Education and demonstration – Anatomy – physiology – therapeutic treatment – or surgery... – Anatomical representation
Reexamination Certificate
2000-05-19
2001-12-25
Nguyen, Kien T. (Department: 3712)
Education and demonstration
Anatomy, physiology, therapeutic treatment, or surgery...
Anatomical representation
C434S274000, C606S064000
Reexamination Certificate
active
06332780
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device for simulating the position and orientation of at least a portion of an implanted fixation system, so that, for example, a spinal fixation rod can be pre-bent for insertion in implanted pedicle screws and/or hooks using a minimally invasive surgical procedure rather than an open surgical procedure.
BACKGROUND OF THE INVENTION
It is often necessary to surgically treat spinal disorders such as scoliosis. Numerous systems have been used for spinal correction and fixation. These fixation systems are well known and usually include one or more elongated members, typically either rods or plates, placed along the vertebral column. The elongated member is attached to the spine typically with a plurality of various fasteners, which may include, but are not limited to, pedicle screws, plates, transverse process hooks, sublaminar hooks, pedicle hooks, and other similar devices.
The fasteners are typically implanted prior to their attachment to the elongated member, with the elongated member then being bent and/or cut to be received by the plurality of fasteners. By fashioning the elongated member to fit implanted fasteners, the overall fit of the fixation system is more likely to be proper than if the elongated member is attached to the plurality of fasteners, each fastener in turn then being attached to the spine.
FIG. 1
illustrates one such prior art fixation system
1
affixed to a spine
19
. Fixation system
1
includes a plurality of fasteners or fixation elements
3
connected by an elongated member or rod
2
, which has been bent appropriately to fit the shape proscribed collectively by fixation elements
3
.
In an open surgery procedure, the wide exposure of the spine and the surrounding anatomy simplifies contouring the elongated element to the fasteners. However, such exposure can result in significant damage to the soft tissue, particularly the muscles. This damage can lead to weakening in the muscular area, and thus to weakening in the retaining system for the spine or other extremities and also entails the risk of scarring, which, in turn, can lead to postoperative problems.
In an effort to avoid the possible complications associated with open surgical procedures, so-called minimally invasive procedures can be used for implantation of a fixation system. During such a procedure, several percutaneous incisions are made, leaving the posterior back muscles largely intact. The fasteners are then placed through the skin, preferably with the help of a computer assisted surgery system (CAS) such as that described, for example, in U.S. Pat. No. 5,383,454. The fasteners are typically inserted through the incisions using an inserter having a shaft of sufficient length so that the end projects through the skin. In such situations, the sensors or transmitters associated with the CAS can be located on either the end of the inserter or directly on the fastener.
Irrespective of whether a CAS is used during a minimally invasive implantation of a fixation system, contouring the elongated element is problematic because unlike an open surgical procedure, the fasteners are not directly visible and it has not been possible to use a trial rod or a bending template.
Thus, there exists a need for a device for simulating the position and orientation of at least a portion of an implanted fixation system, so that, for example, a spinal fixation rod can be pre-bent for insertion in implanted pedicle screws and/or hooks using a minimally invasive surgical procedure.
SUMMARY OF THE INVENTION
The present invention relates to a device for simulating position and orientation of an elongated element with respect to a plurality of fixation elements of a fixation system. The implant simulating device includes a base plate and first and second arms extending from the base plate. Each arm defines a track into which at least two cross members are slidingly engaged. Each cross member also has a locking element for fixing the position of the cross member. A fixation element simulator is associated with each of the cross members and is capable of angular positioning with respect to the cross members. The implant simulating device also includes a correlation system for correlating at least two fixation element simulators to at least two fixation elements of the fixation system. Coupling of an elongated element in the fixation element simulators after correlation by the correlating system allows the elongated element to be configured and dimensioned for coupling to the fixation elements prior to implantation.
Each cross member can include a ball joint for receiving and positioning one of the fixation element simulators. In one embodiment, each cross member comprises top and bottom bars and a center piece located therebetween, in which the ball joint is located. In this embodiment, each cross member is designed such that the ends of the bottom bar slide within the track of the first and second arms so that each cross member is slidable in a direction parallel to the length of the base plate and in a direction parallel to the width of the base plate. If the fixation element simulators have a threaded portion, each ball joint can have a threaded bore for engaging the threaded portion of the fixation element simulator to allow height adjustment of the fixation element simulator.
The cross members can be made to be flexible so that if the elongated element is bent further than the bend needed to contour the elongated element to the fixation element simulators, the cross members deform to simulate changes in anatomy. Advantageously, the elongated element may be used as trial rod or a template for bending a second elongated element that can then be coupled to the fixation elements.
In an exemplary embodiment, the correlation system is a position detecting system comprising at least one signal transmitter, at least one sensor for detecting the signal(s), and an analyzing unit for processing the signal(s) to determine position and orientation of at least some of the fixation elements. A signal transmitter can be associated with each fixation element, either located directly on the fixation element or located on an elongated inserter which is associated with a fixation element and is configured and dimensioned to mate with a fixation element simulator. The signal may be an electromagnetic or acoustic wave. For example, each signal transmitter can be at least one light emitting diode (LED) and the sensor is a digital camera.
In another embodiment, the correlation system uses a mechanical mechanism, such as a pantograph, a scanning device, or a combination thereof. For example, the correlation system can be a translation device for transferring position and orientation of at least some of the plurality of fixation elements. The translation device includes at least two translators and a connecting rod linking the at least two translators. Each of the translators has a positioning pin with first and second ends and a sleeve with first and second ends. The first end of the sleeve receives the first end of the positioning pin and the second end of the sleeve receives at least a portion of an elongated inserter coupled to a fixation element. Each translator also includes a clamp having a first portion coupled to the connecting rod and a second portion coupled to the second end of the positioning pin. The first portion of the clamp rotates with respect to the second portion for adjusting position and orientation of the positioning pin to align the translator with one of the plurality of fixation elements. Transferring each of the translators to one of the fixation element simulators results in the implant simulating device mimicking at least a portion of the fixation system.
The implant simulating device according to the present invention can also include an elongated element inserter for guiding implantation of the elongated element. The elongated element inserter has a handle and an elongated holder extending from the handle in a first direction and having a hollow sh
Traxel Doris
Weber Urs
Nguyen Kien T.
Pennie & Edmonds LLP
Synthes (U.S.A.)
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