Comparison of theoretical fixation stability of three devices employed in medial opening wedge high tibial osteotomy: a finite element analysis

[Biomechanical study of three-dimensional printed filler block design in open wedge high tibial osteotomy]

The use of a filling block can improve the initial stability of the fixation plate in the open wedge high tibial osteotomy (OWHTO), and promote bone healing. However, the biomechanical effects of filling block structures and materials on OWHTO remain unclear. OWHTO anatomical filling block model was designed and built. The finite element analysis method was adopted to study the influence of six filling block structure designs and four different materials on the stress of the fixed plate, tibia, screw, and filling block, and the micro-displacement at the wedge gap of the OWHTO fixation system. After the filling block was introduced in the OWHTO, the maximum von Mises stress of the fixation plate was reduced by more than 30%, the maximum von Mises stress of the tibia decreased by more than 15%, and the lateral hinge decreased by 81%. When the filling block was designed to be filled in the posterior position of the wedge gap, the maximum von Mises stress of the fixation system was 97.8 MPa, which was smaller than other filling methods. The minimum micro-displacement of osteotomy space was -2.9 μm, which was larger than that of other filling methods. Compared with titanium alloy and tantalum metal materials, porous hydroxyapatite material could obtain larger micro-displacement in the osteotomy cavity, which is conducive to stimulating bone healing. The results demonstrate that OWHTO with a filling block can better balance the stress distribution of the fixation system, and a better fixation effect can be obtained by using a filling block filled in the posterior position. Porous HA used as the material of the filling block can obtain a better bone healing effect.

Comparison of the clinical and radiological outcomes of Puddu and TomoFix plates for medial opening-wedge high tibial osteotomy: A two-year follow-up of a randomized controlled trial

PURPOSE

Opening-wedge high tibial osteotomy (OWHTO) requires fixation devices for stabilization of the osteotomy gap. The two most commonly used fixation devices are the Puddu and the TomoFix plates. Based on its design, each implant generates a characteristic stability profile. The aim of this randomized controlled trial (RCT) was to investigate the short-term clinical and radiological outcomes of OWHTO using the Puddu and TomoFix plating systems. We hypothesized that the TomoFix plate would achieve superior clinical and radiographic results compared to the Puddu plate.

METHODS

A total of 60 patients were randomly allocated to undergo OWHTO either using the Puddu plate or the TomoFix plate if conservative treatment failed with symptomatic medial compartment knee osteoarthritis (OA) stage I or II according to Ahlbäck classification, and varus malalignment. All patients underwent clinical and radiological assessment preoperatively, and at 3, 6, 12, and 24months postoperatively. Radiological measurement of the hip-knee-ankle (HKA) angle, and posterior tibial slope (PTS) was performed. Functional assessment was carried out using the Hospital for Special Surgery Knee-Rating Scale (HSS) and the Western Ontario McMaster Universities (WOMAC) Osteoarthritis Index. Patients were also evaluated for intraoperative and postoperative complications throughout the follow-up period.

RESULTS

The mean angular correction was 9.6±4°, and 10.5±4.8° in the Puddu and TomoFix groups, respectively (p=0.488). The mean PTS change was significantly higher in the Puddu group (3.4±1.1°) compared to the TomoFix group (0.8±0.7°) (p<0.001). There was a statistically significant improvement in the mean HSS and WOMAC in both groups until one year postoperatively. Neither HSS nor WOMAC showed a statistically significant difference between the Puddu and TomoFix groups at any time during the first two postoperative years. The overall complication rate was not significantly different between the Puddu and TomoFix groups. However, the TomoFix group demonstrated higher incidence of symptomatic hardware (23% vs. 3.3%) and removal of metalwork (17% vs. 0%) than the Puddu group (p=0.023 and 0.020, respectively).

CONCLUSION

This RCT suggests that the implant choice for OWHTO has no significant impact on functional outcomes during the first 2years postoperatively. While the Puddu plate was associated with an unintentional increase in the PTS during the surgery, both implants allowed coronal and sagittal plane corrections to be preserved postoperatively. The overall complication rates were similar, but the TomoFix required more material to be removed because it is more cumbersome. However, these results need to be confirmed on a larger scale.

LEVEL OF EVIDENCE

II; randomized controlled trial.

Fixation method can affect posterior tibial slope in opening-wedge high tibial osteotomy: a retrospective study

BACKGROUND

Posterior tibial slope (PTS) alterations following open-wedge high tibial osteotomy (OWHTO) can cause instability and excessive tibial translation in the sagittal plane. These changes can be influenced by the type of fixation. This study aims to compare PTS changes between patients undergoing OWHTO with Puddu plate or TomoFix plate fixation.

METHODS

In this retrospective cohort study, we included 104 knees from 85 patients undergoing OWHTO, with a mean age of 41.98 ± 9.95 years; 51.8% of the participants were male. Seventy-two knees were fixed with Puddu plates, while 32 knees were fixed with TomoFix plates. PTS changes, demographic factors, Cincinnati Knee Rating Score (CKRS), Tegner-Lysholm score (TLS), length of stay (LOS), and complications were evaluated. PTS changes were measured preoperatively, immediately postoperatively, and at the 6-month follow-up.

RESULTS

Demographic factors were similar between the Puddu plate and TomoFix groups. There were no significant differences in preoperative, postoperative, or follow-up PTS measurements between the two groups. PTS changes were not significant in the TomoFix group postoperatively or at follow-up. However, the Puddu plate group showed a significant increase in PTS both postoperatively (P = 0.027) and at follow-up (P = 0.014). CKRS, TLS, LOS, and complications did not significantly differ between the groups.

CONCLUSION

While overall PTS changes did not significantly differ between the Puddu Plate and TomoFix Plate groups, analyzing changes within each group revealed distinct results. TomoFix fixation exhibited nonsignificant PTS changes, while Puddu plate fixation resulted in a significant increase in PTS after surgery and at the 6-month follow-up. Our findings suggest that the choice of fixation may influence PTS changes after OWHTO.

LEVEL OF EVIDENCE

Level III.

The results of allogenic cancellous bone graft in medial opening wedge high tibial osteotomy

PURPOSE

There is no clear consensus regarding the optimal filling agent in the medial opening wedge high tibial osteotomy (MOWHTO). In this study, we evaluated the clinical and radiologic outcomes of MOWHTO with an allogeneic cancellous bone graft and TomoFix plate.

METHODS

Medical profiles of 122 patients who underwent MOWHTO with cancellous bone graft from iliac crest were retrospectively reviewed. One hundred and two patients (120 knees) who met the study criteria were included in the analysis. The osteotomy site was fixed with a TomoFix plate. The mean age of the patients was 40.85 ± 22.15 years. The mean follow-up of the patients was 33.2 ± 29 months. The primary outcome measures were the union of osteotomy site and loss of correction that were investigated on postoperative radiographs. Secondary outcome measures were postoperative complications that were extracted from the patients' medical records.

RESULTS

Union of the osteotomy site was observed in all patients within three months after the operation. Loss of correction at the osteotomy site occurred in two knees (1.7%), both of which underwent revision surgery. Three patients had non-infected prolonged wound drainage and underwent reoperation for allograft removal. Nine other complications were also recorded that did not require intervention, including superficial infection (n = 2), compartment syndrome (n = 1), deep vein thrombosis (n = 1), loss of knee flexion (n = 2), and transient pain at the site of the osteotomy (n = 3).

CONCLUSION

Allogenic cancellous bone graft provides efficient gap healing in MOWHTO and can be used as an effective alternative to the autogenous bone graft.

Superior survivorship and plate-related results of TomoFix compared to Puddu plate fixation for opening-wedge high tibial osteotomy: A systematic review of the literature

PURPOSE

This systematic review aimed to compare survivorship and plate-related results of Puddu and TomoFix plates in opening-wedge high tibial osteotomy (OWHTO).

METHODS

PubMed, Scopus, EMBASE, and CENTRAL databases were searched from January 2000 until September 2021 for clinical studies involving patients with medial compartment knee disease and varus deformity undergoing OWHTO using the Puddu or TomoFix plating systems. We extracted survival data, plate-related complications, and functional and radiological outcomes. The risk of bias assessment had been carried out using Cochrane Collaboration's quality assessment tool for randomised controlled trials (RCTs) and Methodological Index for Non-Randomised Studies (MINORS).

RESULTS

Twenty-eight studies were included. The total number of knees was 2568 in 2372 patients. The Puddu plate was used in 677 knees, while the TomoFix plate was used in 1891. The follow-up ranged from 5.8 to 147.6 months. Both plating systems were able to delay conversion to arthroplasty at different follow-up intervals. However, osteotomies fixed by the TomoFix plate achieved higher survival rates, especially at mid-term and long-term follow-ups. In addition, fewer complications were reported with the TomoFix plating system. Although both implants achieved satisfactory functional outcomes, high scores could not be maintained throughout long-term intervals. Regarding radiological results, TomoFix plate was able to achieve and maintain larger degrees of varus deformity, while preserving the posterior tibial slope.

CONCLUSIONS

This systematic review demonstrated the superiority of the TomoFix over the Puddu system as a safer and more effective fixation device in OWHTO. Nevertheless, these results should be interpreted with caution due to the lack of comparative evidence through high-quality RCTs.

Using musculoskeletal modelling to estimate knee joint loading pre and post high tibial osteotomy

BACKGROUND

Both medial knee osteoarthritis and associated varus alignment have been proposed to alter knee joint loading and consequently overloading the medial compartment. Individuals with knee osteoarthritis and varus deformity are candidates for coronal plane corrective surgery, high tibial osteotomy. This study evaluated knee loading and contact location for a control group, a pre-surgery cohort and the same cohort 12 months post-surgery using a musculoskeletal modelling approach.

METHODS

Joint kinematics during gait were measured in 30 knee osteoarthritis patients, before and after high tibial osteotomy, and 28 healthy adults. Using a musculoskeletal model that incorporated patient-specific mechanical tibial femoral angle, the resulting muscle, ligament, and contact forces were calculated and the medial - lateral condyle load distribution was analysed.

FINDINGS

Surgery changed medial compartment contact force throughout stance relative to pre-surgery. This reduction in medial compartment contact force pre- vs post-HTO is observed despite a significant increase in post-surgery walking speed compared to pre-HTO, where increased speed is typically associated with increased joint loading.

INTERPRETATION

This study has estimated the effects of high tibial osteotomy on knee loading using a generic model that incorporates a detailed knee model to better understand tibiofemoral contact loading. The findings support the aim of surgery to unload the medial knee compartment and lateralise joint contact forces.

Effectiveness of bone substitute materials in opening wedge high tibial osteotomy: a systematic review and meta-analysis

BACKGROUND

A meta-analysis of eligible studies was performed to evaluate the effectiveness of bone substitute materials (BSMs) in opening wedge high tibial osteotomy (OWHTO) for knee osteoarthritis.

METHODS

A systematic review and meta-analysis were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). A comprehensive literature search was performed, and studies comparing BSM with bone graft (BG) and without bone graft (WG) were included. The Cochrane risk of bias tool (version 1.0) and Risk of Bias in Non-randomized Studies of Interventions (ROBINS-I) tool were used to assess the risk of bias for randomized controlled trials (RCTs) and non-randomized studies (NRSs), respectively. The outcomes measured were the osteotomy gap size, the occurrence rates of non-union and lateral hinge fractures, knee functional score, infection and the Visual Analogue Scale (VAS). The quality of evidences was evaluated by Grades of Recommendation, Assessment, Development and Evaluation (GRADE) Working Group system.

RESULTS

Five RCTs and eight NRS including 769 participants were included in our meta-analysis. The BSM group had a larger osteotomy gap size than the control group (MD: 0.41 mm, 95% confidence interval (CI): [0.06, 0.76], p=.02, I2=0%), with a significant difference. No significant difference was found between BSM and control group in main analysis in terms of bone non-union, but with a higher non-union rate when BSM combined with long locking plate was used. No significant differences were found in other outcome measures except for VAS from NRS subgroup. The quality of evidence for outcomes was low.

CONCLUSIONS

BSM combined with locking plate techniques offers a safe and efficient alternative option in OWHTO for osteotomy gap larger than 10 mm, but be aware of the possibility of bone non-union. Given the inherent heterogeneity and low quality of the included studies, future well-designed RCTs are essential to verify the findings.KEY MESSAGEThe treatment of the osteotomy gap is still controversial.BSM combined with a locking plate offers a safe and efficient alternative option for OWHTO with an over 10 mm of osteotomy gap over 10 mm.Due to the inherent heterogeneity and low quality of the included studies, the results should be cautiously interpreted in clinical practice.

A biomechanical study: Comparison of three different implant options in high Tibial osteotomy

BACKGROUND

Many implant options could be preferable for fixation after osteotomy in varus knee medial compartment arthrosis. Due to usage characteristics, it is important to compare the biomechanical properties of them. For this purpose, we aimed to examine three different implant types biomechanically in our study.

METHODS

Ovine tibiae undergoing medial open-wedge high tibial osteotomy were fixed in vitro with three different implants using an angular wedge plate, a metal block plate and an external fixator system. The fixed ovine tibiae were subjected to axial tensile, axial loading and three-point bending tests in a test machine. All biomechanical tests were repeated five times, the maximum and minimum values were ignored, and the average values of the remaining three test results were taken into account. The test results were interpreted after converted into force-elongation curves in Trapezium-X software.

FINDINGS

Biomechanical test results revealed some differences between implant types. While the metal block plate had the highest axial tensile strength value, it was the fixation group showing the lowest strength in axial load tests. The used fixator system was the highest strength in axial load tests and the lowest strength in axial tensile tests.

INTERPRETATION

Considering the clinically significant forces related to the biomechanical stability of the three different implants used for high tibial osteotomy, the fixator system would appear to be slightly superior, although it should be noted that torsional forces, as well as parameters that could change in living tissue, might affect the results.

The influence of the number of holes in the open wedge high tibial osteotomy on knee biomechanics using finite element analysis

BACKGROUND

The most significant differences of high tibial osteotomy (HTO) were found in terms of plate length, and this was related to number of holes distal region of the plate below wedge. The purpose of this study is to evaluate the biomechanical effects of three different designs medial opening wedge plates.

HYPOTHESIS

The design of the HTO plate influenced the outcome of the biomechanics.

METHODS

The HTO model was simulated using finite element (FE) model. This FE investigation included three types of loading conditions corresponding to the loads used in the experimental study for model validation and model predictions for clinically relevant loading scenarios. The average stress and contact stress were evaluated.

RESULTS

The highest average stress was observed in the TomoFix. Conversely, the stress on the bone declined in the order of Puddu, Maxi and TomoFix plates. The micromotion in the wedge displayed a similar trend to the stress on bone. The highest and lowest contact stresses on the medial meniscus were observed in the Puddu and TomoFix plate, respectively. However, an opposite trend was observed in the lateral meniscus. The contact stress on medial and lateral menisci decreased and increased, respectively, in all three different plates when compared to those in the intact model.

DISCUSSION

The TomoFix plate exhibited the highest stability relative to the micromotions of the wedge. However, in terms of the stress on the bone and plates, a stress-shielding effect could exist in the TomoFix plate. Additionally, the contact stress on the articular surface suggested that a complicated relationship could exist with respect to the plate design.

LEVEL OF EVIDENCE

IV.

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.

Biomechanical aspects of the posteromedial split in bicondylar tibial plateau fractures-a finite-element investigation

PURPOSE

To gain principal insight into fixation techniques of a posteromedial split fragment in bicondylar tibial plateau fractures.

METHODS

A computer simulation was performed, applying the finite-element method (FEM) to compare four methods of fixation of the posteromedial split fragment: lateral plate (model 1), lateral plate and kickstand screw (model 2), lateral plate and two antero-posterior lag screws (model 3), and lateral and posteromedial plate (model 4). The displacement of the fragment and material stresses in implants and bone under 2500 N axial load were analyzed.

RESULTS

Maximal displacement of the posteromedial split fragment of 2.8 mm was found with a sole lateral plate. An added kickstand screw decreased the displacement to 1.46 mm. Added lag screws improved stability by a factor 4, with a maximal displacement of 0.76 mm. The double-plate configuration revealed 0.27 mm, a decrease of the displacement by a factor 10 compared to model 1. An additional analysis of posteromedial fragment displacements with osteoporotic bone, simulated by dividing the elastic modulus of the bone by a factor 2, turned out to be of relevant impact. For model 1, the calculations did not converge. The influence of bone quality was found to be 70% in model 2, 60% in model 3, and 40% in model 4.

CONCLUSIONS

The results indicate that the additional fixation of a posteromedial split fracture by plate osteosynthesis might be advantageous in bicondylar tibial plateau fractures treated with lateral plating. This might be even more important in patients with low bone quality.

Comparative analysis of fixation configurations and their effect on outcome after medial open-wedge high tibial osteotomy

PURPOSE

The purposes of this study were to analyze and compare 1) the postoperative fixation configurations, and 2) radiological and clinical outcomes between the new conceptual fixation device (LCfit) and the conventional locking plates.

METHODS

Retrospective comparative analysis of 304 cases who underwent open-wedge high tibial osteotomy with four different locking plate systems including the LCfit system was conducted. In analyzing the fixation configuration of each locking plate system, the plate position, the gap between plate and bone, screw angle, and screw length were evaluated from postoperative CT scans. The clinical outcomes and radiological parameters of four patient groups corresponding to the four locking plate systems were also compared.

RESULTS

In the analysis of the fixation configurations, the LCfit system showed more posteromedial plate position, decreased gap between plate and bone, reduced screw angle, and longer screw length compared to the other three locking plates. However, there were no significant differences in clinical outcomes and radiological parameters such as hip-knee-ankle angle, weight-bearing line position, medial proximal tibial angle, and posterior slope between the four groups.

CONCLUSION

The newly designed fixation system (LCfit) for open-wedge high tibial osteotomy showed fixation configurations that have theoretical mechanical advantages over conventional anatomical locking plates. However, there were no significant differences in clinical outcomes and radiological parameters between LCfit and the other locking plate systems.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Biomechanical effect of a lateral hinge fracture for a medial opening wedge high tibial osteotomy: finite element study

BACKGROUND

This study aimed to investigate the biomechanical effect on the Takeuchi classification of lateral hinge fracture (LHF) after an opening wedge high tibial osteotomy (HTO).

METHODS

We performed an FE simulation for type I, type II, and type III in accordance with the Takeuchi classification. The stresses on the bone and plate, wedge micromotion, and forces on ligaments were evaluated to investigate stress-shielding effect, plate stability, and biomechanical change, respectively, in three different types of LHF HTO and with the HTO without LHF model (non-LHF) models.

RESULTS

The greatest stress-shielding effect and wedge micromotion were observed in type II LHF (distal portion fracture). The type II and type III (lateral plateau fracture) models exhibited a reduction in ACL force and an increase in PCL force compared with the HTO without LHF model. However, the type I (osteotomy line fracture) and HTO without LHF models did not exhibit a significant biomechanical effect. This study demonstrates that Takeuchi type II and type III LHF models provide unstable structures compared with the type I and HTO without LHF models.

CONCLUSIONS

HTO should be performed while considering a medial opening wedge HTO to avoid a type II and type III LHF as a potential complication.

Comparative study of medial opening wedge high tibial osteotomy using fixator-cum-distractor device or locking plate in medial unicompartmental osteoarthritis of knee

OBJECTIVE

The aim of our study was to evaluate the role of medial opening wedge high tibial osteotomy (MOWHTO) in medial unicompartmental osteoarthritis of the knee and compare two different fixation devices for stability, duration, outcome, and complications.

METHODS

Fifty-seven patients (60 knees) of age < 60 yrs and either sex with medial unicompartmental osteoarthritis of the knee were divided into 2 groups. Twenty-four patients (25 knees) in Group I underwent MOWHTO using fixator-cum-distractor and 33 patients (35 knees) in Group II underwent MOWHTO using locking plate osteosynthesis. The results were assessed by VAS, KOOS and WOMAC score.

RESULTS

Mean age of the patients in Group I was 53.13 ± 5.20 years and 51.32 ± 6.91 years in Group II. Mean preoperative varus deviation was 11.97 ± 3.34° in Group I and 11.78 ± 3.05° in Group II which was corrected to 3.27 ± 1.75° and 3.56 ± 1.47° valgus respectively. All the patients achieved full weight bearing by 35th day postoperatively in Group I with the mean of 30.27 ± 2.71 days and 38th day in Group II with the mean of 30.32 ± 3.08. The VAS, KOOS, and WOMAC score improved significantly postoperatively in both the groups.

CONCLUSION

The difference between the two methods of fixation was statistically insignificant. Fixator-cum-distractor is minimally invasive giving good control over the final limb alignment; however, it is cumbersome with less patient compliance and has complications like pin tract infection. Locking plate provides better fixation stability than fixator-cum-distractor even without bone grafting; however, it is an invasive procedure requiring more soft tissue exposure and precise amount of wedge removal.

High tibial osteotomy results in improved frontal plane knee moments, gait patterns and patient-reported outcomes

PURPOSE

The purpose of this study was to quantify changes in knee loading in the three clinical planes, compensatory gait adaptations and patient-reported outcome measures (PROMS) resulting from opening wedge high tibial osteotomy (HTO).

METHODS

Gait analysis was performed on 18 participants (19 knees) with medial osteoarthritis (OA) and varus alignment pre- and post-HTO, along with 18 controls, to calculate temporal, kinematic and kinetic measures. Oxford Knee Score, Knee Outcome Survey and visual analogue pain scores were collected. Paired and independent sample tests identified changes following surgery and deviations from controls.

RESULTS

HTO restored frontal and transverse plane knee joint loading to that of the control group, while reductions remained in the sagittal plane. Elevated frontal plane trunk sway (p = 0.031) and reduced gait speed (p = 0.042), adopted as compensatory gait changes pre-HTO, were corrected by the surgery. PROMs significantly improved (p ≤ 0.002). Centre of pressure (COP) was lateralised relative to the knee post-HTO (p < 0.001). Energy absorbed in the sagittal plane significantly increased post-HTO (p = 0.007), whilst work done in the transverse plane reduced (p ≤ 0.008). Pre-operative gait deviations from the control group that were retained post-HTO included smaller sagittal (p = 0.003) knee range of motion during gait, greater stance duration (p = 0.008) and altered COP location (anterior to the knee) in early stance (p = 0.025).

CONCLUSIONS

HTO surgery restored frontal and transverse plane knee loading to normal levels and improved PROMs. Gait adaptations known to reduce knee loading employed pre-HTO were not retained post-HTO. Some gait features were found to differ between post-HTO subjects and controls.

LEVEL OF EVIDENCE

II.

Biomechanical study of optimum anchorage in dome-shaped high tibial osteotomy

PURPOSE

There has been no report to date on any biomechanical study regarding the strength of fixation at the osteotomy site in dome-shaped high tibial osteotomy (HTO). In this study, we evaluated the biomechanical strength of a spacer that we improved and determined the medial site of HTO.

METHODS

HTO correction angles of 15° and 20° were used in all experiments, which were performed on lower leg specimens from pigs ( n = 12). The osteotomy site was fixed by a locking plate and screws with a spacer. Compression (600 N/min until 1100 N) and extended cyclic loading (200 cycles at 1000-2000 N) were performed to compare initial displacements in HTO specimens with and without spacers.

RESULTS

The reduction ratios of displacement with and without spacers at HTO correction angles of 15° and 20° were 37% and 27%, respectively. No effect of the spacer at the correction angle of 15° was observed in the cyclic loading; however, the maximum displacement and amplitude were reduced with the spacer at the correction angle of 20°.

CONCLUSIONS AND CLINICAL RELEVANCE

When the HTO correction angle is small, the effect of the spacer is uncertain. However, the spacer is effective at an HTO correction angle of 20°.

Design optimization of high tibial osteotomy plates using finite element analysis for improved biomechanical effect

Background

High tibial osteotomy (HTO) is a common treatment for moderate osteoarthritis of the medial compartment in the knee joint by the translation of the force center toward the lateral compartment. However, the stability of a short plate such as Puddu used in this procedure was not as effective as other long plates such as Tomofix. No previous studies have used a rigorous and systematic design optimization method to determine the optimal shape of short HTO plate. Therefore, the purpose of this study is to evaluate the improved biomechanical stability of a short HTO plate by using design optimization and finite element (FE) analysis.

Methods

A FE model of HTO was subjected to physiological and surgical loads in the tibia. Taguchi-style L27 orthogonal arrays were used to identify the most significant factors for optimizing the design parameters. The optimal design variables were calculated using the nondominated sorting genetic algorithm II. Plate and bone stresses and wedge micromotions in the initial and optimized designs were chosen as the comparison indices.

Results

Optimal designed HTO plate showed the decreased micromotions over the initial HTO plate with enhanced plate stability. In addition, increased bone stress and decreased plate stress supported the positive effect on stress shielding compared to initial HTO plate design. The results yielded a new short HTO design while demonstrating the feasibility of design optimization and potential improvements to biomechanical stability in HTO design. The newly developed short HTO plate throughout the optimization and computational simulation showed the improved biomechanical effect as good as the golden standard, TomoFix, does.

Conclusions

This study showed that plate design has a strong influence on the stability after HTO. This study demonstrated that the optimized short plates had low stress shielding effect and less micromotion because of its improvement in biomechanical performances. Our result showed that design optimization is an effective tool for HTO plate design. This information can aid future developments in HTO plate design and can be expanded to other implant designs.

[Complication analysis after angle-stable CW and OW high tibial osteotomy]

BACKGROUND

High tibial osteotomy (HTO) is a good joint-preserving alternative to joint replacement in the treatment of isolated medial varus gonarthrosis. It is, however, accompanied by a number of complications, which can compromise the outcome of the treatment.

OBJECTIVES

Analysis and comparison of the complication structure after angle-stable navigated closed wedge (CW) HTO and conventional angle-stable open wedge (OW) HTO, as well as determination of influence factors.

MATERIAL AND METHODS

281 HTO (187 CW- and 94 OWHTO) were analyzed retrospectively. Age, sex, BMI, time of surgery and radiological parameters were included as possible influence factors. A statistical analysis was performed with binary logistic regression.

RESULTS

An overall complication rate of 21.4% was revealed (25.1% after CW- and 13.8% after OWHTO, p = 0.02); the major complications occurred after 13.9% CW- and 10.6% OWHTO (p = 0.27); minor complications were observed after 11.2% CW- and 3.2% OWHTO (p = 0.03). This difference results from complications specific to CWHTO (peroneal lesions and pseudarthrosis fibulae). The incidence of pseudarthrosis tibiae was equal in both procedures (7.5%). Age ≥ 52 years and body mass index (BMI) ≥ 30 kg/m² were the relevant predictors for mechanical complications after CWHTO; these were not relevant for OWHTO.

CONCLUSION

The correct patient selection is essential to avoid postoperative complications after HTO. The overall complication rates are lower after OWHTO, mainly through the avoidance of complications typical for CWHTO. OWHTO offers a wider choice with respect to the selection of patients.

The effect of plate design, bridging span, and fracture healing on the performance of high tibial osteotomy plates: An experimental and finite element study

Objectives

Opening wedge high tibial osteotomy (HTO) is an established surgical procedure for the treatment of early-stage knee arthritis. Other than infection, the majority of complications are related to mechanical factors – in particular, stimulation of healing at the osteotomy site. This study used finite element (FE) analysis to investigate the effect of plate design and bridging span on interfragmentary movement (IFM) and the influence of fracture healing on plate stress and potential failure.

Materials and Methods

A 10° opening wedge HTO was created in a composite tibia. Imaging and strain gauge data were used to create and validate FE models. Models of an intact tibia and a tibia implanted with a custom HTO plate using two different bridging spans were validated against experimental data. Physiological muscle forces and different stages of osteotomy gap healing simulating up to six weeks postoperatively were then incorporated. Predictions of plate stress and IFM for the custom plate were compared against predictions for an industry standard plate (TomoFix).

Results

For both plate types, long spans increased IFM but did not substantially alter peak plate stress. The custom plate increased axial and shear IFM values by up to 24% and 47%, respectively, compared with the TomoFix. In all cases, a callus stiffness of 528 MPa was required to reduce plate stress below the fatigue strength of titanium alloy.

Conclusion

We demonstrate that larger bridging spans in opening wedge HTO increase IFM without substantially increasing plate stress. The results indicate, however, that callus healing is required to prevent fatigue failure.

Cite this article: A. R. MacLeod, G. Serrancoli, B. J. Fregly, A. D. Toms, H. S. Gill. The effect of plate design, bridging span, and fracture healing on the performance of high tibial osteotomy plates: An experimental and finite element study. Bone Joint Res 2018;7:639–649. DOI: 10.1302/2046-3758.712.BJR-2018-0035.R1.

D-hole breakage of 2 angular stable locking plates for medial opening-wedge high tibial osteotomy: Analysis of results from 12 cases

An adequate stable fixation implant should be used for medial opening-wedge high tibial osteotomy (MOWHTO) to promote rapid bone healing without complications. To date, the highest fixation stability has been observed for angular stable locking plates. However, there is still little medical literature regarding breakage of these plates. The purpose of the present study was to report the results of plate breakage around D-hole with the use of both types of locking plate fixation for MOWHTO.Medical records of 12 patients who experienced plate breakage after MOWHTO with either a TomoFix or OhtoFix plate between August 2013 and August 2016 were retrospectively reviewed.A total of 12 patients (7 males and 5 females) who experienced plate breakage at the screw hole just above the osteotomy were evaluated (age, 63 ± 8 years; body mass index (BMI), 28 ± 2 kg/m; opening gap height, 12 ± 2 mm). There were 9 patients (75%) with plate breakage and loss of correction necessitating revision surgery, and 11 patients (92%) had lateral cortical hinge fractures postoperatively. Of the 9 patients with loss of correction necessitating revision surgery, 4 had a TomoFix plate and 5 had an OhtoFix plate. The only statistically significant association with broken plates lost reduction was the presence of lateral cortical hinge fractures (P = .003), but there was no significant association with age, gender, BMI, diabetes, smoking, plate type, opening gap height, and material used to fill the wedge. In addition, mean knee society score in the 12 patients was significantly higher postoperatively than preoperatively (P < .001).Since the amount of plate breakage was just over 1% and with only 12 in total, no true conclusion can be made with certainty. However, in the face of no lateral hinge or cortical disruption, there is a 99% success rate with the plate described. If the lateral hinge is disrupted, a restriction of activity or weight bearing may be needed.

Biomechanical evaluation of opening-wedge high tibial osteotomy with composite materials using finite-element analysis

BACKGROUND

Medial opening-wedge high tibial osteotomy (HTO) has been used to treat osteoarthritis of the medial compartment of the knee. However, this makes the proximal tibia a highly unstable structure and causes the plate to be a potential source of mechanical failure. Consequently, proper design and material use of the fixation device are essential in HTO, especially for overweight or full-weight-bearing patients.

METHODS

This study investigated the biomechanical effects of the TomoFix plate composed of conventional titanium (Ti) in comparison to plates composed of carbon short-fiber-reinforced (CSFR) polyetheretherketone (PEEK) and carbon long-fiber-reinforced (CLFR) PEEK, in medial opening-wedge HTO. A medial opening was simulated with various HTO plate models subjected to a 2500 N vertical load simulating the peak walking force using a validated knee-joint finite-element (FE) model. The stress on the plate and the bone, the contact stress on the menisci and articular cartilage, as well as wedge micromotion were measured.

RESULTS

The results of the FE analysis indicated that the Ti plate showed the best functional outcome in terms of micromotion. However, the CSFR PEEK plate showed a positive effect on relieving stress shielding. In addition, there was less contact stress on the meniscus and articular cartilage with the CSFR PEEK plate in comparison to CLFR PEEK and Ti plates.

CONCLUSION

These results can provide insights into the design of high-performing composite HTO plates to produce more desirable biomechanical effects.

Multi-objective design optimization of high tibial osteotomy for improvement of biomechanical effect by using finite element analysis

Medial opening wedge high tibial osteotomy (HTO) makes the proximal tibia a highly unstable structure and causes plates and screws to be the potential sources for mechanical failure. However, asymmetrical callus and incomplete bone formations underneath the plates (TomoFix) have been recent concerns in clinical and experimental studies related to HTO due to the high stiffness. The purpose of this study was to evaluate the biomechanical effect of the TomoFix plate system with respect to changes in design using a computational simulation. A parametric three-dimensional model of HTO was constructed from medical image data. The design parameters for the HTO plate were evaluated to investigate their influence on biomechanical effects, and the most significant factors were determined using Taguchi-style L27 orthogonal arrays. Multi-objective optimization was used to identify the wedge micromotion stability without the stress shielding effect that occurs in the bone plate. The initial design showed that the high stiffness of the plate caused stress shielding on the bone and plate. However, the optimal design led to sharing the stress and load with the bone plate to eliminate stress shielding. In addition, the stability required for the plate could be found in the micromotions of the wedge for the optimal design. The optimal condition of design parameters was successfully determined using the Taguchi and multi-objective optimization method, which was shown to eliminate stress shielding effects. The results showed that an optimal design demonstrated the feasibility of design optimization and improvements in biomechanical stability for HTO. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2956-2965, 2018.

Satisfactory functional and radiological outcomes can be expected in young patients under 45 years old after open wedge high tibial osteotomy in a long-term follow-up

PURPOSE

To report the long-term outcomes of medial open wedge high tibial osteotomy (MOWHTO) for the treatment of medial compartment knee osteoarthritis in patients younger than 45 years old. It was hypothesized that the correction of knee alignment would result in preservation of knee function in a long-term follow-up.

METHODS

Patients under 45 years old, who underwent MOWHTO for symptomatic medial compartment knee osteoarthritis between 2001 and 2005 were retrospectively reviewed after a minimum of 10 years. The osteotomy was performed utilizing a locking plate without the use of bone graft. Patients were evaluated pre- and postoperatively using the International Knee Documentation Committee Score, the Oxford Knee Score, the Knee injury Osteoarthritis Outcome Score and the Short Form-12 Score. Standardized standing whole-limb radiographs were also obtained to assess mechanical tibiofemoral angle (mTFA) and the grade of osteoarthritis.

RESULTS

A total of 20 patients (18 males, 2 females, mean age 35.4 years) with a mean follow-up of 12.3 years were included in the study. During the follow-up period, one patient required conversion to total knee replacement (95% survival rate). All clinical outcome scores (IKDC, KOOS, OKS, and SF-12) significantly improved postoperatively (p < 0.05), with no significant deterioration over time. Preoperative varus alignment with an mTFA of - 5.8 ± 2.4° was corrected to 2.5 ± 1.9° immediately after surgery (p < 0.05), and remained 2.2 ± 1.7° at the last follow-up. Furthermore, no significant radiographic progression of osteoarthritis was observed.

CONCLUSIONS

MWOHTO with a locking plate is an effective joint preservation method to treat medial compartment OA in active patients less than 45 years. Clinical and radiological results are satisfactory and the survival rate is 95%, 12 years after the procedure.

LEVEL OF EVIDENCE

Level IV therapeutic, retrospective, cohort study.

Role of an anatomically contoured plate and metal block for balanced stability between the implant and lateral hinge in open-wedge high-tibial osteotomy

INTRODUCTION

Open-wedge high tibial osteotomy (OWHTO) is a well-established surgical option for medial compartment osteoarthritis of the varus knee. The initial strength of the fixation plate is critical for successful correction maintenance and healing of the osteotomy site. This study was conducted to verify if a newly designed anatomical plate (LCfit) improves the stability of both the medial implant and lateral hinge area, as well as to evaluate how the metal block contributes to both medial and lateral stability.

MATERIALS AND METHODS

A finite element (FE) tibial model was combined with TomoFix plate, a LCfit plate with and without a metal block. Data analysis was conducted to evaluate the balanced stability, which refers to the enforced lateral stability resulting from redistribution of overall stress. We assessed the balanced stability of the medial implant and lateral hinge area in three cases using the same Sawbones and loads using the tibia FE model.

RESULTS

The LCfit plate reduced stress by 23.1% at the lateral hinge compared to the TomoFix plate (TomoFix vs. LCfit: 34.2 ± 23.3 MPa vs. 26.3 ± 17.5 MPa). The LCfit plate with a metal block reduced stress by 40.1% at the medial plate (210.1 ± 64.2 MPa vs. 125.8 ± 65.7 MPa) and by 31.2% (26.3 ± 17.5 MPa vs. 18.1 ± 12.1 MPa) at the lateral hinge area compared to the reduction using the LCfit plate without a metal block.

CONCLUSION

The newly designed fixation system for OWHTO balanced the overall stress distribution and reduced stress at the lateral hinge area compared to that using a conventional fixation system. The addition of the metal block showed additional benefits for balanced stability between the medial implant and lateral hinge area. However, this conclusion could only be drawn using the FE model in this study. Therefore, further clinical studies are necessary to reveal the clinical effect of reduced lateral stress on the occurrence of the lateral hinge fracture and the biologic effect of the metal block on the healing of the medial cortex.

Comparison of Puddu osteotomy with or without autologous bone grafting: a prospective clinical trial

Objectives

To test the hypothesis that autologous iliac bone grafts do not enhance clinical results and do not decrease complication rates in patients undergoing medial opening-wedge high tibial osteotomy.

Methods

Forty patients allocated in a randomized, two-armed, double-blinded clinical trial were evaluated between 2007 and 2010. One group received bone graft, and the other group was left without filling the osteotomy defect. The primary outcome was the Knee Society Score. Radiographic measurement of the frontal anatomical femoral-tibial angle and the progression of osteoarthritis according to the modified Ahlback classification were used as secondary outcomes.

Results

There was no difference in KSS scale between the graft group (64.4 ± 21.8) and the graftless group (61.6 ± 17.3; p = 0.309). There was no difference of angle between the femur and tibia in the frontal plane between the groups (graft = 184 ± 4.6 degrees, graftless = 183.4 ± 5.1 degrees; p = 1.0), indicating that there is no loss of correction due to the lack of the graft. There was significant aggravation of osteoarthritis in a greater number of patients in a graft group (p = 0.005).

Conclusion

Autologous iliac bone graft does not improve clinical outcomes in medium and long-term follow-up of medial opening-wedge high tibial osteotomy fixed with a first generation Puddu plate in the conditions of this study.

Identification of the critical level of implantation of an osseointegrated prosthesis for above-knee amputees

The aim of our study was to identify potential critical levels of implantation of an osseointegrated prosthesis for above-knee amputees. The implant used was the OPRA system. It was inserted in the femur at four different amputation heights, characterized by their residual limb ratios (0.299, 0.44, 0.58 and 0.73). The stress and strain distribution was evaluated in the bone-implant system during walking, considering a body mass of 100 kg. Considerably high stimulus (11,489 με) in the tissue near the tip was found at the highest implantation level. All models presented small non-physiologic stress values in the tissue around the implant. The results revealed that the implantation level has a decisive effect on bone-implant performance. Mainly, the analysis indicates adverse biomechanical conditions for implantations in very short residual limbs.

High tibial osteotomy in varus knees: indications and limits

Opening wedge high tibial osteotomy (OWHTO) is a surgical procedure that aims to correct the weight-bearing axis of the knee, moving the loads laterally from the medial compartment. Conventional indications for OWHTO are medial compartment osteoarthritis and varus malalignment of the knee; recently OWHTO has been used successfully in the treatment of double and triple varus. OWHTO, in contrast to closing wedge high tibial osteotomy, does not require fibular osteotomy or peroneal nerve dissection, or lead to disruption of the proximal tibiofibular joint and bone stock loss. For these reasons, interest in this procedure has grown in recent years. The aim of this study is to review the literature on OWHTO, considering indications and prognostic factors (body mass index, grade of osteoarthritis, instability, range of movement and age), outcomes at mid-term follow-up, and limits of the procedure (slope modifications, patellar height changes and difficulties in conversion to a total knee arthroplasty).

High Tibial Osteotomy: A Systematic Review and Current Concept

High tibia osteotomy is a common procedure in orthopedic surgery. A precise overview on indications, patients selection, pre-operative planning, surgical technique, methods of fixation, and complications have been presented. This paper focused on the points that should be considered to achieve good long-term outcomes.