Augmented Reality-Supported Rod Bending in Multilevel Spinal Fusion Using the ADVISE Software

BACKGROUND

One of the most common reasons for poor patient outcomes and revision surgery in spinal fusion is hardware failure. Screw loosening or pullout occurs in up to one-quarter of all cases. It is known that even small screw-rod misalignments can cause significant mechanical overloads during rod fixation, which can result in hardware failure. To address this crucial surgical step, a novel augmented reality-assisted software was developed to generate custom rod templates that are precisely adapted to the individual patient.

METHODS

The novel software, which runs on a tablet, is used in spinal fusion surgery and is based on the use of a specific pedicle screw system, in which the polyaxial screw heads are connected to detachable guides. These guides can be recognized by the tablet camera and a light detection and ranging scanner. This image information is processed to determine the spatial positions of the screw heads and to calculate an ideally fitting rod template.

RESULTS

The calculated rod template is displayed in a 1-to-1 scale on the tablet screen. This template is used to cut and bend the rods of the pedicle screw system. Finally, the custom bent rod can be inserted into the screw heads without tension.

CONCLUSIONS

The augmented reality-assisted software is intended to give surgeons access to patient-specific intraoperative real-time data, helping them in bending rods that are more precisely adapted to the individual patient compared with the freehand technique.

Revision surgery following CSF shunt insertion: how often could it be avoided?

BACKGROUND

Cerebrospinal fluid (CSF) shunt revision surgery represents a huge social and economic burden. Few studies, however, have evaluated shunt revision surgeries in the context of their avoidability, and existing data are from paediatric populations. Using ratings from an expert panel, we classified avoidable and unavoidable shunt revisions in a mixed cohort of CSF-shunt patients.

METHODS

In a retrospective review of a prospectively maintained, single-centre database, we identified all shunt systems implanted for the first time over a 10-year period (2007-2016) and all subsequent revision surgeries with a follow-up of at least 1 year. A panel of five expert shunt surgeons classified each revision surgery as avoidable or unavoidable. Rates of each were calculated and correlated with clinical data.

RESULTS

Of 210 revision surgeries (314 patients, mean age, 49.9 years; mean follow-up, 4.2 years), the panel judged 114 as unavoidable (54.3%) and 96 (45.7%) as avoidable. Level of surgeon education correlated with these rates, but even in the most experienced hands, 12.5% of revisions were classified as avoidable. Avoidable revisions occurred significantly earlier than unavoidable interventions (mean; 112 and 448 days, respectively) after the index surgery.

CONCLUSION

Rates of avoidable shunt revision surgery are alarmingly high, even in experienced hands. Avoidable revisions occur significantly earlier, predominantly within the first 3 months after the index surgery.

The use of intraoperative computed tomography navigation in pituitary surgery promises a better intraoperative orientation in special cases

OBJECTIVE

The safety of endoscopic skull base surgery can be enhanced by accurate navigation in preoperative computed tomography (CT) and magnetic resonance imaging (MRI). Here, we report our initial experience of real-time intraoperative CT-guided navigation surgery for pituitary tumors in childhood.

MATERIALS AND METHODS

We report the case of a 15-year-old girl with a huge growth hormone-secreting pituitary adenoma with supra- and perisellar extension. Furthermore, the skull base was infiltrated. In this case, we performed an endonasal transsphenoidal approach for debulking the adenoma and for chiasma decompression. We used an MRI neuronavigation (Medtronic Stealth Air System) which was registered via intraoperative CT scan (Siemens CT Somatom). Preexisting MRI studies (navigation protocol) were fused with the intraoperative CT scans to enable three-dimensional navigation based on MR and CT imaging data. Intraoperatively, we did a further CT scan for resection control.

RESULTS

The intraoperative accuracy of the neuronavigation was excellent. There was an adjustment of <1 mm. The navigation was very helpful for orientation on the destroyed skull base in the sphenoid sinus. After opening the sellar region and tumor debulking, we did a CT scan for resection control because the extent of resection was not credible evaluable in this huge infiltrating adenoma. Thereby, we were able to demonstrate a sufficient decompression of the chiasma and complete resection of the medial part of the adenoma in the intraoperative CT images.

CONCLUSIONS

The use of intraoperative CT/MRI-guided neuronavigation for transsphenoidal surgery is a time-effective, safe, and technically beneficial technique for special cases.

Home telemonitoring of intracranial pressure

BACKGROUND

As technical progress advances, telemonitoring has become an important part of patient care in many areas of medical treatment. However, distanced surveillance of intracranial pressure (ICP) could not be established so far. With the recent introduction of a telemetric ICP measurement probe, new possibilities arise. Here, we report on a new home setup enabling home telemonitoring of intracranial pressure.

METHODS

Twenty patients suffering from disturbances of cerebrospinal fluid circulation, who underwent insertion of a telemetric ICP measurement probe, were provided with medical equipment to read ICP at home and save the data on an internet-enabled computer. Training in handling the equipment was performed during in-patient stay; recorded and uploaded ICP data was then analyzed online. Therefore, the treating medical team was able to access the ICP data via a secure internet connection while telephone conferencing with the patient.

RESULTS

Almost 7400 h of ICP data were recorded at home and evaluated via an internet connection according to the telemonitoring setup. This corresponds to an average record time of about 370 h per patient. ICP profiles were observed following endoscopic treatment, shunting procedures, or valve adjustments. The mean distance between the patients' residence and the consulting hospital was 172 km (range, 16-649 km).

CONCLUSIONS

ICP measurements have become accessible for telemonitoring purposes. This new management of hydrocephalus reflects an alternative method in patient care, especially for those who live far away from specialized centers.

Cerebral vasospasm after endoscopic fenestration of a temporal arachnoid cyst in a child-a case report and review of the literature

INTRODUCTION

Intracranial arachnoid cysts (ACs) represent rare extra-axial CSF-containing lesions. Surgical management mainly depends on the cyst location and its size. Nevertheless, pure endoscopic fenestration represents a relatively straightforward and safe technique, and-in most cases-the treatment of choice for symptomatic intracranial ACs. The postoperative complication rate of the procedure is low including subdural hematomas, hygromas, and intraparenchymal hemorrhages. Symptomatic cerebral vasospasm after endoscopic treatment of ACs is a very uncommon event.

CASE REPORT/RESULTS

To the authors' knowledge, this adverse event in children has not yet been reported in the literature yet. The authors present a case of a 9-year-old child developing an early symptomatic cerebral vasospasm with an insignificant secondary ischemia following endoscopic fenestration of a large temporal arachnoid cyst.

DISCUSSION

The clinical approach, possible pathogenesis, and the therapeutic strategy is discussed particularly with regard to the literature.

The view through the ventricle catheter - The new ShuntScope for the therapy of pediatric hydrocephalus

PURPOSE

Correct placement of the ventricle catheter directly influences the function of cerebral shunt systems. The incidence of proximal catheter misplacement reaches up to 45%. To avoid misplacements and revisions a new intra-catheter endoscope for precise ventricle catheter placement in children was evaluated.

METHODS

The semi-rigid ShuntScope (Karl Storz GmbH & Co.KG, Tuttlingen, Germany) with an outer diameter of 1.0 mm and an image resolution of 10,000 pixels was used in a series of 27 children and adolescents (18 males, 9 females, age range 2 months-18 years). Indications included catheter placement in aqueductal stenting (n = 4), first time shunt placement (n = 5), burr hole reservoir insertion (n = 4), catheter placement after endoscopic procedures (n = 7) and revision surgery of the ventricle catheter (n = 7).

RESULTS

ShuntScope guided precise catheter placement was achieved in 26 of 27 patients. In one case of aqueductal stenting, the procedure had to be abandoned. One single wound healing problem was noted as a complications. Intraventricular image quality was always sufficient to recognize the anatomical structures. In case of catheter removal, it was helpful to identify adherent vessels or membranes. Penetration of small adhesions or thin membranes was feasible. Postoperative imaging studies demonstrated catheter tip placements analogous to the intraoperative findings.

CONCLUSIONS

Misplacements of shunt catheters are completely avoidable with the presented intra-catheter technique including slit ventricles or even aqueductal stenting. Potential complications can be avoided during revision surgery. The implementation of the ShuntScope is recommended in pediatric neurosurgery.

Aqueductal stenting with an intra-catheter endoscope--a technical note

INTRODUCTION

Aqueductoplasty as well as aqueductal stenting is an accepted therapy option in short-segment aqueductal stenosis and isolated fourth ventricle. Over the years, different techniques with only slight modifications by using a conventional neuroendoscope with a working sheath to introduce different instruments have been presented. In summary, the use of Fogarty balloon catheters or flexible endoscopes to pass the narrowed aqueduct is recommended.

METHODS

This technical report describes a substantially new technique for this purpose. Six patients underwent aqueductal stenting with a new intracatheter endoscope.

RESULTS

Aqueductal stenting was possible in 4 out of 6 cases. No complications occurred. Handling of this new technique was good and easy without a prolonged learning curve. All four stents did work appropriately, and the procedure was considered to be successful. Of the two failures, the technique was abandoned and endoscopic third ventriculostomy (ETV) was performed in one. In the other case, suboccipital shunting was done.

CONCLUSION

This technical report describes a substantially new technique for aqueductal stenting. The combination of an intracatheter miniature endoscope and a prepared ventricular catheter enables careful and elegant aqueductal stenting. Large or flexible endoscopes, balloons, or special instruments to place a stent have become completely obsolete in selected cases.

Clinical and radiological findings in long-term intracranial pressure monitoring

BACKGROUND

Advantages of telemetric devices for long-term intracranial pressure (ICP) measurement have been mentioned several times in the literature. However, descriptions of associated complications are lacking. Therefore, the presented observational study focused on clinical and radiological findings after insertion of an intraparenchymal telemetric ICP monitor.

METHODS

Between April 2010 and February 2013, 185 telemetric ICP catheters were implanted for diagnostic purposes. All patients were clinically followed. Radiological, microbiological and clinical data were analysed.

RESULTS

One brain abscess (0.5 %) and two cutaneous infections (1.1 %) occurred in 185 patients. Staphylococcus spp. could be detected in all cases. Six patients (3.2 %) suffered from single new-onset seizures and one patient (0.5 %) from a temporary hemiparesis. Intracerebral haemorrhages occurred in 15.6 %, most of the time as small punctate bleedings. Perifocal oedematous reactions surrounding inserted telemetric catheters could be observed in 46.9 %. Multiple imaging studies revealed a tendency of complete oedema resolution over time.

CONCLUSIONS

Infectious as well as haemorrhagic complication rates are well comparable with the common literature. The long-term implantation of an ICP probe does not seem to increase the risk of wound infections or brain abscess formation. Surprisingly, very high numbers of oedematous reactions after insertion of the intraparenchymal ICP monitor were seen. Reasons therefore could only be speculated upon.

Overcoming CSF overdrainage with the adjustable gravitational valve proSA

BACKGROUND

Despite progress in shunt valve technology, CSF overdrainage is still one of the most frequent complications in shunt-treated hydrocephalus. Particularly with regard to young and adolescent patients, treatment of manifest overdrainage is complicated by several hardly influenceable factors such as increasing height and mobility. Therefore, the aim of this study was to evaluate the therapeutic efficiency of the new adjustable gravitational valve, proSA.

METHODS

Sixty-four shunt-treated young hydrocephalus patients aged 1.8-41.4 years (15.5 ± 10.5 years) suffering from clinical and/or radiological overdrainage underwent shunt revision surgery with the implantation of the new proSA valve. Clinical outcome after a 1-year follow-up period, pumping function of the valve chambers as well as the number of necessary postoperative valve adjustments were examined.

RESULTS

Fifty-five patients completed the study as planned. All reported a significant improvement of their clinical condition; 91 % described a complete resolution in symptoms related to overdrainage. Preoperatively, more than 85 % of the valve chambers showed no or very slow refilling with CSF. After a year of proSA treatment, more than 90 % exhibited a normal valve chamber function. During the follow-up period, a total of 136 valve adjustments were necessary. None of the proSA valves had to be surgically revised.

CONCLUSIONS

The postoperative adjustability of the opening pressure level is the advantage of the new gravitational valve. The good clinical outcome is attributed to the new valve technology. The proSA appears to be a promising shunt valve to overcome overdrainage in adolescent and adult hydrocephalus patients.

An operative technique combining endoscopic third ventriculostomy and long-term ICP monitoring

Neuroendoscopy has been well established in the treatment of many neurological and neurosurgical diseases. Especially its application in occlusive hydrocephalus to restore a physiological cerebrospinal fluid circulation has been extensively examined in the past. Although such procedures are believed to be safe and effective, complication as well as failure rates up to 20% have been described pointing to the importance of long-term postoperative care. Therefore, different and partly invasive procedures as ventricular drain insertions or complex cranial imaging methods have been proposed; however, associated pitfalls and restrictions often limited their prognostic value and long-term benefit. An operative technique combining endoscopic third ventriculostomy and telemetric increased intracranial pressure monitoring has now been developed to optimize the postoperative care management. The main intention is to provide sufficient brain pressure data for long-term observation and early recognition of endoscopy failures and complications. The new operative technique was applied in a series with 24 patients suffering from occlusive hydrocephalus. Surgical technique and future perspectives are presented.

Single pulse analysis of intracranial pressure for a hydrocephalus implant

The intracranial pressure (ICP) waveform contains important diagnostic information. Changes in ICP are associated with changes of the pulse waveform. This change has explicitly been observed in 13 infusion tests by analyzing 100 Hz ICP data. An algorithm is proposed which automatically extracts the pulse waves and categorizes them into predefined patterns. A developed algorithm determined 88 %±8 % (mean ±SD) of all classified pulse waves correctly on predefined patterns. This algorithm has low computational cost and is independent of a pressure drift in the sensor by using only the relationship between special waveform characteristics. Hence, it could be implemented on a microcontroller of a future electromechanic hydrocephalus shunt system to control the drainage of cerebrospinal fluid (CSF).

Association of Chiari malformation and vitamin B12 deficit in a family

PURPOSE

A clear etiology of Chiari malformation is still lacking. Some associations between this disorder and genetical variations have been reported. Documented cases of familial Chiari malformation in three consecutive generations are rare. Furthermore, an association of Chiari disorder and vitamin B12 deficit has rarely been described in literature.

METHODS

In this study, three generations of a family suffering from Chiari 1 or Chiari 0 malformation have been examined with MRI, clinically and laboratory (hemograms).

RESULTS

Chiari malformation could be confirmed in all presented patients: While the F2 generation (children: 1 × ♀, 1 × ♂) and the female F1 generation (mother and sister of mother) suffered from Chiari type 1, the male F0 generation showed Chiari 0 malformation. F0 and F1 generation further presented with syringomyelia (F0: C4-D1; F1: C4-D2). All patients except the grandfather (F0) underwent surgical posterior fossa decompression to relive successfully cerebellar and hydrocephalus associated progressing clinical symptoms. The hemograms of generation 1 and 2 revealed familial vitamin B12 deficit.

CONCLUSIONS

A hereditary component is discussed in Chiari malformation, yet proved etiology is still lacking. As folic acid plays an important role in the development of the neural tube, vitamin B12 deficit might have some impact on the development of Chiari malformations.

Dynamics of cerebrospinal fluid flow in slit ventricle syndrome

INTRODUCTION

Although slit ventricle syndrome (SVS) is identified as a serious complication in shunt-treated hydrocephalus, cerebral spinal fluid (CSF) flow via external ventricular drainage (EVD) or shunts in SVS have not been studied up to now.

MATERIAL AND METHODS

A new apparatus (LiquoGuard(®); Möller-Medical, Fulda, Germany) was used for EVD in a child with SVS. The LiquoGuard actively controls CSF drainage, based on intracranial pressure (ICP).

RESULTS

To achieve well-tolerated clinical conditions, an ICP level of 4 mmHg was necessary; realizable by drainage rates between 0 and 35 mL/h. Drainage rate variations typically occurred with repetitive time intervals of 2 h causing a "saw tooth" shaped CSF flow pattern throughout 24 h.

DISCUSSION

SVS seems to be characterized largely by quickly varying CSF drainage demands. Whether this is a general phenomenon or just true for this case has still to be studied and needs further clarification.

Telemetric ICP measurement with the first CE-approved device: data from animal experiments and initial clinical experiences

The objective was to evaluate the qualification of the new telemetric intracranial pressure (ICP) measurement (t-ICP) device Raumedic(®) NEUROVENT P-Tel and S-Tel. The proof of concept was examined in a pilot animal study measuring intraperitoneal pressure with a telemetric and a conventional ICP measurement probe at five rates for 1 h each. Moderate external pressure load allowed measuring values between 0 and 40 mmHg. To estimate long-term performance 18 t-ICP devices were implanted subdurally or intraparenchymally into minipigs. Reference measurements were performed regularly using conventional ICP probes. From the short-term as well as from the long-term perspective t-ICP proved to have excellent dynamic ICP signal components perception (e.g. pulse amplitude). Some zero drift of static ICP was found, ranging between 5 and 8 mmHg. While all telemetric, intraparenchymal probes kept their functionality throughout the follow-up, 33% of the subdurals failed for reasons detailed in another paper. Raumedic's NEUROVENT(®) P-Tel/S-Tel proved to provide reliable data over periods of up to 18 months. Minor zero drift can be well tolerated as the dynamic ICP signal is measured with excellent stability. Clinicians should focus more on such ICP dynamic signal information than on static ICP when using the device over longer follow-up periods.

Case study of relevant pressures for an implanted hydrocephalus valve in everyday life

Hydrocephalus patients with increased intracranial pressure are generally treated by draining cerebrospinal fluid (CSF) into the abdomen through an implanted shunt with a passive differential pressure valve. To perfectly adapt the valve's opening pressure to the patient's need, more information on the acutal pressure across the valve in everyday life actions like walking, eating, sleeping etc. is necessary.

Long-term performance of a CE-approved telemetric intracranial pressure monitoring

Telemetric intracranial pressure (ICP) monitoring has been a challenge throughout several decades. Major obstruction was to minimize zero drift of absolute pressure sensors. A new promising product demonstrating in-vitro excellent long-term stability has been tested for its reliability in an animal model with a follow-up of up to 2 years. In "minipigs" sub-dural (Raumedic-STel®, Helmbrechts Germany) and intraparenchymal (Raumedic-PTel®) telemetric ICP probes have been inserted. Standard ICP probes (Raumedic Neurovent P®) served as controls. In regular intervals of 3 months the telemetrically and conventionally measured ICP have been compared. For each control a new conventional ICP probe has been inserted frontally to the telemetric device in the generalized anesthetized minipigs, resulting in overall 38 comparisons. Bland-Altman-plots, Chi2-tests and matched pair T-tests (significance level < 0.05) were used for data-analysis. The zero-shift was -1.7 ± 7.6 mm Hg (limits of agreement: 4.4 ± 1.9 mm Hg) and -3.0 ± 6.0 mm Hg (limits of agreement: 3.6 ± 2.6 mm Hg) in STel and PTel respectively meeting well the devices specification of ± 2 mm Hg drift per year. The reliability of both telemetric probes has been proved as quite comparable (p=0.2). These new telemetric ICP probes demonstrate reliable data during at least the first 6 months after implantation.