Utility of preoperative ultrasound in assessing the adequacy of autograft for anterior cruciate ligament reconstruction: a systematic review and meta-analysis

Objective: Anterior cruciate ligament (ACL) reconstruction using tendon autograft requires imaging to evaluate graft adequacy. Ultrasound (US) offers an efficient adjunct to MRI; however, the utility of US is variable in prior literature and should be investigated. The primary aim of this study is to provide a statistical appraisal of literature assessing correlation of preoperative US measurements with intraoperative size of autografts during ACL reconstruction.

Materials and methods: PubMed, Embase, and Web of Science databases were queried for studies comparing preoperative US-based measurements to intraoperative measurements of autografts to assess graft adequacy (defined as > 8 mm diameter). Correlation coefficients from studies comparing combined cross-sectional area (CCSA) of autograft tendons on US to intraoperative autograft tendon diameters were collected and pooled. Random-effects models were generated to compare sensitivity, specificity, positive predictive values (PPV), and negative predictive value (NPV) for the identification of adequate graft sizes.

Results: Eleven studies compared preoperative measurements of autograft size to intraoperative measurements. Meta-analysis of studies assessing hamstring tendon CCSA on US in comparison to intraoperative tendon diameters revealed a pooled correlation coefficient of 0.54 (CI 0.41-0.66, I² = 9.6%). Three studies reported if US correctly identified adequate graft sizes, demonstrating sensitivity of 83% (I² = 0.0%) and specificity of 78% (I² = 49.2%). PPV was 91% (I² = 0.0%), and NPV was 62% (I² = 11.7%).

Conclusion: Hamstring CCSA on US has moderate correlation with intraoperative diameter, high sensitivity (83%), moderate specificity (78%), and very high PPV (91%) for identifying adequately sized autografts for ACL reconstruction.