Intraosseous Portion Research Articles

Variance in relative internode length ( [formula omitted]) in the rat and its presumed significance for the safety factor and neuropathy

1. (1) Previous work has shown that the quotient 1 d (internode length/fiber diameter) is the product of independent variations in internode length (increasing with fiber elongation) and in axon caliber (whose growth is not as yet well understood). Using these guiding principles, the distribution of 1 d in 19 nerves and 7 roots of the rat was determined. 2. (2) Each nerve or root showed a linear decrease of the 1 d with fiber caliber, the thin fibers always having relatively longer internodes than the thick ones. Comparing nerves, the highest 1 d was found for extremity nerves, particularly those in the hindlimbs. Nerves of the trunk (phrenic, intercostal) had lower 1 d with further decreases for the extracranical branches of cranical nerves, the intercranial roots and a minimum for the acoustic nerve. In the facial nerve, the 1 d of the intraosseous portions was distinctly lower than that of its branches in the face. Ventral roots showed a cranio-caudal increase in their 1 d . For some fiber systems, e.g. cranial nerves, the 1 d reflected variance in axon caliber, their internode length being relatively uniform. For others, e.g. roots, the 1 d was dominated by their large variation in internode length. 3. (3) Variation of the 1 d in fiber populations may correlate with such parameters as internodal conduction time, different sensitivities of thick and thin fibers and, particularly, the safety factor. It is also proposed that the regional variation in the 1 d is a critical parameter affecting the regional vulnerability of fiber populations to polyneuropathies or to radiculopathies.

Computer-aided reconstruction of the endolymphatic sac.

Computer-aided three-dimensional reconstruction techniques along with surface area and volume determinations have been applied to the intraosseous portion of Ihe human endolymphatic sac. Three-dimensional reconstruction has revealed that the lumen of the sac is a series of parallel tubules rather than folds. Surface-to-volume ratio determinations may reveal that the resorptive capacity of epithelium in this portion of the sac is significantly reduced in patients with Meniere's disease.

The epithelium contiguous with the neck of intraosseous dental implants.

There are three distinct regions with which a wedge shaped dental implant is in contact; the intraoral, transitional and intraosseous portions. The environment of each of these is different and will require special consideration. This investigation compares the epithelium found associated with a natural tooth to that which is found contiguous with the transitional region of an implant. The possibility of a pseudojunctional epithelium being formed in association with a glass collar processed onto the neck of a wedge shaped implant is examined. The histological appearance of a specimen in situ for 11 months shows an altered epithelial structure compared to that found adjacent to the neck of an unmodified titanium wedge shaped implant. Because the implant and glass must be mechanically separated from the tissue being examined, the value of demeneralized histological sections is limited. However, examination by a Scanning Electron Microscope of the surface of the glass after removal reveals an area of clear glass in the deeper region of the collar. Above this there is a deposit, the exact nature of which is unknown, but which migth be interpreted as the contents of the gingival crevice. Although this might be interpreted as a type of epithelial attachment, other factors are necessary to ensure close gingival adaptation and limitation on epithelial downgrowth.

THE DISSEMINATION OF TUMORS OF THE HEAD AND NECK VIA THE CRANIAL NERVES

Malignant tumors may spread through the perineural and endoneural spaces of the regional nerves. Although the clinical symptoms may be remarkably mild, local neurologic abnormalities should always be considered to be due to neural invasion. An analysis of 40 cases of head and neck cancers has indicated that this form of metastatic disease is most frequently seen with recurrent or advanced tumors. Initial treatment may be inadequate because neural invasion is unrecognized, or neural involvement may result from an inadequately treated tumor. Radiologic exploration of the intraosseous portions of the fifth and seventh nerves has proven useful in the diagnosis of perineural and endoneural invasion. An increase in the diameter of the nerve may be reflected by erosion of one or more foramina or canals. In instances of clinically suspected or radiographically demonstrated neural involvement, serial frozen sections should be made during the surgical procedure until disease-free nerve is encountered or evidence of intracranial extension is obtained. Several of the patients in this series have been salvaged as a result of surgical or radiographic recognition of neural metastases. Undoubtedly, infiltration of the regional nerves will continue to be responsible for some treatment failures. However, we believe that an increasing number of patients may benefit if this form of metastatic disease is appreciated and appropriate diagnostic and therapeutic measures are instituted.

An exercise in radiologic-pathologic correlation.

In Bone the roentgenogram is in fact the gross specimen and may offer more information about the nature of the disease than does the actual gross material in the pathology laboratory. The diagnosis may be suggested by the kinds and degree of mineralization, for example. Radiographs of bone give five major types of information: the location of the lesion within the bone, the broad category to which the disease process belongs (trauma, inflammation, anomalies, neoplasms, metabolic disease, circulatory disturbances, mechanical adaptations), the presence or absence of mineralization, the degree and pattern of destruction of bone (a clue to the rate at which the disease is progressing), and the degree and pattern of bone repair seen in the form of mineralized material. The case presented this month will be analyzed on the basis of such findings. Radiology The findings in Figures 1, A and B, can be outlined as follows: The lesion is located in the lower diaphysis of the ulna and does not involve either epiphysis or metaphysis. The border between disease and normal bone is sharply defined (there is no ragged, ill-defined periphery as might be seen in a rapidly invasive lesion). The bone is obviously destroyed over a fairly wide area, and the laminagram demonstrates that the intraosseous portion of the lesion is fairly extensive. The lesion is expansile, eccentric, devoid of any mineralized matrix, and it expands the bone in every direction except dorsally. On the radial side it has outrun the formation of new cortex. Buttresses at either end indicate the limits of the expansion mechanism, while the gap between the buttresses indicates the lesion expanded faster than the new periosteal bone could form in the middle of the lesion. A few coarse perpendicular streamers signal the direction of growth outward from within the bone and represent thickened areas of nearly successful attempts to contain the lesion. Differential Discussion of the Radiographic Findings: These data indicate a disease beginning within the bone which is breaking out at moderate speed, but not spreading rapidly up or down the bone. There is no evidence of trauma. The lesion is too recent and incomplete for a developmental anomaly. Most metabolic diseases would show more diffuse findings. An inflammation of this magnitude, breaking out at this rate, would have provoked a much greater bone sclerosis and periosteal reaction. Thus, a neoplasm that has arisen within the diaphysis is the favored diagnosis. Diaphyseal lesions include chondromas, osteoblastomas, chondromyxoid fibromas, angiomas, cysts, lipomas, central (desmo-plastic) fibromas, nonossifying fibromas, and fibrous dysplasia. But none of these benign lesions usually breaks out of bone as this one has. Therefore, metastatic tumors or malignant variants of some of the above categories must be considered.