1 General considerations top
In proximal forearm fractures where the articular surface of both bones is involved, there is no place for radial head excision. In unreconstructable fractures of the radial head, prosthetic replacement is indicated
- when associated with an unstable coronoid fracture
- when associated with interosseous membrane injury
- with acute distal radioulnar joint injury (Essex-Lopresti injury)
Repair of 21-C3 fractures
C3 fractures, with extensive comminution of coronoid and radial head are characteristic of posterior transolecranon fracture dislocation. Lateral collateral ligaments are typically disrupted. Restoration of elbow stability requires repair of the proximal ulna, radial head ORIF or replacement, and lateral collateral ligament repair.
A coronoid fragment, if present, may be reduced and fixed through the olecranon fracture and/or a medial extension of the usual posterior approach. Radial fracture repair or replacement then follows. Some C3 proximal ulnar fractures extend into the proximal diaphysis. Their reduction must correct shortening and other deformity to preserve proximal radioulnar joint function. Occasionally, ulnar length can be determined better from the radius, after arthroplasty. Exposure of both fractures is a good initial step.
Stability of the elbow must be confirmed at the conclusion of reduction and fixation. If instability remains, supplementary external fixation may be necessary.
Correct prosthesis size
Select the right prosthesis size to avoid over- or underfilling of the radiocapiteller joint which can cause restricted range of motion (if a too large and/or long prosthesis is chosen) or elbow instability (if a too small and/or short prosthesis is chosen).
If the ulna is fixed first, reconstruct the radial head with the excised fragments and choose the size of the prosthesis accordingly.
Cemented or uncemented prosthesis
The surgeon must choose between cemented and uncemented prosthesis, the latter being easier, but perhaps less stable.
2 Resection of the radial head topenlarge
Resect radial head fragments
Carefully resect all radial head fragments. Preserve the annular ligament for repair, if possible.
Trim the radial neck
Trim the radial neck to fit the prosthesis with of a small rongeur.
3 Replacement topenlarge
Opening the medullary canal
Carefully open the medullary canal with an awl to fit the prosthesis stem.
Trial insertion of the prosthesis
Insert the chosen prosthesis. Assess its length and stability. Cementing the prosthesis may be necessary for optimal stability, and can be determined now.
Avoid lengthening or shortening
To avoid lengthening and overstuffing of the radiocapitellar joint, or shortening and instability, the prosthesis should fit as follows:
The articular surface of the radial head prosthesis should be at the level of, or slightly proximal to, the lateral edge of the coronoid articular surface.
The radius with prosthesis should match radiographs of the opposite (intact) forearm, to ensure correct length.
Check tracking of the prosthesis in flexion, extension, pronation and supination.
Cement the prosthesis in place, if desired, and if its size and position are satisfactory.
If the annular ligament is ruptured, repair it with non-absorbable sutures.
Following repair of the ulnar fracture, replacement of the radial head and repair of ligaments, assess elbow stability through a full range of flexion-extension. Radiocapitellar and ulnohumeral joints should remain located.
Also check supination and pronation. Fixation should be stable. Crepitus or restricted motion should be absent. Check fractures and fixation with image intensifier or x-ray.
If elbow instability or dislocation are identified, it is essential to maintain elbow alignment. This can be done with temporary hinged external fixation. If a hinged external fixator is not available, the significantly unstable elbow should be bridged with a non-hinged external fixator.