The coronal shear fracture of distal humerus is intra-articular fracture that involves radial head and trochlear. This type of fracture has low incidence, accounting for 0.5% to 1.0% of all elbow fractures. Due to the controversy of treatment, more attention has been paid in recent years.

1. Research object: From March 2012 to December 2016, 11 patients (7 males and 4 females) with coronal shear fractures of distal humerus were treated with Kaplan approach combined with micro locking plate. The age ranged from 19 to 54 years with an average of 37.8 years. Causes of injury: 5 cases of fall damage; 3 cases of high falling injury; 3 cases of traffic accident. Two patients had humeral head fractures, and one patient had radial head fractures and avulsion fractures of triceps tendon. According to Dubberley classification, there were 2 cases of IA, 1 case of type IB, 3 cases of type IIA, 3 cases of type IIB, 1 case of type IIIA and 1 case of type IIIB. The time from injury to surgery ranged from 5-10 days, and the mean time was 7.2 days. 2. Operative methods: The examinations including elbow joint X-ray film of anteroposterior and lateral views, CT scan and reconstruction of coronal and sagittal shears were conducted preoperatively to determine the fracture site, the degree comminution and the displacement. As such, the individualized surgical plan was designed. The operation was performed under brachial plexus block or general anesthesia. The patient was placed in supine position, and the balloon tourniquet was used as well. The lateral Kaplan approach for elbow joint was commonly used, and the Kocher approach was adopted at the same incision for patients with humeral head fractures. This approach was made approximately 3 cm proximal to the lateral epicondyle of humerus along superior condylar crest. It went down across lateral epicondyle and bent back toward the posterior edge of ulna. Through the gap between anconeus, common extensor tendon and extensor carpi ulnaris muscle, the elbow extensor muscle was sharply separated from the lateral epicondyle of humerus and turned to the distal side. The deep humeroradial joint capsule was cut open in elbow varus position to expose the capitellum and trochlea of humerus. Holman hook was extended into the medial column with intact cortex, which could directly reveal the entire anterior edge of distal humerus articular surface. During the surgery, the intra-articular hematoma and all free bone and cartilage fragments in the joint capsule were carefully removed. The larger joint fragments were reduced to their original anatomical position and fixed from anterior to posterior with Kirschner wire. The needle or screw for fixation was indwelt, which was flushed with articular surface. The remodeled T-shaped micro-plate (3 holes on the proximal end and 3 holes on the distal end) was placed inferior to the surface of capitellum for anti-slip fixation. The micro-plate on the lateral trochlea of humerus was close to the articular surface of capitellum, and the distal holes were positioned just across proximal fracture line to avoid the over-cover of capitellum cartilage. Locking screw was used for fixation, and the length of distal locking screw was controlled to approximately 10 mm. The elbow joint mobility was checked during the operation especially if there were friction and flick during flexion. All patients underwent intraoperative C-arm fluoroscopy to confirm successful fracture reduction and appropriate length of the screws. The wound was repeatedly irrigated, and the drainage tube was routinely placed. The humeroradial joint capsule was sutured, and the extensors were reattached to the lateral epicondyle of humerus. After that, the wound was closed layer by layer.3. Postoperative management: Antibiotic was routinely used 30 minutes before the operation and postoperatively to prevent infection. Celecoxib was taken for analgesia and prevention of heterotopic ossification. The affected extremity was suspended with forearm sling, and active flexion and extension exercises started 2 to 3 days after the surgery with gradual increase of the range of motion. Some patients were treated with continuous passive motion (CPM) . The X-ray films were reviewed each month postoperatively, and weight-bearing exercise of the upper limb began after fracture healing. 4. Postoperative follow ups and therapeutic evaluation: The patients were followed up in the 1st, 2nd, 3rd, 6th, 9th, 12th and 24th months at the outpatient clinic, including X-ray films of anteroposterior and lateral views, and assessment of the range of motion and stability of elbow joint. The position and healing of fracture fragments were observed under fluoroscopy, and whether there were ischemic necrosis of humeral head, heterotopic ossification and traumatic arthritis were recorded as well. In the last follow up, the elbow joint function was evaluated subjectively and objectively with the Mayo elbow performance score (MEPS) : ≥90 points were regarded as excellent, 75-89 points were regarded as good, 60-74 were regarded as moderate, and <60 points were regarded as poor. In the meanwhile, the mobility of elbow flexion and extension, forearm rotation and the stability of medial and lateral elbow joint were recorded as well.

All the cases were followed up for an average of 16.3 months (12-26 months) . No neurological or vascular injury occurred after the operation. All patients obtained bone healing during the last follow up. One patient had the heterotopic ossification of medial elbow joint. After 75 mg of oral Indomethacin was given each day for 1 month, the heterotopic ossification disappeared. No patient was discovered with internal fixator breakage or loosening. Elbow joint mobility: 7° of extension (0°-15°) and 114° of flexion (95°-125°) . According to the MPES, the mean score was 91 points. There were 8 cases of excellent, 2 cases of good and 1 case of moderate, and the excellent and good rate was 90.9%.

For the fracture types with low incidence and difficult clinical diagnosis and treatment, lateral Kaplan approach can be adopted in the treatment of coronal shear fracture of distal humerus to fully expose the fracture lines and fragments of articular surface fracture. As such, better fracture reduction and fixation can be achieved. The use of cannulated screw alone is not effective, and it is not able to provide adequate stability for early postoperative functional exercises. The application of micro locking plate fixation provides sufficient stability, and the patients obtain good elbow joint function.