Magnetic damping: domain wall dynamics versus local ferromagnetic resonance.

Magnetic relaxation is one of the dominating features of magnetization dynamics. Depending on the magnetic structure and the experimental approach, different magnitudes of the damping parameter are reported even for a given material. In this study, we experimentally address this issue by accessing the damping parameter in the same magnetic nanotracks using different approaches: local ferromagnetic resonance (α=0.0072) and field-driven domain wall dynamics (α=0.023). The experimental results cannot fully be accounted for by modeling only roughness in micromagnetic simulations. Consequently, we have included nonlocal texture induced damping to the micromagnetic code. We find excellent agreement with the observed increased damping in the vortex structures for the same input Gilbert alpha when texture-induced nonlocal damping is included.

Robust spin-orbit torque and spin-galvanic effect at the Fe/GaAs (001) interface at room temperature.

Interfacial spin-orbit torques (SOTs) enable the manipulation of the magnetization through in-plane charge currents, which has drawn increasing attention for spintronic applications. The search for material systems providing efficient SOTs, has been focused on polycrystalline ferromagnetic metal/non-magnetic metal bilayers. In these systems, currents flowing in the non-magnetic layer generate-due to strong spin-orbit interaction-spin currents via the spin Hall effect and induce a torque at the interface to the ferromagnet. Here we report the observation of robust SOT occuring at a single crystalline Fe/GaAs (001) interface at room temperature. We find that the magnitude of the interfacial SOT, caused by the reduced symmetry at the interface, is comparably strong as in ferromagnetic metal/non-magnetic metal systems. The large spin-orbit fields at the interface also enable spin-to-charge current conversion at the interface, known as spin-galvanic effect. The results suggest that single crystalline Fe/GaAs interfaces may enable efficient electrical magnetization manipulation.

A review of orthopedic injuries in three recent U.S. military conflicts.

We conducted a retrospective review of all patients with orthopedic injuries evacuated to a single medical center to evaluate the treatment and outcome of these injuries in three recent U.S. military conflicts: Operation Urgent Fury (Grenada), Operation Desert Shield/Storm (southwest Asia), and Operation Restore Hope (Somalia). Sixteen orthopedic casualties were originally treated at the medical detachment in Grenada before evacuation to the medical center. Most of these injuries were gunshot wounds to the extremities (11), with three known open fractures. Two patients (three extremities) sustained traumatic amputation (19% amputation rate). One hundred eighty-one patients with orthopedic injuries were medically evacuated from southeast Asia to the medical center for definitive treatment. Of these injuries, there were 143 fractures in 69 patients. One hundred of these fractures were open fractures, and 60% of these injuries were blast injuries. Furthermore, there were 26 amputations (14%). Twenty-two patients with orthopedic injuries were treated in Somalia and evacuated to the medical center. Thirteen of the 22 patients (59%) sustained gunshot wounds, and 2 (9%) sustained blast injuries. There were eight open fractures (36%) and three amputations in two patients (14%). Three of the 22 patients underwent successful limb salvage when ablation was the only other surgical alternative. It appears that a large percentage of medical center evacuations from military conflicts are for orthopedic injuries. Many of these injuries are the result of high-velocity weapons or blast injuries. Regardless of the size and/or purpose of the intervention, similar injury patterns and severity can be expected, because 51% of orthopedic patients had open fractures. Similarly, the rate of amputation associated with extremity trauma has not varied significantly since the Vietnam War.

Spine fractures in active duty soldiers and their return to duty rate.

To evaluate the outcome of thoracolumbar spine fractures in active duty soldiers, we conducted a retrospective review of 23 soldiers followed at a single institution. Twenty-two charts were available for review. The average age was 31.9 years (range, 19-49 years), and the average follow-up was 3.6 years (range, 2-11 years). There were 20 males and 2 females. All injuries except one occurred between 1990 and 1994, and all were treated by a single surgeon. We attempted to correlate five independent variables with regard to whether the patient returned to his or her previous duty or was required to undergo a medical evaluation board to determine fitness for duty. The variables included military rank, physical job demands, fracture type, initial neurological status, and initial treatment (operative versus nonoperative). Fourteen of the 22 soldiers (64%) underwent medical evaluation boards, whereas 8 (36%) returned to their previous duties. We found a strong correlation between increasing military rank and return to preinjury duties. As expected, physical job demands correlated strongly with eventual disposition, in that soldiers in jobs with low physical demands were more likely to be retained on active duty in their present position. Neurologic status (except motor deficit), type of fracture (except fracture-dislocation), and initial treatment did not correlate well with eventual disposition.

A review of total joint replacement in active duty soldiers.

Thirty-two active duty soldiers (36 total joint replacements) were followed from 9 months and 18 years (average 4.1 years) to evaluate the outcome of total joint replacement in active duty soldiers. Follow-up consisted of clinical assessment and radiographic evaluation at 6 weeks, 3 months, 6 months, 1 year, and yearly thereafter. A Harris hip rating (HHR) was also completed at each clinic visit. There were 30 total hip arthroplasties in 27 patients with an average age at surgery of 40.8 years (range 31-58) and an average follow-up of 4.1 years. The HHR averaged 93 on latest evaluation. There were three revisions (average 7.2 years). Of the 27 patients, 18 were retained on active duty and 9 were separated from service. Of the senior enlisted (E7 or above) and officers (O4 or above), 16 of 17 (94%) were retained on active duty, whereas only 2 of 10 (20%) of the junior enlisted (E6 or below) were retained on active duty. There were 6 total knee arthroplasties in 5 patients with an average age at surgery of 49.8 years (range 33-58) and an average follow-up of 3.0 years (9 months to 4 years). There were no revisions, and all 5 soldiers were retained on active duty. Preliminary results from this study reveal that a high percentage of soldiers undergoing total joint replacement are retained on active duty (72%) and are able to continue active lives. Rank or seniority also appears to be a significant factor for retention on active duty. The revision rate (10%) and the rate of osteolysis (19%) are comparable with reported rates.

Recombinant human bone morphogenetic protein-2 for grade III open segmental tibial fractures from combat injuries in Iraq.

This is a retrospective consecutive case series of 138 Gustillo-Anderson type IIIB and IIIC segmental tibial fractures treated at Walter Reed Army Medical Center in soldiers injured in Iraq between March 2003 and March 2005. Five patients with a head injury and four who were lost to follow-up were excluded. The patients were treated definitively with either a ringed external fixator or a reamed intramedullary nail, evaluated in terms of supplementary bone grafting with either autogenous bone (group 1, 67 patients) or recombinant human bone morphogenetic protein-2 at 1.50 mg/ml applied to an absorbable collagen sponge (group 2, 62 patients). The mechanism of injury, defect size and classification, associated injuries, presence of infection, preliminary treatment/fixation, number of procedures before definitive management, time to and details of definitive management, subsequent infection, re-operation, smoking history and other complications were noted. Radiographs were assessed for union, delayed union or nonunion by an independent investigator. All the patients were male. Their mean age was 26.6 years (20 to 42) and the mean follow-up was for 15.6 months (12 to 32). Group 2 had a slightly higher profile of concomitant injuries and a slightly worse fracture classification, but these were not significant. The rate of union was 76% (51 of 67) for group 1 and 92% for group 2 (57 of 62; p = 0.015). There was also a higher rate of subsequent infection in group 1 (14.9%) compared with group 2 (3.2%; p = 0.001) and a higher rate of re-operation (28%) in group 1 (p = 0.003). There were no observed hypersensitivity reactions to the recombinant human bone morphogenetic protein-2 implant.

Arthroscopic release for lateral epicondylitis: a cadaveric model.

At least 10 different surgical approaches to refractory lateral epicondylitis have been described, including an arthroscopic release of the extensor carpi radialis brevis tendon. The advantages of an arthroscopic approach include an opportunity to examine the joint for associated pathology, no disruption of the extensor mechanism, and a rapid return to premorbid activities with possibly fewer complications. A cadaveric study was performed to determine the safety of this procedure. Ten fresh-frozen cadaveric upper extremities underwent arthroscopic visualization of the extensor tendon and release of the extensor carpi radialis brevis tendon. The specimens were randomized with regard to the use of either a 2.7-mm or a 4.0-mm 30 degree arthroscope through modified medial and lateral portals. Following this, the arthroscope remained in the joint, and the portal, cannula track, and surgical release site were dissected to determine the distance between the cannula and the radial, median, ulnar, lateral antebrachial, and posterior antebrachial nerves, and the brachial artery and the ulnar collateral ligament. No direct lacerations of neurovascular structures were identified; however, the varying course of the lateral and posterior antebrachial nerves place these superficial sensory nerves at risk during portal placement. As in previous reports, the radial nerve was consistently in close proximity to the proximal lateral portal (3 to 10 mm: mean, 5.4 mm). The ulnar collateral ligament was not destabilized. Arthroscopic release of the extensor carpi radialis brevis tendon appears to be a safe, reliable, and reproducible procedure for refractory lateral epicondylitis. Cadaveric dissection confirms these findings.

Acute and long-term response of the meniscus to partial meniscectomy using the holmium: YAG laser.

The purpose of this study was to evaluate the histological effects of holmium:YAG laser partial meniscectomy in an in vivo rabbit model and compare it with scalpel partial meniscectomy at selected time intervals. Twenty-four adult male New Zealand rabbits underwent bilateral partial medial meniscectomies through the avascular zone. In the right knee, partial medial meniscectomy was performed using a standard surgical blade; in the left knee, an anatomically similar partial medial meniscectomy was performed using a Ho:YAG laser (Coherent, Santa Clara, CA). All animals were randomized and three animals were killed at postoperative days I and 3, and postoperative weeks 1, 2, 3, 4, 6, and 10. Samples of all medial and lateral menisci, with attached synovium and vascular rim, from both knees were harvested and submitted for histological and/or ultrastructural examination. The results indicate that (1) at all time periods, laser cut menisci had more cell loss and matrix degradation; (2) synovial necrosis was more common in laser-treated knees; (3) the Ho:YAG laser creates three zones of damage in the meniscal fibrocartilage: a zone of fibrin and debris at the incision site, a zone of necrosis characterized by degeneration of the collagen and loss of viable cells, and a zone of thermal change characterized by collagen degeneration. The zone of thermal change, with its histological injury was thought at the time of surgery to be the viable border. The zone of thermal change may act as a barrier to delay healing, and the scalpel produced a consistently straighter cut.

Langerhans' cell histiocytosis in patients older than 21 years.

In this retrospective review of 541 patients with Langerhans' cell histiocytosis, 211 (39%) patients were older than 21 years of age, whereas 330 (61%) were younger than 21 years of age. The adult patients had a mean age of 32 years (range, 21-69 years) with 159 (75%) men and 52 (25%) women, whereas the pediatric patients consisted of 176 (55%) boys and 144 (45%) girls. This male predominance in adults was statistically significant. Three adults had the Hand-Schuller-Christian variant, whereas the remaining adults (208) had eosinophilic granuloma. The rib accounted for 25% of the adult lesions and only 8% of the pediatric lesions. Spine involvement was less common in the adult group (3% versus 10%) and was predominantly thoracic. The adult patients had 40 (77%) diaphyseal lesions, 12 (23%) metaphyseal lesions, and no epiphyseal lesions. The pediatric patients had 75 (54%) diaphyseal, 59 (42%) metaphyseal, and five (4%) epiphyseal lesions. Radiographic evaluation revealed similar margin and matrix patterns in both groups, with a geographic lesion without sclerotic borders being the most common pattern. Langerhans' cell histiocytosis is considered a pediatric disease. However, this study showed a significant number (39%) of patients older than 21 years of age with this condition.