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Management of the Posterior Cruciate Ligament-Deficient Knee

Strobel, Michael J. M.D.; Weiler, Andreas M.D.

Section Editor(s): Paulos, Lonnie M.D.

Tips and Pearls
Free

Although the injured posterior cruciate ligament (PCL) has gained more attention during the past few years, we as surgeons are still confronted with a high amount of overlooked or underestimated PCL and multiple-ligament injuries. In order not to overlook a PCL injury or to misdiagnose an isolated anterior cruciate ligament injury in PCL deficiency, the authors present their diagnostic scheme, including the standard use of stress radiography, and discuss possible pitfalls during clinical and arthroscopic examination. Because the outcome after PCL reconstruction is still far from achieving reproducible, good results with conventional surgical techniques and after-treatment protocols, the authors consider differentiated perioperative management of the PCL-deficient knee to be essential to improve results. Therefore, the authors present and discuss factors such as the exclusion of fixed posterior subluxation, anatomic tunnel placement, and rigid post-treatment protocol to improve the outcome. They further focus on technical details during replacement surgery of the PCL and the multiple-ligament-deficient knee.

From Orthopädische Gemeinschaftspraxis, Straubing, Germany (Dr. Strobel) and Trauma & Reconstructive Surgery, Sports Traumatology & Arthroscopy Service, Charité, Campus Virchow Clinic, Humboldt-University, Berlin, Germany (Dr. Weiler).

Address correspondence to Michael J. Strobel, MD, Orthopädische Gemeinschaftspraxis, Hebbelstr. 14a, 94315 Straubing, Germany.

Injuries to the posterior cruciate ligament (PCL) are more frequent than previously anticipated, especially among patients with fractures of the lower extremities.8,9,19,25,52 Although several reports suggest that so-called isolated PCL lesions present a relatively benign injury with respect to functional outcome,5,6,10,29,38,39,41,54 other reports prompt thoughts that progressive cartilage lesions are unavoidable.22,23,43,44 However, the number of patients presenting with a so-called isolated injury to the PCL in a regular, nonsports-related group are rare.7,52 Most of the patients with whom we are confronted during our daily routine present PCL injuries combined with injuries to the anterior cruciate ligament (ACL) or the posterolateral structures. Because a high rate of fair and poor results have been reported after surgical treatment, these patients need thorough, well-defined diagnostic and therapeutic regimes to optimize outcome.

Our knowledge about the course of PCL injuries is still limited when compared with that of the ACL. Although more and more information has become available in recent years with respect to anatomy, biomechanics, and treatment options, unknown variables and controversies considering the diagnosis and treatment of the PCL-deficient knee still remain. A major limitation of the available literature today is that the number of patients studied in most reports is low (N < 50), and nonhomogeneous populations have been investigated. Thus there is no clear treatment guidance available. Between 1992 and 1999, 587 patients with PCL-deficient knees, including those who underwent previous surgery, were seen at the Orthopädische Gemeinschaftspraxis Straubing by one of us (MJS). We also included our experiences from a level-one trauma center, where acute PCL and multiple-ligament injuries are seen weekly by one of us (AW). Based on our experience we have discovered the following:

• PCL injuries are much more often than previously anticipated, especially when the treating institution is aware of this lesion.

• Really isolated PCL injuries are rare or remain undiagnosed.

• There is a rapid progression of degenerative joint changes, even in isolated injuries.

• Surgical treatment using conventional techniques and post-treatment protocols lead to a high rate of fair and poor results concerning the restoration of normal knee laxity.

• There is a high rate of undiagnosed or inadequately estimated combined ligament injuries, leading to incorrect treatment recommendations.

Thus, the goal of the current report is to focus on pitfalls and pearls encountered during diagnostic testing and treatment of the acute and chronic PCL-deficient knee, including combined and multiple-ligament injuries.

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DIAGNOSIS

Injuries of the PCL are less frequent than injuries of the ACL and are often overlooked during the treatment of an acutely injured knee. Even in chronic cases, our experience shows that there is often a long history (as long as several years) of knee pain or instability without a clear diagnosis of PCL insufficiency as a result of inappropriate diagnostics. Thus, we think that a clearly defined diagnostic scheme is necessary to prevent unnecessary delay in treatment, which may have tremendous consequences for the patient in several cases.

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Acute PCL Injuries

In contrast to fresh ACL injuries, most acute PCL lesions do not present with hemarthrosis. Instead, they often present with swelling and hematoma at the hollow of the knee, especially if there is a combined posterolateral corner injury (Fig. 1). In 80% of our patients, tenderness at the dorsal aspect of the knee was reported. Care should be taken to detect indirect clinical signs, such as an anterior tibial blow wound, which can often still be recognized as a scar in chronic cases (Fig. 2). In acute cases, typical spontaneous posterior sagging is rare and can only be seen in cases with combined severe posterolateral instability (Fig. 1). As a good clinical screening method, we palpate the reduction of the tibial step-off by placing a hand on the patella and tibial tuberosity with the metacarpophalangeal joint at the joint line. Because the metacarpophalangeal joint is very sensitive to hyperextension, even a small posterior displacement can be recognized when compared with the uninjured knee (Fig. 3).50

FIG. 1

FIG. 1

FIG. 2

FIG. 2

FIG. 3

FIG. 3

Stress radiography or instrument laxity measurements (KT-1000) may be less useful in acute cases because of pain and muscle tightness. We therefore recommend acquiring conventional lateral radiographs of both knees in 70 to 90° of flexion (when possible) to determine the posterior subluxation against gravity (Fig. 1).42 On conventional anteroposterior and lateral radiographs, any avulsion of the fibular head or any incongruence of the proximal tibiofibular joint is suspicious for a posterolateral corner injury (Fig. 4). A few days after injury, when pain has decreased, we recommend acquiring stress radiographs in 90° of flexion. Stress radiographs should not be acquired more than 14 days after injury so as not to compromise early healing of the PCL.

FIG. 4

FIG. 4

Fractures of the lower extremity are often accompanied by cruciate ligament injuries.8,19 In cases of fractures of the tibia or the femur, in which the initial knee examination is insufficient, we recommend a knee examination while the patient is still in the operating room after fracture stabilization is accomplished. In patients with unclear findings, we document the posterior tibial displacement using an image intensifier (Fig. 5).

FIG. 5

FIG. 5

Magnetic resonance imaging (MRI) is a useful tool in detecting PCL lesions in an acutely injured knee.26,40 In the acute setting, MRI allows for the diagnosis of PCL lesions, especially the rupture localization (femoral, mid substance, or tibial), which may have therapeutic implications. Furthermore, we can determine by contrast enhancement (Gadolinium-DTPA) whether the synovial sheet is intact, which may have a better healing prognosis. MRI also allows, in special cases, one to differentiate between anterolateral and posteromedial bundle disruption. In cases of hyperextension trauma, the anterolateral bundle may remain intact (Fig. 6). In this situation, 30° posterior stress radiographs are recommended to detect the insufficiency of the posteromedial bundle, which may lead to functional instability near extension.

FIG. 6

FIG. 6

A major diagnostic problem in acute knee ligament trauma is severe valgus instability. In the rare setting of posteromedial instability, an additional lesion of the ACL has to be excluded (Fig. 7). In cases of anteromedial instability, clinical examination provides a quick diagnosis, and patients are then scheduled for ACL replacement. However, at a certain degree of valgus instability, the PCL may also be involved, and isolated ACL reconstruction is inappropriate (Fig. 8). We therefore recommend acquiring MR images of all third-degree valgus lesions to exclude ACL involvement in posteromedial instability and PCL involvement in anteromedial instability.

FIG. 7

FIG. 7

FIG. 8

FIG. 8

The patient presented in Figure 9 clearly shows the difficulties in determining the functional status of an acutely injured PCL when relying on arthroscopy and clinical examination alone. If arthroscopy is performed, any indirect signs, such as bleeding or rupture of the anterior fat pad or the synovial sheet of the PCL (Fig. 9), bleeding or hematoma in the posteromedial or posterolateral recess, and any increased lateral joint opening, are highly suspicious for PCL injury. If any of these signs are present, and if there is no clear firm end point during drawer testing, arthroscopic inspection of the PCL via a posteromedial portal is essential (Fig. 9). However, in several cases, when there is incomplete rupture of the PCL, even posteromedial inspection does not necessarily show any obvious pathologic changes. It is known from PCL avulsion injuries that certain intraligamentous structural damage to the PCL, which may not necessarily be seen macroscopically, can lead to instability over time, even if anatomic reduction of the fragment is performed (Fig. 14B) Thus, if, during arthroscopy, the status of the PCL of an acutely injured knee is not absolutely clear, we strongly recommend not performing any intra-articular ligamentous stabilization and suggest that the PCL status be checked with stress radiographs or an image intensifier.

FIG. 9

FIG. 9

FIG. 14

FIG. 14

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Summary

• Fresh PCL injuries often do not present hemarthrosis, thus an intra-articular pathology often remains undiagnosed.

• The diagnosis of a PCL rupture should be clarified as early as possible so as not to delay adequate treatment. We strongly recommend acquiring stress radiographs or lateral radiographs against gravity.

• Patients with fractures of the tibia or the femur often present with accompanying PCL lesions. Thus, PCL status should be checked immediately after fracture stabilization using an image intensifier.

• If conventional radiographs or clinical examination is insufficient to detect acute PCL lesions, MRI is the diagnostic tool of choice, especially in combined ACL-PCL-medial collateral ligament instability.

• Arthroscopy of an acutely PCL-injured knee may not necessarily show clear pathologic findings and may mislead the examiner. PCL status during arthroscopy should be checked via a posteromedial portal.

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Chronic PCL Insufficiency

History and Clinical Examination

The main symptoms in chronic PCL insufficiency are pain or instability. Because PCL insufficiency leads to increased contact pressure at the patellofemoral joint and the medial compartment,43 most chronic PCL patients present early patellofemoral pain, whereas medial pain occurs later if a certain degeneration has been established. Thus, there is often the situation that there is therapy-refractory patellofemoral pain for several years with the history of undefined knee trauma. In these patients a PCL lesion has to be excluded (Fig. 10A). If instability is the predominant symptom, a combined PCL/posterolateral corner lesion has to be considered. Because most isolated PCL injuries lead to instability in higher flexion angles (70-90°), functional instability during daily activities are present near extension, as seen with ACL insufficiency. If there is an additional posterolateral or posteromedial component, instability shifts closer to near extension, which may lead to functional instability during daily activities. With combined PCL/posterolateral corner lesions patients may complain about increased hyperextension of the knee and varus instability during gait. This typical varus-recurvatum knee, however, is much rarer than anticipated according to our textbooks.

FIG. 10

FIG. 10

If there is marked posterior subluxation, clinical examination reveals typical spontaneous posterior sagging of the knee with a clearly positive active quadriceps test. In this setting, the clinical diagnosis of PCL insufficiency should present no difficulties. During clinical examination of knees with only a small posterior displacement or in combined ACL/PCL injuries, the determination of the neutral knee position is often difficult. Good screening methods include palpation of the tibial step-off or the metacarpophalangeal hyperextension test (Fig. 3). However, our experience with previously operated PCL-deficient knees show that approximately 15% of these patients present with a history of ACL surgery. In several operating room records it was documented that the ACL was replaced as a result of elongation with a positive Lachman test. In our opinion there are two major problems during clinical examination. The first problem occurs if there is PCL insufficiency and the Lachman test is performed. The knee is brought from a posterior position to the neutral position, not from neutral to anterior, leading to the wrong diagnosis of an ACL lesion. Furthermore, in several PCL-deficient knees, the firm anterior end point cannot be found clearly because of the phenomenon of fixed posterior subluxation (FPS; discussed later). We therefore recommend testing the Lachman test while a finger is placed on the medial condyle to palpate the tibial step-off during translation (Fig. 3). This test is also very helpful in combined ACL/PCL lesions. The second problem occurs when 90° posterior drawer testing reveals a firm end point. Because most PCL injuries heal with the ligament in continuity,26,40 a firm end point in chronic cases does not imply good function of the PCL. Moreover, if there is a certain posterior laxity, the firm end point is more prominent and may lead to the wrong diagnosis of an ACL lesion.

To determine the involvement of the posterolateral structures we check the increased external rotation in 30° and 90° of knee flexion while the patient is in a prone position. An increased external rotation in 30° alone indicates insufficiency of the posterolateral structures. If there is increased external rotation also in 90° of flexion, this finding indicates a combined PCL/posterolateral corner injury. Because a high number of PCL-insufficient patients present with a history of tibia or femur fracture, the examiner should be aware that several of these fractures are often stabilized with certain rotational malalignment. Thus care should be taken during clinical examination of these patients, because rotational malalignment may lead to the wrong diagnosis of posterolateral rotatory instability or, vice versa, posterolateral rotatory instability may be overlooked (Fig. 11). In this situation we recommend testing the 90° posterolateral drawer.

FIG. 11

FIG. 11

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Radiologic Diagnostics

To overcome these problems when relying on clinical examination only, we strongly recommend acquiring stress radiographs in each patient with PCL deficiency and in any patient with an unclear clinical finding.47,51 It has been shown that stress radiography is superior to clinical examination and instrument laxity measurements.18,37 Although Stäubli and Jakob46 favored the acquisition of posterior stress radiographs near extension, we recommend acquiring stress radiographs in 90° of flexion, because in this position the PCL is the major restraint to posterior displacement, and thus even small changes can be depicted accurately.20,48 Displacement values on stress radiographs are determined according to the technique by Jacobsen21 and Pässler and März31(Fig. 10B). Posterior stress radiography may also allow one to judge the status of the posterolateral corner and the ACL. If there is a side-to-side difference (SSD) in 90° of flexion of more than 12 mm, a combined PCL/posterolateral corner injury should be considered.11,13,50 If there is excessive posterior subluxation (>25 mm), an additional lesion of the ACL should be anticipated (Fig. 10C). On all lateral radiographs we also determine whether there are any ossifications of the posterior intercondylar area, which indicate in chronic cases that the patient underwent PCL injury (Fig. 10D). Ossifications may become a surgical obstacle during PCL replacement.

We acquired routinely 45° flexion posterior-anterior weight-bearing radiographs of both knees according to the technique of Rosenberg et al.36 We found that even isolated PCL-insufficient knees undergo rapid medial degeneration, thus weight-bearing radiographs may depict early joint line changes (Fig. 11). In a series of 191 PCL-deficient patients without any history of previous surgery, we found during arthroscopy that there is an increase of overall cartilage lesion from 13.6 to 39.1% within the first year of PCL insufficiency. After more than 5 years of PCL insufficiency, 77.8% of all patients showed medial cartilage degeneration.

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Fixed Posterior Subluxation

During our clinical routine we were confronted with a special group of PCL-deficient patients in whom a reduction of posterior subluxation to the neutral position was not possible (Fig. 12). These patients sustained severe patellofemoral pain rather than subjective instability. After this phenomenon was detected the first time, we subsequently took additional 90° anterior stress radiographs in all PCL-deficient patients. This new clinical sign-fixed posterior subluxation, or FPS-is defined as a posterior tibial displacement of more than or equal to 3 mm on anterior stress radiographs.53 In a series of 248 PCL-deficient patients with 90° anterior and posterior stress radiographs available, we detected FPS with an incidence of 44%. The following four risk factors for the development of FPS were identified:

FIG. 12

FIG. 12

  1. History of PCL deficiency
  2. Male gender
  3. History of failed PCL surgery
  4. History of previous patellar tendon harvest

The presence of FPS has obvious clinical consequences with respect to diagnosis and treatment. If a patient presents with FPS with only a small posterior displacement and low residual laxity, PCL insufficiency may be easily overlooked when relying on clinical examination alone. Furthermore, these patients seldom complain about instability. If instrument laxity measurements are performed (KT-1000), the neutral knee position cannot be determined, which leads to an underestimation of posterior laxity. If the tibia is locked in a fixed posterior position, reduction is essential before PCL reconstruction; otherwise, FPS can be reduced only against soft-tissue resistance with a posterior force acting already on the graft and its fixation at time zero without taking the natural forces such as the in situ forces in the graft and the hamstring muscle load into account. If the position of the tibia is reducible to a neutral position intraoperatively, high forces resulting from soft-tissue resistance may act already on the reconstruction. If a reduction to the neutral position is not possible during PCL reconstruction, the PCL graft is pretensioned and fixed in a subluxed position combined with high soft-tissue resistance. Thus, the reconstruction may already have a questionable prognosis intraoperatively. Therefore, we consider it essential to diagnose and treat FPS, especially before PCL reconstruction.

If FPS is present and the patient has patellofemoral pain or PCL reconstruction is planned, we use a posterior tibial support (PTS) splint to reduce the subluxation. The splint is worn during the night (discussed later) and the patient is checked at regular intervals (6-8 weeks) with anterior stress radiographs.

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Magnetic Resonance Imaging

Although MRI is a useful diagnostic tool in acute PCL-injured knees, it seems to be less helpful in chronic cases. Because it is known that a high number of PCL ruptures heal with the ligament in continuity,1,26,40 and the fact that MRI shows the morphologic status of the ligament rather than its functional conditions, there are often only indirect findings that indicate PCL insufficiency. Thus there is often the situation that patients present with marked posterior subluxation on stress radiographs, and MRI shows a hypointense ligament that is in continuity. A typical pathologic finding on MRI in this setting is the loss of the normal PCL kinking with a straightened ligament as a sign of spontaneous posterior sagging. In some cases if there is excessive laxity, the PCL cannot be depicted on conventional MR images. In these cases, clinical examination should not be difficult in finding the right diagnosis. Therefore, we do not take routine MR images in chronic PCL cases. MRI may be useful in determining cartilaginous lesions, the status of the ACL, or tunnel conditions in cases of PCL revision surgery.

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Arthroscopy

Although arthroscopy allows for the detection of almost all intra-articular pathologic changes of the knee joint, there are clear limitations in terms of its ability to diagnose a chronic PCL lesion. During routine arthroscopy, an anterior view shows that the PCL is covered by its synovial sheet including a dense fat pat and the ACL. The proximal third of the PCL can then be inspected if the synovial sheet and the fat pad are removed (Fig. 13). Because the PCL heals often in continuity, arthroscopic inspection reveals only indirect signs of PCL insufficiency, such as a "floppy" ACL as a sign of posterior sagging or scarring and tissue inhomogeneity at its femoral insertion (Fig. 13). Therefore, we think that arthroscopy is a poor diagnostic tool to judge the status of a chronically insufficient PCL. However, arthroscopy is more useful in determining medial and patellofemoral cartilage degeneration (Fig. 11D) and lateral joint opening in combined posterolateral injuries. If the upper margin of the lateral meniscus is clearly visible in the figure-of-four position, we consider a pathologic lateral joint opening. If there is excessive lateral joint opening (Fig. 13D) or any damage to the popliteus tendon, severe posterolateral rotatory instability must be considered.

FIG. 13

FIG. 13

With respect to the previously mentioned difficulties encountered during clinical examination and the fact that arthroscopy is a poor tool for detecting PCL insufficiency, care must be taken not to replace accidentally the ACL in a case of PCL insufficiency (Fig. 14A). We strongly recommend the acquisition of stress radiographs in any patient with PCL insufficiency and in patients in whom anterior drawer testing reveals an unclear situation. During any arthroscopic procedure that reveals an ACL that is elongated and in continuity (diagnosis of a slack ACL), a PCL lesion must be excluded before any further surgical intervention.

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Summary

• Patellofemoral pain and a history of undefined knee trauma is suspicious for a PCL lesion.

• If instability is the predominant symptom, a combined PCL/posterolateral corner insufficiency should be considered.

• Especially in isolated or low-grade PCL deficiency, clinical examination bears the risk of overlooking a PCL lesion and diagnosing ACL insufficiency instead.

• Rotational malalignment after lower extremity fracture may lead to under- or overestimation of rotatory instability.

• Stress radiography is the diagnostic tool of choice for determining the functional status of an insufficient PCL.

• FPS is frequent in PCL insufficiency (44%) and should be excluded (anterior stress radiographs) and treated before PCL reconstruction or when patellofemoral pain is present.

• Instrument laxity measurement (KT-1000) is inappropriate to measure posterior laxity on a routine basis because there is a high rate of combined ACL/PCL injuries and a high number of patients with FPS.

• In most patients, arthroscopy and MRI do not assist in determining the functional status of the PCL in detail. These techniques just allow the evaluation of the PCL morphologically.

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THERAPEUTIC MANAGEMENT

Patient Selection

When suggesting operative versus conservative treatment in PCL-deficient knees, the following criteria must be evaluated:

• Chronic or acute case

• Grade of posterior laxity

• Involvement of collateral structures (posterolateral or posteromedial)

• Status of the ACL

• Age and activity of the patient

• Predominant symptoms (instability, pain)

• Presence of FPS

• Status of joint degeneration (cartilage, previous meniscectomy)

• Previous surgery and availability of graft tissue

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Conservative Treatment

Acute PCL Rupture

We recommend treating all acute isolated PCL lesions conservatively. This is because of the fact that the PCL has a good healing capability, especially in isolated cases, and a reported good functional outcome.26,39,40 Because we have found that even isolated PCL deficiency leads to a high rate of medial cartilage degeneration (36.6% in isolated cases versus 60.6% in combined cases) resulting from changes in articular contact pressure, we try to reach the smallest possible residual posterior laxity with our conservative treatment. We therefore do not use an accelerated rehabilitation program with early mobilization and muscle strengthening during the first weeks after trauma. Instead, we use a PTS splint to protect the knee from posterior sagging and use the good healing capabilities of the PCL. The protocol is the same as post-treatment after PCL reconstruction (discussed later). Although there is no large patient population available with PTS splint treatment alone, we have documented a certain restitution of posterior laxity with this treatment in several patients (Fig. 15).

FIG. 15

FIG. 15

FIG. 16

FIG. 16

If there is combined posterolateral or posteromedial instability, we tend more and more to use the PTS splint treatment in these patients as well (Fig. 15), because early surgical intervention is still accompanied by a certain amount of morbidity. If a combined lesion has been initially treated conservatively, the status of the PCL is checked after 6 to 12 weeks with stress radiographs. In patients in whom the reevaluation reveals an SSD of more than 10 mm, delayed PCL reconstruction is recommended. It should be considered in these cases that the initial posterior laxity was higher before conservative treatment, and therefore the remaining posterolateral rotatory instability has to be checked independently from the total amount of posterior displacement seen on stress radiographs. In patients with an acute combined PCL/ACL rupture, the PCL and the concomitant pathology (posteromedial or posterolateral) determines the decision for operative intervention.

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Chronic PCL Insufficiency

If there is an SSD of less than or equal to 10 mm on posterior stress radiographs, we primarily choose conservative treatment with quadriceps strengthening and stretching to reduce patellofemoral contact pressure. If the patient complains about instability (SSD ≤ 10 mm), a brace test (functional PCL brace) is performed and the patient is reevaluated after 6 weeks. If there is a reduction of symptoms, PCL reconstruction should be discussed. If stress radiographs and clinical examination identify an isolated injury but the patient complains about functional instability, posterior stress radiographs in 30° of flexion should be acquired to look for an insufficiency of the posteromedial bundle. If patellofemoral pain is the predominant symptom (SSD ≤ 10 mm), we recommend using the PTS splint test. If reevaluation of the patient reveals marked improvement, PCL reconstruction may also be taken into consideration.

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Operative Treatment

Acute PCL Rupture

In an acutely injured PCL-deficient knee, several factors need to be discussed before surgery. If there is a large wound area, surgery should be performed with great caution, or initial conservative treatment has to be considered to decrease the potential of infection. In patients with multiple injuries, one of the lowest surgical priorities is presented by knee ligament injury. In these patients the application of a PTS splint or an external fixator is recommended to prevent posterior sagging until surgery is indicated. In our opinion, if there is combined posteromedial or posterolateral instability, the decision of early operative treatment of the collateral lesions alone or in combination with PCL surgery needs to be discussed individually with each patient. If there is only a slight lateral or medial joint opening in full extension, we prefer to pretreat the patient conservatively. If there is extensive posterolateral or posteromedial disruption with the tendency for a subluxation, we try to repair all structures within the first 7 days after trauma (Fig. 16).

Surgical treatment of a fresh PCL rupture remains controversial. In principal, it is our opinion that acute PCL replacement with graft tissue should not be performed because the PCL has good healing capabilities, and the functional status after a certain recovery period remains unclear in acute cases. As an appropriate alternative, acute transosseous refixation of a femoral rupture should be discussed. A second appropriate alternative, in contrast to experiences with the ACL, is acute ligament augmentation (semitendinosus tendon, polydioxanone-cord) to reduce the likeliness of persistent tissue elongation. However, so far there is no scientific literature available that clearly supports this approach. Furthermore, we think that accurate treatment with a PTS splint also prevents posterior sagging. If PCL surgery is preferred in an acute case, it must be discussed whether the procedure will be performed in an open fashion or arthroscopically. An arthroscopic approach is advantageous because of the markedly reduced morbidity, but it is difficult to perform and may be limited because of water outflow into the peripheral soft tissue.

Any osseous pathology such as a proximal fibular dislocation (Fig. 4B) or a tibial avulsion fracture of the PCL should be treated acutely. For avulsion fractures, two methods can be used. If there is a small flakelike fragment or a large fragment with anticipated problems for closed or arthroscopic reduction, a posterior approach is recommended and direct fixation (H-plate or lag screws) should be performed (Fig. 14B). If the fragment is large enough and may be reduced easily arthroscopically, an anterior lag screw technique with arthroscopic reduction (posteromedial portal) is preferred.

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Chronic PCL Insufficiency

If the SSD on posterior stress radiographs is more than or equal to 10 mm, we recommend operative treatment. If the SSD is more than or equal to 12 mm, or if there is increased external rotation or a lateral joint opening, we perform additional posterolateral stabilization. Because posterolateral stabilization not only controls rotational and varus instability, it should also be viewed as "extra-articular augmentation" to protect the PCL substitute. We therefore are generous with the indication for additional posterolateral stabilization, because the posterolateral complex is the most important secondary restraint of the PCL.17,56 In cases of combined ACL/PCL, injuries the ACL should not be replaced alone, because tightening of the ACL graft may lead to fixed posterior displacement resulting from PCL insufficiency. Thus, we recommend always replacing both ligaments.

In patients in whom fourth-degree chondromalacia is present, PCL reconstruction may have less benefit for the patient. Although our own experience shows that in selected patients with modified post-treatment and a reduction of activities, PCL reconstruction could lead to a good functional result, other treatment options, such as an osteotomy, have to be evaluated together with the patient. When treatment with an osteotomy is chosen, patellofemoral pain status and extension of the knee should be checked carefully. If there is already severe patellofemoral pain, an osteotomy may be less helpful or may increase symptoms further because of "valgization" and patellar lateralization. If there is an extension deficit, the osteotomy should not be performed with an increase in tibial slope. In this situation, an osteotomy alone may not be able to centralize the knee joint, and additional PCL reconstruction should be taken into consideration.

A basic requirement before PCL surgery is the reduction of FPS. With the use of a PTS splint, which was worn at night, we were able to reduce a mean FPS of 6.9 mm to 2.6 mm after a mean treatment period of 180 days in 59 prospectively documented patients. Even if the patient complains about the long treatment period, we do not recommend compromise, because it is obvious that PCL reconstruction in the presence of FPS has a high failure rate. Most FPS-treated patients report an increase in joint laxity and sometimes complain of an unknown or a new feeling of instability. In this situation, patient education should detail that the more unstable the knee before replacement surgery, the better the expected results. In selected patients, such as those with a long treatment period or third-degree FPS (>10 mm), arthroscopic debridement can be considered. If so, attention should be paid to any scar tissue between the ACL and the PCL. In special cases, in which isolated ACL reconstruction has been performed previously, sacrifice of the ACL graft can be the only way to reduce FPS. If arthroscopic debridement is performed, the tension of the ACL (probe) and the result of any stage of scar tissue removal should be checked with an image intensifier.

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Summary

• Because the PCL has good healing capabilities, the primary goal of conservative treatment of an acutely injured PCL is to prevent persistent elongation.

• In acute combined lesions, posteromedial or posterolateral subluxation should be treated with early surgical repair.

• There is no indication to replace a freshly ruptured PCL with a graft. Instead, acute ligament augmentation or transosseous refixation may be reasonable alternatives.

• Any osseous pathology should be repaired early.

• In combined acute ACL/PCL injuries, the PCL rupture determines all future treatment. In most cases it is inappropriate to address surgically the PCL or the ACL alone.

• In isolated chronic PCL deficiency, conservative treatment does not always lead to patient satisfaction.

• If there is 10 mm or more SSD of posterior laxity, surgery is indicated.

• If SDD exceeds 12 mm, or if there is any increased external rotation or lateral joint opening during arthroscopy, additional posterolateral stabilization is essential for a good result.

• We strongly recommend excluding and treating FPS in any patient if PCL surgery is considered.

• In several cases, if a certain degree of degeneration has already developed, an osteotomy alone may not lead to a satisfactory outcome.

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Preferred Surgical Technique

Because there is a large variety of different surgical techniques reported in the literature, including open versus arthroscopic, single versus double incision, tibial tunnel versus tibial inlay techniques, and so on, we describe our preferred surgical approach and technique, without taking all different variables into account.

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Graft Selection

The extensor apparatus should be viewed as the most important agonist of the PCL. We therefore try to preserve the function of the extensor apparatus and do not recommend harvest of a mid third bone-patellar tendon-bone (BPTB) graft, which is known to weaken the extensor mechanism.34 Furthermore, we have found that BPTB graft harvest increases the likeliness of developing FPS.53 Because patellofemoral pain is a common problem in PCL insufficiency, BPTB graft harvest may worsen this situation.31,35 Regarding the use of a quadriceps tendon graft, there are no scientific data available with respect to its use in PCL reconstruction. Although the graft tissue itself presents favorable structural properties, and the fact that harvest site morbidity is reduced markedly when compared with the BPTB graft, we use an autologous quadriceps tendon graft only in selected PCL cases.

Autologous hamstring tendons are our graft of choice for PCL reconstruction. A multiple-strand graft provides very good structural properties,14 and graft passage through a tibial tunnel can be facilitated easily if no bone block is attached to the graft. We also like to see a certain temporary hamstring weakness during post-treatment because the hamstrings are the strongest PCL antagonists. In cases of a combined PCL/posterolateral or PCL/ACL procedure, the additional use of the contralateral hamstring tendons is appropriate when harvesting the semitendinosus tendon only. So far, however, we have not seen any problems with contralateral hamstring tendon harvest. As a good alternative, if contralateral graft harvest is an issue, we prefer to use allograft material. The preferred structures include the tibialis anterior, the Achilles' tendon, and the quadriceps tendon because all these structures provide strong structural properties and allow for the preparation of a double-bundle graft.

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PCL Reconstruction

For our standard PCL reconstruction, we still prefer to use the conventional tibial tunnel technique. Although, during recent years, the tibial inlay technique has become more and more preferred by other surgeons,2,28 we have not seen any benefit in cases we have seen thus far. Moreover, we also saw a high failure rate (Fig. 14C) with this technique, and the additional problems of surgical morbidity during revisional procedures.

For standard PCL reconstruction we need four portals.45,48 We use a high, lateral arthroscopic portal and a high, medial working portal. To allow for the femoral single-incision technique, as described originally by Kim and Min,24 we create an additional low, anterolateral working portal just above the joint line. A second anterolateral portal is advantageous to avoid the repetitive change of the arthroscopic portal from lateral to medial and it allows for an accurate visualization of the whole femoral PCL insertion site (Figs. 17 and 18). The obligatory posteromedial portal is created after probing with a canual (Fig. 9B). Although it is principally possible to work without a posteromedial portal, visualization of the tibial PCL footprint is difficult from the anterior with a 30° arthroscope. Because good visualization of the tibial footprint is essential, especially if one works without an image intensifier, and because there is easy instrument access to the dorsal proximal tibia, we always create a posteromedial portal and do not use a 70° arthroscope.

FIG. 17

FIG. 17

FIG. 18

FIG. 18

For conventional single-bundle PCL reconstruction, placement of the femoral graft is recommended at the so-called most isometric point.12 However, the normal PCL consists of a posteromedial bundle that is tight in extension, and a stronger anteromedial bundle that is mostly taut in flexion.33 Recent biomechanical studies have focused on so-called anatomic PCL reconstruction in which the graft tissue is fixed directly at the original footprint of the anterolateral and the posteromedial bundle. It was determined that this technique is superior in restoring normal knee laxity compared with conventional so-called isometric reconstruction.15,32 We prefer anatomic femoral tunnel placement in PCL reconstruction. The decision whether to use single anterolateral replacement or double-bundle reconstruction depends on the pathology in each patient. A double bundle is preferred if there is no former PCL tissue remaining, such as during revisional procedures or when the initially treating institution removed the PCL, or in cases with excessive laxity (>20 mm). Because the PCL is a highly vascularized and proprioceptive structure, we try to preserve as much of the PCL tissue as possible during reconstruction. If one decides to perform single anterolateral PCL reconstruction, there are two ways to accomplish this. The first technique preserves almost the entire PCL, and the graft is inserted through a slit in the ligament (Figs. 17 and 20). This technique, however, is very demanding technically. With the second technique, the anterolateral bundle is removed completely and replaced, and the posteromedial bundle and the anterior meniscofemoral ligament remain intact (Fig. 18). To determine correct anterolateral femoral tunnel position, the use of a calibrated probe is helpful (Fig. 17A). The guide wire should be placed 7 mm from the cartilage margin in the 12:30 position (11:30 in the left knee). Final tunnel preparation depends on the preferred fixation technique. In cases of Endobutton fixation, care must be taken not to perforate the medial femoral cortex. Because we favor hybrid graft fixation for soft-tissue grafts3 (e.g., button and interference screw or EndoPearl and interference screw), the tunnel is created 1 mm larger in diameter than the measured graft diameter. After tunnel preparation is finished, a slit is created in line with the PCL fibers, and a channel to the posteromedial recess is created using a shaver (Figs. 17E, F). We prefer to drill the femoral tunnel first to prevent early fluid loss through the tibial tunnel.

FIG. 20

FIG. 20

To explore the tibial footprint of the PCL, a partial synovectomy is performed through the posteromedial portal, and the capsule and scar tissue are then striped off using a special, rounded elevator (Fig. 19). To verify visualization of the tibial foot print, a little mirror is inserted before moving the arthroscope to the posteromedial portal. This avoids an unnecessary change of the arthroscopic portal. We recommend inserting the tibial drill guide before changing the arthroscopic portal. Preservation of the PCL may create difficulties using conventional straight drill guides, leading to a possible medial tibial tunnel placement. We therefore prefer to have three different drill guides available (straight, left curved, right curved; Karl Storz GmbH, Tuttlingen, Germany). The tibial drill guide should be placed 15 to 20 mm below the joint line. If there is no clear vision of the proposed tibial tunnel exit point, the use of an image intensifier is strongly recommended. In patients in whom hardware is still present, we routinely use an image intensifier (Fig. 14D). The angle of the tibial tunnel should not be much steeper than 45°, otherwise there is the risk of a dorsal tibial blowout. After the tibial tunnel is created, the soft tissue is incised to prevent problems during graft passage, and a pull-through suture is advanced and caught by an angled grasper from the anterior direction (Fig. 19). The suture is then inserted into the femoral tunnel using a second pull-through suture. In this situation, any soft-tissue bridging at the anterior working portal should be avoided. To facilitate graft passage, a blunt elevator is inserted through the posteromedial portal, which can be used as a fulcrum (Fig. 20C).

FIG. 19

FIG. 19

After graft passage is complete, we prefer to use biodegradable interference screws for aperture fixation. This technique is advantageous because it promotes tendon-to-bone incorporation,57 and may fill the anterior space between the tunnel wall and the tensioned graft (Fig. 20E), thus leading to a more anatomic graft placement (Fig. 18). If an interference screw is used, anterior screw placement should be avoided because this may lead to a more posterior graft placement (Fig. 21F). To allow for slight screw rotation around the tendon tissue, which should be avoided during ACL surgery, there should only be a little tension on the graft tissue, and the desired screw position should be probed (Figs. 18D-F).

FIG. 21

FIG. 21

If posterolateral stabilization is planned, tibial graft fixation is performed afterward. Because of the very soft bone of the tibia, we always use a hybrid fixation with soft-tissue grafts, such as biodegradable interference screws combined with a periosteal button. If a tendon-bone graft is used, we always place the bone block on the tibial site. This allows for easier graft passage and, because the tibial fixation site is the weak link, bone block fixation here may be advantageous. However, to reach a certain insertion torque, the use of an oversize screw or two interference screws may be necessary. Finally, graft fixation is performed with the knee in 80° of flexion and with an anterior tibial force applied by the assistant.16

After single-bundle reconstruction with preservation of the PCL or the posterolateral bundle, the remaining tension in these structures can be checked with a probe after tibial graft fixation is accomplished. If there is a certain laxity in the posteromedial part while reaching extension, careful radiofrequency shrinkage can be performed.

If a femoral double-bundle technique is used, the anterolateral tunnel is created in the same way as just described. With regard to posteromedial tunnel placement, there are still controversies among PCL surgeons. We prefer to place the tunnel slightly anterior to the anterolateral tunnel, in the 9-o'clock position (3 o'clock in a left knee; Fig. 21B). While the Y-shaped graft is prepared, care should be taken to have a posteromedial bundle that is approximately 1 cm longer than the anterolateral bundle. We recommend using different-color holding sutures to differentiate between the bundles during graft passage. A common problem during graft passage is twisting of both holding sutures (Fig. 21D). If this problem occurs, new pull-through sutures have to be placed, and the holding sutures must be repassed from the anterior position (Fig. 21E). Otherwise, the graft has to be removed and reinserted. With respect to the order of graft fixation, we follow the recommendations of Stähelin et al.,45 which allow for separate tensioning of both bundles in extension and flexion. The posteromedial bundle is fixed first in 90° of flexion followed by tibial fixation of both bundles near extension. This allows for tensioning of the posteromedial bundle near extension. Finally, the anterolateral bundle is fixed in 80° of flexion, with pretension applied to the holding suture.

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Combined PCL/ACL Reconstruction

In a combined PCL/ACL procedure, both femoral tunnels are created first, and PCL tunnel placement follows the previously mentioned steps. Second, the tibial PCL tunnel is drilled and lastly the tibial ACL tunnel is drilled. We first insert the PCL graft followed by the ACL graft. Graft fixation is performed in the order presented in Table 1).

TABLE 1

TABLE 1

Tibial ACL graft fixation always occurs last. The ACL graft should be fixed only with a slight pretension so as not to pull the tibia in a posterior position.

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Posterolateral Stabilization

During the past few years, a large variety of different posterolateral reconstruction techniques have been described.4,27,55 For posterolateral stabilization we prefer to use Larson's technique, which was modified in that instead of a figure-of-eight-shaped graft, a triangular graft is created.45,49 Because a figure-of-eight-shaped graft may have a certain rotational weakness at the site of the tendon strand crossing, a triangular graft may offer higher rotational stability. Furthermore, the posterior graft strand may mimic more closely the course of the popliteofibular ligament.

To explore the fibular head, a longitudinal skin incision is made and the fibular head is exposed subperiosteally (Fig. 22). There must be enough room for a Hohmann hook or a finger to be placed dorsally to the fibular head to protect the peroneal nerve during drilling. From the anterior direction, a guide wire is inserted percutaneously and overdrilled to a diameter of 4.5 to 5 mm. We prefer to use a semitendinosus or tibialis anterior tendon, which should pass easily through the drill whole. Because some tibialis anterior tendons have a large diameter, we recommend splitting them, because with larger diameter drill holes there is the risk of lateral cortex penetration. Using a pull-through suture, the graft and a separate suture for isometry measurement are passed through the drill hole (Fig. 22). To explore the lateral femoral epicondyle the skin is incised horizontally. The iliotibial tract is separated bluntly along its fiber direction and the femoral insertion of the lateral collateral ligament is exposed (Fig. 22). A K-wire is then drilled into the condyle slightly anterior and proximal to the lateral collateral ligament insertion site. Using an Overholt clamp, both graft strands and the isometry suture are delivered separately under the iliotibial tract. Care should be taken to guide the anterior and posterior graft strands separately to create a triangular graft course. The dorsal graft strand should also be delivered below the superficial parts of the biceps tendon. The isometry suture is then placed once around the K-wire, and suture excursion is measured during a full range of motion with the PCL graft tightened. There should be a maximum excursion of 2 to 3 mm. If not, the K-wire position has to be changed. If the correct position is determined, the K-wire direction is changed so as to not perforate the intercondylar notch during later drilling. Next, an 8-mm tunnel (minimum length, 4.5 cm) is created and the graft is shortened to its desired length. After the graft is inserted via the holding sutures and a beath pin, graft fixation is performed with a biodegradable interference screw while maintaining tension on the holding sutures. The knee should be held in approximately 70° of flexion with slight internal rotation and neutralization of posterior sagging.

FIG. 22

FIG. 22

We prefer to fix the posterolateral repair before final PCL graft fixation because during posterolateral repair the knee is positioned at approximately 90°, which may already lead to a certain elongation of the graft construct. Second, we like to check the result of the posterolateral repair manually, which can be performed easily and judged individually if the PCL graft is not yet fixed.

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AFTER-TREATMENT

With respect to the restoration of normal knee laxity after PCL reconstruction, we are still far from reaching reproducible results such as those that occur after the replacement of the ACL. Although during the past few years many refinements for the surgical treatment of the PCL-deficient knee have been introduced, such as anatomic tunnel placement, the tibial inlay technique, a generous indication for a posterolateral stabilization, and so on, we are still confronted with a high rate of fair and poor results. Although these surgical factors may optimize the biomechanical boundary conditions of the healing PCL graft, there is no evidence so far that with newer techniques more stable knees can be expected. Nevertheless, we think that an adequate after-treatment is the essential step in reaching a good result. It is known that the forces that act on a PCL are high during activities of daily living. Although an ACL graft may be exposed to high loads only during certain situations, a PCL graft has to sustain high loads 24 hours a day as a result of gravity and hamstring muscle tone. The fact that an anatomically reduced PCL avulsion fracture may lead to subsequent ligament elongation (Fig. 14B) emphasizes that the high forces acting on the PCL lead to tissue elongation, if there was only certain intraligamentous fiber damage. So how could a remodeling PCL graft lead to a stable knee if these forces are not neutralized during treatment? We think that an early and aggressive rehabilitation program, with protection offered solely by a functional PCL brace, is inappropriate. A major improvement that we have seen during our clinical routine is the consequent neutralization of posterior gravity loads with the use of a PTS splint (Fig. 23). Because the use of the PTS splint is able to reduce posterior laxity during the healing of a freshly injured PCL (Fig. 15), its use is essential to protect the graft after surgery. Our patients wear the PTS splint 24 hours a day for 6 weeks after surgery. During that time, careful mobilization of the knee joint is performed by a physiotherapist while the patient is in the prone position. After 6 weeks, a gradual increase in flexion up to 70° should be reached. The use of a continuous passive motion machine should be avoided, because in most machines the knee shows a certain posterior sagging. After the first 6 weeks, full weight bearing is allowed, the PTS splint is worn only during the night, and a functional PCL brace is worn during the day for another 6 weeks. During that time a continuous increase in flexion should be seen, with a goal of reaching approximately 120° after 12 weeks. Active hamstring exercise should be avoided for at least 3 months.

FIG. 23

FIG. 23

Because this treatment protocol is very conservative, the patient has to be educated in detail before surgery to stress the importance of his compliance during the prolonged after-treatment period. Furthermore, the treating physiotherapist must be informed in detail, because due to their current education, an aggressive physiotherapist should be viewed to be the most dangerous enemy of a healing PCL substitute.

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Summary

• We do not recommend using a BPTB graft as a routine PCL substitute.

• To date, there is no evidence that, including the disadvantages of open surgery, the tibial inlay technique is superior to the conventional tibial tunnel technique.

• The use of an additional posteromedial portal is essential during PCL replacement surgery.

• Even if single-bundle PCL reconstruction is considered, we recommend the creation of an anatomic femoral tunnel instead of the so-called isometric graft placement.

• The use of the double-bundle technique should be taken into consideration if there are no PCL structures left, such as in revisional procedures, or in cases of excessive posterior laxity.

• If there is even a little uncertainty during tibial tunnel placement, the use of an image intensifier is strongly recommended.

• During a combined ACL/PCL reconstruction procedure, the ACL graft should be fixed at last and with little tension only.

• We think that femoral isometry measurements are essential in all posterolateral stabilization techniques.

• Because very high forces act on PCL reconstruction, we do not recommend an accelerated rehabilitation program. Instead, we prefer to neutralize all posteriorly acting forces with a PTS splint.

• The most dangerous obstacle to a healing PCL substitute is an uneducated physiotherapist.31

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Keywords:

Posterior cruciate ligament; Injury; Diagnosis; Treatment; Pitfalls

© 2001 Lippincott Williams & Wilkins, Inc.