Biodegradable fixation for craniomaxillofacial surgery: a 10-year experience involving 761 operations and 745 patients

Abstract

Patient acceptance, safety, and efficacy of poly- l / dl -lactic acid (PLLDL) bone plates and screws in craniomaxillofacial surgery are reported in this article. Included in the sample are 745 patients who underwent 761 separate operations, including more than 1400 surgical procedures (orthognathic surgery (685), bone graft reconstruction (37), trauma (191) and transcranial surgery (20)). The success (no breakage or inflammation requiring additional operating room treatment) was 94%. Failure occurred because of breakage (14) or exuberant inflammation (31). All breakage occurred at mandibular sites and the majority of inflammatory failure occurred in the maxilla or orbit (29), with only two in the mandible. Failures were evenly distributed between the two major vendors. PLLDL 70/30 bone plates and screws may be used successfully in a variety of craniomaxillofacial surgical applications. The advantages include the gradual transference of physiological forces to the healing bone, the reduced need for a second operation to remove the material and its potential to serve as a vehicle to deliver bone-healing proteins to fracture/osteotomy sites. Bone healing was noted at all sites, even where exuberant inflammation required a second surgical intervention.

The quest to develop ideal skeletal fixation methods for the craniomaxillofacial region continues. L uhr , M ichelet et al. , C hampy et al. and others revolutionized the conduct of facial skeletal surgery with the introduction of bone plates and screws designed for the facial skeleton. The functional demands of the craniofacial region (forehead, calvaria) are much less than the maxillofacial region (maxilla, mandible, orbits) where the heavy forces of mastication are applied and dispersed superiorly and inferiorly. The required strength of plates and screws differs depending on the functional demands of the bones to be stabilized.

Initially, bone plates and screws were manufactured from a variety of metals, including stainless steel, vitallium, chromium–cobalt, and other metal alloys. B ranemark and T olman ‘s favourable experience with titanium led to the development of titanium bone plates and screws for use in the craniomaxillofacial region of infants, children and adults . Possible interference with facial growth, the difficulty in removing the material with subsequent surgery, interference with imaging, generalized health safety, and concerns about bone healing and maturation encouraged the development of more biologically and physiologically compatible materials .

Although polylactate polymers for stabilisation in human surgery were introduced more than 40 years ago, their usefulness has only been appreciated recently . The major concerns for use in the maxillofacial region are the strength of the material and its ability to withstand masticatory forces, and the extent of inflammation as the material begins to degrade. Inflammation is necessary for biodegradation, but the materials must be refined so that intense inflammation is not incited during the degradation progress. When intense inflammation develops, symptoms such as swelling, erythema, sterile abscess, drainage and secondary infection may occur.

The ideal fixation system for stabilisation of an osteotomy or bone fracture would provide adequate strength initially to permit bone healing during function, and then decrease in strength so that there was increasing physiological force transference to the bone. Biodegradable polymers can provide that; metals cannot.

In 1998, the senior author, whilst visiting Professors Christian Lindquist and Rita Suuronen at the University of Helsinki, observed multiple patients who underwent sagittal osteotomies of the mandible in which the segments were stabilized with polylactate screws. Returning from this trip, the author felt that biodegradable technology deserved a place in elective facial skeletal surgery, especially orthognathic and craniofacial applications. Identifying vendors whose products had adequate strength, biodegradation characteristics, and United States Food and Drug Administration (US FDA) clearance proved to be a formidable, but not an insurmountable task.

Not all polymers are similar and they vary in strength and degradation characteristics, depending on the exact content, the manufacturing and sterilisation processes. Polylactate is the major ingredient of most biodegradables used in the maxillofacial region. When the d and l isomers of polylactate are combined in a 70/30 ratio and the manufacturing process is controlled properly, adequate strength for use in the maxillofacial skeleton is achievable . Initially, a single vendor (Bionx, LTD, Con Med Linvotech, Key Largo, FL, USA) was identified, whose extruded poly- l / dl -lactic-acid 70/30 (PLLDL) material met the criteria for use in the entire maxillofacial region. The senior author used this material from March 1999 until the vendor withdrew from the North American market in 2002. At that time another vendor (Inion Corp., Tampere, Finland) offered a heat-formed PLLDL70/30 polymer, the characteristics of which were similar, although it was not as strong. The dimensions of the plates and screws were increased, and this material was used subsequently. Both of these products were eventually approved for use in the entire craniomaxillofacial region by the US FDA.

The purpose of this study is to report on patient acceptability, the safety and efficacy of using PLLDL bone plates and screws for craniomaxillofacial surgical applications. It reviews the experience of a single surgeon working in a single institution placing the material in the craniomaxillofacial region. It does not include cranial remodelling surgery performed in infants or children, in which other polymers that degrade more quickly and have other characteristics more suitable to infants and children are used. It does not include the experience of other surgeons working in the same institution using this material, nor does it include the author’s experience outside of the single hospital setting. The exact material studied is PLLDL 70/30. Comparison of failures by vendors, sites of failure, and surgical category are reported, as well as the author’s experience with the vendors and their representatives.

Materials and methods

All patients who underwent placement of PLLDL bone plates and screws in the craniomaxillofacial region by the senior author are included in this investigation. Initially, all orthognathic and craniofacial surgery patients were offered its use indiscriminately. During the past 4 years, patients > 200 lbs (about 90 kg) and those with questionable ability to comply with a soft diet, have been cautioned that their chewing strength may exceed the strength of the material before being allowed to choose between metallic systems or biodegradable systems. The experience includes its use in selected trauma patients, who were offered the material based on their injury and the surgeon’s perception of their ability to comply with postoperative instructions. The majority of trauma patients treated by the senior author were not offered a choice of material. Bone graft reconstruction and pre-dental implant bone graft patients were offered the use of this material only if was clear that breakage was unlikely and the patient would be cooperative.

The demographic characteristics of the sample and the numbers of patients with specific surgical procedures are shown in Table 1 . 745 patients were included in the study. They were involved in 761 separate operating room experiences and more than 1400 procedures. Fifteen patients underwent one additional surgery utilising the same material. One patient underwent three operations utilising the same material. There were 685 instances of orthognathic surgery (90%), 37 reconstructive procedures (5%), 19 patients underwent repair of facial fractures (3%), and 20 underwent transcranial surgery (3%).

Table 1
Patient demographics.
Gender Race
Women Men Caucasian African-American Hispanic Asian Native American
N = 745 457
(61%) 		288
(39%) 		665
(88%) 		59
(7.9%) 		11
(1.5%) 		10
(1.3%) 		10
(1.3%)

Age (years) Mean Range Median
21.95 ± 10.9 1–76 * 18

Type of surgery Orthognathic Reconstructive Trauma Transcranial
685
(90%) 		37
(5%) 		19
(2.5%) 		20
(2.5%)

* Ages have been rounded to the closest year.

The product was used exactly as metallic systems are used, without adding plates and screws to any particular osteotomy or situation. In general, for Le Fort I osteotomies four plates were used for stabilisation (two at the nasal region and two at the zygomaticomaxillary buttress). For sagittal osteotomies, four bicortical screws were placed transorally in a diagonal pattern as previously reported . For genioplasty, three screws were used to secure the segment.

For bone graft stabilisation, generally a single screw was used depending on the size and location of the graft. For larger defects, bone plates and screws were used for stabilisation. Fracture sites were typically secured with a single plate. Just as with titanium systems, exceptional circumstances may require additional screws or plating configuration. Although each vendor has equipment for transbuccal placement, transoral placement without skin incisions was used exclusively when transoral surgery was performed.

Bone plates used to stabilize maxillary osteotomies were from the 2.0 mm system. In the mandible 2.7 mm screws were used at sagittal osteotomy sites and at genioplasty sites when heat-molded material was used. When self-reinforced (extruded) screws were placed at sagittal osteotomy sites or genioplasty sites, they were 2 mm in diameter. When body or symphyseal osteotomies were stabilized, the 2.0 mm plates were used with the extruded system and 2.4 mm bone plates and screws were used with the heat-molded system.

In this investigation, success was defined as evidence of healing in the desired position without the need for additional operating room surgery. Failure is defined as material breakage or an acute inflammatory response during the biodegradation phase, to the extent that another operating room procedure was necessary for restabilisation or for debridement. Low grade, well-controlled degradation with a draining intraoral fistula which was self-limiting and did not require an operating room procedure was not considered failure.

Results

Initially, all patients were informed of the author’s minimal experience with the material and that the material was not US FDA approval. Surprisingly, 337 of the first 344 patients offered the use of this material accepted (98%), which demonstrated that the biodegradable material appealed to patients.

Table 2 lists the operations performed in this series. Although 90% of the patients had orthognathic surgery, most patients underwent multiple procedures at the same setting and many of these procedures were highly complex, involving simultaneous mobilisation of both jaws. The sample includes patients with craniofacial clefts and at least 10 syndromes, including Crouzon, Apert, cleft lip and palate, craniofacial microsomia, craniofrontonasal dysplasia, Down, Tourette, Binder.

Table 2
Types of surgery.
Osteotomies
Le Fort I 314
Le Fort I segmental 139
Le Fort III 13
Transcranial osteotomies 20
Bilateral sagittal osteotomies of the mandible 553
Genioplasty 218
Inverted l osteotomies 37
Condylectomy with immediate reconstruction 26
Total mandibular subapical 10
Anterior mandibular subapical 6
Reconstruction
Bone graft stabilisation 86
Trauma
Mandibular fracture 7
Midface fracture 8
Forehead fracture 4

Table 3 summarizes the usage and results by vendors. Note that Inion was used in 75% of the patients and Bionx in 24%. Overall, the success rate was 94%. The success of the sample was 716 instances (94%), and a failure of 45 instances (6%). Of the 45 failures, 14 (31%) were attributable to breakage of the material and 31 (69%) were due to inflammation. The breakage rate for Inion was 2%, and the inflammation rate was 4%. For Bionx it was 1% breakage and 5% inflammation. In all 14 patients with breakage failure, the site of breakage was the mandible. In the 27 patients with inflammation failure, the maxilla was the region involved in 23 (87%). In two the mandible was involved with an inflammatory problem (7%). In the other two inflammation failures (7%), the orbit was the site of inflammation ( Table 4 ).

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Feb 7, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Biodegradable fixation for craniomaxillofacial surgery: a 10-year experience involving 761 operations and 745 patients

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