Transoral surgery: an anatomic study

A Survey of Transoral Robotic Mechanisms: Distal Dexterity, Variable Stiffness, and Triangulation

Robot-assisted technologies are being investigated to overcome the limitations of the current solutions for transoral surgeries, which suffer from constrained insertion ports, lengthy and indirect passageways, and narrow anatomical structures. This paper reviews distal dexterity mechanisms, variable stiffness mechanisms, and triangulation mechanisms, which are closely related to the specific technical challenges of transoral robotic surgery (TORS). According to the structure features in moving and orienting end effectors, the distal dexterity designs can be classified into 4 categories: serial mechanism, continuum mechanism, parallel mechanism, and hybrid mechanism. To ensure adequate adaptability, conformability, and safety, surgical robots must have high flexibility, which can be achieved by varying the stiffness. Variable stiffness (VS) mechanisms based on their working principles in TORS include phase-transition-based VS mechanism, jamming-based VS mechanism, and structure-based VS mechanism. Triangulations aim to obtain enough workspace and create adequate traction and counter traction for various operations, including visualization, retraction, dissection, and suturing, with independently controllable manipulators. The merits and demerits of these designs are discussed to provide a reference for developing new surgical robotic systems (SRSs) capable of overcoming the limitations of existing systems and addressing challenges imposed by TORS procedures.

Morphometric analysis of posterior cranial fossa and surgical implications

Background

Posterior cranial fossa (PCF) is an important area in terms of anatomy and surgery. It is a common site of many neoplastic, vascular, and degenerative lesions. Craniovertebral surgeries require special attention regarding detailed information about the morphology and morphometry of this region. The aim of this study was to analyze the morphometric characteristics of PCF and distances between the inner base of the skull.

Materials and Methods

An observational, retrospective cross-sectional study was made. Fifty-five dry human skulls of unknown sex were measured ascertained using digital Vernier caliper with 0.01 mm precision.

Results

The morphometric analysis of the mean length and width of the FM was 34.51 mm and 29.85 mm, respectively. We found a significant difference (P < 0.05) among the distance between the posterior tip of occipital condyle and basion of the right and left sides.

Conclusion

According to our observations, the present study yielded detailed morphometry of the PCF and neurovascular relationship. It can facilitate successful instrumentation and minimize neurovascular injuries. Furthermore, it provides safe and suitable data for guiding neurosurgical procedures. The major limitation of this study was the lack of knowledge regarding the age and gender of the participants whose skull base was studied.

A Compliant Transoral Surgical Robotic System Based on a Parallel Flexible Mechanism

Transoral robotic surgery (TORS) allows for access to oropharyngeal regions in an effective and minimally invasive manner. However, safe TORS access to deep pharyngeal (such as hypopharynx) sites remains a great challenge for current surgical robotic systems. In this work, we introduce a novel continuum robot with an optimized flexible parallel mechanism, to meet stringent requirements imposed by TORS on size, workspace, flexibility, and compliance. The system is comprised of two parts, a guidance part and an execution part, and achieves 11 controllable degrees of freedom. The execution part of the robot, based on the optimized flexible parallel mechanism, is able to reach deep sites in the oropharynx and larynx with the assistance of the continuum guidance part. In addition to the mechanical design, extensive analysis and experiments were carried out. Kinematic models were derived and the reachable workspace of the robot was verified to cover the entire target surgical area. Experimental results indicate that the robot achieves significantly enhanced compliance. Additionally, the designed robot can withstand a load of 1.5 N within the allowable range of the deflection. The positioning errors caused by the interference between different mechanisms can be effectively eliminated using the proposed compensation method. The maximum displacement error of this system under various conditions is less than 2 mm and the maximum bending error is less than 7.5°, which are satisfied for TORS. Cadaver trials were conducted to further demonstrate the feasibility. The reduced setup time and the reduced time to access the target site indicate that the developed surgical robotic system can achieve better operative efficiency in TORS when compared with current systems.

Quantification of clival and paraclival exposure in the Le Fort I transmaxillary transpterygoid approach: a microanatomical study

OBJECT

The authors describe a modified Le Fort I maxillotomy with medial and posterior antrectomy and removal of the pterygoid plates, aimed at improving the lateral surgical exposure during open transmaxillary surgery for pathological conditions involving the clivus. A cadaveric microanatomical study was conducted to compare the planimetric exposures allowed by the transmaxillary transpterygoid (TMTP) approach and the standard Le Fort I maxillotomy (STM).

METHODS

Six cadaveric specimens that had been fixed with glutaraldehyde and injected with latex were dissected to obtain morphometric measurements after both TMTP and STM approaches. The anatomical areas exposed by the surgical approaches were calculated using ImageJ 1.37a software.

RESULTS

As expected, the TMTP approach allowed for a greater surgical exposure, with an incremental area exposed ranging from 4.9 to 7.6 cm(2) (mean ± standard deviation 6.4 ± 1.2 cm(2), 95% CI 5.4-7.4 cm(2)). The amount of additional anatomical area visualized, as recorded as a percentage increase after the TMTP approach when compared with the STM approach, ranged from 83 to 109% (mean 99%).

CONCLUSIONS

The lateral surgical exposure allowed by the STM approach is limited by the pterygoid plates. The TMTP approach significantly improves the exposure of the anatomical regions lateral to the clivus, allowing access to the pterygopalatine and medial infratemporal fossae. In comparison with the STM, the TMTP approach allows for a surgical exposure that is nearly double. The authors conclude that the TMTP approach provides a significant improvement in the surgical exposure of the lateral paraclival areas, when compared with the STM approach.