Results and clinical application of the KPS bipolar radial head prosthesis

Fractures of the radial head constitute about 30% of all fractures around the elbow joint [1, 2]. Five to ten percent of all elbow dislocations are associated with peri-articular fractures, most commonly the radial head [3, 4, 5] In comminuted fractures of the radial head anatomic reduction and stable fixation are not always possible. In such cases the treatment is controversial – resection versus replacement. The complications after radial head resection are well known [6], and prosthetic replacement is clearly indicated after radial head resection in the presence of a medial collateral ligament or interosseous membrane injury [2]. With the increasing recognition of “complex instability” the value of the radial head in providing elbow stability is emerging [7]. Unfortunately, no silastic or metal monoblock radial head prostheses that are currently available have proven entirely satisfactory. The most common complications include loosening [8, 9, 10] and damage to the implant/fatigue fracture [8, 10, 11, 12, 13]. Additionally, implantation of a silastic prosthesis is associated with osteoporosis of the capitellum and silicone synovitis [8, 12, 14, 15, 16, 17]. Cadaveric studies have also shown that the silastic implant is unable to adequately resist valgus stress applied to the elbow joint [9, 14, 18, 19]. Recently, bipolar radial head prostheses have been introduced, and these are commercially available in a few countries and used by some medical centers in Europe [20, 21, 22, 23, 24]. Judet et al have reported very promising clinical results, believing that the bipolar design overcomes many of the existing complications [21]. Pomianowski et al and Skalski et al introduced a bipolar radial head prosthesis with a short (2 cm), straight stem and an arc of 30 degrees of angular movement [22, 24]. The additional freedom of movement of a bipolar prosthesis should theoretically reduce the stress on the implant and the implant-bone interface, thereby decreasing the risk of loosening of the implant. The free motion of the radial head might also decrease wear on the capitellum. As the head of a bipolar implant is mobile, the extent to which such a prosthesis can contribute to stability of the elbow was not clear. It has been already proved that a bipolar implant can be as effective as a monoblock radial head prosthesis in restoring valgus stability of the elbow after injury to the medial collateral ligemant [25].