Tibial Malunion

A tibial malunion is a fracture that has healed in a non-anatomic position, causing deformity, functional impairment, or a predisposition to arthritis. The deformity may be angular, rotational or shortening; the functional cost is gait disturbance and joint dysfunction; the arthritis follows abnormal joint loading. Correcting it requires systematic evaluation, preoperative planning that includes calculating the CORA, and the appropriate osteotomy technique.

Acceptable alignment and the threshold for correction. The alignment accepted when a tibial shaft fracture is treated is tighter than the deformity at which an established malunion is corrected. The two sets of numbers answer different questions, and the right-hand columns are the indications for correction.

Epidemiology. Between 5 and 10% of tibial shaft fractures develop a malunion. The peak age is 20-40 years, the years of high-energy trauma, and men outnumber women by 2:1. The distal third is the most common location, with poor blood supply and difficult fixation as the reasons. The risk factors are high-energy injury, an open fracture, poor initial reduction, inadequate fixation and non-compliance with treatment.

The mechanical axis. It runs from the centre of the femoral head through the knee to the centre of the ankle, and it does not pass through the middle of the knee. It normally lies about 8-10mm medial to the knee centre with a spread of roughly 7mm either side, so an axis passing up to around 15mm medial remains within the normal range.

Mechanical axis deviation (MAD). Deviation is significant when it lies medially well beyond that band, or when there is any appreciable lateral deviation. Angular deformity in the femur or the tibia causes it, deviation beyond the normal band causes abnormal compartmental loading, and sustained deviation predisposes to compartmental arthritis.

The CORA. The centre of rotation of angulation is the intersection of the proximal and distal anatomic axes, and it lies at the apex of the deformity. Calculate it by drawing both axes on full-length standing radiographs and identifying where they cross.

Why the CORA decides the osteotomy. An osteotomy at the CORA gives a pure angular correction, without translation. An osteotomy away from the CORA creates a translation deformity, which is undesirable.

Angular malunion. Varus overloads the medial compartment and valgus the lateral, and either predisposes to arthritis. In the sagittal plane an apex-anterior malunion causes knee hyperextension and an apex-posterior malunion a knee flexion contracture, each with a gait disturbance.

Rotational malunion. Internal or external, it makes the foot progression angle abnormal and disturbs gait, and the patient has difficulty with activities that require rotation.

Shortening. It produces gait asymmetry, compensated by pelvic tilt or equinus. The functional cost is fatigue, back pain and joint overload.

A malunion is described by deformity type, by severity and by location. Type determines the treatment approach, severity guides the treatment decision, and location determines the surgical approach and technique.

History. The complaints are activity-related joint pain at the knee or ankle, gait disturbance and difficulty with activities, and a visible deformity or leg length discrepancy. Establish the previous tibial fracture and how it was treated, and the risk factors listed above.

Inspection and palpation. Look for visible angulation, rotation and shortening, check standing alignment and leg length, and watch the gait, which may be antalgic, Trendelenburg, or equinus if the leg is short. Palpate for tenderness at the malunion site and a palpable deformity, and note previous surgical scars.

Movement. Knee movement may be limited by a proximal malunion and ankle movement by a distal one. The foot progression angle is the clinical measure of rotation.

Measuring the deformity. Every component must be assessed: angulation in the frontal and sagittal planes, rotation, shortening and translation. At the bedside:

• Mechanical axis - standing alignment assessment
• Rotation - compared with the contralateral side, knee flexed 90°
• Length - block test and tape measure

Differential diagnosis. The painful, deformed or symptomatic post-fracture lower leg is not always a malunion needing osteotomy. Distinguish the entities below before planning correction.

Radiographs. Full-length standing AP and lateral radiographs, hip to ankle, are essential. They show the mechanical axis, the angular deformity and limb length, and they are the films on which the CORA is calculated. Local AP and lateral views of the tibia show the malunion site and any previous hardware. The key measurements:

• Mechanical axis deviation (MAD)
• Anatomic axis angles
• Limb length discrepancy

CT. CT with 3D reconstruction is essential for preoperative planning. Its uses:

• 3D reconstruction - assesses multiplanar deformity, calculates the CORA and plans the osteotomy
• Rotation protocol - compares with the contralateral limb, quantifies the rotational deformity and plans a derotational osteotomy
• Intra-articular assessment - joint surface step-off and articular congruity, and planning of an intra-articular osteotomy if needed

Other imaging. MRI and bone scan are not routine and are indicated only for specific concerns. MRI assesses the articular cartilage when the malunion is intra-articular, and the soft tissues; a bone scan assesses for arthritis.

The decision. Assess every deformity component on full-length standing radiographs and CT, calculate the CORA and measure the MAD. If the deformity passes the thresholds in the overview, is symptomatic, or predisposes to arthritis, proceed with correction; if the patient is asymptomatic and the deformity minimal, consider observation.

Operative indications. The absolute indications are a symptomatic malunion with significant deformity, or a deformity past its threshold with the consequence that threshold carries: angulation with mechanical axis deviation, rotation with functional impairment, shortening with gait asymmetry. The relative indications are an asymptomatic malunion that predisposes to arthritis, and the patient's preference for correction. Surgery is elective, after the fracture has healed, at 6-12 months post-injury.

Non-operative treatment. Observation suits an asymptomatic malunion with deformity under the thresholds, a patient who prefers it, and a patient with medical contraindications to surgery. It consists of activity modification, orthotics if needed and serial monitoring, and the outcome is acceptable if the malunion is asymptomatic and the deformity minimal.

Planning and the operation. Choose the osteotomy type (closing wedge, opening wedge, dome) and the fixation (plate, nail or external fixator), and consider bone graft if an opening wedge gap is over 1cm. At surgery the osteotomy is made at the CORA, or at the planned location, and every component is corrected. Verify the correction intraoperatively by fluoroscopy and clinical assessment, then fix with a rigid construct.

A two-bone segment. Any plan to realign the tibia must account for the fibula. An intact, or separately malunited, fibula behaves as a lateral strut that tethers the tibia and blocks correction, and it is the most likely mechanical cause when a tibial osteotomy will not reach the planned alignment intraoperatively.

In the published series. The operative series in the evidence base routinely add a fibular procedure: Sanders performed a fibular osteotomy "as needed" during oblique tibial correction, and Hintermann corrected "malunion of the fibula" alongside the distal tibia in every case of his supramalleolar series.

When the fibula tethers correction.

• Angular correction (varus/valgus, especially at the middle and distal thirds) - the fibula resists closing or opening the tibial wedge to the planned angle
• Lengthening - a united fibula prevents distraction of the tibial segments
• Derotation - a solidly healed fibula resists rotating the distal tibial fragment
• Distal-third or ankle malunion - a short, externally rotated malunited fibula holds the talus in a malaligned position, so it must be osteotomised and realigned first to let the talus re-centre under the tibia, the same principle as correcting a malunited ankle fracture

Technique. Make the fibular osteotomy through a separate lateral incision, ideally at a different level from the tibial cut, to reduce the risk of tibiofibular cross-union or synostosis. An oblique cut allows some sliding for length and easier fixation. A proximal fibular osteotomy puts the common peroneal nerve at risk and a distal one the superficial peroneal nerve.

When not to. Do not osteotomise a fibula that is not tethering. For a short-segment sagittal (procurvatum or recurvatum) correction with a compliant fibula, an unnecessary cut simply adds a second bone to heal.

Overall, complications follow 15-20% of corrective osteotomies, among them nonunion, loss of correction and overcorrection.

When it goes wrong. A nonunion is managed by revision fixation with bone graft. Loss of correction needs revision fixation if it is significant, and over- or undercorrection a revision osteotomy if it is symptomatic.

The early phase. A splint is used initially, for 2 weeks, and knee and ankle movement starts immediately, with physiotherapy for range of motion and strengthening. Weight bearing depends on the fixation: a closing wedge held with a rigid plate may allow early weight bearing, whereas opening wedge and dome osteotomies need protected weight bearing for 6-12 weeks.

Rehabilitation protocol.

• Weeks 0-2 - splint or cast; non-weight bearing or touch-down weight bearing; knee and ankle range-of-motion exercises; ice and elevation
• Weeks 2-6 - walking boot if distal; progressive weight bearing if fixation is stable; continued range of motion and strengthening; balance and proprioception
• Weeks 6-12 - progression to full weight bearing, full range of motion, progressive activity
• Weeks 12+ - full weight bearing; return to activity once union is confirmed; continued monitoring with serial radiographs

Union and hardware. Union typically takes 3-4 months postoperatively. Consider hardware removal if it is prominent or symptomatic, usually after union is confirmed, at 6-12 months.

Overall. Corrective osteotomy succeeds, with good correction and union, in 85-90%, and 80-85% return to their pre-injury level at 6-12 months postoperatively. Return depends on deformity severity, treatment method and rehabilitation compliance.

By osteotomy. Union and maintenance of correction differ between the wedges.

Pain. Correction brings immediate pain relief in 70-80%, maintained in the long term if the correction is maintained. Pain relief depends on the quality of the correction and the presence of arthritis.

Arthritis. With correction, 80-85% prevent or delay arthritis; without it, 50-60% develop arthritis at 10 years. Deformity severity and joint involvement are the risk factors.

What predicts a good result. Good preoperative planning with the CORA calculated, rigid fixation, adequate bone graft for an opening wedge, and complete rehabilitation all favour it. Inadequate planning, poor fixation, inadequate bone graft, smoking and premature weight bearing work against it.

Prevention. Primary prevention is proper initial fracture reduction, adequate fixation, close follow-up during healing, and early intervention if a malunion is developing. Once a malunion is present, secondary prevention is corrective osteotomy if indicated, to prevent progression to arthritis and maintain function.

Return to sport. Usually at 6-12 months postoperatively, depending on union and rehabilitation, once the criteria are met:

• Full union confirmed
• Full range of motion, equal to the contralateral side
• Strength greater than 90% of the contralateral side
• No pain or instability

Global Epidemiology

• Tibial shaft fractures are among the most common long-bone fractures, with population incidence commonly quoted around 16-22 per 100,000 per year; high-energy diaphyseal injuries predominate in young men and fragility-type injuries in older women.
• Symptomatic malunion is a minority outcome but a recognised one: long-term cohorts (van der Schoot, PMID 8836057) found roughly half of 88 healed lower-leg fractures retained at least 5 degrees of malalignment while only 20% had any symptoms at 15 years, and a small 3D study after nailing (Boucher/Bhandari, PMID 12172277 - 13 patients) found about 77% malaligned by convention with no measurable functional penalty. The population signal is that most malalignment is tolerated; the 13-patient null is too small to prove it on its own.
• Distal-third deformity is the least forgiving because malalignment is referred to the ankle (Puno, PMID 1941305).

Side-by-Side Guidance

Registry and Outcome Notes

• No arthroplasty-style registry tracks corrective osteotomy itself, but national hip-and-knee registries (NJR UK, AJRR US, AOANJRR Australia, SHAR Sweden) capture the downstream end-points - arthroplasty for post-traumatic arthritis - that uncorrected malalignment can drive.
• High tibial osteotomy registry and series data inform the malunion debate on hinge fractures and loss of correction (e.g. lateral hinge fracture incidence around 24% in opening-wedge HTO, PMID 31273455), reinforcing the value of protecting the far cortex/hinge.

High- vs Limited-Resource Practice

• Well-resourced settings: CT with 3D reconstruction, computer-assisted / patient-specific guides, and hexapod circular frames for gradual multiplanar correction are routine options.
• Limited-resource settings: Correction relies on careful clinical and plain-radiograph planning, acute single-cut osteotomy with plate or nail fixation, and judicious use of simpler external fixators; the deformity-analysis principles are unchanged even where advanced imaging is unavailable.

Related pages: Tibial Shaft Fractures is where this problem is prevented — the acceptable-alignment thresholds argued over on this page are decided at the index operation, and the commonest source of malunion is a proximal-third fracture nailed in the classic apex-anterior, valgus position; Tibial Nonunion is the other failure of union and frequently coexists, which is why the Kane series carded above treats malunion and nonunion in the same breath; Malunion and Delayed Union covers the general principles across long bones; Deformity Analysis - CORA and MAD is the prerequisite for every plan here and holds the joint-orientation angles, the osteotomy rules and the mechanical-axis measurement in full — a correction planned without it is a guess; Taylor Spatial Frame, Hexapod Frame Deformity Correction and Ilizarov External Fixation are the gradual-correction alternatives to the acute osteotomies described here, and are the answer when deformity is multiplanar, when length must be regained, or when the soft tissues will not tolerate an acute correction; Limb Lengthening Principles for the shortening that usually accompanies angular malunion; Pilon Fractures and Tibial Plateau Fractures are the intra-articular injuries whose malunion is a different problem — an incongruent joint surface, not a bent bone, and not correctable by a diaphyseal osteotomy; Ankle Arthritis is the endpoint the Puno data say distal malunion drives, and the page to read before offering a supramalleolar osteotomy; Compartment Syndrome of the Leg is a real risk of acute correction and lengthening in a scarred limb; and Paediatric Rotational Profile for the torsional measurement technique, because a rotational malunion is diagnosed on CT against the contralateral side rather than estimated clinically.

The "safe" thresholds quoted in textbooks are pragmatic conventions, not hard biomechanical limits, and several long-running debates affect everyday decisions.