Avulsion of olecranon and triceps tendon is rare in small animals (5,6,10,14). There are few reports of triceps tendon avulsion in dogs and cats (1,4,16). Rupture of the triceps tendon is typically caused by trauma (6). In addition, injection of corticosteroids can cause triceps tendon avulsion as a result of direct damaging effects (10).

Tension band wiring and plate osteosynthesis are currently recommended for repairing olecranon avulsion fractures; however, the major complication rates are 58% and 16%, respectively (8). In addition, chronic tendon avulsion for more than 4 weeks is challenging to repair owing to muscle and tendon atrophy and retraction (1,13). Tendon avulsion is generally repaired using a modified three-loop pulley and locking loop sutures (17,18). The Krackow stitch was developed in 1986 to improve soft tissue fixation. This technique is particularly well suited to flat tendons or ligaments (15). Synthetic mesh can be used but is rarely reported for tendon reconstruction and is primarily used for repairing herniation (1,21,22).

We report a rare case in which triceps tendon avulsion occurred in a large-breed dog and successfully recovered through a non-degradable synthetic mesh using the Krackow suture technique.

A 3-year-old, 24-kg, intact female Border Collie was referred with severe lameness on the right forelimb 3 weeks after a traumatic elbow injury. The patient had been immediately presented to a local veterinarian following the injury. Conservative management was attempted with the administration of non-steroidal anti-inflammatory drugs, analgesia, cryotherapy, and casts for 2 weeks. However, there was no improvement in lameness.

On physical examination 3 weeks after the initial injury, the patient had toe-touch weight-bearing on the right thoracic limb and moderate pain during palpation of the right elbow. Moderate muscle atrophy of the right thoracic limb and a normal range of motion were observed. Neurological examination results were normal.

Radiographs revealed an irregularly shaped bone fragment (2.0 × 0.4 cm) on the right olecranon. Moderate soft tissue swelling in the right elbow was also observed (Fig. 1).

Figure 1. Preoperative radiograph and computed tomography three-dimensional reconstruction. (A) Craniocaudal view of the right forelimb. (B) Lateral view of the right forelimb. (C) Computed tomography three-dimensional reconstruction. Avulsion of the olecranon is observed and displaced to the caudal, proximal aspect. In addition, mild osteophyte and enthesophyte are observed at the olecranon avulsion fragment.

On computed tomography (CT) examination, a comminuted avulsion fracture of the olecranon was confirmed with proximal displacement. A bony substance surrounding the fracture site was observed (Fig. 1).

Based on history, physical examination, and diagnostic imaging, the diagnosis included olecranon avulsion fracture and triceps tendon rupture. The initial treatment plan was tension-band wiring and tendon suturing.

The patient was sedated using acepromazine (0.05 mg/kg, subcutaneously [SC], SEDAJECT injection, Samwoo median, Seoul, Korea) and medetomidine (0.02 mg/kg, SC, Domitor^®, Zoetis Pharmaceutical Inc., NY, USA). Cefazolin (25 mg/kg, administered intravenously [IV], Hankook Korus Pharm Co., Seoul, Korea) was used as a prophylactic antibiotic. Anesthesia was induced with alfaxalone (2 mg/kg, IV, Alfaxan^®, Jurox Pty Ltd., Australia) and maintained with isoflurane (Ifran^®; Hana Pharm, Seoul, Korea). Sedation was reversed using atipamezole (0.02 mg/kg, administered intramuscularly; AntisednTM; Pfizer, NY, USA).

A lateral surgical approach to the triceps tendon insertion and olecranon was performed. The lateral, long, medial, and accessory head of the triceps brachii muscle and the avulsed bone fragment were identified proximally. Rupture of the long and accessory head of the triceps tendon with an avulsion fracture of the olecranon was confirmed. Partial rupture of the triceps tendon lateral head was confirmed. The triceps tendons and bone fragments were bluntly dissected and mobilized distally to the triceps insertion site of the olecranon. The tension-band wiring technique was applied. Using a 1.5-mm drill bit, a transverse tunnel was made on the proximal ulna. Two 1.2-mm Kirschner wires were inserted through the olecranon into the ulna and directed distally. The proximal ends of the two K-wires were fixed with 0.84-mm stainless steel wire using a tension band pattern. An additional tendon suture using a 1 USP polyester suture (Echibond EXCEL, Ethicon Inc., Somerville, New Jersey, USA) was made over the triceps tendons to reattach the lateral head using a locking loop sutures pattern. Subcutaneous tissue and skin were routinely closed. A spica bandage was applied after surgery for 5 days.

Implant failure occurred on radiography 5 days after surgery (Fig. 2). The avulsion bone fragment was fractured into three pieces. Revision surgery was performed using a mesh graft and external fixation, immediately after implant failure was confirmed. The same approach was used for the previous surgery. The triceps tendons and bone fragments were dissected and mobilized distally to the olecranon.

Figure 2. Postoperative radiograph 5 days after surgery. The radiograph shows olecranon fragment fracture and implant failure that loosened the tension band wire. Osteophytes and enthesophytes are similar to that before this radiograph was acquired.

The long head of the triceps tendon was reattached using a 5 USP polyester suture (Ethibond, Ethicon Inc., Somerville, New Jersey, USA) with a modified three-loop pulley suture pattern. The suture was passed through a drilling hole in the proximal ulna. The lateral head of the triceps tendon was reattached using a 0 USP monofilament absorbable suture (Maxon, Covidien, Mansfield, MA, USA) with a locking loop suture pattern. More proximally, another drilling hole was made on the proximal ulna using a 1.5-mm drill bit. A polypropylene mesh (Surgipro, Covidien, Mansfield, MA, USA) was applied over the triceps repair using a 5 USP polyester suture (Ethibond, Ethicon Inc., Somerville, New Jersey, USA) in a Krackow suture pattern along with the long head of the triceps tendon through another proximal drilling hole (Fig. 3). Subcutaneous tissue and skin were routinely closed.

Figure 3. Intraoperative image showing placement of synthetic mesh graft and external skeletal fixation. (A) Krackow suture pattern. (B) Krackow suture pattern is used to attach the long head of the triceps tendon and synthetic mesh graft. (C) Type IA transarticular external skeletal fixation is used for immobilization of the elbow joint.

A type IA transarticular external skeletal fixator (IMEX Vet, Longview, TX, USA) was placed using three pins each in the humerus and radius, with a single lateral connecting bar (Fig. 3). The elbow joint was fixed at 130° and satisfactory pin placement was confirmed through postoperative radiography. Cefazolin (25 mg/kg), carprofen (4.4 mg/kg, Rimadyl, Zoetis Pharmaceutical Inc, NJ, USA), metronidazole (15 mg/kg), and famotidine (0.5 mg/kg) were administered every 12 h for 14 days, and a soft bandage was applied.

Postoperative management

The external skeletal fixator was managed daily. The patient was discharged from the hospital 6 weeks after surgery.

Postoperative assessments were performed monthly until the external skeletal fixator was removed at 12 weeks and then at 4, 6, and 8 months after surgery.

At 4 weeks, the transarticular connecting bar was temporarily removed to test for passive range of motion of the elbow joint. The external skeletal fixator angle varied from 130° to 125°.

At 8 weeks, the transarticular connecting bar was removed and the Robert Jones bandage was applied over the external skeletal fixator to allow some degree of active elbow joint range of motion and weight-bearing on the triceps repair. The humeral and radial components of the external skeletal fixator were left in place to maintain the bandage position above the elbow and to resist excessive active elbow range-of-motion. Therapeutic exercises were initiated at this time.

At 12 weeks, the entire external skeletal fixator and bandage were removed, and a clinical evaluation was performed. The patient had grade II/VI lameness and mild weight-bearing lameness of the right thoracic limb, with moderate atrophy of the affected limb. Radiography revealed mild displacement of the avulsed bone fragment. On ultrasonography, the olecranon defect healed and a 2-mm gap between the olecranon and avulsed bone fragment was observed.

At 14 weeks, the patient had improved to grade I/VI lameness and mild subtle lameness with full weight-bearing. The passive range-of-motion limit of the elbow joint was 86° of flexion and 130° of extension.

At 6 months, CT revealed healing of the olecranon and a 2-mm gap between the olecranon and avulsed bone fragments.

At 8 months, the patient ambulated normally without activity limitations. However, after long and difficult activities, the patient had subtle lameness according to the owner. There was no clinical evidence of surgical infection or discomfort at the repair site.

At 9 months, the patient licked the surgical site and the owner confirmed discharge and dehiscence. Cytological examination revealed degenerated neutrophils; however, bacteria were not detected. Radiography and ultrasonography revealed proximal bone fragment displacement and no implant failure. Clindamycin (15 mg/kg) was administered orally for 2 weeks. However, after 2 months, the patient was discharged. Radiography and ultrasonography revealed no significant changes. Therefore, a bacterial culture test was performed; however, no bacteria were detected. Carprofen (4.4 mg/kg SID) and cephalexin (22 mg/kg BID) were administered for 1 month without significant improvement.

Implant removal surgery was performed, and the same approach was used as in the previous surgery. Triceps tendon repair was also identified. The suture materials and polypropylene mesh were removed. Gentamycin with Poloxamer 407 (Pluronic F-127, Sigma-Aldrich, St. Louis, MO, USA) was applied to the olecranon. After a passive drain was placed, the subcutaneous tissue and skin were closed.

Four months after surgery, the patient ambulated normally without activity limitations, and radiological evaluation revealed no other changes (Fig. 4). No clinical evidence of surgical infection or discomfort at the repair site was detected.

Figure 4. Postoperative radiograph 14 months after the first surgery. (A) Craniocaudal view of the right forelimb. (B) Lateral view of the right forelimb. Avulsion of olecranon shows other changes, and soft tissue swelling has reduced.

Olecranon avulsion can be repaired successfully using tension band wiring, even in large-breed dogs (14,19). Many complications are associated with the immobilization method (1). In this case, tension band wiring was used for repairing olecranon avulsion, and implant failure was confirmed owing to a comminuted fracture that created a three-piece bone fragment. Although a cast was applied, fixation was insufficient to prevent tensile force in the large-breed dog.

To prevent distraction by tensile strength, the use of synthetic fibers and meshes has been reported in triceps tendon avulsion (1,2). Ultra-high-molecular-weight polyethylene (UHMWPE) fibers are biocompatible materials that offer superior mechanical and biological properties. Reinsertion to the bone is generally challenging and may even become impossible in the presence of comminuted fractures; however, tendon reconstruction using UHMWPE succeeded without complications (2). In addition, reconstruction of chronic triceps tendon avulsion using degradable synthetic mesh in dogs has been reported (1). Degradable porous polyurethane urea reinforces soft tissue with biocompatible properties and acts as a scaffold for cellular ingrowth, stabilizing the tendon to promote neoangiogenesis and neocollagenesis (11,12). During the tendon healing period, mesh augmentation can provide biomechanical support after surgery when a repair is vulnerable to failure (1). In this patient, a polypropylene mesh was used for revision surgery because it had great stability and was biomechanically similar to the natural ligament. Nondegradable synthesis mesh induces fibrous tissue and results in less joint laxity (21). Additionally, to support triceps tendon repair, a transarticular external skeletal fixator was used in revision surgery, and the fixator angle was changed 1 month after repair.

As in the previous case reconstructed by degradable mesh, the tendons were sutured using a modified three-loop pulley and locking loop pattern. The load to failure with the polypropylene mesh was higher than that with the modified three-loop pulley suture, and the mesh with sutures had the greatest load to failure in the in vitro canine model (9). In addition, the Krackow suture pattern has been used for tendon repair and was biomechanically superior to a modified three-loop pulley suture in a canine gastrocnemius avulsion model (1,25,26). In this patient, three-fold polypropylene mesh was sutured to the triceps tendon long head using a Krackow pattern and maintained for 8 months. The application of mesh and Krackow sutures was thought to help sufficiently prevent tensile force.

The degradable mesh did not need to be removed, and no complications were reported (1). However, in this case, a non-degradable mesh was used, and complications were confirmed 9 months after revision surgery. The patient licked the surgical site; however, a bacterial culture test was not performed because the owner first confirmed that dehiscent antibiotics had been prescribed in a local animal hospital. Deep surgical site infections can occur within 1 year if the implant is present (23). Therefore, the complication was thought to be a deep infection associated with the polypropylene mesh, which resolved after the mesh was removed.

Damaged tendons and ligaments cannot heal through the regenerative process but instead form fibrotic scars (24). Ligament reconstruction using knitted scaffolds results in greater mechanical strength and tissue regeneration (3). Adding stem cells to knitted mesh induces tendon regeneration in pig and rabbit models (7,20). In this patient, stem cells were not used; however, the mesh was folded into multiple layers. After mesh removal, the patient was activated normally for long-term follow-up. Polypropylene mesh may play a role as a scaffold for tendon repair.

Although there was chronic inflammation that required mesh removal, the prognosis was excellent for a long period. Therefore, reconstruction using a mesh graft and Krackow sutures may be considered for surgical management.

The authors would like to thank the owner of the dog included in this report.

The authors have no conflicting interests.