Distalization of hinge site with use of hinge wire reduces hinge fracture rates in closing wedge distal femoral osteotomy

Abstract

Purpose Closing wedge distal femoral osteotomies (CWDFO) are attractive treatment options for unicompartmental knee osteoarthritis with coronal plane deformity. However, it has been traditionally associated with high rates of hinge fracture that can adversely impact recovery and patient outcomes. Appropriate siting of hinge point can be an efective method of reducing the incidence of hinge fractures. This study aims to illustrate a case series of CWDFO with low rates of hinge fracture utilising our preferred hinge point site. Methods A retrospective study of a cohort of 39 CWDFO was performed between May 2019 and May 2022. Both medial and lateral CWDFO were included. The hinge point in all cases was placed at the level of the inferior margin of the metaphyseal lare, and inferior to the gastrocnemius origin, with a hinge thickness of 10 mm. Post-operative radiographs were obtained at 2, 4 and 8 weeks after surgery to assess for hinge fracture and union. Results Thirty-nine cases of CWDFO were performed, consisting of eighteen cases of valgus malalignment that underwent medial CWDFO and twenty-one cases of varus malalignment that underwent lateral CWDFO. At surgery, the mean age was 47.6 (± 13.9) years and mean BMI was 29.4 (± 4.9). There were 23 men and 16 women. Three cases of hinge fractures occurred intraoperatively, translating into a hinge fracture rate of 7.69%. However, union was achieved in all three cases and all patients in this case series were able to progress to weight bear as tolerated at 2 months post-osteotomy. Conclusion Distal placement of the hinge at the level of the inferior metaphyseal lare margin with the use of a hinge wire can greatly reduce the rates of hinge fracture in CWDFO. Level of evidence Level III.

Setting hinge position distal to the proximal margin of the distal lateral femur reduces the maximum principal strains of the hinge area and risk of hinge fractures

“…In addition, hinge fractures were not observed in the distal group, whereas displaced fractures were observed in the border and proximal groups. Similar to our results, Teo et al recently reported that the occurrence rate of hinge fractures was reduced when the hinge point was set distal to the metaphyseal flare margin and gastrocnemius origin, which is similar to the area determined in our study [ 17 ]. Therefore, taken together with our results, the optimal hinge location appears to be distal to the proximal border of the lateral condyle.…”

Additional Plate Fixation of Hinge Fractures After Varisation Distal Femoral Osteotomies Provides Favorable Torsional Stability: A Biomechanical Study

“…Thus, several strategies have been reported to prevent these fractures, like the protective hinge wire 35 or positioning of the medial hinge distal to the adductor tubercle. 39 However, a certain rate of hinge fractures remains, 35,39 which may compromise functional outcomes and patient-reported outcome measures. 16,27…”

“…29 The resulting instability and reduced stiffness of the bone-implant construct 3,25,30 may be one reason for delayed consolidation, as evidenced by the increased risk of malunions with associated rates of up to 6.7% and 7.3% after hinge fractures in MCW-DFO 26 and LOW-DFO, 23,24 respectively. Thus, several strategies have been reported to prevent these fractures, like the protective hinge wire 35 or positioning of the medial hinge distal to the adductor tubercle. 39 However, a certain rate of hinge fractures remains, 35,39 which may compromise functional outcomes and patient-reported outcome measures.…”

“…Thus, several strategies have been reported to prevent these fractures, like the protective hinge wire 35 or positioning of the medial hinge distal to the adductor tubercle. 39 However, a certain rate of hinge fractures remains, 35,39 which may compromise functional outcomes and patient-reported outcome measures. 16,27 Thus, this study aimed to (1) examine the effect of hinge fractures on the biomechanical properties of the boneimplant construct, (2) evaluate the biomechanical advantages of an additional fixation of a hinge fracture, and (3) test the biomechanical properties of the different types of varisation DFOs (MCW vs LOW and monoplanar vs biplanar).…”