Mediolateral subchondral tibial bone mineral density difference does not predict osteoarthritis progression.

Data on the relationship between osteoporosis and osteoarthritis are conflicting. Most studies report "snapshot" prevalences, and there are few studies evaluating localized knee bone mineral density (BMD) measurements with respect to subsequent osteoarthritis progression. The authors hypothesize that increased mediolateral difference of the proximal tibial BMD may predict progression of knee osteoarthritis. In this study, 246 female volunteers were followed up prospectively over 2 years. Baseline BMD measurements of bilateral proximal (subchondral) tibiae were performed, and the mediolateral BMD ratio was calculated. Precision studies were performed on healthy volunteers to validate the technique. The patients were divided into osteoarthritis progressors and non-progressors based on Kellgren-Lawrence radiographic criteria at 2-year follow-up. Patients who were taking bisphosphonates or who had a history of inflammatory, infectious, or metabolic bone disease and previous hip and knee surgery were excluded. Demographic data, calcium supplementation, physical activity, baseline knee radiographs, and radiographs at 2-year follow-up were obtained. The study was adequately powered to detect an effect size of 0.4. There were 121 progressors and 125 non-progressors. Mean mediolateral BMD ratio was 1.02 among the progressors and 1.01 among the non-progressors (t=0.632, P=.528). Potential confounders were equally distributed among both groups. The data suggest that there is no link between proximal tibial BMD ratio and progression of knee osteoarthritis.

Total hip replacement using a highly crosslinked polyethylene liner in Asians with small acetabulum.

PURPOSE: To evaluate the medium-term outcomes of total hip replacement (THR) using a thin highly cross-linked polyethylene (HXLPE) liner in an Asian population. METHODS: Medical records of 20 men and 44 women aged 26 to 80 (mean, 59) years who underwent 80 THRs using a thin HXLPE liner by a single surgeon were reviewed. Indications for THR included dysplasia (n = 26), avascular necrosis (n=26), osteoarthritis (n = 22), rheumatoid arthritis (n = 4), and ankylosing spondylitis (n = 2). The surgical technique, implant used, and rehabilitation protocol were standardised. Radiographs were evaluated for cup migration and peri-implant radiolucency. Femoral head penetration was assessed at day 1 and last follow-up using the Kang modification of the Dorr and Wan method and the PowerPoint method. RESULTS: After a mean follow-up of 7.5 (range, 5.0-11.9) years, no patient had undergone acetabular revision. Two hips were revised for the femoral stem. Femoral head penetration did not correlate with sex, age at surgery, hip pathology, acetabular inclination angle, cup size, or liner thickness. The maximum femoral head penetration was 0.09 mm/year, which was below the osteolysis threshold of 0.1 mm/year. The mean ± standard deviation femoral head penetration was 0.29 ± 0.12 mm (or 0.04 ± 0.02 mm/year) by the PowerPoint method and 0.17 ± 0.22 mm (or 0.02 ± 0.03 mm/year) by the Kang modification of the Dorr and Wan method. Femoral head penetration correlated with the number of years of follow-up (p = 0.012). CONCLUSION: The use of a thin HXLPE liner in primary THR for patients with small acetabulum achieved good outcomes after a mean of 7.5 years.

Localized sclerotic bone response demonstrated reduced nanomechanical creep properties.

Sclerosis (tissue hardening) development is a common occurrence in slow growing or benign osteolytic lesions. However, there is lack of knowledge on the mechanical and material property changes associated with sclerotic bone response. The immune system is postulated to play a relevant role in evoking sclerotic bone responses. In this study, localized sclerotic response in an immunocompetent model of Walker 256 breast carcinoma in SD rats showed an apparent increase in new reactive bone formation. Sclerotic rat femurs had significant increases in bone mineral density (BMD), bone mineral content (BMC), bone volume fraction (BV/TV), bone surface density (BS/TV), trabecular number (Tb.N) and a significant decrease in trabecular separation (Tb.Sp) and structural model index (SMI) as compared to control rat femurs. Significantly reduced creep responses (increased η) were observed for both trabecular and cortical bone in sclerotic bones while no significant difference was observed in elastic modulus (E) and hardness (H) values. Therefore, we conclude that viscoelastic creep property using nanoindentation would serve as a more sensitive indicator of localized bone modeling than elastic properties. Moreover, reduced viscoelasticity can contribute towards increased microcrack propagation and therefore reduced toughness. Since significant positive correlations between elastic properties (E) and (H) with viscosity (η) were also observed, our results indicate that sclerotic response of bone metastasis would cause reduced toughness (increased η) with stiffening of material (increased E and H).

'Not Always a Baker's Cyst' - An Unusual Presentation of a Central Voluminous Postero-Medial Meniscal Cyst.

Meniscal cysts are rare and often are a result of extrusion of synovial fluid through a tear of the meniscus, resulting in a one-way valve effect of the tear. Arthroscopic partial meniscectomy of the meniscus with intra-articular cyst drainage has become the standard of care. We report a case of an unusually large symptomatic medial meniscal cyst, situated postero-medially and pressing on the posterior cruciate ligament, which was initially clinically misdiagnosed as a Baker's cyst. The patient had difficulty and pain on squatting. He was successfully treated with arthroscopic debridement and needle decompression; a rarity in literature for such a voluminous perilabral cyst tenting the posterior cruciate ligament. This procedure has the advantage of being able to obtain the cystic fluid for histological and cytological analysis before debridement. This case also highlights the importance of the use of Magnetic Resonance Imaging (MRI) to accurately diagnose a central, posterior knee swelling.

Comparative analysis of uniplanar external fixator and retrograde intramedullary nailing for ankle arthrodesis in diabetic Charcot's neuroarthropathy.

BACKGROUND: Charcot's neuroarthropathy of ankle leads to instability, destruction of the joint with significant morbidity that may require an amputation. Aim of surgical treatment is to achieve painless stable plantigrade foot through arthrodesis. Achieving surgical arthrodesis in Charcot's neuroarthropathy has a high failure rate. This is a retrospective nonrandomized comparative study assessing the outcomes of tibio-talar arthrodesis for Charcot's neuroarthropathy treated by uniplanar external fixation assisted by external immobilization or retrograde intramedullary interlocked nailing. MATERIALS AND METHODS: Records of the authors' institution were reviewed to identify those patients who had undergone ankle fusion for diabetic neuroarthropathy from January 1998 to December 2008. A total of11 patients (six males and five females) with a mean age of 56 year and diabetes of a mean duration of 15.4 years with ankle tibio-talar arthrodesis using retrograde nailing or external fixator for Charcot's neuroarthropathy were enrolled for the analysis. Neuropathy was clinically diagnosed, documented and substantiated using the monofilament test. All procedures were performed in Eichenholz stage II/III.Six patients were treated with uniplanar external fixator, while the remaining five underwent retrograde intramedullary interlocking nail. The outcomes were measured for union radiologically, development of complications and clinical follow-up, according to digital archiving systems and old case notes. RESULTS: All five (100%) patients treated by intramedullary nailing achieved radiological union on an average follow-up of 16 weeks. The external fixation group had significantly higher rate of complications with one amputation, four non unions (66.7%) and a delayed union which went on to full osseous union. CONCLUSION: The retrograde intramedullary nailing for tibio-talar arthrodesis in Charcot's neuroarthropathy yielded significantly better outcomes as compared to the use of uniplanar external fixator.

Vesico-hip fistula from bladder puncture with subsequent infected total hip arthroplasty.

The association of total hip arthroplasty and bladder injury has been well documented. Most cases of fistula formation between the bladder and the hip arthroplasty have occurred, either at the time of hip arthroplasty or subsequently. We report on this rare case where a bladder puncture resulted in infection of the arthroplasty. This occurred through an acetabular floor defect secondary to osteolysis and the subsequent fistula formation.

Contact stresses in the knee joint in deep flexion.

The contact stresses in the knee that arise from activities involving deep flexion have not been given due consideration in view of social and cultural practice amongst many Asians that frequently cause the engagement of these activities. Excessively large stresses (>25 MPa) can cause cartilage damage and may be the precursor to the development of degenerative disease of the joint. In this study, forces in the knee derived from previous studies of human walking and squatting were applied to five cadaver knees that underwent quasi-static mechanical testing. This was conducted using a materials-testing machine and a custom-made apparatus that allowed secure and consistent loading of the knee specimen in flexion beyond 120 degrees. A thin-film electronic pressure transducer was inserted into the cadaver tibiofemoral joint space to measure force and area. Throughout the various positions simulating specific phases of walking, it was found that stresses peaked to 14 MPa (standard deviation was 2.5 MPa). In deep flexion, the peak stresses were significantly larger by over 80%, reaching the damage limits of cartilage. The results from this biomechanical study suggest that the adequacy of articular cartilage to support loads in the knee joint during deep flexion may be questionable.