You are in: eMedicine Specialties > Orthopedic Surgery > KNEE Floating KneeArticle Last Updated: Jun 24, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: S Vidyadhara, MBBS, MD, MS(Ortho), DNB(Ortho), FNB (Spine Surgery), Assistant Professor, Department of Orthopedics and Spinal Surgery, Mahatma Gandhi Medical College Hospital, India S Vidyadhara is a member of the following medical societies: AO Foundation Coauthor(s): Sharath K Rao, MBBS, MS, D'Ortho, Professor and Head of Unit V, Department of Orthopedics, Kasturba Medical College Hospital, India; Mundkur Sudhakar Shetty, MBBS, MS, MCh, Senior Professor and Head Orthopedic Department, Yenapoya Medical College and Hospitals, Mangalore; James J Gnanadoss, MBBS, MS(Ortho), Professor and Head of Unit, Director, Department of Orthopedics and Spine Surgery, Mahatma Gandhi Medical College Hospital, India Editors: Robert D Bronstein, MD, Associate Professor, Department of Orthopedic Surgery, University of Rochester School of Medicine; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Thomas M DeBerardino, MD, Director, John A Feagin, Jr, Sports Medicine Fellowship at West Point, Associate Professor of Orthopedic Surgery, Uniformed Services University of the Health Sciences and Keller Army Community Hospital; Dinesh Patel, MD, FACS, Associate Clinical Professor of Orthopedic Surgery, Harvard Medical School; Chief of Arthroscopic Surgery, Department of Orthopedic Surgery, Massachusetts General Hospital; Carlos J Lavernia, MD, FAAOS, Adjunct Clinical Professor, Department of Orthopedic Surgery, University of Miami School of Medicine; Medical Director, Orthopedic Institute at Mercy Hospital Author and Editor Disclosure Synonyms and related keywords: floating knee injury, floating knee joint, floating-knee fracture pattern, femur fracture, femoral fracture, tibia fracture, tibial fracture, ipsilateral femoral and tibial fractures, ipsilateral fractures of the femur and tibia, simultaneous fractures of the femur and tibia, flail knee joint, femoral shaft fracture, tibial shaft fracture, closed femoral fracture with an open tibial fracture, Bohn–Durbin classification system, Letts and Vincent classification system, type I floating knee, type II floating knee INTRODUCTIONSection 2 of 10
  Floating knee is a flail knee joint resulting from fractures of the shafts or adjacent metaphyses of the femur and ipsilateral tibia (see Image 5). Floating knee injuries may include a combination of diaphyseal, metaphyseal, and intra-articular fractures. This combination of fractures is less common in the pediatric population than in adults. However, epiphyseal injury can adversely affect open growth plates, predisposing a child to limb-length discrepancy and angular deformities. Blake and McBryde initially described this injury, which is generally caused by high-energy trauma. Local trauma to the soft tissues is often extensive, and life-threatening injuries to the head, chest, or abdomen may also be present.1 An initial evaluation to determine the extent of a patient's injuries is of critical importance. This evaluation should be followed by an appropriate sequence of emergency diagnostic and therapeutic measures. Rates of infection, nonunion, malunion, and stiffness of the knee are relatively high. These complications can lead to functional impairment and frequently cause unsatisfactory results. ProblemLittle is recorded in the English-language literature on the subject of ipsilateral fracture of the femur and tibia. FrequencyThis severe injury appears to be increasing in frequency. A male preponderance is observed, particularly in young adults 20-30 years of age. EtiologyRoad traffic accidents are the most common mechanisms of trauma, followed by gunshot wounds and falls from heights. ClinicalFloating knee injuries must be included in assessment and treatment protocols for patients with polytrauma. Damage to the vessels (mainly the popliteal and posterior tibial arteries) and lesions of the nerves (eg, peroneal nerve) are common. Vascular injury is common and may be limb threatening if not recognized and addressed. Often, the vascular injury is to the anterior tibial artery and does not result in ischemia and is not treated with vascular repair or reconstruction. However, vascular status needs to be assessed and addressed as appropriate. Traction usually causes neurapraxia, which often resolves, but complete resolution cannot always be anticipated. The incidence of open fractures is high, approaching 50-70%, at 1 or both fracture sites. The most common combination is a closed femoral fracture with an open tibial fracture. A well-documented finding is injury to the knee ligaments that occur in association with ipsilateral femoral and tibial fractures. Anterolateral rotatory instability is the most common pattern of instability. Knee ligament injury is not always suspected, and joint swelling due to hemarthrosis should not be mistaken for a sympathetic effusion. The ipsilateral femoral and tibial shaft fractures and knee ligament injury appear to be part of a continuum of combined injuries resulting from complex, high-energy forces.2 In skeletally immature patients, floating knee is uncommon. Few studies of this injury have been conducted in children. Data from available studies show that findings observed in children are comparable to those in adults in terms of the mechanism of fracture, the incidence of associated major injuries, and the complexity of treatment. INDICATIONSSection 3 of 10
In adults, all floating knee injuries must be addressed with early anatomic reconstruction and stable surgical stabilization of both fractures. The goal is to allow for early joint mobilization. In children, especially those younger than 10 years, treatment of ipsilateral femoral and tibial fractures is controversial. The treatment protocol for floating knee injuries is summarized in Image 4. WORKUPSection 4 of 10
Imaging Studies
StagingStaging in adults Blake and McBryde used the terms true (or type I) injury and variant (or type II) injury to classify the floating-knee fracture pattern.1, 3
Fraser et al classified floating knee injuries in a similar way by analyzing knee involvement (see Image 1).4
In both classification systems described above, type II fractures with intra-articular involvement have been linked with higher complication rates and poorer functional results than those observed with type I injuries. The criteria Karlstrom and Olerud established are widely accepted for evaluating functional outcomes.5, 6 The following data are recorded and characterized as excellent, good, acceptable, or poor (see Image 2):
Staging in children In children, floating knee injuries are classified according to the Bohn–Durbin or Letts classification systems. In the Bohn–Durbin classification, floating knee injuries are described as follows:
The Bohn–Durbin system does not account for open fractures and cannot be used to predict complications and prognoses. Unacceptable findings are femoral union in a position of greater than 30° anterior angulation, 15° valgus angulation, and 5° posterior or varus angulation, or greater than 2 cm of shortening. Tibial malunion is defined as greater than 5° angulation in any plane or greater than 1 cm of shortening. Rotational malunion is defined as any internal rotational deformity exceeding findings on the unaffected side or greater than 20° external rotation of the extremity, as detected during walking or standing. Letts et al designed a new classification system in which they recognized diaphyseal, metaphyseal, or epiphyseal knee fractures (types A, B, C) and also open fractures (types D and E) (see Image 3). The drawback of their classification system is that they do not indicate how to classify patients with epiphyseal separation in the distal femur and tibia or how to describe the location of open fractures in the epiphysis, metaphysis, or diaphysis.7 Subjective outcomes of floating knee injuries can be evaluated by using the criteria Yue et al reported.8 Their criteria are as follows:
TREATMENTSection 5 of 10
Medical therapyMedical therapy for adults Early reports favored a nonsurgical approach to 1 or both fractures in a floating knee because of the unavailability of internal fixation. High infection rates and lack of knowledge of posttraumatic critical care further delayed the acceptance of internal fixation in this tough clinical situation. However, conservative methods entailed considerable risks of fracture-related shortening and angulation, with delays in fracture union and return to normal activities. As a result of these drawbacks, nonsurgical methods became unfavorable and were gradually replaced by internal fixation techniques. Medical therapy for children Nonsurgical treatment for children consists of skeletal traction for the femoral fracture with closed reduction and casting or splinting for the tibial fracture. A hip spica cast is applied when sufficient femoral healing has occurred.9, 10 The incidence of complications of fracture healing is high in older children treated with conservative methods. Malunion, nonunion, refracture, and limb-length discrepancy are documented in almost 50% of patients receiving closed treatment.7 Surgical therapySurgical therapy for adults Most surgeons currently recommend aggressive treatment with early stabilization of both fractures, integrated with a multisystem approach that emphasizes early mobilization of the patient to facilitate better care and quicker recovery.6, 9, 10, 11, 12, 13 At present, the use of intramedullary nails on either side of the knee joint is the best modality for fracture management. An antegrade technique is usually performed when the nails are applied. The procedure is performed after adequate resuscitation and physiologic stabilization is accomplished. If immediate intramedullary nailing is not possible, a spanning external fixator can be applied to stabilize the entire limb. This fixator can be replaced with internal fixation when the patient's general condition is stable and/or when neurovascular lesions and soft tissue coverage are managed. The technique of antegrade nailing does have drawbacks, such as difficulties in positioning the patient, the need for 2 incisions, prolonged anaesthesia and surgical time, and an inability to perform other surgical procedures at the same time. To overcome these concerns, retrograde intramedullary nailing of the femur with antegrade nailing of the tibia through the same incision has been proposed as an alternative. The fracture of the femoral shaft is always addressed first, for 2 reasons. First, stabilization of the femur permits mobilization of the patient without traction if the patient has decompensation during the operation that requires abandonment of the second procedure. The extremity with the tibial fracture can be placed in a splint or cast, or an external fixator can be applied quickly. Second, stabilization of the femoral shaft fracture allows the surgeon to sufficiently flex the knee to access the starting point in the proximal tibia. In addition, it provides a stable proximal limb for support. When the fracture pattern involves the metaphyseal region of the tibia and/or femur with or without intra-articular extension, stabilization can be achieved by using locking plates. Plate fixation can offer anatomic reduction of the articular surface; this method allows for rigorous mobilization and maximizes the functional outcome. Early diagnosis of ligamentous injuries is essential to facilitate appropriate rehabilitation. Conservative treatment is preferred for an isolated injury to the medial collateral ligament. If necessary, reconstruction of anterior or posterior cruciate ligament tears may be delayed until union of the fractures occurs. Injuries to the posterolateral corner and avulsion fractures of the cruciate ligaments from either the femur or the tibia should be repaired at the time of the initial procedure or in the early postoperative period. Surgical therapy for children Most authors suggest operative treatment of at least the femoral fracture in patients older than 10 years. Surgical treatment reduces complications, hospital stays, and the time to unsupported walking. Therefore, many authors recommend surgical treatment for both the femoral fracture and the tibial fracture in all age groups.9, 10, 11, 12 Even in patients younger than 9 years, at least 1 fracture must be rigidly fixed. With the advent of newer pediatric fracture treatment methods, including flexible nail fixation of pediatric femur fractures, fixation of the femur fracture should be performed. This allows mobilization of the patient and patient discharge whether the tibia is also surgically stabilized or is treated closed. Preoperative detailsAdequate resuscitation and physiologic stabilization is important in patients with a high Injury Severity Score due to associated injuries. Intraoperative detailsPositioning for surgery is illustrated in Image 6. Postoperative detailsEarly joint mobilization is the key to success. Early weight bearing may be helpful in patients with diaphyseal fractures, and delayed weight bearing is preferred for those with intra-articular or metaphyseal fractures. COMPLICATIONSSection 6 of 10
Delayed union, nonunion, malunion, and stiffness of the knee are more prevalent in patients with the floating-knee combination of fractures than in patients with isolated femoral or tibial fractures.6, 10 For patients in general, factors such as older age, an increased number of pack-years of cigarettes smoked at the time of injury, a high Injury Severity Score, and the presence of open and comminuted fractures adversely affect the bony union time and the reoperation rate.14 Complications unique to children In the pediatric population, open growth plates present an additional dynamic factor that leads to complications unique to children. Examples of such complications include overgrowth of the bone after a fracture and premature closure of the ipsilateral physis, genu valgum, and physeal arrest. Mean overgrowths of the femur and tibia are 1.4 and 1.1 cm, respectively. The incidence of leg-length discrepancy is increased in patients younger than 9 years and in those treated nonoperatively. However, subjective limps and length discrepancies of the lower extremities can occur regardless of the type of fracture, the extent of soft tissue injury, or the treatment method. Pediatric patients and their parents must be informed of these possible outcomes and counseled. Patients should be followed up until they reach skeletal maturity to monitor for signs of these complications. Infection The incidence of infection and incidence of osteomyelitis are relatively high in floating knee injuries, especially in patients with open or type II fracture patterns. Strategies that have led to the eradication of infections in most cases include meticulous debridement, continuous suction and irrigation drainage, and use of polymethylmethacrylate beads or sticks impregnated with antibiotics. Knee stiffness Delayed rehabilitation and associated injuries around the knee result in limitation of knee movement. OUTCOME AND PROGNOSISSection 7 of 10
Using the criteria of Karlstrom and Olerud,5, 15, 6 most authors of published series describe excellent-to-good results in as many as 65% of surgically treated patients. After conservative treatment, success rates decrease to 29%. In children, good-to-excellent results have been reported with both conservative and surgical methods. Fixation of 1 or 2 fractures in children aged 9 years or younger offers superior results and minimizes the incidence of long-term dysfunction of the extremity. Regarding intra-articular (type II) injuries, good or excellent results are reported in 24% of patients. The difficulty in obtaining satisfactory function after type II injuries may result from severe injuries to the soft tissue, damage to the knee joint, and/or the complexities of achieving stable reconstruction. Apart from knee involvement and open type III femoral fractures, other significant factors that affect functional outcomes after floating knee injuries are the following15:
FUTURE AND CONTROVERSIESSection 8 of 10
Patients with ipsilateral femoral and tibial fractures present after high-energy trauma. These injuries are associated with an increased risk of morbidity and mortality. Isolated fractures in stable patients can be treated acutely. By contrast, temporary stabilization of the fractures with external fixation is indicated for unstable patients or those in extremis, according to the concepts of damage-control orthopedics. When the patient's physiologic state is stabilized, conversion to internal fixation is desirable (see Image 4). Involvement of the knee joint, severe trauma to the soft tissues, fracture comminution, and open fractures are associated with increased complication rates resulting in worsened functional outcomes. In children, when the physis is involved, the possibility of leg-length discrepancy must always be considered. MULTIMEDIASection 9 of 10
REFERENCESSection 10 of 10
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