Optimization of whispering gallery resonator design for biosensing applications.

Whispering gallery modes (WGMs) within microsphere cavities enable highly sensitive label-free detection of changes in the surrounding refractive index. This detection modality is of particular interest for biosensing applications. However, the majority of biosensing work utilizing WGMs to date has been conducted with resonators made from either silica or polystyrene, while other materials remain largely uninvestigated. By considering characteristics such as the quality factor and sensitivity of the resonator, the optimal WGM sensor design can be identified for various applications. This work explores the choice of resonator refractive index and size to provide design guidelines for undertaking refractive index biosensing using WGMs.

Self-formed cavity quantum electrodynamics in coupled dipole cylindrical-waveguide systems.

An ideal optical cavity operates by confining light in all three dimensions. We show that a cylindrical waveguide can provide the longitudinal confinement required to form a two dimensional cavity, described here as a self-formed cavity, by locating a dipole, directed along the waveguide, on the interface of the waveguide. The cavity resonance modes lead to peaks in the radiation of the dipole-waveguide system that have no contribution due to the skew rays that exist in longitudinally invariant waveguides and reduce their Q-factor. Using a theoretical model, we evaluate the Q-factor and modal volume of the cavity formed by a dipole-cylindrical-waveguide system and show that such a cavity allows access to both the strong and weak coupling regimes of cavity quantum electrodynamics.

Staged arthrodesis for salvage of the septic hallux metatarsophalangeal joint.

Failed surgery at the hallux metatarsophalangeal joint may present substantial difficulties in treatment, especially when complicated by infection. This retrospective study reviews the staged treatment of 5 patients with complications of hallux valgus surgery associated with sepsis of the metatarsophalangeal joint. The initial salvage treatment included debridement with placement of an antibiotic cement spacer and either an intramedullary Kirschner wire (4 patients) or an external fixator (1 patient). At the second stage procedure, the spacer and fixation were removed, and an autogenous tricortical iliac crest graft was inserted into the joint. All patients had clinical control of joint sepsis. Pseudoarthrosis occurred at the proximal end of the tricortical graft in 2 patients. Patients were evaluated at an average of 28 months after the fusion. Staged arthrodesis appears to be a satisfactory approach to postoperative sepsis of the hallux metatarsophalangeal joint.

Morbidity after crush injuries to the foot.

By retrospective review of hospital records and by follow-up clinical examinations, we evaluated 58 patients with crush injuries to the foot treated at our institution between 1986 and 1990. All patients had received initial treatment according to a standardized protocol determined by the type and magnitude of the injury. Patients were examined at a mean interval of 3.3 years (range 2-4) after injury, and the functional outcome was determined according to a foot trauma rating scale. Based on this scoring system, 46% of the patients had good functional outcome, 29% had fair results, and 25% had poor results. There was a significant correlation between a good functional outcome and careful adherence to the treatment protocol; however, some patients fared poorly regardless of treatment. Poor results occurred if treatment was not immediately initiated, if soft-tissue coverage was delayed (in those who experienced severe, mangling-type injuries necessitating partial foot amputation), if patients subsequently had neuritis or reflex sympathetic dystrophy, or if patients were involved in ongoing workers' compensation and litigation. We conclude that because crush injuries of the foot may be associated with prolonged morbidity, initial management should be directed toward recognition and treatment of compartment syndromes, early soft-tissue coverage, and rigid skeletal stabilization to enhance soft-tissue healing.

Management of midfoot diabetic neuroarthropathy.

Between 1986 and 1990, we treated 68 patients with diabetes and neuroarthropathy of the midfoot, 21 of whom had bilateral involvement. Patients were managed according to a strict protocol defined by activity of the neuroarthropathy, instability, ulceration, infection, and ischemia. Initial management of acute neuroarthropathy (18 feet) was open reduction and arthrodesis (8), a total-contact cast or brace (9), and amputation (1). All patients with subacute neuroarthropathy (30 feet) were initially treated in a total contact cast. Four of these feet subsequently required amputation, two required arthrodesis, and one required exostectomy. For chronic neuroarthropathy (41 feet), a total-contact cast or a molded orthotic insert with or without bracing was used initially in all feet. Subsequent surgical salvage for this group included arthrodesis (9), plantar exostectomy (6), amputation (2), and abscess drainage (2). Four patients died during this treatment period and 64 patients (85 feet) were evaluated at a mean interval of 3 years (range 1-6 years) after initiation of treatment. This treatment program was found to be successful in 82 of 85 feet treated.

Clinical applications of a pneumatic intermittent impulse compression device after trauma and major surgery to the foot and ankle.

A prospective study was designed to evaluate the effect of a pneumatic intermittent impulse device in the treatment of postsurgical and posttraumatic swelling of the adult foot and ankle. Two groups of patients and their respective controls were studied. Group A consisted of 19 patients and 19 controls with acute swelling of the foot and ankle after major elective or posttraumatic surgery. Group B comprised 18 patients and 16 controls with chronic postsurgical or posttraumatic swelling. The pneumatic intermittent impulse device was used according to a predetermined daily regimen in both the control and experimental groups. The control patients were treated identically, except that their impulse device was modified to prevent effective compression. Reduction in swelling was measured by volumetric analysis with water displacement at selected intervals for each group. When compared with their respective controls, those patients who used an active impulse device had a statistically significant reduction in swelling. We conclude that this device is effective in the control of both acute and chronic swelling after trauma and surgery of the foot and ankle.