A review of the physiological and histological effects of laser osteotomy.

Osteotomy is the surgical cutting of bone. Some obstacles to laser osteotomy have been melting, carbonisation and subsequent delayed healing. New cooled scanning techniques have resulted in effective bone cuts without the strong thermal side effects, which were observed by inappropriate irradiation techniques with continuous wave and long pulsed lasers. With these new techniques, osteotomy gaps histologically healed with new bone formation without any noticeable or minimum thermal damage. No significant cellular differences in bone healing between laser and mechanical osteotomies were noticed. Some studies even suggest that the healing rate may be enhanced following laser osteotomy compared to conventional mechanical osteotomy. Additional research is necessary to evaluate different laser types with appropriate laser setting variables to increase ablation rates, with control of depth, change in bone type and damage to adjacent soft tissue. Laser osteotomy has the potential to become incorporated into the armamentarium of bone surgery.

Bilateral prosthetic hip joint infections associated with a Psoas abscess. A Case Report.

INTRODUCTION: Psoas abscess is a recognized but under-diagnosed complication of prosthetic hip joint infections. CASE REPORT: We report a case of a 68-year-old man with right and left hip arthroplasties performed 22 and 14 years ago, respectively, who presented with non-specific symptoms and was subsequently diagnosed with left psoas abscess on CT scan. Drainage of the psoas abscess was complicated by the formation of a discharging sinus connected to the left hip. He then developed an infected right thigh haematoma, which also formed a discharging sinus connecting to the right hip post-drainage. He was treated with bilateral two-stage revision total hip arthroplasties and multiple courses of prolonged antibacterial therapy. Both abscesses and hip joints cultured the same species of multi-sensitive Staphylococcus aureus. The causal link between the psoas abscess and the prosthetic hip infections is discussed, as well as the investigation and management. CONCLUSION: We recommend routine exploration of the iliopsoas bursa when revision of an infected total hip arthroplasty is performed to rule out intrapelvic spread of the infection [3]. There should be high index of suspicion of prosthetic hip infection in patients presenting with Psoas abscess and vice versa. A CT scan might be warranted to rule out concomitant infection in both these patients.

Emergence of order in textured patterns.

A characterization of textured patterns, referred to as the disorder function delta(beta), is used to study properties of patterns generated in the Swift-Hohenberg equation (SHE). It is shown to be an intensive, configuration-independent measure. The evolution of random initial states under the SHE exhibits two stages of relaxation. The initial phase, where local striped domains emerge from a noisy background, is quantified by a power-law decay delta(beta) approximately t-(1/2)beta. Beyond a sharp transition, a slower power-law decay of delta(beta), which corresponds to the coarsening of striped domains, is observed. The transition between the phases advances as the system is driven further from the onset of patterns, and suitable scaling of time and delta(beta) leads to the collapse of distinct curves. The decay of delta(beta) during the initial phase remains unchanged when nonvariational terms are added to the underlying equations, suggesting the possibility of observing it in experimental systems. In contrast, the rate of relaxation during domain coarsening increases with the coefficient of the nonvariational term.

Integrating the Kuramoto-Sivashinsky equation in polar coordinates: application of the distributed approximating functional approach.

An algorithm is presented to integrate nonlinear partial differential equations, which is particularly useful when accurate estimation of spatial derivatives is required. It is based on an analytic approximation method, referred to as distributed approximating functionals (DAF's), which can be used to estimate a function and a finite number of derivatives with a specified accuracy. As an application, the Kuramoto-Sivashinsky (KS) equation is integrated in polar coordinates. Its integration requires accurate estimation of spatial derivatives, particularly close to the origin. Several stationary and nonstationary solutions of the KS equation are presented, and compared with analogous states observed in the combustion front of a circular burner. A two-ring, nonuniform counter-rotating state has been obtained in a KS model simulation of such a burner.