Operative Techniques in Orthopaedic Surgery (4 Volume Set) 1st Edition

263. Partial Scaphoid Excision of Scaphoid Nonunions

Joseph E. Imbriglia and Justin M. Sacks

DEFINITION

images The scaphoid is the most frequently fractured bone in the carpus. In acute fractures, appropriate treatment yields union rates greater than 90%.1 However, without proper diagnosis and treatment scaphoid fractures frequently result in nonunion.

images Initial treatment for a scaphoid nonunion is typically open reduction and internal fixation (ORIF) with bone graft, vascularized or unvascularized.

images Despite appropriate internal fixation and bone grafting, failure rates of 15% have been documented.4

images If internal fixation and bone grafting fails, the surgeon is then left with difficult choices:

images Revision ORIF with bone grafting (failure rate of 50%)2

images A salvage procedure with lower morbidity and a higher rate of satisfactory results

images Currently, there are no acceptable prostheses available to replace the scaphoid.

images When the index treatment or procedure has failed and the patient has persistent pain caused by a chronic scaphoid nonunion (FIG 1) with posttraumatic arthritis limited to the distal pole of the scaphoid and radius, partial scaphoid excision (distal fragment) provides a reasonable, low-morbidity alternative treatment option.35

ANATOMY

images The carpus is divided into proximal (scaphoid, lunate, triquetrum, pisiform) and distal (trapezium, trapezoid, capitate, hamate) rows.

images The scaphoid bone represents the bridge between these two rows. Largely covered by articular cartilage, it has important intrinsic and extrinsic ligamentous attachments (radioscaphocapitate, long radiolunate, scapholunate, and scaphotrapezialtrapezoid). In its precarious position as an intercalated rod between the proximal and distal carpal row, the scaphoid is at mechanical risk for fracture when an abnormal stress is applied (eg, forced dorsiflexion).

images After a fracture of the scaphoid, the vascular anatomy specific to this bone contributes to problems in bone healing.7 Taleisnik and Kelly describe three groups of vessels responsible for scaphoid blood supply: laterovolar, dorsal, and distal vessels (FIG 2). The laterovolar vessels are the main contributors to the intraosseous blood supply.

images

FIG 1 • Failed open reduction and internal fixation of a scaphoid nonunion (PA and lateral views).

images

FIG 2 • A. Volar intraosseous blood supply to the scaphoid with laterovolar and distal vessels visualized. B. Dorsal intraosseous blood supply to the scaphoid.

images Variations exist in the exact number and locations of the volar vessels entering the scaphoid, but in all studies the most significant vessels enter the scaphoid distal to its waist.

images The proximal pole is at risk secondary to its tenuous blood supply.7

PATHOGENESIS

images Based on its retrograde pattern of blood supply, a more proximal fracture of the scaphoid will have an increased potential to form a nonunion.

images Patients with scaphoid fractures who present with delays in both diagnosis and treatment can develop a nonunion. In addition, patients with comminution, displacement, or improper immobilization of the scaphoid fracture can develop nonunions.

NATURAL HISTORY

images A scaphoid nonunion leads to the development of posttraumatic arthritis in the region of the radioscaphoid joint. How quickly this arthritis develops and progresses varies, but most patients will show radiographic evidence of degenerative changes within 5 to 10 years of their nonunion.

images Arthritis first develops between the distal pole of the scaphoid and the radial styloid (scaphoid nonunion advanced collapse [SNAC] wrist stage I; FIG 3A).

images The degenerative changes occur at this location due to the abnormal motion between the ununited distal scaphoid fragment and the radial styloid.

images Left untreated, stage I SNAC will progress to involve the entire radioscaphoid articulation (SNAC stage II) and eventually diffuse arthritis of the wrist (SNAC stages III and IV) (FIG 3BD).

images

FIG 3 • A. Arthritis observed between the distal pole of the scaphoid and the radial styloid (scaphoid nonunion advanced collapse [SNAC] grade I). B–D. Stage I SNAC can progress to involve the entire radioscaphoid articulation (SNAC grade II) with eventual diffuse arthritis of the wrist (SNAC grade III and IV).

images

FIG 4 • Chronic nonunion of the scaphoid with scaphoid nonunion advanced collapse (SNAC) in a patient with no previous treatment.

images Patients sometimes do not seek medical care until pain and decreased range of motion in the wrist become increasingly severe. In these cases, initial radiographic studies reveal a scaphoid nonunion and associated arthritis.

PATIENT HISTORY AND PHYSICAL FINDINGS

images Most patients are young to middle-aged men who sustained a dorsiflexion injury to their involved wrist. Some patients will present with no previous treatment and a chronic nonunion (FIG 4), and some will have failed to respond to either operative or nonoperative therapy.

images Pain aggravated by motion and use, loss of motion, and loss of grip strength, all slowly worsening over the preceding years, are consistent presenting complaints.

images It is critical to know the patient's smoking history, occupation, and previous operations, as these will dictate future interventions.

images The examiner should palpate the anatomic snuffbox, which lies on the dorsum of the wrist between the extensor pollicis longus and extensor pollicis brevis tendons. Pain in this region is indicative of a fracture.

images Measurements of grip strength and range of motion (ROM) need to be ascertained.

images Strength is often decreased by as much as 30% to 40% if the patient is experiencing pain.

images There will often be a decrease in extension and radial deviation of the wrist relative to the contralateral unaffected side.

images Limited active ROM of the wrist can indicate carpal pathology.

images Decreased grip strength in association with physical findings can indicate carpal pathology.

images During palmar flexion the examiner may notice both a fullness and a hard bone excrescence on the dorsal radial aspect of the wrist. This fullness is secondary to synovitis and the hard excrescence is the result of the hypertrophic distal pole of the scaphoid.

IMAGING AND OTHER DIAGNOSTIC STUDIES

images We routinely order true posteroanterior (PA), lateral, and ulnar and radial deviation views of the wrist. These views assist in determining whether a partial scaphoid excision is indicated.

images The lateral plain radiograph allows one to determine the degree of dorsal intercalated segment instability (DISI) (FIG 5A).

images If the radiographs reveal intercarpal arthritis (FIG 5B) or a small avascular proximal pole, partial scaphoid excision may be contraindicated.

images If no radioscaphoid arthritis is observed, another procedure (eg, vascularized bone graft) to salvage the scaphoid might be considered.

images MRI is helpful in evaluating the joint surfaces and the blood supply of the proximal scaphoid fragment.

images

FIG 5 • A. Lateral plain radiograph displaying a dorsal intercalated segment instability (DISI) deformity. B. When intercarpal arthritis (SNAC grade III or IV) or an avascular proximal pole are found, partial scaphoid excision may be contraindicated.

images However, MRIs rarely change the decision to perform a distal pole excision, as plain radiographs most often give adequate and accurate information.

images From a radiographic perspective, the ideal candidate for distal pole excision of the scaphoid has a nonunion of the scaphoid fracture in the midwaist or distal pole with concomitant degenerative joint disease between the distal radius and distal pole only.

DIFFERENTIAL DIAGNOSIS

images Scaphoid fracture

images Scaphoid nonunion

images Radioscaphoid arthritis

images Midcarpal arthritis

images Carpometacarpal arthritis

NONOPERATIVE MANAGEMENT

images Nonoperative management of chronic wrist pain should be considered before any surgical intervention. Chronic wrist pain is never an emergency and simple noninvasive techniques can be used to control pain.

images The treatment of any painful joint begins with intermittent immobilization (wrist splinting), activity modification, and nonsteroidal anti-inflammatory medications (NSAIDs).

images If immobilization and NSAIDs are ineffective, temporary pain relief can almost always be gained with a steroid injection. These temporizing treatments also put the pain in perspective for the patient. The patient may conclude that medication and splinting is all that is necessary.

images During the nonoperative management period, the surgeon gains a perspective on the degree of patient discomfort and simultaneously gauges the patient's expectations.

images The operation will work better and the patient will be more satisfied if the patient's expectations and surgeon's expectations are similar.

SURGICAL MANAGEMENT

images Surgical options to treat persistent pain resulting in compromised function in a patient with a scaphoid nonunion and arthritis limited to the area between the distal fragment of the scaphoid and the radial styloid (stage I SNAC wrist arthritis) include:

images Open reduction and internal fixation (ORIF) combined with radial styloidectomy

images Resection of the distal scaphoid fragment

images A patient with an untreated scaphoid nonunion and no arthritis most often has ORIF of the scaphoid with bone grafting as the initial procedure. In a patient with SNAC wrist grade II, it is too late for distal pole excision; this patient may require a proximal row carpectomy or scaphoid excision with intercarpal fusion.

images Most patients requiring excision of the distal pole have undergone prior treatment that has failed and both the surgeon and the patient are searching for a reliable procedure with low morbidity to help alleviate the patient's pain and augment function.

images Distal scaphoid excision requires that the robust and taut radioscaphoid and long radiolunate ligaments exist to support the remaining proximal carpus and prevent collapse (dorsal intercalated segment instability [DISI]) of the wrist.

images Contraindications to distal pole excision include:

images Pre-existing significant DISI deformity. The DISI deformity may indeed get worse with distal pole excision in an individual with poor ligamentous support.

images Proximal pole that is less than half the entire size of the scaphoid. If the distal fragment is greater than 50% of the size of the scaphoid, resultant collapse of the carpus may occur with severe morbidity.

Preoperative Planning

images Before deciding if distal pole excision of the scaphoid is a reasonable choice, radiographs or other images (eg, CT or MRI) must be carefully reviewed.

images If the distal pole is to be excised, there must be enough proximal pole left to support the capitate and the remainder of the carpus. At least one third of the scaphoid must remain. If only a very small (and possibly an avascular) proximal pole remains, the carpus is likely to collapse, resulting in failure of the procedure.

Positioning

images The patient is placed in the supine position with application of a pneumatic tourniquet.

Approach

images The distal pole of the scaphoid can be excised through either a dorsal or palmar approach. The approach may be dictated by existing scars.

images The palmar approach is the preferred method due to the relatively accessible palmar position of the distal fragment.

images An advantage of the dorsal approach is the ease of excision of the posterior interosseous nerve for wrist denervation.

images A radial styloidectomy can be performed through either approach.

TECHNIQUES

VOLAR APPROACH TO DISTAL POLE OF SCAPHOID EXCISION

Incision and Scaphoid Excision

images An incision is made directly over the flexor carpi radialis (FCR) tendon, incorporating any previous incisions (TECH FIG 1A,B).

images The tendon is retracted ulnarly and the subsheath of the tendon incised longitudinally (TECH FIG 1C).

images The radiocarpal joint capsule is opened longitudinally and the distal pole of the scaphoid is excised with osteotomies and rongeurs (TECH FIG 1DG).

Radial Styloidectomy

images If indicated, a radial styloidectomy can be performed at this point using an osteotome.

images In this situation, the distal pole may be too large to excise and a radial styloidectomy can accomplish the same purpose.

images The styloidectomy should be large enough so that the arthritic distal pole no longer touches the radius in radial deviation.

Wound Closure

images The capsule and volar extrinsic ligaments are closed with interrupted absorbable 4-0 sutures.

images The skin is closed with interrupted nonabsorbable 4-0 sutures.

images

TECH FIG 1 • A. Chronic scaphoid nonunion with scaphoid nonunion advanced collapse (SNAC). The patient had no previous treatment. B. An incision is made directly over the flexor carpi radialis (FCR) tendon. C. The tendon is retracted and its subsheath opened longitudinally. D. The radiocarpal joint is opened longitudinally and the scaphoid is visualized. E,F. The distal pole of the scaphoid is excised with osteotomies and rongeurs. If indicated, a radial styloidectomy can be performed at this point. G. Excised distal pole of the scaphoid.

DORSAL APPROACH TO DISTAL POLE OF SCAPHOID EXCISION

images An incision is made over the radial aspect of the carpus, incorporating any old incisions (TECH FIG 2).

images The radial sensory nerve is identified and retracted.

images The interval between the extensor pollicis longus and the radial wrist extensors is entered.

images The radial artery and its branches are retracted and protected, and then the joint capsule is incised.

images The distal scaphoid fragment will be deep and is best removed using rongeurs after defining its borders with a no. 15 blade.

images A radial styloidectomy can be performed if necessary as mentioned above.

images The capsule is closed with absorbable 4-0 suture.

images The skin is closed with interrupted nonabsorbable 4-0 sutures.

images The patient is placed in a well-padded forearm-based splint, leaving the finger metacarpophalangeal joints and thumb interphalangeal joint free. This volar splint is placed after either the volar or dorsal approach.

images

TECH FIG 2 • An incision over the dorsoradial aspect of the wrist may be used when prior surgery has been performed.

images

FIG 6 • A,B. Scaphoid nonunion after pevious internal fixation with development of SNAC wrist arthritis. C,D. Collapse of the scaphoid resulting from too much resection (more than two thirds) of the distal pole of the scaphoid, with evidence of dorsal intercalated segment instability (DISI) deformity on postoperative radiographs.

images

POSTOPERATIVE CARE

images Patients are immobilized for 2 weeks in a well-padded volar splint.

images The splint and sutures are removed 2 weeks after the procedure.

images A removable orthosis is applied and the patient is instructed on active and passive ROM exercises.

images Once active and passive ROM has been achieved, strength exercises are started (usually at 4 weeks postoperatively).

images Regaining full ROM and strength typically takes about 3 months.

images Pain relief is noticeable within 2 to 4 weeks of surgery.

OUTCOMES

images Review of outcomes in the literature suggest that both ROM and grip strength improve postoperatively.35

images Pain relief can be expected if the proper indications for surgery are followed.

images All patients have some degree of DISI preoperatively, and this pattern of deformity may worsen after excision of the distal pole of the scaphoid. DISI deformities that are severe can result in both loss of motion and pain. This problem is not well documented in the literature but certainly exists.5

images In the patient undergoing multiple procedures, outcomes of distal pole excision are better than attempting another bone graft and internal fixation, where the failure rate can approach 50%.1

COMPLICATIONS

images The presence of midcarpal arthritis undiagnosed before distal pole excision can lead to persistent pain.

images Resection of too large a distal pole (more than two thirds) can result in collapse of the scaphoid.

images If the procedure is performed in a very loose-jointed individual, the DISI pattern may significantly worsen, leading to persistent pain.

REFERENCES

1.     Bishop AT. Vascularized bone grafts. In Green DG, Hotchkiss R, Pederson W, eds. Green's Operative Hand Surgery. New York: Churchill Livingstone, 1999.

2.     Chang MA, Bishop AT, Moran SL, et al. The outcomes and complications of 1,2 intercompartmental supraretinacular artery pedicled vascularized bone grafting of scaphoid nonunions. J Hand Surg Am 2006;31A:387–396.

3.     Drac P, Manak P, Pieranova L. Distal scaphoid resection arthroplasty for scaphoid nonunion with radioscaphoid arthritis. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub 2006;150:143–145.

4.     Malerich MM, Clifford J, Eaton B, et al. Distal scaphoid resection arthroplasty for the treatment of degenerative arthritis secondary to scaphoid nonunion. J Hand Surg Am 1999;24A:1196–1205.

5.     Ruch DS, Papadonikolakis A. Resection of the scaphoid distal pole for symptomatic scaphoid nonunion after failed previous surgical treatment. J Hand Surg Am 2006;31A:588–593.

6.     Smith BS, Cooney WP. Revision of failed bone grafting for nonunion of the scaphoid: treatment options and results. Clin Orthop Relat Res 1996;327:98–109.

7.     Taleisnik J, Kelly PJ. The extraosseous and intraosseous blood supply of the scaphoid bone. J Bone Joint Surg Am 1966;48A:1125.



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