Lateral Hinge Research Articles

Finite element analysis confirms the optimal apex position in medial opening wedge high tibial osteotomy to avoid lateral hinge fracture.

Lateral hinge fracture is a significant complication of medial opening wedge high tibial osteotomy. While fracture risk is closely associated with the osteotomy apex position, the optimum position remains variable within the literature. Our hypothesis is that stresses at the osteotomy apex predicted by finite element analysis can be used to identify an apex position which minimises intra and postoperative fracture risks. A finite element model was studied to investigate the effect of varying the hinge position on fracture risk and severity for a given bone geometry; variables analysed included stress, strain and micromotion levels. Nine further knee models were studied to assess the variability between patients' bone properties and examine the effect of apex location on strains. Lateral hinge width and height significantly influence intra-operative stress, strain, and fracture risk, while hinge width predominately determines postoperative stability. Wider hinges improve postoperative stability, but increase the likelihood of intra-articular fractures. Aiming the apex at the fibular head height minimises strain. The osteotomy apex should be located such that the hinge width is equal to 13% of the medial-lateral width to minimise apex stress and fracture risk while preserving sufficient bone at the hinge for stability. The height of the apex from the tibial plateau should maintain a minimum value of 16% of the medial-lateral width to avoid intra-articular fracture, with the apex below the fibula head if necessary. The size of the tibia does not alter the optimal location, making our findings applicable across all tibia sizes. Our study has investigated and verified a proposed optimal apex position, based upon fracture risk prediction and micromotion at the osteotomy apex. This is clinically useful due to the potential use of the apex point on preoperative 2D radiographs when planning surgery. Not applicable.

Evaluating the Effectiveness of a Structural Allograft in Medial Open Wedge High Tibial Osteotomy in Patients With and Without a Lateral Hinge Fracture.

A lateral hinge fracture is a common complication in medial open wedge high tibial osteotomy (MOWHTO) and is associated with delayed union or nonunion. A comparison of outcomes between patients with or without a lateral hinge fracture after MOWHTO with a structural allograft has not been investigated. To validate the outcomes of MOWHTO with a structural allograft, especially in the presence of a lateral hinge fracture. Case series; Level of evidence, 4. We conducted a single-surgeon cohort study at a tertiary referral hospital between April 2017 and August 2022 and included patients who had undergone MOWHTO with a structural allograft for isolated medial compartment osteoarthritis with genu varum. We compared the incidence of delayed union or nonunion events and functional scores between patients with a lateral hinge fracture and those without using the Fisher exact test and independent t test. A total of 88 MOWHTO procedures (77 patients) were analyzed. The overall incidence of lateral hinge fractures was 29.5% (n = 26), including type I (n = 20 [22.7%]) and type II (n = 6 [6.8%]). Notably, 42.3% (n = 11) of these fractures had not been detected intraoperatively but during the follow-up visits. The overall Knee Society Score (KSS), Knee Society Score-Function (KSS-F), and Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores were 90.0 ± 10.0, 93.4 ± 10.8, and 93.8 ± 7.1 points, respectively. None of the patients had delayed union or nonunion, and none underwent a reoperation because of bony union problems. The functional scores (KSS, KSS-F, and WOMAC) were not different between patients who had a lateral hinge fracture and those who did not (P > .05). The routine use of a structural allograft was associated with satisfactory outcomes after MOWHTO, regardless of whether there was a lateral hinge fracture.

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.

Intraoperative Complications in Medial Opening Wedge High Tibial Osteotomy.

Medial opening wedge high tibial osteotomy has been established for treatment of medial symptomatic knee arthrosis with varus malalignment in young and elderly but active patients. To obtain satisfactory results, it is essential for surgeons performing osteotomy to identify, prevent, and treat potential intraoperative adverse events. Lateral hinge fracture (LHF) is the most common intraoperative complication while popliteus artery injury is rare but limb-threatening. Computed tomography is the benchmark to detect LHF, the risk of which increased markedly with the opening gap larger than 11 mm. Setting the lateral hinge in a safe zone is the most important preventive measure. Medial long locking plate fixation may allow patients even with unstable hinge fractures to start early full weight bearing. Additional fixation of LHF is optional, and bone void filling is not routinely used. For protection of popliteus artery injury, flexing the knee joint is unreliable. It is paramount to place a protective retractor just behind the posterior tibial cortex toward the proximal tibiofibular joint before osteotomy, particularly in case of aberrant artery. A repertoire of surgical pearls is described in detail in this review to identify, prevent, and manage those intraoperative complications.

Risk factors for delayed bone union in opening wedge high tibial osteotomy.

The purpose of this study was to investigate the relationship between patient demographics and potential intraoperative factors and delayed bone union in opening wedge high tibial osteotomy (OWHTO). A retrospective review of 65 patients (37 females, 28 males; mean age: 60.1±10.1 years; range, 44 to 77 years) who underwent OWHTO using an angle-stable implant with beta-tricalcium phosphate gap filling between September 2016 and October 2019 was conducted. The osteotomy site was divided into five zones from the lateral hinge on anteroposterior radiographs, and we defined the zone in which bone healing was observed. The bone union area was assessed according to this definition at three, six, nine, and 12 months after surgery, and bone union was defined as union at the fourth zone or greater. A generalized estimating equations approach was employed to investigate longitudinal data pertaining to bone union area as a dependent variable. In addition, the association of bone union at six months postoperatively and predictors were evaluated using cross-sectional statistical methods. The categorical predictors included in the models were smoking, diabetes, hinge fracture, and autologous osteophyte grafting. The continuous variables included in the models were age, body mass index, opening gap width, and plate position. Smoking (odds ratio [OR]=0.478, p<0.01), large opening gap width (OR=0.941, p=0.014), and anterior plate placement (OR=0.971, p<0.01) were significantly associated with decreased bone union area. Union rate at six months in smokers was significantly lower compared to nonsmokers (16.6% and 67.8%, respectively; OR=0.10, p=0.023). Area under the curve in the receiver operating characteristic analysis for bone union at six months was 0.60 for gap width and 0.63 for plate placement. Smoking, large opening gap width, and anterior plate placement are risk factors for delayed bone union after OWHTO. Surgeons should avoid anterior placement of the plate and carefully consider other options for smokers and those who require a large correction.

Clinical course and risk factors for post-operative onset lateral hinge fracture following medial opening-wedge distal tibial tuberosity osteotomy

PurposeThis study aimed to investigate the clinical outcomes of and risk factors for post-operative onset lateral hinge fracture (LHF) following medial opening-wedge distal tibial tuberosity osteotomy (DTO). MethodsA total of 68 patients who underwent DTO were stratified into non-LHF and post-operative onset LHF groups. The groups were compared in terms of radiographic parameters, including the hip–knee–ankle (HKA) angle, and were clinically evaluated using the Knee Society Score (KSS) and 2011KSS. Multiple logistic regression analysis was performed to identify risk factors for post-operative onset LHF. ResultsThe non-LHF and post-operative onset LHF groups included 53 and 15 patients, respectively. The post-operative HKA angle was significantly smaller (valgus) in the post-operative onset LHF group than in the non-LHF group (P ​= ​0.005). Knee and function scores were significantly lower in the post-operative onset LHF group than the non-LHF group at 6 months (P ​= ​0.002 for each comparison). All 2011KSS subscores were significantly lower in the post-operative onset LHF group than the non-LHF group at 6 months (P ​= ​0.001, 0.010, 0.013, and 0.013, respectively). Post-operative HKA angle was a risk factor for post-operative onset LHF (odds ratio ​= ​0.589, 95% confidence interval 0.392–0.886; P ​= ​0.011). ConclusionsPost-operative weight bearing may be delayed to prevent post-operative onset LHF, especially in patients with post-operative large valgus knee alignment.

Analysis of load distribution on the plate and lateral hinge of a valgus opening high tibial osteotomy during weight-bearing: a finite element analysis

IntroductionValgus high tibial osteotomy (HTO) is indicated for managing isolated medial knee osteoarthritis in a young patient with a metaphyseal deformity of the proximal tibia. In a medial opening HTO, maintaining the integrity of the lateral hinge is crucial for ensuring proper healing and correction retention. Using a locked plate to stabilize an HTO is common practice, allowing for earlier weight-bearing. The objective of this study was therefore to measure and track the mechanical load distribution on a locked fixation plate and the lateral hinge of an HTO using a finite element (FE) model simulating single-leg stance loading. HypothesisThe working hypothesis was that during weight-bearing, the plate and the lateral hinge absorb stress asymmetrically, predominantly on the plate. Material and methodsA numerical model of an HTO stabilized with a locked plate was developed based on the actual geometry of a healthy proximal tibia (using Autodesk Fusion 360 and Altair HyperWorks software). In this finite element simulation of loading, a mesh convergence study was conducted to optimize the accuracy of the numerical model results. The primary outcome measure was the maximum stress value in the affected areas (Von Mises stress, in MPa) of the plate and the lateral hinge. ResultsThe maximum stress intensity in the plate was approximately 20.29 MPa. The maximum stress intensity in the bony hinge was about 5.6 MPa. The results of the mesh convergence study for the hinge and the plate enabled defining the most suitable model for future FE studies: a 4 mm mesh for all model elements except for the high-stress area in the plate and the hinge, which were meshed with a 0.7 mm element size. This adaptation provided greater precision in the study. DiscussionThere is a distribution and allocation of stress both on the plate and the hinge, underlining the significance of the plate and the absolute necessity of preserving the hinge. Predictably, the plate absorbs the majority of the load, more than three times that of the hinge. ConclusionThe hypothesis is confirmed; however, additional studies would be necessary to validate these numerical results: an experimental component on instrumented cadaveric bones, as well as comparative studies of different fixation plates. Level of EvidenceV, expert opinion; controlled laboratory study.

Required force for distraction during medial opening wedge high tibial osteotomy may serve as a predictive indicator for lateral hinge fracture.

Medial open wedge high tibial osteotomy is a biological procedure for treating unicompartmental knee osteoarthritis. The literature repeatedly highlights the significance of preserving an intact lateral hinge during this procedure. We investigated the temporal course of distraction forces during distraction at the osteotomy site, aiming to quantitatively measure and analyse temporal changes in distraction forces at different distraction points for intact and fractured lateral hinges. This biomechanical study was conducted on 10 human cadavers, which were divided into two groups: one with preserved 1 cm intact lateral cortexes (ILCs) and the other with completely osteotomised fractured lateral cortexes (FLCs). An experimental setup was custom designed to facilitate the required force measurement during distraction. The distraction forces were recorded with a force gauge at 0.5-mm intervals throughout the distraction. There was a significant difference between the ILC and FLC groups in distraction forces at all points (8-15 mm). The ILC group consistently exhibited higher distraction force values, with FLC recording values ranging from 8.8% to 13.2% of ILC's. Lateral hinge fractures caused an 86.7% reduction in the initial required force for distraction, significantly impacting the force required for distraction. The ILC group displayed a linear increase in the required distraction force up to 12.5 mm of distraction, which reached 3.7 times the initial value at 12.5 mm of distraction. The FLC group had lower baseline required distraction forces, following a relatively linear trend with more limited increases. FLCs in medial opening wedge osteotomy are associated with significant reductions in the force required for distraction, and a sudden decrease in distraction force during distraction may indicate a lateral hinge fracture. Force measurement devices for use during distraction could offer valuable insights and provide surgeons with immediate warnings for LHFs. Level IV.

Influence of variable hinge positioning on coronal and sagittal alignment in uniplanar medial open-wedge high tibial osteotomy.

There is a high risk of increasing the posterior tibial slope (PTS) during medially opening-wedge high tibial osteotomy (mowHTO). Most recently, the idea of intentional simultaneous coronal and sagittal correction, using uniplanar cutting techniques has emerged. This study aims to examine the influences of variable hinge positioning and osteotomy gap height on the sagittal and coronal plane. Twenty uniplanar mowHTOs were performed in standardised (left) solid-foam proximal tibia models. In the different models, hinge position was rotated stepwise by 10°, between 90° (cutting straight medial to lateral) and 0° (cutting straight anterior to posterior) (n = 10). Additionally, gap heights of 5 and 10 mm were produced and analysed. Logistic regression analysis was performed to calculate a predictive regression formula for the relation between gap height, hinge rotation and the changes of medial proximal tibia angle (MPTA), medial and lateral PTS. Between cutting angles of 90 and 20°, the MPTA was mainly influenced by the gap height (0.95° MPTA per 1 mm gap height), but not by the cutting angle. Between 20 and 0°, the MPTA was decreased by 3.6° per 10° of rotation, but not by the gap height. Between cutting angles of 90 and 10°, the PTS was increased linearly by 0.97° per 10° of rotation and by 0.61° per 1 mm gap height. In mowHTO with lateral hinge positions, the MPTA is mainly influenced by gap height. Changes of PTS can be avoided by a straight lateral hinge position. In posterior hinge locations (0-20°), changes of MPTA are mainly caused by hinge rotation, but not by gap height. Level III, Case-control study.

Influence and risk factors of lateral hinge fracture on early effectiveness of supramalleolar osteotomy

To evaluate the influence of lateral hinge fracture (LHF) on the early effectiveness of supramalleolar osteotomy (SMO) and to explore the related risk factors for LHF. A total of 39 patients (39 feet) with varus-type ankle osteoarthritis treated with SMO between January 2016 and December 2022 were analyzed retrospectively. There were 10 males and 29 females, aged from 41 to 71 years (mean, 57.7 years). According to Takakura stage, there were 6 feet in stage Ⅱ, 19 feet in stage Ⅲa, and 14 feet in stage Ⅲb. The LHF was recognized by the immediate postoperative X-ray film. The osteotomy healing time and the changes of pain visual analogue scale (VAS) score, American Orthopaedic Foot and Ankle Society (AOFAS) score, tibial anterior surface angle (TAS), tibial lateral surface angle (TLS), and tibiotalar angle (TT) before and after operation were compared between patients with and without LHF. The age, gender, affected side, body mass index, Takakura stage, preoperative VAS score, preoperative AOFAS score, preoperative TAS, preoperative TLS, preoperative TT, SMO correction angle, osteotomy distraction, distance from medial osteotomy to ankle joint line (MD), and distance from lateral osteotomy to ankle joint line (LD) were compared between with and without LHF patients, and further logistic regression analysis was used to screen the risk factors of LHF during SMO. All patients were followed up 12-54 months (mean, 27.1 months). During operation, 13 feet developed LHF (group A) and 26 feet did not develop LHF (group B). X-ray film reexamination showed that 1 patient in group A complicated with tibial articular surface cleft fracture had delayed osteotomy and healed successfully after plaster fixation; the osteotomy of other patients healed, and there was no significant difference in healing time between the two groups ( P>0.05). At last follow-up, there were significant differences in VAS score, AOFAS score, TAS, TLS, and TT of the two groups when compared with preoperative ones ( P<0.05), but there was no significant difference in the changes of above indicators before and after operation between the two groups ( P>0.05). The differences in SMO correction angle, osteotomy distraction, and LD between with and without LHF patients were significant ( P<0.05), and further logistic regression analysis showed that excessive LD was the risk factor of LHF during SMO ( P<0.05). Too high or too low lateral hinge position during SMO may lead to LHF, but as long as appropriate treatment and rehabilitation measurements are taken, the early effectiveness is similar to that of patients without LHF.

Larger lateral hinges increase the probability of Takeuchi type II and III fractures in high tibial osteotomy.

Lateral hinge fractures are the main complications in the high tibial osteotomy to treat varus deformities. The aim of present study is to answer the question whether the lateral hinge length (H) has an effect on the type of fracture and required force during the opening in high tibia osteotomy. It was hypothesized in this comparative research that extending the hinge length increased opening force and probability of a type II and type III fractures. A monoplanar medial open wedge osteotomy with different intact hinge lengths varying from 9 to 32mm was performed in 20 ostrich bones. A biomechanical experiment using unidirectional tensile testing apparatus was performed to open the wedge, and the required force was increased until a 10mm opening was reached; then, the presence of fracture in the lateral cortex and its direction were evaluated. Lateral hinge fracture type based on direction was classified as suggested by Takeuchi etal. Fracture that grows along the osteotomy line (type I) was observed in 4 samples with the mean hinge length (H) of 11 ± 1.54mm. For seven bones with Takeuchi fracture type II, with downward crack propagation, the mean H was 16 ± 3.36mm. For the mean H of 25 ± 6.53mm, the crack propagated upward to the cutting path, displaying a Takeuchi type III fracture in seven samples. The statistical analysis showed that the fracture type significantly depends on the hinge length (P value < 0.05). Also, the mean opening force significantly increased with hinge lengthening (P value < 0.05). The peak forces at crack initiation were 41.8 ± 21.9, 115.2 ± 41.5, and 167 ± 135.3 N, respectively, for the fracture types I, II, and III samples. The lateral cortical hinge length was significantly associated with hinge fracture type. The experimental tests indicated that the hinge lengthening increases the risk of type II and III fractures, as classified by Takeuchi.

Bone substitute fracture in open wedge high tibial osteotomy: Comparison of two different bone substitutes

PurposeThe aim of this study was to retrospectively compare bone substitute fracture patterns and outcomes in patients who underwent open wedge high tibial osteotomy (OWHTO) with OSferion60 or OSferion60 Marvelous bone substitutes. Patients with and without bone substitute fractures were compared and risk factors for bone substitute fracture were identified. MethodsIncluded patients were physically active non-smokers with knee osteoarthritis and deformity in the proximal tibia, persistent pain, and <5° of flexion contracture. OWHTO was performed with a TriS plate and a target femorotibial angle (FTA) of 170°. Full weight-bearing began the day after surgery. Pre-, intra-, and post-operative evaluations of demographic, clinical, and radiological factors were performed. Regression analysis was performed to identify risk factors for bone substitute fracture. ResultsData for 63 patients were analyzed (OSferion60, n ​= ​28 and Marvelous, n ​= ​35; bone substitute fracture, n ​= ​32 and non-bone substitute fracture, n ​= ​31). No significant differences were found between the bone substitute groups in patient characteristics and pre-operative and 2-year FTA, Japanese Orthopaedic Association (JOA) score, and flexion range. FTA and JOA scores improved significantly 2 years post-operatively (both p ​< ​0.001). There were 32 bone substitute fractures (OSferion60, n ​= ​20; Marvelous, n ​= ​12); all occurred by the 1-month follow-up. Gap filling occurred significantly earlier in the Marvelous group versus the OSferion60 group (p ​< ​0.001). Risk factors for bone substitute fracture were weaker bone substitute [odds ratio (OR) ​= ​8.34; p ​< ​0.001] and lateral hinge fracture (OR ​= ​11.7; p ​= ​0.045). ConclusionsAlthough bone substitute fracture was common in both bone substitute groups, this did not affect outcomes. However, lateral hinge fractures are a particular concern.

Faster Bone Gap Union in Medial Opening Wedge High Tibial Osteotomy With 3D-Printed Synthetic Bioresorbable Polycaprolactone and Tricalcium Phosphate Osteotomy Gap Fillers Compared to Allogeneic Osteotomy Gap Fillers: A Retrospective Matched-Pair Cohort Study.

The use of synthetic bone substitute material (BSM) as osteotomy gap fillers have been reported to improve outcomes in medial opening wedge high tibial osteotomy (MOWHTO). This study aims to evaluate the early radiological outcomes (bone union) and complication rates of the novel patient-specific 3D-printed honeycomb-structured polycaprolactone and tricalcium phosphate (PCL-TCP) synthetic graft compared to allogeneic bone grafts as an osteotomy gap filler in MOWHTO. A retrospective matched-pair analysis of patients who underwent MOWHTO with either PCL-TCP synthetic graft or allogenic femoral head allograft as osteotomy gap filler was performed. The osteotomy gap was split into equal zones (Zone 1-5), and bone union was evaluated on anteroposterior radiographs based on the van Hemert classification at 1, 3, 6, and 12 months postoperatively. Postoperative complications including infection, lateral hinge fractures, and persistent pain was measured. The study and control group were matched for age, smoking status, diabetes mellitus, and osteotomy gap size. Significantly greater bone union progression was observed in the PCL-TCP group than in the allograft group at 1 month (Zones 1-3), 3 months (Zones 1-4), 6 months (Zones 1-2, 4), and 12 months (Zones 2-3, 5) postoperatively (P < 0.05). No significant difference in complications rates was noted between the two groups at 1 year. Bone union rates observed in patients who underwent MOWHTO with the PCL-TCP synthetic graft osteotomy gap filler were superior to those in the allograft group at 1 year postoperatively, with no significant difference in complication rates (postoperative infection, lateral hinge fractures, and persistent pain).

Factors Causing Unintended Sagittal and Axial Alignment Changes in High Tibial Osteotomy: Comparative 3-Dimensional Analysis of Simulation and Actual Surgery

Background: Unintended secondary changes in the posterior tibial slope (PTS) and tibial torsion angle (TTA) may occur after medial open-wedge high tibial osteotomy (MOWHTO). In surgical procedures using patient-specific instruments (PSIs), it is essential to reproduce the PTS and TTA that were planned in simulations. Purpose: To analyze the factors causing unintended sagittal and axial alignment changes after MOWHTO. Study Design: Case series; Level of evidence, 4. Methods: Overall, 63 patients (70 knees) who underwent MOWHTO using a PSI between June 2020 and June 2023 were retrospectively reviewed. Preoperative and postoperative computed tomography scans were 3-dimensionally reconstructed. Simulated osteotomy was performed so that the weightbearing line could pass through the target point. A PSI gapper was 3-dimensionally printed to fit the posteromedial corner of the osteotomy gap in the simulated HTO model. After MOWHTO using the PSI gapper, the actual postoperative model was compared with the preoperative or simulation model. This assessment included PTS, TTA, hinge axis, and osteotomy-related parameters. Cortical breakage around the lateral hinge was evaluated to assess stability. Results: The mean PTS and TTA did not change in the simulation. However, significant changes were observed in the actual postoperative PTS and TTA (change, –2.4°± 2.2° and −3.9°± 4.7°, respectively). The PTS was reduced, while the TTA decreased with internal rotation of the distal fragment. The difference in the axial hinge axis angle (AHA) between the simulation and actual surgery was the factor most correlated with the difference in the PTS (r = 0.625; P < .001). In regression analysis, the difference in the AHA was the only factor associated with the difference in the PTS (β = 0.558; P = .001), and there were no factors that showed any significant associations with the difference in the TTA. In subgroup analyses for the change in the TTA, the correction angle and anterior osteotomy angle were significantly higher in the more internal rotation group (P = .023 and P = .010, respectively). The TTA change was significantly higher in the unstable group with lateral cortical breakage (P = .018). The unstable group was more likely to show an internal rotation of ≥5° (odds ratio, 5.0; P = .007). Conclusion: The AHA was associated with a difference in the PTS between the simulation and actual surgery. The change in the TTA was caused by a combination of multiple factors, such as a large correction angle and anterior osteotomy angle, but mainly by instability of the lateral cortical hinge.

Protective Kirschner Wire Fixation to Reduce the Effect of Lateral Hinge Fracture During the Medial Opening Wedge Low Tibial Osteotomy: A Technical Note

Protective Kirschner Wire Fixation to Reduce the Effect of Lateral Hinge Fracture During the Medial Opening Wedge Low Tibial Osteotomy: A Technical Note

Finite Element Analysis of Protective Measures against Lateral Hinge Fractures in High-Tibial Osteotomy.

Opening wedge high-tibial osteotomy (OWHTO) is widely used for correcting mechanical axis deviations and offloading the medial compartment in unicompartmental osteoarthritis. However, lateral hinge fractures (LHFs) pose a significant complication. This study investigates protective measures to mitigate these fractures, guided by prior observations of mechanical stress impact on LHFs. The study aims to assess the effectiveness of different protective measures, specifically the use of varying sizes of Kirchner wires and drill holes, in reducing the incidence of LHFs during OWHTO. Study Design. The study employs a quantitative, comparative analysis using a finite element method (FEM) based on computed tomography (CT) scans. Using CT-based FEM, the study compares the impact of different sizes of K-wires (1.6 mm, 2.0 mm, and 2.5 mm) and drill holes (3.2 mm and 4.5 mm) on the mechanical stresses around the hinge area in OWHTO. The models were created from a CT scan of a healthy 33-year-old male, focusing on the force required to open the osteotomy gap and the incidence of cracked shell elements. The study found that thicker K-wires increased the force required to open the osteotomy gap, whereas larger apical holes decreased it. The 4.5 mm apical hole model demonstrated significantly fewer cracks compared to the 2.0 mm K-wire model, with no significant difference observed compared to the 2.5 mm K-wire model. Models using a 1.6 mm K-wire or a 3.2 mm drill hole did not significantly reduce cracks compared to the base model. The findings suggest that a 4.5 mm drill hole may be more effective in reducing the risk of LHFs compared to thinner diameter K-wires or smaller apical holes. Both a 2.5 mm K-wire and a 4.5 mm drill hole reduce the number of cracked elements, but the 4.5 mm drill hole also significantly decreases the average and maximum principal stresses as well as the average tensile strength ratio at the hinge area. These findings may be important for surgical planning, particularly in cases requiring increased osteotomy distraction.

Impact of support instruments in medial closed-wedge distal femoral osteotomy: a finite element analysis.

Medial closed-wedge distal femoral osteotomy (MCWDFO) is a valuable treatment approach for lateral knee osteoarthritis with femoral valgus deformity. Improved results have been reported with the upgrade of surgical techniques and locking plates. However, the risk of nonunion and loss of correction increases in cases of lateral hinge fractures. This study aimed to evaluate the mechanical impact of hinge fractures and support instruments in MCWDFO using finite element analysis (FEA). Five femur models were developed using Mechanical Finder 11.0 FEA software. We simulated the following models: only a medial locking plate (MLP) (group A); an MLP with a lateral support screw (group B); and an MLP with a lateral support plate (group C). The equivalent stress around the hinge was evaluated and the percentage of the plastic deformation zone was calculated for the hinge area in the no-hinge fracture model. The equivalent stress of the MLP and the degree of displacement were calculated using the hinge fracture model. The percentages of the plastic deformation zone in groups A, B, and C were 18.0 ± 11.7%, 3.3 ± 2.4%, and 2.3 ± 2.8%, respectively. The percentages tended to be lower in groups B and C than in group A. In the hinge fracture model, the mean equivalent stress of the MLP in group C was significantly less than that in group A. In terms of the mean degree of displacement, group A showed more than 1mm of displacement, which was significantly larger than that of the other groups. The support instruments provided stability to the hinge site and reduced the equivalent stress of the main plate in the MCWDFO with hinge fractures. No significant difference was observed between the two instruments in terms of stability.

Fracturing the Lateral Hinge Improves Radiographic Alignment and Does Not Affect Clinical Outcomes of the Minimally Invasive Akin Osteotomy.

Intraoperative fracture of the lateral cortex is common during Akin osteotomy. In a recent study, lateral cortex fracture did not impede healing or result in loss of correction in a combined cohort of open and percutaneous osteotomies stabilized by K-wire fixation. We hypothesize that undesired lateral cortex fracture will not affect radiographic correction and patient-reported outcomes in a percutaneous cohort stabilized by permanent, rigid screw fixation. Consecutive patients with hallux valgus who underwent first metatarsal osteotomy and percutaneous Akin osteotomy stabilized by permanent, rigid screw fixation between May 2020 and January 2022 were retrospectively reviewed. Patients were stratified based on fractured lateral cortex (FC) or its absence (nonfractured cortex [NFC]). Visual analog scale (VAS) and Foot Function Index (FFI) were used to assess pain and patient-reported outcomes at 1-year follow-up. Patients were polled for satisfaction at 1-year follow-up by yes/no survey. Ninety-eight patients (89% female) were reviewed (98 feet; 43 NFC, 55 FC). Mean age was 48.3 years (range, 18-83 years). Mean preoperative VAS score was 7.5 and 7.7 in NFC and FC groups, which significantly decreased to 0.6 (P < .01) and 0.6 (P < .01), respectively. Mean total FFI was 53.9 and 54.2 and decreased to 17.9 (P < .01) and 17.2 (P < .01) in the NFC group and FC group, respectively. Overall, 97.8% of the NFC group and 96.4% of the FC group reported satisfaction.Mean HVA improved from 27.2 (16-42) degrees to 10.7 degrees (4-12) postoperatively in the NFC group. And in the FC group, HVA improved from 29.3 (19-39) degrees to 7.1 (4-12) degrees postoperatively. Postoperative HVA was significantly lower in the FC group (P < .05). In an exclusively percutaneous surgical cohort with correction maintained by rigid screw fixation, fracture of the lateral cortex is associated with improved postoperative radiologic alignment without detriment to patient-reported outcomes. Level III, retrospective cohort study.

Incidence and risk factors for lateral hinge fractures in medial opening wedge high tibial osteotomy and medial opening wedge distal tibial tuberosity osteotomy

BackgroundThe aims of this study were (1) to compare the incidence of lateral hinge fractures (LHFs) in medial opening-wedge high tibial osteotomy (OWHTO) and medial opening-wedge distal tibial tuberosity osteotomy (DTO), and (2) to investigate the risk factors for LHFs. The incidence of LHFs was hypothesized to be higher in the DTO group than the OWHTO group. The DTO procedure is also a risk factor for LHFs. MethodsA total of 167 knees that underwent OWHTO (n = 65) and DTO (n = 102) were subjected to propensity score matching for the comparison of the groups. The matched variables were sex, preoperative hip-knee-ankle (HKA) angle, and preoperative medial proximal tibial angle. Forty-one matched pairs were enrolled for comparative analysis. Logistic regression analysis was performed to investigate risk factors for LHFs. ResultsThe incidence of LHFs was not significantly different between the groups (34.1% vs. 26.8%, respectively; p = 0.631). Logistic regression analysis showed that age (odds ratio: 1.074, 95% confidence interval (CI): 1.020–1.131, p = 0.007), BMI (odds ratio: 1.150, 95% CI: 1.049–1.260, p = 0.003), and preoperative HKA angle (odds ratio: 1.150, 95% CI: 1.049–1.260, p = 0.035) were significant risk factors for LHFs. The difference in surgical technique between OWHTO and DTO was not a risk factor for LHFs (p = 0.204). ConclusionsThe incidence of LHFs is similar in DTOs and OWHTOs, and the DTO procedure is not a risk factor for LHFs.Level of Evidence: Level III, retrospective cohort study.

Higher fibular head is a risk for lateral hinge fracture in medial open wedge high tibial osteotomy.

To examine the association between the hinge position, fibular head position, and type III lateral hinge fracture (LHF) in patients with knee osteoarthritis (OA) who underwent medial open wedge high tibial osteotomy (MOWHTO). This retrospective study examined patients who underwent MOWHTO. Radiographically, the Kellgren-Lawrence (K/L) classification, distance between the articular surface and the tip of the fibular head (fibular head position), hinge point (hinge position), type of LHF, and safe zone (within the proximal tibiofibular joint) outlier were evaluated. To determine the cut-off value of the hinge position and fibular head position associated with type III LHF, a receiver operating characteristic (ROC) curve analysis was performed. The odds ratio (OR) was calculated from the obtained cut-off values using logistic regression, which was adjusted by age, gender, body mass index, and opening distance. Among 132 knees in 120 patients, the radiographic severity of knee OA was 19 (14%), 73 (55%), and 40 (30%) of K/L grades 2, 3, and 4, respectively. LHF was observed in 40 knees (30%), including types I, II, and III fractures in 21 (16%), 5 (4%), and 14 (11%) knees, respectively. Hinge and fibular head positions were 16 and 10mm, respectively, with significant correlation. Safe zone outlier was observed in 38 knees (29%). The hinge and fibular head positions with type III LHF were significantly higher (more cranial) than those with no fracture or other LHF subtypes. The ROC curve revealed that the cut-off value for the hinge and fibular head positions was 13.3 and 8.6mm, respectively. The OR of the hinge and fibular head positions was 22.42 and 13.86, respectively. A higher hinge position was a risk factor for type III LHF and was associated with a higher fibular head in patients with knee OA who underwent MOWHTO. The hinge position should be placed at a certain distance from the articular surface to avoid type III LHF, especially in participants with higher fibular head position, even if the hinge position is located in the safe zone. Retrospective cohort study, Level III.