The reinfection threshold, revisited.

One mode by which infection-derived immunity fails is when recovery leads to a reduced but nonzero risk of reinfection. This type of partial protection is called leaky immunity with the degree of leakiness quantified by the relative probability a previously infected individual will get infected upon exposure compared to a naively susceptible individual. Previous authors have defined the reinfection threshold, which occurs when the basic reproduction number equals the inverse of the leakiness, however, there has been some debate about whether or not this is a real threshold. Here we show how the reinfection threshold relates to two important occurrences: (1) the point at which the endemic equilibrium changes from being a stable spiral to a stable node, and (2) the point at which the rate of change of the prevalence increases the most relative to leakiness. When the recovery period is short relative to the average lifetime then both occurrences are close to the reinfection threshold. We show how these results are related to the reinfection threshold found in other models of imperfect immunity. To further demonstrate the significance of this threshold in modeling, we conducted a simulation study to evaluate some of the consequences the reinfection threshold might have in parameter estimation and modeling. Using specific parameter values chosen to reflect an acute infection, we found that the basic reproduction number values larger than that of the reinfection threshold value were less identifiable than those below the threshold.

In vivo gastrocnemius muscle fascicle length in children with and without diplegic cerebral palsy.

The effect of spastic cerebral palsy on in vivo gastrocnemius muscle fascicle length is not clear. Similarity of fascicle lengths in children with diplegia and typically developing children, but shortening of fascicle lengths in the paretic legs of children with hemiplegia compared with the non-paretic legs, are both reported. In the former case, comparisons were made between fascicle lengths normalized to leg length, whereas in the latter case, absolute fascicle lengths were compared. The inherent assumptions when normalizing fascicle length (measured via ultrasonography) were not validated, raising the possibility that inappropriate normalization contributed to the controversy. We used statistical methods to control the potential confounding effect of leg length on fascicle length, and tested the feasibility of the normalization method for a group of 18 children with diplegia (nine males, nine females; mean age 8y 7mo [SD 3y 11mo], range 2-15y; Gross Motor Function Classification System levels II and III) and 50 typically developing children (20 males, 30 females; mean age 9y 1mo [SD 2y 4mo], range 4-14y). Children with diplegia, as a group, had shorter absolute and normalized fascicle lengths (p<0.05) but we could not refute the appropriateness of the normalization method. Other methodological issues (such as sample characteristics) might have contributed to the apparent controversy between the studies.

The ferguson medial approach for open reduction of developmental dysplasia of the hip. A clinical and radiological review of 49 hips.

The results of the Ferguson medial approach for open reduction of developmental dysplasia of the hip (DDH) were reviewed for 49 hips with a follow-up of more than 48 months. The mean age at operation was 12.3 months (6 to 23). The mean length of clinical and radiological follow-up was 82 months (48 to 148). Three redislocations occurred. Group I avascular necrosis according to the classification of Kalamchi and MacEwen was seen in four hips, group II in two hips and group III in one hip; 92% of the hips were classified as Severin class I and II. The acetabular index and centre edge (CE) angles were within normal limits at final follow-up, but were still significantly different from the unaffected side. We conclude that the Ferguson procedure is safe and reliable for low dislocations in children aged six to 18 months.

Tamanu (Calophyllum inophyllum) - the African, Asian, Polynesian and Pacific Panacea.

Tamanu or Calophyllum inophyllum has been used traditionally as a local medicine for many different purposes. The oil has been proven to be vulnerary and cicatrising in its effects. The chemicals responsible for this action are calophyllolide and inophyllum in addition to other complex polyphenols.

Abnormal sodium stimulation of carnitine transport in primary carnitine deficiency.

Primary carnitine deficiency is an autosomal recessive disorder of fatty acid oxidation characterized by hypoketotic hypoglycemia and skeletal and cardiac myopathy. It is caused by mutations in the sodium-dependent carnitine cotransporter OCTN2. The majority of natural mutations identified in this and other Na(+)/solute symporters introduce premature termination codons or impair insertion of the mutant transporter on the plasma membrane. Here we report that a missense mutation (E452K) identified in one patient with primary carnitine deficiency did not affect membrane targeting, as assessed with confocal microscopy of transporters tagged with the green fluorescent protein, but reduced carnitine transport by impairing sodium stimulation of carnitine transport. The natural mutation increased the concentration of sodium required to half-maximally stimulate carnitine transport (K(Na)) from the physiological value of 11.6 to 187 mm. Substitution of Glu(452) with glutamine (E452Q), aspartate (E452D), or alanine (E452A) caused intermediate increases in the K(Na). Carnitine transport decreased exponentially with increased K(Na). The E452K mutation is the first natural mutation in a mammalian cotransporter affecting sodium-coupled solute transfer and identifies a novel domain of the OCTN2 cotransporter involved in transmembrane sodium/solute transfer.

Orthopaedic referrals from a cardiothoracic transplant population.

In this study we audited the orthopaedic referrals from the cardiothoracic transplant population at Wythenshawe Hospital, South Manchester. A total of 33 referrals in 29 patients were made during the period of study. The referrals represented 10.3% (33/321) of the transplant population. However, the rate of referral per postoperative year was 37.9/1000, which was of a similar order to that of the general population. The diagnosis at referral was activity related in 24 (72.7%) referrals, with one-half of these being related to some form of sporting activity. Complications of immunosuppression may have contributed in up to 15 (45.4%) of referrals. We believe that musculoskeletal problems after cardiothoracic transplantation do not place an excessive burden on our orthopaedic department and that the pattern of referrals indicates that the transplant programme is a success.

Spinal osteomyelitis presenting with a life-threatening pleural empyema.

STUDY DESIGN: This case report illustrates a rare presentation of spinal osteomyelitis that initially manifested as a life-threatening pleural empyema leading to misdiagnosis. OBJECTIVES: A high index of suspicion is required to make the correct diagnosis of spinal osteomyelitis, especially with unusual presentations. Appropriate antibiotic management should be commenced immediately the diagnosis is made. SUMMARY OF BACKGROUND DATA: A review of the literature reveals five previous cases of vertebral osteomyelitis associated with pleural effusions. In three of these, the effusions were reactive and sterile. There is only one previous case of a pleural empyema related to primary spinal osteomyelitis. There also is one case report of vertebral osteomyelitis presenting as a mediastinal abscess. METHODS: A case is presented of a man thought to have bronchogenic carcinoma with a destructive vertebral metastasis who was sent for palliative radiation therapy. A life-threatening pleural effusion subsequently developed, and after additional investigation, he was found to have spinal osteomyelitis with a pleural empyema. RESULTS: The empyema was drained through an indwelling chest tube, and the patient was administered appropriate antibiotics. He made a complete and uneventful recovery. CONCLUSIONS: The case illustrates a rare presentation of spinal osteomyelitis. It exemplifies the dictum that if a malignant disease is suspected, every effort has to be made to establish a histologic diagnosis to prevent inappropriate management and the potentially devastating consequences of an incorrect diagnosis. It also high-lights the difficulties in diagnosis of vertebral osteomyelitis with empyema. With correct management, the prognosis is excellent.

An integrated case management model: developing standards, evaluation, and outcome criteria.

Case management has become an important strategy in responding to the complex physical and social needs of persons with human immunodeficiency virus (HIV) disease. Yet, inconsistent implementation and professional turf guarding, based on disciplinary differences, have rendered traditional models ineffective. AID Atlanta has adopted an integrated, multisite approach to case management that uses the expertise of social workers, nurses, pastoral counselors, and therapists to develop client-centered plans of care across the continuum of need. This article presents the integrated model and describes the standards of service and outcome evaluation criteria that underpin this model. The impact of nursing expertise on the development of the model is discussed.

The relationship of increased capillary filtration and bone formation.

The effect of functional activity on bone formation and interstitial fluid space in a standardized tibial defect was measured in 19 dogs with one hind limb elevated and the other weight bearing and in 15 dogs bearing weight on all four legs. The interstitial fluid space (V(isf)) of the woven bone of the weight-bearing defect was larger than that in the elevated legs at seven and 14 days. By 28 days, this difference disappeared. In a third group of six dogs, medullary canal pressure was measured in the immobilized and weight-bearing tibias. The pressures were higher in the weight-bearing tibiae at two, three, four, and five days. Because the increase in V(isf) in the weight-bearing defects coincided with the onset of woven bone formation in the defects and an increase in medullary canal pressure, an increase in venous pressure could increase capillary pressure and capillary filtration. Such an increase in filtration might cause the larger V(isf) in the weight-bearing defects and better capillary perfusion of precursor cells of the osteoblast. A hypothesis is that increased fluid flow from increased capillary filtration might produce streaming potentials, a possible signal for increased cellular activity.

Isolated tuberculosis of a skeletal muscle.

A case is described of tuberculosis in the muscle belly of abductor pollicis longus in a 25-year-old Asian woman. The complaint was of swelling and, as there was no evidence of tuberculosis elsewhere, the diagnosis was not made until the lump was explored surgically.

Effect of weight-bearing on healing of cortical defects in the canine tibia.

UNLABELLED: It has been generally accepted that mechanical stimulation is an important factor in the promotion of formation of bone. Fracture-healing consists of periosteal bridging of the fracture, which achieves stability, and proliferation of endosteal bone to fill the defects between the ends of the bone. To evaluate the effect of weight-bearing on bone-healing, an operatively created defect in the tibial cortex was chosen as an experimental model. In one set of dogs (Group 1), a bilateral defect in the tibial cortex was created and weight-bearing was permitted on one tibia but not on the opposite one. In Group 2, a bilateral defect in the tibial cortex was made and weight-bearing was allowed on both tibiae. A third group of dogs of similar age (Group 3) had no tibial defects. Quantitative histomorphometry was used to measure formation and porosity of bone. Weight-bearing was measured with both static and dynamic techniques. Significantly less woven bone formed in the defects in the non-weight-bearing tibiae than in the weight-bearing tibiae. This appeared to be due to a disuse response in the underloaded tibiae, in which less bone formed, rather than to the formation of more bone in the weight-bearing tibiae. The data suggest that weight-bearing is a permissive factor, not a stimulus, for formation of woven bone in a tibial defect. CLINICAL RELEVANCE: This animal model supports the concept that lack of weight-bearing decreases the amount of woven bone that is formed in a healing tibial defect. The results of this study indicate that weight-bearing increases the formation of bone in fracture-healing.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of displaced subcapital fractures with the Charnley-Hastings hemiarthroplasty.

Between December 1982 and June 1986, 98 displaced subcapital femoral neck fractures were treated using the Charnley-Hastings bipolar hemiarthroplasty. Although the patients were elderly, often with associated medical problems, the operation was well tolerated and the mortality at one and six months was 14.4% and 24.5% respectively. Fifty-four hips were reviewed after an average follow-up of 33 months; 64.8% of patients had a good or excellent result. The fair or poor results were seen mainly in patients with poor pre-operative mobility and multiple medical problems. A significant cause of morbidity was dislocation (two interprosthetic) which occurred in six hips. There were two cases of deep sepsis but neither patient was fit for further surgery. There were no cases of acetabular erosion requiring revision surgery.

Parathyroid hormone effects on skeletal exchangeable calcium and bone blood flow.

The effects of alterations in serum calcium levels on the volume of distribution of a calcium tracer in bone and on bone blood flow were investigated in dogs by manipulation of parathyroid status. The volume of distribution increases with increasing serum calcium. This implies that there is a concentration-dependent binding mechanism in the extravascular space of bone, which is not saturated at the levels of serum calcium achieved in these experiments. The skeletal exchangeable calcium was increased in hypercalcemic dogs and decreased in hypocalcemic dogs. Cancellous bone contains proportionately more exchangeable calcium than cortical bone. Bone blood flow was decreased by 50% 15 min after injection of a bolus of parathyroid hormone (PTH) but returned to control values by 240 min. Fifty-two hours after the induction of hypercalcemia with repeated doses of PTH, there was no difference in blood flow over control animals.

Cortical and cancellous bone: age-related changes in morphologic features, fluid spaces, and calcium homeostasis in dogs.

The changes in cortical and cancellous bone that occur with aging were studied by measuring morphologic and physiologic variables for both types of bone in dogs. The percentage area of cortical and cancellous bone, rate of bone formation, vascular volume, bone water, and volume of distribution of calcium tracer all showed statistically significant changes at the time of bone maturity. Canine cortical bone cell volume progressively decreased with advancing age, and cancellous bone cell volume significantly decreased between adult and old dogs. The volume of distribution technique can be used to determine the relative contributions of cortical and cancellous bone to the total body exchangeable calcium ion pool.

A radiological assessment of interprosthetic movement in the Charnley-Hastings hemiarthroplasty.

Forty-six patients with acute displaced subcapital fractures of the femur were treated between December 1982 and December 1984 with Charnley-Hastings bipolar prostheses. The interprosthetic movement in 23 patients was assessed radiologically at least 1 year after surgery. Four patients (17.4 per cent) had no interprosthetic movement in abduction but the remainder (82.6 per cent) had some movement, although only 3 patients (13 per cent) had more than 5 degrees of abduction within the prosthesis.

Transrectal ultrasound in the diagnosis of prostate cancer: location, echogenicity, histopathology, and staging.

Adenocarcinoma of the prostate produces specific ultrasonic findings that can be used in diagnosis. We have examined 211 patients using transrectal ultrasound in both the sagittal and axial planes. Thirty-three carcinomas were detected, and 31 histologically confirmed; 24 by needle biopsy, six by transurethral resection, one by total prostatectomy, and two by the demonstration of distant metastases. On ultrasound, all of the carcinomas were less echogenic than normal prostate. All appeared to originate in the peripheral zone of the prostate and produced asymmetry of the gland. The majority of carcinomas in this series showed capsular involvement and ten penetrated and extended beyond the prostatic capsule. The results of this series indicate that transrectal ultrasound can be used to detect cancer of the prostate gland. Ultrasound demonstrated the extent of tumor involvement and enabled accurate staging of these cancers.

Urinary protein profiles after burn injury.

A study of the change of urinary protein excretion has been made in 26 patients followed from the time of admission to time of discharge from the Yorkshire Regional Burn Centre (7-200 days). Total protein, IgG and albumin (as indicators of glomerular function) and alpha 1-microglobulin, beta 2-microglobulin, retinol binding protein and N-acetyl-beta-D-glucosaminidase (as indicators of proximal tubular function) as well as the patterns on SDS polyacrylamide gel electrophoresis were examined. Patients were divided into three groups according to their urinary protein profiles. The first group was 3 patients who showed little or no evidence of proteinuria; the second group consisted of 7 patients who showed a mild and transient tubular proteinuria, all of whom recovered normal function within one week. The third group, 16 patients, developed moderate to severe proteinuria usually started as a mixed pattern of glomerular and tubular proteinuria, characterized by the excretion of a high level of total protein. After a few days, this pattern changed to a typical tubular proteinuria and the latter could last for as long as 200 days; in some of these patients a secondary increase of low molecular weight protein excretion occurred either due to a latent renal complication or induced by the administration of aminoglycosides. There is a close correlation between the intensity and patterns of the proteinuria and the severity and clinical progress of the burn.