Date of Award

6-1-2014

Document Type

Campus Access Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Maria J. Troulis

Second Advisor

Robert D. Stevenson

Third Advisor

Linda S. Huang

Abstract

PURPOSE: To evaluate bone and soft tissue healing at rates faster than 1 mm/day following automated, continuous, curvilinear distraction osteogenesis in a minipig model.

MATERIALS AND METHODS: 10 Yucatan minipigs in the mixed-dentition stage underwent automated, continuous, curvilinear DO of the right mandible. Animals were distracted 12 mm at rates of 1.5 (n=5) and 3.0 mm/day (n=5) followed by 24 days of fixation. The animals were sacrificed and bone and soft tissue healing was evaluated. A semi-quantitative scale was used to assess the ex vivo clinical appearance of the distraction gap (3=osteotomy not visible; 2=50% visible; 0=100% visible), stability (3=no mobility; 2 and 1=mobility in 1 plane or 2 planes, respectively; 0=mobility in 3 planes), and radiographic density (4=100% of gap opaque; 3=>75%; 2=50% to 75%; 1=

RESULTS: Automated, continuous DO at 1.5 mm/day and 3.0 mm/day had similar bone formation compared to the discontinuous, 1 mm/day positive control. Continuous DO at 1.5 mm/day had significantly increased scores for appearance and radiographic density than the discontinuous 4 mm/day group. The continuous DO 3 mm/day group had significantly greater appearance and radiographic density scores compared with the discontinuous 4 mm/day groups and higher stability compared to the discontinuous 2 and 4 mm/day groups. PSA occupied by bone for the continuous 1.5, 3.0, and discontinuous DO at 1 mm/day were similar (1.5 mm/day PSA=64.36±5.87, 3.0 mm/day PSA=63.83±3.37, and 1.0 mm/day PSA=64.89±0.56), but less than the nonoperated side (PSA=84.67±0.86). PSA occupied by cartilage and hematoma in all groups was minimal (< 1.1%). The digastric muscles had no abnormal tissue or inflammation and PAX7, MyoD, and PCNA expression had returned to baseline levels.

CONCLUSIONS: Results of this study indicate that bone fill of the continuous distraction wound at rates of 1.5 and 3 mm/day was similar to that of discontinuous DO at 1 mm/day. Continuous DO at rates of 1.5 and 3.0 mm/day allows nearly identical PSA occupied by bone when compared to discontinuous DO at 1 mm/day. Digastric muscles exhibited no deleterious effects caused by DO. This supports the potential to shorten treatment time for management of craniofacial deformities.

Comments

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