Effect of outer mandibular cortex osteotomy on local morphology and biomechanics in young miniature pigs

Teriparatide (recombinant parathyroid hormone 1-34) enhances bone allograft integration in a clinically relevant pig model of segmental mandibulectomy

Massive craniofacial bone loss poses a clinical challenge to maxillofacial surgeons. Structural bone allografts are readily available at tissue banks but are rarely used due to a high failure rate. Previous studies showed that intermittent administration of recombinant parathyroid hormone (rPTH) enhanced integration of allografts in a murine model of calvarial bone defect. To evaluate its translational potential, the hypothesis that rPTH would enhance healing of a mandibular allograft in a clinically relevant large animal model of mandibulectomy was tested. Porcine bone allografts were implanted into a 5-cm-long continuous mandible bone defect in six adult Yucatan minipigs, which were randomized to daily intramuscular injections of rPTH (1.75 μg/kg) and placebo (n = 3). Blood tests were performed on Day 56 preoperation, Day 0 and on Day 56 postoperation. Eight weeks after the surgery, bone healing was analyzed using high-resolution X-ray imaging (Faxitron and micro computed tomography [CT]) and three-point bending biomechanical testing. The results showed a significant 2.6-fold rPTH-induced increase in bone formation (p = 0.02). Biomechanically, the yield failure properties of the healed mandibles were significantly higher in the rPTH group (yield load: p < 0.05; energy to yield: p < 0.01), and the post-yield displacement and energy were higher in the placebo group (p < 0.05), suggesting increased mineralized integration of the allograft in the rPTH group. In contrast to similar rPTH therapy studies in dogs, no signs of hypercalcemia, hyperphosphatemia, or inflammation were detected. Taken together, we provide initial evidence that rPTH treatment enhances mandibular allograft healing in a clinically relevant large animal model.

Repairing Cranial Defect With Autogenous Mandibular Outer Plate

BACKGROUND

Autogenous bone is the best material in cranioplasty because of biological advantages. Previously, skull, rib, ilium, and fibula have been used in the reconstruction of cranial defects. However, the application of autologous mandibular outer plate in the treatment of skull defect is rarely reported. This study evaluated the application of the autogenous mandibular outer plate in the reconstruction of cranial defect.

METHODS

Eleven patients who underwent cranioplasty with mandibular outer plate were recruited. Three-dimensional tomography data were collected to calculate the preoperative, immediate postoperative, and long-term follow-up volume of the bone graft area and donor bone site, and then the absorption rate and the regeneration rate of autogenous bone were analyzed.

RESULTS

The majority of the patients were satisfied with the reconstructive outcome. There are statistical differences in the volumetric measurements of the bone graft area and bone donor site at different time periods (P<0.05). The mean absorptivity of mandibular outer plate implanted in the cranial defect area was (17.30 ± 5.03)% after 3 to 24 months postoperatively, the average regeneration rate of mandibular outer plate volume was (41.65 ± 9.85)% at the same period.

CONCLUSION

This report shows that the cranioplasty with mandibular outer plate bone graft may be an optional surgical procedure.

Assessment of a Novel Standardized Training System for Mandibular Contour Surgeries

Importance

Mandibular contour surgeries (MCS) involving reduction gonioplasty and genioplasty are rewarding for patients with square faces; however, the procedure has inherently difficult clinician learning curves and unpredictable skill acquisitions. To our knowledge, there has been no effective, validated training model that might improve training and surgical outcomes for MCS.

Objective

To establish and evaluate a standardized intraoral MCS training system.

Design, Setting, and Participants

Intraoral MCS training models were constructed by 3-dimensional (3D) skull models covered with elastic head cloths. From April 2016 to April 2018, 90 consecutive MCS patients (30 per group) and 15 craniofacial surgery fellow physicians (5 per group) were enrolled in the prospective observational study. They were randomly divided into intervention groups (A and B) and a control group (C). Intervention groups A and B completed 5 training sessions on the intraoral MCS training models before each clinical case. Group A performed both the model training sessions and clinical surgeries with surgical templates. Control group C had no extra training before clinical surgeries. All groups completed clinical surgery under supervision on 6 patients. The duration of follow-up was at least 3 months postoperatively.

Interventions

Intraoral MCS training models were provided to intervention groups (A and B) before clinical surgeries. Surgical templates were provided to intervention group A both in training sessions and clinical surgeries.

Main Outcomes and Measures

The completion time, surgical accuracy, learning curves, operating confidence, surgical skill, and outcome satisfaction of each procedure were recorded and analyzed with paired t test and 1-way analysis of variance test by blinded observers.

Results

All 90 patients (14 men, 76 women; mean [SD] age, 26 [5] years) were satisfied with their postoperative mandible contours. The intervention groups (A and B), especially the group with surgical templates (A) showed improvements in clinical surgery time (mean [SD], group A 147.2 [24.71] min; group B, 184.47 [16.28] min; group C, 219.3 [35.3] min; P = .001), surgical accuracy (mean [SD], group A, 0.68 [0.22] mm; group B, 1.22 [0.38] mm; group C, 1.88 [0.54] mm; P < .001), learning curves, and operators' confidence and surgical skill.

Conclusions and Relevance

The intraoral MCS training model was effective and practical. The optimal intraoral MCS training system included intraoral MCS training models and surgical templates. The system significantly decreased clinical surgery time, improved surgical accuracy, shortened the learning curve, boosted operators' confidence, and was associated with better acquisition of surgical skills.

Level of Evidence

NA.

3D-CT evaluation of mandibular morphology after mandibular outer cortex osteotomy in young miniature pigs: the role of the periosteum

AIM

The purpose of this study was to evaluate the role of periosteum on the healing and growth of mandible after mandibular outer cortex osteotomy using three-dimensional computed tomography.

METHODS

Eighteen 3-month-old miniature pigs were randomized into three groups. The mandibular outer cortex osteotomy was performed on both sides in group I, and on the left side in group II. In groups I and II, the local periosteum on the left side was resected. In group III, no operation was performed. The evaluation of mandibular morphology of all the animals was performed based on multiple spiral CT data before and after surgery.

RESULTS

The bone defects healed well when the periosteum was preserved, whereas they healed poorly with residual bone defects when the periosteum was resected after surgery. When the periosteum was resected, the decrease in the mean thickness of the mandibular body was more than that of the contralateral side after surgery. In group I, about 66.7% of the animals exhibited mandible deviation at 24 weeks after surgery. The median point of mentum was inclined toward the side that the periosteum was preserved. In groups II and III, no mandible deviation was observed.

CONCLUSION

The periosteum plays an important role in bone growth and fracture healing. Mandibular outer cortex osteotomy inhibited the mandibular development and resulted in postoperative mandibular deviation in young miniature pigs. The simultaneous periosteum resection may offset the phenomenon of mandibular deviation to a certain extent.