Lateral Condylar Prominence, Post Corrective Osteotomy of Cubitus Varus: A Study Using Three-Dimensional Reverse Engineering Technique
Banchong Mahaisavariya MD*, Kriskrai Sithiseriprateep DEng**, Nattapon Chantarapanich PhD***, Natapoom Vatanapatimakul BSc**
Affiliation : * Department of Orthopaedic Surgery and Rehabilitation, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand ** National Metal and Materials Technology Center (MTEC), Bangkok, Thailand *** Department of Mechanical Engineering, Faculty of Engineering, Kasetsart University, Chonburi, Thailand
Lateral condylar prominence is a common problem after corrective osteotomy of the cubitus varus, which is believed to result from unequal opposing cut surfaces of lateral-based wedge osteotomy using a medial hinge. This study investigated this issue using a 3-dimensional CT data set consisting of images of the deformed elbow and the normal elbow of a patient with cubitus varus deformity who was scheduled for corrective osteotomy. A CT scan was performed with 3mm slice thickness and a reconstruction was done with 1mm interpolated slice thickness on both the left and right humerus. The CT-data set was then manipulated using reverse engineering software. Three-dimensional models of both the deformed and normal humeri were studied. Several locations or levels of medial hinge placement, each with 4-degree-tilt wedge osteotomy cut options, were then virtually performed and evaluated. The degree of correction was determined from the varus angle plus the normal carrying angle of the normal side. From the study, it was found that the degree of lateral condylar prominence is directly proportional to the distance of placement of the medial hinge above the joint. Differences in the lengths of the osteotomy surfaces have no effect on condylar prominence; only the step-off phenomenon affects condylar prominence. According to our findings, placement of the medial hinge close to the joint with a 10-degree distal osteotomy cut just above the olecranon fossa will result in optimal minimization of condylar prominence or the step-off phenomenon.
Keywords : Cubitus varus, Corrective osteomy
