Limb length disparity is a frequent complication after hip surgery inducing many surgeon-patients conflicts. To date no study has been able to precisely quantify such limb length disparity. EOS® system, currently validated to measure lower limb parameters, allows from two bi-dimensional numerical orthogonal radiographies in standing position to obtain a tri-dimensional reconstruction of lower limbs. A computerized system achieves the parameters calculation.

The aim of this study is to precisely measure the limb length disparities and the other hip parameters following total hip arthroplasty surgical procedure, by using a standard X-rays and using EOS® three-dimensional reconstructions.

Twenty-eight patients programmed for total hip arthroplasty have been included (i.e. thirty lower limbs). Two independent performers have carried out twice the measures either on standard X-rays and using three-dimensional reconstructions of the lower limb disparities prior and after the surgical procedure.

The inter and intra-observer reproducibility for the measure of the lower limb disparities have been of the EOS® measures have been respectively of 0.854 and 0.865 and for the standard X-rays of 0.717 and 0.726.

Mean length disparity observed was before Total Hip Arthroplasty of −0.328 cm (0.705; −1.266/0.530) and was of 0.088 mm (1.326; −1.635/0.632) after. We are able to decrease the lower limbs disparity in 69.1% and for the average of 0,416cm.

Using EOS® system has allowed assessing with greater precision the possibility to restore equal lower limb length.

This assessment has permitted introducing a new planning procedure including EOS® imaging associated to the fusion of the prosthetic tri-dimensional image in order to achieve adequate lower limb length.

Introduction

Osteoporosis is a metabolic disease of the bone responsible for a loss of bone resistance and an increase in fracture risk. World Health Organization (WHO) estimations are about 6.3 millions of femoral neck fractures in the world by 2050. These estimations make osteoporosis a real problem in term of public health.

Knowledge in biological tissues mechanical behaviour and its evolution with age are important for the design of diagnosis and therapeutic tools. From the mechanical aspect, bone resistance is dependent on bone density, bone architecture and bone tissue quality. If the importance of bone density and bone architecture has been well explored, the bone tissue quality still remains unstudied because of the lack of biomechanical tools suitable for testing bone at this microscopic dimension.

Therefore the goal of this study is to estimate the osteoporotic cancellous bone tissue mechanical behaviour at its microscopic scale, using an approach coupling mechanical assays and digital reconstruction.

Introduction

The purpose of this prospective randomized study was to compare the 2-year follow-up penetration of Oxinium versus Metal on polyethylene in a consecutive series of low friction total hip arthroplasty.

Purpose of the study: TKA on genu valgum raises serious problems for the ligament balance. Excessive release of the lateral retracted ligaments exposes the knee to potential instability in the frontal plane. To resolve this problem and avoid implantation of a constrained TKA, we opted for osteotomy of the lateral condyle removing the insertion of the lateral collateral ligament and the popliteal muscle after release of the fascia lata. The purpose of our study was to evaluate the functional and radiographic outcomes of these patients.

Material and methods: This was a retrospective study from 2002 to 2006. All patients with degenerative joint disease of the knee with severe and/or fixed genu valgum were included. These patients were implanted with a navigated posterostabilised Wallaby TKA (Navitrack) associated with osteotomy of the lateral condyle fixed with screws after acquisition of the ligament balance. The diagnosis and surgical history were noted. The preoperative alignement was determined on the full limb x-ray and from navigation data. The following variables were reviewed: polyethylene height, lowering of the lateral condyle, blood loss, operative time. The postoperative alignment was established at least one year after surgery. Intraoperative, postoperative and late complications were noted. The Knee Society function scores were used.

Results: Fifteen patients, mean age 70 years were reviewed at mean 35 months. The mean duration of the operative time was 136 min with mean blood loss of 620 ml. The mean PE height was 13 mm. All operated knees were corrected with mean alignment improving from 17.71 to 1.5 valgus postoperatively. The function score improved from 35 preoperatively to 79 at last follow-up. There were no cases of patellar instability or secondary laxity. Two patients developed late reflex dystrophy. The only case of revision concerned one non-union of the lateral condyle (screw removed at four months) but had a function score of 85 at last follow-up.

Discussion: Performing an osteotomy of the lateral condyle in complement with the navigated posterostabilised TKA for fixed genu valgum enabled good relaxation and satisfactory functional results so that totally constrained implants can be avoided.

Purpose of the study: The purpose of this prospective randomised study was to evaluate the wear of cemented polyethylene cups as a function of the material of the femoral head: oxinium versus metal.

Material and methods: This series included 50 primary arthroplasties implanted from January 2006 to May 2006 in 50 patients (27 women and 23 men), mean age 60.6±11.4 years (21–75). The same femoral piece made of highly polished M30NW stainless steel with a quadrangular section was used for all implants. Similarly, all patients had a polyethylene cup sterilised with ethylene oxide (CMK21, Smith and Nephew). The femoral head was made of stainless steel for 25 hips and oxinium for 25 hips. The major outcome was penetration of femoral head into the cup (associated with true wear and creep) measured at minimum two years follow-up using the Martell method modified according to the recommendations of the author for an all-polyethylene cup. Patient-related and technique-related factors were studied. Non-parametric tests were used for the statistical analysis.

Results: There was no significant difference between the two groups regarding preoperative data. Two patients died, one was lost to follow-up; for three patients, the radiographs were excluded by the software. The analysis thus included 44 hips with a median follow-up of 2.01 years (1.9–2.3), 22 in the Oxinium™ group and 22 in the metal group. The median penetration rate was 0.16 mm/year in the Oxinium^® group versus 0.19 mm/year in the metal group (Mann-Whitney, p=0.46). Annual volumetric penetration in the Oxinium™ group was comparable with that of the metal group (Mann-Whitney, p=0.76). conversely, using the radiograph taken at one year as the reference value (true wear), wear was 0.066 mm/y in the Oxinium™ group versus 0.19mm/y in the metal group (Mann-Whitney, p=0.38).

Discussion and Conclusion: The results of this series indicate that using an oxinium femoral head reduces polyethylene wear. Mid-term results appear to be necessary to confirm these findings.

Purpose of the study: Leg length discrepancy after THA is a common complication and source of recurrent complaints from patients. To date, no reliable and reproducible technique has come forward to enable accurate quantification of all radiological parameters of the lower limb. Nevertheless, preoperative planning for hip arthroplasty requires knowledge of many limb parameters, in particularly leg length discrepancy, femoral offset, or the head-neck angle. The most widely used method is to use the 2D radiographs. The EOS system uses two digitalised 2D images taken orthogonally in a weight-bearing position to enable 3D reconstruction of the lower limb. The inter- and intraoperator reproducibility has been studied and validated. The purpose of our study was to compare the inter- and intra-operator reproducibilities of the measures taken on the standard full-length x-ray and those determined on the 3D EOS reconstructions.

Material and method: Twenty-five patients scheduled for THA were included in this study (50 lower limbs). Two independent operators determine the measures on the AP EOS view and on the 3D reconstructions obtained from two orthogonal EOS images. The following parameters were measured: femur length, tibia length, limb length, HKA, HKS, femoral offset, neck-shaft angle, head diameter, and length of the femoral neck. Each observer performed two series of measurements. Interobserver reproducibility was assessed with the intraclass correlation coefficient (CI: 95%). Student’s t test was used to compare the clinical parameters measured on the 2D and 3D images.

Results: Inter- and intraobserver reproducibility were 0.867 and 0.903 on the 2D x-rays and 0.911 and 0.940 on the 3D reconstructions. The better reproducibility of the EOS reconstruction was confirmed for all parameters tested in this study. Comparison of the 3D and 2D measurements revealed significant differences.

Discussion: Our study demonstrated that measurements made on EOS 3D reconstructions offer better inter- and intraobserver reproducibility than those made on the standard AP view. In addition, the 3D reconstruction takes into consideration of the projection of the anatomic structures in the plane of the AP radiograph. The EOS appears to be a pertinent tool giving reliable results for the pre- and postoperative work-up for arthroplasty of the lower limb.

To date, no technique has proved to be reliable and reproducible in order to precisely calculate radiological lower limb parameters.

EOS^® system allows from two bi-dimensional orthogonal radiographies in standing position to obtain a tridimensional reconstruction. A computerized system achieves the parameters calculation.

The aim of the study was first to evaluate the inter and intraobserver reproducibility of the EOS^® system, secondly to compare EOS^® measures with X-ray orthoroentgenograms.

Twenty-five patients about to receive total hip arthroplasty were included (fifty lower limbs). Two independent performers have carried out twice the measures either on standard X-rays and using three-dimensional reconstructions (femoral parameters (length, offset, collo-diaphy-seal angle, neck length, and head diameter), tibiae length, limb length, HKA, HKS). The reproducibility was estimated by intraclass correlation coefficients.

The inter and intraobserver reproducibility of the EOS^® measures have been respectively of 0.881 and 0.916 and more specifically of 0,997 and 0,997 for femoral length, of 0.996 and 0.997 for tibiae, of 0.999 and 0.999 for limb length, of 0.893 and 0.890 for HKS, of 0.993 and 0.994 for HKA, of 0.892 and 0.914 for femoral offset, of 0.765 and 0.850 for collo-diaphyseal angle.

The inter and intraobserver reproducibility using orthoroentgenograms reached 0.854 and 0.902.

Our results show the EOS^® is a tool allowing reproducible measures. Furthermore 3D EOS^® reconstructions offer better reproducible measures for all parameters that the orthoroentgenograms.

Its use prior to the decision of surgery and during surgery planning for lower limb arthroplasty is for us essential for adjusting surgical procedure accordingly.