Review Question - QID 219534

When subchondral collapse has occurred in the setting of osteonecrosis, arthroplasty is the most reliable long-term solution.

Osteonecrosis of the femoral head may occur idiopathically or after trauma that compromises the medial femoral circumflex artery. The Ficat staging system is used to classify avascular necrosis of the hip and to guide treatment. Patients, regardless of age, with subchondral collapse, as indicated by the crescent sign (Stage III) or more advanced degenerative changes, are most reliably treated with total hip arthroplasty (THA). Patients with lesions identified earlier in the disease process (Ficat stages 0-II) may be candidates for preservation procedures, including core decompression, rotational osteotomies, bone grafting, and vascularized fibula transfers.

Mont et al. wrote a current concepts review for nontraumatic osteonecrosis of the femoral head. They found that nonoperative treatment is ineffective at halting progression, that joint-preserving procedures should be attempted for pre-collapse lesions, and that THA outcomes for osteonecrosis are excellent. For post-collapse osteonecrosis, THA is the only treatment they recommend.

Yoon et al. updated an osteonecrosis of the femoral head staging system in 2019. They staged as follows: Stage 1: x-ray is normal, but either magnetic resonance (MRI) or bone scan is positive; Stage 2: x-ray abnormal (subtle signs of osteosclerosis, focal osteoporosis, or cystic change in the femoral head), but without any evidence of subchondral fracture, fracture in the necrotic portion, or flattening of the femoral head; Stage 3: fracture in the subchondral or necrotic zone as seen on x-ray or computed tomography (CT) scans. This stage is further divided into stage 3A (early, femoral head depression ≤ 2 mm) and stage 3B (late, femoral head depression > 2 mm); and Stage 4: x-ray evidence of osteoarthritis with accompanying joint space narrowing, acetabular changes, and/or joint destruction. This revised staging system does not incorporate the previous subclassification or quantitation parameters, but the panels agreed on the future development of a separate grading system for predicting disease progression.

Figure A is an AP pelvis plain radiograph demonstrating post-collapse osteonecrosis of the right femoral head.

Incorrect Answers:
Answers 1 and 4: These procedures may play a role in pre-collapse AVN.
Answer 2: Hemiarthroplasty would require early revision to THA given this patient's young age.
Answer 3: Hip resurfacing may play a role in treating small AVN lesions. This patient's chronic steroid use and large AVN lesion make him a poor candidate for hip resurfacing, and he would be at high risk of a periprosthetic femoral neck fracture.