Induced membrane spontaneous osteogenesis leading to tibiofibular fusion: a study of case series and literature review

New bone formation along the induced membrane (IM) without classic bone grafts, known as induced membrane spontaneous osteogenesis (IMSO), has been observed in experimental studies and in a small number of patients. We present several unusual cases of tibiofibular fusion (TFF) caused by IMSO and discuss the possible mechanisms and clinical implications. Five patients with TFF above the distal tibiofibular syndesmosis caused by IMSO between January 2019 and September 2023 were retrospectively analyzed. All patients were male, with a mean age of 56.8 years (range: 51–62 years). All had traumatic tibial defects or concurrent infections. Four patients were treated using the two-stage induced membrane technique, and one patient was treated with the Ilizarov technique for tibial defects. Polymethylmethacrylate cement spacers were placed in the tibial defects and extended toward the fibula. A systematic literature review was conducted by searching PubMed and the Cochrane Library from January 2000 to December 2024, utilizing the search terms “Masquelet technique or IM or bone cement”, “spontaneous osteogenesis or bone formation without bone grafting”, and “patient or case”. No postoperative infection or recurrence of infection was observed during the 12–36 month follow-up period. The cement spacer was retained for 8 to 12 weeks. All tibial defects achieved healing, with a mean clinical healing time of 10.2 months (range: 8–12 months). The mean time to TFF without bone grafting was 8.2 months (range: 8–10 months). The mean time to full weight-bearing was 9.4 months. All patients reported satisfaction with their functional recovery. The literature search identified only five case reports involving seven cases of bone defect healing attributed to IMSO. Notably, no reports of TFF specifically caused by IMSO were found. This case series identifies a unique instance of TFF caused by IMSO. The mechanism likely involves osteogenic cell/factor provision via bone marrow overflow from graft sites or bone ends, enhancing the osteogenic function of the induced membrane. As this fusion develops more rapidly than the healing of the primary tibial defects, it can provide supplemental stability, supporting earlier rehabilitation. This graft-free, biologically driven fusion process represents a noteworthy phenomenon with potential implications for optimizing the management of segmental tibial defects.