To compare the radiographic outcome among two different types of locking plate at treatment of distal ulna fracture with concomitant surgically fixed distal radius fracture.
Between 2018 ~ 2023, thirty-seven patients with acute distal ulna fracture associated with distal radius fracture receiving ORIF with locking plate in our hospital were reviewed. Patients with a follow-up duration of less than 4 weeks were excluded, and 30 patients were analyzed finally. All the patient’s distal radius fracture were fixed by locking plate. For distal ulnar fracture fixation, patients who received single-plane locking plate fixation were classified as group A, while those who received multi-plane locking plate fixation were classified as group B. Postoperative radial-ulnar angulation, volar-dorsal angulation, and translation were measured. The rotation deformity was defined by a mismatch in plate position between the antero-posterior and lateral radiographs without angulation or translation. A patient identified as having malalignment or malreduction was found to have at least one of the following findings: angulation greater than 10 degrees, translation exceeding 50% of shaft diameter, or rotation deformity. The incidence of malalignment between the two groups were compared by fisher exact test, with the level of significance set at p < 0.05.
There was no difference of age, gender, site, or fracture classification between these two groups. Thirteen patients were fixed by single plane locking plate fixation (Group A), and 9 patients of them (9/13, 69.2%) was noticed to have malalignment, which was significantly higher than multi-planar locking plate fixation (Group B) (4/17, 23.5%) [p=0.02]. Each radiographic parameter was also compared, and the difference of radial-ulnar angulation met significant level between the two groups (53.8% vs. 11.8%, p=0.02). In addition, group A exhibited a higher ratio of volar-dorsal angulation (3/13, 23.1%), translation deformity (1/13, 7.7%), and rotation deformity (2/13, 15.4%) compared to group B. However, these differences did not reach statistical significance.
Our study found that the single plane locking plate fixation for distal ulnar fracture cause more malalignment compared to multi-plane ones, especially the radial-ulnar angulation. The single plane fixation locking plate was designed to be low-profile with a hook to anchor the ulnar styloid, which was often be separated from the shaft in comminuted distal ulnar metaphyseal fracture, without providing fixation. Besides, the multi-plane design offered different axis and more screw purchase at distal fragment, which theoretically had biomechanical advantage. In conclusion, our study showed that single plane locking plate would cause more malalignment compared to multi-planar locking plate fixation.
