Kinematic analysis of mandibular motion before and after mandibulectomy and mandibular reconstruction in dogs

Abstract

OBJECTIVE To evaluate and quantify the kinematic behavior of canine mandibles before and after bilateral rostral or unilateral segmental mandibulectomy as well as after mandibular reconstruction with a locking reconstruction plate in ex vivo conditions. SAMPLE Head specimens from cadavers of 16 dogs (range in body weight, 30 to 35 kg). PROCEDURE Specimens were assigned to undergo unilateral segmental (n = 8) or bilateral rostral (8) mandibulectomy and then mandibular reconstruction by internal fixation with locking plates. Kinematic markers were attached to each specimen in a custom-built load frame. Markers were tracked in 3-D space during standardized loading conditions, and mandibular motions were quantified. Differences in mandibular range of motion among 3 experimental conditions (before mandibulectomy [ie, with mandibles intact], after mandibulectomy, and after reconstruction) were assessed by means of repeated-measures ANOVA. RESULTS Both unilateral segmental and bilateral rostral mandibulectomy resulted in significantly greater mandibular motion and instability, compared with results for intact mandibles. No significant differences in motion were detected between mandibles reconstructed after unilateral segmental mandibulectomy and intact mandibles. Similarly, the motion of mandibles reconstructed after rostral mandibulectomy was no different from that of intact mandibles, except in the lateral direction. CONCLUSIONS AND CLINICAL RELEVANCE Mandibular kinematics in head specimens from canine cadavers were significantly altered after unilateral segmental and bilateral rostral mandibulectomy. These alterations were corrected after mandibular reconstruction with locking reconstruction plates. Findings reinforced the clinical observations of the beneficial effect of reconstruction on mandibular function and the need for reconstructive surgery after mandibulectomy in dogs.

Case report: Spontaneous mandibular body regeneration following unilateral subtotal mandibulectomy in a 3-month-old French bulldog

“…Reconstructive surgery following segmental or partial mandibulectomies in dogs has been described to help address the functional disturbances associated with these surgeries, such as traumatic malocclusion ( 7 , 8 , 16 ). In young patients, reconstruction following excision would be complicated further by the need to account for continued growth ( 13 ).…”

“…Excision of a considerable portion of the mandible results in changes to the stability and movement of the remaining mandibular anatomy, leading to mandibular drift, traumatic malocclusion, and changes to the temporomandibular joint (TMJ) ( 6 – 9 ). These sequelae can lead to chronic pain and alterations to prehension and mastication, potentially affecting the patient’s long-term quality of life ( 7 ).…”

A Retrospective Study on Mandibular Reconstruction Following Excision of Canine Acanthomatous Ameloblastoma

“…In all cases reported here, the excision created a critical-sized defect with resultant substantial malocclusion that would have remained without the performed reconstruction. As our understanding of mandibular kinematics in the dog evolves, the severe consequences of the loss in mandibular continuity following mandibulectomy are better understood, and the sequelae of the unrestored mandible is increasingly less acceptable as an outcome ( 19 ). Segmental and bilateral rostral mandibulectomy results in mandibular instability that impacts mastication, and recreational activities that require grasping and holding of objects.…”

“…Earlier reports on the use of rhBMP-2 infused into a compression resistant matrix (CRM) in dogs ( 16 – 18 ) reported bone regeneration in critical-size mandibular defetcs following mandibulectomy or gun shot injuries. The technique was later modified to include the use of a single titanium reconstruction plate and locking screws, and shown to successfully restore mandibular continuity and kinematics ( 8 – 10 , 19 ).…”

The Diagnostic Yield of Cone-Beam Computed Tomography for Degenerative Changes of the Temporomandibular Joint in Dogs

“…Also, the joint has an intra-articular fibrocartilaginous disc dividing the joint into two non-communicating compartments ( 2 – 4 ). From a kinematic perspective, the TMJ of dogs is capable of a hinge-like motion (i.e., opening and closing) with limited lateral movement ( 3 , 5 ). In contrast, the TMJ of humans is capable of more diverse kinematics such as opening and closing, rotation, translation, protrusion, retrusion, and laterotrusion ( 2 , 6 , 7 ).…”