Hinge Fracture Research Articles

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

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. 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. 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. 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 novel biplanar medial opening-wedge high tibial osteotomy: the Z-shaped technique. A case series at 7.2\xa0years follow-up

BackgroundHigh tibial osteotomy (HTO) provides reliable and good long-term results, if performed with correct indications, but different techniques and types of fixation have been described. The purpose of this study is to present a novel modified biplanar medial opening-wedge (MOW) HTO technique where the osteotomies are performed in a Z-shaped fashion, and to present the medium-term clinical and radiographic results.Materials and methodsWe present a case series of 75 patients (80 knees) with mean age of 45.8 years, affected by isolated medial knee osteoarthritis and symptomatic varus knee malalignment, who underwent novel biplanar Z-shaped MOWHTO. Clinical and radiological outcomes were collected, retrospectively before surgery and at median follow-up of 7.2 years (95% CI 5.6–9.2 months) after surgery. Clinical results and satisfaction were assessed by visual analog scale (VAS), Western Ontario and McMaster University Osteoarthritis Index (WOMAC), and Likert scale. Radiological assessment involved the evaluation of the medial proximal tibial angle (MPTA), tibial slope (TS), Caton–Deschamps index, and knee osteoarthritis grade according to Ahlbäck classification. Pre- and postoperative results were compared using the two-tailed t-test or Wilcoxon’s test of independent samples for paired data or nonparametric analog. P < 0.05 was considered significant.ResultsAt medium-term follow-up, Z-shaped MOWHTO showed a survival rate of 95 ± 1.7% with failure occurring in four knees due to symptom recurrence and osteoarthritis progression. No perioperative complications were observed (intraarticular fracture, delayed union or nonunion, and neurological injury). Mean bone healing time was 12 weeks. Clinical scores showed significant improvement at last follow-up and a good grade of satisfaction. MPTA increased significantly, while Caton–Deschamps index decreased significantly. No significant TS increase was found.ConclusionsModified biplanar Z-shaped MOWHTO is a safe and reliable technique that offers satisfactory clinical and radiological medium-term outcomes with low knee arthroplasty conversion rate. The unique three-dimensional geometrical conformation potentially provides a favorable environment for bone healing, increased anteroposterior and rotational stability, and safer opening-wedge loading force application with low lateral hinge fracture risk.Level of evidenceLevel IV, retrospective observational case series study.Trial registration The study protocol was approved by the Internal Review Board of our Institution (authorization number 54/2019, 20 November 2019).

Biomechanical analysis of the role of hinge support fixators on hinge stability in medial closing wedge distal femoral osteotomy

BackgroundThis study aimed to examine the hinge-stabilizing biomechanical effects of hinge support fixators, applied for lateral hinge fractures sustained following distal femoral osteotomy. MethodsMedial closing wedge distal femoral osteotomy was performed using a locking plate on 10 cadaveric limbs. The limbs were divided into two groups: the non-fracture group and the lateral hinge fracture group. A cyclic axial load of 400 N was applied to the knee to keep it extended and flexed at 45°. The hinge-stabilizing effects of adding a screw or a short support plate to the lateral fracture site were examined by measuring the translation and rotational angles of the anterodistal and posterodistal hinge positions as well as the surface strains of the medial locking plate. FindingsTranslation and rotation in the fracture group were significantly more pronounced than in the non-fracture group, at the anterodistal and posterodistal positions. Translations at both positions were significantly reduced, by adding the support plate, during both extension and 45-degree flexion in the fracture group. The rotation at the posterodistal position upon extension and the anterodistal position upon 45-degree flexion was significantly reduced by the support plate. The surface strain of the medial plate in the fracture group was significantly reduced by the support plate upon both extension and 45-degree flexion. InterpretationLateral hinge fractures caused abnormal hinge movements, which were significantly reduced by the short support plate. A short support plate could be used if a hinge fracture occurs during distal femoral osteotomy, to improve lateral hinge stability.

Comparison of two osteotomies in the treatment of medial compartment osteoarthritis

To compare the effectiveness of modified distal tibial tubercle-high tibial osteotomy (DTT-HTO) and open-wedge HTO (OWHTO) in the treatment of medial compartment osteoarthritis. A clinical data of 80 patients with medial compartment osteoarthritis treated with HTO between January 2016 and January 2019 was retrospectively analyzed, including 40 patients treated with DTT-HTO (DTT-HTO group) and 40 patients treated with OWHTO (OWHTO group). There was no significant difference in gender, age, body mass index, affected side, disease duration, Kellgren-Lawrence grading of osteoarthritis, and preoperative knee society score (KSS), Hospital for Special Surgery (HSS) score, knee joint visual analogue scale (VAS) score, hip-knee-ankle angle (HKA), posterior tibial slope (PTS), weight-bearing line ratio (WBL), Blackburne-Peel index (BPI), Caton-Deschamps index (CDI), and Insall-Salvati index (ISI) between the two groups ( P>0.05). The operation time, incision length, bleeding volume, hospital stay, and complications in both groups were recorded. The KSS, HSS, and VAS scores were used to evaluated the effectiveness. A self-made questionnaire was used to evaluate the recovery of low-impact sports ability of the knee. X-ray films were used to observe the osteotomy healing and measure the HKA, PTS, WBL, and the patellar height indexes (BPI, CDI, ISI). All operations successfully completed in both groups. The OWHTO group operated longer than the DTT-HTO group ( P<0.05). There was no significant difference in the incision length, bleeding volume, and hospital stay between the two groups ( P>0.05). All incisions healed by first intention in both groups. There were 2 cases of lateral hinge fractures in the OWHTO group, and 1 case of lateral hinge fracture and 2 cases of tibial plateau fractures in the DTT-HTO group. No other complications occurred. The patients in both groups were followed up 2-4 years with an average of 2.8 years. The HSS, KSS, and VAS scores in both groups significantly improved after operation when compared with preoperative scores ( P<0.05). All scores gradually improved with the time and there were significant differences between different time points ( P<0.05). The HSS, KSS, and VAS scores were significantly better in the DTT-HTO group than in the OWHTO group at 3 months after operation ( P<0.05). There was no significant difference between the two groups at 6 months, 1 year, and 2 years ( P>0.05). At 1 year, the low-impact sports ability of the OWHTO group was rated as excellent in 8 cases, general in 25 cases, and poor in 7 cases, and as excellent in 7 cases, general in 26 cases, and poor in 7 cases of the DTT-HTO group. There was no significant difference between the two groups ( Z=-0.715, P=0.475). X-ray film reexamination showed that the osteotomies healed in both groups. The healing time was (4.52±1.23) months in the OWHTO group, and (4.23±1.56) months in the DTT-HTO group, showing no significant difference ( t=0.923, P=0.359). At immediate after operation, the HKA and WBL of the two groups significantly improved when compared with the preoperative values ( P<0.05). However, the pre- and post-operational difference was not significant between the two groups ( P>0.05). The PTS of the OWHTO group was significantly higher than preoperative value ( P<0.05), while the PTS of the DTT-HTO group was lower than preoperative value ( P>0.05). The pre- and post-operational difference between the two groups was significant ( P<0.05). BPI and CDI in the OWHTO group were significantly lower than preoperative values ( P<0.05), but there was no significant difference in ISI when compared with preoperative value ( P>0.05). There was no significant difference in the BPI, CDI, and ISI of the DTT-HTO group between pre- and post-operation ( P>0.05). The pre- and post-operational differences of BPI and CDI between the two groups were significant ( P<0.05), and there was no significant difference in the pre- and post-operational difference of ISI ( P>0.05). The two osteotomies in the treatment of medial compartment osteoarthritis can significantly change the varus deformity and achieve satisfactory effectiveness. The early functional recovery of DTT-HTO is faster, which can avoid the increased PTS and patellar baja of traditional OWHTO. However, neither of the two surgical procedures can restore the patient's ideal low-impact sports ability of the knee.

Reinforcement strategy for medial open-wedge high tibial osteotomy: a finite element evaluation of the additional opposite screw technique and bone grafts

Background and objectivebone grafts (bgs) and the opposite screw insertion technique are reported to enhance initial stability after medial open-wedge high tibial osteotomy (OWHTO); however, it is unclear how the general and local biomechanical stability of the proximal tibia is affected by these reinforcement strategies. In this study, we aimed to assess the biomechanical differences among different fixation configurations for OWHTO under two loading conditions using finite element analysis, and to assess the biomechanical contribution of an opposite screw insertion. MethodsModels of the proximal tibia with three different gap defects were created to simulate different distraction heights in OWHTO. Four groups of models were then assembled with different fixation configurations, including the no BG (NBG) group, BG group, partially threaded screw (PT) group, and fully threaded screw (FT) group. Testing loads were applied to simulate the static forces on the knee joint during double-limb and single-limb standing. For each group, the stresses of the lateral hinge area (LHA) and the medial implant area (MIA), the maximum displacement of the tibia and the relative displacement (RD) of the medial gap were evaluated. ResultsCompared to NBG group, bone block grafting effectively reduced the stress of the tibia and implant, as well as the maximum displacement of the tibia and the RD of the medial gap. The opposite screw group showed similar trends in alleviating the stress concentration on the LHA and MIA, and contributing to the maintaining the medial gap reduction, especially in the FT group; however, additional stresses were concentrated on the opposite screw itself, which indicated the potential risk of screw breakage. ConclusionsCompared to NBG group, the BG group bone graft showed superior biomechanical advantages in decreasing the risk of implant failure and lateral hinge fracture, and maintaining the reduction in OWHTO. The additional opposite screw provided an extra support to the proximal tibia, with similar contributions to improve the structural stability after osteotomy, especially in the FT group.

Double-Level Osteotomy in Severe Varus Malalignment to Optimize Knee Joint Restoration

Background: Lower extremity alignment-correcting procedures for unicompartmental osteoarthritis are experiencing a rapid rise. Medial open-wedge high tibial osteotomy (MOW-HTO) thereby represents the most common technique among osteotomies but is limited in cases of severe malalignment. Some cases make a double-level osteotomy necessary. Indications: If planning of malalignment correction using a MOW-HTO results in a mechanical medial proximal tibial angle (mMPTA) of more than 93° (causing an oblique joint line), double-level osteotomy is indicated to avoid nonphysiological knee kinematics. Technique Description: After clinical examination and detailed analysis of malalignment (full-weight-bearing long-leg radiograph: hip-knee-angle [HKA], mMPTA, mechanical lateral distal femoral angle [mLDFA], joint line convergence angle [JLCA]), as well as individualized planning of the correction, the surgical procedure starts with an arthroscopy to evaluate the cartilage conditions and eventually treat intraarticular pathologies. Then, the femoral supracondylar correction is performed (closed wedge, biplanar osteotomy [ to increase bony healing]) according to the presurgical planning by resecting the osteotomy wedge with the measured length. K-wires are placed to check the correction. An angle-stable plate is used for osteosynthesis. The wedge taken out will be used as bone stock for the MOW-HTO afterward. The biplanar open-wedge tibial osteotomy is then performed subsequently using a medial tibial approach and an angle-stable plate. Opening of the osteotomy is then performed and double checked with intraoperative fluoroscopy using an alignment rod. Postoperative partial weight bearing for 6 weeks is recommended. Results: In recent literature, only few publications report on results of double-level osteotomies. Babis et al reports that it is a valuable procedure for patients with large varus deformity. Nakayama et al noted a significant improvement in patient-registered clinical outcomes in early postoperative evaluation of 20 patients. Schröter et al reports on 37 knees and findings include good clinical results, despite progressive osteoarthritis. Discussion/Conclusion: In cases of severe malalignment, adequate axis correction may require a double-level osteotomy. Exact preoperative planning is essential. Results reported in recent publications are promising. By splitting 1 large correction into 2 smaller ones, complications like hinge fracture and delayed bone healing are lowered.

Influence of lateral hinge fractures on biplanar medial closing-wedge distal femoral osteotomy for valgus knee: a new classification of lateral hinge fracture.

The purpose of this study was to examine the influence of lateral hinge fractures in medial closing-wedge distal femoral osteotomy (MCWDFO) on bone union. Twenty-one patients were followed-up for more than 1year after MCWDFO. The incidence and type of hinge fracture, as well as the course of bone healing, were investigated. Slow healing was defined as bone union was not obtained until 3months after surgery. Hinge fractures were observed in 12 cases (57%). There were three types of hinge fractures. Type 1: the lateral cortex was completely cut through (4 cases), type 2: the osteotomy line was too proximal (6 cases), and type 3: the hinge point was significantly medial (2 cases). There was a significant difference in the mean correction angles between hinge fracture and no-fracture cases, with the mean angles being 13.8 ± 4.0° and 9.6 ± 3.1°, respectively. Sixty-seven percent (8/12) of cases with hinge fractures developed slow healing. Among the hinge fracture cases, when there was no displacement of the hinge fracture and good contact with the anterior flange, 40% (2/5) of cases developed slow healing. If there was displacement of the hinge or no contact of the anterior flange, 86% (6/7) of cases developed slow healing. In contrast, only 11% (1/9) of subjects who did not have a hinge fracture, developed slow healing. In 67% (6/9) of cases with slow healing, a correction loss of 2° or greater (average: 4.3 degrees valgus) was observed. There were no cases of non-union. Clinical outcomes at 1year showed no significant difference between the groups with and without hinge fractures. There is a very high risk of hinge fracture in patients undergoing MCWDFO. Hinge fractures often lead to slow healing and a loss of correction. We recommend the endpoint of the distal lateral cortex of the femur as the ideal hinge point for the prevention of hinge fractures. Bone union is obtained slowly in even all hinge fracture cases without revision surgery. Consequently, surgical results are not affected by the occurrence of hinge fracture at 1year.

Assessment of morphological differences of the proximal tibia in healthy knees: analysis of the 3-dimensional mathematical model.

High tibial osteotomy and many orthopedic surgical procedures around the knee joint requires precise preoperative planning. In-depth knowledge of the tibial plateau morphology is necessary to limit intraoperative complications like lateral hinge fracture. No studies were exploring the differences in proximal tibia surface geometry, in regards to gender and laterality, using a mathematical model. The aim of our study was to assess morphological differences in healthy knees using a three-dimensional mathematical model. Eighty-seven computed tomography examinations collected from 52 patients were selected for the study. The inclusion criteria were: age between 20 and 40 years, knee joint without visible deformities, no history of significant trauma to index knee, no history of systemic and chronic disorders. The average age of the included patients was 32.5±8.9 years old. For the calculation and comparisons, 45 right knee joints (18 females and 27 males) and 42 left knee joints (17 females and 25 males) were used. The male tibial plateau was much larger than the female one, for the right (P=0.001) and left knees (P=0.001). Male knees showed much bigger variability in two-dimensional tibial plateau dimensions especially for the left knees (P=0.001), and there was also a marked difference in variability between sides in males. Three-dimensional variability was significant for medial condyles for both genders. Male knees had a statistically bigger (P=0.04) tibial plateau surface area for all measured condyles. The proximal tibial plateau showed in the designed mathematical models high variability in the two-dimensional and three-dimensional analysis. The males' knees presented great variability between sides and condyles. This finding must be considered during preoperative planning.

Incidence and Factors Affecting the Occurrence of Lateral Hinge Fracture After Medial Opening-Wedge High Tibial Osteotomy

Background:Few clinical studies have reported the predictors of lateral hinge fracture (LHF) after medial opening-wedge high tibial osteotomy (MOWHTO).Purpose/Hypothesis:The purpose was to compare the incidence of LHF on plain radiographs versus computed tomography (CT) scans and to investigate the factors related to the development of LHF after MOWHTO. We hypothesized that (1) a higher LHF detection rate would be seen on CT scans versus plain radiographs and (2) LHF incidence would be related to opening gap width and hinge position.Study Design:Cohort study (diagnosis); Level of evidence, 3.Methods:A total of 97 MOWHTO cases were included. The presence and types of LHF were determined from plain radiographs and CT scans. Radiographic parameters were measured on plain radiographs taken 6 weeks postoperatively. Anterior and posterior opening gap widths, coronal and sagittal osteotomy slopes, and fibular height were calculated from CT scans. The wedge-hinge relationship and the zone of hinge position were assessed, and the patient and radiographic factors related to LHF occurrence were evaluated.Results:Seventeen LHF cases (20.5%) were detected on plain radiographs, while significantly more (37 cases; 44.6%) were found on CT scans (P = .001). Based on Takeuchi classification, 28 LHF cases were considered type 1, 7 were type 2, and 2 were type 3. Logistic regression analysis revealed that opening gap width (odds ratio, 1.615; 95% confidence interval, 1.232-2.118; P = .001) and posterior opening gap width (odds ratio, 3.731; 95% confidence interval, 1.642-4.351; P = .008,) differed significantly between patients with versus without LHF. Other patient and radiographic factors were not significantly related to LHF occurrence. Receiver operating characteristic curve analysis identified the opening gap width cutoff values for LHF as 11.0 mm (area under the curve, 0.81; sensitivity, 78.4%; specificity, 73.9%).Conclusion:The incidence of LHF after MOWHTO can be underestimated on plain radiographs compared with CT scans. Only large opening gap width, especially posterior gap width, was found to have a statistically significant relationship with occurrence of LHF. Therefore, special caution for possible LHF may be needed if a large correction is planned.

Clinical application of split three-dimensional printing patient-specific instrumentation in medial open-wedge high tibial osteotomy

To investigate the accuracy of split three-dimensional (3D) printing patient-specific instrumentation (PSI) in medial open-wedge high tibial osteotomy (MOWHTO) and its effectiveness in treating medial knee osteoarthritis. Clinical data of 14 patients with medial knee osteoarthritis and treated with split 3D printing PSI-assisted MOWHTO between August 2019 and August 2020 were retrospectively analyzed. There were 5 males and 9 females with an average age of 61 years (range, 43-68 years). The disease duration ranged from 1 to 16 years, with an average of 4.7 years. Preoperative Kellgren-Lawrence grading of knee osteoarthritis included grade Ⅰ in 2 cases, grade Ⅱ in 6 cases, and grade Ⅲ in 6 cases. The Hospital for Special Surgery (HSS) score was 59.1±4.9. The weight bearing line ratio (WBL), hip-knee-ankle angle (HKA), medial proximal tibial angle (MPTA), posterior tibial slope angle (PTSA), and actual correction angle of the lower limbs were measured on postoperative imaging data, and compared with the preoperative measurements and the designed target values to evaluate the accuracy of the PSI-assisted surgery. The patients' knee function were evaluated with the HSS score at 3 and 6 months postoperatively, and at last follow-up. One patient suffered from an incision exudation at 2 weeks postoperatively, and the incision healed after symptomatic treatment. The incisions of other patients healed by first intention. All patients were followed up 7-19 months (mean, 14.8 months). There was no neural injuries, hinge fracture, plate or screw fractures, loosening, or other complications. The WBL was maintained at the postoperative level according to the X-ray examination during the follow-up period. The WBL, HKA, MPTA, and PTSA were all within a satisfactory range after operation. The WBL, HKA, and MPTA were significantly improved when compared with the preoperative measurements ( P<0.05). There was no significant difference between preoperative and postoperative PTSA ( P>0.05). The differences in postoperative WBL, HKA, MPTA, and correction angle compared with the preoperative designed target values were not significant ( P>0.05). The HSS scores were 69.2±4.7, 77.7±4.3, and 88.1±5.4 at 3 and 6 months postoperatively, and last follow-up, respectively. The differences between time points were significant ( P<0.05). For patients with medial knee osteoarthritis, the split 3D printing PSI can assist the surgeon in MOWHTO with accurate osteotomy orthopedics and achieve favorable effectiveness.

Detection of Lateral Hinge Fractures After Medial Closing Wedge Distal Femoral Osteotomy: Computed Tomography Versus Plain Radiography

Background: Limited evidence exists in the literature regarding the detection rates of lateral hinge fracture (LHF) on computed tomography (CT) after medial closing wedge distal femoral osteotomy (MCDFO). Moreover, the effect of LHF on bone healing after MCDFO remains unclear. Hypothesis: The detection rates of LHF after MCDFO would be higher on CT than on plain radiography. The incidence of problematic bone healing would be higher in the knees with LHF than in those without LHF. Study Design: Cohort study (diagnosis), Level of evidence, 3. Methods: Patients who underwent MCDFO between May 2009 and July 2019 were retrospectively evaluated. The presence of LHF was evaluated using immediate postoperative plain radiography and CT. The detection rates of LHF on plain radiography and CT were compared. The incidence of problematic bone healing (nonunion, delayed union, and loss of correction) was also compared between the knees with LHF and those without LHF. Results: A total of 55 knees of 43 patients (mean age, 37.7 ± 16.7 years) were included in the study. Although 33 LHFs were detected on CT, only 19 LHFs were detected on plain radiography. The detection rate of LHF was significantly higher on CT than on plain radiography (60% vs 34.5%; P = .008). At 1-year follow-up, 10 cases of problematic bone healing (1 nonunion, 4 delayed unions, and 5 losses of correction) were identified. The incidence of problematic bone healing was significantly higher in the knees with LHF than in those without LHF as shown on plain radiography (36.8% vs 8.3%; P = .001) and CT (30.3% vs 0%; P = .004). Conclusion: LHF can be detected better on CT than on plain radiography and has a negative effect on bone healing after MCDFO. For patients with LHF detected on either plain radiography or CT, careful rehabilitation with close follow-up is recommended.

Orientation and end zone of the osteotomy cut for high tibial osteotomy: Influence on the risk of lateral hinge fracture. A finite element analysis

Introductionthe hinge plays a fundamental role in the support and consolidation of a high tibial osteotomy. The objective of this work was to analyse the influence of the end zone of the osteotomy cut and its orientation in relation to the articular joint line (JL) on the risk of hinge fracture. Hypothesisa specific orientation and end zone of the osteotomy cut can be utilised to decrease the risk of hinge fracture. Material and Methoda finite element (FE) model was used to reproduce the proximal portion of the tibia and the proximal tibiofibular joint with transverse isotropic elastic bone properties. A 1.27mm thick, complete, anteroposterior saw cut was made with a U-shaped saw blade. Five proximal and lateral tibial zones were used according to Nakamura et al corresponding to the end zones of the osteotomy cut. Three angulations of the cut relative to the JL were defined: 10°, 15°, 20°. The tests consisted of simulating 15 possible situations (3 angulations for each of the 5 end zones) on this model. These simulations made it possible to identify the existence of a local stress concentration (von Mises, in MPa) at the level of the hinge, corresponding to the main judgment criterion. ResultsIf we consider only the end zones of the osteotomy cut, regardless of its angulation with respect to the JL, the zone which presents, on average, the lowest local stress concentration is the AM zone (40.3MPa). If we consider only the angulation of the osteotomy cut, with respect to the JL, regardless of the end zone of the cut, the angulation that locally concentrates, on average, the least stress is an angulation at 10° (147.7MPa). Finally, it is important to define the best end zone of the osteotomy cut for each angulation value in relation to the JL: for an angulation of 10°, the end zone must be in AM (38MPa), but also for an angulation of 15° (45MPa), and for an angulation of 20° (38MPa). Discussion–conclusionWith the inherent caveats of the experimental conditions, the hypothesis is confirmed. An end zone of the osteotomy cut exists (AM) and an orientation (10°) that induces the lowest local stress concentration and therefore the least likely to induce lateral hinge fracture. However, the orientation of the osteotomy cut is also a matter of surgical habit, especially regarding complementary osteotomy of the tibial tuberosity that some may want to avoid. Thus, it is equally important to know the best end zone associated with a given angulation of the cut in relation to the JL, which according to these results is the AM zone for each angulation. This information helps guide the operator in their surgical practices according to their habits. Level of evidenceV, expert opinion.

Prediction and Development of Preventive Strategies for Lateral Hinge Fracture During Opening Wedge High Tibial Osteotomy Based on Osteotomy Configurations

Background: Lateral hinge fracture (LHF) is a major complication of opening wedge high tibial osteotomy (OWHTO) and may result in poor outcomes. Purpose/Hypothesis: The purpose of this study was to develop preventive strategies by identifying factors that affect LHFs. We hypothesized that (1) each LHF type would have different affecting factors and that (2) specific operative strategies that can contribute to the prevention of each LHF type can be developed. Study Design: Case-control study; Level of evidence, 3. Methods: We retrospectively analyzed 261 consecutive knees treated with biplanar OWHTO between March 2014 and December 2017. Perioperative radiological variables that can affect LHFs were measured and divided into 2 categories: unmodifiable and modifiable. A regression model was developed, and subgroup analyses involving comparisons between the non-LHF group and each LHF group were performed. The weightbearing line (WBL) ratio was measured at 2 weeks and 1 year after surgery to determine the serial changes in each LHF type. Results: A total of 66 knees (25.3%) were diagnosed with LHFs. From these, 26 (39.4%), 13 (19.7%), 15 (22.7%), and 12 (18.2%) showed type I, II, III, and I-variant LHFs, respectively. In the subgroup analysis, a larger posterior gap and distance X and a smaller fibular height (FH) were significant unmodifiable factors, while the retrotubercular thickness was a significant modifiable factor, for type I LHF. For type II LHF, a smaller lateral condylar slope and a larger distance X were significant unmodifiable factors, while the lateral distal fragment thickness and the osteotomy-condylar angle were significant modifiable factors. For type III LHF, a larger lateral condylar width and distance X and a smaller FH were significant unmodifiable factors, while the lateral proximal fragment thickness and the retrotubercular angle (RA) were significant modifiable factors. A smaller FH and a larger distance X were significant unmodifiable factors for type I-variant LHFs, while the lateral thickness ratio and the RA were significant modifiable factors. Between postoperative week 2 and 1 year, the WBL ratio decreased in cases with type I LHFs (P < .001) and increased in those with type II (P = .001) and type I-variant (P = .006) LHFs. Conclusion: Unmodifiable and modifiable factors for the development of LHFs after OWHTO differ among LHF types. To prevent LHFs, the causes of each LHF must be identified, the patient’s specific geometry be considered in the preoperative planning, and the surgical technique be modified according to the modifiable factors. In addition, during the rehabilitation period after OWHTO, specific caution and close observation are necessary for alignment changes related to each LHF type.

Modelling production mishaps in later Acheulian handaxes from the Area 1 excavation at Amanzi Springs (Eastern Cape, South Africa) and their effects on reduction and morphology

Experimental research examining Later Acheulian handaxes often equates their production with expert knapping skill. Yet knapping mishaps, including step and hinge fractures, mismanaging cross-sectional proportions and transverse breaks are common throughout manufacturing stages and may represent an important source of morphological variability. Recent investigations of handaxes from the ~400 ka Area 1 locality at Amanzi Springs have suggested that the large and asymmetric proportions of these tools may relate the abundance of step and hinge fractures and excessive thick edges that impeded reduction. This study uses both geometric and traditional morphometric techniques to explore the effects of knapping mishaps on the reduction and morphology of Amanzi Springs handaxes. Results suggest that interpretations of Acheulian technological skill can benefit from examining the occurrence of production errors, which may account for some of the morphological differences in handaxes observed on both diachronic and geographic scales.

Mid-term results of medial open-wedge high tibial osteotomy based on radiological grading of osteoarthritis.

To evaluate the mid-term results of medial open-wedge high tibial osteotomy (OWHTO) based on Kellgren-Lawrence (KL) grades. We retrospectively evaluated clinical and radiographic outcomes of 93 patients (mean age 61.4years, mean follow-up 64.2months, 109 consecutive knees) who underwent OWHTO for medial compartment osteoarthritis (OA). KL grade was used to evaluate knee OA (KL-1 22 cases; KL-2, 51 cases; KL-3, 36 cases). The clinical outcomes were assessed using Japanese Orthopaedic Association (JOA) and Lysholm scores. Radiographic outcomes were assessed using pre- and post-operative mechanical axis percentage, femorotibial angle, medial proximal tibial angle, and joint line convergence angle. Hinge fracture frequency and OA progression were also evaluated based on KL grades. The JOA score improved significantly from 70.3 ± 14.9 to 96.2 ± 4.4, 64.1 ± 12.5 to 95.1 ± 5.1, and 68.6 ± 11.4 to 92.1 ± 6.1 in the KL-1, KL-2, and KL-3 groups, respectively. The JOA score in the KL-3 group was significantly lower than in the other groups. The Lysholm score improved significantly from 62.6 ± 8.8 to 97.7 ± 4.7, 62.1 ± 8.1 to 96.7 ± 4.2, and 59.2 ± 9.2 to 95.8 ± 4.6 in the KL-1, KL-2, and KL-3 groups, respectively. The post-operative Lysholm scores were not significantly different among the groups. There were significant differences in radiographic parameters pre-operatively, but not post-operatively, among the groups. Although there were no significant differences in hinge fracture frequency and OA progression, the KL-3 grade predicted OA progression on multivariate analysis. Mid-term results of OWHTO significantly improved. However, clinical score in the KL-3 group was lower than that in the KL-1 and KL-2 groups; radiological OA progression was a risk factor in KL-3.

Lateral femoral closing wedge osteotomy in genu varum

The distal femoral valgisation osteotomy has a variety of indications due to enhanced understanding of segmental deformities of the lower limb. Historically, an overall varus deformity was corrected at the tibia, and a valgus deformity at the femur. This approach of performing an “all in the tibia” correction for an overall varus can nevertheless lead to abnormal postoperative morphology because it is non-anatomical; creating joint line obliquity, and potentially shear stress on the cartilage. An original lateral femoral closing wedge osteotomy technique is described, allowing the correction of a genu varum of femoral or mixed origin, in the event of an associated tibial valgisation osteotomy. The detailed technique minimizes the risk of a hinge fracture while improving post-operative outcomes.

Three dimensional CT analysis of the change in rotational alignment in double level osteotomy after double level osteotomy performed for varus osteoarthritic knees

PurposeTo analyze the change in rotational alignment caused by double level osteotomy (DLO) based on comparative three-dimensional image analysis of pre- and postoperative CT images. MethodsPre- and postoperative CT examination of the lower extremities were performed with informed consent for 39 consecutive knees undergoing DLO for varus knee deformity. The DLO procedure consisted of closed wedge distal femoral osteotomy (CWDFO) and open wedge high tibial osteotomy (OWHTO). Among those cases, 20 knees complicated with hinge fracture at the osteotomy site were excluded from the analysis to eliminate a confounding factor affecting the results. Consequently, data obtained from 19 knees were subjected to the study analysis while osteotomies with hinge fractures complications were excluded from the study. In the three-dimensional CT image analysis of axial plane images, femoral torsion (the angle between midline along the femoral neck axis and the tangent of the posterior edges of the medial/lateral femoral condyles) and tibial torsion (the angle between the tangent of the posterior edges of the medial/lateral tibial condyles and the transmalleolar axis) were measured. The torsion angle was measured in each of the femurs and the tibias on both pre- and postoperative CT axial images, and the change induced by the osteotomy was calculated and statistically(using Wilcoxon signed-rank test) compared. ResultsThe mean pre- and postoperative femoral torsion (anteversion) angles were 29.3° and 31.4° with a significant postoperative increase in internal rotation of the bony segment distal to the osteotomy(P = 0.002). On the tibial side, the mean pre- and postoperative torsion angles were 26.5° and 25.7°, indicating no significant postoperative change(P = 0.199)（NS）. ConclusionsThis study showed that the DLO procedure (combining CWDFO and OWHTO) increased torsion (anteversion) of the femur by 2.1° on average while inducing no significant rotational change on the tibial side.

Medial Closed Wedge Distal Femoral Osteotomy Using a Novel Plate With an Optimal Compression System

Medial closed wedge distal femoral osteotomy (MCWDFO) has been widely performed for lateral-compartment osteoarthritis since the development of a biplanar osteotomy technique using existing MCWDFO-specific plates. To further improve this system and the technique, we have developed a newly designed MCWDFO plate (TriS-MDFO; Olympus Terumo Biomaterials). The improved shape of the plate consists of a larger head–shaft angle to fit the distal femur after MCWDFO, more distally oriented distal screws to enable longer screw insertion, and a diamond-shaped plate head to avoid interference with the medial patellofemoral ligament. Technically, to overcome the difficulty in inserting proximal screws through the vastus medialis muscle, a cannulated screw system was employed. This system can prevent difficulties in removing the screw due to cross-threading when plate removal is required. Furthermore, we designed a novel compression hook device with a bulb-shaped head to hook on a screw hole to apply a compressive force to the osteotomized site. On the plate side, a characteristic 1.5 mm-thickness stopper is installed to prevent slippage of the hook device. This optimal compression system can minimize the risk of lateral hinge fracture during the compression procedure. These improvements in the TriS-MDFO may increase the ease and safety of MCWDFO.

Unstable Lateral Hinge Fracture or Occult Complete Osteotomy Adversely Affects Correction Accuracy in Open-Wedge High Tibial Osteotomy

To verify whether lateral hinge fracture (LHF) affects correction accuracy in open-wedge high tibial osteotomy (OWHTO) and to identify the fracture characteristics responsible for inaccurate correction, including LHF type and hinge location. Patients undergoing OWHTO with locking plate fixation between 2010 and 2016 were retrospectively reviewed. Patients who did not have a minimum 2-year of follow-up or postoperative long-standing hip-to-ankle radiographs were excluded. Correction accuracy was assessed using the weight-bearing line ratio: 57% to 67%, planned correction; 50% to 70%, acceptable correction; otherwise, inappropriate correction. The association between LHF and correction accuracy was assessed using the χ2 test. To identify the fracture characteristics responsible for inaccurate correction, LHF type (stable type 1 and unstable types 2 and 3) and hinge location (shallow osteotomy, deep osteotomy, and occult complete osteotomy) were analyzed using ordinal logistic regression analysis, taking other related demographic and radiologic factors into account. Clinical outcomes according to LHF type were evaluated using the Hospital for Special Surgery scores. A total of 148 cases were included; 41 (27.7%) showed LHF: type 1, 32 cases; type 2, 7 cases; and type 3, 2 cases. Planned, acceptable, and inappropriate corrections were noted in 63 (42.6%), 36 (24.3%), and 48 (32.4%) cases, respectively. LHF had a significant association with correction accuracy (P= .010). Regarding fracture characteristics, unstable LHF and occult complete osteotomy were significant risk factors (P= .016 and P= .004, respectively). Specifically in cases of stable LHF, occult complete osteotomy adversely affected correction accuracy (P= .025). No difference was found in the final Hospital for Special Surgery scores according to LHF type (P= .816). LHF affected the accuracy of coronal alignment correction in OWHTO. Unstable LHF or occult complete osteotomy were risk factors for inaccurate correction. Even among stable LHFs, those with occult complete osteotomy could lead to inaccurate correction. Level III, retrospective cohort study.

Study on stability of filling wall under lateral large-span composite hinge fracture of hard critical block.

There is still a lack of mature researches on the stability mechanism, influencing factors and control technology of the gob-side filling wall, and systematic researches on the cracking forms and characteristics of the stope roof and the stability of the filling wall are rather insufficient. This paper is aimed at investigating the deformation law of the filling wall under the large-span composite hinge fracture of the hard critical block and solving the difficulty that the large-span critical block lateral fracture poses to gob-side entry retaining. Research methods such as theoretical calculation, mechanical analysis, numerical simulation and field test were adopted comprehensively in this study. When the large-span critical block B is divided into two or three parts, its force on the immediate roof decreases with the increase in the number of segments. Meanwhile, as the number of segments grows, the displacement and axial stress of the filling wall both decrease gradually; the tensile failure weakens relatively, while the shear failure changes slightly. Moreover, both the number of shear cracks and the number of tensile cracks in the filling wall are positively correlated with the strain. When the critical block divided into four parts, the amount of lateral displacement is about 190 mm, and the axial displacement reaches the minimum (about 235 mm). The stability of the filling wall along the gob-side entry is closely related to the lateral fracture span of the stope roof. Under the lateral fracture of the hard critical block, a smaller span of the lateral fracture of the critical block corresponds to a smaller force on the filling wall and a weaker damage to the filling wall. The field test result verifies that cleaving the large-span critical block into smaller segments is conducive to reducing surrounding rock and filling wall deformation.