9 Management of Complications of Scaphoid Fracture Fixation

Geert Alexander Buijze, Anne Eva J. Bulstra, and Pak Cheong Ho

Abstract

Scaphoid fractures are notorious for their troublesome healing. Operative scaphoid fracture fixation is reportedly a safe procedure with predictable high rates of union and a low complication rate. However, some series have highlighted complication rates of up to 30% and pertaining mostly to hardware issues and (recalcitrant) nonunion.

There is no progress without failure. Complications after operative treatment of scaphoid fractures due to a technical imperfection, an unfavorable indication, incautious rehabilitation, or plainly by misfortune occur to every surgeon in up to a 30% of cases.1 Hardware problems, delayed union, and (recalcitrant) nonunion and malunion are the main complications seen after operative fixation. This chapter aims to guide the prevention and management of the most frequent complications after surgical treatment of scaphoid fractures and nonunions.

9.2 Hardware Complications

Although under-reported or under-emphasized with highly variably cited rates in the literature, problems related to hardware are likely the most common complication of scaphoid fracture fixation. These include erroneous screw placement protruding in the scaphotrapezial or radiocarpal joint, screw breakage, intraoperative equipment breakage (involving K-wire and/or screw), and K-wire migration. Migration and loosening of any hardware material should alert the surgeon’s suspicion of delayed union.

In one of the scarce papers highlighting complications, Bushnell et al reported a 29% complication rate using the dorsal antegrade percutaneous cannulated screw technique of nondisplaced scaphoid waist fractures.¹ They had 21% (5/24) major complications including three cases involving hardware problems, one nonunion, and one fracture of the proximal pole; and 8% (2/24) minor complications including intraoperative equipment breakage of a K-wire and screw, respectively. Three cases involved problems with the screws, necessitating an additional operation. One patient’s postoperative computed tomography (CT) scan showed errant screw placement with dorsal malpositioning and inadequate capture of the distal fragment. Healing occurred after hardware removal and revision retrograde percutaneous screw fixation. A second patient’s screw was too long distally and caused symptomatic irritation at the scaphotrapezial joint. A third patient had a delayed union that allowed the screw to settle and became symptomatic. The latter two patients had their symptoms resolved with removal of the screws. Another patient had insidious pain several months after consolidation with radiographic evidence of proximal pole fracture around the head of the screw. The idiopathic etiology could be related to devascularization as well as creating fragility of the proximal pole after drilling and advancing a relatively large screw head through the proximal pole. Similarly, we here report a case of proximal third nonunion following retrograde screw fixation with avascular fragmentation of the proximal pole around the tip of the screw.

The authors give a plausible explanation for the highly variable reported rate of complications including the fact that certain authors do not label hardware removal to be one. In addition, the short-term nature of most series will miss long-term complications such as arthritis of the scaphotrapezial joint related to screw prominence.

Long-term osteoarthritic changes at the scaphotrapezial joint have been related to attrition from prominence of the screw. Dias et al reported this problem in four of eight patients with scaphotrapezial joint space narrowing at a mean follow-up of 93 months after screw fixation.2 At 12-year follow-up, Saeden et al reported an incidence of scaphotrapezial osteoarthritis of 61% (14/23) following fixation, and only 25% (4/16) after nonoperative treatment and suggested this difference resulted from possible injury to the scaphotrapezial joint surface during surgery.³ In a meta-analysis comparing operative versus conservative treatment for nondisplaced scaphoid waist fractures, these two studies were pooled for risk of osteoarthritis. It developed in 40% of patients after surgery as compared with 10% of patients after cast immobilization, a nearly significant difference (p = 0.05).⁴

As described in these studies, radiographic scaphotrapezial joint narrowing is seldom symptomatic. In case of several millimeter screw protrusion with attritional degeneration, it is advisable to remove the screw and eventual associated trapezial osteophyte. Otherwise treatment can be conservative most of the time. Advanced symptomatic scaphotrapezial arthritis may require either a 3-mm distal scaphoid pole resection or proximal pole trapezoidotrapezial resection by open or arthroscopic means. In case of associated DISI, pyrocarbon implants or interposition grafts can be added to maintain height of the “radial carpal column” which seems to limit further progression and, in some cases, even correct DISI.

To err on the safe side with screw lengths and avoid prominence, authors have recommended subtracting 6 mm instead of 4 mm from the measured length and to confirm it using a parallel-guidewire technique.¹ Arguments in favor were recently strengthened in a biomechanical model of 18 scaphoids undergoing an osteotomy simulating an oblique proximal fracture.⁵ Screws of three lengths (10, 18, and 24 mm) were randomly assigned for fixation and scaphoids cyclically loaded to failure. The 10-mm screw proved inferior but there was no significant difference in ultimate load between the 18- and 24-mm screw. The authors advocate that as the fracture site is closer to the 18-mm screw midpoint, the distal threads are engaged closer to the fracture.

In a retrospective study of medical records of 43 professional American football players who underwent scaphoid fracture fixation, there were hardware complications in as much as 15% of patients.⁶ Problems related to hardware included screw loosening, hardware breakage, and erosion on the neighboring carpal bones due to prominent hardware. Hence, even though cannulated compression screw fixation is routinely stable and may allow for direct functional range of motion, there is a clear role for careful rehabilitation to be adapted on case-to-case basis. It seems prudent to err on the safe side and protect active patients against overenthusiastic quick return to heavy labor and contact sports. In doubt, the authors recommend obtaining a CT scan to determine early signs of (trouble with) healing to adapt rehabilitation accordingly.

9.2.1 Tips and Tricks

●Subtracting 6 mm (instead of 2–4 mm) of the measured screw length avoids protrusion trouble while still providing adequate stability. Screw lengths longer than 22 to 24 mm are rarely required.

●Be mindful that screw measurement for percutaneous fixation is different from open fixation. For open screw fixation, we may use the measuring gauge as the end can easily press directly onto the bone surface. For percutaneous fixation, as typically the wound is small, using the measuring device can be notoriously inaccurate due to the soft tissue intervening. Therefore, the recommended measuring method should be using a K-wire of same length to mark the length. Second, when measuring the length, one method is to stop the guide pin drilling just before the pin exits from the cortex, i.e., when it is still within the bone. If one measures the pin length when the pin just exits the bone surface, one may need to subtract 2 mm extra. Thus, the screw length measurement depends on how one measures the length and the reference point.

●The four or five standard fluoroscopy views as recommended by the authors will help identify protruding screws (Fig. 9‑1). To judge screw length and protrusion, its perpendicular views are most useful: the semipronated oblique view and the posteroanterior (PA) view in ulnar deviation. When the wrist is ulnarly deviated, it extends/erects the scaphoid and thus gives the appearance of “lengthening the screw.” Another useful view is the “bean” view, i.e., semisupinated. Because of the dorsal convexity of the scaphoid, the most common mistake is to pass the guide pin too dorsally and hence exiting the dorsal cortex too early. However, from the conventional PA or anteroposterior (AP) view, even in full ulnar deviation, the premature exit of the pin may not be noticeable because of the overlap with the proximal pole. Hence the bean view is important for one to catch the right trajectory. Classically, it should hit the junction between dorsal 2/3 and volar 1/3, while going parallel to the anterior cortex of the scaphoid. A fifth view in standard PA or AP format can be added to exclude a pronation deformity of the distal fragment and helps evaluate the scapholunate (SL) interval; however, it should be interpreted with caution as screw length may be misleading.

●Be mindful that changing a cannulated compression screw intraoperatively may jeopardize adequate screw purchase and compression. In doubt, a parallel K-wire can be either temporarily left in place or added. Otherwise an additional temporary K-wire or screw connecting the distal scaphoid pole to the capitate can be used.

●Immobilize the wrist without the thumb for as long as “radiographically” necessary. In compliant patients, early active wrist mobilization can be recommended, if the screw fixation is stable. Strengthening and passive mobilization can be commenced when CT scan shows >50% osseous union and a stable screw fixation. According to biomechanical studies, the strength of the partially united scaphoid augmented with a well-fixed screw approximates that of an intact scaphoid. This is also the time for athletes to resume sport activities.

●Displaced fractures, with or without concomitant perilunate ligament injury, increase the challenge. Under this situation, the most common mistake is the malreduction of the fracture, as reduction based on intraoperative imaging is notoriously unreliable. In specialized centers, it may be recommended to use arthroscopy to assess and facilitate the reduction, particularly at the midcarpal joint. Under direct vision, the two fragments can be controlled with joysticks, or using a probe or freer as equipment to help reducing the gap, step, and rotation problems of the two fragments before passing the guide pin across. Finally, the arthroscope can also be used to assess for any protrusion of the screw from the proximal scaphoid at the radiocarpal joint, if correct screw length is in doubt.

Following operative fixation of a scaphoid fracture, 0 to 25% of patients present with nonunion—defined as absent trabecular bridging on CT in the planes of the longitudinal axis of the scaphoid at 6 months follow-up. Nearly 100% union rates are typically described for non- or minimally displaced scaphoid waist fractures, while fractures of the proximal pole are associated with higher nonunion rates (0–25%). High union rates (98–100%) can also be achieved with screw fixation in displaced fractures,7 though time to union may be prolonged. Clementson et al described delayed healing (>14 wk) in 3/17 (18%) patients with a scaphoid fracture, all of which were diagnosed as severely displaced.⁸ Smoking and presentation delay have been associated with a higher risk of nonunion among acute fractures managed nonoperatively or established scaphoid nonunions managed operatively. Although there is a paucity of data on factors associated with nonunion following operative management of acute fractures specifically, most patient- and fracture-related risk factors are likely comparable, except those that are corrected operatively such as fracture dislocation and angulation (Table 9.1).

As for surgical technique, no superior fixation method or surgical approach (dorsal vs. volar) has yet been identified with regards to clinical outcomes, union rate, and complications. While multiple fixation methods exist—including single head compression screws as the most common method, K-wires, staples, and plates—comparative studies are scarce. A meta-analysis by Kang et al comparing dorsal and volar percutaneous approaches for screw fixation reported no significant difference in terms of nonunion and other complications (Table 9.1).9 Importantly, however, a meticulous surgical technique avoiding eccentric screw placement is considered essential to reduce surgeon-related preventable complications. Although the most popular approach for percutaneous screw fixation of common waist fractures seems retrograde from volar at the scaphoid tubercle, several authors have argued for more central screw placement, either retrograde transtrapezial or antegrade from dorsal—as is common in proximal pole fractures. Advantages of central screw placement or screw fixation perpendicular to the fracture site remain biomechanical as no series, including the meta-analysis by Kang et al, has found significant differences in clinical outcomes and complications.⁹

Recommendations with regard to postoperative immobilization remain inconsistent. While some allow immediate mobilization, others immobilize for 2 to 4 weeks. Avoiding early strenuous wrist activity including unprotected early return to contact sports is important, as return to athletics is a risk factor, particularly in contact sports.6 In a retrospective study on professional American football players undergoing scaphoid fracture fixation, there was a 25% nonunion rate and 34% had degenerative changes consistent with scaphoid nonunion advanced collapse (SNAC) stages 2 and 3.⁶ No detail was provided on time of return to play and rehabilitation. In contrast Rettig et al reported an acceptable low nonunion rate of 3% with a cautious rehabilitation protocol as follows. Return to play was considered safe after open reduction and internal fixation (ORIF) of a scaphoid waist fracture when range of wrist motion had recovered within 10% of the opposite side in absence of pain.¹⁰ Immobilization averaged 12.5 days and time of return to sports 8 (range, 3–21) weeks. Similarly, use of standard crutches in polytrauma patients¹¹ should be avoided to reduce the risk of destabilizing operative reduction and risk of subsequent nonunion.

9.3.2 Treatment

Nonunion treatment consists of hardware removal, and surgical take down of the sclerotic nonunion site until bleeding bone, bone grafting, and stable fixation (Fig. 9.2–Fig. 9.12. Percutaneous placed screws are preferably removed under fluoroscopic guidance with the dedicated K-wire and screwdriver. This part can be tedious and time consuming. If primarily treated elsewhere, it is advisable to check the operative report and order the appropriate removal set beforehand.

Take down of the nonunion site is best performed with a high-speed burr, sawblade, and or osteotome. Use of a rongeur can clear a remaining spike. All techniques emphasize the need to resect substantial portions of the scaphoid nonunion site surfaces in order to encourage healing, under the rationale that the sclerotic fracture ends will not support healing. Bleeding bone can be determined by intermittent tourniquet deflation. On the proximal site, absent bone punctate bleeding may confirm AVN of the proximal pole. Despite AVN of the proximal pole, both vascularized bone grafting (VBG) and nonvascularized bone grafting (NVBG) can lead to high rate of union (Table 9.2). For ABG, the large series of 20 years’ experience of the senior author suggests that in case of AVN, there is still an 81.8% chance of healing through neovascularization from distal and from the ligament of Testut.¹²

Two meta-analyses reported comparable union rates following VBG (84% and 92%) and NVBG (80% and 88%) for established scaphoid nonunions. In the presence of AVN and in case of proximal pole nonunions VBG yielded higher union rates (72% and 97%, respectively) compared to NVBG (62% and 93%).^13,14 With regard to donor site, more complications were reported with the use of iliac crest bone grafts (both VBG and NVBG) (9%) compared to distal radius grafts (1%) while yielding similar union rates (87% and 89%, respectively). Iliac crest grafts are also associated with more pain at the donor site. For all graft types, higher union rates were reported for bone grafting with fixation (88–91%) than for grafting without fixation (79%).¹⁴ Quality of current evidence for the treatment of established nonunions remains limited by high volumes of largely low-level evidence and the inconsistent reporting and use of definitions for AVN, nonunion, and complications. As of yet, no systematic review has identified a statistically substantiated superior treatment approach for scaphoid nonunion (Table 9.2).

With the increasing popularity of wrist arthroscopy, ABG has recently become a more attractive option for many surgeons. The senior author’s outcomes in 124 patients showed an overall union rate of 90.3% (112/124).12 The average radiological union time was 14 weeks (range, 6–80). Final clinical follow-up showed no pain in 67 patients (54%), whereas in the remaining 57 patients visual analog scale (VAS) pain was on average 1.7 (range, 0–7). ADL performance scores improved from 34.2 to 38.6 (p < 0.05) and grip strength from 28.2 to 36.2 kg (p < 0.05). Complications included one case of intraoperative screwdriver breakage, three cases of transient neuropathy, three cases of pin-tract infection, and three cases donor site morbidity at the iliac crest (transient).

Stabilization can be performed by K-wires (with optional temporary scaphocapitate/radiolunate pinning) or volar plate fixation as repeat screw fixation may not provide adequate purchase in the remaining bone. These stabilization methods also reduce the risk of graft extrusion, which is a notorious pitfall in anterior wedge grafting stabilized by a single screw.

Below-elbow cast immobilization with or without thumb immobilization is recommended for 6 up to 12 weeks to diminish risk of K-wire migration (Fig. 9‑1). K-wires are removed upon radiographic confirmation of early bony consolidation.

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