Introduction

A decrease of 15% in femoral off-set (FO) was reported to generate a weakness of the abductor muscle after THA, which may increase the risk of limping and dislocation. However, this value was defined under experimental conditions using a CYBEX machine, which does not correspond to daily life activities. To our best knowledge, there is no reported study about the effect of the FO alteration on the gait, following THA.

Purpose of the study: Total knee arthroplasty (TKA) is considered to be an effective treatment for degenerative knee joint disease when the functional impairment and the pain fail to respond to medical treatment. The success of TKA is determined by the degree of pain relief, functional recovery, and implant survival. For many years, those advocating or not preservation of the posterior cruciate ligament (PCL) have animated lively debates. Although a consensus has not been reached, posterior stabilised prostheses and prostheses with a mobile plateau are commonly implanted. The purpose of our study was to compare the outcomes obtained with fixed plateau TKA with preservation of the PCL with those obtained with other prostheses with or without sacrifice of the PCL with a fixed or mobile plateau.

Material and methods: This was a prospective study in a single centre including a homogenous consecutive series of 12 TKA (cemented EUROP) with a fixed plateau and preservation of the PCL implanted from 1994 to 1996 in 117 patients aged 73 years on average. The International Knee Society scores were used for the clinical and radiographic assessment at ten years.

Results: At ten years follow-up, 23 patients had died, 14 were lost to follow-up and 80 (82 knees) were evaluated clinically and 43 (45 knees) radiographically. The IKS knee score varied from 31 points (0–60) preoperatively to 88 points (30–98) postoperatively at last follow-up. The IKS function score was 40 points (0–90) preoperatively and 80 (25–100) at last follow-up. Lucent lines were noted for 59% of the condyles and 60% of the tibial plateaus. The lucencies were mainly located in the anterior and posterior zones of the femur (zones 1 and 4) and medially on the tibia (zones 1 and2). Two prostheses were revised at 8 and 11 years for loosening. The overall survival was 98.8% at ten years using the Kaplan-Meier method.

Discussion: The clinical and radiological outcomes of prostheses with fixed plateaus and preserving the PCL in our series with one revision at 10 years were very satisfactory. Our results are comparable with earlier reports in the literature with or without sacrifice of the PCL with a fixed or mobile plateau.

Conclusion: Longer term follow-up will be needed to confirm these results beyond ten years.

Introduction: Leg length and offset restoration are known to improve function after total hip arthroplasty, and to minimize the risk of dislocation and limp. Anatomic data of the hip are needed to determine specifications for prosthesis design that restore patient hip anatomy more closely. Furthermore, femoral off-set values calculated on X-Rays may be inaccurate in case of external rotational contracture or high femoral ante-version. The goal of this study was to determine three-dimensional morphological data of the hip in case of primary osteoarthritis, especially for femoral off-set.

Material and Method: 223 hips with primary osteoarthritis have been analysed using a CT-scan and a specific software (HIP-PLAN^®) that allows image post-processing for re-orienting the pelvis or the femur to a standardized orientation. Femoral and acetabular anteversions were measured. The planar (2D) and three-dimensional (3D) values of femoral offset were determined. 3D values were measured as the distance between the femoral head centre and the diaphyseal femur axis; 2D values were calculated as the projection of this distance on the frontal plan.

Results: Measurements precision was good with correlation scores ranging between 0.91 and 0.99. Mean acetabular anteversion angle was 26° +/−6.6° when measured in the Anterior Pelvic Plane and 21.9° +/−6.6° in the frontal plane according to the method of Murray. Mean femoral anteversion was 21.9° +/−9.4 according to the method of Murphy. The Sum of acetabular and femoral anteversion was found to be out of the safe zone regarding dislocation risk in 47% of patients. Mean 3D femoral off-set was found to be 42.2 mm+/− 5, significantly increased by 3.5 mm +/− 2.5 when compared to the 2D femoral off-set values. Femoral off-set was above 45mm in 31% of cases and higher than 50 mm in 12% of cases. The tip of the great trochanter was located higher than the femoral head centre, at a mean distance of about 9 mm.

Discussion: When measured on X-rays, femoral off-set may be significantly under-estimated. This error is probably due to the external rotational contracture of the hip induced by osteoarthritis. If the implants are positioned using the anatomical preoperative anteversion angles, 47% of patients would not be in the safe zone regarding posterior dislocation risk.

Conclusions: Planar measurement using X-Rays underestimates significantly the femoral off-set. Neck and head modularity may be useful to achieve simultaneous restoration of femoral off-set and leg length in 12 to 31% of cases.

Introduction: The goal of the study was to determine the precision of a three-dimensional pre-operative planning tool using a specific software (HIP-PLAN^®) and an anatomic cementless neck-modular stem.

Method: 223 patients who underwent a primary total hip replacement had a CT Scan before and after surgery. A pre-operative three-dimensional planning based on the CT-scan was performed. A cementless cup and a neck-modular stem were used. A computational matching of the pre-operative and the post-operative CT-scans was performed in order to compare the values of the planned anteversions and the planned displacement of the hip rotation center to the post-operative values.

Results: The implanted component was the same as the one planned in 89% for the cup and 94% for the stem. For the mean femoral anteversion, there was no significant difference between the planned value (26.1° +/−11.8) and the post-operative value (26.9° +/−14.1). There was a poor correlation between the planned values and the actual ones for the acetabular cup anteversion (coefficient 0.17). The hip rotation center was restored with a precision of 0.73 mm +/3.5 horizontally and 1.2 mm +/−2 laterally. Limb length was restored with a precision of 0.3 mm +/−3.3 and the femoral off-set with a precision of 0.8 mm +/−3.1. There was no significant modification of the femoral off-set (0.07 p=0.7) which was restored or slightly increased in 93% of cases. Almost all the surgical difficulties were predicted

Conclusion: HIP-PLAN^® software is a reliable three-dimensional pre-operative planning tool which allows acurate prediction of components and hip anatomy.

Introduction: In the last years, the use of second generation cementless anatomical stems has generated an increasing interest in primary total hip arthroplasty. They are believed to offer long term stability through appropriate stress transfer and bone remodelling in the proximal femur. We conducted a monocentric prospective study on a homogeneous series of total hip replacements performed with a cementless anatomic, hydroxyapatite-coated stem. The purpose of the study was to evaluate the contribution of this implant in terms of clinical and radiological results at a minimum 5-year follow-up.

Material and Methods: The continuous homogeneous series included 176 THA performed between September 1997 and December 1998 by a single surgeon with the same implant system (SPS femoral stem and Hilock acetabular cup, Symbios Orthopédie SA). Indications were restricted to primary or secondary degenerative hip diseases. Revisions were excluded. Patients were reviewed for clinical performance (Harris hip score), satisfaction, and radiological outcome. The radiological analysis (implant migration, Ara and Engh scores, Brooker classification) was performed by an independent surgeon unaware of the clinical performance outcome. The survival curve was determined with the Kaplan-Meier method at 95% confidence interval, using exclusively implant revision as the criteria for failure.

Results: The follow-up rate in the series was 93.2%. The five-year implant survival was 98.8%. Two revisions were recorded: one for early instability due to excessive joint laxity after surgery, one due to recurrent dislocation following improper cup positioning during surgery. The clinical improvement was obvious, as the Harris hip score improved significantly (p< 0.0001) from 32.9±1.2 preoperatively to 93.1±0.8 at five years follow-up. Pain was the item exhibiting the largest improvement with only 10.2% of patients complaining of mild pain at last follow-up. The radiological analysis revealed a high stability of the femoral implant with Ara and Engh scores reaching 5.0±0.2 and 20.7±0.5 respectively. The migration remained low at 2.4 mm ±0.3 (p=0.02) and had no incidence on the clinical outcome. Heterotopic ossifications at various grades were observed in a large proportion of patients (65.1%). The polyethylene wear rate was 0.075 mm/yr in the series, below most values commonly reported for Ø28mm PE inserts.

Discussion: The survival rate of the SPS stem is comparable with that of other published series at same follow-up. Both the stem and cup implants used provided good clinical and radiological results at five years. The objectives of good integration and stability of the cementless anatomical stem appeared to be met, despite a significant rate of heterotopic ossifications. The excellent clinical and radiological results recorded at five years should be confirmed at longer follow-up.

The use of two-dimensional plain X-rays for preoperative planning in total hip arthroplasty is unreliable. For example, in the presence of rotational hip contracture the lateral femoral off set can be significantly under-estimated. Pre-operative planning is of particular importance when using uncemented prostheses. The aim of this study was to determine the precision of a novel 3D CT-based preoperative planning methodology with the use of a cementless modular-neck femoral stem.

Pre-operative computerised 3D planning was performed using HIP-PLAN® software for 223 patients undergoing THA with a cement-less cup and cement-less modular-neck stem. Components were chosen that best restored leg length and lateral off set. Postoperative anatomy was assessed by CT-scan and compared to the pre-operative plan.

The implanted component was the same as the planned one in 86% of cases for the cup and 94% for the stem. There was no significant difference between the mean planned femoral anteversion (26.1° +/− 11.8) and the mean postoperative anteversion (26.9° +/− 14.1) (p=0.18), with good correlation between the two (coefficient 0.8). There was poor correlation, however, between the planned values and the actual post-operative values of acetabular cup anteversion (coefficient 0.17). The rotational centre of the hip was restored with a precision of 0.73mm +/3.5 horizontally and 1.2mm +/− 2 laterally. Limb length was restored with a precision of 0.3mm +/− 3.3 and femoral off set with a precision of 0.8mm +/− 3.1. There was no significant alteration in femoral off set (0.07mm, p=0.4) which was restored in 98% of cases. Almost all of the operative difficulties encountered were predicted pre-operatively.

The precision of the three-dimensional pre-operative planning methodology investigated in this study is higher than that reported in the literature using two-dimensional X-ray templating. Cup navigation may be a useful adjunct to increase the accuracy of cup positioning.

Pre-operative computerised three-dimensional planning was carried out in 223 patients undergoing total hip replacement with a cementless acetabular component and a cementless modular-neck femoral stem. Components were chosen which best restored leg length and femoral offset. The post-operative restoration of the anatomy was assessed by CT and compared with the pre-operative plan.

The component implanted was the same as that planned in 86% of the hips for the acetabular implant, 94% for the stem, and 93% for the neck-shaft angle. The rotational centre of the hip was restored with a mean accuracy of 0.73 mm (sd 3.5) craniocaudally and 1.2 mm (sd 2) laterally. Limb length was restored with a mean accuracy of 0.3 mm (sd 3.3) and femoral offset with a mean accuracy of 0.8 mm (sd 3.1).

This method appears to offer high accuracy in hip reconstruction as the difficulties likely to be encountered when restoring the anatomy can be anticipated and solved pre-operatively by optimising the selection of implants. Modularity of the femoral neck helped to restore the femoral offset and limb length.