Percutaneous Fibular Nail for Ankle Fractures: An Anatomic Mapping Study

Introduction

Ankle fractures represent about 9% of all fractures, ¹ with their incidence rising, especially among the geriatric population.^2,3 Since the 1960s, the gold standard for managing displaced ankle fractures has been open reduction and internal fixation (ORIF) with plates and screws, as established by the AO group. ⁴ This technique enables accurate anatomical reduction and stable fixation by providing direct visualization of the fracture site.

However, the use of an open approach with plates and screws is associated with a significant risk of complications.^{5 -7} Wound infections have been reported in up to 26% ⁸ of cases, with hardware-related complaints in up to 50%, ⁹ and mechanical failure occurring in 14%. ¹⁰ The complication rates are particularly elevated in the elderly ¹¹ and those with diabetes or neuropathy. ¹² As the global geriatric population grows and the incidence of comorbidities rises, the number of ankle fractures in this demographic has also increased, thereby amplifying the risk of complications associated with the ORIF technique.^{1 -3}

In order to minimize complications in this patient population, several treatment modalities have been proposed: non-surgical management, external fixation, and intramedullary nailing. Minimally invasive strategies, in particular, offer the advantage to reduce soft tissue complications associated with ORIF. The intramedullary fibular nail (IFN) offers an additional advantage by providing stable internal fixation that is biomechanically superior^13,14 and reduces cutaneous prominence when compared to traditional plates and screws.^15,16 This lower-profile construct reduces the risk of hardware irritation, wound complications, and soft tissue breakdown—particularly important in patients with compromised skin or comorbidities. Early designs introduced in the 1980s had limitations, ¹⁵ but subsequent generations have demonstrated improved biomechanical stability and allow for smaller incisions. Although this procedure can be performed through a standard open approach, percutaneous reduction further minimizes soft tissue trauma and the risk of wound-related complications. This technique appears to show low soft tissue complications, good to excellent functional results, and high consolidation rates.^{17 -19}

Despite the reduced complication rate with IFN, the percutaneous approach may potentially increase the risk of injury to nearby soft tissue structures, and the adequacy of bone reduction remains a concern. The objective of this research was to perform an anatomical study to assess the quality of bone reduction and the risk of damaging surrounding nerve and tendon structures when performing IFN.

Material and Methods

The present study was approved by the institutional review board under the designation number 00003099. It included 10 non-paired fresh frozen cadaveric feet (5 females, 5 males). The specimens were segmented at the proximal tibia shaft and thawed at room temperature 24 hours before dissection. Five specimens were right-sided, and the remaining 5 were left. All specimens were examined for previous incisions, scars, and evidence of pathologic tissue. None of the specimens had indication of lower extremity bony disease or trauma.

The lateral malleolus was percutaneously osteotomized with a 2-mm burr in an oblique direction 10 cm from the tip of the fibula to simulate a Weber B– or C–type fracture. Subsequently, the specimens were subjected to a manual external rotation force until total displacement of the fragments could be identified fluoroscopically. Next, the specimens were instrumented with a contemporary retrograde locked IM fibular nail (ANVISA: 10209780098, Hexagon, BR), which provided 2 distal locking and 2 syndesmotic screw fixation options. The IFN technique requires 3 portals: 1 distal, to introduce the nail at the tip of lateral malleolus, and 1 anterolateral and 1 lateral, with an average 1 to 2 cm each to insert the locking screws. Following incision, a mosquito clamp was used to bluntly dissect the soft tissues, creating a space between the skin and bone to protect adjacent structures at risk. A standardized percutaneously closed reduction with a Backhaus clamp was performed under mini–C-arm fluoroscopic guidance (Figure 1).

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Figure 1.

Fluoroscopic anteroposterior view of ankle fracture reduction with the Backaus clamp and introduction of the nail guide (A) profile view (B).

Initial fracture displacement was confirmed fluoroscopically following manual external rotation torque; however, the precise pre-reduction displacement was not quantitatively measured in millimeters. The final reduction was then strictly assessed against <3 mm cortical offset threshold, as established by White et al, ¹⁶ to evaluate the efficacy of the indirect technique. The nail was then inserted at the tip of the lateral malleolus and then fixed with 2 distal and 2 syndesmotic screws.

All specimens were then dissected using a uniform technique performed by an experienced anatomist (Figure 2). In the context of lower limb anatomy, the structures at risk during this minimally invasive surgery, using the standard 3 portals, include the sural nerve, superficial peroneal nerve, and peroneal tendons. Consequently, the dissection focused on these structures (Figure 3). The shortest distance between the incision sites and the adjacent anatomical structures was measured in millimeters using a digital caliper by 2 independent evaluators. Descriptive statistical methods were applied to analyze the results. The inter-rater reliability for all distance measurements was assessed using the intraclass correlation coefficient (ICC).

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Figure 2.

One of the foot specimens used for the study is shown. Left: the specimen after the procedure, with the lateral portal (1), the anterior portal (2), and the distal portal (3) marked. Right: the same specimen after superficial dissection, showing the superficial peroneal nerve (4) and the sural nerve (5).

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Figure 3.

The same specimen dissected in Figure 1 is shown with the peroneal muscles detached, and no damage was found in this structure. Later, the fibula was deperiostized in order to show the fracture line and its reduction (1).

Fluoroscopy images were used to evaluate fracture reduction (Figure 4). Reduction of the fibula was considered acceptable based on criteria adapted from White et al ¹⁶ : (1) an anatomical mortise and (2) a fibular shaft cortex displacement (typically at the apex of a long posterior spike in a supination-external rotation fracture) of less than 3 mm. This threshold was used as a study-specific metric to evaluate the efficacy of indirect percutaneous reduction.

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Figure 4.

Fluoroscopic image of the ankle during the procedure. (A) Left: Ankle fracture model. (B) Center: AP view of the fracture fixed with the fibular nail showing good reduction. (C) Right: ankle fixed profile view.

To validate these findings, all specimens were assessed both pre- and post-intervention by 2 independent senior surgeons. Reduction quality was classified as good, if they met the aforementioned parameters, regular if the mortise was anatomical but the fibular shaft cortex displacement was up to 5 mm, or poor if the mortise was not anatomical or the displacement exceeded 6 mm.

Results

The dissection successfully identified the sural nerve, superficial peroneal nerve (SPN), and peroneal tendons in all specimens. The measured distances are summarized in Table 1. Inter-rater reliability between the two independent evaluators was assessed using the ICC and found to be high (ICC = 0.882; 95% CI, 0.780-0.940).

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Table 1.

Distance (in millimeters) between percutaneous portal sites used for intramedullary fibular nail fixation and adjacente anatomical structures at risk.

	Investigator 1,Mean ± SD	Investigator 2,Mean ± SD	Mean	Range
Lateral portal to SPN	14.00 ± 6.00	14.30 ± 5.00	14.17 ± 5.25	5.3-23.1
Anterior portal to SPN	5.00 ± 4.50	4.50 ± 3.50	4.52 ± 3.27	0.00-8.80
Distal portal to sural nerve	15.40 ± 3.60	14.50 ± 4.70	14.95 ± 3.99	6.80-22.50

Abbreviation: SPN, superficial peroneal nerve.

The SPN was consistently located more than 5 mm from the lateral portal in all specimens, with an average distance of 14.17 mm (range: 5.3-23.1 mm). Regarding the anterior portal, the SPN was located at a mean distance of 4.52 mm (range: 0-8.8 mm). In 3 cadavers, the SPN was found in direct contact with the skin incision; however, no gross injury was observed on macroscopic assessment. The distance from the sural nerve to the distal portal was 14.95 mm on average (range 6.8-22.5), with a minimum distance of >5 mm in all specimens.

Although the peroneal tendons were in proximity to the distal and lateral portals, no macroscopic damage was observed during anatomical dissection. Their substantial size and reliable palpability may reduce the likelihood of iatrogenic injury; however, as specific tendon-to-portal distances were not measured, a potential risk of injury cannot be entirely excluded. In this cadaveric model, the tendons remained grossly intact after instrumentation. Postoperative radiographs demonstrated that all 10 specimens achieved the study-specific <3-mm reduction goal, as independently confirmed by both surgeons. No case was graded as regular or poor.

Discussion

The primary finding of this study is that the fibular nail is a safe option for the treatment of distal fibular fractures. The risk of injury to surrounding neurovascular and tendon structures is low, provided meticulous surgical execution is observed, particularly when working through the anterior portal. These “safe-zone” distances are specific to the Hexagon BR nail’s portal trajectories and should be extrapolated cautiously to other intramedullary systems with differing locking geometries. In addition, the technique proved to be a reliable and efficient method, permitting adequate fracture reduction and stable fixation. Its minimally invasive nature may further decrease the likelihood of soft tissue complications.

Several studies have assessed the relative risk of damage to adjacent structures when performing ORIF of distal fibula fractures with a lateral plate and screws.^20,21 However, to our knowledge, there’s just 1 publication in the literature that evaluates the structures at risk when performing an IFN in a cadaveric ankle. According to Goss et al, ²² the peroneal tendons and superficial peroneal nerve were at the highest risk of injury; however, no structures were wounded during instrumentation. Their study was limited by the absence of fractures in the specimens, which may have influenced the results. Furthermore, the quality of fracture reduction could not be assessed.

The purpose of a surgical treatment of unstable distal fibular fractures is to achieve anatomical reduction and a stable fixation while minimizing the risk of postoperative complications. ⁴ ORIF with plate and screws remains the gold standard technique, but minimally invasive methods have been developed to mitigate soft tissue damage. Initially, intramedullary screw fixation was described but provided limited stability. Fibular nailing was introduced in the 1980s,^15,23 but early designs were associated with limited to poor rotational and axial stability, which led to nail migration and malunion. ²⁴ Newer designs offer better mechanical stability, excellent clinical results, and less prominent metalwork.^25,26 The nail used in this study allows for screw placement in both the fibula and tibia, enhancing stability and providing the potential for syndesmotic stabilization.

The surgical approach to ankle fractures inherently poses a risk to the surrounding soft tissue structures, such as nerves and tendons. The size and location of the incisions are directly associated with the risk of wound healing complications. This concern has been a driving force behind the development of minimally invasive techniques. The IFN technique requires 3 small portals—distal, anterolateral, and lateral—each approximately 1 to 2 cm in size. Based on anatomical knowledge, the structures at risk are the sural nerve, the superficial peroneal nerve, and the peroneal tendons. Regarding the potential damage to these structures, although we had 3 cases in which the anterior portal corresponded with the location of the superficial peroneal nerve, no damage was found on dissection. Despite the theoretical risk of peroneal tendons injury, ²² we found no lesion to these structures. We believe this is due to strict adherence to percutaneous techniques, including skin-only incisions, blunt dissection down to the bone, and maintaining close proximity between the tissue protection sleeves and the bone throughout the entire procedure.

As an intramedullary device, the fibular nail uses the indirect reduction technique and provides a stable fixation; however, the anatomical reduction of the fracture site is not always easy. Although open reduction allows for precise fracture positioning, internal fixation with plates and screws inevitably causes some significant soft tissue damage.

In this study, the 3-mm threshold for cortical displacement was adopted from previous clinical trials assessing the fibular nail. ¹⁶ Although traditional ORIF aims for absolute anatomical restoration, our findings suggest that, in this cadaveric model, the indirect technique achieved this <3-mm threshold, which has been shown to yield satisfactory functional outcomes in elderly and high-risk cohorts. Despite the use of an indirect technique, this research demonstrates the feasibility of achieving an acceptable reduction, as all operated specimens met the reduction criteria during postoperative evaluation. These findings support the effectiveness of the percutaneous technique in this cadaveric model; however, clinical translation requires further study. However, the need for more precise fracture reduction must be carefully weighed against the risks associated with an open approach.

This study is not without limitations. Chief among them is the use of a Shannon burr for fibular osteotomy; despite adjunct manual external rotation torque, this technique likely under-reproduced the comminution and soft tissue disruption typical of ankle fractures. Furthermore, the lack of quantitative pre-reduction displacement data prevents a statistical comparison of the reduction magnitude. The cohort of 10 specimens also restricts generalizability across anatomic variants. Regarding safety, the assessment of nerve and tendon integrity was limited to macroscopic dissection, and although no gross injuries were observed, this method may miss subtle neurapraxia, and functional or microscopic injuries cannot definitively be excluded. Moreover, although the lack of quantitative distance metrics precludes a statistical confirmation of a “low risk” profile for the peroneal tendons, no macroscopic injuries were observed across all specimens.

Beyond these factors, the study did not evaluate the lateral collateral ligament complex; no dissections, distance metrics, or stress tests were performed on the ATFL, CFL, or PTFL. Similarly, chondral safety was not evaluated, leaving the risk of intra-articular scuffing uncharacterized. It should also be noted that immediate post-osteotomy fixation precluded the evaluation of time-dependent construct behavior, such as cyclic-load tolerance or biologic influences on union. Finally, fresh frozen cadavers exhibit reduced soft tissue compliance compared with anaesthetized patients, limiting inferences regarding closed reduction maneuvers.

Intramedullary nailing of distal fibular fractures holds a significant role in clinical practice. The advantage of reduced soft tissue complications must be balanced against the challenge of achieving optimal anatomical reduction. As a minimally invasive procedure, fibular nailing offers several distinct advantages, although it is not without limitations. The percutaneous approach substantially reduces soft tissue dissection, thereby lowering the complication rates related to wound healing and infection, especially in high-risk patients. Additionally, this technique mitigates issues associated with hardware failure or discomfort and has been associated with improved consolidation rates. Consequently, intramedullary fibular nailing should be strongly considered for patients at elevated risk for soft tissue complications, including elderly individuals and those with comorbidities such as diabetes, neuropathy, vascular disease, or a history of tobacco use.^12,27 According to White et al, ¹⁶ there is no difference in functional outcomes.

To ensure the use of the IFN, future high-quality clinical research is needed to evaluate the functional outcomes and complication rates of this technique compared with the gold standard use of plates and screws.

Conclusion

In this cadaveric anatomic mapping study, percutaneous retrograde intramedullary fibular nailing was associated with no macroscopic injury to the sural nerve, superficial peroneal nerve, or peroneal tendons across all 10 specimens. The superficial peroneal nerve represented the structure at greatest anatomic risk, particularly at the anterior portal, and surgeons should exercise particular caution at this site. All specimens met the study-specific fracture reduction threshold, supporting the feasibility of indirect percutaneous reduction in a cadaveric model. These findings do not establish clinical efficacy or safety, and extrapolation beyond the Hexagon BR nail system and its portal geometry should be made with caution.

Future prospective clinical studies are needed to evaluate functional outcomes, complication rates, and the generalizability of these anatomic findings across patient populations and implant systems.

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