Mixed reality surgical mentoring of combat casualty care related procedures in a perfused cadaver model: Initial results of a randomized feasibility study

BACKGROUND

Most telemedicine modalities have limited ability to enhance procedural and operative care. We developed a novel system to provide synchronous bidirectional expert mixed reality-enabled virtual procedural mentoring. In this feasibility study, we evaluated mixed reality mentoring of combat casualty care related procedures in a re-perfused cadaver model.

METHODS

Novices received real-time holographic mentoring from experts using augmented reality via Hololens (Microsoft Inc, Redmond, WA). The experts maintained real-time awareness of the novice's operative environment using virtual reality via HTC-Vive (HTC Corp, Xindian District, Taiwan). Additional cameras (both environments) and novel software created the immersive, shared, 3-dimensional mixed reality environment in which the novice and expert collaborated. The novices were prospectively randomized to either mixed reality or audio-only mentoring. Blinded experts independently evaluated novice procedural videos using a 5-point Likert scale-based questionnaire. Nonparametric variables were evaluated using the Wilcoxon rank-sum test and comparisons using the χ² analysis; significance was defined at P < .05.

RESULTS

Surgeon and nonsurgeon novices (14) performed 69 combat casualty care-related procedures (38 mixed reality, 31 audio), including various vascular exposures, 4-compartment lower leg fasciotomy, and emergency neurosurgical procedures; 85% were performed correctly with no difference in either group. Upon video review, mixed reality-mentored novices showed no difference in procedural flow and forward planning (3.67 vs 3.28, P = .21) or the likelihood of performing individual procedural steps correctly (4.12 vs 3.59, P = .06).

CONCLUSION

In this initial feasibility study, our novel mixed reality-based mentoring system successfully facilitated the performance of a wide variety of combat casualty care relevant procedures using a high fidelity re-perfused cadaver model. The small sample size and limited variety of novice types likely impacted the ability of holographically mentored novices to demonstrate improvement over the audio-only control group. Despite this, using virtual, augmented, and mixed reality technologies for procedural mentoring demonstrated promise, and further study is needed.

Outcomes in patients with gunshot wounds to the brain

Introduction

Gunshot wounds to the brain (GSWB) confer high lethality and uncertain recovery. It is unclear which patients benefit from aggressive resuscitation, and furthermore whether patients with GSWB undergoing cardiopulmonary resuscitation (CPR) have potential for survival or organ donation. Therefore, we sought to determine the rates of survival and organ donation, as well as identify factors associated with both outcomes in patients with GSWB undergoing CPR.

Methods

We performed a retrospective, multicenter study at 25 US trauma centers including dates between June 1, 2011 and December 31, 2017. Patients were included if they suffered isolated GSWB and required CPR at a referring hospital, in the field, or in the trauma resuscitation room. Patients were excluded for significant torso or extremity injuries, or if pregnant. Binomial regression models were used to determine predictors of survival/organ donation.

Results

825 patients met study criteria; the majority were male (87.6%) with a mean age of 36.5 years. Most (67%) underwent CPR in the field and 2.1% (n=17) survived to discharge. Of the non-survivors, 17.5% (n=141) were considered eligible donors, with a donation rate of 58.9% (n=83) in this group. Regression models found several predictors of survival. Hormone replacement was predictive of both survival and organ donation.

Conclusion

We found that GSWB requiring CPR during trauma resuscitation was associated with a 2.1% survival rate and overall organ donation rate of 10.3%. Several factors appear to be favorably associated with survival, although predictions are uncertain due to the low number of survivors in this patient population. Hormone replacement was predictive of both survival and organ donation. These results are a starting point for determining appropriate treatment algorithms for this devastating clinical condition.

Level of evidence

Level II.

Ureteral obstruction secondary to disseminated penicilliosis in a German shepherd dog

Abdominal ultrasonographic evaluation of a 2-year-old male German shepherd dog evaluated for weight loss demonstrated a right ureteral mass with ipsilateral hydronephrosis, hypoechoic splenic nodules, and hypoechoic and rounded lymph nodes. A fungal mat extending from the renal pelvis into the ureter secondary to disseminated Penicillium was confirmed at necropsy.

Sarcocystis sp.-Associated Meningoencephalitis in a Bald Eagle (Haliaeetus Leucocephalus)

Protozoal meningoencephalitis is uncommon in raptors. An adult female bald eagle ( Haliaeetus leucocephalus) was euthanized after several months of treatment for progressive neurologic signs. The predominant histologic lesion was lymphoplasmacytic and histiocytic meningoencephalitis involving the cerebrum and cerebellum. There was a marked segmental loss of granular cells and Purkinje cells, as well as segmental atrophy of the molecular layer in the cerebellum. Protozoal merozoites and schizonts were observed in the gray matter of the cerebellum. Ultrastructurally, the merozoites were classified as a species of Sarcocystis due to the lack of rhoptries. Immunohistochemistry of the agent revealed a positive reaction for Sarcocystis neurona, while sections were negative for Toxoplasma gondii and Neospora caninum. Sarcocystis sp. infection should be considered as a differential diagnosis in bald eagles with chronic neurologic disease.

Putative Metronidazole Neurotoxicosis in a Cat

A presumptive case of metronidazole toxicity in a 3.4-kg adult cat is described. The cat had been treated for suspected inflammatory bowel disease with an anti-inflammatory dose of prednisone and metronidazole (73.5-147 mg/kg PO q24h) for approximately 40 days prior to presentation. Clinical signs were primarily related to the central nervous system, including acute tetraparesis, unresponsiveness, tremors, and vocalization. The patient was euthanatized after 12 days of supportive care. Necropsy revealed no significant macroscopic lesions. Histologic evaluation revealed multifocal, fairly well-demarcated foci of necrosis in the brainstem, extending from the diencephalon to the medulla oblongata. To our knowledge, this is the first report to document histologic lesions associated with metronidazole administration in a cat.

Bacterial Diskospondylitis Associated with Posterior Paresis/Paralysis in North American Farmed Mink (Mustela vison)

Posterior paresis/paralysis in farmed mink is responsible for significant morbidity and mortality, with individual farms reporting the loss of as many as 700 animals each year. Although this disease has been recognized by North American mink farmers for approximately 40 years, there are few published reports focusing on this entity. The objective of this study was to investigate the etiology and pathogenesis of the disease. Complete necropsy examinations were done on 40 clinically affected mink, ranging from 7 to 10 weeks of age, and on three normal animals in the same age range from two mink farms. Thirty-two of the 40 clinically affected animals had an isolated vertebral lesion characterized by bone lysis and proliferation that usually was centered on an intervertebral disk space in the midthoracic area. An inflammatory reaction, composed primarily of neutrophils, was present within the vertebral sections in 25 of the 40 affected animals (62.5%), and the presence of gram-positive cocci was confirmed in 8 of 10 animals (80%) in which bacterial organisms were observed histologically. Bacterial cultures from 15 affected animals yielded Streptococcus sp. from the intervertebral disk space in 13 of 15 (86.7%) animals and from heart blood in 6 of 8 (75%). A farm visit revealed no history or evidence of traumatic wounds as a source of infection in these animals, and the diet appeared to be adequate for skeletal development. We conclude that posterior paresis/paralysis in farmed mink is associated with bacterial diskospondylitis, likely occurring secondary to bacteremia/septicemia.

Systemic Blastomycosis in a Horse

Progressive multisystemic disease caused by Blastomyces dermatitidis was diagnosed in a 17-year-old Quarter horse broodmare. The mare had been treated unsuccessfully with antibiotics for mastitis 3 months postpartum. The disease progressed to exudative cutaneous lesions affecting the ventrum, pectoral region, and limbs accompanied by weight loss across several months. Yeast bodies were observed in swabs of the cutaneous exudate, suggesting a clinical diagnosis of blastomycosis. Following referral, pleural effusion, cavitated lung lesions, and hyperproteinemia were identified, and the mare was euthanized because of poor prognosis. Necropsy revealed extensive pyogranulomas in the mammary gland, skin, subcutaneous tissues, and lungs, accompanied by thrombi in major blood vessels of the lungs and hind limbs. Histologically, pyogranulomatous inflammation was evident in many tissues, and fungal organisms were seen in sections of mammary gland, skin, subcutis, pericardium, and lung. Blastomyces dermatitidis was cultured from mammary tissue, lungs, lymph node, and an inguinal abscess. Although blastomycosis is endemic in the area of origin of the mare in northwestern Wisconsin, the disease is extremely rare in horses and hence easily misdiagnosed. Unique features of this case included the extent of mammary gland involvement and the presence of thrombi in multiple sites.

Heparin versus enoxaparin for prevention of venous thromboembolism after trauma: A randomized noninferiority trial

BACKGROUND

Research comparing enoxaparin with unfractionated heparin (UFH) given every 12 hours for venous thromboembolism (VTE) prophylaxis after trauma overlooks original recommendations that UFH be given every 8 hours. We conducted a prospective, randomized, noninferiority trial comparing UFH every 8 hours and standard enoxaparin every 12 hours. We hypothesized that the incidence of VTE in trauma patients receiving UFH every 8 hours would be no more than 10% higher than that in patients receiving enoxaparin every 12 hours.

METHODS

Trauma patients who met criteria for VTE prophylaxis at a Level I trauma center were randomly assigned to 5,000-U UFH every 8 hours or 30-mg enoxaparin every 12 hours between November 2012 and September 2014. Surveillance duplex ultrasound was performed twice weekly on intensive care unit patients and weekly on ward patients. Primary end points were deep vein thrombosis diagnosed by duplex ultrasound and pulmonary embolism diagnosed by computed tomography angiography.

RESULTS

Of 495 randomized patients, 220 received UFH and 216 received enoxaparin for analysis. Overall, 105 in the UFH group and 103 in the enoxaparin group underwent VTE surveillance or diagnostic testing. In the analysis of randomized patients who received treatment, UFH was noninferior compared with enoxaparin (absolute VTE risk difference, 3.1%; 95% confidence interval, -1.6% to 7.7%; p = 0.196); however, in the screening ultrasound group, the noninferiority of UFH was inconclusive (absolute VTE risk difference, 6.5%; 95% confidence interval, -2.9% to 15.8%; p = 0.179). The two treatments did not differ with regard to adverse events. The pharmaceutical cost for the regimen of UFH ($2,809) was nearly 20-fold lower than that for enoxaparin ($54,138).

CONCLUSION

A regimen of UFH every 8 hours may be noninferior to enoxaparin every 12 hours for the prevention of VTE following trauma. Given UFH's cost advantage, the use of UFH for VTE prophylaxis may offer greater value.

LEVEL OF EVIDENCE

Therapeutic/care management study, level II.

Parvoviral myocarditis in a 5-week-old Dachshund

OBJECTIVE

To describe a case of myocarditis associated with naturally occurring canine parvovirus type 2 (CPV-2).

CASE SUMMARY

A 5-week-old male intact Dachshund dog presented for acute respiratory distress. Limited diagnostic tests prior to the dog experiencing cardiopulmonary arrest included a lateral thoracic radiograph, which indicated cardiomegaly and diffuse unstructured pulmonary infiltrate. Necropsy was performed and results identified a lymphoplasmacytic myocarditis with positive CPV-2 immunohistochemistry within the myocardium.

UNIQUE INFORMATION PROVIDED

This report describes the natural occurrence of CPV-2-associated myocarditis. In addition to highlighting this rare form of canine parvovirus, cardiomyopathy in survivors of the acute viral myocarditis phase is reviewed.

Bone Disease in the Common Marmoset: Radiographic and Histological Findings

The common marmoset (Callithrix jacchus) is a New World primate that is used in biomedical research due to its small size and relative ease of handling compared with larger primates. Although bone disease in common marmosets is well recognized, there are very few detailed descriptions in the literature that cover the range of lesions seen in these animals. For all animals used to model human disease, it is important to be aware of background lesions that may affect the interpretation of study findings. This retrospective study details bone diseases encountered in marmoset breeding colonies at 2 different institutions. Affected marmosets at Johns Hopkins University had lesions compatible with diagnoses of rickets, fibrous osteodystrophy and osteopenia. Affected marmosets at the Wisconsin National Primate Research Center exhibited severe lesions of osteoclastic bone resorption and remodeling that had an unusual distribution and were not easily categorized into a known disease entity. The purpose of this report is to document these naturally occurring skeletal lesions of common marmosets and suggest an approach to evaluating skeletal disease in prospective studies of these animals that will allow the most accurate diagnoses.

Serum albumin and body weight as biomarkers for the antemortem identification of bone and gastrointestinal disease in the common marmoset

The increasing use of the common marmoset (Callithrix jacchus) in research makes it important to diagnose spontaneous disease that may confound experimental studies. Bone disease and gastrointestinal disease are two major causes of morbidity and mortality in captive marmosets, but currently no effective antemortem tests are available to identify affected animals prior to the terminal stage of disease. In this study we propose that bone disease and gastrointestinal disease are associated disease entities in marmosets and aim to establish the efficacy of several economical antemortem tests in identifying and predicting disease. Tissues from marmosets were examined to define affected animals and unaffected controls. Complete blood count, serum chemistry values, body weight, quantitative radiographs, and tissue-specific biochemical markers were evaluated as candidate biomarkers for disease. Bone and gastrointestinal disease were associated, with marmosets being over seven times more likely to have either concurrent bone and gastrointestinal disease or neither disease as opposed to lesions in only one organ system. When used in tandem, serum albumin <3.5 g/dL and body weight <325 g identified 100% of the marmosets affected with concurrent bone and gastrointestinal disease. Progressive body weight loss of 0.05% of peak body weight per day predicted which marmosets would develop disease prior to the terminal stage. Bone tissue-specific tests, such as quantitative analysis of radiographs and serum parathyroid hormone levels, were effective for distinguishing between marmosets with bone disease and those without. These results provide an avenue for making informed decisions regarding the removal of affected marmosets from studies in a timely manner, preserving the integrity of research results.

Ovarian mixed germ cell tumor with yolk sac and teratomatous components in a dog

Mixed germ cell tumors of the ovary have rarely been reported in veterinary species. A 3-year-old intact female Labrador Retriever dog was presented for lethargy, abdominal distention, and a midabdominal mass. An exploratory laparotomy revealed a large (23 cm in diameter) left ovarian tumor and multiple small (2-3 cm in diameter) pale tan masses on the peritoneum and abdominal surface of the diaphragm. Histological examination of the left ovary revealed a mixed germ cell tumor with a yolk sac component with rare Schiller-Duval bodies and a teratomatous component comprised primarily of neural differentiation. The abdominal metastases were solely comprised of the yolk sac component. The yolk sac component was diffusely immunopositive for cytokeratin with scattered cells reactive for α-fetoprotein and placental alkaline phosphatase. Within the teratomatous component, the neuropil was diffusely immunopositive for S100, neuron-specific enolase, and neurofilaments with a few glial fibrillary acidic protein immunopositive cells. Ovarian germ cell tumors may be pure and consist of only 1 germ cell element or may be mixed and include more than 1 germ cell element, such as teratoma and yolk sac tumor.

Blastomycotic osteomyelitis associated with severe lameness in a horse

A 12-year-old Quarter horse gelding was presented for evaluation of severe right forelimb lameness, 2 draining tracts over the lateral aspect of the right proximal antebrachium, and weight loss. A presumptive diagnosis of blastomycotic osteomyelitis was established based on radiographs and cytology of the exudate. This diagnosis was confirmed at necropsy.

Pulmonary trematodosis (Pharyngostomoides sp.) in a juvenile raccoon (Procyon lotor)

A lethargic, wild, juvenile raccoon died and was subsequently presented for necropsy. The lungs had widely disseminated, finely granular, yellow-tan foci with moderate pulmonary, as well as, thoracic lymphadenopathy. Histopathology revealed numerous cross-sections of larval trematodes morphologically consistent with diplostomid mesocercariae and metacercariae as well as moderate alveolointerstitial pneumonia with a mixed population of eosinophils, macrophages, lymphocytes, and plasma cells. The presence of larval trematodes within lymphatics in multiple organs indicates a route of fluke migration. Live specimens of mesocercariae and metacercariae recovered from refrigerated lung tissue after 7 days were identified as Pharyngostomoides sp., an intestinal diplostomid parasite (trematode) of raccoons and other mammals that is similar in appearance and life cycle to Alaria spp.

Obstructive sleep apnoea and perioperative complications in bariatric patients

BACKGROUND

The objective of this study was to determine the relationship between perioperative complications and the severity of obstructive sleep apnoea (OSA) in patients undergoing bariatric surgery who had undergone preoperative polysomnography (PSG).

METHODS

The records of 797 patients, age >18 yr, who underwent bariatric operations (442 open and 355 laparoscopic procedures) at Mayo Clinic and were assessed before operation by PSG, were reviewed retrospectively. OSA was quantified using the apnoea-hypopnoea index (AHI) as none (≤ 4), mild (5-15), moderate (16-30), and severe (≥ 31). Pulmonary, surgical, and 'other' complications within the first 30 postoperative days were analysed according to OSA severity. Logistic regression was used to assess the multivariable association of OSA, age, sex, BMI, and surgical approach with postoperative complications.

RESULTS

Most patients with OSA (93%) received perioperative positive airway pressure therapy, and all patients were closely monitored after operation with pulse oximetry on either regular nursing floors or in intensive or intermediate care units. At least one postoperative complication occurred in 259 patients (33%). In a multivariable model, the overall complication rate was increased with open procedures compared with laparoscopic. In addition, increased BMI and age were associated with increased likelihood of pulmonary and other complications. Complication rates were not associated with OSA severity.

CONCLUSIONS

In obese patients evaluated before operation by PSG before bariatric surgery and managed accordingly, the severity of OSA, as assessed by the AHI, was not associated with the rate of perioperative complications. These results cannot determine whether unrecognized and untreated OSA increases risk.

Assessment of a goat model of posterolateral knee instability

The development of an in vivo animal model of posterolateral knee instability is desired for devising effective interventions for this injury. Sequential sectioning of the popliteus tendon, lateral collateral ligament, and lateral capsule was done in cadaveric goat knees to create knee joint instability, followed by in vivo studies (Studies 1 and 2) of 7 and 3 months duration, respectively. In Study 1, the popliteus tendon and lateral collateral ligament were sectioned; in Study 2, these structures as well as the lateral joint capsule were sectioned. Biomechanical testing and histological assessments were done to determine the severity of the instability and the morphological changes. Sectioning the lateral collateral ligament and popliteus tendon (Study 1) resulted in a significant increase in varus instability at 90 degrees . Sectioning the lateral collateral ligament, popliteus tendon, and lateral capsule (Study 2) resulted in significant varus instability at 30 degrees , 60 degrees , and 90 degrees , and significant internal-external rotation at 60 degrees and 90 degrees ; however, the lesions of osteoarthritis in the operated knees were similar to those in unoperated control knees. This study confirms that posterolateral knee instability can be created in a goat model, but we were unable to demonstrate lesions of osteoarthritis that were of sufficient severity to allow evaluation of disease reduction in future intervention procedures. Future studies will determine if further manipulation of the model results in sufficient morphological changes to allow its use in the assessment of intervention strategies.

Effects of long-term estrogen replacement therapy on bone turnover in periarticular tibial osteophytes in surgically postmenopausal cynomolgus monkeys

The aims of the present study were to assess the effects of long-term estrogen replacement therapy (ERT) on size and indices of bone turnover in periarticular osteophytes in ovariectomized cynomolgus monkeys and to compare dynamic indices of bone turnover in osteophyte bone with those of subchondral bone (SCB) and epiphyseal/metaphyseal cancellous (EMC) bone. One hundred sixty-five adult female cynomolgus macaques were bilaterally ovariectomized and randomly divided into three age- and weight-matched treatment groups for a 36-month treatment period. Group 1 (OVX control) received no treatment, Group 2 (SPE) received soy phytoestrogens, and Group 3 (ERT) received conjugated equine estrogens in the diet; all monkeys were labeled with calcein before necropsy. A midcoronal, plastic-embedded section of the right proximal tibia from 20 randomly selected animals per treatment group was examined histologically. Forty-nine of the sections (OVX control, n=16; SPE, n=16; ERT, n=17) contained lateral abaxial osteophytes, and static and dynamic histomorphometry measurements were taken from osteophyte bone, SCB from the lateral tibial plateau, and EMC bone. Data were analyzed using the ANOVA and Kruskal-Wallis test, correlation and regression methods, and the Friedman and Wilcoxon signed rank test. There was no significant effect of long-term ERT on osteophyte area or on any static or dynamic histomorphometry parameters. The bone volume, trabecular number, and trabecular thickness in osteophyte bone were considerably higher than in EMC bone; whereas, trabecular separation was considerably lower in osteophyte bone. In all three treatment groups, BS/BV was significantly lower in osteophyte bone vs. EMC bone and significantly higher in osteophyte bone vs. lateral SCB. We conclude that osteophyte area and static and dynamic histomorphometry parameters within periarticular tibial osteophytes in ovariectomized cynomolgus monkeys are not significantly influenced by long-term ERT, but that site differences in static and dynamic bone histomorphometry parameters exist, particularly between EMC and osteophyte bone.

Histologic and immunohistochemical characteristics of failed articular cartilage resurfacing procedures for osteochondritis of the knee: a case series

BACKGROUND

The histologic appearance of the repair tissue after articular cartilage resurfacing procedures in humans is not well documented.

HYPOTHESIS

The histologic and immunohistochemical appearance of the repair tissues in failed articular cartilage resurfacing procedures will be similar, regardless of the procedure that was done, and will not resemble normal articular cartilage.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Graft tissue from 10 patients who underwent an autologous chondrocyte implantation (n = 6), microfracture (n = 3), or periosteal transplantation (n = 1) procedure to treat symptomatic osteochondritis dissecans of the medial femoral condyle was processed for histologic examination after failure of the articular cartilage resurfacing procedure. Serial sections from all slabs were stained with hematoxylin and eosin and toluidine blue and were immunostained using antibodies directed against types I, II, and X collagen.

RESULTS

Specimens from all 3 types of repair procedures were composed primarily of fibrous connective tissue and fibrocartilage. None of the sections stained positively for type X collagen. All 10 cases stained positively for type I collagen (range, 7%-97% of tissue area). Staining for type II collagen was positive in 4 of 6 autologous chondrocyte implantation cases, 3 of 3 microfracture cases, and the periosteal transplant case (range, 2%-65% of tissue area). In 8 of 10 cases, the percentage of the section area exhibiting positive staining for type I collagen was higher than for type II collagen (6 of 6 autologous chondrocyte implantation; 1 of 3 microfracture; 1 periosteal transplant).

CONCLUSION

The histologic appearance of the repair tissue of 3 different failed articular cartilage resurfacing procedures was similar and did not resemble normal articular cartilage.

Anatomy and biomechanics of the posterolateral aspect of the canine knee

The purpose of this study was to describe the anatomy and characterize the biomechanics of the posterolateral aspect of the canine knee. Ten adult canine knees were each used for anatomy and biomechanical testing. Distances and motion limits were measured using a 6 degree-of-freedom electromagnetic tracking system. Canine knee dissection reproducibly identified structures present in the human posterolateral knee. The course and attachment sites of the fibular collateral ligament, popliteofibular ligament, and popliteus tendon were similar to human anatomy. Sequential sectioning of the fibular collateral ligament, popliteofibular ligament, and popliteus tendon all significantly increased varus translation at full extension, 60 degrees , and 90 degrees of knee flexion. Sectioning of the fibular collateral ligament significantly increased external rotation at flexion angles near full extension, while popliteus tendon sectioning also significantly increased external rotation at 90 degrees of knee flexion. Based on the fact that the anatomy of the fibular collateral ligament, popliteus tendon, popliteofibular ligament, and the biomechanical properties of the canine posterolateral knee are similar to the human knee, we believe the canine knee is a suitable model to study the natural history of posterolateral knee injuries. The canine model will also prove valuable in the validation of reconstruction techniques and studying the potential development of medial compartment osteoarthritis following posterolateral knee injuries.

Osteosarcoma at the site of a triple pelvic osteotomy in a dog

An osteosarcoma (OSA) involving the right pelvis was diagnosed in a 12-year-old golden retriever 11 years after triple pelvic osteotomy (TPO) surgery. The dog was presented with a 12-week history of nonweight-bearing lameness of the right hind limb. Radiographs demonstrated an aggressive bone lesion of the right ilium with profound periosteal proliferation and punctate lysis that extended along the ilium caudally and into the right ischium, with its epicenter at the level of the right TPO plate. Necropsy revealed that the entire right hemipelvis, especially the ischium, was markedly thickened and firm with irregular margins. Histopathology was consistent with a diagnosis of OSA.

Effects of long-term estrogen replacement therapy on the prevalence and area of periarticular tibial osteophytes in surgically postmenopausal cynomolgus monkeys

Osteoarthritis (OA) occurs naturally in cynomolgus macaques. The purposes of the present study were to: 1) develop histological measurement schemes to measure the cross-sectional area of axial and abaxial osteophytes in the proximal tibia; 2) determine the effects of long-term estrogen replacement therapy (ERT) on osteophyte prevalence and area; and 3) assess relationships between osteophyte size and risk factors of OA (age and body weight) and concurrent bone and cartilage lesions. Adult female cynomolgus macaques (n=180) were bilaterally ovariectomized (OVX) and were treated for 3 years with ERT, soy phytoestrogens (SPE), or no hormones (OVX controls). At necropsy, the prevalence and cross-sectional area of periarticular tibial osteophytes were evaluated histologically. Treatment effects on osteophyte prevalence and area were evaluated using Chi-square analyses and Kruskal-Wallis test, respectively; other comparisons were evaluated using regression analyses. The prevalence of abaxial osteophytes in the medial tibial plateau was not significantly affected by treatment group; however, the prevalence of abaxial osteophytes in the lateral tibial plateau was significantly lower in ERT group than SPE group (p<0.01). The total number of abaxial osteophytes (sum of lateral and medial) was significantly lower in ERT group compared to OVX and SPE groups. Neither the prevalence of axial osteophytes nor the sum of lateral and medial axial osteophytes was significantly affected by treatment in either tibial plateau. There were no significant treatment effects on axial or abaxial osteophyte cross-sectional area in either tibial plateau. There was a significant positive correlation between abaxial osteophyte area and SCB thickness in the medial tibial plateau (p=0.048); however, there were no significant correlations between abaxial osteophyte area (medial or lateral) and age or body weight. In this model of naturally occurring OA, long-term ERT does not consistently reduce the prevalence, and has no significant effects on cross-sectional area, of periarticular tibial osteophytes.

Pathophysiology of REM sleep behaviour disorder and relevance to neurodegenerative disease

REM sleep behaviour disorder (RBD) is a parasomnia characterized by the loss of normal skeletal muscle atonia during REM sleep with prominent motor activity accompanying dreaming. The terminology relating to RBD, and mechanisms underlying REM sleep without atonia and RBD based on data in cat and rat are presented. Neuroimaging data from the few published human cases with RBD associated with structural lesions in the brainstem are presented, in which the dorsal midbrain and pons are implicated. Pharmacological manipulations which alter RBD frequency and severity are reviewed, and the data from human neuropathological studies are presented. An anatomic framework and new schema for the pathophysiology of RBD are proposed based on recent data in rat regarding the putative flip-flop switch for REM sleep control. The structure in man analogous to the subcoeruleus region in cat and sublaterodorsal nucleus in rat is proposed as the nucleus (and its associated efferent and afferent pathways) crucial to RBD pathophysiology. The association of RBD with neurological disease ('secondary RBD') is presented, with emphasis on RBD associated with neurodegenerative disease, particularly the synucleinopathies. The hypothesized pathophysiology of RBD is presented in relation to the Braak staging system for Parkinson's disease, in which the topography and temporal sequence of synuclein pathology in the brain could explain the evolution of parkinsonism and/or dementia well after the onset of RBD. These data suggest that many patients with 'idiopathic' RBD are actually exhibiting an early clinical manifestation of an evolving neurodegenerative disorder. Such patients may be appropriate for future drug therapies that affect synuclein pathophysiology, in which the development of parkinsonism and/or dementia could be delayed or prevented. We suggest that additional clinicopathological studies be performed in patients with dementia or parkinsonism, with and without RBD, as well as in patients with idiopathic RBD, to further elucidate the pathophysiology and also characterize the clinical and pathophysiological relevance of RBD in neurodegenerative disease. Furthermore, longitudinal studies in patients with idiopathic RBD are warranted to characterize the natural history of such patients and prepare for future therapeutic trials.

Insights into REM sleep behavior disorder pathophysiology in brainstem-predominant Lewy body disease

BACKGROUND AND PURPOSE

Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia reflecting changes in the brain, but which specific neuronal networks are involved in human RBD pathogenesis has not yet been determined. To date, only one case of idiopathic RBD has undergone autopsy, in which "incidental Lewy body disease" was found. Due to the severe neuronal loss and gliosis in the substantia nigra (SN) and locus ceruleus (LC) in this case, degeneration of brainstem monoaminergic neurons was postulated as the underlying substrate for RBD. Additional cases of idiopathic RBD with neuropathologic examination may help clarify which key brainstem structures are involved.

PATIENT AND METHODS

Case report with neuropathologic analysis.

RESULTS

A man with polysomnographically proven RBD (onset age 57 years), but no other neurologic signs or symptoms, underwent neuropathologic examination upon his death at age 72. Histopathologic analysis showed Lewy body disease, but no significant neuronal loss or gliosis was present in the SN or LC.

CONCLUSIONS

This case represents another example of Lewy body disease associated with RBD. The minimal degenerative changes in the SN and LC call into question the role of these nuclei in RBD, at least in our case. We suggest additional cases of idiopathic RBD undergo neuropathologic analyses to better delineate the neurologic substrate of this intriguing parasomnia.

An in vivo injury model of posterolateral knee instability

BACKGROUND

Posterolateral knee instability is a difficult clinical problem to diagnose and treat. To best evaluate its natural history and the effects of interventional treatments, it is important to develop an in vivo model in an attempt to validate human cadaveric and clinical observational studies.

PURPOSE

To develop an in vivo model of posterolateral knee instability in the rabbit and to determine the natural history of untreated posterolateral knee injuries at 6 months postoperatively.

STUDY DESIGN

Controlled laboratory study.

METHODS

The fibular collateral ligament and popliteus tendon were surgically transected in 1 knee in each of 10 skeletally mature New Zealand White rabbits, with the contralateral knee serving as a control knee. At 6 months postoperatively, the rabbits were euthanized, the knees were removed, and biomechanical testing of knee joint stability was performed. After biomechanical testing, histological sections of each proximal tibia and distal femur were evaluated, and each proximal tibia was graded using an osteoarthritis grading scheme.

RESULTS

Biomechanical testing revealed a statistically significant difference in amount of rotation in the operated knees compared with the unoperated control knees to varus moments at 30 degrees , 60 degrees , and 90 degrees and to external rotation torques at 30 degrees and 60 degrees . Morphological analysis revealed no significant difference in lesions of osteoarthritis in the medial compartment of the operated knees compared with the unoperated knees.

CONCLUSIONS

Although the presence of posterolateral knee instability was validated 6 months after surgery in this model, the authors did not identify significant differences in lesions of osteoarthritis in the operated knees compared with the unoperated control knees.

CLINICAL SIGNIFICANCE

This study confirms that posterolateral knee instability can be created in an animal model. It also recapitulates the clinical observation in humans that untreated posterolateral knee injuries do not heal. Similar to animal models of medial collateral ligament sectioning, further studies to validate a posterolateral instability knee model may lead to interventional studies to determine the best way to treat this complex knee instability pattern.

Anatomy of the posterolateral aspect of the goat knee

The purpose of this study was to determine the anatomy of the posterolateral aspect of the goat knee for future in vivo studies using a goat model to examine the natural history of posterolateral knee injuries. Twelve non-paired, fresh-frozen, adult goat knees were dissected to determine the anatomy of the posterolateral corner. The main posterolateral structures identified in the goat knee were the lateral collateral ligament, the popliteus muscle and tendon, popliteomeniscal fascicles, and the lateral gastrocnemius muscle. The lateral collateral ligament was extra-articular and coursed from its proximal attachment, located posterior and proximal to the lateral epicondyle, to its distal attachment on the lateral aspect of the fused proximal tibiofibula. The popliteus muscle attached to the medial edge of the posterodistal tibia, traveled anterolaterally, became intra-articular at its musculotendinous junction, and attached to the lateral femur just distal to the lateral epicondyle. Distinct popliteomeniscal fascicles attached the lateral meniscus to the popliteus muscle and tendon, and a fascial attachment from the musculotendinous junction of the popliteus muscle coursed to the lateral tibial plateau. This study provided information on the structures present in the posterolateral aspect of the goat knee and enhanced our understanding of their relationships to analogous structures in the human knee. This information is important to enable future development of potential models of the natural history of posterolateral knee injuries and also to test surgical techniques and the in vivo effects of these injuries on cruciate ligament reconstructions.

Isolation of an adenovirus and an adeno-associated virus from goat kids with enteritis

A dairy goat operation in Minnesota experienced a sudden, markedly increased mortality among its neonatal goats. Approximately 60 of 130 kids (46%) died. The animals had diarrhea and dyspnea of 1-2 days duration before death. Necropsy of 4 goat kids revealed marked, acute, catarrhal enteritis and fibrinous pleuropneumonia. Mannheimia haemolytica was isolated from the lungs. Basophilic inclusion bodies filling the entire nucleus were present in enterocytes of the ileum of 3 goats. Adenoviral particles were detected in the feces by electron microscopy and adenovirus was subsequently isolated from the intestinal content together with a parvo-like virus (dependovirus). Morphology, physicochemical characteristics, and neutralization tests indicated that the adenovirus resembled ovine adenovirus-2 (OAdV-2). However, the PstI restriction endonuclease pattern produced by the goat adenovirus was distinct from that of OAdV-2. This is the first report of enteritis in goats with an adenovirus antigenically related to OAdV-2 and with a parvo-like dependovirus.

An off-axis hydrothermal vent field near the Mid-Atlantic Ridge at 30 degrees N

Evidence is growing that hydrothermal venting occurs not only along mid-ocean ridges but also on old regions of the oceanic crust away from spreading centres. Here we report the discovery of an extensive hydrothermal field at 30 degrees N near the eastern intersection of the Mid-Atlantic Ridge and the Atlantis fracture zone. The vent field--named 'Lost City'--is distinctly different from all other known sea-floor hydrothermal fields in that it is located on 1.5-Myr-old crust, nearly 15 km from the spreading axis, and may be driven by the heat of exothermic serpentinization reactions between sea water and mantle rocks. It is located on a dome-like massif and is dominated by steep-sided carbonate chimneys, rather than the sulphide structures typical of 'black smoker' hydrothermal fields. We found that vent fluids are relatively cool (40-75 degrees C) and alkaline (pH 9.0-9.8), supporting dense microbial communities that include anaerobic thermophiles. Because the geological characteristics of the Atlantis massif are similar to numerous areas of old crust along the Mid-Atlantic, Indian and Arctic ridges, these results indicate that a much larger portion of the oceanic crust may support hydrothermal activity and microbial life than previously thought.

Diagnosis of pulmonary embolism with use of computed tomographic angiography

Pulmonary embolism (PE) is a common diagnostic problem, particularly in hospitalized patients. It remains a frequent cause of unexpected deaths. Traditionally, the diagnostic work-up for suspected PE has centered on the use of ventilation-perfusion (V-P) radionuclide lung scanning. However, V-P scanning does not provide adequate confirmation or exclusion of the diagnosis in the majority of patients who undergo this test. Although published guidelines advise further diagnostic testing after nondiagnostic V-P scans, clinicians infrequently perform such testing, and management decisions are commonly based on clinical judgment. In recent years, there has been an increasing interest in the use of computed tomographic (CT) angiography in the diagnostic evaluation of patients with suspected PE. Although there are unresolved issues regarding its sensitivity in detecting small peripheral emboli, CT angiography is more accurate than V-P scanning in the diagnosis of PE and yields other intrathoracic diagnoses. Herein we summarize the problems with the traditional approach centered on the use of V-P scanning in the diagnosis of PE and propose an alternative diagnostic strategy based primarily on the use of CT angiography.

Sleep apnea in heart transplant recipients: type, symptoms, risk factors, and response to nasal continuous positive airway pressure

BACKGROUND

We determined the type, symptoms, and risk factors for sleep apnea in heart transplant recipients and the response to nasal continuous positive airway pressure.

METHODS

A retrospective study on heart transplant recipients with sleep apnea was conducted in a tertiary care medical center with follow-up telephone interviews. Between February 1988 and August 1998, 147 patients underwent orthotopic heart transplantation at our institution. Seventeen patients (11.6%) who were suspected of having sleep apnea underwent polysomnography at a mean interval of 17.5 months after transplantation.

RESULTS

All were diagnosed with sleep apnea: 13 had obstructive sleep apnea and 4 had mixed sleep apnea. Mean age at polysomnography was 50.8 years (range, 24-67 years). The patients presented with snoring (100%), excessive daytime somnolence (65%), witnessed apneas (53%), and morning fatigue (53%). Sixteen (94%) had a mean weight gain of 10.4 kg after transplantation, and 1 patient lost 14.6 kg. In the 11 patients with obstructive sleep apnea who underwent nasal continuous positive airway pressure titration, significant improvements occurred in the apnea-hypopnea index (decreased from 37.6 to 10.4; p = 0.01) and mean arousal index (decreased from 44.5 to 19.4; p = 0.01). Only 2 of the 8 patients with sleep apnea for whom nasal continuous positive airway pressure was recommended continued to use it at the time of telephone follow-up.

CONCLUSIONS

Sleep apnea, especially obstructive sleep apnea, occurs frequently in heart transplant recipients. Obstructive sleep apnea appears to present in the typical manner, and although a positive response to nasal continuous positive airway pressure can be documented by polysomnography, long-term use of nasal continuous positive airway pressure may be low.

Ultrastructural and lectin-histochemical differences between the scolex/strobila and bladder teguments of the Taenia taeniaeformis strobilocercus

The strobilocercus stage of the cat tapeworm Taenia taeniaeformis is surrounded by a single syncytial sheet of cytoplasm called the tegument. The outer membrane of the tegument covers both the scolex/strobila (S/S) and the bladder portions of the strobilocercus, but only the S/S region is resistant to intestinal digestion. It has been suggested that the glycocalyx, the surface-exposed glycoconjugates of the outer membrane, may serve to insulate underlying surface membrane components from digestion. In this study, we used lectin binding to test the hypothesis that the glycocalyx of the S/S is different from that of the bladder and that this may serve as the resistance mechanism of the S/S to digestion. Biotin-labeled lectins and an avidin-glucose oxidase detection system were applied to whole strobilocerci and to 1-microm epon-araldite plastic-embedded sections. Lectins bound to either both regions of the strobilocerci, to the S/S regions only, or did not bind at all. The restriction of some glycoconjugates to the glycocalyx of the S/S region only is consistent with our hypothesis.

Rapid eye movement sleep behaviour disorder: demographic, clinical and laboratory findings in 93 cases

We describe demographic, clinical, laboratory and aetiological findings in 93 consecutive patients with rapid eye movement (REM) sleep behaviour disorder (RBD), which consists of excessive motor activity during dreaming in association with loss of skeletal muscle atonia of REM sleep. The patients were seen at the Mayo Sleep Disorders Center between January 1, 1991 and July 31, 1995. Eighty-one patients (87%) were male. The mean age of RBD onset was 60.9 years (range 36-84 years) and the mean age at presentation was 64.4 years (37-85 years). Thirty-two per cent of patients had injured themselves and 64% had assaulted their spouses. Subdural haematomas occurred in two patients. Dream content was altered and involved defence of the sleeper against attack in 87%. The frequency of nocturnal events decreased with time in seven untreated patients with neurodegenerative disease. MRI or CT head scans were performed in 56% of patients. Although four scans showed brainstem pathology, all of these patients had apparently unrelated neurodegenerative diseases known to be associated with RBD. Neurological disorders were present in 57% of patients; Parkinson's disease, dementia without parkinsonism and multiple system atrophy accounted for all but 14% of these. RBD developed before parkinsonism in 52% of the patients with Parkinson's disease. Five of the 14 patients with multiple system atrophy were female, and thus the strong male predominance in RBD is less evident in this condition. Psychiatric disorders, drug use or drug withdrawal were rarely causally related to RBD. Clonazepam treatment of RBD was completely or partially successful in 87% of the patients who used the drug. We conclude that RBD is a well-defined condition and that descriptions from different centres are fairly consistent. It is commonest in elderly males and may result in serious morbidity to patients and bed partners. There is a strong relationship to neurodegenerative disease, especially Parkinson's disease, multiple system atrophy and dementia, and neurologists should explore the possibility of RBD in patients with these conditions. RBD symptoms may be the first manifestations of these disorders and careful follow-up is needed. Neuroimaging is unlikely to reveal underlying disorders not suspected clinically. We confirm the effectiveness of clonazepam, but note that attention to the safety of the bed environment may be sufficient for patients with contraindications to the drug.

Therapeutic bronchoscopy in broncholithiasis

Bronchoscopy is considered the most important diagnostic test for broncholithiasis. However, its role in the treatment of broncholithiasis in a large group of patients has not been studied. To evaluate the therapeutic role of bronchoscopy, we retrospectively reviewed the clinical data of patients with broncholithiasis who also underwent bronchoscopy at Mayo Clinic. Bronchoscopy revealed 127 broncholiths (free or partly eroded calcified material in the airway lumen) in 95 patients (49 men and 46 women) evaluated between 1954 and 1994. Bronchoscopic removal of 71 (56%) broncholiths was attempted in 48 patients (50.5%) during 61 bronchoscopy sessions. Forty-eight of the broncholiths selected for removal were partly eroding into the tracheobronchial lumen and 23 were free. Forty-eight percent (23 of 48) of the partly eroding broncholiths were successfully removed bronchoscopically, with a greater percentage removed with the rigid bronchoscope (67%) than with the flexible bronchoscope (30%). All free broncholiths were completely extracted regardless of the type of bronchoscope used. Complications occurred in only two patients (4% of the bronchoscopic broncholithectomy group), both with partially eroded broncholiths, and consisted of hemorrhage in one patient requiring thoracotomy and acute dyspnea in another patient, caused by a loose broncholith lodged in the trachea. We conclude that flexible and/or rigid bronchoscopic extraction of partly eroded or free broncholiths in the tracheobronchial tree can be considered safe and effective.

Clinical recognition of pulmonary embolism: problem of unrecognized and asymptomatic cases

Dyspnea, pleuritic chest pain, and tachypnea are widely appreciated as common initial features of pulmonary embolism (PE). This knowledge is derived primarily from prospective studies evaluating diagnostic tests or therapeutic interventions in which the study patients are suspected to have PE based on their initial symptoms. Autopsy studies, however, continue to show that most cases of fatal PE are unrecognized and undiagnosed. Data from studies screening for PE in patients with deep venous thrombosis and in postoperative patients suggest that many patients with PE are asymptomatic and that PE is unrecognized. We believe that the current concepts regarding the initial clinical features of PE are too narrow and biased toward symptomatic cases. High clinical suspicion may be insufficient in recognizing PE. Herein we summarize the available data and explore the implications for clinical practice.

REM sleep behavior disorder and degenerative dementia: an association likely reflecting Lewy body disease

BACKGROUND

REM sleep behavior disorder (RBD) has been reported with various neurodegenerative disorders, most frequently in disorders with Lewy body pathology. RBD often precedes the onset of PD, and a recent prospective study showed that 38% of patients with RBD eventually developed PD.

METHODS

We identified 37 patients with degenerative dementia and a history of bursts of vigorous movement of the arms and legs with vocalization during sleep and associated with dream recall. Patients with and without two or more signs of parkinsonism were compared. Clinical, laboratory, and neuropsychometric features were analyzed, and criteria for the clinical diagnosis of dementia with Lewy bodies (DLB) were applied to all patients.

RESULTS

Thirty-four of the 37 patients were male with mean age at onset of 61.5 years for RBD and 68.1 years for cognitive decline. RBD commenced before or concurrently with dementia in all patients but two. Parkinsonism (two or more signs) occurred in 54% of the sample (20/37), with a mean age at onset of 69.1 years. Polysomnography (PSG) confirmed RBD in all patients studied. Neuropsychological testing demonstrated impaired perceptual-organizational skills, verbal fluency, and marked constructional dyspraxia in more than one-half the patients. There were no statistically significant differences in the frequency of clinical features or in neuropsychological performance between patients with and without parkinsonism. Thirty-four patients (92%) met criteria for clinically possible or probable DLB. Three patients were autopsied; all had limbic with or without neocortical Lewy bodies.

CONCLUSIONS

We report a group of predominantly male patients with a characteristic association of RBD and degenerative dementia. The clinical and neuropsychometric features of the groups of patients with and without parkinsonism are similar. We hypothesize that the underlying pathology in these patients is DLB.

Effects of an allicin-based product on cryptosporidiosis in neonatal calves

OBJECTIVE

To evaluate effectiveness of an allicin-based product in neonatal calves inoculated with Cryptosporidium parvum.

DESIGN

Randomized controlled study.

ANIMALS

43 neonatal calves.

PROCEDURE

Calves were inoculated with 1.5 x 10(8) or 7.5 x 10(5) C parvum oocysts within 2 days after birth. Calves were given an allicin-based product once after inoculation or daily for 7 days after inoculation or were not treated. Calves that developed diarrhea were treated by administration of the product. Fecal consistency scores and weight gains were statistically evaluated.

RESULTS

Mean daily weight gain and severity of diarrhea in calves 4 to 21 days old were unaffected by prophylactic use of the product. However, intensive prophylactic administration may have delayed onset of C parvum-induced diarrhea in calves inoculated with the lower dose of oocysts.

CLINICAL IMPLICATIONS

Administration of an allicin-based product did not alter duration of C parvum-induced diarrhea or enhance weight gain in neonatal calves. However, intensive prophylactic administration of an allicin-based product may delay onset of diarrhea in calves exposed to C parvum oocysts.

Sleep-wake cycles and the management of respiratory failure

Sleep is characterized by many changes in the respiratory system, including a reduction in respiratory motor output associated with the loss of wakefulness, increased upper airway resistance, and blunted protective reflexes (such as load compensation), that result in reduced alveolar ventilation. The development of carbon dioxide retention appears to be linked to the exaggeration of sleep-related changes on ventilation by coexistent respiratory system disorders. Sleep-disordered breathing is becoming increasingly recognized in subjects with neuromuscular diseases, who may be prone to nocturnal respiratory events due to diaphragm and bulbar muscle weakness, abnormal central respiratory control, obesity, and sleep position restrictions. Nocturnal gas exchange deterioration may occur in patients with chronic obstructive pulmonary disease, particularly during rapid eye movement sleep when activity of the respiratory muscles other than the diaphragm is inhibited. Concurrent obstructive sleep apnea syndrome may further compromise nocturnal ventilation, thereby contributing to the development of acute or chronic respiratory failure. The use of noninvasive nocturnal ventilation at night has resulted in significant improvements in symptoms of hypoventilation and daytime carbon dioxide retention in various clinical settings, yet important questions remain about implementation of this modality.

Fungal beta-glucan interacts with vitronectin and stimulates tumor necrosis factor alpha release from macrophages

beta-Glucans are polymers of D-glucose which represent major structural components of fungal cell walls. It was shown previously that fungi interact with macrophages through beta-glucan receptors, thereby inducing release of tumor necrosis factor alpha (TNF-alpha). Additional studies demonstrated that vitronectin, a host adhesive glycoprotein, binds to fungi and enhances macrophage recognition of these organisms. Since vitronectin contains a carbohydrate-binding region, we postulated that vitronectin binds fungal beta-glucans and subsequently augments macrophage TNF-alpha release in response to this fungal component. To study this, we first determined the release of TNF-alpha from alveolar macrophages stimulated with fungal beta-glucan. Maximal TNF-alpha release occurred with moderate concentrations of beta-glucan (100 to 200 micrograms/ml), whereas higher concentrations of beta-glucan (> or = 500 micrograms/ml) caused apparent suppression of the TNF-alpha activity released. This suppression of TNF-alpha activity by high concentrations of beta-glucan was mediated by the particulate beta-glucan binding soluble TNF-alpha, through the lectin-binding domain of the cytokine, rendering the TNF-alpha less available for measurement. Next, we assessed the interaction of vitronectin with beta-glucan. Binding of 125I-vitronectin to particulate fungal beta-glucan was dose dependent and specifically inhibitable by unlabeled vitronectin. Furthermore, treatment of beta-glucan with vitronectin substantially augmented macrophage TNF-alpha release in response to this fungal component. These findings demonstrate that fungal beta-glucan can directly modulate TNF-alpha release from macrophages. Further, these studies indicate that the host adhesive glycoprotein vitronectin specifically binds beta-glucan and augments macrophage cytokine release in response to this fungal element.

Rates of DNA-mediated electron transfer between metallointercalators

Ultrafast emission and absorption spectroscopies were used to measure the kinetics of DNA-mediated electron transfer reactions between metal complexes intercalated into DNA. In the presence of rhodium(III) acceptor, a substantial fraction of photoexcited donor exhibits fast oxidative quenching (>3 x 10(10) per second). Transient-absorption experiments indicate that, for a series of donors, the majority of back electron transfer is also very fast (approximately 10(10) per second). This rate is independent of the loading of acceptors on the helix, but is sensitive to sequence and pi stacking. The cooperative binding of donor and acceptor is considered unlikely on the basis of structural models and DNA photocleavage studies of binding. These data show that the DNA double helix differs significantly from proteins as a bridge for electron transfer.

Tendon-healing to cortical bone compared with healing to a cancellous trough. A biomechanical and histological evaluation in goats

This study was performed to test the hypothesis that attaching a tendon to a trough in cancellous bone results in tendon-healing that is biomechanically superior to that after direct fixation of a tendon to cortical bone. Twenty adult female goats were treated with a bilateral tenotomy of the infraspinatus tendon with subsequent reattachment of the tendon. In shoulders randomized to the cancellous-fixation group, a cancellous bed was prepared with a motorized burr and a template measuring twenty by five by five millimeters. The repair in the shoulders randomized to the cortical-fixation group was performed in the same manner, except that the tendon was attached to cortical bone. Three outcome measures were assessed, six and twelve weeks after the repair, with the Student paired t test and analysis of variance: load to failure, energy to failure, and stiffness. The types of repair were not significantly different with regard to any of the three outcomes. When the six and twelve-week data were combined, an average difference in load to failure of 3.9 per cent in favor of cancellous repair was observed but it was not significant (p = 0.78). The associated 95 per cent confidence interval for the difference ranged from 10.5 per cent in favor of cortical repair to 18.3 per cent in favor of cancellous repair. Histological analysis at six and twelve weeks revealed progressive maturation and reorganization of the bone-tendon interface with re-establishment of collagen-fiber continuity between the tendon and bone. This process was indistinguishable between the cortical and cancellous specimens. This study demonstrated no significant benefit from the creation of a trough to expose the tendon to cancellous bone. In this model, at both six and twelve weeks, the tendon-to-bone healing process of the two groups appeared similar and the biomechanical properties were approximately equal.