Injuries of the posterior cruciate ligament and posterolateral corner of the knee

Injury, Int. J. Care Injured (2006) 37, 485—501

www.elsevier.com/locate/injury

REVIEW

Injuries of the posterior cruciate ligament and posterolateral corner of the knee A.A. Malone a,*, G.S.E. Dowd b, A. Saifuddin a a b

The Royal National Orthopaedic Hospital NHS Trust, Brockley Hill, Stanmore, Middlesex HA7 4LP, UK The Wellington Knee Unit, The Wellington Hospital, Wellington Place, London NW8 9LE, UK

Accepted 2 August 2005

KEYWORDS Review; Knee ligament injury; Posterior cruciate ligament; Posterolateral corner; Anatomy; Phylogenetics; Biomechanics; Diagnosis; Treatment

Summary Injuries of the posterior cruciate ligament (PCL) and posterolateral corner (PLC) of the knee are less common than those of the anterior cruciate ligament (ACL) and their significance is often under-appreciated in the acute setting. Even when recognised, knowledge of the natural history and outcome of treatment has lagged behind that of the ACL and has led to confusion over the indications for operative treatment. Recent developments in the understanding of the anatomy and biomechanics of this area of the knee have led to improvements in management and a renewed interest in these potentially disabling injuries. The aim of this review is to bring the trauma generalist abreast of these recent developments and to improve diagnosis through a heightened index of suspicion and use of appropriate special investigations. The principles of management of both isolated and combined injuries to the PCL and PLC, in the acute and chronic settings, are described. # 2005 Elsevier Ltd. All rights reserved.

Contents Introduction–—incidence . . . . . . . . . . . . . . History–—milestones and key figures . . . . . . . Basic principles–—anatomy and phylogenetics . Biomechanics . . . . . . . . . . . . . . . . . . . . . Clinical features . . . . . . . . . . . . . . . . . . . Physical examination . . . . . . . . . . . . . . . . Investigations . . . . . . . . . . . . . . . . . . . . . Magnetic resonance imaging . . . . . . . . . . . Bone scintigraphy . . . . . . . . . . . . . . . . . .

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* Corresponding author. Present address: 127 Lauderdale Road, Maida Vale, London W9 1LY, UK. Tel.: +44 7801 865568; fax: +44 2072 899844. E-mail address: [email protected] (A.A. Malone). 0020–1383/$ — see front matter # 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.injury.2005.08.003

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486 Arthroscopy . . . . . . . . . . . . . . . . . . Natural history . . . . . . . . . . . . . . . . Treatment . . . . . . . . . . . . . . . . . . . Acute PCL injury . . . . . . . . . . . . . Chronic isolated PCL injury . . . . . . Acute PLC injury . . . . . . . . . . . . . Acute combined PLC and PCL injury. Chronic isolated PCL injury . . . . . . Chronic PLC injury . . . . . . . . . . . . Results . . . . . . . . . . . . . . . . . . . . . PLC reconstruction. . . . . . . . . . . . Combined reconstruction. . . . . . . . References. . . . . . . . . . . . . . . . . . .

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Introduction–—incidence Injury of the posterior cruciate ligament (PCL) is uncommon in contact sports, with only 2% of otherwise fit athletes being found to have an isolated injury of the PCL during routine medical examination for entry into the American National Football League.9 The PCL was found to be injured in 7% of acute sporting knee ligament injuries and in half of these, there were additional ligamentous injuries.39 The incidence of damage to other structures, in association with the PCL, increases with energy of injury and in Fanelli’s series of 222 knees with acute haemarthrosis, mostly after high energy injuries,24 85 (38%) had injured the PCL and only 3 of these (4%) had an isolated injury. Injuries to the posterolateral corner of the knee are also rare in isolation, amounting to only 1.6% of knee ligament injuries in a series by DeLee et al.,21 but were found in combination with other ligamentous injuries of the knee in 27% (60) of Fanelli’s series of traumatic haemarthroses.

History–—milestones and key figures Extensive cadaveric dissections accounted for much of the literature regarding the anatomy and the mechanics of the knee up to the beginning of the 20th century, but descriptions of knee ligament injuries only appear in the English and German literature in sporadic isolated cases at the turn of that century.7,27,35,38,75 In 1913, Goetjes32 reviewed the literature and described seven personal cases of cruciate injury, concluding that it was impossible to make the diagnosis of internal derangement of the knee in the acute setting. By the end of the 1920s, larger number of reports of patients with cruciate injuries were beginning to appear; Wittek100 described a series of 19 patients diagnosed by

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arthrography and Felsenreich25 described 32 patients with cruciate injuries in 1934; of these, 15 were combined with medial collateral, 1 with lateral collateral and 13 with ‘posterior capsular’ damage. At the same time, the first descriptions of isolated lateral collateral injuries were published by Watson-Jones, Gebhardt and Merle d’Aubigue,19,30,99 who described, respectively, lateral collateral ligament injuries associated with late peroneal nerve damage, invagination of the fibular fracture and rupture of the lateral head of gastrocnemius. In 1937, Lee57 described the first two cases of injury to the tibial insertion of the PCL. In 1938, Ivan Palmer from Sweden published a seminal text summarising the current knowledge of the anatomy and natural history of knee ligament injuries, as well as the anatomical basis for the anterior and posterior drawer signs.71 He described the mechanism of injury and outcomes of treatment in his series of 58 patients with ligament injuries, including eight cases of isolated PCL injury and one with injury to the posterolateral structures with peroneal nerve injury. In 1940, Brantigan11 drew attention to the wide controversies regarding the knee ligament anatomy and function and performed a large cadaveric study to try to clarify these points of contention. He confirmed the role of the PCL in preventing posterior translation of the tibia and quantified the posterior translation resulting from PCL division. In addition, he identified the role of the oblique popliteal ligament in preventing hyperextension and showed the knee capsule to be most lax at 15— 308 of flexion. Shortly afterwards, Abbott et al.1 identified the importance of early, thorough examination to diagnose complete ruptures of ligaments in his series of six cases with various injuries, stressing the need for surgical repair to avoid otherwise inevitable instability and poor outcome.

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Figure 1 Seebacher’s description of the posterolateral corner (Reprinted from: Seebacher JR, Inglis AE, Marshall JL, Warren RF. The structure of the posterolateral aspect of the knee. J Bone Joint Surg Am 1982;64:537 with permission from The Journal of Bone and Joint Surgery, Inc.).

O’Donaghue69 showed a trend towards better outcome in early versus late (>2 weeks), repairs and reconstructions (>3 months), in the first study, advocating early repair of knee ligaments, to use a form of graphical statistical analysis. The popliteofibular ligament has epitomised the lack of knowledge and confusion, in the latter part of the 20th century, surrounding the various structures of the posterolateral corner (PLC). Not only are there at least five different names given to the ligament, but no reference was made to any such structure in Nomina Anatomica,5 the publication standardising anatomical nomenclature, published in 1955 by the International Congress of Anatomists. Despite Last’s identifying this error,55 the omission remained uncorrected and no mention of this ligament was made in any anatomical textbook, or popular orthopaedic journal, until 1990.61 It was only towards the end of the 20th century that the significance of structures in the posterolateral corner was recognised and specific treatments suggested.

Basic principles–—anatomy and phylogenetics The PCL arises from a broad, part-circular attachment on the posterolateral side of the medial femoral condyle passing infero-posteriorly to a

midline depression 10—15 mm below the level of the medial and lateral tibial plateaux. Its average length is 38 mm31 and mean midpoint width is 13 mm; it can be divided into anterolateral (85% of cross-sectional area) and posteromedial bundles. The ligament lies extra-articularly, in its own synovial sheath, supplied by the middle geniculate artery and innervated with pain receptors and proprioceptor corpuscles. The meniscofemoral ligaments lie anterior (Humphry42) and posterior (Wrisberg73) to the PCL and are phylogenetic remnants found in 70% of knees. They are believed to be secondary restraints to posterior draw36 and to stabilise the posterior horn of the lateral meniscus. The PLC has been described by Seebacher et al. as comprising three layers of increasing depth78 (Fig. 1). The superficial layer contains the iliotibial tract and biceps femoris and their expansions. The second layer is formed by the quadriceps retinaculum, the two patello-femoral ligaments and the patellomeniscal ligament. The deepest layer is the joint capsule (attached to the lateral meniscus by the coronary ligament), the popliteal muscle— tendon—ligament complex and popliteofibular ligament and the lateral collateral, fabellofibular or arcuate ligaments. The contents of the deep layer are variable, representing continued phylogenetic change, subsequent to the major osteological developments

488 from our ancient ancestor, the Eryops, 300 million years ago. This amphibian had a knee with a bicondylar femur, articulating with a broad fibula and tibia and an inefficient sprawling gait. By the Jurassic period (150 million years later), the knee joint had rotated to bring its apex anteriorly, permitting a more efficient midline gait, and thereafter, the fibular head migrated distally with its biceps femoris insertion.22 This evolutionary fibular migration is mirrored in the embryo around the 7th week of gestation and as a result, the popliteal tendon, which has always inserted onto the fibula, acquires additional attachments to the femur and to the lateral meniscus, creating the popliteofibular ligament, identifiable by the 11th week.70,89 The continuing evolution of the contemporary human knee is illustrated by the prevalence of a large calcified sesamoid in the lateral head of gastrocnemius, the fabella. This older alternative to the arcuate ligament was present, in conjunction with a significant fabellofibular ligament, in 62% of 200 cadaveric knees in a meta-analysis of three anatomical studies.78,87,98

Biomechanics Selective ligament sectioning in cadaveric knees has determined the contribution of individual components of knee stability, throughout the range of knee movement. These components can be described as static (ligaments with fixed attachments) or dynamic (tendons inserting into bone or other ligaments) and act as primary restraints (resisting the majority of force in a given direction) or secondary restraints (contributing to stability only after the primary restraint has been removed and further excursion has occurred). The result of a force on a joint is described as either primary motion (in the direction of the applied force) or coupled motion (in an axis different from that of the primary force, occurring as a result of the effect of joint stabilisers), e.g. a posterior force causing external rotation of the tibia as well as posterior translation.68 The posterior cruciate ligament has a primary function in resisting posterior translation of the tibia on the femur (especially in flexion, when the larger anterolateral bundle is under tension) and is a secondary stabiliser to external rotation in flexion, varus angulation in extension33 and hyperextension, via the posteromedial bundle. The primary effect of the structures of the posterolateral corner is to resist external rotation and posterior translation in flexion and varus angulation (in conjunction with the lateral collateral ligament).33,63

A.A. Malone et al. The popliteus tendon is a dynamic stabiliser to external rotation and varus angulation.62 Consequences of PCL laxity include increased patellar flexion,50 increased patello-femoral contact pressures85 and defunctioning of the menisci,2 leading to higher medial joint pressures59 and a greater risk of osteoarthritis.81

Clinical features The classical mechanism for a PCL tear is the ‘dashboard’ injury, with pre-tibial impact with the flexed knee. This mechanism was identified in 50% of cases reviewed by Dandy and Pusey.17 Other mechanisms include falling onto a flexed knee, hyperflexion and hyperextension. The PLC is generally injured by a varus-extension force to the knee or by external rotation of the tibia, e.g. when ski bindings fail to release during a fall.21 Sportsmen may not remember the mechanism, or even a specific incident, and may be able to continue playing, albeit with an odd sensation of hyperextension when standing. Higher energy injuries can cause damage to both structures, via different mechanisms, and are more likely to cause combined PLC and PLC injuries.24 Most patients suffer some pain, although it may be mild in isolated injuries. Localised pain is common in acute injuries, especially on kneeling, or decelerating, and with chronic PLC injuries, progressive joint line pain, in the medial tibio-femoral and patello-femoral compartments, is often a symptom.41,48 Neurological symptoms of numbness, or foot drop, should be sought whenever the PLC is injured and in a meta-analysis of 139 patients,6,21,49,54,94 common peroneal nerve injury was found in 15% of cases. Instability, including a sudden feeling of hyperextension on stairs, or on twisting, is a common symptom in chronic injuries42 and 26% of patients with a PCL-deficient knee report a feeling of instability.17,81 Giving way is a more serious symptom, present in 20% of patients with PLC rupture, and should alert the clinician to the possibility of a more complex injury. Return to sport may have been possible with good rehabilitation after isolated PCL injuries28,81,72 and partial PLC injuries,47,49 but less likely in those with complete PLC, or combined, injuries, who generally have more disability.

Physical examination Inspection of the knee in the acute phase may give some clues as to the magnitude and direction of the

Injuries of the posterior cruciate ligament and posterolateral corner of the knee injuring force, with bruising, or abrasions, commonly found on the front of the leg. Bruising in the popliteal fossa may also indicate damage to well-vascularised posterior structures, including the capsule, and the absence of an effusion should alert the clinician to the possibility of rupture of the capsule, extravasation of fluid and the associated dangers of early arthroscopy. The leg may lie in varus mal-alignment due to lateral ligamentous incompetence, or the patient may stand and walk with the knee slightly flexed to avoid painful hyperextension in a chronic PLC injury.90 There may also be either a varus (or varus-hyperextension) thrust to the chronic gait pattern,94 due to loss of lateral tension bearing structures with convex articular surfaces in the lateral compartment, or flexion in mid-stance phase in an attempt to avoid painful varus thrust. Palpation of the knee may reveal localised tenderness in the acute phase, due to injured ligamentous and capsular structures,21 or bony injury. The basis for diagnosis of injuries to the PCL and PLC are the stress tests performed in varying degrees of flexion to identify incompetence in the two structures. After any internal derangement, particularly combined ligament injuries, the knee may be inflamed and the patient resistant to flexion, precluding full examination. Repeated examination, possibly under anaesthetic, may be necessary. However, by this time, isolated PCL injuries may have started to heal,81 signs may be subtle, and a comparison with the contralateral side essential. With the knees placed symmetrically and flexed to 908, the normal position of the medial tibial plateau is 1 cm anterior to the anterior aspect of the medial femoral condyle. A posterior sag may be present in the relaxed knee under the effect of gravity alone, but may not be obvious in the acute setting. With the patient’s foot gently stabilised, the posterior drawer test is carried out by applying a posterior force to the tibia and measuring the difference in posterior translation between injured and uninjured sides, noting the quality of the endpoint. Shelbourne and Rubinstein82 classified the laxity according to the relative positions of the tibial plateau and the femoral condyle. Grade 1 if the tibia is between 0 and 1 cm anterior to the femur; Grade 2 if the two are in the same plane; Grade 3 if the tibia lies behind the femur. The accuracy of the posterior drawer test for PCL rupture is 96%77 (90% sensitivity and 99% specificity). A firm endpoint to the translation indicates an intact restraint and can be present after as little as 2 weeks following an isolated PCL injury. Another cause of a negative, or equivocal, posterior drawer test is straight medial instability40 (ruptured PCL,

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MCL  ACL, with an intact PLC). Grade 2 or 3 laxity, persistent laxity with the tibia in internal rotation, or at 308 flexion, all suggest combined injury of the PCL and PLC. Other tests for PCL injury include the quadriceps active test,18 where the contraction of the quadriceps muscle reduces the posterior sag and the reverse pivot shift.45 In this test, the knee is flexed and the foot is externally rotated, resulting in posterior subluxation of the lateral tibial plateau on the femur; the examiner then exerts an axial and valgus load whilst gently extending the knee. At about 20— 308 of flexion, the lateral tibial plateau reduces from the subluxed position with a symptomatic jerk. Testing the opposite side excludes a false positive test, present in 35% of patients.15 The most useful test for assessing the stability of the posterolateral corner is the tibial external rotation (Dial) test.94 With the patient prone, external rotation of the tibia exceeding the opposite side by 108 or more, in 308 of flexion (but not at 908), indicates an isolated injury to the PLC. Increased rotation at both 308 and 908 of flexion suggests a combined injury of the PCL and PLC. Hughston et al. described the external rotation recurvatum test41 in which the examiner lifts both relaxed legs by the great toes with the patient supine. Hyperextension, varus and tibial external rotation exceeding the normal side, measured either in degrees or in heel height difference, indicates PCL laxity and posterolateral rotatory laxity, due to PLC damage, graded originally into 1+ mild, 2+ moderate or 3+ markedly positive. The posterolateral drawer test43,44 is performed at 308 and 908 of flexion, with the foot externally rotated to 158; posterior subluxation of the lateral plateau only at 308 indicates isolated PLC injury, but at both 308 and 908 suggests combined injury. No grading was originally described with this test, but other workers21 have suggested the subjective system of 1+ (mild), 2+ (moderate) and 3+ (severe instability). The posterolateral external rotation test is similar, describing palpation of the subluxing lateral plateau with posterior translation and external rotation in two positions of flexion; a positive subluxation was associated with damage to the lateral collateral ligament in addition to PLC and PCL.54 The varus stress test at 308 tests the fibular collateral ligament and is performed with the examining fingers over the joint line to estimate the degree of opening; Grade 1 with 0—5 mm of additional opening when compared to the normal side, Grade 2 injuries with 6—10 mm and Grade 3 with greater than 10 mm and no endpoint. The standard nomenclature of athletic injuries4 (Grade 1 — minimal tearing of the ligament with no abnormal motion, Grade 2 — partial tearing with

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slight or moderate movement or Grade 3 — complete tearing with markedly abnormal movement) has also been used subjectively to describe injuries to the posterolateral corner. The multitude of subjective and objective grading systems makes it difficult to compare studies and to determine an appropriate point for intervention. A careful neurological examination is required to identify any injury to the common peroneal nerve, such injury may affect both the deep branch (foot dorsiflexors and dorsal sensation to the first webspace) and the superficial branch (foot eversion and dorsal sensation to the rest of the foot).

Investigations Plain radiographs of the knee are a useful initial investigation and may show several features of relevance, including avulsion fractures of the PCL from the tibia, of the biceps tendon from the fibular head (Arcuate sign83) (Fig. 2), of the lateral capsule from the lateral tibial plateau6 (Segond fracture79) or of the iliotibial tract from Gerdy’s tubercle.67 A lateral ligamentous complex injury may increase the joint space in the lateral compartment and degenerative changes may be present in any of the three compartments after chronic ligament

Figure 2

The Arcuate sign (fracture of fibular head).

injuries.41 Severe medial compartment degeneration, which may also cause a varus thrust gait, should be excluded. Long-leg, standing AP views assess varus malalignment that occurs in the chronic setting. Stress radiographs can be useful for documentation of preoperative instability, performed with lateral views of the knee (i) in neutral, (ii) with posterior translation and (iii) with the addition of external rotation (Fig. 3); however, there is no consensus in technique and they can be time-consuming to undertake.

Magnetic resonance imaging Magnetic resonance imaging (MRI) of the knee is a useful investigation in acute injuries, so painful as to preclude a full clinical examination. Gross et al.34 demonstrated high levels of accuracy in diagnosing damage to the PCL and Harner and Hoher37 showed that it was possible to identify the site of the rupture. The normal PCL returns low signal intensity (SI) on all pulse sequences, due to its fibrocartilaginous nature, and has the appearance of a posteriorly convex, curved band on midline saggital images (Fig. 4a). Coronal (Fig. 4b) and axial (Fig. 4c) images demonstrate various parts of the ligament and provide further assessment of its femoral and tibial attachments. Acute tears of the PCL appear on MRI as regions of increased SI (intermediate on T1 weighted (T1W), proton density weighted (PDW) and hyperintense on T2W sequences), with diffuse thickening over a portion of the damaged ligament. A complete rupture is rare, but may show increased SI between the two separated low signal ends (Fig. 5). Partial intrasubstance tears show widening of the ligament, with a striated pattern of fibres separated by oedema (Fig. 6a). In practice, MRI may not be able to differentiate a complete rupture from a severe partial rupture (Fig. 6b), but can demonstrate avulsion of the PCL from the tibial attachment, which occurs in 10% of cases (Fig. 7). Associated injuries identified by MRI are reported in 66—72% of cases and include bone bruising (34%), other ligament injuries (42%), most commonly the tibial collateral ligament and meniscal tears (31—52%). Bone marrow oedema (bone bruising) may be evident in a variety of locations, depending on the mechanism of injury, with the ‘dashboard’ injury mechanism, it appears in the anterior tibia (Fig. 8). Chronic PCL injuries may show fibrotic healing, appearing thickened but with relatively normal SI; ligaments healed with elongation may return normal

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Figure 3 (a) Lateral stress radiograph series (neutral); (b) stress radiograph with posterior translation; (c) stress radiograph with external rotation.

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Figure 4 MRI of the normal PCL: (a) sagittal proton density weighted (PDW) image demonstrates the normal PCL as a posteriorly convex low signal intensity (SI) band (arrow); (b) coronal PDW image demonstrates the tibial attachment of the PCL (arrow); (c) axial PDW image demonstrates the femoral attachment of the PCL (arrow).

SI, despite being mechanically unsound and can give a false impression of anterior cruciate ligament (ACL) laxity. The various structures of the PLC can be imaged with a combination of sagittal, coronal and axial T1W/PDW and fat suppressed T2W sequences (Fig. 9a and b). Thin oblique coronal slices through the whole of the fibular head are optimal for demonstration of the popliteofibular ligament (Fig. 10). High levels of accuracy can be obtained by experienced observers, correlating well with intraopera-

tive findings.52,76 Acute PLC injuries manifest as soft tissue oedema, lateral and posterolateral to the knee. The various ligaments may appear thickened and oedematous, or partially/completely disrupted, depending on the severity of injury (Fig. 11a and b). Anteromedial bone bruising of the medial femoral condyle is also a feature in acute ruptures of the PLC, in association with anterior cruciate ligament injury. MRI is useful in identifying injuries of the PLC and associated structures with high levels of accuracy,

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Figure 5 Complete rupture of the PCL. Sagittal T1W image demonstrates increased SI and swelling of the ligament with a complete gap at the site of ligament rupture.

particularly where doubt remains as to the extent or pattern of injury, but should never replace the need for clinical examination and cannot predict the need for surgery.

Bone scintigraphy Symptomatic degenerative disease does not resolve after reconstruction of ligamentous instability and it is important to identify these patients pre-operatively. It has been suggested that scintigraphy has a role in this37; however, asymptomatic internal derangement can cause increased uptake101 and interpretation is highly observer dependent and should only be interpreted in conjunction with other investigations.

Arthroscopy Arthroscopy can identify previously unrecognised injuries of the PLC and PCL, and provide confirmation of the injury pattern in cases still unclear after

Figure 6 Partial PCL injury: (a) sagittal T2W image demonstrates swelling and hyperintensity of the femoral attachment of the ligament (arrow), consistent with a partial rupture; and (b) sagittal PDW image shows a severe partial rupture with focal thinning of the ligament (arrow). However, complete rupture at this site is difficult to exclude.

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Figure 8 Complete rupture of the PCL with bone bruise. Sagittal T1W image demonstrates a gap at the site of ligament rupture (arrow). Note also the anterior tibial bone bruise, manifest as an area of reduced marrow SI (double arrow). (courtesy Dr. Paul O’Donnell) Figure 7 PCL rupture with tibial avulsion. Sagittal PDW image demonstrates avulsion of the tibial attachment of the PCL (arrow). The ligament itself is intact.

clinical assessment. It also offers a valuable opportunity to examine the knee under anaesthetic. However, capsular ruptures may allow extravasation of fluid into the fascial compartments of the leg and arthroscopy should be avoided for at least 2 weeks following acute injury. Posterior laxity should be distinguished from anterior laxity after ACL injury and reactive synovium covering the PCL should be removed for complete inspection; a posteromedial portal may be require for the lower two-thirds of the ligament. A ‘drive through sign’–—easy access to an abnormally lax lateral compartment–—was present in all cases in a series of 30 knees with Grade III PLC injury.51 Arthroscopy offers superior views the popliteomeniscal fascicles (important for the function of the lateral meniscus86), the coronary ligament, popliteal avulsions from the femur and identifies associated injuries to the lateral meniscus or cartilage. The popliteofibular ligament is, however, better observed with an open approach.

Natural history Many papers on the natural history of injuries of the posterior cruciate ligament are retrospective and

contain only symptomatic patients with a mixture of injury severity; others are prospective with small cohorts and short follow up.20,81 The three phases in the natural history of a ruptured posterior cruciate ligament are described by Dejour et al.20 as ‘‘functional adaptation’’, ‘‘functional tolerance’’ and eventual ‘‘arthritic deterioration’’. A feeling of instability is quite common after an isolated injury,81 but symptoms of giving way on activity, present in around 20% of cases,17,72 may be an indication of more complex injury. Return to sport can be expected in over 50% of patients with isolated PCL injury managed conservatively and a high level of satisfaction is reported in these cohorts.91 However, aching type pain, located in the medial part of the of patello-femoral compartment, is present in most patients and appears to increase over time,48 as does radiographic degenerative change.14,20,48 The same paucity of good evidence exists for the natural history of PLC disruptions.16 One study of six patients with a Grade I (mild) instability, treated conservatively, found no residual instability.49 In a larger study, 11 patients with Grade II sprains, treated non-operatively, were all rated good or excellent on standardised scales, at a mean of 8 years,47 with no radiographic degenerative changes: only 2 were asymptomatic, but all had residual laxity. Twelve patients with Grade III sprains had a worse

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Figure 9 Normal MRI anatomy of the posterolateral corner: (a) sagittal T2W image demonstrates the normal popliteus tendon (arrow) lying just posterior to the posterior horn of the lateral meniscus; and (b) coronal T2W image demonstrates the conjoined insertion of biceps femoris and the fibular collateral ligament into the fibular head (long arrow) and the popliteus tendon as it inserts into the lateral femoral condyle (short arrow).

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Figure 10 Oblique coronal MRI technique for optimal demonstration of the popliteofibular ligament: (a) sagittal T1W localiser showing plane of images; and (b) oblique coronal fat suppressed T2W image demonstrates the popliteofibular ligament (arrowhead) running between the fibular head and the popliteus tendon. (courtesy Dr. Jerry Healy)

outcome, with 50% showing radiological evidence of arthritis. However, 10 of these patients had combined injuries of either cruciates, or meniscus; the isolated Grade III sprain is rare and the outcomes of

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Treatment Acute PCL injury The acute, intrasubstance tear of the PCL should heal, if immobilised in an extension brace for 6 weeks and Shelbourne et al.81 found these results similar to those following operative repair, as described by L’Insalata and Harner.58 Bony avulsion of the PCL from the back of the tibia can be fixed internally, via the posteromedial approach described by Trickey,92 retracting the medial head of gastrocnemius laterally, thereby, protecting the neurovascular bundle.

Chronic isolated PCL injury There is currently no information on whether reconstruction of the isolated PCL prevents degenerative arthritis in the long term. If PCL reconstruction could be relied on to provide a stable knee in the anteroposterior plane, then the risk of osteoarthritis might theoretically be decreased in the long term. However, no research has yet produced a significant number of consistently stable knees after reconstruction. The only patient for whom treatment of the isolated PCL injury is recommended by the senior author is one with laxity, pain relieved by bracing and with no evidence of degenerative changes.

Acute PLC injury

Figure 11 PLC injuries demonstrated by MRI. (a) Coronal PDW image showing partial rupture of the popliteofibular ligament. The ligament (arrowhead) is seen extending from the medial fibular head to the popliteus tendon (arrow) and appears thickened and oedematous. (b) Sagittal fat suppressed T2W image demonstrating partial rupture of the popliteus tendon. The tendon is partially discontinuous and surrounded by oedema (arrows).

these patients remain unclear. Those patients with combined injuries generally tend to have greater severity of symptoms and are less likely to return to sport.

Repair of damaged structures in the PLC, within 3 weeks of injury, has been reported to give the best chance of a good outcome6,21,42,49,94,98 and identification of structures after this time becomes difficult due to the healing process. Avulsion fracture of the fibular head should be fixed, restoring the insertion of biceps femoris tendon, the fibular collateral and the popliteofibular ligaments. Repair should progress from the deep layer outwards, with reinforcement, or reconstruction, of any irreparable structures, for example avulsion of the popliteus tendon from its muscle belly.

Acute combined PLC and PCL injury Most authors advocate early repair of both structures in an acute combined injury,16 however, the cruciate reconstruction can be performed after the acute repair of the PLC and when the capsule has healed.

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Chronic isolated PCL injury Hey-Groves38 described the original semitendinosus and gracilis onlay graft to the back of the tibia in 1917 and recent advances are described in the literature,8,12,26,46,88 many involving the arthroscope. The open procedure necessitates an intraoperative position change from supine to prone. Arthroscopic pitfalls, however, include damage to neurovascular structures, graft rupture at the point of angulation over the tibial plateau and causing compartment syndrome from fluid extravasation. Other important operative decisions include the number of bundles, and choices of graft and fixation device. There are yet no results to demonstrate that addition of a posteromedial bundle to the single anterolateral bundle technique affords better functional outcomes. Patellar tendon autograft and Achilles tendon allograft lend themselves well to the onlay technique, and quadruple hamstring autograft and other soft tissue allografts facilitate the arthroscopic method. Fixation implants include interference screws, which may be metallic or bioabsorbable, and transfixation and ‘endobutton’ devices.

Figure 12

Clancy biceps tenodesis.

Chronic PLC injury There is currently no consensus on the best method of treatment for the chronic posterolateral corner injury.16 Marked varus mal-alignment, with lateral thrust during weight bearing phase of gait, should be treated primarily with a valgus, upper tibial osteotomy to prevent excessive tension on any subsequent reconstruction.53,64,95 Techniques for reconstruction of the PLC include a biceps femoris tenodesis, described by Clancy and Sutherland13 where the biceps tendon is rerouted, via fixation, to the lateral femoral condyle, creating a static posterolateral stabiliser (Fig. 12). This technique has been modified to leave in situ half of the tendon, providing dynamic stabilisation,96 but does not address the role of the popliteofibular ligament, or the popliteus tendon93 and may over-constrain movements in varus and external rotation.97 The senior author currently uses the Larson Procedure,84 passing a semitendinosus, or Achilles tendon, allograft anterior-to-posterior, through the fibular head, tensioned with the knee in 308 flexion and the tibia drawn anteriorly, and fixed to an isometric position on the lateral epicondyle (Fig. 13a). If the lateral ligament is also deficient, the graft is brought back down and attached to the anterior part of the fibular head (Fig. 13b). Sling procedures have also been used to reconstruct parts of the popliteus com-

plex,3,10 passing grafts through tunnels in the femoral condyle, or tibia, corresponding to the attachment of the popliteus tendon. One such is the Mu ¨ller popliteus bypass procedure (Fig. 14a), which can also be combined with the Larson procedure for additional stability (Fig. 14b). The circle graft of Noyes and Barber-Westin65 uses allograft passing through the fibular head and over a fixation point at the lateral femoral condyle to reconstruct the fibular collateral ligament. Veltri and Warren94 recommend anatomical reconstruction of the lateral collateral and both attachments of the popliteus complex, although other authors have reported reconstruction of the lateral collateral and posterior cruciate ligaments only.56 The postoperative regimen involves nonweight bearing in a splint, allowing 0—308 flexion for 6 weeks, then passive flexion and progressive weight bearing through to active flexion at 4—6 months.

Results The results of isolated posterior cruciate reconstruction do not yet match those for the anterior cruciate ligament and results produced by newer procedures are awaited. Clancy et al.12 described a

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Figure 14 (a) Mu ¨ller ‘popliteus bypass’ procedure; and (b) combined Mu ¨ller and Larson reconstructions. Figure 13 (a) Modified Larson procedure; and (b) modified Larson with fibular collateral ligament reconstruction.

group of 17 patients undergoing isolated PCL reconstruction, using patellar tendon autograft, for Grade 2+ posterior laxity and showed good results in all of the acute cohort, with good stability in all but one of the chronic group.

PLC reconstruction Of Hughston’s 95 patients with an advancement of the osseous attachment of arcuate ligament complex, approximately 80% rated well on subjective and objective scales. Noyes and Barber-Westin66 reported good results in 13 (64%) of 21 patients after advancement of the osseous attachment of posterolateral structures, which were lax but structurally intact and, in a further study with Noyes and Barber-Westin,67 found good outcomes in 16 (76%) of 21 cases with reconstruction of the lateral collateral ligament and posterolateral structures using a circle graft.

Combined reconstruction Most series of PCL reconstructions describe patients with additional ligament damage. Fanel-

li’s series23of 41 patients all had Achilles tendon allograft PCL reconstruction, biceps tenodesis and posterolateral capsular shift, with improvement in objective and subjective stability ratings. Freeman’s series29 of 17 patients showed that reconstruction of both PCL and PLC produced better results in combined injuries than PCL reconstruction alone. Clancy and Sutherland13 reported good results in 77% of 39 patients treated with a biceps tenodesis for combined injury, with 54% returning to their previous sporting levels. Poor prognostic factors were degenerative changes and compensation claims. Knee dislocation is a significantly more complex injury and accurate diagnosis requires a high index of suspicion in those knees with normal radiographs that have reduced spontaneously. Associated neurological injury is common and expert assessment, with detailed pre-operative planning, is required for this technically difficult surgery. A multidisciplinary team approach, with functional bracing and early manipulation, is essential to avoid stiffness and a poor outcome. Although there are few reports to compare early repair with conservative management,60,74,80 recent trends favour the former, which may also facilitate earlier functional rehabilitation, but results are awaited.

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