Residency · Residency · Orthopedic Surgery

Nonunion and Malunion: Evaluation and Treatment Strategies

Definitions

Nonunion

The FDA defines nonunion as a fracture that has not healed by 9 months with no radiographic progress over 3 consecutive months. Clinically, it represents the cessation of biologic healing processes, meaning the fracture will not unite without further intervention. This is distinct from delayed union, which describes slower-than-expected healing that is nonetheless still progressing.

Malunion

A malunion is a fracture that has healed in a non-anatomic position, involving deformity in angulation, rotation, translation, or shortening. Symptomatic malunion requires corrective osteotomy, while asymptomatic malunion may be observed.

Classification of Nonunion

Weber-Cech Classification (Biologic)

Hypertrophic Nonunion (Viable)

Hypertrophic nonunions have adequate blood supply and biologic healing response. The problem is purely mechanical: insufficient stability. Radiographically, they show abundant callus in an "elephant foot" or "horse hoof" pattern. Treatment focuses on improving mechanical stability through compression plating or exchange nailing. Bone grafting is not needed because the biology is intact.

Oligotrophic Nonunion

Oligotrophic nonunions show some biologic potential but an insufficient healing response, often resulting from inadequate reduction that left a gap at the fracture site. They display moderate callus formation. Treatment requires both mechanical stability and biologic augmentation through stable fixation combined with bone grafting.

Atrophic Nonunion (Avascular)

Atrophic nonunions have poor or absent blood supply to the fracture site. Radiographs show no visible callus, with tapered, sclerotic bone ends. The problem is fundamentally biologic: the healing capacity has been exhausted. Treatment requires debridement of sclerotic bone ends back to viable bleeding bone, opening of the medullary canal, stable fixation, and bone grafting to restart the healing cascade.

Infected Nonunion

Infected nonunion involves concurrent or prior infection at the fracture site. Infection should be assumed until proven otherwise, as it is the most commonly missed cause of nonunion. Management requires a staged approach: eradicate the infection first, then proceed with reconstruction.

Synovial Pseudarthrosis

Long-standing nonunions may develop a synovial-lined cavity with fluid filling the gap between bone ends. Treatment requires excision of the pseudarthrosis membrane, bone grafting, and rigid internal fixation.

Evaluation

History

A thorough history addresses the mechanism of original injury and prior treatment, smoking status (the most important modifiable risk factor), nutritional status, diabetes control, medication use (particularly NSAIDs, steroids, and anticonvulsants), history of wound complications or prior irrigation and debridement procedures, and patient compliance with weight-bearing restrictions and rehabilitation.

Imaging

Plain radiographs (AP, lateral, and oblique views) assess callus formation, fracture line persistence, and hardware integrity; serial comparison is essential to determine whether healing is progressing. CT scan is the gold standard for evaluating bridging callus and can quantify the percentage of cortical bridging (less than 25% suggests nonunion), identify sclerotic bone ends and fracture gaps, and detect hardware failure or screw loosening. MRI is useful for assessing vascularity and detecting infection. Nuclear medicine studies (bone scan or WBC-labeled scan) aid in infection assessment.

Laboratory Workup

An infection screen includes ESR, CRP, and WBC with differential. Elevation of ESR and CRP in the absence of other causes suggests occult infection. Aspiration of the nonunion site for culture (aerobic, anaerobic, fungal, and AFB) provides definitive microbiologic diagnosis. A metabolic workup should include 25-hydroxyvitamin D (deficiency is present in up to 75% of fracture patients), calcium, phosphate, magnesium, PTH (to detect hyperparathyroidism), thyroid function (hypothyroidism impairs healing), albumin and prealbumin (nutritional status), and HbA1c (diabetes control). Nicotine metabolites (cotinine) should be checked to confirm smoking cessation.

The Diamond Concept of Fracture Healing

Successful fracture healing requires four elements: mechanical stability (appropriate fixation), osteogenic cells (viable cells capable of forming bone), an osteoconductive scaffold (matrix for cell attachment and growth), and osteoinductive signals (growth factors such as BMPs and TGF-beta that stimulate differentiation). Nonunion results when one or more of these elements is deficient. Treatment must identify and address all deficient elements simultaneously.

Treatment Strategies

Hypertrophic Nonunion

The problem is mechanical instability, and the solution is enhanced stability. Exchange nailing is highly effective for diaphyseal nonunions that developed after IM nailing: the existing nail is removed, the canal is reamed to a larger diameter (at least 2 mm greater), and a larger nail is inserted. The reaming debris provides autologous bone graft at the fracture site. Success rates range from 70-95% for hypertrophic femoral and tibial nonunions. Compression plating is an alternative for nonunions amenable to plate fixation, using lag screws for interfragmentary compression. Dynamization (removal of interlocking screws) allows axial compression but is appropriate only when cortical contact exists without bone loss, and carries the risk of shortening in comminuted fractures.

Atrophic Nonunion

The problem is biologic failure, requiring enhanced biology combined with stable fixation. Sclerotic bone ends are debrided back to bleeding viable bone. The medullary canal is opened through drilling or reaming. Bone graft is applied along with stable fixation.

Bone Grafting Options

Autograft

Autologous bone graft remains the gold standard, uniquely providing osteogenic, osteoinductive, and osteoconductive properties. Iliac crest bone graft (ICBG) is the most common source, with anterior harvest offering easier access and smaller incisions, and posterior harvest providing larger volumes with less risk of lateral femoral cutaneous nerve injury. Donor site complications include pain (10-25%), hematoma, infection, nerve injury, and fracture. The Reamer-Irrigator-Aspirator (RIA) harvests graft from the femoral or tibial medullary canal, providing higher volumes than ICBG with less donor site morbidity. It contains osteoprogenitor cells and growth factors but carries risks of iatrogenic fracture and embolization.

Allograft

Allograft provides osteoconductive properties only, without viable cells. Cancellous chips fill defects and provide a scaffold for host bone ingrowth. Structural cortical struts augment fixation and provide mechanical support. Disease transmission risk is extremely low with modern processing.

Bone Morphogenetic Proteins (BMPs)

BMP-2 (rhBMP-2, marketed as Infuse) is FDA-approved for open tibial fractures and lumbar fusion. BMP-7 (OP-1) has a humanitarian device exemption for long bone nonunion with limited availability. These are potent osteoinductive agents, but their use is controversial: off-label use is widespread, and complications include heterotopic ossification, excessive soft tissue swelling, theoretical malignancy concerns, and wound problems. Cost-effectiveness is debated, and BMPs should not substitute for good surgical technique.

Demineralized Bone Matrix (DBM)

DBM is processed allograft that retains endogenous growth factors, providing both osteoinductive and osteoconductive properties. Available as putty, gel, or strips, its biologic potency varies between manufacturers and lots.

Masquelet Technique (Induced Membrane)

The Masquelet technique is a two-stage procedure for segmental bone defects exceeding 2 cm. In Stage 1, the defect is debrided and filled with a PMMA cement spacer. Over 6-8 weeks, a biologically active membrane (the induced membrane) forms around the spacer, rich in VEGF, BMP-2, and TGF-beta. External fixation or plate maintains alignment during this period. In Stage 2, the cement spacer is removed while carefully preserving the membrane intact. The membrane tube is then packed with cancellous autograft (from RIA or ICBG). The membrane acts as a biologic chamber that prevents graft resorption, supplies growth factors, and vascularizes the graft. Success rates reach 80-90% for defects up to 25 cm. This technique represents an alternative to distraction osteogenesis for large defects.

Distraction Osteogenesis (Ilizarov Method)

Bone transport using a ring fixator or monolateral frame slowly distracts new bone through a corticotomy site at a rate of 1 mm per day (in 0.25 mm increments, four times daily). New bone forms in the distraction gap. This technique allows simultaneous correction of length, alignment, and rotation, making it suitable for segmental defects and complex nonunions with deformity. However, it requires prolonged treatment time and external fixation, with complications including pin site infection, joint stiffness, regenerate fracture, and significant psychosocial burden.

Adjunctive Treatments

Low-intensity pulsed ultrasound (LIPUS) stimulates osteogenesis and is FDA-approved for fresh fractures and nonunions, though evidence for established nonunions is limited. Electrical stimulation (direct current, capacitive coupling, or pulsed electromagnetic fields) may benefit some patients but evidence remains weak. Extracorporeal shockwave therapy is an emerging modality whose mechanism is not fully understood.

Malunion Management

Evaluation

Assessment determines clinical significance through evaluation of pain, functional limitation, adjacent joint arthrosis, and cosmetic concerns. Radiographic assessment measures angular, rotational, and translational deformity on full-length views. CT with 3D reconstruction characterizes complex deformities. Comparison to the contralateral limb provides a reference standard.

Corrective Osteotomy Principles

Preoperative planning identifies the center of rotation of angulation (CORA). Performing the osteotomy at the CORA allows correction without creating secondary translational deformity. Options include opening wedge, closing wedge, or dome osteotomy depending on the deformity characteristics. Fixation is achieved with plates, nails, or external fixators depending on location and complexity. Opening wedge osteotomies require bone graft to fill the gap. Computer-assisted planning and patient-specific cutting guides improve accuracy for complex corrections.

Common Malunion Locations

Distal radius malunions with extra-articular dorsal angulation are corrected with osteotomy and volar plate fixation. Femoral shaft rotational malunions exceeding 15 degrees require derotational osteotomy. Tibial shaft angular malunions greater than 5 degrees are treated with osteotomy and fixation. Clavicle malunions with shortening exceeding 2 cm and functional limitation are managed with osteotomy and plating.

<image>A comparative radiographic illustration showing hypertrophic versus atrophic nonunion of a tibial shaft fracture. On the left, show a hypertrophic nonunion with abundant callus forming an elephant-foot pattern around the fracture site, a visible fracture line, and hardware (IM nail) in situ with a broken interlocking screw indicating instability. On the right, show an atrophic nonunion with sclerotic tapered bone ends, absent callus, a clear persistent fracture gap, and a well-fixed plate construct. Label the key distinguishing features and indicate the treatment approach for each: improve stability for hypertrophic, enhance biology for atrophic.</image>

<image>A step-by-step illustration of the Masquelet induced membrane technique for a segmental tibial bone defect. Stage 1 (left panel): show the debrided bone defect with a PMMA cement spacer filling the gap, external fixation maintaining alignment, and arrows indicating the biologic membrane forming around the spacer over 6-8 weeks. Stage 2 (right panel): show the cement spacer being removed while preserving the induced membrane tube, the membrane cavity packed with morselized cancellous autograft (from RIA or iliac crest), and definitive fixation (plate or nail). Label all key components and the timeline.</image>

<image>A diagram of the Diamond Concept for fracture healing showing four overlapping circles: mechanical stability (fixation), osteogenic cells (MSCs, osteoblasts), osteoconductive scaffold (bone graft matrix), and osteoinductive signals (BMPs, growth factors). At the center where all four overlap, label "Successful Bone Healing." For each circle, list the clinical interventions that address that element: stability (plates, nails, external fixation), cells (autograft, bone marrow aspirate), scaffold (allograft, synthetic substitutes), signals (BMP, PRP, DBM).</image>

Clinical Pearls

Always rule out infection as a cause of nonunion because it is the most commonly missed diagnosis; obtain ESR, CRP, and aspiration cultures before planning reconstruction. Smoking is the most important modifiable risk factor, and cessation approximately doubles the likelihood of achieving union. Hypertrophic nonunion is a mechanical problem (add stability) while atrophic nonunion is a biologic problem (add biology); confusing the two leads to failed treatment. Exchange nailing is highly effective for diaphyseal hypertrophic nonunion and should include reaming up by at least 2 mm with insertion of a larger nail. Vitamin D deficiency is present in up to 75% of fracture patients and should be screened for and replaced. BMP-2 is powerful but carries real risks and should be used judiciously, never as a substitute for good surgical technique and proper bone grafting. The Masquelet technique has revolutionized management of large segmental defects because the induced membrane is biologically active, not merely a passive barrier. When performing corrective osteotomy for malunion, planning the cut at the CORA minimizes secondary translational deformity.

References

• Giannoudis PV, Einhorn TA, Marsh D. Fracture healing: the diamond concept. Injury. 2007;38 Suppl 4:S3-6.
• Masquelet AC, Begue T. The concept of induced membrane for reconstruction of long bone defects. Orthop Clin North Am. 2010;41(1):27-37.
• Brinker MR, O'Connor DP. Exchange nailing of ununited fractures. J Bone Joint Surg Am. 2007;89(1):177-188.
• Bishop JA, et al. Assessment of compromised fracture healing. J Am Acad Orthop Surg. 2012;20(5):273-282.
• Calori GM, et al. Non-unions. Clin Cases Miner Bone Metab. 2017;14(2):186-188.

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