Ipsilateral fracture of the femur and tibia, known by the moniker “floating knee,” is a serious injury that primarily results from high-energy trauma [1, 2]. Up to 53% of patients with floating knee injuries have concurrent ligamentous injuries ^[3], with the anterior cruciate ligament (ACL) as the most commonly affected ligament ^[4]. When a floating knee is associated with multi-ligament knee injuries (MKIs), defined as injury to two or more of the main ligaments of the knee, diagnostic and therapeutic challenges arise ^[5] due to a high incidence of concurrent life-threatening injuries and limb-threatening complications and morbidity [2, 6]. Moreover, approximately 10% of MKIs consist of injuries to both the ACL and posterolateral corner (PLC) ^[7]. However, the literature reporting the management of this patient population is sparse, particularly with a lack of consensus on the timing and protocol of surgical treatment. Well-characterized treatment guidelines are needed for patients with concomitant floating knee and MKI. Here, we describe a surgical algorithm in a patient with MKIs involving the ACL, PLC, and anterolateral ligament (ALL).

A 26-year-old, previously healthy male involved in a high-speed motor vehicle collision presented with upper and lower extremity, skull, and facial fractures, sacropelvic dissociation, and epidural hematoma. The patient was intubated on the scene. The patient underwent external fixation of bilateral femoral and tibial fractures, followed nine days later by retrograde femoral and tibial intramedullary nail (IMN) placement on the right side for fixation of his floating knee. Intraoperative radiographs demonstrated >10 mm of ligamentous laxity revealed by lateral gapping with varus stress in the anteroposterior plane ^[8]. Hyperextension of the knee in the sagittal plane was seen as well (Fig. 1). On magnetic resonance imaging, tears of the ACL, posterior cruciate ligament, lateral collateral ligament (LCL), popliteus tendon, and popliteofibular ligament, and slight attenuation of the medial collateral ligament were seen. Treatment for the left leg consisted of a retrograde femoral IMN and placement of an Ilizarov frame of the tibia. Table 1 summarizes the timing of surgical intervention for his bilateral lower extremity injuries.

Multiligament knee reconstruction technique

On post-injury day 18, the patient underwent single-stage reconstruction of his MKI of the right knee. The timing of this was chosen to allow for capsular scar formation to aid in arthroscopy. Under anesthesia, the right knee was passively ranged 0–80°. After manipulation, a full range of motion was achieved. A grade 3 posterolateral instability of the knee, grade 3 Lachman’s ^[9], and a grade 3 pivot shift were also observed [10, 11]. A lateral surgical approach was conducted, with tibial and fibular tunnels drilled according to LaPrade’s technique for PLC reconstruction ^[12]. Standard anterolateral and anteromedial arthroscopy portals were created for diagnostic purposes. Scarring of the superior pouch, grade 1 chondromalacia of the medial tibial plateau, and ACL avulsion at the tibial insertion site were noted. Any adhesions seen were lysed and ACL remnants were removed. For ACL reconstruction, an Arthrex FlipCutter (Arthrex Inc, Naples, FL, USA) guide was utilized to create a full-length tibial socket. This technique, however, was unsuccessful for a femoral socket due to the distal locking screws of the IMN. Therefore, an accessory medial portal technique was performed ^[13], through which a +7-mm Arthrex transportal guide was introduced to drill an independent femoral tunnel. This femoral tunnel was then reamed with a 9-mm reamer to a depth of 25-mm, dilated, and tapped with a 9.5-mm tap, creating a final tunnel of 9-mm × 25-mm. These dimensions were appropriate based on the 8.5-mm × 62-mm GraftLink (Arthrex Inc, Naples, FL, USA) that was going to be utilized as a graft. At this point, we proceeded with the lateral femoral dissection to address the PLC, and LaPrade’s technique ^[12] was continued for the dissection of the lateral femur. Of note, the ALL was found to be avulsed off its tibial insertion site. Two guide pins were placed: one at the LCL origin and one at the proximal fifth of the popliteus sulcus, 18-mm distal to the LCL origin. These pins were aimed anteromedially to avoid the femoral IMN. The popliteal tendon tunnel was placed at 30° in axial and coronal planes and the LCL tunnel was placed at 30° and 0° in axial and coronal planes, respectively ^[14]. A 6-mm reamer was used on the LCL origin, whereas a 5.5-mm reamer was used on the popliteus origin. These were key deviations from LaPrade’s technique ^[12], in which larger bone tunnels are normally created to allow for the placement of allograft and bone blocks. For this procedure, soft tissue grafts were used, allowing smaller tunnels to be created to avoid implants and other tunnels. As evidenced on arthroscopy, the lateral tunnels did not violate the femoral ACL tunnel. A tibialis anterior allograft was split longitudinally for use for both the LCL and the ALL, to avoid adding additional tunnels for an ALL graft. A semitendinosus allograft was then prepared for popliteus insertion (Fig. 2). The tibialis anterior graft was docked in the previously created LCL tunnel using a biocomposite interference screw (Arthrex Inc, Naples, FL, USA). The semitendinosus graft was docked in the previously created popliteus tunnel utilizing the same method. Using standard graft-passing techniques, the LCL and popliteal graft arms were passed through their respective tunnels. The ACL was passed using the anteromedial portal passing technique ^[13], provisionally fixed with adjustable loop fixation buttons on both the femoral and tibial sides, and then tensioned at 30° of flexion. The LCL graft was also tensioned at 30° and a biocomposite interference screw was placed into the fibular tunnel for fixation. The semitendinosus graft and the remaining tibialis anterior graft from the LCL arm were passed from posterior to anterior through the tibial tunnel, recreating the popliteofibular and popliteus ligaments. The knee was then flexed to 60°, standard valgus stress was applied, and a 9-mm peek TunneLoc (Biomet, Warsaw, IN, USA) was inserted to achieve tibial fixation. Next, the ALL graft was passed superficially to the lateral structures proximally and attached to Gerdy’s tubercle using an 8-mm × 20-mm bone staple (Arthrex Inc, Naples, FL, USA) in a posteromedial direction. Throughout placement of the allograft, extreme care was taken to avoid violation of the articular surface and PLC tunnel (Fig. 3). All wounds were closed in standard fashion.

Here, we describe early ligamentous reconstruction in a rare case of a polytrauma patient presenting with fractures of the distal femoral and tibial shaft with concomitant MKI of the ipsilateral knee consisting of grade III ACL and PLC tears. The key features of our treatment approach include an early MKI reconstruction after long bone fracture stabilization using allograft in an all-inside ACL technique and a modified anatomical PLC technique. Our surgical algorithm for early MKI reconstruction is outlined in Fig. 4. The first step consists of tibial preparation using a lateral approach to drill tibial and fibular tunnels for PLC reconstruction. This is followed by diagnostic arthroscopy in which the ACL femoral socket is created using an accessory medial portal technique. An ACL tibial socket is created followed by LCL, ALL, and popliteus femoral tunnels. Femoral graft fixation is then performed. With the tibialis anterior autograft docked in the femoral LCL socket, the LCL graft is split to utilize a two-tailed technique to create LCL and ALL limbs. A semitendinosus autograft is docked in the femoral popliteus socket. During tibial graft fixation, ACL graft is passed through both the femur and tibia and fixed; the LCL graft is docked in the fibular tunnel; the popliteus and remaining LCL grafts are passed through the tibia and fixed; the ALL graft is fixed. Previous studies have reported a delay of up to 12–24 months in the diagnosis of knee ligamentous injury after the initial traumatic event in patients with ipsilateral femoral fracture, tibial fracture, or both [15-18]. Thus, a delay in the diagnosis of MKI may further delay treatment, negatively impacting the patient’s prognosis. Our treatment approach involved diagnostic imaging of ligamentous injury a few days after initial fracture stabilization. This allowed for the determination of the exact knee ligamentous lesions to devise a surgical treatment plan early. Currently, there is no consensus regarding the appropriate timing for the treatment of knee ligament injuries. A systematic review by Levy et al. compared early versus late surgery of damaged knee ligaments and reported that early treatment resulted in a higher mean Lysholm score (90 vs. 82, respectively), higher percentage of excellent/good International Knee Documentation Committee scores (45% vs. 31%, respectively), and higher sports activity scores based on the Knee Outcome Survey (89 vs. 69, respectively) [19-21]. In contrast, Sabesan et al. recommend delaying the treatment of MKI until the tibial fracture is healed ^[22]. Moreover, they found that nonoperative treatment can provide good patient satisfaction and adequate functional outcomes in the absence of symptoms of ligamentous instability. We recommend early (1–3 weeks) surgical treatment of MKI for patients without a closed head injury; however, an individualized treatment approach should be sought, considering the severity of ligamentous injuries, pre-injury activity level, extent of soft-tissue damage, and the activity goals of the patient post-injury [22, 23]. Our surgical algorithm involves reconstruction of the ALL which is often debated. However, a recent biomechanical analysis by Spencer et al. ^[24] demonstrated that the ALL is a clinically significant secondary stabilizer along with the ACL, the primary stabilizer to anterolateral rotation. In this case, ALL reconstruction was performed considering our patient’s significant pivot shift test results and Segond fracture. In this patient, we used allograft to reconstruct the ACL and PLC due to the large variety of sizes and types of allografts available and its ability to reduce operative time and site morbidity during MKI reconstruction [25-27]. Some studies suggest a higher risk of failure, rejection, and infection with the use of allografts compared to autografts, yet both types have resulted in comparable outcomes post-MKI treatment [28, 29]. The main limitation of this study is the lack of reported long-term follow-up and outcome results. Nonetheless, we believe that our treatment algorithm may improve outcomes in appropriately selected patients.

Here, we describe a rare instance of a floating knee with multi-ligament knee injury treated with reconstruction of the ACL, PLC, and ALL following stabilization of long bone fractures. We recommend early (1–3 weeks) surgical treatment of multi-ligament knee injuries for patients without a closed head injury; however, an individualized treatment approach should be sought, considering the severity of ligamentous injuries, pre-injury activity level, extent of soft-tissue damage, and the activity goals of the patient post-injury. Our proposed surgical algorithm consists of allograft reconstruction using an all-inside ACL technique and a modified anatomical PLC technique. In patients with floating knee injuries, the proposed surgical algorithm here may be utilized for successful multi-ligament knee injury reconstruction.

Well-characterized treatment guidelines are needed for patients with concomitant floating knee and multi-ligament knee injuries. In this case report, we describe a surgical algorithm for a patient with ipsilateral floating knee and multi-ligament knee injuries involving early reconstruction of the ACL, PLC, and ALL following fixation of the femur and tibia fractures.