Evaluation of Statistical Shape Modeling in Quantifying Femoral Morphologic Differences Between Symptomatic and Nonsymptomatic Hips in Patients with Unilateral Femoroacetabular Impingement Syndrome

Abstract

To determine whether statistical shape modeling can detect subtle morphologic differences in the shape of the proximal femur that correlate with clinical findings of unilateral femoroacetabular impingement syndrome. Methods: Patients who had diagnoses of unilateral femoroacetabular impingement syndrome and who had existing computed tomography scans of their pelvises were included. Three-dimensional shape models in the form of triangle meshes were generated from the computed tomography images. Statistical shapes of cam-type and normal hips were compared to identify structural differences. Results: The study included 33 hips in 17 subjects. Of the subjects, 7 (41.1%) were male, and 10 (58.9%) were female. The subjects ranged in age from 17-60 years of age (mean 36.3 AE 11.0 years old). The statistical shape modeling found mean shapes and modes after optimizing the groupwise correspondence. Symptomatic hips demonstrated 1 mm of thickening as compared to the femoral necks of asymptomatic hips, corresponding to cam lesions. Conclusions: Symptomatic cam deformities were an average of 1 mm more prominent in the femoral neck region as compared to the asymptomatic hips when using statistical shape modeling. The present study provides a proof of the concept that statistical shape modeling can be used to examine and help define cam morphology and that subtle morphologic differences may account for developing femoroacetabular impingement syndrome. Clinical Relevance: Using the methods presented in this study, it would be possible to define cam and pincer morphologies by creating statistical shape models, and this work could potentially lead to the development of a new classification system for femoroacetabular impingement syndrome lesions.

MRI‐­ and CT‐­based metrics for the quantification of arthroscopic bone resections in femoroacetabular impingement syndrome

“…Currently, for the diagnosis and quantification of cam‐­type morphology, the field mainly relies on two­‐dimensional (2D) radiographs. Since abnormal bony morphology clearly constitutes a three­‐dimensional (3D) problem, the clinical use of radiographs as screening modality still represents a significant barrier for the morphological evaluation, despite new techniques have been proposed to three­‐dimensionally approach cam‐­type FAIS resections 5–15 . The consequence of inadequate 3D morphologic assessment is potential incomplete resection of the proximal femur to address cam‐­type FAIS, which has been cited as the primary reason for revision surgery 16–20 .…”

“…Since abnormal bony morphology clearly constitutes a three-dimensional (3D) problem, the clinical use of radiographs as screening modality still represents a significant barrier for the morphological evaluation, despite new techniques have been proposed to three-dimensionally approach cam-type FAIS resections. [5][6][7][8][9][10][11][12][13][14][15] The consequence of inadequate 3D morphologic assessment is potential incomplete resection of the proximal femur to address cam-type FAIS, which has been cited as the primary reason for revision surgery. [16][17][18][19][20] The current clinical approach for the quantification of proximal femur bony morphology also exposes patients to ionizing radiation, in cases of both radiographs and computed tomography (CT).…”

Principal Component Analysis of Distal Femur Based on Statistical Shape Model

“…Traditional registration methods use ICP (Iterative Closest Point) algorithm [17], [18]. This method achieves registration by minimizing the distance between the two models.…”

Noninvasive shape‐fitting method quantifies cam morphology in femoroacetabular impingement syndrome: Implications for diagnosis and surgical planning

“…[12][13][14][15] There is considerable variation in three-dimensional (3D) hip joint bone shape among individuals, which leads to the challenge of differentiating between abnormal bone shape and normal anatomic structural variation. 12,[16][17][18][19][20][21][22] The primary method for evaluating the 3D shape of the femur in people with suspected FAIS is through measure of the alpha angle on standard radiographs. 23,24 However, this two-dimensional (2D) planar approach provides little information on the exact location and extent of the cam deformity, thereby representing a considerable limitation in understanding the role this morphology plays in the development of cam-type FAIS.…”

“…25,26 A number of studies have tried to incorporate 3D patientspecific analyses in the diagnosis and surgical planning for FAIS. [17][18][19][20][34][35][36][37][38] Wong et al 35 found that a preoperative evaluation of a computerized tomography (CT)-based 3D printed model of the hip joint alters the initial surgical plan for FAIS correction.…”