A 59-year-old female presented to our clinic in November 2011 for a second opinion regarding complaints of right foot and ankle pain. She stated that the pain had started approximately 1 year earlier and denied any trauma preceding the event. The patient described the pain as both aching and sharp, rating it as 8 of 10 on a visual analog scale, and that it was aggravated with standing and walking. Temporary immobilization in a below-the-knee boot and nonsteroidal anti-inflammatory drugs did not alleviate her symptoms. Physical examination revealed pain on palpation of the right anterior tibia just proximal to the ankle joint. She denied any pain with passive range of motion to her right ankle joint. Her neurovascular status was fully intact, with no signs of vascular disease to her lower extremities.
The patient had a remote history of ulcerative colitis that had been in remission for nearly 20 years. During the acute stage of the condition, she had been taking high doses of oral corticosteroids. The rest of her medical history and family history were unremarkable. She did not use any tobacco products, although she reported drinking alcohol occasionally. She took iron and vitamin D supplements. She also reported allergies to gluten and sulfa medications.
The previous surgeon she had consulted had ordered a magnetic resonance imaging study and diagnosed AVN of the bilateral distal tibias (Fig. 1 ). Subsequent magnetic resonance imaging studies showed ON in the left calcaneus and right humerus. Only her right tibia was symptomatic. For preoperative planning and to rule out any pathologic fractures, a computed tomography scan was ordered (Fig. 2 ).
The patient was placed on the operating room table in a supine position with a tourniquet on the right proximal thigh and the right leg placed in a thigh holder. After induction of general anesthesia, the patient's right foot was inserted into an ankle distractor, and the ankle was accessed through standard anteromedial and anterolateral portals. Arthroscopy revealed abundant hypertrophied synovitis in the lateral aspect of the ankle joint. On debridement of the synovitis, an osteochondral defect measuring approximately 5 mm in diameter was noted on the anteromedial shoulder (Fig. 3 ). This was subsequently micro-fractured in standard fashion until active bleeding was noted from the subchondral bone of the lesion. On extensive examination using arthroscopy, it was also noted that the tibial articular surface showed no signs of fracture or penetration into the ankle joint. The portal incisions were then closed with 4-0 monofilament suture (Prolene , Johnson & Johnson Medical Ltd, Livingston, UK).
An 8-cm liner incision was made along the anterior aspect of the distal tibia just lateral to the course of the anterior tibial tendon (Fig. 4 ). Dissection was carried down to expose the anterior aspect of the distal tibia, and the periosteum was reflected in a medial and lateral direction. A cortical window measuring approximately 3 cm in length and 2 cm in width was then carefully reflected using a sagittal saw (Fig. 5 ). Care was taken to bevel the cut so as to stabilize the cortical window. Once the cortical window was removed, a combination of rongeurs and curettes was used to remove all the necrotic bone. Once all the necrotic bone had been removed, which was noted to be quite spongy in consistency, an approximately 10-cm3 deficit was left to fill (Fig. 6 ). Specimens of the necrotic bone were sent for both culture and histopathologic examination for further evaluation.
The defect was filled with AlloStem  Stem Cell Bone Growth Substitute (AlloSource, Centennial, CO), and geneX  bone putty (Biocomposites Inc., Wilmington, NC; Fig. 7 ). Once this composite was dry, the cortical window was placed back into its original location and secured with a Synthes/Depuy Mesh Plate (Synthes, Inc., West Chester, PA) to act as a buttress plate. The advantage of this plate was that it can be easily cut and contoured to fit the size of the defect. The plate was secured with a combination of 2.7-mm unicortical and bicortical locking screws, with only 1 screw going directly through the cortical window (Fig. 8 ). Excellent stability was noted before the wound was closed. The wound was then copiously flushed and closed in standard fashion. The patient was placed into a non-weightbearing posterior splint and subsequently discharged home the next day after staying in the hospital for a 23-hour observation period.
The patient was maintained non-weightbearing in the posterior splint for 2 weeks and then transitioned to a removable cast boot for an additional 5 weeks. While in the removable cast boot, the patient was instructed to begin range of motion exercises of her ankle. At 7 weeks, the patient began protective weightbearing in the removable cast boot and started physical therapy. At 9 weeks, the patient began to wean herself out of the removable cast boot into normal shoe gear. Radiographs and computed tomography scanning showed excellent consolidation of the defect with native bone incorporation (Fig. 9 ). The patient began light exercise activity at 11 weeks and returned to work. The cultures and pathology specimens confirmed the diagnosis of ON with no infection present (Fig. 10 ). The patient was subsequently discharged from care at 16 weeks postoperatively, with minimal swelling and no pain. She was instructed to continue with physical therapy to improve her ankle range of motion. The patient was interviewed by telephone at 24 months postoperatively and reported she was doing well with no pain in the right leg or ankle. Final radiographs were also taken at that time and showed excellent deficit incorporation with native bone visible (Fig. 11 ).