Oblique Hand Radiograph as a Method to Measure Fifth Metacarpal Neck Fracture Angulation.

PURPOSE: Fifth metacarpal neck fractures (5MCNFs) comprise up to 18.4% of all hand fractures. Clinical decision making is influenced by radiographic parameters, specifically apex dorsal angulation. Although sagittal computed tomography (CT) and lateral radiographs provide the truest views of the sagittal metacarpal, routine CT is not feasible, and metacarpal overlap on lateral radiograph presents a challenge for reliable measurement. Thus, oblique hand radiographs may be a valuable alternative, providing an isolated view of the fifth metacarpal. This study assesses whether oblique hand radiographs are a reliable and valid method of measuring 5MCNF angulation.

METHODS: A retrospective cohort of patients aged ≥18 years treated nonsurgically for 5MCNFs were recruited from three centers in Calgary. All patients had healed malunions. Radiographs and CT scans were obtained at one clinical visit at least 1-year postinjury. Three physicians measured fracture angulation on oblique hand radiographs and sagittal CT.

RESULTS: In total, 24 patients with malunited 5MCNFs were identified. The average patient age was 40.3 ± 13.3 years and patients were seen on average 2.97 ± 1.70 years postinjury. All patients were treated nonsurgically, and 91.7% were immobilized in a cast or a splint. The average apex dorsal angulation measurement was 42.6° ± 8.55° on oblique hand radiograph and 42.6° ± 8.86° on sagittal CT (P = .825). The interrater intraclass correlation coefficient was 0.795 (95% CI, 0.353-1.000) on oblique hand radiograph and 0.784 (95% CI, 0.414-1.000) on sagittal CT. The mean absolute interobserver difference in angulation measurement was 4.09° ± 2.90° on oblique hand radiograph and 4.66° ± 2.51° on sagittal CT. The intermodal intraclass correlation coefficients was 0.877 (95% CI, 0.659-1.000). The mean absolute angular error was 3.15° ± 1.82°. Bland-Altman analysis demonstrated no proportional bias.

CONCLUSIONS: Oblique hand radiographs demonstrate good reliability and high validity as a modality for the measurement of 5MCNF angulation. This study provides radiographic guidance for the assessment of 5MCNFs.

TYPE OF STUDY/LEVEL OF EVIDENCE: Retrospective reliability study III.