Abstract
Background:
Metacarpal fractures are common orthopedic injuries with potentially debilitating outcomes. Ideal surgical treatment remains a topic of debate, with intramedullary fixation becoming popular as a technique to allow for earlier mobilization with few reported complications. The aim of this study was to report observed outcomes and complications of intramedullary metacarpal fixation using the ExsoMed INnate metacarpal nail.
Methods:
A retrospective chart review of 37 patients with 44 metacarpals treated with the ExsoMed INnate between July 2020 and December 2021 by a single fellowship-trained hand surgeon at a single level 1 trauma center was performed. Variables recorded included both patient and injury demographics, surgical complications, and postoperative outcomes. We also measured metacarpal isthmus diameter of the second to fifth metacarpals on all patients to determine the intramedullary canal diameter to assist in implant size selection.
Results:
Average follow-up was 5.84 weeks with average time to radiographic healing of 5.5 weeks, and time to full activity 6.32 weeks. The mean postsurgical active total arc of motion was 250°, while passive total arc of motion was 259.74°. A total of 10 complications (22%) were identified, including 4 bent screws which occurred as a result of a punching event postoperatively.
Conclusions:
Intramedullary fixation of metacarpal fractures using the ExsoMed INnate metacarpal nail has shown to preserve range of motion and quick return to full activity, with a low rate of major complications. Our study highlights the potential major complication of the bent intramedullary screw and its association with an initial punching mechanism.
Keywords: intramedullary, metacarpal, hand, fracture/dislocation, diagnosis, fixation, outcomes, research and health outcomes, complications
Introduction
Metacarpal fractures are common orthopedic injuries, comprising approximately 33% of all hand fractures, mainly affecting men in their second and third decades of life. 1 These fractures can be debilitating and may pose substantial morbidity for patients both in the short and long term. Optimal treatment of metacarpal fractures provides bony stability to allow for early range of motion and to facilitate quick return to full activity; however, the ideal treatment strategy remains controversial.
While many metacarpal fractures can be successfully treated nonoperatively to achieve the goal of adequate alignment and reliable return to function, surgical fixation often becomes the treatment of choice when rotational deformity, shortening, articular surface step-off, or multiple metacarpal fractures are present. 2 Surgical fixation constructs include Kirschner wires, plate and screw constructs, interfragmentary screws, dynamic traction devices, static external fixators, and intramedullary devices. 3 Owing to the varying strengths and weaknesses of these fixation modalities, the decision of which to use in various circumstances remains a topic of debate.
Metacarpal intramedullary fixation is a newer technique first described in 2010 by Boulton et al 4 in which the device is inserted into the metacarpal shaft in a retrograde fashion through an arthrotomy made within the metacarpophalangeal joint. These devices have been used for the treatment of displaced or comminuted metacarpal fractures. A meta-analysis from 2019 describes intramedullary metacarpal fixation as a safe and effective surgical treatment option that allows patients to mobilize early and return to activity more quickly. 5 In addition, when compared with the other fixation methods listed above, intramedullary nails confer the advantage of decreased extensor tendon irritation from lack of extramedullary hardware and a smaller surgical dissection and thus less scarring and subsequent stiffness due to adhesions. Furthermore, due to the stability conferred by the construct, postoperative immobilization can be minimized or eliminated and earlier range of motion initiated. The current disadvantages of intramedullary fixation include cost of the implant, limited long-term data, and restricted indications for use.
Although intramedullary metacarpal implants have been in use for over a decade, this literature describing their use consists primarily of studies with small patient cohorts. The purpose of this study was to report short-term outcomes and complications in a larger cohort of patients who underwent metacarpal fracture fixation by a single implant, the ExsoMed INnate intramedullary nail (Aliso Viejo, California).
Materials and Methods
After institutional review board approval was obtained, a retrospective chart review was performed of all adult patients aged 18 years or older who underwent surgical fixation of metacarpal shaft fractures from July 2020 to December 2021. Only fractures fixed with the ExsoMed INnate intramedullary nail implant were included in the study. All surgeries were performed by a single fellowship-trained hand surgeon at a single level 1 trauma center. Variables recorded include patient demographics, initial diagnosis, surgical duration, radiographic alignment, time to radiographic healing, intramedullary nail diameter, time to full activity, final active and passive range of motion, number of hand therapy visits, number of postoperative visits, total length of follow-up, and any complications. Radiographs were reviewed by a single orthopedic surgery chief resident. Range of motion measurements were obtained using a goniometer in the office postoperatively by the treating surgeon or by a hand therapist. Data analysis was performed of all numerical data to provide simple descriptive data, including standard deviation using JASP.
Results
A total of 222 patients with surgically treated metacarpal fractures were initially identified. Patients with methods of fixation other than the ExsoMed INnate intramedullary nail were excluded from the study. Metacarpal fractures were evaluated individually in patients who underwent multiple metacarpal nail placement (n = 7). Ultimately, 37 patients with 44 metacarpal fractures met the inclusion criteria. Thirty patients were men and 7 were women. The average patient age was 30.9 years. There were 22 active tobacco users. The fourth metacarpal was the most commonly fractured metacarpal (n = 24, 54.54%). Complete demographic data can be found in Table 1. No patient was immobilized postoperatively; however, patients are instructed to remain nonweightbearing and to avoid lifting or grasping for 4 weeks after surgery. Average follow-up time was 5.84 weeks (SD = 6.37). The average time to radiographic healing was 5.5 weeks (SD = 1.95), and time to full activity was 6.32 weeks on average (SD = 2.79). The mean postsurgical active total arc of motion (metacarpophalangeal joint + proximal interphalangeal joint + distal interphalangeal joint) was 250° (SD = 34.88), while passive total arc of motion was 259.74° (SD = 24.97). A total of 10 complications (5 major, 5 minor) were identified. Major complications included 4 bent screws which occurred as a result of a punching event postoperatively and 1 loss of reduction. Minor complications reported included stiffness (n = 3) and extensor lag (n = 2). Complete outcome data may be found in Table 2.
Table 1.
Patient Demographics.
| Demographic | Result |
|---|---|
| Total nails, N | 44 |
| Age, y, mean (SD) | 30.93 (13.46) |
| Sex | |
| Male, N (%) | 37 (84.09) |
| Female, N (%) | 7 (15.91) |
| Race | |
| White, N (%) | 26 (59.09) |
| African American, N (%) | 6 (13.64) |
| Hispanic, N (%) | 6 (13.64) |
| Tobacco use, N (%) | 22 (50.00) |
| Diabetes, N (%) | 2 (4.55) |
| Hemoglobin A1c, mean % | 6.4 |
| Psychiatric diagnosis, N (%) | 14 (31.82) |
| Laterality | |
| Right, N (%) | 26 (59.09) |
| Left, N (%) | 18 (40.91) |
| Affected metacarpal | |
| 2nd, N (%) | 1 (2.27) |
| 3rd, N (%) | 8 (18.18) |
| 4th, N (%) | 24 (54.55) |
| 5th, N (%) | 11 (25.00) |
Table 2.
Surgical Outcomes.
| Outcome Measure | Result |
|---|---|
| Procedure length (total in room time), min, mean (SD) | 68.82 (22.62) |
| Anesthesia type | |
| General, N (%) | 43 (97.73) |
| Regional, N (%) | 1 (2.27) |
| Coronal + Sagittal displacement, degrees, mean (SD) | 8.13 (19.43) |
| Axial displacement, degrees, mean (SD) | −0.23 (0.78) |
| Time to radiographic healing, wk, mean (SD) | 5.5 (1.95) |
| Other concurrent procedures, N (%) | 19 (43.18) |
| ExsoMed implant size | |
| 3.6 mm, N (%) | 20 (45.45) |
| 4.5 mm, N (%) | 24 (54.55) |
| Time to full activity, wk, mean (SD) | 6.32 (2.79) |
| Final active total arc of motion, degrees, mean (SD) | 250 (34.88) |
| Final passive total arc of motion, degrees, mean (SD) | 259.74 (34.97) |
| Hand therapy visits, N, mean (SD) | 0.55 (2.24) |
| Postoperative visits, N, mean (SD) | 1.66 (1.15) |
| Length of follow-up, wk, mean (SD) | 5.84 (6.37) |
| Complications | |
| Total, N (%) | 10 (22.73) |
| Bent screws N (%) | 4 (9.1) |
| Stiffness N (%) | 3 (6.8) |
| Extensor lag, N (%) | 2 (4.5) |
| Reduction loss, N (%) | 1 (2.3) |
Discussion
Metacarpal fractures are 1 of the most common orthopedic injuries, and intramedullary fixation has been described in increasing frequency as a novel approach to fracture fixation that minimizes complications. The primary purpose of this study was to observe the outcomes and report complications of intramedullary metacarpal fixation in our cohort treated with the ExsoMed INnate metacarpal nail.
Consistent with previous studies, postoperative range of motion averaged 250° with return to full activity occurring at around 6 weeks. 6 This supports previous claims that earlier mobilization can be initiated with intramedullary screw fixation and, thus, less postoperative stiffness can be expected.
Per common teaching and the ExsoMed surgical technique guide, the 3.6-mm screw has been commonly used for the narrower isthmus characteristically encountered in the fourth metacarpal. It is important to note there is a need for an intraoperative or preoperative measurement of both the length and diameter of the fractured metacarpal before selecting the appropriate implant size. Appropriate implant selection is important as undersizing the metacarpal nail appears to be a risk factor for postoperative loss of reduction, as was noted in our 1 case that experienced postoperative loss of reduction.
Interestingly, while the overall complication rate for intramedullary screw fixation has been reported to be as low as 2.5% in some studies, 7 our overall complication rate was 22%. While our overall complication rate is higher than previously reported, 5 (50%) of our complications were minor in nature consisting of digital stiffness or mild extensor lag. Most concerning is our finding of bent screws which occurred in 4 patients following repeat trauma from punching mechanisms, which we consider to be a major complication. We believe our patient demographics played a role in this finding, as 31% have a concomitant psychiatric diagnosis, and all 4 bent screws occurred in patients whose initial injury also occurred via a punching mechanism. Therefore, we recommend a thorough patient evaluation and consideration of the entire patient’s medical, psychiatric, and social history before usage of intramedullary fixation for metacarpal fractures. For example, at our institution, we now consider a punching mechanism of injury to be a contraindication to intramedullary screw fixation, and elect to treat those metacarpals with other fixation methods based on injury pattern. Of note, all bent screws were left in place, given the patients’ noncompliance, relatively insignificant degrees of displacement, and the potential complications and difficulty anticipated with implant removal.
There are a few limitations to our study. This study includes outcomes from a single surgeon at a single institution. Therefore, these results may not be generalizable to the overall population. We also have a mean follow-up of 5 weeks, so a longer length of follow-up would be helpful in determining long-term results and complications of intramedullary screw fixation as compared with more traditional methods. Despite the short-term follow-up, we do believe reporting of short-term outcomes and complications is important here as fracture healing and return to full activity may be expected within 6 weeks after a metacarpal fracture. We also may only report the incidence of bent screws in our study. Further investigation would help delineate operative indications and techniques for treatment, given this unique complication.
Overall, with appropriate patient selection, we find intramedullary fixation of metacarpal fractures using the ExsoMed INnate metacarpal nail to be technically simple, but not without a notable risk of implant failure due to future punching acts. We strongly recommend against the use of this device in patients in whom the initial mechanism of injury was a punching event, as a future punching event can lead to the major complication of a bent intramedullary implant.
Footnotes
Ethical Approval: This study was approved by our institutional review board.
Statement of Human and Animal Rights: All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2008 (5).
Statement of Informed Consent: Institutional review board exemption of the requirement for informed consent was obtained for this retrospective chart review study.
The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: The senior author (W.F.P.) is a consultant for Acumed and MicroAire, but received no external support or funding for this project. The remaining authors have no conflict of interests.
Funding: The author(s) received no financial support for the research, authorship, and/or publication of this article.
ORCID iDs: Stewart Dalton 
https://orcid.org/0000-0003-2225-7969
William F. Pientka
https://orcid.org/0000-0002-4202-9798
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