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Biomedical subjects

F T Wetzel

Publications and source records attributed to F T Wetzel.

At least 19 recordsLinked to original sources
PubMed1999

Hardware failure in an unconstrained lumbar pedicle screw system. A 2-year follow-up study.

STUDY DESIGN: A consecutive study of patients who underwent lumbar spinal arthrodesis with an unconstrained pedicle screw system. OBJECTIVES: To determine the rate of arthrodesis and of clinical success and to examine and characterize the cases of hardware failure with the AO/Dynamic Compression Plate system (Synthes, Paoli, PA). SUMMARY OF BACKGROUND DATA: Although the advantages and disadvantages of nonconstrained versus constrained systems have been studied extensively, instrumentation failure has not. Additionally, the association between pseudarthrosis and hardware failure per se is unclear. METHODS: Seventy-four consecutive cases of lumbar spinal fusion are reviewed. Standard outcome scores based on pain relief and medication usage were tabulated, along with pertinent demographic data. The patients were observed at five intervals after surgery for at least 2 years (range, 24 to 35 months; mean, 27 months). Standard statistical analyses were used to analyze data. Status of the arthrodesis was determined by standard radiographic criteria. RESULTS: The overall fusion rate was 61%. At final follow-up, 60% of patients believed that their back pain had improved, whereas 70% believed that their limb pain had improved. The presence of a solid fusion (r = 3.3, P = 0.010) was correlated positively with a successful clinical outcome; the presence of pseudarthrosis and preoperative narcotic use were negatively correlated with a successful clinical outcome. Twenty-two percent of patients (16) experienced hardware failure. Twelve of the 16 had pseudarthrosis; in the majority of these patients, hardware failure occurred at the level of the pseudarthrosis. CONCLUSIONS: The results of this study demonstrate an extremely high rate of hardware failure and pseudarthrosis using an unconstrained pedicle screw system. Interestingly, the initial rate of pain relief was higher and declined over time and was quite possibly associated with loosening of the hardware. Based on these data, it is difficult to recommend the use of an unconstrained fixation system in the lumbar spine.

Bone Screws↗
PubMed1999

Occipitocervical neutral position. Possible surgical implications.

STUDY DESIGN: The study defines the occipitocervical neutral position using cervical radiographs from 30 subjects. OBJECTIVE: To identify reproducible radiographic measures of the occipitocervical neutral position that can be used during surgery to optimize fusion position. SUMMARY OF BACKGROUND DATA: When performing rigid internal fixation of the occiput to the cervical spine, the ability to determine that the occiput is in a neutral position in relation to the cervical spine is important. Currently, no objective radiographic measures for the occipitocervical neutral position exist. METHODS: Thirty flexion, extension, and neutral lateral cervical spine radiographs radiographs interpreted as normal by an experienced radiologist were studied. The occipitocervical angle and occipitocervical distance were defined and calculated. Two investigators, an orthopedic resident and an experienced orthopedic spine surgeon, measured the occipitocervical angle and occipitocervical distance independently on all radiographs in a blinded manner. Correlation coefficients were obtained to determine interobserver reliability. RESULTS: The mean occipitocervical angles were 24.2 degrees, 44.0 degrees, and 57.2 degrees in flexion, neutral, and extension, respectively. The mean occipitocervical distances were 21.5 mm in neutral, 28.0 mm in flexion, and 14.8 mm in extension. The differences in the occipitocervical angle and occipitocervical distance in neutral, flexion, and extension were statistically significant (P < 0.05 and < 0.001, respectively). There were no significant interobserver differences in any of the measurements. CONCLUSIONS: The radiographic measures of the occipitocervical neutral position reported in this study are reliable, repeatable, and simple to determine on routine lateral radiographs. These measurements should be a valuable intra-operative tool for achieving occipitocervical fusion in appropriate alignment.

Adult↗
PubMed1999

Behavioral dimensions of adjustment in persons with chronic pain: pain-related anxiety and acceptance.

Through empirical methods we now characterize patients with chronic pain as either dysfunctional, interpersonally distressed, or adaptive copers. Studying factors that differentiate these groups may reveal the behavioral processes that determine adjustment to pain. Subjects for this study were 190 patients referred for treatment of chronic pain. They were classified as dysfunctional (n = 41), interpersonally distressed (n = 28) or adaptive copers (n = 59) based on the Multidimensional Pain Inventory (Kerns, R.D., Turk, D.C. and Rudy, T.E., The West Haven-Yale Multidimensional Pain Inventory (WHYMPI), Pain, 23 (1985) 345-356) and compared on measures of pain-related anxiety and pain acceptance. Our analyses showed that the dysfunctional group reported greater pain-related anxiety and less acceptance of pain than the other groups. Additional analyses, statistically controlling for pain severity and depression, showed that the patient subtypes continued to differ on pain-related anxiety and acceptance. Discriminant function analyses including pain-related anxiety and acceptance correctly classified 72.5% of dysfunctional and 90.9% of adaptive copers. Again, anxiety and acceptance contributed uniquely to classification independent of depression and pain intensity. Pain-related anxiety and acceptance of pain appear to be unique behavioral dimensions of adjustment to chronic pain. Decreasing anxiety and increasing acceptance may 'move' patients with chronic pain from the dysfunctional to the adaptive coper category.

Adaptation, Psychological↗
PubMed1998

Controversy. The use of selective nerve root blocks: diagnostic, therapeutic, or placebo?

An increasing number of therapeutic spinal injections are performed each year despite little validation in randomized controlled trials. Additional injections are performed for diagnostic purposes of localizing symptomatic nerve roots, again without detailed evaluation of accuracy, specificity, or sensitivity. Drs. Slosar and White argue that selective nerve root blocks are extremely useful; Dr Wetzel believes that selective nerve root blocks have no role in selecting patients for surgery.

Humans↗
PubMed1997

Extradural sensory rhizotomy in the management of chronic lumbar radiculopathy: a minimum 2-year follow-up study.

STUDY DESIGN: Fifty-one consecutive patients who underwent extradural sensory rhizotomy for chronic radiculopathy after lumbar surgery were reviewed retrospectively. OBJECTIVES: To determine the effectiveness of sensory rhizotomy in the management of chronic radiculopathy in patients selected by extensive imaging techniques and selective nerve root sheath injections. SUMMARY OF BACKGROUND DATA: Results of more central ablative procedures for chronic benign pain problems have been disappointing, with variable reports of pain relief. METHODS: Fifty-one patients were reviewed. All patients underwent extensive evaluation to exclude reversible structural lesions, and all had the diagnosis of chronic radiculopathy confirmed by results of clinical and electrophysiologic examination. Selective nerve root sheath injections under fluoroscopic guidance confirmed the symptomatic nature of the segments. All blocks were repeated at least once. All patients underwent selective sensory rhizotomy or, in some cases, complete rhizotomy. After rhizotomy, 37 patients were available to be observed at selected time intervals for a minimum of 2 years. Clinical results were determined by the presence or absence of pain relief (visual analog scale), sensory and motor deficits, narcotic analgesic usage, and the patient's estimation of the effectiveness of the procedure. RESULTS: At 6 months after surgery, all 51 patients and the outcomes of their surgery were available for review. Fifty-five percent of patients rated were believed to have good or excellent outcomes, whereas the remainder had poor or failed outcomes. For the minimum 2-year follow-up period (range, 2-4.2 years), 37 patients were available for review. At final follow-up examination only 19% of the patients maintained good or excellent outcomes. CONCLUSIONS: The results of the rhizotomy procedures deteriorated over time. Possible reasons for the failure, other than temporal deterioration, were anatomic factors and lack of specificity of diagnostic techniques, specifically selective nerve root sheath injection. At this point rhizotomy cannot be recommended with any confidence whatsoever in the setting of chronic lumbar radiculopathy after lumbar surgery.

Adult↗
PubMed1995

The effectiveness of the cervical halo: open versus closed ring. A preliminary report.

The halo cervical orthosis has proven extremely effective in stabilizing the spine, both non-operatively and as a supplement to operative procedures. Current designs of the available halo utilize either a closed or an open stabilizing ring. Twenty-four patients with various indications for halo application are reviewed. Eleven were treated with a closed ring apparatus (Ace Medical, Los Angeles, California), and thirteen with an open ring device (Bremer, Inc, Jacksonville, Florida). X-rays of the treated patients were compared by group, and patients were interviewed regarding their complaints while wearing the halo. Rates of complication were compared. Results showed no significant differences between radiographs (kyphosis or translation) throughout the follow-up period. Patients experienced a significantly higher incidence of halo-associated pain in the open group. Otherwise, there were no statistical differences in the complication rates of either device. Whether or not the higher incidence of pain in the open group is related to decreased device rigidity is unknown. The open design may theoretically permit bending and opening of the ring to occur, the so-called 'wishbone' effect. Based on these data, it cannot be determined whether the advantages of the open ring--ease of application--are offset by this potential disadvantage. Clearly, a larger, randomized prospective study is required to investigate this.

Adolescent↗
PubMed1994

The treatment of lumbar spinal pain syndromes diagnosed by discography. Lumbar arthrodesis.

STUDY DESIGN: This retrospective review of patients whose discogenic pain syndromes were treated by lumbar arthrodesis was designed to examine the clinical efficacy of this diagnostic modality and analyze possible confounding variables. OBJECTIVES: Clinical outcome was examined with respect to status of the arthrodesis, discographic diagnosis, and demographic variables. SUMMARY OF BACKGROUND DATA: Discography continues to be a controversial diagnostic technique for spinal pain syndromes. The morphologic information provided by discography is well known. However, disagreement exists concerning the clinical utility of the pain provoked by this modality. METHODS: Forty-eight patients were included in this study. In all patients, the chief complaint was low back pain. In all patients, the definitive diagnostic technique was lumbar discography followed by computerized tomographic scanning. All patients underwent lumbar arthrodesis. Data were collected in four categories: 1) demographic characteristics, 2) physical findings, 3) results of diagnostic studies, and 4) characteristics of surgical procedures. Data from these categories were studied with respect to clinical rating and status of the arthrodesis. RESULTS: Overall, 46% were judged to have a satisfactory clinical outcome at final follow-up. Forty-eight percent were judged to have a solid arthrodesis. CONCLUSIONS: Based on the results of this study, it appears that discogenic pain syndromes can be treated by arthrodesis.

Adult↗
PubMed1992

Chronic benign cervical pain syndromes. Surgical considerations.

The results of surgical intervention for chronic benign pain syndromes are generally poor. In this review, pertinent ablative and modulatory techniques are reviewed, with specific reference to their utility for benign pain syndromes. With the possible exception of facet rhizotomy, the ablative modalities have little role in the management of benign pain syndromes. The more extensive techniques of cordotomy, dorsal root entry zone lesioning, ganglionectomy, and rhizotomy, have erratic results and high rates of complication. No long-term studies exist to support the use of facet rhizotomy. It is minimally invasive, however, and has little morbidity. In patients with benign refractory posterior column pain, facet rhizotomy may be worth consideration. Modulatory devices may have a role in benign pain syndromes. While the use of indwelling epidural catheters remains investigational, dorsal column stimulation has been widely studied. In representative reports, significant pain relief has been observed in up to 60% of patients (mean follow-up of two years). In the carefully selected patient, this may represent a valuable therapeutic adjunct.

Cervical Vertebrae↗
PubMed1992

The treatment of chronic extremity pain in failed lumbar surgery. The role of lumbar sympathectomy.

Persistent lower extremity pain after unsuccessful lumbar surgery continues to be a disabling condition. The results of deafferentation procedures for radiculopathy have been disappointing. Hence, the prospect of isolating a potentially reversible component of extremity pain is quite attractive. Given the frequency with which vasomotor complaints occur in this setting, the occurrence of autonomic dysfunction seems quite plausible. Autonomic dysfunction was investigated in 17 patients who had undergone previous lumbar surgery and had chronic limb pain. Patients underwent a preblockade thermogram, sympathetic blockade, and postblockade thermograms. All patients reported substantial relief after blockade, and all underwent retroperitoneal sympathectomy. All patients were followed for at least 2 years. The clinical results were disappointing, with only one patient reporting substantial relief. Although the results of thermography initially seemed to correlate with clinical outcome, further follow-up failed to yield any correlation. Additionally, no specific combination of response to blockade or thermogram was predictive of the clinical success after sympathectomy. Now, lumbar sympathectomy is not recommended in the setting of chronic radiculopathy and persistent extremity pain.

Female↗
PubMed1991

The failed posterior lumbar interbody fusion.

The problems presented by unsuccessful posterior lumbar interbody fusion (PLIF) have not been addressed. The cases of 12 patients who presented with failed PLIF were reviewed. Five patients were male and seven female (age range, 24-50 years; mean age, 40 years). All patients underwent at least one PLIF; many had undergone other procedures. A total of 37 procedures had been performed on the 12 patients. Chronic radiculopathy was present in all patients, as detected with electromyographic or nerve conduction velocity examination. At the time of reconstructive surgery, in the 11 patients in whom the canal was explored, all had extensive epidural fibrosis. Nine of the 12 patients had pseudarthrosis of the previous PLIF. Four patients had evidence of motion segment dysfunction at nearby levels: two had positive discograms adjacent to the PLIFs; one developed a facet syndrome at L5-S1, caudal to an L4-5 PLIF; and one demonstrated frank segmental instability at L2-3, cranial to a previous PLIF at L3-4. Twelve patients underwent a total of 22 procedures after referral. Eleven patients initially underwent decompression and fusion, and one patient underwent a sympathectomy. Seven patients underwent an additional 10 procedures, including repeat decompression, repair of pseudarthrosis, and implantation of an epidural analgesic pump system. After all surgical treatment, five patients rated their pain as improved. Seven patients were thought to have a solid fusion. The presence of a solid fusion did not correlate with satisfactory relief of pain (chi-square). Continued extremity pain was the predominant complaint of all the patients. Two shortcomings of the PLIF were evident.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Biomechanics of the rabbit cervical spine as a function of component transection.

The rabbit cervical spine in the form of the functional spinal unit was tested in a manner analogous to that used to study human functional spinal units. Anatomies and biomechanical similarities and differences with the human were demonstrated. The rabbit cervical spine failed abruptly after a well-defined series of anterior or posterior segmental injuries. However, up to the failure point, the rabbit cervical spine exhibited an increased range of motion after each segmental injury. The results of this study were used to develop an in vivo model for the study of spinal injury in subsequent projects.

Animals↗
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↗