Single-Incision Retrograde SIGN Nailing of the Femur and Antegrade SIGN Nailing of the Tibia for a Delayed-Presentation Floating Knee Injury

Abstract

Floating knee injury, defined as ipsilateral femoral and tibial shaft fractures, is a high-energy traumatic injury frequently seen following road traffic accidents (RTAs), which disproportionately burden low- and middle-income countries. Definitive treatment of this complex injury typically involves internal fixation, and the commonly accepted preferred method is intramedullary nailing of both fractures. This video article describes the surgical technique for managing a floating knee using retrograde Surgical Implant Generation Network (SIGN) nailing of the femur and antegrade SIGN nailing of the tibia through a single infrapatellar incision in a single anesthesia event.

The case involves a 28-year-old female patient in rural Malawi with a floating knee injury sustained in a motorbike RTA, notable for her delayed presentation of three weeks. The key procedural steps, performed under spinal anesthesia, began with a single infrapatellar incision for the subsequent retrograde nailing of the midshaft femur. Due to delayed presentation (22 days from the date of injury to the first exam in the hospital, with 2 more days before surgery) and callus formation, intraoperative fracture fragment mobilization via a second lateral incision was required before securing the femoral nail. The same infrapatellar incision was then used to perform antegrade nailing of the proximal tibial shaft fracture, which was secured after a closed reduction. This single-incision approach provides a definitive, robust fixation solution appropriate for a resource-constrained setting where challenges include delayed patient presentation and limited imaging infrastructure.

Keywords

Fracture fixation, internal; multiple trauma; developing countries; road traffic accidents; SIGN nails; intramedullary nailing.

Case Overview

Background

A disproportionate burden of road traffic accidents (RTAs) occurs in low- and middle-income countries (LMICs); 93% of global road traffic-related deaths occur in LMICs despite having only 60% of the world’s vehicles.¹ The RTA mortality rate in Africa is 26.6 per 100,000 persons, nearly three times higher than in Europe.² RTAs are one of the leading causes of death globally (1.35 million deaths annually) and cause up to 50 million injuries each year.³ In LMICs, motorcycle crashes account for a substantial proportion of RTAs, with nearly 44.7% of all RTAs caused by motorcycles in one study;⁴ the popularity of motorcycles in LMICs continues to grow in the setting of cheaper importing with a lack of organized public transit in some areas.⁵

This video article describes the case of a “floating knee” injury, with ipsilateral femoral shaft and tibial shaft fractures, representing a high-energy trauma with significant risk for complications and morbidity due to soft tissue and vascular injury, including limb compromise.⁶ These injuries present unique treatment challenges in LMICs because delayed presentation, implant availability, and limited imaging frequently influence operative planning. The history and workup of the patient, surgical planning and decision-making, and definitive fixation for this complex traumatic injury are described.

Focused History of the Patient

The patient is a 28-year-old female seen in the surgical wards lying in bed, alert and oriented, with a clearly painful and deformed right leg. She reported being involved in an RTA involving a motorbike approximately 3 weeks prior to the initial clinical exam by the surgical team; there was a delay in presentation to the hospital due to issues with transportation, as well as extended wait time on the wards. She had been reporting pain, received a single preventative dose of ceftriaxone on presentation, and was receiving daily diclofenac for pain. There were no signs of this being an open injury initially, though it is possible, which was presumed to be part of the reason for antibiotic dosing from the intake team. She did not report any other relevant medical comorbidities. No additional clinically significant injuries or medical comorbidities were identified prior to surgery.

Physical Exam

On the initial exam, she reported pain at baseline exacerbated by movement. There was noticeable swelling and deformity in the right upper leg (thigh/femur region) and lower leg (tibia/foreleg region), which was examined in a long leg traction splint initially. She was tender to palpation, and further range of motion testing was limited by the injury and pain, including minimal firing of the extensor hallucis longus and refusal to passively or actively range the knee. Importantly, she was neurovascularly intact distal to her fractures, which is key in assessment of the “floating knee” due to high prevalence of complications such as vascular injuries and compartment syndrome in this injury pattern, which was not found in this patient in the upper or lower leg.⁶ This included full sensation in the saphenous, sural, superficial peroneal, deep peroneal, and tibial nerve distributions of the foot and intact, regular posterior tibial and dorsalis pedis pulses with < 2-second capillary refill of the big toe. While providers often make sure to assess for neurovascular injury due to the critical nature of these findings, “floating knee” injuries are likely to have other soft tissue injuries, and it is key to examine for these injuries as part of a full tertiary exam. This patient had no key soft tissue injuries noted by the surgical team on initial exam.

Imaging

The patient received preoperative diagnostic imaging via plain radiographs, including anteroposterior (AP) x-rays of the femur (full length, Figure 1), knee joint (Figure 2), and tibia and fibula (Figure 3). This remains the cornerstone of initial imaging for “floating knee” injuries.⁶ These radiographs allowed for classification of the fractures. The modified Fraser classification for floating knee injuries considers this patient’s injury pattern to be a Type I extra-articular fracture. Using AO/OTA classification, the femur fracture is a 32C2 (diaphyseal femur fracture with an intact segment) and the tibia fracture is a 42B3 (diaphyseal tibia fracture with a fragmented wedge fracture pattern) and associated fibula fracture considered a 4F2A1 (simple diaphyseal fibula fracture).

Figure 1. Preoperative AP plain radiograph of the right lower extremity (femur) showing midshaft fracture.

Figure 2. Preoperative AP plain radiograph of the right lower extremity (knee joint) 
showing ipsilateral midshaft fracture of the femur and proximal tibial shaft fracture.

Figure 3. Preoperative AP plain radiograph of the right lower extremity (tibia/fibula) showing proximal tibial shaft fracture.

Although workup and radiographs for this patient would ideally include lateral views, Mzuzu and many other hospitals like it face resource constraints (e.g., staffing, patient volume, and education of technicians) that make achieving multiple views for every patient difficult. Similarly, CT scans are often useful for surgical planning and assessing the full extent of injury, but infrastructure limitations and patient volume can limit availability of additional imaging in LMICs where only 6% of district hospitals and 21% of referral hospitals in one study had CT available.⁷ As of 2018 in Malawi, four of 29 hospitals had x-ray capacity of adequate quality to make accurate diagnoses when needed, and just one central hospital had a CT machine and staff with capacity for accurate diagnosis. Plain AP radiography in this case, combined with the history and physical exam, was sufficient diagnostic imaging and adequate for surgical planning, and represents quick, cost-effective imaging with a pragmatic approach to a case such as this with intact neurovascular exam clinically.⁶

Natural History

“Floating knee” is a complicated traumatic injury that often requires careful evaluation due to the varying range of soft tissue injury extent, often high-energy mechanism, and its high risk for complications that range from open fractures, infection, vascular injury, compartment syndrome, additional associated fractures (e.g., pelvic injury), associated chest and abdominal trauma, and head injury.^6,8 This requires careful workup and a full trauma assessment following ATLS guidelines. This injury is due to traffic accidents 93% of the time and occurs predominantly in males (86%) who are young adults (61% occur in ages 16–35 years old).⁸

Most cases of “floating knee” are definitively fixed with open surgical management with good results in 93% of cases.⁶ However, common complications include knee stiffness (38/39 patients in one study),⁸ heterotopic ossification (31% in a large series),⁸ nonunion or delayed union (especially of the tibia, with 4/17 nails requiring exchange in one study),⁹ increased risk of deep vein thrombosis (approximately 15%),⁶ infection, and malunion. These outcomes are dependent on whether the fractures are open, segmental, intra-articular, or need repeated procedures.¹⁰

Overall, outcomes with surgery remain favorable, with union generally achieved in a 3.5- to 6.5-month time frame.⁹ However, the floating knee is a serious injury pattern, with only 72% returning to work at 1 year, and 54% with residual pain at that time.¹¹

Options for Treatment

The range of treatment available for this patient includes nonoperative management (e.g., with external stabilization through splinting), temporizing procedural fixation (primarily external fixation), or a variety of operative management strategies for definitive internal fixation including intramedullary nailing or open reduction and internal fixation with plates or other equipment.⁶ However, the commonly accepted preferred treatment in the literature is intramedullary nailing for both femoral and tibial shaft fractures, with good or excellent outcomes in 93% of cases and shorter hospitalizations compared to nonoperative approaches.⁶ While many types of nails exist to perform this surgery with varying incision patterns, the combination of retrograde femoral nailing and antegrade tibial nailing is a well-established method with satisfactory outcomes when performed through a single incision.⁹

Rationale for Treatment

There are many considerations when selecting between the available treatment options. While nonoperative or external fixation methods could be considered in certain scenarios, early definitive fixation is preferred and intramedullary nailing is the accepted choice for these fracture patterns.⁹ While delayed presentation in the management of the “floating knee” injury is less often cited in the literature, the fundamental surgical principles remain the same regardless of timing. Factors that favored the choice of performing both nailing procedures under a single-entry incision include the risks and benefits weighed with performing both surgeries in a single operative event with a single spinal anesthesia administration; surgical expertise of the team; infection risk with delayed presentation; the need for potentially breaking up callus due to delayed presentation and mobilizing fracture sites intraoperatively to achieve closer to anatomic reduction; and available nailing equipment in this setting.

Special Considerations

Careful attention to the risks of major operations in this setting with limited resources should be considered. Aspirin is a cheap and effective method for the prevention of clots in the management of extremity long-bone fractures, and while no study on floating knee injuries to our knowledge expressly studies the efficacy of DVT prophylaxis options, the risk remains high in this injury pattern and major studies, including randomized controlled trials encompassing DVT prophylaxis for closed and open femur and tibia fractures, show aspirin as effective for its prevention; given its affordability and availability, it is particularly appropriate in a resource-constrained setting. One study done in Malawi showed aspirin available in 84% of district hospitals compared to heparin which was available in none.¹² Many barriers to proper orthopaedic trauma care remain in sub-Saharan Africa, with substantial workforce shortages (1 orthopaedic surgeon for 2.3 million people in the Northern region of Malawi; 0.3 surgeons per district hospital in sub-Saharan Africa), limitations to available orthopaedic implants and equipment, limited imaging (intraoperative fluoroscopy in just 3% of district hospitals, though available for this patient’s case in Northern Malawi), and limited anesthesia coverage.⁷ A Malawian cohort of 287 adults with open tibia fractures showed poor functional outcomes at 1 year, 5 times greater odds of infection in those with delayed presentation of 5 days or more, and improved quality of life at 1 year for those who had intramedullary nailing performed.¹³ Further consideration when making operative decisions in this setting should incorporate the economic impacts of care on patients and their families, especially with debilitating injuries for working adults and homemakers.

Additionally, heterotopic ossification of the knee is more commonly reported in retrograde nailing of femoral shaft fractures; however, research has suggested limited functional impact or correlation with impaired range of motion.¹⁴ This potential complication should be considered with potential surgical approaches to definitive fixation of this injury.

Discussion

The case featured in the video shows retrograde intramedullary nailing of the midshaft femoral fracture and antegrade intramedullary nailing of the proximal tibial shaft fracture through a single infrapatellar incision in a 28-year-old female with a “floating knee” injury in rural Malawi due to a road traffic accident. This case is unique due to the approach to SIGN nailing for a “floating knee” through a single incision in a rural, resource-limited setting (which can be achieved without the use of intraoperative fluoroscopy) and delayed patient presentation requiring intraoperative fracture fragment mobilization. The case was performed supine under spinal anesthesia. 

The case begins with a triangular bolster underneath the knee on the right side with an infrapatellar approach with incision through the patellar tendon. Retrograde intramedullary nailing of the midshaft femur fracture was performed first. Reaming was performed distal to proximal with necessary mobilization of the fracture fragments via a lateral incision in order to achieve anatomic reduction due to delayed presentation and callus formation. The femoral nail was secured using one interlocking screw proximal and two distal interlocking screws. The surgical team then used the same infrapatellar incision to perform antegrade nailing of the proximal tibial shaft fracture, with a closed reduction of the fracture. The tibial nail was secured using two proximal and two distal interlocking screws. Limited availability of intraoperative fluoroscopy constrained the ability to use blocking screws in the proximal tibia for ideal nail positioning or evaluate entry position using fluoroscopy; however, it was available for confirmation of final nail and interlocking screws intraoperatively.

The patient tolerated the procedure well and was discharged to the surgical ward with oral pethidine, oral aspirin, intravenous paracetamol, and intravenous diclofenac. Plain radiographs were taken on postoperative day 1 (Figures 4–8). X-rays obtained from the postoperative 6-week visit show callus formation and healing with intact hardware. Although imaging is not available due to local loss or corruption of the files, the local surgical team’s 3-month follow-up visit notes “complete healing” demonstrated with clinical exam and radiography, which in discussion with the clinical team suggested satisfactory progression of bone healing. At that time, functionally, the patient was weightbearing and mobilizing with some difficulty day to day; there was pain with weightbearing and active range of motion, described as generalized by the patient and attributed to continued scarring, soft tissue healing, and neuropathic pain; and no specific soft tissue or ligamentous injury was noted. 

Figure 4. Postoperative anteroposterior plain radiograph of the right hip.

Figure 5. Postoperative AP plain radiograph of the right femur.

Figure 6. Postoperative AP plain radiograph of the right knee.

Figure 7. Postoperative lateral plain radiograph of the right knee.

Figure 8. Postoperative AP plain radiograph of the right tibia/fibula.

“Floating knee” injuries such as this one (ipsilateral femoral and tibial shaft fractures) represent high-energy traumatic injuries that can have serious complications due to soft tissue damage, vascular compromise, and associated injuries. Regardless of setting, intramedullary nailing is the preferred management of these injuries as opposed to other internal fixation methods or nonoperative treatment. This case shows a delayed fracture that is unique, but unfortunately common in settings such as rural Malawi. This poses a surgical challenge due to infection risk, pre-existing complications, and callus formation which often creates increased intraoperative difficulty and increased operative times.

Equipment

This case was completed using intramedullary nails for the femur and tibia from SIGN Fracture Care (SIGN Fracture Care, 451 Hills St, Ste B, Richland, WA 99354).

Disclosures

Kiran J. Agarwal‑Harding serves as a Section Editor at JOMI for Orthopaedic Surgery and has not been involved in the editorial processing of this article in any capacity other than as an author.

Artificial intelligence was used to enhance the figures, and all figures were manually reviewed and verified for accuracy.

The authors report no other conflicts of interest, financial relationships, funding, sponsorship, equipment support, or other relationships that could be perceived to influence the content of this article.

Statement of Consent

The patient referred to in this video article has given their informed consent to be filmed and is aware that information and images will be published online.

Acknowledgments

The authors would like to acknowledge the team from the Mzuzu Orthopaedic Support and Training program, including the local operating room staff (nurses, transport staff, anesthesia clinical officers), local orthopaedic surgery team (Bitiel Banda, MD and orthopaedic clinical officers), program staff (Gomezgani Jenda), and the Foundation for Orthopaedic Trauma who funded this program. The authors would also like to sincerely thank the patient, who agreed to allow for filming and dissemination of this procedure and its details.