Tendon excursion and moment arm of index finger muscles
Abstract
Tendon excursions during rotation of individual index finger joints were recorded continuously throughout the joints' ranges of motion. Both intrinsic and extrinsic muscles were studied during flexion-extension and abduction-adduction functions. Excursions and joint-displacement relationships were observed to not always be linear. Moment arms of tendons with respect to joint centers were further derived from excursion data. The significance of this information to tendon transfer techniques is discussed. These data are also important for theoretical modeling in muscle force determination.
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Cited by (324)
A Biomechanical Analysis of the H-Taping Method Used by Rock Climbers as Prophylactic or Stabilizing Fixation of Partial A2 Pulley Tears
2023, Journal of Hand SurgeryRock climbing can lead to upper-extremity injuries, such as A2 pulley ruptures, leading to the bowstringing of the flexor tendons. Climbing finger positions are specific and can put undue stress on the pulley systems. This causes severe hand dysfunction and is a difficult problem to treat, and prevention is important. Using a cadaveric, experimental model, we evaluated the effectiveness of the H-taping method, commonly used by rock climbers, to prevent and treat A2 pulley tears.
Using fourteen matched pairs of fresh-frozen cadaveric hands with forearms, four experiments were conducted with 56 paired comparisons evaluating the failure force, fingertip force, and mode of failure (112 total tests). Comparisons were as follows: index fingers- intact versus 50% distal A2 pulley tears without H-taping (control); ring fingers- intact versus H-taping as a prophylactic for A2 pulley tears; little fingers- 50% distal A2 pulley tears with H-tape versus without tape; and middle fingers- H-taping as a prophylactic versus H-taping as a stabilizing treatment of torn pulleys.
The mean index finger failure force was significantly higher in intact vs torn A2 pulleys (control). Failure force for intact H-taped fingers was significantly higher than torn H-taped fingers, but no other finger comparisons for failure force were significant. There were no significant findings in comparison of mean fingertip force values in any of the experiments.
We found that H-taping is not effective as prophylaxis against A2 pulley ruptures or as a stabilizing treatment method for partially ruptured pulleys.
While H-taping has not been recommended as prophylaxis for preventing A2 pulley ruptures, the climbing community has embraced this technique as a preventative measure. The present study provides biomechanical evidence against H-taping for this purpose. Furthermore, it does not appear to aid in increasing fingertip force after injury.
Optimal Distal Tendon Insertion Point for Elbow Flexion in Free-Functioning Gracilis Muscle Transfer for Panbrachial Plexus Injuries: A Cadaveric Study
2023, Journal of Hand SurgeryFollowing pan-brachial plexus injuries, restoration of elbow flexion is widely accepted as the reconstructive priority. A gracilis free functioning muscle transfer (FFMT) can be used to restore elbow flexion alone with insertion into the biceps brachii (BIC) or brachioradialis (BRD) tendons or restore combined elbow and finger flexion with a more distal insertion into the flexor digitorum profundus (FDP) tendons. Using cadaveric experiments, we determined the peak instantaneous moment arm for each insertion option.
Six simulated gracilis transfer surgeries were performed using both arms of three fresh-frozen full body cadaveric specimens (age: 79 + 10 years. 2 female). The gracilis muscles from both legs were harvested and transferred to the contralateral upper extremity. The elbow was manually moved through three flexion-extension cycles while the instantaneous moment arm was calculated from measurements of gracilis excursion and elbow joint angle for the three distal insertion sites.
Peak instantaneous moment arm for all three insertions occurred at an elbow angle between 83° to 92° with a magnitude ranging from 33 mm to 54 mm. The more distal (FDP/BRD) insertions produced a significantly greater (∼1.5 times) peak elbow flexion instantaneous moment arm compared to the BIC insertion.
Based on the instantaneous moment arm, the gracilis FFMT distal insertion locations could result in greater reconstructed elbow flexion strength. In addition, direct measurement of the shape and magnitude of the moment arm curve for differing insertion sites allows high resolution surgical planning and model testing.
This study presents the first direct experimental quantification of the gracilis FFMT instantaneous moment arm. The experimental evidence supports the use of FDP/BRD insertion locations by providing a quantitative explanation for the increased elbow flexion torque observed clinically in patients with a gracilis FFMT and distal FDP insertion.
Sensitivity analysis guided improvement of an electromyogram-driven lumped parameter musculoskeletal hand model
2022, Journal of BiomechanicsEMG-driven neuromusculoskeletal models have been used to study many impairments and hold great potential to facilitate human–machine interactions for rehabilitation. A challenge to successful clinical application is the need to optimize the model parameters to produce accurate kinematic predictions. In order to identify the key parameters, we used Monte-Carlo simulations to evaluate the sensitivities of wrist and metacarpophalangeal (MCP) flexion/extension prediction accuracies for an EMG-driven, lumped-parameter musculoskeletal model. Four muscles were modeled with 22 total optimizable parameters. Model predictions from EMG were compared with measured joint angles from 11 able-bodied subjects. While sensitivities varied by muscle, we determined muscle moment arms, maximum isometric force, and tendon slack length were highly influential, while passive stiffness and optimal fiber length were less influential. Removing the two least influential parameters from each muscle reduced the optimization search space from 22 to 14 parameters without significantly impacting prediction correlation (wrist: 0.90 ± 0.05 vs 0.90 ± 0.05, p = 0.96; MCP: 0.74 ± 0.20 vs 0.70 ± 0.23, p = 0.51) and normalized root mean square error (wrist: 0.18 ± 0.03 vs 0.19 ± 0.03, p = 0.16; MCP: 0.18 ± 0.06 vs 0.19 ± 0.06, p = 0.60). Additionally, we showed that wrist kinematic predictions were insensitive to parameters of the modeled MCP muscles. This allowed us to develop a novel optimization strategy that more reliably identified the optimal set of parameters for each subject (27.3 ± 19.5%) compared to the baseline optimization strategy (6.4 ± 8.1%; p = 0.004). This study demonstrated how sensitivity analyses can be used to guide model refinement and inform novel and improved optimization strategies, facilitating implementation of musculoskeletal models for clinical applications.
The moment arms and leverage of the human finger muscles
2021, Journal of BiomechanicsThe moment arm of a muscle’s force represents the muscle’s leverage or mechanical advantage in producing a joint moment. It is indicative of the muscle’s potential to contribute to actuation of a joint in a particular joint motion direction and defines the role of the muscle, for example, as a joint flexor or abductor. The aims of this study were, firstly, to measure the moment arms of the flexor and extensor muscles of the metacarpophalangeal (MCP), proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints, and the moment arms of the major abductor and adductor muscles of the metacarpophalangeal (MCP) joint of each finger in the hand; secondly, to assess the effect of change in joint angle on these moment arms; and thirdly, to determine if there are differences in a given flexor or extensor’s muscle moment arms between the joints it spans on a given finger, and across its tendon slips to multiple fingers. The tendon-excursion method was used to measure instantaneous muscle moment arms in nine fresh-frozen entire forearm cadaver specimens. Joint flexion angle was found to have significant effects on the moment arms of the extensor muscles at the MCP and PIP joints (p < 0.05). In contrast, the digital flexor muscles maintained relatively constant moment arms through the range of joint flexion. The moment arms of the digital flexors and extensors spanning multiple joints in a finger were largest at the MCP joints and smallest at the DIP joints. The findings demonstrate greater torque generating capacity for tasks such as grasping at the proximal interphalangeal joints, and smaller torque capacity for finer movement control at the distal interphalangeal joints. The dataset generated in this study may be useful in the development and validation of computational models used in surgical planning, and rehabilitation.
Calculation of flexor pollicis longus moment arm for wrist motion in a cadaver model validates the tenodesis effect for therapy
2020, Journal of Hand TherapySynergies of fingers and wrist motion have been incorporated into therapies for finger flexor tendon injuries to improve repair outcomes. Similar synergistic therapy strategies have not been well documented for the thumb.
The purpose of this study was to investigate the extent to which wrist motion enables a synergistic effect at the thumb in a cadaveric model by measuring flexor pollicis longus excursion and calculating the moment arm of this tendon at the wrist joint.
This is a basic science research.
Eight fresh-frozen cadaveric arms were obtained from our anatomical bequest program. The proximal arm was fixed in neutral pronation/supination position, and motion of the wrist was guided through either flexion/extension or radial/ulnar deviation. Fingers were fixed in extension, thumb interphalangeal and metacarpophalangeal joints were fixed in neutral extension, and the carpometacarpal joint was fixed at 30° palmar abduction. The flexor pollicis longus tendon was exposed proximal to the wrist crease and connected to a rotary potentiometer to measure tendon excursion. Optical markers were attached to the hand to capture kinematics. Wrists were moved from a neutral position over the range of flexion and extension and then from the neutral position through the range of radial to ulnar deviation. Moment arms were calculated.
Moment arm calculation indicated that the flexor pollicis longus acts as a wrist flexor over the entire motion range and as a weak radial deviator at ulnarly-deviated positions.
This study provides a mechanistic rationale for passive interphalangeal joint motion in varying wrist positions when treating thumb flexor tendon injuries, with benefits seen primarily for wrist extension.
A multiple fascicle muscle force model of the human triceps surae
2020, Journal of Theoretical BiologyMuscle is typically modelled using a lump sum idealization, scaling a single fascicle to represent the entire muscle. However, fascicles within a muscle have unique orientations, which could result in forces exerted not only in the axis running along the tendon, but also the two perpendicular axes, describing the muscle's width and depth. The purpose of this research was to develop a geometric-based model of the soleus, medial gastrocnemius, and lateral gastrocnemius as distributed force systems which can predict three-dimensional forces. Measurements were taken from the triceps surae in two human cadavers (80 and 85 years old). These models predicted muscle volumes and ankle plantar flexor moments that were realistic considering the age of the cadavers. Small differences were observed in calcaneal tendon force and moment for the distributed force models compared to modelling muscle force using a lump sum idealization. The major finding of the distributed force models was that forces were present in the axes corresponding to the muscle's length, width, and depth. The forces in the width and depth axes may be relevant for evaluating how muscle shape changes during contraction, as well as to investigate stress-strain patterns along the muscle's proximal and distal aponeuroses.