Osteonecrosis is a degenerative joint condition caused by decreased blood flow to a bone to the point that the bone begins to break down. A potentially life altering condition, osteonecrosis most commonly affects the femoral head, knee, shoulder and ankle. Risk of developing osteonecrosis has been associated with increased corticosteroid use, alcohol abuse, sickle cell disease, human immunodeficiency virus, and other immunosuppressive diseases.
The most common site for an osteonecrotic lesion in the ankle is in the talus or distal tibia, with a high prevalence in younger patients. Osteonecrosis can be stratified into four Stages according to the Ficat and Arlet classification system:
Stage 1: no apparent evidence of the disease on radiographs, however changes can be seen on MRI
Stage 2: cystic and/or osteosclerotic lesions on radiograph with a normal contour of the talus AND no evidence of subchondral fractures
Stage 3: crescent sign or sunchondral collapse
Stage 4: end stage disease with a narrowing of the joint space and secondary changes in the distal tibia
The treatment options can be non-joint preserving procedures, such as arthrodesis, talectomy, and arthroplasty, or joint preserving techniques, such as core decompression or bone grafting, which are typically preferred for younger populations. One variation of core decompression, described as percutaneous drilling, has been the subject of recent attention as it has been successful in treating osteonecrosis in the femoral head, knee, shoulder, and ankle.
Researchers recently looked at a total of 101 subjects, eighty-one of which had no previous surgical procedure and twenty of which had unsuccessful prior ankle core decompression. All patients underwent 12 weeks of nonoperative management, including analgesics, partial weight bearing exercise, bone stimulators and orthosis, but continued to have pain and thus elected to undergo percutaneous drilling as an outpatient procedure. This technique differs slightly from other core decompression techniques in that it uses smaller drill bits and is thus less invasive and removes less bone.
Post-operatively, the patients followed the same protocols beginning with partial weight bearing for four weeks, full weight bearing thereafter, and no high impact activities for ten months. At the most recent follow up of these patients, there were significant improvements in the patient reported outcome measures and pain scores and 83 per cent of the ankles demonstrated no further progression of osteonecrotic lesions. Seventeen of the ankles had progressed to a more advanced stage, four of which were at joint collapse, however the presence of sickle cell disease and HIV was associated with this progression.