Introduction: The aim of this study is to assess the safety and efficacy of initial results seen with minimally invasive techniques in navigator-assisted TKR.

Materials and methods: A consecutive series of 50 TKRs with the same model are included in the study. These were carried out by the same surgical team, using a standardized navigator-assisted technique and a minimally invasive “midvastus” approach. Follow-up was from 3 to 24 months. The efficacy of the procedure is studied by assessing preoperative and early postoperative pain and mobility, final alignment obtained and safety, based on any subsequent complications.

Results: Decrease of pain was seen in 49 patients, with a range of movement from 0° to 110° in 47 patients. There were no significant complications such as infection or thromboembolism. There were no alignment (varus/valgus) alterations on the frontal plane greater than 3°, nor relevant alterations on the sagittal plane. Complications with surgical wound healing were seen in 3 cases; these did not require special procedures; 9 cases had slight and transient pain in the proximal area of the surgical wound.

Conclusions: Initial results allow us to consider that the technique studied is effective and safe. However, we have detected problems with pain of doubtful etiology in the proximal part of the surgical wound while healing. We believe that the use of a navigator ensures greater safety in the use of minimally invasive techniques and provides a spatial view of the knee joint.

(*) This study is part of a study financed by the Fund for Health Research of the Biomedical and Health Sciences Promotion Program (Spanish Ministry of Health and Consumption) (File PI05-1065)(Fondo de Investigaciòn Sanitaria del Programa de Promociòn de la Investigaciòn Biomédica y en Ciencias de la Salud (Ministerio de Sanidad y Consumo) (Expediente PI05– 1065)

Introduction: Our aim is to study the morphological changes (and related factors) that occur in the proximal femur in patients with THR with a minimum 10 year follow-up.

Materials and methods: We have included 50 THRs carried out between October 1992 and June 1995 with porous stems with metaphyseal support proximally coated with hydroxyapatite. Changes in the morphology and density of the proximal femur and its relationship with several factors, especially polyethylene wear, were carried out by means of a series of x-rays taken during the whole period of evolution and a spiral CT taken during the last review.

Results: There was no subsidence, stem migrations or femoral revision surgery. After one year, all patients show an sclerotic region in the area of metaphyseal support that remains stable throughout the study period. During this period, only two other types of changes were seen in the proximal area.

lytic areas surrounded by a halo of sclerosis in the greater trochanter (in 18 cases they were very small and in 14 cases of a greater size). These areas were statistically significantly related to a greater rate of wear;

Conclusions: The metaphyseal area of the stem continued to comply with its support function during the period studied. In more than half of the cases there was some sort of bone loss in the proximal area. There is a relationship between polyethylene wear and the appearance of areas of lysis in the trochanter.

Purpose: We assess the advantages of helical computerised tomography as compared to conventional radiological methods in the diagnosis of this problem in the acetabulum.

Materials and methods: We studied 51 patients with 63 porous hemispheric acetabular implants coated with hydroxyapatite who were part of a planned radiological follow-up. After 10 years they were examined with helical computerised tomography according to a protocol designed to minimise metal artefacts. We compared the diagnosis of acetabular osteolysis by the two imaging techniques, taking the presence of delimited areas of absent trabeculation as a criterion.

Results: With computerised tomography we detected 23 osteolytic lesions in 19 hips, of which 5 had been diagnosed by conventional radiology. Only 3 patients presented symptoms in the form of mild-moderate pain. The mean volume of the lesions was 1.61 cc (SD: 1.41) with a minimum of 0.3 and maximum of 5.5 cc.

Conclusions: Computerised tomography can be a useful tool in the diagnosis and follow-up of acetabular osteolysis in total hip replacement. More studies are needed to complete its diagnostic possibilities and specify its indications.

Introduction and purpose: The failure of a TKP is often due to deficiencies related to alignment, stability or fixation. The purpose of this paper is to determine how loads are distributed when each of two tibial stem models are implanted and to assess those loads densitometrically.

Materials and methods: We analyzed 20 patients with a cemented TKR and divided them into two groups according to whether their tibial stem was cylindrical or cruciform. We studied the evolution of periprosthetic bone density under the internal and external bearings and under the stem. We performed a densitometry after 2 years postop and controls after 3 and 7 years.

Results: In the cylindrical stem group the evolution of mean bone density under the internal bearing after 2 and 3 years was 0.92±0.20 to 0.90±0.19 g/cm2 respectively; mean bone density under the external bearing was 0.97±0.36 to 0.97±0.38 and under the stem it was 1.05±0.25 to 1.08±0.26. In the cruciform group, density under the internal bearing was 0.75±0.08 to 0.71±0.05, under the external one it was 0.89±0.01 to 0.85±0.07 and under the stem it was 1.06±0.06 to 1.04±0.29. In the long term (three patients were lost to follow-up), comparing the cylindrical prostheses to one another, we can say that the evolution under the internal bearing after 2, 3 and 7 years was 0.88, 0.84 and 0.80 g/cm2 respectively; under the external bearing it was 0.79, 0.78 and 0.77 and under the stem it was 0.99, 0.96 and 0.99.

Conclusions: After TKR a progressive loss of bone density is observed. Comparatively, the reduction is greater in the cruciform stem. The internal compartment is the most affected one.

Introduction and Objectives: Posterior or posterolateral approaches to the hip joint have classically been associated with higher rates of dislocation. The goal of this study is to investigate the effect of reconstructive procedures of the posterior joint capsule and external rotator muscles in the short term on incidence of luxation and to compare these procedures with anterior or anterolateral approaches in which such procedures were not performed.

Materials and Methods: This is a prospective study of 605 total primary hip arthroplasties based on 2 models that have been widely used in our centre. The cases included 431 biological fixation prostheses coated with hydroxyapatite with 28mm heads and 174 low-friction cemented prostheses with 22.25 mm heads. These surgeries were performed consecutively in our centre, with a minimum follow-up of 6 months. Each patient was assigned to one of two groups based on the individual preference of the surgeon performing the operation: anterior or posterior. Only in the latter group was reconstruction of the capsule and external rotator musculature performed. Cases in which previous surgery had been performed on the hip were not included in this study in order to avoid skewing results, as previous surgery is the factor known to have the greatest impact on dislocation rate.

Results: A procedure involving reconstruction of both the posterior capsule and external rotator musculature significantly reduced the rate of early dislocation in primary total hip arthroplasties done using a posterior approach. Incidence of dislocation in these cases was lower than in cases with anterior approaches where a wider capsulectomy was performed without reconstruction.

Conclusion: The idea that the dislocation rate in total hip arthroplasties is higher with a posterior approach should be reconsidered.

Introduction and Objectives: The purpose of this study is to analyse the clinical and radiographic results of revision total hip prosthesis using femoral stems with diaph-yseal fixation.

Materials and Methods: We assessed failure of the primary prosthesis based on Paprosky’s classification to identify the femoral defect and determine the optimal component for revision, keeping in mind the difficulty of classifying bone defects based on radiographic parameters. The most commonly-used replacement models were KAR revision stems (wide, straight, long necks and hydroxyapatite-coated along the entire length) and Restoration-T3 stems (diaphyseal fixation, modular, fits different necks, Wagner model progression, particularly indicated to facilitate extraction of cement using a buried diaphyseal osteotomy). Clinical evaluation was done using the Merle D’Aubigné and Postel scales modified by Charnley. Radiographic evaluation of prosthetic stability and osseointegration was done using Engh’s criteria, checking for presence or absence of radiolucency, migration, pedestal, and increase or decrease of endosteal and periprosthetic density (calcar, diaphysis, and greater trochanter).

Results: We examined 47 KAR stems and 16 Restoration-T3 stems, with an average follow-up period of 4.1 years (range: 1–9 years) and an average patient age of 69.4 years (range: 40–79 years). Of these, 6 were Paprosky type 1, 36 were type II, 14 were type IIIA, 5 were type IIIB, and 2 were type IV. Average preoperative clinical score was 9.76 points. Aetiology in all cases was aseptic loosening of a primary prosthesis, with the exception of one case of a delayed Corynebacterium infection. There were 2 partial Monk prosthesis revisions and 3 periprosthetic fractures. Average postoperative clinical score was 15.83 points. There were no deep infections or dislocations. Radiolucency was noted in only one case, and no migrations of more than 2 mm were seen. No further stem revisions were required in this series, though we believe a future revision will be necessary in at least one case.

Discussion and Conclusions: The use of femoral stems with diaphyseal fixation is an acceptable alternative in revision surgery of the hip, even in cases of major bone deficit. Modular stems have the added advantage of versatility to adapt to a great variety of prosthetic salvage procedures.