Plating of Distal Femur Fractures by Far Cortical Locking Using MotionLoc Screws

• Fracture Healing [ Time Frame: 6, 12, and 24 weeks post surgery ] [ Designated as safety issue: No ]
  Fracture healing is defined clinically by the ability of pain-free weight bearing, and radiographically by callus formation and bridging.
  
  

• Periosteal Callus Size [ Time Frame: 6, 12, 24 weeks post surgery ] [ Designated as safety issue: No ]
  Periosteal callus size is assessed at the anterior, posterior, and medial aspects on radiographs using a validated computational algorithm.
  
  
• Bridging Callus from CT [ Time Frame: 12 weeks post surgery ] [ Designated as safety issue: No ]
  Cross-sectional image analysis, supported by 3-D rendering, to detect bony bridging at the anterior, posterior, and lateral aspects of the femur.
  
  
• Fixation Failure [ Time Frame: 24 weeks post surgery ] [ Designated as safety issue: No ]
  Assessed in terms of loss of alignment at 12 and 24 weeks post surgery
  
  
• Hardware failure [ Time Frame: 6, 12, 24 weeks post surgery ] [ Designated as safety issue: No ]
  Breakage of screw or plate
  
  

Rigid locked plating constructs can suppress fracture healing, particularly at the near cortex adjacent to the plate where interfragmentary motion is minimal. Dynamic fixation with Far Cortical Locking (FCL) screws reduces construct stiffness and induces axial interfragmentary motion to stimulate symmetric callus formation and healing. Two versions of FCL screws are commercially available, but the clinical durability of this novel concept has not been documented to date. This prospective observational study documented our early clinical experience with MotionLoc® FCL screws for stabilization of distal femur fractures to assess their durability and potential complications.

Thirty-two consecutive patients with 33 distal femur fractures (AO/OTA types 33-A and 33-C) were prospectively enrolled at three trauma centers. Fractures were stabilized by plate osteosynthesis with MotionLoc® FCL screws without supplemental bone graft or bone morphogenic proteins. Thirty patients with 31 fractures were available for follow-up until union or revision. Follow-up visits at 6, 12, and 24 weeks comprised functional and radiographic assessment of implant fixation and fracture healing, including computed tomography scans at week 12. The primary endpoint was fracture healing in absence of complications and revision.

There was no incidence of implant breakage or diaphyseal fixation failure. Thirty of 31 fractures healed within 15.6 ± 6.2 weeks, as evident by bridging callus and pain-free load bearing. There were two revisions, one at 5 days post surgery to correct a mal-rotation, and one at 6 months post surgery to revise a non-union. Periosteal callus distribution at week 6 was symmetrical, with similar amounts of callus at the medial cortex (35%) anterior cortex (30%) and posterior cortex (35%). In 23 fractures (74%), callus formation extended to the lateral cortex under the plate.

Absence of hardware and fixation failure suggests that dynamic plating of distal femur fractures with FCL screws provides safe and effective fixation. Moreover, the amount and symmetric distribution of periosteal callus suggests that dynamic fixation with FCL screws may promote increased fracture healing over standard locked plating. However, this hypothesis on the stimulatory effect of dynamic fixation on fracture healing requires investigation in a future randomized control trial.