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Biomedical subjects

J W Frymoyer

Publications and source records attributed to J W Frymoyer.

At least 19 recordsLinked to original sources
PubMed1999

Hip osteotomy arthroplasty: ten-year follow-up.

We previously reported the initial success of combined osteotomy and arthroplasty of the hip for arthritis with femoral deformity. This technique has gained acceptance. We now report, for the first time, the ten year clinical and radiographic results with histology of 2 specimen. The osteotomies healed and the proximal femoral segment remained viable. One of three patients is symptom free without subsequent operative treatment. One of three patients had revision for acetabular loosening at eight years and biopsy of the proximal femur showed the proximal femoral segment to be viable. One of three patients had loosening of a macrofit bipolar prosthesis which required revision to total hip replacement at five years. Histology revealed viability of the proximal femur. All three patients are doing well at ten year follow-up. Based on the results of this study and current knowledge, the technique of osteotomy and arthroplasty for hip arthritis associated with femoral deformity is effective when combined with current techniques of ingrowth femoral component of total hip arthroplasty.

Arthroplasty, Replacement, Hip↗
PubMed1995

The use of expanded polytetrafluoroethylene as an interpositional membrane after lumbar laminectomy.

STUDY DESIGN: Prevention of post-laminectomy membrane formation was evaluated in a canine model. Fat graft, Silastic sheeting and expanded polytetrafluoroethylene were compared with nonimplanted control sites. OBJECTIVES: The development of an effective barrier to peridural scar invasion is of major importance in optimizing results after lumbar laminectomy. SUMMARY OF BACKGROUND DATA: Postoperative peridural fibrosis represents a normal biologic response after lumbar spinal surgery. A variety of biologic and nonbiologic interpositional materials have been studied. Expanded polytetrafluoroethylene has been shown to limit scar adhesion in the pericardium and peritoneum and has not been studied previously as a postlaminectomy interpositional membrane. METHODS: Eleven adult female cross-bred hounds underwent multilevel standardized laminotomies. Three materials--fat graft, Silastic sheeting, and expanded polytetrafluoroethylene--were compared with nonimplanted controls. The animals were killed 12 weeks after surgery and were evaluated histologically and using gadolinium-enhanced magnetic resonance imaging. RESULT: The magnetic resonance imaging studies were inconclusive in assessing peridural scar extension or identifying the implanted membranes. Histology revealed dense scar tissue at all control sites and replacement of all fat grafts by scar. Scar density was significantly less for the expanded polytetrafluoroethylene membrane surgical sites than for the control, fat graft, and Silastic sheeting sites. CONCLUSIONS: Expanded polytetrafluoroethylene membrane is biocompatible, maintains its structural integrity, and is impervious to fibrous ingrowth. These findings support further investigation of expanded polytetrafluoroethylene membrane as an interpositional material to prevent post-laminectomy peridural fibrosis.

Adipose Tissue↗
PubMed1994

L4-5 isthmic spondylolisthesis. A biomechanical analysis comparing stability in L4-5 and L5-S1 isthmic spondylolisthesis.

The authors have previously reported that the L4-5 isthmic spondylolisthesis lesion often progresses more than the L5-S1 lesion in adult patients. This biomechanical study compares the in vitro stability of the L4-5 isthmic spondylolisthesis lesion compared with the L5-S1 isthmic lesion. The authors also analyzed the role of the L5 iliolumbar ligament as a contributing factor to stability. Six fresh frozen human cadaveric specimens (L4 to the sacrum including the iliolumbar ligamentous complex) were tested by applying 10 Nm flexion-extension moments. Sagittal plane motion was measured with the specimens intact and after sequential transection of the pars interarticulares at L4 and L5 and finally with the iliolumbar ligaments cut at L5-S1. L4-5 and L5-S1 both showed significant increases in rotation with the pars defect compared with normal (L4-5 = +2.0, L5-S1 = +3.2 degrees). Decreased translation of L5-S1 occurred with pars defect at this level. There were no significant differences at the L5-S1 level after sectioning of the iliolumbar ligament. Calculating the percentage difference from normal, L4-5 with a pars defect exhibited significantly greater relative motion compared with L5-S1 with the same defect; 12% more rotation, 33% more shear, and 43% more axial translation. The iliolumbar ligament did not appear to contribute to these differences because there was no significant change in the L5-S1 kinematics after its transection. These results support the hypothesis that L4-5 pars defects are more unstable than L5-S1 lesions. The iliolumbar ligament could not be implicated as the major contributing factor in these differences.

Biomechanical Phenomena↗
PubMed1993

An international challenge to the diagnosis and treatment of disorders of the lumbar spine.

Since its formation 20 years ago, the International Society for Study of the Lumbar Spine has stimulated basic and clinical research. Because few disorders of the lumbar spine are lethal, our usual goal is to improve the quality of life of our patients by relieving pain and improving function. To do so, we must continuously improve the quality of the preventive, diagnostic, and treatment methods we employ. If quality is our goal, we need to be precise in our definition, understand how we measure it, and most importantly, be explicit in how we will improve it. Also, we must understand that our work is being conducted in a shrinking world, where all industrialized nations are profoundly concerned about the costs of health care.

Health Care Costs↗
PubMed1992

Lumbar disk disease: epidemiology.

Sciatica is a common symptom that affects as many as 40% of the adult population at some time. However, clinically significant sciatica is much less common and occurs in only 4% to 6% of the population. Exactly how often the symptom is caused by lumbar disk herniation is uncertain; it is known that herniation can occur independent of symptoms. Among the factors associated with its occurrence are age, gender, occupation, cigarette smoking, and exposure to vehicular vibration. The contribution of other factors such as height, weight, and genetics is less certain. The majority of patients with sciatica appear to recover. Approximately 20% of patients with sciatica caused by lumbar herniation have a strong indication for surgical intervention. In the remainder, indications are based primarily on pain rather than functionally significant neurologic deficits. Because pain is the principle indication, there are wide variations in the rates of surgical intervention between countries, and, even within countries, there are significant regional variations. These variations appear to be driven less by specific medical factors and more by gender, occupation, income, education, and the surgeon's preference. Although the contribution of sciatica to low back pain disability remains uncertain, disability caused by low back pain and sciatica appears to be increasing at a rate disproportionate to population growth. To what degree surgery now contributes to that disability is uncertain, but limited information suggests that it may be substantial.

Adult↗
PubMed1992

Predicting disability from low back pain.

Since World War II, the incidence of chronic low back disability has increased dramatically, at a rate disproportionate to all other health conditions. The factors that contribute to this disability are reviewed. Psychosocial and work environmental factors are far more accurate predictors of disability than physical factors. A predictive risk model is described that allows an estimate of the patient's risk of becoming chronically disabled early in the course of a low back pain episode. This model demonstrates that work environment, perception of compensability, and the duration of the current episode are significantly predictors. Surprisingly, psychologic factors, as measured by the Minnesota Multiphasic Personality Inventory (MMPI), are not predictive in the cohorts studied to date. Although there are inherent limitations in study design, the results offer additional credence to the hypothesis that low back pain disability is often the result of psychosocial and work environmental factors. The model may also be used to address the hypothesis that patients at risk for future disability are more effectively treated by early, aggressive rehabilitation programs.

Back Pain↗
PubMed1992

Diagnosing instability.

The various definitions of instability are reviewed and preference is given to the definition of instability as a loss of stiffness. This definition fits with current laboratory observations. Roentgenographic changes, particularly those associated with degeneration, have no relationship to instability. Multiple roentgenographic images can be of use, but accuracy is limited, and often valuable information at midmotion range or in other planes is missing. Stereoroentgenography appears to offer some promise, but implanted metallic markers are necessary to attain adequate accuracy. Ionizing radiation dose levels are of concern in these techniques. External fixation techniques appear to be of use in some patients. Kinematic linkages and frames containing infrared light emitting diodes are extremely promising, because they give kinematic information in detail.

Humans↗
PubMed1991

Identifying patients at risk of becoming disabled because of low-back pain. The Vermont Rehabilitation Engineering Center predictive model.

A predictive risk model of low-back pain (LBP) disability was developed by a panel of six experts in the fields of chronic pain and disability. It comprised 28 factors organized into eight categories: job, psychosocial, injury, diagnostic, demographic, medical history, health behaviors, and anthropometric characteristics and was administered as a 15-minute written questionnaire. The model was tested prospectively on 250 patients (age range, 18-65 years) attending two secondary-care low-back clinics. Disability, as predicted by the model, was compared with 1) actual disability assessed 3 and 6 months later; 2) predictions of disability made by the attending physicians; and 3) predictions obtained from an empirically derived model. These results showed that 1) the expert-generated risk model had a predictive accuracy of 89% and did better in predicting disability than the physicians across all samples and 2) the empirically weighted model did best of all (91% predictive accuracy), suggesting that the expert model used appropriate factors but that the weights assigned to these factors by the panel of experts could be improved.

Adult↗
PubMed1991

Clinical tests applicable to the study of chronic low-back disability.

This symposium has evaluated the possible directions to be taken in designing reliable and valid questionnaires, screening examinations, and paraclinical tests applicable to studies in LBP. The detailed design of such test instruments, field testing, measures of reliability, and validity represent the next step if the current barriers to collaborative clinical research in LBP are to be overcome.

Back Pain↗
PubMed1991

An overview of the incidences and costs of low back pain.

The basic premise of this article is that low back disorders are extremely prevalent in all societies, and probably have not increased substantially over the past two decades. What has increased is the rate of disability, the reasons for which are uncertain. Not only has this phenomenon heightened the awareness of low back pain, but it has led to an explosion in costs. Although a precise estimate is impossible, it is plausible that the direct medical and indirect costs of these conditions are in the range of more than $50 billion per annum, and could be as high as $100 billion at the extreme. Of these costs, 75% or more can be attributed to the 5% of people who become disabled temporarily or permanently from back pain--a phenomenon that seems more rooted in psychosocial rather than disease determinants. Within this overall equation, spinal surgery plays a relatively small role, although the contribution to disability probably has more than passing significance. The future challenge, if costs are to be controlled, appears to lie squarely with prevention and optimum management of disability, rather than perpetrating a myth that low back pain is a serious health disorder.

Back Pain↗
PubMed1991

Low back pain. The role of spine fusion.

The major objectives of spinal surgery are to relieve pain, improve function, and correct deformity. The surgical strategies to meet these objectives are decompression of neural elements or surgical stabilization by arthrodesis. This article analyzes spinal fusion from the perspective of indications, the broad principles of surgical technique, the results that can be obtained, and the complications of the procedure.

Back Pain↗
PubMed1989

Hip arthroplasty after biplanar femoral osteotomy.

Hip arthroplasty in patients who have had previous biplanar femoral osteotomy (eg, Southwick) is a technical surgical problem. Distorted proximal femoral anatomy may make routine insertion of a femoral prosthesis impossible. The authors report the short-term results in three patients with hip arthroplasty after biplanar femoral osteotomy. The technique consists of a biplanar closing wedge osteotomy at the level of the lesser trochanter to correct the previous surgical deformity. The remaining proximal femur becomes a vascularized bone graft that is skewered by the femoral prosthesis, which also gains purchase in the medullary canal of the proximal femoral shaft. This technique allows restoration of anatomic femoral alignment and the use of standard prostheses with preservation of bone stock. The initial results have been very good. The appearance of the hip is very similar to that in primary hip arthroplasty.

Adult↗
PubMed1989

Experimental instability in the rabbit lumbar spine.

The authors performed mechanical, biochemical, and histologic analyses of changes in the rabbit lumbar spine occurring after instability had been induced by facet removal to find whether this intervention produced an experimental model for intervertebral disc degeneration. Sham operated animals and an unoperated control group were used for comparison. Half of the operated animals were housed under conditions to promote higher physical activity than the other animals housed individually in small cages. Acutely, the removal of facet joints increased the flexibility of intervertebral joints. Over the following year, this increase in flexibility was reduced to close to control levels in all groups of animals. Within the intervertebral discs, there was no significant change in proportions or solubility of collagen or proteoglycans after surgery, nor was there microscopic or macroscopic evidence of disc degeneration. The surgical procedure produced hypermobility of the spine, but there was a subsequent restabilization, and the intended disc degeneration was not produced. These findings indicate that some as yet unidentified soft tissue repair process, facilitated by activity, overcame the hypermobility created at surgery, so degenerative changes in the intervertebral discs did not result. We suggest that other animal models of disc degeneration may represent a failure of reparative response to acute injury.

Animals↗