Purpose:- Rotational deformities of the tibia and femur are known to be associated with patellofemoral (PFJ) disorders. However, they rarely occur in isolation and are commonly associated with other anatomical abnormalities which affect the PFJ. The purpose of this study is to comprehensively describe the prevalence of associated factors known to affect PFJ mechanics in a cohort of patients with significant rotational mal-alignment undergoing corrective osteotomy for PFJ disorders.
Methods
All patients with PFJ disorders who underwent rotational osteotomy of femur/tibia between July 2009 and February 2020 were included. Patients were excluded if there was no preoperative CT scans available on PACS. This resulted in a final study population of 86. Scans were analysed by two independent observers. Parameters of interest were femoral torsion, 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. Group comparison between low grade and high-grade trochlear dysplasia, and between female and male patients were done.
Results
Rotational tibial osteotomy (RTO) was done in 81 (94.2%), who had a mean femoral version of 21.31 ± 11.93, tibial torsion of 45.97 ± 9, and TT-TG of 18.15 ± 5.60. 34 (42%) in RTO group had a pathological value of =20mm. Rotational femoral osteotomy (RFO) was done in 4 (4.7%). Three had excessive femoral anteversion (mean=34±2.3) and one had excessive retroversion (-8). They had a mean tibial torsion of 38.5 ± 5.92, and TT-TG of 22.73 ± 5.28. Two (50%) in RFO group had a pathological value of =20mm. High-grade trochlear dysplasia was found in in 20 (24.7%) in the RTO group, and 2 (50.0%) in the RFO group, while low grade dysplasia was found in 44 (54.3%), and 1 (25.0%). Patella Alta was found in 30 (37.03%) and 2 (50%) in RTO and RFO groups respectively. Group analysis showed that higher grade of trochlear dysplasia associated with higher mean values for TT-TG distance (high grade= 23 ± 5.7, low grade=16.7 ± 4.4, p=<0.001). Only one patient (1.2%) had combined rotational osteotomy of femur and tibia. Greater proportion of female (73.3%) were involved compared to male (26.7%). Females showed higher median values for femoral version (female: 22.2 (-8 – 51), male: 13 (-29 – 50), p=0.017) and lower mean values for TT-TG (female:17.5 ± 5.6, male: 20.6 ± 5, p= 0.020).
Conclusion
Within this geographical population, Females required corrective surgery more commonly than males and correction of Tibial torsion was significantly more prevalent than femoral torsional abnormalities. A high prevalence of several anatomical risk factors can present in variable combinations in patients undergoing rotational osteotomy for PFJ pain and/or instability. Therefore, a comprehensive assessment of all parameters on imaging is required to enable informed decision making regarding surgical correction. Associated pathology should be taken into account when determining the surgical approach to corrective osteotomy in order to address influential pathology and reduce the potential for creating abnormal anatomy which may have a negative effect on the PFJ .