Article
Patients with avascular necrosis of the femoral head have symptomatic anterior or posterior Femoro-acetabular Impingement – a 3D Hip Impingement simulation study
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Authors
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Till Lerch
- Inselspital Bern, University Hospital Bern, Department of orthopedic surgery and traumatology, University of Bern, Bern, Switzerland
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Florian Schmaranzer
- Inselspital Bern, University Hospital Bern, Department of orthopedic surgery and traumatology, University of Bern, Bern, Switzerland
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Simon Steppacher
- Inselspital Bern, University Hospital Bern, Department of orthopedic surgery and traumatology, University of Bern, Bern, Switzerland
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Guoyan Zheng
- ISTB, Institute for Surgical Technologies and Biomechanics, University of Bern, Bern, Switzerland
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Klaus Siebenrock
- Inselspital Bern, University Hospital Bern, Department of orthopedic surgery and traumatology, University of Bern, Bern, Switzerland
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Moritz Tannast
- Inselspital Bern, University Hospital Bern, Department of orthopedic surgery and traumatology, University of Bern, Bern, Switzerland
| Published: | October 22, 2019 |
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Outline
Text
Objectives: Although avascular necrosis of the hip (AVN) is a long-known pre-arthritic condition and many surgical treatment concepts have been proposed, a concise preoperative description of concomitant anterior or posterior femoro-acetabular impingement (FAI) is currently lacking. Patient-specific 3D hip impingement simulation can potentially answer these questions.
Therefore, we asked (1) what is the impingement-free hip range of motion in terms of flexion and internal rotation, (2) where are the (2) acetabular impingement zones, (3) femoral impingement zones and (4) femoral head coverage in hips with avascular necrosis of the femoral head compared to normal hips and hips with anterior FAI using 3D models of the hip.
Methods: This is an IRB-approved, retrospective, diagnostic study. The institutional database (12/2015-03/2018, 469 hips) was reviewed for patients with AVN who underwent complete radiographs and CT of the hip as part of our institutional routine protocol. 18 patients (20 hips; mean age 29 ± 6 years) met the inclusion criteria. CT and MRA of the hip was performed in all patients as part of our institutional routine protocol for staging of the disease.
CT of the pelvis and the distal femoral condyles was performed. Specific software was used for semi-automatic 3D reconstruction and for 3D impingement simulation, range of motion and location of femoral and acetabular impingement. Collision detection with the equidistant method was used for 3D impingement simulation.
Results:
- 1.
- Range of motion in terms of flexion (119 ± 16°, range 92 - 144) was significantly (p=0.046) decreased in patients with avascular necrosis of the femoral head compared to asymptomatic volunteers (125 ± 13°, range 103 - 146). ROM of patients with AVN and anterior FAI did not differ compared to patients with anterior FAI.
- 2.
- 52% of the acetabular impingement zones of patients with avascular necrosis are located on the 2 o clock position, 15% are located on the 3 o clock position, 15% are located on the 1 o clock position.
- 3.
- Most of the femoral impingement zones of patients with avascular necrosis are located on 2 o clock (18%), 3 o clock (20%) and 4 o clock (23%) position.
- 4.
- Femoral head coverage was 61%, inclination was 54° and anteversion was 15° in patients with avascular necrosis.
Conclusion: Anterior intraarticular and posterior extraarticular FAI can be combined with AVN. This is important for planning of hip preserving surgery because both can be corrected at the same time with open FAI surgery or hip arthroscopy.
