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.
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Article info
Publication history
Published online: December 14, 2022
Accepted:
November 11,
2022
Received:
April 11,
2022
Footnotes
See commentary on page 1251
The authors report the following potential conflicts of interest or sources of funding: This work was supported by grants from the Health Commission of Hunan Province (20201907). ICMJE author disclosure forms are available for this article online, as supplementary material.
Zhu Dai, M.D., Jian Li, M.D., and Zhijun Yang, M.D., are co-first authors.
Identification
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© 2022 by the Arthroscopy Association of North America
