Biomedical subjects

Zong-Ming Li

Publications and source records attributed to Zong-Ming Li.

At least 19 recordsLinked to original sources

PubMed2006

Peripheral median nerve block impairs precision pinch movement.

OBJECTIVE: The objective of this study was to investigate the effects of a simulated peripheral median nerve lesion on precision pinch movement by the thumb and index finger. METHODS: A median neuropathy was created by blocking the median nerve at the wrist using an anesthetic. The subjects (n=5) were asked to perform pulp-to-pulp precision pinch movements before and after the nerve block. Digit motion data was obtained with a marker-based motion analysis system. RESULTS: The radial offset of the thumb tip, as defined by the minimum distance of the thumb tip to the flexion-extension plane of the index finger, showed an increase of 11.2mm after the nerve block. For the thumb, the nerve block caused a decrease in the range of motion at the metacarpophalangeal (MCP) joint, and a compensatory increase in the range of motion at the interphalangeal (IP) joint. The range of motion ratio (MCP:IP) changed from 1:4.8 (pre-block) to 1:1.0 (post-block). The maximum flexion angle at the MCP joint increased from 18.8 degrees (pre-block) to 33.7 degrees (post-block), and maximum flexion angle at the IP joint decreased from 42.6 degrees (pre-block) to 18.8 degrees (post-block). For the index finger, the nerve block caused a decrease in the range of motion at the MCP joint, and compensatory increases in the ranges of motion at the proximal and distal interphalangeal (PIP and DIP) joints. The range of motion ratio (MCP:PIP:DIP) changed from 1:1.1:0.7 (pre-block) to 1:2.4:1.8 (post-block). The maximum flexion angle at the MCP joint decreased from 56.8 degrees (pre-block) to 34.6 degrees (post-block), and the maximum flexion angle at the PIP joint increased from 51.2 degrees (pre-block) to 76.0 degrees (post-block), but the change at the DIP joint was insignificant. CONCLUSIONS: The median nerve block caused remarkable degradation of the pinch performance as quantified by an inaccurate pulp-to-pulp contact of the thumb to the index finger and an alteration of joint motion of the digits. SIGNIFICANCE: Many fine manual tasks require accurate pulp-to-pulp positioning of the thumb to the index finger. Within the hand, the median nerve is critical to the fine sensorimotor function due to the motor supply and the sensory endings to the thumb and index finger. People with median neuropathies (for example, carpal tunnel syndrome) experience clumsiness while performing simple manual tasks. The current approach to the examination of precision pinch movement may be utilized to quantify the apparent hand clumsiness observed in individuals with peripheral neuropathy such as carpal tunnel syndrome.

Adult↗

PubMed2006

Coordination of thumb joints during opposition.

Thumb opposition plays a vital role in hand function. Kinematically, thumb opposition results from composite movements from multiple joints moving in multiple directions. The purpose of this study was to examine the coordination of thumb joints during opposition tasks. A total of 15 female subjects with asymptomatic hands were studied. Three-dimensional angular kinematics of the carpometacarpal (CMC), metacarpophalangeal (MCP) and interphalangeal (IP) joints were obtained by a marker-based motion analysis system. Thumb opposition revealed coordination among joints in a specific direction (inter-joint coordination) and among different directions within a joint (intra-joint coordination). In particular, linear couplings existed between the flexion and pronation at the CMC joint, and between the flexion of the CMC joint and flexion of the MCP joint. Principal component analysis showed that only two principal components adequately represented the thumb opposition data of seven movement directions. A term functional degrees of freedom by virtue of principal component analysis was proposed to uncover the extent of movement coordination in functional tasks.

Biomechanical Phenomena↗

PubMed2006

Lower median nerve block impairs precision grip.

The purpose of this study was to investigate precision grip impairment caused by a lower median nerve block at the wrist. The median nerve block was achieved by injecting bupivacaine hydrochloride into the carpal tunnel, which acutely simulated a median neuropathy. Seven healthy male subjects were instructed to grip, lift, and hold an instrumented handle within 60s using precision grip. The same tasks were performed before and after the nerve block. Force and torque data were recorded using two miniature 6-component force/torque transducers. The precision grip was quantified by the safety margin (i.e. the difference between the actual grip force and the minimal grip force to keep the object from dropping), the variation of grip force, and the migration area of center of pressure (i.e. the area defined by the center of pressure at a digit-transducer surface while holding the handle). Two subjects were unable to complete the precision grip tasks after the nerve block, and their data were excluded from the analyses. The median nerve block caused significant increases (P<0.05) in the safety margin of the grip force (>50%), the grip force variation (>80%), and the area of center of pressure migration (>250%). Median nerve block at the wrist impairs the fine motor control during precision grip. Our results corroborate the important role played by sensory function in hand fine motor control. Clinically, the measures related to precision grip have the potential to quantify impairment of hand function caused by neuromuscular disorders, to monitor the progress of a hand disorder, and to evaluate the efficacy of a treatment or rehabilitation procedure.

Adult↗

PubMed2006

A robot-assisted study of intrinsic muscle regulation on proximal interphalangeal joint stiffness by varying metacarpophalangeal joint position.

The tightness of intrinsic hand muscles is a common cause of finger joint stiffness. The purposes of this study were to develop a robot-assisted methodology to obtain torque-angle data of a finger joint, and to investigate the regulation of the intrinsic muscles on finger joint stiffness. Our robot system features the integration of a low payload robot arm, a controller, and a force/torque transducer. The system provided highly reproducible torque-angle curves. Torque-angle data of the proximal interphalangeal joint with the metacarpophalangeal joint at 0 and 60 degrees were obtained from eight asymptomatic hands. The torque-angle curve shifted with the position of the metacarpophalangeal joint. As the metacarpophalangeal joint flexion angle changed from 60 to 0 degrees, the equilibrium of the proximal interphalangeal joint increased more than 20 degrees, and joint stiffness increased more than 50%. The dependence of the stiffness of the proximal interphalangeal joint on metacarpophalangeal joint position supports the regulatory role of the intrinsic muscles on finger joint mechanics. This regulatory mechanics is likely amplified in hands with intrinsic muscle tightness, justifying the commonly used Bunnell Intrinsic Tightness Test.

Adult↗

PubMed2006

Reconstruction of the interosseous ligament unloads metallic radial head arthroplasty and the distal ulna in cadavers.

PURPOSE: Longitudinal radioulnar dissociation may result when a compressive load to the hand results in excessive proximal migration of the radius with interosseous ligament (IOL) disruption and radial head fracture. Interosseous ligament reconstruction has been proposed to restore more normal forearm mechanics. The objective of this study was to evaluate the effect of IOL reconstruction on compressive load transfer through the forearm after excision and metallic replacement of the radial head in cadavers. METHODS: In 8 cadaveric forearms, 138 N of compressive load was applied to the hand in neutral forearm rotation and neutral elbow varus-valgus alignment. We measured proximal radial migration and 3-dimensional force vectors acting on the distal radius, distal ulna, IOL, proximal radius, and proximal ulna. The experiment was repeated in order for 5 conditions: (1) with the IOL intact, (2) with the IOL reconstructed with a double-bundle flexor carpi radialis construct, (3) with the radial head excised, (4) after metallic radial head arthroplasty, and (5) after cutting the IOL reconstruction. Analysis of variance was used for statistical comparisons. RESULTS: With the IOL intact the resultant load in the distal radius was 94% +/- 3% of hand load, with 75% +/- 2% transmitted to the proximal radius. Double-bundle flexor carpi radialis reconstruction effectively restored this relationship. After radial head excision the resultant distal radius load decreased whereas great increases were seen in the resultant distal ulna load, the resultant load in the IOL reconstruction, the resultant load in the proximal ulna, and proximal radial migration. Force continued to transfer through the proximal radius transversely, with a 400% increase in transverse force, a consequence of abutment of the radial stump caused by proximal radioulnar convergence (there was no contact at the capitellum). After radial head arthroplasty loads transferred across the wrist remained closer to intact but the resultant load on the distal ulna and proximal radius remained increased. With cutting of the IOL reconstruction transverse forces in the forearm became negligible, the resultant distal ulna load increased by 50%, and the resultant radial head load increased by 25%. Proximal migration of the radius was small and was increased by 4.6 mm with radial head excision and by 1 mm after radial head replacement compared with the IOL-reconstructed, radial head-intact state. CONCLUSIONS: Interosseous ligament reconstruction may help improve treatment of longitudinal radioulnar dissociation but remains an experimental procedure.

Aged↗

PubMed2005

Tendon and nerve displacement at the wrist during finger movements.

BACKGROUND: Repetitive motion of the hand has been suggested as a major factor of pathogenesis of cumulative trauma disorders (e.g., carpal tunnel syndrome). The purpose of this study was to investigate the 3D displacement of the median nerve and extrinsic finger flexor tendons (flexor digitorum superficialis; flexor digitorum profundus) as a function of flexion/extension of metacarpophalangeal joints of the index and middle fingers. METHODS: Shim markers were placed on the median nerve, flexor digitorum superficialis, and flexor digitorum profundus tendons at the wrist region of seven cadaveric specimens for the purpose of digitization of tendon and nerve locations. The metacarpophalangeal joint of the index or middle finger was moved from 15 degrees extension to 75 degrees of flexion while the markers were digitized at increments of 15 degrees. Marker displacements were determined in the longitudinal, radial-ulnar, and dorsal-palmar directions. FINDINGS: Movement of metacarpophalangeal joint of the index or middle finger caused tendon and nerve displacements in the longitudinal, radial-ulnar, and dorsal-palmar directions. The longitudinal displacements of the median nerve and the flexor tendons were linearly correlated with angular movement of the metacarpophalangeal joint. The maximum longitudinal displacements of the flexor digitorum superficialis tendon, flexor digitorum profundus tendon, and median nerve were, on average, 14.7 mm, 11.9 mm, and 3.0 mm, respectively, for the index finger; and 18.4 mm, 14.5 mm, and 4.0 mm, respectively, for the middle finger. The radial-ulnar and dorsal-palmar displacements were irregular and relatively small. The maximum displacements in these transverse directions fell in the range of 1.4-5.1 mm for the median nerve and 1.9-7.3 mm for the flexor tendons. INTERPRETATIONS: Finger flexor tendons and median nerve move not only concurrently, but also differentially, in all anatomical directions. Tendon and nerve movement during prolonged repetitive hand movement may cause hand disorders such as carpal tunnel syndrome.

Aged↗

PubMed2005

Coupling between wrist flexion-extension and radial-ulnar deviation.

BACKGROUND: Conventional wrist joint goniometry evaluates range of motion in isolated directions. The coupling between wrist flexion-extension and radial-ulnar deviation was investigated. METHODS: Ten healthy young male subjects performed wrist flexion-extension, radial-ulnar deviation, and circumduction motions. Flexion-extension and radial-ulnar deviation angles were computed from the coordinates of surface markers attached to the forearm and hand. A motion analysis system recorded marker motion. FINDINGS: During radial-ulnar deviation, the amount of accompanying flexion-extension movement was linearly related to the amount of radial-ulnar deviation. The secondary (flexion-extension) range of motion (48.3 degrees) was about 75% of the primary (radial-ulnar deviation) range of motion (55.1 degrees). During the flexion-extension task, the coupling was less linear. The motion range in radial-ulnar deviation (21.2 degrees) was about 20% of the primary (flexion-extension) range of motion (108.3 degrees). The radial-ulnar deviation and flexion-extension motions combined extension with radial deviation, and flexion with ulnar deviation. The convex hull of the flexion-extension and radial-ulnar deviation angles during circumduction was "egg-shaped" and asymmetric with respect to the anatomically defined flexion-extension and radial-ulnar deviation axes. Wrist position in one direction strongly influenced the range of motion in the other. Maximum range of motion in flexion-extension occurred with the wrist near the neutral radial-ulnar deviation position, and vice versa. Wrist deviation from neutral position in one direction diminished wrist range of motion in the other. INTERPRETATION: Wrist movements in flexion-extension and radial-ulnar deviation are coupled. Maximal wrist range of motion is near the neutral position. To account for the naturally coupled wrist motion in work station design and rehabilitation, the wrist should be placed at a neutral position.

Activities of Daily Living↗

PubMed2005

Reconstruction of the interosseous ligament restores normal forearm compressive load transfer in cadavers.

PURPOSE: Longitudinal radioulnar dissociation may result when compressive load to the hand causes excessive proximal migration of the radius with interosseous ligament (IOL) disruption and radial head fracture. Although radial head salvage or arthroplasty and temporary distal radioulnar joint pinning constitute the current treatment for this injury IOL reconstruction has been proposed to restore normal forearm mechanics. To help provide a biomechanical basis for IOL reconstruction we measured load transfer and proximal migration of the radius with the IOL intact, cut, and reconstructed while leaving the radial head intact. METHODS: We dissected the central third of 12 normal cadaveric forearms to bone-IOL-bone. We applied 136 N of compressive load to the hand and measured proximal radial migration and 3-dimensional force vectors acting in the distal radius, distal ulna, IOL, proximal radius, and proximal ulna. Experiments were performed in neutral forearm rotation and neutral elbow varus-valgus. The protocol was repeated with the IOL intact, cut, and reconstructed with single and double flexor carpi radialis allografts. RESULTS: With the IOL intact 94% +/- 3 % of hand load was in the distal radius with 75% +/- 2% was transmitted to the proximal radius. With the IOL cut 92% +/- 2% of hand load was in the distal radius and this was unchanged at the proximal radius. With single flexor carpi radialis reconstruction 94% +/- 3% of hand load was in the distal radius and 80% +/- 2% was in the proximal radius; with double flexor carpi radialis reconstruction these numbers changed to 95% +/- 3% and 74% +/- 2%, respectively. Forces in the forearm were mainly in the longitudinal and transverse directions with negligible components in the dorsal-volar direction. Transverse force in the IOL was about half that of the longitudinal force in the intact and reconstructed states. CONCLUSIONS: When the IOL is cut and load is applied to the hand the unloading of the proximal radius and the transversely directed force that compresses normally across the proximal and distalradioulnar joints is lost. Reconstruction of the IOL can restore the normal load transfer characteristics. These data help provide a biomechanical basis for IOL reconstruction. Further research on the biomechanics of IOL reconstruction in the setting of radial head replacement along with clinical evaluation is needed.

Aged↗

PubMed2005

Structural properties of reconstruction constructs for the interosseous ligament of the forearm.

PURPOSE: The Essex-Lopresti fracture-dislocation, also termed longitudinal radioulnar dissociation (LRUD), results in major functional impairment from pain and limitation of motion at the wrist and elbow. Interosseous ligament (IOL) reconstruction has been proposed to help treat LRUD and restore forearm stability. The objective of this study was to evaluate the biomechanical structural properties of 3 different IOL reconstruction constructs and of the intact IOL for comparison. METHODS: Structural tensile testing was performed on 24 fresh-frozen cadaveric forearms with 4 different forearm conditions: IOL intact and IOL reconstructed with Achilles tendon, flexor carpi radialis (FCR) tendon, and bone-patellar tendon-bone. Isolated radius-IOL-ulna constructs were loaded to failure in a materials testing machine with force applied along the local fiber direction. RESULTS: Stiffness in the intact IOL was 129 +/- 31 N/mm, which was significantly stiffer than any of the constructs tested. The intact IOL was 8 times stiffer than the Achilles tendon construct, 7 times stiffer than the FCR construct, and 3 times stiffer than the bone-patellar tendon-bone construct. The Achilles tendon and FCR constructs were similar to each other biomechanically but the bone-patellar tendon-bone construct was slightly stiffer than the Achilles tendon and FCR constructs. CONCLUSIONS: All graft constructs tested were inferior structurally to the intact IOL. The results of this study provide a biomechanical basis for graft selection for reconstruction of the IOL.

Aged↗

PubMed2005

Quantifying the effect of the distal intrinsic release procedure on proximal interphalangeal joint flexion: a cadaveric study.

PURPOSE: The distal intrinsic release procedure is a popular treatment for intrinsic hand tightness. The literature remains ambiguous regarding the optimal amount of extensor hood to excise. Our goals were to quantify the mathematic relationship between the amount of extensor hood excised and proximal interphalangeal (PIP) joint flexion and to determine the minimum amount of extensor hood excision required to significantly change PIP joint flexion capability (the ability to achieve a change from the initial PIP joint angle). METHODS: We simulated the distal intrinsic release procedure by sequentially excising 5-mm strips (perpendicular to the long axis of the finger) of the extensor hood of cadaveric fingers beginning 5 mm proximal to the PIP joint center. We tensioned the intrinsic muscles to each digit to produce an intrinsically tight state and tensioned the flexor digitorum superficialis to produce an antagonist force and simulate the intrinsic tightness test. We measured PIP joint angle (the angle of the long axis of the middle phalanx relative to the proximal phalanx) in response to greater portions of excised extensor hood to quantify its contribution to intrinsic tightness. RESULTS: The relationship between the amount of extensor hood excised and the PIP joint flexion capability appeared quadratic, not linear. For the index, ring, and small fingers significant changes in PIP joint flexion were detected after resection of 59%, 26%, and 33%, respectively, of the extensor hood length. Although our results did not show statistical significance for the middle finger we project the critical amount to be at least 65%. CONCLUSIONS: We show PIP joint flexion changes after the distal intrinsic release procedure. We recommend excising a finger-dependent minimum amount of tissue before expecting a significant increase in PIP joint flexion capability.

Cadaver↗

PubMed2005

Thumb strength affected by carpal tunnel syndrome.

UNLABELLED: We examined the effects of carpal tunnel syndrome on thumb strength in multiple directions to test the hypothesis that a force deficit would be most severe in directions associated with abduction. Twelve right-handed women with carpal tunnel syndrome in the right hand, and 12 age-matched, gender-matched, right-handed control subjects were included. Thumb strength was measured in all directions in the transverse plane perpendicular to the longitudinal axis of the thumb. Force envelopes, the boundary of maximal force magnitude, were constructed using the directional forces. The force envelope or envelope area did not differ between the control subjects and the patients with carpal tunnel syndrome. The percentage contributions of force quadrant to the envelope area did not differ between the patients and the control subjects. Our results support the concept that thumb strength is relatively preserved with carpal tunnel syndrome, and failed to support the traditional belief that carpal tunnel syndrome preferentially impairs thumb abduction strength. The data suggest the commonly used testing of thumb abduction strength may not be an effective means to evaluate the existence or severity of carpal tunnel syndrome. LEVEL OF EVIDENCE: Diagnostic study, Level III (study of nonconsecutive patients; without consistently applied "gold" standard). See the Guidelines for Authors for a complete description of levels of evidence.

Adult↗

PubMed2004

Thumb force deficit after lower median nerve block.

PURPOSE: The purpose of this study was to characterize thumb motor dysfunction resulting from simulated lower median nerve lesions at the wrist. METHODS: Bupivacaine hydrochloride was injected into the carpal tunnel of six healthy subjects to locally anesthetize the median nerve. Motor function was subsequently evaluated by measuring maximal force production in all directions within the transverse plane perpendicular to the longitudinal axis of the thumb. Force envelopes were constructed using these measured multidirectional forces. RESULTS: Blockage of the median nerve resulted in decreased force magnitudes and thus smaller force envelopes. The average force decrease around the force envelope was 27.9%. A maximum decrease of 42.4% occurred in a direction combining abduction and slight flexion, while a minimum decrease of 10.5% occurred in a direction combining adduction and slight flexion. Relative decreases in adduction, extension, abduction, and flexion were 17.3%, 21.2%, 41.2% and 33.5%, respectively. Areas enclosed by pre- and post-block force envelopes were 20628 +/- 7747 N.N, and 10700 +/- 4474 N.N, respectively, representing an average decrease of 48.1%. Relative decreases in the adduction, extension, abduction, and flexion quadrant areas were 31.5%, 42.3%, 60.9%, and 52.3%, respectively. CONCLUSION: Lower median nerve lesion, simulated by a nerve block at the wrist, compromise normal motor function of the thumb. A median nerve block results in force deficits in all directions, with the most severe impairment in abduction and flexion. From our results, such a means of motor function assessment can potentially be applied to functionally evaluate peripheral neuropathies.

Journal Article↗

PubMed2004

Circumferential force production of the thumb.

We developed an apparatus to measure maximal continuous circumferential forces of a digit in the transverse plane that is perpendicular to the longitudinal axis. Subjects with asymptomatic hands were asked to produce maximal forces in all directions at the proximal phalanx of the thumb. The force components during circumferential trials were used to construct a force envelope for each subject. The force envelope enlarged as the number of trials increased, and converged to a stable pattern after several trials. The shape of the force envelope was asymmetric and oblique, skewed towards the flexion/adduction direction. Maximal force (112.1 +/- 14.8 N) was generated in the direction combining flexion and adduction. The lowest force produced was only 50.3% of the maximal force in a direction combining extension and abduction. The forces in the direction of adduction, extension, abduction, and flexion were 60.1%, 61.9%, 51.5%, and 92.9% of the maximal force, respectively. The forces generated by circumferential exertions were comparable to the forces by focused directional exertions except in the flexion direction. Our methods have the potential to identify deviations from the normative force output pattern and help detect underlying impairments resulting from neuromuscular disorders.

Adult↗

PubMed2004

Motion enslaving among multiple fingers of the human hand.

The purpose of the current study was to examine motion enslaving characteristics of multiple fingers during isolated flexion of the distal interphalangeal joints. Because the distal interphalangeal joints are flexed by multiple tendons of the single flexor digitorum profundus, the current experimental design provided a unique advantage to understand inter-finger enslaving effects due to the flexor digitorum profundus. Eight subjects were instructed to flex the distal interphalangeal joint of each individual finger from the fully extended position to the fully flexed position as quickly as possible. Maximal angular displacements, velocities, or accelerations of individual fingers were used to calculate the enslaving effects. An independence index, defined as the ratio of the maximal displacement of a master finger to the sum of the maximal displacements of the master and slave fingers, was used to quantify relative independence of each finger. The angular displacements of the index, middle, ring, and little fingers were 68.6(degrees) (+/-7.7), 68.1(degrees) (+/-10.1), 68.1(degrees) (+/-9.7), and 74.7(degrees) (+/-13.3), respectively. The motion of a master finger was invariably accompanied by motion of 1 or 2 slave fingers. Angular displacements of master and slave fingers increased to maximum values with time monotonically. Velocity curves demonstrated bell-shaped profile, and the acceleration curves were sinusoidal. Enslaving effects were generated mainly on the neighboring fingers. The amount of enslaving on the middle and ring fingers exceeded more than 60% of their own maximum angular displacements when a single adjacent finger moved. The index finger had the highest level of independence as indicated by the lowest enslaving effects on other fingers or by other fingers. The independence indices of the index, middle, ring, and little fingers were 0.812 (+/-0.070), 0.530 (+/-0.051), 0.479 (+/-0.099), and 0.606 (+/-0.148), respectively. In all tasks, motion of slave fingers always lagged with respect to the master finger. Time delays, on average, ranged from 7.8 (+/-5.0) to 35.9 (+/-22.1) ms. Our results suggest that there exist relatively large enslaving effects among the compartments of the flexor digitorum profundus, and functional independence of fingers in daily activities is likely enhanced through synergistic activities of multiple muscles, including flexors and extensor.

Adult↗

PubMed2003

Matrix analyses of interaction among fingers in static force production tasks.

The fingers on a hand show interactions in force production tasks. The interfinger connection matrices (IFMs) quantify these interactions (Li et al. 2002; Zatsiorsky et al. 2002b; Danion et al. 2003). The goal of the present study was to explore the differences in the IFMs of individual subjects and, in particular, to establish a procedure that may be used in the future for diagnostic purposes. Subjects ( n=20) pressed downward maximally with ten different combinations of the four fingers, index (I), middle (M), ring (R), and little (L): I, M, R, L, IM, MR, RL, IMR, MRL, and IMRL. Voluntary activation of a subset of the four fingers was accompanied by an involuntary force production by fingers that were not intentionally activated (enslaving). Interfinger connection matrices were computed for each subject by the artificial neural network. The similarities/dissimilarities (proximities) between the individual matrices were determined. This procedure was performed twice: (a) for nonnormalized IFMs whose elements represented the amount of force (in newtons) exerted by a finger i in response to a unit command to a finger j; and (b) for normalized IFMs, after dividing the elements of each IFM by the total force produced by the four fingers acting together (the elements of the matrix are in percents). The 20x20 matrix of the proximities was subjected to multidimensional scaling (MDS) to reduce the number of dimensions and identify the major ones. To interpret the meaning of the computed dimensions, they were regressed on a set of finger force parameters described in the text. For the nonnormalized IFMs an interpretable dimension was the strength of the subjects. For the normalized IFMs two dimensions were interpreted: (a) the location of the point of resultant force application along the mediolateral axis that is defined by the pattern of force sharing among the fingers and (b) the total contribution of the enslaved forces into the total finger force. We speculate that the similarity of typical everyday tasks across the population promotes the similarity of the IMFs reflecting optimal hand functioning over these tasks.

Adult↗

PubMed2003

Reconstruction of the interosseous ligament of the forearm reduces load on the radial head in cadavers.

Excision of the radial head after fracture may be complicated by longitudinal radio-ulnar instability (Essex-Lopresti lesion) if the forearm interosseous ligament has also been torn. In such cases proximal migration of the radius occurs, and ulnar impaction at the wrist and radiocapitellar contact at the elbow may impair function. Although metal radial head arthroplasties are now used for irreparable radial head fractures, the long-term clinical outcome may still be unsatisfactory because of excessive radiocapitellar load causing pain. Interosseous ligament reconstruction might improve outcome by restoring normal load transfer from the radius to ulna, but the biomechanical effect of reconstruction has not been reported. This study evaluated forearm load transfer following interosseous ligament reconstruction with an Achilles tendon allograft in a cadaveric model with the radial head intact. Interosseous ligament reconstruction reduced proximal radius loading by transferring force to the proximal ulna, but force transfer by the reconstruction was only half that by the intact ligament.

Achilles Tendon↗

PubMed2003

Multi-directional strength and force envelope of the index finger.

OBJECTIVE: The purpose of this study was to biomechanically evaluate the motor function of the index finger based on multi-directional strengths. DESIGN: An experimental apparatus was developed to measure force production of a digit at various points of force application along the digit and in any direction of force application within the transverse plane of the longitudinal axis of the digit. BACKGROUND: Most existing tests of hand motor function are subjective, semiquantitative, and/or non-specific. METHODS: Eight normal subjects with asymptomatic hands were tested. Maximum voluntary isometric contraction forces were measured at the middle of the proximal phalanx of the index finger in 16 directions that were evenly distributed within 360 degrees. RESULTS: The highest force, 110.7 (SD 9.0) N, was generated in flexion, while the lowest force was generated in extension. The forces in extension, abduction and adduction were 37.6%, 97.9% and 79.3% of the flexion force, respectively. The area of the force envelope was 25739 (SD 3688) N-N. The average percentage quadrant areas, relative to the total force envelope area, for extension-adduction, extension-abduction, flexion-abduction, and flexion-adduction were 12.9%, 20.4%, 36.0%, and 30.8%, respectively. The average percentage quadrant areas for extension, abduction, flexion, and adduction were 9.1%, 33.3%, 35.6%, and 22.1%, respectively. CONCLUSION: The current study provides an advanced level of quantification of hand motor function. RELEVANCE: The methods may be used as a basis to detect changes in the motor function resulting from pathological conditions, disease progression, as well as rehabilitation and treatment of these disorders.

Adult↗

PubMed2003

Anatomic parameters for planning of interosseous ligament reconstruction using computer-assisted techniques.

PURPOSE: Longitudinal radioulnar dissociation may result when both interosseous ligament (IOL) disruption and radial head fracture occur. Although radial head salvage or arthroplasty and temporary distal radioulnar joint pinning constitute the standard treatment for this injury, IOL reconstruction has been proposed to restore more normal forearm axis mechanics. To help provide an anatomic basis for IOL reconstruction, the purpose of this study was to characterize the geometry of the central band of the IOL and simulated IOL reconstructions. METHODS: Twenty forearms free of pathology were dissected to bone-IOL-bone and computed tomography scans were taken. Computer models of radius-IOL-ulna were created from the computed tomography CT images, and computer-aided design software was used to measure key parameters for IOL reconstruction and simulate anatomic IOL reconstructions. RESULTS: The insertion site locations of the IOL central band along the radius and ulna from the wrist were 57 +/- 3% and 34 +/- 4% of bone length, respectively. The angle at which the IOL central band inserts with the ulna was 24 +/- 4 degrees, which agrees with previously reported values. We found that the minimum graft length needed to anatomically span both cortices through tunnels was 112 +/- 14 mm. CONCLUSIONS: These data will help to provide a basis for planning and performing IOL reconstruction in cases of longitudinal radioulnar dissociation.

Computer Simulation↗