Poster 245: Clinical Measurement of the Standard Q-Angle Correlates Poorly with Tibial Tuberosity to Trochlear Groove Distance in Awake Patients and Anesthetized Patients with Patella Alta and Trochlear Dysplasia

• Published in: Orthopaedic journal of sports medicine 2023-07, Vol.11 (7_suppl3)
• Main Authors: Mowery, Alia, Raad, Micheal, Bressner, Jarred, Elias, John, Cosgarea, Andrew, Mikula, Jacob
• Format: Article
• Language: English
• Subjects: Knee; Patients
• ISSN: 2325-9671; 2325-9671
• DOI: 10.1177/2325967123S00225

Objectives: The quadriceps angle (Q-angle) measures the force vector of pull of the extensor mechanism of the knee. A larger Q-angle is thought to be a predisposing factor for patellar dislocation, but previous literature has reported poor reliability and validity of clinically measured Q-Angle. In response to poor reliability, a new “Standard Q-Angle” (SQA) was developed by Merchant et al. (Merchant 2020) in an attempt to create a standardized and repeatable method of clinically measuring the Q-Angle. The SQA may be a practical, inexpensive, and valuable part of physical examinations to help clinicians decide if concomitant medializing osteotomy is indicated in patellar stabilization procedures. However, SQA has not yet been validated in patients with anatomic risk factors for recurrent patellar instability such as patella alta and trochlear dysplasia. Furthermore, while SQA has previously been demonstrated to have strong interrater reliability, it has never been shown to correlate with standardized measurements for a lateralized tibial tuberosity, such as the Tibial Tuberosity – Trochlear Grove (TT-TG) distance. Therefore, the purpose of our study was to determine the correlation between SQA and TT-TG distance in patients with recurrent patellar instability. We hypothesized that there would be a positive correlation between SQA and TT-TG distance. 1. Merchant AC, Fraiser R, Dragoo J, Fredericson M. A reliable Q angle measurement using a standardized protocol. Knee. 2020;27(3):934-939. Methods: Patients at a single institution treated by a single surgeon with recurrent patellar instability who had previously obtained a dynamic 4D CT scan were included in this study. Patients who had previous patellar stabilization procedures were excluded. The Standard Q-angle was measured as previously described by Merchant et al. (Merchant 2020). The patient was placed in the supine position with the knee extended. A long-arm goniometer was centered over the patella with the distal arm over the tibial tuberosity and the proximal arm extended up to the anterior superior iliac spine (ASIS). The examiner then centered the patella within the trochlear groove and the SQA was measured. A second examiner stood at foot of the patient’s bed to confirm positioning. Measurements were taken in the office, as well as in the operating room after the induction of general anesthesia. All measurements were performed by the senior author (***). Utilizing 4D CT scans, the TT-TG, Caton-Des