Clin Orthop Surg.  2017 Dec;9(4):521-528. 10.4055/cios.2017.9.4.521.

Analysis of Radiographic Parameters of the Forearm in Traumatic Radial Head Dislocation

• Kim HT
• Can LV
• Ahn TY
• Kim IH

• KMID: 2412254
• DOI: http://doi.org/10.4055/cios.2017.9.4.521

Abstract

BACKGROUND
Various deformities can occur in the forearm bones when the traumatically dislocated radial head is untreated for a long period. Without correction of all deformities, reduction of the dislocated radial head is difficult to maintain, and forearm and elbow motion will deteriorate after reduction. We evaluated radiographic parameters of forearms with traumatically dislocated radial heads (and of the normal sides) to understand the resulting deformities and the effectiveness of surgical treatment.
METHODS
We analyzed pre- and postoperative anteroposterior and lateral radiographs of 22 forearms (22 patients) with traumatic radial head dislocation. We divided the forearm into three equal parts and measured various morphological parameters. All patients underwent surgical treatment and evaluation of radial head reduction and range of motion pre- and postoperatively.
RESULTS
Before treatment, the middle of the ulna was significantly different from the unaffected side in both anteroposterior and lateral views. After surgery, the proximal ulna was significantly different from the unaffected side and the abnormal proximal radial neck angle persisted. The radial head was successfully reduced in 20 of 22 cases. Overall, the mean range of motion decreased after surgery, except for increased flexion-extension.
CONCLUSIONS
Complicated deformities developing during long-term remodeling after injury indicate that stable reduction is difficult to achieve with conventional one-bone osteotomy. Even after successful reduction, secondary deformity in the proximal ulna and/or remaining deformity in the proximal radius can hinder forearm rotation.

Keyword

Radial deformity; Ulnar deformity; Radiographic parameter

MeSH Terms

Adolescent
Child
Child, Preschool
Elbow Joint/*diagnostic imaging/*injuries/physiopathology
Female
Forearm/physiopathology
Humans
Joint Deformities, Acquired/*diagnostic imaging/etiology/physiopathology/surgery
Joint Dislocations/complications/*diagnostic imaging/surgery
Male
Postoperative Period
Preoperative Period
Pronation
Radiography
Radius/*diagnostic imaging/surgery
Range of Motion, Articular
Retrospective Studies
Supination
Ulna/diagnostic imaging

Figure

• 

  Fig. 1 Anteroposterior radiograph of a forearm with an anteriorly dislocated radial head showing mid-axial lines in the proximal, middle, and distal radius and ulna used for measurement of the parameters. The line AA’ indicates the rotational axis of the forearm connecting from the center of the radial head to the center of the distal ulna. Proximal radial tilt angle, the angle between lines AA’ and a; proximal ulnar tilt angle, the angle between lines AA’ and e; proximal radioulnar angle, the angle between lines a and e; middle radial tilt angle, the angle between lines AA’ and c; middle ulnar tilt angle, the angle between lines AA’ and f; distal radial tilt angle, the angle between lines AA’ and d; and distal ulnar tilt angle, the angle between lines AA’ and g. a: the axis of the radial neck, b: the axis of the proximal radius, c: the axis of the middle radius, d: the axis of the distal radius, e: the axis of the proximal ulna, f: the axis of the middle ulna, g: the axis of the distal ulna.

• 

  Fig. 2 Lateral radiograph showing mid-axial lines in the same segments of the radius and ulna as in the anteroposterior radiograph. The line AA’ indicates the rotational axis of the forearm. The white line from the proximal to the distal ulna is used for measurement of anterior ulnar bowing. a: the axis of the radial neck, b: the axis of the proximal radius, c: the axis of the middle radius, d: the axis of the distal radius, e: the axis of the proximal ulna, f: the axis of the middle ulna, g: the axis of the distal ulna.

• 

  Fig. 3 Anteroposterior radiograph showing maximal radial bow and the location of maximal radial bow (calculated as a ratio of the distance from maximal radial bow to bicipital tuberosity to the distance from the bicipital tuberosity to the most ulnar aspect of the radius at the wrist). BB’: the distance from the bicipital tuberosity to the most ulnar aspect of the radius at the wrist, CC’: the maximal distance between the radius and ulna.

• 

  Fig. 4 Anteroposterior (AP, A) and lateral (B) radiographs of a 7-year-old boy with anterior dislocation of the radial head. He slid down and underwent cast immobilization at another hospital 2 years ago (when he was 5 years old). In the lateral radiograph, the ulna was bowed anteriorly at the middle of the shaft with a positive ulna bow sign. The radial head was located anteriorly and beyond the anterior margin of the capitellum, suggesting overgrowth of the radius. He was treated with corrective osteotomy in the middle of the ulna (the area of maximal deformity). Also, a radial shortening osteotomy was performed to reduce the radial head. In addition, a notchplasty in the proximal ulna and annular ligament reconstruction were performed to maintain stable reduction because the radial head was translated out of the ulnar notch when the forearm was pronated. This meant the reduced radial head and ulna did not rotate on the same rotational axis of the forearm. AP (C) and lateral (D) radiographs taken 2 years after surgery (before metal removal) showing reduction of the radial head and correction of the ulnar deformity. The elbow extension-flexion and forearm supination arcs were similar to the normal side but the pronation arc was decreased (15° less than the normal side). Increased proximal radial tilt angle and proximal ulnar tilt angle in the AP radiograph compared to the preoperative values (and the normal side) and a radiological finding of mild radial neck-notching suggest that a secondary deformity occurred during the 2 years the patient had forceful range of motion exercises. Remaining or unrecognized bony deformities and/or tight ligament reconstruction might have contributed to these deformities and also affected the state of reduction of the radial head. Further close follow-up was required because the lateral radiograph showed slight anterior subluxation of the radial head which varied with the amount of supination-pronation. AP (E) and lateral (F) radiographs taken 10 years after surgery showing reduction of the radial head. Clinically, the patient had no limitation in daily activities and had a good result.

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