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Biomedical subjects

I D Learmonth

Publications and source records attributed to I D Learmonth.

At least 55 records · Page 3Linked to original sources
PubMed1997

The pathogenesis of osteolysis in two different cementless hip replacements.

Wear of ultra-high molecular weight polyethylene has been incriminated in the osteolysis associated with aseptic loosening of hip implants. A variety of different factors can contribute to accelerated patterns of polyethylene wear and subsequent osteolysis. This paper examines the incidence of osteolysis observed in two different well-matched cohorts of cementless total hip arthroplasties. The patterns of osteolysis observed, which are ascribed to the generation of polyethylene debris, are interpreted with reference to the design of the individual prostheses.

Biocompatible Materials↗
PubMed1996

Poor reproducibility in radiographic grading of femoral cementing technique in total hip arthroplasty.

The first study of the reproducibility of a widely accepted grading system for femoral cementation in total hip arthroplasty is reported. Sixty postoperative radiographs were graded on two occasions at least 2 weeks apart by two experienced observers. The test-retest reproducibility rate was 60% for observer 1 and 70% for observer 2. The interobserver reproducibility varied between 60 and 63% for the different assessments. Between 5 and 6% of cases differed by more than one grade between tests. Kappa statistical analysis confirmed that reproducibility was poor in all cases. This cement grading system, even in the hands of experienced observers, has too high a rate of intraobserver and interobserver error to recommend its use.

Bone Cements↗
PubMed1996

Osteolytic properties of the synovial-like tissue from aseptically failed joint prostheses.

Relationships were found between the bone-resorbing ability of conditioned media (CMs) from culture of peri-prosthetic tissues and their levels of bone-remodelling agents. Bone-resorbing activity was measured by 45Ca release from pre-labelled mouse calvaria and 23 of 40 CMs exhibited bone-resorbing activity. Cytokine and prostanoid levels in the CMs were measured by immunoassay, and the levels of interleukin (IL)-1 beta, IL-6, tumour necrosis factor alpha (TNF alpha) and prostaglandin E2 (PGE2) correlated with each other, except for the latter two. Significantly higher levels of IL-6 were present in those CMs with bone-resorbing activity than in those without, and a similar pattern was observed for PGE2 and IL-1 beta. However, some CMs with high levels of IL-1 beta, IL-6, TNF alpha and PGE2 failed to induce resorption, whereas a few CMs with low levels of these agents induced resorption. Moreover, neither dialysis of CMs nor addition of neutralizing antisera to IL-1 alpha and IL-1 beta to CMs, either alone or in combination, reduced the bone-resorbing activity of the CMs. It is considered that these agents may act synergistically to mediate osteolysis around failed joint implants, but that other unidentified bone-resorbing agent(s) must be involved.

Adult↗
PubMed1996

Preliminary observations on possible premalignant changes in bone marrow adjacent to worn total hip arthroplasty implants.

Previous epidemiologic studies have suggested that there may be a risk of malignancy, especially lymphoma and leukemia, after joint replacement, but the followup has been relatively short. This is a preliminary study to see if there is any biologic basis for such a risk. Blood and bone marrow samples from 71 patients at revision arthroplasty of a loose or worn prosthesis and 30 control patients at primary arthroplasty were analyzed with cytogenetic techniques and molecular biology. There was a higher chromosomal aberration rate in cells adjacent to the prosthesis at revision surgery compared with iliac crest marrow from the same patients or with femoral bone marrow at primary arthroplasty. Clonal expansion of lymphocytes without a serum paraprotein was seen in 2 of 21 patients at revision arthroplasty performed more than 10 years after primary arthroplasty. The results of this preliminary study suggest that future epidemiologic studies should concentrate on patients with longer postoperative intervals to see if there is any risk that would be pertinent to a young patient at primary arthroplasty.

Aged↗
PubMed1996

Unpredictable progression of osteolysis following cementless hip arthroplasty. 24 femoral components followed for 6-10 years.

We reviewed 24 hips that developed femoral osteolytic lesions following cementless total hip replacement with a Porous-Coated Anatomic prosthesis after a mean of 8 (6-10) years. 15 of the hips showed hardly any radiographic deterioration in the osteolysis. 2 became much worse with dramatic loss of bone stock. Both of these hips required revision of the acetabular component as well as bone grafting of the otherwise well-fixed femoral component. The remaining 7 hips showed mild-to-moderate enlargement of the lesions. All 24 hips were asymptomatic. Blood tests and bone scintigraphy were of no predictive value in assessing the probable progression of the lesions. Serial radiography remains the cornerstone of the monitoring of osteolysis, following cementless hip replacement, the extent of bone loss being usually far greater than indicated by radiographic examination.

Adult↗
PubMed1996

The omega lateral approach to the hip.

We describe a modified lateral approach to the hip which exploits the function continuity of gluteus medius and vastus lateralis and their dense crescentic attachment to the greater trochanter. The gluteus medius is not incised or split, but is detached and mobilised with gluteus minimus as one unit. This facilitates reattachment of the glutei and helps to preserve abductor function.

Fascia Lata↗
PubMed1995

Loss of bone stock with cementless hip arthroplasty.

One hundred four porous-coated anatomic cementless hip arthroplasties followed from 2 to 6.5 years (mean, 50 months) were studied. Ninety-four percent had excellent clinical results. Thigh pain occurred in 23% of patients, but was severe in only two. "Cancelization" and rounding off of the calcar were noted in 83% of hips, whereas localized osteolysis occurred in 24 femurs and one acetabulum. Ten of these measured more than 10 mm, and all of those in the femur were located proximally. None of these patients were symptomatic and none have come to revision. Ultrahigh-molecular-weight polyethylene wear and plastic debris were implicated as the cause of osteolysis. Lytic lesions were seen only after 3 years and occurred only in patients with 32-mm femoral heads in whom the outer diameter of the acetabular component was 52 mm or less. Use of excessively thin ultrahigh-molecular-weight polyethylene in these patients may have predisposed them to accelerated wear. Section modulus mismatch resulting in stress protection is considered as an alternate mechanism of proximal bone resorption.

Adolescent↗
PubMed1995

Patch-grafting for regional femoral bone loss in cementless revision hip arthroplasty.

The authors reviewed 33 revision hip arthroplasties using the long-stemmed porous coated anatomic (PCA) prosthesis that required adjuvant patch-grafting for proximal defects of the femur. All hips were revised for aseptic loosening. The mean follow-up period was 3.7 years (2.0-5.8 years). The hips were clinically evaluated by means of the Harris Hip Score: 26 (79%) were found to be good or excellent, 3 (9%) fair and 4 (12%) poor. Graft incorporation occurred in 31/33 cases (94%). Proximal stress protection bone resorption was not seen, although cancellisation of the calcar was noted in 20/33 (60%) hips. Serial radiological review demonstrated some degree of subsidence of the femoral stem in 20/33 (60%) hips. The authors conclude that patch-grafting of the proximal femur at revision surgery incorporates and is not inhibited by the presence of a rigid long-stemmed implant.

Adult↗
PubMed1994

The A1 pulley in rheumatoid flexor tenosynovectomy. To retain or divide?

We report a detailed comparative evaluation of flexor tenosynovectomy in 55 fingers in which the A1 pulley was divided and 45 fingers in which the A1 pulley was retained. The metacarpophalangeal joint subluxed volarly in 49% when the A1 pulley was divided, compared to 11% when the pulley was preserved. Bowstringing occurred in 7% and only when the A1 pulley was divided. Ulnar deviation was 7 degrees worse when the pulley was divided. Active range of movement was limited in both groups. It was 11 degrees less when the A1 pulley was divided.

Adult↗
PubMed1994

Do abnormal hemipelvic bone stresses contribute to loosening and migration of screw-threaded cups?

Excellent long-term results have been reported with the Charnley low-friction arthroplasty. Failure of the cemented acetabular component has been identified as a problem in the longer term, while cemented hip replacements in active young patients have exhibited a disconcerting incidence of early clinical or radiological failure. This resulted in the development of the cementless arthroplasty. Bone responds favourably to an optimal stress window and reacts dynamically to metal implants that have a greatly differing modulus of elasticity. This study represents a comparative qualitative analysis of the peri-acetabular hemipelvic stresses after loading two cementless (press-fit and screw-threaded) acetabular components inserted into identical bone models. A simplified model of the artificial hip joint was constructed and the very sensitive stress analysis technique of holographic interferometry was used for the investigation. Peri-acetabular stress concentrations were noted with the screw-threaded cup. This may predispose to bone resorption and it is suggested that these could be implicated in the migration of these cups described in published reports.

Cadaver↗
PubMed1994

Current thoughts on total hip replacement.

Opinion leaders in the field of total hip arthroplasty express antipodal views with bewildering frequency. New trends notwithstanding, Charnley low-friction arthroplasty has a record of outstanding success, and we should attempt to identify specific problems, and address these accordingly. Biological and biomechanical matching remain important and increased attention to meticulous cement technique should favourably improve the long-term performance of cemented implants. The concept of cementless replacement should not, however, be summarily discarded, particularly for the younger patient. The discovery of existing design limitations should lead to further development based on sound scientific research. In an era of exploding technology, cost-containment must remain a pragmatic reality in the provision of a health-care service to the community. At this stage we would recommend a cementless hip replacement for the very young, hybrid replacement (cemented stem, uncemented cup) for the middle-aged and a fully cemented replacement for the elderly.

Biocompatible Materials↗
PubMed1993

Fracture and loosening of Charnley femoral stems. Comparison between first-generation and subsequent designs.

We report the results of a 4- to 17-year clinical and radiological follow-up of 264 Charnley first-generation stems in comparison with those of 402 second- and subsequent-generation stems. The incidence of fracture was 4.1% in first-generation stems and 0.5% in second- and subsequent-generation stems. The incidence of stem loosening requiring or likely to require revision was 3.1% in first-generation and 11.4% in second-generation stems. We believe that the increased loosening rate in second- and subsequent-generation stems is due to their larger cross-sectional area, which produces an increase in flexural stiffness.

Adolescent↗
PubMed1993

811 Charnley hips followed for 3-17 years.

10-12 year survivorship analysis of 811 primary or conversion Charnley arthroplasties showed 89 percent probability of mechanical survival (revision excluding sepsis). The mechanical failure rate was 7 percent, and more stems required revision than sockets. The anterio-posterior radiographs of 630 unrevised hips, with a minimum 3-year follow-up, were evaluated using the CART system of terminology. Cement-bone radiolucency was present in 50 percent of sockets and 18 percent of stems. Substantial loosening was present in 6 percent with 94 percent probability of survival at 10-12 years.

Adolescent↗
PubMed1993

Treatment of grade III osteonecrosis of the femoral head with a Charnley/Bicentric hemiarthroplasty.

Thirty-eight hips with Charnley/Bicentric hemiarthroplasties were reviewed. Preoperatively all hips had a Grade III osteonecrosis (Arlet & Ficat) of the femoral head. Follow-up ranged from 42 to 72 months with a mean of 56 months. The mean age was 36 years (range 16-52 years). Three hips with gross loosening of the femoral prosthesis were revised to a cementless total hip replacement: a further two hips exhibited radiological changes indicative of loosening and pending failure. In one hip with progressive loss of joint space and secondary degenerative changes the Bicentric cup was revised to a cemented Charnley component. Acetabular migration was not encountered. Six of 38 hips (15.8%) were thus considered failures. The mean total movement from full abduction to full adduction at the cup-acetabular articulation was 21 degrees, compared to 14 degrees at the inner component articulation. The results of cemented femoral components are predictably unfavourable in this young age group. However, the double articulation of the bipolar cup offers an acceptable method of treatment for this grade of osteonecrosis in the medium term.

Adolescent↗
PubMed1993

Prevention of infection in the 1990s.

Deep sepsis after arthroplasty surgery represents a catastrophe. People remain the primary source of bacterial contamination. This paper discusses the potential sources of infection and reviews the appropriate measures required to reduce contamination and combat infection.

Anti-Bacterial Agents↗
PubMed1992

A scoring system to determine radiological loosening in cemented total hip arthroplasty.

A radiological scoring system was developed to identify grades of loosening of the components of a cemented hip replacement. In grade 1, there are mild changes, usually of minor significance; in grade 2 moderate changes which need regular observation, and in grade 3 severe changes which indicate impending failure. Three parameters are used for the socket, giving a score of 10 points, and 5 for the stem, with a score of 15 points. This method can be used to provide a comparison between different series with a long-term follow up.

Evaluation Studies as Topic↗