The contralateral femur is frequently used for preoperative templating of total hip arthroplasty assuming femoral symmetry. We aimed to define the degree of asymmetry between left and right proximal femurs and whether if affected by demographics parameters.

A CT-scan based modeling and analytics system of 346 CT-scans was used for this study, including pelvis and bilateral femora from 211 men and 135 women (mean age 61 ±16 years, mean BMI 26± 5 kg/m²⁾. The femoral neck shaft angle (NSA), femoral offset (FO), femoral neck version (FNV), femoral length (FL), canal flare index (CFI) and femoral head diameter (FHD) were calculated for each patient. We then, analyzed symmetry based on absolute differences(AD) and percentage of asymmetry(%AS).

An asymmetry >2% was found for NSA (mean AD=2.9°; mean %AS=2.3; p=0.03), FO (AD=3.8mm; %AS=9.1; p=0.01), FNV (AD=5.1°; %AS=46.7; p=0.001) and CFI (AD=0.2mm; %AS=5.4; p=0.7). Percentage of asymmetry was <2% for FL (AD=3.6mm; %AS=0.8; p=0.7) and FHD (AD=0.3mm; %AS=1.2; p=0.8). No correlation and predictive value was found between either AD or %AS and age, ethnicity, gender, height, weight or BMI.

Our data support assumptions of substantial asymmetry of the proximal femur which is not affected by demographics or proximal femoral size.

Clinical relevance: Upper femurs are not symmetric. Preoperative planning on contralateral femur might be affected this geometrical bias.

Introduction. Total hip arthroplaty (THA) using direct anterior minimal invasive (AMI) surgery is an attractive option to achieve a quicker habilitation. However, high complication rates were reported and very often related to technical difficulties at the time of surgery. We hypothesized that 3D preoperative planning may allow to anticipate these difficulties and to decrease the complications rates when using an AMI approach. Material and methods. A prospective observational study included 191 consecutive patients who underwent a primary cementless THA using an AMI. A 3D CT-scan based pre-operative planning was performed in order to anticipate the potential difficulties that may be encountered especially regarding the hip anatomy reconstruction and the implants stability. The components size and position were planned in order to restore the leg length, the offsets, and the anteversions. Postoperatively, a CT scan was performed in order to compare the final anatomy to the planning. Results. The real implants were the same than the ones planned in 94% for the cup, 96% for the stem and 100% for the neck. The hip anatomy was restored with a high accuracy: 0.1±3mm for the hip rotation centre, −1.6±3 mm for the leg length and 0.1±2.5mm for the femoral offset. All the surgical difficulties were anticipated. No false route and no dislocation occurred. A motorized reaming procedure of the femur was required in 6 patients because a very dense bone associated to a narrow femoral diaphysis. A varus neck was used in 60 % of cases mainly in order to compensate a decrease in the acetabular offset generated by the reaming procedure imposed by the acetabular dysplasia. A retroverted neck was used in 8% of patients because of a torsional abnormality and allowed to increase the stability (Figure 1). A severe femoral dysplasia was treated with a custom stem in 7% of cases in order to avoid a rotational osteotomy of the femur a trochanteromy (Figure 2). Discussion. No complication happened at the time of surgery and no dislocation occurred afterwards. False routes were avoided probably also thanks to the shape of the anatomic stem which presents an anterior sagittal curvature. This shape allowed an easier rasping procedure despite the limited exposure of the femur. Conclusion. 3D planning anticipates the potential surgical difficulties at the time of THA, and allow to increase the safety and the accuracy of the surgical procedure

Introduction

Humeral head subluxation in patients with cuff tear arthropathy (CTA) and in patients with primary arthrosis has been classified by Hamada and by Walch (type B). These classifications are based on 2D evaluation techniques (AP X-ray view, axial CT images). To our knowledge no 3D evaluation of the direction of humeral head subluxation has been described

Background

There is no consensus on which glenoid plane should be used in total shoulder arthroplasty. Nevertheless, anatomical reconstruction of this plane is imperative for the success of a total shoulder arthroplasty.

Introduction: The accurate positioning of the cup implant is a relevant prognostic factor for both short- and long-term results after total hip replacement. Conventional, manual control has proved to be less than optimal. Navigation systems might improve the accuracy. We designed this study to validate the accuracy of a non image based navigation system for cup orientation during total hip replacement, with post-operative 3D CT-scan analysis. Material and methods: 60 cases of navigated total hip replacement have been analysed. Navigation was performed with the OrthoPilot® system (Aesculap, Tuttlingen, FRG), a non image based system. A localizer was implanted on a screw on the anterior iliac crest. Three relevant landmarks (both antero-superior iliac spines and pubis) were palpated with a navigated stylus, defining the anterior pelvic plane (Lewinnek plane). Acetabular preparation and cup implantation were performed under navigation control. Safe zone for acetabular implantation was defined pre-operatively: 40 to 50° of abduction, 10 to 20° of flexion in comparision to the anterior pelvic plane. The final orientation of the cup was registered intra-operatively by the navigation system, and compared to the 3D CT-scan measurement of the cup positioning with the same reference frame. Results: There was no significant difference between the intra-operative and post-operative measurements of the cup abduction. There was a significant difference between the intra-operative and post-operative measurements of the cup flexion, mainly ±5°. 50 implants were positioned within the safe zone (83%). Discussion: The navigation system used allowed an accurate positioning of the cup in abduction. The flexion positioning was less accurate, but the differences observed (mainly less than 5°) are probably clinically irrelevant. Furthermore, the accuracy was higher than that observed with conventional, manual implantation. Conclusion: The navigation system used allows improving the accuracy of cup placement in comparison to conventional, manual techniques

Purpose: Classical instrument sets for implantation of total knee arthroplasty (TKA) can be perfected. Computer-assisted implantation appears to offer improved technical quality. The purpose of this study was to compare a matched series of TKA implanted with the conventional method and with a computer-assisted navigation system. Material and methods: Seventy-eight prostheses implanted with a computer-assisted system based on 3D CT-scan reconstruction of the lower limb were matched with 78 prostheses implanted by a highly-trained operator. The knees were matched for gender, aetiology, surgical approach, and axial deviation. There were no significant differences between the groups for these variables. An intramedullary aiming device was used for knees undergoing the conventional procedure. Navitrack(r) was used for the computer-assisted implantations. The same prosthetic system (Wallaby) was used for both series. An independent operator assessed the double-foot stance gonometries. The femorotibial axis was measured as was the individual position of the tibial and femoral pieces. Results: Axis was within 3° varus and 3° valgus for 92% of the knees operated on with the navigation system. This same range was found for 59% of the conventional procedures. The difference was significant (p< 0.0001). Analysis of the individual femoral and tibial components did not demonstrate any significant difference. Discussion: Results of TKA are dependent in part on operative technique. The objective is generally achieved with the computer-assisted technique but is not with the conventional technique. Navigation could be useful to achieve successfully short-term objectives. Its contribution to mid-term outcome remains to be demonstrated