Malunion, Delayed Union and Nonunion

Oligotrophic is the trap. It shows no callus on X-ray and looks avascular, but the bone scan is positive: the biology is there, the fragments are simply too unstable or too poorly apposed to bridge, and it is treated as a hypertrophic nonunion.

Vascular (hypertrophic) nonunions

Avascular (atrophic) nonunions

Non-Union Scoring System (NUSS), Calori et al., is the first multifactorial score for nonunion. It grades 15 items across three domains, bone condition, soft-tissue status and the patient's general health, to give a total from 4 to 100.

What the score is for. NUSS does not predict whether the nonunion will heal. It tells you how much treatment to bring, through Calori's "Ladder Strategy", built on the diamond concept of mechanics plus biology.

Representative components. This list is abbreviated. The published instrument has 15 items, so a score built from this list alone will read falsely low.

Paley (malunion). A malunion is classified by deformity analysis using the CORA, the centre of rotation of angulation, and the description has three parts: where the deformity is, in how many planes, and how complex the correction will be.

Level

• Articular (intra-articular malunion)
• Metaphyseal
• Diaphyseal

Plane

• Uniplanar (varus/valgus or sagittal only)
• Biplanar (oblique: combined coronal and sagittal)
• Multiplanar (includes a rotational component)

Complexity

• Simple: single CORA, no translation
• Complex: multiple CORAs, translation, rotation, or associated infection

Each modality answers a different question: the radiograph asks whether the fracture is bridging and the implant intact, the CT asks it precisely, and nuclear medicine and MRI ask whether the nonunion is infected.

Radiographs. Four views: AP, lateral and obliques, plus the joints above and below. Look for persistence of the fracture line (a visible gap), the callus pattern (hypertrophic versus atrophic) and implant failure: broken screws, a bent plate, a fractured nail.

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Laboratory workup. The bloods look for infection and for the metabolic reasons a fracture fails to heal:

• FBC, CRP, ESR (mandatory)
• Vitamin D level (under 50 nmol/L is associated with delayed healing)
• HbA1c (diabetic control)
• Albumin, prealbumin (nutritional status)
• Thyroid function tests (if a metabolic cause is suspected)

The differential. A painful fracture site months after injury is not always a nonunion, and a nonunion is not always aseptic.

A limited role. Once a nonunion is established (over 9 months) non-operative treatment is primarily adjunctive, and the adjuncts are weak. LIPUS (low-intensity pulsed ultrasound) has conflicting evidence: the TRUST trial (BMJ 2016) showed no benefit in fresh tibial fractures, and the evidence for established nonunions is weak. Electrical stimulation, capacitive coupling or pulsed electromagnetic fields, has weak evidence too.

Metabolic optimisation is the other adjunct: vitamin D replacement, smoking cessation and protein supplementation.

Indication. An aseptic hypertrophic femoral or tibial shaft nonunion. This is the gold standard for hypertrophic shaft nonunions, and it is minimally invasive.

Why it works. The operation supplies both halves of the diamond at once. Reaming deposits morselised autograft at the nonunion, the biological effect, and the larger nail that follows increases bending and torsional stiffness, the mechanical effect. The step-by-step technique, including how far to over-ream and up-size, is in Surgical Technique.

Indication. Atrophic nonunions, metaphyseal locations, and the forearm or humerus, where nailing is less ideal.

Judet decortication. The nonunion is widely exposed and an osteotome lifts shingles of cortical bone off the surface. That creates a bleeding vascular bed, and it is this bed, with a compression plate (LCP or DCP) across it and iliac crest autograft packed around it, that restores biology and stability together.

Graft options.

• Iliac crest autograft
• RIA (Reamer-Irrigator-Aspirator)
• Allograft (scaffold only)
• BMP-2 (osteoinduction only; expensive)

Indication. Large bone defects (over 3-4cm), or infected nonunions requiring resection. This is the standard for segmental defects, and it is done in two stages.

Stage 1 (debridement and spacer)

1. Radical debridement of all dead bone and infected tissue
2. Insert a PMMA cement spacer (with antibiotic if infected)
3. Stabilise with an external fixator or plate to maintain length
4. Allow the induced membrane to form over 6-8 weeks

Stage 2 follows at 6-8 weeks: the membrane is opened and preserved, the spacer removed, and the defect packed with cancellous autograft (RIA or iliac crest) inside the biological chamber before the membrane is closed over it. The steps are in Surgical Technique.

Indication. Infected nonunions, complex deformity, and large defects (bone transport). Frame treatment is reserved for complex cases.

The law of tension-stress (Ilizarov). Gradual traction on living tissues creates stress that stimulates regeneration and active growth. The frame applies it in three ways:

• Compression at the nonunion site to promote healing
• Distraction osteogenesis at a separate corticotomy site to restore length
• Bone transport, moving a segment of bone to fill a defect

The trade. A frame can treat infection, nonunion and deformity simultaneously, and it generates new bone without a graft. Against that, treatment is prolonged (the healing index below), pin-site infections occur, and the patient has to comply.

Setup. Supine on a traction table for the femur, or supine on a radiolucent table for the tibia, with the image intensifier positioned for AP and lateral views. Make sure the same brand of nailing system is available, to remove the old nail.

Procedure

1. Incision: use the previous incision over the nail entry point
2. Expose the nail: identify the end cap or locking screws
3. Remove hardware: remove the end cap and locking screws
4. Extract the nail: use the appropriate extraction device
5. Assess the canal: pass a flexible reamer to assess the nonunion site
6. Over-ream: ream to 1-2mm larger than the previous reamer size
7. Collect the reaming debris: this is the autograft
8. Insert a larger nail: 1-2mm greater diameter than the previous nail
9. Lock the nail: static or dynamic depending on stability, static initially; it may be dynamised later
10. Poller screws: consider them if the canal is wide or unstable

What matters. Do not strip the soft tissue at the nonunion site. The larger nail is critical, because the increase in stiffness is the mechanical half of the operation. Blocking screws improve alignment where the fracture extends into the metaphysis.

Setup. Supine with an arm table for the upper limb, or supine or lateral for the lower limb, with a tourniquet if the upper limb.

Procedure

1. Approach: use the appropriate surgical approach for the bone and location
2. Expose the nonunion: full exposure of the nonunion site
3. Debride: remove the fibrous tissue from between the bone ends
4. Decorticate: Judet shingling, lifting cortical shingles with an osteotome
5. Reduce: obtain an anatomical reduction of the bone ends
6. Apply the plate: a compression plate (LCP or DCP)
7. Compress: eccentric drilling or an articulated tension device for axial compression
8. Harvest graft: iliac crest or RIA for autograft
9. Apply graft: pack the graft around the nonunion site
10. Close: layered closure over a drain

What matters. Use a long plate with at least 8 cortices of purchase each side, put the compression screws nearest the nonunion, and onlay the graft circumferentially. The operation provides biological augmentation with mechanical stability.

Describing the deformity. A malunion has up to four components, and every one has to be measured before the correction is planned, because a correction that addresses three of them fails on the fourth.

Finding the CORA (centre of rotation of angulation). The correction is planned on long-leg radiographs, and the CORA is where the two mechanical axes meet:

1. Identify the mechanical axis on long-leg radiographs
2. Draw the proximal and distal joint orientation lines
3. Draw the proximal and distal mechanical axis lines
4. Their intersection is the CORA

Paley's osteotomy rules. An osteotomy at the CORA gives a simple angular correction and the realignment is perfect. An osteotomy away from the CORA needs translation as well as angulation.

Osteotomy types. Each type has a different effect on length and a different way of healing, which is what decides the choice.

Setup. Stage 2 is done 6-8 weeks after Stage 1, through the previous approach, with autograft harvest equipment (RIA or iliac crest) and internal fixation ready if converting from an external fixator.

Procedure

1. Incision: open the previous wound
2. Identify the membrane: preserve the induced membrane capsule
3. Open the membrane: a longitudinal incision in the membrane
4. Remove the spacer: extract the cement spacer carefully
5. Prepare the bed: light curettage of the bone ends
6. Harvest graft: RIA from the femur, or iliac crest
7. Pack graft: fill the defect completely with morselised cancellous graft
8. Close the membrane: repair the membrane over the graft
9. Stabilise: convert to internal fixation or maintain a stable frame
10. Close: layered closure

What matters. The membrane is the key biological component, so it is preserved, not discarded. Pack the graft tightly to fill all dead space, and fix stably, because graft incorporation depends on it.