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Biomedical subjects

I M Pinder

Publications and source records attributed to I M Pinder.

At least 19 recordsLinked to original sources
PubMed2003

Role of abrasion of the femoral component in revision knee arthroplasty.

We carried out 60 revision procedures for failed porous coated anatomic total knee replacements in 54 patients, which were divided into two groups. The 14 knees in group I had a well-fixed femoral component at surgery which was retained, and in the 46 knees in group II both tibial and femoral components were loose and were revised using a variety of implants. Our review comprised clinical and radiological assessment. A total of 13 knees required a second revision. Six (42%) in group I failed very early (mean 2.1 years) when compared with seven (15%) in group II (mean 6.8 years). Failure was due to wear of the polyethylene insert by the abraded, retained femoral component (crude odds ratio 4.07; 95% CI 1.07 to 15.5). We recommend a complete change of primary bearing surfaces at the time of revision of an uncemented total knee replacement in order to prevent early wear of polyethylene.

Adult↗
PubMed2002

Does body weight influence outcome after total knee arthroplasty? A 1-year analysis.

Obesity has been considered an adverse influence on the outcome of total knee arthroplasty (TKA), and overweight patients often are advised against having a TKA. The role of body weight has not been shown conclusively using objective outcome measures. A group of 180 patients undergoing primary TKA performed by a single surgeon for osteoarthritis was studied prospectively. Their baseline health status and knee scores were recorded, and changes in these measures were studied at 3 and 12 months after surgery. The Nottingham Health Profile was used to assess health status, and the Knee Society score was used to assess clinical outcome. Body mass index was used as a measure of obesity. We found that body weight did not influence adversely the outcome of TKA in the short-term.

Adult↗
PubMed2002

Measured ambulation and self-reported health status following total joint replacement for the osteoarthritic knee.

OBJECTIVE: To quantify the increase in ambulation produced by total knee replacement for osteoarthritis (OA) of the knee and to compare this with questionnaire-derived data. METHODS: We compared the measured ambulatory activity and self-reported Nottingham Health Profile (NHP) data of 19 subjects with OA of the knee before and after total knee replacement (TKR). RESULTS: Subjects were considerably restricted in their measured activity before operation compared with subjects with less severe disease. At 6 months the activity had increased by an average of 79% (P=0.02). The pain scale of the NHP had significantly improved at 3 months, as had the mobility scale. Between 3 and 6 months, however, at the same time the measured activity was increasing, self-reported mobility declined. CONCLUSIONS: Replacement of a knee for OA is an effective way of improving ambulation. At 6 months the average increase amounted to 79%. Self-reported mobility did not correlate with mobility measured objectively.

Aged↗
PubMed2001

Postphlebitic syndrome after total knee arthroplasty: 405 patients examined 2-10 years after surgery.

We assessed the prevalence and relevance of putative risk factors for significant postphlebitic syndrome (PPS) in a cohort of 405 patients who underwent single limb cemented total knee arthroplasty. All patients were studied by means of a questionnaire and clinical examination to detect the presence of lower limb venous insufficiency. We found 52 (13%) new cases of postphlebitic syndrome. Comparison of those patients with and without PPS revealed no significant differences in the median age, sex ratio, preoperative mass, primary joint pathology or relevance of primary or revision surgery. A confirmed history of pre- or post-operative deep vein thrombosis was associated with the development of disease. Most cases seemed to develop within 5 years of surgery.

Adult↗
PubMed2001

The effect of socket design, materials and liner thickness on the wear of the porous coated anatomic total hip replacement.

The wear of joint replacement prostheses represents the greatest challenge to their continued development. Parameters such as polyethylene quality, liner thickness and metal backing have all been implicated as potential detractors in the search for the lowest-wearing socket. This study examined the effect of these parameters through an extensive study of the two versions of the porous coated anatomic (PCA) hip prosthesis (one-piece socket and snaplock socket). For the whole cohort the wear rate was found to be 88 (SE 10) mm3/year and the clinical wear factor was 2.00 (SE 0.28) x 10(-6) mm3/N m. When the two socket types were investigated individually, the wear factors found were 2.39 (SE 0.44) x 10(-6)mm3/N m and 0.99 (SE 0.25) x 10(-6) mm3/N m for the one-piece and snaplock, respectively. This illustrates that the metal backing per se does not predispose these sockets to rapid wear. The good wear performance of the snaplock liner may be attributed to the high quality of the ultra-high molecular weight polyethylene (UHMWPE) used and the shorter implantation period compared to that for the one-piece design. No correlation was found between the thickness of the liner and the clinical wear factor. Within the range of thicknesses tested here, UHMWPE thickness is not an influential parameter for the hip prosthesis and this is confirmed

Arthroplasty, Replacement, Hip↗
PubMed2000

A novel technique for the detailed size characterization of wear debris.

The accurate and detailed characterization of artificial joint wear debris is important in determining both the wear rate of prostheses and understanding the role that the debris plays in the development and progression of aseptic loosening. The novel application of low angle laser light scattering (LALLS) to the particle size characterization of ultra high molecular weight polyethylene (UHMWPE) wear debris is described. The results demonstrate that both ex vivo and in vitro origin wear debris samples, at concentrations typical of those produced via an alkali-digestion retrieval route, can be reproducibly analyzed via LALLS. Because the LALLS route enables particle size analysis of the entire debris sample to be acquired non-destructively and whilst in suspension, artefacts associated with filtering, drying and agglomeration of debris are avoided, in contrast to currently used techniques such as filtration and scanning electron microscopy (SEM) observation.

Journal Article↗
PubMed2000

Are clinical and patient assessed outcomes affected by reducing length of hospital stay for total hip arthroplasty?

This prospective observational study investigated the relationship between the length of hospital stay (LOS) and outcomes at 3 months for primary total hip arthroplasty for osteoarthritis. Mean length of postoperative stay was 9.5 +/- 2.8 days. Predictors of LOS were patient's age, sex, and number of comorbidities; preoperative Charnley scores and Nottingham Health Profile measures; complications; and hospital in which surgery took place. LOS was found to have a small negative correlation with outcome. The dominant association with improved outcome was the severity of the patients' impairment preoperatively. These data suggest that in situations in which adequate rehabilitation and support are available after discharge, a marginal reduction in postoperative LOS--from the average of 10.3 days observed at 1 hospital to the average of 8 days observed at another--would not adversely affect the short-term outcome.

Aged↗
PubMed1999

The influence of femoral head surface roughness on the wear of ultrahigh molecular weight polyethylene sockets in cementless total hip replacement.

A theoretical relationship was recently proposed relating the wear behavior of polymetric bearing materials articulating against hard counterfaces.(1) This model attempts to predict the influence of surface roughness on wear. Laboratory-based studies have been used to establish the validity of these relationships, but their application to the clinical situation has not been investigated fully. Forty-two retrieved PCA hip joints have been assessed. The total wear volume was calculated from the penetration measured using the shadowgraph method, and roughness of the articulating surfaces was recorded using noncontacting profilometry. The roughness of the explanted femoral heads was observed to increase (median S(a) - 10. 35 nm worn region, 3.05 nm peripheral region), while that of the acetabular liner fell dramatically (median S(a) - 41 nm worn region, 212 nm unworn region). No evidence of a relationship between the topography of the worn regions of the femoral head and that of the acetabular liner could be found. Similarly, the strength of the association between the surface roughness and the clinical wear factor was considerably poorer than that achieved in laboratory experiments. A number of reasons for this observation are proposed. Most deleterious was considered to be the inability of the roughness parameters to describe the damaging features of the surface adequately. Uncertainty as to when the surface of the component degrades during its life serves to introduce further doubt as to the application of the wear models in the clinical environment. In conclusion, this study fails to provide clinical evidence to substantiate the relationship between surface finish and wear rate. The adoption of standardized measurement parameters and techniques would facilitate the direct comparison of joint types and the selection of the most advantageous materials.

Arthroplasty, Replacement, Hip↗
PubMed1999

Health outcome after total knee replacement in the very elderly.

Between 1992 and 1994 we performed a prospective study of the effect of total knee replacement (TKR) on the health status of 119 patients over the age of 80 years who had had a primary unilateral TKR. The Nottingham Health Profile was used to assess this before and at three and 12 months after operation. We found a significant improvement in the scores for pain, emotional reaction, sleep and physical mobility at three months. After 12 months, the scores for pain and sleep were well maintained. The other factors had deteriorated slightly but remained better than before operation. Our findings show that TKR leads to a significant improvement in the general health status of the very elderly.

Aged↗
PubMed1998

Wear in retrieved acetabular components: effect of femoral head radius and patient parameters.

Forty-seven explanted Porous Coated Anatomic (PCA, Howmedica, Rutherford, NJ) cementless acetabular components were acquired at revision surgery. All the components articulated against CoCrMo femoral heads of 32-mm diameter. The penetration depth and angle were measured using the shadowgraph technique. The wear volume was then calculated using Kabo's formula. Using weighted linear regression analysis, the mean penetration rate and mean volumetric wear rate were calculated to be 0.23 (SE, 0.03) mm3/y and 96 (SE, 13) mm3/y, respectively. The creep component was not found to be significantly different from zero. The clinical wear factor, k(clinical), for this cohort was also calculated using linear regression analysis but with the assumption that creep was zero. The value found, k(clinical) = 1.93 (SE, 0.29) x 10(-6) mm3/N-m, was similar to those in previous studies involving cemented joints with a 22-mm femoral head diameter. The similar k(clinical) values of these substantially different joint types suggest that the high volumetric wear rate for the PCA joint can be attributed entirely to its larger head size and the younger, more active, patient profile. Fixation technique and metal backing seem not to influence the rate of wear.

Acetabulum↗
PubMed1998

The frictional behaviour of explanted PCA hip prostheses.

The frictional characteristic of 22 explanted and two unused PCA total hip arthoplasties were assessed using the Durham hip simulator. The friction of the explanted joints was not found to be significantly different from that of the unused joints. In contrast, explanted Charnley joints often exhibit increased frictional characteristics. This discrepancy is accounted for by the lack of cement ingression in the PCA design.

Adult↗
PubMed1996

Kinematic condylar total knee arthroplasty. 14-year survivorship analysis of 208 consecutive cases.

We performed an independent survivorship analysis on 208 Kinematic Condylar knee replacements with a minimum follow-up of ten years and a mean of 12 years. Seven patients had been lost to follow-up. At ten years the estimated survival was 92% (95% confidence limits 95% and 87%) and when stratified for diagnosis and thickness of polyethylene there was no statistical difference (p > 0.05) in survivorship of knees with osteoarthritis or rheumatoid arthritis. We conclude that the original design of the Kinematic Condylar knee replacement has a good record and that adequate evaluation of new designs of implant should be undertaken before they are widely introduced.

Adult↗
PubMed1996

Survivorship analysis of the Kinematic Stabilizer total knee replacement: a 10- to 14-year follow-up.

The Kinematic Stabilizer is a posterior-cruciate-substituting design of total knee replacement. We have reviewed 109 primary total knee replacements in 95 patients at a mean follow-up time of 12.7 years (10 to 14). We used survival analysis with failure defined as revision of the implant. This gave a cumulative survival rate of 95% (95% CI +/- 5%) at ten years and (87% +/- 10%) at 13 years. These results from an independent centre confirm the value of an established design of cemented total knee replacement and question the wisdom of the introduction of modifications and new designs without properly controlled trials.

Adult↗
PubMed1996

Systemic release of cobalt and chromium after uncemented total hip replacement.

We measured the levels of cobalt and chromium in the serum in three groups of patients after uncemented porous-coated arthroplasty. Group 1 consisted of 14 consecutive patients undergoing revision for aseptic loosening. Group 2 comprised 14 matched patients in whom the arthroplasty was stable and group 3 was 14 similarly matched patients with arthritis awaiting hip replacement. Specimens were analysed using atomic absorption spectrophotometry. Aseptic loosening of a component resulted in a significant elevation of serum cobalt (p < 0.05), but not of serum chromium. The relative risk of a component being loose, if the patient had a serum cobalt greater than 9.0 nmol/l, was 2.8.

Adult↗
PubMed1994

Six-year follow-up of multiple joint replacement surgery to the lower limbs.

We report a 6-yr follow-up study of an original population of 50 patients who had three or more major joints (hips and knees) replaced. Thirty-one of 32 surviving patients were still ambulant in the community, and all patients described significant pain relief. No RA patient was requiring permanent inpatient or residential care and the family remained the main social support. They remained a very disabled group with a median Health Assessment Questionnaire score of 2.75. Ten required revision surgery: three hips and seven knees; four patients required their fourth lower limb joint (hip/knee) replaced and seven patients required surgery to the upper limbs and nine feet during the follow-up period. The median 10-yr survival of hip and knee arthroplasties in multiple joint replacement (MJR) patients with RA was 90.5 and 78.6% respectively. There was an increased incidence of cervical myelopathy in MJR patients 16.9%. The mortality rate was higher than expected (standardized mortality ratio = 590) but the actual surgery was not implicated. MJR therefore appears to be a worthwhile policy, even at long-term follow-up.

Arthritis, Rheumatoid↗
PubMed1994

Results of uncemented porous-coated anatomic total hip replacement.

We reviewed a consecutive series of 241 uncemented, porous-coated anatomic (PCA) hip replacements at an average follow-up of five years (2 to 9). Of these, 32 had failed (13%), 26 at the acetabular component (11%) and six at the femoral component (2%). Acetabular failure was associated with local osteolysis and excessive polyethylene wear in 20 cases: in these histological examination showed giant macrophages incorporating numerous particles of high-density polyethylene. The femoral failures were related to a poor intramedullary fit with subsequent subsidence. Using the recommendation for revision as the end point, the cumulative survival rate for prostheses was 91% at six years (95% CI +/- 6%), 73% (+/- 11%) at seven years, and 57% (+/- 20%) at eight years. The result of uncemented PCA hip replacement is satisfactory up to six years, but then increasing failure of the acetabular component appears to be due to polyethylene wear, leading to osteolysis, loosening and component migration. At first, failure is often asymptomatic; routine follow-up of uncemented hip replacement is essential, especially after five years.

Acetabulum↗