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Mirror Image Modeling of Acetabular Rim Thickness Differences in Patients With Unilateral Femoroacetabular Impingement Syndrome.

ABSTRACT: Purpose:To use mirror imaging to identify the location and magnitude of difference in acetabular rim morphology between the symptomatic and unaffected acetabula in patients with symptomatic unilateral pincer-type or mixed femoroacetabular impingement syndrome (FAIS) using 1-dimensional models created with computed tomography (CT). Methods:CT scans of bilateral hips in 33 patients diagnosed with unilateral pincer-type or mixed FAIS were obtained. Three-dimensional bilateral hip models were constructed, and the unaffected hemipelvis was superimposed onto the symptomatic side to compare acetabular thickness. Protrusion of the symptomatic side was recorded, and rim morphology was divided into clock face quadrants to analyze the location of greatest magnitude of difference between affected and unaffected acetabula. Analysis of the quadrants was performed using analysis of variance with post hoc Bonferroni correction. Results:The study group consisted of more females (51.6%) than males, with an average age of 35.72 ± 7.8 years and an average body mass index of 24.3 ± 4.1 kg/m2. Of the 33 hips included, 14 were isolated pincer-type FAIS and 19 were mixed. The average preoperative symptomatic side lateral center edge angle was 37.5° ± 7.2° compared with 29° ± 5.1° on the asymptomatic side (P = .001). The symptomatic acetabular rim was on average 0.43 ± 0.18 mm thicker than the corresponding location on the unaffected rim. When the acetabulum was divided into clock face quadrants, the 12 to 3 o'clock position showed the greatest difference between symptomatic and unaffected sides (0.55 ± 0.18 mm) compared with the 3 to 6 o'clock position (0.4 ± 0.28 mm; P = .006), 6 to 9 o'clock (0.34 ± 0.07 mm; P < .001), and 9 to 12 o'clock (0.38 ± 0.03; P = .001). Conclusions:Patients with unilateral, symptomatic pincer-type or mixed FAIS show statistical differences in rim thickness between the affected and unaffected acetabula. Small changes in acetabular rim morphology on the order of ?0.5 mm may be the difference between symptomatic FAIS and the unaffected hip. Level of Evidence:IV, case series.

SUBMITTER: Riff AJ

PROVIDER: S-EPMC7120855 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Mirror Image Modeling of Acetabular Rim Thickness Differences in Patients With Unilateral Femoroacetabular Impingement Syndrome.

Riff Andrew J AJ Weber Alexander E AE Keating Timothy C TC Nwachukwu Benedict U BU Beck Edward C EC Inoue Nozomu N Krivicich Laura M LM Nho Shane J SJ

Arthroscopy, sports medicine, and rehabilitation 20190806 1

<h4>Purpose</h4>To use mirror imaging to identify the location and magnitude of difference in acetabular rim morphology between the symptomatic and unaffected acetabula in patients with symptomatic unilateral pincer-type or mixed femoroacetabular impingement syndrome (FAIS) using 1-dimensional models created with computed tomography (CT).<h4>Methods</h4>CT scans of bilateral hips in 33 patients diagnosed with unilateral pincer-type or mixed FAIS were obtained. Three-dimensional bilateral hip mod ...[more]

PMID: 32266335

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Project description:BackgroundFemoroacetabular impingement is increasingly recognized as a cause of hip pain but its incidence after an innominate osteotomy for the correction of acetabular dysplasia has not been determined. This information would be essential for the orthopaedic surgeon because it has the potential to produce a poor outcome in the long term when trying to balance acetabular instability and overcorrection.Questions/purposesThe purposes of our study were (1) to determine the frequency with which clinically relevant femoroacetabular impingement (FAI) occurs after an innominate osteotomy for the treatment of acetabular dysplasia; (2) to determine risk factors for the development of FAI; and (3) to compare postoperative radiographic and clinical outcomes in patients having undergone an innominate osteotomy for the correction of acetabular dysplasia both with and without FAI.MethodsThis was a retrospective review of 154 hips (132 patients) that had undergone an innominate osteotomy for acetabular dysplasia and were evaluated at a minimum followup of 10 years (mean = 12 years). Mean age at the time of surgery was 3 years, 114 hips had a concomitant open reduction, and 54 hips also had femoral shortening. One hundred eight hips had a Salter osteotomy and 46 had a Pemberton osteotomy. Radiographs were analyzed to determine the lateral center-edge angle (CE angle) and the presence of a crossover sign. The diagnosis of FAI was established when the CE angle was greater than 40°, there was a positive crossover sign, and the patient had groin pain when flexing the hip less than 90°. Comparisons between nonparametric variables were performed with a Mann-Whitney's U test. Categorical variables were compared with a chi-square test. Change in acetabular index (correction) was dichotomized considering 20° of correction as the cutoff point. Association is presented as odds ratio (95% confidence interval), and logistic regression was performed.ResultsAccording to our criteria, 18 of 154 hips had FAI (12%). Of the 18 patients with FAI, 10 had undergone a Pemberton osteotomy (10 of 46 [22%]) and eight a Salter osteotomy (eight of 108 [7%]). A change in the postoperative acetabular index greater than 20° was associated with a greater likelihood of developing FAI. The mean postoperative acetabular index was lower for the group with FAI, for whom it was 20°, compared with the group without FAI, for whom it was 27° (p = 0.04). The mean Iowa Hip Score for the group with FAI was 85, whereas for those without FAI, it was 93 (p = 0.03).ConclusionsFAI is not common after an innominate osteotomy for the treatment of acetabular dysplasia; however, overcorrection is related to a higher incidence. When FAI is present, it can affect the outcome. Overcorrection should be avoided when performing an innominate osteotomy for the treatment of acetabular dysplasia because it can create iatrogenic FAI and have an adverse effect on outcome.Level of evidenceLevel III, therapeutic study.

Dataset Information

Mirror Image Modeling of Acetabular Rim Thickness Differences in Patients With Unilateral Femoroacetabular Impingement Syndrome.

Publications

Mirror Image Modeling of Acetabular Rim Thickness Differences in Patients With Unilateral Femoroacetabular Impingement Syndrome.

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