Low-density lipoprotein cholesterol-to-lymphocyte count ratio (LLR) is a promising novel predictor of postoperative new-onset deep vein thrombosis following open wedge high tibial osteotomy: a propensity score-matched analysis.

BACKGROUND: The association of low-density lipoprotein cholesterol (LDL-C) and lymphocyte counts with the development of deep vein thrombosis (DVT) has been demonstrated in many fields but remains lacking in open wedge high tibial osteotomy (OWHTO). This study aimed to assess the predictive value of LDL-C to lymphocyte count ratio (LLR) in screening for postoperative new-onset DVT. METHODS: Clinical data were retrospectively collected from patients who underwent OWHTO between June 2018 and May 2023. The limited restricted cubic spline (RCS) was conducted to evaluate the nonlinear relationship between LLR and the risk of postoperative new-onset DVT. The receiver operating characteristic (ROC) curves were plotted and the predictive value of biomarkers was assessed. After adjusting for intergroup confounders by propensity score matching, the univariate logistic regression was applied to assess the association between LLR and DVT. RESULTS: 1293 eligible patients were included. RCS analysis showed a linear positive correlation between LLR and the risk of DVT (P for overall = 0.008). We identified LLR had an area under the curve of 0.607, accuracy of 74.3%, sensitivity of 38.5%, and specificity of 80.7%, and LLR > 1.75 was independently associated with a 1.45-fold risk of DVT (95% CI: 1.01-2.08, P = 0.045). Furthermore, significant heterogeneities were observed in the subgroups of age, BMI, diabetes mellitus, hypertension, Kellgren-Lawrence grade, the American Society of Anesthesiologists (ASA) score, and intraoperative osteotomy correction size. CONCLUSION: LLR is a valuable biomarker for predicting postoperative new-onset DVT in patients with OWHTO, and routine screening is expected to yield positive benefits.

Postoperative patient-reported outcome measures after medial open-wedge high tibial osteotomy was improved by decreased joint line convergence angle.

PURPOSE: To evaluate the relationship between pre- and postoperative joint line convergence angle (JLCA) changes and patient-reported outcome measures related to medial open-wedge high tibial osteotomy (MOWHTO). METHODS: Sixty-one patients (71 knees) who underwent MOWHTO were examined. Preoperative and 2-year postoperative radiographic parameters (hip-knee-ankle angle, weight-bearing line ratio, medial proximal tibial angle and JLCA) were measured, and knee injury and osteoarthritis outcome scores (KOOS) were assessed. Patients were divided into two groups: group D (decreased JLCA compared with preoperative status) included 44 knees with a ΔJLCA < 0° and group I (increased JLCA and no-change JLCA compared with preoperative status) included 27 knees with a ΔJLCA ≥ 0°. KOOS sub-scores and the proportion of patients whose improvement exceeded the minimum clinically important difference (MCID) were compared between both groups using Student's t tests, Mann-Whitney U tests and chi-square tests. Multiple regression analysis was performed to determine the factor that had an influential effect on the postoperative KOOS total. RESULTS: Significant differences in 2-year postoperative KOOS were observed between the two groups, including total, symptom, pain and activities of daily living scores. Group D had significantly more patients who achieved MCID for both KOOS symptoms and pain scores than group I did. Multivariate analysis indicated that JLCA change and body mass index were significantly associated with the postoperative KOOS total. CONCLUSION: Patients with decreased JLCA had better 2-year post-MOWHTO KOOS and better symptom and pain improvements. Therefore, strategies that reduce JLCA are crucial to improving clinical outcomes, and efforts should be made to improve JLCA in surgical techniques. LEVEL OF EVIDENCE: Level Ⅳ, Case series.

Cartilage regeneration is related to superior mid-term patient-reported outcomes after open-wedge high tibial osteotomy.

PURPOSE: Medial open-wedge high tibial osteotomy (OWHTO) is related to cartilage improvement in the medial compartment. This study aimed to evaluate factors associated with cartilage improvement and patient-reported outcomes (PRO) after OWHTO. It was hypothesised that cartilage improvement is associated with favourable PRO. METHODS: This retrospective study included 94 patients who underwent OWHTO. The mean follow-up period was 5 years. The weight-bearing line ratio (WBLR) was defined as the ratio of the distance from the medial tibial edge to the tibial insertion of the weight-bearing line and the tibial width. The International Cartilage Research Society grade evaluated the medial femoral condyle (MFC) and medial tibial plateau (MTP) at initial and second-look arthroscopy, and cartilage improvement after OWHTO was assessed. Postoperative knee injury and osteoarthritis outcome scores (KOOS) were compared between the groups with improved and non-improved cartilage. Additionally, factors related to cartilage improvement and postoperative KOOS scores were analysed. RESULTS: Regarding the MFC, KOOS pain, symptoms, activities of daily living (ADL) and quality of life (QOL) were significantly higher in the cartilage-improved group than in the non-improved group (p = 0.012, 0.003, 0.001, 0.006), and cartilage improvement was significantly related to KOOS pain, ADL and QOL (p = 0.021, 0.039, 0.013). In addition, the postoperative WBLR was associated with cartilage improvement, with a cutoff value of 54.0% (p = 0.046). Regarding the MTP, KOOS ADL and QOL (p = 0.026, 0.022) were significantly higher in the cartilage-improved group than in the nonimproved group. Body mass index (BMI) was significantly related to the postoperative QOL (p = 0.018) and associated with cartilage improvement, with a cutoff value of 25.9 kg/m2 (p = 0.002). CONCLUSION: A postoperative WBLR greater than 54.0% and a preoperative BMI below 25.9 kg/m2 were associated with cartilage improvement, positively impacting PRO after OWHTO. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Effect of hardware removal and second-look arthroscopy after open-wedge high tibial osteotomy.

INTRODUCTION: Open-wedge high tibial osteotomy (OWHTO) is the standard and safe procedure for medial compartment osteoarthritis. Although hardware removal (HWR) is performed after post-OWHTO bone union, the effects of HWR on OWHTO have been rarely reported. We hypothesised that HWR would improve range of motion (ROM) and implant-related complications. Thus, this study aimed to investigate the effects of HWR on postoperative ROM, the Japan Orthopaedic Association (JOA) score/visual analogue scale (VAS) score and hardware-related complications after OWHTO. METHODS: Patients who underwent OWHTO between January 2016 and June 2018 and HWR were retrospectively reviewed. To perform OWHTO, locking plates and prosthetic bone were used to achieve optimal stabilisation of biplanar osteotomy. HWR was performed after a second-look arthroscopy through the previous skin incision. For clinical evaluation, the JOA score, VAS score, and ROM were assessed before and 1 year after HWR using the Wilcoxon rank test. Logistic regression analysis was performed to identify the predictors of post-HWR improvement. RESULTS: Of 98 knees examined (91 patients), 80 (73 patients; 39 men and 34 women) were included. At the time of OWHTO, mean age was 64.0 ± 9.7 years and body mass index, 25.5 ± 3.1 kg/m2; Kellgren-Lawrence (KL) grade 1 was seen in 20 cases, KL-2 in 46, and KL-3 in 14. Mean periods between OWHTO and HWR were 13.4 ± 2.0 months, and 11.9 ± 1.2 months between HWR and evaluation. The JOA score and flexion angle significantly improved after HWR (The JOA score: p = 0.026 flexion angle: p < 0.001); however, the VAS score and extension angle did not (VAS score: p = 0.162, extension angle: p = 0.934). Hardware irritation was observed in four cases (5%), which improved after HWR. Logistic regression analysis revealed that lower preoperative KL grade and flexion angle were predictors of improvement after HWR [KL grade: p = 0.008; odds ratio 3.244, 95% confidence interval (CI) 1.350-7.794; flexion angle: p < 0.001; odds ratio 1.150, 95% CI 1.062-1.245]. CONCLUSION: HWR improves flexion angle, clinical outcomes and hardware-related complications after OWHTO. Preoperative KL grade and flexion angle are predictors of improvement after HWR in patients who have undergone OWHTO.

Relationship between increased knee joint line obliquity after medial open-wedge high tibial osteotomy and patient-reported outcome measures.

INTRODUCTION: This study evaluated the correlation between postoperative knee joint line obliquity after medial open-wedge high tibial osteotomy and patient-reported outcome measures excluding excessively overcorrected knees. This study further identified preoperative radiological factors related to the increased postoperative knee joint line obliquity. MATERIALS AND METHODS: We retrospectively evaluated patients who underwent medial open-wedge high tibial osteotomy between March 2013 and March 2021. Postoperative excessively overcorrected knees with hip-knee-ankle angle > 7° were excluded. We investigated radiological parameters and patient-reported outcome measures preoperatively and at the last follow-up. The following radiologic parameters were measured: hip-knee-ankle angle, weight-bearing line ratio, mechanical medial proximal tibial angle, mechanical lateral distal femoral angle, lateral distal tibial angle, joint line convergent angle, knee joint line obliquity, ankle joint line obliquity, hip abduction angle, tibial posterior slope, Carton-Deschamps index, and patella tilting angle. Clinical outcomes were evaluated using Japanese knee outcome measures. This assessment criterion is based on the Western Ontario McMaster Universities Arthritis Index and MOS Short Form 36. Multiple regression analysis was performed to evaluate the association between postoperative knee joint line obliquity and patient-reported outcome measures or preoperative radiological factors (P < .05). RESULTS: A total of 52 knees were included. The mean age at the time of the surgery was 61.6 ± 9.0 years and the mean follow-up period was 30.6 ± 10.1 months. Increased postoperative knee joint line obliquity was associated with lower Japanese knee outcome measures. The preoperative hip-knee-ankle angle was significantly associated with postoperative knee joint line obliquity. CONCLUSIONS: Increased knee joint line obliquity after medial open-wedge high tibial osteotomy is associated with inferior clinical outcomes. Care should be given to the center of the rotational angulation in around-knee osteotomy to avoid postoperative increased knee joint line obliquity. LEVEL OF EVIDENCE: Retrospective comparative study, Level III.

[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.

Earlier consolidation and improved knee function of medial open wedge high tibial osteotomy with autologous bone graft.

PURPOSE: Medial knee osteoarthritis can be treated with medial open wedge high tibial osteotomy (OWHTO). We sought to investigate osseous consolidation of the osteotomy with and without autologous bone grafts (ABG) to detect possible benefits of ABG in osseous healing and functional outcome. METHODS: In this prospective study, patients without graft transplantation were compared to those receiving ABG after medial OWHTO. They were followed up 6 weeks, 12 weeks, 6 months and 12 months postoperatively. Radiographic progress of consolidation, clinical scores, contrast-enhanced ultrasound (CEUS) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) were assessed at each appointment. RESULTS: A total of 35 patients were enrolled, 20 without and 15 with graft transplantation. Radiologic evaluation showed a significantly earlier consolidation of the osteotomy gaps (p = 0.012) in patients with ABG, resulting in a significantly higher rate of consolidation 12 months after surgery (60% without bone graft vs. 100% with bone graft, p = 0.006). At 6 weeks as well as 6-month follow-up, a tendency of earlier consolidation with ABG was apparent, but not statistically significant (6 weeks: 50% vs. 80%, p = 0.089; 6 months: 30% vs. 60%, p = 0.097). CEUS and DCE-MRI showed physiological perfusion of the osteotomy gaps in both groups. A tendency to better function and less pain in patients with ABG was recognizable. CONCLUSION: In our study, autologous bone grafting evocated earlier osseous consolidation after medial OWHTO and showed a tendency to a better functional outcome.

Development and validation of a nomogram for predicting the risk of immediate postoperative deep vein thrombosis after open wedge high tibial osteotomy.

PURPOSE: This study aimed to identify independent risk factors for immediate postoperative deep vein thrombosis (DVT) in patients with open wedge high tibial osteotomy (OWHTO) and to develop and validate a predictive nomogram. METHODS: Patients who underwent OWHTO for knee osteoarthritis (KOA) from June 2017 to December 2021 were retrospectively analyzed. Baseline data and laboratory test results were collected, and the occurrence of DVT in the immediate postoperative period was regarded as the study outcome event. Multivariable logistic regression identified independent risk factors associated with a higher incidence of immediate postoperative DVT. The predictive nomogram was constructed based on the analysis results. The stability of the model was further assessed in this study using patients from January to September 2022 as an external validation set. RESULTS: 741 patients were enrolled in the study, of which 547 were used in the training cohort and the other 194 for the validation cohort. Multivariate analysis revealed a higher Kellgren-Lawrence (K-L) grade (III vs. I-II OR 3.09, 95% CI 0.93-10.23. IV vs. I-II OR 5.23, 95% CI 1.27-21.48.), platelet to hemoglobin ratio (PHR) > 2.25 (OR 6.10, 95% CI 2.43-15.33), Low levels of albumin (ALB) (OR 0.79, 95% CI 0.70-0.90), LDL-C > 3.40 (OR 3.06, 95% CI 1.22-7.65), D-dimer > 1.26 (OR 2.83, 95% CI 1.16-6.87) and BMI ≥ 28 (OR 2.57, 95% CI 1.02-6.50) were the independent risk factors of immediate postoperative DVT. The concordance index (C-index) and Brier score of the nomogram were 0.832 and 0.036 in the training set, and the corrected values after internal validation were 0.795 and 0.038, respectively. The receiver-operating characteristic (ROC) curve, the calibration curve, the Hosmer-Lemeshow test, and the decision curve analysis (DCA) performed well in both the training and validation cohorts. CONCLUSION: This study developed a personalized predictive nomogram with six predictors, which allows surgeons to stratify risk and recommended immediate ultrasound scans for patients with any of these factors. LEVEL OF EVIDENCE: III.

Association of the joint line orientation angle of the contralateral limb with the alignment change of the unilateral and bilateral opening-wedge high tibial osteotomy.

PURPOSE: This study aimed to evaluate and compare unilateral and bilateral open-wedge high tibial osteotomy (OWHTO) using mid-term serial assessment of clinical and radiological outcomes, especially focussing on coronal lower extremity alignment. METHODS: Serial radiological assessments were performed in 40 patients (80 knees) with bilateral OWHTO and 49 patients (49 knees) with unilateral OWHTO. Both groups were further divided into four subgroups to compare each limb (unilateral involved and non-involved limbs and bilateral primarily and secondarily treated limbs). Radiological and clinical outcomes were evaluated and compared among the four groups. For the alignment change assessment, the pelvic tilt angle (PTA), weight-bearing line ratio (WBLR), joint line orientation angle (JLOA), medial proximal tibia angle (MPTA), joint line convergence angle (JLCA), distal tibia articular angle (DTAA), and talar inclination (TI) were measured pre- and postoperatively at 3, 6, and 12 months and annually thereafter. Student's t-test, one-way repeated-measures analysis of variance, and correlation analysis were used to compare the groups. RESULTS: Patients in the unilateral and bilateral OWHTO groups had similar postoperative radiological and clinical outcomes. Each unilaterally involved limb and primarily treated bilaterally involved limb were negatively affected by the contralateral limb with respect to increased JLOA during the postoperative period (unilateral OWHTO group: r = -0.350, p = 0.023; bilateral OWHTO group: r = -0.520, p = 0.005). The correction change of the ankle parameters in the secondarily treated limb showed greater varus alignment than the primarily treated limb after bilateral OWHTO (DTAA (0.1 ± 3.0 vs. -0.5 ± 3.8°, p = 0.014) and TI (0.9 ± 3.2° vs. -0.3 ± 2.9, p = 0.001)). CONCLUSION: Unilateral and bilateral OWHTOs shared similar postoperative radiological and clinical outcomes. Alignment changes of the unilateral OWHTO and the primarily treated limb of the bilateral OWHTO were associated with the JLOA of the contralateral limb. LEVEL OF EVIDENCE: Cohort study; Level III.

Development of a machine learning model to predict lateral hinge fractures by analyzing patient factors before open wedge high tibial osteotomy.

PURPOSE: Several methods have been developed to prevent lateral hinge fractures (LHFs), using only classic statistical models. Machine learning is under the spotlight because of its ability to analyze various weights and model nonlinear relationships. The purpose of this study was to create a machine learning model that predicts LHF with high predictive performance. METHODS: Data were collected from a total of 439 knees with medial osteoarthritis (OA) treated with Medial open wedge high tibial osteotomy (MOW-HTO) from March 2014 to February 2020. The patient data included age, sex, height, and weight. Preoperative, determined, and modifiable factors were categorized using X-ray and CT data to create ensemble models with better predictive performance. Among the 57 ensemble models, which is the total number of possible combinations with six models, the model with the highest area under curve (AUC) or F1-score was selected as the final ensemble model. Gain feature importance analysis and the Shapley additive explanations (SHAP) feature explanation were performed on the best models. RESULTS: The ensemble model with the highest AUC was a combination of a light gradient boosting machine (LGBM) and multilayer perceptron (MLP) (AUC = 0.992). The ensemble model with the highest F1-score was the model that combined logistic regression (LR) and MLP (F1-score = 0.765). Distance X was the most predictive feature in the results of both model interpretation analyses. CONCLUSION: Two types of ensemble models, LGBM with MLP and LR with MLP, were developed as machine learning models to predict LHF with high predictive performance. Using these models, surgeons can identify important features to prevent LHF and establish strategies by adjusting modifiable factors. STUDY DESIGN: Retrospective cohort study.

Closed-wedge high tibial osteotomy is more advantageous to maintain the correction than open-wedge high tibial osteotomy in osteopenic patients.

PURPOSE: To compare the incidence of correction loss and survival rate between closed-wedge and open-wedge high tibial osteotomies (CWHTO and OWHTO, respectively) in patients with osteopenic and normal bone. METHODS: Retrospective review was conducted for 115 CWHTOs and 119 OWHTOs performed in osteopenic patients [- 2.5 < Bone mineral density (BMD) T scores ≤ - 1] and 136 CWHTOs and 138 OWHTOs performed in normal patients (BMD T score > - 1) from 2012 to 2019. Demographics were not different between CW- and OWHTOs in osteopenic and normal patients (n.s., respectively). Radiographically, the mechanical axis (MA), medial proximal tibial angle (MPTA), and posterior tibial slope (PTS) were evaluated pre- and postoperatively (2 weeks after HTO). The occurrence of hinge fractures was investigated using radiographs taken on the operation day. The correction change was calculated as the last follow-up value minus postoperative MPTA. Correction loss was defined when the correction change was ≥ 3°. The survival rate (failure: correction loss) was investigated. RESULTS: There were no significant differences in the pre and postoperative MA, MPTA, PTS, and value changes between CW- and OWHTOs in osteopenic and normal patients (n.s., respectively); the incidence of unstable hinge fractures also did not differ significantly (CWHTO vs. OWHTO = 7 vs. 7.6% in osteopenic patients; 2.9 vs. 3.6% in normal patients; n.s., respectively). The average correction change (CWHTO = - 0.6°, OWHTO = - 1.3°, p = 0.007), incidence of correction loss (CWHTO = 1.7%, OWHTO = 9.2%, p = 0.019), and 5-year survival rates (CWHTO = 98.3%, OWHTO = 90.8%, p = 0.013) differed significantly in osteopenic patients; there were no significant differences in these results in normal patients (n.s., respectively). CONCLUSION: CWHTO was more advantageous than OWHTO regarding the correction loss in osteopenic patients. Intra- and postoperative care that consider poor bone quality will be required when performing OWHTOs in osteopenic patients. LEVEL OF EVIDENCE: III.

Influence of medial open wedge high tibial osteotomy on tibial tuberosity-trochlear groove distance.

PURPOSE: Medial open wedge high tibial osteotomy (MOWHTO) is an effective treatment option for realignment of a varus knee. However, a simple supra-tuberositary osteotomy can lead to patella baja and potentially increases the tibial tuberosity-trochlear groove distance (TTTG). The purpose of this study was to quantify the influence of MOWHTO on TTTG. METHODS: Three-dimensional (3D) surface models of five lower extremities with a varus hip-knee-ankle angle (HKA) and a borderline TTTG (≥ 15 mm), five lower extremities with a varus HKA and a normal TTTG (< 15 mm) and a 3D statistical shape model (SSM) of a neutrally aligned healthy knee were analysed by simulating MOWHTO with a stepwise increment of one degree of valgisation from the preoperative coronal deformity (0°-15°) for each patient, resulting in a total of 165 simulations. Postoperative 3D TTTG and tibial torsion (TT) were measured for each simulation. A mathematical formula was developed to calculate the increase of TTTG after MOWHTO. Mean differences between simulated and calculated TTTG were analysed. RESULTS: Mean preoperative HKA was 6.5 ± 3.0° varus (range 0.8°-11.5°). Mean TTTG increased from 14.2 ± 3.2 mm (range 9.6-19.1) preoperatively to 18.8 ± 3.8 mm (range 14.5-25.0) postoperatively (p = 0.001). TTTG increased approximately linear by + 0.5 ± 0.2° (range 0.3-0.8) per 1° of valgisation with a high positive correlation (0.99, p = 0.001) from 0° to 15°. Mean difference between simulated and calculated TTTG was 0.03 ± 0.02 mm (range 0.01-0.07) per 1° of valgisation (p < 0.001). CONCLUSION: MOWHTO results in an approximately linear increase in TTTG of + 0.5 mm per 1° of valgisation in the range from 0° to 15° and the lateralisation of the tibial tuberosity can be calculated reliably using the described formula. Preoperative analysis of TTTG in patients undergoing MOWHTO may prevent unintentional patellofemoral malalignment. LEVEL OF EVIDENCE: III.

Additional anteromedial staple fixation prevents changes in the posterior tibial slope in retrotuberosity bi-planar open-wedge high tibial osteotomy.

PURPOSE: To compare the changes in posterior tibial slope (PTS) between retrotuberosity biplane open-wedge high tibial osteotomies (RT-OWHTOs) with and without additional anteromedial staple fixation. METHODS: Seventy-nine and 77 cases of RT-OWHTOs without (Group N) and with (Group S) additional staple fixation, respectively, were retrospectively reviewed. All procedures were performed using a locking spacer plate. Demographics and preoperative knee condition were similar between the groups. Clinically, the Western Ontario and McMaster Universities Arthritis Index and range of motion were evaluated preoperatively and 2 years postoperatively. Radiographically, the mechanical axis (MA), medial proximal tibial angle (MPTA), and PTS were evaluated preoperatively and within 2 years postoperatively. Hinge fractures were investigated using computed tomography at 2 weeks postoperatively. PTS loss was defined as the difference between the corresponding values at 2 weeks and 2 years postoperatively. The incidence of PTS failure (PTS loss ≥ ± 3°) was also investigated. RESULTS: The clinical results were not significantly different between groups N and S preoperatively and 2 years postoperatively. There were no significant differences in the MA, MPTA, and PTS between the groups preoperatively and 2 weeks postoperatively; changes in these variables did not differ significantly between the groups. The incidence of hinge fractures, all of which were categorized as Takeuchi type 1, did not differ significantly. PTS loss within 2 years postoperatively was significantly greater in group N than in group S (1.0° vs. 0.1°; p < 0.01). The incidence of the PTS failure was 16.5% (13/79) and 2.6% (2/77) in groups N and S, respectively (p < 0.01). CONCLUSION: Additional anteromedial staple fixation could prevent changes in the PTS in RT-OWHTO. It is a simple method for preventing an increase in the PTS after RT-OWHTO. LEVEL OF EVIDENCE: III.

A significant rate of tibial overcorrection with an increased JLO occurred after isolated high tibial osteotomy without considering international consensus.

PURPOSE: The recent ESSKA consensus recommendations defined indications and outlined parameters for osteotomies around a degenerative varus knee. The consensus collated these guidelines based on the published literature available to answer commonly asked questions including the importance of identifying the site and degree of the lower limb deformity. In the consensus, the authors suggest that a knee joint line obliquity (JLO) greater than 5° or a planned medial proximal tibial angle (MPTA) > 94° preferentially indicates a double level osteotomy (DLO) compared to an isolated opening wedge high tibial osteotomy (OWHTO). This study aimed to analyze the corrections performed on a cohort of isolated opening wedge high tibial osteotomies (OWHTOs) prior to the recent ESSKA recommendations, with a focus on the impact of knee joint line obliquity (JLO) and medial proximal tibial angle (MPTA) on the choice of osteotomy procedure. METHODS: This monocentric, retrospective study included 129 patients undergoing medial OWHTO for symptomatic isolated medial knee osteoarthritis (Ahlbäck grade I or II) and a global varus malalignment (hip-knee-ankle angle ≤ 177°). An automated software trained to automatically detect lower limb deformity was implemented using patients preoperative long leg alignment X-rays to identify suitability for an isolated HTO in knee varus deformity. Based on the ESSKA recommendations, the site of the osteotomy was identified as well as the degree of correction required. The ESSKA consensus considers avoiding an isolated high tibial osteotomy if the planned resultant knee joint line orientation exceeds 5 ̊ or MPTA exceeds 94°. A preoperative abnormal MPTA was defined by a value lower than 85° and a preoperative abnormal LDFA by a value greater than 90°. The cases of DLO or DFO suggested by the software and the number of extra-tibial anomalies were collected. Multiple linear regression models were developed to establish a relationship between preoperative values and the risk of being outside of ESSKA recommendations postoperatively. RESULTS: Based on ESSKA recommendations and on threshold values considered abnormal, the software suggested a DLO in 17.8% (n = 23/129) of cases, a distal femoral osteotomy in 27.9% (n = 36/129) of cases and advised against an osteotomy procedure in 24% (n = 31/129) of cases. The software detected a femoral anomaly in 34.9% (n = 45/129) of cases and an JLCA > 6° in 9.3% (n = 12/129). Postoperatively, the MPTA exceeds 94° in 41.1% (n = 53/129) and the JLO exceeds 5° in 29.4% (n = 38/129). On multivariate analysis, a high preoperative MPTA was associated with higher risk of postoperative MPTA > 94° (R2 = 0.36; p < 0.001). Similarly, the probability of the software advising a DLO or DFO was associated with the presence of an "normal" preoperative MPTA (R2 = 0.42; p < 0.001) or an abnormal preoperative LDFA (R2 = 0.48; p < 0.001) or a planned JLO > 5° (R2 = 0.27; p < 0.001). CONCLUSIONS: Analysis of patients who underwent an isolated OWHTO prior to the ESSKA guidelines, demonstrated a significant rate of post-operative tibial overcorrection and a resultant increased JLO. Pre-operative planning that considers the ESSKA guidelines, allows for better identification of those patients requiring a DFO or DLO and avoidance of resultant post-operative deformities. LEVEL OF EVIDENCE: IV, case-series.

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.

Bone mineral density around the knee after open wedge high tibial osteotomy measured up to 24 months in 51 patients.

PURPOSE: To evaluate bone mineral density (BMD) and radiographic and clinical outcomes of patients with varus knee osteoarthritis treated with open wedge high tibial osteotomy (OWHTO). We hypothesised that medial condyle BMD would decrease and lateral condyle BMD would increase after OWHTO. METHODS: Overall, 51 patients (mean age: 65.3 years; female: 40, male: 11) treated with OWHTO were prospectively enrolled. Several angles using whole single-leg radiographs were measured preoperatively and up to 24 months postoperatively. Five square tibial regions of interest (ROI) located below the proximal tibia as T1-T5 from medial to lateral regions and two square femoral ROI as F1 and F2 from medial and lateral regions, respectively, were defined. M/L BMD ratio was used to define the medial-to-lateral condyle BMD ratio. Femoral condyle BMD (F1 and F2) around the knee, as well as lumbar spine, and ipsilateral and contralateral femoral neck BMD, were measured before OWHTO and 3, 6, 12 and 24 months after OWHTO using dual-energy X-ray absorptiometry. Furthermore, tibial condyle BMD (T1-T5) around the knee was measured before and 24 months after OWHTO. Clinical outcomes were evaluated using the Knee Society knee and function scores, the Knee Injury and Osteoarthritis Outcome Score, and the Lysholm score preoperatively and 24 months postoperatively. A power analysis was performed. RESULTS: F1 BMD decreased by 19.2% from before to 3 months postoperatively. F2 BMD did not change up to 24 months after OWHTO. Femoral M/L BMD ratio decreased by 22.2% 3 months after OWHTO. T1 BMD and tibial M/L BMD ratio decreased, whilst T3, T4 and T5 BMD increased 24 months after OWHTO. Mean hip-knee-ankle angle (HKA) and weight-bearing line ratio were corrected from - 6.8° to 4.5° and 14.7 to 60.7%, respectively, postoperatively. Lumbar spine BMD did not change up to 12 months postoperatively. Ipsilateral femoral neck BMD decreased up to 6 months after OWHTO. CONCLUSION: Medial femoral condyle BMD decreased rapidly within 3 months and continued to decrease up to 12 months, but lateral femoral condyle BMD did not change after OWHTO. BMD measurements around the knee condyle enabled the evaluation of the changes in stress distribution before and after OWHTO with accelerated rehabilitation. LEVEL OF EVIDENCE: II.

Medially and distally inserted tuberosity screw fixation of the osteotomized tubercle is safe and effective in retro-tubercular bi-planar opening-wedge high tibial osteotomy.

PURPOSE: The purpose of this study was to develop a safe and effective method of inserting one tuberosity screw and to determine whether retro-tubercular (RT)-Open-wedge high tibial osteotomy (OWHTO) with tuberosity screw fixation can be conducted to overcome the problem of osteotomized tubercle and produce favorable outcomes compared to RT-OWHTO without tuberosity screw fixation. METHODS: From 2018 to 2020, patients who underwent bi-planar RT-OWHTO were allocated as two groups (RT-OWHTO without tuberosity screw fixation as group I and with screw fixation as group II). Computed tomography (CT) was used to analyze osteotomy configurations such as RT gap and tip distance, and union of the main and second plane osteotomy sites. The RT gap distance was measured as the length of the osteotomy gap. The RT tip distance was measured as the length of the gap at the tip of the tibial tubercle. Post-operative complications were analyzed also. To evaluate the neurovascular (NV) approximity of screw fixation group, the pre-operative magnetic resonance imaging (MRI) images were referenced on the post-operative CT for the assessment of the safe zone. RESULTS: In total, 44 knees in group I and 46 knees in group II were enrolled. The RT gap distance (2.58 ± 0.69 mm vs. 0.57 ± 0.57 mm; p < .001) and RT tip distance (4.31 ± 1.60 mm vs. 1.48 ± 1.42 mm; p < .001) were significantly larger in group I than in group II. The sum of union grade in the second plane osteotomy site (17.93 ± 2.18 points vs. 22.24 ± 2.57 points; p < .001) was statistically different between two groups at three months post operatively. Post-operative tuberosity prominence occurred in five knees only in group I (p = 0.025), although tibial tuberosity fracture developed in seven cases in group II compared with two cases in group I with no statistical significance. NV was safe when the screw was inserted medially. CONCLUSION: RT-OWTHO with one-screw fixation for the tuberosity was effective in terms of tuberosity prominence and the union of the second plane osteotomy site. However, it also produced another problem, such as tuberosity fracture. In addition, a tuberosity screw was safe when it was inserted in the medial-distal direction. LEVEL OF EVIDENCE: Cohort study; level III.

Can double-level osteotomy prevent patellofemoral osteoarthritis progression compared with open wedge high tibial osteotomy?

PURPOSE: To compare radiographic, clinical, and arthroscopic findings in patellofemoral (PF) osteoarthritis (OA) between open wedge high tibial osteotomy (OWHTO) and double-level osteotomy (DLO) with the same operative indication. METHODS: After adjustment for patient age, and coronal alignment, 36 knees with OWHTO alone and 36 knees with DLO were compared. Radiographic, clinical, and arthroscopic findings were documented before osteotomy. Arthroscopic findings were observed 1 year after osteotomy, and clinical and radiographic findings were observed 2 years after osteotomy. Patellar height was evaluated using the Insall-Salvati (IS) ratio, Carton-Deschamps (CD) index, and Blackburne-Peel (BP) index. Lateral patellar tilt and patellar shift were measured. A power analysis was performed. RESULTS: The postoperative CD and BP indices in the OWHTO group were lower than those in the DLO group (p < 0.001 and p = 0.001, respectively). The CD and BP indices in both groups significantly decreased postoperatively (all p < 0.001). Tilting angles in the OWHTO and DLO groups significantly decreased postoperatively (p < 0.001 and p = 0.002, respectively). There were no significant differences in American Knee Society scores, Kujala score, and the Knee Injury and Osteoarthritis Outcome Scores between both groups. The PF OA progression of the trochlear in the OWHTO group was higher than that in the DLO group (p = 0.002), and the PF OA progression of the patellar facet in the DLO group and anterior femoral condyle in both groups on the lateral side were higher than those on the medial side (p = 0.006, 0.032, and 0.041, respectively). CONCLUSIONS: DLO decreased the rate of low patellar height compared with OWHTO. DLO decreased the rate of PF OA progression in the trochlea compared with OWHTO. There were no significant differences in clinical outcomes in both groups. LEVEL OF EVIDENCE: Level III, case-control study.

Analysis of the determinant factor of the medial joint space width after medial opening wedge high tibial osteotomy.

INTRODUCTION: The decrease in the medial joint space width (MJSW) in patients with osteoarthritis (OA) is proportional to the degree of arthritis. The purpose of this study was to evaluate the affecting factors of the MJSW by serial radiologic assessment after medial open wedge high tibial osteotomy (MOW-HTO). MATERIALS AND METHODS: Between March 2014 and March 2019, 162 MOW-HTO knees that underwent serial radiologic assessment and follow-up MRI were enrolled. Changes in the MJSW were analyzed by dividing into three groups: group I, low quartile (< 25%); II, middle quartile (25-75%); and III, high quartile (> 75%), according to the magnitude of the MJSW. The correlation between the MJSW and weight-bearing line ratio (WBLR), hip knee ankle angle (HKA), joint line convergence angle (JLCA), medial proximal tibial angle (MPTA), mechanical lateral distal femoral angle (m-LDFA), joint line orientation angle (JLOA), and MRI cartilage status was analyzed. Multiple linear regression analysis was used to analyze factors affecting the amount of change in the MJSW. The clinical outcome was also correlated with the MJSW. RESULTS: The amount of change in the JLCA, which has the largest beta value (weight-bearing standing anteroposterior (AP) view and 45° flexion posteroanterior view (Rosenberg view) ß = - 0.699 and ß = -5.221, both p < 0.001, respectively), had the greatest contribution to the change in the MJSW. The WBLR was also related (standing AP and Rosenberg ß = 0.177 and ß = 0.264, p = 0.015 and p = 0.004, respectively). There was no statistical difference between the amount of change in the MJSW and the change in cartilage. The clinical outcomes did not differ between the groups. CONCLUSION: The JLCA was the most important contributing factor for the MJSW, followed by WBLR. This contribution was more pronounced in Rosenberg view than standing AP view. Changes in cartilage status were not related to the MJSW and JLCA. The clinical outcome was not related to the MJSW, either. Level of evidence Cohort study; level III.

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

PURPOSE: To evaluate the mid-term results of medial open-wedge high tibial osteotomy (OWHTO) based on Kellgren-Lawrence (KL) grades. MATERIALS AND METHODS: We retrospectively evaluated clinical and radiographic outcomes of 93 patients (mean age 61.4 years, mean follow-up 64.2 months, 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. RESULTS: 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. CONCLUSIONS: 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.