Description
Purpose:
Hinge fracture (HF) is a common complication in distal femoral osteotomies and is associated with pain, loss of correction and malunion. Hinge placement has been suggested to affect HF rates. This biomechanical study aims to assess and compare the (1) HF rate and (2) hinge rigidity and strength between proximal and distal hinge placements. We hypothesize that a distal hinge would have a lower rate of HF and exhibit greater stability than a proximal hinge.
Methods:
Medial Closing Wedge Distal Femoral Osteotomy (MCWDFO) was performed by an Orthopaedic consultant on 12 goat femur specimen, with equal numbers in distal and proximal hinge groups. To quantitatively evaluate the stability of the bone hinge, a custom fixture was employed to secure the specimens at the distal femur, and they were attached to an Instron machine. The femoral diaphysis underwent cyclic loading, which caused the osteotomy gap to open and close repeatedly, and the maximum load (N) and stiffness (N/mm) sustained before hinge fracture and failure was measured.
Results:
During the MCWDFO, six out of the twelve specimens experienced HF. Five of these belonged to the proximal-hinge group (83.3%) and one was from the distal-hinge group (16.6%) (p=0.025). In the presence of HF, distal hinge specimens had a significantly higher stiffness and durability (p=0.011), but there was no significant difference in maximum load between both groups (p=0.057).
Conclusions:
Decreased hinge fracture rate and greater hinge stiffness were observed with a distal hinge placement.
