Role of the Circadian Clock in the Metabolic Syndrome and Nonalcoholic Fatty Liver Disease.

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in industrialized nations and is strongly associated with the metabolic syndrome. The prevalence of NAFLD continues to rise along with the epidemic of the metabolic syndrome. Metabolic homeostasis is linked to the circadian clock (rhythm), with multiple signaling pathways in organs regulated by circadian clock genes, and recent studies of circadian clock gene functions suggest that disruption of the circadian rhythm is associated with significant morbidity and mortality, including the metabolic syndrome. In the industrialized world, various human behaviors and activities such as work and eating patterns, jet lag, and sleep deprivation interfere with the circadian rhythm, leading to perturbations in metabolism and development of the metabolic syndrome. In this review, we discuss how disruption of the circadian rhythm is associated with various metabolic conditions that comprise the metabolic syndrome and NAFLD.

A novel computational method for evaluating osteochondral autografts in distal radius reconstruction.

BACKGROUND: We describe a novel computational method for assessing the fit of an osteochondral graft. We applied our software to five normal wrist computed tomography (CT) scans to determine the fit of the scaphoid to the lunate fossa of the distal radius. METHODS: CT scans of five wrists were digitally rendered. The capitate facet of the scaphoid was fit to the lunate fossa of the distal radius using custom software based on the iterative closest point (ICP) algorithm. This approach iteratively determines the optimal position of a model surface to minimize the sum of squares of distances from all points on a target surface. The fit of the two surfaces was reported by calculating the mean residual distance (MRD) between each point on one surface and its nearest neighbor on the other. RESULTS: The MRD for the five subjects was found to be 0.25 mm, with 82.8-98.3 % of the articular surfaces within 0.5 mm of each other. CONCLUSIONS: We have developed a software algorithm for comparing two articular surfaces to test fit for a proposed joint reconstruction. The software is versatile and may be applied to any bony surface to identify new graft donor sites. The fit assessment renders a richer, three-dimensional understanding of the fit of the graft as compared to traditional two-dimensional assessments. LEVEL OF EVIDENCE: Decision analysis, Level V.

Radiographic evaluation of the modified Brunelli technique versus a scapholunotriquetral transosseous tenodesis technique for scapholunate dissociation.

PURPOSE: To compare reduction of the scapholunate articulation using a transosseous tenodesis through the scaphoid, lunate, and triquetrum (SLT) with the modified Brunelli technique (MBT) in a cadaver model, as measured by scapholunate (SL) angle and diastasis on radiographs. METHODS: Twelve fresh-frozen cadaveric wrists were radiographically examined in a neutral posture, ulnar deviation, and clenched fist position. The SL angle and diastasis were recorded in each position with the SL ligament intact, after sectioning the ligament and secondary restraints, and after reconstruction by either the MBT (6 wrists) or SLT technique (6 wrists). Wrists were cycled through their maximum flexion and extension arc 100 times to simulate wrist motion after ligament sectioning and reconstruction. RESULTS: After sectioning and cycling, all wrists demonstrated radiographic evidence of SL diastasis. After ligament reconstruction and cycling, there was no statistically significant difference in diastasis in the MBT reconstructions compared with the SLT reconstructions (3.0 vs 2.4 mm). The SLT group demonstrated better maintenance of the restored SL angle than the MBT reconstructions. CONCLUSIONS: In this cadaveric model, both MBT and SLT reconstructions restored anatomic parameters in the SL joint, with correction of SL diastasis and SL angle. Future studies to assess the clinical outcomes of SLT tenodesis in patients with chronic SL disruptions are important. CLINICAL RELEVANCE: The SLT tenodesis, with a central biologic tether along the SL axis and dorsal reinforcement, may prove clinically useful.

Is a silastic radial head still a reasonable option?

BACKGROUND: The importance of the radial head to elbow function and stability is increasingly apparent. Although preservation of the native radial head is preferred, severely comminuted fractures may necessitate resection or arthroplasty. Silastic radial head arthroplasty has been condemned on the basis of several sporadic reports of silicone synovitis. However, problems of "overstuffing," cartilage wear, and motion loss are becoming apparent with metal prostheses, indicating this also is not an ideal solution. Thus, the choices remain controversial. QUESTIONS/PURPOSES: We asked whether intact or reconstructed primary elbow stabilizers permit use of silastic radial head implants without fragmentation, failure, and silicone synovitis. METHODS: We retrospectively reviewed 23 patients with unreconstructable radial head fractures who were treated with silastic radial head arthroplasty and concomitant repair and/or reconstruction of the medial ulnar collateral ligament and/or lateral ulnar collateral ligament. Analysis included range of motion, pain, stability, and radiographic assessments; Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire; and Mayo Elbow Performance Score (MEPS). The minimum followup was 16 months (average, 69.6 months; range, 16-165 months). RESULTS: At last followup, the mean elbow flexion was 145°, extension 11°, supination 80°, and pronation 83°. The mean MEPS score was 88.9. The mean DASH score was 11.8. There were eight reoperations, none resulting from failure of the radial head implants. CONCLUSIONS: These results demonstrate silastic radial heads can be used with low complication rates and without evidence of synovitis when concomitant elbow ligament repair or reconstruction is performed. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

The emerging role of elbow arthroscopy in chronic use injuries and fracture care.

Arthroscopy is emerging as an invaluable tool for diagnosing and treating elbow pathology. In addition to the advantages of less scarring, decreased risk of infection, less postoperative pain, and a more thorough visualization of the elbow joint, arthroscopy is particularly well suited to the treatment of athletes trying to minimize rehabilitation and inactivity. Indications for elbow arthroscopy now extend well beyond diagnosis and loose body removal, and include the treatment of impingement, arthritis, contractures, fragment stabilization for osteochondritis dessicans, and treatment of certain fractures. This article reviews the basic principles and techniques of elbow arthroscopy and their application to common sports-related conditions, such as valgus overload syndrome, medial collateral ligament insufficiency, and the various causes of lateral elbow pain. Newer applications of elbow arthroscopy in fracture care are addressed as well.

The relationship between greater tuberosity osteopenia and the chronicity of rotator cuff tears.

This study investigated whether a relationship exists between greater tuberosity osteopenia and chronicity of rotator cuff tears. In a retrospective study, anteroposterior radiographs of 28 shoulders in 27 patients who had undergone surgical repair for rotator cuff tears were reviewed. Greater tuberosity osteopenia scores were created using National Institutes of Health digital image software. There was no significant difference in the mean age between patients with minimal to mild rotator cuff tear retraction (63.1 +/- 6.14 years) and patients with moderate to severe rotator cuff tear retraction (63.4 +/- 9.76 years; P = .77). Of the 13 patients with minimal to mild rotator cuff tear retraction, 10 (77%) were women and 3 (23%) were men. Of 14 patients (50%) with moderate to severe rotator cuff tear retraction, 7 were men and 7 were women. The mean greater tuberosity osteopenia score in the 15 patients with moderate to severe retraction (0.48 +/- 0.095) was significantly less than the greater tuberosity osteopenia score in the 13 patients with minimal to mild retraction (0.58 +/- 0.135; P < .05). Furthermore, the mean greater tuberosity osteopenia score in 6 patients with chronic retracted rotator cuff tears (0.48 +/- 0.125) was significantly less than in the 6 patients with acute minimally retracted tears (0.64 +/- 0.119, P < .05). There were significantly greater osteopenic changes in the greater tuberosity in patients with chronic retracted rotator cuff tears. The greater tuberosity osteopenia may affect anchor pullout strength and the healing biology that influences overall rotator cuff repair healing rates.

Caenorhabditis elegans: plague bacteria biofilm blocks food intake.

Bubonic plague is transmitted to mammals, including humans, by the bites of fleas whose digestive tracts are blocked by a mass of the bacterium Yersinia pestis. In these fleas, the plague-causing bacteria are surrounded by an extracellular matrix of unknown composition, and the blockage depends on a group of bacterial genes known as the hmsHFRS operon. Here we show that Y. pestis creates an hmsHFRS-dependent extracellular biofilm to inhibit feeding by the nematode Caenorhabditis elegans. Our results suggest that feeding obstruction in fleas is a biofilm-mediated process and that biofilms may be a bacterial defence against predation by invertebrates.