Introduction: Low-molecular-weight heparin is commonly used for thromboprophylactic therapy post orthopaedic surgery. Studies in the past have suggested that it may have a negative effect on osteoblasts and some have implicated its use with the risk of developing osteoporosis. Recently, Rivaroxaban, an oral Factor Xa inhibitor is gaining impetus for antithrombotic therapy over the last year and has been recommended for licensing by the FDA for this purpose. The effect of Rivaroxa-ban on bone and osteoblasts, if any, remains to be seen.

Methods: In a standardized in vitro model, human osteoblasts were cultured and exposed to a range of Enoxaparin and Rivaroxaban concentrations including their therapeutic dose. We evaluated the effects of these drugs on osteoblastic proliferation and activity using CellTiter 96 AQueous non-radioactive cell proliferation (MTS) and alkaline phosphatase assays respectively. Gene expression of Runt-related transcription factor 2 (Runx2), osteocalcin and bone morphogenetic protein 2 (BMP-2) were evaluated using Real time-polymerase chain reaction (RT-PCR) studies. Statistical analyses (t-test) were conducted using Microsoft Excel 2007.

Results: Rivaroxaban and Enoxaparin significantly reduced alkaline phosphatase activity (p< 0.05) however, no negative effects on osteoblastic proliferation was seen at all concentrations of both drugs. Rivaroxaban decreased Osteocalcin and Runx2 mRNA expression levels at 24 hours at therapeutic concentrations (p< 0.05). This effect was similarly found at therapeutic levels of Enoxaparin. Both Rivaroxaban and Enoxaparin significantly reduced BMP-2 mRNA expression both at 24 hours and 7 days at therapeutic concentrations. (p< 0.05).

Conclusion: Our study suggests that Rivaroxaban has similar negative effects on osteoblasts compared to Enoxaparin in the early stages. The increased duration of recommended Rivaroxaban therapy (2 and 5 weeks) post arthroplasty compared to Enoxaparin therapy (around 1 week) may have a more pronounced effect on bone homeostasis.

Slipped capital femoral epiphysis (SCFE) is the most common hip disorder in adolescents and its incidence is on the increase. Obesity is purported to be a significant risk factor in the pathogenesis of this condition. Measurements for weight and BMI’s are good techniques in identifying children at risk and those who are obese. In this retrospective review, we provide clear evidence of a relationship between SCFE and obesity based on weight-to-age percentiles. 64 patients with radiologically diagnosed SCFE were compared with 88 controls without histories of hip pathology. In the SCFE group, 45.3% were above the 95th percentile as opposed to 12.1% in the control group (P=< 0.0001). In addition, the obesity risk group (85–95th percentile) numbers were much higher in the SCFE group (15.6%) compared to controls (7.7%) (P=< 0.0001). Obesity is a modifiable risk factor in most cases and thus, identifying children at risk using weight-to-age percentile charts correcting for gender is potentially beneficial in reducing the incidence of SCFE.

As the numbers of revision total knee arthroplasty (RTKA) rise, we continually need current information regarding the etiology/modes of failure and functional disability of patients presenting for RTKA. We used a prospective cohort study to assess these fundamental aspects of RTKA.

290 consecutive subjects presenting for RTKA had relevant clinical information, including modes of failure, collected from surgeon-completed documents. Patients themselves also completed quality of life and functional questionnaires, including the SF-36 and WOMAC Osteoarthritis Index.

Mean patient age was 68.6 years (55 to 79 years). Mean SF-36 and WOMAC score at baseline indicated significant functional disability. The mean time from primary procedure to RTKA was 7.9 years (6 months to 27 years). Our series included 31 percent ‘early’ (under 2 years) revisions and 69 percent ‘late’ revisions. Sepsis was the cause of 10.4 percent revisions. The tibia needed revision in 78 percent, femur in 71 percent and patella in 31 percent of cases. The predominant modes of failure (non-exclusive frequency values as patients could have more than one cause) were (in percentages): instability (28.9), malalignment (27.5), tibial osteolysis (27.5), polyethylene wear (24.5), femoral osteolysis (22.5) and tibial loosening (22.2).

These patients are relatively young, and considerably disabled by their failed primary procedure. Many modes of failure are within surgical control and direct us toward improved techniques and approaches. Other modes confirm the need for continued development of implants and materials. Information gained here will allow better formulation of measures and resource allocation that may prevent RTKAs.