Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
1999-04-12
2001-03-27
Dawson, Glenn K. (Department: 3761)
Surgery
Instruments
Orthopedic instrumentation
C128SDIG008, C604S264000
Reexamination Certificate
active
06206885
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an improved apparatus and method for penetrating a human cranium at an angle of 90 degrees to the surface. More particularly, the invention relates to an improved guide for a drilling device and an improved guide for ventricular catheter placement to ensure that both the perforation of the cranium and the catheter insertion are oriented at the correct angle of 90 degrees. The drill guide may be used in combination with a drill to ensure the the drill perforates the cranium at the required 90 degree angle. An improved guide for ventricular catheter placement may, subsequent to the removal of the drill, be inserted into the drill guide to facilitate the correct positioning of a catheter device within a ventricular portion of the patient's brain.
BACKGROUND OF THE INVENTION
The four ventricles of the human brain are interconnected cavities that produce and circulate cerebrospinal fluid (CSF). Procedures involving ventriculostomy, i.e., placement of a catheter into the ventricular system of the brain, form a major part of a neurosurgeon's clinical practice. General areas of application of ventricular catheter placement include intracranial pressure monitoring (ICP), draining or shunting of CSF, and the instillation of pharmacological therapeutic agents.
Intracranial pressure monitoring. i.e., the monitoring of ventricular pressure, is critical to the management of patients after severe head trauma, fulminant meningitis, Reyes's syndrome, encephalitis, stroke, cerebral hemorrhage, or subarachnoid hemorrhage producing stupor or coma. However, the ventricles are usually compressed after head trauma and thus they are technically difficult to cannulate for ICP monitoring. Accordingly, subarachnoid pressure monitoring, which is not as true a measure of cerebral pressure as intraventricular pressure monitoring, is generally used.
CSF drainage is essential for patients with congenital or acquired hydrocephalus. This procedure, which can only be performed with an intraventricular catheter, is a life-preserving step, because it can immediately reduce intracranial pressure. The ventricular catheter used to drain cerebrospinal fluid is connected to a peripheral subcutaneous drainage system, i.e., to the peritoneal cavity or systemic circulation via the heart. In hydrocephalus, the ventricles are enlarged and are an easier target for cannulation. However, reports in neurosurgical literature indicate that suboptimal placement in dilated ventricles can subsequently produce catheter obstruction when the ventricles are decompressed and become smaller, thus emphasizing the need for accurate placement.
Catheter placement in cerebral ventricles is widely performed on patients with carcinomatous and fungal meningitis for the administration of well-known antineoplastic and antifungal chemotherapeutic agents, respectively. Invariably, the ventricles in these patients are small or normal sized and difficult to cannulate.
Standard procedures for ventricular catheterization are disclosed in the textbook literature. See, for example,
Neurosurgery
, edited by Robert H. Wilkins and Setti S. Rengachary, Section A, Chapter 13, Techniques of Ventricular Puncture (McGraw Hill 1984).
The most frequently chosen site for ventricular catheterization is the coronal region. In most cases, a catheter is inserted in the anterior horn of the lateral ventricle through an orifice or burr hole drilled just anterior to the coronal suture in the midpupillary line of the cranium, i.e., in the frontal bone over the ventricle. This is known in the field as Kocher's point. The burr hole, only slightly larger than the diameter of the selected catheter to ensure a snug fit and provide a seal against CSF leakage, is placed approximately 1 cm. anterior to the coronal suture, approximately 10 to 12 cm. above the nasion, and approximately 2 to 3 cm. from the midline over the nondominant hemisphere. After the burr hole is made, the dura and underlying pia-arachnoid are opened and coagulated, for example, with a fine-tipped blade, after cauterizing the dural surface.
The lateral ventricles of the human brain form an arc parallel to the arc of the cranium, i.e., the contour of the lateral ventricles parallels the arc of the surface of the skull. Thus, a catheter guided perpendicular to the cranial surface at the point of entry into the cranium will enter the ventricular system. Specifically, any line penetrating a burr hole in the surface of the skull at a 90° angle also bisects the lateral ventricle.
Various methods have been utilized in the prior art in an attempt to ensure the correct placement of a catheter device in the patient's cerebral ventrical. One such method involves the use of a pre-measured catheter having a stylet which may be introduced and directed freehand through the burr hole, approximately in the coronal plane, and angled towards the medial canthus of the ipsilateral eye, using external landmarks such as the inner canthus of the eye in the frontal plane and a point just in front of the external auditory meatus in the lateral plane as guided to placement. CSF should flow freely from the catheter tip at a depth of approximately 4 to 5 cm. from the interior cranial surface.
A distinctive “give”, or release of opposition, can often be felt when the ventricle is penetrated. Pressure should be measured at this point, however, since an artificially low value will be obtained even if small amounts of fluid are lost. Then, after removal of the stylet from the catheter, advancement another 1 cm. or so should insure placement in the frontal horn at a depth of about 5 to 6 cm. from the external table of the skull, care being taken that CSF continues to flow.
Intraoperative fluoroscopy and air ventriculography, well known techniques in the art, have been used to confirm freehand catheter placement. While these procedures can be helpful in placing the catheter if the ventricles are small, they also add to the complexity of the overall procedure.
Aside from the cost and time constraints of such radiographic confirmation of catheter placement, many published reports of postoperative studies have revealed misplacement of catheter tips in cerebral matter or subarachnoid space. This misplacement results in increased neurological morbidity and the need for additional operation time. Moreover, multiple passes of the catheter into cerebral matter are quite common before the ventricles are properly penetrated. Finally, the anxiety a neurosurgeon experiences when trying to place a catheter by freehand into the ventricular system makes first pass success that much more difficult and further increases the risks involved in the procedure.
A recently developed procedure to ensure correct catheter placement was disclosed and claimed by one of the present applicants in U.S. Pat. No. 4,613,324 (the '324 patent), issued Sep. 23, 1986. The disclosure of that patent is therefore specifically incorporated herein by reference. The apparatus comprises a guide assembly which, when positioned over an orifice drilled in the cranium above the anterior horn of the lateral ventricle, guides a catheter and obdurator through the orifice and into the lateral ventricle at an angle normal to an imaginary plane formed by a tangent to the cranium at the orifice.
The method of utilizing the claimed device of the '324 patent comprises providing an orifice in the cranium just anterior to the coronal suture in a midpupillary line of the cranium and inserting a ventricular catheter containing an obdurator through the orifice towards a lateral ventricle, wherein the catheter containing the obdurator is guided through the orifice, by means of a guide assembly, at an angle normal to an imaginary plane formed by a tangent to the cranium at the orifice.
This orientation of 90° is required for proper placement of the catheter within the ventricular portion of the patient's brain since, if the burr hole deviates by more than about 7 degrees from the perpendicular to a plane tangent to the po
Ghahremani Fathali
Ghajar Jamshid
Dawson Glenn K.
Levisohn, Lerner, Berger & Langsam
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