[Classification and Ilizarov reconstruction strategies for post-infectious calcaneal bone defects]

To retrospectively analyze the clinical data of patients with post-infectious calcaneal bone defects from multiple centers and to propose a clinical classification system and corresponding reconstruction strategies for calcaneal bone defects following infection.

A retrospective analysis was performed on 94 patients with post-infectious calcaneal bone defects treated at five hospitals between January 2017 and June 2025. The study population consisted of 61 males and 33 females, with a mean age of 36.5 years (range, 15-65 years). There were 67 cases of open calcaneal fractures and 27 cases of closed calcaneal fracture. The infections were located at the calcaneus alone in 71 cases, both the calcaneus and talus in 20 cases, and the calcaneus, talus, and tibia in 3 cases. The disease duration was 7-68 months (mean, 42.7 months). A staged treatment protocol was adopted. The first stage involved radical debridement and implantation of antibiotic-loaded bone cement for bone defect management. After infection control, secondary reconstruction was performed according to the extent of calcaneal bone loss and the condition of adjacent bones surrounding the calcaneus. The recurrent infection, repeat debridement, amputation or limb salvage, duration of external fixation, occurrence of abnormal bone transport trajectories, pin tract infections, displacement, and the need for repeat corrective or fusion surgeries were recorded. Functional outcomes at last follow-up were evaluated using the American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot score.

Based on the integrity of the major weight-bearing cortical framework of the calcaneus after debridement, the proportion of calcaneal bone loss, hindfoot deformity, subtalar joint involvement, and the condition of adjacent bones, the bone defects were classified into four types with eight subtypes. Among the 94 patients, there were 28 cases of type Ⅰ, 16 cases of type ⅡA, 5 cases of type ⅡB, 13 cases of type ⅢA, 9 cases of type ⅢB, 9 cases of type ⅣA, 11 cases of type ⅣB, and 3 cases of type ⅣC. All patients were followed up 12-63 months (mean, 25.6 months). One patient (type ⅣC) underwent amputation because of intolerance to bone transport. Seven patients experienced recurrent infection; infection was controlled after debridement in 5 patients, whereas 2 (type ⅢB and type ⅣB) eventually underwent amputation. Ultimately, 91 limb-salvage patients completed the second-stage treatment and were included in the outcome assessment at last follow-up. The duration of external fixation ranged from 6 to 13 months (mean, 7.7 months). Three patients developed abnormal bone transport trajectories, which were corrected after adjustment of the external fixator. Seven patients developed pin tract infections, which healed after local treatment and oral antibiotics. Two patients experienced 1-2 mm displacement after screw fixation. At last follow-up, the functional outcomes were assessed using the AOFAS ankle-hindfoot score; there were 10 cases of excellent and 18 cases of good in type Ⅰ patients; 7 cases of excellent, 13 cases of good, and 1 case of fair in type Ⅱ patients; 4 cases of excellent, 11 cases of good, and 6 cases of fair in type Ⅲ patients; 11 cases of good, 9 cases of fair, and 1 case of poor in type Ⅳ patients.

The proposed four-type eight-subtype classification system, based on the integrity of the major calcaneal weight-bearing structure after debridement, the proportion of calcaneal bone loss, hindfoot deformity, subtalar joint involvement, and the condition of adjacent bones, may provide a reference for stratified reconstruction of post-infectious calcaneal bone defects.