Volar Rim Morphology and Plate Congruence in Fragment-Specific Distal Radius Fixation

Fragment-specific fixation of distal radius fractures often requires implants positioned at or beyond the watershed line, which may increase the risk of flexor ultrasound-detected flexor tendon abnormalities. However, tendon conflict may depend not only on plate position but also on how the implant adapts to individual volar rim morphology. This study assessed whether volar rim morphology, classified according to the Dolomites concept, was associated with plate application and ultrasound-detected flexor tendon abnormalities after fragment-specific fixation. We hypothesized that Dolomites volar rim morphology would be associated with plate-to-bone application and with ultrasound-detected flexor tendon abnormalities.

A single-centre prospective cohort study included adult patients treated surgically for distal radius fractures requiring fragment-specific fixation at or beyond the watershed line. At 6 months, postoperative CT was used to classify volar rim morphology as Dolomites type 1 or type 2 and to assess plate application. Distal plate-to-bone incongruence was defined as a plate-to-bone distance greater than 2 mm at the most palmar point of the distal radius. Systematic ultrasound was performed to identify flexor tendon abnormalities. Associations between volar rim morphology, plate application, and ultrasound-detected flexor tendon abnormalities were analyzed overall and by plate type.

Of 152 initially included patients, 123 were available for analysis. Dolomites type 1 anatomy was present in 95 patients (77.2%) and type 2 in 28 patients (22.8%). Overall, distal plate-to-bone incongruence was observed in 30 cases (24.4%) and ultrasound-detected flexor tendon abnormalities in 43 cases (35.0%). Dolomites anatomy was not significantly associated with distal plate-to-bone incongruence when all plate types were analyzed together: 26 of 95 type 1 cases (27.4%) versus 4 of 28 type 2 cases (14.3%; p = 0.212). However, among hook plates, distal plate-to-bone incongruence was significantly more frequent in type 1 than in type 2 anatomy: 11 of 22 cases (50.0%) versus 2 of 23 cases (8.7%; p = 0.003). Distal plate-to-bone incongruence was strongly associated with ultrasound-detected flexor tendon abnormalities, which occurred in 28 of 30 incongruent plates (93.3%) compared with 15 of 93 congruent plates (16.1%; p < 0.001).

Ultrasound-detected flexor tendon abnormalities were substantially more frequent in cases of distal plate-to-bone incongruence. Although Dolomites morphology was not associated with distal plate-to-bone congruence in the overall cohort, exploratory subgroup analysis suggested a potential association between volar rim morphology and hook plate congruence. Further validation is required before this classification can be incorporated into routine implant selection.

III; prospective cohort study.