Joseph E. Imbriglia and Justin M. Sacks
DEFINITION
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.
Initial treatment for a scaphoid nonunion is typically open reduction and internal fixation (ORIF) with bone graft, vascularized or unvascularized.
Despite appropriate internal fixation and bone grafting, failure rates of 15% have been documented.4
If internal fixation and bone grafting fails, the surgeon is then left with difficult choices:
Revision ORIF with bone grafting (failure rate of 50%)2
A salvage procedure with lower morbidity and a higher rate of satisfactory results
Currently, there are no acceptable prostheses available to replace the scaphoid.
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.3–5
ANATOMY
The carpus is divided into proximal (scaphoid, lunate, triquetrum, pisiform) and distal (trapezium, trapezoid, capitate, hamate) rows.
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).
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.
FIG 1 • Failed open reduction and internal fixation of a scaphoid nonunion (PA and lateral views).
FIG 2 • A. Volar intraosseous blood supply to the scaphoid with laterovolar and distal vessels visualized. B. Dorsal intraosseous blood supply to the scaphoid.
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.
The proximal pole is at risk secondary to its tenuous blood supply.7
PATHOGENESIS
Based on its retrograde pattern of blood supply, a more proximal fracture of the scaphoid will have an increased potential to form a nonunion.
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
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.
Arthritis first develops between the distal pole of the scaphoid and the radial styloid (scaphoid nonunion advanced collapse [SNAC] wrist stage I; FIG 3A).
The degenerative changes occur at this location due to the abnormal motion between the ununited distal scaphoid fragment and the radial styloid.
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 3B–D).
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).
FIG 4 • Chronic nonunion of the scaphoid with scaphoid nonunion advanced collapse (SNAC) in a patient with no previous treatment.
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
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.
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.
It is critical to know the patient's smoking history, occupation, and previous operations, as these will dictate future interventions.
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.
Measurements of grip strength and range of motion (ROM) need to be ascertained.
Strength is often decreased by as much as 30% to 40% if the patient is experiencing pain.
There will often be a decrease in extension and radial deviation of the wrist relative to the contralateral unaffected side.
Limited active ROM of the wrist can indicate carpal pathology.
Decreased grip strength in association with physical findings can indicate carpal pathology.
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
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.
The lateral plain radiograph allows one to determine the degree of dorsal intercalated segment instability (DISI) (FIG 5A).
If the radiographs reveal intercarpal arthritis (FIG 5B) or a small avascular proximal pole, partial scaphoid excision may be contraindicated.
If no radioscaphoid arthritis is observed, another procedure (eg, vascularized bone graft) to salvage the scaphoid might be considered.
MRI is helpful in evaluating the joint surfaces and the blood supply of the proximal scaphoid fragment.
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.
However, MRIs rarely change the decision to perform a distal pole excision, as plain radiographs most often give adequate and accurate information.
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
Scaphoid fracture
Scaphoid nonunion
Radioscaphoid arthritis
Midcarpal arthritis
Carpometacarpal arthritis
NONOPERATIVE MANAGEMENT
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.
The treatment of any painful joint begins with intermittent immobilization (wrist splinting), activity modification, and nonsteroidal anti-inflammatory medications (NSAIDs).
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.
During the nonoperative management period, the surgeon gains a perspective on the degree of patient discomfort and simultaneously gauges the patient's expectations.
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
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:
Open reduction and internal fixation (ORIF) combined with radial styloidectomy
Resection of the distal scaphoid fragment
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.
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.
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.
Contraindications to distal pole excision include:
Pre-existing significant DISI deformity. The DISI deformity may indeed get worse with distal pole excision in an individual with poor ligamentous support.
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
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.
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
The patient is placed in the supine position with application of a pneumatic tourniquet.
Approach
The distal pole of the scaphoid can be excised through either a dorsal or palmar approach. The approach may be dictated by existing scars.
The palmar approach is the preferred method due to the relatively accessible palmar position of the distal fragment.
An advantage of the dorsal approach is the ease of excision of the posterior interosseous nerve for wrist denervation.
A radial styloidectomy can be performed through either approach.
TECHNIQUES
VOLAR APPROACH TO DISTAL POLE OF SCAPHOID EXCISION
Incision and Scaphoid Excision
An incision is made directly over the flexor carpi radialis (FCR) tendon, incorporating any previous incisions (TECH FIG 1A,B).
The tendon is retracted ulnarly and the subsheath of the tendon incised longitudinally (TECH FIG 1C).
The radiocarpal joint capsule is opened longitudinally and the distal pole of the scaphoid is excised with osteotomies and rongeurs (TECH FIG 1D–G).
Radial Styloidectomy
If indicated, a radial styloidectomy can be performed at this point using an osteotome.
In this situation, the distal pole may be too large to excise and a radial styloidectomy can accomplish the same purpose.
The styloidectomy should be large enough so that the arthritic distal pole no longer touches the radius in radial deviation.
Wound Closure
The capsule and volar extrinsic ligaments are closed with interrupted absorbable 4-0 sutures.
The skin is closed with interrupted nonabsorbable 4-0 sutures.
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
An incision is made over the radial aspect of the carpus, incorporating any old incisions (TECH FIG 2).
The radial sensory nerve is identified and retracted.
The interval between the extensor pollicis longus and the radial wrist extensors is entered.
The radial artery and its branches are retracted and protected, and then the joint capsule is incised.
The distal scaphoid fragment will be deep and is best removed using rongeurs after defining its borders with a no. 15 blade.
A radial styloidectomy can be performed if necessary as mentioned above.
The capsule is closed with absorbable 4-0 suture.
The skin is closed with interrupted nonabsorbable 4-0 sutures.
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.
TECH FIG 2 • An incision over the dorsoradial aspect of the wrist may be used when prior surgery has been performed.
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.
POSTOPERATIVE CARE
Patients are immobilized for 2 weeks in a well-padded volar splint.
The splint and sutures are removed 2 weeks after the procedure.
A removable orthosis is applied and the patient is instructed on active and passive ROM exercises.
Once active and passive ROM has been achieved, strength exercises are started (usually at 4 weeks postoperatively).
Regaining full ROM and strength typically takes about 3 months.
Pain relief is noticeable within 2 to 4 weeks of surgery.
OUTCOMES
Review of outcomes in the literature suggest that both ROM and grip strength improve postoperatively.3–5
Pain relief can be expected if the proper indications for surgery are followed.
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
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
The presence of midcarpal arthritis undiagnosed before distal pole excision can lead to persistent pain.
Resection of too large a distal pole (more than two thirds) can result in collapse of the scaphoid.
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.