A methodology report of a randomized prospective clinical trial to assess velopharyngeal function for speech following palatal surgery

Cleft lip and palate occurs in approximately 1 in every 750 live human births, making it one of the most common congenital malformations. Surgical closure of the palatal cleft does not always result in a velopharyngeal port capable of supporting normal speech. The University of Florida (UF), in collaboration with the University of São Paulo (USP), is engaging in a 5-year prospective, randomized controlled study to compare velopharyngeal function for speech outcomes between patients undergoing palatoplasty for complete unilateral cleft lip and palate performed using the von Langenbeck procedure with intravelar velarplasty and those receiving the Furlow double-reversing Z-plasty palatoplasty. The von Langenbeck procedure was selected as the time-tested standard against which the Furlow procedure could be judged. The Furlow procedure, a relatively new operation, has been reported to yield substantially higher rates of velopharyngeal competency for speech than have most other reported series and theoretically should result in less disturbance to midfacial growth. A total of 608 patients will be entered into one of two age categories. Inclusion of two age groups will allow a comparison of results between patients having surgery before 1 year of age (9-12 months) and patients undergoing surgery at approximately 1.5 years of age (15-18 months). Speech data will be collected and will be available for definitive analysis throughout the last 3 years of the study. Collection of preliminary growth data will require more than 5 years; growth analysis is anticipated to continue until all patients have reached maturity. The Hospital for Research and Rehabilitation of Patients with Cleft Lip and Palate at the University of São Paulo (USP-HPRLLP) in Bauru, Brazil, is uniquely situated for conducting this study. The well-equipped and modern facilities are staffed by well-trained specialists representing all disciplines in cleft-palate management. In addition, an already existing social services network throughout Brazil will ensure excellent follow-up of study cases. The clinical caseload at this institution currently exceeds 22,000, and more than 1200 new cases are added annually. This project represents a unique opportunity to obtain prospective data from a large number of subjects while controlling the variables that have traditionally plagued cleft-palate studies. This study is designed to determine which of the two proposed surgical procedures is superior in constructing a velum capable of affecting velopharyngeal competency for the development of normal speech.

The acoustic and structural properties of the human femur

This study evaluates the variations in the acoustic properties of the human femur at ten evenly spaced locations along its length, as well as differences that exist within given transverse sections. Six pairs of human femora, three male and three female, were sectioned, ground, and polished, and scanned with a microprocessor-driven scanning acoustic microscope. Images with a resolution of approximately 140 microns were used to calculate the average acoustic impedances for each transverse cross section and each quadrant within a cross section. The mean acoustic impedance for all the cross sections was 7.69 +/- 0.18 Mrayls. Variations were observed among the cross sections, and the central sections (4-7) had values that were statistically greater than the other more distal and proximal sections. Within the cross sections, the posterior quadrant had a lower average acoustic impedance compared to the other quadrants and this was statistically significant (Tukey's multiple comparison test). The cross sections were further analyzed to determine several geometric parameters including the principal moments of inertia, polar moment of inertia, and the biomechanical shape index. The product of the acoustic impedance and the maximum moment of inertia provided a result that attempted to account for the acoustic property variation and the change in shape at the different section locations.

Regional and temporal changes in the acoustic properties of fracture callus in secondary bone healing

Controlled fractures were created in the right femora of 17 male Sprague-Dawley rats. The fractured limbs were harvested at 2, 4, 6, and 8 weeks after fracture, fixed, and embedded in polymethylmethacrylate. Midsagittal sections from each animal were evaluated with a scanning acoustic microscope, a device that generates an acoustic impedance map of the scanned material. The impedance of the fracture callus was measured in six regions on each specimen. These regions were chosen in an effort to distinguish between the impedance of the callus formed through intramembranous or endochondral ossification, and we found that the time course of increasing impedance differed for the fracture callus formed through the two pathways. Additionally, we found a significant difference in the mean impedance of the callus at each time period (p < or = 0.0013 for all comparisons), which resulted in an extremely linear relationship (r2 = 0.999) between mean callus impedance and healing time. This experimental model has become a popular choice for the investigation of fracture healing. As such, an accurate determination of the mechanical properties of the fracture callus is often sought. We propose that the implementation of scanning acoustic microscopy in the study of fracture healing may determine the changes in the material properties more accurately than conventional testing methods.

A prospective, clinical study evaluating arthroscopic ACL reconstruction using the semitendinosus and iliotibial band: 2- to 5-year follow up

Seventy-three ACL-deficient knees were reconstructed using a modified Zarins and Rowe arthroscopic procedure utilizing the semitendinosus tendon and iliotibial band (ITB). Fifty of 73 patients returned for 2- to 5-year follow up. On follow-up visit each patient completed a questionnaire pertaining to subjective results, including level of pain and return to, activities. Physical examination included the Lachman test, anterior drawer, pivot shift, and anterior subluxation tests (using the Stryker KT 1000), each graded 0 to 3. All patients have shown a statistically significant improvement between preoperative and postoperative knee scores (P < .0001). According to the knee scoring scale, 34 patients (68%) were clinically rated as excellent, 12 (24%) as good, 4 (8%) as fair, with no poor results. All patients have returned to pre-injury jobs (or school), while most resumed some level of sporting activities. No patients complained of patella femoral symptoms postoperatively. Complications included pain over the staple which was used for fixing the ITB to the tibia, requiring removal in 5 patients. These preliminary results are encouraging, with 92% of the patients rating good to excellent. This modified procedure offers advantages over other procedures, as it is entirely arthroscopic with minimal incisions, does not damage the extensor mechanism, and permits an enhanced rehabilitation program.

Biomechanical and histological analysis of an HA coated, arc deposited CPTi canine hip prosthesis

The interfacial shear strength and bone tissue response was investigated for an arc deposited (AD) commercially pure titanium implant surface, with (AD/HA) and without (AD) plasma-sprayed hydroxyapatite (HA) coating. Ten purpose bred coonhounds received bilateral femoral stem implantation (AD and AD/HA) in the proximal femurs (hemiarthroplasty). The femoral prosthesis consisted of a modular CoCr alloy head, modular Ti-6Al-4V neck, and a 10-mm diameter cylindrical Ti-6Al-4V femoral stem. The AD surface had 30-35% greater surface roughness than the AD/HA surface. The HA coating had a purity greater than 90% and a crystallinity greater than 65%. After 6, 12, and 24 weeks, the implants were retrieved and analyzed with mechanical testing, qualitative and quantitative histology, and electron microscopy. The AD/HA implants had equivalent interfacial shear strengths to the AD implants at all time periods. The AD/HA implants had significantly greater linear bone contact than the AD implants. The 6-week implants had significantly thicker cortical bone than the 12- and 24-week implants. The HA coating was very stable in vivo, evidenced by no thickness reduction at any time period. Qualitatively, the AD/HA implants primarily had bone contacting the implant surface with little fibrous tissue present, and the AD implants had bone and fibrous tissue contacting the implant surface. The electron microscopy analysis showed that the mechanically tested implants exhibited a mixed failure mode at the bone, HA coating, and titanium interfaces.

Evaluation of poly(DTH carbonate), a tyrosine-derived degradable polymer, for orthopedic applications

The polymerization of desaminotyrosinetyrosylhexyl ester (DTH) with phosgene gives rise to poly(DTH carbonate), a new pseudopoly(amino acid). To evaluate the performance of this bioabsorbable material in orthopedic applications, the tissue responses elicited by compression-molded pins of poly(DTH carbonate) and clinically used polydioxanone pins (PDS; Orthosorb) were compared. The two types of pins were implanted in the paravertebral muscle and in the metaphyseal proximal tibia and distal femur of 10 White New Zealand Rabbits for 1, 2, 4, and 26 weeks. The tissue response was evaluated using histologic staining of soft- and hard-tissue sections, fluorescent bone marker of incorporation, and backscattered electron imaging. In soft tissue, both poly(DTH carbonate) and PDS elicited a mild inflammatory response resulting in encapsulation. During the disintegration phase, the PDS implants triggered a foreign body response involving the phagocytosis of polymeric debris by histiocytes and giant cells. No such response was observed for poly(DTH carbonate). In hard tissue, close bone apposition was observed throughout the 26-week test period for poly(DTH carbonate) implants. At the 26-week time point, the poly(DTH carbonate) implants exhibited surface erosion and were penetrated by new bone. In contrast, an intervening fibrous tissue layer was always present between the PDS pins and the bone. At 26 weeks, the PDS implants had partially resorbed and a foreign body response characterized by infiltration in several of the implantation sites. This study indicates that poly(DTH carbonate) and PDS exhibit fundamentally different interactions with hard tissue, and that poly(DTH carbonate) is a promising orthopedic implant material.

The application of scanning acoustic microscopy in a bone remodeling study

Scanning acoustic microscopy (SAM) was used in the evaluation of bone remodeling around a cylindrical unicortical defect. SAM is a technique for the nondestructive evaluation of materials, and has only recently been employed as an orthopaedic research tool. The utility of SAM was demonstrated by using it to measure an elastic property known as acoustic impedance. Specifically, the acoustic impedance of bone formed by remodeling around a cylindrical defect was measured. The defects were filled with either a low modulus "void" or rigid inclusion to create various states of stress in the bone in the vicinity of the defect. After six months of implantation of the inclusions in the sheep metatarsal, new bone formation on periosteal and endosteal surfaces about the defect region was observed. These regions of new bone were less stiff and had 18.0 +/- 6.5% lower acoustic impedance than the pre-existing bone in the intracortical region of the metatarsal. There was no difference in the degree of new bone formation about void and rigid inclusions. Both underwent significant adaptational changes in response to the elevated stress about the defect. These changes affected the basic structure of the bone cross-section at the level of the defect and effectively reduced the stress levels about the defect. By using SAM to measure acoustic impedance, it was seen that little internal remodeling occurred in the intracortical region. Hence, the primary mechanism of strain-induced bone remodeling observed in this experimental model was surface remodeling.

The porous-coated anatomic (PCA) total hip arthroplasty: a review of 73 uncemented cases with 2-year follow up

A total of 73 hips in 62 patients who underwent non-cemented total hip arthroplasties (THA) with porous-coated anatomic (PCA, Howmedica) prostheses have been reviewed. A complete evaluation including preoperative and postoperative Harris hip scores (HHSs), a complete radiographic study, and complication determination has been completed with greater than 2-year follow up. Diagnoses included osteoarthritis (74.0%), rheumatoid arthritis (4.1%), avascular necrosis (15.1%), and posttraumatic arthritis following fracture (6.8%). The complication rate was 10.9% (8 complications/73 arthroplasties); 20 patients (35.6%) received bilateral implants. The mean preoperative HHS for the entire group was 38.7, and the mean postoperative score, irrespective of postoperative time, was 93.6. Key findings regarding the consecutive radiographic review of each arthroplasty included: 9.6% lucencies, 43.8% stress shielding, stable fibrous ingrowth in 74.0%, tip sclerosis in 19.2%, and cortical widening in 4.1%. The finding of loose beads from the pore ingrowth area of the prosthesis was minimal (7 beads in 6 patients). These results demonstrate the efficacy of the PCA prosthesis.

Materials and design concepts for an intervertebral disc spacer. II. Multidurometer composite design

The main function of the intervertebral disc is to transmit and attenuate compressive and torsional forces, and stabilize the intervertebral joint. Unfortunately, the disc may be displaced or damaged due to trauma or disease causing the nucleus to herniate and protrude into the vertebral canal or intervertebral foramen. Pressure on the spinal nerve may cause pain or paralysis in the area of its distribution. At present, the surgical procedures used to alleviate this condition include disc excision, and/or spinal fusion. A more desirable situation would involve removing the nucleus pulposus and part or all of the annulus fibrosis and implanting a suitable biofunctional equivalent. Such a prosthesis should attenuate stresses and prevent abnormal stress at adjacent intervertebral joints. Maintenance of normal disc height would prevent impingement of the posterior facet joints and facet joint syndrome. In a previous companion paper (J. Applied Biomat. 5:125-132; 1994), the mechanical behavior of disc prostheses manufactured from fiber reinforced, elastomeric thermoset resins were examined. In order to develop devices which were more practical from a manufacturing standpoint and extremely reproducible, the fiber reinforced thermoset resins were replaced by multi-durometer thermoplastic elastomeric materials. In the present paper, the mechanical properties of thermoplastic multicomponent designs have been investigated.

The acoustic properties of normal and imbedded bovine bone as measured by acoustic microscopy

The acoustic impedance of bovine femoral cortical bone was measured with a scanning acoustic microscope used in the reflection mode. The bone was measured in the unimbedded state and after plastic imbedding. The acoustic impedance of the unimbedded specimens was also measured with a standard transmission ultrasonic technique. For the unimbedded bovine specimens there was a good correlation between the bulk transmission impedance and the reflection surface impedance (r2 = 0.976) and the values were 9.32 and 9.29 MRayls, respectively. Plastic imbedding produced a consistent and statistically significant increase in the acoustic impedance of the bone (9.71 MRayls). This experiment verified the use of acoustic microscopy as a quantitative materials analysis technique and it demonstrated the potential for material property analysis of imbedded bone.

A biomechanical analysis of four humeral fracture fixation systems

A biomechanical study was initiated to compare four fracture fixation devices: the AO dynamic compression plate, a distal fin locking nail, a solid locked intramedullary nail, and paired flexible nails for humeral fracture fixation. Eighteen pairs of fresh-frozen, intact humeri were harvested, standardized midshaft transverse osteotomies were created in each specimen, and left and right specimens were fixed with plates and nails, respectively. The bending properties of the plate-fixed humeri were significantly greater than the nailed humeri in both the anteroposterior and mediolateral planes on a paired basis. The distal fin nail and solid locked nail had comparable bending properties, and both had bending properties superior to those measured for the paired flexible nails. The torsional properties of humeri fixed with plates and solid locked nails were equivalent, except for rigidity and stiffness, which were superior for the nail. Both fixation methods resulted in torsional properties significantly greater to those measured for humeri fixed with paired flexible nails or a distal fin nail.

The biomechanics and histopathology of chemically processed patellar tendon allografts for anterior cruciate ligament replacement

A study was initiated to examine chemically processed patellar tendon allografts in sheep anterior cruciate ligament repairs, both mechanically and histologically. One group of animals received frozen, untreated allografts, one group received frozen grafts that were processed with a chloroform-methanol solvent extraction technique, and one group received frozen tendons treated with a permeation-enhanced extraction technique. All animals were operated on unilaterally, with the contralateral knee acting as a normal, intact control. Histologic analysis after 2 months of implantation revealed similar enhanced cellular repopulation in both chemically treated ligament allografts compared with the more hypocellular, untreated grafts. At 6 months the chloroform-methanol group demonstrated a more aggressive chronic cellular response with numerous thick-walled vessels relative to the untreated and permeation-enhanced grafts. Mechanical testing after 6 months of implantation showed statistically similar anterior drawer resistance in all grafted knees, yet the two chemically extracted grafts had significantly less stiffness than untreated anterior cruciate ligament grafts. Both treatment groups also tended to be weaker than the untreated allografts. All anterior cruciate ligament reconstructions showed excessive anterior drawer laxity and, regardless of treatment, had lower strength and less stiffness than normal anterior cruciate ligament tissue at the 6-month period.

Investigation of an organic delivery system for demineralized bone matrix in a delayed-healing cranial defect model

The osteogenic potential of demineralized bone matrix (DBM) has been demonstrated in multiple animal models and clinical applications. A particulate form of DBM is generally used to fill defects because it is easily packed into a defect site without operative planning or shaping. One potential disadvantage in the use of a particulate is the migration of particles from the defect site. To stem this, glycerol was added to DBM to improve handling properties. A study was undertaken to compare two forms of DBM with glycerol, with DBM particulate and autograft in a bony defect site. The model chosen consisted of bilateral 8-mm trephine defects created in the parietal skull of 40 rabbits. Animals were sacrificed at 2 and 8 weeks. Results demonstrated both cartilage and bone induction with the three forms of DBM, with 75-90% of the linear width of the defect filled with new bone by 2 weeks. This was similar to the autograft (86%) and significantly greater than the unfilled defects (26%) at 2 weeks. The addition of glycerol to the DBM did not affect the inductive capacity, and produced a response similar to that of DBM particulate alone or autogenous bone.

Mechanical evaluation of a canine intervertebral disc spacer: in situ and in vivo studies

An elastomeric intervertebral disc spacer with hydroxyapatite ingrowth surfaces was implanted in a canine model. We studied (a) the mechanical behavior of motion segments at time 0 and at 3, 6, and 12 months and (b) the effect of the interface between the spacer and vertebral bone on implant stability and bone ingrowth. A polymeric spacer was designed with compressive and torsional properties similar to those of the isolated canine lumbar disc. Implantation of the spacer in canine cadaver motion segments permitted in situ biomechanical evaluation at time 0. An in vivo study permitted continuous neurological monitoring of animals, with evaluation of mechanical behavior, stability, and ingrowth at 3, 6, and 12 months. Mechanical testing of cadaver motion segments with the spacer in situ resulted in decreased compressive and torsional stiffnesses, averaging 25 and 42%, respectively. This decrease was due to a combination of the surgical insult to the annulus and decortication of adjacent vertebral endplates. In the in vivo study, all 12 animals tolerated the surgery well and none had permanent neurological impairment. The measured parameters indicated that behavior of the spacer-motion segment composite appeared to return to normal within 3-6 months. However, despite use of a porous hydroxyapatite on the implant surface, there was no significant bone ingrowth. Instead, a layer of dense fibrous connective tissue was formed at the spacer-vertebral bone interface. Early migration of five of the 12 spacers resulted in eccentric loading patterns with consistent reactive osteophyte formation.

Mechanics of interbody spinal fusion. Analysis of critical bone graft area

Bone graft subsidence is a serious complication of interbody spinal fusion. In this study, 66 mechanical tests were performed on 35 thoracic vertebral bodies to investigate the in situ mechanics of interbody spinal fusion. The relationships among trabecular bone density, bone strength, and size of bone graft area were analyzed. All vertebral bodies were scanned by quantitative computer tomography (QCT) to determine their bone density before mechanical testing. The decorticated trabecular beds of the vertebral bodies, void of all posterior elements, were loaded in a manner similar to that which occurs after surgical interbody fusion. That is, rectangular blocks of polymethylmethacrylate, representing bone grafts, were used to transfer controlled compressive loads to the decorticated vertebral trabecular surface. Both destructive and nondestructive tests were performed. The relationship between QCT bone density and trabecular bone strength was related by a power function, and, on average, the bone density and trabecular bone strength were 0.137 g/cm3 and 3.97 MPa, respectively. Eighty percent of the vertebral bodies with graft covering 25% of the total end plate area or less failed at loads less than 600 N, while 88% of the vertebral bodies with 30% or greater covered were able to carry a load greater than 600 N. The results suggest that the intrinsic behavior of trabecular bone loaded within the vertebral body is little different from the behavior of the whole body, that QCT bone density is indicative of bone strength, and that interbody graft area should be significantly greater than 30% of the total end plate area to provide a margin of safety.(ABSTRACT TRUNCATED AT 250 WORDS)

Sebaceous carcinoma of the head and neck. Case report and literature review

Sebaceous carcinoma is uncommon, with fewer than 400 cases reported. Usually, lesions arise in the meibomian glands of the eyelid; however, extraocular lesions within the head and neck have been reported. Regardless of the location, sebaceous malignancies must be considered aggressive neoplasms with a potential for regional and distant metastasis. Diagnosis may be difficult, given the low incidence and inconsistencies in histopathologic classification. Recently, needle aspiration cytologic characteristics have been delineated, with this procedure becoming increasingly useful in establishing the diagnosis. Treatment requires wide surgical excision with removal of involved regional lymph nodes. Opinions are divided regarding the use of postoperative irradiation or chemotherapy. Records of all patients with sebaceous carcinoma of the head and neck treated at UCLA Medical Center, Los Angeles, over the last 35 years were reviewed. The clinical and pathologic features are discussed, and the literature is summarized.

Shear stability of an elastomeric disk spacer within an intervertebral joint: a parametric study

A parametric study was conducted to compare the resistance to shear force provided by three surgical implantation techniques and three endplate designs for use with a polymeric lumbar intervertebral disk spacer. While under an axial load, the implant was pushed out laterally through the surgical window created for implantation. Force at 0.3 mm displacement, slope of the initial portion of the force-displacement graph, and maximum force were measured. The results indicate that implants with pegs, inclined planes, or domes on the surfaces of the disk will add significantly to the shear stability of the implant while maintaining the simplicity of a single part device.

The mechanical properties of the canine lumbar disc and motion segment

A study was initiated to measure the mechanical properties of the canine lumbar spine disc and motion segment at two specific levels. Compressive stiffness was determined to be 717.8 N/mm at L2-3 and 949.0 N/mm at L5-6. Torsional stiffness was found to be 1.04 Nm/deg at L2-3 and 1.72 Nm/deg at L5-6. These data were then compared to human lumbar spine disc and motion segment properties that have been reported in the literature. After normalizing for size differences, the canine lumbar disc showed a similar axial modulus (14.03 MPa for L2-3 and 16.30 MPa for L5-6) and a significantly higher torsional modulus (30.80 MPa for L2-3 and 26.17 MPa for L5-6) when compared to human values. The relative contributions of ligaments, posterior elements, and intervertebral disc to overall stability of the motion segment was found to be similar in canines and humans. As has been shown in human spine research, the posterior elements including the facet joints were found to be significant structures in providing torsional rigidity of the canine spine.

Extranodal American Burkitt's lymphoma of the head and neck

Burkitt's lymphoma was first described in 1958 as a mandibular malignancy found in African children. The American, or nonendemic, form of the disease differs from the African form in that the tumor most often presents with abdominal or bone marrow involvement. Head and neck manifestations of American Burkitt's lymphoma are encountered in less than a quarter of the reported cases and usually present as cervical adenopathy. A review of all cases of American Burkitt's lymphoma treated at the UCLA Medical Center, Los Angeles, Calif, from 1971 to 1989 revealed an unusual subset of seven patients with American Burkitt's lymphoma of the head and neck who presented with extranodal disease of the soft tissues or bones of the face. The medical literature was reviewed to compile similar cases of extranodal American Burkitt's lymphoma. The clinical and pathologic features of these cases, their radiographic findings, and treatment are described.

Computer-assisted instruction in otolaryngology: the use of a database for examination review

A database of questions and answers has been developed to assist residents in reviewing current topics in otolaryngology-head and neck surgery. Each question/item has an associated answer, general category, specific category, and reference that allows cross-referencing on the computer system. The user can search the database for categories of interest and obtain a specific subset of questions. This allows an efficient means of knowledge acquisition and review for Board examinations. Additional data entry is also facilitated to expand the database as desired. Currently there are more than 2300 items in the database.

Biomechanical comparison of fixation devices in experimental scaphoid osteotomies

This study determined the force, bending rigidity, and bending moment at failure of three types of internal fixation systems for the scaphoid bone. A pair of parallel, 0.045-inch Kirschner wires were compared on a paired, bilateral basis with either a Herbert screw or a 3.5 millimeter cannulated screw in repairing a transverse waist osteotomy in cadaver scaphoids. The mean values at failure of the Herbert screw and the cannulated screw versus the paired, parallel Kirschner wires for force (65 N and 77 N versus 23.7 N), rigidity (0.47 Nm2 and 0.54 Nm2 versus 0.16 Nm2) and bending (0.98 Nm and 1.15 Nm versus 0.36 Nm) were approximately three times greater. These differences were statistically significant when compared on a paired basis. This experiment demonstrates that the Herbert screw and cannulated screw are significantly stronger in resisting bending forces than paired, parallel Kirschner wires.

Gunshot wounds to the extremities. Experience of a level I trauma center

Gunshot wounds to the extremities are more common today, largely because civilian handgun injuries have increased. Such injuries, which are usually caused by low-velocity missiles, should be treated differently from those caused by high-velocity (military) missiles. Bone involvement, including fractures and joint injuries, necessitates orthopaedic management. At the University of Medicine and Dentistry of New Jersey-New Jersey Medical School's (UMDNJ-NJMS) University Hospital, a level I trauma center, 44 gunshot wounds (32 lower-extremity and 12 upper-extremity) with orthopaedic complications were treated between January 1986 and December 1988. The protocol/questionnaire used by the UMDNJ-NJMS is presented here to assist the orthopaedic surgeon in the evaluation and treatment of these problematic injuries.

Development of a prosthetic intervertebral disc

This article is a preliminary report of a 10-year investigation of the development of an intervertebral disc prosthesis. Spinal fusion is a method for the treatment of chronic, disabling low-back pain that does not respond to nonoperative treatments. Spinal fusion, however, has various adverse effects, and the results of spinal fusion are often unpredictable. The goal of this research project was to develop disc prostheses that have mechanical properties very similar to those of natural, normal discs. Two types of disc prosthesis, one with fiber-reinforced polyurethane and the other with multicomponent, non-fiber-reinforced polymers (C-Flex), have been designed and manufactured. The fiber-reinforced disc was made of polyurethane end-plates with A100 hardness, a homogenous nucleus with A40, and 12 layers of multidirectional (0, +45 degrees), fiber-reinforced anulus with A40 polyurethane. The design and modeling of the multicomponent polymers (non-fiber-reinforced) was made of C-Flex endplates with A90 hardness, a nucleus with A35 occupying 35% of the volume, and an anulus with 70A. Mechanical testing of these disc prostheses demonstrated similar mechanical properties to those of natural, normal discs.

Effects of environmental exposure on carbon polysulphone composites

In vivo and in vitro studies were designed to characterize the material degradation associated with implantation of carbon fibre-reinforced polysulphone (C/PS). Composite plates were compression moulded for both studies, and a fibre orientation of 0 degrees with the long axis and a fibre volume fraction of approximately 55% were used. The in vitro experiment involved soaking three groups of four plates each at 4, 12 and 26 wk in 0.9% saline solution at 37 degrees C. The plates were measured for weight gain after each time period and mechanically tested non-destructively in four-point bending to determine modulus. The in vivo experiment involved implanting three groups of eight composite plates (24 total) subcutaneously in the abdomens of 12 rabbits (two implants/animal). Implants were harvested at 4, 12 and 26 wk after implantation and evaluated for changes in weight or modulus of elasticity. In vitro results showed a statistically significant (P less than 0.05 paired t-test) increase in weight for all time periods: 0.41, 1.25 and 0.93% weight gain for the 4, 12 and 26 wk periods respectively. In vivo results were similar to those in vitro: 0.66, 1.06 and 1.15% weight gain for the 4, 12 and 26 wk periods respectively (P less than 0.05 paired t-test). There was no statistically significant difference between the pre- and post-implantation modulus of elasticity for any time period in vivo or in vitro. However, in both studies, on average, the modulus tended to increase with environmental exposure.

Preliminary characterization of bioresorbable and nonresorbable synthetic fibers for the repair of soft tissue injuries

Preliminary characterizations of two new synthetic fibers were performed to determine their potentials for use in soft tissue scaffolding devices. A slowly bioresorbing random copolymer of dimethyltrimethylene carbonate (DMTMC) and trimethylene carbonate (TMC) was the first fiber evaluated. The second was a nonresorbable high-strength synthetic fiber of highly oriented polyethylene. Their in vitro mechanical behavior was evaluated by loading fibers in uniaxial tension to determine mechanical properties in dry and wet (saline) environments. The polyethylene fiber had a dry strength of approximately 2.0 GPa, an ultimate strain of 3 to 4%, a tangent modulus of 57 GPa, and was not affected by the saline environment. The bioresorbable fiber had a dry strength of approximately 500 MPa, an ultimate strain of 35%, and tangent modulus of 5.4 GPa. The in vitro resorption of the bioresorbable fibers produced a 15% loss in strength over a 10-week period. In vitro cell-fiber compatibility studies were conducted to assay material biocompatibility and fiber substrate efficacy. Fibroblasts proliferated and migrated on both the polyethylene and bioresorbable fibers at rates similar to those previously found for other compatible fibers, thus demonstrating the new materials to be similar in their in vitro biocompatibility profiles. Morphological assessment with SEM also confirmed that these materials were suitable substrates for cell attachment. A rabbit Achilles tendon repair model using oriented polyethylene or bioresorbable fiber tows was evaluated after 12 and 26 weeks of implantation. The mechanical performances of both types of tendon repairs were similar to those found in previous studies using carbon or PET fibers. The polyethylene fibers elicited a low-grade chronic inflammatory tissue response. The bioresorbable fibers were still intact at 26 weeks and remained relatively inert in the host tissue, eliciting a minimal foreign body response.

The sphenoid sinus--a site for metastasis

While metastatic tumors to the nose and the paranasal sinuses overall are unusual, metastasis to the sphenoid sinus is exceedingly rare. Presented are 26 cases of metastasis to the sphenoid sinus. Seven were treated at UCLA between 1955 and 1988, and 19 additional cases were discovered from a search of the medical literature. The patients ranged from 14 months to 79 years of age. The most common tumor sites from which sphenoid metastases arose were the prostate and the lung. In 11 of the 26 cases, the sphenoid sinus metastasis was the first presentation of malignancy. Patients manifested signs and symptoms that were indistinguishable from those from primary tumors of the sinus. They included headache, facial pain, visual changes, and single or multiple cranial neuropathies. While cure of patients with sphenoid metastasis has not been reported, significant palliation with resolution of morbidity is possible in many patients with radiation therapy. Although metastasis to the sphenoid sinus is an uncommon entity, when present, signs and symptoms relating to this metastasis are frequently the first presentation of disease. As such, patients with sphenoid sinus symptoms suggestive of sphenoid sinus malignancy should be vigorously evaluated for the possibility of primary as well as metastatic tumor of the sinus.

The evaluation of cortical bone remodeling with a new ultrasonic technique

Total hip arthroplasty causes biomechanical changes in the normal femur including a redistribution and concentration of stress. These mechanical alterations in the femur cause local remodeling and resorption that affect the geometry and mechanical properties of the bone. Three complementary techniques were used to study the local adaptive remodeling of bone due to prosthesis implantation. A graphics package was used to obtain section geometrical information, an ultrasonic wave propagation technique to determine elastic properties, and a new scanning acoustic microscope (SAM) to map the acoustic impedance profile of each section. The effects of the implantation of two different types of hip prostheses were investigated, an uncemented bipolar prosthesis with an Austin-Moore type stem and a cemented Charnley prosthesis. Prosthesis implantation resulted in an increase in cortical area and mediolateral diameter and a decrease in anterio-posterior diameter. Both prostheses had a detrimental effect on local elastic properties as determined by acoustic velocity measurements. Finally, the SAM system provided information about local inhomogeneities in bone properties not obtainable by any other means. The acoustic impedance maps highlighted bone resorption and bone remodeling on a microstructural level.

Bone attachment to hydroxyapatite coated polymers

Bone attachment to two classes of hydroxyapatite (HA) coated polymers was evaluated mechanically and histologically. Particulate HA was molded into the surface of thermoplastic implants and cast into the surface of thermoset implants. Coated and uncoated implants of both types were implanted in the distal femurs of rabbits for four and twelve weeks. After sacrifice, the bone/implant interface was evaluated mechanically via a push-out test with a servohydraulic test system. Paired statistical analysis revealed significantly greater shear strengths for coated vs. uncoated implants for both polymer systems at both time periods. Mixed mode of failure occurred with particle removal from the polymer surface and from the bone. One animal at each time period was saved for histology. Histology at both time periods indicated direct bone apposition to the HA coating as compared to a fibrous encapsulation about the uncoated implants. This was confirmed with backscatter scanning electron microscopy and scanning acoustic microscopy. Hydroxyapatite coatings significantly improve the bond strength between polymers and bone by allowing direct bone apposition and some mechanical interlocking with the bone.

Tension band wiring-bone grafting for spondylolysis and spondylolisthesis. A clinical and biomechanical study

Patients with spondylolysis or spondylolisthesis with persistent symptoms often require surgical treatment. The purpose of this article is to present a new surgical technique and clinical results of 13 patients with symptomatic spondylolysis/spondylolisthesis who were treated with tension band wiring (intra- or intersegmental) and bone grafting techniques. This article also presents the results of biomechanical effects of these tension band wiring methods on canine lumbar spines with experimental spondylolytic defects. Thirteen adult patients, three with spondylolysis, and ten with spondylolytic spondylolisthesis, were treated with intrasegmental or intersegmental wiring with bone grafting technique, and the clinical results were evaluated at the mean follow-up period of 20 months. Patients with spondylolysis were treated with intrasegmental wiring (transverse processes to the spinous process of the same segment) with bone grafting at the lytic defect. Patients with spondylolytic spondylolisthesis were treated with intersegmental wiring (transverse process of the segment with defect to the spinous process of the same segment and to the spinous process of the segment below) with bone grafting to the defect and one-level fusion. All 13 patients had a solid spinal fusion and/or healing of the defect at the follow-up evaluation. Eleven had excellent clinical results; one a good, and one a fair result. The results of the biomechanical study showed that the experimental spondylolytic defect produced a significant decrease in bending stiffness (flexion-extension), and the wiring techniques (both the intra- and intersegment) increased the bending stiffness to that of the normal intact spinal segment.

Maxillary ameloblastoma. A potentially lethal neoplasm

Ameloblastomas are benign tumors derived from the odontogenic apparatus. Of these tumors, 80% originate in the mandible, while 20% originate in the maxilla. Six cases of maxillary ameloblastoma treated at the UCLA hospitals are presented; four of these cases showed extensive and destructive tumor growth involving vital structures, including the orbit, base of skull, and parasellar structures. Two of four patients with extensive disease died of their tumors, one, with extensive involvement of the base of the skull, became unavailable for follow-up, and, one year after diagnosis, one is alive with middle cranial fossa disease. A review of the medical literature provides further evidence of the locally aggressive behavior and potentially lethal nature of this tumor. No effective treatment has evolved for extensive ameloblastomas of the maxilla that have invaded surrounding vital structures. When tumor-free surgical margins are not possible, radiation therapy may offer palliation of disease.

The evaluation of bone remodeling about orthopaedic implants with ultrasound

Total hip arthroplasty causes biomechanical changes in the normal femur, including a redistribution and concentration of stress. These mechanical alterations in the femur cause local remodeling and resorption that affect the geometry and mechanical properties of the bone. Two complementary ultrasonic techniques were used to study the local adaptive remodeling of bone due to prosthesis implantation. An ultrasonic wave propagation technique was used to determine elastic properties and a new scanning acoustic microscope (SAM) mapped the acoustic impedance profile of each section. The effects of the implantation of two types of hip prostheses, an uncemented bipolar prosthesis with an Austin-Moore type stem and a cemented Charnley prosthesis, were investigated. Both prostheses had a detrimental effect on local elastic properties as determined by acoustic velocity measurements. The SAM system provided information about local inhomogeneities in bone properties not obtainable by any other means. The acoustic impedance maps highlighted bone resorption and bone remodeling on a microstructural level.

Granular cell tumors of the head and neck

Granular cell tumors have a predilection to occur in the head and neck. Thirty granular cell tumors have been diagnosed during the past 26 years at UCLA; 13 of which presented in the head and neck. Of these 13 cases, 10 were correctly diagnosed on the primary pathological specimen, which included one fine-needle aspirate and three frozen sections. Four cases required diagnostic confirmation with electron microscopy or histochemistry. The tongue accounted for more than one third of the cases. Three lesions exhibited locally aggressive behavior, but none of the tumors metastasized. Initial treatment was wide local excision in all but one case; recurrence was noted in two cases. Fine-needle aspiration can be used to provide preoperative diagnosis of granular cell tumors. Wide local excision with histologically confirmed clear margins provides definitive treatment.

Treatment of impending carotid rupture with detachable balloon embolization

Acute carotid artery rupture is frequently heralded by prodromal arterial bleeding. This warning signal provides the physician with a brief interval in which to hemodynamically stabilize a patient, electively occlude the carotid, and consequently improve the patient's chance of survival. For three years, we have employed an initial nonoperative approach to patients with impending carotid rupture. A trial of endovascular balloon occlusion followed by detachable balloon embolization of the carotid artery has been utilized. Patients unable to tolerate temporary occlusion underwent a vascular bypass procedure followed by embolization. Six patients have undergone this approach, and all had permanent cessation of bleeding. None died as a result of the procedures. One patient developed permanent neurologic deficits. Balloon embolization offers improved results over elective ligation and should be considered as an alternative treatment for patients in this dire predicament.

Auditory brain stem evoked response characteristics in developing infants

The auditory brain stem response (ABR) of a single group of developing normal infants was examined longitudinally, from newborn through 6 months of age. A sufficiently broad range of stimulus variables was included to ensure that the auditory system was adequately sampled in order to demonstrate developmental principles. Findings indicate that there are no differences in wave V latency-intensity functions between infants and adults. For waves I, III, and V, absolute and interwave latency-repetition rate functions differ between infants and adults and undergo systematic changes throughout the first 6 months of life. The most dramatic ABR changes (between any two sequential test sessions in infants) occurred between the ages of newborn and 2 weeks, with less pronounced ABR changes beyond 2 weeks of age. The pattern of latency change for wave I was different from that for waves III and V. After 2 weeks of age, wave I latency was the same as the adult value at all repetition rates. In contrast, waves III and V were characterized by decreasing latency throughout the follow-up period. A curvilinear developmental model provided a satisfactory fit to ABR latency data.

Auditory brain stem evoked response characteristics in the full-term newborn infant

The auditory brain stem response to click stimuli was investigated in a group of 50 full-term healthy newborns, as well as in a group of 20 older children and adults. The stimulus parameters of click level and click repetition rate were varied systematically to quantify the characteristics of the auditory brain stem response in the full-term newborn infant. The results reveal increased latencies for waves I, III, and V for all conditions among the newborns, relative to the older age group. The results suggest that the neurological system is the primary source of differences between newborns and older subjects, but do not rule out the possibility that external ear, middle ear, or cochlear mechanisms may also contribute to the differences observed.