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Background: Anatomical structure affects function. The morphology of articulations dictates the way forces will travel through the joint. A better understanding of the structure and function of the wrist will enhance our ability to diagnose and treat wrist conditions. Two wrist types have been described based on the morphology of the midcarpal joint. Biomechanically it is important to see if these 2-dimensional (2D) observations reflect articular contact areas. Our purpose was to assess the correlation between measurements performed on wrist radiographs (2D) to measurements performed on 3-dimensional (3D) computed tomography (CT).

Methods: Retrospective review of a database of normal wrist radiographs and corresponding normal CT scans. Only imaging pairs with normal carpal alignment and technically optimal imaging were included. Evaluations included lunate, capitate and wrist type, capitate circumference, percent capitate circumference and volume that articulates with the lunate, scapholunate ligament, scaphoid, hamate, trapezoid, base of the index and middle and ring metacarpal bones.

Results: Midcarpal joint radiographic measurements were positively correlated with measurements on CT scans. Correlations were 0.51 for capitate type and 0.71 for lunate type with both p < 0.001. Percent contact of the lunate with the hamate: r was 0.74 p < 0.001. Using logistic regression analysis, percent lunate-hamate contact on CT was a significant predictor of radiographic lunate type 2 p < 0.001. Percent contact area between lunate and hamate > 7.8% on CT scan achieved a sensitivity of 100% and specificity 79.4% for a type 2 lunate.

Conclusions: 1) Good correlations found between CT and plain radiographs in lunate type, capitate type, and midcarpal joint contact support the use of plain radiographs to describe contact between the carpal bones in the clinical setting. 2) The retrospective nature of this study limited the technical quality of the measurements. Volumetric analysis may aid in a more exact evaluation of surface contact area.

Background: The aim of this study was to investigate what should be considered when diagnosing and treating displaced extra-articular fractures based on plain radiographs.

Methods: We included 181 extra-articular distal radius fractures with marked displacement requiring surgery, which were diagnosed with posteroanterior (PA) + lateral (Lat) + oblique views (obl). We compared the plain radiographs with CT scans to determine whether the diagnosis was properly made. We described the types of articular involvement incidentally found on CT scans and how the articular involvement was treated. We tested the inter-observer and intra-observer reliability with three orthopedic surgeons.

Results: Forty-two (32%) out of 181 displaced extra-articular fractures diagnosed by plain radiographs had intra-articular involvement on CT scans. Dorso-ulnar intra-articular fragment was most commonly found. Thirty-three (78.6%) out of 42 intra-articular involvements required additional reduction and a dorsal approach was used in eight patients. Inter-observer and intra-observer reliability ranged from “substantial” to “almost perfect”.

Conclusions: When treating displaced extra-articular fractures requiring surgery, CT scans might be necessary to find intra-articular involvement and at least, an oblique view showing the dorso-ulnar corner of the articular surface should be added. Surgeons should consider that extra-articular fractures with marked displacement, which are diagnosed by plain radiographs alone, might have intra-articular involvement requiring additional reduction or fixation via a different incision.