Analysis of the cephalometric changes in the first 3 months after spring-assisted cranioplasty for scaphocephaly.

BACKGROUND: Spring-assisted cranioplasty (SAC) has become an accepted treatment for patients with sagittal craniosynostosis; however, the early effects of springs on skull dimensions have never been assessed with objective measurements in the literature. The present study evaluated the changes in skull dimensions and intracranial volume (ICV) during the first 3 months after SAC for sagittal synostosis. METHODS: Sixteen patients with sagittal synostosis underwent SAC. The cephalic index (CI) and the distance between the spring foot plates were chronologically measured until spring removal at 3 months. Pre- and post-treatment CT scans available for 6 patients were used to assess changes in head shape. Thirteen patients underwent objective aesthetic assessment using pre- and post-operative photographs. Statistical analysis was performed using the linear mixed model for chronological data, t-test statistics for normative data comparisons and Wilcoxon's signed rank test for non-parametric data. RESULTS: For scaphocephalic patients, pre-operative and post-operative CIs were 0.70 and 0.74 (p = 0.001), respectively. Cranial widening towards normative values was observed (p = 0.0005). A continuous expansion in the distance between the spring foot plates was observed over the treatment period. Frontal and occipital angles were not affected by SAC despite apparent clinical improvements in frontal bossing and occipital prominence. CT analysis demonstrated relative reduction in the anterior cranial volume (p = 0.01) and relative expansion of the superior occipital volume (p = 0.03). CONCLUSIONS: Spring expansion was most marked in the hours following spring insertion. The expansion rate reduced to the minimum by day 1 post-operatively. Clinical benefits of SAC resulted from an increase in the bi-temporal width that camouflaged the frontal bossing. Improvement in occipital prominence was due to superior occipital volume expansion, allowing the occiput to remodel to a more rounded shape.

Sialoblastoma arising in ectopic salivary gland tissue.

Sialoblastoma is a rare, congenital or perinatal tumour predominately affecting the parotid or submandibular salivary glands. We report a case of sialoblastoma arising in ectopic salivary gland tissue in the anterior cheek of a female infant. This lesion clinically and on ultrasound mimicked a haemangioma. Following imaging and tissue diagnosis, the lesion was surgically excised with clear margins. The patient remained disease free at 6 months follow up.

Resistance forces acting on suture needles.

Understanding the resistance forces encountered by a suture needle during tissue penetration is important for the development of robotic surgical devices and virtual reality surgical simulators. Tensile forces applied to skin and tendon during suturing were measured. Fresh sheep achilles tendons were tensioned with a static load 4.9 N, 9.8 N or 19.6 N and sheepskin with 0.98 N, 2.9 N or 4.9 N static load. A straight 2/0 cutting suture needle in series with a load cell on a materials testing machine penetrated the tissue at 90 degrees with a velocity of 1, 5 or 10mm/s for each tissue tension (n=5). Continuous load versus displacement data was obtained and penetration load and stiffness were noted. The load versus displacement curve for skin during needle penetration demonstrated two characteristic peaks, corresponding to initial penetration and emergence of needle from the undersurface of the tissue. Increasing the tension within the tissue (skin and tendon) increased the amount of force required to penetrate the tissue with a suture needle (p<0.05). Needle displacement rate did not affect the resistance to needle penetration (p<0.05). This study provides a simple model for measuring force-feedback during needle penetration of soft tissues and is a good starting point for future studies of the penetration resistance properties of human tissues.

Grasper trauma during laparoscopic cholecystectomy.

BACKGROUND: The present study characterized the histopathological nature of laparoscopic grasper trauma during laparoscopic cholecystectomy in a prospective, blinded trial in order to establish a model for laparoscopic grasper trauma. The null hypothesis that graspers cause no histologically distinct tissue injury was tested. METHODS: The gall bladders of 19 patients undergoing laparoscopic cholecystectomy were examined. The area of gall bladder that had been grasped by Debakey laparoscopic forceps was excised (sample), along with an area of gall bladder that had not been grasped (control). Paired specimens were examined by a pathologist (blinded) to identify which was 'sample' and which was 'control' and to assess for histological markers of crushed tissue injury. The data were analysed by chi-squared or Fisher's exact tests. RESULTS: The pathologist was able to identify the sample (gripped) specimen in 13 of the 19 cases. In the remaining six cases the pathologist was unable to determine the specimen that had been gripped due to either absence of damage (four cases), or severe inflammation precluding assessment (two cases). The ability of the pathologist to distinguish the sample from the control specimen was significant (chi-squared test, P = 0.003). Of the histological markers of crushed tissue injury, focal thinning of the gall bladder wall and epithelial loss were present in significantly more sample (gripped) specimens than control specimens (chi-squared test, P = 0.0002 and P < 0.0001, respectively). CONCLUSIONS: Laparoscopic graspers cause tissue trauma that can be assessed histologically. The current study presents a relevant, reproducible, ethically acceptable human model for assessing the interaction between laparoscopic graspers and soft tissues.

Patterns of failure at the instrument-tissue interface.

BACKGROUND: The effect of jaw design on grip security and tissue trauma is poorly understood. This project establishes an in vitro model of the instrument-tissue interface. MATERIALS AND METHODS: Aluminum jaws with teeth of differing size and shape gripped fresh sheep stomach with variable apposing (squeeze) pressure. The tissue was extracted at a rate of 50 mm/min until either the grip or the tissue failed. The load at which the grip failed, the maximum (peak) load generated, and the mode of failure were noted. The data were analyzed using ANOVA and a post hoc Duncan's multiple range test when appropriate. RESULTS: Increasing the apposing pressure increased grip security. Grip security of 1- and 2-mm pitch teeth were significantly greater than for plane jaws and smaller-pitch teeth (P < 0.001). Of the wave pattern jaws, 2-mm pitch waves also had significantly greater grip security than plane jaws and smaller pitch waves (P < 0.01). Wave pattern jaws produced significantly less tissue trauma than teeth (P < 0.0001). CONCLUSIONS: Increasing the size of instrument teeth increases grip security but at the expense of tissue trauma. Wave pattern jaws result in significantly less tissue trauma than teeth. This model measures grip security precisely and allows for comparison between jaws of different patterns.

Does the sheep mandible relapse following lengthening by distraction osteogenesis?

AIM: Distraction osteogenesis is a technique used to lengthen the shortened mandible. However, the long term stability of the distracted mandibular bone is not known. The aim of this study was to assess if the sheep mandible relapses following lengthening, and to assess the quality of distracted bone up to 1 year post lengthening. METHODS: Twenty-four sheep had bilateral external mandibular distractors applied, with three sheep as controls. Titanium marker screws were positioned both proximal and distal to the distraction zone in all sheep. Following a 5 day latency period, the interdental gap was distracted 1 mm/day for 20 days, with a subsequent 20 day consolidation period. Ante-mortem serial X-rays were used to assess for relapse by measuring the distance between the screws. The animals were sacrificed at either 3, 6, 9 or 12 months post-distraction. At post mortem, the distance between the screws was re-measured. The distracted bone was assessed mechanically and histologically. RESULTS: The mean mandibular lengthening obtained was 13.2 mm. There was no relapse of the mandible over 12 months. The distracted bone had attained the strength and stiffness of undistracted bone by 6 months post-distraction (p < 0.05). Histological evaluation revealed significant amounts of lamellar bone by 6 months post-distraction. CONCLUSIONS: No relapse occurred for 12 months post distraction lengthening. The bone formed following distraction was stable and of good quality. These findings lend support to the use of distraction osteogenesis in clinical practice.