Technique and Outcome of Nares Amputation (Trader’s Technique) in Immature Shih Tzus

Introduction

Stenotic nares are known to occur in dogs and, less commonly, cats of brachycephalic conformation.^1–3 Stenotic nares are most frequently observed as components of the brachycephalic syndrome that can include the following anatomical abnormalities: elongated soft palate, secondary eversion of laryngeal saccules or worsening degrees of laryngeal collapse, and, in some specific breeds (such as the English bulldog), hypoplastic trachea.^1–8 The bulldog, pug, Pekingese, and Boston terrier represent some of the most common breeds treated for stenotic nares.^5,6,9

The condition of stenotic nares alone can contribute significantly to the respiratory problems these dogs experience.^3–5 This functional obstruction is caused by congenital malformation of the external nares, resulting in a decrease in the transverse diameter of the naris.³ The resistance in airflow that results from the upper airway narrowing requires the generation of increased negative upper airway pressures to overcome the airflow resistance leading to stridor and secondary upper airway edema.⁸ Recommendations are for stenotic nares to be addressed surgically as early as possible, as this procedure can improve breathing and decrease inspiratory effort.^4,8 In one report, brachycephalic dogs that underwent surgical correction of their stenotic nares and soft palate had significantly better clinical outcomes than those dogs that only had their soft palate repaired.⁵

While the shih tzu is commonly listed as a breed that may be affected by stenotic nares, this breed is uncommonly represented in studies that have examined stenotic nares in dogs. A 10-year retrospective study examining the surgical treatment of stenotic nares in dogs reported that shih tzus made up <10% of the cases included.⁵ Other clinical studies investigating stenotic nares did not include any shih tzus.^9,10 To date, the clinical signs associated with stenotic nares or the surgical repair of stenotic nares in the shih tzu puppy have not been reported.

Numerous surgical techniques for stenotic nares repair have been described. Most of these techniques call for removal of a wedge-shaped piece of the epithelium and underlying tissue of the alar fold via sharp dissection with a blade or with electrocautery.^1,4,7,8,11 Vertical, horizontal, and lateral wedge resection techniques require sutures to achieve apposition of the nasal epithelium.^1,7 Crescentshaped wedge removal of the dorsolateral alar cartilage described by Knecht also calls for suturing of the skin to the mucous membranes to promote apposition and hemostasis.³ Yet another type of wedge resection can be performed by incising the caudal aspect of the external nose and apposing the epithelial surfaces with nonabsorbable sutures.⁴ Alapexy, another recently described alternative, fixes the alae into an abducted position by creating two elliptical incisions—one in the ala and the other in the skin lateral to the ala—and suturing the epithelium of the incisions together.⁹

This study investigated the clinical response to surgical correction of stenotic nares in the shih tzu puppy as well as the effectiveness and cosmesis of a simple excisional technique first described by Trader in 1949.¹² The authors hypothesized that the excision procedure would provide both clinical improvement as well as an aesthetically pleasing appearance in shih tzu puppies affected with stenotic nares.

Materials and Methods

All dogs enrolled in the study were presented to Michigan State University Veterinary Teaching Hospital between February 2005 and November 2006 for wellness examinations or for surgical consultation for upper airway obstruction. All dogs were otherwise healthy, with no other complicating respiratory problems or signs of upper airway disease, and all were <6 months of age. Weight and age were recorded for each puppy. Criteria for inclusion in this study consisted of a diagnosis of stenotic nares on physical examination by an ACVS diplomate and a preoperative owner assessment for the presence or absence of nasal discharge/ noise, breathing difficulty, and exercise limitations. These lay terms were utilized for the owners and represent nasal discharge/upper airway noise, dyspnea, and exercise intolerance.

Animals were routinely premedicated and anesthetized following standard protocol at Michigan State University Veterinary Teaching Hospital. Positioning consisted of sternal recumbency with the head elevated slightly, with surgical towels placed under the puppy’s mandible. The head was positioned such that symmetry of the facial features was achieved.Ano. 11 blade was seated firmly in the dorsal-most opening of the external nares, and it was angled ventrolaterally to the 3:30 or 8:30 clock positions on the puppy’s left or right side, respectively. A single incision was made, allowing partial amputation of the wing of soft tissue cranioventral to the dorsolateral nasal cartilage [Figures 1, 2].¹³ Firm pressure was applied to the surgical site for 5 to 10 minutes to provide hemostasis. No sutures were placed in the incision; the wound was allowed to heal by second intention. To achieve symmetry, the completed side was evaluated visually for size and shape of the resulting naris opening before repeating the process on the contralateral side. Each puppy was recovered routinely from anesthesia and surgery.

A single follow-up visit or interview was completed for each puppy between 1 and 58 weeks postsurgery. Only two of 15 puppies total were lost to follow-up. Each puppy was assessed by the owners at the time of follow-up for nasal discharge/noisy breathing (nasal discharge/upper airway noise), breathing difficulty (dyspnea), and exercise limitations (exercise intolerance). Owners were also asked if they felt that their puppy’s nose looked aesthetically pleasing. The frequency of clinical signs, before and after surgery, was compared by means of McNemar’s test for paired observations. The P values were reported. Descriptive data were reported as mean ± standard deviation.

Results

Thirteen shih tzu puppies (seven males, six females) were evaluated in this study. The mean weight was 3.3±1.0 kg, and mean age was 16.8±4.1 weeks. Preoperatively, 11 had nasal discharge/noise, five had breathing difficulty (dyspnea), and seven had exercise limitations (exercise intolerance). Postoperatively, none of the puppies had nasal discharge/ noise (P=0.001), none had breathing difficulty (dyspnea) (P=0.07), and none had exercise limitations (exercise intolerance) (P=0.01). No scarring or nasal depigmentation was noted in any of the puppies, and all owners indicated a favorable and aesthetic outcome.

Discussion

The changes in nasal discharge/noise and exercise limitations were highly significant. While the changes in breathing difficulty were not significant, based on the P value a 93% confidence remains that the observed changes were not due to chance. In two of the 13 cases, the owners did not perceive the clinical signs as problematic, but they volunteered on postoperative examination that the puppy had more energy and was more active after surgery compared to before.

This study was initially designed as a large prospective trial with a control (no surgery) group; informed consent was obtained from the owners prior to inclusion in the study. The objective of this trial was to investigate the effect of stenotic nares on the development of the brachycephalic syndrome and elongation of the soft palate in brachycephalic dogs. The authors observed immediate and dramatic improvement in shih tzus enrolled in the surgical group. Therefore, shih tzu puppies were excluded from this clinical trial, and the control group was discontinued for ethical reasons. The shih tzu study was continued as a prospective case series study.

The technique described by Trader was assessed to be effective at opening the nares and providing a cosmetic result. This particular technique has fallen out of favor in lieu of various wedge resections and pexy procedures used today, which have been perceived to provide a more cosmetic and clinically effective result as well as involve less immediate hemorrhage.^11,12,14 By not utilizing suture, the procedure’s technical difficulty as well as surgical time are decreased when compared to various wedge techniques described in the literature.^1,4,5,7,9,10 Additionally, a greater amount of tissue could be removed with the amputation technique when compared to wedge resection. The Trader technique does result in an open wound that must granulate, epithelialize, and contract. Until the healing process is complete, the wound may not be considered to be aesthetically pleasing. The bleeding that does occur is at first brisk, but it attenuates after several minutes of direct pressure. The authors have found in other cases treated by wedge resection and suture that scarring and discoloration may occur in the healed wound. It is the authors’ opinion that this described excision technique produces a highly cosmetic result as well as excellent widening of the nares [Figures 3A, 3B].

Conclusion

Based on the evidence of this study, resection of the thickened and collapsed tissues associated with stenotic nares leads to clinically and statistically significant improvement in the clinical signs associated with stenotic nares in the shih tzu. All animals enrolled in this study demonstrated complete resolution of all clinical signs associated with stenotic nares. The resection method originally described by Trader was shown to be very effective at opening the nares and providing a cosmetic outcome. The authors recommend this procedure be considered as a treatment for immature shih tzus with bilateral stenotic nares.

Acknowledgment

The authors thank Michele Fritz, RVT, for her help in organizing this study and obtaining pre- and postsurgical data.