Abstract. Background. Scaphoid non-union can result in pain, altered wrist kinematics leading to a Scaphoid Non-union Advance Collapse, ultimately to symptomatic radio-carpal arthritis. Open techniques have their limitations. We describe the rationale, surgical technique and outcomes of our series of arthroscopic bone-grafting (ABG) and fixation of scaphoid non-union. Methods. We performed a prospective single-surgeon series of 22 consecutive patients with clinico-radiologically established scaphoid non-union between March 2015 and April 2019. Data was collected from Electronic Patient Records, Patient Archived Computer system (PACS) and hand therapy assessments. We collected demographic data including age, hand-dominance, occupation and mechanism of injury. The Disabilities of the Arm, Shoulder and Hand Score (Quick DASH), Mayo wrist score, Patient Rated Wrist Evaluation (PRWE) and grip-strength measurements were collected preoperatively and at follow-up appointments. Results. There was an improvement in all outcome measures when comparing preoperative and postoperative results. The Quick DASH score improved by a mean of 24 points, Mayo wrist and PRWE scores improved by 15.1 and 29.7 points, respectively. Grip-strength analysis also improved by 6.1 kgf (Right) and 3.3kgf (Left). Follow-up computerised tomography scans revealed union in 18/22 patients with 2 patients lost to follow-up. One patient required revision ABG procedure to achieve union. Conclusion. Arthroscopic bone grafting and fixation of scaphoid non-union allows a minimally invasive method of managing these injuries. It has advantages of minimal morbidity and accurate articular reduction resulting in less postoperative stiffness and increased functional outcomes. It is an effective alternative to conventional open treatment of established scaphoid non-union

Scaphoid non-union results the typical humpback deformity, pronation of the distal fragment, and a bone defect in the non-union site with shortening. Bone grafting, whether open or arthroscopic, relies on fluoroscopic and direct visual assessment of reduction. However, because of the bone defect and irregular geometry, it is difficult to determine the precise width of the bone gap and restore the original bone length, and to correct interfragmentary rotation. Correction of alignment can be performed by computer-assisted planning and intraoperative guidance. The use of computer navigation in guiding reduction in scaphoid non-unions and displaced fractures has not been reported. Objective. We propose a method of anatomical reconstruction in scaphoid non-union by computer-assisted preoperative planning combined with intraoperative computer navigation. This could be done in conjunction with a minimally invasive, arthroscopic bone grafting technique. Methods. A model consisting of a scaphoid bone with a simulated fracture, a forearm model, and an attached patient tracker was used. 2 titanium K-wires were inserted into the distal scaphoid fragment. 3D images were acquired and matched to those from a computed tomography (CT) scan. In an image processing software, the non-union was reduced and pin tracts were planned into the proximal fragment. The K-wires were driven into the proximal fragment under computer navigation. Reduction was assessed by direct measurement. These steps were repeated in a cadaveric upper limb. A scaphoid fracture was created and a patient tracker was inserted into the radial shaft. A post-fixation CT was obtained to assess reduction. Results and Discussion. In both models, satisfactory alignment was obtained. There were minimal displacement and articular stepping, and scaphoid length was restored with less than 1mm discrepancy. This study demonstrated that an accurate reduction of the scaphoid in non-unions and displaced fractures can be accurately performed using computed navigation and computer-assisted planning. It is the first report on the use of computer navigation in correction of alignment in the wrist