11 Limited Combined Approach for Scaphoid Nonunion


11 Limited Combined Approach for Scaphoid Nonunion

Piñal, Francisco del, García Bernal, Francisco J.

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 ).

Fig. 11.1 The scooped-out scaphoid as shown by (A) a plain radiograph, (B) sagittal computed tomography (scaphoid level), and (C) sagittal magnetic resonance imaging (lunate level). (From del Piñal F. Treatment of non-union of the scaphoid by a limited combined approach. J Bone Joint Surg Br 2001;83B:78–82. With permission of the The British Editorial Society of Bone and Joint Surgery.)
Fig. 11.2 Junctional nonunion as shown by (A) a plain radiograph and (B) coronal and (C) sagittal magnetic resonance imaging. (From del Piñal F. Treatment of non-union of the scaphoid by a limited combined approach. J Bone Joint Surg Br 2001;83B:78–82. With permission of the The British Editorial Society of Bone and Joint Surgery.)
Fig. 11.3 Diagram showing the deformities and the theoretical results depending on the route selected for treatment. (A) Scooped-out scaphoid. (B) Junctional nonunion. (C) The palmar approach for A or B requires violation of the scaphotrapezial joint (1) and sectioning of the radioscaphocapitate and long radiolunate ligaments (2). Difficulties of purchase are highlighted (3). POWG, palmar opening wedge graft. (D) Treatment of A or B by the dorsal route leaves a dorsal intercalated segmental instability deformity. (E,F) Correction of the deformity and rigid fixation by the limited combined approach. (From del Piñal F. Treatment of non-union of the scaphoid by a limited combined approach. J Bone Joint Surg Br 2001;83B:78–82. With permission of the The British Editorial Society of Bone and Joint Surgery.)

▪ Indications

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.

▪ Contraindications

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.

Fig. 11.4 (A) Photographs showing an intraoperative palmar view before and (B) after insertion of the bone graft (G). Most of the radioscaphocapitate ligament (*) is preserved. The outlines of the scaphoid have been defined. (C) Inset: the corresponding panoramic view.
Fig. 11.5 The lamina spreader is separating the distal and proximal poles maximally. This maneuver corrects the humpback deformity.

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.

Fig. 11.6 (A) The intraoperative dorsal view while the Herbert screw is being tightened. Notice that the entrance points of these are within the scapholunate interosseous membrane (*) Inset: the corresponding panoramic view. (B) Artistic representation to highlight the importance of invading with the Kirschner wire the scapholunate ligament in order to ensure that the trailing part is completely contained within the proximal pole. (C) Otherwise the threads may pass into the bone graft, providing a less stable biomechanical construct. ([6A] from del Piñal F. Treatment of non-union of the scaphoid by a limited combined approach. J Bone Joint Surg Br 2001;83B:78–82. With permission of the The British Editorial Society of Bone and Joint Surgery.)
Fig. 11.7 Technique of percutaneous screw insertion for the limited combined approach (left column intraoperative and right column corresponding fluoroscopic view). (A,B) The graft is maintained in a reduced position by the volar K-wire (1), while the second guide wire (2) is introduced dorsally, with the wrist in maximal flexion following the central axis of the scaphoid. (C,D) When introducing the drill, the surgeon stabilizes the soft tissue with the thumb to avoid entanglement and the index finger to avoid volar graft extrusion. Resistance to drill insertion is suspicious for a loss of direction, which should be checked fluoroscopically, because of the risk of cutting the guide wire inside the scaphoid with the drill (a major disaster). (E,F) Prior to retrieving the needle (1), the cannulated screw is fully inserted, except the last turn is done with the reducing K-wire (1) removed to allow final compression.

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.

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Jul 12, 2020 | Posted by in ORTHOPEDIC | Comments Off on 11 Limited Combined Approach for Scaphoid Nonunion

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