Synchrotron CT of an equine digit at the Australian Synchrotron Imaging and Medical Beamline.

Laminitis is an extremely painful and debilitating condition of horses that can affect their athletic ability and even quality of life. The current gold standard for assessment of laminar tissue is histology, which is the only modality that enables detailed visualization of the lamina. Histology requires dissection of the hoof and therefore can only represent one specific time point. The superior spatial and contrast resolution of synchrotron computed tomography (sCT), when compared with readily available imaging modalities, such as radiographs and conventional CT, provides an opportunity for detailed studies of the lamina without the need for hoof dissection and histological assessment. If the resolution of histology can be matched or even approached, dynamic events, such as laminar blood flow, could also be studied on the microscopic tissue level. To investigate this possible application of sCT further, two objectives are presented: (i) to develop a protocol for sCT of an equine digit using cadaver limbs and (ii) to apply the imaging protocol established during (i) for sCT imaging of the vasculature within the foot using an ex vivo perfusion system to deliver the vascular contrast. The hypotheses were that sCT would allow sufficient resolution for detailed visualization to the level of the secondary lamellae and associated capillaries within the equine digit. Synchrotron CT enabled good visualization of the primary lamellae (average length 3.6 mm) and the ex vivo perfusion system was able to deliver vascular contrast agent to the vessels of the lamina. The individual secondary lamellae (average length 0.142 mm) could not be seen in detail, although differentiation between primary and secondary lamellae was achieved. This approaches, but does not yet reach, the current gold standard, histology, for assessment of the lamellae; however, with further refinement of this imaging technique, improved resolution may be accomplished in future studies.

Meta-analysis of the effect of oral selenium supplementation on milk selenium concentration in cattle.

Soils in many regions of the world have a low Se content. Consequently, forages and crops grown on these soils may provide inadequate dietary Se for humans and grazing animals. Selenium supplementation has been used to enhance Se status and milk Se concentration, but results conflict. Milk Se concentration appears to be a useful indicator of animal and herd Se status, and reflects the responsiveness to supplementation. A systematic review and meta-analysis were carried out to summarize all available scientific evidence for the effect of oral Se supplementation on milk Se concentration in cattle. The literature search was based on electronic and nonelectronic databases. Fixed- and random-effects models of meta-analysis were used, and a meta-regression was carried out to evaluate heterogeneity among studies. Random-effects meta-analysis was performed on 42 studies published between 1977 and 2007. Oral Se supplementation resulted in an average increase in milk Se content of 0.16 (95% confidence interval: 0.117, 0.207) micromol/L, with a significant heterogeneity among studies. Weak publication bias was evident, but it did not change the average effect. The continent where the study was performed, Se source, Se dose, and the interaction between source and dose explained 71% of the between-study variance. On average, American cows supplemented with Se yeast (e.g., 6 mg/h per day) had greater milk Se concentrations (approximately 0.37 micromol/L) 75 d after the beginning of supplementation when compared with those supplemented with inorganic forms of Se. This information provides a basis for tailoring daily animal requirements and for enhancing the Se intake of consumers of dairy products.

Modeling access, cost, and perceived quality: computer simulation benefits orthodontic clinic staffing decisions.

Given limited financial resources, simulation permits a financial analysis of the optimum staffing levels for orthodontists and dental assistants in an orthodontic clinic. A computer simulation provides the information for managerial review. This study, by building a computer simulation of an orthodontic service, set out to determine the most efficient mix between providers and support staff to maximize access, maximize perceived quality, and minimize expenditures. Six combinations of providers and support staff were compared during an animated, computer-generated what-if analysis. Based on the clinic workload and size, on the cost per patient, and on the cost per quality point, the research team recommended a staffing mix of one orthodontist and three assistants. This study shows that computer simulation is an enormous asset as a decision support tool for management.

Interference fixation versus postfixation of bone-patellar tendon-bone grafts for anterior cruciate ligament reconstruction. A biomechanical comparative study in porcine knees.

This study compares biomechanical characteristics of interference screw fixation to "postfixation" (sutures tied over cancellous screw and washer) of bone-patellar tendon-bone grafts in porcine anatomic specimen knees. Maximum pull-out strength (ultimate failure load), displacement of the bone graft at 110 N of force, and mode of failure were compared in a progressive load to failure test. Interference screw fixation demonstrated statistically significantly (p = 0.04) higher mean ultimate failure loads (535 N) compared to postfixation (309.1 N). Interference fixation also demonstrated statistically significantly (p = 0.0003) less displacement of the bone graft at 110 N of force (0.32 mm vs. 2.21 mm). All failures occurred at the fixation site. The authors conclude that interference fixation is stronger than postfixation and, in the immediate postoperative period, should better protect the graft from loosening after anterior cruciate ligament reconstruction, improving stability and allowing more aggressive rehabilitation.

Dislocation of the knee.

The complications of knee dislocations may be disastrous and must be anticipated. In most series, a 25 to 30 per cent incidence of arterial damage is reported. If the artery is not repaired, the incidence of amputation can be up to 72.5 per cent. The popliteal artery should be evaluated and vascular repair performed as needed. This must be completed within a 6 to 8-hour period after injury for optimal results. Peroneal nerve injuries are common, and permanent neurologic damage may result. The neurovascular injury should be well documented both at the time of injury and in the preinjury state. After all problems affecting limb survival are solved, open repair of all ligamentous injuries is recommended to provide ligamentous stability and congruity of the joint. Prior to performing the procedure, a surgeon must have a thorough knowledge of the anatomy of the knee. Rehabilitation techniques and early postoperative motion are important for guiding the injured patient through the immediate and late postoperative period.

Segond tibial condyle fracture: lateral capsular ligament avulsion.

Avulsion fractures in the appendicular skeleton are a result of stress on a specific structure that is firmly attached to bone. A small avulsion fracture from the directly lateral surface of the lateral tibial condyle results from excessive tension on the lateral capsular ligament of the knee joint. Recognition of this fracture on an anteroposterior radiograph of a traumatized knee represents substantial evidence of major injury to the lateral joint capsule. This fracture also has a strong association with rupture of the anterior cruciate ligament. The avulsed tibial fragment is remarkably constant in site and appearance. The typical fragment is isolated by a longitudinal fracture line separating a small piece of bone from the lateral tibia. It is elliptical in outline (10 X 3 mm), with its proximal border lying 4 mm distal to the subarticular cortex of the lateral tibial condyle. A hemarthrosis of the knee joint is consistently visible.

Rehabilitation of the injured knee.

The basis of rehabilitation is to return the patient to the preinjury status. The physician must recognize that muscle is made up of both Type I and Type II fibers, Type I having endurance and Type II having speed capabilities. Immobilization for long periods of time is destructive to the ligaments, muscles, and cartilage of the affected area. Some immobilization is required, however, for the healing of tissues. The basis of any postinjury rehabilitation program should take into account that controlled motion can decrease the deleterious effect of immobilization. At the same time, it allows for healing. The ranges of motion that are allowed must be determined for each specific injury. An approach to determining the losses in the psychological and physiologic states of the patient is identified and recommendations for rehabilitation are given.