Advancing Exoskeleton Development: Validation of a Robotic Surrogate to Measure Tibial Strain.

Bone stress injuries are prevalent among athletes and military recruits and can significantly compromise training schedules. The development of an ankle-foot orthosis to reduce tibial load and enable a faster return to activity will require new device testing methodologies capable of capturing the contribution of muscular force on tibial strain. Thus, an actuated robotic surrogate leg was developed to explore how tibial strain changes with different ankle-foot orthosis conditions. The purpose of this work was to assess the reliability, scalability, and behavior of the surrogate. A dual actuation system consisting of a Bowden cable and a vertical load applied to the femur via a material testing system, replicated the action-reaction of the Achilles-soleus complex. Maximum and minimum principal strain, maximum shear strain, and axial strain were measured by instrumented strain gauges at five locations on the tibia. Strains were highly repeatable across tests but did not consistently match in vivo data when scaled. However, the stiffness of the ankle-foot orthosis strut did not systematically affect tibial load, which is consistent with in vivo findings. Future work will involve improving the scalability of the results to match in vivo data and using the surrogate to inform exoskeletal designs for bone stress injuries.

Modified Cephalic Index Measured at Superior Levels of the Cranium Revealed Improved Correction With Helmet Therapy for Patients With Sagittal Suture Craniosynostosis.

OBJECTIVE: Historically, studies have shown that cranial remolding therapy improves surgical correction and protects against regression for patients with sagittal suture craniosynostosis. This study aimed to define the most responsive cranial height for measuring cephalic index (CI) following cranial remolding therapy for infants with sagittal suture craniosynostosis. METHODS: The authors performed a retrospective analysis of data between January 2018 and August 2019. The outcomes measured were CI-3 (level of glabella) through CI-7 (superior to eurions), where each value was defined as the width at levels 3 through 7 divided by the length at level 3. Differences between baseline- and post-treatment measurements were assessed using a 5 × 2 repeated measures analysis of variance. RESULTS: Data from thirty-four patients (19 males, 15 females, and mean age 2.79 months) were analyzed. Mean treatment duration was 4.59 ±â€Š1.86 months. There was a significant increase between baseline and posttreatment measurements (baseline: 72.60% ±â€Š0.70%, post: 76.30% ±â€Š0.80%; F1,33 = 27.74, P < 0.001). The interaction effect for CI level ∗ baseline-post was also significant (F1.43,47.16 = 6.75, P = 0.006). Post hoc analyses revealed the posttreatment measures were significantly greater than baseline measures at every CI level. The magnitude of the measured differences systematically decreased from CI-7 to CI-3, with a greater effect size at the most superior level (ie CI-7) of 0.961 compared to 0.778 at the traditional level (ie CI-3). CONCLUSIONS: The CI measurement at level 7 demonstrated the greatest responsiveness to treatment, whereas the traditional CI measurement taken at level 3, the current standard, proved the least responsive.