Biomedical subjects

P D Siney

Publications and source records attributed to P D Siney.

At least 19 recordsLinked to original sources

PubMed2006

The angle-bore acetabular component and dislocation after revision of a failed total hip replacement.

We reviewed 1039 revision total hip replacements where an angle-bore acetabular component was used. After a mean follow-up of nine years (0 to 20.6), the incidence of revision for dislocation was 2.1% (22 revisions), a success rate of 97.9%. In 974 revisions, where the indication was other than dislocation, the success rate was 98.5%. Of the 65 revisions for dislocation, 58 (89.2%) were successful after the first revision and a further five after the second revision, an overall success of 96.9%. Two patients elected to have their implants removed. Dislocation after revision of failed total hip replacement is a complex issue. There is often no single cause and no simple solution. The angle-bore acetabular component, in combination with a 22.225-mm diameter femoral head, offers a high level of success.

Acetabulum↗

PubMed2006

The Charnley hip replacement -- 43 years of clinical success.

The Charnley low-frictional torque arthroplasty of the hip with 22.225 mm diameter head and thick ultra high molecular weigh polyethylene cup, both components grouted with cold curing acrylic cement, has reached 43 years of clinical success. Follow-up past 30 years is now available. Over 96% of patients are satisfied with the result. Post operative activity level is a reflection of patient selection. The neuropathic nature of the new joint does not reflect the mechanical state of the arthroplasty: regular follow-up with good quality radiographs is essential. Revisions may have to be undertaken for asymptomatic radiographic changes: a principle that must be understood and accepted before the primary procedure. The long-term problems are wear and cup loosening and strain shielding of the proximal femur. Long-term success will be further extended by understanding and practical application of the principles at the primary procedure and use of low wear materials for the articulation. The operation of total hip arthroplasty marks the beginning and not the end of treatment.

Arthroplasty, Replacement, Hip↗

PubMed2005

Low-friction arthroplasty of the hip using alumina ceramic and cross-linked polyethylene. A 17-year follow-up report.

We report the results of our continued review of 11 total hip arthroplasties using 22.225 mm alumina ceramic femoral heads on a Charnley flanged stem, articulating with chemically cross-linked polyethylene. There was an initial bedding-in of up to 0.41 mm at the articular surface in the first two years. This had not progressed further, at a minimum follow-up of 15 years. Radiographically no femoral or acetabular component showed loosening or osteolysis.

Adult↗

PubMed2004

Wear of the cup in the Charnley LFA in the young patient.

Since wear and loosening of the ultra-high-molecular-weight polyethylene cup are factors which limit the life of an arthroplasty we have attempted to identify factors associated with either low wear (0.02 mm/year or less) or high wear (0.2 mm/year or more). In a series of 1434 Charnley low-friction arthroplasties (1092 patients) 190 (13.2%) showed low wear while 149 (10.4%) showed high wear. We used chi-squared test to assess the significance of various factors. The significant factors of the low-wear group were female gender (p = 0.042), rheumatoid arthritis (p = 0.014), Charnley grade C (p = 0.03) and varus position of the stem (p = 0.003). The use of acetabular cement pressurisation (p = 0.07) and medialisation of the cup (p = 0.07) approached significance. In the high-wear group there was a predominance of men (p = 0.042) with osteoarthritis (p = 0.006) as the underlying hip pathology, and the stem in a valgus position (p = 0.023). Support of the cup by the rim of the acetabulum approached significance (p = 0.07). There was no statistical significance between the two groups for revision for aseptic loosening of the stem or fracture of the stem (p = 0.49). There was a highly significant difference (p < 0.0001) between the two groups for revision for wear and aseptic loosening of the cup, 5.3% compared with 39%. Changes in the cup geometry are probably sufficient to explain the increasing incidence of loosening and revisions with the increasing depth of penetration of the cup. There is much to be gained from the use of a low-wearing ceramic-ultra-high-molecular-weight combination. Tissue reaction to the polyethylene particles cannot be the cause of aseptic loosening of the stem.

Adolescent↗

PubMed2003

Determination of the trabecular bone direction from digitised radiographs.

There is increasing evidence for monitoring the bone trabecular structure to explain, in part, the mechanical properties of bone. Despite the emergence of Computed Tomography, a radiograph is the standard format as it is cheap and used for assessing implant performance. Furthermore, various image-processing techniques developed to assess the trabecular structure from radiographs have regained interest owing to improvements in imaging equipment. This study assessed the precision and accuracy of the Co-occurrence and Run-length matrix, Spatial-frequency and Minkowski-fractal techniques to infer the trabecular direction from radiographs. Ten clinical images of femoral neck regions were obtained from digitised pelvic radiographs and subsequently analysed. These data were also used to generate synthetic images where the trabecular thickness, separation and directions were controlled in order to calculate the accuracy of the techniques. Additionally, a Laplacian noise was added in order to infer the precision of the techniques. All methods assessed the trabecular direction with a high degree of accuracy in these synthetic images including a single direction and no noise. However, only the Spatial-frequency and Co-occurrence matrix methods performed well on the clinical and heavily corrupted synthetic images. This demonstrated the possibility of inferring a linear trabecular direction in clinical conditions.

Algorithms↗

PubMed2003

Wear of enhanced ultra-high molecular-weight polyethylene (Hylamer) in combination with a 22.225 mm diameter zirconia femoral head.

We have prospectively studied the wear of enhanced ultra-high molecular-weight polyethylene (Hylamer) in combination with a zirconia femoral head of 22.225 mm diameter on a cemented, triple-tapered, collarless, polished stem, the C Stem. The 71 patients who underwent total hip arthroplasty had a mean follow-up of six years (3 to 8). No patient died or was lost to follow-up. The clinical results were excellent with 96% of patients satisfied. There were no revisions. Two cups were considered to be loose radiologically. One was avulsed from the cement in a skiing accident, with a periprosthetic fracture of the femur, but has remained stable for more than seven years. One femur shows radiological appearances which are compatible with a healing infection. One femoral component is at risk of loosening. The mean rate of penetration of the cup was 0.22 mm/year (0.06 to 0.55). Our results appear to be within the guidelines set by the National Institute of Clinical Excellence. We have discontinued the use of Hylamer despite excellent clinical results and no revisions to date because the high initial rates of penetration did not settle to the expected low levels within the anticipated time.

Adolescent↗

PubMed2002

Charnley low-frictional torque arthroplasty in patients under the age of 51 years. Follow-up to 33 years.

Between November 1962 and December 1990 a group of 1092 patients, 668 women and 424 men, under the age of 51 years at the time of surgery, underwent 1434 primary Charnley low-frictional torque arthroplasties and are being followed up indefinitely. Their mean age at operation was 41 years (12 to 51). At the latest review in June 2001 the mean follow-up had been for 15 years 1 month. Of the 1092 patients 54 (66 hips) could not be traced, 124 (169 hips) were known to have died and 220 (248 hips) had had a revision procedure. At a mean follow-up of 17 years and 5 months, 759 patients (951 hips) are still attending. In this group satisfaction with the outcome is 96.2%. The incidence of deep infection for the whole group was 1.67%. It was more common in patients who had had previous surgery (hemi- and total hip arthroplasties excluded), 2.2% compared with 1.5% in those who had not had previous surgery, but this difference was not statistically significant (p = 0.4). There were fewer cases of deep infection if gentamicin-containing cement was used, 0.9% compared with 1.9% in those with plain acrylic cement, but this was not also statistically significant (p = 0.4). There was a significantly higher rate of revision in patients who had had previous hip surgery, 24.8% compared with 14.1% in those who had not had previous surgery (p < 0.001). At the latest review, 1.95% are known to have had at least one dislocation and 0.4% have had a revision for dislocation. The indication for revision was aseptic loosening of the cup (11.7%), aseptic loosening of the stem (4.9%), a fractured stem (1.7%), deep infection (1.5%) and dislocation (0.4%). With revision for any indication as the endpoint the survivorship was 93.7% (92.3 to 95.0) at ten years, 84.7% (82.4 to 87.1) at 15 years, 74.3% (70.5 to 78.0) at 20 years and 55.3% (45.5 to 65.0) at 27 years, when 55 hips remained 'at risk'.

Adolescent↗

PubMed2001

The effect of activity levels of total hip arthroplasty patients on socket penetration.

Survivorship of total hip arthroplasties (THAs) has been linked to penetration of the femoral head into the polyethylene acetabular cup and to polyethylene wear. The activity level of patients with THAs is considered to be an important factor affecting wear, and the purpose of this study was to explore the relationship between activity as recorded by pedometers and cup penetration. The measurement of daily activity levels of normal subjects and THA patients of various ages are discussed in another article ([1]). Subjects were monitored continuously during 2- to 4-week periods using simple pedometer devices. Patients (n = 54; mean age, 58 years) from the Centre for Hip Surgery at Wrightington Hospital for whom the penetration data also were available were included in the study. The average activity level for the patient group was 1.426 million loading cycles on each hip joint per year. Radiographic penetration measurements were compared for 81 hips in 54 patients with a mean follow-up of 13.1 years (range, 1.3-26.4 years). The overall correlation of penetration with implantation period is known to be poor, however, and did not improve significantly when the penetration was plotted against a new parameter that took account of not only implant life, but also the level of activity and patient weight. The considerable scatter of penetration levels was noted to increase with increasing implantation period, which indicates that in the multifactorial problem of polyethylene wear, other factors, particularly femoral head surface finish or polyethylene deterioration, may predominate.

Acetabulum↗

PubMed2001

Comparative study of the activity of total hip arthroplasty patients and normal subjects.

The walking activity of normal subjects and total hip arthroplasty (THA) patients from the Wrightington Hospital for Joint Disease and The General Infirmary at Leeds was assessed by means of electronic pedometers. The principal objectives were to establish the extent to which joint arthroplasty patients recover their activity relative to normal subjects and to establish the number of loading cycles to which prostheses should be subjected in joint simulator studies of implant performance. A further objective was to establish an experimental procedure for the assessment of the role of activity in contributing to the well-known scatter in the measurements of femoral head penetration into acetabular cups in in vivo studies of implant performance. The last-mentioned issue is addressed in another article ([1]). The walking activity of 2 normal subjects of disparate ages was assessed during 1 full year. It was concluded that fair estimates of activity could be achieved by recording pedometer readings during successive 2- to 4-week periods. This approach was adopted in the full assessment of the walking activity of cohorts of normal subjects and THA patients. Linear regression expressions relating the number of steps taken daily and the annual number of loading cycles on each leg to age are presented for normal subjects and THA patients. In all cases, activity declines with age, but it is shown that total joint arthroplasty is not at all restrictive on walking activity-a remarkable testimony to the efficacy of total joint arthroplasty. Attention is drawn, however, to different levels of activity of THA patients recorded in the present United Kingdom study and a similar survey conducted in California.

Activities of Daily Living↗

PubMed2001

Triple taper polished cemented stem in total hip arthroplasty: rationale for the design, surgical technique, and 7 years of clinical experience.

Successful long-term clinical results with the Charnley low-friction torque arthroplasty have identified proximal femoral strain shielding as a long-term problem to be addressed. The problem has arisen because of the load transfer by a distally supported stem that is no longer subject to fracture. To overcome this problem and improve proximal load transfer to the femur, a continuous triple-tapered stem--the C stem--was designed. This article describes the first 500 primary hip arthroplasties at a mean follow-up of 3 years, 5 months (range, 1-7 years). There have been no revisions for aseptic stem loosening, and no stem is considered to be at risk for loosening. In 20% of cases, there was subjective radiologic improvement of the bone-cement interface.

Adolescent↗

PubMed2001

Incidence of loose bodies in an osteoarthritic hip.

In a prospective study of 75 consecutive primary Charnley low friction arthroplasties carried out for osteoarthritis, loose bodies were found in nine hip joints; an incidence of 12%. Whether their presence is the cause or the effect of the condition remains unclear. Their discoid or spherical shape suggests that they were free and had been subjected to sliding or rolling motion. Those of irregular shape may have remained partly attached within the capsule, or become confined to a space.

Adult↗

PubMed2000

Fatal pulmonary embolism and mortality after revision of failed total hip arthroplasties.

To assess the effect of extensive surgery and delayed mobilization on postoperative incidence of fatal pulmonary embolism, we reviewed the mortality rate in 1,294 patients undergoing 1,483 revisions of failed total hip arthroplasties, in which mobilization of the patients was delayed for up to 3 weeks. There were 6 deaths (mortality rate, 0.4%). All were submitted to autopsy; only 1 death was the result of pulmonary embolism. The results of our review do not support the view that more extensive surgery and delayed mobilization of the patient, as in revision of failed total hip arthroplasties, carries a high incidence of fatal pulmonary embolism.

Arthroplasty, Replacement, Hip↗

PubMed2000

Charnley low-friction arthroplasty with an autograft of the femoral head for developmental dysplasia of the hip. The 10- to 15-year results.

Between 1983 and 1988 we carried out 45 Charnley low-friction arthroplasties with autografts from the femoral head in 41 patients for developmental dysplasia of the hip. The preoperative radiographs were assessed for the severity of DDH according to the classifications of Crowe et al, Hartofilakidis et al and Sharp. The postoperative and follow-up radiographs were analysed for coverage of the socket by the graft, for loosening and for the outcome of the fixation of the bone graft. Two patients died (two hips) at four and seven years after THR from causes unrelated to the surgery and were excluded from the final radiological analysis. The mean age of the patients at the time of operation was 46 years 3 months. The autograft of the femoral head covered a mean 26% (16 to 35) of the acetabular component. All the grafts united. Some degree of resorption of the bone graft occurred in 27 patients, and always involved the lateral part of the graft, which was beyond the margin of the socket. After a mean follow-up of 11 years there had been no revisions and 38 patients had no pain or only slight discomfort. One socket migrated and four others were fully demarcated. Our findings indicate that the Charnley LFA with an autograft of the femoral head for DDH remains successful at a follow-up of 15 years.

Adult↗

PubMed2000

Revision of failed total hip arthroplasty with a proximal femoral modular cemented stem.

We have designed a modular cemented femoral component for revision of failed total hip arthroplasty in which deficiency of the proximal femur is such as to require a variable extrafemoral portion of the stem. We present the results of the first 74 operations in 72 patients; 56 of the patients had grade-3 or grade-4 femoral deficiency as defined by Gustilo and Pasternak and 24 had fractures of the proximal femur, of which 22 were periprosthetic. There was or had been infection in 19 hips. At a mean follow-up of 5 years 9 months (1 to 12 years) nine stems were radiologically loose of which three had been revised. There were no failures in 45 cases in which there was fixation of the distal stem of 10 cm or more. Dislocation occurred in nine patients and there were four cases of infection in the 19 which were, or had been, infected previously. There were no neurovascular complications and no intraoperative femoral fractures. The femoral bone stock improved radiologically in 45 hips of which 29 showed considerable reformation of the proximal femur; 27 remained unchanged and two showed increasing osteoporosis.

Adult↗

PubMed2000

The calcar femorale in cemented stem fixation in total hip arthroplasty.

The calcar femorale is a vertical plate of bone lying deep to the lesser trochanter and is formed as a result of traction of the iliopsoas which separates the femoral cortex into two distinct layers, the calcar femorale and the medial femoral cortex. They fuse together proximally to form the medial femoral neck. A stem placed centrally will abut against the calcar femorale with little or no space for cement. Clearing of the calcar will offer space for a cement layer, which will support the stem proximally on the posterior aspect. We compared two consecutive groups of Charnley low-friction arthroplasties, with and without clearing of the calcar. In 330 patients who had an arthroplasty without clearing the calcar, there were ten revisions for aseptic loosening of the stem and six other stems were considered 'definitely loose', giving a rate of failure of 4.8%. In 111 patients in whom the calcar was cleared there was only one revision for aseptic loosening and no stems were classed as 'definitely loose', giving a rate of failure of 0.9%. Survivorship analysis has again shown the need for long-term follow-up; the differences became clear after ten years but because of the relatively small numbers, statistical analysis is not yet applicable. We now clear the calcar femorale routinely and advocate optimal access to the medullary canal and insertion of the stem in the area of the piriform fossa.

Adolescent↗

PubMed1999

Discrepancy in the length of the tibiae in unilateral congenital dislocation of the hip.

We measured discrepancy in the length of the tibiae in cases of unilateral congenital dislocation of the hip (CDH) in 10 patients. The mean shortening of the tibia on the affected side was 1 cm and was not related to the severity of the dislocation. Patients who are about to undergo total hip arthroplasty for CDH should be warned that the operation is unlikely to restore normal leg length.

Adult↗

PubMed1999

Low-friction arthroplasty of the hip using alumina ceramic and cross-linked polyethylene. A ten-year follow-up report.

We report the results of our continued review of 14 hip arthroplasties using alumina ceramic femoral heads with cross-linked polyethylene cups. There have been no complications and a very low rate of penetration. This was 0.02 mm per year after an initial 'bedding-in' period of two years. There has been no change in the mean rate between our earlier study at six years and the current results at 10 to 11 years. The use of these bearing surfaces appears to reduce the potential amount of polyethylene debris and may provide the next logical stage in the development of the Charnley low-friction arthroplasty.

Adult↗

PubMed1999

Charnley low-frictional torque arthroplasty of the hip. 20-to-30 year results.

We reviewed 261 patients with 320 Charnley low-friction arthroplasties who had a mean follow-up of 22 years 10 months (20 to 30). Of these, 93.9% considered the operation to be a success; 82.3% were free from pain and 11.6% had occasional discomfort. Satisfactory function was achieved in 59.6% and 62% had an excellent range of movement. The clinical results did not correlate well with the radiological appearance; radiologically loose components did not affect the clinical outcome. The main long-term problem was wear and loosening of the UHMWPE cup. Our findings suggest that the radiological appearance of the arthroplasty is a more reliable indication of the state of the arthroplasty than the clinical results.

Adolescent↗