Summary

Tibial torsion is commonly associated with other anatomical abnormalities associated with patellofemoral pain and or instability. Osteotomy at the level of the tibial tubercle is most commonly warranted.

Abstract

Purpose

Rotational deformity of the tibia is known to be associated with patellofemoral (PFJ) disorders. However, it rarely occurs in isolation and is commonly associated with other anatomical abnormalities which affect the PFJ. The purpose of this study was to comprehensively describe the prevalence of associated factors known to affect PFJ mechanics in a cohort of patients undergoing corrective rotational tibial osteotomy and their potential relevance to the site of correction.

Methods

All patients with PFJ pain/instability who underwent rotational tibial osteotomy between July 2009 and February 2020 were included. Patients were excluded if there were no preoperative CT/MRI scans available for review on PACS. This resulted in a final study population of 80 knees. Scans were analysed by two independent observers. Parameters of interest were femoral version, tibial torsion, trochlear dysplasia, lateral trochlear inclination angle (LTI), tibial tuberosity–trochlear groove (TT–TG) distance, Insalle-Salvati (IS) and Catone Deschamps Index (CDI). Interclass correlation coefficients (ICCs) and Cohen’s kappa statistics were used to evaluate the interobserver reliability.

Results

The studied population had a mean femoral version of 21.0 ± 11.7deg , tibial torsion of 45.9 ± 9.1 deg, TT-TG of 18.3 ± 5.5 mm and LTI of 11.4 ± 14.7. 34 knees (42.5%) had a pathological TT-TG value of ≥ 20mm on CT. Patella alta/Baja was found in 42 knees (54%) based on CD or IS >1.2 on CT/MRI. High-grade trochlear dysplasia was found in in 20 knees (25%), while low grade dysplasia was found in 44 (55%). 23 knees (29%) had a tibial torsion but normal TT-TG and patella height. 14 knees (18%) had abnormal TT-TG but normal patellar height. A greater proportion of females 59 (73.8%) underwent correctional rotational osteotomy compared to males 21 (26.2%).

Conclusion

Within this population, Females required corrective tibial derotational osteotomy more commonly than males. A high prevalence of associated anatomical risk factors were present in variable combinations. Based on the associated abnormalities of patella height and tubercle lateralisation, 18% of the population were suitable for supra-tubercle osteotomy and 29% of patients were suitable for diaphyseal or distal tibial osteotomy. A tibial tubercle osteotomy was required in 54% of patients making a through tubercle approach the most appropriate option for the majority of patients.