Transthoracic Vertebral Distraction and Stabilization in 10 Dogs with Congenital Thoracic Vertebral Malformations

Objective The aim of this study was to describe the surgical technique and outcomes of dogs with congenital thoracic vertebral body malformations (CTVBM) treated with unilateral vertebral distraction and stabilization with monocortical screws and polymethylmethacrylate (PMMA). Study Design Medical records of 10 client-owned dogs with CTVBM were retrospectively searched for signalment, history, neurological examination, neurological grade based on the modified Frankel scale (MFS), diagnostic method, CTVBM location, Cobb's angle, and vertebral canal angle (VCA), surgical procedure, complications and long-term follow-up. Results One dog suffered cardiac arrest 24 hours post-surgery and died. Median follow-up in nine dogs was 26.5 months (12–50 months). Cobb's angle improved from 33–83 to 10–46 degrees and the VCA ratio from 97–138 to 122–164 degrees. The MFS improved from 3 (n = 3)–4 (n = 7) to 4 (n = 2)–6 (n = 7). Seven dogs recovered full function. Nine dogs improved after surgery compared with preoperative status, recovering ambulation when lost or achieving normal neurological examination in seven cases. No complications were reported during the follow-up period (12–50 months). Conclusion Unilateral transthoracic vertebral distraction and stabilization with monocortical screws and PMMA for treatment of compressive myelopathy due to CTVBM achieved long-term neurological improvement in 9 of 10 dogs.

Biomechanical Evaluation of a New Fixation Method for Stabilization of Sagittal Split Ramus Osteotomy After Mandibular Advancement

Study Design: Biomechanical in vitro study. Mandibular advancement after sagittal split ramus osteotomy (SSRO) is a common procedure in orthognathic surgery. Several fixation methods are used for stabilization of SSRO. Objective: The aim of this study was to compare a new fixation method (gridplate) with more contemporary applied methods of fixation. Material and Methods: In this study, 50 polyurethane hemimandibles with a prefabricated SSRO were used as specimens. All hemimandibles were advanced by 8 mm and divided into 5 groups with different fixation methods: (A) one 4-hole miniplate with 4 monocortical screws; (B) two 4-hole miniplates with 8 monocortical screws; (C) one 4-hole miniplate with 4 monocortical screws and 1 bicortical screw in the retromolar area (hybrid method); (D) 3 bicortical screws in an inverted-L pattern; and (E) one 8-hole gridplate with 8 monocortical screws. Loads in newtons were recorded at displacements of the mandibular incisive edge at 1 mm, 3 mm and 5 mm. Results: Fixation with 3 bicortical screws and the gridplate presented the most stability, followed by two 4-hole miniplates. Fixation with the hybrid method or the single miniplate showed the least stability. Conclusion: According to the results of this study, the 8-hole gridplate design appears a sufficient fixation method regarding stabilization of SSRO with larger mandibular advancement.

Management of Mandibular Angle Fracture in a 9-year-old with Miniplate and Monocortical Screws: A Clinical Challenge

ABSTRACT The main characteristic feature of the pediatric mandible is that of decreased dimension, which leads to compromises in the open reduction and internal fixation (ORIF). In the dental segment, the cervically bulbous short stature primary teeth might act an obstacle during the maxillomandibular fixation conventionally. An increased osteogenic potential of bones favors rapid consolidation and remodeling in the affected region. The mixed dentition of the ugly duckling stage adds more burden while stabilizing the fractured segments. The main goal of the clinician is to achieve and restore the facial appearance and function. Hereby, we present a clinical challenge depicting a 9-year-old male with mandibular angle fracture managed by miniplate and monocortical screws fixation. How to cite this article Shunmugavelu K, Subramaniam K. Management of Mandibular Angle Fracture in a 9-year-old with Miniplate and Monocortical Screws: A Clinical Challenge. Int J Clin Pediatr Dent 2017;10(4):391-393.

Pullout strength of monocortical and bicortical screws in meta -physeal and diaphyseal regions of the canine humerus

Summary Objective: Monocortical screws are commonly employed in locking plate fixation, but specific recommendations for their placement are lacking and use of short monocortical screws in metaphyseal bone may be contra indicated. Objectives of this study were to evaluate axial pullout strength of two different lengths of monocortical screws placed in various regions of the canine humerus compared to bicortical screws, and to derive cortical thickness and bone density values for those regions using quantitative computed tomography analysis (QCT). Methods: The QCT analysis was performed on 36 cadaveric canine humeri for six regions of interest (ROI). A bicortical, short monocortical, or 50% transcortical 3.5 mm screw was implanted in each ROI and axial pullout testing was performed. Results: Bicortical screws were stronger than monocortical screws in all ROI except the lateral epicondylar crest. Short monocortical metaphyseal screws were weaker than those placed in other regions. The 50% transcortical screws were stronger than the short monocortical screws in the condyle. A linear relationship between screw length and pull-out strength was observed. Clinical significance: Cortical thickness and bone density measurements were obtained from multiple regions of the canine humerus using QCT. Use of short monocortical screws may contribute to failure of locking plate fixation of humeral fractures, especially when placed in the condyle. When bicortical screw placement is not possible, maximizing monocortical screw length may optimize fixation stability for distal humeral fractures.

Tomographic Evaluation of Mandibular Thickness on Premolar and Molar Regions Related to Monocortical Screws

The aim of this study was to measure the thickness of the mandible from the external cortical plate to the teeth roots on premolar and molar regions using CT scan to determine the safety margin for the application of monocortical screws for internal rigid fixation. Thirty-one patients underwent CT-scan imaging for surgical planning. The images were used to measure bilaterally the distance from the external cortex of the mandible to the roots of teeth on premolar and molar region by means of Dental Slice software (Bioparts Prototipagem Biomedica, Brasília, DF, Brazil). Mean, median, standard deviation, one-way ANOVA and post hoc Tukey's test were used for statistical analysis. No statistical differences for thickness were found between right and left side ( p = 0.1652). The mean thickness for the left side was 4.17 ± 1.68 mm and for right side 3.93 ± 1.49 mm. Increase in mandibular thickness from anterior to posterior regions in both sides was observed and statistical difference was found among the different groups according to the measured region ( p < 0.05). The present results can predict the safety zone for the use of monocortical screws in the mandible, but the use of CT scan is imperative and individual analysis is desired owing to anatomical variations. Further studies with larger samples are necessary to confirm these data and should include other anatomic structures, different regions of mandible/maxilla, as well as other ethnic groups.

A biomechanical comparison of unilateral and bilateral String-of-Pearls™ locking plates in a canine distal humeral metaphyseal gap model

SummaryObjective: To compare the in vitro biomechanical performance of two String-of-Pearls (SOP) plate constructs in a canine distal humeral metaphyseal gap model.Methods: Seven pairs of canine cadaveric humeri, including the elbow joints, were prepared. One group consisted of a unilateral medially placed SOP plate with bicortical screws (UNI). The second group consisted of bilateral caudo-medial and caudo-lateral SOP plates applied with monocortical screws (BI). A 2 cm ostectomy was performed immediately proximal to the supratrochlear foramen. Constructs were tested in torsion and axial compression.Results: The UNI constructs had significantly lower stiffness in torsion and axial compression than the BI group. However, UNI constructs had a significantly higher ultimate strength than BI constructs. All UNI constructs failed by bending of the transcondylar screw and SOP plate. All BI constructs failed by axial pullout of the distal most screws.Clinical significance: In stabilizing canine supracondylar humeral fractures as modeled here, both the UNI model and the BI model demonstrated biomechanical advantages. The incorporation of a transcondylar screw through the medial plate appears to be beneficial to construct strength.