Percutaneous or minimally invasive surgery describes the “length of an incision,” but more importantly, a surgical portal to pathology. It is suggested that surgical repairs performed using minimal incisions prevent further soft tissues injuries, including those to key ligaments and blood supply. A reduction in swelling and further soft tissue injury permits an early restoration of hand function (1). This results in a high union rate with minimal complications and an early return to work or avocation (1,2,3,4,5,6). The surgical goal of fracture treatment is reduction of the fracture fragments and stabilization to prevent shearing at the repair site until sufficient bone healing and remodeling has occurred. These goals can be also be accomplished by a standard open approach, which violates uninjured structures and introduces other soft tissue injuries.

The tools of percutaneous surgery are arthroscopy and mini-fluoroscopy. Arthroscopy aids in the reduction of displaced carpal fractures and identifies occult ligament injuries for treatment (1,7,8). Real-time imaging using mini-fluoroscopy allows for an improved understanding of fracture geometry. Mini-fluoroscopy, used in conjunction with arthroscopy, improves efficiency by directing portal entry; arthroscopy confirms fracture reduction and implant placement observed with imaging. This chapter describes percutaneous techniques, including the dorsal approach for repair of scaphoid fractures and nonunion, using mini-fluoroscopy and arthroscopy (Fig. 12-1).

Percutaneous or minimally invasive surgery is most commonly used to treat nondisplaced scaphoid waist fractures. Unstable fractures, displaced scaphoid fractures, and selected fracture nonunion can be treated using these same techniques (9,10). To achieve successful union, evaluate the fracture for its location, fracture plane, and bone integrity to determine the best implant and the optimal position for rigid fixation. Evaluate nonunions for bone viability, bone attrition, and loss, resulting in cystic changes and deformity. This information is needed because viable bone cells and a blood supply are necessary to achieve a successful union. Stability of fixation depends on the strength of a fracture fragment–implant construct. Strength is determined by five independent variables: bone quality, fragment geometry, fracture reduction, implant choice, and implant placement (10).

Finally, one more key factor determines the stability of fixation and that is the magnitude and direction of force acting on the fracture fragment–implant construct. The scaphoid is a tie-rod connecting the proximal and distal carpal row. Micromotion at a fracture site disrupts or delays healing. Fracture location and the direction and magnitude of displacement forces will determine the stress and strains and the resulting micromotion at the fracture site to which the healing scaphoid is subjected.

Bone healing depends on fracture stability. During the repair phase of fracture healing, chemical and mechanical factors determine the type of bone healing. The repair phase stimulates vascular ingrowth of progenitor cells and growth factors, extending Haversian canals across the fracture site. Fracture hematoma forms a collagenous extracellular matrix. During this phase, stability determines the degree of strain at the fracture site, and strain determines the type of bone healing. Strains less than 2% result in primary bone healing. Strains between 2% and 10% result in secondary bone healing. Finally, with strains greater than 10% bone cannot heal and fibrous or granulation tissue is formed (11). The goal of fracture stabilization is to prevent or to minimize shearing at the fracture site until successful healing has occurred.

Operative repair of scaphoid fractures is indicated by the need to treat unstable scaphoid fractures and specific social needs of the patient, which prohibit plaster immobilization of stable scaphoid fractures. Stable scaphoid fractures traditionally are treated with plaster immobilization, but require computed tomographic (CT) scans to confirm healing (12). Stable fractures can also be treated with percutaneous fixation because the union rate may be higher, the complication rate relatively low, and the difficulties of nonunion numerous.

Some authors, however, disagree on which scaphoid fractures are stable. Cooney et al. (13) felt a complete scaphoid waist fracture with less than 1 mm of displacement (type IIB) could be stable, whereas Filan and Herbert (14) felt these are always unstable and recommended rigid fixation (13,14). Filan and Herbert classified stable scaphoid fractures as incomplete fractures and distal scaphoid tubercle fractures (type A).

In most cases, standard radiographs are sufficient for preoperative planning. If there are questions about fracture displacement, comminution humpback deformity, or other characterization of the fracture, then preoperative CT is a valuable adjunct for planning purposes. With questions about proximal
scaphoid pole vascularity, then a preoperative magnetic resonance imaging (MRI) is valuable, because it is helpful to know before scheduling if a vascularized bone graft is needed. Mini-fluoroscopy is extremely useful for evaluating scaphoid alignment, bone integrity, and carpal ligament disruption. Arthroscopy is useful for confirming fracture reduction, the extent of ligament injuries, occult injuries, and the presence of degenerative arthritis in nonunions. Finally, evaluate scaphoid vascularity by placing a small joint arthroscope into base of the proximal pole after reaming.