Challenging Orthopedic Case: Multiple Epiphyseal Dysplasia & Severe Hip Osteoarthritis
Key Takeaway
Multiple Epiphyseal Dysplasia (MED) in adults often presents with progressive joint pain, severe osteoarthritis, and gait abnormalities like Trendelenburg. A case of a 28-year-old male with a COMP gene mutation demonstrates advanced bilateral hip osteoarthritis, requiring thorough clinical examination and diagnostic imaging to manage the complex orthopedic implications of this skeletal dysplasia.
A 28-year-old male presents with a 5-year history of worsening bilateral hip pain, Trendelenburg gait, and limited ADLs. He was diagnosed with Multiple Epiphyseal Dysplasia (MED) at age 5. Examination reveals a fixed flexion contracture of 20 degrees and significantly restricted ROM. AP pelvis radiographs are shown below.
Describe the radiographic findings and discuss the underlying pathophysiology of his hip condition.
Candidate: The X-ray shows severe bilateral hip osteoarthritis. The femoral heads are flattened and enlarged, which is coxa magna/plana. The acetabula are shallow, suggesting dysplasia. There is complete loss of joint space and osteophyte formation. This is due to his underlying MED, which affects how his epiphyses grow, leading to early joint wear.
Focusing only on the "arthritis" without linking it to the systemic nature of MED. Candidates often fail to mention the "true" acetabular anatomy, the importance of the coxa magna morphology in surgical planning, or the specific genetic implications of the *COMP* mutation typically associated with Fairbank type MED.
Start by describing the skeletal architecture: "The radiographs demonstrate severe secondary osteoarthritis in a patient with MED, characterized by bilateral coxa magna, coxa plana, and profound acetabular dysplasia. The pathophysiology involves an autosomal dominant mutation—frequently in the COMP gene—causing disordered enchondral ossification. This leads to irregular, fragmented epiphyseal development, resulting in a non-spherical femoral head-acetabular mismatch. This incongruity drives premature, severe wear patterns, typically manifesting in the 3rd to 5th decade."
You have decided to proceed with a Total Hip Arthroplasty (THA). The CT scan shows a narrow medullary canal and significant distortion of the acetabulum. How does the presence of MED change your preoperative planning and your choice of implants?
Candidate: I would use the CT to template the cup size and femoral stem. Because the canals are narrow, I might need a smaller, perhaps custom or specialized, stem. I need to be careful with the acetabulum to find the true floor and avoid lateralizing the cup.
Neglecting the "Offset" and "Center of Rotation" restoration. Failing to mention intraoperative fluoroscopy for finding the true acetabular floor, or assuming standard components will fit, which leads to iatrogenic femoral fracture during stem insertion.
Structure the plan: 1. Acetabular: Focus on identifying the true hip center of rotation; use CT to assess bone stock for a cementless hemispherical cup and determine if augmentation/grafting is required. 2. Femoral: Anticipate narrow, potentially irregular canals; plan for smaller, tapered, proximally-coated stems to avoid fracture. 3. Biomechanics: Emphasize restoring femoral offset and limb length to address the pre-existing Trendelenburg gait. Mention the use of 3D templating to mitigate the risk of component malposition due to abnormal femoral version.
During the procedure, you have performed the osteotomy and are now preparing the acetabulum. What are the specific technical risks associated with THA in a patient with Multiple Epiphyseal Dysplasia, and how would you manage them?
Candidate: The main risks are breaking the femur during reaming because the bone is hard and the canal is narrow. Also, it's hard to find the right acetabular spot. I would use slow reaming, check with fluoroscopy, and release the soft tissues carefully to avoid nerve injury.
Failure to discuss the "Soft Tissue" component—contractures are significant in these patients. Candidates often overlook the need for extensive capsular release, which is essential to regain ROM and prevent early dislocation.
Identify four key domains: 1. Iatrogenic Fracture: Use incremental, conservative reaming/broaching of the femoral canal. 2. Component Positioning: Use fluoroscopy to ensure the cup is in the true acetabulum, not the false superior socket, avoiding vertical/retroverted placement. 3. Soft Tissue Balancing: Address the fixed flexion contracture and limited abduction via systematic releases of the posterior capsule and external rotators. 4. Neurovascular Safety: Be aware of potential anatomical shifts and exercise caution with aggressive retraction near the sciatic nerve.
