The types of ulnar fracture were transverse and complete in three cases, oblique and complete in two, and greenstick and incomplete in seven. There was plastic deformation in four cases and physeal fracture of the olecranon in one case. The sites of ulnar fracture were the proximal physis in 1, proximal metaphysis in 10, and the middle third in 2.
Directions of the radial head dislocation were anterior in five patients, anteromedial in four, lateral in one, and anterolateral in seven. Posterior interosseous nerve palsy (PINP) was observed in eight patients. Other associated fractures were medial epicondylar fracture in one, medial condylar fracture in one, and radial neck fracture in two.
Most of the patients were referred to us from local orthopaedic clinics because of irreducibility of the radial head. The final treatment was done at our department within 7 days after the injury in most patients.
Under general anesthesia, the ulnar fracture was reduced and fixed with one or two intramedullary Kirschner wires if the fracture displaced, after which we attempted to reduce the radial head manually in a closed manner. All attempts were unsuccessful. We therefore performed open reduction of the radial head using a lateral approach, splitting the common extensor at its origin, in 15 cases. An anterior approach was used in two cases to check the posterior interosseous nerve (PIN). During surgery, we confirmed that the causes of irreducibility of the radial head were the annular ligament being trapped between the capitellum and the radial head in 15 patients, the posterior interosseous nerve being interposed between the radial head and the capitellum in 1, and the biceps tendon being wrapped around the radial neck in 1.
Postoperatively, the elbow was fixed with a long-arm plaster cast in 90° of flexion and a slightly supinated position for 3 to 4 weeks. Active range of motion of the elbow and the forearm was encouraged after cast removal.
Although patient follow-up was attempted, half of them were not followed up directly. Most of the families had moved out of the area. Long-term clinical follow-up was not a primary goal of this study, as many reports have already demonstrated that Monteggia lesions in children have a good prognosis. Therefore, regarding the patients who could not be followed up at this time, we used their final visit with us from their charts and radiographs. Finally, the mean postoperative follow-up period was 3.8 years (range, 6 months to 14 years 4 months) (Table 1).
All patients except cases 2 and 3 regained elbow and forearm motion within 3 months. No patients complained of any disability regarding the activities of daily living or sports activity, although two patients lacked some pronation (case 2 at 20° and case 3 at 70°). Seven of eight patients who had PINP regained nerve function within 4 months. Nerve function did not recover in one patient (case 3), however, so tendon transfer was undertaken, after which her wrist and finger motion became nearly normal, except for limited motion of pronation.
Radiographically, the radiocapitellar alignment was normal in all patients. The carrying angle was the same as that in the opposite elbow both clinically and radiographically.
A 6-year-old boy sustained a fall on his hand, injuring the right elbow. A local orthopaedic surgeon diagnosed a Monteggia fracture. Attempts at closed reduction without anesthesia were unsuccessful. Three days after the injury, he was referred to us for further treatment.
Examination of the right elbow at the time of admission revealed moderate swelling and bony bulging in the antecubital fossa. Sensation in the hand was intact, and the patient could extend the wrist with radial deviation. He could not extend his thumb or the metacarpophalangeal joints of the fingers. Plain radiography revealed anterolateral dislocation of the radial head with a greenstick fracture of the proximal metaphysis of the ulna (Figure 1).
With the patient under general anesthesia, general anesthesia, we attempted to reduce the radial head manually but could not obtain stable reduction. Open reduction was then performed using a lateral approach. The radial head was not found in the joint. Intraoperatively, the annular ligament was found to be interposed and trapped between the capitellum and the radial head, thereby preventing reduction (Figure 2, A). We confirmed that the radial head had become dislocated through the disrupted sacciform recess (Figure 2, B). We therefore lifted the intact annular ligament and reduced the radial head through the disrupted sacciform recess (Figure 2, C). After reduction, the radial head was stable in both supination and pronation positions (Figure 2, D).
Postoperatively, the elbow was immobilized in a plaster cast, with the elbow in 90° flexion and the forearm in a 30° supination position for 3 weeks. After removing the cast, active range of motion exercises at home were encouraged. Posterior interosseous nerve palsy recovered at 3 months after surgery. When last seen at 9 months postoperatively, the patient had regained full range of elbow and forearm motion. Radiographs showed that the radial head was in a normal anatomic position (Figure 3).
A 5-year-old girl had fallen off a sofa and presented to an emergency department with complaints of pain and swelling in her left elbow. There was no neurovascular deficit. Radiographs revealed incomplete fracture of the proximal metaphysis of the ulna with anterolateral subluxation of the radial head (Figure 4). Closed reduction without anesthesia was attempted, but stable reduction was not obtained. Soon after, she was referred to our department.
Under general anesthesia, closed reduction was again attempted. The radial head seemed to be reduced in a supination position but subluxated in a pronation position (Figure 5). We considered that these findings indicate some type of pseudoreduction. Therefore, we decided to reduce the radial head surgically. Open reduction was performed using the same approach as in case 4. The intraoperative findings were nearly the same as in case 4. That is, the annular ligament was interposed between the capitellum and the radial head. Hence, we reduced the radial head using the same maneuver that was successful in case 4.
The patient's postoperative course after surgery was uneventful, and she resumed nearly normal elbow motion 3 months after surgery. At the final follow-up, 7 months after injury, she had a normal carrying angle and full range of motion of the elbow and forearm. Plain radiography showed that the radial head was in a normal position even in pronation (Figure 6).
Discussion and Summary
Reports of irreducible dislocation of the radial head are rare. We reviewed the English-language literature4-9 for this occurrence and found only six pediatric cases. When we extended our review to include the Japanese literature, we found that 19 cases were reported. Most of these reports were of a single case. The details of the English- and Japanese-language cases, including the current series, are summarized in Table 2.
As shown in Table 2, the patients' ages were 2 to 12 years (mean, 6.9 years). Boys were injured twice as often as girls. There was no preponderance of the injury on the right or left side, except in our cases. The prevalence of ulnar fractures also showed some differences between the reported cases and our cases. Cases of isolated radial head dislocation without ulnar fracture were reported in both English- and Japanese-language literature, although none of our patients had an isolated dislocation. Overall, the proximal metaphyseal area was the more common site of the ulnar fracture. Plastic bowing of the ulna was also reported. Regarding the direction of the radial head dislocation, anterior dislocations were most common in the overall literature, whereas the lateral or anterolateral dislocation was seen in 47% of our cases.
Several factors that contribute to irreducibility have been reported, including displacement or entrapment of the annular ligament, anterior capsule, osteochondral fragment, biceps tendon, and PIN (Table 2). Among these factors that hinder reduction of the radial head, annular ligament entrapment is the most common. In our experience, as shown by intraoperative findings (Figure 2), the radial head had dislocated through the sacciform recess and lay anteriorly on the intact annular ligament. The interposed annular ligament between the capitellum and radial head then inhibits reduction.
Tan et al10 described pathology of the annular ligament in pediatric Monteggia fractures. They treated 35 children surgically, assessing all the radial heads. They found that the annular ligaments were intact in all patients, and the ruptures were at the lower part of the ligament (which probably means the sacciform recess). Most of the annular ligaments were interposed in the radiocapitellar joint, although the radiographs showed reduction of the radial head. These authors emphasized that radiological reduction of the radial head often does not represent anatomic reduction.
In the current series, 10 of the 17 cases were considered to be a type of pseudoreduction. In these cases, the radial head was nearly reduced in a supination position but redislocated or subluxated in a pronation position (Figure 5). Tan et al10 noted that if the forearm was pronated, the lateral face of the radial head appeared outside the annular ligament, allowing redislocation of the radial head. They emphasized that frequent radiographic examinations are therefore necessary.
In contrast to our findings and to the report of Tan et al,10 Shinohara et al11 described two cases of incomplete reduction, in which the radial head was reduced in a supination position but redislocated during rotation from a neutral position to pronation position. Instead of open reduction of the radial head, they treated these cases using a hinged elbow splint. They stated that the purpose of the splint was to reduce the traction force of the biceps muscle on the radial head while allowing the soft tissue surrounding the radial head to heal and stabilize the proximal radioulnar joint.
We treated one patient (case 15) conservatively with a cast in a supination position. In this case, the radial head seemed to be reduced in a supination position, despite showing subluxation in a pronation position. Four weeks later, however, the radial head dislocated completely (Figure 7). The surgeon who treated this boy thought that the radial head was in a reduced position. If the radiocapitellar line12 is precisely visualized, however, a line drawn along the radial shaft misses the capitellum. We therefore emphasize that whenever reduction of the radial head is attempted, it is important to confirm that a line drawn along the radial shaft intersects the center of the capitellum. Also, if the radial head is unstable in supination and pronation positions, we recommend open reduction.
Other causes of hindered reduction, such as PIN and biceps tendon interference, seemed to be rare. Usually, recovery from associated PINP occurs spontaneously if there is early reduction of the dislocated radial head. If the PIN is entrapped in the radiocapitellar joint, preventing reduction of the radial head, spontaneous recovery cannot be expected. Thus, the PIN must be removed from the radiocapitellar joint and the radial head reduced. In case 3 of our series, we attempted closed reduction, causing the PIN to become interposed between the capitellum and the radial head. When we explored the radiocapitellar joint 5 months later, we found that the nerve was severely damaged. We had to reconstruct finger extension by tendon transfer because the nerve did not recover. Morris,13 Spur14, and Li et al15 reported similar experiences and emphasized that the PIN may become wrapped around the anterolaterally dislocated radial head during attempted closed reduction. Hence, exploration of the radiocapitellar joint is necessary in cases of associated PINP with irreducible radial head dislocation.
The biceps tendon is a rare cause of hindered reduction of the radial head. In all the reported cases6,7,16 including our case 2, the radial head displaced in the anteromedial direction. Yoshihara et al16 proposed a possible mechanism in which hyperextension of the elbow with hyperpronation of the forearm causes the tendon to cling to the radial neck. It is very difficult to identify the cause of irreducibility of the radial head preoperatively. Therefore, whenever we encountered such cases, we considered surgical confirmation mandatory.
In conclusion, we reported 17 cases of irreducible radial head dislocation in pediatric Monteggia lesions. The most frequent factor hindering reduction was interposition of the annular ligament in the radiocapitelar joint. In those cases, the radial head seemed to be reduced in a supination position but redisplaced in a pronation position. After closed reduction, it is important to determine whether the radial head is stable in both pronation and supination positions. If the radial head is irreducible or unstable during manual reduction, it is crucial to identify the cause and remove the impediment.
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Copyright © 2018 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Orthopaedic Surgeons
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