Tibial Malunion

Tibial malunion occurs when a tibial fracture heals in a non-anatomic position, causing deformity, functional impairment, or predisposition to arthritis. Correction requires systematic evaluation, preoperative planning (including CORA calculation), and appropriate osteotomy technique.

Definition

Malunion: Fracture that has healed in a non-anatomic position, causing:

• Deformity: Angular, rotational, or shortening
• Functional impairment: Gait disturbance, joint dysfunction
• Predisposition to arthritis: Abnormal joint loading

Acceptable alignment (tibial shaft fractures):

• Varus/valgus: Under 5 degrees
• AP angulation: Under 10 degrees
• Rotation: Under 10 degrees
• Shortening: Under 10mm

Malunion thresholds (indications for correction):

• Angular: Over 10-15 degrees (causes mechanical axis deviation)
• Rotational: Over 15-20 degrees (causes functional impairment)
• Shortening: Over 2cm (causes gait asymmetry)

Epidemiology

• Incidence: 5-10% of tibial shaft fractures develop malunion
• Location: Distal third most common (poor blood supply, difficult fixation)
• Age: Peak 20-40 years (high-energy trauma)
• Gender: Male predominance (2:1 ratio)
• Risk factors: High energy, open fracture, poor initial reduction, inadequate fixation

Mechanical Axis

Normal mechanical axis:

• Passes from center of femoral head through center of knee to center of ankle
• Should pass through knee center (medial to tibial spine)
• Deviation causes abnormal joint loading

Mechanical axis deviation (MAD):

• Normal: 0-10mm medial to knee center
• Significant: Over 10mm deviation
• Causes: Angular deformity, predisposes to arthritis

CORA Concept

Center of Rotation of Angulation (CORA):

• Definition: Intersection of proximal and distal anatomic axes
• Location: At apex of deformity
• Significance: Osteotomy at CORA corrects angulation without translation
• Calculation: Draw proximal and distal anatomic axes, identify intersection point

Osteotomy location:

• At CORA: Pure angular correction (no translation)
• Away from CORA: Creates translation deformity (undesirable)
• Planning: Use full-length standing radiographs to identify CORA

Pathophysiology

Angular malunion:

• Varus: Medial compartment overload, predisposes to arthritis
• Valgus: Lateral compartment overload, predisposes to arthritis
• Apex anterior: Knee hyperextension, gait disturbance
• Apex posterior: Knee flexion contracture, gait disturbance

Rotational malunion:

• Internal rotation: Foot progression angle abnormal, gait disturbance
• External rotation: Foot progression angle abnormal, gait disturbance
• Functional impact: Difficulty with activities requiring rotation

Shortening:

• Gait asymmetry: Compensatory mechanisms (pelvic tilt, equinus)
• Functional impact: Fatigue, back pain, joint overload

History

Symptoms:

• Pain: Joint pain (knee or ankle), activity-related
• Functional impairment: Gait disturbance, difficulty with activities
• Deformity: Visible deformity, leg length discrepancy
• Previous fracture: History of tibial fracture, treatment method

Risk factors:

• High-energy trauma
• Open fracture
• Poor initial reduction
• Inadequate fixation
• Non-compliance with treatment

Physical Examination

Inspection:

• Deformity: Visible angulation, rotation, shortening
• Gait: Antalgic, Trendelenburg, equinus (if shortening)
• Alignment: Standing alignment, leg length discrepancy

Palpation:

• Tenderness at malunion site
• Deformity palpable
• Previous surgical scars

Range of Motion:

• Knee ROM (may be limited if proximal)
• Ankle ROM (may be limited if distal)
• Foot progression angle (rotational assessment)

Special tests:

• Mechanical axis: Standing alignment assessment
• Rotation: Compare to contralateral (knee flexed 90 degrees)
• Length: Block test, tape measure

Associated Conditions

• Post-traumatic arthritis: Joint degeneration from abnormal loading
• Limb length discrepancy: Functional impact
• Gait abnormalities: Compensatory mechanisms

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.

Nonunion

10-15% incidence (opening wedge):

• Cause: Gap must heal, inadequate graft, poor fixation, smoking
• Prevention: Bone graft if gap over 1cm, rigid fixation, smoking cessation
• Management: Revision fixation with bone graft

Loss of Correction

5-10% incidence:

• Cause: Inadequate fixation, premature weight bearing, poor bone quality
• Prevention: Rigid fixation (minimum 6 cortices each side), protected weight bearing
• Management: Revision fixation if significant

Overcorrection/Undercorrection

10-15% incidence:

• Cause: Inadequate preoperative planning, poor intraoperative assessment
• Prevention: Meticulous planning, intraoperative verification (fluoroscopy, clinical)
• Management: Revision osteotomy if symptomatic

Immediate Postoperative

• Immobilization: Splint initially (2 weeks)
• Weight bearing: Depends on fixation
  • Closing wedge with rigid plate: May allow early weight bearing
  • Opening wedge: Protected weight bearing 6-12 weeks
  • Dome: Protected weight bearing 6-12 weeks
• ROM: Early knee and ankle ROM (immediate)
• PT: ROM exercises, strengthening

Rehabilitation Protocol

Weeks 0-2:

• Splint or cast
• Non-weight bearing or touch-down weight bearing
• Knee and ankle ROM exercises
• Ice and elevation

Weeks 2-6:

• Transition to walking boot (if distal)
• Progressive weight bearing (if fixation stable)
• Continue ROM and strengthening
• Balance and proprioception

Weeks 6-12:

• Progressive to full weight bearing
• Full ROM
• Progressive activity

Weeks 12+:

• Full weight bearing
• Return to activity (when union confirmed)
• Continue monitoring with serial X-rays

Union and Hardware Removal

Union timeline: Typically 3-4 months postoperatively.

Hardware removal: Consider if prominent or symptomatic, usually after union confirmed (6-12 months).

Overall Outcomes

Corrective osteotomy outcomes:

• Success rate: 85-90% (good correction, union)
• Functional outcomes: 80-85% return to pre-injury level
• Complications: 15-20% (nonunion, loss of correction, overcorrection)

Union rates:

• Closing wedge: 90-95% (inherently stable)
• Opening wedge: 85-90% (requires graft, higher nonunion risk)
• Dome: 85-90% (technically demanding)

Functional Outcomes

Return to activity:

• Timeline: 6-12 months postoperatively
• Rate: 80-85% return to pre-injury level
• Factors: Deformity severity, treatment method, rehabilitation compliance

Pain relief:

• Immediate: 70-80% pain relief with correction
• Long-term: Maintained if correction maintained
• Factors: Correction quality, arthritis presence

Long-Term Prognosis

Arthritis prevention:

• With correction: 80-85% prevent or delay arthritis
• Without correction: 50-60% develop arthritis at 10 years
• Risk factors: Deformity severity, joint involvement

Correction maintenance:

• Closing wedge: 90-95% maintain correction
• Opening wedge: 85-90% maintain correction
• Loss of correction: 5-10% (usually minor)

Factors Affecting Outcomes

Positive factors:

• Good preoperative planning (CORA calculation)
• Rigid fixation
• Adequate bone graft (if opening wedge)
• Complete rehabilitation

Negative factors:

• Inadequate planning
• Poor fixation
• Inadequate bone graft
• Smoking
• Premature weight bearing

Prevention

Primary prevention:

• Proper initial fracture reduction
• Adequate fixation
• Close follow-up during healing
• Early intervention if malunion developing

Secondary prevention (after malunion):

• Corrective osteotomy if indicated
• Prevent progression to arthritis
• Maintain function

Return to Sport

Criteria:

• Full union confirmed
• Full ROM (equal to contralateral)
• Strength greater than 90% of contralateral
• No pain or instability

Timeline: Usually 6-12 months postoperatively, depending on union and rehabilitation.

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

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 healed lower-leg fractures retained at least 5 degrees of malalignment, and 3D analysis after nailing (Boucher/Bhandari, PMID 12172277) found about 77% malaligned by convention - though most remain asymptomatic.
• 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.