Biomedical subjects
Publications and source records attributed to J O Roberts.
An estimated 3.5 million people ride horses in the United Kingdom (Cannon, 1989). Injuries consequent to falls are common (Edixhoven et al., 1981), but those sustained while leading horses are less well recognized. In eight cases inappropriate grip of the reins or halter rope while leading a horse or pony resulted in an avulsion injury to a finger or thumb. It is suggested that people at risk be informed of such injuries.
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A fifteen-year-old boy with a long-standing history of congenital arteriovenous malformation in his left arm was seen with an acute posterior interosseous nerve palsy. Exploration showed this to be caused by bleeding from a congenital arteriovenous malformation in the radial tunnel. Decompression and evacuation of the haematoma resulted in full recovery.
Two cases of macrosyndactyly of the foot are reported which were successfully treated by shortening of the affected digits and free nail grafting.
A case of flexor pollicis longus tendon rupture as a complication of a Colles' fracture in a 17-year-old male is described. Tendon repair by means of a one-stage tendon graft produced a good functional result.
We describe three instances of ruptured flexor pollicis longus tendons due to bony spurs within the carpal tunnel. In each case, the bony spur was excised and the remaining exposed bone was covered with a flap of flexor retinaculum.
Three cases of forearm muscle hernia are described. Their aetiology differed but, in all three, symptoms were sufficiently severe to interfere with the patient's work. Surgical repair of the myocoeles, by closure of the fascial defects using lata onlay grafts or an interweave of palmaris longus tendon, produced complete resolution of symptoms and enabled the patients to return to full employment.
A case of ulnar nerve compression at the wrist caused by a reversed palmaris longus muscle is reported. We are not aware of any previous reports of ulnar nerve compression due to this particular muscle anomaly.
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An experimental comparison of two techniques for direct monitoring of anastomoses postoperatively is presented. Arterial differential temperature measurements indicated arterial occlusion (n = 24) in island flaps by mean temperature decreases in the affected artery of 0.5 degrees = C, but temperature changes in cases of venous occlusion (n = 17) were small (mean, 0.2 degrees C), inconsistent, and not of predictive value. The technique did not distinguish success (n = 4) from failure (n = 2) in experimental free flaps, and occlusion of deep arteries produced little or no change in the arterial wall temperature. In contrast, an implanted ultrasound Doppler probe reliably indicated arterial and venous occlusion in island flaps (n = 10), because in both circumstances the mean arterial Doppler signal invariably decreased to 0. The two could be distinguished between by changes in Doppler sound and instantaneous signal. In experimental free flaps, success (n = 10) was clearly distinguished from failure (n = 3) by characteristic patterns of Doppler sound and signal. Arterial differential thermometry had serious limitations, but implanted ultrasound Doppler showed great potential as a postoperative monitor applicable to all microvascular procedures.
An experimental investigation is presented into the use of pulsed ultrasound Doppler flowmetry with a percutaneously implanted probe as a monitor of microvascular anastomotic patency. The method accurately indicated and distinguished between experimental arterial and venous occlusion in epigastric island flaps. In free flaps it had advantages over manipulative, intraoperative tests of anastomotic patency and was a reliable post-operative monitor of flap circulation in the experimental model. The technique appears to have great potential as a post-operative monitor for free flaps, including those without a visible surface.
Since its introduction (Yang et al., 1981; Song et al., 1982), the radial forearm flap has proved to be one of the safest and most versatile free flaps. However, the donor defect is significant and an otherwise excellent result is often impaired by a poor graft take over the exposed flexor carpi radialis tendon, even when great care has been taken to preserve its paratenon. This results in delayed healing, with frequent dressing changes, and often produces an area that is later prone to breakdown following minor trauma. The authors would like to present their method of preventing these complications, which the senior author has been using for two years but which we have not seen previously used or reported.
It has been suggested that direct monitoring of arterial temperature using implanted thermocouples, may have value as a clinical postoperative monitor for vascularized free tissue transfers, including those with no visible surfaces. This study evaluated the technique in experimental animals, using simple, inexpensive equipment. Mean arterial differential temperature changes, with ipsilateral (n = 20) and contralateral (n = 21) references, of 0.6 degrees C and 0.5 degrees C respectively, reliably indicated occlusion of the superficial femoral artery in situ. In epigastric island flaps, arterial occlusion (n = 24) produced mean arterial temperature changes of 0.5 degrees C, but changes after venous occlusion were not significantly greater than unoccluded base line fluctuation. Venous differential temperature did not change significantly after either arterial or venous occlusion. In six epigastric free flaps, success or failure could not be distinguished, as the wide variation in measurements in the four successful flaps overlapped the recordings in the two which failed. It was shown that the nearer to the body core, the less the temperature difference between arterial wall and periarterial tissue. Occlusion of deeply sited arteries produced little or no change in arterial temperature. In view of these findings and because of the invasive nature of the technique, the authors did not pursue it clinically.
Black, uppercase letters, subtending 6.0' of arc in height, were presented tachistoscopically to 6 subjects. An exposure duration was chosen to keep the subject's identification performance at about 50% correct. On each trial a single letter was presented, and the subject was required to identify the letter by verbal response. The resulting 26 X 26 confusion matrix was based on 3,900 trials (150 trials per letter). Several models of visual processing were used to generate predicted confusions among letter pairs. Models based on template overlap, geometric features, and two-dimensional spatial frequency content (Fourier transforms) were tested. The highest correlation (.70) between actual and predicted confusions was attained by the model based on the Fourier transformed letters filtered by the human contrast sensitivity function. These results demonstrate that the spatial frequency content of visual patterns can provide a valuable metric for predicting their psychological similarity. The results further suggest that spatial frequency models of visual processing are competitive with feature analysis models.
Karmel's check-pattern preference data for 13-week-old infants were reanalyzed using linear systems analysis. The two-dimensional Fourier amplitude spectrum was calculated for each of his eight checkerboard and random check patterns. The mean contrast sensitivity data for 3-month-old infants of Banks and Salapatek and the spatial frequency amplitudes of the patterns were used to derive three metrics to predict the looking times observed by Karmel. One was based on the sensitivity of the visual system to the single pattern component highest above threshold (maximum amplitude), the second was based on the total amount of pattern energy above threshold (total summation), and the third was based on the maximum amplitude with summation over nearby spatial frequency components (limited summation). The predictive power of the maximum amplitude and the total summation metrics depended on whether the pattern type was checkerboard or random check. The limited summation metric predicted looking times well for both pattern types. A linear function of the logarithm of the limited summation metric accounted for 91% of the total variance in looking time.