models. An area under the curve of 0.70 (95% CI, 0.60-0.80) was reported for the final multivariable model, implying at best poor to acceptable ability of the model to estimate PCL-R failure risk based on the variables considered.

Conclusion: Patients with isolated primary PCL-R had a high (45%) rate of short-term clinical failure, and traffic-related injury was associated with increased odds of failure. No modifiable risk factors were determined as potential predictors of failure. Clinicians treating patients with isolated PCL-R associated with a traffic-related injury mechanism should be aware of a >6-fold increased odds of revision surgery and inferior knee-related quality of life at short-term follow-up.