Assessment of validity and reliability of femoral shaft-patellar tendon angle measured on MRI
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SCIENTIFIC ARTICLE
Assessment of validity and reliability of femoral shaft-patellar tendon angle measured on MRI Himanshu Gupta 1
&
Himanshu Kataria 1 & Nafisa Shakir Batta 2 & Sunil Yadav 1 & Vineet Jain 1
Received: 18 June 2020 / Revised: 29 September 2020 / Accepted: 29 September 2020 # ISS 2020
Abstract Introduction Clinically measured Quadriceps angle (Q-angle) has low reliability. Measurement of angle between femoral shaft and patellar tendon (FSPT angle) on routine knee MRI was described in this study to represent the lateral vector forces of quadriceps mechanism. The cross-sectional study was designed to compare this angle between subjects with objective patellofemoral instability (PFI) versus those without PFI, to assess its reliability, and to assess its validity in terms of its ability to differentiate between PFI and non-PFI subjects using the “Receiver Operating Characteristic” (ROC) curve. Materials and methods MRI scans of 20 subjects with PFI and 20 without PFI were obtained. FSPT angle was measured in each MRI by three different raters. In addition, the clinical Q-angle was also measured in the control group. Results The FSPT angle was significantly higher in PFI group as compared with the non-PFI group (p < 0.001). It had substantial inter-rater reliability of 0.82 (95% CI = 0.67–0.92) in the non-PFI group and 0.89 (95% CI = 0.78–0.95) in the PFI group. Testretest reliability was more than 0.90. The AUC for the ROC curve was 0.86 (95% CI = 0.74–0.97). The clinical Q-angle measured in non-PFI subjects had inter-rater reliability of only 0.48 (95% CI = 0.21–0.72), and showed a fair correlation of 0.58 with the MRI angle. Conclusion Measurement of FSPT angle was described on MRI with substantial intra-rater and inter-rater reliability. The angle was significantly higher in PFI versus non-PFI subjects and also showed a good ability to differentiate between these two groups in the ROC curve. Keywords Quadriceps angle . MRI . Patellofemoral instability . Reliability . Patellar dislocation
Introduction
* Himanshu Gupta [email protected] Himanshu Kataria [email protected] Nafisa Shakir Batta [email protected] Sunil Yadav [email protected] Vineet Jain [email protected] 1
Department of Sports Injury Centre, VMMC & Safdarjung Hospital, New Delhi 110029, India
2
Mahajan Imaging, New Delhi 110029, India
The Quadriceps angle (Q-angle) is a measure for the resultant lateral vector of the combined forces of the quadriceps and the patellar tendon acting on the patella [1–3]. Clinically, it is defined as the supplementary angle formed in the 2D coronal plane by two vectors extending from the mid-patella, superiorly to the anterior superior iliac spine (ASIS) and inferiorly to the tibial tuberosity [4]. A larger Q-angle represents a larger lateral vector on the patella [1, 2]. This angle is used, in conjunction with several other common clinical measures like patellar glide test and J-sign, in the assessment of patellofemoral instability (PFI) and patellofemoral pain syndrom
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