Biomechanical evaluation of high tibial osteotomy plate with internal support block using finite element analysis

Background/Objective High tibial osteotomy (HTO) is a common treatment for medial knee arthrosis. However, a high rate of complications associated with a plate and a significant loss of correction have been reported. Therefore, an internal support block (ISB) is designed to enhance the initial stability of the fixation device that is important for successful bone healing and maintenance of the correction angle of the osteotomy site. The purpose of this study was performed to examine if an internal support block combined with a plate reduces the stress on the plate and screw area. Methods Finite element models were reconstructed following three different implant combinations. Two loading conditions were applied to simulate standing and initial sit-to-stand postures. Data analysis was conducted to evaluate the axial displacement of the posteromedial tibial plateau, which represents the loss of the posteromedial tibial plateau in clinical observation. Moreover, the stresses on the bone plate and locking screws were evaluated. Results Compared to the TomoFix plate, the ISB reduced the axial displacement by 73% and 76% in standing and initial sit-to-stand loading conditions, respectively. The plate with an ISB reduced stress by 90% on the bone plate and by 73% on the locking screw during standing compared to the standalone TomoFix plate. During the initial sit-to-stand loading condition, the ISB reduced the stress by 93% and 77% on the bone plate and the locking screw, respectively. Conclusion The addition of the PEEK block showed a benefit for structural stability in the osteotomy site. However, further clinical trials are necessary to evaluate the clinical benefit of reduced implant stress and the internal support block on the healing of the medial bone tissue.

BIPLANAR OPEN WEDGE HIGH TIBIAL OSTEOTOMY IN THE MEDIAL COMPARTMENT OSTEOARTHRITIS OF THE KNEE JOINT: COMPARISON BETWEEN THE AESCULAAND TOMOFIX PLATE AT ORTHOPAEDICS DEPARTMENT OF JLNMCH, BHAGALPUR, BIHAR.

Background: The purpose of this study was to compare the results of Aescula and TomoFix plates used for biplanar open wedgehigh tibial osteotomy in medial osteoarthritis of the knee joint with varus deformity. Methods: A consecutive series of 50 cases of biplanar open wedge high tibial osteotomy were evaluated retrospectively. GroupA contained 25 cases treated by using the Aescula plate, and group T contained 25 cases treated by using the TomoFix plate. Full weight-bearing was permitted at 6 weeks after surgery in group A and at 2 weeks in group T. Clinical evaluations were performed at the final follow-up by using postoperative knee scores and functional scores. Radiographic analysis included postoperative mechanical femur-tibia angle, change in posterior tibial slope angle, and complications related to implants. The mean follow-up periods were 30 months in group A and 26 months in group T. Results: The knee and functional scores were improved at the final follow-up in both groups (p< 0.05), but no differences wereobserved between the two groups (p> 0.05). An acceptable correction angle was obtained in 52% of group A and in 84% of group T (p = 0.015). Change in posterior tibial slope angle was larger in group A than in group T (p< 0.001), showing better maintenance of posterior tibial slope in group T. In group A, there were 3 cases of screw loosening and 4 cases of delayed union. In addition, there were residual varus deformities in 7 cases (6 in group A and 1 in group T). Conclusions: This study shows that firm fixation using a TomoFix plate for open wedge high tibial osteotomy produces better radiologic results and a low complication rate than those of the Aescula spacer plate.

Computational comparison of different plating strategies in medial open-wedge high tibial osteotomy with lateral hinge fractures

Background Lateral hinge fracture (LHF) is associated with nonunion and plate breakage in high tibial osteotomy (HTO). Mechanical studies investigating fixation strategies for LHFs to restore stability and avoid plate breakage are absent. This study used computer simulation to compare mechanical stabilities in HTO for different LHFs fixed with medial and bilateral locking plates. Methods A finite element knee model was created with HTO and three types of LHF, namely T1, T2, and T3 fractures, based on the Takeuchi classification. Either medial plating or bilateral plating was used to fix the HTO with LHFs. Furthermore, the significance of the locking screw at the combi hole (D-hole) of the medial TomoFix plate was evaluated. Results The osteotomy gap shortening distance increased from 0.53 to 0.76, 0.79, and 0.72 mm after T1, T2, and T3 LHFs, respectively, with medial plating only. Bilateral plating could efficiently restore stability and maintain the osteotomy gap. Furthermore, using the D-hole screw reduced the peak stress on the medial plate by 28.7% (from 495 to 353 MPa), 26.6% (from 470 to 345 MPa), and 32.6% (from 454 to 306 MPa) in T1, T2, and T3 LHFs, respectively. Conclusion Bilateral plating is a recommended strategy to restore HTO stability in LHFs. Furthermore, using a D-hole locking screw is strongly recommended to reduce the stress on the medial plate for lowering plate breakage risk.