Dimensional radiographic analysis of distal interphalangeal joint morphometry for fusion implant suitability – A Singapore population study

Background Distal interphalangeal joint (DIPJ) fusion is a commonly used surgical technique for the treatment of osteoarthritis. It can be challenging due to the small size of the phalanges. Objectives This study aims to determine the nominal dimensions of middle and distal phalanges of digits in the Singapore population via radiographic measurements, to facilitate the selection of appropriate implants for DIPJ fusion. Materials and methods De-identified plain radiographs of 250 fingers from 250 adult Singaporeans from July 2020-2023 were retrospectively obtained and measured using the authors’ institution’s radiograph software. Lateral and anteroposterior diameters of the distal and middle phalanges were recorded and compared with the smallest commercially available headless compression screw (Medartis 1.7 mm) currently available in Singapore. Results Female phalanges were smaller than that of males. Anteroposterior diameters of middle phalanges in females were significantly smaller than that of males in all fingers except for the thumb and middle finger ( p < 0.05*). Anteroposterior diameters of distal phalanges in females were significantly smaller than that of males for all fingers (p < 0.05*). The compatibility rate of the Medartis 1.7 mm cannulated screw between the two genders was found to be on average: 94% in the thumb, 44% for the index finger, 38% for the middle finger, 30% for the ring finger and 12% for the little finger. Conclusion Apart from the thumb, less than 50% of the digits in the Singapore population were found to be compatible with the smallest available screw. The findings highlight the need for more suitable fixation devices or techniques for DIPJ fusion.