Non-constrained implant arthroplasty for the distal radioulnar joint.

A variety of surgical techniques are used to treat the arthritic distal radioulnar joint, which is influenced by aetiology and previous procedures. Four types of ulnar head arthroplasty exist: total ulnar head, partial ulnar head, unlinked total distal radioulnar joint, and linked distal radioulnar joint. Although long-term outcome studies are sparse, short-term clinical and biomechanical studies have shown encouraging results, leading to expanded indications. Based on our experience and a literature review, patients are advised that pain is improved but minor pain is common after strenuous activity. Ulnar neck resorption is common, however, implant loosening is rare. Sigmoid notch erosion is concerning, but appears to stabilize and not affect outcome. A partial ulnar head replacement that retains bony architecture and soft tissue restraints may have benefit over a total ulnar head in appropriate patients. If appropriate selection criteria are met, ulnar head replacement typically produces reliable results, with low revision.

cel-mir-237 and its homologue, hsa-miR-125b, modulate the cellular response to ionizing radiation.

Elucidating the mechanisms involved in sensitizing radioresistant tumors to ionizing radiation (IR) treatments while minimizing injury to surrounding normal tissue is an important clinical goal. Due to their sequence-derived specificity and properties as gene regulators in IR-affected pathways, microRNAs (miRNAs) could serve as adjuvant therapeutic agents that alter cellular sensitivity to radiation treatment. To identify radiosensitizing miRNAs, we initially utilized the Caenorhabditis elegans vulval cell model, an in vivo system developed to study IR-dependent radiosensitivity as a measure of clonogenic cell death. We tested several candidate miRNA-deletion mutants post γ-irradiation and identified cel-mir-237 as a miRNA which when deleted caused animals to be more resistant to IR, whereas cel-mir-237 overexpressing strains were IR sensitive. In addition, wild-type animals downregulated cel-mir-237 levels post IR in a time-dependent manner. We identified jun-1 (JUN transcription factor homolog) as a novel target of cel-mir-237. Specifically, jun-1 transcript levels increased in wild-type animals post γ-irradiation, and loss of cel-mir-237 also resulted in higher jun-1 expression. As expected, loss of jun-1 resulted in IR sensitivity, similar to the phenotype of cel-mir-237 overexpressors. As miR-237 is the homolog of human miR-125, we validated our findings in MCF-7 and MDA-MB-231 breast cancer cell lines, which harbor lower hsa-miR-125b levels than normal human mammary epithelial cells (HMECs). Forced expression of hsa-miR-125b in these cells resulted in radiosensitivity, as seen by reduced clonogenic survival, enhanced apoptotic activity and enhanced senescence post IR. Finally, re-expression of c-JUN in MDA-MB-231 cells promoted radioresistance and abrogated miR-125-mediated radiosensitization. Our findings suggest that overexpression of cel-mir-237 and its homolog, hsa-miR-125b, functions as sensitizers to γ-irradiation in both a nematode in vivo model and breast cancer cells, and could potentially be utilized as an adjuvant therapeutic to enhance radiation sensitivity.

Kinetics of Oxygen Reduction in Aprotic Li-O2 Cells: A Model-Based Study.

A comprehensive and general kinetic model is developed for the oxygen reduction reaction in aprotic Li-O2 cells. The model is based on the competitive uptake of lithium superoxide by the surface and solution. A demonstrative kinetic study is provided to demystify the origin of curvature in Tafel plots as well as the current dependency and aberrant diversity of the nature and morphology of discharge products in these systems. Our results are general and extend to any system where solubilization of superoxide is favored, such as where phase-transfer catalysts play an important role.

Honoring the Admiral: Boerhaave-van Wassenaer's syndrome.

Dr. Herman Boerhaave (1668-1738) first described esophageal rupture and the subsequent mediastinal sepsis based upon his careful clinical and autopsy findings and hundreds of references have since been written about Boerhaave's syndrome. Several fine historical accounts of this brilliant scientist have been published over the years and he has received appropriate credit for his valuable contributions. But what about that unfortunate propositus that Dr. Boerhaave attended to, performed necropsy upon, and subsequently received acclaim with? Medical history pays inadequate regard to the Baron Jan Gerrit van Wassenaer heer van Rosenberg, Prefect of Rhineland and Grand Admiral of the Dutch Fleet. This figure was a nobleman and war hero at the peak of the Dutch Golden Age who played his role in steering the course of European history. Without this nobleman's heroic contemporaneous account, Boerhaave's celebrated impact on medical science would never have been realized. Therefore, we offer an overdue recitation of Admiral van Wassenaer's biography. Based on found precedent we propose that spontaneous rupture of the esophagus be henceforth referred to as the 'Boerhaave-van Wassenaer's syndrome'.

The anion gap does not accurately screen for lactic acidosis in emergency department patients.

INTRODUCTION: Lactic acidosis portends a poor prognosis in trauma, sepsis, and other shock states and is useful for triaging and resuscitating emergency department (ED) patients. The authors sought to determine whether the AG is a reliable screen for lactic acidosis when applied specifically in the ED setting. METHODS: The authors performed a retrospective cohort study over a seven month period. Subjects were all ED patients that had a serum lactate obtained. Sensitivity analyses of the AG for detecting presence of lactic acidosis were calculated for the traditional AG normal value (AG <12) and for the lower AG normal value when using newer ion selective electrode assays (AG <6). RESULTS: Serum lactate levels were ordered in the ED on 440 occasions. 137 samples were excluded by protocol. Using an AG cutoff of 12, the sensitivity for detecting lactic acidosis was 58.2%, specificity was 81.0%, and the negative predictive value was 89.7%. Using the AG cutoff of 6, the sensitivity was 93.2%, the specificity was 17.3%, and the negative predictive value was 91.8%. CONCLUSIONS: The traditional definition of AG >12 was insensitive for the presence of lactic acidosis. Using the revised AG of >6 is more sensitive but non-specific for lactic acidosis. The authors conclude that employing the AG as a screen for LA may be inappropriate in ED patients. Instead, they recommend ordering a serum lactate immediately upon suspicion of a shock state. A prospective study to confirm these findings is needed.

Influence of articular geometry on prosthetic wrist stability.

Ellipsoid and toroid-shaped articulations for total wrist prostheses were evaluated using computer modeling and laboratory experiments. An ellipsoidal design was found to accommodate greater width of the concave proximal component, resulting in better capture and prosthetic stability than a toroid shape. An ellipsoid articulation also provides greater contact area through the available arc of motion. An ellipsoidal articulation is a reasonable design for total wrist arthroplasty.

Reconstruction of the posttraumatic unstable distal radioulnar joint.

Although not a common problem, the posttraumatic unstable distal radioulnar joint can be difficult to treat. This article focuses on the various methods for reconstruction of the unstable distal radioulnar joint. Attention focuses specifically on anatomic reconstruction of distal radioulnar ligaments. The authors' technique is presented in detail.

Wrist arthrodesis: review of current techniques.

Wrist arthrodesis is a well-established procedure that predictably relieves pain and provides a stable wrist for power grip. Although a variety of techniques for achieving a solid fusion have been described, the combination of rigid stabilization with a dorsal plate and autogenous cancellous bone grafting results in a high fusion rate and obviates the need for prolonged postoperative cast immobilization. Successful results with dorsal plating with or without local bone graft have recently been reported for patients with posttraumatic conditions. Rod or pin fixation is an established procedure for patients with inflammatory arthritis or a connective tissue disorder; however, plate fixation for these conditions is becoming a more acceptable alternative. Complications are relatively common and range from minor transient problems to major problems, such as wound dehiscence, infection, extensor tendon adhesions, and plate tenderness, which may require implant removal. Preoperatively, patients should be assessed for the presence of carpal tunnel syndrome, distal radioulnar joint arthritis, or ulnocarpal impaction syndrome, which may become or remain symptomatic after arthrodesis. Wrist arthrodesis results in a high degree of patient satisfaction with respect to pain relief and correction of deformity. Patients are able to accomplish most daily tasks and activities by learning to adapt to, and compensate for, the loss of wrist motion.

Electrical and ultrasound stimulation for scaphoid fractures.

The standard treatment for delayed union or nonunion of the scaphoid is operative management. Electrical stimulation has been employed in these clinical situations in patients unable or unwilling to undergo surgical intervention. Recent interest has also focused on the use of low-intensity ultrasound as an adjunct to healing in distal radius and tibial fractures. Results with the use of ultrasound for scaphoid fractures is encouraging. A review of the mechanisms of action, clinical results, and possible indications is presented for these two nonoperative modalities.

Ulnar translocation instability of the carpus after a dorsal radiocarpal dislocation: a case report.

An unusual case of ulnar translocation of the carpus after a radiocarpal dislocation is described. Persistent instability was noted despite attempted reattachment of the avulsed palmar capsuloligamentous structures. A successful outcome occurred after radiolunate arthrodesis and external fixation of the wrist.

Amlodipine overdose causes prolonged calcium channel blocker toxicity.

Amlodipine is a relatively new agent that has the longest half-life of all calcium channel blockers. This report describes a severe overdose that resulted in prolonged and severe hemodynamic compromise for up to 10 days, but responded to aggressive therapy with calcium, glucagon, and other vasoactive medicines.

The role of antibiotics in the management of elective and post-traumatic hand surgery.

The use of prophylactic antibiotics in elective and emergency hand surgery is an unsettled issue. Although their benefit in general surgical cases and certain orthopedic cases is well established, the lower infection rates in elective and emergency hand surgery have made attempts to prove the efficacy of prophylaxis more difficult. Valid arguments can be made for the use of antibiotics in human and animal bites. Prophylactic antibiotic use is efficacious in the following scenarios: (1) soft-tissue reconstructive procedures with large flaps, (2) total elbow or wrist implant arthroplasty, (3) procedures of long duration, and (4) complex open hand trauma with wound contamination and extensive soft-tissue and bony injury. Antibiotic prophylaxis does not appear warranted in clean, elective procedures lasting fewer than 2 hours. The duration of antibiotic use should be as short as possible to minimize complications and the development of bacterial resistance. The selection of a particular antibiotic regimen remains the surgeon's choice, but many inexpensive and relatively safe antibiotic agents are available. Although uncommon, potentially serious hazards exist with the use of antibiotics. Definitive guidelines on the use of antibiotics in hand surgery are not available; hand surgeons should apply basic principles of prophylaxis and be aware of the existing controversies.

Staged extensor tendon reconstruction in the finger.

Staged extensor tendon reconstruction using a silicone implant followed by tendon grafting was done to restore proximal interphalangeal (PIP) joint extension in 6 fingers with severe injuries to the dorsal skin and extensor mechanism. Abrasions to the joint capsule and cortical surfaces were also present. To avoid finger stiffness, the reconstruction was delayed and range of motion exercises were initiated early. The skin injury was managed by split-thickness skin grafting or allowed to heal by secondary intention to avoid prolonged immobilization. During surgery, the peritendinous fascia of the extensor tendon is used to guide insertion of the implant, and it serves as a premade tunnel that appears to aid the gliding and stability of the implant and subsequent tendon graft. Active extension of the PIP joint was restored in all fingers; there was an average extension lag of 15 degrees. PIP joint flexion averaged 95 degrees. On the basis of this experience, the author believes the technique to be a reliable treatment alternative for severely injured fingers with extensor mechanism loss.

Bioabsorbable pin fixation of intercarpal joints: an evaluation of fixation stiffness.

OBJECTIVE: Bioabsorbable pins made of poly-p-dioxanone (Johnson and Johnson Orthopaedics, Raynham, Massachusetts) were compared to steel pins in the fixation of the scapholunate and lunotriquetral intercarpal joints of the wrist. DESIGN: An in vitro experiment was performed using fresh-frozen cadaver wrists. BACKGROUND: In the surgical treatment of wrist ligament injuries, temporary intercarpal joint fixation is required. Although steel pins are currently used, there are several clinical problems associated with their use. These complications could potentially be reduced by using bioabsorbable fixation. METHODS: The carpal bones were mounted between sets of plates which were then attached to a materials testing machine. Two parallel pins were used for joint fixation; steel pin fixation was tested first in each joint. Seven scapholunate joints and seven lunotriquetral joints were each tested in three different modes: translation in two orthogonal directions, and rotation. RESULTS: Bioabsorbable pin fixation provided an average of 46% of the stiffness of steel pin fixation. CONCLUSIONS: Although bioabsorbable pin fixation was statistically less stiff than steel pin fixation, relatively high loads were required to induce significant intercarpal joint translation and rotation. RELEVANCE: The strength retention profile of poly-p-dioxanone pins and the quality of fixation demonstrated in this study indicate that these bioabsorbable pins could provide satisfactory fixation of the scapholunate and lunotriquetral joints in the treatment of partial injuries of the intercarpal ligaments.

Assessment of thumb positioning in the treatment of ulnar collateral ligament injuries. A laboratory study.

In the treatment of ulnar collateral ligament injuries in the metacarpophalangeal joint of the thumb, a cast or splint is often molded with the thumb and hand positioned so the patient can return quickly to a particular sport or activity. However, it is unknown whether a given position of immobilization or whether an early rehabilitation program will compromise ligament healing by causing undue tension in the ligament. To better define acceptable positions for thumb immobilization and a safe range of motion, this laboratory study measured strain in the ulnar collateral ligament at different degrees of metacarpophalangeal joint flexion. Ligament strain was found to increase with increasing joint flexion; the most significant increases in strain occurred as the joint moved from 0 degree to 25 degrees of flexion, with the dorsal portion of the ligament demonstrating greater strain than the palmar portion. Based on these results, immobilization of the metacarpophalangeal joint in excessive flexion and unrestricted early rehabilitation exercises should be done with caution and guided by the grade of injury or the quality of repair.

Classification of distal radius fractures: an analysis of interobserver reliability and intraobserver reproducibility.

The Frykman, Melone, Mayo, and AO classification systems for distal radius fractures were evaluated for interobserver reliability and intraobserver reproducibility in a clinical setting using initial plain radiographs. Two attending orthopedic hand surgeons and two attending radiologists classified 55 sets of distal radius fractures. kappa-statistics were used to establish a relative level of agreement between observers for the two readings and between separate readings by the same observer. Interobserver agreement was rated as moderate for the Mayo classification and fair for the Frykman, Melone, and AO classifications. Intraobserver agreement was substantial for only one of four observers for each of the Frykman, Melone, and Mayo, while the remaining three observers achieved only fair to moderate reproducibility. Intraobserver agreement for the AO classification was fair for all four of the observers. Neither interobserver or intraobserver agreement was affected by combining similar subclasses in the Melone classification or by reducing the number of categories in the AO system from 27 to 9. However, further reducing the AO system to its three main types brought agreement to the "substantial" level. No difference was found in interobserver agreement between the first and second readings or in interobserver or intraobserver agreement between orthopedic hand surgeons and radiologists. Understanding the limitations of fracture classifications based solely on plain radiographs can help avoid undue reliance on them. Given the low degree of interobserver and intraobserver agreement for each of the distal radius fracture classifications in this study, their use as the sole means for determining the direction of treatment or for the direct comparison of results among different studies is not warranted.