Patent Application
20090192514
The present invention pertains generally to distraction osteogenesis and, more particularly, to an osteogenesis distraction device comprising attachment members securable to separate bone segments and moveable in relation to each other to generate a distraction force, a power source for powering relative movement of the attachment members, and wherein the entire device, including the attachment members and power source, is dimensioned for implantation entirely subdermally in the body of a patient.
Distraction osteogenesis is a method of generating new bone in a gap between two bone segments, by the gradual application of tensile stress across the bone gap (Swennen G, Schliephake H, Dempf R, Schierle H, Malevez C.: Craniofacial distraction osteogenesis: a review of the literature. Part I: clinical studies, Int J Oral & Maxillofac Surg 30:89-103, 2001). The clinical technique was first applied to craniofacial implications in 1992 by McCarthy et al.; most subsequent research has focused on developing more effective distraction via empirical examination with a variety of clinical parameters such as latency period, distraction rate, and distraction frequency (Swennen G, Schliephake H, Dempf R, Schierle H, Malevez C.: Craniofacial distraction osteogenesis: a review of the literature. Part I: clinical studies, Int J Oral & Maxillofac Surg 30:89-103, 2001). The main criticisms of external apparatuses are unsightly scars and/or injuries to the facial nerve resulting from the transcutaneous pins, and thus lack of acceptance by the patients (Schmelzeisen R, Neumann G, Von der Fecht R.: Distraction osteogenesis in the mandible with a motor-driven plate: a preliminary animal study, Brit J of Oral Maxil Surg 34:375-378, 1996. Overcoming these limitations, internal or intra-oral distraction devices have become the most common clinical apparatus in craniofacial distraction osteogenesis (Swennen G, Schliephake H, Dempf R, Schierle H, Malevez C.: Craniofacial distraction osteogenesis: a review of the literature. Part I: clinical studies, Int J Oral & Maxillofac Surg 30:89-103, 2001). In both external and internal devices, however, the actuation of distraction process relies upon manual length adjustment under patients' compliance, introducing inconvenience and potential error in the procedure. More importantly, continuous distraction by application of a low strain magnitude with multiple steps, and leading to greater osteogenic activity (Ilizarov G A.: The tension-stress effect on the genesis and growth of tissues: II. The influence of the rate and frequency of distraction. Clin Orthop 239:263-85, 1989; Kessler P, Neukam F W, Wilffang J.: Effects of distraction forces and frequency of distraction on bony regeneration. Br J Oral Maxillofac Surg 43:392-398, 2005), is restricted by the manual operation protocol, which limits the distraction frequency under 2-4 times per day.
Kessler et al. (2005) showed that continuous osteodistraction resulted in intramembraneous regeneration of bone, whereas intermittent osteodistraction (used by all present distraction devices) caused chondroid ossification in the regenerate of bone. In addition, continuous osteodistraction caused speedier regeneration and distraction forces, maximum pressure peaks and mean distraction force for maximum extension, respectively, were lower (mean value 1.0 N/mm2 and 28.3 N, respectively) than with intermittent distraction (mean value 2.7 N/mm2 and 76.3 N, respectively). These critical limitations of intermittent force application with both internal and external procedures motivate the development of new devices for distraction osteogenesis, which are termed “continuous automatic distracters (CAD).”
Continuous distraction has shown definitive advantages over intermittent distraction. For example, Kessler et al. (2005) demonstrated a faster rate of regeneration with less force application. In discontinuous distraction, a rate of 1 mm/day is the most successful, and the most frequently used parameter in previous experimental and clinical studies (Swennen et al., 2001). Those empirical data have shown lower rates of distraction tend to cause mechanical problems (pin loosening, breakage) in devices, while higher distraction rates lead to premature ossification of the callus during distraction osteogenesis (Meyer et al., 2004).
The present invention provides an implantable device which overcomes the problems of prior art devices, both intra-oral and external, and in which the rate of distraction, whether intermittent or continuous in nature, can be attained with a high degree of precision.
The present invention addresses the problems of prior art osteogenesis distraction devices, and encompasses other features and advantages, by providing an osteogenesis distraction method and device. The method comprises the steps of providing an osteogenesis distraction device for securement to separate bone segments in the body of a patient and operative to generate new bone between said bone segments by the gradual application of a distraction force, the device comprising attachment members securable to separate bone segments and moveable in relation to each other to generate a distraction force, a power source for powering relative movement of the attachment members; and implanting the entire osteogenesis distraction device, including the attachment members and power source, subdermally in the body of a patient.
In implementation of the foregoing method, there is disclosed herein an osteogenesis distraction device for securement to separate bone segments in the body of a patient and operative to generate new bone between the bone segments by the gradual application of a distraction force. The device comprises attachment members securable to separate bone segments and moveable in relation to each other to generate a distraction force, and a power source for powering relative movement of the attachment members. The entire device, including the attachment members and power source, is dimensioned for implantation entirely subdermally in the body of a patient.
According to one feature of the invention, movement of the attachment members is effected by an actuator operable to generate a distraction force between the attachment members. The actuator may, per one aspect of the invention, comprise an electric motor operatively connected to a rotary-to-linear mechanism. The electric motor may comprise a DC micromotor, for example.
Per another feature, the rotary-to-linear mechanism is a lead screw operatively connected to one of the attachment members.
Per still another feature, the electric motor is operatively coupled to a transmission. The transmission may, according to one embodiment, comprise a planetary gearhead having a high reduction ratio (e.g., 4096:1).
Per another feature of the invention, the power source is a battery, such as, for example, a lithium-polymer battery.
According to another feature, the device may further comprise a controller operative to control operation of the actuator.
The actuator may, per one embodiment, be remotely, wirelessly operable. An RF receiver may, per this feature, be operatively connected to the controller, and the device may be operable by RF signals originating outside of the body of a patient.
Per another embodiment of the invention, the device may further comprise a force sensor for sensing a force applied by the actuator. According to this embodiment, the controller is operatively connected to the force sensor and is further operable to adjust the operation of the actuator in response to the force sensed by the force sensor.
Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered with the accompanying drawings, wherein:
As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale, some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.
Referring to
The entire device, including the attachment members and power source, is dimensioned for implantation entirely within the body of a patient and so may be used in situ, directly in communication and contact with an affected bone structure, to a achieve displacement of the bone for distraction osteogenesis.
The device 10 as shown in the illustrated embodiment more particularly includes a first bone attachment member 12 and a second bone attachment member 14 for securement to separate bone segments. The first bone attachment member 12 and the second bone attachment member 14 define a first axis denoted as X. The first bone attachment member 12 and the second bone attachment member 14 are operatively attached to one another by actuator 16. Power source 18 is operatively connected to the actuator 16. A controller in the form of an electronic control module 20 is in electrical communication with power source 18 and actuator 16. The actuator 16 is adapted to move the second bone attachment member 14 away from the first bone attachment member 12 in a direction along the first axis denoted by X. That is, the actuator 16 provides the distraction force necessary to spatially separate or move the second bone attachment member 14 relative the first bone attachment member 12.
The actuator 16 more particularly includes a direct current (DC) micro-motor 22, a planetary gear head 24 (Faulhaber Micromo Electronics, Clearwater, Fla.) attached to one end thereof having a high reduction ratio (4096:1), and a rotary to linear mechanism having a lead screw 26. The lead screw 26 includes threads which engage a nut 29 attached to a threaded aperture 28 disposed in the second bone attachment member 14 such that when the DC motor 22 is energized, the rotation of the motor 22 through the gear head 24 causes the lead screw 26 to rotate within the nut 29 causing the second bone attachment member 14 to be spatially separated from or to move away from the first bone attachment member 12. The actuator 16 is supported by and rotates within a thrust bearing 25 disposed within the first bone attachment member 12.
Guide pins 30 are disposed within both the first bone attachment member 12 and the second bone attachment member 14 in order to provide support for the second bone attachment member 14 as it is moved away from the first bone attachment member 12, and also to maintain the travel of the second bone attachment member 14 along the desired axis of travel as denoted by X.
The osteogenesis distraction device 10 further includes apertures 32 disposed within the first bone attachment member 12 for mounting the device 10 to a desired bone fixation/attachment point and apertures 34 are disposed within the second bone attachment member 14 for the same purpose. Screws 36, which are shown in
Referring to
The DC motor 22 (Faulhaber Micromo Electronics, Clearwater, Fla.) is selected to be utilized in combination with planetary gear head 24 having a high reduction ratio (e.g., 4096:1), and a rotary to linear mechanism by lead screw 26, as this assembly provides the necessary structural stability to transmit sufficient loads with sufficient strain accuracy during distraction osteogenesis. It should be noted that other suitable motors may be utilized in the device 10 of the present invention, as would be readily identifiable by one of ordinary skill in the art.
In an embodiment of the osteogenesis distraction device 10 of the present invention, power source 18 is a battery, such as, by way of example, a lithium-polymer rechargeable battery (UBC322030, Ultra Life Batteries, Newark, N.Y.). Such a battery meets the requirement for a power source having high current discharge. That is, the discharging profile required to perform distraction osteogenesis having a distraction rate of at least 1 mm per day was applied for a total length of 15 mm. The lithium-polymer battery was shown to meet the requirements necessary for performing distraction osteogenesis. The lithium-polymer was able to satisfy the pulse-load profile required by clinical distraction osteogenesis protocols for the necessary duration, i.e., 15 days. This type of battery also demonstrated the necessary performance to cope with prolonged periods of inactivity along with demanding high pulse currents during the distraction period of distraction osteogenesis. The lithium-polymer rechargeable battery was found to satisfy the required high-current discharge (50-70 mA) temperature requirements (i.e., <42.2° C.) and size requirements.
In order to provide the device 10 with the ability to provide continuous distraction force, control of the implantable distraction osteogenesis device 10 of the present invention requires that the speed of the DC motor 22 and the corresponding distraction rate be controlled by controller 20. The controller 20 includes integrated circuit chips, including a clock-counter and a logic gate which can be used to intermittently control the motor speed and the corresponding distraction rate of the device 10. The interval of pulses is dependent upon pin-connections of the clock-counter into the logic gate. Thus, by simply changing the composition of the passive components and their connectivity, the power pulse can be modulated to generate different distraction parameters, such as distraction rate and frequency. Controllers of this type are well known to those of ordinary skill in the art. The controller was assembled using standard surface-mount circuit components on a custom printed circuit board (PCB). The electronic controller 20 can be programmed to perform intermittent or continuous distraction osteogenesis or a combination of both, if desired.
The device 10 can be activated/deactivated to facilitate, cease or stop, respectively, distraction osteogenesis by a variety of mechanisms including, but not limited to, magnetic activation/deactivation of a magnetic switch coupled to the controller 20, radio frequency (RF) activation/deactivation of the controller 20 by the provision of an RF receiver/transmitter operatively connected to the controller 20 and operative to convey data (such as operation instructions, for example) wirelessly received from a remote source, as well as other means well known to those skilled in the art.
Referring to
While the exemplary embodiment of the osteogenesis distraction device comprehends single axis (X) distraction, modifications thereto are possible to allow multi-axial distraction osteogenesis. That is, the device 10 can be configured to allow for distraction osteogenesis in at least two directions or dimensions. In order to do so, the device may in one exemplary modification thereof comprise two or more of the devices 10 of the exemplary embodiment oriented to effect osteogenesis in non-parallel axes.
According to one embodiment of the invention, shown in
The foregoing operation may be effected in a closed-loop operating system, such as shown in
An optional radio frequency (RF) transmitter and, optionally, receiver 21, shown in
Optionally, remote control of the controller 20 could be affected by a user wirelessly conveying to the RF receiver instructions for effecting a change in the actuator's operation via the controller 20 based upon information transmitted to the monitor 60. However, monitoring could also be entirely passive.
The clinical applications and anatomical sites for which the implantable osteogenesis device 10 of the present invention may be utilized includes, but is not limited to, craniomaxillofacial (CAF) such as craniosynostosis; cranium; cleft lip/palate; maxilla; mid-face advancements: maxilla zygoma; frontal bone, orbits; mandibular advancement; mandible; vertical augmentation of alveolar ridges of the maxilla and mandible; sleep apnea; maxilla and mandible; and s/p tumor reconstruction of mandible; transport distraction osteogenesis (used to fill in a continuity defect as opposed to lengthening a bone); and any other bones of the facial skeleton. Orthopedic applications include lengthening of long bones (extremities) such as humorous, ulna, radius, femur, fibula, and tibia. This includes both classical distraction osteogenesis, as well as transport osteogenesis.
As previously stated, the device 10 of the present invention is fully implantable within the subject. No portion of the device 10 is externally disposed or exposed on the subject. Unlike prior distraction osteogenesis devices, once implanted, no portion of the device 10 protrudes through the outside of the subject's body. Distraction osteogenesis is performed without any application of external force.
In operation, the implantable osteogenesis distraction device 10 is implanted within a subject according to the following process. First, access to the site or location for the regeneration of tissues (bone) must be made by a medical/dental practitioner. The medical/dental practitioner then performs an osteotomy in order to sever or divide the bone at the desired site into at least two sections where bone elongation and/or reshaping is desired. The osteogenesis distraction device 10 is then implanted and affixed to the desired location by the application of screws which can be made from titanium or a biodegradable material such as PLA/PGA polymer composite, or the like. The medical/dental practitioner skilled in the relevant art will have knowledge as to the proper location and orientation of the device 10. Proper orientation of the device will also depend upon the desired distraction path and the bone geometry at the attachment site. Following attachment of the device 10 to the desired site, the medical/dental practitioner closes the incision thereby completely disposing the device 10 within the patient. That is, upon completion of the procedure to implant the device 10, no portion of the device is externally disposed on the subject. Following closing of the incision, the device 10 is not immediately activated to begin the distraction osteogenesis process. Rather, the device 10 remains inactive for a predetermined amount of time in order to allow bone cells to begin growing at the site where the bone has been severed. Following this latency period, the device 10 is activated to apply tension between the bone segments and performs distraction osteogenesis at the desired rate for the desired length of time.
The components of the device 10 which come in contact with living tissue, must be formed from non-immunogenic material that is fully biocompatible within the body of the subject which is generally a mammal such as a human, but can also include other animals. Suitable materials include, but are not limited to, titanium, titanium alloys, stainless steel, polycarbonate ISO, and/or other materials known to those skilled in the art. Subsequent to the completion of the distraction osteogenesis in the subject, the device is removed from the subject.
While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in this specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention
This application is related to, and claims the benefit of priority from, U.S. Provisional Patent Application Ser. No. 60/978,472, filed Oct. 9, 2007, the disclosure of which application is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60978472 | Oct 2007 | US |
