The aim of this study was to determine the long term 20 year survival and outcomes of high tibial osteotomy (HTO). 100 consecutive subjects underwent HTO under the care of a single surgeon between 2000 and 2002, consented to participation in a prospective study and completed preoperative WOMAC scores. Subjects were reviewed at 10 years, and again at a minimum of 20 years after surgery. PROMS included further surgery, WOMAC scores, Oxford Knee Score (OHS), KOOS, and EQ-5D, and satisfaction with surgery. 20 year survival was assessed with Kaplan-Meir analysis, and failure defined as proceeding to subsequent knee arthroplasty. The mean age at HTO was 50 years (range 26-66), and 72% were males. The 5, 10, and 20 year survival of the HTO was 88%, 76%, 43% respectively. On multiple regression analysis HTO failure was associated with poor preoperative WOMAC score of 45 or less (HR 3.2, 95% CI 1.7-6.0, p=0.001), age at surgery of 55 or more (HR 2.3, 95% CI 1.3-4.0, p=0.004), and obesity (HR 1.9, 95% CI 1.1-3.4, p=0.023). In patients who met all criteria of preoperative WOMAC score of 45 or less, age <55 years and body mass index of <30 HTO survival was 100%, 94%, and 59% at 5, 10 and 20 years respectively. Of those who had not proceeded to TKA the mean Oxford Score was 40, KOOS Pain score was 91 and KOOS function score was 97. 97% reported they were satisfied with the surgery and 88% would have the same surgery again under the same circumstances. At 20 years after HTO 43% had not proceeded to knee arthroplasty, and were continuing to demonstrate high subjective scores and satisfaction with surgery. HTO survival was higher in those under 55 years, with BMI <30 and baseline WOMAC score of >45 at 59% HTO survival over 20 years. HTO may be considered a viable procedure to delay premature knee arthroplasty in carefully selected subjects

High tibial osteotomy is an efficient treatment for medial compartment osteoarthritis of the knee; its used for middle aged patients with high activity levels and can delay the need for total arthroplasty. The results of total knee arthroplasty after failed high tibial osteotomy are controversies; several authors reported inferior outcomes, but others have concluded that tibial osteotomy doesn't bias following total arthroplasty. The aim of this study was to evaluate the results of failed high tibial osteotomy subsequently converted to total knee arthroplasty and compare the results to group of patients underwere primary arthroplasty; the authors evaluate some of technical problems that a previous high tibial osteotomy can generate, like scar tissue, patellar tendon shortening and changes of proximal tibial anatomy. Methods. 50 total knee arthroplasty performed after a previous closed wedge osteotomy were matched with 50 patients operated with a primary knee prosthesis for osteoarthritis. The time from a proximal tibial osteotomy to a prosthesis operation was in mean eight years. Results. the Knee Society clinical and radiographic score system and W.O.M.A.C. evaluation were used to evaluate knees before surgery and at each follow up (average 5 years). At an average of five years follow up, the clinical results of total knee arthroplasty after high tibial osteotomy were similar to those of primary knee prosthesis. Discussion. in our study revision of failed proximal tibial osteotomy appears to have more technical difficulties but with overall outcomes that remain comparable at results after primary total knee arthroplasty, so tibial osteotomy is considered a valid option in younger and very active patients with unicompartmental arthritis

This study aimed to examine the effect of high tibial osteotomy (HTO) on the ankle and subtalar joints via analysis of static radiographic alignment. We hypothesised that surgical alteration of the alignment of the proximal tibia would result in compensatory distal changes. 35 patients recruited as part of the wider Biomechanics and Bioengineering Centre Versus Arthritis HTO study between 2011 and 2018 had pre- and postoperative full-length weightbearing radiographs taken of their lower limbs. In addition to standard alignment measures of the limb and knee (mechanical tibiofemoral angle, Mikulicz point, medial proximal tibial angle), additional measures were taken of the ankle/subtalar joints (lateral distal tibial angle, ground-talus angle, joint line convergence angle of the ankle) as well as a novel measure of stance width. Results were compared using a paired T-test and Pearson's correlation coefficient. Following HTO, there was a significant (5.4°) change in subtalar alignment. Ground-talus angle appeared related both to the level of malalignment preoperatively and the magnitude of the alignment change caused by the HTO surgery; suggesting subtalar positioning as a key adaptive mechanism. In addition to compensatory changes within the subtalar joints, the patients on average had a 31% wider stance following HTO. These two mechanisms do not appear to be correlated but the morphology of the tibial plafond may influence which compensatory mechanisms are employed by different subgroups of HTO patients. These findings are of vital importance in clinical practice both to anticipate potential changes to the ankle and subtalar joints following HTO but it could also open up wider indications for HTO in the treatment of ankle malalignment and osteoarthritis

Background. High tibial osteotomy is a common procedure to treat symptomatic osteoarthritis of the medial compartment of the knee with varus alignment. This is achieved by overcorrecting the varus alignment to 2–6° of valgus. Various high tibial osteotomy techniques are currently used to this end. Common procedures are medial opening wedge and lateral closing wedge tibial osteotomies. The lateral closing wedge technique is a primary stable correction with a high rate of consolidation, but has the disadvantage of bone loss and change in tibial condylar offset. The medial opening wedge technique does not result in any bone loss but needs to be fixated with a plate and may cause tibial slope and medial collateral ligament tightening. Purpose. The purpose of this article is to examine correlation between femoral rotational angle and subjective satisfaction of high tibial osteotomy outcome of the range of motion of knee joint. Materials and methods. The subjects were 15 patients (6 males, 9 females) with primary osteoarthritis undergoing high tibial osteotomy from June of 2004 to August of 2008. They were CT tested on the knee joint before and after high tibial osteotomy. TEA and Akagi's line are analysed as percentages. The Kendall's and Spearman's nonparametric correlation coefficient were used for the statistical tests with 0.5 level of significance. Results. We observed a negative linear relationship (p = 0.0001) between the femoral component external rotation (measured by TEA) and active and passive ROM. Pearson Coefficient was −0.80, −0.57, respectively. We can find a negative linear relationship (p=0.001) between Akagi's line and passive ROM, and Pearson coefficient was −0.863. Preoperative flexion contracture, age, tibiofibula angle, pain, and other factors do not influence the ROM of the patient. Follow up duration do not influence the ROM of the patient. Conclusion. The result reveals that femoral rotational angle correlates with not the range of motion of knee joint but subjective satisfaction of the patients. In HTO, beside deformity correction in coronal plane, rotation of the femur contributes postoperative pain relief

High tibial osteotomy is a well established joint preserving procedure for the treatment of unicompartmental knee osteoarthritis. Of particular interest are the alterations in knee loading compartments during dynamic activities such as locomotion. Computer modelling can indirectly assess contact and muscle forces in the patient. This study aimed to develop a valid model representative of high tibial osteotomy to assess the medial joint contact force at the knee during gait. Software for Interactive Musculoskeletal Modelling (version 2, SIMM Inc, USA) was used to develop a model to replicate the effects of high tibial osteotomy surgery on tibial alignment. The program was then used to perform a detailed analysis on gait data collected from two high tibial osteotomy patients preoperatively and 6 months post operatively. Inverse dynamics simulations were conducted to investigate knee joint contact force on the medial compartment of the two patients during the stance phase of their operated limbs. Significant decreases (p<0.05) in the medial joint contact force were observed during both early and late stance for both patients. Force generated in muscles crossing the knee was found to be the major contributor to the joint contact force. Total muscle force was found to increase significantly (p<0.05) following surgery, however decreased loads were calculated for the medial compartment. The pattern and magnitude of joint reaction force was found to be consistent before and after surgery and replicated the results of previous studies. The HTO-specific model was valid and sensitive to changes in joint reaction force, medial joint contact force and muscle forces crossing the knee. High tibial osteotomy reduced the medial joint contact force at the knee as a result of the coronal realignment of the limb. Osteoarthritis symptoms were relieved in terms of knee pain and function. Finally, a difference in compensatory strategies was observed between patients. This novel technique allows non-invasive assessment of the mechanical effect of procedures such as HTO. This should allow more accurate planning and assessment of such surgical procedures

High tibial osteotomy (HTO) is largely conducted as an inpatient procedure, imposing the significant cost of hospital admission. Here we examine patient-related outcomes and cost benefit of altering HTO to a day-case procedure. A retrospective questionnaire was conducted with patients that underwent HTO in the one and half years prior to the change to day-case, and those in the one and half years afterwards. We considered pre-operative and post-operative KOOS scores, patient pain-scoring and whether they would, given their experience, undergo HTO as an outpatient again. Thirty-three patients were included in the trial: twenty-three inpatient admissions and ten day-cases. Average KOOS score improvement for inpatients was 24.68 and outpatients was 31.8. Outcomes such as post-operative pain and nausea/vomiting were found to be similar between groups. The outpatient group unanimously agreed that if undergoing HTO again they would desire to be treated in the outpatient setting again. Currently HTO is conducted as an inpatient procedure in the majority of institutions. We have demonstrated that patients have comparable outcomes and agree that if undergoing HTO again they would wish to do so as day-case outpatient. This represents a significant cost saving for institutions conducting HTO as well as an improvement in service

Introduction. High tibial osteotomy (HTO) is a commonly used surgical technique for treating moderate osteoarthritis (OA) of the medial compartment of the knee by shifting the center of force towards the lateral compartment. The amount of alignment correction to be performed is usually calculated prior to surgery and it's based on the patient's lower limb alignment using long-leg radiographs. While the procedure is generally effective at relieving symptoms, an accurate estimation of change in intraarticular contact pressures and contact surface area has not been developed. Using electromyography (EMG), Meyer et al. attempted to predict intraarticular contact pressures during gait patterns in a patient who had received a cruciate retaining force-measuring tibial prosthesis. Lundberg et al. used data from the Third Grand Challenge Competition to improve contact force predictions in total knee replacement. Mina et al. performed high tibial osteotomy on eight human cadaveric knees with osteochondral defects in the medial compartment. They determined that complete unloading of the medial compartment occurred at between 6° and 10° of valgus, and that contact pressure was similarly distributed between the medial and lateral compartments at alignments of 0° to 4° of valgus. In the current study, we hypothesised that it would be possible to predict the change in intra-articular pressures based on extra-articular data acquisition. Methods. Seven cadavers underwent an HTO procedure with sequential 5º valgus realignment of the leg up to 15º of correction. A previously developed stainless-steel device with integrated load cell was used to axially load the leg. Pressure-sensitive sensors were used to measure intra-articular contact pressures. Intraoperative changes in alignment were monitored in real time using computer navigation. An axial loading force was applied to the leg in the caudal-craneal direction and gradually ramped up from 0 to 550 N. Intra-articular contact pressure (kg) and contact area (mm2) data were collected. Generalised linear models were constructed to estimate the change in contact pressure based on extra-articular force and alignment data. Results. The application of an axial load results in axial angle changes and load distribution changes inside the knee joint. Preliminary analysis has shown that it is possible to predict lateral and medial compartment pressures using externally acquired data. For lateral compartment pressure estimation, the following equation had an R of 0.86: Lateral compartment pressure = −1.26*axial_force + 37.08*horizontal_force − 2.40*vertical_force − 271.66*axial_torque − 32.64*horizontal_torque + 18.98*vertical_torque − 24.97*varusvalgus_angle_change + 86.68*anterecurvature_angle_change − 17.33*axial_angle_change − 26.14. For medial compartment pressure estimation, the following equation had an R2 of 0.86: Medial compartment pressure = −2.95*axial_force −22.93*horizontal_force − 9.48*vertical_force − 34.53*axial_torque + 6.18*horizontal_torque − 127.00*vertical_torque − 110.10*varusvalgus_angle_change − 15.10*anterecurvature_angle_change + 55.00*axial_angle_change + 193.91. Discussion. The most important finding of this study was that intra-articular pressure changes in the knee could be accurately estimated given a set of extra-articular parameters. The results from this study could be helpful in developing more accurate lower limb realignment procedures. This work complements and expands on previous research by other groups aimed at predicting intra-articular pressures and identifying optimal alignment for unloading arthritic defects. A possible clinical application of these findings may involve the application of a predetermined axial force to the leg intra-operatively. Given the estimated output from the predictive equation, one could then perform the opening wedge until the desired estimated intra-articular pressure is achieved. With this method, an arthrotomy and placement of intra-articular pressure sensors would not be needed. This work is not without its limitations. This experiment was performed on cadaveric specimens. Therefore, we cannot directly predict what the pressures would be in a de-ambulating patient. However, these sort of experiments do help us understand the complex biomechanics of the knee in response to alterations in multi-planar alignment. Further in vivo research would be warranted to validate these results. Additionally, given our current experimental setup, only axial loading could be performed for testing. Further experiments involving dynamic motion of the lower limb under load would further help us understand the changes in pressure at difference flexion angles. Continued experiments would help us gather additional data to better understand the relationship between these variables and to construct a more accurate predictive model. In summary, we have established a framework for estimating the change in intra-articular contact pressures based on extra-articular, computer-navigated measurements. Quantifying the resulting changes in load distribution, alignment changes, torque generation and deflection will be essential for generating appropriate algorithms able to estimate joint alignment changes based on applied loads

The optimal correction of the weight bearing line during High Tibial Osteotomy has not been determined. We used finite element modelling to simulate the effect that increasing opening wedge HTO has on the distribution of stress and pressure through the knee joint during normal gait. Subject-specific models were developed by combining geometry from 7T MRI scans and applied joint loads from ground reaction forces measured during level walking. Baseline stresses and pressures on the articulating proximal tibial cartilage and menisci were calculated. Progressive osteotomies were then simulated to shift the weight-bearing line from the native alignment towards/into the lateral compartment (between 40 – 80% of medial-lateral tibial width). Changes in calculated stresses and pressures were recorded. Both stress and pressure decreased in the medial compartment and increased in the lateral compartment as increasingly valgus osteotomies were simulated. The models demonstrated a consistent “safe zone” for weight bearing line position at 50%-65% medial-lateral tibial width, outside of which compartment stresses and pressures substantial increased. This study suggests a safe correction zone within which a medial opening wedge HTO can be performed correcting the WBL to 55% medio-lateral width of the tibia

High tibial osteotomy (HTO) is a common surgical procedure for treatment of patients with varus mal-alignment. The success rate of the procedure is strongly dependent on the quality of the correction. Thus, an accurate pre-planning is essential to ensure that the precise amount of alignment is achieved postoperatively. The purpose of this study was to simulate the HTO in a patient with varus deformity in order to explore the interactions between the wedge angle, the mechanical axis, and the knee joint configuration. A finite element model of the knee joint of a patient with varus deformity was developed. The geometry was obtained using the whole limb CT scans the knee MR images. The bones were assumed as rigid bodies, the articular cartilage and the meniscus as elastic solids, and the ligaments as nonlinear springs. A 600N force was applied at the femoral head in the line of the mechanical axis and the resulting knee configuration was studied. The HTO was simulated assuming insertion of wedges with different angles beneath the tibial plate and applying the resulting alteration of the loading axis to the model. The results indicated that the actual change of the mechanical axes was always smaller than what predicted by a geometric pre-planning approach that does not consider the post-operative change of the knee joint configuration. It was suggested that subject-specific models are needed to simulate the HTO in patients before surgery and determine the appropriate wedge angle that locates the mechanical axis in the middle of the knee

Purpose. Long-term clinical and radiographic results and survival rates were compared between closed-wedge high tibial osteotomy (HTOs) and fixed-bearing unicompartmental knee arthroplasty (UKA) in patients with similar demographics. Methods. Sixty HTOs and 50 UKAs completed between 1992 and 1998 were retrospectively reviewed. There were no significant differences in preoperative demographics. The mean follow-up period was 10.7 ±5.7 years for HTO and 12.0 ±7.1 years for UKA (n.s.). The Knee Society knee and function scores, WOMAC, and range of motion (ROM) were investigated. The mechanical axis and femorotibial angle were evaluated. Kaplan–Meier survival analysis was performed (failure: revision to TKA), and the failure modes were investigated. Results. Most of the clinical and radiographic results were not different at the last follow-up, except ROM; ROM was 135.3 ±12.3° in HTO and 126.8 ±13.3° in UKA (p=0.005). The 5-, 10-, 15-, and 20-year survival rates were 100%, 91.0%, 63.4%, and 48.3% for closed-wedge HTO, respectively, and 90.5%, 87.1%, 70.8%, and 66.4% for UKA (n.s.). The survival rate was higher than that for UKA until 12 years postoperatively but was higher in UKAs thereafter, following a remarkable decrease in HTO. The most common failure mode was degenerative osteoarthritic progression of medial compartment in HTO and femoral component loosening in UKA. Conclusions. Long-term survival did not differ significantly between closed-wedge HTO and fixed-bearing UKA in patients with similar preoperative demographics and knee conditions. The difference in postoperative ROM and failure mode should be considered when selecting a procedure

High tibial osteotomy (HTO) is an established treatment for medial compartment osteoarthritis of the knee; the aim being to achieve a somewhat valgus coronal alignment, thereby unloading the affected medial compartment. This study investigated knee kinematics and kinetics before and after HTO and compared them with matched control data. A three dimensional motion analysis system and two force platforms were used to collect kinematic and kinetic data from eight patients with medial compartment knee osteoarthritis during walking preoperatively and 12 months following HTO (opening wedge). Nine control participants of similar age and the same sex were tested using the same protocol. Sagittal and coronal knee angles and moments were measured on both the operated and non-operated knees and compared between the two time points and between HTO participants and controls. In addition, preoperative and postoperative radiographic coronal plane alignments were compared in the HTO participants. The point at which the mechanical axis passed through the knee joint was corrected from a preoperative mean of 10% tibial width from the medial tibial margin to 56% postoperatively. Stride length and walking speed both improved to essentially normal levels (1.57 m and 1.5 m/s) ostoperatively. In the coronal plane the mean peak adduction angle during stance reduced from 14.3° to 5.2° (control: 6.8°). Mean maximum adduction moments were similarly reduced to levels less than in control participants, in keeping with the aim of the surgical procedure: peak adduction moment 1: pre 3.8, post 2.7, control 3.6 peak adduction moment 2: pre 2.5, post 1.7 and control 2.6. In the sagittal plane, both mean maximum flexion and extension during stance increased postoperatively—extension to greater than in control participants and flexion to almost control levels. The maximum external knee flexor moment during stance also increased to near normal postoperatively. High tibial osteotomy appears to achieve the intended biomechanical effects in the coronal plane (reduced loading of the medial compartment during stance). At the same time there were improvements in sagittal plane kinematics and kinetics which may reflect a reduction in pain. The net effect was to reduce quadriceps demand

Introduction. The management of degenerative arthritis of the knee in the younger, active patient presents a challenge to the orthopaedic surgeon. Surgical treatment options include: high tibial osteotomy (HTO), unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA). The aim of this study was to examine the long-term survival of closing wedge HTO in a large series of patients up to 19 years after surgery. Methods. Four hundred and fifty-five consecutive patients underwent lateral closing wedge HTO for medial compartment osteoarthritis (MCOA) between 1990 and 2001. Between 2008-2009, patients were contacted via telephone. Assessment included: incidence of further surgery, current body mass index (BMI), Oxford Knee Score, and British Orthopaedic Association (BOA) Patient Satisfaction Scale. Failure was defined as the need for revision HTO or conversion to UKA or TKA. Survival analysis was completed using the Kaplan-Meier method. Results. High tibial osteotomy survival was determined on 413 patients (91%) and, of the 397 patients who were alive at the time of final review, 394 (99%) were contacted for follow-up via telephone interview. The probability of survival for HTO at 5, 10 and 15 years was: 95%, 79% and 56% respectively. Multivariate regression analysis showed that age < 50 years (p=0.001), BMI < 25 kg/m. 2. (p=0.006) and ACL deficiency (p=0.03) were associated with better odds of survival. Mean Oxford Knee Score was 40/48 (range 17-48). Overall, 85% of patients were enthusiastic or satisfied and 84% would undergo HTO again at mean 12 years follow-up. Conclusion. High tibial osteotomy can be effective for periods longer than 15 years. However, results do deteriorate over time. Age < 50 years, normal BMI and ACL deficiency were independent factors associated with improved long-term survival of HTO

Limited literature exists providing comprehensive assessment of complications following opening wedge high tibial osteotomy (OWHTO). We performed a retrospective study of local patients who underwent OWHTO for isolated medial compartment knee osteoarthritis from 1997–2013. One hundred and fifteen patients met inclusion criteria. Mean follow-up = 8.4years. Mean age = 47 (range 32–62). Mean BMI = 29.1 (range 20.3–40.2). Implants used included Tomofix (72%), Puddu plate (21%) and Orthofix (7%) (no significant differences in age/ sex/ BMI). Wedge defects were filled with autologous graft (30%), Chronos (35%) or left empty (35%). Five year survival rate (conversion to arthroplasty) = 80%. Overall complication rate = 31%. 25% of patients suffered 36 complications including minor wound infections (9.6%), major wound infections (3.5%), metalwork irritation necessitating plate removal (7%), non-union requiring revision (4.3%), vascular injury (1.7%), compartment syndrome (0.9%), and other minor complications (4%). No thromboembolic complications were observed. A higher BMI (mean 34.2) was apparent in those patients suffering complications than those not (mean 26.9). No significant differences existed in complication rates relative to implant type, type of bone graft used or patient age at surgery. Complications following OWHTO appear higher than previously reported in the literature; serious complications appear rare

Objective. Open-wedge high tibial osteotomy (OWHTO) involves performing a corrective osteotomy of the proximal tibia and removing a wedge of bone to correct varus alignment. Although previous studies have investigated changes in leg length before and after OWHTO using X-rays, none has evaluated three-dimensional (3D) leg length changes after OWHTO. We therefore used 3D preoperative planning software to evaluate changes in leg length after OWHTO in three dimensions. Methods. The study subjects were 55 knees of 46 patients (10 men and 36 women of mean age 69.9 years) with medial osteoarthritis of the knee or osteonecrosis of the medial femoral condyle with a femorotibial angle of >185º and restricted range of motion (extension <–10º, flexion <130º), excluding those also suffering from patellofemoral arthritis or lateral osteoarthritis of the knee. OWHTO was simulated from computed tomography scans of the whole leg using ZedHTO 3D preoperative planning software. We analyzed the hip-knee-ankle angle (HKA), flexion contracture angle (FCA), mechanical medial proximal tibial angle (mMPTA), angle of correction, wedge length, 3D tibial length, 3D leg length, and 3D increase in leg length before and after OWHTO. We also performed univariate and multivariate analysis of factors affecting the change in leg length (preoperative and postoperative H-K-A angle, wedge length, and correction angle). Results. Mean HKA increased significantly from −4.7º ± 2.7º to 3.5º ± 1.3º, as did mean mMPTA from 83.7º ± 3.3º to 92.5º ± 3.0º (p <0.01). Mean FCA was 4.7º ± 3.6° preoperatively and 4.8º ± 3.3º postoperatively, a difference that was not significant (p = 0.725). The mean correction angle was 9.1º ± 2.8º and the mean wedge length was 9.4º ± 3.2º mm. Mean tibial length increased significantly by 4.7 ± 2.3 mm (p <0.01), and mean leg length by 5.6 ± 2.8 mm (p <0.01). The change in leg length was strongly correlated with wedge length (R = 0.846, adjusted R. 2. = 0.711, p <0.01). Discussion and Conclusion. Mean 3D leg length after OWHTO increased significantly by 5.4 ± 3.1 mm. A difference in leg length of >5 mm is believed to affect back pain and gait abnormalities, and changes in leg length must therefore be taken into consideration. The 3D dimensional change in leg length was strongly correlated with wedge length, and could be predicted by the formula (change in leg length in mm) = [(wedge length in mm) ×0.75) − 1.5]. For any figures or tables, please contact authors directly

C-Arm fluoroscopy is limited by its 2D imaging modality and is incapable of providing accurate 3D quantitative assessment of operative anatomy. In High Tibial Osteotomy (HTO), assessing the distance between the mechanical axis of the leg and the centre of the knee joint is difficult to accomplish due to limited fluoroscopic view size. A previously developed sensor-based tracking system (TC-Arm)adds on to C-arm equipment to provide additional quantitative capabilities. A new image-based tracking module was developed for TC-Arm using a reference panel with an array of fiducial markers. The image analysis software segments the marker positions in each image and identifies image coordinates with respect to the panel. Each image's parameters are identified by 2D-3D matching of the panel's 3D model to the marker's epipolar geometries. Finally, the defined linear transformation matrices are applied for positioning all the fluoroscopic images with respect to the same global reference. A Sawbone model of the leg was used as a phantom and marked with radio-dense fiducial markers at the centres of each joint. An Optotrak optoelectronic tracking system data was used to validate the new module's functions. First, tracking accuracy was determined by comparing orthogonal-stereo views and the reconstructed positions of the panel's design. Secondly, TC-Arm's results were compared to the corresponding digitised references points on the Sawbone model to calculate errors in the varus/valgus angle and mechanical axis deviation. The new addition to the TC-Arm has a reasonable tracking accuracy (<3.6mm, <4°) considering HTO: The system measured the mechanical axis deviation for HTO application with an accuracy of 1.3 mm and 1.4°. Comparing these results with the acceptable tolerance of less than 10 mm for MAD reported in the literature, our demonstrated results are considered to be within an acceptable range. With the new module, the capability for three-dimensional quantitative assessments of operative anatomies of any size can be added to any C-arm equipment in the OR. This can have great potential for many complex orthopaedic trauma, reconstruction, or preservation surgeries including HTO

Opening-wedge High Tibial Osteotomy (HTO) has been shown to be an effective procedure to treat mild to moderate osteoarthritis of the medial compartment of the knee in active individuals. It has also become a mandatory surgical adjunct to articular cartilage restoration when there is preoperative mal-alignment. However, its efficacy is directly correlated with the accuracy of the correction, which must be within 3° of the preoperative target. Achieving this goal is a significant challenge with conventional techniques. Therefore, computer-assisted navigation protocols have been developed; however, they do not adequately address the technical difficulties associated with this procedure. We present an integrated solution dedicated to the opening-wedge HTO. Advantages to the technique we propose include: 1) a minimum number of implanted bone trackers, 2) depth control of the saw, 3) improved 3-D accuracy in the location of the lateral tibial hinge, and 4) micrometric adjustment of the degree of correction. The proof of concept has been completed on all six specimens. The following key points have been validated: a) Compatibility with a minimally-invasive (5–6 cm) surgical incision b) The compact navigation station can be placed close to the operative field and manipulated through a sterile draping device c) Only two trackers are necessary to acquire the required landmarks and to provide 3-D control of the correction. These can be inserted within the surgical wound without any secondary incisions d) The optimised guide accurately controlled the external tibial hinge in all six cases e) The implant cavity could be milled effectively f) The distractor used to complete the desired realignment maintained stability of the distraction until final fixation with the PEEK implant g) The PEEK implant could be fixed to the tibia with excellent stability in a low-profile fashion. The solution presented here has the potential to help surgeons perform a medial opening-wedge HTO more safely and accurately. This will likely result in an increase in the number of HTOs performed for both isolated medial compartment osteoarthritis as well as for lower extremity realignment in association with cartilage restorative procedures

Introduction. Opening wedge high tibial osteotomy is an attractive surgical option for physically active patients with early osteoarthritis and varus malalignment. Unfortunately use of this surgical technique is frequently accompanied by an unintended increase in the posterior tibial slope, resulting in anterior tibial translation, and consequent altered knee kinematics and cartilage loading(1). To address this unintended consequence, it has been recommended that the relative opening of the anteromedial and posterolateral corners of the osteotomy are calculated pre-operatively using trigonometry (1). This calculation assumes that the saw-cut is made parallel to the native posterior slope; yet given the current reliance on 2D images and the ‘surgeon's eye’ to guide the saw-cut, this assumption is questionable. The aim of this study was to explore how accurately the native posterior tibial slope is reproduced with a traditional freehand osteotomy saw-cut, and whether novel 3D printed patient-specific guides improve this accuracy. Methods. 26 fourth year medical students with no prior experience of performing an osteotomy were asked to perform two osteotomy saw-cuts in foam cortical shell tibiae; one freehand, and one with a 3D printed surgical guide (Embody, London) that was designed using a CT scan of the bone model. The students were instructed to aim for parallelity with a hinge pin which had been inserted (with the use of a highly conforming 3D printed guide) parallel to the posterior slope of the native joint. For the purpose of analysis, the sawbones were consistently orientated along their mechanical and anatomical tibial axes using custom moulded supports. Digital photographs taken in the plane of the osteotomy were analysed with ImageJ software to calculate the angular difference in the sagittal plane between the hinge-pin and saw-cut. Statistical analysis was performed with SPSS v21 (Chicago, Illinois); a paired t-test was used to compare the freehand and patient-specific guide techniques. Statistical significance was set at a p-value <0.05. Results. Using the traditional freehand technique, the mean difference in angle between the hinge pin and osteotomy saw-cut was 5.40 (SD 4.6), which contrasted with 1.40(SD 1) when the osteotomy was performed using a 3D printed guide [See Figure 1]. This difference was significant (p<0.001). Discussion. This study highlights the large degree of error in the posterior slope of an osteotomy saw-cut when performed using a freehand technique, and which is likely to be a factor in the unintended change in tibial slope commonly observed in post-operative patients. We found that a 3D printed patient-specific osteotomy guide significantly improved the accuracy and reduced the variability of this procedure. A follow-up multi-centre clinical trial is currently underway to ascertain whether these results are replicated in-vivo

Background. Open-wedge high tibial osteotomy (OWHTO) is an operation involving proper load re-distribution in the treatment for medial uni-compartmental arthritis of the knee joint. Therefore, stable fixation is mandatory for safe healing of this additive type of osteotomy to minimize the risk of non-union and loss of correction. For stability, screws provide optimal support and anchorage of the fixator in the condylar area without risking penetration of either the articulating surface. The purpose of the study was to evaluate the screw insertion angle and orientation with an anatomical plate that is post-contoured to the surface geometry of the proximal tibia after OWHTO. Methods. From March 2012 to June 2014, 31 uni-planar and 38 bi-planar osteotomies were evaluated. Postoperative computed tomography data obtained after open wedge high tibial osteotomy using a locking plate were used for reconstruction of the 3 dimensional model with Mimics v.16.0 of the proximal tibia and locking plate. Measurement data were compared between 2 groups (gap lesser than or equal to 10 mm (Group 1) and gap greater than 10 mm(Group 2)). These data were also compared between the uniplanar (Group 3) and bi-planar (Group 4) osteotomy groups. Result. The dimensions of ‘L1’, ‘L2’, and ‘a’ were not statistically different, regardless of the correction degree and operative technique. Also, X1 and X3 were not statistically different, regardless of the correction degree and operative technique. In the axial plane, the angles ‘A_θ1, A_θ2, A_θ3, and A_θ4’ of screw insertion to the lateral hinge point were not statistically different, regardless of the correction degree and surgical technique(Figure 1). Also, the angles ‘C_θ1, C_θ2, C_θ3, and C_θ4’ of screw insertion to the lateral hinge point were not statistically different in the coronal plane, regardless of the correction degree and surgical technique in the coronal plane(Figure 1). Angles of screw insertion, based on quantitative assessment of the tibial bony surface to the lateral hinge point were larger at the A_θ1 and A_θ4 than A_θ2 and A_θ3 in the axial plane. Angle of the C_θ1 was smallest in the coronal plane and it was less than 90°. Angles of C_θ2, C_θ3, and C_θ4 were larger than 90°(Table 1). Discussion & Conclusion. Dimensions of the medial proximal tibia of the sagittal plane, positions of the screw hole in the sagittal plane, and angles of screw insertion of all planes were not statistically different, regardless of the correction degree and operative technique. Additionally, angles of screw insertion were larger at the most anterior and posterior screw in the axial plane and most inferior screw showed smallest angle in the coronal plane. Using a post-contoured plate, the position and angle of the screw insertion were not different in the direction of the lateral hinge, regardless of the correction degree and operative technique. In our study, we evaluated the coronal insertion angle with targeting the lowest portion of the safe zone. Therefore, most screws of the proximal fragment could be inserted in the superior oblique direction if they are targeted to the ‘Safe Zone’. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

The purpose of this study was to compare posterior tibial slope preoperatively and postoperatively in patients undergoing navigational opening-wedge High tibial osteotomy (HTO) and to compare posterior slope changes for 2 and 3-dimentional (D) navigation versions. Between May 2009 and September 2010, 35 patients with unicompartmental osteoarthritis and varus deformity were treated by navigation-assisted open-wedge HTO. Patients were randomly divided into two groups according to the version of the Orthopilot (Aesculap) navigation system used; 2D group (18 patients, 2-D version) and 3D group (17 patients, 3-D version). Radiologic evaluations were conducted using pre- and postoperative leg axes. Posterior slope of proximal tibiae were measured using the proximal tibial anatomic axis method. Postoperatively the mechanical axis was corrected adequately to a mean valgus of 2.81° in 2D group and of 3.15° in 3D group. Mean posterior slopes were well maintained, and measured 7.9° and 10.3° preoperatively and 8.99° and 9.14° postoperatively in 2D and 3D groups, respectively. No significant difference was found between the two navigation versions with respect to posterior tibial slope; mean tibial slope changes were 1.09° and −0.2° in 2D and 3D groups (p = 0.04). Navigation-assisted opening-wedge HTO greatly improves the accuracy of the desired postoperative mechanical femorotibial axis and posterior tibial slope, and the use of 3D navigation results in significantly less change in posterior tibial slope. The authors recommend the use of the 3D navigation because they provide real time intraoperative information about coronal, sagittal, and transverse axis, which are important for the maintenance of a normal posterior tibial slope

Introduction:. High tibial osteotomy (HTO) is a common treatment for medial compartment arthritis of the knee in younger, more active patients. The HTO shifts load away from the degenerative medial compartment and into the lateral compartment. This change can be accomplished with either a lateral closing or a medial opening wedge HTO. An HTO also potentially affects leg length. Mathematical models predict that the osteotomy type (opening versus closing) and the magnitude of the correction determine the change in leg length, but no in vivo studies have been published. The purpose of this study is to quantify and compare leg length change following opening and closing wedge HTO. Study Design:. Retrospective cohort study – Level III evidence. Methods:. Thirty-two medial opening and 32 lateral closing HTO's were selected from patients treated at our institution between 2006 and 2009. Pre-operative and one-year post-operative full-length lower extremity radiographs were obtained along with operative reports. Pre- and post-operative coronal plane alignment and leg length were measured and surgical details were collected. Results:. The 64 osteotomies were performed in 62 patients (43 male, 19 female) at an average age of 57 years. The mean opening wedge was 9.3 mm (range: 5 to 17 mm) and the mean closing wedge was 8.0 mm (range: 6 to 10 mm). Knee alignment changed from a mean of 174 degrees pre-operatively to a mean of 183 degrees post-operatively in both groups. In the medial opening wedge group, total leg length was found to increase from 836.3 ± 63.5 mm pre-operatively to 841.8 ± 64.1 post-operatively, a change of 5.5 ± 4.4 mm (p < 0.0001). A significant correlation was found between the amount of correction and the increase in overall leg length (r. 2. = 0.21, p = 0.009). In the lateral closing wedge group, total leg length was found to decrease from 840.6 ± 51.5 mm pre-operatively to 837.9 ± 52.0 post-operatively, a decrease of 2.7 ± 4.0 mm (p = 0.0008). No correlation was found between the amount of correction and the change in overall leg length. The difference in mean leg length change between opening and closing wedge osteotomies was 8.2 ± 5.9 mm (p < 0.0001). Conclusions:. Medial opening wedge HTO can result in significant leg lengthening depending on the degree of opening. Leg length changes associated with lateral closing wedge HTO are generally smaller. Both techniques results in less leg length change than mathematical models predict. Pre-operative leg length discrepancy should be considered when choosing an osteotomy technique