Patellofemoral joint arthroplasty: patient selection,surgical technique and outcomes

Isolated patellofemoral arthritis is an increasingly recognized entity, and is usually associated with previous patellofemoral dysplasia or instability. Patellofemoral arthroplasty (PFA) has evolved significantly in recent years, both in terms of implant design and importantly in the understanding of appropriate patient selection. This review outlines the indications and investigations for PFA, provides a brief history of the development of contemporary implants, and presents the clinical outcomes for the prostheses most commonly used in the UK. In addition, it provides a detailed surgical technique for implantation of an onlay implant, with tips on how to optimize patellofemoral biomechanics and thus achieve a consistently good outcome.     

Erythroleukemia with high fetal hemoglobin after therapy for ovarian carcinoma

The authors report the association of erythroleukemia (FAB M6) and fetal hemoglobin (HbF) level of at least 65% after therapy for ovarian carcinoma. The patient's erythrocytes had many signs of reversion to fetal-like erythropoiesis including: elevated HbF with a fetal G gamma/A gamma (gly/ala) of 3/1, low hemoglobin A2 (HbA2), macrocytosis, and increased i antigen. These data and data from other case reports suggest that elevation of HbF to greater than 25% with reversion to fetal-like erythropoiesis is useful in differentiating erythroleukemia from other preleukemic disorders.     

Behavioral measurement of axonal thresholds

A behavioral method for measuring the electrical sensitivity of directly stimulated elements in the brain is described and applied to the medial forebrain bundle (MFB) reward path and the tectospinal circling path. Equations are derived from which threshold current densities may be calculated from knowledge of the electrode tip dimensions and the current required to produce criterion behavior, which is a function of electrode size. Four different sizes of electrode were implanted in the MFB of rats and self-stimulation rates plotted against stimulating current. The mean currents for criterion bar-pressing rates of 25% and 55% of maximum rate were determined for each electrode size and the values used to calculate average threshold current densities. Two sizes of electrode were implanted in the tectospinal tract of rats and the average currents to produce circling at 0.2 and 0.4 turns/s were measured. The threshold current densities for self-stimulation axons were about 5 times as large as those for circling, in accordance with other evidence that tectal circling path axons are larger than those of the MFB reward path.     

Cutaneous afferent activity in the median nerve during grasping in the primate

Neural activity was recorded from the median nerve of a monkey during grasping and lifting, using a chronically implanted cuff electrode. At the onset of lifting, there was an initial dynamic response during which the intensity of the neural signal increased rapidly. This neural response attained its peak value well before the displacement, the load force or the grip force. The time course and peak of the rectified, integrated neurogram were best correlated with the rate of change of grip force. The neural activity declined exponentially to a steady value following the initial peak. During steady holding the mean amplitude of the neurogram was best correlated with the mean grip force. At the end of the holding phase there was a short burst of neural activity as the monkey relaxed the grip force and released the object. During some blocks of trials pulse perturbations were applied to the object. When the monkey did not increase the grip force in advance of the perturbation, the perturbation produced a relatively large displacement of the object and a burst of neural activity whose onset coincided with the onset of displacement. When the monkey anticipated the perturbation by increasing the grip force during the holding period preceding the perturbation, the perturbation produced a relatively small displacement and relatively little increase in neural activity.     

Diffuse cavernous haemangiomas of the upper limb

In the upper limb, diffuse cavernous haemangiomas occur infrequently but their treatment is often unsatisfactory and the result of surgical excision disappointing. Four cases of these diffuse haemangiomas are described and their management discussed.     

Right temporal-lobe contribution to global visual processing

The performance of 92 patients with unilateral temporal- or frontal-lobe excisions and 35 normal control subjects was tested under two experimental conditions (global, local) of a Stroop-type reaction-time task, employing either hierarchically structured letters or abstract designs as stimuli. In the local condition, subjects were asked to focus their attention on the small forms and to ignore the large form, whereas they were instructed to do the reverse in the global condition. The results showed that, in the local condition, the patients with right temporal-lobe lesions were less affected than the other groups by interference from the global aspect of the stimulus. This reduced sensitivity to the overall configuration of the stimulus was unrelated to the extent of hippocampal removal or to the presence of visual-field defects. These findings support the hypothesis that the human right temporal neocortex contributes to the global processing of visual information.