Radius neck-to-humerus trochlea transposition elbow reconstruction after proximal ulnar metastatic tumor resection: case and literature review

Reconstruction processes addressing the defects produced by wide excision of portions of the proximal ulna are difficult to treat because of the complex biomechanical interactions surrounding the hinge joint of the elbow. The function of the elbow relies on a complex combination of restraints achieved by the dynamic muscles of the elbow and the static bony and capsuloligamentous structures to which they are attached. Under normal conditions, valgus stress ranges from 31 % in extension to 33 % in 90° flexion, with the radial head acting as a secondary stabilizer, minimizing valgus instability [1]. Removal of significant portions of the ulna can reduce the stabilization provided by the radial head, resulting in symptomatically impaired mechanical function of the elbow. Subsequent to reconstructive surgery, improper healing may also represent significant impairments that are not immediately evident, but instead manifest as symptomatic sensitivity or mobility limitations months or years after the surgical procedure.In order to successfully reconstruct the biomechanical interactions between osseous and capsuloligamentous structures required for normal elbow function, structural vascularized bone grafts with internal fixation, elbow arthrodesis, and custom or modular prosthetic elbow arthroplasty are often conducted in clinical settings [2,3]. Bone grafts induce restoration of natural osteoconduction, osteoinduction, and osteogenic cells, particularly when composite grafting is applied [4]. Arthrodesis, while commonly selected for the treatment of traumatic elbow damage, often results in improper healing, necessitating extensive rehabilitation before mobility is restored [5]. Prosthetic total elbow arthroplasty (TEA) often depends highly on the varus-valgus interplay between the humeral and ulnar components, and is rarely used to treat cases where the ulnar head is impaired [6]. The appropriate treatment choice varies highly among different cases, often related to the pat