Sonographic Patellar and Quadriceps Tendon Length Pre- and Post-Autograft Harvest: Reliability and Concurrent Validity.

Extensor mechanism autografts used for anterior cruciate ligament reconstruction, namely bone-patellar tendon-bone (BPTB) and quadriceps tendon (QT), may result in harvest-site tendon elongation. Extended field of view (EFOV) ultrasound imaging has the potential to evaluate changes in tendon length, but the reliability and validity of these methods in this population are unknown. This study evaluated the reliability and concurrent validity of measurement methods to assess sonographic quadriceps and patellar tendon lengths before and after autograft harvest. Reliability: EFOV ultrasound images were collected by one examiner pre- and post-graft harvest and measured by three examiners in 20 participants (10 BPTB, 10 QT). Measurements were repeated by one examiner blinded to the initial results. Examiners utilized two measurement methods: (1) traditional bony landmarks; (2) novel landmarks less likely to be compromised by bone plug harvest. Validity: EFOV measurements were compared to direct caliper measurements in 20 cadavers. Reliability and validity were examined using intraclass correlation coefficients (ICCs), Pearson's correlation coefficients, and measures of error. Intra-rater reliability for both methods were good to excellent (Pre: Patellar: 0.81-0.99, Quadriceps: 0.97; Post: Patellar 0.82-0.91, Quadriceps: 0.91-0.92) and moderate to excellent for inter-rater (ICCs Pre: Patellar: 0.90-0.99, Quadriceps: 0.96; Post: Patellar: 0.80-0.96, Quadriceps: 0.71-0.75). Standard errors of the measurement were lower for the traditional method for each tendon. ICCs for concurrent validity were moderate to good (Patellar: 0.73, Quadriceps: 0.83). STATEMENT OF CLINICAL SIGNIFICANCE: EFOV ultrasound can reliably measure patellar and quadriceps tendon length before and after autograft harvest for ACLR.