Patellar Tendon-Trochlear Groove Angle Measured on a Single Computed Tomography Slice of the Distal Femoral Trochlear Groove Is a Reliable Measurement for the Evaluation of Patellar Instability

Zhu Dai; Jian Li; Zhijun Yang; Ying Liao; Biao Wu; Wen Huang; Yuxi Chen

doi:10.1016/j.arthro.2022.11.021

Patellar Tendon-Trochlear Groove Angle Measured on a Single Computed Tomography Slice of the Distal Femoral Trochlear Groove Is a Reliable Measurement for the Evaluation of Patellar Instability

Arthroscopy. 2023 May;39(5):1244-1250. doi: 10.1016/j.arthro.2022.11.021. Epub 2022 Dec 14.

Authors

Zhu Dai¹, Jian Li², Zhijun Yang², Ying Liao², Biao Wu², Wen Huang², Yuxi Chen²

Affiliations

¹ Department of Orthopedics, the First Affiliated Hospital, Hengyang Medical School, University of South China, Hunan, China. Electronic address: oliverdai@hotmail.com.
² Department of Orthopedics, the First Affiliated Hospital, Hengyang Medical School, University of South China, Hunan, China.

PMID: 36526511
DOI: 10.1016/j.arthro.2022.11.021

Abstract

Purpose: To verify the reliability of patellar tendon-trochlear groove angle (PTTG-A) measured by computed tomography (CT) and the clinical significance in evaluation of patellar instability.

Methods: A retrospective study of hospitalized patients with knee pain or injury and had knee CT from January 2017 to June 2021 was performed. PTTG-A and tibial tuberosity-trochlear groove (TT-TG) distance were measured on CT. Spearman correlation analysis was analyzed between the 2 measurements. The intraclass correlation coefficient was determined for inter- and intraobserver reproducibility. The capacity of PTTG-A and TT-TG to predict patellar instability was evaluated by the receiver operating characteristic curve. Data from the control group were used to determine the pathologic thresholds and logistic regression analysis.

Results: Included were 113 patients. There were 60 patients with the history of at least 2 episodes of patellar dislocation (study group) and 53 patients without a history of patellar dislocation (control group). The respective PTTG-A and TT-TG distances in the study group (35.2 ± 8.4° and 19.6 ± 4.6 mm) were significantly greater than those of the controls (20.8 ± 5.8° and 13.3 ± 4.5 mm) (P < .001). The correlation between the 2 measurements was strong (r = 0.730, P < .001). The inter- and intraobserver reliability of the PTTG-A were better than TT-TG distance in both groups. The AUC of PTTG-A was greater than that of the TT-TG distance (0.895 vs 0.769, respectively). With the cutoff value of PTTG-A and TT-TG being 26.3° and 16.3 mm, the value of the pathologic threshold of PTTG-A was 30.0°, with a dominance ratio of 16.88 (95% confidence interval 2.88-98.89, P = .002).

Conclusions: The PTTG-A measured on a single CT slice of the distal femoral trochlear groove is a more reliable measurement than TT-TG distance for the prediction of patellar instability.

Level of evidence: III; A retrospective cohort study.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Humans
Joint Instability* / pathology
Magnetic Resonance Imaging
Patellar Dislocation* / pathology
Patellar Ligament*
Patellofemoral Joint* / pathology
Reproducibility of Results
Retrospective Studies
Tibia / pathology
Tomography, X-Ray Computed