Restoration of long bone defects treated with the induced membrane technique: protocol and outcomes

This prospective study was undertaken at a regional tertiary referral centre to evaluate the results of treatment of bone defects managed with the induced membrane (IM) technique. Inclusion criteria were patients with bone defects secondary to septic non-union, chronic osteomyelitis and acute fracture with bone loss. Pathological fractures with bone loss were excluded. Data collection included patient demographics, pathology, previous surgical intervention, size of bone defect, type of graft implanted, time-to-union and complications/reinterventions. The minimum time of follow up was 12 months. Forty-three patients (32 males) met the inclusion criteria with a mean age of 47.9 years (range 18-80 years). 22 patients had an acute traumatic bone loss associated with open fracture and 21 presented with an infected non-union or underlying osteomyelitis requiring bone excision. The most common microorganisms grown were staphylcoccous aureus and coagulase negative staphylococcous. The mean length of the bone defect area was 4.2 cm (range 2-12 cm). All patients were managed with the two stage technique receiving composited grafting (Autologous bone graft (Iliac crest/RIA), graft expander as required, osteoprogenitor cells, growth factor) during the second stage. There was one failure (humeral infected non-union) in a previous background of bone radiation that necessitated reconstruction with a free fibula vascularized graft. One patient had a fall and sustained implant failure (humeral defect) 3 months after reconstruction and following re-plating progressed to union 4 months later. Two patients required re-grafting due to failure of healing in one of the defect sides. One patient presented with a discharging sinus 2 years after successful healing of a tibial defect that was treated successfully with soft tissue and bone debridement without necessitating further interventions. One patient despite union (distal 1/3 tibia) underwent a below knee amputation due to a dysfunctional ankle/foot (previous foot compartment syndrome-regional pain syndrome). Of those patients, with lower limb injuries, 4 patients had leg length discrepancies of 1 cm, 1.5 cm, 2 cm (two patients) respectively. The mean time to radiological union was 5.4 months (range 2-12 months). The average time of healing of 1 cm bone defect was 1.24 months. Patients with upper limb reconstruction recovered earlier than those with lower limb injuries. At the latest follow up all patients were able to mobilize full weight bearing without residual pain. The induced membrane technique appears to be an alternative good option for the management of large bone defects secondary to acute bone loss or infected non-unions. The incidence of re-interventions was low in this challenging cohort of patients. The technique should be considered in the surgeon's armamentarium as it is effective and is associated with a low rate of complications.