Our aim was to investigate whether it is possible to predict post-operative kinematics (Post-Ope) from intra-operative kinematics (Intra-Ope) after total knee arthroplasty. Our study were performed for 11 patients (14 knees) who underwent primary PS TKA using CT-based navigation system between Sept.2012 and Sept.2014. The mean subject age was 71.5 ± 5.5 years at the time of surgery. Intra-Ope was measured using the navigation system after implantation during passive full extension and flexion imposed by the surgeon. Under fluoroscopic surveillance, each patient was asked to perform sequential deep knee flexion under both non-weight bearing (NWB) and weight bearing (WB) conditions from full extension to maximum flexion. To estimate the spatial position and orientation, we used a 2- to 3- dimensional (2D3D) registration technique. Intra-Ope and Post-Ope had a common coordinate axis for bones. Evaluations were range of motion (ROM), external rotation angles (ER). The level of statistical significant difference was set at 0.05. Mean ROM in Intra-Ope(130°± 7.9°) was statistically larger than both NWB(121.1°±10.5°) and WB(124.0°±14.7°). No Statistically significant difference was found in the mean ER from 10° to 120° among Intra-Ope (11.2°± 8.5°) and NWB(7.1°±6.0°) and WB(5.3°±3.2°). It is suggested that we could predict Post-Ope from Intra-Ope by considering the increase of the range of motion due to the muscle relaxation condition and the amount of change in the ER

We hypothesized that using the navigation system, intra-operative knee kinematics after implantation measured may predict that post-operative kinematic in activities of daily living. Our aim was to compare intra-operative knee kinematics by a computed tomography (CT)-based navigation system and post-operative by the 2- to 3-dimensional registration techniques (2D3D). This study were performed for 8 patients (10 knees, medial osteoarthritis) who underwent primary PS TKA using CT-based navigation system. The median follow-up period from operation date to fluoroscopic surveillance date was 13 months (range 5 – 37 months). Navigation and 2D3D had a common coordinate origin for components. Medial and lateral femoral condyle anterior-posterior translation (MFT and LFT) were respectively defined as the distance of the projection of the points (which was set on the top of the posterior femoral pegs) onto the axial plane of the tibial coordinate system. Intraoperative kinematics was measured using the navigation system after final implantation and closure of the retinaculum during passive full flexion and extension imposed by the surgeon. Under fluoroscopic surveillance in the sagittal plane, each patient was asked to perform sequential deep knee flexion under both weight bearing (WB) and non-weight bearing (NWB) conditions from full extension to maximum flexion. Repeated two-way ANOVA (tasks × flexion angles) were used, and then post-hoc test (paired t-tests with Boferroni correction) were performed. The level of statistical significant difference was set at 0.05 on two-way ANOVAs and 0.05 / 3 on post-hoc paired t-tests. Mean range of motion between femoral and tibial components were Intra-operative (Intra): 28.0 ± 9.7, NWB conditions: 120.6 ± 11.1, WB conditions: 125.1 ± 12.9°, respectively. Mean ER (+) / IR (−) from 0° to 120° were Intra-operative (Intra): 9.3 ± 10.2°, NWB conditions: 8.1 ± 8.9, WB conditions: 5.2 ± 7.0, respectively. Mean MFT /LFT from 0° to 90° were Intra; 4.4 ±14.8/ 4.2± 8.5mm, NWB; 6.2 ± 6.9 / 9.2 ± 3.1 mm, WB; 9.2 ± 3.5 / 7.4 ± 2.8 mm, respectively. Mean MFT /LFT from 90° to 120° were Intra; −4.4 ± 2.5 / −5.7 ± 2.9 mm, NWB; −5.5 ± 1.8 / −8.2 ± 0.6 mm, WB; −4.0 ± 1.9 / −5.4 ± 2.3mm, respectively. Mean ADD/ABD from 0° to 120° were Intra;-4.2 ± 3.0, NWB; −0.2 ± 2.1, WB; −0.1 ± 0.8, respectively. Repeated two-way ANOVA showed a significant all interaction on kinematic variables (p<0.05). No statistically significant difference at post-hoc test was found in ER/ IR of all tasks and MFT /LFT of Intra vs NWB and Intra vs WB from 0° to 120° (p>0.05 / 3). The Conditions of these tasks were different from each others. Our study demonstrated that intra-operative kinematics could predict post-operative kinematics

Objectives

We have observed clinical cases where bone is formed in the overlaying muscle covering surgically created bone defects treated with a hydroxyapatite/calcium sulphate biomaterial. Our objective was to investigate the osteoinductive potential of the biomaterial and to determine if growth factors secreted from local bone cells induce osteoblastic differentiation of muscle cells.

A cadaver study using six pairs of lower limbs was conducted to investigate the accuracy of computer navigation and standard instrumentation for the placement of the Birmingham Hip Resurfacing femoral component. The aim was to place all the femoral components with a stem-shaft angle of 135°.

The mean stem-shaft angle obtained in the standard instrumentation group was 127.7° (120° to 132°), compared with 133.3° (131° to 139°) in the computer navigation group (p = 0.03). The scatter obtained with computer-assisted navigation was approximately half that found using the conventional jig.

Computer navigation was more accurate and more consistent in its placement of the femoral component than standard instrumentation. We suggest that image-free computer-assisted navigation may have an application in aligning the femoral component during hip resurfacing.

Our aim was to assess the intra- and inter-observer reliability in the establishment of the anterior pelvic plane used in imageless computer-assisted navigation. From this we determined the subsequent effects on version and inclination of the acetabular component.

A cadaver model was developed with a specifically-designed rod which held the component tracker at a fixed orientation to the pelvis, leaving the anterior pelvic plane as the only variable. Eight surgeons determined the anterior pelvic plane by palpating and registering the bony landmarks as reference points. The exact anterior pelvic plane was then established by using anatomically-placed bone screws as reference points.

The difference between the surgeons was found to be highly significant (p < 0.001). The variation was significantly larger for anteversion (sd 9.6°) than for inclination (sd 6.3°). The present method for registering pelvic landmarks shows significant inaccuracy, which highlights the need for improved methods of registration before this technique is considered to be safe.