Biomedical subjects
Publications and source records attributed to S P Chow.
The mechanical rigidity of five different methods of pin fixation in two proximal phalangeal fracture models was studied and absorbable implants were compared with metallic implants in a biomechanical cadaver study. Thirty phalanges were tested in apex palmar bending, compression and torsion. Results showed that rigidity of absorbable implants was comparable with metallic implants, except in torsion.
We report a prospective study of dynamic splintage following extensor tendon repair. Eighty-four patients with 101 extensor tendon injuries were studied. Using Dargan's evaluation system, there were 97% excellent results for the thumb and 93% excellent and good results for the fingers. The average total active motions were 107 degrees for thumbs and 245 degrees for fingers. Over 80% of patients regained good power grip. Patients with associated digital fractures or with ragged lacerations had poorer results. Overall, we found that dynamic splintage was a satisfactory method after extensor repair.
Thirty-four displaced intra-articular fractures of the distal aspect of the radius in thirty-four patients were treated with open reduction and internal fixation with plates and screws. Although there was a high rate of complications (nine [26 per cent] of thirty-four fractures), twenty-eight patients (82 per cent) had a good or excellent result according to the system of Gartland and Werley and twenty patients (59 per cent) had a good or excellent result according to the modified system of Green and O'Brien at the most recent evaluation. Immediately postoperatively, the articular surface of the distal aspect of the radius was restored to a mean of 2 degrees of volar tilt and 20 degrees of radial angulation and radial length was improved by a mean of ten millimeters compared with the preoperative length. The articular surface was restored to congruity or to at most one millimeter of step-off in twenty-six patients (76 per cent). By the time of the most recent evaluation, the initial postoperative alignment had changed markedly in three patients (9 per cent) and degenerative osteoarthrosis (grade II or III) had developed in six patients (18 per cent). We considered that the initial postoperative alignment had changed markedly when the articular surface was displaced by two millimeters or more, when the extra-articular alignment had changed by more than 10 degrees of radial tilt, or when there was more than five millimeters of radial shortening. The potential for restoration of normal alignment and the stability of the fixation are the main advantages of internal fixation with plates. Restoration of congruity to the joint was the major difficulty in this group of patients.
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A prospective study of 1129 patients with 1358 digital fractures of the hand was carried out between March 1984 and March 1994; of these, 924 fulfilled the criteria for inclusion. Functionally stable fractures with acceptable alignment were managed with immediate active mobilization. Unstable fractures, or fractures with unacceptable alignment, were openly reduced and fixed internally so that active mobilization could begin immediately after operation. The function results using various systems of evaluation were excellent or good in over 90 per cent of the fractured thumbs, and excellent or good in 58.7 per cent to 76.5 per cent of the fingers. Patients who did not require surgery did much better than those in the operated group. Comminuted, open and multiple fractures proved to be of poor prognostic value. However, rigid fixation was statistically significant in influencing the outcome.
A prospective study was made of 1500 elderly patients who suffered from acute hip fractures from 1986 to 1990. There were 36 per cent more fractures in the 6 colder months from November to April than in the rest of the year (P < 0.001). A strong correlation between the monthly adjusted fracture rate and the average lowest ambient temperature was also observed (P < 0.001). The fractures occurred in the older and less active patients during the 6 colder months. More importantly, they needed to wait longer for the operation during this 'high' season. This might be responsible for the higher medical complication rate after the operation. Better health care planning to help with the increased patient load in the 'high' season is essential to reduce the waiting time for the operation and the postoperative medical complication rate.
The mechanical rigidity obtained by external fixation in a comminuted phalangeal fracture model was assessed and the results compared with two other types of internal fixation commonly used (lateral plate and crossed Kirschner wires) in a biomechanical cadaver study. Each fixation technique was tested in apex palmar bending, compression and torsion. The results showed that lateral plating provided the best rigidity in apex palmar bending and compression and that external fixation and Kirschner wires showed the same mechanical properties. For the torque test, external fixation provided the best rigidity.
The rigidities of five fixation methods have been studied with a comminuted phalangeal fracture model. Mechanical testing of compression, bending and torsion were performed for each fixation. Lateral plating with six screws seems to provide the most rigid fixation. If such lateral plating is not practicable, the four-Kirschner wire method would be a satisfactory alternative.
We examined the effects of dorsal root ganglion isografts on the denervation process of skeletal muscle. A segment of sciatic nerve was removed from each of 25 inbred Wistar-Kyoto rats. Fifteen were set aside as controls. In the remaining 10 rats, isogeneic cervical dorsal root ganglia were grafted to the severed distal stump of the common peroneal nerve. Between day 72 and day 286 postoperatively, both controls and recipients were killed after twitch and tetanic tension recording of the extensor digitorum longus was performed. The wet muscle weight and the twitch and tetanic tensions of the denervated extensor digitorum longus in the graft group were significantly greater than those in the control group. The mean area of the denervated tibialis anterior muscle fibers in the graft group also was significantly larger than that in the control group. In electron and light microscopic images, nerve cells along the periphery of each dorsal root ganglion were found surviving with regenerating axons throughout the experimental period. Numerous myelinated axons were observed in the common peroneal nerve of the graft group, and there were significantly more axonal branches in the extensor digitorum longus of the graft group than in the extensor digitorum longus of the control group. Thus sensory nerve fibers from the grafted dorsal root ganglia had certain beneficial effects to slow the denervation process, presumably secreting trophic factors into the denervated muscle. Clinically, we have transferred avulsed dorsal root ganglia in cases of total brachial plexus avulsion directly into denervated skeletal muscle. This procedure, accompanied by nerve crossing procedures, will probably keep denervated skeletal muscle in a better condition until regenerating motor axons from the repair site reach their target muscle.
In a review of 52 consecutive intra-articular fractures of the wrist (mean age 41 years), 18 developed one of five carpal malalignment patterns. Seven patients developed a volar intercalated collapse pattern. Although showing some loss of motion and/or grip strength, this group remains relatively pain free on follow-up. Patients who developed dorsal translation (six cases) or a dorsal intercalated collapse pattern (one case) were the most symptomatic, with loss of grip strength, decreased range of motion and pain being prevalent.
Closed avulsion of both flexor digitorum profundus and superficialis from the same finger is rare. Only ten cases have been described in the literature. The majority were treated with a two stage reconstruction of the flexor digitorum profundus. We describe a case in which primary repair of both tendons was performed.
Experience in treating 80 subcapital femoral neck fractures by AO/ASIF cancellous screws is reported. Immediate full-weight bearing was allowed routinely. The mean follow-up was 28 months. Non-union occurred in 2% and late segmental collapse in 12% of patients with undisplaced fractures. Non-union occurred in 16.7% and late segmental collapse in 30% of patients for displaced fractures. Regression of screws occurred in 30% of patients, all of which were detected within the first month after the operation. It was associated with a significantly higher risk of non-union and late segmental collapse for both undisplaced (P < 0.01) and displaced (P < 0.001) fractures.
A prospective clinical trial was conducted involving patients with prolapsed lumbar intervertebral disk proven myelographically, who had anterior diskectomy and disk replacement with a titanium-mesh block implant. A pilot study was done in 1971 on six patients. In this trial, 28 patients were operated on with informed consent. Twenty-three had a minimum of five years' follow-up study. There were 14 men and boys, and nine women and girls. The average follow-up period was eight years and four months (range, five to 12 years three months). The average age at operation was 36 years four months (range, 13-66 years). Symptomatic improvement were divided into three groups. Sixteen patients were in Group 1, three in Group 2, and three in Group 3. Flexion-extension radiographs showed 14 patients with no movement between the vertebral bodies adjacent to the operated disk, five with minimal movement, and four with definite movement. At the implant-bone interface, no radiolucent zone was seen in 18 patients, and a definite radiolucent zone was seen in five. Twenty implants were intact, three implants had developed a crack, and three were deformed. There were no complications. The titanium-mesh block implant is an effective substitute for autogenous bone grafting in interbody fusion.
72 fingers with divided digital nerves on one side alone had their nerves repaired and the sensory recovery assessed at different intervals of up to 2 years. Another 36 fingers with similar digital nerve injuries had their divided nerves left unrepaired and sensory recovery similarly assessed for comparison. In the "repaired" group, the result continued to improve and by 2 years, 90% reached S3+ or above. In the "unrepaired" group, improvement plateaued after 6 months, and at 2 years only 6% reached S3+ or above, although all had regained some protective sensibility.
We report a prospective study of 92 articular fractures of the digits. The treatment protocol was based on functional stability and acceptable alignment rather than on joint congruity. 54% of patients had good results, with 22% fair and 24% poor results being recorded. These results are similar to reports of treatment of finger fractures in general and suggest that for articular fractures of the digits, stability and alignment are more important factors than joint congruity in determining short-term outcome. Compound fractures and those associated with comminution, significant soft tissue damage and marked displacement at presentation have a worse prognosis.
127 patients with amputated thumbs or fingers between the level of the DIP and MP joints were followed up at regular intervals until one year after injury. Sensory disturbances subsided rapidly except for numbness which was still present in 50% at one year. Range of movement was regained early. Although pronation and supination improved to 70% only a few months after injury, it took a year for power grip and key pinch to regain 70%. Further analysis showed that power grip was worst in amputees of multiple fingers, thumb, and the middle finger through the proximal phalanx. For key pinch, almost all were impaired to a level of 50% to 60%. Multiple finger amputees also had decreased pronation, and thumb amputees had decreased supination. Other factors were not significant. One-quarter had to change their jobs and one-fifth showed concern with the appearance.
A skin flap in the anterior abdominal wall of the S-D rat was designed so that it was supplied by the superficial epigastric branch of the femoral artery on the right side. Venous drainage was effected through one of five designs: (1) the superficial epigastric vein on the same side, (2) the lateral abdominal vein on the same side, (3) the lateral abdominal vein on the opposite side, (4) the superficial epigastric vein on the opposite side, or (5) a combination of the latter three. Seventy-seven rats were available for final analysis. The surviving percentage area of the flap was found to improve with increased venous drainage and when the arterial blood had to traverse the flap to reach the diagonally situated draining vein. The use of venae commitante as the draining vein is not satisfactory.
One hundred and twenty patients with acute hip fractures treated operatively were randomized into two groups. In the 'drape' group (n = 65) the operation site was covered with plastic adhesive drape after preparation. In the 'no drape' group (n = 55) the operation site was left uncovered. The two groups were otherwise matched. Swabs for culture were taken from skin adjacent to the wound before closure. The drape group had four positive wound swabs. There was only one positive wound swab for the no-drape group. There was no difference in the post-operative wound infection rates.