Distraction Osteogenesis: Two Case reports

by Dr. Mac Whitesides

en Espanol

Thirty years of surgery on the facial bones has demonstrated that bones of the face can be acutely moved significant distances and grafted to produce predictable results. Ten years of distraction osteogenesis (DO) surgery has showed that surgeons can produce equally dramatic results with simple osteotomies followed by slow distraction of the bone segments.

The biological principles behind distraction osteogenesis are sound. A simple osteotomy followed by a latency period, then active stressing of the bone and soft tissue by distraction will predictably produce new bone and soft tissue once the consolidation period has elapsed.

I would like to present two cases where the principles of distraction osteogenesis surgery were employed to produce successful long-term results.

CASE I: BB: 38-year-old white female.

Fig 1: pre-op face	Fig 2: pre-op profile

Fig 3: pre-op ceph

Findings:

1. Maxillary hyperplasia/VME (gummy smile)
   
2. Retrogenia

Treatment Plan:

1. Maxillary LeFort I maxillary osteotomy with impaction of maxilla and rigid fixation
2. Bilateral vertical osteotomy of the mandible and placement of bilateral Dynaform^™ distraction device
3. Advancement genioplasty with rigid fixation.

 

Fig 4: intra-op view illustrating extent of mandibular advancement required after maxilla is impacted

 

Fig 5: post-op panorex pre-distraction

 

 

Fig 6: occlusion at end of distraction phase	Fig 7: profile at end of distraction phase

Fig 8: photo (frontal) 8 months post distraction	Fig 9: profile 8 months post distraction

Fig 10: ceph 1 yr post distraction

Fig 11: occlusion right 14 months post distraction	Fig 12: occlusion left 14 months post distraction	Fig 13: : occlusion (front) 14 months post distraction

BB initially presented to our office from her orthodontist fully expecting to discuss traditional orthognathic surgery. After completing her orthognathic surgery evaluation, reviewing the clinical photos, and cephalometric analysis, my partner & I felt BB would be better treated by using traditional surgical techniques (LeFort I maxillary osteotomy) to address her VME. We elected to employ distraction osteogenesis surgical techniques (mandibular vertical osteotomy and placement of bilateral Dynaform^™ distraction devices) to treat her mandibular hypoplasia. A standard advancement genioplasty with rigid fixation would be used to address her retrogenia.

The stability and success of the LeFort I osteotomy maxillary impaction procedure and genioplasty is well documented and will not be discussed here.

The question therefore remains; why use distraction osteogenesis to lengthen the mandible instead of a traditional BSSRO with rigid fixation for this patient?

1. Length of advancement: Close examination of the cephalometric radiograph demonstrates that prior to the maxillary surgery the amount of mandibular advancement is significant (12 mm). Post LeFort I osteotomy and impaction of the maxilla this figure is actually increased to approximately 15 mm because as the maxilla is impacted, the mandible must advance farther in the sagittal plane to provide a Class I occlusion. A 15 mm advancement in a 38-year-old can be done without a bone graft; however, with such a significant advancement of the mandible there may be insufficient overlap of bone to provide adequate surface area for rigid fixation. Additionally, such a major advancement of the mandible can have significant relapse. The gradual separation of bone & soft tissue in DO is believed to result in little, if any, relapse. Although I have observed no relapse in my advancement patients thus far, long-term follow-up studies are needed to confirm this claim.

2. Bone structure of the patient: Examination of the preop Panorex and cephalometric radiograph demonstrate that BB has a high mandibular plane angle and thin condylar neck. These two findings in association with the magnitude of advancement contribute to the increased incidence of the patient experiencing post- operative TMJ pain secondary to the torqueing of the mandible & the TMJ. Distraction osteogenesis surgery is believed to place minimum of stress on the temporomandibular joint by virtue of its gradual method of displacing bone and soft tissue. Less stress on the TMJ is believed to result in less sequela as a result of the surgery.

3. Neurosensory factors: A significant advancement of the mandible in patients of any age is associated with some degree of neurosensory impairment, either temporary or permanent. As patients increase in age, the degree of impairment with this surgery increases accordingly. Distraction osteogenesis is believed (and thus far I have noted it to be true) to result in far less neurosensory deficit in patients. This may be because of the slow displacement of tissue and/or the nerve’s ability to recuperate after each activation experience.

CASE II: PS: 24-year-old white male.

Findings:

1. Mandibular constriction and crowding
2. Impacted wisdom teeth

Treatment Plan:

1. Orthodontic expansion of maxilla
2. Surgical expansion of the mandible
3. Removal of impacted wisdom teeth.

Fig 14: pre-op showing mandibular crowding	Fig 15: intra-op showing osteotomy & dynaform in place	Fig 16: clinical photo showing distraction phase

Fig 17: panorex at end of distraction

Fig 18: occlusal x-ray 1 month post distraction	Fig 19: occlusal x-ray 6 months post distraction	Fig 20: occlusal x-ray 15 months post distraction

Fig 21: occlusion 1 yr post distraction & orthodontic expansion of maxillary arch	Fig 22: occlusion 2 yrs post distraction & orthodontic expansion of maxillary arch

Fig 23: panorex: 2 yrs post distraction & orthodontic expansion of maxillary arch

PS Presented to my office for extraction of four of his bicuspids to provide room for the orthodontist to correct his malocclusion and relieve the dental crowding. We discussed this procedure, as well as orthodontic expansion of his maxilla combined with surgical expansion (using DO) of his mandible. The patient elected to retrain his bicuspids and undergo maxillary and mandibular expansion.

The reason for using orthodontic expansion in the maxilla in association with mandibular expansion using distraction osteogenesis in this case is less clear cut. Certainly, one could extract four bicuspids "rack back" the occlusion and arrive at an acceptable result for this patient in his early 20’s. By not extracting his bicuspids, we were able to preserve more of the patient’s dentoalveolar structure. This will help him to maintain a more youthful appearance as he ages.

SUMMARY

Distraction Osteogenesis is not a panacea for all surgical conditions. It has its limitations and drawbacks. Not every patient is a candidate and not every candidate is an acceptable patient. DO surgery requires a great deal of diligence & devotion from the doctor & patient. Hardware can & does fail, thus both doctor & patient need to accept this as a possibility when undergoing the process.

Like any new surgical technique much research needs to be done to verify in the lab what surgeons are observing in the field. With continued research and clinical experience DO will most likely prove to be an indispensable part of every surgeon’s armamentarium.

doctormac@mindspring.com