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Prosthetic Radial Head Replacement


Introduction

In general, the management of type I fractures is well understood and accepted. Controversy does surround the type II and type III fracture due to increased complexity from treatment of associated injuries. Our treatment logic is described in Chapter 37 ( Fig. 39.1 ). The essential role of implant replacement is when the head cannot be fixed and there are associated injuries dictating a stable radiohumeral joint. This is observed in about 50% of type II and 80% of type III injuries ( Table 39.1 ). Radial head fracture with a fracture of 50% or more of the coronoid process is an absolute indication for replacement if fixation of the head is not possible. Deficiency of the medial collateral ligament or disruption of the distal radioulnar joint are additional well-recognized indications for radial head function. Longitudinal instability of the radius (Essex-Lopresti injury) continues to be an extremely different problem, as noted earlier. Acute management may be adequate in up to 80%, but reconstruction is effective in only about 30%. Reestablishing the integrity of the radiohumeral joint is considered essential when reconstructing this difficult problem.

FIG 39.1, The treatment logic forms the basis for the use of the radial head implant. Notice the device is reserved for complicated type III fractures.

TABLE 39.1
Summary of 15 Years of Literature Involving Prosthetic Radial Head Replacement for Acute Injuries
Author Year Prosthetic Intervention Total No. (% Satisfactory) Follow-Up (Years)
Knight 1993 Mono 31 (94) 4.5
Judet 1996 Bipolar (fixed) 7 (100) 4
Smets 2000 Bipolar (fixed) 13 (77) 2
Popovic 2000 Bipolar (fixed) 11 (83) 2.5
Holmenschlager 2002 Bipolar (fixed) 10 (100) 1.5
Alnot 2003 Bipolar (fixed) 18 (100) 1.5
Bain 2005 Mono (loose) 10 (100) 2.8
Doornberg 2007 Mono (loose) 27 (82) 3.5
Papovic 2007 Bipolar (fixed) 51 (79) 8.4
Chien 2010 Mono (loose) 10 (90) 3.2
Burkhart 2010 Bipolar (fixed) 9 (91) 8.8
Chen 2011 Mono (loose) 22 (91) 1.3
Lamas 2011 Mono (pyrocarbon) 47 (89) 4
Katthagen 2013 Mono (fixed) 16 (92) 2.4
Total 282 (92) 3.6

Indications

A Mason III fracture with four or more fragments is generally considered not amenable to open reduction internal fixation (ORIF). This fracture will require resection and replacement, with associated coronoid fracture or collateral ligament disruption. a

a References .

If the elbow is stable, then simple excision might be considered (see Chapter 37 ). Instability after radial head resection requires prosthetic replacement. In general, displaced isolated type II fractures should be fixed; type III fractures should be replaced.

Contraindications

The use of an implant is obviously contraindicated in the presence of sepsis. A stable elbow after resection need not be replaced. Malalignment that does not allow proper articulation with the capitellum is a relative contraindication but can often be addressed with a bipolar articulation. Articular trauma to the capitellum is a relative contraindication because some patients will do well even with some degree of capitellar damage.

Design Considerations

An increasing number of designs have recently appeared on the market. There are several considerations when selecting a prosthetic radial head implant: (1) sizing flexibility; (2) stem fixation; and (3) articulation philosophy: anatomic or axisymmetric. Additional variables to consider are the shape and material properties of the articulation and, especially, the ease and reproducibility of the technique ( Figs. 39.2, 39.3, and 39.4 ).

FIG 39.2, (A) A biologically fixed monoblock radial head implant

FIG 39.3, The biopolar implant particularly useful in reconstructive modes. (A) The floating head long stem biologically fixed or cemented (Courtesy of Tornier, Montbonnot Saint Martin, France). (B) The rHead Recon biologically fixed or stabilized with cement. (Courtesy of Stryker, Kalamazoo, MI.) (C) Catalyst allows axial alignment options.

FIG 39.4, Polycarbon articular implant. (A) Modular pyrocarbon radial head prosthesis (MoPyC) allows alignment of head after implantation biological fixation.

Flexibility

The wide range in the level of resection, as well as considerable individual size variation, dictates a system with several stem and head diameter and length options. One of the most important features distinguishing the systems available today is the ability to accommodate significant proximal resection or resorption. The option of allowing for build-up or shim of the radial neck is an important consideration to offer the maximum flexibility of a replacement system. Hence, the system must offer modularity and flexibility to match stem, head diameter, and neck length. Finally, malalignment of the resected radius with the capitellum, especially in chronic applications, prompts the availability of a bipolar or intraoperatively adjustable articular option.

Stem Fixation

There are three basic fixation philosophies: (1) loose fitting spacer, with a smooth, polished stem; (2) cemented stems; and (3) press fit/biological fixation. The round, smooth stem of the Evolve device (Wright Medical Technology, Inc., Arlington, TN) makes no attempt at achieving rigid fixation, but rather the stem is used only to align the articular disk with the capitellum. The smooth, polished stem appears to be effective, is well tolerated, and is not commonly a source of pain.

There is adequate clinical experience demonstrating the short, textured stem can be reliably stabilized by biologic fixation or the stem may be cemented at the surgeon's preference. However, symptomatic loosening has been reported for all design concepts, and stress shielding has also been reported for the rigidly fixed devices.

Articulation

Whether a fixed or mobile articulation is employed is based on the reliability of aligning the fixed articulation that is the most stable construct. When the radial head is being replaced for a secondary salvage-type indication, alignment of the proximal radius is altered and often is difficult to restore. Therefore, the major requirement is that the prosthetic radial head aligns and articulates with the capitellum. When pathology alters the radial/humeral relationship, the fixed articulation implants become vulnerable to subluxation, dislocation, or erosion of the capitellum. This is the setting in which a mobile bearing is used.

Experimental data suggest both fixed and articulated devices can be effective, but in the grossly unstable circumstance, the nonmobile head is preferable. In addition, the mobile bearing is vulnerable to generating wear particles, possibly causing local osteolysis, and has the potential to become less stable over time.

Technique

Common features of radial head replacement with any system include:

  • Adequate exposure of the shaft to allow preparation and insertion

  • Variable release of the lateral collateral ligament origin

  • Accurate resection of the radial neck

  • Preparation of the proximal radius consistent with planned fixation

  • Assurance of proper tracking with rotation throughout flexion arc

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