Management of Dynamic Hip Screw (DHS) Barrel Crossing the Fracture Site
When a Dynamic Hip Screw barrel crosses the fracture site, revision surgery with repositioning of the implant or conversion to a different fixation method is required to prevent mechanical failure and ensure proper fracture healing.
Understanding the Problem
The DHS barrel crossing the fracture site represents a technical complication that can lead to several adverse outcomes:
- Impaired sliding mechanism of the DHS, preventing controlled fracture compression
- Increased risk of implant cut-out through the femoral head
- Higher likelihood of mechanical failure and non-union
- Potential for varus collapse of the fracture
Diagnostic Evaluation
- Obtain immediate post-operative radiographs in anteroposterior and lateral views to confirm barrel position relative to the fracture line
- Assess the tip-apex distance (TAD), which should ideally be less than 25mm to minimize failure risk 1
- Evaluate the position of the lag screw in the femoral head (central-inferior position is optimal) 2
- Determine fracture stability pattern, as unstable fractures with improper barrel placement have significantly higher failure rates 3
Management Algorithm
1. For Stable Fracture Patterns with Minimal Displacement:
- Close monitoring with serial radiographs at 2,6, and 12 weeks
- Restricted weight-bearing until evidence of callus formation
- Consider early revision if any signs of:
- Progressive varus collapse >10°
- Lag screw migration >5mm
- Fracture displacement
2. For Unstable Fracture Patterns or Significant Displacement:
- Immediate revision surgery is indicated 4, 5
- Surgical options include:
- Repositioning of the DHS with correct barrel placement lateral to the fracture line
- Conversion to intramedullary fixation device (proximal femoral nail)
- For severely comminuted fractures in elderly patients, consider conversion to arthroplasty
Technical Considerations During Revision
- Ensure proper entry point and trajectory of the lag screw
- Position the barrel completely lateral to the fracture line
- Maintain the tip-apex distance <25mm 1
- Consider additional stabilization techniques for unstable fractures:
- Cerclage wiring for lesser trochanteric fragments 6
- Trochanteric stabilization plate for lateral wall fractures
- Bone grafting for significant bone defects
Perioperative Care
- Implement thromboprophylaxis with low molecular weight heparin 4
- Administer prophylactic antibiotics within one hour of skin incision 4
- Employ active warming strategies to prevent hypothermia 4
- Provide adequate analgesia with multimodal approach 5
- Consider regional anesthesia techniques when appropriate 4
Post-Revision Rehabilitation
- Begin early mobilization as tolerated based on fracture stability and fixation quality
- Implement weight-bearing restrictions based on:
- Fracture pattern (more restrictive for unstable patterns)
- Quality of fixation achieved during revision
- Bone quality (more restrictive in severe osteoporosis)
- Initiate physical therapy focusing on:
- Quadriceps strengthening
- Hip abductor exercises
- Gait training with appropriate assistive devices
Common Pitfalls to Avoid
- Failing to recognize the barrel crossing the fracture site on immediate post-operative radiographs
- Delaying revision in unstable fracture patterns
- Inadequate fixation during revision surgery
- Allowing early weight-bearing after revision of unstable fractures
- Not addressing associated lesser trochanteric or lateral wall fractures
Prognosis
The prognosis after revision surgery depends on:
- Patient age and bone quality
- Fracture pattern and stability
- Time between initial surgery and revision
- Quality of reduction and fixation achieved during revision
Early recognition and appropriate management of DHS barrel crossing the fracture site can significantly improve outcomes and reduce the risk of mechanical failure, non-union, and need for further surgical intervention.