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Fracture of the femoral stem of the Ring TCH hip prosthesis.

We report the clinical and operative details of seven cases of fracture of the femoral stem of the Ring TiMESH cementless hip prosthesis (two were cemented and five uncemented). Six fractures occurred in the proximal one-third of the stem and one at mid-stem. The failures are attributed mainly to two defects in stem design, the narrowness of the anteroposterior dimensions and the depth of the recess for the titanium mesh pads. Great difficulty was experienced in removing the osseo-integrated distal fragments of the broken stems.

Biomechanical Phenomena↗

Design-related fretting wear in modular neck hip prosthesis.

An accelerated cyclic loading corrosion test was used to determine the corrosion behavior of a commercial (GSP) and a prototype titanium hip prosthesis each with a modular neck. Four GSP and four prototype stems were subjected to a 2-Hz cyclic load ranging between 200 and 2,100 N for 1,000,000 cycles. Three stems were tested in an environment of FeCl3 solution, three stems were tested in Ringer's solution, and two stems were tested in air. After cyclic loading, the specimens were carefully examined with optical and scanning electron microscopy (SEM). None of them showed macroscopic or microscopic signs of corrosion, regardless of the environment to which the specimens were subjected. However, macroscopic evidence of mechanical fretting was present at the neck-stem modular junction, primarily concentrated at the medial contact point between stem and neck, especially for the prototype stems. SEM analysis confirmed these observations. The appreciable differences observed between the two designs suggest that the problem can be minimized or eliminated with an accurately designed taper fitting.

Chlorides↗

Infection of a hip prosthesis by Actinomyces naeslundii.

We present the case of a 77-year-old woman who developed an Actinomyces naeslundii infection of a hip prosthesis. The isolate grew well aerobically with 5% CO(2). Possible diagnostic problems may arise in the microbiological laboratory because aerobic growth is not sufficiently accounted for in some of the traditional identification schemes and commercial test kits. Therefore, besides presenting an unusual pathogen in this setting, this report focuses on possible diagnostic problems in the microbiological laboratory.

Actinomyces↗

[Results of cement-free St. Nabor hip prosthesis implantation and clinical and radiological results after 8 to 10 years].

PURPOSE OF THE STUDY: The aim of the retrospective study was to analyse the medium-term results of the cementless hip prosthesis St. Nabor. METHOD: 46 patients with complete postoperative and radiographic documentation were available for clinical review. The average follow-up was eight years and five months (range from eight years, one month to ten years). The average age at the last follow-up was 60 years. Ten patients showed severe coxarthritis and 32 patients a dysplasia of the acetabulum before surgery. Two patients suffered from a severe osteonecrosis of the femoral head and two patients had fractures of the acetabulum or femoral neck, respectively. RESULTS: The medium-term follow-up for the acetabular component showed a survival rate of 97.8%. The radiographic data visualized one loosening as a result of a low grade infection, 18 months after surgery. There was no migration of the acetabular component according to Sutherland et al. and no protrusion was found. None of the acetabular components showed radiolucent lines or was loose according to radiographic criteria. In comparison to the first post-operative radiograph, 26 of the hips were found with a significant reduction of lacunae, twelve of them showed a complete absence at last follow-up. The overall Harris hip score averaged 92 points (range 58 to 100 points) for the entire group. 41 (92%) of all hips were rated as excellent or good. Two hips (4%) of all hips were rated as fair and two hips (4%) were rated as poor. CONCLUSION: The high rate of good and satisfying results in medium-term follow-up proves this St. Nabor acetabular component system to be an excellent implant in total hip arthroplasty for younger patients with or without dysplasia.

Adult↗

Development of a carbon-carbon hip prosthesis.

This article deals with the use of carbon-fiber-reinforced-carbon materials for the manufacture of hip prosthesis stems. It considers the manufacturing process of carbon-carbon (C-C) composites made of carbon fibers infiltrated either with dense pyrolytic carbon or silicon carbide (SiC) through chemical vapor infiltration. The chemicophysical properties of these composites are examined according to their structures. The long-term response (2 years) of cortical bone to various types of carbon-carbon was evaluated mainly for bone contact and ingrowth. Carbon-carbon coated with calcium phosphate was found to speed up the bone formation as compared to pyrolytic carbon or SiC coatings. The low modulus of elasticity of the C-C materials could be responsible for quicker bone contact as compared to a much stiffer material like sintered aluminum oxide. The biomechanical performance of C-C hip stems was assessed through (a) implantations into cadaver femurs, (b) fatigue testing, and (c) finite element analysis. These tests showed: (a) a better stress transfer as compared to a metal prosthesis having the same design, (b) no fatigue damage, (c) a computerized stem stress distribution in accordance with the fractures obtained during static mechanical testing.

Biocompatible Materials↗

Space orientation of total hip prosthesis. A method for three-dimensional determination.

A method for in vivo determination of orientation and relation in space of components of total hip prosthesis is described. The method allows for determination of the orientation of the prosthetic components in well defined anatomic planes of the body. Furthermore the range of free motion from neutral position to the point of contact between the edge of the acetabular opening and the neck of the femoral component can be determined in various directions. To assess the accuracy of the calculations a phantom prosthesis was studied in nine different positions and the measurements of the space oriented parameters according to the present method correlated to measurements of the same parameters according to Selvik's stereophotogrammetric method. Good correlation was found. The role of prosthetic malpositioning and component interaction evaluated with the present method in the development of prosthetic loosening and displacement is discussed.

Arthrography↗

[Biomechanical experiment of non-stemmed anatomical total hip prosthesis arthroplasty in vitro].

Biomechanical test in vitro was performed to study the biomechanical characteristics of the femoral component in the non-stemmed anatomical total hip prosthesis (A-Fix) arthroplasty. It mimics two stages, the early stage with cementless and the later stage with cement fixation that imitates bone ingrowth. The results were compared with that of normal proximal femur by normalized coefficient analysis. Translation of femoral head after hip replacement is slightly more than normal. The strain of femoral neck after replacement is lower than that of normal. It changes flatly. The security coefficient in early stage is raised by 13% on the tensile side and by 27.6% on the compressive side of femoral neck; that in later stage is raised by 29.6% and by 22.1% separately. The maximal torsional angle of femoral head is minimal, it is 0.02 times that of normal in early stage and 0.01 times in later stage. It demonstrated that A-Fix arthroplasty has the characteristics of low stress and deformation, high intensity and rigidity, and anti-loosening, thus affording mechanical evidences for its clinical use.

Adult↗

[Prognosis of the total hip prosthesis].

The prognosis of total hip arthroplasty is excellent and as many publications show, the survival of a good type of implant is well above 90 per cent at the 10-year follow-up. The results of the average orthopaedic surgeon may not match those obtained by the experts who have published these results. Therefore, in 1979 a prospective multicentre study was started in Sweden to evaluate the outcome of total hip arthroplasty. This National Hip Register has shown that the outcome is related to type of prosthesis, patient selection and operative technique. The results from one orthopaedic department to another differed considerably. The feedback from the Register resulted in improvements of the overall outcome and decrease of the differences between the orthopaedic departments in Sweden A Dutch National Implant Register is needed.

Arthroplasty, Replacement, Hip↗

Inflammatory reactions in primary osteoarthritis of the hip and total hip prosthesis loosening.

In 14 patients [9 with loosened total hip arthroplasty (THA), 5 with primary osteoarthritis], the inflammatory cell infiltrate was characterized in cryostat tissue sections using antibodies against subsets of macrophages and lymphocytes. In all patients the abundance of a mature type macrophage (25F9+) was observed, whereas 27E10+ macrophages, characteristic of acute inflammatory reactions, were not seen in primary osteoarthritis but were found in 4 out of 9 patients with THA loosening. The RM3/1 + macrophage phenotype was seen in some of both sets of patients (osteoarthritis 4/5; THA loosening 4/9). The markers MRP8 and MRP14 typical of immature macrophages, were found in all patients with osteoarthritis and in some (4/9 and 8/9 respectively) of those with THA loosening. IOT4+ T-helper cells were only present in 1/5 5 patients with osteoarthritis and in 2/9 patients with THA loosening. IOT8+ T-suppressor lymphocytes were more frequently present (in 4/5 and 5/9 respectively). The data reveal remarkable differences between the two groups of patients. While the inflammatory infiltrate in patients with osteoarthritis lacks the characteristics of acute inflammation, in patients THA loosening the inflammatory process seems to be determined by periods of acute reactions. The occasional presence particularly of T-helper cells suggests that the inflammatory process is less T-cell but rather macrophage-driven.

CD4-CD8 Ratio↗

[Technical development and radiological surveillance of the Schmitt minimadreporic uncemented total hip prosthesis. Evaluation of 275 arthroplasties with a follow-up of more than 6 years for the oldest cases].

The authors describe a porous-coated uncemented total hip prosthesis which has been used for more than six years: the Schmitt minimadreporic prosthesis. A homogenous series of 275 arthroplasties has been reviewed with a mean follow-up of three years and five months. The method of radiological assessment of the position of the femoral and acetabular components and their possible loosening is described in detail. Infection (0.72%) and aseptic loosening (1.8%) specific to this type of prosthesis was rare. For the series as a whole there were 92% of good, very good and excellent results and for 81 arthroplasties with a follow-up greater than four years the figure was 90%. The frequency of secondary displacement of the femoral component is emphasised, with 15 prostheses sinking downwards and 96 displacing into varus. Statistical analysis has shown the principal factors affecting the clinical result and has demonstrated the effect of resorption of the calcar in causing downward displacement of the femoral stem and insufficient filling of the medullary cavity on the development of varus angulation of the prosthesis.

Bacterial Infections↗

Stem fracture of the cementless spongy metal Lübeck hip prosthesis.

We performed 204 cementless total hip arthroplasties using a fully porous stem made of a cast cobalt-chrome-molybdenum alloy. Five stems fractured at the middle part. Champagne-fluted canals (P<.0001) and low canal fillings 1 cm below the lesser trochanter (P =.02) significantly correlated with stem fractures. Subsequent surgery revealed that all of the proximal parts were surrounded by fibrous tissue, and the distal parts showed bone ingrowth. Numerous voids were present close to the surface of the implant body. The core diameters of the fractured stems were 4 to 5 mm. The fractures may be attributed to the combination of the lack of proximal support, a champagne-fluted canal, the fully porous stem made of a cast cobalt-chrome-molybdenum alloy, and the narrow dimension of the stem core.

Adult↗

Models of hip prosthesis mobilisation.

The mechanisms of prosthetic hip mobilisation are analysed, both in regard to the acetabular component and the femoral component. These are correlated with the clinical and radiographic manifestations with the aim of facilitating the comprehension and memorisation of different types of mobilisation. These are summarised in a chart illustrating the eight different mechanisms which provide both the orthopaedist and the radiologist with a rapid "aide memoire" when faced with a radiograph in a case of aseptic prosthetic hip mobilisation.

Acetabulum↗

The hip cast-brace for hip prosthesis instability.

The use of a hip cast-brace in the treatment of unstable hips following prosthetic replacement is described. A retrospective study of 21 patients with 22 hip prostheses treated with the cast-brace is reported. Seventeen Charnley low friction arthroplasties (LFA) were treated--four cast-braces were used for prophylaxis, five for single dislocations and eight for recurrent dislocations. To date, only four hips have required an operation to achieve stability. Five patients with Thompson hemi-arthroplasties were treated following dislocation with only one requiring surgery to achieve stability. A hip cast-brace is recommended as a useful alternative to surgical management of prosthetic instability.

Adult↗

[Anterior approach in hip prosthesis].

The anterior approach for total hip endoprosthetics (THE) developed by K. J. Keggy was used in about 3,000 patients. It is characterized by rapid accomplishment, the possibility of anatomical inspection of the joint and correct orientation of the acetabular component of the endoprosthesis. Difficulties are not encountered in exposure of the femur and favorable conditions are provided for separation of the soft tissues. Considering our preference for noncemented THE, we have been using in the recent years a modified approach. The average duration of the operation, except for revision THE, did not exceed 90 minutes. The approach is atraumatic for the para-articular soft tissues, which provides the possibility of early postoperative mobilization and rehabilitation and reduced the duration of postoperative in-patient treatment to 7.3 days. The incidence of complications was not higher, and in many respects was even lower, than that reported in the literature dealing with primary and revision THE. At present we still use the anterior approach in all operations for THE although essential contradictions occur in discussion of the advantages of cemented implants over noncemented prostheses. The suggested method for THE is best for most patients.

Adolescent↗

[Fixation of the osteotomised greater trochanter by total hip prosthesis in 181 cases. Advantages of the fixation with intramedullary Kirschner wire and the figure-of-eight wire loop (author's transl)].

It is mostly possible to implant a total hip prosthesis without an osteotomy of the greater trochanter. It is however necessary to do it in some cases such as an ankylosed hip, a reimplantation and a severe form of the coxarthrosis. 181 patients have been followed up. The fixation by intramedullary Kirschner wire and figure-of-eight wire loop has been of success. It is a simple method. No fracture of the greater trochanter has been observed.

Aged↗

[Dissociation of a modular acetabular component in an uncemented total hip prosthesis. Effect of the modular design and anti-luxation rim. A case report].

We report a case of dissociation between polyethylene and metal-backing of the acetabular component of a total hip prosthesis after reduction of a late dislocation. We refer to advantages and disadvantages of an elevated-rim acetabular liner in total hip arthroplasty. The position of the metallic markers of the polyethylene and/or excentric situation of the neck-head complex from the metal-back allowed us to diagnose it. An appropriate surgical technique avoiding the joint laxity, firm assembly of the modular components when they are implanted, gentle reduction of an eventual dislocation and fluoroscopic control, are factors which can avoid this rare complication.

Female↗

[Fat embolism syndrome after surgery to replace the femoral stem of a hip prosthesis].

A 66-year-old woman developed hemodynamic instability, oliguria, prostration, fever, and coagulopathy 4 hours after surgery to replace the femoral stem component of a hip prosthesis under a combined subarachnoid-epidural block. Dyspnea and tachypnea developed, and a petechial rash appeared 24 hours later. The diagnosis was fat embolism after other possible causes were ruled out. Supplementary oxygen, fluid replacement therapy, and inotropic support were started. The patient's condition improved and she was discharged from the postoperative recovery unit 5 days after admission. Although fat embolism usually appears in young men after large bone fractures, it should be considered when symptoms consistent with this diagnosis arise in patients who have undergone orthopedic surgery so that appropriate treatment can be started early.

Aged↗

[Periprosthetic femoral fractures in total hip prosthesis implantation. Functional and radiological comparison between plate osteosynthesis and proximal femur replacement].

AIM: Clinical and radiological examinations were performed to compare plate osteosynthesis (group 1) with replacement of the proximal femur by tumor prosthesis (group 2) in patients with ipsilateral femoral fractures around a hip prosthesis. METHOD: Of 24 consecutive patients with 25 fractures, nine had died and one could be contacted by telephone leaving 14 hips (in one case only recent X-rays were available) for final review (nine patients from group 1; five from group 2). RESULTS: At the time of examination four patients of group 1 were using one cane or were walking without any support, all patients of group 2 needed one or two crutches. In 5 of 9 patients in group 1 and in 4 of 5 in group 2 a firm fit of the prosthesis was observed. CONCLUSION: Group 1 achieved better clinical results in postoperative mobility, whereas femoral replacement showed better radiological results. Survival of patients with tumor prostheses was considerably superior to that of patients with plate osteosynthesis.

Activities of Daily Living↗