Bone grafting for repairing scaphoid nonunion

Abstract

BACKGROUND: Due to the relatively special symptoms and anatomical structure of scaphoid fractures, untreated fractures or those with delayed treatment often lead to non-union of the fracture, carpal joint collapse, or loss of function, subsequently resulting in persistent or intermittent pain, swelling, and limited mobility in the carpal joint. Currently, although there are a wide variety of bone grafting techniques and the choice of treatment methods is complex, there is still no consensus on which bone grafting surgical method is superior. OBJECTIVE: To review the research status of scaphoid nonunion, summarize different bone grafting surgeries for the treatment of nonunion of fractures at home and abroad in recent years, explore the clinical efficacy, advantages and disadvantages of various bone grafting techniques, and provide guidance for clinical diagnosis and treatment. METHODS: A computer was used to search for relevant articles published in the PubMed, MEDLINE, EMBASE, CNKI, China Medical Library, VIP, and WanFang databases from 1980 to 2024. The Chinese and English search terms were “scaphoid nonunion, surgery, bone graft, bone flap, scaphoid proximal pole.” A total of 687 articles were retrieved, and 54 articles were selected for review through inclusion and exclusion criteria. RESULTS AND CONCLUSION: (1) Non-vascularized graft is still the mainstream treatment for scaphoid nonunion. Among them, simple cancellous bone transplantation has fast bone formation (healing rate 85%-100%) and is suitable for cases without deformity; cortical cancellous bone has strong support (healing rate 88%-93%), which is more conducive to restoring the morphology of the scaphoid. (2) There is no significant difference in the healing rate between iliac bone and distal radial donors, but the distal radial donor site has fewer complications (5% vs. 18%). (3) Vascularized grafts can significantly improve the efficacy of complex cases: radial styloid bone flap healing rate 81%-92%, pronator quadratus pedicled flap healing rate 93.3%, free medial femoral condyle flap has outstanding effect on joint surface reconstruction (healing rate 95%), free iliac bone flap success rate 91.7%-100%, but high technical requirements. (4) The treatment of scaphoid nonunion needs to follow the principle of individualization: non-vascularized grafts are suitable for simple, well-vascularized fractures, while vascularized grafts are aimed at ischemic necrosis or complex deformities. (5) In the future, standardized imaging evaluation (such as MRI grading), biological enhancement techniques (bone morphogenetic protein 2, 3D printed scaffolds), and the popularization of microsurgery are needed to improve efficacy, while combining patient age and occupational needs to formulate the optimal plan, balancing functional recovery and complication prevention.

1. Introduction

Currently, the clinical treatment of scaphoid nonunion remains a major challenge, especially in cases accompanied by avascular necrosis. Nonunion often leads to persistent or intermittent wrist pain, swelling, and further progression to limited wrist motion. Statistics indicate that scaphoid fractures account for 2%-3% of all fractures, 10% of all hand fractures, and 60%-80% of carpal bone fractures. Fractures typically occur after a fall or during sports when the wrist is in a radially deviated and dorsiflexed position; women are more prone to low-energy injuries, while men often sustain high-energy injuries. The annual incidence ranges from 1.5 to 29 per 100,000 people. Kakar et al. consider intraoperative assessment of bleeding from the proximal fragment as the gold standard for diagnosing scaphoid fractures. Due to the relatively unique symptoms and anatomical structure of the scaphoid, untreated or delayed fractures frequently result in nonunion.

The diagnostic criteria for scaphoid nonunion are inconsistent, leading to varying reported incidence rates. According to the literature, 5%-15% of scaphoid fractures progress to nonunion, with much lower rates for non-displaced fractures when adequately treated and protected (approaching zero). However, when proximal pole fractures are displaced, the nonunion rate can reach nearly 55%. High-risk factors for nonunion include delayed diagnosis, inadequate immobilization, fracture displacement, and proximal location. The primary anatomical factor is the blood supply: the dorsal carpal branch of the radial artery enters the scaphoid at the waist and tubercle, supplying 70%-80% of the blood flow to the distal pole, while the proximal pole, covered almost entirely by articular cartilage, has no vascular entry, receiving only about 30% of the blood supply. This unique vascularity predisposes the proximal pole to avascular necrosis and nonunion.