Masquelet Induced-Membrane Technique for Segmental Bone Loss

Indication. A critical-size segmental bone defect that will not heal with simple grafting — most often an infected nonunion after radical debridement, but also post-traumatic loss after high-energy open fractures, aseptic defects after failed fixation, defects following tumour resection, and selected congenital pseudarthroses. Conservative care and primary bone work have usually already failed by the time this technique is reached. Primary indications - Post-traumatic segmental bone loss greater than 2 cm after high-energy open fractures (Gustilo IIIB/C)

• Infected nonunion with a bone defect after radical debridement (the most common indication)
• Aseptic nonunion with a segmental defect after failed prior fixation
• Bone defects after tumour resection (primary bone tumours or metastases) when limb salvage is planned
• Congenital pseudarthrosis of the tibia or other dysplastic segmental defects (selected cases) Contraindications - Absolute: active uncontrolled infection with systemic sepsis; an inadequate soft-tissue envelope that cannot be reconstructed; severe peripheral vascular disease precluding graft vascularisation; a patient unable or unwilling to comply with staged surgery and prolonged rehabilitation.
• Relative: defects less than 2 cm (direct autografting or acute shortening is preferable); defects greater than 8 to 10 cm in the tibia (bone transport or a free vascularised fibula may be superior); heavy smokers or poorly controlled diabetics (optimise first or consider an alternative). The one decision that matters — defect size. The length of the defect drives the choice of reconstruction:

Consent specifically for the two-stage nature of the procedure, autograft donor-site pain or morbidity, pin-site problems if an external fixator is used, a small risk of recurrent infection or graft resorption requiring further surgery, and a long timeline to union (6 to 12 months). Setup. Supine on a radiolucent table with a bump under the ipsilateral buttock for tibial or femoral defects; the arm is abducted on a hand board for upper-limb cases. Prep and drape to expose both the defect and the ipsilateral iliac crest donor site. Use a tourniquet only if absolutely necessary for visualisation, and release it before the final debridement assessment to confirm bleeding bone. Give broad-spectrum antibiotic prophylaxis (for example cefazolin plus vancomycin) in infected cases, continued until culture results guide targeted therapy.

The goal of stage one is to convert a contaminated, non-viable defect into a clean, stable cavity lined by an induced biomembrane; the goal of stage two, four to eight weeks later, is to remove the spacer, preserve that membrane intact, and pack the cavity with autograft that the membrane will then vascularise and consolidate. The exposure and radical debridement are the heart of the procedure — everything downstream depends on them.

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Rehabilitation | Stage | Timing | Weight-bearing | Key milestones | |-------|--------|----------------|----------------| | 1 (spacer in) | 0-6 weeks | As tolerated in the frame (lower limb); protected (upper limb) | Pin-site care daily; targeted IV antibiotics 4-6 weeks then oral suppression; soft-tissue or flap healing | | 2 (after grafting) | 0-6 weeks post-graft | Protected, 10-20 kg (lower limb) | Membrane healing; inflammatory markers trended down | | Consolidation | 6 weeks to 6 months | Progressive loading to full by 4-6 months (tibia) | Radiographs at 6-week intervals guided by callus; CT at 6 months if union uncertain | | Maturation | 6-18 months | Full activity; return to heavy labour or sport at 12-18 months | Union confirmed (6-9 months for 3-5 cm defects; 9-12 months for 5-8 cm defects) | Review clinically at 2, 6 and 12 weeks, then 3-monthly until union. Check inflammatory markers monthly until they normalise after stage two. Remove any remaining external fixator once internal fixation is stable and early callus is seen (typically 3-4 months after stage two). Complications

Outcomes. Masquelet's original 2000 description reported union in 35 of 35 patients with defects averaging 4.7 cm. Subsequent series have confirmed union rates of 80-95% for defects of 2-6 cm when radical debridement and stable fixation are achieved. The induced membrane is the biological engine that distinguishes the technique from grafting into a scarred bed. The induced membrane — why it works. The PMMA spacer provokes a foreign-body reaction that produces a highly vascularised, 1-2 mm thick membrane within 4-8 weeks. Histologically it contains abundant capillaries and venules oriented perpendicular to the spacer surface, fibroblasts and myofibroblasts, inflammatory cells, and high concentrations of VEGF, TGF-beta1, BMP-2, IGF-1 and SDF-1. These factors create an osteoinductive environment that promotes angiogenesis into the graft and differentiation of mesenchymal cells into osteoblasts. The membrane also acts as a mechanical barrier, preventing dispersion of the graft and protecting it from surrounding scar tissue. Common sites. The distal femur and proximal tibia (high-energy peri-articular fractures) and the tibial shaft (the most frequent site for infected nonunion after open fracture) dominate; the humeral shaft and forearm bones are less often involved but the technique is identical. The anteromedial tibial surface is subcutaneous and ideal for spacer placement and later membrane access, while the posterolateral compartment contains the posterior tibial neurovascular bundle. Choosing between techniques. Defect size, the infection environment, soft-tissue quality and patient factors together drive reconstruction choice:

Limitations of the Masquelet technique. It requires two major operations, carries autograft donor-site morbidity for large defects, and is not ideal for very long defects (greater than 8 cm), where transport or a vascularised graft is generally better. Smoking and poorly controlled diabetes increase failure across all of these methods and should be addressed before reconstruction.