No changes in bone mineral density following total knee arthroplasty using an all-polyethylene tibial component.

PURPOSE: Polyethylene particles produced from metal-backed tibial (MBT) implants are understood to contribute to bone loss and component loosening. This, along with advanced surgical techniques, improved materials and increasing costs, has renewed interest in all-polyethylene tibias (APTs). We investigated peri-APT bone mineral density (BMD) in patients, expecting to find no differences between two post-operative values. METHODS: Patients over 65 years, with BMI ≤ 37.5 kg/m2 and no previous joint replacements were recruited to have computer-navigated total knee arthroplasty using an APT. The study cohort (n = 27) had mean age of 71.9 (SD 4.35) and BMI of 31.2 (SD 3.8). The BMD examinations were performed 6 weeks and 18 months post-operatively. Six regions of interest (ROI) were identified on anterior/posterior and lateral dual-energy X-ray absorptiometry scans. For each ROI, BMD relative differences (RDs) were determined between limbs and RDs at the two time points were compared. RESULTS: No differences were found between the RDs for any ROI. No revisions or complications were reported. At 18 months post-operatively, 79.2% of the cohort were very satisfied or satisfied with the outcome of their surgery and Oxford Knee Scores improved significantly compared to pre-operatively (p < 0.001). Mean knee range of motion was 102° (SD 10.7°), and mean leg alignment was 2.0° valgus (1-6°valgus). CONCLUSION: Results from BMD analysis suggest that implants were well fixated without compromising function. We believe that using APTs with computer navigation is a viable cheaper option to MBTs for patients who are less active, have lower BMI and good bone quality.

Patient compliance with hip precautions 12 weeks following primary elective total hip arthroplasty.

INTRODUCTION: Patients are routinely advised to follow hip precautions following their total hip arthroplasty (THA) surgery. There is lack of evidence regarding compliance with these precautions and when patients return to activities of daily living following their surgery. MATERIALS AND METHODS: We designed a new questionnaire to discover when patients return to their activities of daily living. Two hundred and ninety seven consecutive patients who attended 12 week follow up arthroplasty clinic following their primary elective THA were asked to complete the questionnaire. RESULTS: All patients who attended the follow up clinic at 12 weeks responded to the questionnaire. Only 6.3% (n = 19) of the patients reported that they restricted their daily activities, as prescribed for the full 12 week period, while 50% (n = 148) of patients stopped using prescribed adaptive equipment by 6 weeks after their operation. There were no dislocations recorded among the study group. CONCLUSION: We found that the majority of patients do not adhere to hip precautions advice. They return to their activities of daily living prior to the end of prescription period based on their pain and activity level. Lack of adherence to hip precautions do not predispose to hip dislocation in the immediate post-operative period.

Analysis of Osteoclastogenesis/Osteoblastogenesis on Nanotopographical Titania Surfaces.

A focus of orthopedic research is to improve osteointegration and outcomes of joint replacement. Material surface topography has been shown to alter cell adhesion, proliferation, and growth. The use of nanotopographical features to promote cell adhesion and bone formation is hoped to improve osteointegration and clinical outcomes. Use of block-copolymer self-assembled nanopatterns allows nanopillars to form via templated anodization with control over height and order, which has been shown to be of cellular importance. This project assesses the outcome of a human bone marrow-derived co-culture of adherent osteoprogenitors and osteoclast progenitors on polished titania and titania patterned with 15 nm nanopillars, fabricated by a block-copolymer templated anodization technique. Substrate implantation in rabbit femurs is performed to confirm the in vivo bone/implant integration. Quantitative and qualitative results demonstrate increased osteogenesis on the nanopillar substrate with scanning electron microscopy, histochemical staining, and real-time quantitative reverse-transcription polymerase chain reaction analysis performed. Osteoblast/osteoclast co-culture analysis shows an increase in osteoblastogenesis-related gene expression and reduction in osteoclastogenesis. Supporting this in vitro finding, in vivo implantation of substrates in rabbit femora indicates increased implant/bone contact by ≈20%. These favorable osteogenic characteristics demonstrate the potential of 15 nm titania nanopillars fabricated by the block-copolymer templated anodization technique.

Posterior dislocation of long head of biceps tendon following traumatic anterior shoulder dislocation: imaging and intra-operative findings.

A case of posterior dislocation of the long head of biceps tendon, a rare occurrence following traumatic anterior glenohumeral dislocation, along with complete rotator cuff rupture and large haemarthrosis is presented with imaging and intra-operative findings. The interposed tendon prevented complete reduction. Appearances at MRI were diagnostic and directed the surgical approach.

Large-scale population-based study shows no association between common polymorphisms of the TGFB1 gene and BMD in women.

UNLABELLED: The TGFB1 gene is a strong functional candidate for regulating genetic susceptibility to osteoporosis. We studied five common polymorphisms of TGFB1 in relation to osteoporosis-related phenotypes in a population-based cohort of 2975 British women, but found no significant association with bone mass, bone loss, bone markers, or fracture. INTRODUCTION: The gene encoding TGFB1 is a strong functional candidate for genetic susceptibility to osteoporosis. Several polymorphisms have been identified in TGFB1, and previous work has suggested that allelic variants of TGFB1 may regulate BMD and susceptibility to osteoporotic fracture. MATERIALS AND METHODS: We studied the relationship between common polymorphisms of TGFB1 and several osteoporosis-related phenotypes including BMD at the lumbar spine and femoral neck, measured by DXA; bone loss over a 6-year period; biochemical markers of bone turnover (urinary free deoxypyridinoline and free pyridinoline/creatinine ratio and serum N-terminal propeptide of type 1 collagen), and fractures in a population-based study of 2975 women from the United Kingdom. Participants were genotyped for single nucleotide polymorphisms (SNPs) in the TGFB1 promoter (G-800A; rs1800468; C-509T; rs1800469), exon 1 (T29C; rs1982073 and G74C; rs1982073); and exon 5 (C788T; rs1800471) on PCR-generated fragments of genomic DNA. Haplotypes were constructed from genotype data using the PHASE software program, and genotypes and haplotypes were related to the phenotypes of interest using general linear model ANOVA, with correction for confounding factors including age, height, weight, menopausal status, hormone replacement therapy (HRT) use, physical activity score, and dietary calcium intake. RESULTS: The polymorphisms were in strong linkage disequilibrium, and four common haplotypes accounted for >95% of alleles at the locus. There was no association between individual SNPs and BMD, bone loss, or biochemical markers of bone turnover. Haplotype analysis showed a nominally significant association with femoral neck BMD (p = 0.042) and with incident osteoporotic fracture (p = 0.013), but these were not significant after correcting for multiple testing. CONCLUSIONS: Common polymorphic variants of the TGFB1 gene did not influence BMD or bone loss in this population.

Femoral neck shape and the spatial distribution of its mineral mass varies with its size: Clinical and biomechanical implications.

The femoral neck (FN) is a cantilever with external and internal dimensions determining its size, shape, the spatial distribution of the mineralized cortical and trabecular bone tissue mass, and its strength. Geometric indices of FN strength are often derived using FN dimensions estimated in vivo from dual X-ray absorptiometry (DXA) assuming that the FN cross section approximates a circle or a square. As DXA does not measure FN depth, we examined whether circular, square, or elliptical models of FN cross sections predict FN depth, and so its external volume, shape, volumetric bone mineral density (vBMD), and geometric indices of strength. We studied paired FN specimens from 13 Caucasian female cadavers (mean age 69 years, range 29 to 85) using DXA, micro-computed tomography (mu-CT), and direct calliper measurements. DXA accurately measured FN width (supero-inferior diameter) but models assuming a circular and a square cross section overestimated FN depth (antero-posterior diameter) and volume, and so underestimated vBMD by 15.0 +/- 5.8% (circular cross section) and by 33.2 +/- 4.6% (square cross section) (both P < 0.05). As depth was less than the width, an elliptical model with a constant depth/width ratio of 0.75 reduced the accuracy error in vBMD to 14.0 +/- 8.5% (P = 0.10). However, as FN width increased, FN depth increased relatively less. An elliptical model using a quadratic equation to mimic this changing in shape with increasing size reduced the error in vBMD to 4.4 +/- 7.7% (NS). Circular cross-section models overestimated section modulus at the mid-FN by about 51%. The elliptical models reduced the error two- to three fold. Images from micro-CT scanning show that the FN cross-sectional shape resembles an ellipse with the long axis and the maximum moment of inertia (I(max)) oriented in the supero-inferior direction, and the cortical mass concentrated inferiorly. The larger the cross section, the more elliptical the shape, and the greater the I(max) supero-inferiorly, while I(min) (in the antero-posterior direction) remains relatively constant. The shape, spatial distribution of bone, and moments of inertia are likely to be adaptations to bending moments during bipedalism. Assuming the FN cross section approximates a circle or square produces errors in FN depth, volume, vBMD, and geometric indices of bone strength. Studies are needed to determine the effects of age, sex, and race on FN size and shape in health and disease.