Characterizing Basic and Complex Usage of i2b2 at an Academic Medical Center.

Developed to enable basic queries for cohort discovery, i2b2 has evolved to support complex queries. Little is known whether query sophistication - and the informatics resources required to support it - addresses researcher needs. In three years at our institution, 609 researchers ran 6,662 queries and requested re-identification of 80 patient cohorts to support specific studies. After characterizing all queries as "basic" or "complex" with respect to use of sophisticated query features, we found that the majority of all queries, and the majority of queries resulting in a request for cohort re-identification, did not use complex i2b2 features. Data domains that required extensive effort to implement saw relatively little use compared to common domains (e.g., diagnoses). These findings suggest that efforts to ensure the performance of basic queries using common data domains may better serve the needs of the research community than efforts to integrate novel domains or introduce complex new features.

Biomechanical analysis of bursal-sided partial thickness rotator cuff tears.

BACKGROUND: Treatment of partial thickness supraspinatus tendon tears is controversial with no clearly defined treatment algorithms based on severity of tears. This study aims to evaluate the relationship between depth of partial thickness tears and strain. METHODS: Bursal-sided partial thickness tears were created at 1 mm increments in depth at the anterior portion of the supraspinatus tendon to 3/4 tendon width on ten fresh-frozen shoulder specimens. The supraspinatus muscle was dynamically loaded from 0-50N, and strain recorded at both the anterior and posterior portions of the tendon. RESULTS: Strain in the intact posterior portion increased monotonically with tear depth and supraspinatus force. Strain in the torn anterior portion decreased with increasing tear thickness and loading force. At 60% thickness tear, strain was significantly higher (P = 0.023) in the intact posterior portion compared to intact tendon. As the tear thickness exceeded 50% tendon thickness, the strain in the intact tendon rapidly increased nonlinearly. CONCLUSIONS: Biomechanical results herein suggest increasing potential for tear propagation in the transverse plane with increasing depth of tears, and biomechanically supports repairs of grade III (>50% thickness).

Arthroscopic distal clavicle resection: a biomechanical analysis of resection length and joint compliance in a cadaveric model.

PURPOSE: The purposes of this study were to assess the effects of a distal clavicle resection of less than 5 mm on bony contact and compliance in the acromioclavicular (AC) joint and to localize areas of persistent contact in the AC joint. The hypothesis of this study was that AC contact can be avoided by excising less than 5 mm of bone from the distal clavicle. METHODS: Ten human AC joints underwent compressive loading of the distal clavicle into the acromion after the following: disk excision, distal clavicle resection of 2.5 mm, and distal clavicle resection of 5 mm. The joint resistance force, stiffness, and presence and location of contact were monitored. RESULTS: Excising 2.5 mm or less resulted in no bone-to-bone abutment in 6 of 10 specimens. A 5-mm resection resulted in successful decompression in all specimens. The specimens that required a 5-mm resection had minimal contact after the 2.5-mm resection (inferior-posterior quadrant only). AC joint stiffness decreased significantly with increasing amounts of clavicular resection (P = .01). CONCLUSIONS: A 5-mm distal clavicle resection guaranteed no abutment but decreased joint stiffness. Persistent contact occurred only in the inferior-posterior quadrant of the joint after a 2.5-mm resection. CLINICAL RELEVANCE: These findings support the efficacy of a 5-mm distal clavicle resection for eliminating bony contact but suggest that there is a bony contribution to AC joint stiffness. A resection of 2.5 to 5.0 mm could be adequate if care is taken to excise a greater depth of bone in the inferior-posterior quadrant.

Two-part surgical neck fractures of the proximal part of the humerus. A biomechanical evaluation of two fixation techniques.

BACKGROUND: Successful internal fixation of fractures of the surgical neck of the humerus can be difficult to achieve because of osteopenia of the proximal aspect of the humerus. The purpose of this study was to compare the biomechanical stability of a proximal humeral intramedullary nail and a locking plate for the treatment of a comminuted two-part fracture of the surgical neck in a human cadaver model. METHODS: Twenty-four cadaveric humeri were instrumented with use of either a titanium proximal humeral nail (PHN) or a 3.5-mm locking compression plate for the proximal part of the humerus (LCP-PH). The specimens were matched by bone mineral density and were separated into four experimental groups with six humeri in each: PHN bending, LCP-PH bending, PHN torsion, or LCP-PH torsion. Comminuted fractures of the surgical neck were simulated by excising a 10-mm wedge of bone. Bending specimens were cyclically loaded from 0 to 7.5 Nm of varus bending moment at the fracture site. Torsion specimens were cyclically loaded to +/-2 Nm of axial torque. The mean and maximum displacement in bending, mean and maximum angular rotation in torsion, and stiffness of the bone-implant constructs were compared. RESULTS: In bending, the LCP-PH group demonstrated significantly less mean displacement of the distal fragment than did the PHN group over 5000 cycles (p = 0.002). In torsion, the LCP-PH group demonstrated significantly less mean angular rotation than did the PHN group over 5000 cycles (p = 0.04). A significant number of specimens in the PHN group failed prior to reaching 5000 cycles (p = 0.04). The LCP-PH implant created a significantly stiffer bone-implant construct than did the PHN implant (p = 0.007). CONCLUSIONS: The LCP proximal humeral plate demonstrated superior biomechanical characteristics compared with the proximal humeral nail when tested cyclically in both cantilevered varus bending and torsion. The rate of early failure of the proximal humeral nail could reflect the high moment transmitted to the locking proximal screw-bone interface in this implant. CLINICAL RELEVANCE: The high failure rate in torsion of the proximal humeral nail-bone construct is concerning, and, with relatively osteoporotic bone and early motion, the results could be poor.