Application of a navigation system for contouring anatomical plasty of the distal end of the humerus

Abstract

The effectiveness of navigation systems in performing accurate orthopaedic surgery has been reported previously, but there have been no reports on the application of navigation in surgeries involving bone resection around the elbow joint. In this study, anatomical plasty or bone resection was performed to restore anatomical morphology in 10 cases of osteoarthritis of the elbow and deformity of the distal end of the humerus. Bone resection was performed on the distal end of the humerus using navigation and on the proximal end of the ulna via freehand surgery. Postoperatively, the elbow function was evaluated and pre- and postoperative CT images were used to measure the bone resection. There were no complications arising from the use of navigation, and elbow function was improved in all cases. By evaluating the CT images, it was found that navigated resection of the fossae of the distal humerus was more effective than freehand resection of the processes of the proximal ulna, thus confirming the usefulness of navigation. In future, to fully confirm this finding, it will be necessary to conduct prospective controlled studies of cases in which navigation is used to perform arthroplasty, including those that involve the proximal end of the ulna.

Figure 1

Registration and surface matching, (a) A reference array was placed on the medial side of the humerus. (b) A global registration was performed using 4 points, including the medial and lateral epicondyles and the two points on the edge of the olecranon fossa. Since the navigation software was designed for use in spinal surgery, the distal humerus was designated as vertebra LI, as shown in the screen shot, (c) Surface matching was then performed with 20 points on the posterior aspect of the distal humerus. The term “Accuracy: 1.0 mm” visible at the bottom of this screen was automatically displayed by the system.

Figure 2

Navigation-assisted surgery. A drill burr with a mounted reference array is used for bone resection of the distal humerus. (a) Anterior side of the joint. The drill burr is shown as a gold rod that is drilling out the osteophyte on the coronoid fossa, (b) Posterior side of the joint. The drill is burring out the olecranon fossa.

Figure 3

Measurement of bone morphology. A CT image of a sagittal plane through the bottoms of the coronoid and olecranon fossae of the distal humerus. The maximal values of the heights of the bone protruding from the contour surface, which is assumed to be the normal anatomical morphology, are shown. The heights of the bones (yellow lines with arrows) and their areas (in blue) are measured.