Background. There are a variety of ways to surgically manage patients with scaphoid waist fractures. The purpose of this study is to compare the rate of union achieved with a nitinol compression staple versus that of a headless compression screw in the treatment of scaphoid waist fractures.

Methods. We performed a retrospective review of patients with middle-third scaphoid fractures treated surgically. Patients were stratified into 2 groups based on fixation device: a nitinol compression staple or headless compression screw (HCS). Primary outcome was radiographic union. Secondary outcomes included time from surgery to union, development of avascular necrosis (AVN), complication rate, and need for revision.

Results. Forty-one patients were included in the final analysis. The median follow-up time was 5.7 months. Twenty patients were treated with staples, 21 with HCS. Thirty-seven patients achieved union. All who failed to unite were treated with HCS. Eight patients had postoperative complications, including postoperative AVN, all of whom were in the HCS cohort. This treatment group had a higher rate of revision surgery as well. Staples required less time to achieve union and fewer weeks of immobilization. Postoperative scapholunate angles were similar between the groups.

Conclusions. Fixation of scaphoid waist fracture with nitinol compression staples is at least as likely to achieve union as fixation with HCS in patients without prior surgical intervention. This treatment also demonstrated equivalent or better secondary outcomes, including postoperative AVN, complication and revision rates, time to union, and weeks immobilized.

Introduction

Scaphoid fractures account for 60% of carpal fractures and 2.4% of wrist fractures. Between 66% and 82% occur in males with peak incidence occurring in the second and third decades of life.^1,2 Nondisplaced fractures have a 5% to 10% incidence of nonunion and 55% chance of nonunion if they are displaced more than 1 mm.^3,4 If untreated, persistent nonunion may lead to degenerative radiocarpal osteoarthritis with persistent pain and impaired functionality.⁵ Scaphoid nonunions are often treated with headless compression screws, achieving union in greater than 80% of cases.^6,7 However, the use of headless compression screws may result in complications related to its application, such as penetration of the screw into the intra-articular space.⁸ There has been recent evidence, however, demonstrating similar rates of union and fewer complications with use of nitinol staples compared with headless compression screws in the treatment of scaphoid delayed union and nonunion.^9-13 Both in independent and comparative head-to-head studies, nitinol alloy staples provided greater and more durable compression at physiologic temperatures than do other staple constructs or compression screws.^14-20 By comparing these 2 treatment modalities, we hypothesize patients treated with nitinol compression staples will have a greater incidence of union and have fewer complications compared with those treated with headless compression screws.

Methods and Materials

Following Institutional Review Board approval, all patients who underwent a repair of the scaphoid with open reduction and external fixation by 1 of 4 board-certified hand surgeons between 2010 and 2020 were identified by Current Procedural Terminology (CPT) codes 25440 and 25628. Subsequent chart review was performed to determine fracture location, union status, and surgical fixation technique. Patients who had surgical fixation of a scaphoid waist fracture with either a single nitinol compression staple via a volar approach (Figure 1) or a single headless compression screw were included (Figure 2). They were then stratified into 2 groups by fixation device that was based on surgeon preference. Patients with a staple were required to have undergone a volar approach as described by Congiusta et al.²¹ Exclusion criteria included prior intervention, pathologic fracture, less than 12 weeks follow-up, and less than 4 weeks between injury and surgery. Once identified, a full chart review was performed to collect data for statistical analysis.

Figure 1. Fixation with a single nitinol compression staple via a volar approach.

Figure 2. Fixation with a single headless compression screw.

Union, as determined radiographically in conjunction with snuffbox tenderness, was the primary outcome. If uncertainty persisted with regard to fracture healing following x-ray and physical exam, computed tomography scan was obtained at the discretion of the operating surgeon. Secondary outcomes included time to union, revision and complication rates, loss of alignment, postoperative avascular necrosis (AVN), postoperative resolution of preoperative AVN, weeks immobilized in nonremovable splint or cast, and postoperative scapholunate angle. AVN was diagnosed radiographically as sclerotic and bony changes consistent with avascular bone. Complications were defined as persistent nonunion, new or persistent AVN (AVN on presentation that does not resolve following surgical intervention) following surgical fixation, loss of alignment following fixation, infection, cellulitis, or hardware complications. Initial follow up was performed at 2 weeks and subsequently at monthly intervals; however, not all patients were strictly adherent to this schedule.

Categorical variables were compared using chi-squared or Fisher exact-tests where appropriate with Haldane-Anscombe^22,23 adjustments of 0.5 applied to correct for incidences of 0. Continuous variables were analyzed using independent samples t tests for parametric data, whereas, in cases of nonparametric distributions, medians with associated interquartile ranges were reported and Mann-Whitney U tests were used for comparison. Statistical significance was set at P < .05. Analysis was conducted using SAS Enterprise Guide, Version 7.1of the SAS System for Windows (SAS Institute).

Results

In total, 46 patients with scaphoid waist nonunion were identified. Of these, 5 (11%) were excluded due to insufficient follow-up. Thirty-four of the remaining 41 patients were male (83%). The median age was 22 years. Most injuries were right-sided (58%). The most frequent mechanism of injury was a fall, followed by motor vehicle collisions and motorcycle collisions. Characteristic data was not different between the 2 treatment groups. All patients presented with pain as their primary complaint, while nine (22%) also complained of decreased range of motion. Fifteen (37%) patients presented with proximal pole AVN. There was no difference in median follow-up time between the 2 groups (Table 1).

Table 1

A total of 20 (49%) patients were treated with a single nitinol compression staple and 21 (51%) with a headless compression screw, which was similar to the sample sizes of other studies.^9-11,13 Thirty-seven (90%) patients achieved union postoperatively. The 4 patients who failed to unite were treated with headless compression screws (19%). Median time to union was 2.7 months in those patients treated with a staple and 4.2 months in those treated with screws, a difference of 1.5 months. Patients treated with compression screws were at a greater risk for persistent or postoperative AVN, both of which were exclusive to this group. There were 8 complications, 4 persistent nonunion and 4 new or persistent AVN postoperatively, all occurring in the screw cohort, which was statistically significant. There was no loss of alignment, postoperative infection, cellulitis, or hardware complications in either group. Five patients required revision surgery, all of whom were in the group treated with screws (23%). This bordered statistical significance. On average, the staple group was immobilized in a cast or nonremovable splint for significantly fewer weeks compared with those treated with screws. The scapholunate angles of the 2 treatment groups were also assessed and were not significantly different. Outcome data is shown in Table 2.

Table 2

Analysis of covariates showed no difference between the treatment groups with regard to age, time from injury to surgery, preoperative scapholunate angle, AVN on presentation, type of graft, and bone stimulator use. Further multivariate analysis showed no confounding effect of these variables on primary or secondary outcomes. Post-hoc bivariate analysis revealed that iliac crest graft, utilized in 10 patients in the overall cohort (24%) and 3 of those treated with headless compression screws (14%), was independently associated with persistent nonunion.

Discussion

This non-inferiority study demonstrates the comparable effectiveness of nitinol compression staples in the treatment of scaphoid waist fractures as compared with headless compression screws. Patients treated with a single nitinol compression staple from a volar approach were at least as likely as those treated with a single headless compression screw to achieve union. Secondary outcomes evidenced improvement with the use of a nitinol staple over a headless compression screw. Stapling resulted in fewer revisions, complications, and new or persistent AVN. These patients also achieved union faster and were immobilized for fewer weeks than those with headless compression screw fixation. Our study further supports union rates found in the literature for both fixation methods, albeit with a slightly higher rate than what has been thus far reported with compression staples,^9-13,24-36 which is likely attributable to our use of the nitinol alloy staple as well as variations in fracture location, surgical technique, and bone grafting, while demonstrating a similar time to union^{9,12,13,28,36} and complication rate.^37-41 While numerous studies have found success treating acute, delayed, and nonunion scaphoid waist fractures with compression staples,^9-13,24-27 this technique remains underutilized.

Limitations

There are multiple limitations to this study. Although initial follow up was performed at 2 weeks with subsequent follow-up being scheduled at 1-month intervals at least until union was achieved, patients were not universally adherent to this schedule, which may affect the time at which union was identified. Further research is necessary to evaluate outcomes over a longer follow-up period as a median follow-up of 5.6 months is relatively short. However, it should be noted that those patients who did not achieve union following surgical intervention had a median follow up of 15.7 months with a range of 7.5 to 27.2 months. Additionally, functional data such as grip strength; range of motion; disabilities of the arm, shoulder, and hand (DASH) scores; and time to return to work were not universally collected. Analysis of these factors could provide essential insight into the clinical relevance of this head-to-head fixation comparison, and prospective investigation to evaluate these functional outcomes is a necessary next step in the assessment of these 2 techniques. Furthermore, a comparison of surgical time would be clinically relevant; however, this has not yet been established in the case of nitinol compression staples.

Conclusions

In the experience of the authors, treatment of scaphoid waist fractures with a nitinol compression staple versus a headless compression screw require similar amounts of time; however, they have found staple fixation to be the overall more efficient technique and may prevent graft extrusion owing to a buttressing effect of the staple. Staple fixation also offers technical advantages in that the scaphotrapezial joint is avoided (retrograde screw fixation) as is the proximal cartilage (anterograde screw fixation), and impingement of the distal radius is avoided utilizing techniques similar to those employed in other scaphoid plating and is described more thoroughly in Congiusta et al.²¹ With a mind to cost-conscious care, neither device provides benefit over the other as the price of the constructs are similar.

Acknowledgments

Authors: Adam M. Kurland, BA¹; Dominick V. Congiusta, MD, MPH¹; Ashley Ignatiuk, MD²; Abram E. Kirschenbaum, MD¹; Michael M. Vosbikian, MD¹; Irfan H. Ahmed, MD¹

Affiliations: ¹Department of Orthopaedic Surgery, Rutgers New Jersey Medical School, Newark, New Jersey; ²Department of Surgery, Plastic & Reconstructive Surgery Division, Rutgers New Jersey Medical School, Newark, New Jersey

Correspondence: Dominick V. Congiusta, MPH; dvc33@njms.rutgers.edu

Ethics: IRB study ID: Pro20170000549, "Orthopaedic Hand Surgery Outcomes and Complications: Retrospective Review."

Disclosures: The authors disclose no potential conflicts of interest in the information and production of this manuscript.

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