Background Rate of torque development (RTD) measures the ability of a muscle to produce torque quickly. Decreased quadriceps RTD may impair performance of sporting tasks after surgery. Currently, little is known about variations in quadriceps RTD between ACL reconstructed and non-injured limbs. Purpose To determine the differences in RTD of the quadriceps, the rate and timing of knee extensor moment (KEM) development, and knee flexion excursion during running following ACL reconstruction with patellar tendon autograft. Study Design Cross-Sectional Methods Twenty-one (11 females) subjects 6-months post-ACL reconstruction with patellar tendon autograft. (Median±IQR) age 18±4 years, mass 68.18±13.64 kg, height 1.74±0.11 m. Subjects performed four, 5-second maximal voluntary isometric strength trials of both limbs on an isokinetic dynamometer. RTD was calculated as the mean slope of the torque-time curve between 20 – 80% of total time to peak torque. Then, subjects underwent 3-D motion analysis while running on an instrumented treadmill at a self-selected running speed (mean 2.68 ± 0.28 m/s). Rate of knee extensor moment (RKEM) was calculated as the mean slope of the moment curve between 10–30% of stance phase. Between-limb comparisons were determined with a paired t-test for peak KEM, RKEM, knee flexion excursion during 10–30% of stance, and time to generate KEM. Results Deficits in peak rate of quadriceps torque development existed both isometrically (RTD 257.56 vs. 569.11 Nm/s, p<0.001) and dynamically (RKEM 16.47 vs. 22.38 Nm/kg*m*s, p<0.001) in the reconstructed limb. The reconstructed limb also generated a KEM later in the stance phase (11.37 vs. 9.61 % stance, p<0.001) and underwent less knee flexion excursion (15.5 vs. 19.8°, p<0.001) than the non-injured limb. Conclusions Following ACL reconstruction with patellar tendon autograft, patients have lower RTD and RKEM in the reconstructed limb. Deviations in RTD and the timing of the KEM can change the way the knee is loaded and potentially increases injury risk and future development of post-traumatic osteoarthritis. Clinical Relevance Deficits in RTD affect the ability of the limb to generate sufficient KEM at the appropriate time during dynamic tasks. Rehabilitation should consider exercises designed to improve RTD and prepare the limb for the demands of sport performance.

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A biodegradable piezoelectric scaffold excited by exercise promotes chondrogenesis and cartilage regeneration in rabbit osteochondral defects.

Purpose: To evaluate the feasibility of implementation, acceptance, and perceived efficacy of a joystick-operated ride-on-toy intervention to promote upper extremity (UE) function in 3-to 14-year-old children with hemiplegic cerebral palsy. Methods: Exit questionnaires were collected from children, caregivers, and clinicians/camp staff following a 3-week ride-on-toy training program incorporated within a summer camp for children with hemiplegic cerebral palsy. Training encouraged children to use their affected UE to maneuver the ride-on-toy. Questionnaires included Likert scale and open-ended questions to assess enjoyment, acceptance, feasibility, and perceived efficacy of the training. Results: All stakeholder groups indicated that the training was enjoyable. Clinicians/staff and caregivers indicated that the training increased children's motivation to use their affected UE and reported perceived improvements in UE movement control and function following training. Conclusions: Our promising preliminary findings call for future research to systematically assess the efficacy of ride-on-toys to promote UE control and function in children with hemiplegic cerebral palsy.

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