Arthroscopic Versus Open Cancellous Bone Grafting for Scaphoid Delayed/Non-union in Adults: Study Protocol for a Randomized Clinical Trial

A scaphoid fracture is the most common injury to the carpal bones. The incidence is 107-151/100.000 per year and fractures are predominantly sustained by males in their twenties. Scaphoid non-union is defined as a lack of healing 6 months after injury and develops in 5-25% of cases after non-operative treatment. Delayed union is defined as incomplete healing 2-6 months after injury. However, some potential for a union probably exists, especially in nondisplaced fractures, otherwise this condition is associated with a transition into a persistent non-union. The risk of non-union increases with delayed diagnosis and treatment, displaced fractures, proximal pole fractures, smoking, poor vascularity, and advancing age.

The scaphoid is primarily covered with cartilage and has a retrograde blood supply. The dorsal branch of the radial artery accounts for 80% and a separate volar branch for 20 % of the extramedullary blood supply. The proximal pole is only supplied by the intramedullary flow. Compromised blood supply can explain the potential of non-union and avascular necrosis of the proximal pole. The healing process can be complicated by volar angulation of the fracture leading to humpback deformity. This will disrupt carpal kinematics, and result in lunate instability and dorsal intercalated segment instability (DISI). Untreated scaphoid non-union can lead to degenerative changes, called scaphoid non-union advanced collapse (SNAC), and irreversible impairment such as pain and altered hand function.

X-ray is commonly applied to evaluate the scaphoid, although CT scans are reportedly superior in terms of displacement, angulation and union[9]. Different measurements to describe the angulation and deformity of the scaphoid are suggested. The Height length ratio (HLR) and dorsal cortical angle (DCA) are found to be the most reliable measurements.

Surgical treatment of scaphoid delayed/non-union is technically demanding and often results in a long period with a supportive bandage until union is established. Current treatment strategies for delayed union and non-union include vascularized or non-vascularized bone graft with internal fixation. Kirchner wires or screws have been the gold standard for fixation.

Arthroscopic reconstruction with C chips and internal fixation is predominantly applied in delayed union and stable non-union. The advantages of arthroscopy include thorough wrist assessment, evaluation of concomitant ligamentous injury and minimal trauma to the ligament structures, joint capsule, and the tenuous blood supply.