Surgical Treatment of Combined ACL and Lateral Side Injuries
11.3 Clinical Evaluation
A proper diagnosis is the foundation for developing an appropriate and successful treatment plan in the patient with a ligamentous knee injury. It is essential to do a complete clinical workup that should consist of obtaining a careful history, performing a thorough physical exam, and obtaining appropriate imaging studies. After all these steps have been accom- plished, the surgeon must develop a comprehensive preoperative plan with the patient prior to entering the operating room.
At our institution, this is commonly achieved during the preoperative visit.
It is important to note that the clinical fi ndings associated with the combined ACL/PLC injury have a direct correlation to the mechanism of injury. Several authors have reported that the application of a varus force in the hyperextended knee is the most common injury mechanism to the posterolateral knee structures [ 21, 22 ] . This knee position stresses not only the lateral and posterolateral knee structures but also the ACL. Ross et al. reported that in their cohort of 13 patients who sustained ACL/PLC combined injuries from sports-related trauma, all occurred via a hyperextension and varus mechanism [ 23 ] .
11.3.1 History and Physical Examination
The importance of performing a thorough history and physical exam in the evaluation of the patient with the multiple- ligament-injured knee cannot be understated. Although ACL injury is often readily identi fi ed through the mechanism, history, and exam, it is not uncommon for concomitant injury to the lateral and posterolateral knee to be initially missed, with some authors reporting a mean delay in diagnosis of 30 months [ 1, 14, 24– 26 ] . As the failure to recognize and treat PLC instability can have a negative effect on the success of ACL reconstruction, it is imperative that these injuries be identi fi ed early [ 1, 2 ] . In fact, many authors have suggested that a primary cause of ACL graft failure can be attributable to undiagnosed PLC injury [ 1, 18, 20, 24, 27 ] .
The clinical diagnosis of an anterior and lateral combined knee injury begins with obtaining a good history of the injury.
Patient-directed questions should assess the mechanism of injury (with higher suspicion with a varus-hyperextension force), whether or not there was the sensation of a “pop,” presence and timing of associated swelling, and any subsequent feelings of instability or loss of motion (typically full extension).
The physical exam should begin with a thorough neurovascular exam. Documentation of distal pulses and function is crucial, especially in the setting of a grossly unstable knee. The incidence of peroneal nerve injury in the setting of a postero- lateral corner injury has been reported to be 12–16% [ 21, 22 ] . Serial examinations should be done to ensure an occlusive vascular lesion is not developing on a delayed basis, and the utilization of the ankle-brachial index (ABI) may be useful in determining a need for further evaluation and intervention [ 28 ] . Key points with regard to the ABI are to take the blood pres- sures supine, use the ipsilateral upper extremity as the denominator, and realize that it may be unreliable in patients with peripheral arterial disease or vessel calci fi cations. An ABI <0.9 should alert the physician to an increased likelihood of signi fi cant arterial injury [ 29 ] .
The physical examination should continue with an assessment of the patient’s standing alignment. Any varus malalign- ment, which cannot be attributable to lateral structural injury, should be identi fi ed and further worked up with a standing
hip-to-ankle radiograph. The surgeon should also evaluate the patient’s gait pattern, speci fi cally checking for a varus thrust.
These fi ndings are both clinically important as they may be indicators of concomitant lateral and posterolateral structural injury as described by Noyes et al. in the “double and triple varus” knees (Fig. 11.1 ) [ 30 ] . As ligamentous reconstruction in the setting of baseline varus malalignment has an increased risk of failure due to increased graft forces, some of these patients may bene fi t from a high tibial osteotomy in addition to ligament reconstruction [ 20, 27, 30 ] .
Important tests to assess the integrity of the ACL include the Lachman test and the pivot shift test. The Lachman test is the most sensitive physical exam maneuver for the ACL and should be performed with the knee in 20–30° of knee fl exion [ 31, 32 ] . A technical point when doing this exam is to ensure that the proximal hand simply stabilizes the thigh and does not inadvertently push posteriorly, as this can dampen the anterior tibial translation noted by the distal hand. The pivot shift maneuver is performed by applying a valgus and internal rotation force to the tibia while fl exing the knee [ 33 ] . A palpable clunk may be appreciated as the subluxed tibia reduces with increasing knee fl exion. While this exam is the most speci fi c test for the ACL, it has relatively poor sensitivity (32% reported by some authors) due to the discomfort it can elicit in the awake patient who thus guards against it [ 31 ] .
It cannot be emphasized enough that the posterolateral complex of the knee should be examined in every patient with a suspected ACL injury. Varus and valgus stability should be tested with the knee both in 0° and in 20–30°. Instability at 30°
suggests a collateral ligament injury, while continued instability at 0° is indicative of an additional cruciate ligament injury.
Maneuvers such as the posterolateral drawer test and the external rotation recurvatum test can be useful in establishing a diagnosis of posterolateral corner injury (Fig. 11.2 ) [ 34 ] . The posterolateral drawer test is performed with the hip fl exed 45°, the knee fl exed 80°, and at 10–15° of external rotation [ 8, 35 ] . In the setting of PLC de fi ciency, the lateral tibial plateau externally rotates around the PCL, and there is relative posterior translation with a posteriorly directed force. The external rotation recurvatum test assesses the PLC in extension and is performed by grasping the great toes of both feet and elevating the legs off the bed [ 8, 35 ] . Careful observation will reveal a relative tibia vara and hyperextension of the lateral knee in the
Fig. 11.1 Categories of varus angulation based on clinical fi ndings. ( a ) Tibiofemoral geometry causes include loss of medial meniscus or articular cartilage. ( b ) Separation of the lateral compartment is due to lateral soft tissue de fi ciency. ( c ) Varus recurvatum includes chronic stretching or traumatic injury to the posterolateral ligament structures. From [ 30 ] , reprinted by permission of SAGE Publications
patient with PLC injury. Finally, the dial test, which has been described in either the prone position or supine with the leg hanging off the bed, may also be bene fi cial in differentiating a PLC injury from a combined PCL/PLC injury [ 36, 37 ] . If there is asymmetric tibial external rotation of 10° or more in 30° of knee fl exion, then it is suggestive of a posterolateral corner injury. If this asymmetric rotation also occurs in 90° of knee fl exion, then there is likely a combined PCL/PLC injury present.
Besides the aforementioned speci fi c exam maneuvers, careful palpation of the soft tissue and bony structures may provide clues as to the nature of the injury. A biceps femoris tear may be present, and a defect is often palpable just proximal to the fi bular head [ 23 ] . While most intra-articular knee injuries are accompanied by a large intra-articular effusion, the absence of a contained knee effusion can be suggestive of a complete posterolateral corner injury with concomitant capsular disruption [ 23 ] .
11.3.2 Imaging
Plain radiographs of the knee should be obtained not only to assess for the presence of any periarticular or intra-articular fractures but also to evaluate for certain secondary fi ndings which may be seen in the setting of a ligamentous knee injury (Fig. 11.3 ). A small avulsion fragment off of the fi bular head, termed the arcuate sign, may be noted and is indicative of injury to the posterolateral knee structures, particularly the LCL and/or biceps femoris [ 38 ] . In a study by Juhng et al., 89%
Fig. 11.2 Clinical photographs demonstrating the posterolateral drawer test for the assessment of posterolateral corner insuf fi ciency. ( a ) Note the relative posterior translation upon application of a posterior force with the knee at 80° and slight external rotation. ( b ) Reduced knee state
Fig. 11.3 Radiographs portraying secondary signs of knee ligamentous injury. ( a ) Arcuate sign, suggestive of a posterolateral corner injury ( aster- isk ). From Malone WJ, Verde F, Weiss D, Fanelli GC. MR imaging of knee instability. Magn Reson Imaging Clin N Am. © 2009;17:697–724, vi–vii. Reprinted with kind permission from Elsevier. ( b ) Segond fracture, suggestive of an anterior cruciate ligament injury
of patients with this fi nding had a concomitant cruciate ligament injury, and 25% of these were isolated injuries to the ACL [ 38 ] . There may also be an avulsion fracture of the lateral tibial plateau, termed a Segond fracture, which is due to the pull of the lateral capsule and seen with an ACL injury [ 39 ] .
As discussed earlier, a standing hip-to-ankle AP radiograph is warranted if there is any clinical suggestion of varus malalignment or a varus thrust gait pattern. In the normally aligned knee, a line drawn from the center of the femoral head to the center of the ankle (mechanical axis) should pass through the 62% point of the knee, where 0% is medial and 100% is lateral [ 30, 40 ] .
MRI is useful to assess the extent of injury and facilitate preoperative planning. It has been reported to be 92.3% sensitive in identifying acute grade III tears of the ACL in the multiple-ligament-injured knee [ 41 ] . While it is excellent at identifying injuries on the lateral side of the knee as well, especially to the LCL or popliteus, it is reported to be less accurate (53–68%) in assessing the popliteo fi bular ligament [ 42, 43 ] . LaPrade et al. have recommended obtaining T2-weighted coronal oblique views to assist in identifying injuries to the PLC (Fig. 11.4 ) [ 42 ] .
Bone bruises are also another MRI fi nding which not only help the surgeon understand the mechanism of injury but can also facilitate the prediction of injured structures. They can be identi fi ed in 71–88.6% of patients with an ACL injury and are commonly located on the anterolateral femoral condyle near the sulcus terminalis and the posterolateral tibial plateau [ 41, 44 ] . In patients with a combined posterolateral complex and cruciate ligament injury, there is also often a bony contu- sion of the anteromedial femoral condyle, which should increase the surgeon’s suspicion for such an injury pattern [ 45, 46 ] . Geeslin et al. recently published a case series of 102 patients with acute PLC injuries [ 46 ] . In the 38 patients that had a concomitant ACL tear, 50% (19 patients) had evidence of an anteromedial femoral condyle bone bruise on MRI, and 29%
(11 patients) had a posteromedial tibial plateau bone bruise (Fig. 11.5 ). They advised that in the setting of an ACL tear, the surgeon should have an increased suspicion for a secondary PLC injury if the MRI portrays these additional bone bruises.
Oftentimes the lateral knee injury is distal, where the LCL and popliteo fi bular ligaments are avulsed from the fi bula, and the capsule is torn from the proximal lateral tibia [ 23 ] . It is also imperative to evaluate the biceps femoris insertion as it may be injured in up to 46% of patients with combined ACL/lateral knee injuries [ 23 ] . These fi ndings are crucial to note preopera- tively, as they are associated with anterior displacement of the common peroneal nerve 89% of the time, and the surgeon should approach the lateral knee with this expectation to avoid iatrogenic nerve injury [ 47 ] .
11.3.3 Diagnostic Arthroscopy
There are certain fi ndings that can be noted at the time of arthroscopy in the patient with an ACL/lateral knee injury. Again, these become increasingly important to investigate for in the patient undergoing the routine ACL reconstruction with no clear preoperative suspicion of posterolateral knee injury so that a concomitant lateral knee injury is not missed. The popliteus tendon can be easily visualized from the lateral compartment, but the surgeon should also investigate the lateral gutter where the popliteo fi bular ligament can be assessed as the vertical fi bers descending from the inferior surface of the
Fig. 11.4 T2-weighted coronal oblique MR images depicting ( a ) intact popliteo fi bular ligament and ( b ) disrupted ligament ( arrow )
popliteus tendon (Fig. 11.6 ) [ 48 ] . LaPrade et al. described an arthroscopic “drive-thru” sign of the knee where opening of the lateral compartment greater than 1 cm with varus stress at 30° was indicative of a grade III injury to the lateral knee [ 49 ] . A “lateral gutter drive thru” sign has also been described, where the arthroscope may be placed deep into the posterolateral compartment via the lateral gutter due to an increased interval between the lateral femoral condyle and the popliteus tendon seen with injury [ 50 ] .