Cartilage and subchondral bone distributions of the distal radius: a 3-dimensional analysis using cadavers.

OBJECTIVE: To quantify the spatial distributions of cartilage and subchondral bone thickness of the distal radius. DESIGN: Using 17 cadaveric wrists, three types of 3-dimensional models were created: a cartilage-bone model, obtained by laser scanning; a bone model, rescanned after dissolving the cartilage; and a subchondral bone model, obtained using computed tomography. By superimposing the bone model onto the cartilage-bone and the subchondral bone models, the cartilage and subchondral bone thickness were determined. Measurements along with the spatial distribution were made at fixed anatomic points including the scaphoid and lunate fossa, sigmoid notch and interfossal ridge, and compared at each of these four regions. RESULTS: Cartilage thickness of the interfossal ridge (0.89 ± 0.23 mm) had a larger average thickness compared to that of the scaphoid fossa (0.70 ± 0.18 mm; p = 0.004), lunate fossa (0.75 ± 0.17 mm; p = 0.044) and sigmoid notch (0.64 ± 0.13 mm; p < 0.001). Subchondral bone was found to be thickest at the scaphoid (2.18 ± 0.72 mm) and lunate fossae (1.94 ± 0.93 mm), which were both thicker than that of sigmoid notch (1.63 ± 1.06 mm: vs scaphoid fossa, p = 0.020) or interfossal ridge (1.54 ± 0.84 mm: vs scaphoid fossa, p = 0.004; vs lunate fossa, p = 0.048). In the volar-ulnar sub-regions of the scaphoid and lunate fossa, the subchondral bone thickened. CONCLUSIONS: Our data can be applied when treating distal radius fractures. Cartilage thickness was less than 1 mm across the articular surface, which may give an insight into threshold for an acceptable range of step-offs. The combined findings of subchondral bone appreciate the importance of the volar-ulnar corner of the distal radius in the volar locking plate fixation.

Cartilage wear patterns in severe osteoarthritis of the trapeziometacarpal joint: a quantitative analysis.

OBJECTIVE: The present quantitative study aimed to assess the three-dimensional (3-D) cartilage wear patterns of the first metacarpal and trapezium in the advanced stage of osteoarthritis (OA) and compare cartilage measurements with radiographic severity. DESIGN: Using 19 cadaveric trapeziometacarpal (TMC) joints, 3-D cartilage surface models of the first metacarpal and trapezium were created with a laser scanner, and 3-D bone surface model counterparts were similarly created after dissolving the cartilage. These two models were superimposed, and the interval distance on the articular surface as the cartilage thickness was measured. All measurements were obtained in categorized anatomic regions on the articular surface of the respective bone, and we analyzed the 3-D wear patterns on the entire cartilage surface. Furthermore, we compared measurements of cartilage thickness with radiographic OA severity according to the Eaton grading system using Pearson correlation coefficients (r). RESULTS: In the first metacarpal, the cartilage thickness declined volarly (the mean cartilage thickness of the volar region was 0.32 ± 0.16 mm, whereas that of the dorsal region was 0.53 ± 0.18 mm). Conversely, the cartilage evenly degenerated throughout the articular surface of the trapezium. Measurements of the categorized regions where cartilage thinning was remarkable exhibited statistical correlations with radiographic staging (r = -0.48 to -0.72). CONCLUSIONS: Our findings indicate that cartilage wear patterns differ between the first metacarpal and trapezium in the late stage of OA. There is a need for further studies on cartilage degeneration leading to symptomatic OA in the TMC joint.