Salvage procedures for scaphoid nonunion

Indications

• Proximal row carpectomy (PRC) and scaphoidectomy with four-corner fusion (4CF) are motion-preserving salvage operations for patients with proximal wrist degeneration or advanced ligamentous injury.

  • There are variations on the 4CF involving different intercarpal (two bone, three bone) fusions; however, the only “partial wrist fusion” technique we will discuss in this chapter is the traditional 4CF.

• Examples of pathology or surgical diagnoses include:

  • Static scapholunate instability

  • Scaphoid nonunion advanced collapse (SNAC), stage 1 or mild stage 2

  • Scapholunate advanced collapse (SLAC), stage 1 or 2

  • Kienbock, stage 3b or 4

• Indications for PRC and 4CF are similar, but the midcarpal joint must be preserved (most notably the capitate articular surface) for PRC.

• Compared with 4CF, PRC does not require hardware or osseous union.

• The option for total wrist arthrodesis is preserved with either procedure.

• In elderly, low-demand patients, nonoperative management with splinting and nonsteroidal antiinflammatory drugs (NSAIDs) should be attempted even for advanced degenerative changes. Surgery is reserved for failure of nonsurgical management and intractable pain.

• For the younger, higher-demand patient, some believe that surgery may prevent further progression of arthritis.

Clinical examination

• A thorough wrist examination is necessary, including range of motion, locations of point tenderness, and any soft-tissue abnormalities.

• The wrist should be examined dorsally and volarly with direct palpation over bone intervals to identify pain and inflammation.

• Check for tendon excursion because the overall kinematics at the wrist can change with shortening.

• A predictable pattern of wrist arthritis develops with untreated scaphoid nonunion or static scapholunate instability, termed scaphoid nonunion advanced collapse (SNAC) and scapholunate advanced collapse (SLAC), respectively ( Fig. 27.1 ).

  • Degenerative changes of the radioscaphoid articulation are common because of the incongruent shape of the scaphoid fossa on the scaphoid with positional change and uneven loading. The lunate fossa is resistant to degenerative change because of the spherical shape that remains congruent with loading in all positions of the wrist.

  • Patients are often seen for persistent wrist pain, and the diagnosis is confirmed radiographically or arthroscopically.

  

• With stage III SNAC or SLAC arthritis, partial wrist fusion/4CF is preferred over a proximal row carpectomy (PRC) because the capitolunate articulation has been affected. Removal of the proximal row will result in contact of the arthritic capitate on the lunate fossa of the radius and will lead to continued pain.

Imaging

• Standard PA, oblique, and lateral x-rays of the wrist should be obtained ( Fig. 27.2A–C ). These views are often sufficient for diagnosing wrist arthritis and confirming whether or not the capitolunate or radiolunate articulations are affected.

  

• Ulnar translation of the carpus suggests that the palmar extrinsic wrist ligaments are stretched and may not reliably support PRC.

• Advanced imaging such as computed tomography (CT) can be used to determine the status of the midcarpal joint; however, most surgeons do not find this necessary.

• Arthroscopy is the reference standard for diagnosing and characterizing the degree of wrist articular wear and can be used to guide the treatment algorithm if x-rays are unclear; however, patients are made aware preoperatively that an intra-operative decision to convert to a limited wrist fusion can be made if there is excessive, unrecognized midcarpal joint degenerative change.

Surgical anatomy

• The volar extrinsic ligaments (radioscaphocapitate, short and long radiolunate) originate from the volar radius and extend obliquely to the carpus. These should be left intact. Attenuation, insufficiency, or iatrogenic injury may lead to ulnar translation and instability, especially after PRC ( Fig. 27.3 ).

  

• The dorsal ligaments of the wrist—dorsal radiocarpal (DRC) and dorsal intercarpal (DIC) have a conjoined insertion on the triquetrum. They provide the capsulotomy landmarks for ligament-sparing wrist exposure ( Fig. 27.4 ).

  

• The posterior interosseous nerve can be found on the floor of the fourth dorsal compartment. Distal neurectomy at the wrist can be performed to aid in postoperative pain control.

Exposures

• A longitudinal, 6-cm incision is centered over the third metacarpal, just ulnar to the Lister tubercle ( Figs. 27.5 and 27.6 ). Flaps are elevated sharply at the level of the extensor retinaculum, with care taken to not injure the dorsal sensory nerves.

  
  

• Dissection is carried out to the extensor retinaculum and the extensor pollicis longus (EPL) is identified within its third dorsal compartment.

• An incision is made between the second and fourth dorsal compartments and the EPL is transposed radially.

• If wider exposure is needed, especially for 4CF, elevate retinacular flaps radially and ulnarly, through the intercompartmental septae for the second through fifth dorsal compartments. This exposes the contents of these compartments but keeps the dorsal retinaculum intact as a “roof” that can be repaired later.

• The wrist can be entered in two different ways:

  • Continuing the longitudinal incision through the dorsal wrist capsule exposes the proximal carpal row ( Fig. 27.7 ).

    

  • For a “ligament-sparing approach,” a radially based dorsal capsular flap is designed over the proximal carpal row. This is then incised along the DIC and DRC ligaments ( Fig. 27.8A–B ).

    

• Once the wrist is exposed, inspect the capitolunate and radiolunate articulations to confirm which procedure is appropriate.

Four-corner fusion with circular plate

Step 3: Stabilize the remaining carpal bones

After confirming neutral reduction of the lunate, the remaining carpal bones can be held in alignment using additional 0.045-inch (1.45-mm) K-wires ( Fig. 27.12 ).

STEP 3 PEARLS

The K-wires should be positioned volarly within the carpal bones to avoid interfering with the reamer.

Step 4: Ream the carpal bones in preparation for plate placement

The reamer is centered over the four carpal bones, and the dorsal surface is reamed until the dorsal surfaces of the carpal bones lie within the two lines on the reamer ( Figs. 27.13 and 27.14 ).

STEP 4 PITFALLS

Reaming must be deep enough to permit placement of the entire circular plate beneath the dorsal cortices of the carpal bones. Failure to do so may result in impingement of the plate on the distal radius.