Biomedical subjects

K N An

Publications and source records attributed to K N An.

At least 73 records · Page 4Linked to original sources

PubMed2000

Calcaneocuboid distraction arthrodesis for posterior tibial tendon dysfunction and flatfoot: a cadaveric study.

Nine fresh-frozen foot specimens were studied to determine the mechanical behavior of the foot using calcaneocuboid distraction arthrodesis, an operation designed for treatment of posterior tibial tendon dysfunction with flatfoot deformity. Flatfoot deformity was created in cadaveric specimens, and to simulate toe-off phase of gait, loads were applied to the plantar surface of the foot and six tendons. Three-dimensional tarsal bone positions were determined with a magnetic tracking system. With ligament sectioning, flatfoot deformity was observed and average arch height decreased 53 +/- 3.5 mm. Height arch increased after calcaneocuboid distraction arthrodesis an average of 3.2 +/- 3.6 mm and was less than normal arch at an average of 2.1 +/- 2.4 mm. Metatarsotalar alignment compared with flatfoot improved after calcaneocuboid distraction arthrodesis in adduction and inversion to the extent that these were not significantly different from intact foot positions. Calcaneotalar position improved after calcaneocuboid distraction arthrodesis in adduction and inversion. Calcaneocuboid alignment compared with flatfoot improved after calcaneocuboid distraction arthrodesis in adduction, plantar flexion, and eversion, but compared with an intact foot was overcorrected in all three planes of motion. Arch alignment in simulated toe-off phase of gait in cadaveric feet was improved significantly with calcaneocuboid distraction arthrodesis but was not reduced anatomically.

Aged↗

PubMed2000

Effects of mechanical stress/strain and estrogen on cancellous bone structure predicted by fuzzy decision.

A theoretical model was developed on the basis of fuzzy decision to predict cancellous bone structure following changes in mechanical stress/strain and estrogen. The model was validated experimentally by simulation of the normal structure of a rat distal femur, and further used to predict the structural alterations following ovarian hormone deficiency. The results show that net bone resorption after ovariectomy occurs in the metaphysis at locations where trabecula were subjected to the lowest mechanical stress/strain. These findings, consistent with experimental results, suggest that estrogen deficiency increase the mechanostat set point at which bone cells perceive mechanical stress/strain. Additionally, the results show that changes in bone architecture which are due to alterations in bone remodeling can be simulated by fuzzy decision without precise mathematical description, and multiple factors can also be readily incorporated into the model.

Animals↗

PubMed2000

Comparison of mechanical properties of various suture repair techniques in a partially lacerated tendon.

The technique of surgical repair for zone two flexor tendon injuries has been debated extensively throughout the years, yet adhesion formation, suture rupture, and suture locking on the pulley edge remain possible consequences of a poor repair. The partially lacerated tendon is especially challenging to treat since there can be justification for not intervening surgically. In a partial laceration canine model we measured failure load and suture gap formation for tendons repaired with the Lee, modified four-strand Savage, Kessler, modified Kessler, and Augmented Becker core suture techniques and with a simple running peripheral suture. The modified Kessler (106.3 N, SD 18.8 N) and modified Savage (108.2 N, SD 19.9 N) repair techniques had a significantly higher failure load than the Lee (85.0 N, SD 20.6 N) suture method (P < 0.05), while there were no differences among the other techniques. There were no significant differences in resistance to gap formation among the repair techniques, with the mean values ranging from 38.9 N/mm (SD 15.7 N/mm) using the simple running suture to 53.2 N/mm (SD 25.8 N/mm) with the Kessler repair. The mean load to produce a 1.5 mm repair site gap ranged from 71.1 N (SD 21.5 N) in the Lee repair to 91.3 N (SD 22.2 N) in the Augmented Becker repair although there were no significant differences among repair methods. All repair methods were much weaker than tendons left unrepaired (184.7 N, SD 41.3 N).

Animals↗

PubMed2000

Mechanical properties of a biodegradable bone regeneration scaffold.

Poly (Propylene Fumarate) (PPF), a novel, bulk erosion, biodegradable polymer, has been shown to have osteoconductive effects in vivo when used as a bone regeneration scaffold (Peter, S. J., Suggs, L. J., Yaszemski, M. J., Engel, P. S., and Mikos, A. J., 1999, J. Biomater. Sci. Polym. Ed., 10, pp. 363-373). The material properties of the polymer allow it to be injected into irregularly shaped voids in vivo and provide mechanical stability as well as function as a bone regeneration scaffold. We fabricated a series of biomaterial composites, comprised of varying quantities of PPF, NaCl and beta-tricalcium phosphate (beta-TCP), into the shape of right circular cylinders and tested the mechanical properties in four-point bending and compression. The mean modulus of elasticity in compression (Ec) was 1204.2 MPa (SD 32.2) and the mean modulus of elasticity in bending (Eb) was 1274.7 MPa (SD 125.7). All of the moduli were on the order of magnitude of trabecular bone. Changing the level of NaCl from 20 to 40 percent, by mass, did not decrease Ec and Eb significantly, but did decrease bending and compressive strength significantly. Increasing the beta-TCP from 0.25 g/g PPF to 0.5 g/g PPF increased all of the measured mechanical properties of PPF/NVP composites. These results indicate that this biodegradable polymer composite is an attractive candidate for use as a replacement scaffold for trabecular bone.

Absorbable Implants↗

PubMed2000

The effect of a glenoid defect on anteroinferior stability of the shoulder after Bankart repair: a cadaveric study.

BACKGROUND: An osseous defect of the glenoid rim is sometimes caused by multiple recurrent dislocations of the shoulder. It is generally thought that a large defect should be treated with bone-grafting, but there is a lack of consensus with regard to how large a defect must be in order to necessitate this procedure. Some investigators have proposed that a defect must involve at least one-third of the glenoid surface in order to necessitate bone-grafting. However, it is difficult to determine (1) whether a defect involves one-third of the glenoid surface and (2) whether a defect of this size is critical to the stability of the shoulder after a Bankart repair. The purposes of the present study were (1) to create and quantify various sizes of osseous defects of the glenoid and (2) to determine the effect of such defects on the stability and motion of the shoulder after Bankart repair. METHODS: The glenoids from sixteen dried scapulae were photographed, and the images were scanned into a computer. The average shape of the glenoid was determined on the basis of the scans, and this information was used to design custom templates for the purpose of creating various sizes of osseous defects. Ten fresh-frozen cadaveric shoulders then were obtained from individuals who had been an average of seventy-nine years old at the time of death, and all muscles were removed to expose the joint capsule. With use of a custom multiaxis electromechanical testing machine with a six-degrees-of-freedom load-cell, the humeral head was translated ten millimeters in the anteroinferior direction with the arm in abduction and external rotation as well as in abduction and internal rotation. With a fifty-newton axial force constantly applied to the humerus in order to keep the humeral head centered in the glenoid fossa, the peak force that was needed to translate the humeral head a normalized distance was determined under eleven sequential conditions: (1) with the capsule intact, (2) after the creation of a simulated Bankart lesion, (3) after the capsule was repaired, (4) after the creation of an anteroinferior osseous defect with a width that was 9 percent of the glenoid length (average width, 2.8 millimeters), (5) after the capsule was repaired, (6) after the creation of an osseous defect with a width that was 21 percent of the glenoid length (average width, 6.8 millimeters), (7) after the capsule was repaired, (8) after the creation of an osseous defect with a width that was 34 percent of the glenoid length (average width, 10.8 millimeters), (9) after the capsule was repaired, (10) after the creation of an osseous defect with a width that was 46 percent of the glenoid length (average width, 14.8 millimeters), and (11) after the capsule was repaired. RESULTS: With the arm in abduction and external rotation, the stability of the shoulder after Bankart repair did not change significantly regardless of the size of the osseous defect (p = 0.106). With the arm in abduction and internal rotation, the stability decreased significantly as the size of the osseous defect increased (p<0.0001): the translation force in shoulders in which the width of the osseous defect was at least 21 percent of the glenoid length (average width, 6.8 millimeters) was significantly smaller than the force in shoulders without an osseous defect. The range of external rotation in shoulders in which the width of the osseous defect was at least 21 percent of the glenoid length was significantly less than that in shoulders without a defect (p<0.0001) because of the pretensioning of the capsule caused by closing the gap between the detached capsule and the glenoid rim. The average loss of external rotation was 25 degrees per centimeter of defect. CONCLUSIONS: An osseous defect with a width that is at least 21 percent of the glenoid length may cause instability and limit the range of motion of the shoulder after Bankart repair.

Aged↗

PubMed2000

Dynamic glenohumeral stability provided by the rotator cuff muscles in the mid-range and end-range of motion. A study in cadavera.

BACKGROUND: Both static and dynamic factors are responsible for glenohumeral joint stability. We hypothesized that dynamic factors could potentially operate throughout the entire range of glenohumeral motion, although capsuloligamentous restraints (a static factor) have been thought to be primarily responsible for stability in the end-range of motion. The purpose of this study was to quantitatively compare the dynamic glenohumeral joint stability in the end-range of motion (the position of anterior instability) with that in the mid-range by investigating the force components generated by the rotator cuff muscles. METHODS: Ten fresh-frozen shoulders from human cadavera were obtained, and all soft tissues except the rotator cuff were removed. The glenohumeral capsule was resected after the rotator cuff muscles had been released from the scapula. A specially designed frame positioned the humerus in 60 degrees of abduction and 45 degrees of extension with respect to the scapula. The compressive and shear components on the glenoid were measured before and after a constant force was applied individually to each muscle with the humerus in five different positions (from neutral to 90 degrees of external rotation). The dynamic stability index, a new biomechanical parameter reflecting these force components and the concavity-compression mechanism, was calculated. The higher the dynamic stability index, the greater the dynamic glenohumeral stability. RESULTS: In the mid-range of motion, the supraspinatus and subscapularis provided higher dynamic stability indices than did the other muscles (p < 0.05). On the other hand, when the position of anterior instability was simulated in the end-range of motion, the subscapularis, infraspinatus, and teres minor provided significantly higher dynamic stability indices than did the supraspinatus (p < 0.005). CONCLUSIONS: The rotator cuff provided substantial anterior dynamic stability to the glenohumeral joint in the end-range of motion as well as in the mid-range. CLINICAL RELEVANCE: A glenohumeral joint with a lax capsule and ligaments might be stabilized dynamically in the end-range of motion if the glenoid concavity is maintained and the function of the external and internal rotators, which are efficient stabilizers in this position, is enhanced.

Aged↗

PubMed2000

Analysis of the shoulder implant.

Total shoulder arthroplasty (TSA) is implemented for the relief of pain and better joint function. It is desirable that the TSA can achieve and maintain a long-term and secure fixation of the implanted components. The previous biomechanical studies of shoulder implants were simplified and limited to the two-dimensional (2-D) computational finite element analysis (FEA). In this research, reliable 3-D FEA models were established and used to examine the contact stress distribution, contact region and deformation of implant. Based on FEA results, the design of current shoulder implants can be modified for optimum performance. The substantiated 3-D FEA models can provide important engineering data and clinically useful information toward the development of better shoulder implants for a long-term fixation.

Arthroplasty, Replacement↗

PubMed1999

Chimpanzee thumb muscle cross sections, moment arms and potential torques, and comparisons with humans.

This study investigates the morphological basis of differences between humans and chimpanzees in the kinematical and dynamical parameters of the musculature of the thumb. It is partly intended to test an hypothesis that human thumb muscles can exert significantly greater torques, due to larger muscle cross-sectional areas or to longer tendon moment arms or to both. We focus on the estimation of the potentials of thumb muscles to exert torques about joint axes in a sample of eight chimpanzee cadaver hands. The potential torque of a muscle is estimated by taking the product of a muscle's physiological cross-sectional area (an estimator of force) with its dynamical moment arm (derived from the slope of tendon excursion versus joint angular displacement, obtained during passive movements of cadaver thumb joints). Comparison of our results with similar data obtained for humans at the same Mayo Clinic laboratory shows significant differences between humans and chimpanzees in potential torque of most thumb muscles, those of humans generally exhibiting larger values. The primary reason for the larger torques in humans is that their average moment arms are significantly longer, permitting greater torque for a given muscle size. An additional finding is that chimpanzees and humans differ in the direction of secondary thumb metacarpal movements elicited by contraction of some muscles, as shown by differences in moment arm signs for a given movement in the same muscle. The differences appear to be related to differences in the musculo-skeletal structures of the trapeziometacarpal joint.

Animals↗

PubMed1999

Periosteum responds to dynamic fluid pressure by proliferating in vitro.

Periosteum provides a source of undifferentiated chondrocyte precursor cells for fracture healing that can also be used for cartilage repair. The quantity of cartilage that can be produced, which is a determining factor in fracture healing and cartilage repair, is related to the number of available stem cells in the cambium layer. Cartilage formation during both of these processes is enhanced by motion of the fracture or joint in which periosteum has been transplanted. The effect of dynamic fluid pressure on cell proliferation in periosteal tissue cultures was determined in 452 explants from 60 immature (2-month-old) New Zealand White rabbits. The explants were cultured in agarose suspension for 1-14 days. One group was subjected to cyclic hydrostatic pressure, which is referred to as dynamic fluid pressure, at 13 kPa and a frequency of 0.3 Hz. Control explants were cultured in similar chambers without application of pressure. DNA synthesis ([3H]thymidine uptake) and total DNA were measured. The temporal pattern and distribution of cell proliferation in periosteum were evaluated with autoradiography and immunostaining with proliferating cell nuclear antigen. Dynamic fluid pressure increased proliferation of periosteal cells significantly, as indicated by a significant increase in [3H]thymidine uptake at all time points and a higher amount of total DNA compared with control values. On day 3, when DNA synthesis reached a peak in periosteal explants, [3H]thymidine uptake was 97,000+/-5,700 dpm/microg DNA in the group exposed to dynamic fluid pressure and 46,000+/-6,000 dpm/microg in the controls (p < 0.001). Aphidicolin, which blocks DNA polymerase alpha, inhibited [3H]thymidine uptake in a dose-dependent manner in the group subjected to dynamic fluid pressure as well as in the positive control (treated with 10 ng/ml of transforming growth factor-beta1) and negative control (no added growth factors) groups, confirming that [3H]thymidine measurements represent proliferation and dynamic fluid pressure stimulates DNA synthesis. Total DNA was also significantly higher in the group exposed to dynamic fluid pressure (5,700+/-720 ng/mg wet weight) than in the controls (3,700+/-630) on day 3 (p < 0.01). Autoradiographs with [3H]thymidine revealed that one or two cell cycles of proliferation took place in the fibrous layer prior to proliferation in the cambium layer (where chondrocyte precursors reside). Proliferating cell nuclear antigen immunophotomicrographs confirmed the increased proliferative activity due to dynamic fluid pressure. These findings suggest either a paracrine signaling mechanism between the cells in these two layers of the periosteum or recruitment/migration of proliferating cells from the fibrous to the cambium layer. On the basis of the data presented in this study, we postulate that cells in the fibrous layer respond initially to mechanical stimulation by releasing growth factors that induce undifferentiated cells in the cambium layer to divide and differentiate into chondrocytes. These data indicate that cell proliferation in the early stages of chondrogenesis is stimulated by mechanical factors. These findings are important because they provide a possible explanation for the increase in cartilage repair tissue seen in joints subjected to continuous passive motion. The model of in vitro periosteal chondrogenesis under dynamic fluid pressure is valuable for studying the mechanisms by which mechanical factors might be involved in the formation of cartilage in the early fracture callus and during cartilage repair.

Aging↗

PubMed1999

Normative values of agonist-antagonist shoulder strength ratios of adults aged 20 to 78 years.

OBJECTIVE: To determine normative values for isometric flexion/extension, abduction/adduction, and external/internal rotation strength ratios about the shoulder and to determine if these ratios are affected by age or gender. STUDY DESIGN: A cross-sectional study of 120 healthy volunteers (60 men, 60 women) aged 20 to 78 years. SETTING: Orthopedic research laboratory. METHODS: Flexion and extension strengths were measured isometrically using a Cybex II dynamometer at arm flexion angles of 30 degrees, 60 degrees, and 90 degrees. Abduction and adduction strengths were measured at 30 degrees, 60 degrees, and 90 degrees abduction. Internal and external rotation strengths were measured (1) with the arm abducted 15 degrees and neutral external/internal rotation and (2) with the arm abducted 90 degrees and externally rotated 30 degrees above the transverse plane. OUTCOME MEASURES: Isometric strength ratios for flexion/extension, abduction/adduction, and external/internal rotation. RESULTS: No statistically significant differences in agonist/antagonist strength ratios were found between dominant and nondominant sides or between genders. Age was associated with changes in strength ratios for measurements taken with the arm flexed or abducted 90 degrees. Posture was found to affect strength ratios. CONCLUSIONS: These data can serve as a normative reference for clinical use.

Adult↗

PubMed1999

The effects of wrist distraction on carpal kinematics.

Changes in carpal kinematics under wrist distraction were studied in fresh cadaveric specimens. A magnetic tracking device measured kinematic motions of the scaphoid, lunate, and third metacarpal relative to the fixed radius in 3 planes of passive motion (coronal, sagittal, and "dart throwers") under progressive distraction loads. The change in percent contribution of the radiocarpal and midcarpal joints was calculated. Radiocarpal motion during extension was decreased as increasing traction was applied, but it increased with flexion. Motion of the scaphoid relative to the lunate was smaller in the oblique plane, resulting in less radiocarpal motion than in the sagittal plane. In the coronal plane, traction had little effect on radial deviation, but ulnar angulation of the scaphoid was greater with ulnar deviation of the wrist. These results suggest that different degrees of tension exist in the palmar and dorsal ligaments with the wrist under traction and during different planes of wrist motion. If wrist motion is desired during fixed traction, such as used clinically with external fixation, the dart-throwers motion (wrist extension with radial deviation and wrist flexion with ulnar deviation) appears to have the least impact on radiocarpal motion. If greater radiocarpal motion is desired, however, such as during postoperative mobilization, flexion-extension and radioulnar deviation will create more radiocarpal motion than the dart-thrower's motion.

Biomechanical Phenomena↗

PubMed1999

In-vivo function of the thumb muscles.

OBJECTIVE: The purpose of this study is to quantify the electrical activity of the thumb muscles responsible for the production of force in different directions of thumb movement. DESIGN: The isometric forces and electromyographic activity generated by seven thumb muscles were measured on five normal healthy test subjects. BACKGROUND: The thumb is very important for proper hand function. Presently available electromyographic studies of the thumb muscles provide only limited information. Most thumb muscles have more than one function. Additional studies are required to carefully examine and confirm the in-vivo relationship between the thumb muscle electromyogram and mechanical output. METHODS: The direction and magnitude of the force vector generated at the interphalangeal joint and the relative electrical activity were obtained for eight directions of thumb action. The regions of function were defined for the abductor pollicis brevis, opponens pollicis, flexor pollicis brevis, adductor pollicis, flexor pollicis longus, extensor pollicis longus, and the abductor pollicis longus. Data was collected during voluntary isometric contraction, both before and after blocking the median nerve at the wrist. RESULTS: The highest force production was obtained during flexion. The region of maximal muscle electrical activity varied for each muscle studied. The areas of maximal in-vivo muscle activity agreed with the moment arm data reported in the literature. The median nerve block eliminated the ability to produce force in abduction. CONCLUSIONS: This study has demonstrated that by combining electromyographic measurement and biomechanical analysis it is possible to confirm the relationship between in-vivo thumb muscle function and muscle mechanics in a novel manner. The findings of this study indicate the importance of the local anatomy in controlling the direction of force production.

Adult↗

PubMed1999

Abduction moment arm of transposed subscapularis tendon.

OBJECTIVE: The purpose of this study was to analyze the effects of the procedure of superior transposition of the subscapularis on the biomechanics of glenohumeral abduction. DESIGN: The abduction moment arms of the subscapularis muscle for the normal attachment and transposed tendon were measured on 10 cadaver shoulders and compared to that for the normal supraspinatus tendon for which it is intended to substitute. BACKGROUND: Superior transposition of the subscapularis tendon has been recommended for surgical repair of massive tears of the rotator cuff, but the effect of this procedure on shoulder biomechanics has not been reported. METHODS: The moment arm about an instantaneous center of rotation was derived, based on the slope of tendon excursion-glenohumeral angle curve. To simulate the insertion of the transposed subscapularis tendon, pseudo-insertion sites were created. RESULTS: Superior transposition of the subscapularis tendon significantly increased its abduction moment arm. The effect was optimal when the simulated insertion site was lateral rather than medial and, to a lesser extent, anterior versus posterior. CONCLUSIONS: The results provided a biomechanical rationale for subscapularis tendon transposition in restoring the loss of abduction strength of the shoulder in a massive cuff tear.

Adult↗

PubMed1999

Optimum length of muscle contraction.

OBJECTIVE: The purpose of this study was to develop a mathematical method to determine optimum muscle length and muscle stress based on the measurable physiological and biomechanical data. DESIGN: The values of optimum muscle length and muscle stress are investigated. BACKGROUND: Understanding the characteristics of muscle function in vivo is important for assisting the design of the tendon transfer and other rehabilitation procedures. In vivo determination of the physiological and anatomical parameters of muscle contraction is difficult but not impossible. Optimum muscle length and muscle stresses are important parameters for understanding muscle function. METHODS: A Cybex dynamometer was used to measure isometric elbow flexion torque in eight different joint positions in seven subjects. Then the optimization method was used to determine optimum muscle length and muscle stress of three major elbow flexors, the biceps brachii, the brachialis, and the brachioradialis based on the model and joint torque data. RESULTS: The calculated muscle stress for each subject was on average 109 N/cm(2), while the optimum muscle length for the biceps brachii, the brachialis, and the brachioradialis was on average 14.05, 6.53, 17.24 cm, respectively. The joint angles corresponding to these optimum muscle lengths are 110 degrees, 100 degrees and 50 degrees of elbow flexion, respectively. CONCLUSIONS: Optimum muscle length and muscle stress can be properly predicted using an analytical mathematical model along with an experimentally measured joint torque. RELEVANCE: The estimate of optimum muscle length is important for muscle modeling and tendon transfer surgery by taking advantage of length-tension relationship of individual muscles.

Adult↗

PubMed1999

Identification of optimal strategies for increasing whole arm strength using Karush-Kuhn-Tucker multipliers.

OBJECTIVE: The purpose of this study was to develop a computer model for identifying muscles critical to improving functional upper extremity strength. DESIGN: A three-dimensional biomechanical model of the upper extremity was developed, and the predictions were compared to maximal arm strength data collected from healthy volunteers. BACKGROUND: Although several optimization-based mathematical models of the shoulder have been developed, none have utilized the mathematical properties of the Karush-Kuhn-Tucker multipliers to efficiently estimate the effect of strengthening individual muscles on functional strength of the whole arm. METHODS: A static three-dimensional biomechanical model of the glenohumeral, radio-humeral, ulno-humeral and wrist joints was developed for predicting maximal hand exertion forces. The model was formulated as a linear program. Constraints consisted of moment equilibrium conditions and limits on maximum and minimum allowable muscle forces. Predicted arm strengths were compared to maximal pull strength measurements made on 10 subjects (5 male; 5 female). The task involved pulling toward the mid-sagittal plane of the body with the arm flexed 45 degrees. The Karush-Kuhn-Tucker variables associated with the maximal limits on muscle force were computed to estimate the effect of altering the strength of individual muscles on functional arm strength. RESULTS: Maximum pull strengths were predicted well by the model. Karush-Kuhn-Tucker values ranged from 0 (for muscles not at their upper force limits) to 0.11 for the flexor carpi radialis and pectoralis major muscles. Karush-Kuhn-Tucker multipliers were found to be insensitive to the assumed specific tension of muscle. CONCLUSIONS: Upper extremity strength can be predicted from musculoskeletal geometry and physiology using linear programming. RELEVANCE: Karush-Kuhn-Tucker multipliers associated with the muscle force upper limits give insight into the effect of strengthening individual muscles on whole arm exertion strength. Such an analysis may provide insight into the development of optimal rehabilitation protocols.

Adult↗

PubMed1999

Biomechanical analysis of the trapeziometacarpal joint after surface replacement arthroplasty.

A biomechanical analysis of the trapeziometacarpal joint was performed in 7 fresh-frozen normal human cadaveric hands to compare the kinematics of the trapeziometacarpal joint before and after surface total joint replacement. Using a 3-space magnetic Isotrak system (Polhemus, Colchester, VT), which provides a 3-dimensional analysis of motion of joints as well as translation, we found that kinematics and stability of the trapeziometacarpal joint could be duplicated by joint surface replacement arthroplasty provided that normal ligament tensions were present.

Arthroplasty, Replacement↗

PubMed1999

An anatomic study of the stabilizing ligaments of the trapezium and trapeziometacarpal joint.

We provide a detailed and comprehensive anatomic description of the ligaments stabilizing the trapezium and trapeziometacarpal joint. Sixteen ligaments were identified. Fourteen ligaments inserted onto the trapezium and 2 others attached independently to the thumb metacarpal. The ligaments inserting onto the trapezium were the superficial anterior oblique, deep anterior oblique (beak ligament), dorsoradial, posterior oblique, ulnar collateral, dorsal trapezio-trapezoid, volar trapezio-trapezoid, dorsal trapezio-second metacarpal, volar trapezio-second metacarpal, trapezio-third metacarpal, volar scaphotrapezial, radial scaphotrapezial, transverse carpal, and trapezio-capitate ligaments. The remaining 2 ligaments attach onto the thumb metacarpal and are the proper intermetacarpal and the dorsal intermetacarpal. The dorsoradial and deep anterior oblique ligaments play a substantial role in stabilizing the trapeziometacarpal joint, and the deep anterior oblique ligament may function as a pivot for the first metacarpal during palmar abduction to allow rotation (pronation). The dorsal trapezio-second metacarpal, volar trapezio-second metacarpal, and trapezio-third metacarpal ligaments function as tension bands and are required to prevent instability from cantilever bending forces on the trapezium.

Aged↗

PubMed1999

Constraint and material properties of the subregions of the scapholunate interosseous ligament.

The material and constraint properties of the dorsal, proximal, and palmar regions of the scapholunate ligament were studied using isolated bone-ligament-bone preparations from 24 adult intact cadaver wrists. Determinations of constraint to differential rotation and translation as well as failure strength were made using a servohydraulic testing machine incorporating an additional rotatory actuator. The dorsal region of the scapholunate ligament offered the greatest constraint to differential translation, while both the dorsal and palmar regions demonstrated statistically significant combined constraints to differential rotation between the scaphoid and lunate. The greatest yield strength was found in the dorsal region (260.3 N +/- 118.1 N), followed by the palmar region (117.9 N +/- 21.3 N) and the proximal region (62.7 N +/- 32.2 N).

Adult↗