Flexion-extension Plane Research Articles

Development and application of a multi-axis dynamometer for measuring grip force

Objective: This paper describes the development and application of a novel multi-axis hand dynamometer for quantifying 2D grip force magnitude and direction in the flexion-extension plane of the fingers. Methods: A three-beam reconfigurable form dynamometer, containing two active beams for measuring orthogonal forces and moments regardless of point of force application, was designed, fabricated and tested. Maximum grip exertions were evaluated for 16 subjects gripping cylindrical handles varying in diameter. Results: Mean grip force magnitudes were 231 N (SD = 67.7 N), 236 N (72.9 N), 208 N (72.5 N) and 158 N (45.7 N) for 3.81 cm, 5.08 cm, 6.35 cm and 7.62 cm diameter handles, respectively. Grip force direction rotated clockwise and the centre of pressure moved upward along the handle as handle diameter increased. Conclusions: Given that the multi-axis dynamometer simultaneously measures planar grip force magnitude and direction, and centre of pressure along the handle, this novel sensor design provides more grip force characteristics than current sensor designs that would improve evaluation of grip characteristics and model-driven calculations of musculoskeletal forces from dynamometer data.

Effect of surface patterning on frictional heating of vitamin E blended UHMWPE

Friction between articulating surfaces cause temperature rise in the acetabular cup and femoral head. This heating may influence the rate of wear, fatigue, creep and oxidative degradation of bearing materials. The objective of this study is to determine the effect of surface patterning on frictional temperature rise of the articulating surfaces of vitamin E blended ultra-high molecular weight polyethylene acetabular component paired with a cobalt–chromium (CoCrMo) femoral component. For this reason concave dimples were formed on inner surface of the acetabular cup with 0.5mm diameter and 0.5mm depth. Temperature rise between the bearing surfaces was measured under different loading conditions. Frictional measurements of the joints were carried out on a custom made hip joint friction experimental set up. The prostheses were of 28mm diameter. Applied static loads were changed from 200N to 1500N. In the flexion–extension plane, a simple harmonic oscillatory motion between ±24° was applied to the ultra high molecular weight polyethylene acetabular component. The frequency of motion was 1Hz and the tests were run up to 11,000 cycles. Temperature rise in acetabular and femoral component was recorded with embedded thermocouples. Lower temperature rise in patterned sample pairs were measured than unpatterned samples. So it can be said that the surface patterning contributes to reduction of frictional heating of sliding surfaces.

How much vertical displacement of the symphysis indicates instability after pelvic injury?

Measures of pubic symphyseal widening are used by at least two classification systems as determinants of injury grade. Recent work has challenged the commonly used parameter of 2.5 cm of pubic symphysis as an accurate marker of pelvic injury grade and has suggested a role of rotation in the flexion-extension plane as a determinant of pelvic stability. We investigated pelvic stability in the flexion-extension plane to determine a threshold of rotational displacement of the hemipelvis above which the potential for instability exists. Cadaveric specimens were mounted onto a servohydraulic biaxial testing machine and subjected to a vertically directed flexion moment. Position of hemipelvis was recorded using a three-dimensional motion capture system and video recording. Displacement of the pubic symphysis and changes in length and position of the sacrospinous and sacrotuberous ligaments were recorded. Amount of force applied was measured and recorded. A yield point was determined as the first point at which the force plot exhibited a decrease in force and was correlated to the corresponding displacement. The mean vertical displacement of the pubic symphysis at the yield point was 16 mm (95% confidence interval, 11-22 mm). Mean sacrospinous ligament strain at yield point was 4% (range, 1.0-9.5%). Pelves with vertical rotational symphyseal displacement of less than 11 mm can reasonably be expected to have rotational stability in the flexion-extension plane. Those with displacement of greater than 22 mm can be expected to have lost some integrity regarding resistance to pelvic flexion. These values may allow clinicians to infer pelvic stability from amount of vertical symphyseal displacement.

Analysis of Radiocarpal and Midcarpal Motion in Stable and Unstable Rheumatoid Wrists Using 3-Dimensional Computed Tomography

The kinematic evaluation of carpal motion, especially midcarpal motion, in rheumatoid arthritis (RA) has been extremely difficult because of limited imaging techniques previously available. The purpose of this study was to evaluate the amount of radiocarpal and midcarpal motion in the flexion-extension plane in both stable and unstable rheumatoid wrists using three-dimensional computed tomography. We acquired in vivo kinematic data on 30 wrists with RA by three-dimensional computed tomography with the wrist in 3 positions: neutral, maximum flexion, and maximum extension. All cases were radiographically classified into 1 of 2 subtypes, the stable form or unstable form, according to the classification by Flury et al. We evaluated the precise range of radiocarpal and midcarpal motion using a markerless bone registration technique and calculated the individual contributions to the total amount of wrist motion in the flexion-extension plane in the different radiographic subtypes of RA. The average range of motion of radiocarpal and midcarpal joint was 27 degrees +/-15 and 32 degrees +/-17, respectively. The average contribution of midcarpal motion to the total amount of wrist motion was 54%. The average contribution of midcarpal motion in the unstable form was 67%, which was significantly higher than 47% (p< .05) in the stable form. Midcarpal motion of rheumatoid wrists in the flexion-extension plane was better preserved than previously thought. The contribution of midcarpal motion to the total amount of wrist motion was significantly greater (p< .05) in the unstable form than in the stable form of RA.

Peripheral median nerve block impairs precision pinch movement

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

Monopolar Radiofrequency Electrothermal Shrinkage of the Scapholunate Ligament

This study examined whether radiofrequency electrothermal shrinkage has a role in the treatment of patients with symptomatic dynamic and predynamic scapholunate (SL) instability without advanced degenerative changes. From January 1999 to July 2001, 19 wrists with laxity of the SL ligament, but with symptomatic instability, were treated with arthroscopic electrothermal shrinkage of the SL ligament using a monopolar radiofrequency probe. Before surgery, all patients underwent wrist arthroscopy to confirm the diagnosis and exclude arthritis. The sample included 16 men and 3 women with an average age of 23.3 years (range, 18 to 27 years). The average time from injury to operation was 17.2 months (range, 14 to 28 months). All patients underwent follow-up at our clinic regularly for an average of 28.1 months (range, 24 to 34 months). All 19 patients had attenuation or laxity of the continuity SL ligament in the radiocarpal joint. Modified Mayo wrist scores revealed the following functionality: the total arc of wrist motion in the flexion-extension plane loss averaged 5.1 degrees (P > .01). Grip force improved significantly, with 14.7% improvement of that on the normal side (P < .01). The Wilcoxon signed-rank test was used to compare the results: the postoperative scores were significantly better than the preoperative scores (P < .01). Fifteen patients (79%) were fully satisfied with the results and returned to their preinjury activity. Four patients (21%) had recurrent laxity of the SL joint. Electrothermal shrinkage of the SL ligament in patients with symptomatic, predynamic and dynamic SL instability had a 79% success rate at a minimum of 2 years' follow-up. Level IV, case series.

Control of finger force direction in the flexion-extension plane

We have examined the interaction among individual finger forces in tasks that required the production of the total force by a subset of fingers in a particular direction in the flexion-extension plane. Nine subjects produced fingertip forces in a prescribed direction with a maximum voluntary contraction (MVC) effort and held the peak force for two seconds. Six finger combinations were tested, four single-finger tasks--Index (I), Middle (M), Ring (R) and Little (L)--one two-digit task (IM), and one four-digit task (IMRL). The subjects were asked to generate the finger forces in two directions, 0 degrees (perpendicular to the surface of the transducer) and 15 degrees toward the palm. In all task conditions, there were two experimental sessions, with and without visual feedback on the task force vector. The main findings were: 1. The target direction significantly affected the constant error (CE) but not the variable error (VE) while removal of the feedback resulted in an increase in VE. 2. The direction of the forces produced by fingers that were not explicitly required to produce force (enslaved fingers) depended on the target direction. 3. In multi-finger tasks, the individual fingers produced force in directions that could differ significantly from the target direction, while the resultant force pointed in the target direction. There was a negative co-variation among the deviations of the directions of the individual finger forces from the target direction. If a finger force vector deviated from the target, another finger force vector was likely to deviate in the opposite direction. We conclude that a multi-finger synergy is involved in the control of the finger force direction.

Dorsal capsulodesis and ligamentoplasty for chronic pre-dynamic and dynamic scapholunate dissociation.

Scapholunate (SL) instability is the most common cause of carpal instability. Pre-dynamic and dynamic type SL instability is difficult to diagnose and treat. This series reviews 17 soldiers with pre-dynamic or dynamic SL instability diagnosed by midcarpal arthroscopy and treated with dorsal capsulodesis and augmentation ligamentoplasty with partial dorsal radiocarpal (DRC) ligament procedure between 1997 and 2000. The sample included 14 males and three females. The dominant hand was involved in 15 patients. Moreover, the average patient age was 29.3 years (range 19-36 years). The diagnosis was based on clinical and arthroscopic criteria. Fifteen patients were followed up at our clinic regularly, with the follow-up period ranging from 12 to 39 months (mean 25.2 months). Fourteen patients had excellent or good results, and one patient had poor result based on Mayo Modified Wrist Score. Wrist motion in the flexion-extension plane loss averaged 18.4 degrees. Grip force increased significantly following treatment, with improvement totaling 15% of normal side. No complications were found in this series. Consequently, dorsal capsulodesis and ligamentoplasty with partial DRC ligament is considered a valuable therapeutic option for cases of pre-dynamic and dynamic SL instability.

The Triquetrum-Hamate joint: an anatomic and in vivo three-dimensional kinematic study

Purpose: To obtain anatomic and kinematic information regarding the relative motion of the triquetrum-hamate (TqH) joint. Methods: In this anatomic study the contact surface constraints of the TqH joint that affect TqH motion were investigated by passively simulating TqH motion according to the kinematic data. Two fresh and 28 embalmed cadaver wrists were dissected. In the kinematic study we studied the in vivo 3-dimensional (3D) kinematics of the TqH joint during radioulnar deviation (RUD) and wrist flexion and extension motion (FEM) in 5 healthy wrists using a magnetic resonance image (MRI)-based markerless bone registration algorithm. Animations of the relative motion of the TqH joint were created and accurate estimates of the relative positions and orientations of the bones and axes of rotation of TqH motion during RUD and FEM were obtained. Results: The anatomic study revealed that the contact surface constraints of the TqH joint include primarily the oval convex surface of the hamate. In the kinematic study TqH motion was likely to be not helicoidal but rotational around an oval convex surface of the hamate. In RUD the triquetral movement was rotation in an ulnoflexion-radial extension plane of the wrist. In FEM it was rotation in an almost flexion-extension plane of the wrist. The axes of rotation of the TqH joint in all wrist motions always ran distal to the TqH joint. Conclusions: Typical motion of the TqH joint in functional range of motion is not a helicoidal motion on the saddle, but rather a rotational motion on an oval, whose axes of rotation are located on the distal side of the joint.

Functional outcome of AO type C distal humeral fractures

Purpose: To review the functional outcome of AO type C distal humeral fractures (bicondylar fractures) managed with dual orthogonal plate fixation. Method: Twenty-three patients were reviewed retrospectively at a mean of 45.1 months. Patient-rated outcomes (Disabilities of the Arm Shoulder and Hand [DASH], Patient Rated Ulnar Nerve Evaluation [PRUNE], American Shoulder and Elbow Surgeons Elbow form [ASES-e], and Short Form-36 [SF-36]), clinical, radiographic, and objective evaluations were used to assess outcomes. Results: Almost 40% of patients required a third plate for adequate fixation. Patients identified minimal subjective deficits (10%) with a mean satisfaction of 93%. The arc of motion was decreased in the flexion-extension plane (122° relative to 138°, p < .01), whereas strength was lower for both elbow flexion-extension and forearm rotation (p < .05). The overall complication rate was 48%, however, most were minor and resolved without further surgery. No ulnar neuropathies were identified at follow-up after routine ulnar nerve transposition. Conclusions: Outcomes of AO type C distal humeral fractures were good with dual orthogonal plating, ulnar nerve transposition, and early motion. Additional plating may be required with distal fracture patterns or osteopenic bone. (J Hand Surg 2003;28A:294-308. Copyright © 2003 by the American Society for Surgery of the Hand.)

Global spinal motion in subjects with lumbar spondylolysis and spondylolisthesis: does the grade or type of slip affect global spinal motion?

This was a prospective pilot study to investigate the global motion characteristics of the spondylolysis and spondylolisthesis populations. The aim of this study is to determine the influence of a spondylolisthesis or a spondylolysis on global spinal motion and to establish whether this is dependent on the cause of the slip or the degree/grade of the slip. The condition of spondylolisthesis has been extensively discussed in the literature with respect to its etiology and management. However, the mechanics and movement of the spine in relation to pathology and the effect of this condition on function have received scant attention. The motion of the lumbar spine was investigated in 31 patients (19 men, 12 women, mean age 47.7 +/- 17.8 years) who were diagnosed as having either a lumbar spondylolysis or a spondylolisthesis. These patients were compared with a preexisting database of 203 normal subjects (100 men, 103 women, mean age 39.8 +/- 13.4 years). Patients were graded according to the type of spondylolisthesis or spondylolysis they had, and the extent of slip was rated using Meyerding's classification (1932) and measured directly using methods of Boxall et al (1979) and Wiltse et al (1983). Direct measurements of the extent of slip using Boxall et al (1979) and Wiltse et al (1983) methods were found to have no significant correlation with the resultant range of motion (ROM) or the speed of movement. This study suggests that motion parameters are influenced by the grade of slip in patients with spondylolisthesis, and the type of spondylolisthesis i.e., whether isthmic or degenerative. In the A-P flexion-extension plane, the results indicate that subjects with a defect only, i.e., a spondylolysis, and thus no slip present with a spinal hypermobility (P < 0.01). Subjects with an isthmic slip tend to be either slightly hypermobile or within the anticipated range of motion, whereas those subjects with a degenerative slip tend to be hypomobile (P < 0.05). Movements into lateral flexion were restricted in both the isthmic and degenerative spondylolisthesis patients, whereas rotation was only influenced by the level at which the defect occurred. In terms of degree of displacement, in higher grades of displacement, there was a trend towards hypermobility. The findings of this study suggest that the grade and type of spondylolisthesis do influence global motion parameters. This information may be useful in the clinical assessment of this patient group.

Reinforcement of thoracolumbar burst fractures with calcium phosphate cement. A biomechanical study.

A biomechanical study on the stabilization of thoracolumbar burst fractures. To demonstrate that the addition of a calcium phosphate cement into the fractured vertebral body through a transpedicular approach is a feasible technique that improves the stiffness of a transpedicular screw construct. Short segment pedicle screw instrumentation is a commonly used method for reduction and stabilization of unstable burst fractures. Recent investigators, however, have reported a high rate of instrumentation failure and sagittal collapse when there is a loss of anterior column support. In this study, the ability of a new hydroxyapatite cement to augment anterior column support was investigated in a burst fracture model. A cadaveric L1 burst fracture model was stabilized using short segment pedicle screw instrumentation. Specially instrumented-pedicle screws recorded screw-bending moments. The L1 vertebral body was reinforced with the hydroxyapatite cement through a transpedicular approach. Mechanical testing of the instrumented and instrumented-reinforced constructs were performed in flexion, extension, side bending, and torsion. Construct stiffness and screw-bending moments were recorded. Transpedicular vertebral body reconstruction with hydroxyapatite cement reduced pedicle screw-bending moments by 59% in flexion and 38% in extension. Mean initial stiffness in the flexion-extension plane was increased by 40% (P < 0.05). There were no statistically significant differences in these parameters with lateral bending or torsional movements. This hydroxyapatite cement compound augments anterior column stability in a burst fracture model. This technique may improve outcomes in burst fracture patients without the need for a secondary anterior approach.

Evaluation of handgrip force from EMG measurements

A series of experiments were performed in order to investigate whether estimates of handgrip force could be derived with fair accuracy from surface EMG levels recorded on the finger flexors of the forearm, taking into account the position of the wrist in the flexion-extension plane and in the ulnar-radial deviation plane. Handgrip forces (on a JAMAR dynamometer) and corresponding surface EMG levels (on the finger flexors of the forearm) were recorded for 20 subjects in 11 postures of the wrist and for 30% and 70% of the MVC in neutral posture. A mathematical empirical model was developed using multiple non-linear regression analysis. Although quite simple, it provides very reliable results, the correlation coefficient between predicted and observed forces being 0.895. Its use must, however, be restricted to work situations where: (a) the hand efforts are of the same type and involve the same muscles as those exerted on the dynamometer; (b) the hand is in neutral pro-supination; and (c) no voluntary effort is exerted by the wrist flexors except for maintaining the wrist posture.

Passive resistance of the human knee: The effect of remobilization

Changes of circumferential dimensions and passive resistance of the human knee caused by immobilization, were studied during remobilization. Patients immobilized with a long leg cast after tibial fractures or ligamentous injuries were studied immediately after removal of the cast and after mean periods of 18, 36 and 81 days of remobilization. Immobilization resulted in a decrease of circumferential dimensions. The difference in mid-thigh circumference between the immobilized and the unaffected leg was still present after 81 days of remobilization both for the patients with tibial fractures and for the patients with ligamentous lesions. An increase of midpatellar circumference was present exclusively in the patients with ligamentous lesions at all four testing dates, indicating that this is an effect of the ligamentous lesion and not of immobilization per se. Variables of the hysteresis diagrams, resulting from sinusoidal movement of the knee at a range of knee angles, were used to quantify passive resistance of the knee in the flexion-extension plane (the muscles crossing the knee are inactive). Variables related to the elastic storage and release of energy, and variables related to energy dissipation were discerned. During remobilization the increased resistance to flexion (shown by the variables related to the elastic storage of energy), as found immediately after removal of the cast, disappears and the resistance becomes identical to the resistance of the unaffected leg. This may indicate a rapid readaptation of the length of ventral structures (shortened due to immobilization in a shortened position) to almost normal values. The variables related to energy dissipation, which do not differ between the two legs immediately after immobilization, are low in comparison with the unaffected knee during the whole remobilization period studied, indicating a remaining atrophy (as is also shown by the still decreased aircumference of the lower limb). All resistance variables are still lower at the last date of testing when the knee is extended. The remobilization period studied was not long enough to achieve complete restoration of the dimensions of the lower limb and full return of normal passive resistance of the knee.

Passive resistance of the human knee: The effect of immobilization

The effects of immobilization on both the circumferential dimensions of the lower limb, and the passive resistance of the knee to sinusoidal motion in the flexion-extension plane, were studied in patients immobilized after tibial fractures or ligamentous injuries of the knee. Immobilization resulted in a decrease of circumferential dimensions of the lower limb, indicating atrophy of thigh and calf musculature. The equilibrium angle of the knee, i.e. the angle at which the net passive moment equals zero, approached the angle of the knee during immobilization. At knee angles of 60° (the maximal angle imposed on the immobilized knee) and 45°, the resistance was increased, and at angles of 30° and 15°, the resistance was decreased. The passive resistances at ± 22.5, 15 and 7.5° relative to the equilibrium angle were all increased. A simple model, taking into account changes in the length of muscles at the anterior and posterior side of the knee, explains changes in passive resistance. The duration of immobilization for patients with ligamentous injuries of the knee was less than 50% of that for patients with tibial fractures, whose ankle joint was not immobilized, both resulted in a smaller muscular atrophy for patients with ligamentous injuries. Differences in passive resistance between unaffected and immobilized legs were the same in both groups of patients. Changes in passive resistance in the immobilized leg for those with ligamentous injury are probably not the effect of immobilization alone but the combined effect of immobilization and ligamentous lesions.

Inter-individual differences in the passive resistance of the human knee

The passive resistance of the knee to angular motion in the flexion-extension plane was investigated in groups of healthy males ( n = 29) and females ( n = 20). ‘Least square’ fitting procedures proved to be reliable for approximating the equilibrium angle of the knee and variables of the moment/angle diagrams. To assess the influence of the dimensions of the lower limb on the resistance of the knee, a multiple regression analysis was performed, using seven dimensional parameters of the lower limb. The results indicate that for males 35–77% (mean 58%) of the total variance is accounted for by the dimensional parameters. For females this range is 9–74% (mean 44%). Differences between males and females exist in all selected resistance variables. To decrease the influence of dimensional parameters, the slopes of the exponential curves relating moment and knee angle are expressed as percentages of the absolute moment values. When the values of these ‘relative slopes’ are used, differences between males and females become less in flexion and are absent when the knee is extended. These results indicate that male-female differences can partly be ascribed to differences in dimensions.

Passive resistance of the knee after anterior cruciate ligament reconstruction

In this study the data of dynamic mechanical tests were used as objective criteria to evaluate the results of a combined extra- and intra-articular reconstruction of the anterior cruciate ligament (ACL). With these tests the passive response of the knee and its surrounding tissues to sinusoidal strain in the flexion-extension plane was quantified.

The Calcar Replacement Femoral Component for Total Hip Arthroplasty

A new femoral component for total hip arthroplasty (THA) has been designed for use in patients in whom the calcar region is missing, hence called the calcar replacement device. Experience with its use in 18 hips has indicated that common causes for calcar deficiency requiring this implant are resorption of the calcar region secondary to failure of a prior THA, settling of an endoprosthesis or destruction by tumor. The use of a conventional femoral component in these situations is not recommended because of the lack of adequate bony support. The device is also valuable in restoring leg length in cases of substantial bone loss in the proximal part of the femur. In an entirely different indication, this device may be used to restore hip motion in patients with severely restricted movement secondary to extensive heterotopic ossification. In three of four hips with this condition, excision of the heterotopic bone and use of the calcar replacement device achieved restoration of an arc of 75 degrees or more in the flexion-extension plane.