Cannulated Intramedullary Screw Fixation of Distal Fibular Fractures

Introduction

Ankle fractures are a common occurrence faced by orthopaedic surgeons, with an incidence of 187 in 100 000 people a year. ¹ While already accounting for approximately 9% of all fractures, ² population studies have shown that ankle fracture incidence has been steadily increasing, particularly in elderly patients.^1-4 Over time, surgical approaches to ankle fracture repair have remained almost unchanged, dating back to the 1960s. Traditional, and most commonly used, surgical methods for distal fibula fractures require an invasive lateral incision by utilizing open reduction and internal fixation (ORIF).^5,6 Despite a high frequency of postoperative wound complications, ORIF, particularly locking plates and screws, remains the method of choice for surgical repair of distal fibular fractures. Because of its invasive approach, complication rates are as high as 30%, ⁵ wound infections can affect up to 26% of patients, and hardware complications have been reported in up to 50% of patients.^7-9 Additionally, mechanical hardware failure has been reported in up to 14% of cases. ⁸ Complications occur more frequently in patients with significant comorbidities, including those who smoke and those who are elderly, osteoporotic, and diabetic.^1,10-12 Notably, these patients are also more vulnerable to developing soft-tissue conditions and have seen a continual increase in ankle fracture occurrence.^1,13 The prevalence of serious complications in patients with soft-tissue conditions is as high as 42%.^14,15

Nearly 70% of ankle fractures are unimalleolar, with the majority being lateral malleolar fractures. ² Fractures of the lateral malleolus, or distal fibula, can occur during a high-energy trauma, such as a motor vehicle accident, or during a low-energy trauma, such as a short fall. Patients with fibular fractures associated with higher-energy injuries have high occurrences of wound complications, with increased risk of complications especially if an open fracture occurs.^16-18 Distal fibular fractures may involve only the fibula or may occur in association with a tibial or ankle fracture. Standard treatment for lateral unimalleolar open fractures, fractures with severe soft-tissue conditions, and fractures at risk of infection involves stabilization of the fracture with an external fixator to first facilitate initial soft-tissue healing, followed by ORIF. ¹⁹ Common ORIF methods include the use of plates, screws, intramedullary rods, tension bands, or K-wires.^12,20-24 Plate and screw fixation remains the most common ORIF technique, despite fibular plating having up to a 30% complication rate consisting primarily of wound breakdown, infection, and hardware irritation. ²⁵ Hardware pain and operative wound infection are commonly associated with ORIF and have become more prevalent with the use of newer locking plates.^9,26,27

Recently, the literature has suggested that intramedullary fibular nail fixation can outperform the conventional fixation plate and screws while using a less-invasive approach.^28-34 Although intramedullary fibular nail fixation has been used for more than 25 years, recent design improvements, including an interlocking nail, fibula-specific intramedullary nails, and a hole for syndesmosis screw placement, have led to the emergence of intramedullary nail fixation as a viable alternative approach for treatment of distal fibular fracture.^12,35 Intramedullary nail fixation is often an advantageous choice for patients with poor skin conditions, comorbidities such as diabetes, and very osteoporotic or comminuted bone. Recently, another minimally invasive method has emerged: the cannulated intramedullary screw. However, there is no clinical report studying its use as a minimally invasive approach for distal fibular fractures. The purpose of this study is to analyze the outcome of 45 patients who had a distal fibular fracture repaired using cannulated intramedullary screws.

Patients and Methods

This retrospective study looked at 45 patients with distal fibular fractures treated with percutaneous cannulated intramedullary screw fixation from 2010 and 2013; all 45 patients were treated at a level 1 trauma center. Data were examined after approval from the institutional review board.

The patient cohort included 13 male and 32 female patients with a mean age of 54 (range, 15-94) years; 14 patients were older than 60 years, and 7 of those patients were 65 years old or older and considered elderly. All patients included in the cohort had either poor soft-tissue conditions and/or medical comorbidities, which increased their risk for wound complication if traditional ORIF were used. Medical comorbidities consisted of diabetes mellitus, coronary artery disease, morbid obesity, peripheral neuropathy, peripheral vascular disease, recent methicillin-resistant Staphylococcus aureus infection, and immunocompromised. Among the patients, 15 had diabetes, 9 had peripheral neuropathy, 9 had coronary artery disease, and 22 were either current or former smokers. In all, 28 patients had one or more medical comorbidities. All patients included in the study had either a comorbidity or soft-tissue condition, often both. Patient demographics and comorbidities are summarized in Table 1.

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Table 1.

Demographics and Comorbidities of the 45 Patients.

Demographics
Mean age, years (range)	54	(15-94)
Elderly, n (%)	7	(16)
Gender, n (%)
Female	32	(71)
Male	13	(29)
Comorbidities, n (%)
Diabetes mellitus	15	(21)
Coronary artery disease	9	(12)
Peripheral neuropathy	9	(12)
Hypertension	7	(10)
Peripheral vascular disease	4	(5)
Chronic obstructive pulmonary disease	4	(5)
End-stage renal disease	3	(4)
Deep-vein thrombosis	3	(4)
Morbid obesity	3	(4)
Rheumatoid arthritis	3	(4)
Chronic heart failure	2	(3)
MRSA	2	(3)
Osteomyelitis	2	(3)
Acute myelogenous leukemia	1	(1)
Chronic kidney disease stage 3	1	(1)
Decubitus ulcers	1	(1)
Mental retardation developmental disorder	1	(1)
S/P bone marrow transplant	1	(1)
Von Willebrand disease	1	(1)
Number of comorbidities, n (%)
⩾5	4	(9)
4	3	(7)
3	4	(9)
2	13	(29)
1	4	(9)
0	17	(38)
Smoking, n (%)
Yes	13	(29)
No	23	(51)
Previous	9	(20)

Abbreviations: MRSA, methicillin-resistant Staphylococcus aureus; S/P, Status Post.

Of the 45 patients, 35 had soft-tissue conditions consisting of abnormal swelling, fracture blisters, or open wounds/abrasions. Swelling was determined to be a soft-tissue condition, based on severity or abnormality, at the discretion of the attending physician. According to American Society of Anesthesiologists classification, 9% were grade I, 27% were grade II, 55% were grade III, and 9% were grade IV. A summary of the soft-tissue conditions is shown in Table 2.

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Table 2.

Soft-Tissue Conditions.

Soft-Tissue Conditions	n (%)
Swelling	21 (47)
None	10 (22)
Blisters	7 (16)
Swelling, medial wound	2 (4)
Blisters, abrasion	1 (2)
Blisters, fasciotomy wound	1 (2)
Blisters, open fixation	1 (2)
Open fixation, swelling	1 (2)
Open wound	1 (2)

Figures 1A to 1F show the X-rays of a 17 year old male, Motorcycle Crash, Supination External Rotation Fracture Type IV (17M MCC, SER IV) with significant soft-tissue abrasions. This patient developed deep-vein thrombosis, swelling, and fracture blisters.

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Figure 1.

17M MCC, SER IV with significant soft-tissue abrasions, developed deep-vein thrombosis, swelling, and fracture blisters. A. Preoperative anteroposterior (AP) radiograph. B. Preoperative oblique radiograph. C. Preoperative lateral radiograph. D. Postoperative AP radiograph. E. Postoperative oblique radiograph. F. Postoperative lateral radiograph.

Although all included patients had distal fibular fractures, some also had associated injuries and were treated with a cannulated intramedullary screw as a means of fixation. Any fracture involving the distal third of the fibula, either open or closed, was included in this study. Any fracture involving the proximal two-thirds of the fibula was excluded. Of the 45 patients in the study cohort, 36 had closed fractures, and 9 had open fractures. Also, 11 patients had associated tibial fractures, including 5 pilon and 6 distal tibial fractures; 34 had isolated lateral malleolar fractures with no associated fractures and were classified using the Weber classification. Accordingly, 6 cases were type A, 26 were type B, and 2 were type C. Fracture classification is shown in Table 3.

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Table 3.

Fracture Type.

Fracture Type	n (%)
Weber B	26 (58)
Weber A	6 (13)
Lateral malleolus and distal tibia	6 (13)
Pilon	5 (11)
Weber C	2 (4)

The mechanism of injury consisted of motor vehicle crashes, motorcycle crashes, falls, and twisting or low-energy falls. Mechanisms of injury distribution are shown in Table 4.

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Table 4.

Mechanism of Injury.

Mechanism of Injury	n (%)
Simple fall	34 (76)
Motor vehicle crash	7 (16)
Crush	2 (4)
Fall from height	1 (2)
Motor cycle crash	1 (2)

Figures 2A to 2E show the preoperative and postoperative images of a 41-year-old man with distal fibular fracture secondary to a high-energy traumatic fall.

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Figure 2.

A 41-year-old man who had a high-energy trauma fall, 43-C2 articular simple, metaphyseal multifragmentary. A. Preoperative anteroposterior (AP) radiograph. B. Preoperative lateral radiograph. C. Postoperative AP radiograph with external fixator. D. Postoperative lateral radiograph with external fixator. E. 12-Week postoperative AP radiograph.

Reduction quality was determined using radiological and clinical results according to the McLennan and Ungersma method. ³⁶ Using the radiograph and clinical results, the fracture was assessed by one principal attending physician, and reduction quality was determined accordingly. Using this method, good reduction was defined as <1 mm medial clear space widening and <2 mm posterior displacement. Fair reduction was defined as 1 to 3 mm medial clear space widening; 2 to 3 mm posterior displacement, and <2 mm fibular shortening. Poor reduction was defined as >3 mm medial clear space widening, >4 mm posterior displacement, and >2 mm fibular shortening (Table 5).

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Table 5.

Quality of Reduction according to McLennan and Ungersma’s Criteria.

Quality of Reduction	MCS Widening	Posterior Displacement	Fibular Shortening
Good	<1 mm	<2 mm	None
Fair	1-3 mm	2-4 mm	<2 mm
Poor	>3 mm	>4 mm	>2 mm

Results

The average follow-up time was 6 months (range = 2-35 months). The average time to surgery from the date of injury was 8 days (range = 0-63 days). Average time to union for all the patients was 10 weeks (range = 8-36 weeks). The average time to weight bearing was 14 weeks (range = 8-40 weeks). Reduction quality was determined using the McLennan and Ungersma method. ³⁶ Accordingly, 25 patients showed good fracture reduction, 15 showed fair reduction, and 5 showed poor reduction. Nonunion was seen only in 1 patient.

A total of 42 patients had the screw placed without reaming, whereas the remaining 3 patients had the screw placed with reaming. Syndesmotic screws were used in 5 patients. Overall, of the 45 patients, none developed lateral wound complications or infections. Five patients developed infections at the medial incisions or open fracture site; 1 patient developed an infection at the pin sites of the Taylor Spatial Frame during external fixation. Fibular cannulated intramedullary screws were removed in 2 patients. One patient had symptomatic hardware that resulted in hardware removal. The other patient required the removal of the cannulated screw because of a distal fragment that was not fixed with the screw, which resulted in nonunion; the fracture was then treated with a locking plate. A summary of complications is shown in Table 6.

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Table 6.

Summary of Complications.

Description	Number
Hardware removal	2 Fibular screws (1 nonunion, 1 symptomatic hardware)
Infection	4 Medical incisions or open fracture sites; 1 pin site during external fixation
Nonunion	1 Case

Discussion

Ankle fractures are commonly treated with ORIF, resulting in a high incidence of complications. Patients with comorbidities, such as diabetes or neuropathy, a history of smoking, or compromised local soft tissue, are at an even higher risk of postoperative complications. ³⁷ In addition to a high prevalence in patients with significant comorbidities, lateral malleolar fractures commonly occur in vulnerable patients, such as the elderly, who often present with a higher frequency of comorbidities. A 40% complication rate has been reported in the elderly when using ORIF. ³ Furthermore, even when initial complications are avoided in these high-risk patients, a proportion of patients will later require removal of metalwork.

Previous literature shows little differences in outcomes between various ORIF treatment methods of distal fibular fractures. Noh et al ³⁸ compared metallic implants and biodegradable implants and found that 53 patients treated with metallic implants achieved a 100% rate of union, with an average time to union of 15.8 weeks, whereas 47 patients treated with biodegradable implants had a 96% rate of union, with an average time to union of 17.6 weeks. Asloum et al ¹⁵ found a 94% rate of union in 35 patients treated with plate fixation. Using cerclage wires and lag screw fixation, Bajwa and Gantz ³⁹ reported a 100% rate of union in 52 patients. Zhenhua et al ⁴⁰ achieved a 100% rate of union in 20 patients using hook plates. Comparatively, results from this study, using cannulated intramedullary screw fixation, achieved a 98% rate of union in 45 patients, with an average time to union of 10 weeks.

Recently, intramedullary nail fixation has emerged as a less-invasive alternative to traditional ORIF with comparable union rates and potentially fewer complications. Fibular intramedullary devices require smaller incisions and have less prominent metal structure while resulting in fewer complications and having a potential for greater mechanical stability.^28-34 Rajeev et al ¹² reported a 100% rate of union in 24 patients, with an average time to union of 8.7 weeks using a fibular intramedullary nail. Asloum et al ¹⁵ reported a 100% rate of union in 36 patients treated with intramedullary nail fixation. A union rate of 100% was also found by Stewart et al ⁴¹ using a retrograde intramedullary nail. Intramedullary nail fixation of distal fibula fractures has been heavily discussed in the recent literature, largely with positive outcomes. Some authors, however, have reported potential shortcomings. Goss et al ³⁰ reported that peroneal tendons and superficial peroneal nerve are at high risk when using intramedullary nailing. Recently, Coifman et al ²⁹ reported a low rate of complications but high secondary procedure occurrence, mainly for hardware removals when using fibular intramedullary devices. A recent systemic review reported a high risk of bias toward favorable outcomes for intramedullary nail groups in the recent literature. ³² Fibular intramedullary nails have been reported to lack prevention of rotation at the fracture site, discouraging use for some surgeons. ²⁸ However, recent improvements such as the interlocking technology in the Inyo nail ³⁶ and a hole for a syndesmosis screw seen in the Acumed fibular nail ³ have improved its ability to prevent rotation at the fracture site. It should be noted that malrotation is also a concern for screws and k-wires. Particularly, cannulated intramedullary screws may also lack prevention of rotation and should be monitored appropriately when used; however, rotation at the fracture site was not seen in this patient cohort.

The complication rate from this study was low (4%)—only 2 patients out of the 45 treated with a cannulated intramedullary screw. Of the complications, 1 patient had symptomatic hardware and required screw removal; another patient had nonunion. The complication rate of this study compares favorably to complication rates of different treatment methods, including intramedullary nails. Bajwa and Gantz ³⁹ reported a 0% complication rate among 52 patients treated with cerclage wires and lag screw fixation. Asloum et al ¹⁵ reported a 7% complication rate among 36 patients treated with intramedullary nailing, compared with 56% in 35 patients treated with plate fixation. Rajeev et al ¹² reported a 0% complication rate among 24 patients treated with a fibular locking nail. Tambe et al ²³ reported a 15% complication rate among 20 patients treated with percutaneous k-wire fixation. Stewart et al ⁴¹ had 1 hardware removal out of 23 patients treated with the retrograde intramedullary nail technique.

Cannulated intramedullary screw fixation, as a minimally invasive procedure, for distal fibular fractures provides a biological environment that is more conducive to bone healing. The preservation of periosteal blood supply also allows for a faster healing and reduces infections. In addition, the small incision reduces soft-tissue damage, which decreases chances of complications and results in less scarring. The maintenance of the biological environment is advantageous for patients who are at a statistically increased risk of complications, such as patients who smoke, elderly patients, and patients with comorbidities such as diabetes, peripheral vascular disease, and neuropathy. ³⁸ The use of cannulated screws, as opposed to solid screws, allows a more accurate screw placement because of the use of guide wires and fluoroscopy. The guide wire can also appropriately determine the length of screw. ⁴² Because of these advantages, cannulated intramedullary screw fixation, compared with intramedullary nailing, can provide a biological environment that is more conducive to healing with a less-invasive approach. This method can be considered a preferred treatment for patients at high risk for wound complications resulting from poor soft-tissue conditions and/or medical comorbidities.

Despite the high-risk inclusion criteria of the patient cohort in this study, the high union rate and low complication rate suggests that cannulated intramedullary screw fixation can serve as a minimally invasive alternative treatment for distal fibular fractures. Importantly, in comparison to another minimally invasive approach, the intramedullary nail, cannulated screw fixation shows similar union rates and complication rates. Cannulated screws may provide an advantage because of the ease of insertion over a guide wire, increased accuracy resulting from the use of fluoroscopy, and preservation of periosteal blood supply, allowing faster healing and reduced risk of infection.

This retrospective study does have some limitations, including a small sample size of 45 patients and a lack of a random control group for comparison. The follow-up time was 6 months (range = 2-35 months). The patient cohort contains a variety of fracture types, including Weber A, Weber B, Weber C, pilon, and lateral malleolus and distal tibia. Additionally, swelling was considered a soft-tissue condition, based on abnormality or severity, at the discretion of the attending physician. Furthermore, there is a lack of comparative clinical studies using cannulated intramedullary screw fixation on distal fibula fractures to corroborate the findings.

In conclusion, cannulated intramedullary screw fixation can serve as a minimally invasive, safe, and satisfactory treatment for distal fibular fractures, with high union rates and low complication rates. This method can be considered a preferred treatment for distal fibular fractures in patients with high wound complication risks, soft-tissue conditions, and comorbidities and in elderly patients.