The Effects of Boxing Glove Design on Thumb Position When Making a Fist for Striking.

ABSTRACT: Peveler, WW, Schoffstall, J, Coots, J, Kilian, J, and Glauser, J. The effects of boxing glove design on thumb position when making a fist for striking. J Strength Cond Res 38(5): 948-950, 2024-It has been suggested that boxing glove design alters thumb position increasing the risk of injury. The purpose of this study was to determine the effects of boxing glove design on thumb joint angles when making a fist. Ten experienced fighters participated in this study. A DEXA scan was used to produce an x-ray image of thumb position for all conditions (no gloves and 10-oz boxing gloves). Mean values for dependent measures were compared using a paired-sample T test and an alpha of 0.05. The carpometacarpal (CMC) joint angle was significantly different between no glove (14.1 ± 6.54°) and boxing glove (34.2 ± 7.60°) at p ≤ 0.001. The metacarpophalangeal (MP) joint angle was significantly different between no glove (132.6 ± 12.74°) and boxing glove (149.40 ± 8.15°) at p ≤ 0.001. The IP joint angle was not significantly different between no glove (135.50 ± 19.12°) and boxing glove (144.40 ± 17.39°) at p = 0.269. The perpendicular distance from the second metacarpal of the hand to the center of the MP joint was significantly different between no glove (0.48 ± 0.54 cm) and boxing glove (1.84 ± 0.29 cm) at p ≤ 0.001. Use of a boxing glove resulted in abduction of the thumb away from the hand and increased CMC and MP joint angles that were significantly different in relation to making a fist without a glove. Information from this study may provide insight into the high rate of thumb injury and provide insight for future boxing glove design.

The mechanics of the collateral ligaments in the metacarpophalangeal joints: A scoping review.

BACKGROUND: The metacarpophalangeal (MCP) joint's collateral ligaments have been extensively debated, with no clear consensus on their mechanics. Understanding their function is crucial for comprehending joint movement and stability. METHODS: A thorough search was conducted across databases, including PubMed, Scopus, Cochrane library and grey literature. A total of 59 articles were identified, and after rigorous evaluation, six articles were included in the review. RESULTS: The analysis underscores two principal findings. Firstly, the principal and accessory collateral ligaments exhibit consistent tension influenced by the MCP joint's position. This tension varies across different sections of the ligaments. Secondly, the ligaments' interaction with the joint structure plays a pivotal role in defining the range of motion of the joint. CONCLUSION: Preliminary findings from this review indicate that MCP joint collateral ligament tension varies with joint position. Increased tension in the principal collateral ligament during flexion and isometric behavior of its volar portion in extension are observed. The accessory ligament may tighten during extension. The shape of the metacarpal head appears to influence this tension. These insights, while informative, call for further detailed research to deepen our understanding of MCP joint mechanics.

Arthroscopic mobilization for metacarpophalangeal joint extension contracture.

BACKGROUND: As a first-line surgical treatment for treating metacarpophalangeal (MCP) joint extension contractures, mobilization surgery with open dorsal approach has been indicated. However, this procedure has the possibility to result in postoperative recurrence over the course of time because its invasive open dorsal approach has a negative impact on the postoperative gliding of the extensor mechanism. We report the preliminarily outcomes of patients who underwent a minimally invasive arthroscopic mobilization to alter and enhance their existing surgical strategy in place of MCP joint extension contractures. METHODS: This retrospective study included seven patients with 13 MCP joint extension contractures who had received an arthroscopic release of the bilateral collateral ligament and/or dorsal capsule of affected MCP joint. The extension contractures were caused by long-time immobilization with inadequate extended position of the MCP joint after either hand and wrist fractures, extensor tendon injury, or peripheral nerve palsy. All patients received sufficient exercise under the supervision of a physical therapist for more than 3 months before surgery. However, physical therapy did not improve the MCP joint extension contractures. We measured the active and passive flexion angles preoperatively at 1 and 6 months after surgery. The passive flexion angle was also measured after arthroscopic mobilization on the operation table. Surgery-related complications regarding nerve, vessel, skin, and tendon were also assessed. RESULTS: In all patients, significant improvements were observed in both the active and passive flexion angles 1 month after surgery, and continued to improve 6 months after surgery. Two out of 13 metacarpophalangeal joints developed blisters on the dorsal side of the joint, but conservatively recovered. CONCLUSIONS: Based on the positive improvements observed in our patients, we conclude that this minimally invasive arthroscopic technique has the potential to alter and enhance the surgical treatment strategy for MCP joint extension contractures.

Palpation of the lateral bands of the extensor apparatus of the fingers. Anatomy of a neglected clinical finding.

This study aimed to determine by ultrasonography, and cadaveric dissection, whether the firm cords felt by palpation at the sides of the proximal phalanx (PP), actively flexing, and extending the proximal interphalangeal (PIP) joint while keeping the metacarpophalangeal (MCP) joint extended are the lateral bands (LBs) of the extensor apparatus. If so, palpation of the LBs could help evaluate hand conditions that impact the digits' intrinsic muscles. To this end, the PP of the middle and ring fingers of the dominant hand of seven subjects were studied by palpation on both sides. Ultrasonography (US) was performed with a hockey-stick transducer placed on the ulnar side. Five cadaveric hands were dissected, exposing the dorsal extensor apparatus. On palpation, a firm cord was consistently felt at the PP's sides in all subjects. These cords moved widely forward on PIP flexion and backward with PIP extension. By US scanning, the cords corresponded to the LBs. However, the forward movement had only a median of 1.8 mm (range 0.7-3 mm) in the middle finger and a median of 1.1 mm (range 0.3-2.7 mm) in the ring finger compared with an estimated 5-10 mm upon palpation. Cadaveric dissection confirmed the forward movement of the LBs in PIP flexion. We concluded that the firm cords felt at the PP sides are the LBs of the extensor apparatus. We confirmed their movement with the active flexion/extension of the PIP joint. Comparing the wide palpatory and the meager US motion, a haptic illusion of motion may be present.

Heterogenous bone response to biologic DMARD therapies in rheumatoid arthritis patients and their relationship to functional indices.

Objectives: Previous studies of high-resolution peripheral quantitative computed tomography (HR-pQCT) imaging of hand joints in patients with rheumatoid arthritis (RA) have suggested that erosion healing may occur. Our objective was to examine changes in erosion volume, joint space width (JSW), bone mineral density (BMD), and bone remodelling, and their association with clinical outcomes and measures of patient hand function.Method: We examined 48 patients who achieved a good response to a newly initiated biologic therapy. HR-pQCT images of the dominant hands' second and third metacarpophalangeal joints were obtained 3 and 12 months after therapy initiation. Bone erosion volume, JSW, BMD, and bone remodelling were quantified from HR-pQCT images, with improvement, no change (unchanged), or progression in these measures determined by least significant change. Disease activity and hand function measures were collected.Results: There were no significant group changes in HR-pQCT outcomes over the 9 month period. Twenty-two patients had total erosion volumes that remained unchanged, nine showed improvement, and two progressed. The majority of JSW and BMD measures remained unchanged. There was a significant association between the baseline Health Assessment Questionnaire score and the change in minimum JSW, but no other significant associations between HR-pQCT outcomes and function were observed.Conclusions: The vast majority of patients maintained unchanged JSW and BMD over the course of follow-up. Significant improvements in total erosion volume occurred in 27% of patients, suggesting that biologic therapies may lead to erosion healing in some patients, although this did not have an impact on self-reported and demonstrated hand function.

Predictive value of metacarpophalangeal stabilization tests for simulated ulnar nerve lesion measured by a sensor glove.

STUDY DESIGN: A within-subject research design was used in this study. The difference of the range of motion (ROM) with and without ulnar nerve block was analyzed. INTRODUCTION: For the clinical evaluation of the functional effects of ulnar nerve palsy at the hand the relevance of clinical tests is in discussion. PURPOSE OF THE STUDY: The aim of the study was to evaluate the predictive value of 2 clinical tests for a simulated ulnar nerve lesion by motion analysis with a sensor glove. METHODS: In 28 healthy subjects, dynamic measurements of the finger joints were performed by a sensor glove with and without ulnar nerve block at the wrist. In the 0° metacarpophalangeal (MCP) stabilization test, the subjects were asked to stabilize the MCP joints actively in 0° while moving the interphalangeal joints, whereas at the 90° MCP stabilization test, the subjects stabilized the MCP joints actively in the 90° position. RESULTS: In the 0° MCP stabilization test, no remarkable changes of the ROM were found at the MCP joints; at the proximal interphalangeal joints 2-5, the ROM decreased with ulnar nerve block, significantly at the index, middle, and ring fingers (P < .05). In the 90° MCP stabilization test, the average ROM of the MCP joints 2-5 significantly increased with ulnar nerve block (P < .05), whereas at the PIP joints, the average ROM decreased (P < .05). DISCUSSION: The 90° MCP stabilization test had a high predictive value for the discrimination between healthy subjects and subjects with a simulated peripheral ulnar nerve lesion. CONCLUSIONS: The results could be relevant for the determination of the functional effect of ulnar nerve palsy and the quantification of clawing in hand rehabilitation. LEVEL OF EVIDENCE: II.

Mechanics of Metacarpophalangeal Joint Extension.

PURPOSE: It is a common belief that extension of the metacarpophalangeal (MCP) joint of the finger is achieved via the sagittal bands acting as a sling or lasso to attach the extensor tendon to the base of the proximal phalanx. The aim of this study was to test the hypotheses that (1) division of the sagittal bands reduces extension force or torque of the MCP joint, and (2) division of the extensor tendon distal to the sagittal band will not affect the extension force or torque of the MCP joint. METHODS: Ten cadaver limbs were secured to a jig to allow for testing of the extension force of the MCP joints of the index, middle, and ring fingers. A 1-kg load was applied to the forearm extensor digitorum communis tendon and the extension force was measured with the MCP joint positioned at 0° (neutral extension) and again at 45° flexion. These measurements were repeated after the sagittal bands were divided in 15 specimens; in the other 15 specimens, the extensor tendon was divided just distal to the sagittal bands. RESULTS: After sagittal band division, extension force was similar in the 2 groups (0.11 N reduction after division with the MCP joints in neutral and 0.14 N in 45° flexion). There was significantly less extension force after division of the extensor tendon in both joint positions (0.95 N reduction after division in neutral extension and 0.66 N in 45° flexion). CONCLUSIONS: The sagittal bands do not primarily extend the MCP as a sling or lasso. The extensor tendon continuation to the extensor hood and middle phalanx is the major extension motor. The MCP joint is extended by the torque generated by the extensor tendon passing the joint carrying a force and possessing an extension moment arm. CLINICAL RELEVANCE: This principle should be correctly understood in the literature to ensure that clinical decisions related to injury and/or repair of the extensor tendon and sagittal bands are based on a sound understanding of their mechanics.

Functional range of motion in the metacarpophalangeal joints of the hand measured by single axis electric goniometers.

BACKGROUND: The functional range of motion (fROM) of the metacarpophalangeal (MCP) joints during the performance of activities of daily living (ADL) has not yet been established. This study aimed to determine the fROM of all five digits and verify the accuracy and reproducibility of dynamic angle measurement using a single-axis electric goniometer (EG) during ADL movements of the hand. METHODS: This was a cross-sectional study. In EG suitability testing, we first confirmed the angles of a three-dimensional calibration device 10 times, and then compared EG readings with those determined by tomosynthesis images. Next, we determined the fROM of the MCP joints by evaluating all five digits of the dominant hands of 10 healthy adults performing 16 ADL. Intra-rater reproducibility of MCP joint data during task performance was assessed in two healthy adults. RESULTS: Static measurements of the triangular object showed variance to be within one degree in 39 of 40 trials. Differences between angles measured by the EG and those depicted by radiograph were a range of plus or minus five degrees in 88 of 96 digits. The fROM values for the thumb and index, middle, ring, and little fingers were -7.5 to 35.3, 10.6 to 67.8, 4.0 to 79.9, 3.0 to 83.9, and 2.9-91.4 degrees of flexion, respectively. Flexion angle in the fROM of the index finger was significantly smaller than those of the ring and little fingers. The flexion and extension angles of the thumb were significantly smaller than those of the four ulnar fingers. The intra-rater correlation coefficients of two participants were high at 0.94 and 0.93, respectively. CONCLUSIONS: The method adopted in this study exhibited excellent accuracy and reproducibility and was therefore considered suitable for the real-time establishment of fROM flexion-extension angles of the MCP joints for all five digits. Our data are useful as a target arc of motion in the treatment of MCP joint disease or injury.

Biomechanics and Pinch Force of the Index Finger Under Simulated Proximal Interphalangeal Arthrodesis.

PURPOSE: To analyze the effect of simulated proximal interphalangeal (PIP) joint arthrodesis on distal interphalangeal (DIP) joint free flexion-extension (FE) and maximal voluntary pinch forces. METHODS: Five healthy subjects were tested with the PIP joint unconstrained and constrained to selected angles to produce (1) free FE movements of the DIP joint at 2 selected angles of the metacarpophalangeal joint, and (2) maximal voluntary tip (thumb and index finger) and chuck (thumb, index, and middle fingers) pinch forces. Kinematic data from a motion analysis system, pinch force data from a mechanical pinch meter, and electromyography (EMG) data recorded from 2 flexor and extensor muscles of the index finger were collected during free FE movements of the DIP joint and pinch tests for distinct PIP joint constraint angles. RESULTS: The EMG root mean square (RMS) values of the flexor digitorum profundus (FDP) and extensor digitorum (ED) did not change during free FE of the DIP joint. The extension angle of the range of motion of the DIP joint changed during free FE. It increased as the PIP constraint angle increased. The EMG RMS value of FDP and ED showed maximum values when the PIP joint was unconstrained and constrained at 0° to 20° of flexion during tip and chuck pinch. Neither the index finger metacarpophalangeal and DIP joint positions nor pinch force measurements differed with imposed PIP joint arthrodesis. CONCLUSIONS: The PIP joint arthrodesis angle affects DIP joint extension. A minimal overall impact from simulated PIP arthrodesis in muscle activity and pinch force of the index finger was observed. The EMG RMS values of the FDP and ED revealed that a PIP arthrodesis at 0° to 20° of flexion leads to a more natural finger posture during tip and chuck pinch. CLINICAL RELEVANCE: This study provided a quantitative comparison of free FE motion of the DIP joint, as well as FDP and ED forces during pinch, under simulated index finger PIP arthrodesis angles.

"On-Top Plasty" for Radial Polydactyly Reconstruction.

PURPOSE: To introduce the "on-top plasty" technique and report our long-term outcomes. METHODS: We evaluated 5 thumbs in 5 patients who underwent radial polydactyly reconstruction using the "on-top plasty" technique between 1998 and 2003. This technique was used when it was felt that neither thumb possessed adequate proximal and distal structures to provide a functional and aesthetically pleasing thumb. Our study group included 1 Flatt type III and 4 Flatt type VII thumbs. The average age at time of surgery was 1.4 years and at final follow-up was 13.5 years. Subjective patient evaluation, objective outcomes values, and validated patient-oriented outcome measures were obtained. RESULTS: There was no soft tissue loss and union was achieved in all thumbs with no further surgery required in any thumb. Mean flexion-extension arc for the metacarpophalangeal joint was 60° (range, 10° extension to 70° flexion) and at the interphalangeal joint was 19° (range, 25° extension to 35° flexion). Mean percentage of age-matched norms for lateral, tripod, and tip pinch were 47.0%, 45.9%, and 47.8%, respectively. Mean grip strength was 54.2% of age-matched norm. The mean Pediatric Quality of Life Inventory (PedsQL) score for parent questionnaires was 89.0 and for teen/child questionnaires was 89.1. The Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire revealed a mean score of 4.3. CONCLUSIONS: For patients with radial polydactyly in which neither thumb possesses adequate distal and proximal components, the on-top plasty is a reliable method of polydactyly reconstruction with durable results at longer than 10 years' follow-up. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic V.

Factors affecting extension lag after tendon reconstruction for finger extensor tendon rupture due to distal radioulnar lesion.

BACKGROUND: Although extensor tendon rupture associated with distal radioulnar joint disorder is often encountered, its treatment has not yet been established. We report the postoperative results for reconstruction of finger extensor tendon rupture due to distal radioulnar lesion and analyse the factors affecting postoperative extension lag. METHODS: We examined 74 index, middle, ring, or little fingers with extensor tendon rupture of 34 hands. Primary diseases were rheumatoid arthritis in 24 hands and osteoarthritis in 10. Reconstruction methods included tendon graft in 45 fingers, extensor indicis proprius tendon transfer in 15, and end-to-side adjacent tendon suture in 14. At final postoperative follow-up ranging from 12 to 40 (mean: 18) months, we measured metacarpophalangeal (MCP) joint range of motion and extension lag and statistically evaluated the relationship between postoperative extension lag and several clinical factors. RESULTS: We encountered no cases of re-rupture or worsening of finger flexion range after reconstruction. Mean postoperative active flexion of the MCP joint was 78.1 (range: 45-95) degrees. Mean postoperative extension lag was 10.3 (range: 0-50) degrees. We observed that postoperative extension lag was significantly larger in fingers associated with extensor tendon rupture in two or three additional fingers in the affected hand or in fingers of patients aged 80 years or over. The interval from rupture to reconstruction, reconstruction method, or arthritis type did not remarkably affect outcome. CONCLUSIONS: This study uncovered that surgical intervention for extensor tendon rupture should be performed before three fingers become affected.

Three-dimensional finger joint angles by hand posture and object properties.

The objective of this study was to identify three-dimensional finger joint angles for various hand postures and object properties. Finger joint angles were measured using a VICON system for 10 participants while they pinched objects with two, three, four and five fingers and grasped them with five fingers. The objects were cylinders and square pillars with diameters of 2, 4, 6 and 8 cm and weights of 400, 800, 1400 and 1800 g. Hand posture and object size more significantly affected the joint flexion angles than did object shape and weight. Object shape affected only the metacarpophalangeal (MCP) joint angle of the index finger and the flexion angle of the MCP joint of the little finger. Larger flexion angles resulted when the hand posture was grasping with five fingers. The joint angle increased linearly as the object size decreased. This report provides fundamental information about the specific joint angles of the thumb and fingers. Practitioner Summary: Three-dimensional finger joint angles are of special interest in ergonomics because of their importance in handheld devices and musculoskeletal hand disorders. In this study, the finger joint angles corresponding to various hand postures and objects with different properties were determined.

Impact of Joint Position and Joint Morphology on Assessment of Thumb Metacarpophalangeal Joint Radial Collateral Ligament Integrity.

PURPOSE: A 2-part biomechanical study was constructed to test the hypothesis that coronal morphology of the thumb metacarpophalangeal joint impacts the assessment of instability in the context of radial collateral ligament (RCL) injury. METHODS: Fourteen cadaveric thumbs were disarticulated at the carpometacarpal joint. Four observers measured the radius of curvature of the metacarpal (MC) heads. In a custom jig, a micrometer was used to measure the RCL length as each thumb was put through a flexion and/or extension arc under a 200 g ulnar deviation load. Strain was calculated at maximal hyperextension, 0°, 15°, 30°, 45°, and maximal flexion. Radial instability was measured with a goniometer under 45 N stress. The RCL was then divided and measurements were repeated. Analysis of variance and Pearson correlation metrics were used. RESULTS: The RCL strain notably increased from 0° to 30° and 45° of flexion. With an intact RCL, the radial deviation was 15° at 0° of flexion, 18° at 15°, 17° at 30°, 16° at 45°, and 14° at maximal flexion. With a divided RCL, instability was greatest at 30° of flexion with 31° of deviation. The mean radius of curvature of the MC head was 19 ± 4 mm. Radial instability was inversely correlated with the radius of curvature to a considerable degree only in divided RCL specimens, and only at 0° and 15° of flexion. CONCLUSIONS: The RCL contributes most to the radial stability of the joint at flexion positions greater than 30°. The results suggest that flatter MC heads contribute to stability when the RCL is ruptured and the joint is tested at 0° to 15° of metacarpophalangeal flexion. CLINICAL RELEVANCE: The thumb MC joint should be examined for RCL instability in at least 30° of flexion.

Contribution to the study of stresses in the thumb column during key pinch grip.

OBJECTIVES: The aim of this study was to calculate the stress acting on the trapeziometacarpal joint during an key pinch grip. METHOD: We used profile X-rays of the thumb to measure the various bony and muscle lever arms. We assessed the angles of action of the muscular elements involved in the thumb column. Based on this data, we established a two-dimensional geometric model that enabled us to determine the forces at each joint level, as a function of stresses and muscular contributions. We were also able to calculate the participation of the different muscle groups in obtaining a balanced situation. RESULTS: Our results, as a function of the degree of flexion of the interphalangeal and metacarpophalangeal joints, show a multiplying factor of 2.9-3.19 in relation to the key pinch grip force. DISCUSSION: Previous studies modelling a key pinch grip are showed multiplying factors from 6 to 13 in relation to the key pinch grip force. They are not compatible with the characteristics of the polyethylene used for trapeziometacarpal prostheses, whereas numerous articles in the literature show survival rates that are more or less comparable to those of total hip prostheses. These studies required an excessive number of assumptions, which could lead to error. Our results are compatible with the results of trapeziometacarpal prosthesis and with those of a recent study measuring intra-articular trapeziometacarpal pressure in a cadaveric model. Our model allows us to test different configurations of the thumb spine depending on the degree of flexion of the interphalangeal and metacarpophalangeal joints.

Intrinsic hand muscle function, part 2: kinematic comparison of 2 reconstructive procedures.

PURPOSE: Reconstruction of grasp is a high priority for tetraplegic patients. Restoration of finger flexion by surgical activation of flexor digitorum profundus can result in roll-up finger flexion, interphalangeal (IP) joint before metacarpophalangeal (MCP) joint flexion, which can be improved by restoring intrinsic function. This study compares grasp kinematics between 2 intrinsic balancing procedures-Zancolli-lasso and House. METHODS: The intrinsic muscles of 12 cadaver hands were reconstructed by either the Zancolli-lasso or the House procedure (n = 6 each) and tested by deforming the flexor digitorum profundus (FDP) with a motor to simulate hand closure. Results were compared with 5 control hands. All 17 hands were studied by video analysis. Kinematics were characterized by the order of MCP joint and IP joint flexion. Optimal grasp was defined as the maximal fingertip-to-palm distance during the arc of finger closure. RESULTS: Kinematics differed between the 2 procedures. The Zancolli-lasso reconstructed hands flexed first in the IP joints, and then in MCP joints, resembling an unreconstructed intrinsic-minus hand whereas the House reconstructed hands flexed first in the MCP joints and then in the IP joints, resembling an intrinsic-activated hand. Maximal fingertip-to-palm distance did not differ significantly between the 2 procedures, and both showed improvement over unreconstructed controls. CONCLUSIONS: Both intrinsic balancing techniques improved grasp. Only the House procedure restored hand kinematics approximating those of an intrinsic-activated hand. Improvement in fingertip-to-palm distance in Zancolli-lasso hands resulted primarily from the initial resting MCP joint flexion of 40°. We therefore advocate the more physiological House procedure for restoration of intrinsic function in tetraplegic patients. CLINICAL RELEVANCE: This study provides a rationale for advocacy of 1 reconstructive procedure over another.

Relationship of serum relaxin to generalized and trapezial-metacarpal joint laxity.

PURPOSE: The reproductive hormone relaxin acts to loosen pelvic ligaments in preparation for childbirth and is thought to be a mediator of joint laxity. The purpose of this study was to evaluate the correlation of serum relaxin with radiographic laxity at the trapezial-metacarpal joint and with generalized joint laxity. METHODS: We enrolled 289 healthy subjects prospectively. Participants completed a demographic questionnaire and were examined for generalized joint hypermobility using the Beighton-Horan scale. Stress radiographs of the trapezial-metacarpal joint were obtained in 163 subjects (56%). Blood samples were collected, and serum relaxin was measured for 287 subjects using enzyme-linked immunosorbent assay for human relaxin-2. RESULTS: The mean serum relaxin level among all subjects was 1.84 pg/mL (range, 0-45.25 pg/mL). Relaxin was not detectable in 166 of 287 samples, whereas the mean serum relaxin level among the 121 subjects with a detectable relaxin level (of 287 total relaxin samples) was 4.37 pg/mL (range, 0.46-45.25 pg/mL). Mean trapezial-metacarpal subluxation ratio scores were higher among those with a detectable relaxin level compared to those without a detectable relaxin level (0.34 vs 0.30 pg/mL). The average Beighton-Horan laxity score was 1.8 (range, 0-9). There was no correlation between generalized joint laxity measures and serum relaxin levels. CONCLUSIONS: In a large volunteer population, we demonstrated a relationship between circulating relaxin and trapezial-metacarpal joint laxity. However, we were unable to show a direct link between serum relaxin and generalized joint laxity. TYPE OF STUDY/LEVEL OF EVIDENCE: Prognostic II.

Essential motion of metacarpophalangeal joints during activities of daily living.

STUDY DESIGN: Bench research. INTRODUCTION: Although information on the range of motion (ROM) required to perform activities is important when setting ROM goals to enable patients to engage in them, there are few studies reporting the required ROM of fingers. PURPOSE OF THE STUDY: To analyze the range of joint motion required of the finger MCP joint to perform activities and to compare the maximum flexion and maximum extension angle required of the finger MCP joints in the individual fingers. METHODS: We used an electrogoniometer to measure the ROM of four finger MCP joints in the dominant hand in healthy adults (n = 20) performing 19 activities. Finger MCP joint angles were analyzed throughout each of the 19 tasks. RESULTS: The mean ROM of finger MCP joints of the index, middle, ring, and little fingers required to perform all 19 activities ranged from -10 to 60°, -10 to 75°, -10 to 80°, and -10 to 85°, respectively. The mean maximum flexion angle of the finger MCP joints gradually increased as the finger MCP joints were compared moving from the radial to the ulnar side. CONCLUSION: The data obtained in this study on MCP joint motions that are required to perform activities may be beneficial in setting ROM goals for patients with finger MCP joint impairment. LEVEL OF EVIDENCE: NA.

Effects of metacarpophalangeal joint position and finger joint movement speed on lumbrical muscle activity.

OBJECTIVES: The effect of metacarpophalangeal joint position and finger joint movement speed on lumbrical muscle activity remains unproven and was examined in this study. MATERIAL AND METHODS: Twenty-four healthy adults performed flexion-extension movements of the index finger in different metacarpophalangeal joint positions (extension or flexion) and movement speeds (60, 120, 240, and 360 beats per minute). The activities of the first lumbrical, first dorsal interosseous, and extensor digitorum muscles were evaluated using surface electromyography, and compared with those during finger joint extension. RESULTS: The metacarpophalangeal joint positions affected only lumbrical muscle activity, which was greater during extension. Further, finger movement speed affected the lumbrical and extensor digitorum muscle activities, which increased with increasing movement speeds. CONCLUSION: The present study suggests that position and movement speed can influence the lumbrical muscle activity during metacarpophalangeal joint extension. These findings may help expound lumbrical function and develop suitable strategies for inducing lumbrical muscle activity.

Hypothesis: terminal transverse limb defects with "nubbins" represent a regenerative process during limb development in human fetuses.

BACKGROUND: Terminal transverse limb defects with nubbins occur in one arm at one of several levels (distal humerus, proximal forearm, wrist, and at the metacarpal-phalangeal joint in the hand). The associated nubbins contain osteocartilaginous tissue and small nails and are not associated with evidence of amnion disruption. METHODS: We present affected newborn infants whose terminal transverse limb defects are at one of these three levels: proximal forearm, elbow, or metacarpal-phalangeal joint. RESULTS: We hypothesize that the presence of residual digit-like structures reflects a regenerative process that has occurred during limb development in these infants. DISCUSSION: Only limited regeneration of digit-like structures can occur in the human fetus.

Relationship between Metacarpophalangeal Joint Angle and Muscle Activity of Healthy Persons while Using the Finger Extensor Facilitation Training Device "iPARKO".

Applying an external force to a person's hyperextended fingertip produces electrical activity in the extensor digitorum communis, even if the person does not try to open their hand. Based on this, a finger extensor facilitation technique conducted by therapists was developed. In this study, we developed a finger extensor facilitation training device named iPARKO that imitates this technique. We examined the relationship between the metacarpophalangeal (MP) joint angle of the four fingers and the activities in the extensor digitorum communis resulting from active training using iPARKO. At the same time, the relationship between the MP joint angle and the reduced activities in the flexor digitorum superficialis was also examined. The experiments were conducted on five healthy subjects. It was found that as the MP joint approached its own maximum hyperextension position, the amount of activity of the extensor digitorum communis increased, and the amount of activity of the flexor digitorum superficialis decreased.