Introduction

Scapholunate ligament injuries can ultimately result in progressive degenerative injuries at the carpal level, known as scapholunate advanced collapse (SLAC). Initially, osteoarthritis is limited to the radial styloid–scaphoid portion of the radioscaphoid joint (SLAC I), progressing to involve the entirety of the radioscaphoid joint (SLAC II), the scaphocapitate and/or capitolunate joints (SLAC III), and eventually the whole carpus (SLAC IV) [1, 2]. In addition to radiography, CT and MRI may be of value for accurate staging of SLAC. Carpal instability arising from a nonunited scaphoid fracture can progress along relatively comparable degenerative stages, to pancarpal arthrosis. Wrist arthrosis occurring in the context of a long-standing nonunited scaphoid fracture is known as “scaphoid nonunion advanced collapse” (SNAC) [2].

This article reviews the surgical options available for SLAC wrist (salvage procedures, total wrist arthrodesis, and total wrist arthroplasty) with an emphasis on normal postoperative imaging and complications associated with each surgical option.

Salvage procedures

Scaphoidectomy with four-corner arthrodesis and proximal row carpectomy

The SLAC wrist may be associated with significant pain and dysfunction. For patients with intractable pain in whom nonoperative treatments have failed, surgical intervention is recommended. Salvage procedures can be performed in stages I, II or III SLAC. These procedures are designed to relieve pain, while maintaining some wrist motion (in contrast to total wrist arthrodesis). The two standard salvage operations for SLAC are scaphoidectomy with four-corner arthrodesis (FCA) and proximal row carpectomy (PRC) [3]. PRC is usually reserved for older (>40 years old), lower demand patients, whereas four-corner arthrodesis (or its modifications) is typically preferred for younger, higher demand patients [3, 4]. Both operations require the presence of a normal radiolunate articulation. Additionally, PRC requires a relatively well-preserved midcarpal articulation (i.e., SLAC I or II).

FCA: surgical technique

In four-corner arthrodesis, after scaphoid resection, meticulous decortication of the capitolunate, capitohamate, triquetrohamate, and lunotriquetral joints is performed. The dorsal intercalated segmental instability (DISI) is corrected with attainment of neutral radiolunate and capitolunate angles. The capitate, lunate, hamate, and triquetrum are fused using bone graft (cancellous autograft from distal radius or iliac crest, allograft, synthetic materials or combinations thereof) and a variety of fixation devices [5]. Care must be taken to preserve the volar radiocarpal ligaments to prevent postoperative ulnar carpal translocation. The procedure may be accompanied by resection of the dorsal rim of the distal radius and radial styloidectomy.

FCA: fixation devices

Traditional fixation methods include Kirschner wires (K-wires), headless compression screws, or conventional staples. These methods result in low nonunion rates (3–18%), but demonstrate the following potential drawbacks: the need for subsequent surgery for pin removal (typically 8–10 weeks after the index procedure), pin-tract infection, pin migration or tendon impingement, and intra-articular screw penetration [5]. More recent fixation methods include shape-memory staples and dorsal plates. Shape-memory staples for FCA have a quadripodal design and are made of nitinol (nickel–titanium alloy) [6, 7]. Nitinol is biocompatible and can change shape from a low-temperature open form to a high-temperature closed form (the transition takes place at a temperature that depends on the composition of the alloy). After implantation of the memory staple in the open form, the staple is heated to above transition temperature, causing it to revert to the closed form. This transition from open to closed forms ensures compression of the four-corner arthrodesis.

The dorsal plates for four-corner fusion were first introduced in 1999, and are available in a variety of evolving designs. Most published series have evaluated the Integra® Spider™ Limited Wrist Fusion System (Fig. 1a, b). This is a Food and Drug Administration (FDA)-approved, stainless steel, nonlocking dorsal circular plate with a reported nonunion rate of 0–63%, and a hardware failure rate of 0–27% [5]. The radiographic assessment of fusion is challenging with this construct and computed tomography (CT) imaging has been advocated to assess union about the Spider plate [5].

Fig. 1
figure 1

Four-corner arthrodesis (FCA) with dorsal plates (different patients). a Photograph of the Spider™ and Mini Spider™ Limited Wrist Fusion Systems, consisting of stainless steel plates with eight-hole and six-hole designs respectively (courtesy of Integra LifeSciences). b Posteroanterior wrist radiograph in a 50-year-old woman shows a Spider Limited Wrist Fusion System. c Photograph of a Medartis Aptus Four-Corner Fusion® plate (courtesy of Medartis). The plate has four inner holes designed for nonlocking screws and 12 outer holes intended for angular stable fixation with locking screws. d Posteroanterior wrist radiograph in a 34-year-old man shows a Medartis Four-Corner fusion plate (arrow points to distal radial autograft donor site). e Computer rendered image of an Xpode cup dorsal locking circular plate demonstrates a PEEK-Optima plate with locking screws (courtesy of TriMed). f Posteroanterior wrist radiograph in a 74-year-old man demonstrates an Xpode cup dorsal locking circular plate. The radiolucent plate of this construct significantly facilitates fusion assessment (compare with the metallic plates in b and d)

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More recent FDA-approved, dorsal plate designs include the Medartis (Basel, Switzerland) Aptus Four-Corner Fusion® plate and the Xpode® cup (TriMed, Santa Clarita, CA, USA). The Medartis Aptus Four-Corner Fusion® plate (Fig. 1c, d), is composed of a titanium/titanium alloy, low-profile (1.4 mm thick) plate. The plate has 12 plate holes: the four inner holes are designed for nonlocking screws, whereas the 12 outer ones are designed for angular stable fixation with locking screws. One study demonstrated that in the short to medium term, the Aptus plating system, demonstrated comparable results with other methods of fixation for four-corner fusion [8]. Mean union time with this construct may be longer than with other types of constructs (6 months versus 1.5–4 months for other types of four-corner fusion fixation devices) [8].

The Xpode® cup is a dorsal locking circular plate composed of a radiolucent polyether-ether-ketone (PEEK-Optima; Fig. 1e, f). The radiolucent plate permits for more accurate radiographic assessment of union, compared with stainless steel designs. Reported fusion rates for this construct are 80–96%, with a hardware failure rate of 13% [5, 9].

Radiographic appearance of uncomplicated FCA

Wrist radiographs (containing at least posteroanterior and lateral views of the wrist) and to a lesser extent CT are the mainstays of postoperative imaging. On uncomplicated postoperative radiographs, the wrist should be in neutral alignment on the lateral view. Optimally positioned dorsal plates are centered on the four fused carpal bones, with the plate recessed just beneath the dorsal carpal cortex, to avoid dorsal impingement (Fig. 2) [5, 8]. It is preferable that dorsal plates be transfixed via two screws to each of the four fused carpal bones (especially the lunate and capitate) [5].

Fig. 2
figure 2

A 40-year-old man with FCA and dorsal plate impingement. a Lateral wrist radiograph demonstrates the dorsal plate, located dorsal to the dorsal lunate cortex (long arrow) and impinging on the distal radius. The short arrow points to a screw remnant from previous surgery. b Revision surgery after placement of a new Medartis Aptus Four-Corner Fusion plate demonstrates a correctly positioned plate: the dorsal plate is recessed just beneath the dorsal carpal cortex (long arrow). Observe the persistent and uncorrected dorsal intercalated segmental instability deformity in both a and b

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PRC: surgical technique

Proximal row corpectomy is less technically demanding than FCA. In PRC, complete removal of the scaphoid, lunate, and triquetrum results in a simple hinge joint between the radius and the capitate. Care must be taken to preserve the volar radiocarpal ligaments to prevent postoperative ulnar carpal translocation. The procedure may be accompanied by radial styloidectomy.

FCA and PRC: outcomes and complications

In a systematic review of the literature that compared the outcomes of four-corner fusions and PRCs, both procedures resulted in reliable pain relief, a wrist flexion–extension arc in the 70° to 80° range (slightly less than preoperative motion), and 70% to 75% grip strength in comparison with the contralateral wrist [10]. Complications were significantly more common and more varied with four-corner fusions (Figs. 2, 3, 4 and 5; Table 1) [10]. Progressive radiocapitate osteoarthritis is the most common complication of PRC owing to the incongruent distal radius and capitate articular surfaces (Fig. 6) [4]. Radiocapitate osteoarthritis in the context of PRC, is usually not associated with poor clinical outcomes [11]. In addition to persistent pain and poor patient outcomes, proximal row carpectomies may also be complicated by postoperative soft-tissue infection, hematoma, and tendon injury [13].

Fig. 3
figure 3

A 59-year-old man with FCA and hardware failure. Lateral wrist radiograph shows a dorsal circular plate (Spider limited wrist fusion system) with fracture and pull-out of several of the screws

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Fig. 4
figure 4

A 43-year-old man with FCA using two headless compression screws and hardware complications. Posteroanterior wrist radiograph shows loosening of the screws. There is also impingement of the third carpometacarpal joint by the distal tip of the triquetrohamate screw

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Fig. 5
figure 5

A 48-year-old woman with FCA using a spider plate and hardware complications. Lateral wrist radiograph shows that two of the proximal screws have backed out. Longitudinal ultrasound image at the level of the fourth extensor compartment shows the backed out screw (arrowhead) causing a high-grade tear of the adjacent extensor digitorum communis slip to the middle finger (arrows)

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Table 1 Complications of scaphoidectomy with four-corner fusion [5, 8, 9, 11, 12]
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Fig. 6
figure 6

A 44-year-old woman with proximal row carpectomy and development of radiocapitate osteoarthritis. a Immediate postoperative posteroanterior wrist radiograph. b Posteroanterior wrist radiograph obtained 7 months later demonstrates development of radiocapitate osteoarthritis. Observe the distal radial suture anchors

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FRC: assessment of union

The goal of four-corner fusion is to first obtain fusion (seen as bridging trabeculae at the fused level), then gradually mobilize the wrist with physical therapy, with the goal of obtaining a full range of wrist motion when solid union has been achieved. After FCA, the wrist is immobilized in a cast for 4–8 weeks to permit fusion of the capitolunate joint. Capitolunate fusion per se produces successful clinical results, irrespective of the fusion status of the hamate or triquetrum [5, 11].

Thorough clinical examination and wrist radiographs, at times complemented by CT imaging, are used for evaluation of union. Although there is no set of universally accepted criteria for determining union, successful union may be defined as consolidation of the capitolunate bridging trabeculae (Fig. 7), in addition to the absence of pain to palpation or range of motion at the fusion site [5, 14]. CT is the most reliable imaging method for evaluation of osseous union, especially in the presence of metallic plates.

Fig. 7
figure 7

A 40-year-old man with FCA and capitolunate union (same patient as in Fig. 2). Sagittal reconstructed CT image shows solid fusion of the capitolunate articulation

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The time frame for the formation of bridging trabeculae at the level of the midcarpal fusion is usually between 6 and 16 weeks [14]. One study demonstrated a longer mean union time (6 months) for the Medartis Aptus Four-Corner Fusion plate. Union rates of FCA with traditional fixation devices, the Spider Limited Wrist Arthrodesis System, and the Xpode cup dorsal locking circular plate are 82–97%, 37–100%, and 80–96% respectively [5, 9, 11].

Modifications of salvage procedures

Numerous modifications of scaphoidectomy with FCA have been described, including scaphoid (± triquetral) resection with capitolunate arthrodesis (Fig. 8), scaphoidectomy and bicolumnar fusion, or three-corner arthrodesis (arthrodesis of the capitate, hamate, and lunate) with excision of the scaphoid and triquetrum. In bicolumnar fusion, arthrodesis of the capitolunate and triquetrohamate joints is performed, without fusion of the lunotriquetral and capitohamate joints. The outcomes of both of these modified techniques are comparable with traditional four-corner fusions [3].

Fig. 8
figure 8

A 34-year-old man with scaphoid excision and capitolunate fusion. Posteroanterior wrist radiograph shows a broken capitolunate Acutrak screw. Patient subsequently underwent revision four-corner arthrodesis

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In the presence of midcarpal arthritis (i.e., SLAC III), PRC can be combined with capitate resurfacing, using either an osteochondral resurfacing autograft (obtained from the normal articular surfaces of the resected carpal bones), a resurfacing capitate pyrocarbon or a metallic implant [15, 16]. An additional modification to the PRC procedure, is PRC in conjunction with capsular interposition. In this technique, a dorsal capsular carpal flap is turned down over the distal radius articular surface and sutured to the volar wrist capsule [17, 18]. This latter procedure may be further augmented with capitate leveling (i.e., resection of the proximal end of the capitate head and hamate).

Alternatives to scaphoidectomy with four-corner arthrodesis and PRC

Alternatives to the standard salvage operations and their modifications include: radial styloidectomy with or without partial wrist fusion, radioscapholunate arthrodesis with distal scaphoid excision, and excision arthroplasty (excision of the proximal scaphoid alone or in combination with the lunate and capitate head) combined with interposition of an osteochondral autograft or a pyrocarbon interposition implant [16, 19]. In addition, wrist denervation (i.e., division of the afferent articular pain fibers) is an established treatment for addressing pain in the arthritic wrist. Wrist denervation may be performed in isolation or combined with various salvage procedures [3].

Radical procedures for end-stage arthritis

Total wrist arthrodesis

In total wrist arthrodesis, the distal radius is fused across the proximal and distal carpal rows to the base of the third metacarpal bone (the procedure may be combined with proximal row carpectomy). Total wrist arthrodesis is indicated for the primary treatment of painful, stage IV SLAC, particularly in high demand patients with adequate bone stock and healthy soft tissues [4]. It can also be used after failed limited wrist fusions or unsuccessful partial or total wrist arthroplasties. Total carpal fusion reliably relieves pain and improves strength [16]. In comparison with other joints, the loss of mobility associated with total carpal arthrodesis is considered less disabling because of the compensatory motions of the forearm, elbow and shoulder [20]. Patient satisfaction rates with this procedure range from 80 and 100% [16].

Because of high union rates, standard fixation of total wrist arthrodesis for degenerative or post-traumatic conditions is performed with low-profile, dorsal compression plates [16, 21]. Current plate designs are straight or contoured, and are designed to hold the wrist in approximately 10° of extension in patients without rheumatoid arthritis [22]. The dorsal locking plate is then secured with two to four screws into the metacarpal base of the middle finger and as many screws into the distal radius (a screw may also be inserted into the capitate). The plate should be flush with the dorsal bone cortex and there should be good purchase of the screws. The most commonly fused joints include the radioscaphoid, radiolunate, scapholunate, scaphocapitate, and lunocapitate articulations [21]. Fusion of the long CMC joint remains controversial [23]. Supplemental bone graft from the iliac crest or distal radius is commonly used. Union rates are high (96–100%) and fusion should be complete within approximately 6 months [13, 16, 21].

In addition to nonunion, potential complications after total wrist arthrodesis include soft-tissue complications, neurovascular injury, infection, hardware-related complications (such as, hardware failure, peri-hardware fracture, loss of purchase of the dorsal plate) and ulnocarpal impaction (Figs. 9 and 10). Soft-tissue complications include hematoma, minor skin dehiscence (20–30%), superficial infection (approximately 3% of patients), carpal tunnel syndrome (up to 10% of patients; half of whom require carpal tunnel release), and extensor tendon adhesions [13, 24]. Symptomatic dorsal compression plates, with painful prominence, bursitis or extensor tenosynovitis, have been reported in as many as one-third to two-thirds of patients, and frequently require hardware removal (Fig. 9) [24]. Ulnocarpal impaction is more commonly encountered when fusion is performed in excessive ulnar deviation and may be treated with ulnar shortening osteotomy or distal ulnar excision (Fig. 9c) [24].

Fig. 9
figure 9

A 32-year-old man with total wrist arthrodesis complicated by ulnar-sided wrist pain (owing to ulnocarpal impaction) and symptomatic dorsal compression plate. a Posteroanterior and b lateral wrist radiographs show total wrist arthrodesis with a contoured dorsal compression plate. c Follow-up posteroanterior wrist radiograph shows removal of the wrist fusion plate (due to overlying extensor tendon irritation) and distal ulnar excision. Observe the solid fusion mass (arrows) at the level of the radiocarpal, scapholunate, scaphocapitate, and lunocapitate articulations. Dorsal plates are not removed unless they cause symptoms

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Fig. 10
figure 10

A 61-year-old woman with total wrist arthrodesis and pain. Lateral wrist radiograph shows pull-out of the distal-most screw (on physical examination, the screw tented the skin). Observe the focal lucency (arrow) at the site of the backed-out screw. Cultures obtained during subsequent hardware removal were negative for infection

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Total wrist arthroplasty

Designs

Total wrist arthroplasty (TWA) is a motion-preserving alternative for the treatment of advanced, painful wrist osteoarthritis. It is generally reserved for older patients or those with fewer physical demands who have adequate bone stock [24]. Wrist hemiarthroplasty (Fig. 11) is a newer motion-preserving technique that may be an option for younger, more active patients [25].

Fig. 11
figure 11

Wrist hemiarthroplasty. Posteroanterior wrist radiograph shows a KinematX™ midcarpal joint hemiarthroplasty. This device is CE-marked, but not approved by the FDA (courtesy of Extremity Medical)

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The wrist is a highly complex joint with high functional demands. Therefore, there are substantial design challenges in developing wrist implants. The first TWA was made of ivory and implanted by Themistocles Gluck in 1890 [26]. Seventy years after that, the first commercially available Swanson TWA implant was developed. The Swanson implant is a one-piece, interpositional implant and is often described as a first-generation implant. Since then, several other designs of wrist implants have been introduced, and subsequently withdrawn from the market because of high complication rates [26]. The newer generation TWA devices include a proximal, mostly stemmed component affixed to the distal radius and a distal component fixed to the distal carpus and metacarpals. The second-generation implants have a ball-and-socket or hemispherical design. The third-generation implants include the Biaxial total wrist prosthesis, the Trispherical prosthesis, and the Universal total wrist implant.

The contemporary fourth-generation arthroplasties have different designs, fixation principles, and articulations. To decrease complications, strategies implemented in the design of the current fourth-generation implants include mostly cementless fixation, preservation of the distal radioulnar joint (DRUJ), and limited bone removal [20, 24]. Porous titanium or cobalt–chrome–molybdenum (Co–Cr–Mo) surfaces with coats of plasma-sprayed titanium, hydroxyapatite, or resorbable calcium–phosphate is used in areas of bone ingrowth in all modern wrist implants and promotes osteointegration. The fourth-generation implants include: the Universal 2™ total wrist implant system (Integra LifeSciences; Plainsboro, NJ, USA), RE-MOTION™ total wrist system (SBI, Morrisville, PA, USA), Maestro™ wrist reconstructive system (Biomet Orthopedics, Warsaw, IN, USA), Total Modular Wrist (OrthoCube, Baar, Switzerland), and Motec® wrist joint prosthesis (Swemac Orthopedics, Linköping, Sweden) [20].

Fourth-generation implants

The three currently approved total wrist implants by the Food and Drug administration, are the Universal 2 (Fig. 12), RE-MOTION, and Maestro (Fig. 13) prostheses. These three implants share common design features: press-fit radius stems and carpal plates with a capitate peg and smooth radial and ulnar carpal screws that traverse one or more carpometacarpal joints, and articular bearings made of ultra-high-molecular-weight polyethylene (UHMWPE) for improved wear characteristics [20, 26]. The articular surface is ellipsoid in the Maestro and Universal 2 prostheses and egg-shaped, partly hemispheric, in the RE-MOTION implant. The UHMWPE is placed on the convex side in the Universal 2 and RE-MOTION implants and on the concave side in the Maestro design. The Maestro implant can be used in both TWA and carpal hemiarthroplasty.

Fig. 12
figure 12

Universal 2 total wrist implant system on posteroanterior wrist radiograph. The Universal 2 implant evolved from the original third-generation Universal total wrist implant design. The implant is composed of a porous coated cobalt–chrome proximal component (long white arrow) with an elliptic surface, a radiolucent ultra-high-molecular-weight polyethylene (UHMWPE) bearing attached to the proximal component, and a titanium porous coated carpal plate transfixed with a central peg (black arrow) and radial and ulnar-sided screws. The prosthesis allows 60° of extension, 40° of flexion, and 20° of radial and ulnar deviation. Ulnar head implant (short white arrow)

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Fig. 13
figure 13

Maestro wrist arthroplasty on posteroanterior and lateral wrist radiographs. The radial component is composed of a press fit titanium alloy radius stem and a coated cobalt–chrome–molybdenum (Co–Cr–Mo) radial body. The UHMWPE articular bearing is placed on the concave radial body. The Co–Cr–Mo carpal plate is fixed via a coated titanium alloy central peg to the capitate and two radial (trapezoid/second metacarpal) and ulnar (hamate) titanium alloy screws

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The total modular wrist has a press-fit radius stem, a reverse concave–convex articulation, and a distal carpal plate fixed to the second to fourth metacarpals via three metacarpal screws. The proximal egg-shaped, partly hemispheric component articulates with the UHMWPE socket of the carpal plate distally. Options available with the total modular wrist include optional DRUJ prosthesis, uncoated radius component for cemented fixation, and a constrained articulation.

The Motec wrist joint prosthesis (Fig. 14) has a different design principle from the other fourth-generation implants. Threaded and coated, titanium alloy conical screws fix the implant into the distal radius and capitate–third metacarpal bone (the third carpometacarpal joint is fused). Centrally, a Co–Cr–Mo ball and socket articulation with a chromium–nitride coat fits into the conical screws.

Fig. 14
figure 14

Motec wrist joint prosthesis. a Posteroanterior and b lateral wrist radiographs and c photograph of the Motec implant. Threaded titanium alloy conical screws (with a resorbable calcium–phosphate coat) fix the implant into the distal radius and capitate–third metacarpal bone. Centrally, a Co–Cr–Mo ball and socket articulation fits into the conical screws (courtesy of Swemac Innovation AB)

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Appearance of uncomplicated TWAs on postoperative imaging

Routine wrist radiographs are the most common imaging method used for evaluation of TWAs. The degree of distal radius and carpal resections observed on postoperative imaging depend on the arthroplasty design and patient factors (for example, when limited wrist extension is observed intraoperatively after placement of the trial radial and carpal components of the prosthesis, more of the distal radius would be resected) [26]. On radiographs of uncomplicated wrist prostheses, carpal height and alignment should be restored to neutral. Associated distal ulnar resection (usually performed because of distal radioulnar joint arthritis) may also be seen on postoperative imaging [26].

Outcomes and complications

Current fourth-generation prostheses demonstrate a 90–100% survivorship at 5 years and good to excellent clinical outcomes with regard to functional motion and pain relief [20, 26, 27]. Nevertheless, implant survival declines between 5 and 8 years and complications occur at a rate of 6% to 47% [26, 28]. Complications may occur in the intraoperative/immediate postoperative period or be more delayed. Delayed complications may occur at the level of the prosthesis (Figs. 15 and 16), in the surrounding soft tissues, in the distal radioulnar joint or at multiple levels (Table 2). Instability and implant loosening (particularly of the distal component) are the most common complications. Periprosthetic lucency (> 2 mm in width) on wrist radiographs does not necessarily correlate with clinical loosening, and continued close follow-up is recommended for such patients [29].

Fig. 15
figure 15

A 50-year-old woman with total wrist arthroplasty (TWA) and polyethylene wear (same patient as in Fig. 13). Posteroanterior wrist radiograph demonstrates a Maestro wrist arthroplasty. There is polyethylene wear seen as narrowing of the radial body–carpal head interval (compare with Fig. 13)

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Fig. 16
figure 16

A 54-year-old man with TWA and hardware failure. Posteroanterior and lateral wrist radiographs demonstrate a Maestro wrist implant. There is volar dislocation of the carpal component (compare the position of the carpal component of the prosthesis with Fig. 13) and fracture of the radial carpal plate screw

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Table 2 Potential complications after total wrist arthroplasty
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Conclusion

Salvage procedures can be performed in SLAC stages I, II or III. Salvage operations for SLAC are scaphoidectomy with four-corner arthrodesis and proximal row carpectomy, along with modifications of these techniques. Total wrist arthrodesis or TWA may be used to address end-stage arthritis. Successful postoperative imaging interpretation of SLAC necessitates familiarity with the various surgical techniques used in the management of SLAC, along with their expected postoperative appearance and complications.