Metal-on-metal (MOM) hip joints have regained a favor in arthroplasty since they own excellent wear resistance. In this study, wear tests by using a hip joint simulator were conducted with MOM bearings of specified 40 mm femoral heads. The influence of clearance on the wear behavior was investigated. Furthermore, an optimized radial clearance was estimated by lubricant film thickness and contact pressure analysis. Co-27Cr-5Mo-0.13N-0.05C (hereafter CCMN) alloy (mass %) was used. The ingots were vacuum induction melted, homogenized and hot forged successively. The microstructure shows equiaxed crystal grains with abundant annealing twins but no carbides. Two groups of bearings, indicated as The contact pressures on the hip joints were also analyzed by using ABAQUS. The femoral heads were set 40 mm with radial clearances of 0–200 μm. Half models were set up and only the maximum force of 3 kN converted as pressure was applied as boundary condition.Introduction
Materials and methods
We evaluated the impact of pre-coating the tibial
component with polymethylmethacrylate (PMMA) on implant survival
in a cohort of 16 548 primary NexGen total knee replacements (TKRs)
in 14 113 patients. In 13 835 TKRs a pre-coated tray was used while
in 2713 TKRs the non-pre-coated version of the same tray was used.
All the TKRs were performed between 2001 and 2009 and were cemented.
TKRs implanted with a pre-coated tibial component had a lower cumulative
survival than those with a non-pre-coated tibial component (p =
0.01). After adjusting for diagnosis, age, gender, body mass index,
American Society of Anesthesiologists grade, femoral coupling design, surgeon
volume and hospital volume, pre-coating was an independent risk
factor for all-cause aseptic revision (hazard ratio 2.75, p = 0.006).
Revision for aseptic loosening was uncommon for both pre-coated
and non-pre-coated trays (rates of 0.12% and 0%, respectively).
Pre-coating with PMMA does not appear to be protective of revision
for this tibial tray design at short-term follow-up. Cite this article:
Anterior only procedure for stable thoraco-lumbar burst fractures is controversial. Prospective collection of clinical and radiological data in stable burst fractures with neurological deficit undergoing anterior only decompression and stabilisation with 2-year follow-up. 14 consecutive patients (8 females, 6 males) with two-column thoracolumbar burst fracture and neurological deficit underwent anterior corpectomy/hemi-corpectomy and instrumentation, from February 2007 to February 2009. Radiological data included classification of fracture (AO classification), kyphus angle and degree of canal compromise. Post-operative CT scans done to assess radiological improvement. Clinical data included neurological deficit at presentation, improvement or changes in neurology, length of surgery, estimated blood loss, post-operative complications and length of stay. Commonest mechanism was fall from height. 10 patients had incomplete burst fractures amenable to hemi-corpectomy. 8 of our patients were ASIA D, 4 were ASIA C or lower. They all improved by at least one grade. 2 patients had identical ASIA grade pre and post operatively. Pre-operative spinal canal compromise averaged 52.6% and vertebral body height loss averaged 48.9%. The mean kyphotic angles improved from 19.6° to 7.9 °. There were two cases with minor injury to the diaphragm, one developing a pneumothorax. Mean length of surgery and hospital stay were 4hours and 21minutes and 11.8 days respectively. The fractures in which the top part is burst and causing canal compromise, could be dealt with by top hemi-corpectomy requiring smaller approach. One stage anterior – only stabilization can yield successful clinical results.
Magnetic Resonance Imaging (MRI) is the cornerstone investigation for cervical disc disease (CDD). However, MRI changes suggestive of CDD are found in people above forty, even in asymptomatic healthy individuals [1]. Mere presence of MRI changes of CDD does not exclude the presence of concomitant extra-foraminal pathology. No study design. We present here a series of three cases where use of ‘high resolution ultrasound’ has allowed accurate diagnosis of concomitant extra-foraminal pathology in patients with MRI-proven CDD. The three cases were acute neuropraxia of aberrant C5 nerve root, anterior interossous nerve compression due to pseudo-aneurysm of brachial artery and ‘acute brachial neuritis’ respectively. No outcome measure. Use of diagnostic high resolution ultrasound revealed accurate diagnosis of concomitant extra-foraminal pathology in all three cases. The cases with acute neuropraxia and acute brachial neuritis recovered with conservative treatment. Pseudo-aneurysm was treated successfully with surgery. High resolution ultrasound of the brachial plexus and peripheral nerves may be useful in following scenarios to identify an extra-foraminal pathology: (1) when symptoms and signs are out of proportion to the MRI findings of CDD; (2) when there is obvious discordance between MRI and nerve conduction findings; (3) where an entrapment neuropathy is suspected but the site of nerve lesion cannot be located.
The patellofemoral joint is an important source of symptoms in osteoarthritis of the knee. We have used a newly designed surgical model of patellar strengthening to induce osteoarthritis in BALB/c mice and to establish markers by investigating the relationship between osteoarthritis and synovial levels of matrix metalloproteinases (MMPs). Osteoarthritis was induced by using this microsurgical technique under direct vision without involving the cavity of the knee. Degeneration of cartilage was assessed by the Mankin score and synovial tissue was used to determine the mRNA expression levels of MMPs. Irrigation fluid from the knee was used to measure the concentrations of MMP-3 and MMP-9. Analysis of cartilage degeneration was correlated with the levels of expression of MMP. After operation the patellofemoral joint showed evidence of mild osteoarthritis at eight weeks and further degenerative changes by 12 weeks. The level of synovial MMP-9 mRNA correlated with the Mankin score at eight weeks, but not at 12 weeks. The levels of MMP-2, MMP-3 and MMP-14 mRNA correlated with the Mankin score at 12 weeks. An increase in MMP-3 was observed from four weeks up to 16 weeks. MMP-9 was notably increased at eight weeks, but the concentration at 16 weeks had decreased to the level observed at four weeks. Our observations suggest that MMP-2, MMP-3 and MMP-14 could be used as markers of the progression of osteoarthritic change.
