Basic Science
Radiocapitellar joint contacts after bipolar radial head arthroplasty

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Purpose

The purpose of this study was to determine radiocapitellar contacts before and after radial head replacement, using the bipolar design of Judet.

Methods

Joint contacts were measured by moulding the joint surfaces of 6 fresh-frozen cadaveric specimens, in various positions of elbow flexion and forearm rotation.

Results

Expressed as function of the radial cup, contact areas averaged 44% in the normal elbow, decreasing with flexion and increasing with supination (P < .05). After prosthetic implantation, contact areas averaged 33% and remained quite similar, irrespective of elbow position. Subluxation of the prosthetic head over the lateral margin of the trochlea was seen systematically with supination.

Conclusions

Because of intraprosthetic mobility, contact areas were not dependant on elbow position. This adaptability, however, also led to abnormal positioning of the prosthetic radial head with supination, subluxing over the trochlea lateral margin.

Section snippets

Materials and methods

Radiocapitellar joint contact areas were measured by moulding the joint surfaces under physiological loads, in various elbow positions; the contact corresponds to the area devoid of moulding material. Pilot studies demonstrated that the best moulding material was Xantopren®, a silicon (Polysiloxane) impression material generally used in dentistry for tooth prints. Capsular and ligamentous structures were removed, and the product was then injected in the radiocapitellar joint. In laboratory

Reproducibility

The reproducibility of the measurements was good, with a standard deviation (SD) of 5 mm2 for an average of 113 mm2 for the measurement of 30 photographs of an identical moulding, a SD of 7 mm2 for an average of 171 mm2 for the measurement of 10 contact mouldings of the same specimen in the same position, and a SD of 2° for 10 measurement of the elbow flexion angle.

Radial head biometry

The right-left radial head biometrical parameters from each pair were compared and found to be quite different, allowing the use of

Discussion

Comminuted radial head fractures, with or without elbow dislocation, usually occur in young individuals; when osteosynthesis is impossible, the implantation of a radial head prosthesis is frequently necessary to restore elbow stability. The long-term results of radial head arthroplasty are unknown; however, capitellar degeneration may be feared in the case of excessive pressures applied on its hyaline cartilage. Indeed, a previous study by Liew et al8 has reported a marked decrease (by two

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