Biomedical subjects

K N An

Publications and source records attributed to K N An.

At least 37 records · Page 2Linked to original sources

PubMed2001

Gliding resistance after repair of partially lacerated human flexor digitorum profundus tendon in vitro.

OBJECTIVE: This study reports the gliding resistance between repaired, partially lacerated tendon and pulley in human cadaver digits, using several commonly employed repair techniques. BACKGROUND: Suture techniques with multi-strands and locking loops have been recommended to reduce the risk of rupture of the repair tendon with early active motion. Such sutures may increase the gliding resistance, and the gliding resistance after tendon repair is also an important factor influencing the rehabilitation. METHOD: 105 specimens of second, third, or fourth fingers from 36 adult human hands were tested for the gliding resistance between flexor digitorum profundus tendon and A2 pulley in the normal condition. After an 80% laceration, each tendon was repaired with one of the following suture techniques: (1) Kessler; (2) modified Kessler; (3) Savage; (4) Lee; (5) Tsuge; and (6) Becker. All suture techniques were reinforced with a circumferential epitenon simple running suture. After tendon repair, the gliding resistance was remeasured. RESULTS: The gliding resistance of the Becker repair was significantly greater than each of the other four repairs (P<0.05). The resistance of the modified Kessler repair was significantly less than that of the Kessler, Savage, or Tsuge repairs. CONCLUSIONS: We conclude that the type of tendon repair can significantly affect the gliding resistance between the tendon and pulley system after tendon repair. RELEVANCE: The design of the tendon repair, through its effect on friction, may have an adverse effect on the clinical results of tendon mobilization.

Aged↗

PubMed2001

Dynamic contributions to superior shoulder stability.

It has been suggested that superior decentralization of the humeral head is a mechanical factor in the etiology of degenerative rotator cuff tears. This superior decentralization may be caused by muscular imbalance. The objective of this study was to investigate the contribution of individual shoulder muscles to superior stability of the glenohumeral joint. In 10 fresh frozen cadaver shoulders the tendons of the rotator cuff, teres major, latissimus, pectoralis major, deltoid and biceps were prepared. The shoulders were tested in a shoulder-loading device in 0 degrees, 30degrees, 60 degrees and 90 degrees of glenohumeral abduction. A constant superior force of 20 N was applied to the humerus. Tensile loads were applied sequentially to the tendons in proportion to their cross-sectional areas and translations of the humeral head relative to the glenoid were recorded with a 3Space Fastrak system. Depression of the humeral head was most effectively achieved by the latissimus (5.6 +/- 2.2 mm) and the teres major (5.1 +/- 2.0 mm). Further studies should elucidate their possible in vivo role in the frontal plane force couple to counter balance the deltoid. The infraspinatus (4.6 +/- 2.0 mm) and subscapularis (4.7 +/- 1.9 mm) showed similar effects while the supraspinatus (2.0 +/- 1.4 mm) was less effective in depression. Therefore, the infraspinatus and subscapularis should be surgically repaired whenever possible. The supraspinatus may be of less importance for superior stability than previously assumed.

Biomechanical Phenomena↗

PubMed2001

The enhancement of periosteal chondrogenesis in organ culture by dynamic fluid pressure.

Cartilage repair by autologous periosteal arthroplasty is enhanced by continuous passive motion (CPM) of the joint after transplantation of the periosteal graft. However, the mechanisms by which CPM stimulate chondrogenesis are unknown. Based on the observation that an oscillating intra-synovial pressure fluctuation has been reported to occur during CPM (0.6-10 kPa), it was hypothesized that the oscillating pressure experienced by the periosteal graft as a result of CPM has a beneficial effect on the chondrogenic response of the graft. We have developed an in vitro model with which dynamic fluid pressures (DFP) that mimic those during CPM can be applied to periosteal explants while they are cultured in agarose gel suspension. In this study periosteal explants were treated with or without DFP during suspension culture in agarose, which is conducive to chondrogenesis. Different DFP application times (30 min, 4 h, 24 h/day) and pressure magnitudes (13, 103 kPa or stepwise 13 to 54 to 103 kPa) were compared for their effects on periosteal chondrogenesis. Low levels of DFP (13 kPa at 0.3 Hz) significantly enhanced chondrogenesis over controls (34 +/- 7% vs 14 +/- 5%; P < 0.05), while higher pressures (103 kPa at 0.3 Hz) completely inhibited chondrogenesis, as determined from the percentage of tissue that was determined to be cartilage by histomorphometry. Application of low levels of DFP to periosteal explants also resulted in significantly increased concentrations of Collagen Type II protein (43 +/- 8% vs 10 +/- 5%; P < 0.05). New proteoglycan synthesis, as measured by 35S-sulphate uptake was increased by 30% in periosteal explants stimulated with DFP (350 +/- 50 DPM vs 250 +/- 75 DPM of 35S-sulphate uptake/microg total protein), when compared to controls though this difference was not statistically significant. The DFP effect at low levels was dose-dependant for time of application as well, with 4 h/day stimulation causing significantly higher chondrogenesis than just 30 min/day (34 +/- 7 vs 12 +/- 4% cartilage; P < 0.05) and not significantly less than that obtained with 24 h/day of DFP (48 +/- 9% cartilage, P > 0.05). These observations may partially explain the beneficial effect on cartilage repair by CPM. They also validate an in vitro model permitting studies aimed at elucidating the mechanisms of action of mechanical factors regulating chondrogenesis. The fact that these tissues were successfully cultured in a mechanical environment for six weeks makes it possible to study the actions of mechanical factors on the entire chondrogenic pathway, from induction to maturation. Finally, these data support the theoretical predictions regarding the role of hydrostatic compression in fracture healing.

Animals↗

PubMed2001

Gliding characteristics of tendon repair in canine flexor digitorum profundus tendons.

The gliding resistance between the flexor digitorum profundus (FDP) tendon and the proximal pulley system was measured using the method of S. Uchiyama, J.H. Coert, L. Berglund, P.C. Amadio, K.N. An (J. Orthop. Res. 13 (1995) 83) in 108 adult dog digits in vitro. The FDP tendons were then lacerated to 80% of their transverse section. Each tendon was repaired with one of the following six suture techniques: Kessler, modified Kessler, Savage, Lee, Becker and simple running suture alone. Each repaired tendon was then tested again using the same method. The Student-Newman-Keuls test for multiple comparisons was performed for statistical analysis. The average gliding resistances of the Kessler, Savage, and Becker repairs were significantly greater than the resistances of the Lee, modified Kessler, and running suture alone repairs (P < 0.05). The Lee suture technique had a significantly greater resistance than the modified Kessler repair and the running suture (P < 0.05). The results of the peak gliding resistance followed the same trends, except that the modified Kessler repair was significantly higher than the running suture alone (P < 0.05). Suture techniques with a multi-strand core suture, with knots located outside the tendon surface, and with multiple-loops on the tendon surface may result in increased gliding resistance between the tendon and pulley system after tendon repair.

Animals↗

PubMed2001

The reversal of antagonists facilitates the peak rate of tension development.

OBJECTIVE: The present study was designed to test the effects of the reversal of antagonists on the peak rate of tension development (dF/dt(max)) of the elbow extensors. DESIGN: Experimental, with matched controls. SETTING: A biomechanics research laboratory. PARTICIPANTS: Twenty-six healthy women without a history of upper extremity injury or neurologic disorder, randomly assigned to experimental (n = 13) or control (n = 13) groups. INTERVENTIONS: Two groups of healthy subjects followed identical exercise protocols, except that the control group performed maximal isometric contractions of the elbow extensors and the experimental group executed a maximal isometric elbow flexion contraction immediately before a maximal elbow extension contraction. Both groups performed 5 cycles of a 2-second contraction with 22-second rest periods between agonist muscle contractions and were evaluated at 4 test sessions spaced 2 weeks apart. MAIN OUTCOME MEASURES: All measurements were done with the shoulder and elbow at 90 degrees of flexion in the sagittal plane to ensure reproducibility. A load cell was used to measure elbow extension moment and to calculate the peak rate of tension development (dF/dt(max)). Biceps and triceps brachii surface electromyographic activity was monitored concurrently. The electromyographic measures were mean spike (peak-to-peak) amplitude and mean spike frequency of the biceps and triceps brachii activity. RESULTS: Intraclass dF/dt(max) and electromyographic reliability was good (r > or = .72) in both groups. Because biceps electromyographic measures were considerably less reliable (r < or = .53), they were not included in our analysis. While dF/dt(max) increased quadratically in both groups (p <.05), the experimental group was on average 36.1Nm. s(-1) (63%) greater across sessions 2 to 4 (p <.05). In contrast, triceps electromyographic activity did not differ significantly between groups (p >.05). The means averaged across groups exhibited a quadratic increase from session 1 to session 4: 91microV or 48% for mean spike amplitude (p <.05) and 7Hz or 16% for mean spike frequency (p <.05). CONCLUSIONS: The greater dF/dt(max) for the experimental group was not associated with increased electromyographic activity. The experimental group appeared to use the biomechanic properties of the pretensioned extensor muscle-tendon complex, rather than neurologic biasing, to accomplish its power gains.

Analysis of Variance↗

PubMed2001

The effects of a lumbar support on repositioning error in subjects with low back pain.

OBJECTIVE: To determine whether a lumbar support improves trunk repositioning error (RE), an aspect of proprioception. DESIGN: RE was measured with and without a lumbar support. SETTING: Outpatient clinic. PARTICIPANTS: Twenty subjects with chronic low back pain (LBP) and 20 control subjects. INTERVENTIONS: Subjects wore the lumbar support for 2 hours and then testing was repeated. MAIN OUTCOME MEASURES: Standing with legs and pelvis immobilized, subjects moved to a predetermined target position and then attempted to replicate the position. The 3-dimensional position of the trunk was measured with a 3Space Tracker. RE was calculated as the absolute difference between the actual target position and the subject-perceived target position. Testing was performed with and without a lumbar support both before and after wearing the support for 2 hours. RESULTS: In subjects with LBP, RE was significantly lower with a support in flexion, extension, and right lateral bending. In control subjects, RE was significantly lower when wearing the support in left bending only, and RE was significantly higher in control subjects after wearing the support for 2 hours. CONCLUSION: A lumbar support improves trunk RE. In subjects with LBP, this result was significant in the sagittal plane and in right lateral bending, whereas in control subjects, it was significant only in left lateral bending.

Adult↗

PubMed2001

Contact geometry at the undersurface of the acromion with and without a rotator cuff tear.

PURPOSE: The purpose of this study was to investigate the difference in contact geometry at the undersurface of acromion in shoulders with and without a rotator cuff (RC) tear. TYPE OF STUDY: Case-control study. METHODS: Forty fresh cadaveric shoulders (average age at death, 61 years) without gross osteoarthritic changes were divided into the intact RC group (n = 20) and the RC tear group (n = 20). Clinical impingement was simulated by compressing the humeral head and the intact portion of the RC against the coracoacromial arch with an axial compressive force of 25 kg while the humerus was held abducted 20 degrees in the scapular plane. The contact pattern between the acromion and the RC was measured with Fuji Prescale super low-pressure-sensitive film (Fuji Photo Film Co, Ltd, Tokyo, Japan). The imprint image was analyzed using Global Lab image software (Automatix, Marlboro, MA). RESULTS: The percentage of the maximum anteroposterior dimension of the imprint on Fuji film to the anteroposterior diameter of the acromial undersurface was 29% +/- 9% in intact RC shoulders, and 39% +/- 13% in shoulders with an RC tear (P >.05). The percentage of the maximum mediolateral dimension of the imprint to the mediolateral diameter of the corresponding part of the acromial undersurface was 27% +/- 12% in intact RC shoulders, and 48% +/- 11% in shoulders with an RC tear. This difference was statistically significant (P <.005). CONCLUSIONS: The contact geometry of the acromial undersurface with the underlying RC in the anteroposterior dimension, which might be related to the appearance in supraspinatus outlet view, was not significantly different between shoulders with and without an RC tear. These findings suggest that factors other than acromial shape play a significant role in the pathogenesis of RC tears. The implication regarding the role of acromioplasty remains to be clarified.

Acromion↗

PubMed2001

Radial styloidectomy: a biomechanical study on stability of the wrist joint.

We investigated the influence of radial styloidectomy on carpal alignment and examined translation of the wrist after sequentially increased styloidectomy of 8 cadaver wrists. The radial aspect of the scaphoid fossa of the distal radius was cut obliquely at 3, 6, and 10 mm from the radial styloid guided by real-time fluoroscopy. Radiographic analysis of the changes of carpal alignment was performed with the wrist in neutral position. Force-displacement curves from the neutral to the radioulnar and palmar-dorsal directions were obtained using a multi-axis testing machine. Results demonstrated no significant malalignment of the carpal bones after radial styloidectomy. Significantly increased radial translation (>40% reduction in stiffness), however, was observed due to the loss of radial articular contact after 6- and 10-mm radial styloidectomies. Significant ulnar and palmar carpal displacement also was noted after 6- and 10-mm radial styloidectomies, with 6 specimens demonstrating moderate ulnar and palmar translation and 2 demonstrating notable increased palmar and ulnar translations. We conclude that there is a definite risk of increased carpal instability with radial styloidectomy procedures. A styloidectomy of no more than 3 to 4 mm is recommended.

Aged↗

PubMed2001

Tensile properties of suture methods for repair of partially lacerated human flexor tendon in vitro.

The decision to treat zone II partially lacerated flexor tendons is challenging, because there can be justification for either repair or no repair, depending on the surgeon's assessment of the strength of the residual intact portion of the tendon. In this study tensile properties of various repair techniques were compared. Cadaveric human flexor tendons (n = 118) were lacerated to 75% of their cross-section and repaired with either a core suture method (Kessler, modified Kessler, Savage, Lee, augmented Becker, or Tsuge all finished with a circumferential running suture), an epitendinous suture alone (circumferential or partial), or the tendons were left unrepaired. Among the core suture methods there was no significant difference (p >.05) in maximum failure force (overall mean, 211.2 N; SD, 53.2) or force to produce a 1.5-mm gap (74.1 N; SD, 49.7). Likewise there was no significant difference (p >.05) in tendon stiffness (41.0 N/mm; SD, 14.0) or resistance to gap formation (52.3 N/mm; SD, 23.1). In comparison, repairs without the core suture, including unrepaired tendons, were significantly weaker (144.7 N, p <.001) and had a marginally lower stiffness (p =.04) but had a similar resistance to gap formation (43.5 N/mm).

Hand Injuries↗

PubMed2001

Trapezial tilt: a radiographic correlation with advanced trapeziometacarpal joint arthritis.

Trapeziometacarpal (TMC) joint arthritis is a common and debilitating condition of the hand. We defined a radiographic measure of trapezial inclination (trapezial tilt) and found a positive correlation between an increased trapezial tilt and severity of TMC joint arthritis. Radiographs (Robert's views) were obtained from 50 pairs of normal hands to evaluate the trapezial tilt to assess radial inclination of the trapezium with respect to the second metacarpal. The trapezial tilt was also measured in 65 hands from 43 patients with various stages of TMC joint arthritis and compared with the normal value. The trapezial tilt for hands without arthritis was 42 degrees +/- 4 degrees, Eaton stages I and II was 42 degrees +/- 4 degrees, and Eaton stages III and IV was 50 degrees +/- 4 degrees. Trapezial tilt angles from the Eaton III and IV group were significantly greater than those of the normal and Eaton I and II groups. Advanced TMC joint arthritis (Eaton III and IV) is associated with an increased trapezial tilt. Mild TMC joint arthritis with an increased trapezial tilt may be treated surgically. We speculate that a trapezio-trapezoid and trapezio-II metacarpal arthrodesis, or an opening wedge osteotomy of the trapezium might arrest the progression of TMC joint arthritis by resetting the slope of the trapezium and decreasing the shear stress within the TMC joint.

Adult↗

PubMed2001

Suture techniques with high breaking strength and low gliding resistance: experiments in the dog flexor digitorum profundus tendon.

We studied the breaking strength and gliding resistance between the pulley and flexor tendon for various suture techniques. Canine flexor digitorum profundus tendons were transected and sutured using one of eight repair techniques: modified Kessler (MK); Tsuge (Tsuge); two variations of a double modified Kessler (DK1, DK2); combined modified Kessler-modified Tsuge (MKT); augmented Becker (Becker); Cruciate (Cruciate); and modified double Tsuge (DT). The force to produce a 1.5 mm gap, ultimate failure load, resistance to gap formation, and gliding resistance were measured. The force to produce a 1.5 mm gap and the ultimate breaking force were higher with the DK1, DK2, MKT, Becker, Cruciate, and DT repairs than they were with the MK and Tsuge repair, while the gliding resistance of the Becker was higher than that of the MK, DK1, DK2, MKT. Cruciate, and UT repairs. In addition to confirming that repair strength increases as the number of strands crossing the repair increases, we also found that these stronger repairs need not produce higher gliding resistance than less robust repairs.

Animals↗

PubMed2001

Mechanical behavior of the Lisfranc and dorsal cuneometatarsal ligaments: in vitro biomechanical study.

OBJECTIVES: To define the anatomy and mechanical properties of two ligaments stabilizing the medial tarsometatarsal joints: the Lisfranc ligament and the dorsal cuneometatarsal ligament. DESIGN: Cadaveric study in normal feet. SETTING: Biomechanics laboratory. PATIENTS OR PARTICIPANTS: Twelve fresh-frozen cadaveric feet were studied. INTERVENTION: The Lisfranc and dorsal cuneometatarsal ligaments were dissected, dimensions measured, and material properties determined with a servohydraulic MTS machine on bone-ligament-bone preparations. MAIN OUTCOME MEASUREMENTS: Stiffness, strain, stress, modulus, failure load, ligament length, width, thickness, and cross-sectional area were determined. RESULTS: Dorsal ligament stiffness was 66.3+/-18.3 newtons per millimeter and the Lisfranc ligament stiffness was 189.7+/-57.2 newtons per millimeter. The failure load of the dorsal ligament averaged 150.7+/-33.1 newtons and for the Lisfranc ligament, 368.8+/-126.8 newtons. CONCLUSIONS: The stiffness and load to failure of the dorsal cuneometatarsal ligament were much higher than anticipated, which indicates that it contributes significantly to stabilizing the second metatarsal to the first cuneiform.

Aged↗

PubMed2001

The effect of suture technique on adhesion formation after flexor tendon repair for partial lacerations in a canine model.

BACKGROUND: Adhesion formation is a serious problem after flexor tendon repair. Many repair techniques have been developed to increase the suture strength after tendon repair surgery. The purpose of this study was to assess adhesion formation with different suture techniques in an in vivo canine model. METHODS: Sixty flexor digitorum profundus tendons were partially lacerated (80%) and repaired with either a modified Kessler (MK) or Becker (MGH) suture technique and supplemented with a simple running suture. The dogs were sacrificed at 1 week, 3 weeks, or 6 weeks after surgery and the repaired tendons were evaluated for adhesion breaking strength. RESULTS: At 1 week there was no significant difference between the two repair groups (p > 0.05). At 3 and 6 weeks, the adhesion breaking strength in the MK suture group was significantly less than that of the MGH suture group (p < 0.05). CONCLUSION: High friction suture techniques may cause more adhesion formation than the lower friction suture techniques under passive postoperative therapy.

Analysis of Variance↗

PubMed2001

Neural adaptations to fatigue: implications for muscle strength and training.

PURPOSE: This paper investigates the neural mechanisms responsible for the increase in strength that occurs during serial isometric contractions. METHODS: A three-session design was used. Thirteen subjects (N = 13) were asked to perform five maximal isometric elbow extension strength trials to serve as baseline. After a 5-min rest, the subjects were administered a 30-trial fatigue protocol. This process was repeated two more times at 2-wk intervals. Elbow extension torque and surface electromyography (EMG) of the triceps and biceps brachii were monitored concurrently. The criterion measures were elbow extension torque, root-mean-square EMG amplitude, and mean power frequency (MPF). RESULTS: Intraclass reliability ranged from good to excellent. Within each experimental session, the fatigue protocol resulted in a decrease in maximal isometric elbow extension torque as well as biceps and triceps EMG amplitude and MPF (P < 0.05). However, the mean of the 30 trials and the magnitude of the linear decrease in elbow extension torque increased across the three sessions (P < 0.05). Biceps and triceps EMG amplitude increased and MPF decreased as the number of sessions increased (P < 0.05). CONCLUSIONS: These findings suggest that the fatigue protocol served as a training stimulus to down regulate motor-unit firing frequency.

Adult↗

PubMed2001

Determination of the compressive material properties of the supraspinatus tendon.

A methodology was developed for determining the compressive properties of the supraspinatus tendon, based on finite element principles. Simplified three-dimensional models ure re reated based on anatomical thickness measurements of unloaded supraspinatus tendons over 15 points. The tendon material was characterized as a composite structure of' longitudinally arranged collagen fibers within an extrafibrillar matrix. The matrix was formulated as a hyperelastic material described by the Ogden form of the strain energy potential. The hyperelastic material parameters were parametrically manipulated until the analytical load-displacement results were similar to the results obtaizned from indentation testinrg. In the geometrically averaged tendon, the average ratio of experimental to theoretical maximum indentation displacement was 1.00 (SD: 0.01). The average normalization of residuals was 2.1 g (SD: 0.9 g). Therefjore, the compressive material properties of the supraspinatus tendo'n extrafibrillar matrix were adequately derived with a first-order hyperelastic formulation. The initial comnpressive elastic modulus ranged from 0.024 to 0.090 MPa over the tendon surface and increased nonlinearly with additional compression. Using these material properties, the stresses induced during acromional impingement can be analyzed.

Cadaver↗

PubMed2001

Effects of the glenoid labrum and glenohumeral abduction on stability of the shoulder joint through concavity-compression : an in vitro study.

BACKGROUND: Although the glenohumeral joint is the most mobile articulation of the human body, it is known to exhibit ball-and-socket kinematics. Compression into the glenoid labral concavity keeps the humeral head centered. The purpose of the present study was to determine the effects of joint position on glenohumeral stability through concavity-compression. METHODS: Ten cadaveric shoulders were tested. The glenoid was mounted horizontally onto a six-component load-cell while the humerus was clamped to a vertically unconstrained slide. An x-y stage translated the load-cell with the glenoid underneath the humeral head in eight different directions. Compressive loads of 20, 40, and 60 N were applied. The tests were repeated in 0 degrees, 30 degrees, 60 degrees, and 90 degrees of glenohumeral abduction with and without the labrum. Relative translations between the glenoid and the humeral head and the forces resisting translation were recorded. Then the stability ratio, defined as the peak translational force divided by the applied compressive force, was calculated. RESULTS: The average stability ratio was higher in the hanging-arm position than it was in glenohumeral abduction. The highest stability ratio was detected in the inferior direction (59.8% 7.7%) when the labrum was intact and in the superior direction (53.3% 7.9%) when the labrum had been resected. Under both conditions, the anterior direction was associated with the lowest stability ratio (32.0% 4.4% with the labrum and 30.4% 4.1% without the labrum). Resection of the glenoid labrum resulted in an average decrease in the stability ratio of 9.6% 1.7%. With increasing compressive load, the average stability ratio slightly decreased. CONCLUSIONS: Glenohumeral stability through concavity-compression was greater in the hanging-arm position than it was in glenohumeral abduction. The average contribution of the labrum to glenohumeral stability through concavity-compression was approximately 10%, about one-half of the value previously reported. With the labrum intact, the glenohumeral joint was most stable in the inferior direction. Without the labrum, it was most stable in the superior direction. Under both conditions, it was least stable in the anterior direction. Glenohumeral joint stability through concavity-compression decreases with higher compressive loads.

Aged↗

PubMed2001

Contribution of monoblock and bipolar radial head prostheses to valgus stability of the elbow.

BACKGROUND: The purpose of this study was to evaluate the stabilizing effect of radial head replacement in cadaver elbows with a deficient medial collateral ligament. METHODS: Passive elbow flexion with the forearm in neutral rotation and in 80 degrees of pronation and supination was performed under valgus and varus loads (1) in intact elbows, (2) after a surgical approach (lateral epicondylar osteotomy of the distal part of the humerus), (3) after release of the anterior bundle of the medial collateral ligament, (4) after release of the anterior bundle of the medial collateral ligament and resection of the radial head, and (5) after subsequent replacement of the radial head with each of three different types of radial head prostheses (a Wright monoblock titanium implant, a KPS bipolar Vitallium [cobalt-chromium]-polyethylene implant, and a Judet bipolar Vitallium-polyethylene-Vitallium implant) in the same cadaver elbow. Total valgus elbow laxity was quantified with use of an electromagnetic tracking device. RESULTS: The mean valgus laxity changed significantly (p < 0.001) as a factor of constraint alteration. The greatest laxity was observed after release of the medial collateral ligament together with resection of the radial head (11.1 degrees +/- 5.6 degrees). Less laxity was seen following release of the medial collateral ligament alone (6.8 degrees +/- 3.4 degrees), and the least laxity was seen in the intact state (3.4 degrees +/- 1.6 degrees). Forearm rotation had a significant effect (p = 0.003) on valgus laxity throughout the range of flexion. The laxity was always greater in pronation than it was in neutral rotation or in supination. The mean valgus laxity values for the elbows with a deficient medial collateral ligament and an implant were significantly greater than those for the medial collateral ligament-deficient elbows before radial head resection (p < 0.05). The implants all performed similarly except in neutral forearm rotation, in which the elbow laxity associated with the Judet implant was significantly greater than that associated with the other two implants. CONCLUSIONS AND CLINICAL RELEVANCE: This study showed that a bipolar radial head prosthesis can be as effective as a solid monoblock prosthesis in restoring valgus stability in a medial collateral ligament-deficient elbow. However, none of the prostheses functioned as well as the native radial head, suggesting that open reduction and internal fixation to restore radial head anatomy is preferable to replacement when possible.

Aged↗

PubMed2001

An integrated approach to assess structure-to-function relationships in the skeleton.

In general, the disciplines of biomechanics, morphology, densitometry, biochemistry, cell biology and molecular biology have advanced independently of one another. In spite of this fragmentation, there have been incremental increases in our understanding of the organization, mechanical properties, growth, remodeling and repair of the tissues comprising the skeleton. As a practical application, this increased knowledge has greatly improved our capabilities for early diagnosis of bone loss and has proven similarly useful in determining the efficacy of interventions to prevent osteoporosis. This approach, however, has been much less successful in countering several other important musculoskeletal disorders, including arthritis. In the immediate future, a major emphasis will be placed on tissue regeneration (engineering) to restore lost mechanical function to a compromised skeleton. To accomplish this goal, it will be necessary to employ much more sophisticated approaches toward evaluating the structure-to-function relationships, ones which will include integration of the respective contributions of gene expression, cell number and activity, matrix composition and architecture to achieve adequate tissue function.

Journal Article↗