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. 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.Introduction
Methods
Introduction. Computer hexapod assisted orthopaedic surgery (CHAOS) has previously been shown to provide a predictable and safe method for correcting multiplanar femoral deformity. We report the outcomes of tibial deformity correction using CHAOS, as well as a new cohort of femoral CHAOS procedures. Materials and Methods. Retrospective review of medical records and radiographs for patients who underwent CHAOS for lower limb deformity at our tertiary centre between 2012–2020. Results. There were 70 consecutive cases from 56 patients with no loss to follow-up. Mean age was 40 years (17 to 77); 59% male. There were 48 femoral and 22 tibial procedures. Method of fixation was intramedullary nailing in 47 cases and locking plates in 23. Multiplanar correction was required in 43 cases. The largest correction of rotation was 40 degrees, and angulation was 28 degrees. Mean mechanical axis deviation reduction per procedure was 17.2 mm, maximum 89 mm. Deformity correction was mechanically satisfactory in all patients bar one who was under-corrected, requiring revision. Complications from femoral surgery included one under-correction, two cases of non-union, and one pulmonary embolism. Complications from
Malalignment is a common complication following
Introduction:. Patient-specific cutting guides (PSCG) built from imaging of the extremity can improve the accuracy of bone cuts during total knee replacement (TKR). Some reports have suggested that PSCG offer only marginal improvement in the accuracy of alignment and component positioning in TKA. We compared outcomes between TKRs done with PSCG versus standard, intramedullary-based instrumentation. Methods:. Blood loss, duration of surgery, alignment of the mechanical axis of the leg, and implant position on standing, long-leg, and standard lateral digital radiographs were compared between a CT-guided, custom-built TKA implant (n = 50; ConforMIS iTotal, Boston, MA) implanted with PSCG, versus an off-shelf posterior stabilized TKA implanted with standard instrumentation (n = 50; NKII total knee, Zimmer, Warsaw, IN). The fraction of outliers (>3 degrees) was calculated for the two groups. Results:. The mean mechanical axis of iTotal was 181 degrees with a fraction of outliers of 0.2, versus 178 degrees for NKII with fraction of outliers of 0.7. For frontal plane positioning of femoral components, fraction of outliers for iTotal was 0.04, versus 0.6 for NKII. For tibial components, corresponding values were 0.1 and 0.6, respectively. Sagittal plane outliers were 0.2 and 0.9, respectively, for femoral components; and 0.2 and 0.6 for
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