Mandibular deformities: single-vector distraction techniques for a multivector problem

Evaluation of effect of single vector mandibular distraction for correction of postankylotic mandibular hypoplasia requiring multiplanar correction: A prospective case series

Introduction

Uniplanar devices have been criticized for being insufficient to correct complex mandibular deformities and associated problems of open bite and cross bite. The use of oblique vector to correct complex multiplanar deformities using uniplanar mandibular distraction devices is the uniqueness of the present case series.

Aim and Objective

The aim of the present case series is to describe the successful use of uniplanar mandibular distraction devices for the correction of complex multiplanar deformities.

Material and Method

The technique of callous molding was employed to overcome any open bite. A total of 40 mandibular distractors in 20 patients (mean age 13 ± 2.67 years) were placed on the mandible for correction of the facial deformity associated with the lower jaw(mandible) in vertical, horizontal and/or sagittal plane, secondary to temporomandibular joint ankylosis. The distraction was done before and after the gap arthroplasty in 15 and 5 patients, respectively. A latency period of 3-5 days was applied, and distraction was performed at a rate of 1 mm/day with the rhythm of 0.5 mm twice daily.

Results

The significant lengthening was observed in both mandibular height (Ar Go) (50.40 ± 1.52 mm from 38.80 ± 4.38mm, P = 0.006) as well as in mandibular corpus length (Go Pg) (79.40 ± 2.28 from 58.80 ± 4.09, P = 0.001). Statistically significant changes in mandibular dimensions, facial proportions, and soft tissue profile were seen, which was assessed with the help of COGS analysis done on lateral cephalogram taken preoperatively and postoperatively.

Conclusion

With intelligent vector planning and callus molding multiplanar complex deformities can be corrected by using semiburieduniplanar devices.

Congenital Mandibular Hypoplasia: Patient-Specific Total Joint Replacement as a Line Extension in the Treatment of Complex Craniofacial Anomalies

Introduction

Congenital mandibular hypoplasia (CMH) remains challenging because of the underlying combined hard and soft tissue deficiency. Treatment options include craniofacial distraction, orthognathic surgery, and autologous grafts, although the latter produces inadequate results after distraction and autologous grafting. Unsatisfactory long-term stability may cause relapse, necessitating reoperation.

Material and Methods

We investigated the feasibility of using alloplastic total joint replacement (TJR) in growing and young adult CMH patients. The primary outcome was long-term reconstruction stability, without implant failure. Secondary outcomes were TMJ function and pain, and jaw movements achieved during surgery.

Results

Three patients (age: 9–22 years) were treated by the same surgeon at one institution during 2018–2021. Anamnesis and clinical parameters were obtained from patient records. Preoperative 3D-scans were superimposed with postoperative 3D-scans and preoperative plans, including TJR-implant STL files, to measure jaw movement. All patients underwent prior reconstructive surgery. Mandibular movement of 16.4–20.1 mm in the sagittal direction was achieved. Post-TJR follow-up ranged from 24 to 42 months. No long-term complications occurred. At the latest follow-up, the maximal interincisal opening was between 21 and 40 mm, and all implants were functioning, without failure.

Conclusion

In selected CMH cases, alloplastic TJR can deliver satisfactory medium-term results with predictable and stable outcomes, even in growing patients.

Modern Mandibular Distraction Applications in Hemifacial Microsomia

Phenotypic severity dictates the timing and type of surgical intervention required. Mandibular distraction in children without respiratory and feeding difficulties remains controversial with regard to long-term mandibular growth outcomes and reducing surgical burden. Early mandibular distraction does not obviate secondary orthognathic surgery at skeletal maturity; it provides improved functional, aesthetic, and psychosocial outcomes, at least in the short term. Costochondral rib grafting for Pruzansky type IIB and III mandibles can produce reliable results, especially when combined with subsequent mandibular distraction. Secondary 2-jaw orthognathic surgery plus genioplasty at skeletal maturity benefits from improved bone volume from prior mandibular distraction.

Fully-customized distraction assembly for maxillofacial distraction osteogenesis: a novel device and its experimental accuracy verification

Background

A new distraction osteogenesis assembly system comprising a fully customized CAD/CAM-based fixation unit and ready-made distraction unit was developed. The aim of this study was to introduce our new distraction system and to evaluate its accuracy level in a sampled mandibular distraction osteogenesis.

Methods

Our system consists of a fully customized CAD/CAM-based fixation plate unit with two plates for each moving and anchoring part, and a ready-made distraction unit with attachment slots for fixation plates. The experimental distractions were performed on 3D-printed mandibles for one control and two experimental groups (N = 10 for each group). All groups had reference bars on the chin region and teeth to measure distraction accuracy. The control group had the classical ready-made distraction system, and experimental groups 1 and 2 were fitted with our new distraction assembly using a different distractor-positioning guide design. All distracted experimental mandibles were scanned by CT imaging, then superimposed on a 3D simulation to get their discrepancy levels.

Results

The measured 3D distances between the reference landmarks of the surgical simulations and the experimental surgeries for the three groups were significantly different (p < 0.0001) by statistical analysis. The errors were greater in the control group (with a total average of 19.18 ± 3.73 mm in 3D distance between the simulated and actual reference points) than those in the two experimental groups (with an average of 3.68 ± 1.41 mm for group 1 and 3.07 ± 1.39 mm for group 2). The customized distraction assembly with 3D-printed bone plate units in group 1 and 2, however, did not show any significant differences between simulated and actual distances (p > 0.999).

Conclusion

Our newly-developed distraction assembly system with CAD/CAM plate for the distraction osteogenesis of the mandible produced a greater level of accuracy than that of a conventional distraction device. The system appears to address existing shortcomings of conventional distraction devices, including inaccuracy in vector-controlled movement of the system. However, it also needs to be further developed to address the requirements and anatomical characteristics of specific regions.

Craniofacial Microsomia

Clinicians use different diagnostic terms for patients with underdevelopment of facial features arising from the embryonic first and second pharyngeal arches, including first and second branchial arch syndrome, otomandibular dysostosis, oculoauriculovertebral syndrome, and hemifacial microsomia. Craniofacial microsomia has become the preferred term. Although no diagnostic criteria for craniofacial microsomia exist, most patients have a degree of underdevelopment of the mandible, maxilla, ear, orbit, facial soft tissue, and/or facial nerve. These anomalies can affect feeding, compromise the airway, alter facial movement, disrupt hearing, and alter facial appearance.

Treacher collins syndrome

Treacher Collins syndrome is a genetic disorder resulting in congenital craniofacial malformation. Patients typically present with downslanting palpebral fissures, lower eyelid colobomas, microtia, and malar and mandibular hypoplasia. This autosomal dominant disorder has a variable degree of phenotypic expression, and patients have no associated developmental delay or neurologic disease. Care for these patients requires a multidisciplinary team from birth through adulthood. Proper planning, counseling and surgical techniques are essential for optimizing patient outcomes. Here the authors review the features, genetics, and treatment of Treacher Collins syndrome.

Craniofacial microsomia

Craniofacial microsomia (CFM) is one of the most common congenital conditions treated in craniofacial centers worldwide. This condition is variably associated with anomalies of the jaws, ears, facial soft tissue, orbits, and facial nerve function and can be associated with extracranial anomalies. The cause of this condition is unknown, though CFM has been associated withprenatalexposures and genetic abnormalities. Diagnosis, treatment, and outcome assessment in CFM is challenging due to the wide phenotypic spectrum observed in this condition. Surgical treatment requires a coordinated team approach involving multiple specialties, which can include plastic surgery, craniofacial surgery, orthognathic surgery, and microsurgery. A wide variety of surgical options exist, and individual treatment plans should be based on the patient's needs. Although CFM can be challenging to treat, successful outcomes are rewarding. We provide a review of the common craniofacial surgical treatments for individuals with CFM.

MANDIBULAR ASYMMETRY CHARACTERIZATION USING GENERALIZED TENSOR-BASED MORPHOMETRY

Quantitative assessment of facial asymmetry is crucial for successful planning of corrective surgery. We propose a tensor-based morphometry (TBM) framework to locate and quantify asymmetry using 3D CBCT images. To this end, we compute a rigid transformation between the mandible segmentation and its mirror image, which yields global rotation and translation with respect to the cranial base to guide the surgery's first stage. Next, we nonrigidly register the rigidly aligned images and use TBM methods to locally analyze the deformation field. This yields data on the location, amount and direction of "growth" (or "shrinkage") between the left and right sides. We visualize this data in a volumetric manner and via scalar and vector maps on the mandibular surface to provide the surgeon with optimal understanding of the patient's anatomy. We illustrate the feasibility and strength of our technique on 3 representative patients with a wide range of facial asymmetries.

Correction of rabbit model with mandibular ramus shortening by distraction osteogenesis at condylar neck

PURPOSE

The rabbit model has been established to mimic the effect of temporomandibular joint (TMJ) arthroplasty of ankylosis, and distraction at the level of the condylar neck is used to elongate the ascending ramus. The histomorphologic changes of TMJ and distraction gap were investigated.

MATERIALS AND METHODS

The unilateral condyles and articular discs were extirpated, and the experimental mandibular rami were shortened by 5 mm. An embedded distracter was used to restore the height of the mandibular ramus by unilateral condylar neck distraction (0.8 mm daily for 7 days). A total of 12 adult white rabbits were used, 8 in the experimental group and 4 in the control group. Of the 8 rabbits in the experimental group, 4 each were killed at 4 and 8 weeks after completion of distraction. The TMJ and distracted calluses were harvested and processed for radiographic and histologic examination.

RESULTS

An open bite was seen in all rabbits postoperatively that had diminished at the end of distraction. The newly formed condyles radiologically showed remodeling, flattening, and sclerosis. The bony transport disc had gradually remodeled to a new condyle that was similar to the original condyle in appearance and structure. The surface of the transport disc was covered with a fibrous tissue. Moreover, the bony regeneration was perfect in the distraction gap.

CONCLUSION

These results suggest that distraction osteogenesis at the condylar neck using the traditional preauricular approach of TMJ surgery, without the additional incision, can be performed concurrently with arthroplasty of TMJ ankylosis at the same region.