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Biomedical subjects

A J Hamer

Publications and source records attributed to A J Hamer.

At least 19 recordsLinked to original sources
PubMed2006

Clinical and radiological outcome of total hip replacement five years after pamidronate therapy. A trial extension.

Bisphosphonates reduce peri-prosthetic bone loss in the short term after total hip replacement but the mid- and longer term effects are not known. The aims of this randomised trial were to examine the effect of a single dose of 90 mg of pamidronate on the clinical and radiological outcome and peri-prosthetic bone mineral density in 50 patients (56 hips) over a five-year period, following total hip replacement. At five years, 37 patients (42 hips) returned for assessment. The Harris hip scores were similar in the pamidronate and placebo groups throughout the study. Also at five years, four patients, two from each group had osteolytic lesions on plain radiography. These were located around the acetabular component in three patients and in the femoral calcar in one. The femoral and acetabular peri-prosthetic bone mineral density in the pamidronate group and the control group was similar at five years. Pamidronate given as a single post-operative dose does not appear to influence the clinical outcome or prevent the development of osteolytic lesions at five years after total hip replacement.

Absorptiometry, Photon↗
PubMed2006

Bone remodelling around a cemented polyethylene cup. A longitudinal densitometry study.

The aims of this study were to examine the repeatability of measurements of bone mineral density (BMD) around a cemented polyethylene Charnley acetabular component using dual-energy x-ray absorptiometry and to determine the longitudinal pattern of change in BMD during the first 24 months after surgery. The precision of measurements of BMD in 19 subjects ranged from 7.7% to 10.8% between regions, using a four-region-of-interest model. A longitudinal study of 27 patients demonstrated a transient decrease in net pelvic BMD during the first 12 months, which recovered to baseline at 24 months. The BMD in the region medial to the dome of the component reduced by between 7% and 10% during the first three months, but recovered to approximately baseline values by two years. Changes in BMD in the pelvis around cemented acetabular components may be measured using dual-energy x-ray absorptiometry. Bone loss after insertion of a cemented Charnley acetabular component is small, transient and occurs mainly at the medial wall of the acetabulum. After two years, bone mass returns to baseline values, with a pattern suggesting a uniform transmission of load to the acetabulum.

Absorptiometry, Photon↗
PubMed2006

Total hip replacement in a patient with systemic mastocytosis: a case report.

Systemic mastocytosis is a rare condition that often involves the bone marrow. We report the case of a patient with systemic mastocytosis who underwent total hip replacement. Technical difficulties encountered during the procedure included a narrow medullary canal and abnormally hard bone, later confirmed by laboratory measurements. Follow-up at five years showed a good clinical and radiological outcome.

Arthroplasty, Replacement, Hip↗
PubMed2005

Changes in bone mass and bone turnover following tibial shaft fracture.

INTRODUCTION: Bone loss occurs in the regional bone following tibial shaft fracture. An earlier cross-sectional study showed that measurements made at the metaphyseal region of the tibia using peripheral quantitative computed tomography (pQCT) and the ultradistal region of the tibia using dual-energy X-ray absorptiometry (DXA) were the most responsive at monitoring this bone loss. Biochemical markers of bone turnover enable us to assess the activity of bone formation and resorption during fracture healing. The aim of this longitudinal study was to determine the pattern and distribution of bone loss and bone turnover following a tibial shaft fracture treated with either plaster cast or intramedullary nail. METHODS: Eighteen subjects underwent bone mass measurements using DXA at the tibia and hip and quantitative ultrasound (QUS) at the tibia and calcaneus of both limbs at 2 weeks, 8 weeks, 12 weeks and 24 weeks following fracture, with hip and tibia DXA measurements also performed at 52 weeks. Nine of the patients treated with plaster cast had pQCT measurements at the tibia at 24 weeks. We measured three bone formation markers, bone alkaline phosphatase (bone ALP), osteocalcin (OC) and procollagen type 1 N-terminal peptide (PINP), a marker of bone resorption, serum C-telopeptides of type 1 collagen (beta-CTX) and a marker of collagen III turnover, procollagen type III N-terminal peptide (PIIINP) at 1 day, 3 days and 7 days and at 2, 4, 8, 12, 16 and 24 weeks following fracture. The greatest bone losses were observed at the ultradistal region of the tibia using DXA (28%, p <0.001) and the metaphyseal region of the tibia using pQCT (26-31%, p <0.001) at 24 weeks. In the hip, the greatest loss was in the trochanter region at 24 weeks (10%, p <0.001). The greatest loss at the calcaneus measured using QUS was for broadband ultrasound attenuation (BUA) measured using CUBA Clinical at 24 weeks (13%, p =0.01). RESULTS: At 1 year, there was a small recovery in bone loss (ultradistal tibia DXA, 20%, p <0.01; trochanter DXA 9%, p <0.001). Bone turnover increased following fracture (PINP +72+/-21%, p <0.0001, bone ALP +199+/-22%, p =0.004, beta-CTX +105+/-23%, p <0.0001, all at 24 weeks). There was a smaller +33+/-10% increase in osteocalcin at 24 weeks. PIIINP concentration peaked at week 8 (+57+/-9%, p <0.0001). The bone resorption marker beta-CTX showed an earlier rise (week 2, 139+/-33%) than the bone formation markers. CONCLUSIONS: We conclude that: (1) bone loss following tibial shaft fracture occurs both proximal and distal to the fracture; (2) the decreased BMD is largest for trabecular bone in the tibia with similar measurements using DXA and pQCT; (3) there is limited recovery of bone lost at the hip and tibia at 1 year; (4) tibial speed of sound (SOS) demonstrated a greater decrease than calcaneal SOS when comparing z -scores; (5) BUA is the QUS variable that shows the biggest decrease of bone mass at the calcaneus; (6) increase in bone turnover occurs following fracture with an earlier increase in bone resorption markers and a later rise in bone formation markers.

Absorptiometry, Photon↗
PubMed2005

Irradiated allograft bone for acetabular revision surgery. Results at a mean of five years.

We report the results of the revision of 123 acetabular components for aseptic loosening treated by impaction bone grafting using frozen, morsellised, irradiated femoral heads and cemented sockets. This is the first large series using this technique to be reported. A survivorship of 88% with revision as the end-point after a mean of five years is comparable with that of other series.

Adult↗
PubMed2002

Precision of EBRA-Digital software for monitoring implant migration after total hip arthroplasty.

We assessed the precision of the EBRA-Digital software (EBRA, University of Innsbruck, Innsbruck, Austria) for measuring implant migration after total hip arthroplasty. Study subjects (n = 29) underwent consecutive, standardized, plain radiographic examinations of the hip on the same day after repositioning. The resulting radiograph pairs were digitized and analyzed using EBRA. The precision (95% confidence interval) of the method for measuring migration and wear was <+/-0.9 mm for both implant components. The 95% confidence intervals for measurement of cup inclination and anteversion and femoral stem/shaft angle were <+/-1.7 degrees. Measurement precision was not strongly related to patient gender, digitization method, or observer. The EBRA-Digital method has sufficient precision to detect clinically relevant migration to allow individual patient monitoring after total hip arthroplasty. The method requires careful patient positioning and radiographic technique to produce consistently images suitable for analysis.

Arthroplasty, Replacement, Hip↗
PubMed2001

Effect of pamidronate in preventing local bone loss after total hip arthroplasty: a randomized, double-blind, controlled trial.

Acute periprosthetic bone loss occurs after total hip arthroplasty. Bone loss undermines the support of the implant and may contribute to prosthetic failure. At present, there is no established prophylaxis for this process. We studied the effect of a single-dose infusion of 90 mg of pamidronate on early periprosthetic bone mineral density (BMD), biochemical markers of bone turnover, radiological, and clinical outcome in a 26-week, prospective, randomized, double-blinded study of 47 men and women undergoing total hip arthroplasty. Pamidronate therapy led to a significant reduction in bone loss compared with placebo for both the proximal femur and the pelvis (repeated measures analysis of variance [ANOVA]); p = 0.001 and p = 0.01, respectively). Pamidronate therapy was associated with suppression of all biochemical markers of bone turnover compared with placebo (repeated measures ANOVA; p < 0.05 for all comparisons), with the exception of urinary free deoxypyridinoline. Pamidronate did not interfere with the clinical improvement in symptoms after total hip arthroplasty, or radiological outcome, and was not associated with an increase in adverse events. This study provides clinical data on the efficacy and safety of bisphosphonates for the prevention of bone loss after total hip arthroplasty and supports the establishment of larger-scale clinical trials to determine the long-term clinical efficacy of this intervention using implant failure as the primary endpoint.

Aged↗
PubMed2000

Effect of mixing technique on the properties of acrylic bone-cement: a comparison of syringe and bowl mixing systems.

Syringe mixing systems have been introduced, but few data exist regarding the mechanical performance of cement they produce. We compared the properties of polymethyl methacrylate cement produced by these systems with that produced by a multiaxial bowl. Mixtures of cement were prepared using the Optivac, Cemvac, and Summit syringes and the Summit bowl. The mixtures were cured in molds to create casts that were radiographed and analyzed for void content, then cut into strips, weighed, measured, and tested to failure in 4-point bending. Syringe-mixed cement was of greater density, bending modulus, and bending strength than bowl-mixed cement (Mann-Whitney, P < .01) and contained fewer microvoids and macrovoids (Mann-Whitney, P < .01). No significant differences between the syringes were found for these variables (Kruskall-Wallis, P > .05).

Bone Cements↗
PubMed1999

The role of collagen in the declining mechanical properties of aging human cortical bone.

The importance of the mechanical role of collagen in bone is becoming increasingly more clear as evidence mounts on the detrimental effects of altered collagen on the mechanical properties of bone. We previously examined a set of mechanical properties (material stiffness, strength, and toughness) of human femoral bone (ages 35-92) and found that a gradual deterioration in these properties occurs with age. The present study examines the collagen of the same specimens and relates the collagen properties to the mechanical ones. In the collagen we measured the concentration of stable mature crosslinks, the shrinkage temperature, and the rate of contraction during isometric heating. The changes in the concentration of mature (pyridinium and deoxypyridinium) crosslinks showed no clear relationship to age nor did they correlate with the mechanical properties. The shrinkage temperature declined with age and correlated with a bone's toughness. The maximum rate of contraction was strongly correlated with three different measures of tissue toughness, but much less to stiffness and strength. Our results reinforce speculation regarding the toughening role of collagen in bone mechanics and suggest that the fragility of aging bone may be related to collagen changes.

Adult↗
PubMed1999

Changes in allograft bone irradiated at different temperatures.

Secondary sterilisation of allograft bone by gamma irradiation is common, but the conditions under which it is performed vary between tissue banks. Some do so at room temperature, others while the bone is frozen. Bone is made brittle by irradiation because of the destruction of collagen alpha chains, probably mediated by free radicals generated from water molecules. Freezing reduces the mobility of water molecules and may therefore decrease the production of free radicals. We found that bone irradiated at -78 degrees C was less brittle and had less collagen damage than when irradiated at room temperature. These findings may have implications for bone-banking.

Adult↗
PubMed1997

Histologic evidence of cortical allograft bone incorporation in revision hip surgery.

There is no published evidence concerning the histology of cortical allograft bone implanted during revision arthroplasty surgery. Five cases are reported in which cortical allograft bone had been used where biopsies were available between 2 and 27 months after implantation. All cases showed favorable histologic features, with soft tissue attachment by fibrous adhesion, union of graft to host, and osseous remodeling.

Adult↗
PubMed1997

Detection of glove puncture and skin contamination during caesarean section.

Measures that can be taken to reduce exposure to potentially infected body fluids are of particular relevance in obstetric and gynaecological surgery due to high rates of glove puncture and relatively higher prevalence of human immunodeficiency virus seropositivity in the obstetric age group. We describe the use of a simple electronic device that alarms following puncture of surgical gloves or the creation of a fluid bridge between surgeon and patient. Further exposure to potentially infected body fluids is thus prevented. This present study was performed in the context of caesarean section, but the application of the technique to gynaecological procedures is appropriate.

Cesarean Section↗
PubMed1996

Biochemical properties of cortical allograft bone using a new method of bone strength measurement. A comparison of fresh, fresh-frozen and irradiated bone.

There have been conflicting reports on the effects of gamma irradiation on the material properties of cortical allograft bone. To investigate changes which result from the method of preparation, test samples must be produced with similar mechanical properties to minimise variations other than those resulting from treatment. We describe a new method for the comparative measurement of bone strength using standard bone samples. We used 233 samples from six cadavers to study the effects of irradiation at a standard dose (28 kGy) alone and combined with deep freezing. We also investigated the effects of varying the dose from 6.8 to 60 kGy (n = 132). None of the treatments had any effect on the elastic behaviour of the samples, but there was a reduction in strength to 64% of control values (p < 0.01) after irradiation with 28 kGy. There was also a dose-dependent reduction in strength and in the ability of the samples to absorb work before failure. We suggest that irradiation may cause an alteration in the bone matrix of allograft bone, but provided it is used in situations in which loading is within its elastic region, then failure should not occur.

Adolescent↗
PubMed1993

Whiplash injury and surgically treated cervical disc disease.

The incidence of a previous whiplash injury in 215 unselected patients who underwent an anterior cervical discectomy and fusion between 1988 and 1991 was found to be twice that of a control population of 800 general orthopaedic outpatients (P < 0.05). The mean age at which the whiplash injury occurred in the surgical group was 37 years and in the control group 36 years. The mean age at operation of those patients with a previous whiplash injury (45 +/- 12 years) was significantly less than those patients without a previous whiplash injury (55 +/- 14 years, P < 0.001). This study provides further evidence that whiplash injury causes structural changes predisposing to premature degenerative disc disease.

Adult↗