Positional Stability of Electromagnetic Transponders Used for Prostate Localization and Continuous, Real-Time Tracking

PURPOSE

To determine the relative positional stability of implanted glass-encapsulated circuits (transponders) used in continuous electromagnetic localization and tracking of target volumes during radiation therapy. Ideally, the distances between transponders remains constant over the course of treatment. In this work, we evaluate the accuracy of these conditions.

METHODS AND MATERIALS

Three transponders were implanted in each of 20 patients. Images (CT scan or X-ray pair) were acquired at 13 time points. These images occurred from the day of implant (2 weeks before simulation) to 4 weeks posttreatment. The distance between transponders was determined from each dataset. The average and standard deviation of each distance were determined, and changes were evaluated over several time periods, including pretreatment and during therapy.

RESULTS

Of 60 transponders implanted, 58 showed no significant migration from their intended positions. Of the two transponders that did migrate, one appears to have been implanted in the venous plexus, and the other in the urethra, with no clinical consequences to the patients. An analysis that included the planning CT scan and all subsequent distance measurements showed that the standard deviation of intertransponder distances was < or =1.2 mm for up to 1 month after the completion of therapy.

CONCLUSIONS

Implanted transponders demonstrate the same long-term stability characteristics as implanted gold markers, within statistical uncertainties. As with gold markers, and using the same implant procedure, basic guidelines for the placement of transponders within the prostate help ensure minimal migration.

Displacement of a maxillary third molar into the infratemporal fossa: case report

The case of a maxillary third molar displaced into the infratemporal fossa, with difficulty in localization due to the synchronous creation of oroantral communication, is described in this article. The patient was referred to the oral and maxillofacial department and underwent successful surgical treatment through an intraoral access. The causes of tooth displacement into the infratemporal fossa, the aid of a computerized tomography (CT) scan in tooth localization, and the difficulty in treating this complication, particularly when the tooth migrates toward the base of the skull, are emphasized. Prevention of maxillary third molar displacement into the infratemporal fossa predominates over removal and is achieved by adequate flap design, correct extraction technique, and a distal retractor during surgical extraction. In the case of displacement, no effort to retrieve the tooth is recommended because of the risk of hemorrhage, neurologic injury, and further displacement of the tooth. The patient should be treated with antibiotics and referred to an oral and maxillofacial department.

Spontaneous expulsion of a bullet, in the body of second cervical vertebrae, via the mouth

Gunshot wounds to the upper cervical spine without neurological deficit occur infrequently. In this report, we describe a case with spontaneous expulsion of a bullet located in the body of second cervical vertebrae (C2) via mouth.

Occipital nerve stimulation for chronic headache--long-term safety and efficacy

The aim of this study was to examine the safety and efficacy of occipital nerve stimulation for medically intractable headache. Electrical stimulation of large sensory afferents has an antinociceptive effect. Occipital nerve stimulation may be effective for the treatment of medically intractable headache. Retrospective analysis was performed of 15 patients with medically refractory headache who underwent implantation of an occipital nerve stimulator. Pre- and postimplant data regarding headache frequency, severity, disability, depression and poststimulator complications were collected. Twelve patients were female and three male. Ages ranged from 21 to 52 years (mean 39 years). Eight patients had chronic migraine, three chronic cluster, two hemicrania continua and two had post-traumatic headache. Eight patients underwent bilateral and seven had unilateral lead placement. Patients were measured after 5-42 months (mean 19). All six mean headache measures improved significantly from baseline (P < 0.03). Headache frequency per 90 days improved by 25 days from a baseline of 89 days; headache severity (0-10) improved 2.4 points from a baseline of 7.1 points; MIDAS disability improved 70 points from a baseline of 179 points; HIT-6 scores improved 11 points from a baseline of 71 points; BDI-II improved eight points from a baseline of 20 points; and the mean subjective percent change in pain was 52%. Most patients (60%) required lead revision within 1 year. One patient required generator revision. Occipital nerve stimulation may be effective in some patients with intractable headache. Surgical revisions may be commonly required. Safety and efficacy results from prospective, randomized, sham-controlled studies in patients with medically refractory headache are needed.

Antireflux stents for palliation of malignant esophagocardial stenosis

Placement of self-expanding metal stents (SEMS) for palliation of malignant stenoses at the gastroesophageal junction is often associated with stent migration and reflux symptoms. SEMS with an antireflux mechanism have been developed to overcome the latter problem. The aim of this study was to evaluate the safety and efficacy of antireflux Z-stents. Patients with advanced squamous cell or adenocarcinoma of the distal esophagus or cardia suffering from dysphagia received an antireflux Z-stent. Technical success, complications of the procedure, clinical symptoms before and after stent placement, reinterventions and survival were recorded. Follow-up was accomplished by patient interviews and a standardized questionnaire for primary care physicians. Eighteen consecutive patients received an antireflux Z-stent. Seventeen of 18 stents were placed technically successful in a single endoscopic procedure. Mean dysphagia score improved from 2.2 to 0.6. Four patients (22%) had permanent reflux symptoms, an additional nine (50%) were taking proton pump inhibitors on a regular basis. In 10 patients, a re-intervention was necessary mainly due to dislocation of the stent. To ensure adequate nutrition three and two patients received a percutaneous gastrostomy and a jejunostomy, respectively. Median survival from stent insertion was 54 days (range, 3-201). Although placement of an antireflux Z-stent is technically feasible, its application is hampered by frequent stent migration and insufficient prevention of gastroesophageal reflux. Further technical improvements of stents or alternative methods like brachytherapy are required for satisfactory palliation of malignant gastroesophageal stenosis.

Acetabular outcome after hip hemiarthroplasty in patients with tumors

Hip hemiarthroplasty is performed routinely on patients with tumors of the proximal femur, although the long-term effect on the native acetabulum is unknown. We measured the amount of femoral head migration that would occur with intermediate and long-term followup. We also measured the amount of groin pain experienced by patients with longer followup and the overall rate of conversion to total hip arthroplasty. From a surgical database, we identified 442 patients with tumors who had 447 hip hemiarthroplasties without or with an allograft composite. We reviewed the medical records and radiographs of 32 patients with at least 5 years followup (median followup, 10 years) to determine their clinical and radiographic outcomes. The median proximal and medial migration measurements were 3 mm (range, 0-24 mm) and 2 mm (range 0-20 mm), respectively. Thirty-one patients had minimal or no groin pain. Seven of the 447 arthroplasties (1.6%) were converted to total hip arthroplasties. Even patients with long-term followup usually had minimal pain and radiographic changes. The overall rate of conversion to total hip arthroplasty was low. Concern regarding excessive acetabular wear resulting in conversion to total hip arthroplasty in patients with tumors is not supported by our data.

Pregnancy in a patient with a displaced levonorgestrel-releasing intrauterine system: a case report

We report the case of a 39-year-old woman who became pregnant despite a levonorgestrel-releasing intrauterine system (LNG-IUS), which was inserted 40 months before the pregnancy was detected. When a Caesarean section was performed, the LNG-IUS was found within the omentum majus. It has been reported, that displaced LNG-IUS can cause amenorrhea and high plasma levels of LNG in affected women, probably due to the higher resorptive capacity of the peritoneum, recommending a removal of the displaced LNG-IUS. Our case report demonstrates that a dislocated LNG-IUS does not necessary has the ability to suppress ovulation and therefore pregnancy. Therefore, every gynaecologist should be aware of a pregnancy despite a dislocated LNG-IUS.

Late prevertebral abscess following anterior cervical plating: The missing screw

A 51-year-old man underwent a C5-C7 anterior decompression and fusion. Six years later the patient complained of dysphagia caused by displacement of the cervical plate. One week after the scheduled removal of the implanted material, the patient developed a painful cervical swelling and fever. His cervical radiographs showed that a screw was missing compared to previous studies. Computerized tomography showed a large prevertebral abscess anterior to C4-C7. He underwent emergency surgical drainage of the abscess that was followed by total recovery. This report is aimed at describing this unusual complication of cervical instrumentation and to briefly review its pathogenesis and management options.

Tracheal replacement by allogenic aorta in the pig

BACKGROUND

To assess whether fresh aortic allografts (AAs) can be used for tracheal replacement.

METHODS

Twenty-one male minipigs underwent tracheal replacement using AAs harvested from female pigs. The length of replaced segments exceeded 50% of the trachea. A stent was implanted into the lumen of the AA to prevent collapse. The animals were killed at 3-month intervals, and AAs were assessed for ingrowth of respiratory epithelium and cartilage formation and tested for type II collagen formation and the presence of the SRY gene.

RESULTS

A high stent migration rate was observed. Only 10 pigs and 4 pigs made it to follow-up periods exceeding 3 months and 9 months, respectively. Neither rejection nor ischemia were observed. At 3 months, a metaplastic epithelium lined the graft. At 10 months, a posterior membrane could be seen with immature cartilage and disorganized elastic fibers. SRY gene assay showed that the cells engrafted in the AAs, particularly at the level of the newly formed cartilage, were of male origin and thus originated from the recipient.

CONCLUSION

This study confirms that a fresh AA, replacing more than half of the trachea of the pig, transforms into a conduit containing the major tracheal components. These components are relatively immature and do not as of yet replicate the form and function of the native trachea. Questions remain concerning the exact mechanisms of this process. Further research on the role of tracheal replacement is recommended.

A wandering fish bone

A unique case is described of an ingested fish bone migrating into the common hepatic duct, without perforation. Most foreign bodies are known to pass through the gastrointestinal tract uneventfully. Sharper objects such as fish bones have been known to cause perforation. This is more common, in countries where fish consumption is considerably higher, such as, south east Asia. However, even in these regions there have been no reports of such a proximal migration.

Self-expandable stent loaded with 125I seeds: feasibility and safety in a rabbit model

OBJECTIVE

To evaluate technical feasibility and acute and subacute radiotolerance of a self-expandable stent loaded with (125)I seeds in the rabbit esophagus.

METHODS

A self-expandable stent designed for esophageal application was made of 0.16mm nitinol wire and loaded with (125)I seeds (CIAE-6711). Twenty-seven stents with three different radioactive dosages (n=9 in each dosage group) were implanted in the esophagus of healthy rabbits, while nine stents alone were used as controls. The stents were perorally deployed into the esophagus under fluoroscopic guidance. Radiological follow-up included plain chest film, CT scan, and barium esophagography which were undertaken in all rabbits of each group at 2, 4, and 8 weeks, respectively, which were correlated to histopathological findings. The stented esophageal segments along with their adjacent tissues were harvested for histopathological examinations.

RESULTS

The stent was successfully deployed into the targeted esophageal segment in all rabbits. Neither (125)I seeds dislodged from the stent during the deployment, nor they did during the follow-up period. The greatest (16.2Gy) absorbed dose was found in the tissue 10mm from (125)I seeds at 8 weeks. Slight epithelial hyperplasia on the stent surface and submucosal inflammatory process developed at 2 weeks, which reached the peak at 8 weeks after the procedure. Significant thickness of the esophageal muscular layer was found at 8 weeks only in the groups with (125)I seeds. On radiologic follow-up, moderate strictures on both ends of the stents developed at 4 weeks and became severe at 8 weeks after the procedure in all groups.

CONCLUSION

Deployment of a self-expandable stent loaded with (125)I seeds is technically feasible and safe within the first 8 weeks. Acute and subacute radiotolerance of the treated esophagus and its adjacent tissues by (125)I seeds is well preserved in a healthy rabbit model.

Sequestrated lumbar intervertebral disc in the posterior epidural space: a report on two cases and review of the literature

BACKGROUND

Posterior epidural migration is an interesting but rare path taken by a prolapsed intervertebral disc fragment. There are only seven cases reported of a similar migration of the disc fragment in the lumbar spine.

PURPOSE

To diagnose the unusual presentation and interpretation of the sequestrated disc in the posterior epidural space.

STUDY DESIGN

Case report.

METHODS

Two cases of migration of the sequestrated disc into the posterior epidural space are presented. In one patient there was weakness of the ankle dorsiflexors, foot invertors, and toe extensors of the left foot, with sensory loss over the back of the calf and over the lateral three toes. The left ankle jerk was also absent. However, in the other case, there was no objective evidence of neurological deficit distally.

RESULTS

Gadolinium magnetic resonance imaging scans showed ring enhancement preoperatively. Biopsy of the specimen taken from surgery confirmed it to be sequestrated disc fragment.

CONCLUSION

Diagnosis of posterior epidural migration of the sequestrated discs may be difficult. It may present with subtle clinical features even though the disc transgresses through numerous anatomic restraints including the nerve roots in such cases.

Migration of Implanon

OBJECTIVE

To determine whether or not migration of the Implanon rod does occur if correctly positioned and, if indeed migration does occur, to measure the degree of such migration.

METHODS

A prospective study of 100 women who requested and had Implanon rods inserted by one fully trained health care professional holding the Faculty of Family Planning and Reproductive Health Care Letter of Competence in Subdermal Contraceptive Implant Techniques. Measurements were made from the insertion site to the distal end of the rods at 3 and 12 months post-insertion.

RESULTS

Of the 100 women studied, 95 were seen for follow-up at 3 months. There was no migration of Implanon in 58 (61%) patients. Of the remaining 37 (39%) patients where migration had occurred, 34 showed migration caudally and only three demonstrated cranial migration. With regard to the degree of migration, all but one case showed this to be less than 2 cm either cranially or caudally. At 1-year follow-up 87 patients were seen. No migration was noted in 39 (45%) patients. In the remaining 48 (55%) patients where migration had occurred, 44 showed migration caudally and only four demonstrated cranial migration, which in one case was over 2 cm. With regard to the degree of migration, all but one case showed this to be less than 2 cm either cranially or caudally. The measurement in the single case showing migration over 2 cm at 3 months remained the same at the 1-year follow-up.

CONCLUSIONS

These results show that up to 1 year after insertion of Implanon significant migration of the rod does not occur. The degree of migration noted in all cases except one was less than 2 cm. Where migration was noted, in the majority of cases this occurred caudally towards the insertion site. There were no cases of deep migration.

Cranial migration of complete ventriculo-peritoneal shunt assembly

A 10-month-old male child with severe congenital hydrocephalus due to aqueduct stenosis presented with cranial migration of the entire ventriculo-peritoneal (VP) shunt. The complete shunt assembly, including the shunt chamber, was noted in the dilated ventricles. The migrated shunt was left in situ. A VP shunt was performed on the opposite side. The complete intraventricular migration of a VP shunt is a rare complication. This complication may be avoided by firm anchoring of the connector sites to the periosteum, and avoidance of large burr holes and dural openings. The possible mechanisms of such an event and the relevant literature are discussed.