An 18-year-old man presented with left elbow pain and limited range of motion after being struck by a motor vehicle while on a bicycle. On physical examination, the patient was noted to have full flexion but lacked approximately 10° of terminal extension and 5° of supination and pronation.
Figure: Anteroposterior (A) and lateral (B) radiographs of the left elbow.
The authors are from the Division of Orthopaedic Surgery, Albany Medical Center, Albany, New York.
The authors have no relevant financial relationships to disclose.
Correspondence should be addressed to: Andrew J. Rosenbaum, MD, Division of Orthopaedic Surgery, Albany Medical Center, 1367 Washington Ave, Ste 202, Albany, NY 12206 (firstname.lastname@example.org).
Answer to Radiologic Case Study
Congenital Posterior Dislocation of the Radial Head
An 18-year-old man presented with left elbow pain and limited range of motion after being struck by a motor vehicle while on a bicycle. On physical examination, the patient was noted to have full flexion but lacked approximately 10° of terminal extension and 5° of supination and pronation. Anteroposterior and lateral radiographs of the left elbow showed a posterior dislocation of a dysplastic-appearing radial head (Figure 1). Radiographs of the forearm and wrist were negative for fracture and dislocation distal to the elbow. Fluoroscopy was used to assess the dynamic stability of the left elbow (Figure 2) and also to evaluate the right elbow, which was found to have a reduced radiocapitellar joint with a benign-appearing radial head (Figure 3). Computed tomography (CT) confirmed the isolated posterior dislocation of the radial head. Computed tomography also better delineated the dysplastic appearance of the radial head, depicting a dome-shaped radial head with no central depression (Figure 4).
Anteroposterior (A) and lateral (B) radiographs of the left elbow showing a posterior dislocation of the radial head. Note the dome-shaped radial head lacking a central depression and the mild bowing of the proximal ulna.
Lateral fluoroscopic image of the left elbow showing the dysplastic radial head. Examination revealed a stable elbow, supporting a congenital etiology for the radial head dislocation.
Lateral fluoroscopic image of the contralateral right elbow showing the reduced radiocapitellar joint in the absence of dysplastic features.
Coronal (A) and sagittal (B) computed tomography scans of the left elbow showing the dysplastic (A) and dislocated (B) radial head. It is important to note that computed tomography is not required for the diagnosis of a congenital radial head dislocation. Computed tomography was performed in this case to rule out other pathology because the patient presented after a high-energy trauma.
Congenital radial head dislocation is the most common congenital anomaly of the elbow, with an estimated incidence rate of 0.06% to 0.16%.1–3 Dislocations are most commonly posterior, with anterior or lateral dislocations evident in one-third of cases. In approximately 60% of all cases, congenital dislocation of the radial head is seen in conjunction with various syndromes (eg, nailpatella syndrome, Silver’s syndrome, Ehlers-Danlos syndrome), congenital radioulnar synostosis, mental retardation, and scoliosis.4,5 Furthermore, posterior dislocations may have an autosomal-dominant or X-linked recessive inheritance. Although it is most often bilateral, unilateral congenital radial head dislocation has been described.6
Congenital dislocation of the radial head is typically discovered incidentally because it is most frequently an asymptomatic phenomenon in which patients experience minimal functional limitations.7 It may become painful in adolescence or adulthood secondary to degenerative changes. On examination, a posterolateral elbow prominence may be appreciated, along with restricted elbow extension and forearm rotation.
Plain radiographs (anteroposterior, lateral, and oblique) are crucial in helping clinicians distinguish congenital dislocations from chronic, traumatic dislocations of the radial head. Radiographic findings consistent with congenital dislocation, particularly in the absence of a history of trauma to the involved elbow, include a dome-shaped radial head with no central depression, a flattened or hypoplastic capitellum, and/or mild bowing of the proximal ulna.8 Advanced imaging (eg, CT, magnetic resonance imaging) is not required to diagnose congenital dislocation of the radial head. However, it can be a useful diagnostic adjunct when concern exists for more subtle osseous injury in the setting of a recent trauma.
Observation is indicated for the majority of patients with congenital dislocation of the radial head because functional impairment is usually minimal.9 However, in the setting of severe pain or restricted motion, radial head resection can be performed in skeletally mature patients. The procedure is contraindicated in children with open physes because the radial head will regrow following resection. Of note, radial head resection has been shown to provide effective pain relief but only modest functional improvements.7
Congenital dislocation of the radial head is often bilateral and associated with various syndromes.4,5 However, it can also be found as an isolated, unilateral process; therefore, congenital dislocation of the radial head must always be considered in the differential diagnosis of isolated radial head dislocation.6 The presentation of the case described herein was in the setting of presumed elbow trauma. However, the dysplastic appearance of the radial head on plain radiographs and the patient’s minimal functional impairment favor the diagnosis of congenital dislocation. Observation is all that is required for most patients, with radial head resection reserved for only the most severe cases in the skeletally mature.
- Mardam-Bey T, Ger E. Congenital radial head dislocation. J Hand Surg. 1979; 4:316–320. doi:10.1016/S0363-5023(79)80067-2 [CrossRef]
- Almquist EE, Gordon LH, Blue AI. Congenital dislocation of the head of the radius. J Bone Joint Surg Am. 1969; 51:1118–1127.
- Kelly DW. Congenital dislocation of the radial head: spectrum and natural history. J Pediatr Orthop. 1981; 1:295–298. doi:10.1097/01241398-198111000-00009 [CrossRef]
- Wiley JJ, Loehr J, McIntyre W. Isolated dislocation of the radial head. Orthop Rev. 1991; 20:973–976.
- McFarland B. Congenital dislocation of the head of the radius. Br J Surg. 1936; 24:41–49. doi:10.1002/bjs.1800249306 [CrossRef]
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- Bengard MJ, Calfee RP, Steffen JA, Goldfarb CA. Intermediate-term to long-term outcome of surgically and nonsurgically treated congenital, isolated radial head dislocation. J Hand Surg. 2012; 37:2495–2501. doi:10.1016/j.jhsa.2012.08.032 [CrossRef]
- Campbell CC, Waters PM, Emans JB. Excision of the radial head for congenital dislocation. J Bone Joint Surg Am. 1992; 74:726–733.
- Echtler B, Burckhardt A. Isolated congenital dislocation of the radial head: good function in 4 untreated patients after 14–45 years. Acta Orthop Scand. 1997; 68:598–600. doi:10.3109/17453679708999034 [CrossRef]