Mechanics of Metacarpophalangeal Joint Extension

PURPOSE

It is a common belief that extension of the metacarpophalangeal (MCP) joint of the finger is achieved via the sagittal bands acting as a sling or lasso to attach the extensor tendon to the base of the proximal phalanx. The aim of this study was to test the hypotheses that (1) division of the sagittal bands reduces extension force or torque of the MCP joint, and (2) division of the extensor tendon distal to the sagittal band will not affect the extension force or torque of the MCP joint.

METHODS

Ten cadaver limbs were secured to a jig to allow for testing of the extension force of the MCP joints of the index, middle, and ring fingers. A 1-kg load was applied to the forearm extensor digitorum communis tendon and the extension force was measured with the MCP joint positioned at 0° (neutral extension) and again at 45° flexion. These measurements were repeated after the sagittal bands were divided in 15 specimens; in the other 15 specimens, the extensor tendon was divided just distal to the sagittal bands.

RESULTS

After sagittal band division, extension force was similar in the 2 groups (0.11 N reduction after division with the MCP joints in neutral and 0.14 N in 45° flexion). There was significantly less extension force after division of the extensor tendon in both joint positions (0.95 N reduction after division in neutral extension and 0.66 N in 45° flexion).

CONCLUSIONS

The sagittal bands do not primarily extend the MCP as a sling or lasso. The extensor tendon continuation to the extensor hood and middle phalanx is the major extension motor. The MCP joint is extended by the torque generated by the extensor tendon passing the joint carrying a force and possessing an extension moment arm.

CLINICAL RELEVANCE

This principle should be correctly understood in the literature to ensure that clinical decisions related to injury and/or repair of the extensor tendon and sagittal bands are based on a sound understanding of their mechanics.

Measurement of inflammatory markers in the breath condensate of children with cystic fibrosis

Identifying noninvasive markers of pulmonary inflammation would be useful in assessing new therapies in children. Breath condensate is a simple and potentially acceptable sample medium even in small children. The technique has previously been used in adults, but not children with cystic fibrosis. The technique was assessed in 36 children with cystic fibrosis (mean age 10.4 yrs) and 17 control subjects, analysing samples for nitrite, interleukin(IL)-8 and salivary and nasal contamination. Correlations were made between levels of the inflammatory markers and forced expiratory volume in one second/forced vital capacity, chest radiograph score and use of inhaled steroids. On samples without significant contamination (<10 u x L(-1) amylase) nitrite was detected in 93% of samples at a median concentration of 3.0 microM compared with 50% of control samples at a median of 0.5 microM. Condensate amylase levels did not correlate with the nitrite value obtained (r=0.31). IL-8 was detected in 33% of CF samples. Breath condensate is an acceptable method of sample collection in children. Nitrite was raised in breath condensate from patients with cystic fibrosis when compared with control subjects.

Intestinal inflammation in cystic fibrosis

BACKGROUND

There is controversy about whether the inflammatory response observed in the cystic fibrosis (CF) lung occurs secondary to bacterial infection or is caused by a dysregulation of the inflammatory response associated with the basic cellular defect of CF.

AIMS

To study the inflammatory response in the gastrointestinal tract of children with CF; and to investigate whether there is increased inflammation in the gastrointestinal tract of CF children with fibrosing colonopathy.

METHODS

Whole gut lavage was performed on 21 pancreatic insufficient children with CF, who were clinically well, five children with CF and fibrosing colonopathy, and 12 controls. Intestinal outputs of plasma derived proteins (albumin, alpha(1) antitrypsin, IgG), secretory immunoglobulins (IgA and IgM), cellular constituents (eosinophil cationic protein and neutrophil elastase), and cytokines (interleukin 8 and interleukin 1beta) were measured.

RESULTS

Compared to controls, the 21 CF patients, with no intestinal complications, had increased intestinal outputs of albumin, IgG, IgM, eosinophil cationic protein, neutrophil elastase, interleukin 1beta, and interleukin 8. Similar values were obtained for the CF patients with fibrosing colonopathy.

CONCLUSIONS

These data suggest that there is immune activation in the gastrointestinal mucosa of children with cystic fibrosis, which may result from the basic cellular defect. Fibrosing colonopathy does not appear to be associated with increased inflammation.

Recombinant DNase in cystic fibrosis: a protocol for targeted introduction through n-of-1 trials. Scottish Cystic Fibrosis Group

Nebulized recombinant human deoxyribonuclease (DNase) reduces sputum viscosity and improves lung function in some cystic fibrosis patients, but individual responses are unpredictable. The aim of this study was to investigate how DNase can be targeted to those cystic fibrosis patients who would benefit most. The Scottish Cystic Fibrosis Group agreed on a randomized, double-blind, placebo-controlled n-of-1 assessment protocol. Patients underwent a maximum of three 4-week assessment periods (2 weeks saline, 2 weeks DNase each). Measurements performed at hospital (exercise, oximetry and spirometry) and home (symptom scores) were used to derive a scoring system to discriminate maximally between DNase and placebo effects. The data on 89 4-week assessments in 52 patients were reported. Twenty-four patients have completed the assessment process (12 responders and 12 nonresponders) to date. Forced expiratory volume in one second (FEVI) was the best discriminator of response, rising by >200 mL after DNase in 33 of 89 (37%) assessments compared with 3 of 89 (3%) after saline. N-of-1 trials, while laborious, permitted genuine treatment effects to be quantified within individuals with confidence, permitting appropriate treatment targeting. This provides a model of how other new expensive therapies may be introduced to maximize patient benefit.

Direct assessment of gastrointestinal inflammation and mucosal immunity in children with cystic fibrosis

Fibrosing colonopathy is a recently described complication of cystic fibrosis, of unknown aetiology but possibly related to treatment with high-dose pancreatic enzyme supplements. We have used a whole gut perfusion technique to study subclinical gut inflammation in cystic fibrosis patients; concentrations of haemoglobin, IgG, albumin, alpha-1-antitrypsin, granulocyte elastase, IL1 beta, and IL8 were measured in whole gut lavage fluid: 23 tests were performed in 17 children with cystic fibrosis (20 elective tests, three lavages to treat distal intestinal obstruction syndrome (DIOS)). None has had fibrosing or haemorrhagic colitis. There were 12 tests in control children with constipation or precolonoscopy. Moderately abnormal results were obtained for many of the parameters studied, in specimens from all the cystic fibrosis children; however there were no significant differences between tests on high-dose and low-dose enzyme supplements of the same brand in the five children who had duplicate tests performed electively. The lavage fluid specimens from two cystic fibrosis children were strikingly abnormal in all tests apart from haemoglobin and alpha-1-antitrypsin. These were two of the three children with DIOS, and were also the only cases in the series taking Nutrizym 22. These data suggest that the majority of cystic fibrosis children, including those on high-dose enzyme supplements, do not have clinically significant colitis, but that there is subclinical mucosal inflammation in a minority (two of 17 in this series), for which DIOS and/or Nutrizym 22 treatment may be risk factors. Alternatively, inflammation and dysmotility in the proximal colon may be directly produced by a drug or other agent, producing a clinical syndrome indistinguishable from DIOS. Tests for indices of inflammation in gut lavage fluid offer a new approach to the detection and measurement of iatrogenic intestinal and colonic injury.

Gut inflammation in children with cystic fibrosis on high-dose enzyme supplements

We used a whole-gut perfusion technique to study subclinical gut inflammation in children with cystic fibrosis (18 elective tests, three lavages to treat distal intestinal obstruction syndrome); and in 12 control children with constipation or pre-colonoscopy. We assayed for haemoglobin, IgG, albumin, alpha-1-antitrypsin, granulocyte elastase, interleukin-1 beta (IL-1 beta) and IL-8 concentrations in whole-gut lavage fluid. Results for two children with distal intestinal obstruction syndrome, the only children in the series taking Nutrizym 22, were strikingly abnormal. This new test has revealed subclinical gut mucosal inflammation in a minority of CF children, for which distal intestinal obstruction syndrome, Nutrizym 22 treatment, or both, may be risk factors.

An audit of medical paediatric out-patient appointments and letters

All medical out-patient appointments of a firm of three consultants at the Royal Hospital for Sick Children were reviewed over a four week period. Of 758 appointments initially offered, 490 (64%) patients attended; 19% of patients cancelled and 17% did not attend without cancelling. Delay from referral to attendance ranged from 0 to 9 weeks. The characteristics of those patients experiencing prolonged registrar-only follow-up are described. The content of subsequent letters to family practitioners was usually adequate compared to accepted standards. Delays in dictation of letters were usually short in comparison to delays in typing. Such delays and the intervals between consultant review of out-patients may prove costly to providers. Potential improvement strategies are discussed.

Riboflavin-responsive ethylmalonic-adipic aciduria

A patient presenting with a condition resembling Reye's syndrome was found to have a urinary organic acid excretion pattern similar to those previously described in a single patient with ethylmalonic-adipic aciduria. The present patient responded clinically to riboflavin supplementation and his fibroblasts, when cultured in riboflavin-depleted medium, showed an abnormal reduction in the rate of butyrate oxidation.