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PubMed1990

Stiffness and strength tailoring of a hip prosthesis made of advanced composite materials.

This work is concerned with the design of hip prostheses using advanced fiber reinforced composite materials. The major focus of the study is to evaluate how the stiffness and strength of composite hip prostheses can be affected by variations in ply orientation and stacking sequence for a selected manufacturing method. This investigation involved both analytical and experimental work. An analytical model was developed which consists of a stress analysis and a failure analysis. A finite element program was developed during the course of the investigation for analyzing stresses, strains, and deformations of composite stems with a simplified configuration. Failure and mode of failure were predicted by appropriately selected failure criteria. Experiments were also performed on T300/976 graphite/epoxy composites to verify the analysis and the computer calculations. Both testing and analysis accounted for the various combinations of in-plane and out-of-plane (torsion) loading that can act on the prosthetic hip. Simplified composite stems with a 120 layer thickness were fabricated and tested. An excellent agreement was found between the measured strain data and the numerical calculations. Using the program, parametric studies were performed. It was found that an optimal design of hip stems can be achieved by using advanced fiber-reinforced composite materials, but great care must be taken when selecting the appropriate ply orientation and stacking sequence for a chosen fabrication method.

Biocompatible Materials↗
PubMedDate not supplied

Implantation of an uncemented total hip prosthesis. Technique and initial results of 100 arthroplasties.

A porous-coated modular total hip system was developed for uncemented implantation in dogs. The operative technique was developed in cadaver bones and live animals. One hundred uncemented total hip arthroplasties were performed in 92 dogs. Results were successful in 98% of the joints during follow-ups of 3 months or more. Complications included three luxations of the prosthetic joint, two fissure fractures of the femoral cortex, and one complete displacement of the acetabular component from its bony bed. Four complications were resolved successfully.

Acetabulum↗
PubMed2006

The Kent hip prosthesis: an evaluation of 145 prostheses after a mean of 5.1 years.

The Kent hip is a distally-locked femoral stem which was developed to address severe proximal bone loss, severe bony deformity and peri-prosthetic fracture. We reviewed the results of 145 consecutive Kent hips implanted into 141 patients between 1987 and 2000. The indications for implantation were aseptic loosening (75 hips), septic loosening (two), peri-prosthetic and prosthetic fracture (37), severe bony deformity (24), and fracture through a proximal femoral metastasis (seven). The median time to full weight-bearing after surgery was two days and the mean length of follow-up was 5.1 years (2 to 15). Further revisions were required for 13 femoral stems. With removal of the stem for any reason as an end-point, the cumulative survival at five, ten and 15 years was 93%, 89% and 77%, respectively. In patients aged>or=70 years, the cumulative survival at 15 years was 92%, compared with 68% in those aged<70 years. Because of these findings, we recommend the use of interlocking stems in patients aged>or=70 years, particularly in those with a peri-prosthetic fracture, for whom alternative methods are limited. Outcome scores and survival data, compared with other systems, indicate that the Kent hip should be used with caution in younger patients.

Adolescent↗
PubMed1990

[Prevention of deep vein thrombosis by enoxaparin after total hip prosthesis].

Once daily dosing of Enoxaparin to prevent deep vein thrombosis (DVT) after total hip replacement has been defined through two double-blind prospective, randomized multicentric trials. A previous prospective study including 228 consecutive patients had determined optimal dose to be 40 mg daily (4000 anti Xa U) begun 12 hours pre-operatively. The first trial (118 patients) compared two modes of administration of the dose of 40 mg--either 40 mg once daily or 20 mg twice daily, every twelve hours. Results were a figure of 6% for total DVT detected by ascending bilateral phlebography, 5% of wound hematoma and did not shown a statistically significant difference between the two modes of administration as regard tolerance. The second trial (237 patients) compared unfractionated calcic Heparin (5000 U.I. every eight hourly begun two hours before surgery) with Enoxaparin, 40 mg/day begun twelve hours before surgery. In the unfractionated Heparin group, we observed 27 total DVT (25%) 20 proximal DVT (12.5%) and one case of non fatal pulmonary embolism. In the Enoxaparin group, we observed 15 total DVT (12.5%), 9 proximal DVT (7.5%) no case pulmonary embolism. Red-cell transfusion requirements and hemoglobin levels on the third post-operative day shown a significant better tolerance in the Enoxaparin group. Theses results are coherent with those observed in the placebo controlled trial of Turpie, Levine, et al (1986). They used a dose of 30 mg twice daily (6000 anti Xa IU) begun 12/24 hours post-operatively, and observed a figure of 12% for total DVT and 4% for proximal DVT. Tolerance was the same than in the placebo group.

Female↗
PubMed1989

[Therapeutic concepts in infected hip prosthesis].

In the period from January 1980 to December 1987, 62 patients with infected hip joint arthroplasties were treated. The duration of observation was on average 37 months (minimum 12 months, maximum 91 months). The choice of treatment modality depended on the type of infection, the state of anchorage of the endoprosthesis, the general condition of the patient, the type of bacterium and the state of the tissue surrounding the implant. 42 arthroplasties (67%) healed primarily. The remaining 20 were subject to 46 further operations (2.3 relapse operations/patient). 14 subsequently healed (23%) and six cases remained definitively infected.

Debridement↗
PubMed1995

[Abrasion reducing polyethylene ceramic-metal compound hip prosthesis head].

There are two specific problems in using metallic or ceramic heads for hip prostheses: (1) the amount of polyethylene abrasions in the cup caused by the heads (especially a metal head). (2) the polyethylene abrasions caused by Al2O3 ceramic heads is far less than metal heads, but its ability to adapt geometrically is limited due to its being less strong. The abrasions appear because of geometric differences in the prosthetic joint, local problems in the surface architecture and physical/chemical interactions between the different materials. In this study we compare the new "Titan-Niob Ceramic Multilayer Sandwich Head" (built three layers of microsegregation phases and three in-between layers of ultrathin metal, 8-10 microns thick, and a surface with integrated grease holes) with the common CoCrMo heads and Al2O3 ceramic heads. Testing 2,000,000 cycles in a bodylike liquid under permanent loads of 90 kPa, periodically increasing up to 250 kPa, simulating normal stress situations (i.e., walking), the "Titan-Niob Ceramic Multilayer Sandwich Head" showed major advantages over the metal heads and also over the ceramic heads even though the ceramic head has been accepted so far to have the best friction coefficient. Furthermore, there has been no problem in surface fracture with the "Titan-Niob Ceramic Multilayer Sandwich Head".

Biomechanical Phenomena↗
PubMed2003

Primary total hip arthroplasty with a second-generation cementless total hip prosthesis in patients younger than fifty years of age.

BACKGROUND: The early experience with cementless total hip replacement led to design modifications to increase the initial press-fit and stability of the femoral component, to reduce the diameter of the femoral head, and to improve the acetabular component, including the locking mechanism of the shell and the quality of the polyethylene liner. We performed a prospective study to assess the results in young patients who had been followed for a minimum of eight years after treatment with a primary total hip arthroplasty with a second-generation cementless prosthesis. METHODS: Eighty patients (118 hips) were included in the study. There were fifty-eight men and twenty-two women; the mean age at the time of the operation was 46.8 years (range, twenty-one to forty-nine years). We used a cementless Duraloc series-100 or 1200 acetabular component with or without screw fixation, a polyethylene liner with a 22-mm inner diameter, and a cementless Profile femoral component in all hips. The average duration of follow-up was 9.8 years (range, eight to eleven years). Clinical follow-up (with use of the Harris hip score) and radiographic follow-up were performed at six weeks; at three, six, and twelve months; and yearly thereafter. Linear and volumetric wear were measured, and bone-remodeling and osteolysis were assessed. RESULTS: The average Harris hip score improved from 48.8 points preoperatively to 92 points at the final follow-up examination. The prevalence of transitory thigh pain was 10% (twelve of 118 hips). There was no aseptic loosening. One hip was revised because of recurrent dislocation. The average amount of linear wear was 1.18 mm, and the average wear rate was 0.12 mm/yr. Fourteen hips (12%) had osteolysis in the calcar femorale and eleven hips (9%) had acetabular osteolysis, but all of the osteolytic lesions were <1 cm (2). CONCLUSIONS: The mechanical fixation of the anatomic fit cementless Profile stem was excellent in this study of young patients who were particularly difficult to treat because of a high prevalence of osteonecrosis and developmental dysplasia. Although there was no aseptic loosening of the components and a relatively low prevalence of osteolysis, there was a high rate of linear wear of the polyethylene liner. LEVEL OF EVIDENCE: Therapeutic study, Level IV (case series [no, or historical, control group]). See p. 2 for complete description of levels of evidence.

Adult↗
PubMed1986

Asymptomatic total hip prosthesis: natural history determined using Tc-99m MDP bone scans.

A prospective study was performed with 97 patients who had undergone total hip replacement surgery and who were not experiencing pain or other symptoms or problems. The study was intended to determine the normal postoperative appearance of radionuclide scans of the hip following administration of technetium-99m methylene diphosphonate. Five areas of the prostheses were evaluated. Results showed that 6 months after implantation activity around the lesser trochanter and prosthesis shaft became insignificant. Activity around the acetabulum, greater trochanter, and prosthesis tip stabilized approximately 2 years after surgery; approximately 10% of patients in the study had persistent activity in these areas. Familiarity with this normal progression is fundamental to interpretation of postoperative bone scans in patients with total hip prosthesis.

Acetabulum↗
PubMed1989

Poor fixation of the Mittelmeier hip prosthesis. A clinical, radiographic, and scintimetric evaluation.

We have evaluated 30 Mittelmeier hips on an average 3.3 years after the operation. Seven hips had been revised because of severe pain and mechanical loosening and one because of fracture of the threaded ceramic cup. Only five of the remaining 22 hips were asymptomatic. There was radiographic migration of the acetabular and femoral components in more than one third of the hips and increased scintimetric values around the femoral component in all but two hips. Unfavorable design of the Mittelmeier prosthesis may be an important etiologic factor contributing to poor component fixation and inferior clinical results.

Adult↗
PubMed1989

[Total hip prosthesis with or without preventive use of antibiotics].

514 patients with total hip replacement were operated in 3 years in our county hospital. The patients were divided in two groups: 1. high risk patients: these patients had an antibiotica prophylaxis with 3 doses of 2 g of cefamandole beginning at the time of the induction of the anaesthesia; 2. patients without risks: they had no antibiotica. The two groups of patients were controlled at 3 and 12 months after the operation. 159 patients had a risk for an infection and had antibiotica, 355 patients had no antibiotica. The infection rate after 1 year was 0.6% in the group of patients with antibiotica, and 1.4% in the group of patients without antibiotica. This gave no statistical significance. The only statistical difference between the 2 groups was a significantly higher rate of urinary infection in the group with antibiotica. Thus it has been shown that urinary infections after total hip replacement correctly treated with antibiotica are not a high risk for an infection in the prosthesis. We conclude that antibiotica prophylaxis for total hip replacement in patients with high risk factors (like diabetes, corticotherapy, intraarticular injection, obesity and operation on the same hip) may help to have a postoperatively low infection rate, in our case 0.6%.

Anti-Bacterial Agents↗
PubMed1989

[Our experience with the uncemented isoelastic total hip prosthesis].

Between May 1981 and May 1987, 250 isoelastic hip prostheses were implanted. The first 180 (from May '81 till May '86) were called for a visit. 130 (72%) came and were assessed with a minimum review time of 1 year. We ignore the reasons for which 28% of the patients did not turn up (death or others). 81% of the patients had good or very good results after surgery. Three patients developed infections (2.3%); none of these was revised. Four developed loosening of the femoral component; two of these underwent revision surgery and are doing well now. We did not notice any loosening of the acetabular component. The recommended period of gait support was of 2 months of no weight bearing with two canes and of two months of partial weight bearing with one cane. No component had broken. We had 1 femoral fracture incurred during surgery which healed with routine management. These early results are very encouraging, but the effectiveness of this prosthesis will require longer follow-up data to be confirmed.

Adult↗
PubMed1977

Design of total hip prosthesis: the femoral stem.

This report is a summary of the research carried out in an effort to improve the reliability of total hip replacement procedures. The current state of knowledge of hip mechanics was examined and found adequate in its description of the normal hip, but totally lacking in any but qualitative terms in its description of the diseased hip, or the load transfer between prosthesis and bone in reconstructed hips. The mechanics of the hip joint and femur indicate that the positioning of the femoral head is crucial in achieving a correct balance between muscle force and joint load. Consequently, it is recommended that a great deal more attention be devoted to the positioning of the prosthesis at hip surgery. Experimental and theoretical studies were directed to one aspect of total hip replacement - the design of the femoral stem. Results indicate that all current designs should be adequate if set in acrylic, and provided subsequent bone resorption is small. Further results indicated satisfactory load transfer from a long thick prosthesis stem, fitted without acrylic cement.

Acetabulum↗
PubMed1984

Tissue reaction to a failed Bion hip prosthesis in a dog.

The tissue reaction in a dog to a failed constrained total hip replacement system with a Bion elastomer component was evaluated. The device consisted of Ti-6A1-4V alloy acetabular and femoral components connected with a Bion component. At necropsy the Bion component was found to have fractured. The tissue surrounding the Bion was granulomatous with numerous blackened regions. Histologically a severe chronic inflammatory response was present in the surrounding tissue with numerous giant cells and Bion laden macrophages.

Alkadienes↗
PubMed2002

Revision of failed total hip prosthesis with insertion of hydroxyapatite-coated femoral component.

As the population ages, primary total hip arthroplasty (THA) is becoming one of the most common orthopedic procedures. Therefore, revisions for mechanical loosening after THA should also increase in future years. Loosening is a progressive phenomenon that, along with intracortical granuloma, causes bone destruction. The main concern in total hip revision surgery is the reduced bone stock, which makes it difficult to obtain optimal stability of the femoral stem (Case 1: Figs. 1 a, b).

Adult↗
PubMed1987

Cementless R.M. isoelastic total hip prosthesis in revision surgery for loose prostheses.

Forty-three patients with aseptic mobilization of hip prostheses were submitted to revision surgery using cementless R.M. isoelastic total hip prostheses. The femoral component was substituted in all cases, the acetabular component in 37. Autoplastic bone grafts were required in 27 cases to replace severe bone defects in the acetabulum or femoral diaphysis. All the patients were followed up for an average of 46 months (range 36 to 59 months). The results were good in 38 cases, evaluated both on the Harris scale (average 87 points) and the Charnley method (5.4 points for pain, 5.0 for walking, and 5.2 for movement). There were 2 cases of ankylosis, one case of infection, one paralysis of the peroneal nerve and one proximal migration of the acetabular component. Therefore we believe that the use of cement is contraindicated in revision surgery of the hip, particularly in the presence of severe osteolysis and in younger patients. The isoelastic stem encourages bone reconstruction and cortical thickening in the femoral diaphysis. When there is bone deficiency the cementless acetabulum must always be associated with autoplastic bone grafting.

Biocompatible Materials↗