Joshua D. Winters

Preliminary investigation of rate of torque development deficits following total knee arthroplasty

BACKGROUND To assess changes in maximal strength and rate of torque development (RTD) following TKA, and examine the relationships between these measures and physical function. METHODS Thirty-five TKA patients and 23 controls completed isometric knee extensor torque testing preoperatively, 1, and 6 months after surgery. Maximal strength was calculated as the peak torque during a maximal voluntary isometric contraction (MVIC) of the knee extensor muscles, peak RTD (RTD(peak)) was calculated as the maximum value from the 1st derivative of the isometric knee extension torque data, RTD(25%) and RTD(50%) were calculated as the change in force over the change in time from force onset to 25% and 50% MVIC. Physical function was measured using a timed-up-and-go (TUG) and stair climbing test (SCT). RESULTS RTD was significantly lower in the TKA group, at all-time points, compared to the Controls. MVIC and RTD significantly decreased 1-month following surgery (p=0.000 for all measures). RTD(peak) measures added to linear regressions with strength improved the prediction of TUG scores (p=0.006) and the SCT scores (p=0.015) 1-month post-surgery. Adding RTD(50%) to the regression model, following MVIC, improved predicting both TUG (p=0.033) and SCT (p=0.024). At 6-months, the addition of RTD(25%) to the regression model, following MVIC, improved the prediction of TUG (p=0.037) and SCT (p=0.036). CONCLUSION Following TKA, physical function is influenced by both the maximal strength and the rate of torque development of the knee extensors, and the prediction of function is improved with the addition of RTD compared to that of maximal strength alone.

The impact of hip implant alignment on muscle and joint loading during dynamic activities

Background Component alignment is an important consideration in total hip arthroplasty. The impact of changes in alignment on muscle forces and joint contact forces during dynamic tasks are not well understood, and have the potential to influence surgical decision making. The objectives of this study were to assess the impact of femoral head/stem and cup component placement on hip muscle and joint contact forces during tasks of daily living and to identify which alignment parameters have the greatest impact on joint loading. Methods Using a series of strength‐calibrated, subject‐specific musculoskeletal models of patients performing gait, sit‐to‐stand and step down tasks, component alignments were perturbed and joint contact and muscle forces evaluated. Findings Based on the range of alignments reported clinically, variation in head/stem anteversion‐retroversion had the largest impact of any degree of freedom throughout all three tasks; average contact forces 413.5 (319.1) N during gait, 262.7 (256.4) N during sit to stand, and 572.7 (228.1) N during the step down task. The sensitivity of contact force to anteversion‐retroversion of the head/stem was 31.5 N/° for gait, which was similar in magnitude to anterior‐posterior position of the cup (34.6 N/m for gait). Additionally, superior‐inferior cup alignment resulted in 16.4 (4.9)° of variation in the direction of the hip joint contact force across the three tasks, with the most inferior cup placements moving the force vector towards the cup equator at the point of peak joint contact force. Interpretation A quantitative understanding of the impact and potential tradeoffs when altering component alignment is valuable in supporting surgical decision making. HighlightsHip arthroplasty alignment parameters with greatest impact on loading were identified.Subject‐specific musculoskeletal models simulating daily activities were used.Head/stem anteversion‐retroversion had the largest impact throughout all three tasks.Inferior cup placements resulted in forces towards the cup equator at peak loads.Alignment impact supports surgical decision‐making and instrumentation development.

Epidemiological Analysis Of Injuries Occurring In Marine Corps Forces Special Operations Personnel: 3086 Board #151 June 3, 3

Special Operation Forces have been shown to sustain greater rates of musculoskeletal injuries than conventional forces. These injuries result in loss in deployable operators, which negatively impacts force readiness. In addition to Operators (OPs), Marine Corps Forces Special Operations Command (MARSOC) also utilizes Combat Support Personnel (CSP) to support OP missions. These CSP may also be at risk for sustaining similar injuries and mechanisms as OPs. PURPOSE: Describe injury epidemiology in MARSOC personnel and compare injury patterns between OPs and CSP. METHODS: A total of 141 MARSOC personnel (85 OPs, 56 CSP) completed an injury history questionnaire and described musculoskeletal injuries that occurred in the previous 12 months. Injury proportions were calculated for OPs and CSP. Proportions of injured subjects were compared between OPs and CSP using Fisher’s exact tests. RESULTS: A total of 43 injuries were reported within the previous 12 months, 25 of which were classified as preventable (15 in OPs, 10 in CSP). There were no statistically significant differences in the proportion of injured subjects between OPs and CSP. Preventable injuries were sustained by 14% of OPs and 16% of CSP. Both OPs and CSP sustained the majority of preventable injuries while performing lifting and running activities (27% and 40% for OPs and 40% and 50% for CSP, respectively). Also, the knee and lumbopelvic region were the most commonly reported location of preventable injuries for OPs (20% each) and CSP (30% each). The top three most common injury types were muscle strain, tendinopathy, and pain/spasm. CONCLUSION: Approximately 15% of MARSOC personnel experienced preventable injuries within 12 months prior to the questionnaire. Therefore, the force would significantly benefit from performance and injury prevention programs to mitigate preventable injuries and optimize force readiness. Because the majority of injuries were sustained during physical training there is a need to monitor training readiness to avoid overtraining and fatigue. Additionally, OPs and CSP seem to sustain similar injury patterns with similar mechanisms, suggesting CSP should also be included in injury prevention initiatives to optimize force readiness.