Management of postoperative dysphagia after prosthetic laryngoplasty or arytenoidectomy

Equine laryngoplasty: Effects of three anchoring techniques in the muscular process and three positions for suture implantation in the cricoid cartilage

OBJECTIVE

To compare the effects of three anchoring techniques in the muscular process and three positions of laryngoplasty suture implantation in the cricoid cartilage on abduction of the arytenoid cartilage and interaction with the cricoarytenoid dorsalis (CAD) muscle compartments.

STUDY DESIGN

Experimental study.

SAMPLE POPULATION

Twenty-two cadaveric equine larynges.

METHODS

Three implantation techniques were assessed in the left muscular process. They were the use of a titanium corkscrew (CS), a standard caudal passage using a Jamshidi needle (JCa), and a standard cranial passage using a Jamshidi needle (JCr). Each was assessed in combination with three caudal locations in the cricoid cartilage (right, left, and left lateral). Each suture combination was tightened to submaximal abduction (Dixon grade 2). Force on the suture, degree of larynx caudal rotation, and CAD muscle indentation were evaluated.

RESULTS

The force required for optimal arytenoid cartilage abduction was lower (p < .01) for constructs involving a CS (7.45 ± 4 N). The CS also resulted in lower (p < .01) CAD muscle indentation (2.01 ± 1.25 mm) and less larynx rotation (9 ± 3.87°; adjusted p < .05).

CONCLUSION

When inserted into the muscular process at the CAD tendon insertion point, the biomechanical properties of the CS reduced the force required for optimal arytenoid cartilage abduction. The CS also minimized interference with the CAD muscle compartments and reduced caudal displacement of the left arytenoid cartilage when it was under suture tension.

CLINICAL SIGNIFICANCE

The CS implantation avoided larynx deformation and muscle interaction, offering the possibility to combine a nerve graft and laryngoplasty as a treatment for recurrent laryngeal neuropathy.

Computational fluid dynamic analysis of upper airway procedures in equine larynges

Introduction

Computational fluid dynamics (CFD) has proven useful in the planning of upper airway surgery in humans, where it is used to anticipate the influence of the surgical procedures on post-operative airflow. This technology has only been reported twice in an equine model, with a limited scope of airflow mechanics situations examined. The reported study sought to widen this application to the variety of procedures used to treat equine recurrent laryngeal neuropathy (RLN). The first objective of this study was to generate a CFD model of an ex-vivo box model of ten different equine larynges replicating RLN and four therapeutic surgeries to compare the calculated impedance between these procedures for each larynx. The second objective was to determine the accuracy between a CFD model and measured airflow characteristics in equine larynges. The last objective was to explore the anatomic distribution of changes in pressure, velocity, and turbulent kinetic energy associated with the disease (RLN) and each surgical procedure performed.

Methods

Ten equine cadaveric larynges underwent inhalation airflow testing in an instrumented box while undergoing a concurrent computed tomographic (CT) exam. The pressure upstream and downstream (outlet) were measured simultaneously. CT image segmentation was performed to generate stereolithography files, which underwent CFD analysis using the experimentally measured outlet pressure. The ranked procedural order and calculated laryngeal impedance were compared to the experimentally obtained values.

Results and discussion

The CFD model agreed with the measured results in predicting the procedure resulting in the lowest post-operative impedance in 9/10 larynges. Numerically, the CFD calculated laryngeal impedance was approximately 0.7 times that of the measured calculation. Low pressure and high velocity were observed around regions of tissue protrusion within the lumen of the larynx. RLN, the corniculectomy and partial arytenoidectomy surgical procedures exhibited low pressure troughs and high velocity peaks compared to the laryngoplasty and combined laryngoplasty/corniculectomy procedures. CFD modeling of the equine larynx reliably calculated the lowest impedance of the different surgical procedures. Future development of the CFD technique to this application may improve numerical accuracy and is recommended prior to consideration for use in patients.

Laryngeal reinnervation using the spinal accessory nerve: Electromyographic study of the sternomandibularis muscle

BACKGROUND

Selective laryngeal reinnervation using the first and second cervical nerve (C1C2) is a treatment option for recurrent laryngeal neuropathy that aims to restore the function of the cricoarytenoideus dorsalis muscle (CAD). Despite the technique's satisfying success rate, it has several limitations. These triggered the search for another potential donor nerve that could reduce CAD muscle fatigue and shorten rehabilitation. The ventral branch of the spinal accessory nerve, providing motor innervation to the sternomandibularis (SM) muscle, was identified as a potentially well adapted nerve.

OBJECTIVES

To gather normative data from SM muscle activity induced by physiological spinal accessory nerve stimulation at rest and during exercise, and to determine SM muscle activity and fibre type recruitment relative to posture, gait, and respiratory cycle.

STUDY DESIGN

Clinical observational study.

METHODS

Surface electromyography of the SM muscle was performed in 9 horses: trained warmbloods, Thoroughbreds and Standardbreds. Signals were recorded in different feeding postures and at exercise, which included standardised treadmill exercise tests, lungeing and ridden work.

RESULTS

Timing of the SM muscle contraction coincided with inspiration at gallop. Intra-individual mean SM muscle activity increased with exercising speed (4 times higher in Thoroughbreds at gallop compared to walk and 7 times higher in Standardbreds at high-speed trot compared to walk). Moreover, the SM muscle was strongly activated at rest when the horse was grazing (7 times more compared to when it was eating out of a hay net or stable feeder). Frequency domain analysis revealed a predominant type I muscle fibre recruitment during feeding and at exercise (Type I muscle fibre activity was at least 2.5 times higher than type II muscle fibre activity).

MAIN LIMITATIONS

Lack of reference data on equine electromyography.

CONCLUSIONS

This study confirmed the potentially advantageous properties of the spinal accessory nerve for laryngeal reinnervation.

Influence of unilateral and bilateral vocal cordectomy on airflow across cadaveric equine larynges at different Rakestraw grades of arytenoid abduction

Objective

To assess the effect of vocal cordectomy on airflow across equine larynges at different Rakestraw grades of arytenoid abduction using a unidirectional airflow model.

Study design

Ex vivo, repeated measures.

Sample population

Twenty cadaveric equine larynges.

Methods

The right arytenoid cartilage was maximally abducted in all larynges. Each larynx was assigned a Rakestraw grade A or B, and the left arytenoid was abducted accordingly. Each larynx was tested under 3 conditions: intact, left vocal cordectomy (LVC), and bilateral vocal cordectomy (BVC). Translaryngeal pressure and airflow were measured, and digital video footage was obtained. Translaryngeal impedance (TLI) was calculated, and the arytenoid left‐to‐right quotient angle (LRQ) and rima glottis cross‐sectional area (CSA) were measured from standardized still images.

Results

Vocal cordectomy reduced TLI by 14.5% in LVC in comparison with intact larynges at Rakestraw grade B (P = .014). In Rakestraw grade A position, neither unilateral nor bilateral vocal cordectomy had any effect on TLI. Regardless of Rakestraw allocation, both LVC and BVC increased CSA in comparison with intact larynges (P < .005), with BVC larynges experiencing a greater effect than LVC (P < .0001).

Conclusion

Using a unilateral airflow model, LVC improved TLI in larynges where arytenoid position approximated Rakestraw grade B. However, when the arytenoid position approximated Rakestraw grade A, there was no effect on TLI following LVC or BVC.

Clinical significance

Surgeons considering a vocal cordectomy should take into account the degree of arytenoid abduction before performing the procedure, as it may not be warranted from a TLI point of view.