Patient-Specific 3-D Magnetic Resonance Imaging–Based Dynamic Simulation of Hip Impingement and Range of Motion Can Replace 3-D Computed Tomography–Based Simulation for Patients With Femoroacetabular Impingement: Implications for Planning Open Hip Preservation Surgery and Hip Arthroscopy

Abstract

Background: Femoroacetabular impingement (FAI) is a complex 3-dimensional (3D) hip abnormality that can cause hip pain and osteoarthritis in young and active patients of childbearing age. Imaging is static and based on 2-dimensional radiographs or computed tomography (CT) scans. Recently, CT-based 3D impingement simulation was introduced for patient-specific assessments of hip deformities, whereas magnetic resonance imaging (MRI) offers a radiation-free alternative for surgical planning before hip arthroscopic surgery. Purpose: To (1) investigate the difference between 3D models of the hip, (2) correlate the location of hip impingement and range of motion (ROM), and (3) correlate diagnostic parameters while comparing CT- and MRI-based osseous 3D models of the hip in symptomatic patients with FAI. Study Design: Cohort study (Diagnosis); Level of evidence, 2. Methods: The authors performed an institutional review board–approved comparative and retrospective study of 31 hips in 26 symptomatic patients with FAI. We compared CT- and MRI-based osseous 3D models of the hip in the same patients. 3D CT scans (slice thickness, 1 mm) of the entire pelvis and the distal femoral condyles were obtained. Preoperative MRI of the hip was performed including an axial-oblique T1 VIBE sequence (slice thickness, 1 mm) and 2 axial anisotropic (1.2 × 1.2 × 1 mm) T1 VIBE Dixon sequences of the entire pelvis and the distal femoral condyles. Threshold-based semiautomatic reconstruction of 3D models was performed using commercial software. CT- and MRI-based 3D models were compared with specifically developed software. Results: (1) The difference between MRI- and CT-based 3D models was less than 1 mm for the proximal femur and the acetabulum (median surface distance, 0.4 ± 0.1 mm and 0.4 ± 0.2 mm, respectively). (2) The correlation for ROM values was excellent ( r = 0.99, P < .001) between CT and MRI. The mean absolute difference for flexion and extension was 1.9°± 1.5° and 2.6°± 1.9°, respectively. The location of impingement did not differ between CT- and MRI-based 3D ROM analysis in all 12 of 12 acetabular and 11 of 12 femoral clock-face positions. (3) The correlation for 6 diagnostic parameters was excellent ( r = 0.98, P < .001) between CT and MRI. The mean absolute difference for inclination and anteversion was 2.0°± 1.8° and 1.0°± 0.8°, respectively. Conclusion: Patient-specific and radiation-free MRI-based dynamic 3D simulation of hip impingement and ROM can replace CT-based 3D simulation for patients with FAI of childbearing age. On the basis of these excellent results, we intend to change our clinical practice, and we will use MRI-based 3D models for future clinical practice instead of CT-based 3D models. This allows radiation-free and patient-specific preoperative 3D impingement simulation for surgical planning and simulation of open hip preservation surgery and hip arthroscopic surgery.

Inclusion of the Acetabular Labrum Reduces Simulated Range of Motion of the Hip Compared With Bone Contact Models

“…A number of previous studies have evaluated the FADIR examination with varying degrees of flexion and adduction using ROM simulation in control participants, as well as patients, such as those with FAI or acetabular dysplasia. 6,8,9,12 For clarity, comparison with only the results from the control cohorts are included herein. The internal rotation achieved in control subjects by Kubiak-Langer et al 8 was reduced when compared with the angles we observed by approximately 10-15 for all simulation Table 2, the ROM is within 5 of internal rotation for 0 adduction, 90 flexion).…”

“…9 Lerch et al evaluated internal rotation at 0 and 10 adduction between 90 and 120 flexion and reported values that appear to be within approximately 5 of those found herein (see Fig 4, A and B in Lerch et al). 12 Relative to the 3 adduction angles at 90 flexion, our bone-to-bone simulations resulted in 11-17 less internal rotation than that measured by Iwai et al 6 Our results agree with previous studies evaluating internal rotation at 90 flexion, which found maximum internal rotation to occur between 35 and 50 for control populations (35 by Kubiak-Langer et al, 35 by Tannast et al, 44 and 50 by Nakahara et al, and 40 by Iwai et al). 6,[8][9][10][11] As observed in previous studies, the maximum internal rotation ROM decreased with increased flexion and adduction; however, our results did not indicate as large an effect due to adduction as that observed by Nakahara et al 9,10 Few studies have evaluated the location of contact between the femur and acetabulum using ROM simulations.…”

“…Therefore, previous studies have used computer models based on 3-dimensional (3D) reconstructions of bony anatomy segmented from computed tomography (CT) or magnetic resonance imaging data to identify ROM limitations and the location of impingement in an effort to elucidate the pathomechanics of FAI. [3][4][5][6][7][8][9][10][11][12] This technique has been validated to within 5.0 AE 5.6 of ROM measured in cadavers using an optoelectronic camera system. 11 More recently, models have evaluated the extent that ROM is altered by surgical intervention, such as femoral osteochondroplasty for the treatment of cam FAI or rotational acetabular osteotomy for the treatment of acetabular dysplasia.…”

“…4,6 All previous studies that have used ROM simulations of the hip have only evaluated bone-to-bone contact between the femur and the acetabulum. [3][4][5][6][7][8][9][10][11][12] However, use of bone-to-bone contact may oversimplify hip contact mechanics, since these models remove all soft tissue, including the cartilage and labrum. Given the anatomy of the intact, pre-arthritic hip, the femoral neck or articulating surface of the femur would be expected to come into contact with the acetabular cartilage and labrum before there is bone-to-bone collision with the acetabulum.…”

Bone-to-Bone and Implant-to-Bone Impingement: A Novel Graphical Representation for Hip Replacement Planning

“…9,22,23,27,30,34,36 However, the majority of the studies explored only the effect of implant design and position on PI. 23,27,34,36 There are limited studies in the literature focusing on only BTBI, 9,12,25,33 which mainly explored the effect of implant design and positions, bone morphology and hip joint ROM on BTBI. However, to the best of the authors' knowledge, pre-operative identification of subject-specific bony impingement (BI) areas which should be resected to avoid post-THA BTBI and ITBI for a given implant design and position has not previously been reported in the literature.…”