Initial Evaluation Of The Acutemultiple-ligament-injured Knee

INITIAL EVALUATION OF THE ACUTE MULTIPLE-LIGAMENT-INJURED KNEE TIMOTHY C. WILSON, MD, and DARREN L. JOHNSON, MD

The multiple-ligament-injured knee is an orthopaedic emergency. The initial assessment of this injury must include a thorough and expedient physical examination, with particular attention directed to the vasculari~ of the extremity. Vascular injuries should be ruled out immediately because a pulseless extremity may result in a belowknee amputation if the leg is not reperfused within 6 to 8 hours. All patients with a normal vascular examination must have serial pulse examinations or undergo an arteriogram, because intimal tears may present on a delayed basis. The neurological examination, particularly of the peroneal nerve, should be documented. A detailed examination of the knee ligaments is performed on the anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament, and posterolateral anatomic structures. Initial and postreduction radiographs require thorough evaluation to assess for peri-articular fractures, direction of dislocation, and adequacy of reduction. Magnetic resonance imaging will provide detailed information about the ligaments, bone or subchondral bone, menisci, and articular cartilage. The physical examination must be correlated with the magnetic resonance imaging findings for preoperative planning. This article provides a treatment algorithm that can be helpful in the initial assessment and decision-making process of the multiple-ligament-injured knee. KEY WORDS: knee dislocation, multiple-ligament-injured knee, vascular injury © 2003 Elsevier Inc. All rights reserved.

A knee dislocation is one of the few true orthopaedic emergencies. The initial management of these injuries must be thorough and expedient. Failure to recognize the full extent of these injuries may have disastrous complications. Although a knee dislocation leading to a multiligament-injured knee is relatively uncommon, a multipleligament-injured knee has a high rate of associated injuries that may be limb threatening. The actual incidence of these injuries is unknown because most of these injuries present spontaneously reduced and, therefore, are often misdiagnosed. Consequently, the treating physician must have a high index of suspicion. To appropriately diagnose and treat these injuries, the treating physician must have a full understanding of knee dislocations, their associated injuries, and their potential complications. An appropriate history with a thorough physical examination is helpful in making the correct diagnosis, which will direct the next course of action. Specific tests such as radiographs, magnetic resonance imaging, and angiograms will provide useful information for diagnosis and management. Once a limb-threatening injury has been ruled out, a preoperative plan can be established to address the ligament injuries. This article presents basic information on knee dislocations, and provides a treatment algorithm for the initial evaluation of multiple-ligament knee injuries.

From the Kentucky Clinic, Lexington, KY. Address reprint requests to Darren L. Johnson, MD, University of Kentucky School of Medicine, The Kentucky Clinic, K415, Lexington, KY 40536-0284. © 2003 Elsevier Inc. All rights reserved.

1060-1872/03/1103-0003530.00/0 doi:10.1053/otsrn.2003.35912

DEFINITION OF INJURY Many knee dislocations (>50%) spontaneously reduce before a physician's evaluation. Therefore, the term "multipie-ligament knee injury" may be more appropriate. A true knee dislocation implies complete displacement of the tibiofemoral articulation. This is seldom seen. For practical consideration, a knee with 2 or more ligaments completely disrupted should be classified as a multiple-ligament injury or knee dislocation. 1 This diagnosis should alert the examiner to associated injuries and their potentially devastating complications.

INCIDENCE The true incidence of knee dislocations is unknown. Most authors agree that the actual incidence is higher than the 0.001% to 0.013% per year published in the literature. 2 Spontaneous reductions, other distracting injuries, and examiner inexperience may account for this diagnosis often being overlooked. All knees with 2 or more ligaments completely disrupted should be classified as a multi-ligament knee injury, requiring the treating physician to evaluate for secondary associated injuries with an appropriate examination and ancillary tests. CLASSI FICATION

Historically, knee dislocations are classified according to the position of the tibia in relation to the femur. Kennedy's classification system described knee dislocations as anterior, posterior, medial, lateral, and rotational. Anterior dislocations are the most common (40%), followed by posterior (33%), lateral (18%), medial (4%), and rotational (5%).3 This classification system is limited because most dislocations spontaneously reduce.

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Schenk describes a classification system based on what ligaments are torn. A KD I is an anterior dislocation with the anterior cruciate ligament (ACL) torn and the posterior cruciate ligament (PCL) intact. A KD II involves the ACL and PCL with the collaterals intact. A KD III M is an ACL, PCL, and medial collateral ligament (MCL) injury, and a KD III L is an ACL, PCL, and lateral injury. A KD IV involves injury to all 4 ligaments. 4 This classification was modified by Wascher to include a KD V, which includes a peri-articular fracture. 5 The KD classification is useful with regards to a specific ligament diagnosis. In addition to the anatomic classifications, there is a difference between high energy and low energy with regards to associated injuries. Low-energy dislocations have been shown to have a much lower incidence of associated injuries, with vascular injury rates of 5%, meniscal injury rates of 20%, and an osteochondral fracture rate of 5%. 6 In high-energy dislocations, the rate of popliteal artery injury ranges from 14% to 65%. Fifty to 60% of patients will have fractures, and 41% of patients will have multiple fractures. Patients with these high-energy injuries often have other significant injuries to their head or chest, which precludes early aggressive treatment of their knee ligaments. 5 The chronicity of the injury is also important with regards to associated injuries and surgical planning. Surgical treatment gives improved results in acute versus chronic cases. Some structures may be repaired if treated acutely, whereas late treatment may require a reconstruction procedure. Although there is no official classification with regard to timing, a knee dislocation is acute if seen within the first 3 weeks. Three weeks to 3 months may be considered subacute, and after 3 months, chronic. 7 This classification takes into account that the acute knee injury has tissue that may be more easily repaired within the first few weeks.

MECHANISM The mechanism of injury provides useful information with regards to the direction and degree of injury. Anterior and posterior dislocations are the most common. These injuries are caused by force from the opposite direction. For example, a posterior dislocation is caused by an anterior blow to the knee. This injury pattern is commonly seen in the "dashboard knee." Anterior dislocations commonly occur from extreme knee hyperextension. This happens when an anterior blow occurs to the tibia against a fixed foot, and the femur is forced posterior to the tibia. Medial and lateral dislocations are most likely to occur in highenergy accidents with varus and valgus rotational forces. 3 Knee dislocations can occur from a variety of mechanisms and can be divided into high velocity or low velocity. The most common cause of knee dislocation is a motor vehicle accident. These traumatic "high-velocity" knee dislocations can occur as a result of a variety of forces, and they have a high rate of associated injuries, s Knee dislocations can also result from sports-related, or low-velocity, injuries. Shelborne reported the most commonly involved sports were football (35%), wrestling (15%), and running (10%). Low-velocity knee dislocations have a lower rate of associated injuries. 6 Industrial accidents and falls are other common mechanisms. 9

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Knowledge of each patient's mechanism of injury will be useful in determining what structures may be injured, and the potential risk for associated injury.

VASCULAR INJURIES A knee dislocation should raise suspicion for a possible vascular injury. The most serious and limb-threatening injury associated with a knee dislocation is a popliteal artery disruption or thrombosis. These injuries usually occur as the result of a traction injury or a complete disruption. The popliteal artery is the main blood supply to the lower leg. The intimate anatomical relationship between the artery and the knee places the vessel at risk. Proximally, the vessel is tethered at "Hunter's canal" or adductor hiatus located at the adductor tubercle of the femur. Distally, the vessel is tethered at the fibrous arch or trifurcation of the vessels at the soleus muscle. Within the popliteal space, the popliteal artery gives off the superior lateral, superior medial, middle, inferior lateral, and inferior medial geniculate arteries. These branches do not provide collateral flow to the lower leg in the case of a popliteal artery injury. Vascular injuries can occur with all types of dislocations. The risk of arterial injury with knee dislocations is between 10% and 64o/0.7 Green and Allen reported rupture of the artery to be as high as 44% with posterior dislocations. Anterior dislocations are associated with arterial injury as high as 39%, and the incidence with medial injury was 25% and with lateral injury was 6%. 9 Kennedy showed that rupture of the popliteal artery occurs when the knee is forced beyond 50 ° of hyperextension.3 Complete rupture of the popliteal artery is more common with posterior dislocations, and anterior dislocations more commonly cause intimal tearing. The arterial ruptures associated with posterior dislocations are usually obvious on examination with loss of distal pulses. The intimal tears of the artery may present in a delayed fashion and are more difficult to diagnose. The initial physical examination may be completely normal in a knee with an intimal tear. Intimal tears cause a gradual thrombosis, which may propagate to complete arterial occlusion. Therefore, it is recommended that these patients undergo admission to the hospital for close observation of their vascular status for 48 to 72 hours. Any change in vascular status mandates immediate evaluation and treatment. The initial physical examination must include assessment of the vascular status of the injured extremity. Absence of pulses is a vascular emergency. A warm foot with good capillary refill but absent pulses is not normal. Capillary refill is a poor indicator of blood flow. If the injured extremity is pulseless for 6 to 8 hours, then permanent damage may occur, and the amputation rate may be as high as 86%. This compares to an amputation rate of 13% when a vascular repair is performed within 8 hours. 9 If the knee is pulseless and still in a position of dislocation, then the knee should be immediately reduced and the pulses reassessed. Persistent absence of the pulses requires immediate vascular surgery consultation. Time should not be wasted getting an arteriogram in the radiology suite or arranging any other study. The vascular surgeon can get appropriate studies, such as an on-table arteriogram, in WILSON AND JOHNSON

the operating room. A present pulse that is diminished compared with the contralateral extremity necessitates further vascular study. As long as the extremity shows signs of perfusion, such as good capillary refill, appropriate color, and warmth, an angiogram may be performed in the radiology suite. Abnormal pulses may develop as a result of vessel spasm, thrombosis, or progression of an intimal tear. Though less common, injury to the popliteal vein may also occur with multi-ligament knee injuries. Richter reported 10 ruptures of the popliteal vein in 89 patients with knee dislocations, compared with 8 arterial ruptures. 1° These injuries can present with lower extremity edema, venous stasis changes, thrombophlibitis, and even death from a pulmonary embolism. Even though these injuries are rare, they must be evaluated because of their devastating consequences if missed.

NERVE INJURIES The incidence of nerve injuries with knee dislocations is between 16% and 40%J -3 The peroneal nerve is most commonly injured, but injuries to the tibial nerve have occurredJ l Injuries to the lateral and posterolateral corner of the knee place the peroneal nerve at increased risk, because of its superficial location as it curves around the fibular head. Posterior dislocations have a high incidence of nerve injuries. The prognosis of peroneal nerve injuries is poor. Complete nerve injuries only recover about 50% of the time. Nerve injuries are generally followed conservatively for 3 months. Of these injuries, about one third will recover, one third will have minor deficits, and one third will have a complete palsy. 2

OTHER PATHOLOGY Open dislocations may occur with 19% to 35% of highenergy dislocations. 12,~3 The highest incidence of open injuries is seen in anterior and posterior dislocations. Cole and Harner report injuries to the patella tendon or biceps femoris in 20% of these patients. Fractures of the tibia plateau occur in at least 10% to 20% of high-energy knee dislocations. 7 The other pathology must be addressed in the treatment approach to these injuries.

EMERGENT SURGICAL CONDITIONS Vascular injuries, open dislocations, irreducible dislocations, and compartment syndromes require prompt diagnosis and immediate treatment. Vascular emergencies have already been discussed. Open dislocations must be reduced with subsequent irrigation and debridement in the operating room, and be treated with intravenous antibiotics for 48 hours. Soft-tissue wounds should be evaluated for problems with closure, as plastic surgery consultation is sometimes necessary. Lateral knee dislocations may present as an irreducible dislocation. The medial femoral condyle may become buttonholed through the medial retinaculum and present with the dimple sign. TM This particular type of dislocation may require open reduction. Prolonged dislocation in this position may cause EVALUATING ACUTE MULTIPLE-LIGAMENT-INJURED KNEE

skin necrosis. Compartment syndrome must always be ruled out, and emergent fasciotomies are required -when this condition exists or is impending.

INITIAL EVALUATION AND MANAGEMENT Although some knee dislocations present with obvious deformity, most multiple-ligament knee injuries spontaneously reduce. One must have a high index of suspicion for these injuries. The patient's history provides essential information regarding the mechanism of injury and potential associated injuries. The direction of the force to the knee and the position of the leg are important variables. Contact versus noncontact is worth documenting. A highenergy motor vehicle accident is important to differentiate from a sports-related dislocation, because of the usual severe soft-tissue injury and associated injuries. 5,6 After obtaining the history, a thorough physical examination is performed. Examination of the entire extremity is critical. A visual inspection should note any obvious deformity or wound, as well as any subtle changes in skin discoloration. The presence of a dimple sign or tight compartments should also be assessed. A detailed neurovascular examination follows the visual inspection. The dorsalis pedis and posterior tibialis pulses are palpated. Never assume that a decreased pulse is normal and the result of spasm. Ankle brachial indices are assessed; a decrease of 0.15 or greater indicates a significant vascular injury, s The patient is also asked to actively dorsiflex his or her foot and to activate the extensor hallicis longus tendon. These specific tests assess the peroneal nerve function. Sensation in all of the nerve distributions, as well as motor function of the tibial nerve should be examined. A knee that presents still dislocated should undergo an expedient examination so that an immediate reduction can be obtained. Immediate reduction is performed with the application of longitudinal traction, and this can be facilitated by the use of sedatives and analgesics. The presence of a dimple sign suggests that an open reduction may be necessary. After a reduction is achieved, a repeat neurovascular examination is necessarv. It is important to document all examination finding before and after reduction. An examination of the mjured ligaments may be performed after reduction. The presence of sedation and analgesia will allow the stability examination to be performed. Testing varus and valgus in full extension may often illicit positive findings in a multiple-ligament-injured knee. Opening to varus or valgus stress in full extension suggests that one or both of the cruciates as well as a collateral ligament a n d / o r capsule has been disrupted. It is important to distinguish between a stable and unstable knee injury. Stability is judged on the ability of the knee to remain in a reduced position. A stable knee may be immobilized in extension, whereas an unstable knee must be placed in an external fixator in the operating room. Postreduction radiographs must be obtained, and the knee will need to be followed clinically and with radiographs to assure that reduction is maintained. After manual or spontaneous reduction of the dislocation, a period of observation is appropriate to watch for any delayed vascular changes. We prefer to admit the patient overnight to the hospital. Because of the high

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incidence of vascular injuries, an arterial injury should be assumed until proven otherwise. Signs of obvious vascular injury, such as pulselessness, coolness, and pallor, require immediate consultation with a vascular surgeon. If gross signs are not present, then serial exams may be performed. The decision to get routine arteriograms on patients with a knee dislocation in the presence of a normal examination is controversial. Many surgeons will argue that the presence of a normal examination does not rule out an occult or intimal tear. An intimal tear may clinically present on a delayed basis. 15,16 Although an arteriogram procedure is not without complications, most surgeons agree that the complications of a missed arterial injury are more severe and outweigh the potential complications of the diagnostic procedure. Fanelli and Feldman recommend arteriography in patients with acute three-ligamentinjured knees to rule out vascular damage, especially intimal tears. 17 Several studies have shown that serial examinations are an effective method of ruling out a significant arterial injury. Arteriogram studies have shown a relatively low incidence of arterial injury from knee dislocations associated with normal examsJ s-20 Dennis reported that a physical examination predicted the need for vascular surgery with 100% accuracy. The 7 minimal arterial lesions found by arteriography in the 36 patients with a normal examination were treated nonoperatively.21 Treiman also reported the distal pulse examination to be 100% accurate for identifying patients who will need vascular surgery. This study found the physical examination to be 85% sensitive at diagnosing an arterial injury. 2° At our institution, all patients with a knee dislocation are admitted for observation and serial examinations, with particular attention to the neurovascular assessment. A vascular surgery consultation is obtained as well to prevent any delay in the treatment of a vascular injury should one develop on a delayed basis. The initial evaluation follows the basic steps of a treatment algorithm (Fig 1). After the initial assessment of the knee dislocation, anterior/posterior and lateral radiographs are obtained. The knee joint is evaluated for associated fractures and the adequacy of the reduction. Reduction should not be delayed for radiographs. Other views include intercondylar notch and patellofemoral radiographs. These images assess the extensor mechanism, and may visualize possible ligament avulsion fractures. Magnetic resonance imaging (MRI) is necessary to evaluate the ligamentous structures and other soft tissues. It may help diagnose a patella tendon or quadriceps rupture; in these injuries, an early repair is indicated. An MRI may also identify meniscus injuries, cartilage lesions, bone bruises, and occult fractures. The information obtained by these studies is useful in preoperative planning. We recommend obtaining an MRI in all cases in which a repair, reconstruction, or both is planned. This imaging study can be obtained in a nonemergent fashion.

EXAMINATION OF SPECIFIC LIGAMENTOUS STRUCTURES In the acute setting, swelling and pain often prevent a detailed ligament examination. However, the best possible

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assessment should be obtained. Gross instability to varus and valgus testing in extension suggests injury to one or both cruciate ligaments, the joint capsule, and the collateral ligaments. If the joint capsule has been disrupted, then there may not be an effusion. Flexion is often not possible. This precludes anterior and posterior drawer testing. The information obtained from the physical examination should be correlated with the history and mechanism of injury. The four main ligamentous structures include the anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament (MCL) with the posteromedial capsule, and the posterolateral corner (PLC). The PLC is composed of the lateral collateral ligament, popliteus tendon, popliteofibular ligament, arcuate ligament, fabellofibular ligament, and the posterolateral joint capsule. It is important to specifically examine each of the 4 elements carefully. The MRI should not be relied on solely, because the accuracy of the test is diminished without clinical correlation. ACL

The ACL serves as the primary restraint to anterior translation of the tibia in relation to the femur. It provides 86% of the resistance to anterior translation. 22 The ACL also serves as a secondary stabilizer to varus, valgus, and rotational stresses about the knee. 23 The most reliable and sensitive test for assessing ACL deficiency is the Lachman test. In multiple-ligament-injured knees, this test is more difficult to perform. For example, PCL-deficient knees can mislead the examiner because of the abnormal translation. Also, a complete MCL disruption can give a false-positive Lachman test if care is not taken to perform the test in internal rotation. This results from the anteromedial rotational instability secondary to MCL disruption. PCL

The PCL serves as the primary restraint to posterior translation of the tibia. 22 The physical examination of the PCL includes the posterior drawer test, posterior sag sign, quadriceps active test, and Godfrey's test. The most sensitive test is the posterior drawer test. The anterior tibialfemoral step-off is important to note when performing this test. Normal step-off is 8 to 10 mm (tibia anterior to the femur with the knee flexed 90°). This test is graded according to the amount of translation with a posterior directed force. MCL

The MCL is the primary restraint to a valgus knee stress at 20 ° to 30 ° flexion. It is also a secondary restraint to anterior translation. Testing is performed by applying a vagus stress at 20 ° to 30 ° flexion. This test is graded according to the amount of joint line opening in millimeters and the presence of an endpoint. The knee is also tested in full extension. Opening to valgus testing in full extension implies damage to the posteromedial capsule in addition to the superficial MCL.24 The posteromedial capsule is part of the deep MCL, and it may need to be repaired or reconstructed in certain cases. WILSON AND JOHNSON

Multiple-Ligament Knee Injuries

Fig 1. Treatment algorithm for multiple-ligament knee injuries.

Open Skin

"Dimple Sign"

Skin Intact

Reduction ~

No Reduction

Reduction

To OR Immediately

To OR Immediately

Physical Exam

Irrigation

Open Reduction

Pulses Present

Pulses Absent

Unstable

Stable

PE for Stability

Vascular Consult

Ex-Fix

B~ace

Stable

Unstable

OR/Arteriogram

IV Antibiotics

Immobilize

To OR

NL

Observe

X-ray

Reduction

Reduction Repair

Reduced Unreduced

Ex-Fix

Stable Unstable

Injury

Ex-Fix

"a Observe To OR

Observe Immobilize Ex-Fix

Reduce

Observe Observe

Observe

Ex-Fix

+

Observe

PLC The PLC resists v a r u s a n d rotational forces to the knee. The a n a t o m i c structures of the PLC can be d i v i d e d into 3 layers. L a y e r 1 is c o m p o s e d of the iliotibial b a n d a n d the biceps femoris tendon. L a y e r 2 consists of the lateral retin a c u l u m a n d lateral patellofemoral ligaments. Layer 3 is the d e e p e s t a n d contains the lateral collateral l i g a m e n t or fibular collateral ligament, the fabellofibular ligament, the popliteus, the arcuate complex, a n d the i m p o r t a n t popliteofibular ligament. Testing of the PLC consists of v a r u s stressing the knee at 0 ° a n d 30 °. Increased external rotation of the tibia at 30 ° a n d 90 ° is tested a n d c o m p a r e d w i t h the contralateral knee. O t h e r tests include the posterolateral d r a w e r test, external rotation d r a w e r test, a n d reverse p i v o t shift test. Increased o p e n i n g to v a r u s stress at 30 ° w i t h o u t o p e n i n g at 0 ° or other signs of a PLC injury suggests an isolated tear of the FCL. 25 Failure to diagnose EVALUATING ACUTE MULTIPLE-LIGAMENT-INJURED KNEE

a n d treat an injury of the PLC of the knee in a patient w h o has a tear of the ACL or PCL can result in failure of the reconstructed ligament.

CONCLUSIONS The initial diagnosis of a knee dislocation or multiplel i g a m e n t knee injury is an orthopaedic emergency. A vascular injury m u s t be a s s u m e d until it can be ruled out. A t h o r o u g h n e u r o v a s c u l a r e x a m i n a t i o n should be perf o r m e d before a n d after reduction of the knee joint. These patients should then be o b s e r v e d for a n y changes in their vascular examination. All patients w i t h a p e r f u s e d extremity b u t a b n o r m a l vascular status should u n d e r g o an arteriogram. Patients w i t h o u t pulses or a n o n p e r f u s e d extremity should go i m m e d i a t e l y to the operating r o o m w i t h a vascular s u r g e o n w h o can p e r f o r m an on-the-table anglo-

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gram. After the vascular status has been documented, radiographs followed by MRI should be obtained. A complete ligament examination will help correlate the findings of the MRI, and a preoperative plan can be established.

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12. Shields L, Mital M, Cave E: Complete dislocation of the knee experience at the Massachusettes General hospital. J Trauma 9:192-215, 1969 13. Meyers M, Harvey JJ: Traumatic dislocation of tile knee joint. A study of eighteen cases. J Bone Joint Surg Am 53:16-29, 1971 14. Quinlan A: Irreducible posterolateral dislocation of the knee with button-holing of the medial femoral condyle. J Bone Joint Surg Am 48:1619-1621, 1966 15. O'Donnell TJ, Brewster D, Darley R, et al: Arterial injuries associated with fractures and/or dislocations of the knee. J Trauma 17:775-784, 1977 16. Ottolenghi C: Vascular complications in injuries about the knee joint. Clin Orthop 165:148-156, 1982 17. Fanelli GC, Feldman DD: Management of combined anterior cruciate ligament/posterior cruciate ligament/posterolateral complex injuries of the knee. Op Tech Sports Med 7:143-149, 1999 18. Applebaum R, Yellin AE, Weaver FA, et al: Role of routine arteriography in blunt lower-extremity trauma. Am J Surg 160:221-225, 1990 19. Fanelli GC: PCL: Indications, techniques, results. Proceedings of the American Academy of Orthopaedic Surgeons 66th Annual Meeting, Anaheim, CA, February 4-9, 1999 20. Trieman GS, Yellin AE, Weaver FA: Evaluation of the patient with a knee dislocation for selective arteriography. Arch Surg 127:10561063, 1992 21. Dennis JW, Jagger C, Butcher L, et al: Reassessing the role of arteriograms in the management of posterior knee dislocations. J Trauma 35:692-697, 1993 22. Butler DL, Noyes FR, Grood ES: Ligamentous restraints to anteriorposterior drawer in the human knee: a biomechanicat study. J Bone Joint Surg Am 62:259-270, 1980 23. Wilson SA, Vigorta VJ, Scott WN: Anatomy, in Scott WN (ed): The Knee. St. Louis, Mosby, 1994, pp 15-54 24. Tria AJ: Clinical examination of the knee, in Insall JN, Scott WN (ed): Surgery of the Knee (ed 3). New York, Churchill Livingstone, 2001, pp 161-174 25. Covey DC: Injuries of the posterolateral corner of the knee. J Bone Joint Surg Am 83:106-118, 2001

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