Arthroscopic partial wrist fusions

Introduction

The most common indications for a partial wrist fusion include scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC) patterns. Other conditions include Kienböck disease, radiocarpal joint arthrosis secondary to a malunited distal radius fracture (DRF), and scaphotrapeziotrapezoidal (STT) osteoarthritis (OA). The pathophysiology of these conditions has been discussed in previous chapters. A variety of partial wrist fusions can be performed depending on the specific pathology and the joints that are involved. Chronic painful carpal instabilities with or without secondary degenerative changes are additional indications, including palmar midcarpal instability (PMCI) and ulnar translocation. There is a steep learning curve for performing these types of procedures arthroscopically with operative times of up to 4 hours. This is partly due to the lack of dedicated arthroscopic instrumentation needed for carpal bone resection. Miniarthrotomy incisions can help reduce the tourniquet time significantly by allowing the use of rongeurs for removal of carpal bone remnants. Fixation is typically performed using percutaneous headless screws and/or K-wires, which requires postoperative cast immobilization in many cases. Contraindications include conditions that preclude reduction of carpal malalignment such as severe arthrofibrosis, joint contractures, longstanding carpal collapse deformities, and sepsis.

Instrumentation and methodology

Every type of fusion has common features that require a similar setup. A 2.7-mm 30-degree angled arthroscope with a camera attachment, traction tower, arthroscopic burrs ranging from 3.0 mm to 3.5 mm, a 4-mm shoulder abrader, 2.0-mm and 2.5-mm full-radius resectors, and a variety of arthroscopic forceps, small curettes, and straight and angled rongeurs. A diathermy probe may also be of use for debridement. A K-wire driver and 3.0-mm and 3.5-mm headless cannulated screws are requisite. Bone graft substitutes including cancellous allograft and demineralized bone matrix should be available. A minifluoroscopy unit or C-arm is integral to the procedure.

The patient is positioned supine on the operating table with the arm abducted 90 degrees on an arm table and suspended in a traction tower with 10 to 15 pounds of traction. Either general anesthesia and/or a regional block are used due to the long operative times. A tourniquet is placed on the upper arm and inflated to 250 mm Hg. It is useful to start the procedure under portal site local anesthesia as described by Ong et al., using 0.25% bupivacaine hydrochloride injection and 1:200,000 units of epinephrine to conserve the tourniquet time. The procedure can be alternated between saline irrigation using a pressure bag or pump, and dry arthroscopy as described by Del Pinal et al. Rather than using an outflow portal, it is my preference to use intermittent fluid irrigation through the arthroscope while using the full-radius resector and/or arthroscopic burr for intermittent suction. Debridement is simpler and faster without fluid irrigation to prevent the synovial fronds and fibrous tissue from floating in front of the arthroscope and obstructing the view. Similarly, any residual articular cartilage can be removed with intermittent irrigation. Fluid irrigation is often needed during the bony resection to keep down the joint temperature and to clear the debris.

A quick joint survey can be performed using the standard dorsal portals including the 3,4, 4,5, midcarpal radial (MCR), and midcarpal ulnar (MCU) portals. Special-use portals are used as an aid to bony resection and can include the STT, the triquetrohamate (TH), the volar radial (VR) and volar ulnar (VU), and the volar central portals.

The specific articular surfaces that are to be fused are then decorticated using a 2.9-mm arthroscopic burr. It is easier to decorticate the articulations that will be fused before performing any carpal bone resection, because the distorted anatomy and residual carpal instability make this step more difficult. Any residual articular cartilage is removed and the subchondral bone is resected to a bleeding cancellous surface while maintaining the joint congruity.

Next the carpal deformity is corrected using K-wires as joysticks and the fusion site is provisionally held with K-wires. The cancellous autograft or bone graft substitute is then inserted through a 4- to 5-mm arthroscopic cannula in the appropriate portal and used to fill any voids. If the final fixation is performed using headless cannulated screws, the traction is released before screw insertion.

Arthroscopic-assisted capitolunate fusion and scaphoidectomy