Weight Bearing After Proximal Femoral Nail for Comminuted Intertrochanteric Fracture
Patients with comminuted intertrochanteric fractures treated with proximal femoral nail fixation should begin immediate weight bearing as tolerated starting on postoperative day one. 1, 2
Evidence-Based Weight Bearing Protocol
Immediate Postoperative Period (Day 1 Onwards)
Full weight bearing as tolerated is recommended immediately after surgery for all intertrochanteric fractures treated with cephalomedullary nail fixation, regardless of fracture stability or comminution pattern 1, 2
The AAOS guidelines specifically state this as a "limited strength option" based on available evidence, but it represents the current standard of care for these injuries 1
Patients naturally self-limit their weight bearing in the early postoperative period, typically bearing only 51% of normal weight on the injured limb at one week, gradually increasing to 87% by twelve weeks 3
Biomechanical Justification
Statically locked intramedullary nails with two distal locking screws demonstrate fatigue strengths exceeding 2100 newtons, which is sufficient to withstand immediate full weight bearing even in comminuted femoral shaft fractures 4
The proximal femoral nail construct provides adequate stability for immediate mobilization in unstable proximal femoral fractures when proper surgical technique is employed 5
Clinical Outcomes Supporting Early Mobilization
Studies demonstrate that immediate full weight bearing after PFN fixation does not increase nonunion rates (14.7% overall) or implant failure rates (4.4%), regardless of fracture complexity 6
Functional outcomes at 6 months show good results in 62.5% and excellent results in 28.1% of patients when early weight bearing is permitted 7
Early mobilization reduces complications associated with prolonged bed rest in elderly patients and may decrease hospital length of stay 4
Critical Caveats and Contraindications
When to Restrict Weight Bearing
- Do NOT allow immediate weight bearing if:
- Inadequate reduction was achieved intraoperatively (loss of medial cortical continuity or abnormal neck-shaft angle) 2
- Suboptimal implant positioning occurred (lag screw not within 5-10mm of subchondral bone, or use of inappropriately short proximal screws) 5
- Pathologic fractures are present, as bone healing will not occur and alternative treatment should be considered 2
Technical Factors Affecting Weight Bearing Decisions
Ensure anatomic reduction with restoration of medial cortical continuity before allowing weight bearing, as inadequate reduction leads to malunion and hardware failure 2
Verify proper lag screw positioning within 5-10mm of subchondral bone on intraoperative fluoroscopy, as two cases of cut-out occurred with inappropriately short screws 5
Confirm bicortical purchase of distal locking screws, as failure of interlocking screws (4.4% incidence) is more common in osteoporotic bone 6
Practical Implementation
Patient Instructions
Instruct patients to "weight bear as tolerated" rather than prescribing specific weight limits, as elderly patients naturally self-regulate loading based on pain and stability 3
Provide assistive devices (walker or crutches) for the first 2-3 weeks to aid balance and confidence, even though full weight bearing is permitted 1
Emphasize that progressive increase in weight bearing over 6-12 weeks is normal and expected 3
Monitoring and Follow-Up
Clinical follow-up at 6 weeks should assess weight bearing status, with most patients (93%) achieving full weight bearing by this timepoint 5
Radiographic follow-up should evaluate for signs of implant failure (screw back-out, nail bending) or loss of reduction, though these complications are rare with proper technique 4, 6
Refer patients for bone health evaluation and osteoporosis treatment, as this addresses the underlying pathology and reduces future fracture risk 1, 2