A holder for standardized radiological investigation of the stability of the ulnar ligament of the thumb metacarpophalangeal joint

Aim of the study: To evaluate the usefulness of a self-constructed holding device for standardized,investigator-independent-radiodi agnostics for ulnar capsule-ligamentous lesions of the thumb metacarpophalangeal joint compared to the uninjured side. Material and methods: A holding device for stress roentgenograms was constructed. Normal abduction arcs were evaluated in 20 degrees flexion in 28 healthy volunteers. The investigator-dependent variance was assessed. The study group comprised 123 consecutive patients (68 male, 55 female, aged 7 to 68 years, mean age 30 years). Results: The normal are of abduction was calculated to be 12 degrees (range 3 degrees to 24 degrees),while the mean individual difference in side by side comparison in volunteers was 0,3 degrees (SD 2,69 degrees, range 0 degrees -8 degrees). A rupture was diagnosed in 47 patients;41 were operated. The preoperative diagnoses confirmed correct in all operated patients. A difference of greater than 6 degrees is indicative of a rupture with a sensitivity of 66,7% and a specificity of 96,9%. Conclusions: In summary,the holding device is useful for the practical work. Individual differences of less than 4 degrees are negative, between 4 degrees and 7 degrees questionable positive, between 7 degrees and 12 degrees are positive and over 12 degrees proof indicator of a rupture of the ulnar collateral ligament of the thumb metacarpophalangeal joint.