Use of Kinesiography to Assess Mandibular Function Following Segmental Resection and Microvascular Reconstruction

Prediction of jaw opening function after mandibular reconstruction using subject-specific musculoskeletal modelling

BACKGROUND

Mandibular reconstruction patients often suffer abnormalities in the mandibular kinematics. In silico simulations, such as musculoskeletal modelling, can be used to predict post-operative mandibular kinematics. It is important to validate the mandibular musculoskeletal model and analyse the factors influencing its accuracy.

OBJECTIVES

To investigate the jaw opening-closing movements after mandibular reconstruction, as predicted by the subject-specific musculoskeletal model, and the factors influencing its accuracy.

METHODS

Ten mandibular reconstruction patients were enrolled in this study. Cone-beam computed tomography images, mandibular movements, and surface electromyogram signals were recorded preoperatively. A subject-specific mandibular musculoskeletal model was established to predict surgical outcomes using patient-averaged muscle parameter changes as model inputs. Jaw bone geometry was replaced by surgical planning results, and the muscle insertion sites were registered based on the non-rigid iterative closest point method. The predicted jaw kinematic data were validated based on 6-month post-operative measurements. Correlations between the prediction accuracy and patient characteristics (age, pathology and surgical scope) were further analysed.

RESULTS

The root mean square error (RMSE) for lower incisor displacement was 31.4%, and the error for peak magnitude of jaw opening was 4.9 mm. Age, post-operative infection and radiotherapy influenced the prediction accuracy. The amount of masseter detachment showed little correlation with jaw opening.

CONCLUSION

The mandibular musculoskeletal model successfully predicted short-range jaw opening functions after mandibular reconstruction. It provides a novel surgical planning method to predict the risk of developing trismus.

Microvascular Reconstruction of the Anterior Skull Base

Anterior skull base defects present a unique reconstructive challenge. Risk factors such as previous operation, radiation and infection require a multidisciplinary approach to create a stable wound. Reconstructive microsurgery serves an important role when attempts with pericranial flap placement and nonvascularized graft obliteration fail. Our series analyzes the outcomes of 5 patients who underwent vascularized reconstruction of craniofacial defects at Northwestern Memorial Hospital from 2014-2021. Each patient presented with a complex, hostile scalp and bony wound. Common risk factors included previous craniotomy, failed obliteration, chemoradiation, osteomyelitis and epidural abscess. Patients underwent multi-stage procedures to obtain wound source control, reconstruct the frontal sinus and skull base, and frontal bone cranioplasty. Each patient underwent successful free flap reconstruction without flap loss or donor site complications. No patients suffered ongoing symptomatic CSF leak or pneumocephalus. However, only two patients have had sustained success with their alloplastic cranioplasty. A perfect, watertight seal is required to prevent seeding the implant and avoiding infection. Overall, free flap reconstruction of the skull base and frontal sinus is a necessary solution when patients fail more conservative locoregional options. Close collaboration with neurosurgery can help with diagnosis and establish the optimal timing for surgical care.