Preoperative planning of medial opening wedge high tibial osteotomy using 3D computer-aided design weight-bearing simulated guidance: Technique and preliminary result

A preoperative simulation of medial open-wedge high tibial osteotomy for predicting postoperative realignment

Three-dimensional preoperative surgical simulation of the medial open-wedge high tibial osteotomy (OWHTO), simplified as the rigid rotation around the hinge axis, has been performed to predict postoperative realignment. However, the practicality of this highly simplified simulation method has not been verified. This study aimed to investigate the validity of realignment simulation simplified as a rotation around a hinge axis compared with a postoperative CT model. A three-dimensional surface model of the tibia and femur was created from preoperative computed tomography (CT) images (preoperative model) of three patients. The simulation of medial OWHTO created sixty computer simulation models in each patient simplified as the rigid rotation of the proximal part of the tibia relative to the distal part from 1° to 20° around three types of hinge axes. The simulation models were compared with the actual postoperative model created from postoperative CT images to assess the reality of the simulation model. The average surface distance between the two models was calculated as an index representing the similarity of the simulation model to the postoperative model. The minimum value of average surface distances between the simulation and postoperative CT models was almost 1 mm in each patient. The rotation angles at which the minimum value of average surface distances was represented were almost identical to the actual correction angles. We found that the posterior tibial tilt and the axial rotation of the proximal tibia of the simulation model well represented those of the postoperative CT model, as well as the valgus correction. Therefore, the realignment simulation of medial OWHTO can generate realistic candidates for postoperative realignment that includes the actual postoperative realignment, suggesting the efficacy of the preoperative simulation method.

Design and Manufacturing of a Novel Trabecular Tibial Implant

The elastic modulus of traditional solid titanium alloy tibial implants is much higher than that of human bones, which can cause stress shielding. Designing them as a porous structure to form a bone-like trabecular structure effectively reduces stress shielding. However, the actual loading conditions of bones in different parts of the human body have not been considered for some trabecular structures, and their mechanical properties have not been considered concerning the personalized differences of other patients. Therefore, based on the elastic modulus of the tibial stem obtained from Quantitative Computed Tomography (QCT) imaging between 3.031 and10.528 GPa, and the load-bearing state of the tibia at the knee joint, a porous structure was designed under compressive and shear loading modes using topology optimization. Through comprehensive analysis of the mechanical and permeability properties of the porous structure, the results show that the Topology Optimization-Shear-2 (TO-S2) structure has the best compressive, shear mechanical properties and permeability and is suitable as a trabecular structure for tibial implants. The Gibson-Ashby model was established to control the mechanical properties of porous titanium alloy. A gradient filling of porous titanium alloy with a strut diameter of 0.106-0.202 mm was performed on the tibial stem based on the elastic modulus range, achieving precise matching of the mechanical properties of tibial implants and closer to the natural structure than uniformly distributed porous structures in human bones. Finally, the new tibial implant was printed by selective laser melting (SLM), and the molding effect was excellent.

Design and performance analysis of 3D-printed stiffness gradient femoral scaffold

Studies on 3D-printed porous bone scaffolds mostly focus on materials or structural parameters, while the repair of large femoral defects needs to select appropriate structural parameters according to the needs of different parts. In this paper, a kind of stiffness gradient scaffold design idea is proposed. Different structures are selected according to the different functions of different parts of the scaffold. At the same time, an integrated fixation device is designed to fix the scaffold. Finite element method was used to analyze the stress and strain of homogeneous scaffolds and the stiffness gradient scaffolds, and the relative displacement and stress between stiffness gradient scaffolds and bone in the case of integrated fixation and steel plate fixation. The results showed that the stress distribution of the stiffness gradient scaffolds was more uniform, and the strain of host bone tissue was changed greatly, which was beneficial to the growth of bone tissue. The integrated fixation method is more stable, less stress and evenly distributed. Therefore, the integrated fixation device combined with the design of stiffness gradient can repair the large femoral bone defect well.

An artificial intelligence based on a convolutional neural network allows a precise analysis of the alignment of the lower limb

PURPOSE

The objective of this study was to develop a numeric tool to automate the analysis of deformity from lower limb telemetry and assess its accuracy. Our hypothesis was that artificial intelligence (AI) algorithm would be able to determine mechanical and anatomical angles to within 1°.

METHODS

After institutional review board approval, 1175 anonymized patient telemetries were extracted from a database of more than ten thousand telemetries. From this selection, 31 packs of telemetries were composed and sent to 11 orthopaedic surgeons for analysis. Each surgeon had to identify on the telemetries fourteen landmarks allowing determination of the following four angles: hip-knee-ankle angle (HKA), medial proximal tibial angle (MPTA), lateral distal femoral angle (LDFA), and joint line convergence angle (JLCA). An algorithm based on a machine learning process was trained on our database to automatically determine angles. The reliability of the algorithm was evaluated by calculating the difference of determination precision between the surgeons and the algorithm.

RESULTS

The analysis time for obtaining 28 points and 8 angles per image was 48 ± 12 s for the algorithm. The average difference between the angles measured by the surgeons and the algorithm was around 1.9° for all the angles of interest: 1.3° for HKA, 1.6° for MPTA, 2.1° for LDFA, and 2.4° for JLCA. Intraclass correlation was greater than 95% for all angles.

CONCLUSION

The algorithm showed high accuracy for automated angle measurement, allowing the estimation of limb frontal alignment to the nearest degree.

Is Patient-Specific Instrumentation Accurate and Necessary for Open-Wedge High Tibial Osteotomy? A Meta-Analysis

The purpose of this meta-analysis was to identify if patient-specific instrumentation (PSI) could increase the accuracy of the correction in high tibial osteotomy (HTO) and to explore the assessment indices and the necessity of using a PSI in HTO. A systematic search was carried out using online databases. A total of 466 patients were included in 11 papers that matched the inclusion criteria. To evaluate the accuracy of PSI-assisted HTO, the weight bearing line ratio (WBL%), hip-knee-ankle angle (HKA), mechanical medial proximal tibial angle (mMPTA), and posterior tibial slope angle (PTSA) were measured preoperatively and postoperatively and compared to the designed target values. Statistical analysis was performed after strict data extraction with Review Manager (version 5.4). Significant differences were detected in WBL% (MD = -36.41; 95% CI: -42.30 to -30.53; p < 0.00001), HKA (MD = -9.95; 95% CI: -11.65 to -8.25; p < 0.00001), and mMPTA (MD = -8.40; 95% CI:-10.27 to -6.53; p < 0.00001) but not in PTSA (MD = 0.34; 95% CI: -0.59 to 1.27; p = 0.47) between preoperative and postoperative measurements. There was no significant difference between the designed target values and the postoperative correction values of HKA (MD = 0.14; 95% CI: -0.19 to 0.47; p = 0.41) or mMPTA (MD = 0.11; 95% CI -0.34 to 0.55; p = 0.64). The data show that 3D-based planning of PSI for HTO is both accurate and safe. WBL%, HKA, and mMPTA were the optimal evaluation indicators of coronal plane correction. Sagittal correction is best evaluated by the PTSA. The present study reports that PSI is accurate but not necessary in typical HTO.

Custom-Made Devices Represent a Promising Tool to Increase Correction Accuracy of High Tibial Osteotomy: A Systematic Review of the Literature and Presentation of Pilot Cases with a New 3D-Printed System

Background: The accuracy of the coronal alignment corrections using conventional high tibial osteotomy (HTO) falls short, and multiplanar deformities of the tibia require consideration of both the coronal and sagittal planes. Patient-specific instrumentations have been introduced to improve the control of the correction. Clear evidence about customized devices for HTO and their correction accuracy lacks. Methods: The databases PUBMED and EMBASE were systematically screened for human and cadaveric studies about the use of customized devices for high tibial osteotomy and their outcomes concerning correction accuracy. Furthermore, a 3D-printed customized system for valgus HTO with three pilot cases at one-year follow-up was presented. Results: 28 studies were included. The most commonly used custom-made devices for HTO were found to be cutting guides. Reported differences between the achieved and targeted correction of hip-knee-ankle angle and the posterior tibial slope were 3° or under. The three pilot cases that underwent personalized HTO with a new 3D-printed device presented satisfactory alignment and clinical outcomes at one-year follow-up. Conclusion: The available patient-specific devices described in the literature, including the one used in the preliminary cases of the current study, showed promising results in increasing the accuracy of correction in HTO procedure.

Repair of bone defects in rhesus monkeys with α1,3-galactosyltransferase-knockout pig cancellous bone

Introduction: Since xenografts offer a wide range of incomparable advantages, they can be a better option than allografts but only if the possibility of immunological rejection can be eliminated. In this study, we investigated the ability of α1,3-galactosyltransferase (α1,3-GT) gene knockout (GTKO) pig cancellous bone to promote the repair of a femoral condyle bone defect and its influence on heterologous immune rejection.

Materials and methods: Cylindrical bone defects created in a rhesus monkey model were transplanted with GTKO bone, WT bone or left empty. For immunological evaluation, T lymphocyte subsets CD4⁺ and CD8⁺ in peripheral blood were assayed by flow cytometry, and the IL-2 and IFN-γ contents of peripheral blood serum were analyzed by ELISA at 2, 5, 7, 10, and 14 days post-surgery. Micro-CT scans and histological assessment were conducted at 4 and 8 weeks after implantation.

Results: Compared with WT-pig bone, the heterologous immunogenicity of GTKO-pig bone was reduced. The defect filled with fresh GTKO-pig bone was tightly integrated with the graft. Histological analysis showed that GTKO-pig cancellous bone showed better osseointegration and an appropriate rate of resorption. Osteoblast phenotype progression in the GTKO group was not affected, which revealed that GTKO-pig bone could not only fill and maintain the bone defect, but also promote new bone formation.

Conclusion: GTKO-pig cancellous bone decreased the ratio of CD4⁺ to CD8⁺ T cells and cytokines (IFN-γ and IL-2) to inhibit xenotransplant rejection. Moreover, GTKO group increased more bone formation by micro-CT analysis and osteoblastic markers (Runx2, OSX and OCN). Together, GTKO-pig cancellous bone showed better bone repair than WT-pig cancellous bone.

Geometrical Planning of the Medial Opening Wedge High Tibial Osteotomy—An Experimental Approach

This article presents an experimental approach to the geometrical planning of the medial opening wedge high tibial osteotomy surgery which, as it is known, is an efficient surgical strategy quite widely used in treating knee osteoarthritis. While most of the published papers focus on analyzing this surgery from a medical point of view, we suggest a postoperative experimental evaluation of the intervention from a biomechanical point of view. The geometrical planning and, more specifically, the determination of the point of intersection between the corrected mechanical axis and the medial-lateral articular line of the knee, is a problem quite often debated in literature. This paper aims to experimentally investigate the behavior of the tibia with an open wedge osteotomy fixed with a locking plate, TomoFix (DE Puy Synthes), taking into account two positions of the mechanical axis of the leg on the width of the tibial plateau, measured from medial to lateral at 50% and 62.5% (Fujisawa point), respectively. The variations of the force relative to the deformation, strains, and displacements resulting from the progressive loading of the tibial plateau are studied. The research results reveal that using the Fujisawa point is better for conducting the correction not only for medical reasons, but also from a mechanical point of view.

CAS and PSI increase coronal alignment accuracy and reduce outliers when compared to traditional technique of medial open wedge high tibial osteotomy: a meta-analysis

PURPOSE

Medial open-wedge high tibial osteotomy (MOWHTO) is an accepted option in the treatment of medial compartment osteoarthritis of the knee in young and active patients. Functional results are closely correlated to the correction of the mechanical axis of the lower limb. Although several angular and geometrical methods and values have been proposed in the past, the ideal target is still debated. In addition, it is important to have a deep correlation between the planned correction and the achieved correction after surgery. The aim of the present systematic review was to identify the ideal coronal correction after MOWHTO and the most accurate method to achieve it.

METHODS

A systematic review of the literature was completed on July 3rd 2020 in the Pubmed, Medline, Cochrane Reviews, and Google Scholar databases using the Medical Subject Headings (MeSH) terms: "high tibial osteotomy" AND "accuracy" OR "planning".

RESULTS

28 studies were included; 18 were focused on computer-assisted surgery (CAS) and 10 on patient-specific instrumentation (PSI). There were 598 patients in the CAS group and 501 in the control group; the rate of outliers was 16% and 38.2% respectively (P = 0.04), while there was no significant difference between the two groups (SMD = - 0.10; 95% CI 1.31 to 1.12; P = n.s.) in terms of coronal accuracy. Likewise, there were 318 patients in the PSI group and 40 in the control group; the rate of outliers was 15% and 40% respectively (P = 0.98), while there was no significant difference between the two groups (SMD = 0.01; 95% CI 0.58 to 0.59; P = 0.98).

CONCLUSIONS

A statistically significant reduced outlier rate and a non-significant increased accuracy emerged with the use of CAS when compared to the traditional surgical technique, whereas the results of PSI were still inconclusive. In addition, it emerged clearly that no consensus still exists on the ideal correction target to be achieved after surgery.

LEVEL OF EVIDENCE

III.

Differences in preoperative planning for high-tibial osteotomy between the standing and supine positions

Introduction

Previous studies have reported that alignment changes depend on the patient’s position in orthopedic surgery. However, it has not yet been well examined how the patient’s position affects the preoperative planning in high-tibial osteotomy (HTO). Therefore, the aim of this study was to investigate the effects of the patient’s position on preoperative planning in HTO.

Materials and methods

A total of 60 knees in 55 patients who underwent HTO were retrospectively examined. Virtual preoperative planning for medial open-wedge HTO (OWHTO), lateral closed-wedge HTO (CWHTO), and hybrid CWHTO were performed by setting the percentage of the weight-bearing line (%WBL) at 62% as an optimal alignment. The correction angle differences between the supine and standing radiographs were measured. The virtual %WBL (v%WBL) was determined by applying the correction angle obtained from the standing radiograph to the supine radiograph. The %WBL discrepancy (%WBLd) was calculated as v%WBL − 62 (%) to predict the possible correction errors during surgeries. A single regression analysis was performed to examine the correlation between the correction angle difference and %WBLd.

Results

The mean correction angle was significantly higher when the preoperative planning was based on standing radiographs than when based on supine radiographs (P < 0.001), and the mean difference was 2.2 ± 1.5°. The difference between the two conditions in the medial opening gaps for OWHTO, lateral wedge sizes (mm) for CWHTO, and hybrid CWHTO were 2.6 ± 2.0, 2.3 ± 1.6, and 1.9 ± 1.4, respectively. The mean v%WBL was 71.2% ± 7.3%, and the mean %WBLd was 10.1% ± 7.4%. A single regression analysis revealed a linear correlation between the correction angle difference and %WBLd (%WBLd = 4.72 × correction angle difference + 0.08). No statistically significant difference in the parameters was found between the supine and standing radiographs postoperatively.

Conclusions

We found significant differences in the estimated correction angles between the supine and standing radiographs in the planning for HTO. Therefore, surgeons should carefully consider the difference between supine and standing radiographs and estimate the possible correction error during surgery when planning a HTO.

Medial Opening Wedge High Tibial Osteotomy in Knee Osteoarthritis—A Biomechanical Approach

This paper provides an analysis from a biomechanical perspective of the medial opening wedge high tibial osteotomy surgery, a medical procedure commonly used in treating knee osteoarthritis. The aim of this research is to improve the analysed surgical strategy by establishing optimal values for several very important parameters for the geometric planning of this type of surgical intervention. The research methods used are numerical and experimental. We used finite element, a numerical method used to study the intraoperative behavior of the CORA area for different positions of the initiation point of the cut of the osteotomy plane and for different correction angles. We also used an experimental method in order to determine the maximum force which causes the occurrence of cracks or microcracks in the CORA area. This helped us to determine the stresses, the maximum forces, and the force-displacement variations in the hinge area, elements that allowed us to identify the optimal geometric parameters for planning the surgery.

Medium-term survival and clinical and radiological results in high tibial osteotomy: Factors for failure and comparison with unicompartmental arthroplasty

INTRODUCTION

High tibial osteotomy (HTO) and unicompartmental knee arthroplasty (UKA) are two surgical solutions for isolated medial tibiofemoral osteoarthritis. Results depend on preoperative criteria and patient selection, but also on postoperative factors: implant positioning, limb alignment. Factors for HTO survival need identifying to reduce risk of failure requiring total knee arthroplasty (TKA).

HYPOTHESIS

Age, gender, weight, osteoarthritis grade, degree of correction, type of osteotomy, technique and intraoperative complications impact HTO survival.

MATERIAL AND METHOD

As part of a symposium of the French Society of Arthroscopy (SFA), a multicenter retrospective study compared 2 series. The HTO series comprised 488 patients: 153 female (31.4%); mean age, 55.1 years; mean weight, 83.1kg; mean body-mass index (BMI), 28.6. The UKA series comprised 284 patients: 172 female (60.6%); mean age, 64.1 years; mean weight, 75.3kg; mean BMI, 27.6. The main endpoint was comparative survival at 5, 8 and 10 years; secondary endpoints comprised pre- and post-operative hip-knee-ankle (HKA) angle, mechanical femoral angle (mFA) and mechanical tibial angle (mTA), surgical technique, satisfaction, time to and level of return to work, WOMAC and Tegner scores and complications rates. The significance threshold was set at p<0.05; 95% confidence intervals were calculated.

RESULTS

Age>54 years, male gender, BMI>25, medial tibiofemoral wear severity Ahlback ≥3, ≥0.9° varus joint component, HKA correction<8°, postoperative HKA<180° and hinge fracture were significantly associated with poorer survival. There was no impact of type of osteotomy, navigation assistance or postoperative HKA 183-186°. Ten-year survival was 74.3% for HTO and 71% for UKA (non-significant); however, survival curves crossed at 6 years.

CONCLUSION

HTO showed survival and functional results comparable to those of UKA in selected patients when target limb alignment correction was achieved. The present study determined selection criteria. A predictive score for results of either procedure would facilitate decision-making.

LEVEL OF EVIDENCE

IV, retrospective cohort study.

Is patient-specific instrumentation more precise than conventional techniques and navigation in achieving planned correction in high tibial osteotomy?

INTRODUCTION

Preoperative planning in high tibial osteotomy (HTO) is a critical step for achieving the desired correction and a clinically satisfactory outcome. Conventional radiography, navigation assistance and patient-specific instrumentation (PSI) are the 3 means of planning, but no prospective studies have compared precision between the 3. The aims of the present study were: (1) to analyze and compare correction precision between the 3 planning approaches at 1 year's follow-up; (2) to compare results to those reported in the literature; and (3) to analyze factors influencing the achievement of planned correction.

HYPOTHESIS

The study hypothesis was that PSI provides more precise and reproducible planned correction than conventional methods or navigation.

MATERIAL AND METHOD

Between June 2017 and June 2018, a multicenter non-randomized prospective observational study was conducted in 11 centers. One hundred and twenty-six patients with Ahlbäck grade I, II or III idiopathic medial tibiofemoral osteoarthritis with stable knee were included and allocated to 3 preoperative planning groups: conventional (group 1), navigation (group 2) and PSI (group 3). Mean age at surgery was 51.2 years (range, 19-69 years; median, 53.2 years); 100 male, 26 female. Complete weight-bearing radiographic work-up was performed preoperatively and at 1 year's follow-up. The PSI group also underwent CT as part of guide production. Target angular correction and mechanical Hip-Knee-Ankle (HKA) axis were set preoperatively. The main endpoint was the difference between planned HKA and HKA at a minimum 12 months.

RESULTS

Mean HKA difference was 1.1±3 in group 1, 2.1±2.6 in group 2 and 0.3±3.1 in group 3. Precision was better with PSI, but not significantly when comparing all 3 groups together. On pairwise intergroup comparison, there was a significant difference only between groups 2 and 3, in favor of PSI (P=0.011).

DISCUSSION

None of the 3 techniques demonstrated superiority in achieving target correction at 1 year. The study hypothesis was thus not confirmed. All 3 techniques proved reliable and precise in HTO planning.

LEVEL OF EVIDENCE

III, prospective non-randomized comparative study.