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Indian Journal of Plastic Surgery, Vol. 36, No. 1, Jan-June, 2003, pp. 49-52 Preliminary Communication A design for midface distraction Krishna Rao, Biraj Naithani, Raj Kurnar Mlshra, A. K.Singh, S. K. Bhatnagar Post Graduate Department of Plastic and Reconstructive Surgery, King George's Medical College, Lucknow.
Code Number: pl03014 Midface retrusion is commonly seen in patients with cleft lip and palate, other craniofacial syndromes and maxillofacial trauma. It is now widely understood that the extensive subperiosteal dissection in palatoplasty and alveolar bone grafting has a definite contributory role in the occurrence of this deformity. Midface retrusion can be treated either surgically or by slow distraction. The advantage of distraction advancement of the maxilla is that there is a reduced chance of precipitation of velopharyngeal incompetence. There is also a reduced likelihood of relapse after distraction advancement than after surgical advancement. The use of distraction osteogenesis for maxillary advancement was first done by Rachmiel et al in 1993 for advancement of the maxilla in sheep. A preliminary report of the use of rigid external haloframe distractor for maxillary distraction was published by Cohen et al2 in 1997. Molina et a13 used rigid external haloframe distraction of the maxilla for maxillary advancement in 38 patients with maxillary hypoplasia due to cleft lip-palate. All the patients in this study had mixed dentition. The authors went on to recommend this as the procedure of choice in patients with severe maxillary hypoplasia who had mixed dentition. Cedars et al4 used a custom made internal distraction system for maxillary distraction. Hierl et a15 used a novel retention system using miniplates and wires for maxillary distraction in an edentulous patient with post-traumatic midface retrusion. Currently no indigenous haloframe rigid external distraction systems are available in our country. The haloframe distractors manufactured abroad are exceedingly expensive. Considering the present situation it is important that an indigenous distraction device be developed which is cheap and easy to use. It is in this setting that an effort was made at our institution to develop an indigenous midface distraction device. This haloframe distractor would have wide applicability in patients with cleft lip and palate, other craniofacial clefting syndromes and patients with craniofacial trauma. DESIGN The midface distraction system designed in our institution is a haloframe type rigid external distractor. The parts of this device are:
The aluminum haloframe (Figure 1a) and is basically a horse shoe shaped aluminum piece with a thickness of 5 mm, the size of which is designed to fit around the head. Aluminum was chosen for this purpose as it is very light (a comparably sized iron or steel frame would be twice as heavy). This haloframe can be conveniently fabricated is a foundry. This haloframe has holes for attaching fixation pins. Though these holes a perforated brass block (Figure 1b) is attached for attachment to fixation screws (Figure 1c). Brass blocks can be easily made at any lathe workshop. Initially we had fabricated screws from Steinman pins but due to practical problems we switched over to pins fabricated from medical grade stainless steel. The middle portion of this screw is threaded for securing to the haloframe using perforated brass blocks. A nylon block (Figure 1d) is attached to the anterior position of the haloframe for anchorage of the threaded rods. Nylon is sufficiently inelastic and light for this purpose. A step is created at one end of the nylon block for easy fixation to the haloframe. A long threaded rod is passed through this nylon block and secured with nuts. An additional metallic strip (Figure 1g) may be used for stabilizing this rod against the angulation stress created during distraction. This threaded rod is articulated to another threaded rod through a cross pipe joint. This horizontal joint is made by welding two small pipes- 3 inches long in a perpendicular arrangement. The horizontal threaded rod has a tapered and threaded end, which fits, into a threaded slot in the palatoalveolar splint. The palatoalveolar splint has three components i) Silver arch bar
The arch baris made from silver, as silver is both malleable and strong with a good resistance to fracture. This is made from thick silver wire of a rectangular cross section on to which pieces of the same silver wire are soldered (the teeth of the arch bar). In the anterior end of the arch bar a silver plate with a pair of holes for fixation of the articulation block is soldered. The articulation block is a brass block, which is fitted on to the arch bar. This block has a threaded hole into which the tapered end of the horizontal threaded rod is fitted (Figure 2). After this assembly the arch bar is moulded to the shape of the dental model of the patient. Acrylic palatal splint is then fabricated on the dental model. This assembly is put together and is applied the day before the surgery (Figure 2). The assembly of haloframe, nylon block and the vertical threaded rod is done before the surgery for conservation of time. OPERATIVE DETAILS The first step in the surgery is the performance of LeFort I or II osteotomy as per the preoperative planning. After the osteotomy is completed and the mobility of the osteotomized fragment is confirmed fixation of the haloframe is started with simultaneous closure of the mucosal incision. Fixation of the haloframe is best done at a plane just below that connecting the frontal and parietal eminences. The fixation should be such that the appliance does not protrude behind the head of the patient (so that the patient is able to sleep). It is better to give skin incisions during fixation of the haloframe. The screws are fixed in a manner similar to that of the Crutchfield device (the Crutchfield device is used for cervical traction in patients with cervical spine trauma) ie the screw should abut on the outer table of the calvaria and not pierce it. Four screws are enough to stably fix the haloframe to the skull. After the stability of the haloframe is confirmed the crosspipe is fitted on the vertical threaded rod followed by the passage of the horizontal threaded rod. No attempt is made to advance the maxilla at this stage (Figure 3). Following surgery a latency period of about 3 days is given following which distraction may be started after minimal retightening of the screws. The tightness of the screws should be confirmed at regular intervals. During the entire period of distraction osteogenesis the patient can be allowed a soft diet orally. The patient also has to be instructed about maintaining the cleanliness of the palatoalveolar splint. Thus this midface distraction device can be easily fabricated using easily available materials. PATIENT DETAILS This midface distraction device was used for midface distraction in a 19 year old patient with severe midface retrusion due to cleft maxillary hypoplasia. This patient had been operated in childhood for cleft lip at the age of 1 year and cleft palate at the rate of 3 years. The patient developed progressive midface retrusion with growth. On examination there was midface hypoplasia with a cleft alveolus (two piece maxilla). This patient was taken up for distraction advancement of the maxilla after a proper informed consent. The patient was also properly explained that the distraction device was still very much in a developmental stage. The fixation of the device and LeFort I osteotomy were done as described above. Distraction was commenced 5 days after the surgery. During this period the patient was allowed a soft diet orally. Initially in this patient screws fabricated from Steinman's pins were used but around 2 weeks after surgery the screws became lax necessitating an emergency change of the screws. New screws were fabricated from stainless steel to replace the faulty ones. This presumably has caused a costly lapse in the treatment. The distraction had to be stopped for a period of about 10 days. Following this when the distraction was restarted the advancement gained was much less and the distraction had to be stopped after a period of 10 days. The distraction device was retained in situ for a period of six weeks and then removed. A total of 8 mm advancement of the maxilla was achieved in this patient. A vertical lengthening of the maxilla of 6mm was achieved. The malocclusion was greatly reduced following the surgery (Figures 4 & 5). The success of the procedure can probably be augmented by bony fixation in addition to the orthodontic fixation. This can be done using either wire fixation only or wire and miniplate fixation. This was just a preliminary case in the development and understanding of halofiame midface distractor. The device still needs a lot of fine-tuning to make it optimally effective. The indigenous designing of this distraction system can reduce the cost of treatment greatly bringing it within the reach of the common man. REFERENCES
Copyright 2003 - Indian Journal of Plastic Surgery. The following images related to this document are available:Photo images[pl03014f3.jpg] [pl03014f4.jpg] [pl03014f2.jpg] [pl03014f5.jpg] [pl03014f1.jpg] |
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