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Biomedical subjects

F T Wetzel

Publications and source records attributed to F T Wetzel.

25 records · Page 2Linked to original sources
PubMed1989

Temporal biomechanics of posterior cervical spine injuries in vivo in a rabbit model.

There are numerous clinical and biomechanical criteria for determination of acute spinal instability. No data, however, exist on the biomechanical behavior of the injured, untreated spine during the healing period. Using a rabbit model, this study was designed to quantify changes in the mechanical properties of the injured spine over time. Sixteen rabbits were assigned to four injury groups: Injury 1 (C4-5 supra/intraspinous ligament transection), Injury 2 (C4 laminectomy), or Injury 3 (C4 laminectomy, plus bilateral facet capsular ligament transection). The fourth injury group was Sham (posterior exposure of C4-5, no spinal injury). Preinjury range of motion was determined by standardized flexion-extension radiographs on all animals. Postinjury flexion-extension radiographs were taken at 4, 8, and 12 weeks. At the end of 12 weeks, animals were killed. Mean range of motion at C4-5 for all injury groups decreased from preinjury values. The greatest decrease was for the most severe injury. At 8 weeks, the range of motion for this injury was less than half of the preinjury level and increased to 62% of the preinjury level at 12 weeks.

Animals↗
PubMed1989

Grisel's syndrome.

Grisel's syndrome is a unilateral or bilateral subluxation of C1 on C2, associated with an infectious condition in the head or neck. Anatomic studies have demonstrated the existence of a periodontoidal vascular plexus that drains the posterior superior pharyngeal region. No lymph nodes are present in this plexus, so septic exudates may be freely transferred from the pharynx to the C1-C2 articulation. The resulting synovial and vascular engorgements may cause mechanical and chemical damage to the transverse and facet capsular ligaments leading to subluxation. The primary treatment of Grisel's syndrome is medical: the underlying infectious organism must be isolated and appropriate antibiotics prescribed. The subluxation is reduced in halter or skeletal traction. The authors use the classification scheme of rotary subluxation proposed by Fielding, so that treatment appropriate to the specific type of subluxation is used. Based on biomechanical data predicting articular instability and canal compromise proportional to the extent of ligamentous injury, the following specific forms of immobilization are recommended to ensure ligamentous healing: Fielding Type I (transverse ligament intact and bilateral facet capsular injury) soft collar; Type II (transverse ligament and unilateral facet capsular injury) Philadelphia collar or SOMI brace; and Type III (transverse ligament and bilateral facet capsular ligament injury) halo. Following six to eight weeks of immobilization, stability is assessed by the study of flexion-extension roentgenograms. Should residual instability be demonstrated, arthrodesis is indicated.

Adolescent↗
PubMed1986

Poor growth prior to early childhood: decreased health and life-span in the adult.

Previous studies in animal populations have shown that stunted neural and thymolymphatic growth early in development may result in permanently impaired neural and immune function, decreased body growth, vertebral wedging, and decreased life-span. In the human adult, small vertebral neural canal (VNC) diameters may reflect early stunted neural and immune development and impaired function that leads to decreased health (inferred by greater vertebral wedging) and life-span in the adult. VNC, which complete their growth by early childhood (age 4), are markers of early development in adults. On the other hand, features following general body growth, such as height, weight (represented here by vertebral body height) continues to grow until young adulthood. They are less reliable, because they readily experience catch-up growth (even in chronically stressed populations) and, unlike VNC, may mask poor early growth. To test associations between early growth and adult health and life-span in humans, we measured 2,060 VNC, vertebral heights, vertebral wedging, nerve-root tunnel lengths, severity of vertebral osteophytosis, and ages at death in 90 adult (aged 15-55 years) prehistoric skeletons (950-1300 A.D.). Tibial lengths were also measured in a subsample (n = 30). Multivariate, bivariate, and nonparametric analyses showed that small VNC are significantly associated with greater vertebral wedging and decreased life-span (P less than 0.05-0.00001). VNC are independent of vertebral body heights and tibial lengths (general body growth). VNC, but not statural components, are useful in predicting adult health, presumably because they reflect neural and immune development and do not readily experience catch-up growth. Thus, longitudinal retrospective measures of early growth and adult health were systematically linked within individuals regardless of confounding factors operating over the 350-year time period. Since this research was completed, this model has repeatedly been independently confirmed in four living urban industrial populations. Longitudinal retrospective analysis was employed together with direct measures of VNC, neural and immune function. Together these results suggested that it may be essential to improve growth prior to early childhood in order to maximize adult health and life-span.

Adolescent↗
PubMed1985

Can infant malnutrition cause adult vertebral stenosis?

Does infant malnutrition produce smaller adult spinal canals? Lumbar and thoracic vertebrae (n X 1073), from a prehistoric American Indian population (15-55 yrs of age), were measured for anteroposterior (AP) and transverse (TR) vertebral canal sizes, nerve root tunnel (intervertebral foramen) widths (NRT), vertebral heights (VH), vertebral osteophytosis (VO), and tibial lengths. They underwent a dietary change from hunting-gathering, protein rich (PR), to maize agriculture, protein deficient (PD), between 950 and 1300 A.D. Multivariate analyses controlled for age, sex, culture, NRT, VH, VO, and wedging. Canal size was significantly smaller in the PD. AP diameters were generally and highly correlated with NRT, and thus both spinal stenosis and sciatica may have a developmental basis. Canal size was independent of statural components. Consequently, canal size is a most powerful tool in assessing the presence infant malnutrition. Moreover, perhaps the association between canal size and low-back pain (LBP) found in living populations has been underestimated, and this component of LBP is preventable.

Adult↗
PubMed1978

Hormonal control of male reproductive behavior in the lizard, Anolis carolinensis: role of testosterone, dihydrotestosterone, and estradiol.

The androgen aromatization hypothesis was examined in the male lizard, Anolis carolinensis. After castration, sc silastic implants of testosterone (T) restored both challenge and courtship behavior, while dihydrotestosterone (DHT) or 17beta-estradiol (E) had no effect on male behaviors. Both T and DHT, but not E, stimulated hypertrophy and colloid production by the renal sex segment, a secondary sexual characteristic of male lizards. In two separate studies, castrates received DHT in combination with E. In each replicate, half of the castrates responded with increases in courtship behavior after hormone treatment. Epithelial cell height of the sex segment of all DHT and E-treated castrates was comparable to T- or DHT-treated castrates, but colloid production was not stimulated. These experiments indicate that in this species, treatment with T stimulates both sexual behavior and secondary sex character development, whereas treatment with E alone is without effect centrally or peripherally.

Animals↗
PubMedDate not supplied

Freeze-dried fibular allograft in anterior spinal surgery: cervical and lumbar applications.

Fifty-six patients who underwent anterior fusion utilizing fibular allograft are reviewed. Thirty-two patients underwent multiple-level anterior cervical discectomy and fusion utilizing fibular strut allograft, and 24 underwent anterior lumbar discectomy and fusion using fibular strut allograft. Cervical surgery was performed via the strut technique of Whitecloud and LaRocca and lumbar surgery was performed via a transperitoneal or retroperitoneal approach. Postoperatively, patients were assigned a clinical grade based on symptomatic relief and medication usage. X-rays were visually inspected, and quantitatively digitized for Cobb angle and translation in order to assess the status of arthrodesis. In the cervical group, the rate of clinical success (87.5%) exceeded the arthrodesis rate. By inspection, 65% fused, at a mean time of 23.5 months postoperatively. In the lumbar group, the overall clinical success rate was 68%. This correlated quite strongly with a fusion rate of 58%. Smoking was a negative correlate with arthrodesis. Patients receiving Workers' Compensation were also more likely to have an unsatisfactory clinical outcome. The results of this study highlight the difference between anterior arthrodesis in the cervical and lumbar spine. The biomechanical stability afforded by the fibular strut in the cervical spine appears to outweigh the disadvantages of delayed time to union. The rate of posterior cervical fusion to salvage symptomatic pseudoarthrosis was quite low (9.3%), thus suggesting that additional posterior surgery in this particular group of patients should not be considered for a minimum of two years postoperatively. In the lumbar group, status of arthrodesis correlated closely with clinical outcome. Fusion rate in this group was disappointing, corresponding to other reports in the literature. Based on these data, primary anterior body fusion without allograft in the lumbar spine cannot be recommended, as a viable alternative to conventional autograft.

Adult↗