▪ Pathophysiology

The scaphoid is almost entirely covered by hyaline articular cartilage, and the blood supply enters distally through dorsal and palmar ligamentous attachments. The proximal pole is supplied in a retrograde fashion through a dorsal branch of the radial artery.14 The dorsal vessels are dominant, supplying up to 80% of the scaphoid. The volar blood supply accounts for only 20 to 30% of the scaphoid’s internal vascularity and primarily supplies the distal portion.14 There is little collateral circulation within the scaphoid, and much of the bone is dependent on a single nutrient vessel.14 ^, 16 Thus injury to the nutrient artery through trauma or infarction could lead to ischemia throughout the scaphoid, predisposing it to the development of osteonecrosis.

It has been hypothesized that the dominant dorsal vessel is exposed to compression and injury with moderate wrist flexion. Buttermann et al showed that significant pressure occurs at the dorsal scaphoid ridge at the point of vessel entry into the scaphoid during wrist extension due to contact from the radial wrist extensors.13 The highest pressures occurred with 60 to 90 degrees of flexion and 15 degrees of ulnar deviation. The authors speculate that wrist loading in the flexed position may result in swelling and inflammation in the region, potentially affecting scaphoid perfusion.13 This mechanism has yet to be demonstrated clinically.

Disruption of the blood supply can lead to osteonecrosis. The process of osteonecrosis has been identified in many different bones and has been generally classified into four different phases: (1) the avascular phase, (2) the revascularization phase, (3) the repair phase, and (4) the deformity phase. The avascular phase begins after infarction of the bone. The overlying cartilage hypertrophies in an attempt to heal by enchondral ossification. Radiographic changes in this phase are often minimal. Osteopenia may be seen as a result of the inflammatory response and resultant osteoclast activation. The revascularization phase is characterized by increased osteoblast and osteoclast activity. Radiographs demonstrate areas of lucency and sclerosis. Necrosis of cortical and subchondral bone can lead to fragmentation and collapse. The repair phase begins with revascularization and is characterized by bony healing.17 ^, 18 The degree of bone healing is dependent on the severity of the initial insult and degree of bone loss, the patient’s healing response, and any ongoing repetitive load or trauma seen by the scaphoid during the healing process. Failure to heal the defect can result in further fragmentation, collapse, and arthrosis.

▪ Patient Presentation and Diagnosis

Patients will typically present with complaints of radialsided wrist pain localizing to the anatomical snuffbox and dorsal wrist.19 ^– 21 Examination may reveal synovitis and scaphoid tenderness over the anatomical snuffbox. Restricted range of motion and decreased grip strength may also be present.19 However, the diagnosis may be elusive in its early stages because radiographs may be read as normal, and patients may have preservation of functional wrist motion.22

Patients with persistent pain, which is consistently localized to the snuffbox, should undergo magnetic resonance imaging (MRI) of the wrist if plain radiographs are negative. MRI with gadolinium contrast will help establish the diagnosis and the degree of scaphoid involvement.20 Although MRI is not yet capable of directly accessing bone vascularity; normal marrow elements produce high-intensity signals on T1-weighted images. Avascularity or marrow edema will lead to alterations in these signals ( Fig. 32.1 ).23 ^, 24

▪ Radiographic Classification

Once the diagnosis has been made, radiographic classification of the disease should be performed because it may have relevance to the patient’s expected outcome.20 ^, 25 ^, 26 Herbert and Lanzetta initially classified Preiser disease into four stages based on radiographic appearance19 ( Table 32.1 ). Type I disease describes patients that present with normal radiographs but an abnormal bone scan or abnormalities within the scaphoid on MRI ( Fig. 32.1 ). Stage II disease reveals increased proximal pole density with generalized osteopenia. Stage III disease shows fragmentation of the proximal pole with or without pathological fracture. Stage IV disease shows evidence of carpal collapse and osteoarthritis ( Fig. 32.2 ). Although the majority of the literature describes Preiser disease as pertaining to diffuse involvement of the scaphoid, Herbert and Lanzetta proposed that the process begins in the proximal pole and then advances digitally producing global involvement.19

Most recently, Kalainov described two types of Preiser disease based on the degree of scaphoid involvement on MRI20 ( Table 32.2 ). Type I includes patients with global avascularity on MRI. Type II patients have localized scaphoid avascular necrosis ( Fig. 32.3 ). Generally speaking, patients with global scaphoid involvement (type I) had a worse prognosis despite treatment.20

▪ Treatment Overview

Treatment of Preiser disease is controversial. There are no prospective comparative trials to guide treatment, and treatment is largely a matter of surgeon preference. Proposed treatments run the gamut from observation to wrist arthrodesis. Nonoperative approaches include immobilization, nonsteroidal antiinflammatory, and electrical stimulation.4 ^, 22 ^, 27 ^, 28 Operative approaches are even more varied and include scaphoid preservation and salvage procedures. Scaphoid-preserving procedures include closing wedge osteotomy of the radius,29 curettage with or without bone grafting,4 ^, 19 ^, 27 vascularized bone grafting,3 ^, 25 ^, 26 arthroscopic drilling, and arthroscopic debridement.30

Salvage procedures should be considered for cases of established radioscaphoid arthritis or significant scaphoid fragmentation. Surgical options following scaphoid excision have included silicone replacement,4 ^, 8 ^, 19 ^, 27 ^, 31 scaphoid excision and four-corner fusion,20 ^, 25 ^, 26 wrist arthroplasty,22 and wrist arthrodesis.3 ^, 11 ^, 28 Unfortunately treatment protocols are still based on small series, and until definitive level I evidence is available treatment methods should be tailored to the patient’s needs and expectations for wrist use following surgery. In the absence of severe pain and disability a conservative approach may be warranted and should also be discussed with the patient at the time of consultation.

The following section reviews the most common surgical procedures in detail.

▪ Scaphoid Preservation Surgery

Scaphoid preservation surgery is indicated only in early disease, Herbert stage I or stage II, where the cartilage shell of the scaphoid is preserved and the midcarpal and radioscaphoid joints are free of arthritis.25 ^, 26 If radiocarpal arthritis is present but limited to the radial styloid one can consider scaphoid preservation, but a radial styloidectomy must be included with the scaphoid-preserving surgery. Our operation of choice is a pedicled vascularized bone graft from the distal radius based on the 1,2 intercompartmental supraretinacular artery (1,2 ICSRA). If the patient is skeletally immature, the pedicled graft must be taken proximal to the physis, and any additional cancellous graft harvest should be directed away from the physis.

Contraindications to vascularized grafting include previous dorsal wrist surgery that may have compromised the pedicle to the 1,2 and 2,3 ICSRA grafts. In this case, alternative options include a pedicled graft based on the 4 + 5 extracompartmental arteries or free vascularized grafts from the medial femoral condyle or iliac crest26 ( Fig. 32.4 ). Patients with peripheral vascular disease, smokers, and females may be at higher risk of failure after pedicled vascularized bone grafting.32 If intraoperatively the surgeon identifies that the cartilage surface of the scaphoid is not intact or if there is evidence of carpal collapse or arthrosis, then the operation should be converted to one of the wrist salvage procedures discussed following here.

Technique of Vascularized Bone Grafting for Preiser Disease

The use of the 1,2 ICSRA for the treatment of scaphoid nonunions is discussed in chapter 24; however, there are some additional technical challenges specific to the treatment of Preiser disease that may lead to less favorable outcomes when compared with proximal pole fracture.25 First of all, it is difficult to perform a complete debridement of all devitalized bone while preserving the cartilage shell, and this is particularly true within the proximal pole ( Fig. 32.5 ).

The large grafts that are required to fill the void necessitate leaving the dorsal capsule open to prevent compression of the pedicle. Lastly, fixation of the graft within the scaphoid void can be a challenging and we have opted to use only K-wires.32 ^, 33 To overcome some of these problems Lauder and Trumble have recommended the use of a “matchstick-like” graft from the base of the second metacarpal.21 We do not have experience with this graft in the treatment of Preiser disease.

For use of the 1,2 ICSRA pedicled graft for Preiser disease, the patient is positioned supine with the operative extremity on a hand table. After surgical preparation, the extremity is exsanguinated by elevation alone, and the tourniquet is inflated. This incomplete exsanguination facilitates vessel identification and pedicle dissection. A gentle curvilinear dorsoradial incision is used to expose the scaphoid and bone graft donor site ( Figs. 32.4 and 32.6 ). Branches of the superficial radial nerve are identified and protected. The 1,2 ICSRA pedicle is identified between the first and second extensor compartments. The vessels are dissected distally to their anastomosis with the radial artery in the anatomical snuffbox. The pedicle is then protected during dorsal capsulotomy. A transverse dorsoradial capsulotomy is made and the scaphoid is exposed. The scaphoid is inspected for signs of collapse, cartilage loss or disruption, fissuring, and arthritis at the midcarpal and radiocarpal articulations. If any of these adverse signs are found then a salvage procedure is performed; however, if the scaphoid is preserved then the operation proceeds to 1,2 ICSRA bone grafting.

The retinaculum is incised on either side of the pedicle overlying the first and second extensor compartments. This creates a cuff of retinaculum with the pedicle. The graft harvest site is centered 1.5 cm proximal to the radiocarpal joint to include the perforating nutrient vessels.34 After the vascular pedicle is dissected, attention is directed at preparation of the scaphoid. A dorsal window is created in the scaphoid with a high-speed burr. The scaphoid is debrided with the use of curettes ( Fig. 32.5 ). A long rectangular graft is typically required to fill the void after scaphoid debridement ( Fig. 32.6 ). The graft harvest site is designed and centered over the nutrient vessels 1.5 cm proximal to the radiocarpal joint. The 1,2 ICSRA vessels are ligated proximal to the graft harvest site. The vessels are mobilized distal to the graft, freeing them from the radius and wrist capsule to allow for graft rotation and inset. Sharp osteotomes are used to cut the graft free from the radius. The pedicle is carefully mobilized to allow for the distal osteotomy and is completed in two stages on the radial and ulnar aspects.

The graft is trimmed to size using bone cutters and burrs as necessary. The graft is then passed deep to the radial wrist extensors. The graft is inserted in a press-fit manner into the defect. Additional cancellous graft can be harvested from the distal radius as needed. The graft is stabilized with K-wires to prevent extrusion. The wrist capsule is loosely approximated as able without kinking or compressing the pedicle to the graft.

An external fixator may be used to unload the scaphoid and immobilize the wrist. This may benefit scaphoid healing during the revascularization period where the scaphoid may exhibit osteolysis and bone weakening ( Fig. 32.7 ).35 Alternatively, the wrist is immobilized in a sugar tong splint, followed by a long-arm cast for 6 to 8 weeks. A protective splint is then worn for an additional 4 weeks as gentle active range of motion is initiated.

Related posts:

27 Dorsal Vascularized Graft from the Radius for Scaphoid Nonunio 28 The Use of a Vascularized Graft from the Dorsal Radius for Scaphoid Nonumion 29 The Volar Carpal Artery Vascularized Bone Graft for Scaphoid Nonunion 30 Thumb Metacarpal Vascularized Bone Grafts 31 Free Vascularized Medial Femoral Condyle Grafs for Scaphoid Nonunion 7 Nonoperative Treatment of Scaphoid Fractures

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