Distal radioulnar joint stability measured with radiostereometry during the piano key test

Abstract

Distal radioulnar joint instability is difficult to grade by clinical examination and interobserver reliability is low. This study used a new and precise radiostereometry method for measurement of distal radioulnar joint translation. Eight human donor arms were positioned in a custom-made fixture and a standardized piano key test was done with pressure on the ulnar head. Examination was done before and after dividing the styloid and foveal insertions of the triangular fibrocartilage complex. In the intact wrists, the piano key test induced a mean 1.36 mm translation of the ulnar head, which increased statistically significantly to 1.96 mm after a lesion of the styloid ligament insertion and to 2.3 mm after combined lesions of the styloid and foveal ligament insertions. This experimental cadaver study demonstrates a radiological method for precise quantification of distal radioulnar joint stability after different grades of triangular fibrocartilage complex injury.

Distal radioulnar joint stabilization with open foveal reinsertion versus tendon graft reconstruction: an experimental study using radiostereometry

“…The native DRUJ was previously described to be stabilized in pronation by the bony sigmoid notch concavity [ 3 ] and moreover, by the proximal component of the TCFF which insert in the fovea [ 12 , 22 , 29 ]. In a previous radiostereometric study on intact cadaverarms, the DRUJ position ratio was 0.61 (95% CI 55;67) when applying the Piano-key test, which is comparable to the final DRUJ position ration obtained after surgery in both the foveal TFCC reinsertion and Adams TFCC reconstruction groups in the present study [ 30 ].…”

“…However, the method tended to reduce the DRUJ translation to nearly zero. In a previous study on uninjured cadaver wrists with normal arthroscopic Hook test and trampoline test, examined with a similar radiostereometry setup, we found a DRUJ translation of mean 1.36 mm (95% CI 0.17;2.55) [ 30 ]. It is unknow if overtightening of the radioulnar ligaments during TFCC surgery will obstruct the rehabilitation of supination and pronation motions or result in pain.…”

“…A radiolucent motorized fixture was used [ 30 ]. It allowed for a 7 kg load to be applied on the ulnar head by use of a fixture lever to imitate the clinical Piano-key test examination in a standardized setting [ 11 ].…”

“…An quivalent force was described not to give “obvious disruption of the soft tissues” in an experimental study [ 29 ]. In the test set-up the humerus was fixed in a 90 degrees vertical position, the forearm was pronated, and the hand was fixed to a horizontal plate, in zero degrees wrist extension and wrist deviation [ 30 ].…”

“…Investigations of the stabilizing effect of different surgical methods should preferably be performed in cadaver studies prior to clinical introduction. A non-invasive method for automated radiostereometric analysis (AutoRSA) was recently shown to provide precise quantification of DRUJ translation during the Piano-key test in cadavers [ 30 ].…”