Lip avulsion often results from orofacial trauma that occurs primarily in younger dogs and cats (9). This occurs due to caudally directed forces (e.g., traffic accident, bite, falling, and stepping) against the gingiva and labial mucosa (5,9,14). Bilateral rostral lower lip avulsion is particularly common in cats (9). Concurrent injuries are frequent and include tooth fracture, facial injury, traumatic brain damage, and mandibular fracture. Furthermore, the anatomical location, severity, and concurrent injuries associated with the lip avulsion play an important role in selecting surgical techniques and accurate prognosis (9).

The purpose of lip avulsion treatment is to restore the normal function of the oral cavity by repairing the damaged skin and occlusion. To achieve ideal lip avulsion recovery, thorough debridement of necrotizing tissue and sufficient lavage are required (1,8,12). Then, tension-free sutures should be used because excessive tension may occur due to the nature of the oral cavity, which is characterized by considerable movement (3,6,10,13). If there is increased tension due to excessive loss of normal tissue, appropriate flap technique or reinforcement with stents may be necessary for stable repair (2,7). If there are any concurrent injuries, such as mandibular fracture, which may cause mandibular instability, additional treatment should also be undertaken before soft tissue repair (14,15). Wound dehiscence is the most common complication of lip avulsion (9). Appropriate tension-free sutures and the treatment of the concurrent injuries of the lip avulsion are of great importance in repairing lip avulsion and avoiding postoperative wound dehiscence.

Severe bilateral lower lip avulsions are diagnosed based on physical and oral examinations in these cases. Due to the oral structure characteristics, such as extensive movements, surgery using tension-free sutures is planned for the stable repair of lip avulsion. The present case report aims to demonstrate the outcomes of tension-free sutures to repair severe bilateral lower lip avulsions in two domestic cats.

A 4-year-old, 4.47 kg neutered male Korean short-haired cat was referred to the Veterinary Medical Teaching Hospital, Chonnam National University, for the treatment an avulsion of the mandibular lip resulting from unknown causes. The mandibular lip was avulsed, and necrotic tissue was found on the avulsed lip on physical examination (Fig. 1A). There was also mild soft tissue contraction on the avulsed lip. The patient could not close their mouth spontaneously. No other abnormalities associated with vehicular trauma were observed on examination, including skull radiography or neurologic examination (Fig. 1B). The cat was diagnosed with bilateral lower lip avulsion. There was no abnormality in the pre-anesthetic examination including blood tests (complete blood count, blood chemistry, blood gas, and electrolytes) and chest radiography. Surgical repair of the lip avulsion and assessment of any other abnormalities performed under general anesthesia were scheduled for the same day.

Figure 1. Photographs of the first patient before treatment. (A) Preoperative photograph. A mandibular lip avulsion is observed, and the mandibular bone is exposed. (B) Preoperative skull radiograph. Fracture lines are not observed. (C) Photograph after lavage. The debridement of the non-vital tissue followed the lavage.

Preoperatively, the cat was administered famotidine 0.5 mg/kg intravenously (IV) (Dong-A Gaster Inj.^TM, DONG-A ST, Seoul, Korea), marbofloxacin 2 mg/kg IV (Marbocyl^®, Vetoquinol Korea, Goyang, Korea), cefotaxime 20 mg/kg IV (Korus Cefotaxime Inj, Hankook Korus Pharm., Chuncheon, Korea), and maropitant 1 mg/kg subcutaneosuly (SC) (Cerenia^®, Zoetis, Seoul, Korea). The cat was premedicated with morphine 0.3 mg/kg IV (Hana Morphine HCl Inj, Hana Pharm Co., Seoul, Korea), midazolam 0.3 mg/kg IV (Vascam Inj., Hana Pharm Co., Seoul, Korea), and ketamine at a continuous rate infusion of 10 µg/kg/min (Yuhan Ketamine 50 Inj., Yuhan Co., Seoul, Korea). After induction using 3 mg/kg IV propofol (Provive injection 1%, Myungmoon Pharm Co., Seoul, Korea), general anesthesia was maintained with sevoflurane (Sojourn^TM, Kyongbo Pharm, Asan, Korea) in oxygen.

An oral examination confirmed the absence of mandibular instability and teeth mobility. The lip avulsion had occurred at the gingiva. The avulsed lip of the mandible extended caudally to the rostral part of the mandibular first molar teeth bilaterally. Intraoral dental radiographs were obtained using a bisecting angle technique. There were no fractures present in the maxilla and mandible. Based on these results, tension-free sutures were planned for lip avulsion repair.

Before surgery, the oral cavity was rinsed with 0.12% chlorhexidine solution and the exposed and traumatized soft tissue and mandibles were cleaned with 0.9% normal saline. The area was draped and prepared for surgery. Debridement of non-vital tissue and removal of foreign materials were performed. Ultrasonic scaling and a thorough lavage were performed (Fig. 1C). Labial mucosal flaps were constructed with a combination of blunt and sharp dissection techniques. Appositional repair with 5-0 poliglecaprone 25 (MONOCRYL^TM, ETHICON, NJ, USA) was performed for avulsed lip reattachment to the ventral midline fascia in the mandibular symphysis region (Fig. 2A); 18-G hypodermic needles were used to create an intra-osseous bone tunnels in a labial-to-lingual direction for suture anchorage (Fig. 2B). A non-absorbable monofilament suture was passed through the needles with the suture ends on the labial aspect. The needles were removed, and horizontal mattress sutures were applied around each teeths. Knots were placed on the labial aspect of the dental arcade with intravenous fluid tubing as rubber tube stents (Fig. 2C). To adhere the attached gingiva and labial mucosa between previously placed horizontal mattress sutures, simple interrupted sutures were used with 5-0 monofilament sutures at 2-3-mm intervals (Fig. 2D). After surgery, the patient received cimetidine (5 mg/kg; H-2 INJ, 100 mg/mL, JW Pharm., Seoul, Korea) and amoxicillin hydrate/diluted potassium clavulanate (12 mg/kg; Amocla INJ 0.6 g; Kuhnil Pharm, Seoul, Korea) IV for 3 days, and then, carprofen (2.2 mg/kg; Rimadyl tablet, 25 mg/tab; Zoetis Inc., Parsippany, NJ, USA) and amoxicillin hydrate/potassium clavulanate (12 mg/kg; Lactamox tablet, amoxicillin 50 mg/tab; clavulanate 125 mg/tab; Aprogen Pharma, Sungnam, Korea) were administered orally twice per day for 12 days. The owner was instructed to clean the patient’s mouth with 0.12% chlorhexidine solution and feed the patient a soft diet.

Figure 2. Intraoperative photographs of the first patient. (A) Soft tissue reattachment to the ventral midline fascia in the mandibular symphysis region. (B) 18-G hypodermic needles were pierced in labial-to-lingual direction for each tooth. (C) Application of a rubber tube stent on the skin after needle removal. (D) Horizontal mattress suture on the labial aspect of the dental arcade. Simple interrupted sutures were performed between the horizontal mattress sutures.

At 2 weeks postoperatively, the cat showed good activity and was eating well. There were no other abnormalities on physical examination. At 4 weeks postoperatively, intraoral soft tissue had healed, and the rubber tube stents were removed. The patient could close the mouth and had obtained a normal occlusion (Fig. 3A, B).

Figure 3. Postoperative photographs of the first patient after 27 days. (A) Frontal view. (B) Left lateral view. The intraoral soft tissues are healed. The patient obtained a normal occlusion and could close the mouth.

A 4-year-old, 4.47 kg neutered male Korean short-haired cat was referred to the Veterinary Medical Teaching Hospital, Chonnam National University, for the treatment an avulsion of the mandibular lip resulting from unknown causes. The mandibular lip was avulsed, and necrotic tissue was found on the avulsed lip on physical examination (Fig. 1A). There was also mild soft tissue contraction on the avulsed lip. The patient could not close their mouth spontaneously. No other abnormalities associated with vehicular trauma were observed on examination, including skull radiography or neurologic examination (Fig. 1B). The cat was diagnosed with bilateral lower lip avulsion. There was no abnormality in the pre-anesthetic examination including blood tests (complete blood count, blood chemistry, blood gas, and electrolytes) and chest radiography. Surgical repair of the lip avulsion and assessment of any other abnormalities performed under general anesthesia were scheduled for the same day.

Figure 1. Photographs of the first patient before treatment. (A) Preoperative photograph. A mandibular lip avulsion is observed, and the mandibular bone is exposed. (B) Preoperative skull radiograph. Fracture lines are not observed. (C) Photograph after lavage. The debridement of the non-vital tissue followed the lavage.

Preoperatively, the cat was administered famotidine 0.5 mg/kg intravenously (IV) (Dong-A Gaster Inj.^TM, DONG-A ST, Seoul, Korea), marbofloxacin 2 mg/kg IV (Marbocyl^®, Vetoquinol Korea, Goyang, Korea), cefotaxime 20 mg/kg IV (Korus Cefotaxime Inj, Hankook Korus Pharm., Chuncheon, Korea), and maropitant 1 mg/kg subcutaneosuly (SC) (Cerenia^®, Zoetis, Seoul, Korea). The cat was premedicated with morphine 0.3 mg/kg IV (Hana Morphine HCl Inj, Hana Pharm Co., Seoul, Korea), midazolam 0.3 mg/kg IV (Vascam Inj., Hana Pharm Co., Seoul, Korea), and ketamine at a continuous rate infusion of 10 µg/kg/min (Yuhan Ketamine 50 Inj., Yuhan Co., Seoul, Korea). After induction using 3 mg/kg IV propofol (Provive injection 1%, Myungmoon Pharm Co., Seoul, Korea), general anesthesia was maintained with sevoflurane (Sojourn^TM, Kyongbo Pharm, Asan, Korea) in oxygen.

An oral examination confirmed the absence of mandibular instability and teeth mobility. The lip avulsion had occurred at the gingiva. The avulsed lip of the mandible extended caudally to the rostral part of the mandibular first molar teeth bilaterally. Intraoral dental radiographs were obtained using a bisecting angle technique. There were no fractures present in the maxilla and mandible. Based on these results, tension-free sutures were planned for lip avulsion repair.

Before surgery, the oral cavity was rinsed with 0.12% chlorhexidine solution and the exposed and traumatized soft tissue and mandibles were cleaned with 0.9% normal saline. The area was draped and prepared for surgery. Debridement of non-vital tissue and removal of foreign materials were performed. Ultrasonic scaling and a thorough lavage were performed (Fig. 1C). Labial mucosal flaps were constructed with a combination of blunt and sharp dissection techniques. Appositional repair with 5-0 poliglecaprone 25 (MONOCRYL^TM, ETHICON, NJ, USA) was performed for avulsed lip reattachment to the ventral midline fascia in the mandibular symphysis region (Fig. 2A); 18-G hypodermic needles were used to create an intra-osseous bone tunnels in a labial-to-lingual direction for suture anchorage (Fig. 2B). A non-absorbable monofilament suture was passed through the needles with the suture ends on the labial aspect. The needles were removed, and horizontal mattress sutures were applied around each teeths. Knots were placed on the labial aspect of the dental arcade with intravenous fluid tubing as rubber tube stents (Fig. 2C). To adhere the attached gingiva and labial mucosa between previously placed horizontal mattress sutures, simple interrupted sutures were used with 5-0 monofilament sutures at 2-3-mm intervals (Fig. 2D). After surgery, the patient received cimetidine (5 mg/kg; H-2 INJ, 100 mg/mL, JW Pharm., Seoul, Korea) and amoxicillin hydrate/diluted potassium clavulanate (12 mg/kg; Amocla INJ 0.6 g; Kuhnil Pharm, Seoul, Korea) IV for 3 days, and then, carprofen (2.2 mg/kg; Rimadyl tablet, 25 mg/tab; Zoetis Inc., Parsippany, NJ, USA) and amoxicillin hydrate/potassium clavulanate (12 mg/kg; Lactamox tablet, amoxicillin 50 mg/tab; clavulanate 125 mg/tab; Aprogen Pharma, Sungnam, Korea) were administered orally twice per day for 12 days. The owner was instructed to clean the patient’s mouth with 0.12% chlorhexidine solution and feed the patient a soft diet.

Figure 2. Intraoperative photographs of the first patient. (A) Soft tissue reattachment to the ventral midline fascia in the mandibular symphysis region. (B) 18-G hypodermic needles were pierced in labial-to-lingual direction for each tooth. (C) Application of a rubber tube stent on the skin after needle removal. (D) Horizontal mattress suture on the labial aspect of the dental arcade. Simple interrupted sutures were performed between the horizontal mattress sutures.

At 2 weeks postoperatively, the cat showed good activity and was eating well. There were no other abnormalities on physical examination. At 4 weeks postoperatively, intraoral soft tissue had healed, and the rubber tube stents were removed. The patient could close the mouth and had obtained a normal occlusion (Fig. 3A, B).

Figure 3. Postoperative photographs of the first patient after 27 days. (A) Frontal view. (B) Left lateral view. The intraoral soft tissues are healed. The patient obtained a normal occlusion and could close the mouth.

Bilateral rostral lower lip avulsion is the most common form of lip avulsion, accounting for 53.8 % of lip avulsions in cats. Concurrent injuries frequently noted in cats and dogs are tooth fractures (34.8%), facial wounds and abrasions (34.8%), traumatic brain or nerve injury (21.7%), bony fractures (21.7%) and mandibular symphyseal separation (8.7%) (9). In the present cases, the two cats were admitted with bilateral rostral lower lip avulsion; oral examination revealed that the cat in the second case also had concurrent injury associated with mandibular fracture.

Lower lip avulsions usually occur when a force is applied directly to the lower lip. Lip avulsion tends to occur at the mucogingival junction or gingiva, depending on the strength of the force or the position at which the force is applied (9). Generally, mild-to-moderate lip avulsion occurs at the mucogingival junction, and severe avulsions occur at the gingiva. In our cases, lip avulsions had occurred at the gingiva.

Lip avulsions can be repaired by second intention, primary closure, or flap and grafting techniques. Healing by second intention has been advocated for younger patients with contracted scar tissue as necessary (9). In our cases, there was some necrotic tissue on the avulsed lip, and reconstruction surgery was performed immediately to prevent further infection or soft tissue contraction.

Some lip avulsions are complicated by insufficient tissue in the oral cavity to reposition the lip. The lip can be anchored to the remaining incisors or underlying bone by pre-drilling holes into the mandible as anchor points for sutures (12). The cats in this report had no sufficient tissue for tension-free suture of the oral mucosa with the lip tissue. Therefore, the lip was anchored to the remaining incisors and underlying bone by pre-drilling holes in the mandible in a horizontal mattress suture pattern using non-absorbable suture material.

There can be significant shear forces on the repair in highly mobile areas such as the lips. The closure of highly mobile lesions such as lip avulsion can be further reinforced with a stent (12). Therefore, rubber tube stents were applied on the skin in our cases to stabilize the suture against the shear force; the gingiva seemed to be attached to the mandible postoperatively.

Concurrent maxillofacial injuries are common and must be stabilized to ensure successful lip avulsion repair (7,12). A retrospective study found that all cases with wound dehiscence had either a mandibular symphyseal separation or bone fracture. An unaddressed instability may be a contributing factor for wound dehiscence (9). Alveolar fracture is not a common traumatic dentoalveolar injury; however, if it occurs, it tends to occur in the incisive region (11). The cat’s condition in the first case was recovered using tension-free suture or stents because it did not have a concurrent injury. However, the cat in the second case had a mandibular alveolar fracture, and wound dehiscence occurred 1 week postoperatively. Fracture healing is slower if adjacent teeth are present in the fracture line (4). In this case, a left mandibular second incisor and canine teeth were present in the fracture line. As the patient lived far from the hospital and could not be brought for frequent visit, more definitive treatment was needed. Thus, adjacent teeth were extracted to enable faster fracture recovery. Bone graft and collagen membrane were also applied to the fracture site before placing the cerclage wire. Postoperative radiography revealed that the wiring was slightly oblique after the procedure, but there was no movement of the mandibular alveolar fracture when moved with the hand. At 8 weeks postoperatively, the cat showed a good prognosis without long-term complications.

Although the number of cases about lip avulsion was small and the follow-up period was relatively short, these two cases showed successful prognosis. Since tension-free suture was applied to only two cats, further studies will be necessary to evaluate the effects of the combination of rubber tube stents and tention-free suture on larger populations.

We reported lower lip avulsion in two cats. Reports of surgical correction of the lower lip avulsion in the gingiva in cats are rare in Korea. In this report, an excellent prognosis was confirmed following surgery for severe lip avulsions. Therefore, our results could help treat lip avulsion in domestic cats.

This work was carried out with the support of “Cooperative Research Program for Agriculture Science and Technology Development (Project No. PJ016392)” Rural Development Administration, Republic of Korea.

The authors have no conflicting interests.