A hinge position distal to the adductor tubercle minimizes the risk of hinge fractures in lateral open wedge distal femoral osteotomy

Abstract

Purpose To evaluate the incidence and morphology of medial cortical hinge fractures in lateral open wedge distal femoral osteotomy (LOW-DFO) and to determine a safe zone for the position of the osteotomy hinge to minimize the risk of hinge fractures. Methods Consecutive patients who underwent LOW-DFO for symptomatic valgus malalignment were screened for eligibility for this retrospective observational cohort study. Demographical and surgical data were collected. The incidence and morphology of medial cortical hinge fractures were evaluated on standard postoperative anterior–posterior knee radiographs. Comprehensive measurements evaluating the osteotomy gap and the position of the osteotomy hinge were taken. Additionally, each osteotomy hinge was assigned to a corresponding sector of a proposed five-sector grid of the distal medial femur. Results A total of 100 patients (60% female) with a mean age of 31 ± 13 years were included. The overall incidence of medial cortical hinge fractures was 46% and three distinct fracture types were identified. The most frequently observed fracture type was extension of the osteotomy gap (76%), followed by a proximal (20%) and distal (4%) course of the fracture line in relation to the hinge. Group comparison (hinge fracture vs. no hinge fracture) showed statistically significant higher values for the height of the osteotomy gap (p = 0.001), the wedge angle (p = 0.036), and the vertical distance between the hinge and the proximal margin of the adductor tubercle (AT; p = 0.002) in the hinge fracture group. Furthermore, a significantly lower horizontal distance between the hinge and the medial cortical bone (p = 0.036) was observed in the hinge fracture group. A statistically significant higher incidence of medial cortical hinge fractures was observed when the position of the osteotomy hinge was proximal compared to distal to the proximal margin of the AT (53% vs. 27%; p = 0.023). Conclusion Medial cortical hinge fractures in LOW-DFO are a common finding with three distinct fracture types. To minimize the risk of medial cortical hinge fractures, it is recommended to aim for a position of the osteotomy hinge at the level of or distal to the proximal margin of the adductor tubercle. Level of evidence Prognostic study; Level III

Dislocated hinge fractures are associated with malunion after lateral closing wedge distal femoral osteotomy

“…Measurements were performed as previously described [ 53 ] and modified for the CW-technique: on the preoperative hip–knee–ankle radiographs, the preoperative osteotomy planning conducted via mediCAD ® software (mediCAD Hectec GmbH, Altdorf, Germany) was identified and the wedge angle (angle α) and the height of the osteotomy wedge (interval “b”) were measured. In the postoperative standard AP radiographs, the length (interval “a”) and the inclination of the osteotomy (angle “ß”) were measured after identification of the osteotomy hinge and the anatomical axis of the femoral diaphysis.…”

“…For consecutive analysis, the two-dimensional position of the osteotomy hinge was assigned to a corresponding sector in a sector grid as previously described for LOW-DFO [ 53 ]. Bony landmarks (AT, medial femoral cortical bone, femoral condyles) were used to define two columns (M, L) and three rows (I, II, III) of the grid.…”

“…Hinge fractures in distal femoral osteotomies (DFO)—resulting in increased rotational movement across the osteotomy plane [ 3 , 41 ]—may explain a considerable number of delayed unions or losses of correction reported [ 4 , 6 , 8 , 9 , 14 , 25 , 54 ]. While technical factors and vulnerable anatomical zones associated with an increased risk of hinge fractures have been reported for HTO [ 16 , 31 – 33 , 49 ], medial closing wedge (MCW) DFO [ 21 , 39 ] and LOW-DFO [ 53 ], the only report investigating hinge fractures in LCW-DFO to-date was performed in a relatively small collective and could not identify any risk factors [ 36 ].…”

Osteotomies for lateral compartment knee osteoarthritis

“…Biplanar technique facilitates the osteotomy to be more distal at the metadiaphyseal junction and reduces the risk of hinge fracture. 33 We find that using an external fixator to allow controlled correction reduces the risk of hinge fracture. If hinge fracture results in destabilization of osteotomy, contralateral screw or staple is an option.…”

“…The incidence can be as high as 48% for medial closing wedge 31 and 39% 32 to 46% 33 in lateral opening wedge osteotomies. Although loss of correction and non-union of osteotomy have been attributed to it, Winkler et al 33 have also shown that in spite of high incidence of this complication in open wedge correction, there is no difference in the complication risk for patients with or without medial hinge failure. Common causes for medial cortex fracture are leaving a thicker medial bridge or too rapid opening of wedge.…”