Radial Head Replacement Using Evolve Proline Modular Radial Head System (Wright Medical)
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Radial head fractures are common (approximately 20% of acute elbow injuries) and occur as a result of a fall onto an outstretched hand with the elbow in extension and wrist in pronation. The force is transmitted as an axial load through the wrist and through the radial head. They are more common in females and peak in the 4th decade.
The classification of radial head fractures is based a description of radial head fractures by Mason, but later modified by Broberg & Morrey and Hotchkiss . The classification is as follows and can be used in the decision making about which fractures may benefit from replacement of the radial head :
Type I – Undisplaced or minimally displaced (<2mm) or marginal lip fracture with no mechanical block
Type II – Displaced (>2mm) or angulated fracture, with mechanical block, without severe comminution
Type III – Comminuted and displaced fracture, not amenable to fixation
Type IV – Radial head fracture with associated dislocation
It must be appreciated by those treating these fractures that Radial head trauma can range from a simple, isolated fracture to complex fracture patterns with significant associated soft tissue components such as :
Lateral collateral ligament (LCL) injury. The most common association from axial loading in supination
Medial collateral ligament (MCL) injury .Occurring due to axial & valgus force
Combination LCL & MCL injuries. These are a higher energy and sit at the severe end of spectrum
Coronoid fractures. Occurring due to axial load in extension +/- dislocation
Fracture dislocation. These may result in “terrible triad” injuries of elbow dislocation, radial head fracture and coronoid fracture.
Essex-Lopresti injury. An associated distal radioulnar joint injury with rupture of the interosseous membrane
Radial head replacement is reserved for fractures that are significantly displaced, cause a mechanical block to motion or are not reconstructible. Other indications are discussed in the indications section following .There are various prostheses manufactured to replace the radial head.
The Evolve Proline Modular Radial Head System (Wright Medical Group) has several design features of note that recommend it. Firstly the prosthesis is modular so allows for variations in normal anatomy. The aim is restore the particular radial height and stability of the elbow joint in motion which requires this flexibility. Secondly the prosthesis utilises a spacer concept with a smooth stem that fits loosely into the radial neck. This allows motion at this level so that the prosthesis can conform with the articular surface throughout the range of movement.
Author:Mr Samuel Chan FRCS (Fr & Orth)
Institution: The Queen Elizabeth Hospital ,Birmingham ,UK.