Factors affecting the disparity between preoperative planning and postoperative correction status in distal femoral osteotomy

Morphological analysis of the distal femur as a surgical reference in biplane distal femoral osteotomy

Distal femoral osteotomy (DFO) is performed alone or with high tibial osteotomy (HTO) for patients with osteoarthritis and distal femur deformities. DFO is technically demanding, particularly when creating an anterior flange. Herein, we examined the morphological characteristics of the distal femur based on the cortical shape as a surgical reference for biplanar DFO. Computed tomography images of 50 valgus and 50 varus knees of patients who underwent biplanar DFO or total knee arthroplasty were analyzed. Axial slices at the initial level of the transverse osteotomy in the DFO and slices 10 mm proximal and 10 mm distal to that level were selected. The medial and lateral cortical angles and heights (MCLA, LCLA, MCH, and LCH) were measured on axial slices. Statistical comparisons were performed between the medial and lateral cortices and valgus and varus knees. MCLA and MCH were significantly smaller and lower, respectively, than LCLA and LCH (P < 0.01). The MCLA and MCH of varus knees were significantly smaller and lower, respectively, than those of valgus knees (P < 0.01). Surgeons should carefully observe morphological differences in the distal femur cortex, distinguishing between medial and lateral knees and varus and valgus knees during the creation of the anterior flange in the DFO.

Distal femoral osteotomy planning: Reversed Miniaci's method is more accurate than Dugdale and Paley methods

PURPOSES

The purpose of this study was to validate the reversed Miniaci method for distal femoral osteotomies and to compare the accuracy with Dugdale and Paley methods.

METHODS

Between January 2019 and October 2021, 59 DFO were performed in a single center. Following application of the eligibility and exclusion criteria, radiographic measurements and analysis was performed for 24 patients by two independent observers, then repeated after one month. Medical planning software: PeekMed v2.3.7.6® was used. For all patients the following measurements were performed: Hip-Knee-Ankle (HKA), mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), joint line convergence angle (JLCA), joint line obliquity (JLO), width of the proximal tibia and the weight-bearing line (WBL). Each image was then analysed using the following planning methods for realignment surgery: Reversed Miniaci, Dugdale and Paley. Measurements were recorded post deformity correction. Difference between target and post-correction WBL was evaluated. This difference was adjusted by the objective in order to limit biases related to the different objectives according to the method.

RESULTS

Eighteen patients were managed for a varus osteotomy and 6 for a valgus osteotomy. Preoperative data was, HKA at 176.7±6.3, mLDFA at 90.6±5.4, MPTA 88.9±1.1, a WBL for valgus 80.9%±9.1 and for varus deformity 23.5%±11.7. Inter- and intra-rater reliability was>0.8 for every method. After normalizing reported precision on the amount of correction expected, reversed Miniaci method was the most accurate with a mean deviation from the target of 3%, compared to the Dugdale's method with 9% (p<0.001) and to Paley's method with 8.6% (p<0.001).

CONCLUSION

The reversed Miniaci method is effective and reliable for planning distal femoral osteotomies. Compared to other planning methods, it is the most accurate approach for achieving a correction goal.

LEVEL OF EVIDENCE

IV; retrospective cohort study.

Predictive Factors for Lateral Hinge Fracture in Medial Closing Wedge Distal Femoral Osteotomy

BACKGROUND

Recent studies have reported that lateral hinge fracture (LHF) has a negative effect on bone healing at the osteotomy site after medial closing wedge distal femoral osteotomy (MCDFO). However, limited evidence exists in the literature regarding the predictive factors for LHF in MCDFO.

HYPOTHESIS

A large medial closing gap and a lateral hinge position in the supracondylar area would increase plain radiography-based and/or computed tomography (CT)-based LHF in MCDFO.

STUDY DESIGN

Case control study; Level of evidence, 3.

METHODS

We retrospectively evaluated 67 knees of 53 patients (mean age, 37.4 ± 16.9 years) who underwent MCDFO between May 2009 and June 2021. The surgical indications for MCDFO were genu valgum deformity combined with either lateral compartment osteoarthritis or recurrent patellar dislocation. The presence of LHF was evaluated based on immediate postoperative plain radiography and CT scans. The predictive factors for LHF in MCDFO were investigated using multivariate logistic regression analysis.

RESULTS

LHFs were identified in 21 knees (31.3%) through plain radiography and in 40 knees (59.7%) through CT. Multivariate logistic regression analysis showed that the medial closing gap and lateral hinge position were predictive factors for plain radiography- and CT-based LHF after MCDFO. Controlling for other variables, we found that an increase in the medial opening gap by 1 mm increased the likelihood of plain radiography-based LHF by a factor of 1.805 (95% CI, 1.291-2.525; P = .001) and CT-based LHF by 1.333 (95% CI, 1.003-1.772; P = .048). Moreover, a lateral hinge position in the supracondylar area increased the likelihood of plain radiography-based LHF by a factor of 9.870 (95% CI, 2.179-44.720; P = .003) and CT-based LHF by 5.686 (95% CI, 1.124-28.754; P = .036).

CONCLUSION

A large medial closing gap and lateral hinge position in the supracondylar area are associated with LHF in MCDFO. Care should be taken to prevent LHF in MCDFO with a large medial closing gap. Moreover, a lateral hinge position in the supracondylar area should be avoided to decrease the incidence of LHF in MCDFO.

Analysis of bone union after medial closing wedge distal femoral osteotomy using a new radiographic scoring system

INTRODUCTION

To compare bone union after medial closing wedge distal femoral osteotomy (MCWDFO) with that after lateral closing wedge distal femoral osteotomy (LCWDFO) using a novel scoring system.

MATERIALS AND METHODS

The data of 30 patients who received biplanar MCWDFO for valgus knees (MCWDFO group) were retrospectively examined and compared to that of 22 patients (25 knees) who underwent biplanar LCWDFO via a double-level osteotomy (DLO) for varus knees (LCWDFO group). The progression of bone union of the transverse osteotomy plane in the femur was assessed using a newly developed scoring system using radiographs taken immediately after surgery and 3 and 6 months postoperatively. The scoring system is based on a scale of zero to six points with higher scores indicating better bone union. The incidence of hinge fractures was assessed using CT images, and the rates of reoperation were evaluated using medical record data.

RESULTS

The mean bone union score was significantly lower in the MCWDFO group than in the LCWDFO group 3 months (2.1 ± 1.9 vs. 3.7 ± 1.7, P < 0.01) and 6 months (3.8 ± 2.1 vs 4.9 ± 1.5, P < 0.05) postoperatively. The incidence ratio of hinge fractures was significantly higher in the MCWDFO group than in the LCWDFO group (70.0% vs. 32.0%, P < 0.01). Two patients in the MCWDFO group underwent reoperation for delayed bone union or non-union.

CONCLUSION

Bone union progression was slower and hinge fractures were more frequently observed after MCWDFO than after LCWDFO via DLO. MCWDFO is technically challenging, and patients must be monitored closely during and after surgery.

Editorial Commentary: Patient-Specific Instrumentation for Knee High Tibial Osteotomy Addresses the Bony but Not the Soft-Tissue Aspect of Deformity Correction

Both bony and soft-tissue components should be considered during preoperative planning and intraoperative performance of knee high tibial osteotomy to achieve accurate correction. 3D-printed patient-specific instrumentation may aid in addressing the bony component. Even with appropriate preoperative planning for bony and soft-tissue correction, appropriate adjustments must be made intraoperatively to achieve successful outcomes, and accurate correction is impossible unless the soft-tissue component is considered.

Biomechanical analysis of the role of hinge support fixators on hinge stability in medial closing wedge distal femoral osteotomy

BACKGROUND

This study aimed to examine the hinge-stabilizing biomechanical effects of hinge support fixators, applied for lateral hinge fractures sustained following distal femoral osteotomy.

METHODS

Medial closing wedge distal femoral osteotomy was performed using a locking plate on 10 cadaveric limbs. The limbs were divided into two groups: the non-fracture group and the lateral hinge fracture group. A cyclic axial load of 400 N was applied to the knee to keep it extended and flexed at 45°. The hinge-stabilizing effects of adding a screw or a short support plate to the lateral fracture site were examined by measuring the translation and rotational angles of the anterodistal and posterodistal hinge positions as well as the surface strains of the medial locking plate.

FINDINGS

Translation and rotation in the fracture group were significantly more pronounced than in the non-fracture group, at the anterodistal and posterodistal positions. Translations at both positions were significantly reduced, by adding the support plate, during both extension and 45-degree flexion in the fracture group. The rotation at the posterodistal position upon extension and the anterodistal position upon 45-degree flexion was significantly reduced by the support plate. The surface strain of the medial plate in the fracture group was significantly reduced by the support plate upon both extension and 45-degree flexion.

INTERPRETATION

Lateral hinge fractures caused abnormal hinge movements, which were significantly reduced by the short support plate. A short support plate could be used if a hinge fracture occurs during distal femoral osteotomy, to improve lateral hinge stability.

Detection of Lateral Hinge Fractures After Medial Closing Wedge Distal Femoral Osteotomy: Computed Tomography Versus Plain Radiography

BACKGROUND

Limited evidence exists in the literature regarding the detection rates of lateral hinge fracture (LHF) on computed tomography (CT) after medial closing wedge distal femoral osteotomy (MCDFO). Moreover, the effect of LHF on bone healing after MCDFO remains unclear.

HYPOTHESIS

The detection rates of LHF after MCDFO would be higher on CT than on plain radiography. The incidence of problematic bone healing would be higher in the knees with LHF than in those without LHF.

STUDY DESIGN

Cohort study (diagnosis), Level of evidence, 3.

METHODS

Patients who underwent MCDFO between May 2009 and July 2019 were retrospectively evaluated. The presence of LHF was evaluated using immediate postoperative plain radiography and CT. The detection rates of LHF on plain radiography and CT were compared. The incidence of problematic bone healing (nonunion, delayed union, and loss of correction) was also compared between the knees with LHF and those without LHF.

RESULTS

A total of 55 knees of 43 patients (mean age, 37.7 ± 16.7 years) were included in the study. Although 33 LHFs were detected on CT, only 19 LHFs were detected on plain radiography. The detection rate of LHF was significantly higher on CT than on plain radiography (60% vs 34.5%; P = .008). At 1-year follow-up, 10 cases of problematic bone healing (1 nonunion, 4 delayed unions, and 5 losses of correction) were identified. The incidence of problematic bone healing was significantly higher in the knees with LHF than in those without LHF as shown on plain radiography (36.8% vs 8.3%; P = .001) and CT (30.3% vs 0%; P = .004).

CONCLUSION

LHF can be detected better on CT than on plain radiography and has a negative effect on bone healing after MCDFO. For patients with LHF detected on either plain radiography or CT, careful rehabilitation with close follow-up is recommended.