Prevalence and diagnostic accuracy of in-toeing and out-toeing of the foot for patients with abnormal femoral torsion and femoroacetabular impingement: implications for hip arthroscopy and femoral derotation osteotomy.

Lerch, Till; Eichelberger, Patric; Baur, Heiner; Schmaranzer, Florian; Liechti, Emanuel F.; Schwab, Joe M; Siebenrock, Klaus A.; Tannast, Moritz (2019). Prevalence and diagnostic accuracy of in-toeing and out-toeing of the foot for patients with abnormal femoral torsion and femoroacetabular impingement: implications for hip arthroscopy and femoral derotation osteotomy. The Bone & Joint Journal, 101-B(10), pp. 1218-1229. British Editorial Society of Bone and Joint Surgery 10.1302/0301-620X.101B10.BJJ-2019-0248.R1

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AIMS Abnormal femoral torsion (FT) is increasingly recognized as an additional cause for femoroacetabular impingement (FAI). It is unknown if in-toeing of the foot is a specific diagnostic sign for increased FT in patients with symptomatic FAI. The aims of this study were to determine: 1) the prevalence and diagnostic accuracy of in-toeing to detect increased FT; 2) if foot progression angle (FPA) and tibial torsion (TT) are different among patients with abnormal FT; and 3) if FPA correlates with FT. PATIENTS AND METHODS A retrospective, institutional review board (IRB)-approved, controlled study of 85 symptomatic patients (148 hips) with FAI or hip dysplasia was performed in the gait laboratory. All patients had a measurement of FT (pelvic CT scan), TT (CT scan), and FPA (optical motion capture system). We allocated all patients to three groups with decreased FT (< 10°, 37 hips), increased FT (> 25°, 61 hips), and normal FT (10° to 25°, 50 hips). Cluster analysis was performed. RESULTS We found a specificity of 99%, positive predictive value (PPV) of 93%, and sensitivity of 23% for in-toeing (FPA < 0°) to detect increased FT > 25°. Most of the hips with normal or decreased FT had no in-toeing (false-positive rate of 1%). Patients with increased FT had significantly (p < 0.001) more in-toeing than patients with decreased FT. The majority of the patients (77%) with increased FT walk with a normal foot position. The correlation between FPA and FT was significant (r = 0.404, p < 0.001). Five cluster groups were identified. CONCLUSION In-toeing has a high specificity and high PPV to detect increased FT, but increased FT can be missed because of the low sensitivity and high false-negative rate. These results can be used for diagnosis of abnormal FT in patients with FAI or hip dysplasia undergoing hip arthroscopy or femoral derotation osteotomy. However, most of the patients with increased FT walk with a normal foot position. This can lead to underestimation or misdiagnosis of abnormal FT. We recommend measuring FT with CT/MRI scans in all patients with FAI. Cite this article: Bone Joint J 2019;101-B:1218-1229.

Item Type:

Journal Article (Original Article)

Division/Institute:

04 Faculty of Medicine > Department of Orthopaedic, Plastic and Hand Surgery (DOPH) > Clinic of Orthopaedic Surgery

UniBE Contributor:

Lerch, Till; Schmaranzer, Florian; Liechti, Emanuel; Siebenrock, Klaus-Arno and Tannast, Moritz

Subjects:

600 Technology > 610 Medicine & health

ISSN:

2049-4394

Publisher:

British Editorial Society of Bone and Joint Surgery

Language:

English

Submitter:

Kathrin Aeschlimann

Date Deposited:

10 Oct 2019 14:42

Last Modified:

25 Oct 2019 02:28

Publisher DOI:

10.1302/0301-620X.101B10.BJJ-2019-0248.R1

PubMed ID:

31564157

Uncontrolled Keywords:

Femoral derotation osteotomy Femoral torsion Femoroacetabular impingement Foot progression angle Hip arthroscopy In-toeing Out-toeing Tibial torsion

BORIS DOI:

10.7892/boris.133834

URI:

https://boris.unibe.ch/id/eprint/133834

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