Bone remodeling following mandibular reconstruction using fibula free flap.

To investigate bone remodelling responses to mandibulectomy, a joint external and internal remodelling algorithm is developed here by incorporating patient-specific longitudinal data. The primary aim of this study is to simulate bone remodelling activity in the conjunction region with a fibula free flap (FFF) reconstruction by correlating with a 28-month clinical follow-up. The secondary goal of this study is to compare the long-term outcomes of different designs of fixation plate with specific screw positioning. The results indicated that the overall bone density decreased over time, except for the Docking Site (namely DS1, a region of interest in mandibular symphysis with the conjunction of the bone union), in which the decrease of bone density ceased later and was followed by bone apposition. A negligible influence on bone remodeling outcome was found for different screw positioning. This study is believed to be the first of its kind for computationally simulating the bone turn-over process after FFF maxillofacial reconstruction by correlating with patient-specific follow-up.

Effects of buccal thickness augmentation on bone remodeling after maxillary anterior implantation.

The biomechanics associated with buccal bone thickness (BBT) augmentation remains poorly understood, as there is no consistent agreement in the adequate BBT to avoid over-loading resorption or over-augmenting surgical difficulty. This study utilizes longitudinal clinical image data to establish a self-validating time-dependent finite element (FE)-based remodeling procedure to explore the effects of different buccal bone thicknesses on long-term bone remodeling outcomes in silico. Based upon the clinical computed tomography (CT) scans, a patient-specific heterogeneous FE model was constructed to enable virtual BBT augmentation at four different levels (0.5, 1.0, 1.5, and 2.0 mm), followed by investigation into the bone remodeling behavior of the different case scenarios. The findings indicated that although peri-implant bone resorption decreased with increasing initial BBT from 0.5 to 2 mm, different levels of the reduction in bone loss were associated with the amount of bone augmentation. In the case of 0.5 mm BBT, overloading resorption was triggered during the first 18 months, but such bone resorption was delayed when the BBT increased to 1.5 mm. It was found that when the BBT reached a threshold thickness of 1.5 mm, the bone volume can be better preserved. This finding agrees with the consensus in dental clinic, in which 1.5 mm BBT is considered clinically justifiable for surgical requirement of bone graft. In conclusion, this study introduced a self-validating bone remodeling algorithm in silico, and it divulged that the initial BBT affects the bone remodeling outcome significantly, and a sufficient initial BBT is considered essential to assure long-term stability and success of implant treatment.

Investigation on masticatory muscular functionality following oral reconstruction - An inverse identification approach.

The human masticatory system has received significant attention in the areas of biomechanics due to its sophisticated co-activation of a group of masticatory muscles which contribute to the fundamental oral functions. However, determination of each muscular force remains fairly challenging in vivo; the conventional data available may be inapplicable to patients who experience major oral interventions such as maxillofacial reconstruction, in which the resultant unsymmetrical anatomical structure invokes a more complex stomatognathic functioning system. Therefore, this study aimed to (1) establish an inverse identification procedure by incorporating the sequential Kriging optimization (SKO) algorithm, coupled with the patient-specific finite element analysis (FEA) in silico and occlusal force measurements at different time points over a course of rehabilitation in vivo; and (2) evaluate muscular functionality for a patient with mandibular reconstruction using a fibula free flap (FFF) procedure. The results from this study proved the hypothesis that the proposed method is of certain statistical advantage of utilizing occlusal force measurements, compared to the traditionally adopted optimality criteria approaches that are basically driven by minimizing the energy consumption of muscle systems engaged. Therefore, it is speculated that mastication may not be optimally controlled, in particular for maxillofacially reconstructed patients. For the abnormal muscular system in the patient with orofacial reconstruction, the study shows that in general, the magnitude of muscle forces fluctuates over the 28-month rehabilitation period regardless of the decreasing trend of the maximum muscular capacity. Such finding implies that the reduction of the masticatory muscle activities on the resection side might lead to non-physiological oral biomechanical responses, which can change the muscular activities for stabilizing the reconstructed mandible.

Biomechanical analysis of bone remodeling following mandibular reconstruction using fibula free flap.

Whilst the newly established biomechanical conditions following mandibular reconstruction using fibula free flap can be a critical determinant for achieving favorable bone union, little has been known about their association in a time-dependent fashion. This study evaluated the bone healing/remodeling activity in reconstructed mandible and its influence on jaw biomechanics using CT data, and further quantified their correlation with mechanobiological responses through an in-silico approach. A 66-year-old male patient received mandibular reconstruction was studied. Post-operative CT scans were taken at 0, 4, 16 and 28 months. Longitudinal change of bone morphologies and mineral densities were measured at three bone union interfaces (two between the fibula and mandibular bones and one between the osteotomized fibulas) to investigate bone healing/remodeling events. Three-dimensional finite element models were created to quantify mechanobiological responses in the bone at these different time points. Bone mineral density increased rapidly along the bone interfaces over the first four months. Cortical bridging formed at the osteotomized interface earlier than the other two interfaces with larger shape discrepancy between fibula and mandibular bones. Bone morphology significantly affected mechanobiological responses in the osteotomized region (R2 > 0.77). The anatomic position and shape discrepancy at bone union affected the bone healing/remodeling process.

Lesser metatarsophalangeal instability: presentation, management, and outcomes.

BACKGROUND: Lesser metatarsophalangeal (MTP) instability is a common cause of forefoot pain. In this prospective study, we looked at its presentation, management and outcome. METHODS: We studied characteristics of patients presenting to a specialist foot and ankle clinic with lesser MTP instability. We used the drawer test to diagnose and stage instability. Patients were followed up in clinic or by telephone interview. RESULTS: We identified 154 patients with lesser MTP instability; 127 (82%) were female, median age was 56 years. One foot was affected in 107 patients (69%). The second toe only was affected in 99 patients (64%) and multiple toes in 52 (34%) but always involving the second toe if multiple toes involved. 150 toes (52%) had Grade 1 instability, 108 (37%) Grade 2 and 21 (7%) Grade 3 instability. Twelve toes (4%) presented dislocated. Ninety nine patients (64%) were treated nonoperatively, using functional taping, shoe modifications, and injections. Fifty five patients (36%) were treated operatively, including lesser toe straightening, flexor-extensor transfer, Weil and Stainsby procedures. At followup, the mean AOFAS score and standard deviation was 69 ± 16.3 for the nonoperative group compared to 67 ± 17.8 in the operative group. The mean pain score and standard deviation was 31 mm ± 23.7 mm for the nonoperative group and 23 mm ± 24.1 mm in the operative group. Thirty-nine patients (52%) were either satisfied or very satisfied with treatment in the nonoperative group compared to 31 patients (66%) in the operative group. None of these differences were statistically significant. CONCLUSION: Painful MTP instability is a common cause of forefoot pain. Most patients can be treated nonoperatively. Operatively treated patients had no significant improvement in outcomes with regards to pain or function.

Development and validation of a screening checklist for temporomandibular disorders.

AIMS: To develop and validate a short screening tool for temporomandibular disorders (TMD) from the comprehensive Research Diagnostic Criteria for TMD (RDC/TMD) assessment. METHODS: Complete RDC/TMD assessments of four subject groups (96 TMD; 102 dental pain; 68 headache; 115 no-pain patients) were compared. Classification tree and multiple logistic regression analyses were utilized to develop the tool. To test external validity, a further 54 TMD and 51 non-TMD subjects whose diagnoses had been established by RDC/TMD assessment were reassessed with the new screening tool. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and likelihood ratios (LRs) were calculated for the screening tool in the validation set of subjects. RESULTS: A short TMD checklist was developed. This screening instrument had sensitivity of 94.4% (95% confidence intervals [CI], 84.9% to 98.1%), specificity of 94.1% (95% CI, 84.1% to 98%), PPV of 94.4% (95% CI, 84.9% to 98.1%), NPV of 94.1% (95% CI, 84.1% to 98%), and positive and negative LRs of 16.056 (95% CI, 5.346 to 48.219) and 0.059 (95% CI, 0.02 to 0.178) in an independent validation set. CONCLUSION: A short TMD screening checklist with high validity has been developed. This checklist may have good utility in general practice as a primary screening tool for TMD.

From movement to models: a tribute to professor Alan G. Hannam.

This tribute article to Professor Alan G. Hannam is based on 7 presentations for him at the July 1, 2008 symposium honoring 3 "giants" in orofacial neuroscience: Professors B. J. Sessle, J. P. Lund, and A. G. Hannam. This tribute to Hannam's outstanding career draws examples from his 40-year academic career and spans topics from human evolution to complex modeling of the craniomandibular system. The first presentation by W. Hylander provides a plausible answer to the functional and evolutionary significance of canine reduction in hominins. The second presentation, by A. McMillan, describes research activities in the field of healthy aging, including findings that intensity-modulated radiotherapy improves the health condition and quality of life of people with nasopharyngeal carcinoma in comparison to conventional radiotherapy. The developments in dental imaging are summarized in the third paper by E. Lam, and an overview of the bite force magnitude and direction while clenching is described in the fourth paper by M. Watanabe. The last 3 contributions by G. Langenbach, I. Staveness, and C. Peck deal with the topic of bone remodeling as well as masticatory system modeling, which was Hannam's main research interest in recent years. These contributions show the considerable advancements that have been made in the last decade under Hannam's drive, in particular the development of an interactive model comprising, in addition to the masticatory system, also the upper airways. The final section of the article includes a final commentary from Professor Hannam.

Topical review: new insights into the pathology and diagnosis of disorders of the temporomandibular joint.

The collection of conditions affecting the temporomandibular joint (TMJ) and masticatory muscles, the so-called temporomandibular disorders, can be classified according to the Research Diagnostic Criteria for Temporomandibular Disorders. Of the 3 subgroups--muscle disorders (Group I); disc displacements (Group II); and arthralgia, arthritis, and arthrosis (Group III)--the muscle disorders are most frequently seen in community samples; Group II and Group III diagnoses are less prevalent. This may explain the relative scarcity of studies involving intracapsular TMJ disorders. In this review, new insights into the functional anatomy, imaging, and pathology of disorders of the TMJ are presented. Studies of TMJ dynamics may provide insight into the functional anatomy of the TMJ and thereby into the consequences of Group II and Group III disorders. The clinical use of imaging modalities such as computed tomography and magnetic resonance imaging for the TMJ and related structures remains controversial. Nevertheless, imaging is regularly used in the diagnosis of some Group II and Group III disorders. Magnetic resonance imaging may be of use not only for the visualization of disc displacements but also for the study of bone mineral density of the condyle. Cytokines such as interleukin-1 (IL-1) and tumor necrosis factor alpha (TNFalpha) play an important role in TMJ pathology. For example, IL-1beta, which has been associated with TMJ pain, hyperalgesia, and anterior bite opening, is mostly absent in the synovial fluid of healthy joints. Since both IL-1 and TNFalpha are involved in the development of chronic pain and joint destruction, they may be the targets for specific treatments. While the advances reviewed in this paper are significant, multidisciplinary efforts and formation of international research collaborations will be necessary to continue advancement in the understanding of TMJ pathology and diagnosis.