The proximal ulna dorsal angle (PUDA): a systematic review

The proximal ulna dorsal angulation (PUDA) is an anatomical feature of the ulna pertinent to proximal ulna fracture reduction and implant design. This systematic review primarily aims to establish normative values for the PUDA through synthesis of the existing literature, with the secondary aim of evaluating methodological variability and identifying sources of heterogeneity across studies.

Following Preferred Reporting Items of Systematic Reviews and Meta-Analyses guidelines, MEDLINE, Embase, and Cochrane Library were searched between January 2000 and November 2024. Eligible studies reported quantitative measurements of PUDA in adults without pathology. Imaging modality, measurement technique, and risk of bias (assessed using the Newcastle-Ottawa Scale) were extracted and analyzed. Weighted means were calculated and intergroup differences assessed using one-way analysis of variance with Tukey's honestly significant difference.

Twenty-one studies were included, comprising over 2000 ulnae across 3 imaging modalities: computed tomography (CT) (n = 6), lateral radiographs (n = 7), and cadaveric (n = 8). The weighted mean PUDA was 5.8° ± 1.4°. Cadaveric studies reported significantly higher mean (7.8° ± 2.87°), compared to CT (5.2° ± 1.07°) and radiographic (5.1° ± 0.43°) (P < .001). The weighted mean tip-to-apex distance was 53.7 mm ± 17.6 (25.8% ± 5.4% of ulna length). Cadaveric studies reported a significantly higher mean (79.5 mm ± 16.9), compared to CT (49.1 mm ± 6.1) and radiographs (51.8 mm ± 3.5) (P < .001). Substantial variation was observed such as ulna landmark reference points and line measurement technique across modalities.

This review identified significant methodological heterogeneity across modalities, with radiological methods demonstrating greater reproducibility. These findings underscore the importance for standardization of measurement methodology, clinical practice, and implant design.