11 Limited Combined Approach for Scaphoid Nonunion
An unstable1 nonunion of the middle third of the scaphoid with collapse is commonly treated with a palmar opening-wedge bone graft to correct the shortened scaphoid and fixed using a retrograde (palmar) cannulated scaphoid screw fixation through a palmar (Russe type) incision.
A palmar approach may be arduous when dealing with a nonunion of the proximal pole because purchase of the screw in the proximal fragment cannot be assured. In this situation, the recommended treatment is cancellous bone grafting and antegrade (dorsal) cannulated screw fixation.2 – 7 It is, however, difficult to graft the palmar bone loss and restore normal scaphoid length when there is a humpback deformity of the scaphoid through a dorsal approach. Fortunately, this does not occur with a proximal pole nonunion.
There are situations that do not fit into this grouping and combine both: a small proximal pole and a palmar deficiency. This is seen, for example, in nonunions of the middle third following curettage of the nonviable bone and fibrous tissue, leaving an empty proximal pole (scooped-out scaphoid). Similarly erosion of the volar cortex of the scaphoid is not uncommon with nonunions of the junction of the proximal and middle third (junctional nonunion)8 ( Figs. 11.1 and 11.2 ). In these scenarios optimal results cannot be achieved by standard methods ( Fig. 11.3 ) because if the palmar approach is used, there is a high risk of poor fixation of the proximal fragment, or the screw threads may cross the fracture line. Additionally, a considerable amount of dissection of the palmar radiocarpal ligaments is required, which may cause iatrogenic carpal instability.9 However, if the dorsal route only is used, the deficiency of the palmar aspect of the scaphoid remains uncorrected, leading to carpal collapse and a humpback scaphoid malunion with its attendant problems.10
To correct the palmar deficiency of the scaphoid and, at the same time, achieve rigid fixation, a limited combined approach has been proposed.8 First, a palmar incision is made, preserving the long radiolunate and most of the radioscaphocapitate ligament, and an interpositional bone graft from the iliac crest is inserted to restore scaphoid length. The construct is then stabilized with an antegrade cannulated screw inserted through a limited dorsal or percutaneous approach ( Fig. 11.3 ).
A combined approach is indicated in cases where there is a small proximal fragment that is best stabilized through dorsal screw fixation combined with a palmar bone loss, which requires a volar wedge graft to restore scaphoid length.
A fragmented or avascular proximal pole is a contraindication to this technique.
▪ Surgical Technique
The limited combined approach is similar to the standard palmar and dorsal approaches, but the incisions and dissection are smaller ( Fig. 11.4 ). The wrist capsule is divided on the radial side of the flexor carpi radialis tendon through a 2.5 to 3.0 cm incision. The wrist is placed in maximal ulnar deviation and dorsiflexion and the scaphotrapezial joint is identified with a needle to avoid violating it. While the assistant distracts the thumb with longitudinal traction, the nonunion is located with the tip of the scissors.
A small part of the radioscaphocapitate ligament is sectioned to visualize the nonunion site. The nonunion is debrided without using power tools, but if the bone within the proximal fragment is considered to be sclerotic, multiple 1 mm holes are made with a power-driven Kirschner wire (K-wire). This in general produces an even transverse distal portion and a somewhat hollowed-out proximal fragment.
At this moment, the flexion deformity is corrected by using a lamina spreader to open the nonunion site ( Fig. 11.5 ), and the largest wedge-shaped bone graft from the iliac crest that will fit is inserted. Appropriate restoration of the scaphoid length is checked by fluoroscopy. A K-wire is inserted from the distal pole maintaining the reduction of the construct and to prevent extrusion of the graft during wrist flexion in the following step.
Next a dorsal approach is used for screw insertion. ( Fig. 11.6 ). A 1.5 to 2.0 cm transverse incision is made centered over, but slightly distal to, the Lister tubercle. Only the most distal part of the extensor retinaculum, in line with the Lister tubercle, requires division. The extensor pollicis longus is retracted radially and the finger extensors ulnarly. A transverse capsular incision is made to expose the proximal pole of the scaphoid and the scapholunate ligament. Throughout this part of the procedure the wrist is flexed to bring the proximal row into view and minimize the dissection. A 1.0 mm K-wire is inserted down the central axis of the scaphoid starting at the apex of the proximal pole, near the insertion of the scapholunate ligament, which ensures that the proximal screw threads will engage the small proximal fragment. Fluoroscopy is used at this stage to confirm the K-wire position. Once it is acceptable a cannulated screw is inserted down the wire in an antegrade manner. Image intensification is again used to recheck the position of the screw before final tightening, until the trailing head becomes buried beneath the articular surface of the proximal pole. The palmar K-wire, which was holding the construct and preventing rotation of the fragments during screw insertion, is now removed. We presently attempt to insert the screw percutaneously to minimize the soft tissue dissection, but this technique is more demanding and requires central placement of the K-wire before it is attempted ( Fig. 11.7 ). If any undue difficulty is found during the insertion of the guide wire or the surgeon is unsure about its location on the scaphoid, a mini-open approach is used as described earlier.
The skin is closed with a subcuticular suture without attempting to close the capsule or any other deep structure. After surgery, the arm is maintained for 6 weeks in a short-arm thumb spica cast. After this period the patients are then allowed to use their wrist and hands for light activities, wearing a removable palmar splint for a further 2 weeks or until they feel confident without it.