Arvind Nana

What’s New in Musculoskeletal Infection: Update on Biofilms

Infections involving orthopaedic surgical implants present unique challenges when compared with infections that do not involve implants. Microorganisms have a high affinity for adhering to foreign materials commonly used in orthopaedics, including cobalt-chromium, titanium, polyethylene, and polymethylmethacrylate (PMMA) cement. When bacteria adhere to these surfaces, they can form a complex structure surrounded by a self-generated extracellular polymeric substance (EPS) matrix formed by multiplex agents of biopolymers consisting of proteins, polysaccharides, lipids, nucleic acids, and humic substances1-3. The term “biofilm” is commonly used to describe this network of microorganisms, a term popularized by Dr. J. William Costerton et al. in 19784.nnBiofilms are formed by a confluence of bacteria commonly encountered in orthopaedic infections. Up to 65% of bacterial infections are caused by biofilm-producing organisms5. Staphylococci, specifically Staphylococcus aureus ( S. aureus ) and Staphylococcus epidermidis ( S. epidermidis ), are the most common biofilm-forming bacteria found in orthopaedics, and, when combined with Pseudomonas aeruginosa ( P. aeruginosa ), they represent nearly 75% of biofilm infections observed in medical devices6. Propionibacterium acnes ( P. acnes ), an organism commonly found in shoulder infections, has also been shown to form biofilm. Biofilms can be composed of a single organism or can be polymicrobial; polymicrobial biofilms are more difficult to eradicate7.nnOnce bacteria adhere to the surface of implants, they may replicate and may form a complex network of microorganisms that communicate with one another via cell-to-cell signaling that facilitates the participation of bacteria in quorum sensing7. Quorum sensing serves as an elementary endocrine system whereby bacteria sense the local cell population density and regulate gene expression by releasing extracellular molecules to facilitate synchronized changes in the bacteria within the biofilm. These transcriptional changes can occur with the exchange of plasmids between bacteria, which can confer genes …

Adult trauma: getting through the night.

There has been a dramatic change in the approach to the treatment of acute musculoskeletal injuries over the past decade. The previous emphasis on so-called “early total care,” which advocated immediate definitive repair of all injuries, has shifted to an approach emphasizing “damage control orthopaedics” for a multiply injured patient. In this new paradigm, definitive repair of fractures is delayed until the patient is stabilized physiologically, associated soft-tissue injuries (if present) have healed, and optimum resources are available. However, there remain situations in which immediate treatment may be needed, such as in a patient with a pelvic ring injury and hemodynamic instability, a compartment syndrome, or an irreducible joint dislocation with associated neurovascular compromise. In these circumstances, there may not be time to safely transfer the patient to a specialized center, and emergent treatment directed at the specific problem must be provided. Emergent treatment of open fractures, compartment syndrome, and hemodynamic instability in a patient with a pelvic fracture as well as damage control in multiply injured patients should be understood by all who treat musculoskeletal injuries. Finally, a less-often discussed but no less important aspect of surgical care that may affect initial treatment decisions and outcome is sleep deprivation and fatigue of the members of the surgical team.nnLook for this and other related articles in Instructional Course Lectures, Volume 59, which will be published by the American Academy of Orthopaedic Surgeons in March 2010:nnTraditionally, the initial management of open fracture wounds was debridement within six hours after the injury to prevent infection. That guideline was based on animal experiments performed in the 1890s and …

Dual small fragment plating improves screw-to-screw load sharing for mid-diaphyseal humeral fracture fixation: A finite element study

BACKGROUNDnA smaller humerus in some patients makes the use of a large fragment fixation plate difficult. Dual small fragment plate constructs have been suggested as an alternative.nnnOBJECTIVEnThis study compares the biomechanical performance of three single and one dual plate construct for mid-diaphyseal humeral fracture fixation.nnnMETHODSnFive humeral shaft finite element models (1 intact and 4 fixation) were loaded in torsion, compression, posterior-anterior (PA) bending, and lateral-medial (LM) bending. A comminuted fracture was simulated by a 1-cm gap. Fracture fixation was modelled by: (A) 4.5-mm 9-hole large fragment plate (wide), (B) 4.5-mm 9-hole large fragment plate (narrow), (C) 3.5-mm 9-hole small fragment plate, and (D) one 3.5-mm 9-hole small fragment plate and one 3.5-mm 7-hole small fragment plate.nnnRESULTSnModel A showed the best outcomes in torsion and PA bending, whereas Model D outperformed the others in compression and LM bending. Stress concentrations were located near and around the unused screw holes for each of the single plate models and at the neck of the screws just below the plates for all the models studied. Other than in PA bending, Model D showed the best overall screw-to-screw load sharing characteristics.nnnCONCLUSIONnThe results support using a dual small fragment locking plate construct as an alternative in cases where crutch weight-bearing (compression) tolerance may be important and where anatomy limits the size of the humerus bone segment available for large fragment plate fixation.

Relationship Between Multiple Joint Movements Using Fitts Law

Fitts Law predicts the time required to move to an object given the distance to the objects center and its size. Over the years, Fitts law has been tested on various body parts/joints such as the elbow, wrist, fingers and even tongues. In this paper, we extend Fitts law to model movement by multiple joints. To accomplish this, we first establish a relationship between the performances of different joints, using the concept of atomic movement. We define the atomic movement as the movement of the fastest joint from amongst the joints under consideration. We propose that every other joint movement is a multiple of this atomic movement.

CORR Insights®: Distribution of Locally Delivered Antimicrobials is Limited by Cortical Bone: A Pilot Study

This CORR Insights®is a commentary on the article “Distribution of Locally Delivered Antimicrobials is Limited by Cortical Bone: A Pilot Study by Odgers and colleagues available at: DOI:10.1007/s11999-013-2853-6. n nThe author certifies that he, or a member of his immediate family, has no funding or commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. n nAll ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request. n nThe opinions expressed are those of the writers, and do not reflect the opinion or policy of CORR® or the Association of Bone and Joint Surgeons®. n nThis CORR Insights® comment refers to the article available at DOI: 10.1007/s11999-013-2853-6.

Editorial Comment: Symposium: 2012 Musculoskeletal Infection Society

Interdisciplinary academic collaborations, reviews, and discussions are the mainstay of the Musculoskeletal Infection Society (MSIS). The MSIS was founded in 1989 as a multidisciplinary educational and scientific forum for clinicians and scientists. Our mission is to advance knowledge in the field of musculoskeletal infection and its treatment by: (1) educating clinician and research members; (2) educating the medical community and the general public; and (3) promoting and maintaining professional standards in order to provide the best professional care to patients with musculoskeletal infection.