Abstract:
An expander for lengthening a patient&#39;s palate comprises two substantially rigid sections, each of which sections has one or more downwardly extending members capable of being affixed to a surface; and a threading system attached to each section, the threading system being capable of predictably adjusting the spacing between the rigid sections. The expander is useful for lengthening a patient&#39;s palate, for example, for the treatment of velopharyngeal incompetence.

Description:
This application claims the benefit of provisional application No. 60/109,863, filed on Nov. 24, 1998. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a palate expander. More particularly, this invention relates to an apparatus and method for expanding a palate in a posterior direction. 
     BACKGROUND OF THE INVENTION 
     Velopharyngeal incompetence is a condition in which the palate cannot adequately seal off the oral cavity from the nasal cavity, resulting in abnormal speech. It is sometimes present in patients who have had a cleft palate repaired, but it can also be caused by other conditions such as congenital palatal insufficiency, a situation in which the palate is too short to reach the posterior pharyngeal wall. Many corrective procedures for velopharyngeal incompetence have been described, including palatoplasties, pharyngoplasties, and pharyngeal flaps. No single operation has been predictively effective. 
     One of the main focuses of this invention, but not the only focus, is on cleft palate patients. These patients have been treated with a procedure whereby two portions of a divided palate have been joined together. In many instances the resulting repaired palate is short or relatively immobile, resulting in velopharyngeal incompetence to the extent that the patients have speech problems (often hypernasal speech). 
     OBJECTS OF THE INVENTION 
     It is an object of this invention to provide a method and apparatus for treating velopharyngeal incompetence. 
     It is also an object of this invention to provide a method and apparatus for lengthening a palate in the posterior direction. 
     It is a further object of the invention to provide a method and apparatus for improving the speech of a patient with hypernasal speech such as may be observed after a cleft palate is repaired. 
     These and other objects of the invention will become more apparent from the discussion below. 
     SUMMARY OF THE INVENTION 
     According to the invention, a patient&#39;s velopharyngeal incompetence is treated by causing a palate to be lengthened in the posterior direction. This procedure is known as “distraction osteogenesis.” The palate is divided in a transverse fashion, and then an extender having “foot pads” is affixed to the separated sections of the palate. The extender comprises two main sections that are moved relative to each other by mechanical means, each section having one or two foot pads that are attached to a section of the separated palate. The extender is adjusted regularly to cause the anterior and posterior palate sections to slowly move apart The space between the sections tends to fill in with bone according to natural processes of healing. The result is that after an appropriate period of time the patient has a palate that is longer and now extends more posteriorly than before, thus helping to correct velopharyngeal incompetence. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of an expander according to the invention in position on two sections of a repaired cleft palate; 
     FIG. 2 is a top plan view of the embodiment of the invention shown in FIG. 1 where the sections of the cleft palate have been moved apart after the palate has been cut transversely; 
     FIG. 3 is an oblique plan view of an expander useful according to the invention; 
     FIG. 4 is a partial cross-sectional view of a section of a threading system useful in the expander; and 
     FIG. 5 and 6 are each a partial cross-sectional view of another expander useful according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention can perhaps be better appreciated from the embodiments of the invention set forth in FIGS. 1 to  6 . In FIG. 1 an expander  2  has metal foot pads  4  that have been removably attached with metal screws  6  to palate sections  8  and  10 , each of which comprise portions of a cleft palate that have been joined together previously at fusion point  12 . Metal screws  6  extend through the metal pads  4  and attach the device to palate sections  8  and  10 . 
     Typically there will be four pads  4 , although the number of pads  4  could vary from 2 to 4. Each pad  4  will have at least one screw, preferably 2 or 3, and most probably 2 screws oriented transversely. The pad and screw configuration can vary dependent upon the palate to which the device is attached. 
     Prior to installation of expander  2 , the palate was divided at line  14  to create sections  8  and  10 . The severing can be done by known surgical means, such as using osteotomies (chisel-like instruments) to make the needed osteotomies, i.e., bone cuts. Additional osteotomies are made along each side of the posterior section  10  to separate this section from the teeth so that it can be advanced posteriorly independent of the teeth. 
     Expander  2  comprises threading system  16 , which is capable of precise adjustment to carefully separate sections  18  and  20 , and thus palate sections  8  and  10 . For example, after expander  2  is installed, threading system  16  is adjusted to cause palate sections  8  and  10  to move apart approximately 0.5 to 1 mm per day for as many days as needed until the palate is sufficiently lengthened (or reaches the expander&#39;s maximum lengthening capacity of 10-20 mm). The screw  26  is turned by a narrow metal pin (not shown) that is temporarily inserted into a central hole in screw  26 , and then rotated. After the screw  26  is turned, the pin is removed until it is next needed to turn screw  26 . 
     Expander  2  may have one or more threading systems  16 . In FIG. 3, there is one centrally located threading system  16  and two guiding systems  40 . Systems  40  can each comprise a rod  42  that is received in a cylinder  44 . 
     As shown in FIG. 4, a threading system  16  can comprise two aligned cylinders  22  and  24  where an internal screw  26  forces cylinders  22  and  24  apart. Screw  26  engages threading  28 , while the distal end  30  of screw  26  has a recess  32  that rotates within annular ring  34  of cylinder  24 . 
     FIG. 5 represents a partial cross-sectional view of another embodiment of an expander  50 , where the threading system  52  and guide systems  54  are internal. Each guide system  54  comprises a rod  56  which is received within a cylinder  58 . Threading system  52  comprises an internal screw  60  that forces sections  62  and  64  apart. Screw  60  engages threading  66 , while the distal end of screw  60  has a recess  68  that rotates within annual ring  70 . 
     In FIG. 6 an expander  72  comprises a base unit  74  with legs  76  attached to foot pads  78 . Screw unit  80  comprises guide pins  82  that extend to and are slidably received in channels or openings  84  in base unit  74 . Screw unit  80  also comprises, or is attached to foot pads  86 , which may comprise an extension of guide pins  82  or may have separate attaching members. Screw member  88 , which is rotatably but attached to screw unit  80 , extends into threaded opening  90  in base unit  74 . When the proximal end  92  of screw member  88  is turned, the spacing between base unit  74  and screw unit  80 , and thus between foot pads  78  and foot pads  86 , is adjusted. 
     The expander and its components are made from suitable rigid, sterilizable, preferably metallic, materials. Useful materials include titanium, stainless steel, nitinol, and similar alloys. It is within the scope of the invention that rigid polymeric materials could be used as well. 
     Certain testing regarding the invention has been conducted The purpose of one study was to determine if a canine hard palate can be lengthened by distraction osteogenesis in a cleft palate model. The testing was conducted as follows: 
     Five mongrel dogs were used. After mucoperiosteal flaps were raised, a midline strip of bone was removed from the hard palate of each dog to simulate the bony defect seen in a cleft palate. A transverse osteotomy was then made to separate the posterior segment of the hard palate from the anterior segment. Posterior osteotomies were also made laterally parallel to the teeth so that the two posterior segments (one on either side of the bony cleft) were mobile. An intraoral distractor that was partially submucosal was attached to the anterior hard palate and both segments of the mobilized posterior hard palate. Radio-opaque bone markers were placed, and X-rays obtained. After a 10 day latency period, the distractor was expanded 0.625 mm per day until 10.125 mm of distraction had been achieved. Distractors were left in place for an additional 2 to 3 months prior to sacrifice. Follow-up X-rays, tetracycline bone labeling, and histologic examinations were performed. New bone formation was found at the site of distraction in all dogs. This new bone was well seen on the follow-up X-rays, as well as on histologic examination of the hard palates using both H &amp; E staining and tetracycline bone labeling. 
     The preceding specific embodiments are illustrative of the practice of the invention. It is to be understood, however, that other expedients known to those skilled in the art or disclosed herein, may be employed without departing from the spirit of the invention or the scope of the appended claims.