Clinical efficacy of preoperative 3D planning for reducing surgical errors during open-wedge high tibial osteotomy

High Tibial Osteotomy in Knee Reconstruction and Joint Preservation

High tibial osteotomy is a dynamic operation, used as an effective procedure in both joint preservation and knee stability. Applications and indications are expanding, with good results in the treatment of malalignment associated with arthrosis, knee instability, meniscus deficiency or transplants, and/or cartilage restoration. Appropriate patient selection and preoperative planning are critical to achieving good outcomes after surgery. Coronal and sagittal plane corrections made through the proximal tibia can effectively alter joint mechanics creating a more favorable environment for cartilage, meniscus, and ligamentous structures about the knee. Advancing techniques and technologies have allowed for more precise planning and execution of osteotomies.

3D osteotomies-improved accuracy with patient-specific instruments (PSI)

PURPOSE

Three-dimensional (3D) printed patient-specific instruments (PSI) have been introduced to increase precision and simplify surgical procedures. Initial results in femoral and tibial osteotomies are promising, but validation studies on 3D planning, manufacturing of patient-specific cutting blocks and 3D evaluation of the attained results are lacking.

METHODS

In this study, patient-specific cutting blocks and spacers were designed, fabricated, and used to perform a high tibial osteotomy (HTO). After segmentation of CT data sets from 13 human tibiae, 3D digital planning of the HTO was performed with a medial opening of 8 mm. These 3D models were used to fabricate patient-specific cutting blocks and spacers. After the surgical procedure, accuracy was evaluated measuring 3D joint angles and surface deviations.

RESULTS

The lowest mean deviation was found to be 0.57° (SD ± 0.27) for the MPTA. Medial and lateral tibial slope deviated from the 3D planning by an average of 0.98° (SD ± 0.53) and 1.26° (SD ± 0.79), respectively, while tibial torsion deviated by an average of 5.74° (SD ± 3.24). Color analysis of surface deviations showed excellent and good agreement in 7 tibiae.

CONCLUSION

With 3D cutting blocks and spacers, the 3D planning of the HTO can be translated into reality with small deviations of the resulting joint angles. Within this study, the results of the individual steps are examined for errors and thus a critical evaluation of this new and promising method for performing patient-specific HTOs is presented.

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.

Larger bone marrow lesion volume before medial open-wedge high tibial osteotomy correlates with better improvement of clinical scores in patients with knee osteoarthritis

PURPOSE

This study evaluated the clinical outcomes of medial open-wedge high tibial osteotomy (MOWHTO) and bone marrow lesion (BML) scores and volumes. The hypotheses were that quantitative BML volume is more associated with clinical outcomes of MOWHTO than qualitative BML evaluations, and pre-operative BML volume is associated with the improvement of clinical outcomes.

METHODS

Patients who underwent MOWHTO were retrospectively enrolled. The Knee Injury and Osteoarthritis Outcome Score (KOOS) was recorded before the initial surgery and at plate removal surgery. Using pre-operative short-time inversion recovery magnetic resonance imaging, BMLs were evaluated using three qualitative scores, reflecting the maximum length, proportion, and intensity of BML. For quantification, BMLs of the femur and tibia were separately defined as lesions with a threshold greater than the mean signal intensity plus two standard deviations, using the corresponding lateral condyles as controls. The association between the KOOS scales and BML scores/volume was evaluated using Spearman's correlation coefficient. Multivariate linear regression analyses for post-operative KOOS scales were performed using the tibial BML volume as one of the four independent variables.

RESULTS

The final analysis included 40 MOWHTO cases. Two qualitative BML scores correlated only with pre-operative KOOS sports. Femoral and tibial BML volumes were correlated with post-operative KOOS QOL (ρ = 0.40, p = 0.01) and sports (ρ = 0.36, p = 0.02), respectively. Tibial BML volume was significantly correlated with all five delta KOOS scales (ρ = 0.39-0.51, p = 0.01-0.001), however, femoral BML volume was only correlated with delta KOOS QOL (ρ = 0.41, p = 0.01). In multivariate analyses, tibial BML volume was a significant positive predictor for every post-operative KOOS scale, while post-operative % mechanical axis was also a positive significant variable, except post-operative KOOS pain.

CONCLUSION

Tibial BML volume was positively correlated with one post-operative KOOS scale and all delta KOOS scales. A larger pre-operative tibial BML and appropriate alignment correction were associated with a better post-operative KOOS scales. Pre-operative large BML had no negative influence on post-operative clinical outcomes; hence, surgeons need not hesitate to perform MOWHTO in patients with large BMLs in the medial condyles.

LEVEL OF EVIDENCE

Retrospective case series, Level IV.

Opening-Wedge High Tibial Osteotomy With High Hinge Position Risks Lateral Hinge Fracture in Men With Posterolateral Tibial Condyle Protrusion

PURPOSE

The primary aim of this study was to evaluate the 3-dimensional morphology of the proximal tibia around the osteotomy plane in open-wedge high tibial osteotomy, focusing on the posterolateral (PL) and posteromedial (PM) tibial condyles, and to clarify the changes in morphologic parameters due to differences in patient characteristics and hinge position. The secondary aim was to examine whether morphologic features were associated with insufficient osteotomy, which increases the risk of lateral hinge fracture (LHF).

METHODS

The PL and PM anteroposterior distance, asymmetry ratio, and discrepancy between PL and PM distances along the tibial osteotomy plane were measured. We investigated changes in the parameters due to differences in patient characteristics and hinge position. Osteotomy configurations and LHFs were evaluated using postoperative computed tomography scans.

RESULTS

The 3-dimensional preoperative plans of 117 knees (male, 41 knees; female, 76 knees) were evaluated. PL distances were larger than PM distances in almost all cases. The average asymmetry ratio was 1.35, and the standard deviation was 0.22. Higher hinge position was associated with a larger asymmetry ratio and discrepancy (P < .001). The asymmetry ratio and discrepancy were independently positively correlated with male sex (P = .002 and P = .001, respectively) and gentle posterior tibial slope (P < .001 and P < .001, respectively). Osteotomies with type III LHFs showed lower osteotomy sufficiency than osteotomies without LHFs (P < .001).

CONCLUSIONS

PL tibial condyle protrusion was more pronounced in male patients and those with a high hinge position, and may result in insufficient PL osteotomy, which is a risk factor for type III LHF during open-wedge high tibial osteotomy. The optimal hinge position was located approximately 15 mm and 20 mm distal to the lateral tibial plateau in female and male patients, respectively.

LEVEL OF EVIDENCE

IV: retrospective case series.

Application of SolidWorks software in preoperative planning of high tibial osteotomy

Purpose

Open-wedge high tibial osteotomy (HTO) is a common surgical treatment for medial osteoarthritis in young and active patients. The accuracy of osteotomy is closely associated with postoperative efficacy. The accuracy of digital preoperative planning is higher than that of the preoperative manual measurement and several computer software with varying accuracy and convenience are used for digital preoperative planning. This study aimed to use the SolidWorks software for HTO preoperative planning and to determine its accuracy and reliability in HTO preoperative planning.

Methods

We reviewed the data of 28 patients with 54 with medial compartment knee arthritis who underwent open-wedge HTO preoperative planning using SolidWorks between June 2019 and March 2021. The standard anteroposterior standing whole-leg radiographs were assessed before and 6 weeks after the surgery. The correction angle, weight-bearing line (WBL) ratio, mechanical femorotibial angle (mFTA), and medial proximal tibial angle (MPTA) before and after the surgery were compared. The clinical results were evaluated using the Knee Society score.

Results

At 6 weeks after the surgery, the WBL ratio was corrected from 16.8% to 50.5%, mFTA was corrected from 6.4° varus to 1.2° valgus, and MPTA was corrected from 83.4° to 89.3°. No significant difference was observed between the predicted correction angle before the surgery and the correction angle measured 6 weeks after the surgery (t = -1.745, p = 0.087). The knee score and function score of Knee Society increased from 76.4 and 80.7 before surgery to 95.0 and 95.7, respectively.

Conclusions

The SolidWorks software showed high accuracy and reliability in preoperative planning of open-wedge HTO in patients with medial compartment knee arthritis.

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.

The relationship between the ''Fujisawa point'' and anatomical femorotibial angle following simulated open wedge high tibial osteotomy

Background

We evaluated the relationship between the weight-bearing line (WBL) ratio and anatomical femorotibial angle (FTA) by simulated open wedge high tibial osteotomy (OWHTO). This study evaluated the correlation between the ‘‘Fujisawa point’’ and FTA, and identified factors which caused deviations between the two measurement methods. We hypothesized that the Fujisawa point corresponded with 170° of the FTA.

Methods

Preoperative antero-posterior full-length lower limb radiographs of 82 patients were obtained for the OWHTO to place the WBL ratio at a target of 62.5% of the width of the tibial plateau (Fujisawa point). The coronal alignment was measured pre- and post-planning. The patients were divided into two groups by the post-planning FTA: a correspondence group (168.5°≦FTA≦171.5°) and a non-correspondence group (FTA < 168.5°, 171.5° < FTA). The relationship between the Fujisawa point and the FTA was analyzed with multivariate regression analysis.

Results

The post-planning FTA was 169.8 ± 1.1° and within 170 ± 1.5° in 69 cases (84.1%) when the WBL ratio was 62.5%. The neck shaft angle was 128.1 ± 5.2° in the correspondence group, and 122.3 ± 6.3° in the non-correspondence group. The multivariate linear regression analysis revealed that the neck shaft angle was the only factor that predicted the correspondence of the Fujisawa point with the FTA at 170° (p = 0.006, odd 1.28).

Conclusions

The post-planning FTA converged at 170° when the WBL ratio passed through the Fujisawa point and the neck shaft angle was the only predictor.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05734-7.

A Computer-Assisted Approach Regarding the Optimization of the Geometrical Planning of Medial Opening Wedge High Tibial Osteotomy

Opening wedge high tibial osteotomy (OWHTO) is a surgical procedure often used to eliminate the effects of knee osteoarthritis, a disease that is becoming more widespread worldwide. Optimizing the geometric planning of this operation is a very important preparatory step for the success of the intervention and rapid postoperative recovery. This optimization is performed in two main directions. The first direction evaluates the intraoperative behavior of the tibia during the osteotomy by optimizing four geometric parameters that characterize geometric planning. The second direction aims at a postoperative evaluation of the flat tibia-osteosynthesis assembly taking into account the optimal position on the medial–lateral articular line through which the corrected mechanical axis of the tongue passes and implicitly offloads the transfer from the medial area to the side of the knee. The research methods used are exclusively computer-assisted such as: computer-aided design (hereinafter CAD) for geometric modeling of the tibia taking into account the real bone structure, the finite element method (hereinafter FEM) for performing numerical analyses and design of the experiment (hereinafter DOE) for the design of the research. The results obtained are eloquent and clearly presented and can be important elements for orthopedic doctors at the geometric planning stage of the OWHTO.

Reliability of 3D planning and simulations of medial open wedge high tibial osteotomies

Purpose: In medial open-wedge high tibial osteotomy (HTO) hinge axis and osteotomy plane influence the resulting anatomy, but accurate angular quantifications using 3D-planning-simulations are lacking. The objectives of this study were developing a standardized and validated 3D-planning method of an HTO and to perform several simulated realignments to explain unintended anatomy changes. Methods: The cutting direction of the main osteotomy was defined parallel to the medial tibial slope and the hinge axis 1.5 cm distal to the lateral plateau. For interobserver testing, this 3D planning was performed on 13 digital models of human tibiae by two observers. In addition, four different hinge axis positions and five differently inclined osteotomy planes each were simulated. The osteotomy direction ranged from medial 0°-30° anteromedial, while the tilt of the osteotomy plane compared to the tibial plateau was -10° to +10°. All anatomic angular changes were calculated using 3D analysis. Results: Multiple HTO plannings by two medical investigators using standardized procedures showed only minimal differences. In the 3D-simulation, each 10° rotation of the hinge axis resulted in a 1.7° significant increase in slope. Tilting the osteotomy plane by 10° resulted in significant torsional changes of 2°, in addition to minor but significant changes in the medial proximal tibial angle (MPTA). Conclusion: Standardized 3D-planning of the HTO can be performed with high reliability using two-observer planning. 3D-simulations suggest that control of the osteotomy plane is highly relevant to avoid unintended changes in the resulting anatomy, but this can be a helpful tool to modify specific angles in different pathologies in the HTO.

Effect of bone morphology of the tibia plateau on joint line convergence angle in medial open wedge high tibial osteotomy

Background

Change in the joint line convergence angle (JLCA) of the knee after high tibial osteotomy (HTO) is difficult to predict accurately. Given that any change in JLCA is intra-articular, the shape of the articular surface, including the bone morphology of the proximal tibia, may affect the alignment of the knee joint postoperatively. The purpose of this study was to investigate the relationship between the shape of the tibial plateau and postoperative alignment of the knee joint by focusing on changes in JLCA.

Methods

One hundred and nine knees that underwent HTO were retrospectively reviewed. The shape of the tibial plateau was classified based on the slope of the medial and lateral articular surfaces as depressed, flat (within 3 degrees), or convex (pagoda-like). The relationship between the shape of the tibial plateau and radiological parameters was investigated.

Results

The shape of the tibial plateau was depressed in 38 knees, flat in 52 knees, and pagoda-like in 19 knees. There was a moderate correlation between the postoperative change in JLCA and the preoperative hip-knee-ankle angle for knees with a pagoda-shaped tibial plateau (r = 0.56) but not for the other two shapes.

Conclusions

These findings suggest that knees with marked varus deformity before HTO are likely to show more change in JLCA postoperatively if the tibial plateau is pagoda-shaped than if it has a depressed or flat shape. The advantage of focusing on the bone morphology of the proximal tibia is that surgeons can easily perform visual assessment using preoperative radiograph.

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.

Hinge fractures reaching the tibial plateau can be caused by forcible opening of insufficient posterior osteotomy during open-wedge high tibial osteotomy

PURPOSE

The purpose of this study was to use the finite element method (FEM) to reproduce fracture lines that reach the lateral tibial plateau during open-wedge high tibial osteotomy (OWHTO) in patients with Type III lateral hinge fracture (LHF). It was hypothesized that the FEM could clarify biomechanical causes of Type III LHF, enabling prevention of adverse complications.

METHODS

This study used the nonlinear FEM to analyze the data of eight knees in eight patients (two males and six females) with Type III LHF among 82 patients who underwent OWHTO, as well as the data of eight individuals with no LHF. To predict the onset of Type III LHF, simulation models were also developed in which posterior osteotomy sufficiency varied from 50% to perfect, the latter defined as osteotomy reaching the hinge point.

RESULTS

Real-life instances of Type III LHF caused by insufficient posterior osteotomy were reproduced in all patient-specific FEM models, and these models accurately predicted fracture types and locations. During opening of the osteotomy gap, the fracture line reached the lateral tibial plateau, and extended vertically from the end of the insufficient posterior osteotomy, avoiding the rigid proximal tibiofibular joint. In contrast, sufficient posterior osteotomy resulted in a lack of LHF. Posterior osteotomy extension ≥ 70% of the width of the osteotomy plane was the cut-off value to prevent Type III LHF.

CONCLUSION

Forced opening of insufficient posterior osteotomy was found to be a biomechanical cause of Type III LHF that extended perpendicularly to the lateral tibial plateau, avoiding the proximal tibiofibular joint. The clinical significance of this study is that sufficient posterior osteotomy during OWHTO, defined as at least 70% of the width of the osteotomy plane, can prevent Type III LHF.

A new 3D software for analysis and planning of lower limb and patellofemoral alignment: Reliability and accuracy

BACKGROUND

The new software, mediCAD® 3D Knee Sport (mediCAD Hectec GmbH, Altdorf/Landshut, Germany), promises to combine automated digital 3D bone model generation, 3D analysis of lower limb geometry including analysis of the patellofemoral joint, and osteotomy planning. The aim of this study was to evaluate its reliability and accuracy.

METHODS

In this retrospective multi-observer study, three post-mortem CTs were analysed by three observers at three points in time. Reliability was evaluated by calculating the intraclass correlation coefficient (ICC) of interobserver agreement. Accuracy was evaluated using the mean deviation D from the mean and the standard deviation SD from D.

RESULTS

Ten of 18 alignment parameters showed excellent, two good and three moderate interobserver agreement. Poor agreement was found for the mechanical medial proximal tibial angle, the trochlear sulcus angle and trochlea depth. Mean interobserver ICC of all parameters ranged from 0.32 to 0.99. Fifteen of 18 parameters showed a low mean deviation D from the mean of < 2 mm / 2°. Three parameters related to the patellofemoral joint showed medium or high D (patella tilt, trochlear sulcus angle, patellar ridge angle). These parameters also showed the highest values for the SD of D. The trochlear sulcus angle was found to be the only parameter with high mean deviation (D ≥ 5 mm/5°) with D being 5.67 ± 3.23°.

CONCLUSIONS

The current version of the software achieves good interobserver reliability and accuracy with the exception of a few measurement parameters.

Axial But Not Sagittal Hinge Axis Affects Posterior Tibial Slope in Medial Open-Wedge High Tibial Osteotomy: A 3-Dimensional Surgical Simulation Study

PURPOSE

The purpose of this 3-dimensional (3D) surgical simulation study was to investigate the effects of axial and sagittal hinge axes (hinge axes in the axial and sagittal planes) on medial and lateral posterior tibial slope (PTS) in medial open-wedge high tibial osteotomy (OWHTO), and evaluate the quantitative relationship between hinge axis and PTS change.

METHODS

Preoperative computed tomography data from patients with varus knee deformity were collected. A standard hinge axis (0°) and 12 different hinge axes (6 axial hinge axes and 6 sagittal hinge axes: ±10°, ±20°, and ±30°) were defined in a 3D surgical simulation of OWHTO using a bone model. The differences between before and after simulation surgery in medial and lateral PTS, medial proximal tibial angle, opening gap, and opening wedge angle were measured.

RESULTS

In total, 93 varus knees in 93 patients were included for study. Compared with the standard hinge axis, axial hinge axis significantly affected medial and lateral PTS (P < .001). In contrast, sagittal hinge axis had no significant effect on medial and lateral PTS (P > .05). Every 10° change in axial hinge axis with a mean coronal valgus correction of 10° might result in approximately 1.6° of alteration in PTS. Stepwise regression analysis showed that axial hinge axis is the most significant factors affecting PTS (β coefficient = 0.78, P < .001), followed by opening wedge angle (β coefficient = 0.36, P < .001) and gap ratio (β coefficient = 0.12, P < 0.001).

CONCLUSION

Based on our findings of 3D OWHTO simulation, axial hinge axis significantly influences medial and lateral PTS in OWHTO, but sagittal hinge axis has no effect on change in PTS. Every 10° change of axial hinge axis with a 10° coronal valgus correction caused approximately 1.6° change of PTS.

CLINICAL RELEVANCE

Hinge axis in the axial plane significantly affects PTS, but hinge axis in the sagittal plane has no effect on PTS. To maintain PTS, surgeons should make hinge axis at the true lateral position of the tibia in the axial plane. To intentionally alter PTS, an anterolateral axial hinge axis could be used to decrease PTS or a posterolateral axial hinge axis could be used to increase PTS. Opening wedge angle or gap ratio is also useful for intentional modification of PTS.

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.

High Tibial Osteotomy for Genu Varum in Adults: Do Proprietary Implants Limit the Quality of Correction?

The surgical technique of proximal tibial osteotomy for genu varum in adults has evolved from a procedure using closing wedges of estimated sizes with staple fixation in the 1960s to using standard trauma internal fixation implants and, more recently, to gradual correction with software-guided hexapod external fixators. In the last two decades, implant manufacturers have also produced anatomical implants specific for such corrective osteotomies. This study evaluates the limits of using such proprietary implants for proximal tibial osteotomy in genu varum.

Materials and methods

Scanograms (teleradiograms) of lower limbs of a patient were used to derive skiagrams (two-dimensional bony outlines of the extremities). From these, two-dimensional and three-dimensional models of varus deformities of the tibia with different values of mechanical medial proximal tibial angle (mMPTA, from 85° to 40°) were created. An analysis of the created deformity was carried out and a simulation for surgical correction was performed using an open wedge high tibial osteotomy with fixation using a proprietary (Tomofix, Synthes) implant. In addition, a 3D simulation technique was used to check the accuracy of the results obtained from the 2D simulation.

Results

In cases of mMPTA ≥80° with localisation of the apex of varus deformity at the level of the knee joint line, the standard technique used with the proprietary medial tibial plate produces good results.In cases of mMPTA ≤70°, fixation of the osteotomised fragments by the proprietary medial plate is poor owing to the anatomical contours of the implant. In these cases, a different type of osteosynthesis is needed.In cases of mMPTA ≤70°, the distance between the lower edge of the bone plate and the medial surface of the tibia after a proximal tibial osteotomy exceeds 11 mm and will result in unacceptable soft tissue tension around the implant.Mechanical axis deviation to the Fujisawa point produces mMPTA values outside the reference range of normal values.

Conclusion

An osteotomy of the proximal tibia using a prescribed technique linked to a proprietary implant achieves good results only if performed within a certain range of deformity values. Pronounced varus deformities require a fundamentally different approach. This study reveals that surgeons undertaking corrective proximal tibial osteotomies for genu varum need to perform a comprehensive analysis of the deformity to allow for appropriate selection of patients. This will enable a consideration of the size and other characteristics of the deformity that will reduce the technical complications that may arise if the correction was performed using the recommended technique linked to a proprietary implant.

How to cite this article

Solomin LN, Chugaev DV, Filippova AV, e t a l. High Tibial Osteotomy for Genu Varum in Adults: Do Proprietary Implants Limit the Quality of Correction? Strategies Trauma Limb Reconstr 2020;15(1):13-22.

Large medial proximal tibial angles cause excessively medial tibiofemoral contact forces and abnormal knee kinematics following open-wedge high tibial osteotomy

BACKGROUND

Recurrent varus deformity and poor outcome sometimes occur following open-wedge high tibial osteotomy, but the mechanism remains unclear. The hypothesis of this study was that an excessively large medial proximal tibial angle with lateral joint surface inclination can worsen postoperative knee biomechanics.

METHODS

A computer-simulated knee model was validated based on a volunteer knee. Osteotomy models with medial proximal tibial angles ranging from 90° to 97° in 1° increments were developed. Varus alignment correction of the distal femur was performed in each model to maintain identical coronal alignment passing through a point 62.5% lateral to the tibial plateau. The peak tibiofemoral contact forces and knee kinematics were compared in each model during walking and squatting.

FINDINGS

All the osteotomy models demonstrated higher peak contact forces on the lateral tibiofemoral joints than on the medial tibiofemoral joints during walking. However, larger medial proximal tibial angles caused excessive increases in medial tibiofemoral contact forces, and the dominant tibiofemoral contact forces shifted to the medial side. Increased medial proximal tibial angles also caused progressive medial collateral ligament tension in knee flexion, but partial medial collateral ligament release effectively reduced medial tibiofemoral contact forces. Models with large medial proximal tibial angles showed nonphysiological roll-forward of the lateral femoral condyle during squatting and no screw-home movement around knee extension.

INTERPRETATION

Excessively large medial proximal tibial angles following open-wedge high tibial osteotomy resulted in increased medial tibiofemoral contact forces and abnormal knee kinematics during knee flexion due to medial joint line elevation and ligament imbalance.

Classical target coronal alignment in high tibial osteotomy demonstrates validity in terms of knee kinematics and kinetics in a computer model

PURPOSE

The purpose of this study was to determine the ideal coronal alignment under dynamic conditions after open-wedge high tibial osteotomy (OWHTO). It was hypothesised that, although the classical target alignment was based on experimental evidence, it would demonstrate biomechanical validity.

METHODS

Musculoskeletal computer models were analysed with various degrees of coronal correction in OWHTO during gait and squat, specifically with the mechanical axis passing through points at 40%, 50%, 60%, 62.5%, 70%, and 80% of the tibial plateau from the medial edge, defined as the weight-bearing line percentage (WBL%). The peak load on the lateral tibiofemoral (TF) joint, the medial collateral ligament (MCL), and anterior cruciate ligament (ACL) tensions, and knee kinematics with or without increased posterior tibial slope (PTS) were evaluated.

RESULTS

The classical alignment with WBL62.5% achieved sufficient load on the lateral TF joint and maintained normal knee kinematics after OWHTO. However, over-correction with WBL80% caused an excessive lateral load and non-physiological kinematics. Increased WBL% resulted in increased MCL tension due to lateral femoral movement against the tibia. With WBL80%, abnormal contact between the medial femoral condyle and the medial intercondylar eminence of the tibia occurred at knee extension. The screw-home movement around knee extension and the TF rotational angle during flexion were reduced as WBL% increased. Increased PTS was associated with increased ACL tension and decreased TF rotation angle because of ligamentous imbalance.

CONCLUSIONS

The classical target alignment demonstrated validity in OWHTO, and over-correction should be avoided as it negatively impacts clinical outcome.

LEVEL OF EVIDENCE

IV.

Three-dimensional assessment of lower limb alignment: Reference values and sex-related differences

BACKGROUND

Three-dimensional (3D) preoperative planning and assisted surgery is increasingly popular in deformity surgery and arthroplasty. Reference ranges for 3D lower limb alignment are needed as a prerequisite for standardized analysis of alignment and preoperative planning in 3D, but are not yet established.

METHODS

On 60 3D bone models of the lower limbs based on computed tomography data, fifteen parameters per leg were assessed by standardized validated 3D analysis. Distribution parameters and differences between sexes were evaluated. Reference values were generated by adding/subtracting one standard deviation from the mean.

RESULTS

Women had a significantly lower mean mechanical lateral distal femoral angle compared with men (86.4 ± 2.1° vs. 87.8 ± 2.0°; P < .05) and significantly lower mean joint line convergence angle (-2.5 ± 1.4° vs. -1.3 ± 1.2; P < .01), but higher mean hip knee ankle angle (178.9 ± 1.9° vs. 177.8 ± 2.3°; P < .05) and mean femoral torsion (18.2 ± 9.5° vs. 13.2 ± 6.4°; P < .05), resulting in a tendency towards valgus alignment and vice versa for men. Differences in mean medial proximal tibial angle were not significant. The mean mechanical axis deviation from the tibial knee joint center was 6.9 ± 7.3 mm medial and 1.4 ± 16.1 mm ventral without significant differences between sexes.

CONCLUSIONS

We describe total and sex-related reference ranges for all alignment relevant axes and joint angles of the lower limb. There are sex-related differences in certain alignment parameters, which should be considered in analysis and surgical planning.