TY - JOUR
T1 - External Validation of the FEAR Index in Borderline Acetabular Dysplasia
AU - Schwabe, Maria T.
AU - Clohisy, John C.
AU - A. Graesser, Elizabeth
AU - Pascual-Garrido, Cecilia
AU - Nepple, Jeffrey J.
N1 - Funding Information:
One or more of the authors has declared the following potential conflict of interest or source of funding: This study was funded in part by the Curing Hip Disease Fund (to J.C.C.) and the Jacqueline and W. Randolph Baker Fund (to J.C.C.). J.C.C. has received research support from Zimmer; education payments from Elite Orthopedics; consulting fees from MicroPort, Smith & Nephew, and Zimmer; nonconsulting fees from MicroPort and Synthes; and royalties from MicroPort and Wolters Kluwer Health–Lippincott Williams & Wilkins. E.G. has received education payments from Elite Orthopedics. C.P.-G. has received research support from AOSSM/Sanofi and Zimmer, education payments from Elite Orthopedics and Zimmer, consulting fees from ARVIS, and hospitality payments from Stryker. J.J.N. has received research support from Smith & Nephew and Zimmer; education payments from Arthrex; consulting fees from Ceterix, Responsive Arthroscopy, and Smith & Nephew; nonconsulting fees from Smith & Nephew; and royalties from Responsive Arthroscopy. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.
Publisher Copyright:
© The Author(s) 2022.
PY - 2022/8
Y1 - 2022/8
N2 - Background: Given the lack of established, externally validated criteria for the diagnosis of unstable hips, the Femoro-Epiphyseal Acetabular Roof (FEAR) index has been proposed as a useful tool for identifying hips with instability in the setting of borderline acetabular dysplasia. Purposes: To (1) determine the external performance of the FEAR index in identifying hips with a clinical diagnosis of instability in the setting of borderline dysplasia and (2) assess the performance of the FEAR index compared with acetabular inclination or physeal scar angle alone. Study Design: Cohort study (diagnosis); Level of evidence, 3. Methods: The authors reviewed 176 patients with borderline acetabular dysplasia (lateral center-edge angle, 20°-25°). A positive FEAR index was defined as ≥5°. An alternative threshold ≥2° was also assessed. Significant instability was determined by the senior surgeon based on the combination of patient and radiographic features; unstable hips were treated with periacetabular osteotomy (with or without hip arthroscopy), and stable hips were treated with isolated hip arthroscopy. Results: Only 18% of borderline hips had a positive FEAR index. The ≥5° positive FEAR index threshold had a sensitivity of 33% (23/70) and specificity of 92% (98/106) in predicting the clinical diagnosis of instability. The ≥2° FEAR index threshold had a sensitivity of 39% (27/70) and specificity of 89% (94/106) in predicting the clinical diagnosis of instability. No alternative threshold for the FEAR index resulted in high levels of sensitivity and specificity. A threshold of –5° was required to reach an adequate sensitivity of 74%. The FEAR index remained a significant predictor of hip instability even after controlling for acetabular inclination (odds ratio, 1.12; P <.001) or physeal scar angle (odds ratio, 1.6; P <.001). Conclusion: In the current study, a positive FEAR index was generally indicative of the presence of clinical instability, but the FEAR index alone remained inadequate to fully define the instability of a given hip, as it demonstrated low sensitivity (only 33%) in the external validation. The FEAR index is best used in the context of other clinical and radiographic features.
AB - Background: Given the lack of established, externally validated criteria for the diagnosis of unstable hips, the Femoro-Epiphyseal Acetabular Roof (FEAR) index has been proposed as a useful tool for identifying hips with instability in the setting of borderline acetabular dysplasia. Purposes: To (1) determine the external performance of the FEAR index in identifying hips with a clinical diagnosis of instability in the setting of borderline dysplasia and (2) assess the performance of the FEAR index compared with acetabular inclination or physeal scar angle alone. Study Design: Cohort study (diagnosis); Level of evidence, 3. Methods: The authors reviewed 176 patients with borderline acetabular dysplasia (lateral center-edge angle, 20°-25°). A positive FEAR index was defined as ≥5°. An alternative threshold ≥2° was also assessed. Significant instability was determined by the senior surgeon based on the combination of patient and radiographic features; unstable hips were treated with periacetabular osteotomy (with or without hip arthroscopy), and stable hips were treated with isolated hip arthroscopy. Results: Only 18% of borderline hips had a positive FEAR index. The ≥5° positive FEAR index threshold had a sensitivity of 33% (23/70) and specificity of 92% (98/106) in predicting the clinical diagnosis of instability. The ≥2° FEAR index threshold had a sensitivity of 39% (27/70) and specificity of 89% (94/106) in predicting the clinical diagnosis of instability. No alternative threshold for the FEAR index resulted in high levels of sensitivity and specificity. A threshold of –5° was required to reach an adequate sensitivity of 74%. The FEAR index remained a significant predictor of hip instability even after controlling for acetabular inclination (odds ratio, 1.12; P <.001) or physeal scar angle (odds ratio, 1.6; P <.001). Conclusion: In the current study, a positive FEAR index was generally indicative of the presence of clinical instability, but the FEAR index alone remained inadequate to fully define the instability of a given hip, as it demonstrated low sensitivity (only 33%) in the external validation. The FEAR index is best used in the context of other clinical and radiographic features.
KW - FEAR index
KW - borderline dysplasia
KW - instability
UR - http://www.scopus.com/inward/record.url?scp=85136198380&partnerID=8YFLogxK
U2 - 10.1177/23259671221113837
DO - 10.1177/23259671221113837
M3 - Article
C2 - 35990876
AN - SCOPUS:85136198380
SN - 2325-9671
VL - 10
JO - Orthopaedic Journal of Sports Medicine
JF - Orthopaedic Journal of Sports Medicine
IS - 8
ER -