Inverse distance weighting to rapidly generate large simulation datasets

Obtaining large biomechanical datasets for machine learning is an ongoing challenge. Physics-based simulations offer one approach for generating large datasets, but many simulation methods, such as computed muscle control (CMC), are computationally costly. In contrast, interpolation methods, such as inverse distance weighting (IDW), are computationally fast. We examined whether IDW is a low-cost and accurate approach for interpolating muscle activations from CMC.IDW was evaluated using lateral pinch simulations in OpenSim. Simulated pinch data were organized into grids of varying sparsity (high, medium, and low density), where each grid point represented the muscle activations associated with a unique combination of mass and height of a young adult. For each grid, muscle activations were calculated via CMC and IDW for 108 random mass-height pairs that were not coincident with simulation grid vertices. We evaluated the interpolation errors from IDW for each grid, as well as the sensitivity of lateral pinch force to these errors. The root mean square error (RMSE) associated with interpolated muscle activations decreased with increasing grid density and never exceeded 4%. While CMC received a target thumb-tip force of 40 N, errors from the interpolated muscle activations never impacted the simulated force magnitude by more than 0.1 N. Furthermore, the computation time for CMC simulations averaged 4.22 core-minutes, while IDW averaged 0.95 core-seconds per mass-height pair.These results indicate IDW is a practical approach for rapidly estimating muscle activations from sparse CMC datasets. Future works could adapt our IDW approach to evaluate other tasks, biomechanical features, and/or populations.

Reconstruction of lateral pinch in an isolated paralysis of the first dorsal interosseous muscle - A new surgical technique

Lack of function of the first interosseous muscle (FDI) might be responsible for insufficient stabilisation of the index finger during lateral pinch, and may induce disability in hand function. The first cause of FDI palsy is ulnar nerve palsy. We describe a new tendon transfer to reanimate the FDI muscle, using the extensor indicis proprius tendon. The tendon is sectioned at its distal insertion and rerouted in the first extensor tendon compartment. We report one case of isolated first interosseous muscle palsy secondary to direct trauma. Preoperatively, the patient complained of a severe lack of strength during key pinch with an ulnarly deviated index finger. Thirty months postoperatively, the patient recovered active abduction of the index finger and lateral pinch was measured at 5.5kg (54N). Compared to the original Bunnell transfer our technique restores the native moment arm of the FDI muscle and does not require a tendon graft.

Influences of gender, hand dominance, and anthropometric characteristics on different types of pinch strength: A partial least squares (PLS) approach

The relationships of demographic and anthropometric characteristics (17 dimensions related to the hand, wrist, and arm) with four different pinch strengths (lateral pinch, key pinch, three-jaw chuck pinch and tip-to-tip pinch strengths) were evaluated among 196 (96 males and 100 females) young adults aged 19-30 years. For both dominant and non-dominant hands, the lateral pinch was greatest, followed by the key pinch, three-jaw chuck pinch and tip-to-tip pinch strengths. Mean pinch strengths of the dominant and non-dominant hands of females varied between 62%-78% and 61%-73% of those exerted by males, respectively. Strength of the dominant hand was 5.3%-7.5% stronger than of that of the non-dominant hand, with this difference being generally higher in females than in males. Hand length and forearm length showed the strongest correlation with all types of pinch strengths exerted by both the dominant and non-dominant hands. In the partial least squares analysis, 10 out of 17 anthropometric indices including hand length, forearm length, arm length, middle finger width, thumb length, index finger width, thumb width, wrist depth, palm depth and index finger depth had considerable loadings in the extracted component, explaining 37% of the total variance. These findings can fill the gap in the strength data, or used by health professionals and designers in the field.

Ulnar Nerve Tendon Transfers for Pinch

Power and tip pinch are an integral part of intrinsic hand function that can be significantly compromised with dysfunction of the ulnar nerve. Loss of power pinch is one component that can significantly affect an individual's ability to perform simple daily tasks. Tip pinch is less affected, as this task has significant contributions from the median nerve. To restore power pinch, the primary focus must be on restoring the action of the adductor pollicis primarily, and if indicated the first dorsal interosseous muscle and flexor pollicis brevis.

Pinch strengths in healthy Iranian children and young adult population

BACKGROUND

Data on the physical strength capabilities are essential for designing safe and usable products and are useful in a wide range of clinical settings especially during treatment of disease affecting the function of the hand. The purpose of this study was to determine peak lateral pinch strength, key pinch strength, tip-to-tip pinch strength and three-jaw pinch strength exertions in a healthy Iranian children and young adult population.

METHODS

The study was conducted among 511 participants (242 males and 269 females) aged 7-30 years. Measurements were carried out with both dominant and non-dominant hands in standard sitting posture using a B&L pinch gauge. Two repetitions of each strength measurement were recorded for each condition and the average value of the two trials was used in the subsequent analysis.

RESULTS

The results showed significant differences in the pinch strength data in terms of the age, gender and hand dominance. The lateral pinch strength, key pinch strength, tip-to-tip pinch strength and three-jaw pinch strength exertions by females were 68.4%, 68.8%, 78.8% and 81.8% of those exerted by males, respectively. Strength exertions with the non-dominant hand were 6.4%, 5.2%, 6.6% and 5.1% lower than strength exertions of the dominant hand for the lateral pinch strength, key pinch strength, tip-to-tip pinch strength and three-jaw pinch strength exertions, respectively.

CONCLUSION

These findings can be used to fill the gaps in strength data for Iranian population.