• Hiroshi Ono, Takeshi Katayama, Kazuhiko Furuta, Daisuke Suzuki, Ryotaro Fujitani, and Manabu Akahane.
• Department of Orthopaedic Surgery, Kokuho Central Hospital, 404-1 Miyako, Tawaramoto, Nara 636-0302, Japan. onokota@kinet-tv.ne.jp
• J Orthop Sci. 2012 Jul 1;17(4):443-9.

PurposeA persistent articular gap and a step-off of ≥1 mm after a distal radial fracture (DRF) may lead to post-traumatic arthritis of the radiocarpal joint. This study aims to arthroscopically assess the reduction in the articular surface in patients requiring volar locked-plate fixation for DRF via fluoroscopy-guided open reduction and internal fixation (ORIF).MethodsSeventy consecutive patients with DRF were prospectively enrolled. Posteroanterior and lateral radiographs and axial, coronal, and sagittal computed tomography (CT) scans were obtained before ORIF for DRF. The widest articular gap (pregap) and step-off (prestep-off) at the radiocarpal joint surface of the distal radius were measured on all radiographs and CT images. Total predisplacement was defined as the sum of all pregaps and prestep-offs. The DRF was reduced under fluoroscopic guidance, and a volar locked-plate was applied after fluoroscopic ORIF. The residual maximum articular gap and step-off (postgap and poststep-off) were measured arthroscopically with a calibrated probe. Total incongruity was defined as the sum of postgap and poststep-off. The receiver operating characteristic curve was applied within the pregaps, prestep-offs and total incongruity in order to identify the cutoff values of pregap and prestep-off beyond which total incongruity would exceed 1 mm.ResultsOf the 70 patients, 40 had a postgap of ≥1 mm, and 15 had a poststep-off of ≥1 mm. All pregap and prestep-off cutoff values were judged to be unsuitable as the screening criteria for arthroscopic reduction of DRF because of their low sensitivity and specificity. The cutoff value obtained from total predisplacement was 7.85 mm, and its sensitivity and specificity were 90 and 70 %, respectively.ConclusionsSince the cutoff value of 7.85 mm derived from total predisplacement is a good indicator of post-ORIF residual total incongruity of ≥1 mm, it is also a good indicator of the need for arthroscopic reduction.

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