We assessed the clinical and radiological outcome of a single uncemented total hip replacement (THR) after twenty years, analysing polyethylene wear and osteolysis.

82 hips implanted between 1992 and 1995 were prospectively evaluated. Mean follow-up was 20.6 years (18–23). A hemispherical porous-coated cup matched to a proximally hydroxyapatite-coated anatomic stem. A 28mm PE liner, sterilised by gamma irradiation in air, was used in all hips. Radiological position, eventual loosening and osteolysis were recorded over time. Penetration of the head into the liner was measured by the Roentgen Monographic Analysis (ROMAN) Tool at 6 weeks, 6 months, one year and yearly thereafter.

Six cups were revised due to wear and four cups because of late dislocation. All stems showed osseointegration and all cups appeared radiographically well-fixed. Six unrevised hips showed osteolysis on the acetabular side and two hips on the proximal femur. Creep at one year was 0.30±0.23 mm. Mean total femoral head penetration was 1.23mm at ten years, 1.52mm at 15 years and 1.92mm at 23 years. Overall mean wear was 0.12±0.1 mm/year and 0.09±0.06 mm/year after the creep period. Mean wear was 0.08±0.06 mm/year in hips without osteolysis and 0.14±0.03 mm/year in hips revised or hips with osteolysis (p<0.001).

Although continued durable fixation can be observed with porous-coated cups and proximally hydroxyapatite-coated anatomic stems, true wear continues to increase at a constant level over time. PE wear remains as the main reason for osteolysis and revision surgery in uncemented THR after twenty years.

Background

Although the tribological characteristics are excellent, cup fixation has been one of the limitations in alumina-on-alumina total hip replacement (THR), so different types of materials and surfaces have been developing. We analysed the clinical and radiological outcome of two different uncemented cups for the same alumina-on-alumina THR.

Background and aim

Recent proposals have been introduced to modify stem design and/or femoral fixation in total hip replacement (THR). New designs need to consider previous design features and their results. The aim of this study has been to evaluate the clinical and radiological results of six different designs of tapered uncemented stems implanted in our Institution.

Total hip replacement (THR) in young patients has been associated to higher revision rates than in older population. Different conditions may lead to end-stage arthritis of the hip in these patients. We compared the clinical and radiological outcome of two different groups of young and very young patients who underwent a ceramic-on-ceramic THR.

120 hips were prospectively followed for a mean of 10.4 years (range, 5 to 17). 38 patients (46 hips) were less than 30 years old (group 1), and, 68 (74 hips) were between 31 and 40 years old (group 2). Weight (p<0.001) and physical activity level were greater in group 2 (p<0.001). Preoperative function (p=0.03) and range of mobility (p=0.03) were worse in group 1. Primary osteoarthritis was not found in any case. Rheumatoid juvenile arthritis was the most frequent diagnosis in group 1 and avascular necrosis of the femoral head in group 2. A femoral funnel-shaped type 1 according to Dorr was more frequent in group 2 (p=0.04). The same ceramic-on-ceramic uncemented THR was used in all cases. Screws for cup fixation were only used when strictly needed. We analysed the clinical results according to the Merle-D´Aubignè and Postel scale, the postoperative radiological reconstruction of the hip and the radiological appearance of cup loosening. Kaplan-Meier survivorship analysis was used to estimate the cumulative probability of not having a revision surgery.

Screw use required to obtain a secured interference fit of the acetabular component was found more frequently in group 1 (p=0.01). Postoperative pain (p=0.002) and function (p=0.002) were better in group 1. Mean acetabular abduction angle of the cup was greater in group 1 (p=0.03) and reconstruction to the hip rotation center according to Ranawat (p=0.01) was better in group 2. Placement of the acetabular component inside the Lewinnek´s zone and stem position were similar in both groups. No hips were revised due to complications related to ceramic or to stem loosening. Three cups were revised for aseptic loosening in group 1 and four in group 2. The survival rate for cup aseptic loosening at 15 years was 92.3% (95% CI: 83.7 to 100) for group 1 and 93.1% (95% CI: 85.3 to 99.9) for group 2 (Log rank, p=0.88).

Ceramic-on-ceramic uncemented THR is an excellent option for young and very young patients. Despite worse preoperative conditions in patients under the age of 30 years, a similar clinical outcome was found in this series.

The biological response to implant-derived wear particles is recognized as one of the main factors involved in the development of periprosthetic osteolysis. Wear particles induce a foreign-body inflammatory response that results in the formation of a periprosthetic membrane and progresses over time to aseptic loosening and implant failure. Upon exposure to particles, macrophages and other cell types release inflammatory cytokines to the periprosthetic milieu such as inter-leukin-1 beta (IL-1 beta, tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) which contribute to bone resorption. Heat shock proteins (HSP) are intra-cellular proteins involved in the maintenance of cellular homeostasis. The stress inducible form of the Hsp70 family protein, Hsp72, has been detected in circulation, acting as a factor capable of regulating pro-inflammatory cytokines secretion and it has been demonstrated that induces the production of pro-inflammatory cytokines via the CD14 and Toll-like receptor-mediated signal transduction pathway.

We hypothesized that Hsp72 could be involved in the inflammatory response to wear particles. To this aim, we investigated Hsp72 and its receptor, CD14, in interfacial membrane specimens obtained from patients undergoing revision surgery for aseptic loosening of uncemented acetabular cups (n=7). Distribution of both proteins was assessed by immunofluorescence and examined by confocal laser scanning microscopy. Hsp72 was detected in the periprostehetic membranes, colocalizing with CD14. Explants of membranes were cultured in vitro and levels of Hsp72 and IL-6 were determined by ELISA after 24, 48 and 72 h (n=9). Cultured membranes released IL-6 to culture medium in a time-dependent manner (p< 0.05), while Hsp72 levels decreased during same observation period (p< 0.05). These data suggest that, rather than being produced by the periprosthetic tissue, Hsp72 might be recruited by CD14+ cells from extracellular fluids. In this regard, preliminary data indicated that soluble Hsp72 levels in sera from patients undergoing revision surgery due to aseptic loosening were significantly lower than those from age-matched control subjects (n=6; p< 0.001). To investigate the involvement of Hsp72 in the inflammatory response to wear particles, we used a cell culture model of THP-1 cells driven to the monocyte/macrophage differentiation pathway. These cells were exposed to titanium particles of phagocytosable sizes, either in the presence or absence of exogenously added Hsp72. results obtained to date indicate that Hsp72 is able to modulate the titanium-induced TNF-alpha, IL-1 beta and IL-6 secretion (p< 0.05). Altogether, our data suggest that Hsp72 could be a novel mediator involved in wear particles-induced osteolysis and prosthetic failure.

Introduction and Objectives: We compared the clinical and radiographic results of patients with JRA and primary arthritis using a non-cemented THR with an alumina-alumina THA.

Materials and Methods: We studied 29 THR (Cerafit cup and Multicone stem) implanted in 19 patients with JRA in group 1 and 135 with primary arthritis in group 2. Mean follow-up was 59.0 months. It was seen that 13 hips in group 1 had moderate-severe acetabular protrusion and allograft was used in 12 hips. The center of rotation was determined pre and postoperatively in group 1 according to Ranawat.

Results: In group 1 age (p< 0.001), weight (p< 0.001), and level of activity (p< 0.001) were less. Type A acetabulum (p=0.014) and a cylindrical femur (p< 0.01), according to Dorr, were more frequent in group 1. There was no noise or alumina breakage. There were two intraoperative femur fractures in group 1. There was a revision of 1 cup in group 1 and infection of 1 stem in group 2. In most of the group 1 cases anatomical position was recovered (p< 0.001). The preoperative center of rotation of the hip with acetabular protrusion was 23.2 mm and in the postoperative X-ray 5.6 mm.

Discussion and Conclusions: In spite of the differences, THR with alumina-alumina allows similar results to be obtained in the medium term in patients with JRA. The use of an allograft in those patients with severe acetabular protrusion makes it possible to reconstruct the center of rotation of the hip.

Introduction and Objectives: We compared the clinical and radiological results in patients under and over 40 years of age who had received a non-cemented alumina-alumina hip replacement.

Materials and Methods: We studied 337 Cerafit acetabular cups implanted in 4 hospitals in association with Multicone-Hydroxyapatite stems with alumina-alumina bearing surfaces. Group 1 consisted of 63 patients under 40 years of age and group 2 of 274 patients over 40 years of age. Mean follow-up was 59.0 months. Demographic data and clinical and radiological results of both groups were compared.

Results: There were no cases of primary arthritis in group 1, however severe hip dysplasia and juvenile rheumatoid arthritis were frequent (p< 0.001). Weight (p< 0.001) and degree of activity (p=0.003) were greater in group 2. Preoperative function (p=0.03) and mobility (p< 0.001) were worse in group 1. There were 3 cup revisions in group 1 and 4 (including an alumina breakage) in group 2. Survival with no revision due to any cause was 91.4+5.1% in group 1 and 97.0+ 1.1 in group 2 (p=0.4007). There were no noises. Clinical and radiological results were similar in both groups.

Discussion and Conclusions: Diagnoses were different in both groups, the younger patients were in worse conditions. In spite of these differences, the alumina-alumina prosthesis showed similar results in both groups in the medium term. Long-term follow-ups are necessary to confirm these results.

Introduction and purpose: Highly cross-linked polyethylenes (HXLPE) sterilized in an air-free environment have been used to prevent osteolysis and loosening of implants. This prospective randomized study analyzes the results of a series in which one single type of prosthesis but made with one of two different kinds of polyethylene (PE) has been used.

Materials and methods: We assessed 45 Allofit cups with a Sulene-PE liner (sterilized in nitrogen) and 45 with Durasul-PE liner (highly cross-linked) associated with an Alloclassic stem (femoral head: 28 mm) with a minimum follow-up of 5 years (mean 66.3 months). Femoral head penetration was analyzed by means of a digital program at 6 weeks, and at 6 and 12 months and once a year, using the Dorr method given the non-spherical shape of the cups.

Results: All assessed hips had good outcomes determined clinically and by x-rays. There was no loosening of any component. There were no radiolucent lines or osteolysis. Femoral head penetration at 6 weeks was 47.4% less in the Durasul group (0.19+0.06 mm for the Sulene-PE and 0.09+0.03 for the Durasul-PE [p< 0.0001]). Mean annual penetration was 20% less in the Durasul group (0.04+0.02 and 0.008+0.008 [p< 0.0001] respectively. The differences increased by the third year. Mean penetration at 5 years was 39.1% less in the Durasul group (p< 0.0001).

Conclusions: There was significant femoral reduction in the Durasul-PE group. Long term results are necessary to confirm that these prostheses lead to a lower rate of osteolysis.

Introduction and purpose: Different bearing surfaces have been used to prevent osteolysis, such as alumina-alumina. We present here an analysis of the results of a prospective multi-center study of complications related to the use of alumina-alumina bearings.

Materials and methods: In 4 hospitals 319 cups with hydroxyapatite stems and alumina-alumina bearing surfaces were implanted with a mean follow-up of 5.6 years (range: 3–8). The mean age of the patients was 52.7 (range: 14–70). Alumina wear was calculated by means of a special program.

Results: Revision was performed of 5 cups and 2 stems. In one hip with a horizontal acetabular angle (35°) and a thin alumina liner (size 50/32), an acetabular liner fracture occurred 36 months after surgery. The probability of not undergoing revision due to any cause was 96.9% (CI 95%:94.7–99.1%). None of the patients reported any type of noise. All the non-revised cases showed good results both on clinical and X-ray exam at the end of the follow-up. The difference between the center of the head of the femur and the center of the head of the cup at 6 weeks after surgery was −2.45+0.53 mm, with no further changes seen during the follow-up.

Conclusions: These data suggest that the prosthetic alumina-alumina bearing surface has excellent results over 5 years and that alumina fractures are infrequent. No changes were seen in terms of the penetration of the femoral head in any case. Longer follow-ups are necessary to determine if the reduction of wear translates into less osteolysis and loosening.

Introduction and purpose: This is a prospective analysis of the clinical and radiographical results of two different types of PE, both associated to the same kind of prosthesis (Zimmer-Centerpulse).

Materials and methods: A total of 101 Allofit shells were analyzed; 56 had Sulene-PE (nitrogen sterilized) and 45 had Durasul highly cross-linked PE, associated to an Alloclassic stem (femoral head: 28 mm). They were all implanted between 1999 and 2002. Mean follow-up was 29.4 months for Sulene-PE and 25.3 for Durasul-PE. PE wear was assessed by means of image digitalization with special software (AutoCAD 14R) after six weeks (initial settling or position zero), after 6 and 12 months and on a yearly basis.

Results: Three cases dislocated and were thus excluded from the study. There were no infections. All cases assessed had good clinical and radiological results. There were no instances of implant loosening. There were no radiolucent lines, osteolysis, cortical hyperthrophy or proximal osteopenia. On the initial radiograph (position zero), the distance between the axes of the femoral head and those of the shell was 0.30+0.094 mm for the Sulene-PE group and 0.20+0.074 for the Durasul-PE one (p=0.029). Mean wear, taking position zero as a reference point, was 0.1035+0.0686 and 0.0819+0.078 (p=0.108) respectively.

Conclusions: In spite of the higher error rates found in the wear measurements of the Allofit cup, a greater position zero was found in Sulene-PE than in Durasul-PE. Although mean wear was higher in Sulene-PE than in Duarsul-PE, the differences found were not significant 3 years postop.

Aims: internal fixation is not generally accepted as election treatment for displaced femoral neck fractures in patients older than 70. Results and risk factors are analysed in this later group of patients. Patients and Methods: 155 patients older than 70 with displaced femoral neck fractures were treated with closed reduction and parallel cannulated screws and prospectively followed for 2 years. Patients were allowed postoperative full weight bearing with aids. Quality of reduction and osteosynthesis were radiologically analysed. Results: 24 patients (15%) were lost. At the end of follow-up 52% of patients were asymptomatic, 13% had mild pain, 28% suffered a 2nd surgery (arthroplasty) and 7% were badly ill for aditional surgery. 57% presented uncomplicated consolidation, 28% non-union and 8% ischemic necrosis. Poor-quality reduction (p= 0.039) and poor-quality osteosynthesis (p=0.051) were significant risk factors for failure. A higher age (p=0.36), displacement (Eliason criteria) (p=0.26) and delay in surgery (p=0.53) were not significant risk factors. Conclusions: closed reduction and percutaneous fixation of displaced femoral neck fractures achieves good/fair results in only 65% of patients older than 70 years. Poor-quality reduction and osteosynthesis are risk factors for clinical and/or radiological failure.

Introduction and Objectives: This is a prospective analysis of clinical and radiographic outcomes of total hip prosthesis with alumina-on-alumina friction coupling implants performed at two hospitals.

Materials and Methods: This study analyzes 60 prostheses with alumina-on-alumina friction coupling (Ceraver-Osteal) (May 1999-May 2002). The Cerafit cup was used in association with 32 Multicone-HAC stems and 28 Anatomic-HAC. Of these cases, 36 were male, and 24 were female, with average age being 47.05+/−12.60 years. Mean follow-up time was 2.3 years. There were no lost or revised cases. Radiographic analysis was done according to Johnston et al., and wear was assessed using the Sychterz method in a special computer program (Auto-CAD R14).

Results: All cases had good clinical and radiographic outcomes. There were no revisions or loosening of the implants. There was one dislocation and one intraoperative fracture, which were both treated by conservative means. There were no infections. The distance between the centres of the femoral head and the cup on the initial radiograph (position zero) was 2.49+/−0.70mm. This measurement stayed constant with time, and no changes were observed associated with so-called early wear or initial seating. Mean wear with respect to a reference of position zero was 0.0184+/−0.0187. This figure is below the error level of the measuring system and thus is not measurable.

Discussion and Conclusions: The alumina-on-alumina prosthesis (Ceraver) yields positive clinical and radiographic results at 4 years. Even though the alumina partially distorts the radiographic image, no evidence of early wear due to seating of the components was observed at four years of follow up using the Sychterz digitalized method.