Effects of anatomic variability on blood flow and pressure gradients in the pulmonary capillaries.

A theoretical model is developed to simulate the flow of blood through the capillary network in a single alveolar septum. The objective is to study the influence of random variability in capillary dimension and compliance on flow patterns and pressures within the network. The capillary bed is represented as an interconnected rectangular grid of capillary segments and junctions; blood flow is produced by applying a pressure gradient across the network. Preferred flow channels are shown to be a natural consequence of random anatomic variability, the effect of which is accentuated at low transcapillary pressures. The distribution of pressure drops across single capillary segments widens with increasing network variability and decreasing capillary transmural pressure. Blockage of one capillary segment causes the pressure drop across that segment to increase by 60%, but the increase falls to < 10% at a distance of three segments. The factors that cause nonuniform capillary blood flow through the capillary network are discussed.

The outcome of all-inside meniscal repair with relation to previous anterior cruciate ligament reconstruction.

BACKGROUND: Arthroscopically assisted all-inside meniscal repair has become a popular treatment for meniscal tears. Previous studies have suggested a beneficial effect of concomitant anterior cruciate ligament reconstruction on meniscal repair outcomes. The effect of prior cruciate ligament reconstruction (predating the meniscal injury) on meniscal repair success is unreported. The aim of this study was to assess the success of meniscal repair in our practice. Further aims were to analyze the effect of concomitant- and past-anterior cruciate ligament reconstruction on meniscal repair outcomes. METHODS: Retrospective review of all patients undergoing arthroscopic meniscal repair during a 53 month period was performed. Mean followup was 13.5 months (mean 6-50). The primary outcome measure was meniscal reoperation. RESULTS: Sixteen of 104 patients required reoperation, giving an overall meniscal repair success rate of 85%. Patients undergoing concomitant anterior cruciate ligament reconstruction enjoyed significantly improved outcomes (91%, p=0.049), while those with a past history of anterior cruciate ligament reconstruction had significantly worse meniscal repair success rates (63%, p=0.016). CONCLUSIONS: Arthroscopic meniscal repair in a selected patient group offers good success rates, especially when performed with concomitant anterior cruciate ligament reconstruction. We have identified a subgroup of patients, those with a past history of anterior cruciate ligament reconstruction predating the meniscal injury, who appear to have relatively poor outcomes from meniscal repair. Potential reasons for this finding are discussed. LEVEL OF EVIDENCE: Level IV, case series.

The costs of late detection of developmental dysplasia of the hip.

PURPOSE: Debate currently exists regarding the economic viability for screening for developmental dysplasia of the hip in infants. METHODS: A prospective study of infant hip dysplasia over the period of 1998-2008 (36,960 live births) was performed to determine treatment complexity and associated costs of disease detection and hospital treatment, related to the age at presentation and treatment modality. The involved screening programme utilised universal clinical screening of all infants and selective ultrasound screening of at-risk infants. RESULTS: One hundred and seventy-nine infants (4.8/1,000) presented with hip dysplasia. Thirty-four infants presented late (> 3 months of age) and required closed or open reduction. One hundred and forty-five infants presented at < 3 months of age, 14 of whom failed early Pavlik harness treatment. A detailed cost analysis revealed: 131 early presenters with successful management in a Pavlik harness at a cost of £601/child; 34 late presenters who required surgery (36 hips, 19 closed/17 open reductions, one revision procedure) at a cost of £4,352/child; and 14 early presenters with failed management in a Pavlik harness requiring more protracted surgery (18 hips, four closed/14 open reductions, seven revision procedures) at a cost of £7,052/child. CONCLUSIONS: Late detection causes increased treatment complexity and a sevenfold increase in the short-term costs of treatment, compared to early detection and successful management in a Pavlik harness. DISCUSSION: Improved strategies are needed for the 10 % of early presenting infants who fail Pavlik harness treatment and require the most complex and costly interventions.

Lipid-laden macrophage index in healthy canines.

BACKGROUND: The quantity of lipids in alveolar macrophages is used clinically as an indicator of aspiration, which is associated with increased lung inflammation. This is determined in the macrophages obtained from bronchoalveolar lavage (BAL) and is expressed as lipid-laden macrophage index (LLMI). Although there is ample data on LLMI in human subjects, there is no published data pertaining to the baseline measures of the LLMI in canines, which are extensively used for experimental studies on gastroesophageal reflex (GER) and airway diseases. Primary aim of the present study was to collect data pertaining to the cytology and LLMI in BAL fluids obtained from healthy dogs. MATERIALS AND METHODS: Eight dogs underwent a bronchoscopy with BAL collection, and esophageal pH monitoring to determine the reflux index (RI). The BAL fluid was processed and reviewed under a microscope to determine the proportions of the various cell types and the LLMI. RESULTS: The median RI among the subjects was found to be 0.6 (0.0, 1.2). The BAL cytology analysis showed 77.5% (71.0, 83.5) macrophages, 21.0 (13.0, 24.5) lymphocytes and 2.5 (1.5, 5.0) neutrophils. The median LLMI was found to be 156 (111, 208). CONCLUSIONS: Although the differential cell counts in the dogs' BAL fluid was comparable to that of other experimental animals and humans, the LLMI was distinctly higher than the corresponding value reported for other species. As LLMI is a valuable modality for evaluation of intrapulmonary pathophysiology, these data on LLMI can be used as a species-specific standard for canine subjects used for experimental studies on GER and airway diseases.

The surgical management of renovascular hypertension in children and young adults.

OBJECTIVES: To assess the outcome and durability of operative revascularisation in young patients with renovascular hypertension. DESIGN: Retrospective study. METHOD: The records of all young patients (under 25 years) operated on for renovascular hypertension at St Mary's Hospital 1988-1998 were reviewed. We assessed the aetiology of hypertension, operations performed, effect of treatment on blood pressure, renal function and requirement for antihypertensive medication during follow-up. RESULTS: Ten patients were identified who had been considered for surgery, of median age 16 years (22 months to 22 years). Fibromuscular dysplasia was present in five patients, mid-aortic syndrome (MAS) in four and neurofibromatosis in one. Operations performed were aortorenal bypass (three), aorto-aortic bypass+/-renal bypass (three), splenorenal bypass (one) and autotransplantation (one). Of the three patients treated by balloon angioplasty, only one had a successful result. One patient with MAS is currently awaiting surgery. Over a median follow-up of 24 months (8-144), seven patients are normotensive off all antihypertensive medication. Of two patients on reduced doses of medication, one (splenorenal bypass) required surgical repair of a late (9 years) coeliac stenosis. CONCLUSIONS: The surgical treatment of renovascular hypertension in carefully selected young patients gives durable results. Blood pressure is well controlled long-term, and the need for antihypertensive medication is removed altogether in the majority of patients.