Treatment of Healing Nondisplaced Medial and Posterior Malleolar Fractures at 4 Weeks Post-Injury
For nondisplaced fractures of both the medial and posterior malleoli identified on MRI at 4 weeks post-injury, continue conservative management with immobilization and protected weight-bearing, as these fractures demonstrate excellent healing rates with non-operative treatment when truly nondisplaced and stable. 1, 2
Initial Stability Assessment
The critical first step is confirming true stability, as the combination of medial and posterior malleolar involvement raises concern for ankle mortise disruption 3:
- Obtain weight-bearing mortise radiographs immediately to measure the medial clear space, which must be <4mm to confirm stability 3, 4
- Assess for any displacement >2mm on any view, as this mandates surgical consideration 3, 2
- Evaluate the posterior malleolar fragment size on CT if not already performed, as fragments comprising >25% of the tibial plafond surface area often extend to the medial malleolus and may require fixation 5, 6
Conservative Treatment Protocol
If stability is confirmed (medial clear space <4mm, no displacement >2mm), proceed with continued immobilization 1, 2:
- Continue cast immobilization for an additional 2-4 weeks (total 6-8 weeks from injury) to ensure adequate healing 1, 7
- Maintain non-weight-bearing or protected weight-bearing status until radiographic evidence of healing is demonstrated 1
- Obtain serial radiographs at 2-week intervals to monitor fracture healing and confirm maintenance of alignment 3
Surgical Indications
Immediate surgical referral is required if any of the following are present 3, 6, 2:
- Medial clear space >4mm on weight-bearing views, indicating deltoid ligament incompetence and mortise instability 3, 4
- Any fracture displacement >2mm on any radiographic view 3, 2
- Posterior malleolar fragment comprising >25% of tibial plafond with articular incongruity 5, 6
- Evidence of tibiotalar subluxation or loss of mortise congruency 6
Critical Timing Considerations
At 4 weeks post-injury, you are in the subacute phase (3 weeks to <6 months per ACR criteria), which affects management 8:
- If surgery becomes indicated, perform within 24-48 hours once soft tissue conditions permit, as further delay increases malunion risk 3
- The 4-week timeframe is still within the window for good surgical outcomes if instability is discovered, though earlier intervention is preferable 3
Common Pitfalls to Avoid
Failure to recognize occult instability is the most critical error in managing these combined fractures 3, 4:
- Do not rely solely on non-weight-bearing radiographs, as dynamic instability may only manifest with weight-bearing 3, 9
- Do not assume that "nondisplaced" on MRI equals "stable"—the combination of medial and posterior malleolar fractures disrupts ankle mortise stability more than either fracture alone 3
- Do not miss associated syndesmotic injury, which occurs in 15% of cases and requires additional fixation 8, 3
- Do not underestimate posterior malleolar involvement, as medial-extension type posterior malleolar fractures (19% of cases) can involve almost the entire medial malleolus 5
Follow-Up Protocol
For confirmed stable fractures managed conservatively 1, 7:
- Serial radiographs at weeks 6,8, and 12 post-injury to confirm healing progression 3, 1
- Transition to weight-bearing as tolerated once radiographic union is evident (typically 6-8 weeks) 1, 7
- Initiate structured rehabilitation with early mobilization once adequate healing is confirmed to prevent chronic instability 3
Expected Outcomes
Isolated medial malleolar fractures treated conservatively achieve union rates of 96.5% with mean functional scores of 89.8/100 when truly nondisplaced 1, 2. However, the addition of posterior malleolar involvement creates inherently less stability, making meticulous assessment of mortise integrity essential 3, 5.