Biomedical subjects

E P France

Publications and source records attributed to E P France.

17 recordsLinked to original sources

PubMed1996

A biomechanical and clinical evaluation of a patellofemoral knee brace.

A clinical and biomechanical evaluation of a patellofemoral knee brace was conducted to determine subjectively and objectively if the brace was effective in controlling knee motion and relieving patellofemoral pain symptoms. The subjective results indicated that the patellofemoral brace was able to significantly improve the level of perceived knee stability and decrease the level of pain experienced by all the subjects during their daily living and athletic activities. The objective results showed that the patellofemoral brace had no effect on knee flexion angle during gait or level walking, stair ascent, or stair descent for 2 groups of subjects (patellofemoral patients and controls). Joint pain and stability are affected by factors other than knee flexion angle.

Adolescent↗

PubMed1995

Measurement of creep strain of flexor tendons during low-force high-frequency activities such as computer keyboard use.

The aim of this study was to measure tendon strain during low-force, high-frequency activities such as computer keyboard use. Prior to creep strain testing an estimate of flexor tendon force during keyboard use was made. Tendon force was measured indirectly by comparing electromyographic activity of the flexor and extensor digitorum muscles in five human volunteers for various hand activities. Results of the electromyographic study showed that flexor tendon forces during keyboard use may be as high as 60 N. Sixty eight flexor digitorum tendons from 17 fresh-frozen cadaver hands were used for the creep strain tests. Three loading conditions (static, 1 Hz cyclic, (1/4) Hz cyclic) and four load levels (10, 20, 50, 100 N) were used. Results of the creep study showed that for a flexor tendon force of 60 N the total strain of the tendon would be approximately 1.8%. This does not appear to be enough strain to cause permanent damage to the tendon according to current cumulative strain models. RELEVANCE: Recent studies have shown an increase in hand and wrist tendinitis among computer users. At the present time the aetiology is unknown, but risk factors commonly associated with tendinitis are hand forces, wrist postures, and frequency of finger movements. This research looks at tendon creep due to repeated force as a possible aetiology.

Journal Article↗

PubMed1992

Differences in cortical bone in overloaded and underloaded femurs from ovariectomized rats: comparison of bone morphometry with torsional testing.

Osteopenia and mechanical incompetence are the defining features of osteoporosis, yet the effects of changes in bone structure on mechanical properties are not completely understood. The primary objective of this study was to determine if in a rodent model, changes in cortical bone structure, as measured by static morphometry, would correlate with functional properties, as measured by torsional testing. For this, cortical bone structure and stiffness were determined in overloaded and underloaded limbs in rats rendered ovarian hormone-deficient by ovariectomy (OVX). Rats were OVX and six weeks later a hind limb was immobilized by casting for an additional six weeks. In all cases the femur from the underloaded, casted limb was compared with that from the contralateral, overloaded limb. The success of this experimental protocol was confirmed by differences in femoral cancellous bone volume by microradiography and single photon absorptiometry, with the overloaded limb having a greater bone volume and bone mineral density than the contralateral, immobilized controls. Morphometric differences in the femoral diaphyseal cortical bone included greater endocortical perimeter and endocortical osteoclast surface, less cortical area, less minimum cortical width, and less minimum cortical width at fracture planes when the bones were tested for stiffness in the underloaded, compared with the contralateral, overloaded limbs. Using a torsional test, the ultimate torque to failure and stiffness were less in the underloaded femurs compared with the contralateral, overloaded femurs. These results emphasize the importance of mechanical loading on bones from a gonad-deficient animal.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Biomechanics of the lateral ligaments of the ankle: an evaluation of the effects of axial load and single plane motions on ligament strain patterns.

Strain behavior in the anterior talofibular and calcaneofibular ligaments of the ankle, with and without axial load, was evaluated using human cadaveric specimens, a specially designed instrumented test fixture, and Hall-Effect strain transducers. Ligament strain patterns were significantly altered with axial loading in some conditions. This data may have clinical relevance both in the diagnosis and rehabilitation of lateral ligament injuries.

Adult↗

PubMed1991

Radiographic assessment of instability of the knee due to rupture of the anterior cruciate ligament. A quadriceps-contraction technique.

We compared the results of a radiographic technique for the measurement of instability of the knee with those obtained with a KT-1000 arthrometer. The study was conducted on both knees of sixty patients who had a ruptured anterior-cruciate ligament in one knee, as well as in ten control subjects. The radiographic technique included the examination of a true lateral radiograph, made while the knee was in full extension and the quadriceps was maximally contracted, with a 66.7-newton downward force produced by a 6.8-kilogram weight suspended from the ankle. As demonstrated by both techniques, the maximum difference between the displacements of the right and left knees in the control subjects was 2.5 millimeters and the mean difference between the displacements in the two knees in the patients was 7.5 millimeters. In fourteen of the sixty knees in which the ligament was ruptured, the injury was acute. The forward translation of the medial side in these fourteen knees was compared with that in the forty-six knees in which the injury was chronic. The mean difference in the displacement of the medial side in the right and left knees was 3.5 millimeters in the fourteen patients who had an acute injury and 5.0 millimeters in the forty-six patients who had a chronic injury. Thirteen of the sixty patients had disruption of the posteromedial corner of the injured knee, and the translation of the medial side in these knees was significantly increased compared with that in the intact knees of the same patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1990

Choosing functional knee braces.

Choosing a functional brace for knee injury is a complex issue complicated by a lack of quantitative research on the subject and an increasing number of braces currently on the market. The correct brace decision will be facilitated by a better understanding of knee injury biomechanics and by a thorough understanding of the choices available. The ultimate selection of a brace should be based on sound mechanical criteria and individualized for each patient. The brace must be mechanically effectual and one the patient likes, has confidence in, and will tolerate. In combination with aggressive rehabilitation, the functional brace can make a significant contribution to returning individuals to functional activity.

Anterior Cruciate Ligament↗

PubMed1990

In vitro assessment of prophylactic knee brace function.

In an attempt to evaluate the effectiveness of prophylactic knee bracing and to determine the influence of brace design and material characteristics on the protection of knee ligaments, a series of biomechanical studies were completed. The first series of tests were preliminary parametric tests of brace function utilizing cadaver limbs to understand the failure biomechanics of the medial restraints during low- and high-rate valgus-producing knee trauma. Static and dynamic mechanical properties of the braces were also studied. Finally, a limited series of brace/cadaver knee low-rate loading response tests were performed. With the information obtained from preliminary testing, an instrumented surrogate knee was developed and validated for lateral impact responses. The surrogate allowed for the measurement of ligament force time response during a controlled impact. Special impact facilities were constructed to allow the measurement and control of impact momentum. The effectiveness of six different prophylactic braces in preventing MCL and ACL injury was evaluated using the surrogate and impact facility. Impact parameters of mass, velocity, knee flexion angle, and limb restraint were varied to simulate different direct lateral impact conditions of game play. Testing results were normalized and expressed as an impact safety factor to allow for comparison of braces. An ISF of 1.5 (representing a ligament force reduction of 30%) was arbitrarily chosen as the minimum standard for brace performance. The majority of prophylactic knee braces tested proved to be biomechanically inadequate for protecting the MCl from a direct lateral impact. A few, however, appear to protect the ACL preferentially. In the case of a controlled, direct lateral blow, all but a few braces tested provided some beneficial protection to the MCL and ACL, but performed well below the standard 1.5 ISF level. Therefore, based on the biomechanical research, it is our opinion that the concept of prophylactic lateral knee bracing can be effective. We recommend that prophylactic braces not be abandoned, but rather improved, biomechanically validated, and further evaluated through well-controlled prospective clinical studies.

Anterior Cruciate Ligament↗

PubMed1989

Endosteal bone loss after total hip arthroplasty.

Femoral endosteal bone loss has been shown to be part of the natural aging process and may be a factor in femoral component loosening following total hip arthroplasty (THA). In this study, changes in the femoral medullary canal width in 30 patients with aseptic femoral loosening following primary THA were compared with 30 matched control patients. The rate of canal expansion on the operated side was twice that of the nonoperated side and four times that of the control. After the onset of symptoms in the failure group, the rate of femoral expansion of the operated side doubled. Iliac crest biopsies showed a decrease in male patients for osteoid surface and appositional and bone formation rates when compared with literature controls. These results suggest that femoral medullary canal expansion may be a factor in femoral component loosening following THA. The increased rate of canal expansion after the onset of symptoms demonstrates the need for early surgical intervention to avoid excessive bone loss.

Adult↗

PubMed1983

Simultaneous quantitation of knee ligament forces.

An apparatus and experimental technique have been developed which allow the simultaneous quantitation of human cadaver knee ligament forces with the knee in various positions and subjected to various loads. The methodology permits all the major ligaments of the knee to be kept intact, thus preserving much of their normal relative load-bearing function. A novel measurement technique was employed for ligament force measurement. Strain gauges were placed at the ligamentous insertions and origins either on cortical bone or the cancellous/cortical transition. Gauge output was subsequently calibrated quantitatively by cutting the ligaments and subjecting them to known loads. The gauging technique was thermally stable, and the method as a whole yielded reproducible relative ligament force data when knee positions and loads were repeated for a given knee specimen. Three fresh human cadaver knee specimens have been subjected to testing thus far with gauges at six ligamentous sites. Initial evaluation of the data indicate that ligamentous loading patterns were quite different from those reported in the literature as determined by other methods.

Humans↗

PubMedDate not supplied

Poroelastic dynamic structural models of rhesus spinal motion segments.

Finite element models (FEMs) and analytical and experimental models based on poroelastic constitutive laws were developed for rhesus spinal motion segments (SMSs). Long-time creep, transient creep, and impact were studied for SMSs with normal and simulated degenerated discs. The results suggested that long-time creep observed in excised SMSs may be reduced in the in vivo SMS. The fluid phase included in these FEMs was shown to play a significant role in the mechanical response of SMSs. Relative fluid motion fields predicted in the SMS could be related to nutritional paths to the avascular interior of the disc and were found to be very sensitive to changes in discal stiffness. Reduced disc height, increased discal bulge, altered fluid motion, and stresses were quantified and may be related to mechanical failure, disc degeneration, and low-back pain.

Animals↗

PubMedDate not supplied

The biomechanics of lateral knee bracing. Part I: Response of the valgus restraints to loading.

To better understand the role of preventive knee braces in injury prevention, a biomechanical study using fresh frozen cadaveric knees (N = 18) was conducted. Ligament tensions and joint displacements were measured at static, nondestructive valgus forces as well as low-rate destructive forces. After quantifying and establishing individual ligament contributions to valgus restraining function, knees were then braced with two different laterally applied preventive braces, the McDavid Knee Guard and the Omni Anderson Knee Stabler. The effects of lateral bracing were analyzed according to valgus force, joint line opening, and ligament tensions. Valgus applied forces, with or without braces, consistently produced medial collateral ligament (MCL) disruptions at ligament tensions surprisingly higher than the anterior cruciate ligament (ACL) and higher than or equal to the posterior cruciate ligament (PCL). Although large joint displacements were necessary for complete ligament failure, bundle disruption in the MCL, ACL, and PCL was noted at much smaller joint openings. In Part I of this study, no significant protection could be documented with the two preventive braces used. Also, four potentially adverse effects were noted: MCL preload, center axis shift, premature joint line contact, and brace slippage.

Adult↗

PubMedDate not supplied

The biomechanics of lateral knee bracing. Part II: Impact response of the braced knee.

In Part I of our study on lateral knee bracing, we evaluated brace effectiveness using cadaveric knees and two commercially available braces (McDavid and Omni). The results indicated that for low-rate dynamic valgus loading, neither brace provided significant protection against MCL injury. Also, four potentially adverse effects were noted. The goals in Part II were to: 1) determine the clinical significance of brace induced MCL preload; 2) define the functional character of an "ideal" brace; 3) design and validate a surrogate knee model for testing brace effectiveness; and 4) determine brace performance under impact loading using the surrogate knee and six commercially available brace types (manufactured by DonJoy, McDavid, Mueller, Omni Scientific, Stromgren-Scott, and Tru-Fit). Knee braces, modified to measure varus/valgus bending force, were used to determine MCL preload effects in 13 human volunteers. An anatomically correct surrogate knee model, instrumented to measure ligament/tendon tension and medial joint opening, was developed and validated using information from our previous cadaver studies and results of analyses on the effects of high strain rates (100% versus 1000% strain/sec) on MCL failure. Over 500 impact tests were performed on the surrogate knee in unbraced versus braced conditions. Tests were conducted for three impactor masses, two flexion angles, and free or constrained limb positions. Impact safety factors (ISF) were calculated for each test condition and brace type. An ISF of 1.50 (MCL load reduction of 30%) was considered significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Athletic Injuries↗

PubMedDate not supplied

Comparison of rehabilitative knee braces. A biomechanical investigation.

A biomechanical comparison of eight popular commercially available rehabilitative knee braces was undertaken using a specially designed mechanical surrogate and computerized data acquisition system. Tests conducted included passive extension, valgus rotation, and anterior-posterior tibial translation. Most of the braces tested significantly reduced both translations and rotations compared to the unbraced limb under static test conditions. Braced versus braced performance varied and was found to depend upon a number of mechanical and design factors.

Biomechanical Phenomena↗

PubMedDate not supplied

Biomechanical evaluation of rotator cuff fixation methods.

Initial fixation strength and failure mode for various rotator cuff reattachment techniques (variations of the McLaughlin technique) were evaluated. Repair methods included standard suture (control), reinforced suture [expanded polytetrafluoroethylene (PTFE) patch and polydioxanone (PDS) tape augmentation] and stapling (nonarthroscopic and arthroscopic soft-tissue staples). The average strength of intact rotator cuff tissue (supraspinatus tendon) was also determined. The different rotator cuff repairs, including at least one control, were performed on fresh-frozen human cadaver shoulder pairs. Repairs were tested to failure in pure tension with the shoulder fixed in 60 degrees of abduction. Load and displacement data were normalized to controls, grouped according to failure modes, and statistically analyzed. The two basic failure modes observed were 1) bone failure, or suture tearing through the bone (indicating weak bone stock) and 2) tendon failure, or suture tearing of the rotator cuff. Gross comparisons between intact and repaired tendons indicated that the intact tendon was two to three times stronger than the repaired tendon. Based on the mode of failure and lack of increased strength after repair, the use of staples for cuff attachment is discouraged. PDS tape suture reinforcement did not increase fixation strength. In contrast, PTFE patch suture augmentation demonstrated statistically higher initial failure loads than did the control and was of specific benefit for shoulders with weak bone stock.

Adult↗

PubMedDate not supplied

The current state of functional knee bracing research. A review of the literature.

This paper reviews recent research on functional knee bracing. Research is categorized by subject, approach, or technique. The authors conclude that, while there is a good deal of excellent research available, there is little data to assist the clinician in selecting an orthosis for a specific application. The authors recommend that future investigations address the physiologic aspects of functional knee bracing and that brace manufacturers assume more responsibility in the validation of both existing and future brace designs.

Braces↗

PubMedDate not supplied

Impact biomechanics of lateral knee bracing. The anterior cruciate ligament.

We evaluated the effects of six different prophylactic braces on ACL ligament strain under dynamic valgus loads using a mechanical surrogate limb validated against human cadaveric specimens. Medical collateral ligament and anterior cruciate ligament peak forces, medial collateral ligament and anterior cruciate ligament tension initiation times, and impact safety factors were calculated for both braced and unbraced conditions. These tests were conducted to determine whether or not application of a prophylactic brace might provide protection to the anterior cruciate ligament under valgus loading conditions. The results of this study indicate that those braces that increased impact duration appear to differentially protect the anterior cruciate ligament more than the medial collateral ligament, and that most of the braces tested appear to provide some degree of protection to the anterior cruciate ligament under direct lateral impacts. These findings should be confirmed clinically.

Anterior Cruciate Ligament↗

PubMedDate not supplied

Soft tissue fixation to bone. A biomechanical analysis of spiked washers.

The initial fixation strengths of two spiked-washer designs were evaluated using human femurs and fascia lata tissue. Fascia lata was attached to the femur using the fixation devices, and then each femur-washer-fascia lata complex was loaded in tension to failure. Load-elongation curves were recorded, the initial failure load, initial failure displacement, stiffness, ultimate load, and ultimate displacement were determined for each test, and failure modes were recorded. Results indicated that the 6-spike design provided superior initial fixation strength in the 19-mm diameter size. This washer design was then compared with two commercially available fixation devices: the spiked AO washer and soft tissue fixation plate. Fixation provided by the prototypal washer design was not different in most instances from that provided by the AO fixation devices. Based on these results, important design characteristics for soft tissue spiked washers are identified and discussed.

Acetals↗