Monday, February 10, 2020

Scaphoid Nonunion


Nonunion of the scaphoid could be an incidental finding after re-injury to the wrist. Risk fractures for nonunion include fractures with displacement more than 1mm, fractures that have inadequate treatment, fractures with instability, fractures that are displaced in a cast, proximal pole fractures, and delayed immobilization more than 4 weeks increases the rate of nonunion. An untreated scaphoid nonunion will have a high incidence of wrist arthritis. Early arthritis will start at five years. At 10 years, the patient will have significant arthritis. Arthritis will develop in stages: SNAC wrist (Scaphoid Nonunion Advanced Collapse). The three stages of arthritis: stage I arthritis is between the radial styloid and the scaphoid, stage II scaphocapitate arthritis in addition to stage I, and stage III periscaphoid arthritis including capitolunate arthritis. Scaphoid fractures that are left untreated will have carpal collapse and 100% development of degenerative arthritis. There is tendency for the fracture to gap open dorsally. Up to 35% of the patients have a humpback deformity and 40% have a DISI deformity. A CT scan along the scaphoid axis is the best test to check for nonunion of the scaphoid bone. Treat scaphoid fracture nonunion early (before 5 years) because the healing rate is much better. Correct the deformity and restore the scaphoid length and alignment. Use bone graft and do rigid internal fixation. Volar approach is used for waist fractures and fracture in the distal third of the scaphoid. You may want to remove the edge of the trapezium to place the screw in the volar approach. The humpback deformity is better corrected through the volar approach. The dorsal approach is better for proximal nonunion because of direct visualization of the nonunion. It helps reduction and also bone grafting can be done through the same incision from the distal radius if necessary. For a nonunion without AVN and no humpback deformity, do ORIF and bone graft or percutaneous technique. The Russe procedure is used for distal or waist fractures, patients with minimal deformity and no collapse, no excessive humpback deformity, and over 90% union rate. The dorsal approach can also be used for waist scaphoid fracture nonunion in addition to proximal nonunion. If the patient has a nonunion and no AVN, but there is a significant humpback deformity, there is a tendency of the fracture to pen dorsally. A significant number of patients will have a DISI deformity (there is association between a humpback deformity and DISI deformity). This patient will need an opening wedge interposition graft to restore the scaphoid length and alignment. The humpback deformity is best corrected from a volar approach (use interposition bone graft). Nonunion that is associated with AVN, but there is no humpback deformity, do ORIF and vascularized bone graft (1,2 ICSRA vascularized graft from the dorsal aspect of the distal radius). This technique can also be used for nonunion of the proximal pole. If the nonunion has an associated AVN and a major humpback deformity, because it is an AVN, you will use a vascularized graft, and because you have a humpback deformity, you will need a larger graft, so you will use a vascularized bone graft from the medial femoral condyle (use this technique if there is no arthritis, it utilizes the descending genicular artery pedicle). Punctate bleeding of bone during surgery may indicate good prognosis for healing of the nonunion. To treat a stage I SNAC wrist, do radial styloid excision plus bone graft for the nonunion. Do not remove more than 4mm of the radial styloid; avoid injury of the radioscaphocapitate ligament. To treat stage II & III SNAC wrist, do scaphoid excision and four corner fusion in younger patients; do proximal row carpectomy. Do not do proximal row carpectomy if the capitolunate joint is involved with arthritis. Preservation of the radioscaphocapitate ligament will prevent ulnar subluxation of the carpus (it is the primary stabilizer of the wrist following proximal row carpectomy). You can do arthrodesis for pancarpal arthritis.