Figures & data
Figure 1. The specimen mounted on an elbow testing apparatus in the horizontal position. Threaded pins were used to lock the forearm in neutral rotation. Markers for the Optotrak Certus® motion tracking system were affixed to the humerus clamp and the ulna.
Figure 2. Simulated osteophytes made from harvested cortical bone were affixed to the anterior and posterior surface of the distal humerus. The simulated osteophytes were positioned such that they would partially obstruct the coronoid and olecranon fossae and impinge with the coronoid and olecranon tips during flexion and extension motions, respectively.
Figure 3. Deviation of the center of a circle fitted to the greater sigmoid notch of the ulna (GSN) from the flexion-extension (FE) axis defined by the center of a circle fitted to the trochlea and a sphere fitted to the capitellum of the distal humerus. Larger deviations indicate that the ulnohumeral joint is undergoing non-physiologic subluxation. Shaded regions indicate the mean ±1 standard deviation of the corresponding data gathered during all trials.
Figure 4. Illustration of non-physiologic subluxation of the ulnohumeral joint during flexion motions with simulated osteophytes attached. The deviation of the GSN from the FE axis is small at initial impingement when the physiologic flexion limit is met, but increases as the flexion angle is increased further. While this pathologic flexion motion occurs, the joint is hinging about the impingement point on the osteophyte, rather than the FE axis.
Figure 5. Examination of the simulation-predicted impingement locations. Flexion was limited by impingement of the coronoid process in the coronoid fossa. Extension was limited by impingement of the olecranon in the olecranon fossa.
Table I. Elbow range of motion measured during experiments and simulated by the computer model. Experiment ROM represents the average ROM at bony impingement measured across 5 flexion and extension trials. The physiologic ROM was based on the ROM before non-physiological joint subluxation occurred, determined through visual inspection of .