Biomedical subjects

Peter Tang

Publications and source records attributed to Peter Tang.

6 recordsLinked to original sources

PubMed2007

Carpal kinematics after proximal row carpectomy.

PURPOSE: Proximal row carpectomy (PRC) is a clinically useful motion-sparing procedure for the treatment of certain degenerative conditions of the wrist. Clinical outcome studies after PRC have shown that wrist flexion-extension averages approximately 60% of that of the contralateral wrist. The purpose of this study was to determine how the kinematics of the wrist are altered after PRC. METHODS: Eight fresh-frozen cadaver forearms were scanned with computed tomography before and after PRC. Forearms were scanned in 5 different wrist positions (neutral, extension, flexion, radial deviations, and ulnar deviation). Wrists were positioned dynamically and then held statically in a custom fixture through forces applied to the 4 wrist flexor/extensor tendon groups. Three-dimensional computer models of the radius, lunate, and capitate were generated from the computed tomographic images, and the kinematics of the capitate and lunate were calculated relative to the neutral position. For the intact wrist, the motion of the capitate was calculated relative to both the lunate (midcarpal motion) and the radius (overall wrist motion) and the motion of the lunate was calculated relative to the radius (radiocarpal motion). After PRC, only the movement of the capitate relative to the radius was calculated, which represents radiocapitate and overall wrist motion. All motions were plotted in 3 dimensions for purposes of qualitative visualization. RESULTS: After PRC, the capitate articulated with the lunate fossa of the radius for all positions in all samples. Overall wrist motion decreased 28%, 30%, 40%, and 12% in flexion, extension, radial deviation, and ulnar deviation, respectively. Motion at the radiocarpal joint after PRC, however, was greater compared with motion at the radiocarpal and midcarpal joints of the intact wrist during flexion and extension. This was not the case in radial deviation because of impingement of the trapezoid on the radial styloid. In radial and ulnar deviation, motion of the capitate head changed from predominantly rotational in the intact wrist (midcarpal joint) to a combination of rotation and translation after PRC (radiocarpal joint). CONCLUSIONS: Removal of the proximal carpal row decreased normal wrist flexion and extension. Although ulnar deviation was preserved, radial deviation was limited by impingement of the trapezoid on the radial styloid. Radiocapitate range of motion after PRC was greater than capitolunate range of motion in the intact wrists. Compared with previously published requirements, wrist range of motion observed after PRC was sufficient for activities of daily living.

Adolescent↗

PubMed2007

HMDB: the Human Metabolome Database.

The Human Metabolome Database (HMDB) is currently the most complete and comprehensive curated collection of human metabolite and human metabolism data in the world. It contains records for more than 2180 endogenous metabolites with information gathered from thousands of books, journal articles and electronic databases. In addition to its comprehensive literature-derived data, the HMDB also contains an extensive collection of experimental metabolite concentration data compiled from hundreds of mass spectra (MS) and Nuclear Magnetic resonance (NMR) metabolomic analyses performed on urine, blood and cerebrospinal fluid samples. This is further supplemented with thousands of NMR and MS spectra collected on purified, reference metabolites. Each metabolite entry in the HMDB contains an average of 90 separate data fields including a comprehensive compound description, names and synonyms, structural information, physico-chemical data, reference NMR and MS spectra, biofluid concentrations, disease associations, pathway information, enzyme data, gene sequence data, SNP and mutation data as well as extensive links to images, references and other public databases. Extensive searching, relational querying and data browsing tools are also provided. The HMDB is designed to address the broad needs of biochemists, clinical chemists, physicians, medical geneticists, nutritionists and members of the metabolomics community. The HMDB is available at: www.hmdb.ca.

Databases, Factual↗

PubMed2006

Does open reduction increase the chance of infection during intramedullary nailing of closed tibial shaft fractures?

OBJECTIVE: To evaluate whether an open technique used to obtain reduction during intramedullary nailing of closed tibial shaft fractures increases the risk of infection, compared to closed reduction and nailing. SETTING: University level 1 trauma center. DESIGN: Retrospective database analysis. PATIENTS/PARTICIPANTS: One hundred seventeen patients with 119 fractures from our trauma database who had sufficient follow-up and met study criteria. The patients were grouped by open versus closed reduction. Only OTA fracture types 42 A to C were included in this study. INTERVENTION: Locked reamed intramedullary nailing for closed tibial shaft fractures accomplished through either open or closed reduction. MAIN OUTCOME MEASUREMENT: The presence or absence of infection as determined by the clinical presentation (erythema, warmth, purulent drainage, fevers, chills, increased pain at the fracture site), indicative laboratory work (complete blood count, erythrocyte sedimentation rate, C-reactive protein), and/or positive culture. RESULTS: There were 85 males and 32 females. The average age was 35.7 years; the average follow-up was 14.3 months. Of the 119 fractures, 79 had closed reduction whereas 40 had open reduction. The open reductions consisted of 13 with a formal incision (>1 cm in length), 22 with percutaneous incisions, and 5 with fasciotomies. There were no infections in the closed reduction group and 2 infections (5%) in the open reduction group. This difference was not statistically significant (P=0.1). The average time to union was 7.0 months in closed reductions and 7.3 months in open reductions. By latest follow-up, 107 fractures had reached union (89.9%), 1 had not (0.8%), and 11 were lost to final follow-up (9.2%). CONCLUSIONS: Limited open techniques can greatly facilitate the reduction of closed tibial shaft fractures but raise concern for infection through exposure of the fracture site. This study found that the rate of infection for open versus closed reductions was higher but not statistically different. Judicious use of open reduction techniques during intramedullary nailing of closed tibia fractures seems to have a minimal risk of infection.

Adult↗

PubMed2005

Dynamic cellular automata: an alternative approach to cellular simulation.

A wide variety of approaches, ranging from Petri nets to systems of partial differential equations, have been used to model very specific aspects of cellular or biochemical functions. Here we describe how an agent-based or dynamic cellular automata (DCA) approach can be used as a very simple, yet very general method to model many different kinds of cellular or biochemical processes. Specifically, using simple pairwise interaction rules coupled with random object moves to simulate Brownian motion, we show how the DCA approach can be used to easily and accurately model diffusion, viscous drag, enzyme rate processes, metabolism (the Kreb's cycle), and complex genetic circuits (the repressilator). We also demonstrate how DCA approaches are able to accurately capture the stochasticity of many biological processes. The success and simplicity of this technique suggests that many other physical properties and significantly more complicated aspects of cellular behavior could be modeled using DCA methods. An easy-to-use, graphically-based computer program, called SimCell, was developed to perform the DCA simulations described here. It is available at http://wishart.biology.ualberta.ca/SimCell/.

Algorithms↗

PubMed2003

A quantitative analysis of valgus torque on the ACL: a human cadaveric study.

The loads needed to elicit a positive pivot shift test in a knee with an anterior cruciate ligament (ACL) rupture have not been quantified. The coupled anterior tibial translation (ATT), coupled internal tibial rotation (ITR), and the in situ force in the ACL in response to a valgus torque, an inherent component of the pivot shift test, were measured in 10 human cadaveric knee specimens. Using a robotic/universal force-moment sensor testing system, valgus torques ranging from 0.0 to 10.0 Nm were applied in nine increments on the intact and ACL-deficient knee in flexion ranging from 0 degrees to 90 degrees. At 15 degrees of knee flexion, the coupled ATT and ITR were significantly increased in the ACL-deficient knee when compared to the intact knee. Coupled ATT increased a maximum of 291% (6.7 mm, p<0.05), while coupled ITR increased a maximum of 85% (5.1 degrees, p<0.05). At 30 degrees, the increases in coupled ATT and ITR were significant at valgus loads of 3.3 Nm and greater with a maximum increase in coupled ATT of 137% (6.3 mm, p<0.05) and a maximum increase in coupled ITR of 38% (3.6 degrees, p<0.05). At 45 degrees, coupled ATT increased significantly (maximum of 69%, 4.4 mm, p<0.05), but only at torques > or =6.7 Nm. The in situ force in the ACL was less than 20 N for all flexion angles when a torque between 3.3 and 5.0 Nm was applied. Low valgus torque elicited tibial subluxation in the ACL-deficient knee with low in situ ACL forces, similar to a positive pivot shift test. Thus, application of a valgus torque may be suitable to evaluate ACL-deficient and ACL-reconstructed knees, since subluxation can be achieved with minimal harm to the ACL graft. This work is important in understanding one load component needed for the pivot shift examination; further studies quantifying other load components are essential for better comprehension of the in vivo pivot shift examination.

Adult↗

PubMed2002

Surgical treatment of hemangiomas of soft tissue.

Hemangioma is one of the most common soft tissue tumors comprising 7% of all benign tumors. The etiology is unclear. Many treatment modalities for the symptomatic deep subdermal or intramuscular hemangioma have been used, but surgical excision is the preferred treatment. During the past 20 years, 89 patients with soft tissue hemangiomas were treated by surgical excision at the authors' institution. This study was done to define the clinical characteristics of pathologically proven hemangiomas and to evaluate the outcome of the operative procedures. Intralesional or marginal excision for symptomatic hemangiomas yields satisfactory results for pain relief, functional recovery, and avoidance of recurrence. According to the data a hemangioma of the soft tissues is a benign lesion in which more aggressive surgery (wide or radical excision) or other modalities such as radiation usually are not warranted.

Adolescent↗