Surgical complications with open treatment of mandibular condylar process fractures

PURPOSE

This study assessed the surgical complications after open treatment for fractures of the mandibular condylar process.

PATIENTS AND METHODS

A total of 178 patients with unilateral fractures of the mandibular condylar process, 85 treated closed and 93 treated open, were included in this study. A tabulation of surgical findings and intraoperative and postoperative complications was prospectively performed. Standardized animating facial photographs were obtained at several postsurgical intervals and were examined and scored by a prosthodontist and an orthodontist for signs of facial nerve palsy and the quality of the surgical scar. Standard statistical methods were used to assess differences between open and closed treatment groups.

RESULTS

There were very few intraoperative or postoperative complications. At the 6-week point, 17.2% of patients treated open had some weakness of their facial nerve. This had resolved by 6 months. The scars were judged either wide or hypertrophic in 7.5% of cases.

CONCLUSIONS

Based on this study, surgical complications of open treatment of condylar process fractures that lead to permanent dysfunction or deformity are uncommon.

Bite forces in patients treated for mandibular angle fractures: implications for fixation recommendations

Voluntary bite forces were recorded at varying periods in 35 males treated with rigid internal fixation for fractures of the mandibular angle. Bite forces were also obtained in 29 male controls for comparison. It was found that molar bite forces in patients were significantly less than in controls for several weeks after surgery. Further, molar bite forces on the side of the fracture were significantly less than on the nonfractured side. The results of this study indicate that recommendations for the amount of fixation required for a given fracture may be reduced.

Mandibular motion after closed and open treatment of unilateral mandibular condylar process fractures

PURPOSE

This study compared mandibular and condylar mobility after open or closed treatment for fractures of the mandibular condylar process.

PATIENTS AND METHODS

One hundred thirty-six patients (111 male, 25 female), 74 treated by closed and 62 by open methods, were included in this study. They underwent testing of mandibular and condyle mobility at 6 weeks, 6 months, and 1, 2, and 3 years postsurgery. A jaw-tracking device was used to assess mandibular motion. Radiographs that were traced and digitized were used to assess condylar displacement and condylar mobility. Standard statistical methods were used to assess differences between groups.

RESULTS

Patients treated by open reduction had significantly greater initial displacement of their condylar processes than did the group treated closed. Immediately after treatment and uprighting of the condyles in the open treatment group, patients treated closed had significantly more displacement. At 6 weeks, patients treated closed had some measures of mandibular mobility that were significantly greater than those in patients treated by open reduction. However, after the 6-week period there were minimal differences in mandibular mobility between groups. At 6 weeks, patients treated by open reduction had significantly greater vertical mobility of the condyle than patients treated closed despite less mouth opening. After the 6-week period, patients treated by open reduction continued to have greater condylar mobility on the fractured side than did patients treated by closed methods. No measures of postsurgical displacement correlated with mobility measures in patients treated by open reduction. However, several measures of mandibular displacement correlated with measures of mobility in patients treated closed, indicating that the more displaced the condylar process, the more limited the mobility of the mandible.

CONCLUSIONS

Based on this study, patients treated for fractures of the mandibular condylar process by open reduction had somewhat greater condylar mobility than patients treated closed, even though the former group had more severely displaced fractures before surgery. Therefore, open reduction may produce functional benefits to patients with severely displaced condylar process fractures.

Facial symmetry after closed and open treatment of fractures of the mandibular condylar process

PURPOSE

This study compares vertical measures of mandibular and facial morphology after open or closed treatment for fractures of the mandibular condylar process.

PATIENTS AND METHODS

One hundred forty-six patients (121 male, 25 female), 81 treated by closed and 65 by open methods, were included in this study. Towne's and panoramic radiographs, taken at several intervals, were used to quantify the displacement of the condylar process fractures. Posteroanterior cephalograms taken at 6 weeks, 6 months, 1 year, and 2 to 3 years after treatment were used to assess posterior facial height and bigonial and occlusal plane angles. Additionally, panoramic radiographs were used to assess ramus height at the same periods. Standard statistical methods were used to assess differences between groups.

RESULTS

Patients whose condylar process fractures were treated by closed methods had significantly shorter posterior facial and ramus heights on the side of injury, and more tilting of the occlusal and bigonial planes toward the fractured side, than patients whose fractures were treated by open methods. Most of the asymmetry in patients treated by closed methods was present by 6 weeks after injury.

CONCLUSIONS

Patients treated by closed methods develop asymmetries characterized by shortening of the face on the side of injury. It is likely that loss of posterior facial height on the side of fracture in these patients is an adaptation that helps reestablish a new temporomandibular articulation.

Further displacement of condylar process fractures after closed treatment

PURPOSE

This study examined the changes in the position of the fractured condylar process immediately before and immediately after application of arch bars and at 6 weeks after surgery in a group of patients who underwent closed treatment.

PATIENTS AND METHODS

Sixty-five patients over the age of 16 years underwent closed treatment of unilateral mandibular condylar process fractures. Coronal and sagittal displacement of the condylar process was examined using Towne's and panoramic radiographs before treatment, immediately after placement of arch bars, and at 6 weeks. The change in position of the condylar process from one time to the next was analyzed statistically.

RESULTS

There was a statistically significant difference (mean, -5.5 degrees) in the coronal position of the condylar processes from immediately after injury to immediately after placement of arch bars. There was great variability, with some segments becoming more medially displaced and some more laterally displaced. In contrast, mean change in the sagittal position of the condylar process was not statistically significant, although some became more anteriorly and others became more posteriorly displaced. Similarly, from immediately after placement of arch bars to 6 weeks, there was great variability in position of the condylar process, but the overall change was not statistically significant.

CONCLUSIONS

The results of this study showed that position of the condylar process is not static in patients treated for condylar process fractures by closed means. These results suggest that care must be taken in basing treatment decisions on the degree of displacement or dislocation of the condylar process in presurgical radiographs.

Asymmetrical bipolar nanosecond electric pulse widths modify bipolar cancellation

A bipolar (BP) nanosecond electric pulse (nsEP) exposure generates reduced calcium influx compared to a unipolar (UP) nsEP. This attenuated physiological response from a BP nsEP exposure is termed "bipolar cancellation" (BPC). The predominant BP nsEP parameters that induce BPC consist of a positive polarity (↑) front pulse followed by the delivery of a negative polarity (↓) back pulse of equal voltage and width; thereby the duration is twice a UP nsEP exposure. We tested these BPC parameters, and discovered that a BP nsEP with symmetrical pulse widths is not required to generate BPC. For example, our data revealed the physiological response initiated by a ↑900 nsEP exposure can be cancelled by a second pulse that is a third of its duration.  However, we observed a complete loss of BPC from a ↑300 nsEP followed by a ↓900 nsEP exposure. Spatiotemporal analysis revealed these asymmetrical BP nsEP exposures generate distinct local YO-PRO®-1 uptake patterns across the plasma membrane. From these findings, we generated a conceptual model that suggests BPC is a phenomenon balanced by localized charging and discharging events across the membrane.

Identifying optimal parameters for infrared neural stimulation in the peripheral nervous system

Significance: Infrared neural stimulation (INS) utilizes pulsed infrared light to selectively elicit neural activity without exogenous compounds. Despite its versatility in a broad range of biomedical applications, no comprehensive comparison of factors pertaining to the efficacy and safety of INS such as wavelength, radiant exposure, and optical spot size exists in the literature. Aim: Here, we evaluate these parameters using three of the wavelengths commonly used for INS, 1450 nm, 1875 nm, and 2120 nm. Approach: In an in vivo rat sciatic nerve preparation, the stimulation threshold and transition rate to 100% activation probability were used to compare the effects of each parameter. Results: The pulsed diode lasers at 1450 nm and 1875 nm had a consistently higher ( ∼ 1.0    J / cm 2 ) stimulation threshold than that of the Ho:YAG laser at 2120 nm ( ∼ 0.7    J / cm 2 ). In addition, the Ho:YAG produced a faster transition rate to 100% activation probability compared to the diode lasers. Our data suggest that the superior performance of the Ho:YAG is a result of the high-intensity microsecond spike at the onset of the pulse. Acute histological evaluation of diode irradiated nerves revealed a safe range of radiant exposures for stimulation. Conclusion: Together, our results identify measures to improve the safety, efficacy, and accessibility of INS technology for research and clinical applications.

Multi-modal nonlinear optical and thermal imaging platform for label-free characterization of biological tissue

The ability to characterize the combined structural, functional, and thermal properties of biophysically dynamic samples is needed to address critical questions related to tissue structure, physiological dynamics, and disease progression. Towards this, we have developed an imaging platform that enables multiple nonlinear imaging modalities to be combined with thermal imaging on a common sample. Here we demonstrate label-free multimodal imaging of live cells, excised tissues, and live rodent brain models. While potential applications of this technology are wide-ranging, we expect it to be especially useful in addressing biomedical research questions aimed at the biomolecular and biophysical properties of tissue and their physiology.

Wavefront shaping enhanced Raman scattering in a turbid medium

Spontaneous Raman scattering is a powerful tool for chemical sensing and imaging but suffers from a weak signal. In this Letter, we present an application of adaptive optics to enhance the Raman scattering signal detected through a turbid, optically thick material. This technique utilizes recent advances in wavefront shaping techniques for focusing light through a turbid media and applies them to chemical detection to achieve a signal enhancement with little sacrifice to the overall simplicity of the experimental setup. With this technique, we demonstrate an enhancement in the Raman signal from titanium dioxide particles through a highly scattering material. This technique may pave the way to label-free tracking using the optical memory effect.

Visualizing Lipid Dynamics Role in Infrared Neural Stimulation using Stimulated Raman Scattering

Infrared neural stimulation, or INS, uses pulsed infrared light to yield label-free neural stimulation with broad experimental and translational utility. Despite its robust demonstration, INS's mechanistic and biophysical underpinnings have been the subject of debate for more than a decade. The role of lipid membrane thermodynamics appears to play an important role in how fast IR-mediated heating nonspecifically drives action potential generation. Direct observation of lipid membrane dynamics during INS remains to be shown in a live neural model system. We used hyperspectral stimulated Raman scattering (hsSRS) microscopy to study biochemical signatures of high-speed vibrational dynamics underlying INS in a live neural cell culture model. Findings suggest that lipid bilayer structural changes are occurring during INS in vitro in NG108-15 neuroglioma cells. Lipid-specific signatures of cell SRS spectra varied with stimulation energy and radiant exposure. Spectroscopic observations agree with high-speed ratiometric fluorescence imaging of a conventional lipophilic membrane structure reporter, di-4-ANNEPS. Overall, the presented findings support the hypothesis that INS causes changes in the lipid membrane of neural cells by changing lipid membrane packing order. Furthermore, this work highlights the potential of hsSRS as a method to study biophysical and biochemical dynamics safely in live cells.

Measurement of rat and human tissue optical properties for improving the optical detection and visualization of peripheral nerves

Peripheral nerve damage frequently occurs in challenging surgical cases resulting in high costs and morbidity. Various optical techniques have proven effective in detecting and visually enhancing nerves, demonstrating their translational potential for assisting in nerve-sparing medical procedures. However, there is limited data characterizing the optical properties of nerves in comparison to surrounding tissues, thus limiting the optimization of optical nerve detection systems. To address this gap, the absorption and scattering properties of rat and human nerve, muscle, fat, and tendon were determined from 352-2500 nm. The optical properties highlighted an ideal region in the shortwave infrared for detecting embedded nerves, which remains a significant challenge for optical approaches. A 1000-1700 nm hyperspectral diffuse reflectance imaging system was used to confirm these results and identify optimal wavelengths for nerve imaging contrast in an in vivo rat model. Optimal nerve visualization contrast was achieved using 1190/1100 nm ratiometric imaging and was sustained for nerves embedded under ≥600 µm of fat and muscle. Overall, the results provide valuable insights for optimizing the optical contrast of nerves, including those embedded in tissue, which could lead to improved surgical guidance and nerve-sparing outcomes.

Functional characteristics of patients with anterior open bite before and after surgical correction

The purposes of this investigation were to compare functional performance between controls and a sample of patients with skeletal anterior open bite prior to surgical correction and to examine how the patients' oral motor function adapted after treatment. Five female patients with skeletal open bite malocclusion were treated with Le Fort I osteotomy and compared to sex-, size-, and age-matched controls. Measurements of skeletal morphology, mandibular range of motion, occlusal force, and muscle efficiency were taken on all subjects over time. Prior to surgery, all patients had lower occlusal forces than did controls at all bite positions. After surgery, occlusal forces at several occlusal positions increased significantly from the presurgical recordings but remained below the level of controls. The mechanical advantages of the muscles of mastication were not significantly different between controls and patients either before or after surgery. The results of this study suggest that correction of skeletal open bite malocclusion may improve occlusal force, but a larger sample is needed to confirm this finding.

Infrared neural stimulation markedly enhances nerve functionality assessment during nerve monitoring

In surgical procedures where the risk of accidental nerve damage is prevalent, surgeons commonly use electrical stimulation (ES) during intraoperative nerve monitoring (IONM) to assess a nerve's functional integrity. ES, however, is subject to off-target stimulation and stimulation artifacts disguising the true functionality of the specific target and complicating interpretation. Lacking a stimulation artifact and having a higher degree of spatial specificity, infrared neural stimulation (INS) has the potential to improve upon clinical ES for IONM. Here, we present a direct comparison between clinical ES and INS for IONM performance in an in vivo rat model. The sensitivity of INS surpasses that of ES in detecting partial forms of damage while maintaining a comparable specificity and sensitivity to more complete forms. Without loss in performance, INS is readily compatible with existing clinical nerve monitoring systems. These findings underscore the clinical potential of INS to improve IONM and surgical outcomes.

Label-free intraoperative nerve detection and visualization using ratiometric diffuse reflectance spectroscopy

Iatrogenic nerve injuries contribute significantly to postoperative morbidity across various surgical disciplines and occur in approximately 500,000 cases annually in the US alone. Currently, there are no clinically adopted means to intraoperatively visualize nerves beyond the surgeon's visual assessment. Here, we report a label-free method for nerve detection using diffuse reflectance spectroscopy (DRS). Starting with an in vivo rat model, fiber- and imaging-based DRS independently identified similar wavelengths that provided optimal contrast for nerve identification with an accuracy of 92%. Optical property measurements of rat and human cadaver tissues verify that the source of contrast between nerve and surrounding tissues is largely due to higher scattering in nerve and differences in oxygenated hemoglobin content. Clinical feasibility was demonstrated in patients undergoing thyroidectomies using both probe-based and imaging-based approaches where the nerve were identified with 91% accuracy. Based on our preliminary results, DRS has the potential to both provide surgeons with a label-free, intraoperative means of nerve visualization and reduce the incidence of iatrogenic nerve injuries along with its detrimental complications.