Technique for Biplanar Lateral Opening Wedge Distal Femoral Osteotomy in the Valgus Knee

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.

Comparison of double chevron-cut and biplanar distal femoral osteotomy techniques: A biomechanical study

OBJECTIVE

This study aimed to compare the stability and mechanical properties of the double chevron-cut (DCC) and biplanar (BP) distal femoral osteotomy (DFO) techniques, along with analyzing their respective contact surface areas.

METHODS

Biomechanical testing was performed using sawbone and 3D modeling techniques to assess axial and torsional stability, torsional stiffness, and maximum torque of both osteotomy configurations. Additionally, 3D models of the sawbone femur were created to calculate and compare the contact surface area of the DCC, BP, and conventional single-plane DFO techniques.

RESULTS

Axial stiffness and maximum strength did not significantly differ between the two osteotomy techniques. However, in terms of torsional properties, the DCC technique exhibited superior torsional stiffness compared to the BP group (27 ± 7.7 Nm/° vs. 4.5 ± 1.5 Nm/°, p = 0.008). Although the difference in maximum torque did not reach statistical significance (63 ± 10.6 vs. 56 ± 12.1, p = 0.87), it is noteworthy that the DCC group sawbone model exhibited fracture in the shaft region instead of at the osteotomy site. Therefore, the actual maximum torque of the DCC construct may not be accurately reflected by the numerical values obtained in this study. The contact surface area analysis revealed that the BP configuration had the largest contact surface area, 111% larger than that of the single-plane configuration. but 60% of it relied on the less reliable axial cut. Conversely, the DCC osteotomy offered a 31% larger contact surface area than the single-plane configuration, with both surfaces being weight-bearing.

CONCLUSION

The DCC osteotomy exhibited superior mechanical stability, showing improved rotational stiffness and maximum torque when compared to the BP osteotomy. Although the BP osteotomy resulted in a larger contact surface area than the DCC osteotomy, both were larger than the conventional single-plane configuration. In clinical practice, both the DCC and BP techniques should be evaluated based on patient-specific characteristics and surgical goals.

Computer-aided Design of Distal Femoral Osteotomy for the Valgus Knee and Effect of Correction Angle on Joint Loading by Finite Element Analysis

Objective

Lateral open‐wedge distal femoral osteotomy (DFO) has been used to treat valgus deformity of the knee, with good clinical outcomes. However, there is a lack of biomechanical studies regarding the angle of correction. The objective of this study was to apply computer‐aided design (CAD) for osteotomy planning in a three‐dimensional (3D) anatomical model and to assess the biomechanical differences among the varying correction angles on joint loading by finite element analysis (FEA).

Methods

To model different angles of lateral open‐wedge DFO correction, the CAD software package Mimics 21.0 was used to accurately simulate the operated knee. The femur was cut to 0°, 2°, 4°, 6°, 8°, and 10° of varus (equivalent to hip‐knee‐ankle angles of 180°, 178°, 176°, 174°, 172°, and 170°, respectively). The original knee model and the corrected models were processed by FE software. Then, the FE models were subjected to an axial force to obtain the von Mises stress (VMS) and shear stress distributions within the femoral cartilages and menisci.

Results

Under a compressive load of 740 N, the highest VMS in lateral and medial compartments of the intact knee model was 3.418 and 3.303 MPa. The maximum value of both the VMS and the shear stress in the lateral compartment decreased as the varus angle increased, but the corresponding values in the medial compartment increased. When the hip‐knee‐ankle (HKA) angle was 180°, the VMS in the lateral and medial compartments was balanced (3.418 and 3.303 MPa, respectively). Meanwhile, when the HKA angle was 178° (3.488 and 3.625 MPa, respectively), the shear stress in the lateral and medial compartments was balanced. In addition, the magnitude of change in the stress was significantly higher in the medial compartment (90.9%) than in the lateral compartment (19.3%).

Conclusion

The optimal correction angle of the valgus knee is close to neutral alignment or slightly varus (0° ‐ 2°). Overcorrection is not recommended, as it can result in a steep increase of the stress within the medial compartment and may accelerate the process of medial compartment OA.

[Research progress of osteotomy around knee in the treatment of valgus knee osteoarthritis]

OBJECTIVE

To review the research progress of surgical methods of osteotomy around the knee in the treatment of valgus knee osteoarthritis.

METHODS

The relevant literature on the surgical treatment of valgus knee osteoarthritis at home and abroad in recent years was reviewed, and the advantages, disadvantages, and effectiveness of different surgical methods of osteotomy around the knee were summarized.

RESULTS

For young and active patients with symptomatic valgus knee osteoarthritis, osteotomy around the knee is a safe and reliable treatment option. At present, the main surgical methods include medial closing wedge distal femoral osteotomy, lateral opening wedge distal femoral osteotomy, medial closing wedge high tibial osteotomy, and lateral opening wedge high tibial osteotomy. The indications, advantages, and disadvantages of different osteotomies are different, and the selection of appropriate surgical method is the key to achieve good effectiveness.

CONCLUSION

There are many osteotomies in the treatment of valgus knee osteoarthritis. In order to achieve good results, improve survival rate, and reduce postoperative complications, the most reasonable surgical strategy needs to be developed according to different situations.