Estimating the adequacy of the free quadriceps tendon autograft length using anthropometric measures in anterior cruciate ligament reconstruction.

ABSTRACT

OBJECTIVE: This prospective study aimed to predict the adequacy of free quadriceps tendon (QT) autograft length using simple anthropometric measures. MATERIALS AND METHODS: One hundred and eighty-four consecutive patients who underwent knee high-resolution MRI were enrolled in this study. The QT and native anterior cruciate ligament (ACL) length were measured using the oblique sagittal section. The adequate free QT length was calculated using the native ACL length and 30 mm for femoral and tibial tunnels in each patient. A QT shorter than the calculated length was considered inadequate. Age, sex, height, weight, body mass index, thigh circumference, and activity score were used to predict the adequacy of QT length with regression analysis. RESULTS: There were 92 men and 92 women with a mean age of 34.1 ± 8.0 years (range 18-45). The mean QT and ACL lengths were 69.0 ± 8.8 mm (range 48.1-90.3 mm) and 35.6 ± 2.5 mm (range 29.2-42.6 mm), respectively. The QT and the ACL lengths were longer in men (p < 0.001 for both). Twenty-three men and 39 women (total 62, 33.7%) had inadequate QT length for a free QT autograft, and 6 patients (3 males, 3 females, 3.3%) had inadequate QT length with the bone block technique. There was a weak positive correlation between QT length and height (p < 0.001), weight (p < 0.001), and activity score (p = 0.007). Height was the only independent variable that predicted the QT length adequacy (r2 = 0.051, p = 0.009) but ROC analysis showed that height did not have an ability to detect a subject with an inadequate QT length (AUC 0.384, 95% CI 0.300-0.468). CONCLUSIONS: Free QT autografts may be inadequate in one-third of the patients, while a QT autograft with a bone block is almost always sufficient. Inadequate free QT autograft is more common in women. Although QT length correlated with height, it cannot be used as an accurate diagnostic tool to identify patients with an inadequate QT autograft. Preoperative measurement of the ACL and QT lengths by MRI might be beneficial to decide whether QT is usable, especially when harvesting without a bone block. LEVEL OF EVIDENCE Level II, diagnostic, prospective cohort study.