Quantification of rotator cuff tear geometry: the repair ratio as a guide for surgical repair in crescent and U-shaped tears

Surgical repair of symptomatic, retracted rotator cuff tears unresponsive to non-operative treatments requires closure of the tear without undue tension and reattaching the torn tendon to its former insertion site. In this study, the length of the torn tendon edge was hypothesized to be longer than the length of the humeral insertion site. The objective of this study was to quantify the discrepancy in length of the torn tendon edge and the length of the avulsed humeral insertion site. Full thickness, rotator cuff tears that were found in twelve fresh frozen cadaver shoulders was studied. The length of the torn tendon edge, the length of the avulsed humeral insertion site and the retraction were measured using digital calipers. Each tear involved the supraspinatus and the infraspinatus was additionally torn in six. The size of the tear was medium in eight and large in four. The length of the torn tendon edge was always longer than the length of the avulsed humeral insertion site. Retraction was 29.9 ± 9.3 mm (range 21–48 mm). The repair ratio, defined as the ratio of length of torn tendon edge to the length of avulsed humeral insertion site, was 2.6 ± 0.4 (range 2.1–3.5). As only the length of the torn tendon edge equal to the length of the avulsed humeral insertion site can be repaired to bone, a repair ratio more than one precludes a simple repair and an additional repair technique such as margin convergence would be necessary for the remaining unapproximated torn tendon edge in rotator cuff tears. Repair ratio may aid in selection of the surgical repair technique of these rotator cuff tears

The genomes of two key bumblebee species with primitive eusocial organization

Background: The shift from solitary to social behavior is one of the major evolutionary transitions. Primitively eusocial bumblebees are uniquely placed to illuminate the evolution of highly eusocial insect societies. Bumblebees are also invaluable natural and agricultural pollinators, and there is widespread concern over recent population declines in some species. High-quality genomic data will inform key aspects of bumblebee biology, including susceptibility to implicated population viability threats. Results: We report the high quality draft genome sequences of Bombus terrestris and Bombus impatiens, two ecologically dominant bumblebees and widely utilized study species. Comparing these new genomes to those of the highly eusocial honeybee Apis mellifera and other Hymenoptera, we identify deeply conserved similarities, as well as novelties key to the biology of these organisms. Some honeybee genome features thought to underpin advanced eusociality are also present in bumblebees, indicating an earlier evolution in the bee lineage. Xenobiotic detoxification and immune genes are similarly depauperate in bumblebees and honeybees, and multiple categories of genes linked to social organization, including development and behavior, show high conservation. Key differences identified include a bias in bumblebee chemoreception towards gustation from olfaction, and striking differences in microRNAs, potentially responsible for gene regulation underlying social and other traits. Conclusions: These two bumblebee genomes provide a foundation for post-genomic research on these key pollinators and insect societies. Overall, gene repertoires suggest that the route to advanced eusociality in bees was mediated by many small changes in many genes and processes, and not by notable expansion or depauperation

INJURY TO THE GLENOHUMERAL CAPSULE DURING ANTERIOR DISLOCATION RESULTS IN DAMAGE TO THE ANTEROINFERIOR CAPSULE SBC2011-53840

INTRODUCTION The glenohumeral joint is the most frequently dislocated major joint in the body with about 2% of the population dislocating their shoulders between the ages of 18 and 70 MATERIALS AND METHODS Six fresh-frozen cadaveric shoulders were dissected down to the glenohumeral capsule. The scapula and humerus were potted in epoxy putty, and a 7x11 grid of strain markers was adhered to the anteroinferior capsule using cyanoacrylate. The markers were positioned on the glenohumeral capsule as previously described The joint was placed at 60° of external rotation (and 60° glenohumeral abduction) and an anterior dislocation was simulated by translating the humerus at least half of the largest anterior-posterior width of the glenoid in the anterior direction using a robotic/universal force-moment sensor testing system. The joint was allowed to translate in 3 degrees of freedom during this motion, but its orientation was fixed. The positions of the markers at dislocation were recorded. After a 30 minute recovery period, the specimen was returned to the reference strain configuration and the positions of the markers were recorded again (non-recoverable strain state). The positions of the markers for the reference strain state, at dislocation and in the nonrecoverable strain state were then input to a finite element analysis package (ABAQUS, Abaqus, Inc.) to calculate the maximum principle strains in all 60 elements of the glenohumeral capsule. A previous study determined the repeatability of the entire testing procedure to be ±3.5% for maximum principle strains The elements of the glenohumeral capsule were then divided into four sub-regions: anterior band glenoid side, anterior band humeral side, axillary pouch glenoid side, and axillary pouch humeral side. The average strains were determined for each sub-region at dislocation and in the non-recoverable strain state. A paired t-test was used to compare the average strain in the glenoid and humeral sub-regions in both the anterior band and axillary pouch. Significance was set at α = 0.05. RESULTS In general, the glenoid side of the capsule experienced higher strains at dislocation than the humeral side ( INJURY TO THE GLENOHUMERAL CAPSULE DURING ANTERIOR DISLOCATION RESULTS IN DAMAGE TO THE ANTEROINFERIOR CAPSULE DISCUSSION In this study, we have determined the strain distribution in the glenohumeral capsule during anterior dislocation of the glenohumeral joint, as well as the non-recoverable strain. Greater strains were found on the glenoid side of the capsule compared to the humeral side in both regions. The amount of non-recoverable strain was not significantly different between the glenoid and humeral sides. Thus, the magnitude of injury throughout the anteroinferior capsule due to anterior dislocation is similar, and is not localized to any specific subregion. Therefore, surgeons should consider plicating the entire anteroinferior capsule when performing repair procedures following anterior dislocation. Malicky and coworkers found similar magnitudes of nonrecoverable strain, even though they only subluxed the glenohumeral joint [3]. Therefore, the magnitude of translation required for subluxation was probably close to our definition of dislocation, and this experimental injury model is reasonable for producing injury to the capsule. The definition of dislocation used in the current study moved the humeral head out of the glenoid, but did not push it over the rim, thus allowing the robotic/universal force-moment sensor testing system to repeat this motion without damaging other structures. During the experimental protocol, only the strains in the midsubstance of the capsule were measured. Therefore, higher strains could have occurred near the insertion sites. In addition, injury to the capsule may have occurred during dislocation in regions outside our strain marker grid. Future studies will determine the mechanical properties of the injured capsule from this study and compare them to the normal capsule. ACKNOWLEDGMENT