In this case report a cleft patient with tentative diagnosis of craniofrontonasal dysplasia who was treated with a ‘chin wing’ osteotomy is described. Alternative treatment options are discussed. A satisfactory and stable result was seen one year after surgery. The initial complaints of obstructive sleep apnea syndrome however didn’t improve.
With a chin wing osteotomy, protrusion of the chin and broadening of the lower jaw line can be achieved.
Chin wing is a treatment option in syndromic patients to avoid extensive and invasive surgical procedures.
Obstructive Sleep Apnea syndrome is not always objectively better after chin wing osteotomy.
One of the most important challenges in maxillofacial and more specific, in orthognathic surgery, is correcting facial asymmetry and facial harmony. This is especially difficult in syndromic patients. One of the methods to adjust the bony contour of the lower jaw is performing a chin wing osteotomy. This technique was first described by Triaca et al. [ ] A chin wing osteotomy is useful in patients with a large retrogenia, a pointed chin and when no alteration of occlusion is needed with the surgical advancement [ , ].
In this case report, a cleft patient with tentative diagnosis of craniofrontonasal dysplasia and excessive retrognathia is presented. He was treated by a chin wing osteotomy.
A 20-year old Caucasian male with a medical history of bilateral cleft lip and palate and a tentative diagnosis of craniofrontonasal dysplasia was seen at the Department of Oral and Maxillofacial Surgery of University Hospitals Leuven, Belgium. His main desire was to resolve his OSAS (Obstructive Sleep Apnea Syndrome) and to improve his aesthetic appearance, since he had an extreme retrognathic mandible which limited his social interaction. Pre-operative polysomnography revealed an AHI-index (Apnea-Hypopnea Index) of 22.1.
Background of the case
There was no family history of craniofrontonasal dysplasia or other syndromic disorders. Extensive clinical and radiographic examination revealed several congenital deformities: bilateral cleft lip and palate, ocular hypertelorism, blepharophimosis, proptosis, low-set ears, synostosis of the coronal suture, and underdevelopment of the midface with a hypoplastic maxilla and mandible. Other abnormalities were a diaphragmatic hernia, clinodactyly of second and fourth fingers in both hands, syndactyly of several fingers and toes, and an abnormal fold of skin extending around the base of the penis (shawl scrotum). The patient also had conductive hearing loss. During removal of the mandibular third molars, several samples of mucosal and bone tissue were taken to assay for EFNB1-gene mutations. This analysis was negative. A possible explanation is mosaicism. Clinical diagnosis of craniofrontonasal dysplasia was held [ , ].
During infancy, several operative procedures were performed to correct most of these deformities. Of interest for this case report are closure of cleft lip and palate, advancement of the orbital rim and bilateral mandibular distraction osteogenesis.
It has to be noted that the patient was already receiving active orthodontic treatment with brackets to correct the malocclusion. In the past, different kinds of orthodontic treatment were also performed.
The surgical treatment consisted of a chin wing osteotomy with appliance of iliac crest bone grafts due to the large advancement.
A comparable operative technique was used as described by Triaca et al. and in the technical note by Coopman et al. [ , ] An illustration of the osteotomy is shown in Fig. 1 . In this case, no cutting guides were used since there was insufficient space for fixation of the cutting guide on the lower border of the mandible under the inferior alveolar nerve, as demonstrated in the nerve tracing from the pre-operative CBCT (Cone Beam Computed Tomography) in Fig. 2 .
After stable rigid Intermaxillary Fixation (IMF), mucosal incision from region 36 to region 46 was performed, followed by elevation of the mucoperiostium. The bone was cut bicortically using the piezotome in the region of the symphysis. Once distal to the mental foramen the cut changed from a horizontal direction towards an oblique direction trying to preserve only the buccal plate including the lower border, hoping to avoid the inferior alveolar nerve.
Mobilisation of the bone segment with chisel was performed. Unfortunately, during mobilisation of the osteotomy segment, the left inferior alveolar nerve was damaged, without being transsected. Nerve ends were approximated and intrafascicularly sutured with Vicryl 8–0.
After mobilisation of the lower mandibular border, fixation was performed using 2×6-hole plates fixed with 3 screws and a 4-hole chin plate (KLS Martin, Tuttlingen, Germany). Bone fragments harvested from the iliac crest were placed in the osteotomy gap which were held in place using Tisseel®. It was observed that after mobilisation the lower border widened at the region of the mandibular angle, increasing the mandibular width at gonion.
In the immediate post-operative period, bilateral hypoesthesia of the lower lip was anticipated, but fortunately, there was no complete anaesthesia on the left side despite the damage of the left inferior alveolar nerve. After one year, the bilateral hypoesthesia remains present, but only in a limited area of the chin.
At one year follow-up, a new polysomnography was carried out, which could not demonstrate an improvement in AHI-index (Apnea-Hypopnea Index). This was 23.73/h compared to a pre-operative value of 22.1/h. It should however be mentioned that the pre-operative Epworth Sleepiness Scale (ESS) was 11/24, whereas the post-operative score was 0/24.
Additionally, 3D-airway analysis based on CBCT scans was performed. Post-operative CBCT scans (1 week and 1 year post-operative) were registered on the pre-operative CBCT scan based on cranial base using voxel based matching in Amira software (Thermo Fisher Scientific, Waltham, Massachusetts, USA). The airways were segmented using thresholding the gray values from −1000 to −500. The FHP (Frankfort horizontal plane) and 2 planes parallel to the FHP were defined. The first plane went through the most upper anterior point of vertebra C1 and the second through the highest point of the vertebral body of C4. These 2 planes were used to cut the upper and lower borders of the segmented airways ( Fig. 3 ). The pre-operative volume was 5977.23 mm³ compared to a 1 week post-operative volume of 6584.72 mm³ (10.2% increase compared to the pre-operative situation). However, the airway volume at 1 year post-operative dropped to a value of 4357.55 mm³ (37.2% decrease compared to the pre-operative situation).