Scaphoid Nonunion — Vascularised Bone Graft (1,2-ICSRA and Medial Femoral Condyle)

Indication. An established scaphoid nonunion in which the proximal fragment is avascular, or one with a structural humpback deformity that a conventional graft cannot correct. The operation revascularises the proximal pole and restores scaphoid length and alignment, preventing progression to a SNAC wrist. Absolute indications for a vascularised graft - Established scaphoid nonunion with proximal pole avascular necrosis (AVN) confirmed by MRI or intraoperative assessment.

• Failed prior conventional (non-vascularised) bone grafting with persistent nonunion.
• Humpback deformity with greater than 3 mm scaphoid shortening or DISI greater than 15 degrees requiring structural correction.
• Proximal pole nonunion with sclerotic, cystic changes and poor bleeding points after tourniquet release. Relative indications - Nonunion of greater than 2 years duration with established proximal pole AVN.
• Smoker or patient with vascular risk factors where conventional graft has a lower expected success.
• High-demand patient (athlete, manual worker) where rapid revascularisation and union are prioritised.
• Revision of failed percutaneous screw fixation with bone loss and AVN. When a non-vascularised graft is sufficient. A waist nonunion without proximal pole AVN and minimal deformity (less than 2 mm shortening, DISI less than 10 degrees), a distal pole nonunion (excellent vascularity), an acute displaced fracture treated with ORIF plus cancellous graft, or a paediatric scaphoid nonunion (robust healing potential) do not need a vascularised graft. Contraindications. Absolute: advanced SNAC wrist Stage III or IV (capitolunate or radiolunate arthritis) — reconstruction will not address the arthritic pain; active infection at the wrist or donor site; a patient unable or unwilling to comply with prolonged immobilisation and rehabilitation. Relative: severe osteoporosis or bone loss precluding stable screw fixation; ipsilateral knee pathology precluding MFC harvest (consider an alternative donor); a heavy smoker unwilling to cease — counsel on markedly reduced union rates. The one decision that matters — which graft, and whether to add hardware:

Consent specifically for the union rate (80–95 percent for the 1,2-ICSRA, 85–100 percent for the MFC), the risk of pedicle failure (5–10 percent), donor-site morbidity (knee pain or instability with the MFC), persistent nonunion requiring a salvage procedure, progression to a SNAC wrist despite union, and the need for prolonged immobilisation (8–12 weeks). Setup. Supine with the arm abducted 90 degrees on a hand table. For the dorsal 1,2-ICSRA graft the forearm is pronated; for volar approaches it is supinated. A tourniquet is applied to the upper arm. Anaesthesia is a regional (axillary or supraclavicular) block or general anaesthesia — WALANT is not suitable for vascularised grafting because patient movement risks pedicle injury. Position a mini C-arm for true posteroanterior, lateral and scaphoid views throughout. Loupe magnification is mandatory — pedicle dissection is the whole game.

The goal: expose the nonunion through the dorsal snuffbox, confirm the proximal pole is genuinely avascular, elevate the 1,2-ICSRA pedicled graft from the distal radius while protecting the dorsal sensory branch of the radial nerve and the radial artery, correct the humpback and DISI with a volar trapezoidal wedge, and stabilise the construct with a central-axis headless compression screw. The exposure and pedicle work are laid out as the first steps below — they are the heart of the operation.

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Medial femoral condyle graft — the structural alternative. The MFC graft is harvested from the medial femoral condyle through a longitudinal incision over the medial epicondyle. The descending genicular artery (pedicle length 6–8 cm, vessel diameter 1.5–2.5 mm) is dissected to its origin from the superficial femoral artery and gives articular branches to the condyle plus a saphenous branch. A corticocancellous block up to 3 by 2 cm is elevated with a cuff of periosteum and muscle. - Free MFC graft: microvascular anastomosis end-to-side to the radial artery and vein in the snuffbox (or end-to-end to the dorsal carpal branch), then shaped, inset and fixed exactly as for the pedicled graft.

• Volar pedicled MFC: the descending genicular pedicle is dissected distally and routed through the interosseous membrane or a subcutaneous tunnel to the volar wrist, inset through a volar Henry approach. It avoids microsurgery but demands meticulous pedicle routing to prevent kinking at the elbow or forearm. When to choose the MFC over the 1,2-ICSRA: scaphoid shortening greater than 4 mm or a humpback requiring greater than 5 mm of volar wedge; proximal pole fragmentation or bone loss too large for the 1,2-ICSRA block; or a failed prior 1,2-ICSRA graft with persistent nonunion.

Rehabilitation | Phase | Timing | Immobilisation | Therapy | |-------|--------|----------------|---------| | 1 | 0–8 weeks | Short-arm thumb spica cast (10–14 weeks for an MFC free graft) | Protected active finger and thumb motion only; no wrist motion | | 2 | 8–12 weeks | Removable splint | Gentle active wrist motion once radiographic bridging appears | | 3 | 12–16 weeks | Splint for heavy tasks | Progressive strengthening, proprioception and grip exercises | | 4 | 16 weeks + | None | Graded return to function | Serial radiographs at 2, 6, 10 and 14 weeks assess graft incorporation and screw position; a CT at 12–16 weeks is the gold standard for confirming union before advancing rehabilitation, especially when radiographs are equivocal. Most patients return to heavy manual work or sport at 4–6 months when CT confirms solid union and full strength is recovered. Outcomes. Union runs at 80–95 percent for the 1,2-ICSRA pedicled graft and 85–100 percent for the MFC, with time to union of 8–16 weeks and 10–20 weeks respectively. Successful union with corrected alignment restores roughly 70–85 percent of contralateral grip strength and 60–80 percent of wrist motion. Factors associated with failure are persistent smoking (union drops to 60–70 percent), a severe humpback not corrected at surgery, inadequate debridement leaving sclerotic bone, intraoperative pedicle kinking or tension, and advanced SNAC (Stage II or greater) at the time of grafting. Complications

Scaphoid vascular anatomy — why the proximal pole is a watershed. The scaphoid receives its blood supply from the radial artery via dorsal and volar branches. The dorsal branch enters through the dorsal ridge at the waist and supplies the proximal 70–80 percent of the bone in retrograde fashion; the volar branch enters at the distal tubercle and supplies only the distal 20–30 percent. The proximal pole is therefore a vascular watershed, dependent on retrograde flow from the waist. A fracture at the waist or proximal pole disrupts that retrograde supply, and proximal pole AVN occurs in 30–50 percent of waist nonunions and in greater than 80 percent of proximal pole nonunions — the single most important predictor that a conventional graft will fail. 1,2-ICSRA pedicle anatomy. The 1,2-ICSRA arises from the radial artery 2–3 cm proximal to the radiocarpal joint and travels distally in the groove between the first and second extensor compartments, superficial to the extensor retinaculum. At the snuffbox it anastomoses with the radial artery or its dorsal carpal branch, allowing retrograde flow; the pedicle length is 2–4 cm. The bone block is a 1.5 by 1 cm corticocancellous graft from the dorsal distal radius between the first and second compartments. In 5–10 percent of wrists the vessel is hypoplastic or absent, and the 2,3-ICSRA or the fourth extensor compartment artery are the alternatives. Medial femoral condyle pedicle anatomy. The descending genicular artery arises from the superficial femoral artery just proximal to the adductor hiatus, giving articular branches to the medial femoral condyle and a saphenous branch. The pedicle is 6–8 cm long with a vessel diameter of 1.5–2.5 mm — suitable for microsurgical anastomosis — and the graft can be harvested as a corticocancellous block up to 3 by 2 cm. The descending genicular can also be dissected distally for a volar pedicled transfer through the interosseous membrane to the volar wrist. Carpal kinematics — humpback and DISI. On a true lateral radiograph the scaphoid long axis forms an angle of 30–60 degrees with the radius, and the lunate is colinear (radiolunate angle 0–15 degrees). In the humpback deformity the distal fragment flexes volarly while the proximal fragment extends with the lunate (DISI), and the scaphoid shortens by 3–8 mm. DISI greater than 15 degrees and scaphoid shortening greater than 3 mm are the thresholds for corrective grafting: uncorrected deformity causes abnormal loading across the radioscaphoid and scaphocapitate joints and predicts progressive SNAC arthritis even with solid union.

Natural history. Untreated scaphoid nonunion leads to predictable carpal collapse and degenerative change (the SNAC wrist) within 5–10 years, which is why a vascularised graft is indicated to prevent progression whenever the proximal pole remains viable enough to reconstruct.