Laryngoplasty: a novel prosthesis

Evaluation of a prototype dynamic laryngoplasty system in vitro with an equine vacuum airflow system

OBJECTIVE

To evaluate a prototype dynamic laryngoplasty system (DLPS) in a static airflow model.

STUDY DESIGN

Experimental.

SAMPLE POPULATION

Ten equine larynges.

METHODS

The right arytenoid was fixed in abduction in all specimens. A left-sided laryngoplasty was performed with No. 2 Fiberwire and a FASTakII anchor. Each larynx was tested in a static airflow model. The system was adjusted to a flow rate of 55 L/s and prelaryngeal pressure of 12 mm Hg prior to testing in maximal arytenoid abduction. In phase 1, the left suture was loosened, shortened, and tested in 3-mm steps from 0 to 30 mm. In phase 2, the suture was tied with the DLPS in position at a target left-to-right quotient angle (LRQ) of 0.5. The DLPS was activated to target psi of 0, 25, and 50 for testing. Translaryngeal impedance (TLI), LRQ, cross-sectional areas (CSA), and resultant change in LRQ and CSA between, before, and during airflow testing were calculated.

RESULTS

In phase 1, TLI was reduced by suture shortening up to 6 mm (P = .001) but not by additional shortening (P > .05). In phase 2, activation of the DLPS reduced the TLI from 0 psi (0.43 ± 0.08 mm Hg/L/s) to 25 psi (0.16 ± 0.04 mm Hg/L/s, P < .001), but no further reduction was detected at maximal psi (P = .10).

CONCLUSION

Activation of the DLPS effectively reduced TLI.

CLINICAL SIGNIFICANCE

These results justify further investigation of the DLPS to assess its clinical applicability.

In vitro evaluation of the effect of a prototype dynamic laryngoplasty system on arytenoid abduction

OBJECTIVE

To determine the effect of a prototype dynamic laryngoplasty system (DLPS) on arytenoid abduction.

STUDY DESIGN

In vitro experimental.

STUDY POPULATION

Ten equine larynges.

METHODS

Dissected larynges were mounted, and the right arytenoid was maximally abducted for testing. A left-sided laryngoplasty (LP) was performed by using a strand of No. 2 FiberWire and a FASTakII anchor. Phase 1 involved tightening the suture, without the DLPS device in place, in 1-mm increments and acquiring a digital image of the rima glottidis at each increment. Phase 2 involved tying the suture with the DLPS in place at a left to right quotient (LRQ) of 0.7. Digital images were subsequently taken at 3 stages of DLPS activation (0, 25, and 50 or maximal psi) and analysed to calculate LRQ.

RESULTS

All tests were completed for 9 larynges. In phase 1, a total shortening of 25.89 ± 1.27 mm was possible, which increased the LRQ from 0.59 ± 0.02 to 1.07 ± 0.12. In phase 2, activation of the DLPS increased the LRQ from 0.70 ± 0.05 to 0.97 ± 0.09. This change in LRQ equated to 18.7 mm of shortening on the basis of phase 1 results. The maximum psi of the DLPS achieved was 37.33 ± 5.96.

CONCLUSION

The DLPS increased the degree of arytenoid abduction in vitro. This change in LRQ equated to 18.7 mm of shortening of the LP suture based on phase 1 results.

CLINICAL IMPACT

These results support further evaluation of the DLPS to determine the effect of changes in DLPS on airway resistance.

In vitro comparison of 3 techniques of prosthesis attachment to the muscular process of the equine arytenoid cartilage

OBJECTIVE

To determine the degree and ease of arytenoid abduction achieved with abaxial placement of a FASTak II suture anchor compared to 2 suture patterns with different directions of insertion-caudomedial to craniolateral and medial to lateral.

STUDY DESIGN

Ex vivo experimental.

STUDY POPULATION

Cadaveric larynges from 10 Standardbred racehorses.

METHODS

Each larynx was sequentially instrumented with all 3 arytenoid suture attachment in random order: (1) abaxial placement of a FASTak II suture, (2) caudomedial to craniolateral suture, and (3) medial to lateral suture placement. Each construct was abducted at 5N increments from 0 to 25N and the left to right quotient angle ratio (LRQ) measured from digital pictures acquired at each sequential increment.

RESULTS

Arytenoid abduction (higher LRQ) was greater with FASTak II construct than either of the suture patterns. The largest difference occurred at 5N. Approximately 50% less force was required to achieve an LRQ of 1.0 with the FASTak II anchor compared to the suture patterns. No difference was detected between the 2 suture constructs throughout the study.

CONCLUSION

Use of the FASTak II suture anchor improved arytenoid abduction compared to 2 suture patterns and minimized the suture loads required to achieve maximum arytenoid abduction.

CLINICAL RELEVANCE

Use of the FASTak II anchor may decrease the suture load required to achieve arytenoid abduction in clinical cases. This may reduce the load placed on the laryngoplasty, thereby, minimizing postoperative loss of abduction.

Long-term survey of laryngoplasty and ventriculocordectomy in an older, mixed-breed population of 200 horses. Part 2: Owners' assessment of the value of surgery

REASONS FOR PERFORMING STUDY

There is continuing debate on the clinical benefit of laryngoplasty (LP) in the treatment of equine laryngeal paralysis. In particular, there is little information available on the clinical value of this surgery in older horses, in non-Thoroughbreds or in sports or pleasure horses; nor on the relationship between the degree of LP abduction achieved and the clinical value of LP.

OBJECTIVES

To evaluate the owner's assessment of the value of LP (and combined ventriculocordectomy) in an older, mixed breed and mixed workload population of horses and to also assess the relationship between the degree of LP abduction present and the clinical value of this surgery.

METHODS

A study (1986-1998) of 200 horses of mixed breed and workload, median age 6 years (prospective 136 cases and retrospective 64 cases) undergoing LP and ventriculocordectomy was undertaken. The degree of laryngoplasty abduction achieved and maintained was semiquantitatively evaluated using a 5-grade system.

RESULTS

A survey of 198 owners, a median of 19 months after LP surgery, showed that 91% of cases had returned to full work and 3% to reduced work, including 95% of horses with good (Grade 2) laryngoplasty abduction at 6 weeks after surgery, 91% with moderate (Grade 3) abduction, 88% of cases with minsimal (Grade 4) abduction and just 25% of cases with total loss of surgical abduction (Grade 5). Once back in work, 73% of cases were reported to make no abnormal exercise-related noises ('noises') at exercise, with reduced 'noises' reported in some of the 21% of horses that still made 'noises'. In the other 6% of cases, owners were unsure if 'noises' were present. The absence or presence of 'noises' once back at work correlated significantly with the degree of surgical arytenoid abduction present at 6 weeks after LP. Once back in work, 'noises' were less commonly detected in sports and pleasure horses (absent in 76% of cases) than in racehorses (absent in 60%) of cases. Exercise performance following surgery was reported to be markedly increased in 75% of cases, with 10% showing no difference in exercise performance, 3% showing worse performance, and owners unsure of any effect on exercise performance in 13% of cases. Improved work was reported in 70% of sports and pleasure horses and in 67% of racehorses. Overall, 86% of owners believed LP was worthwhile, 7% believed it was not worthwhile and 6% were unsure of its value. Surgery was reported to be of most benefit to sports horses (e.g. reported worthwhile for 100% of show jumpers) and of least benefit to National Hunt (long distance) racehorses where 71% of owners believed it to be worthwhile.

CONCLUSIONS AND POTENTIAL RELEVANCE

Most horse-owners believe that LP and combined ventriculocordectomy are of clinical value, especially in sports and pleasure horses. Large scale physiological studies on clinical cases, pre- and post operatively, are required to examine more critically the value of such surgery.