The fate of fresh, layered, nonsutured and sutured, autogenous cartilage in the rabbit model.

OBJECTIVE: To compare the thickness, area, and volume of sutured and nonsutured multilayered cartilage grafts in a rabbit population. DESIGN: Autogenous rabbit cartilage grafts were harvested, layered, and placed in the contralateral auricle. Half the grafts were sutured; the other half were nonsutured. Graft thickness, area, and volume were measured before implantation, after 90 days in vivo, and after explantation. RESULTS: The area and volume of the cartilage grafts increased during the 90-day period. Histologically, this was caused by increased fibrous tissue around the cartilage grafts. Minimal cartilage resorption was observed. No differences were noted between sutured and nonsutured grafts. CONCLUSIONS: Autogenous, fresh, uncrushed, layered nonsutured or sutured cartilage grafts are well tolerated. Statistically significant increases in the area and volume of autogenous, fresh, uncrushed, layered cartilage grafts occurred primarily because of fibrous tissue formation at the margins of the layered grafts. Suturing had no effect on the postoperative volume retention of these layered grafts. This information will be helpful to the facial plastic surgeon when using fresh-layered autogenous cartilage grafts during cosmetic or reconstructive procedures. Arch Facial Plast Surg. 2000;2:256-259

Biomechanics of nasal septal trauma.

Fractures of the nasal complex are the most common facial fracture. This is due to the fact that the nose is the most anteriorly projecting facial structure and is a composite structure of bone, cartilage, and soft tissue. Furthermore, the forces required to cause significant injury are less than that causing other facial fractures. Because of the wide range of activities and mishaps that cause nasal trauma, the instruments of injury range from bicycle handles to elbows. The causes, clinical anatomy, and future considerations regarding nasal septal trauma are discussed in this article.

Electrical interactions via the extracellular potential near cell bodies.

Ephaptic interactions between a neuron and axons or dendrites passing by its cell body can be, in principle, more significant than ephaptic interactions among axons in a fiber tract. Extracellular action potentials outside axons are small in amplitude and spatially spread out, while they are larger in amplitude and much more spatially confined near cell bodies. We estimated the extracellular potentials associated with an action potential in a cortical pyramidal cell using standard one-dimensional cable theory and volume conductor theory. Their spatial and temporal pattern reveal much about the location and timing of currents in the cell, especially in combination with a known morphology, and simple experiments could resolve questions about spike initiation. From the extracellular potential we compute the ephaptically induced polarization in a nearby passive cable. The magnitude of this induced voltage can be several mV, does not spread electrotonically, and depends only weakly on the passive properties of the cable. We discuss their possible functional relevance.

Septorhinoplasty. Form versus function.

Septorhinoplasty is the most difficult and complicated procedure in facial plastic surgery. Because of the complex interdependency of the anatomical parts, alteration of one may have an impact on another. Three-dimensional relationships are important, as is the maintenance of a proper framework for the internal and external nose. Form and function are completely interwoven in septorhinoplasty.

Shunting inhibition does not have a divisive effect on firing rates.

Shunting inhibition, a conductance increase with a reversal potential close to the resting potential of the cell, has been shown to have a divisive effect on subthreshold excitatory postsynaptic potential amplitudes. It has therefore been assumed to have the same divisive effect on firing rates. We show that shunting inhibition actually has a subtractive effect on the firing rate in most circumstances. Averaged over several interspike intervals, the spiking mechanism effectively clamps the somatic membrane potential to a value significantly above the resting potential, so that the current through the shunting conductance is approximately independent of the firing rate. This leads to a subtractive rather than a divisive effect. In addition, at distal synapses, shunting inhibition will also have an approximately subtractive effect if the excitatory conductance is not small compared to the inhibitory conductance. Therefore regulating a cell's passive membrane conductance-for instance, via massive feedback-is not an adequate mechanism for normalizing or scaling its output.

Ulnar variance and age.

Ulnar variance was determined on 1,023 radiographs of normal wrists taken in standardized fashion. There were 468 women and 555 men. The age range was 13 to 109 years. In both sexes, ulnar negative variance decreased significantly with increasing age. Possible reasons for this are discussed.

The interface of academic and community practice in medical and graduate medical education.

Historically, the interaction between academic departments of otolaryngology-head and neck surgery and the community practice of the specialty has been erratic, anecdotal, and often strained. A general sense of autonomy and isolationism that has characterized many university programs coupled with a paranoia on the part of many practitioners with respect to concerns about protecting their patient base have led to an uneasy relationship. Difficulties with managed care now threaten this relationship even more. It is clearly time to seek a solution that can enhance the educational opportunities for medical students and residents.

Comparison of discharge variability in vitro and in vivo in cat visual cortex neurons.

1. In neocortical slices, the majority of neurons fire quite regularly in response to constant current injections. But neurons in the intact animal fire irregularly in response to constant current injection as well as to visual stimuli. 2. To quantify this observation, we developed a new measure of variability, which compares only adjacent interspike intervals and is therefore less sensitive to rate variations than existing measures such as the coefficient of variation of interspike intervals. 3. We find that the variability of firing is much higher in cells of primary visual cortex in the anesthetized cat than in slice. The response to current injected from an intracellular electrode in vivo is also variable, but slightly more regular and less bursty than in response to visual stimuli. 4. Using a new technique for analyzing the variability of integrate-and-fire neurons, we prove that this behavior is consistent with a simple integrate-and-fire model receiving a large amount of synaptic background activity, but not with a noisy spiking mechanism.

Effects of air pollution on the upper aerodigestive tract.

The main route of contamination of the human body with airborne pollutants is through the upper air and food passages. Because of the delicate balance of the mucous membranes and special sensory organs of these passages with respect to mucociliary activity, local and recruited immune responses, rapid uptake of chemicals, and carcinogenic potential, the ingestion or inhalation of pollutants in the air can be harmful to these internal body barriers. The particular target organs for air pollution effects on the upper aerodigestive tract include the mucosa, olfactory epithelium, auditory receptor cells, glottic epithelium, and adjacent neural and muscular tissues. Hearing loss caused by noise exposure may be aggravated by the concomitant inhalation of solvents. The strongest evidence for the carcinogenic effect of occupational inhalants in the nasal cavity and paranasal sinuses is seen with exposure to hardwood dust, tobacco smoke, furniture making, and leather tanning. With the exception of tobacco smoke, which produces squamous cell carcinomas, the majority of the occupationally related cancers are adenocarcinomas, usually of the intestinal variety. Tobacco smoke, passive or active, may lead to end-artery obliteration at the level of the otic end organ, causing a progressive sensorineural hearing loss. Further environmental research in the upper aerodigestive tract should aim at developing biologic markers to determine early, premalignant tissue changes; identifying the effects of chronic, low-dose toxic exposure on mucous membranes and neurosensory organs; providing field-tested tools for the standardized screening of large at-risk populations.

Compensation, work status, and disability in low back pain patients.

STUDY DESIGN: A prospectively designed study was performed to assess the influence of employment status and a compensation claim on patients experiencing low back pain. OBJECTIVES: To determine the factor that most influences disability arising from low back pain, unemployment or a compensation claim. SUMMARY OF BACKGROUND DATA: Two hundred sixty-nine consecutive patients were assessed from a low back pain clinic. METHODS: Disability was assessed using the Oswestry Disability Score, and employment, and compensation status were recorded. RESULTS: Both unemployment and patients involved in compensation had higher disability scores. However, by controlling the data for employment and assessing only the compensation group it was found that those claiming compensation, but still working had significantly less disability than those claiming compensation who were unemployed. CONCLUSIONS: Both unemployment and compensation claims influence disability, but employment status is the most important factor.

Osseointegrated implants in oro-dental and facial prosthetic rehabilitation.

A basic prerequisite for establishing true and lasting tissue integration of a nonbiologic prosthesis is the minimal risk of adverse local or general tissue reactions. It consists of a detailed understanding of the response behavior of highly differentiated hard and soft tissues to the surgical preparation of a recipient site and the installation of the prosthesis, as well as long-term tissue adaptation and the functional demands on the anchorage unit. The complex arrangement of titanium implant material, surface physics, and biocompatibility with the host tissues will be reviewed in this article.

Talocalcaneal coalition in patients who have fibular hemimelia or proximal femoral focal deficiency. A comparison of the radiographic and pathological findings.

The prevalence of congenital anomalies of the foot was studied in ninety-nine children (105 limbs) who had fibular hemimelia or proximal femoral focal deficiency, or both. Twenty-six of these patients had had a Syme amputation at our institution and the specimens were analyzed anatomically; they were found to include fourteen talocalcaneal coalitions (54 per cent). The preoperative radiographs of these same patients, however, revealed only four such coalitions (15 per cent). Thirty-seven of the ninety-nine patients had had a Syme amputation previously at another facility (with subsequent follow-up at our institution), and ten of them (ten feet) had radiographs that were adequate for analysis of congenital anomalies. Forty-two feet that had not yet been amputated were also analyzed radiographically. Nine of these fifty-two feet included in the radiographic analysis had a talocalcaneal coalition, a radiographic prevalence similar to that found on the preoperative radiographs of the twenty-six patients included in the anatomical analysis. The true prevalence of talocalcaneal coalition remains to be determined; however, this can be done only at the time of skeletal maturity. Examination of the twenty-six amputation specimens revealed only one talocalcaneal coalition in the nine patients who had proximal femoral focal deficiency alone, six such coalitions in the eight patients who had only fibular hemimelia, and seven coalitions in the nine patients who had both proximal femoral focal deficiency and fibular hemimelia. These findings should be useful in the evaluation of the radiographic anatomy of the feet in children who have proximal femoral focal deficiency or fibular hemimelia, or both, particularly if limb-lengthening is considered as a treatment option.