Correction for biases in a population-based study of family history and coronary heart disease. The Newcastle Family History Study I.

In this paper, the authors report on the design of a population-based case-control study of family history as a risk factor for coronary heart disease (CHD). They studied the characteristics of subjects who completed a detailed family history questionnaire in 1992-1994 as well as the accuracy of recall of family history in order to quantify both selection and recall biases. Coronary disease cases were enrolled through the Newcastle MONICA Project (Monitoring Trends and Determinants in Cardiovascular Disease), which registered all suspected heart attacks and sudden cardiac deaths in the Lower Hunter region of New South Wales, Australia, between August 1984 and March 1994. Controls were selected at random from the New South Wales electoral roll. The response rate was 76% in cases and 62% in controls; the major factor associated with participation in the study was perceived family history of CHD, more so in the control series than in the case series. Accuracy was determined by comparing information obtained from the proband with that recorded on death certificates. In first-degree relatives, sensitivity of CHD recall was 85% (95% confidence interval (CI) 74-92%) in cases and 95% (95% CI 84-99%) in controls, while specificity was 59% (95% CI 49-69%) and 74% (95% CI 65-82%), respectively. The net bias in both selection and recall is toward the null and hence the comparisons provide a conservative estimate of risk of CHD associated with a positive family history.

Threaded titanium cages for lumbar interbody fusions.

STUDY DESIGN: This study evaluated safety, fusion success rate, and clinical outcome of a new lumbar interbody hollow, threaded titanium fusion cage in a multicenter, prospective 236-case program adhering to a United States Food and Drug Administration Investigational Device Exemption controlled protocol. OBJECTIVES: The results were evaluated to demonstrate the safety and effectiveness of this new method to achieve solid lumbar interbody fusions. SUMMARY OF BACKGROUND DATA: Interbody fusions have certain distinct mechanical advantages over lateral or posterolateral ones. Autologous, cancellous bone is the preferred graft material, but is too soft to maintain the space during fusion without mechanical support. Various methods have been used in the past to maintain the graft integrity during fusion development. METHODS: An initial pilot study began on 10 patients (followed for 84 months, average 80 months). Two years after that investigation started, the multicenter United States Food and Drug Administration Investigational Device Exemption study began, with cases followed for 28-46 months (average, 32). Ninety-six percent of the investigational Device Exemption study cases had severe, disabling back pain; in addition, 74% had major annular degeneration; 57% had herniations; 21% had osteophytes; and 43% had disc height reduced by greater than 10%. Forty-five percent of cases had previous spinal surgeries, and none were posterior lumbar interbody fusions. Titanium fusion cage pairs were screwed into bored and threaded, parallel intradiscal holes, and 3-8 ml autologous cancellous bone was packed inside each. Fusion success was judged by absence of motion on flexion-extension radiographs, absence of bone halo around the implants, and maintenance of visible bone inside the cages on Ferguson view radiographs. RESULTS: Segments fused rapidly; the pilot study cases fused at 10 (91%) of 11 levels, with a reported 80% average clinical improvement. Ninety-six percent of the 208 2-year follow-up Investigational Device Exemption cases had fusion, and the Prolo socioeconomic/ functional improvement scale showed: 40% excellent, 25% good, 21% fair, and 14% poor results. Less than 1% of Investigational Device Exemption cases had complications that persisted beyond the average 5 days of hospitalization, and none were serious. CONCLUSIONS: The Ray titanium fusion cage (Surgical Dynamics, Norwalk, CT) implant method has been found to be an effective, rapid, safe procedure for lumbar spine fusions, demonstrating a high fusion rate and clinical success with rare, serious, or permanent complications.

Threaded fusion cages for lumbar interbody fusions. An economic comparison with 360 degrees fusions.

STUDY DESIGN: This study compared the surgical and hospitalization costs, operating times, and blood loss attributable to lumbar interbody fusions at one and two lumbar levels by the use of two device systems: 1) the Ray Threaded Fusion Cage, and 2) an anteroposterior interbody technique with pedicle screw and rod stabilization (360 degrees fusion). The clinical efficacy and complication rate of each method were similar. OBJECTIVES: Data were analyzed to compare the newer threaded fusion cage method with the well established 360 degrees technique. SUMMARY OF BACKGROUND DATA: Interbody bone grafts are a proven concept to obtain solid spinal fusions. A variety of mechanical means are used to stabilize the graft material during the fusion growth and have been shown to be important in facilitating both the rate and ultimate quality of the fusion. METHODS: In a cohort of 50 prospectively selected patients having severe, disabling back pain with discal degeneration, 25 received Ray Threaded Fusion Cages and 25 had anteroposterior interbody fusion procedures using pedicle screws (360 degrees technique) over the period 1991 to 1995. All implants were performed by the same surgeon in the same hospital. All fusions were judged solid by established radiologic criteria. Cost comparisons were made from pertinent medical records using inflation-corrected 1995 U.S. dollars. RESULTS: The average combined (surgeon, hospital, anesthesiologist) costs attributed to one-level threaded fusion cage procedures were $25,171, and $41,813 to equivalent 360 degrees procedures, a difference of 40% or $16,642. Costs for two-level cases were $33,113 and $47,320, respectively, differing by 30% or $14,207. The average saving through preferential use of the threaded fusion cage was $14,639 per case, or $365,966 for the 25-patient subgroup. Ten of the 360 degrees fusion cases required later instrumentation removal, adding $8,635 to the costs of each such case, a final difference of $22,889 compared with an equivalent threaded fusion cage case. The actual collections on threaded fusion cage cases were 81% of billed costs and the actual collections on 360 degrees cases were 73% of billed costs. CONCLUSIONS: Assuming that the fusion success, clinical outcome, and complication rates are sufficiently similar between these two techniques, the striking improvement in overall surgical and hospitalization costs, surgical time, and blood losses provided by the threaded fusion cage technique can be major decision points in method selection. Further, no threaded fusion cage case having a normal adjacent level preoperatively developed a fusion transition syndrome over a followup period from 3 to 29 months (averaging 24 months) that required a second fusion procedure, and no cage had to be removed because of instrumentation-associated pain, although each of these problems are known to occur in at lease 10% of pedicle screw implants. Ten of the 25 (40%) 360 degrees fusion cases in this study required subsequent instrumentation removal, although no case has required adjacent level surgery for transition syndrome.

Acute effect of ethanol on renal electrolyte transport in the rat.

1. Despite human and animal studies, the direct effect of ethanol on renal water and electrolyte transport is poorly understood. The acute effect of increasing plasma concentrations of ethanol was evaluated in a water diuretic anaesthetized rat model which inhibits endogenous arginine vasopressin (AVP) release. 2. Ethanol at a plasma concentration of 1.69 +/- 0.28 mmol/L produced an immediate increase in urine flow (174 +/- 11 microL/min pre-ethanol and 189 +/- 13 and then 206 +/- 12 microL/min during the ethanol infusion; P < 0.01) as well as an increase in fractional sodium excretion (0.17 +/- 0.04 to 0.28 +/- 0.05 and 0.27 +/- 0.05%; P < 0.01). There was also a brief phosphaturia. These increases in electrolyte excretion had returned to control values by 20 min despite a further increase in the plasma ethanol concentration. 3. The urinary excretion of potassium, calcium and magnesium was not altered nor was glomerular filtration rate or renal plasma flow. 4. Ethanol at a mean concentration of 1.60 mmol/L did not alter the action of a maximal concentration of AVP (75 ng/kg) on water or electrolyte transport. However, the antidiuretic effect of a submaximal concentration of AVP (7.5 ng/kg) was augmented by ethanol at concentrations of 1.63 and 0.98 mmol/L. 5. These studies suggest that the ethanol induced diuresis commonly ascribed to inhibition of AVP secretion may also be due to other intrarenal effects of ethanol, possibly acting within the proximal tubule. These results also confirm recent in vitro findings that while ethanol does not inhibit the action of a maximal concentration of AVP, it does modulate the effects of lower AVP concentrations.

Acute effect of physiological concentrations of vasopressin on rat renal function.

1. The antidiuretic, pressor and electrolyte transport effects of arginine vasopressin (AVP) were simultaneously evaluated in the anaesthetized water diuretic rat. Increasing concentrations of AVP (7.5, 75 and 750 ng/kg bolus and per h), were used to produce plasma levels which approximate the physiological range (408 +/- 2.4, 35.7 +/- 12.5, 85.2 +/- 16.1 pg/mL respectively). 2. Administration of a minimally effective antidiuretic dose (7.5 ng) increased mean urine osmolality (from 101 +/- 7 to 312 +/- 89 mosmol/kg) without altering mean arterial pressure (MAP), renal plasma flow (RPF) or glomerular filtration rate (GFR). A maximal antidiuretic dose of AVP (75 ng) increased mean urine osmolality to 2002 +/- 109 mosmol/kg and was associated with significant mean increases in MAP (9 mmHg), RPF and GFR (25%) by 30-60 min. A further ten-fold increase in AVP (750 ng) produced a greater increase in MAP (116 +/- 6 to 134 +/- 7 mmHg; P < 0.01) as well as increasing RPF and GFR by 35.5 and 38.9% respectively. 3. Increasing concentrations of AVP also progressively increased the fractional excretion of sodium, potassium and phosphate. However, fractional calcium and magnesium excretion was significantly decreased with maximal and supramaximal concentrations. 4. These studies support evidence that AVP is a pressor hormone in physiological concentrations in baroreceptor intact animals. Its role in renal electrolyte transport is unclear. Measured increases in RPF and GFR with the maximal and supramaximal AVP concentrations appear to be correlated with the increase in MAP.

Noise pollution in the operating room: a hazard to surgeons, personnel, and patients.

Noise levels up to 118 dB--a level that is potentially damaging to the hearing--were measured in the operating room, notably during the use of high-speed gas turbine bone-cutting drills. Suction tips, which had trapped tissue "whistles" inside, yielded noise levels of up to 96 dB. Surgeons, staff, and patients should be cautioned against such noises and shielded in prolonged cases. We offer a review of acoustical criteria for various practical noises and duration of safe exposure.

Clinical neurosurgery as it relates to the lumbar spine: what it does versus what it says.

Neurosurgeons may derive as much as 62% of their professional income from and perform proportionately as large a number of procedures on the lumbar spine. Publications in neurosurgical journals, presentations at national and international neurosurgical meetings, and participation in organized neurosurgical symposia are, however, relatively sparse in this area of activity. It appears, therefore, that the lumbar spine must have minimal academic interest to neurosurgeons, as compared with the surgical areas where they have clinical domain, i.e., the brain and spinal cord. In that this clear discrepancy between what they do (their source of income) and what they talk about and publish is apparently not well known to neurosurgeons or their professional society directors, this paper is presented as objective, awakening evidence. The potential impact on future patient draw, professional prowess, and income, which may result from a continuation of this wide gap, is also discussed.

Transfacet decompression with dowel fixation: a new technique for lumbar lateral spinal stenosis.

Auto-stabilization consequent to spinal segment instability involves osteophyte formation. The most common lumbar spinal stenoses are due to uncinate process spurs at L 5. These spurs inaccessibly lie ventral to the facet joints. Most surgical methods for lateral stenotic lesions do not address the incipient instability. Facet destructive approaches further destabilize the segment. The new decompressive technique here preserves and stabilizes posterior supporting structures: ligaments are left intact; laminas (and facets) are distracted; 11 mm transfacet holes are bored, exactly dorsal to both the spurs and entrapped ganglia; the entrapment (even a lateral herniated disc) is decompressed through the drilled hole. 12 mm bone dowels are then driven into the holes, immediately stabilizing the segment. The dura is not exposed. Reviewed are fifty transfacet cases. In four, a posterior interbody fusion was performed via the transfacet holes. The procedure presents a new window to spinal lesions.

New kneeling attachment and cushioned face rest for spinal surgery.

Surgical frames, kneeling attachments, and special operating tables for lumbar spinal surgery are designed to promote good positioning, lower the intraabdominal pressure, and reduce epidural bleeding. The frame reported here fulfills these objectives and produces either lumbar spinal extension to reduce paraspinal muscle tension or mild flexion to distract the neural arches. The new frame unit is made of lightweight fiberglass and aluminum, weighing only 14 lb (6.5 kg), and utilizes the hydraulic elevator pump of the operating table as a means to raise or lower the frame. Thus, adjusting the horizontal plane of the lumbar spine requires no separate crank system. The anterior tibial cushions, lying in hemicylindrical troughs, and the ergonomically designed cushions for chest and buttocks improve the distribution of body weight. A new, fully adjustable, cushioned face rest is used to maintain the neck in a neutral position, with the patient placed fully face-down.

Bone impactors. New instruments for spinal decompression.

I have used these new instruments, designed for the reduction of nerve structure compression by the principle of impaction (driving inward of the outer surface), with success in well over 300 cases; they have proved to be useful, and often indispensible, in most cases having decompressions for lateral stenosis.