Cerebral palsy (CP) is a neural condition that impacts and impairs the musculoskeletal system. Skeletal muscles, particularly in the lower limb, have previously been shown to be significantly reduced in volume in CP compared to typical controls. Muscle volume is a gross measure, however, and does not capture shape characteristics which—if quantified—could offer a robust and novel assessment of how this condition impacts skeletal muscle form and function in CP. In this study, we used mathematical shape modelling to quantify not just size, but also the shape, of soleus muscles in CP and typically developing (TD) cohorts to explore this question.

Shape modelling is a mathematical technique used previously for bones, organs, and tumours. We obtained segmented muscle data from prior MRI studies in CP. We generated shape models of CP and TD cohorts and used our shape models to assess similarities and differences between the cohorts, and we statistically analysed shape differences.

The shape models revealed similar principal components (PCs), i.e. the defining mathematical features of each shape, yet showed greater shape variability within the CP cohort. The model revealed a distinct feature (a superior –> inferior shift of the broad central region), indicating the model could identify muscular features that were not apparent with direct observation. Two PCs dominated the differences between CP and TD cohorts: size and aspect ratio (thinness) of the muscle.

The distinct appearance characteristic in the CP model correspond to specific muscle impairments in CP to be discussed further. Overall, children with CP had smaller muscles that also tended to be long, thin, and narrow. Shape modelling captures shape features quantitatively, which indicate the ways that muscles are being impacted in CP. In the future, we hope to tailor this technique toward informing diagnosis and treatments in CP.

Introduction: There is scant information on the trends of simultaneous bilateral total knee arthroplasties (BTKA). The safety of BTKR has been put into question because of a possible association with increased morbidity and mortality. We hypothesized that substantial changes in BTKA patients demographics, in-hospital complications and mortality have occurred over time in the United States.

Methods: We analyzed information collected for the National Hospital Discharge Survey (NHDS) from 1990 to 2004, to elucidate temporal changes in the utilization, demographics, comorbidity profiles, hospital stay, and in-hospital complications of patients undergoing BTKA in the United States. Three five-year periods were created (1990–1994, 1995–1999, 2000–2004) to facilitate temporal analysis. Temporal changes in patient and health care variables were analyzed.

Results: 153,259 discharges after BTKR were identified (20.18% performed between 1990 and 1994, 28.73% between 1995 and 1999 and 51.08% between 2000 and 2004). Utilization of BTKR more than doubled for the entire civilian population and almost tripled among females. All age groups experienced an increase in utilization of BTKR throughout the study period, except those 85 and older. Most recently a decline of approximately 50% was seen. The distribution of BTKR procedures among age groups changed significantly, with an increased proportion of patients between the ages of 45–64 receiving this procedure (32.83% in 1990–1994; 43.62% in 2000–2004). Comorbidity burden increased steadily over time for hypertension, diabetes mellitus, hypercholesteremia, obesity and renal disease, with half of all patients being affected by hypertension in the most recent time period. The prevalence of coronary artery disease and pulmonary disease decreased from the second to the third time period. Length of hospital stay decreased by half from 9.27 (range 2–53) days between 1990–1994 to 5.44 (range 1–44) days between 1995–1999 and to 4.68 (range 1–33) days between 2000–2004. Overall, procedure related complications rates decreased over time from 19.85% in the first time period to 8.89% in the most recent time period studied.

Discussion: We identified a number temporal changes associated with BTKR performed during the same hospitalization. While utilization in general increased over time, operations on patients above the age of 85 years and amongst those with cardiac and pulmonary disease decreased during the last decade. Overall, procedure related complication rates fell by approximately 50% over the study period.

A prospective study of serum and urinary ion levels was undertaken in a triathlete who had undergone a metal-on-metal resurfacing arthroplasty of the hip four years previously. The one month study period included the final two weeks of training, the day of the triathlon, and the two weeks immediately post-race. Serum cobalt and chromium levels did not vary significantly throughout this period, including levels recorded on the day after the 11-hour triathlon. Urinary excretion of chromium increased immediately after the race and had returned to pre-race levels six days later. The clinical implications are discussed.