PCL/PLC/LCL & MCL CONCEPTS
Jonathan Beacon FRCS
The PCL has been the centre of debate for nearly a Century. The function of the PCL has been argued by some as crucial to the knee mechanics and by others as incidental. The ACL has received considerably more attention, but perhaps this is ill deserved. Trickey in the 1970’s referred to the PCL as the silent partner in the knee joint. This author prefers to regard the PCL as the “senior partner” in the knee joint.
It is recommended the whole paper is read, however we have supplied these fast links to the specific sections. You can jump to the start here.
Simple Terminology
Words can be treacherous. No apology is given in providing very basic definitions. The “acute” injury is 0 to 3 weeks, the sub-acute is 3 weeks to 6 months, and the chronic condition is 6 months and over. Ligament “reconstruction” means that the natural ligament is either absent or so damaged that a whole substitute “graft” is put in its place. This involves making tunnels at the sites of the attachment of the natural ligament. A ligament “repair” means suturing, or in some way attempting to preserve, the natural ligament material. The terms “augmentation”, “stenting” or “scaffolding” mean the use of a small diameter “graft” to reinforce a damaged natural ligament or a different “graft”, without removing a significant amount of principle ligament material (whether natural ligament, autograft, synthetic or allograft combination).
The term the “isolated” PCL injury means that grossly there is no other significant ligament damage within a knee joint. It should be understood that there is probably some damage to associated soft tissues, but that at the time of assessment this damage is undetectable. It is important to have a clear definition of the basic terms used in this paper, but this does not pre-suppose that other surgeons will agree these definitions!
Acute Versus Chronic – Patient Perspective
A patient satisfaction survey on my own group of patients (following all ligament surgery) reflects patient satisfaction outcomes of some other surgeons in the PCL study group. About 90% of patients who have undergone acute surgical intervention are well satisfied, as compared with 60% in the chronic group. In those patients with multi-ligament damage, surgery is indicated.
It is of interest that the PCL and the ACL were termed the crucial ligaments of the knee by the early 20th century surgeons. In about 1926 the first of many papers were published in which the terminology had been changed to the cruciate ligaments. This was probably due to the apparent form of the ligaments, which when viewed tangentially appear to cross. The term crucial does, however, contain much merit. These two ligaments are fundamental in providing the fine control of knee stability.
Trickey Cadaveric Knee Study: Internal Rotation of the Tibia on the Femur
This can be confirmed by preparing an isolated knee dissection to demonstrate the prime role of the cruciates is to provide stability to the knee joint by internal rotation of the tibia on the femur. All the soft tissue structures, other than the ACL and PCL, are dissected from a cadaveric knee. The femur is “fixed” or grasped in one hand, whilst the tibia is grasped in the other hand. Firm but gentle internal rotation of the tibia on the femur is then performed.
As the tibia is progressively internally rotated the congruent articular surfaces are progressively apposed. This produces joint stability. The progressive apposition of the tibia against the femur, through internal rotation of the tibia, allows the congruent bony surfaces to “dock”. It will be noted that whilst gentle internal rotation of the tibia is maintained the knee joint is totally stable. There is a full excursion of movement from full extension to full flexion. There is no draw test either at 90 or 30 degrees and the joint is stable to varus and valgus stressing. There is full internal rotational stability. The end point of the ligament tests remain firm. This simple model demonstrates that an intact ACL and PCL are able to provide full joint stability.
In contrast, if initially a normal knee joint is examined, in which all the ligaments are intact and gentle internal rotation of the tibia on the femur is performed in the same manner, then an identical “feel” of stability is obtained. In an identical manner full movements in the flexion/extension arc is noted. Draw testing at 90 and 30 degrees is stable as is varus/valgus stressing. If now in this specimen only the ACL and PCL are divided, it will be noted that it is not possible to gain firm end point stability. There is a soft end point to extension, there is translational AP/PA draw, and internal rotation increases as does varus/valgus “rock”. This basic cadaveric study was demonstrated in a series of cadaveric knees prepared by Trickey. In effect the ACL and PCL are crucial to joint stability and must be intact in order to provide full and physiological knee stability. These two ligaments may not be the strongest ligaments around the knee but are intimately involved in all knee movements. During the course of the “life” of a knee joint these two ligaments operate as “guiding check-reins” or joint “locators” and supply high level proprioceptive input. Parts of these passive restrainers are taut, thereby providing perfect joint position and permit the muscle groups to move the joint with precise co-ordination. It is only during periods of high activity or unexpected overloading, that these ligaments are damaged either completely or partially.
Preponderance of PCL/ACL Knee Damage
If the ligament strength exceeds the disruptive load, then the joint is “checked” and stability is retained. It the load exceeds the ligaments strength then rupture occurs. It is interesting to note the number of ACL and PCL operations that are performed by knee surgeons, as compared to the number of MCL’s, LCL’s popliteal ligament or any other group of knee ligament operations. If these two ligaments are so regularly damaged this suggests that they must be actively, and crucially, engaged in knee function.
“Functional” PCL/ACL Mechanics
The PCL is a relatively large fan-shaped ligament. The femoral attachment extends along the medial wall of the notch. The tibial attachment is to the posterior surface of the tibia. The footprint is approximately rectangular. The individual fibres of the PCL are attached to incredibly specific sites. Although the overall length and shape of the ligament changes during knee movement, the three thousand or so individual fibres themselves are almost inextensible. This has been measured at 50 microns. It is the extraordinary arrangement of the individual fibres, which confers the characteristics of the ligament. Probably the best description of the action of the fibres is still that of Brantigan and Voshell.
Three Functinal Bundle Concept: PMB/CB/ALB
The overall “action” of the ligament can be identified in three “functional bundles”. (Schema “A”).
The postero-medial bundle (PMB) is composed of the fibres lying in the posteror part of the notch. The tibial pole is attached to the medial part of the tibial footprint. This functional bundle becomes taut in extension and slackens in flexion. The PMB acts in concert with the ACL and the MCL. Valgus stress is resisted and these bundles contribute towards postero-medial rotational stability (PMRS). These fibres become taut during internal rotation of the tibia on the femur throughout the range of flexion and extension.
The antero-lateral bundle is taut in flexion. This bundle works in concert with the PLC and resists varus and external rotation forces. As with the PMB these fibres are taut during internal rotation of the tibia on the femur.
There are also more vertically orientated central fibres (CB). The femoral attachment is in the central section of the notch and similarly the tibial attachment is in the central part of the tibial footprint. This part of the PCL seems to have an extra function. By working with the more posterior fibres of the ACL it contributes towards maintaining the central axis of rotation of the knee joint. Not infrequently this bundle survives in partial PCL and ACL tears. One advantage of “open” surgery, through an extended Smilie incision, is that the PCL or the remnants can be seen and palpated. The texture of intact PCL and ACL ligament tissue is sharp, strong and easily identifiable. The fibres can be seen and accurately identified. The shape of the CB is more reminiscent of an inverted triangle. The tibial attachment is the sharp point of the triangle, and the long base forms the “fanned out” attachment to the femur. The ACL/CB and PMB all resist posterior displacement of the tibia.
There are many excellent detailed anatomical studies published but the division of the ligament into “three sections” or “working bundles” reflects a surgical impression over 25 years. If the central bundle is present, and is retained, then any reconstruction/stenting procedure seems to have an improved outcome.
Tunnel Placement and Graft Orientation
The position of the drill tunnels is critical. The attachment of any graft should endeavour to “mimic” the sites of attachment of the natural fibres. Synthetic ligaments are unforgiving whereas auto and allografts are more tolerant. It is therefore imperative to obtain exact tunnel positions if synthetics are being employed. The use of one or two smaller grafts allows reconstruction of one or two bundles selectively.
Selective “Bundle” Replacement
The mechanism of injury is reflected in the pattern of the ligament damage. Selective bundle reconstruction is therefore preferred. If the ACL is damaged and the PMB and CB are intact, then a small diameter graft (6 mm or 7 mm) can be used to replace the ALB only. A large diameter graft will, by sheet bulk, increase the chances of removal of good ligament material and reduce proprioception. If the PMB is damaged, and the ALB is intact, then reconstruct the PMB only.
Two bundles demand two tibial tunnels and two femoral tunnels to achieve “limited non-isometricity”. From my own series (1982-1992) in 63 PCL reconstructions the use of one “lateral” tibial tunnel and a two bundle reconstruction with two femoral tunnels was not good. Improvement was gained by using two tibial tunnels and two graft bundles. The PMB tunnel is positioned just medial to the tibial tuberosity and the ALB tunnel just lateral to the tibial tuberosity.
Graft Orientation
As stated by Heygrove (1919) the crucial ligaments lie obliquely across the notch. The PCL has an obliquity of a “medial slant” from tibia to femur. The PCL also holds the tibia “forwards”. The tibia tunnels should exit the posterior tunnel well below the posterior rim – 10 to 12 mm. In order to achieve the natural ligament the femoral tunnels must be position very precisely. Unfortunately there are “no fixed” reference markers supplied by Mother Nature! The PMB tunnel is situated in the medial notch with an anterior bias. Think of the knee in full extension. The femoral tunnel must accommodate a forward slope of the graft to prevent subluxation of the tibia posteriorly. View the medial notch with the knee in extension per-operatively. Once this “line” (which lies in plane of the longitudinal axis of the femur) has been defined in the AP.PA plane (coronal), then adjustment of the tunnel position in the proximal/distal plane can be carried out. A helpful guide for this is the junction between the flat side-wall of the notch and the “base” of the curve of the root. The femoral tunnel position for the ACL is more straightforward. The leading edge of the tunnel is about 3 to 6 mm “internally” from the articular margin and about 11 o’clock (left) of one o’clock (right) on the medial wall/roof site. The central bundle tunnels lies between the PMB and ALB positions. Some knees are large and some small. Some notches are deep and narrow, others wide and shallow. All that is necessary is to have a mental image of the working bundle configuration with the knee in extension. Although the knee is in flexion during most operations, it is better to translate mentally back to the flexed position from the extended position. As with most surgical procedure, practice and experience are eventually the ultimate teachers.
Mechanism of PCL Injury – High and Low Impact Forces: a) uni-planar
The review of PCL injuries in my date is compatible with this view. The classical PCL injury is the “dashboard” type of injury. This usually occurs in “head-on” car crashes in which the interior dash or shelf strikes the 90 degree flexed knee, of the victim, just below the joint line. In this position the antero-lateral fibres of the PCL are specifically taut. Assuming a marked impact force, the tibia is driven backwards and either a partial, or in extreme circumstances, a complete tear occurs to all bundles of the ligament. The PCL can therefore be damaged by excessive PA translational forces. In those knees in which hyper-extension occurs – for example in a rugby scrum, in which another player falls onto the extended knee, of the motorcyclist who is thrown forwards “over the handle bars” and the “knee” is forced backwards as the body weight is thrown forwards back-locking the knee – damage occurs to the postero-medial bundle, which is specifically taut in extension. This often involves the central bundle and even the antero-lateral bundle in major episodes. In these knees in which “over-forced back-locking” occurs either partial or complete PCL tears result.
The PCL is also involved in resisting valgus and varus injuries. In road traffic accidents or sports collisions in which a lateral impact of the knee joint occurs the joint is forced into valgus. The postero-medial bundle of the PCL is damaged. This is nearly always in association with an MCK injury and ACL injury. Conversely a varus injury can occur on the sports field, especially football or on the ski-slopes. A “low speed” injury occurred simply by “missing a footing and slipping off a kerb” in one patient admitted to my hospital. The adduction of the tibia was so great as to tear the LCL completely as well as completely tear the Lateral Popliteal Nerve (6 cases). Therefore not only high impact, but low speed and low impact injuries can tear the PCL. Damage to the PLC , the LCL and even the lateral menisco-tibial ligament can occur. Varus forces involving the ALB often extend across to the CB of the PCL but the PMB is spared. These tibial adduction type injuries (varus) are essentially uni-planar and are serious injuries.
Multi-planar Impact Forces: Internal Rotation
The combination of rotational forces as well as uni-planar forces leads to serious PCL and associated ligament damage. From a series of cadaveric knee studies carried out at the Westminster Hospital, London (Beacon 1979), it was noted that on internal rotation of the tibia on the femur most of the fibres of the PCL and the ACL are “co-opted” to resist increasing internal tibial rotation. Of interest the fibres slacken during external rotation. These fibres are particularly taut during running, or in the “planted” limb kicking a ball. It is the “planted” knee which is at risk. As the opposite “foot” kicks the ball the planted limb knee joint is subject to considerable internal rotational torque. As the opposite half of the pelvis and lower limb swing through, the femur is passively externally rotated “across” the knee joint. In essence the tibia undergoes passive internal rotational movement. (Schema “O”).
This can cause serious damage to all three bundles of the PCL which are taut, if overloaded. If the knee joint happens to “buckle” as well (flexion) further damage can be caused to the antero-lateral bundle which is taut in flexion.
Multi-planar Impact Forces: External Rotation
Multi-direction injuries result in complex injury patterns. Another and different multi-directional injury occurs in ballgame players who “kick” with the “inside of the foot” or in skiers in whom the front part of the ski is rotated outwards or in the motorcyclist who puts a foot “out” as balance is lost causing the tibia to externally rotate. Commonly, there is an associated valgus component, combined with either flexion or extension. These injuries are complex. The forced external rotation of the tibia is resisted passively by the passive restrainers of the postero-lateral complex, in association with active contraction of the popliteus (a powerful internal rotator of the tibia). If the forced external rotation is excessive, there is rupture of postero-lateral structures including the popliteo-fibular ligament and the PCL ligament. The intra-muscular septae of the tendon of popliteus are frequently “torn” within the muscle “belly”, which is rendered mechanically incompetent, either partially or totally. The muscle contracts but “slides down” the tendon. As the tibia is forced into further external rotation the central axis of the knee is shifted medially. As this occurs the antero-lateral bundle of the PCL is overloaded and tears. This damage can extend further medially involving the central bundle. During this type of episode the ACL is often “wound” around the “front” of the lateral femoral condyle and is overstretched and torn. There are therefore a wide variety of injured ligament patterns. The ultimate damage to the PCL and associated ligaments, is the dislocated knee in which massive damage occurs to all the passive restrainers.
These injury patterns are compatible with the observations of the biomechanics of the cruciate ligaments in the Trickey “isolated” knee dissections. The crucial roles of the PCL and the ACL ligaments, their involvement in passive restraint in extension and varus/valgus and AP/PA translation and internal rotation make them structures of prime importance and vulnerability. It is perhaps therefore unsurprising that the PCL and ACL ligaments comprise the commonest group of passive restrainers requiring treatment and surgical intervention.
Data Comparison Problems
The concepts of PCL injury and surgical intervention are difficult to analyse. The number of PCL injuries an orthopaedic surgeon sees and treats us relatively small. A postal survey carried out by my unit in the UK NHS circulated 1600 Fellows of the British Orthopaedic Association (consultants). Only about 40 surgeons regularly operate on PCL injuries, in the order of 5 per annum. The PCL study group has about 150 participating members from all around the world. This group has met at 18 monthly intervals and exchanged highly detailed information. The numbers of patients in the surgical series, even by these specialist knee surgeons, is in the 30 to 50 range for some, and low 100’s for a few others. The combined experience of these surgeons in this group is, however, unparalleled.
Surgical Practice Variation
The surgical practices of specialists, even in the same country, can vary considerably. Some surgeons treat high profile athletes with high demands physically and pressing “rehabilitation” timetables. Other surgeons see ordinary people who simply wish to play, run, skip and hop with their children or enjoy a skiing holiday. In some countries, such as the USA, allografts are freely available whereas synthetics are banned. In Europe there is a strong tradition of autografts. The surgical views expressed in the literature and at meetings is therefore “subjectively” influenced. Further difficulties arise by philosophical polarisation into the “rights” and “wrongs”. As with most surgery the more opinions available usually means the less is known about the subject. The point being made is that apples must be compared with apples and with pears or oranges. This appertains to the groups of patients, as well as surgeons as well as the type of orthopaedic practice and the grafts available. A working background in elective practice is very different from a trauma practice. The vagaries of state health systems as compared with private/insurance systems must be recognised. Finally well defined injury types and injury severity must be objectively assessed. Pears with pears and oranges with oranges.
It is the suggestion of this review that authors should state briefly their background. This author works in a state system (NHS) and in private practice. The patients are derived from a District General Hospital population of around 500,000. Acute and elective work is undertaken. As the specialist interest develops, patients were then referred from other surgeons from other parts of the country. Over a 20 year period a database recording 368 PCL and PLC combination ligament interventions has been collected. The views recorded in this paper are based on this UK experience, and influence of the PCL study group discussions.
Acute Versus Chronic – Delays in Diagnosis
The first problem in PCL injury (in the UK) seems to be diagnosis. Rare and complex knee injuries (on average) take around 1 or 2 years to be recognised within the NHS systems. Patients often present to an Accident & Emergency Department or their GP with a swollen knee and a limp. Some form of bandage or a cast is supplied and the knee is “monitored” for a few weeks. Many get better with physiotherapy and time, but those “knees” with a PCL injury that are symptomatic persistently return to their medical attendants. It is this group of symptomatic PCL injuries which eventually “turn up” at a specialist knee clinic, but is this too late? This also raises the question of the true incident of PCL injury, as many patients are probably asymptomatic. (Schema “B”).
Acute Versus Chronic – To operate or not to operate
In other health “systems” or if the patient is fortunate to be “picked-up” early – say within the first 7 days, and is correctly diagnosed, this poses the dilemma of the ideal management. It can be far from clear. What are the key factors upon which a surgeon bases a PCL management programme? To operate, or not to operate, that is the question!
Acute PCL Tear
The following points need to be borne in mind. Any significant acute injury is painful and the knee capsule is tense. In order to attain a meaningful examination this must be carried out under a general anaesthetic (EUA). Hughston’s description of a positive examination is definitely namely “Combined positive response to posterior draw test, anterior draw in internal rotation, abduction and adduction stress performed with knee in full extension indicates a PCL tear”. If an anaesthetic is to be administered then it is appropriate to perform an arthroscopy. A PCL injury will cause a haemarthrosis. With judicious use of fluid management systems the joint can be inspected and a damaged PCL is evident. At this point the PCL injury can be classified into the “isolated” category or combined category (multi-ligaments injury).
Synchronous Multi-Ligament Surgery: Vital Posterior Sag Sign
The ideal intervention for the combined category (assuming there is no neuro-vascular or articular bony injury) involves surgery to all the major structures which have been damaged. Synchronous ligament surgery should be carried out whenever possible. If the PCL damage is significant there will be posterior subluxation of the tibia. This is usually detected at the EUA for as soon as the patient “relaxes” the tibia “sags” backwards (post-sag sign). There may be hyper-extension indicating PCL rupture with associated post capsule tears often involving the popliteal ligament. The PA draw and Lachman reverse test are positive.
The “isolated PCL injury” is far more of a conundrum. Conservative treatment of most PCL injuries or indeed no treatment at all, for a variety of reasons, is perceived to provide a reasonable outcome. Many athletes have chronic PCL instability and perform well. Dandy’s paper is one amongst many which advocate conservative treatment. The question then remains should acute isolated PCL injuries receive surgery. If there is no posterior sag, conservative treatment, by cast or brace maintaining the tibia in “neutral” for say 4-6 weeks is appropriate.
Modern Methods – Acute PCL Surgery Now Possible
The situation nowadays has altered. It is the availability of allografts and synthetic ligaments, combined with arthroscopic techniques that has once again opened the operative door. It is interesting that the ubiquitous PCL injury in which a bone fragment is avulsed from the posterior tibia has been regarded as a suitable PCL injury for repair. Re-attachment using some form of pin or screw has been advocated over the years. In principle, why operate on this type of injury it is deemed satisfactory to leave a ruptured PCL because surgery is “not necessary” as they “do well” with conservative management?
Intervention Versus Conservation
It may be that surgeons will, quite correctly, operate if there is a good surgical solution available to them. It may also be that the isolated, or the combined PCL and ACL injury does not “do well” enough after chronic reconstruction. Increased rates of osteoarthritis, or subsequent meniscal failure, joint unsteadiness restricting life activity and certainly a reduction of sporting levels are commonly encountered in patient complaints after conservative treatment and even reconstructions. A late sequellae of the PCL deficient knee say 5 to 20 years on, is “kneecap pain”, deu to secondary retro-patellar osteoarthritis. Through the altered mechanics due to the loss of the PCL integrity, the tibia develops chronic posterior translational instability. The knee attempts to compensate for this by using the quadriceps to provide an “anterior translation” or “counter force”. This increases loading across the patellofemoral joint. Connor at Oxford reported, in cadaveric studies, an increase in patello-femoral joint loading in the order of 20 times. (Schema “C”).
Perhaps a PCL injury in an 18 year old is not as benign as initially considered. Perhaps it is “too late” to operate after degenerative changes have occurred. Clancy has noted that marked osteoarthritic changes can appear within 6 months or injury and Keller – Shelbourne of 65% lower activity level. (Schema “D” and “E”).
The developments in knee surgery over the past decade have been considerable. New techniques and grafts are now available. Is there now an indication for surgery in the “acute” phase, in order to engender an improved outcome?
The Posterior Draw and Sag: Avoid “Fixed” Post Tibia Subluxation by Single CB Bundle Surgery
The first key finding is posterior tibial draw or a posterior sag. This is an indicating for some form of stabilisation. Once the posterior draw/sag becomes “fixed” then it is too late. Chronic posterior subluxation of the tibia disturbs the whole of the knee mechanics. There is a secondary “sag” caused to the ACL which becomes inefficient. The MCL and LCL are also adversely affected. The patellofemoral joint is overloaded and the femoral condyles tend to overload the anterior half of the menisci. The relatively straightforward implantation of allograft or a synthetic ligament as a single central bundle (in the CB position) acutely, to bring the tibia forward, is of great service. Laboureau likens this to a fracture and a bone plate. A fracture is not allowed to heal with a mal-union and then, once united, refracture and reduction is carried out with bone-plate fixation. In the same way the graft can be viewed as the bone plate, achieving primary reduction of the tibia to neutral and thus permitting soft tissue healing in the “reduced” position. A single strand graft from the “centre” of the PCL footprint on the tibia, to the centre of the PCL footprint on the medial notch, usually sufficient to reduce the tibia to neutral translation. Furthermore, if strong “scarring” can hold a tibia subluxed for the long-term, then this sane “scarring” can perhaps perform the same task, and hold the tibia in neutral. The presence of a graft will probably act in an “augmentation role”. Over the long-term the tibia seems to remain in neutral if stented acutely of sub-acutely. Chronic reconstructions are less effective.
Role of Stenting
The natural damaged PCL is “unloaded” by using a 6 mm, or at most a 7 mm, stent graft. By placing the stent graft along a border of the natural ligament, the ligament has the opportunity to “heal” and heal at the correct length. It is also “shielded” during post-op rehabilitation which can commence very soon post-operatively and without bracing. The healing potential of the PCL is remarkably good. If this healing is allowed to proceed in the sub-acute, or chronic phases in the presence of sag, then the ligament will “heal long”. The point of PCL stenting is to permit healing at the correct length, and thus, regain bio-mechanical function. Although the ligament may look good, even on MRI, an increase of even 2 or 3 mm length will render it mechanically inefficient.
Proprioceptive Retention and Vascularisation
The cruciates, and especially the PCL are essential in providing proprioceptive input. The loss of any of the natural ligament by excision, of “shaving” remnants to see in the notch it to be viewed with concern. Every strand and every fibre of a damaged PCL is gold dust and must be preserved. The less of proprioceptive “afferents” is detrimental to knee function.
This point is also related to graft size and maybe choice. If a synthetic is selected the ligament design is critical. Open parallel fibres of biocompatible polyester allows good invasion by fibrous tissue. For this to occur every piece of living tissue in the vicinity should be preserved in order to promote vascularisation and “collagenisation” of the prosthetic stent. The practice of “notch clearance” should be avoided at best, and if essential, should be employed sparingly. This is not so important if an allograft is used, still the loss of PCL fibres pertains.
The advent of arthroscopy means that the PCL can be inspected with relative ease as compared with classical exposures. The development of dedicated instrumentation for arthroscopic work, and specialist arthroscopic tools and techniques now provides a reasonable surgical approach. Acute intervention no longer involves massive exposure.
If inspection is preferred by direct vision, the PCL, can be viewed and surgery performed via an extended Smilie arthrotomy. This provides easy access anteriorly, and with the development of “open” dedicated PCL jigs and instrumentation a single bundle stenting is relatively simple from the front of the knee only.
The improvement in surgical techniques have abolished the need for massive classical approaches and have again provided surgeons with the opportunity for acute surgical intervention.
Remember Ligament Repairs: Especially in Adolescents
A further thought relates to ligament repair. In some fresh tears there is often good PCL tissue which can be sutured with absorbable material. If the tear is sited close to the femoral or tibial pole, the damaged pole can be attached to a strong suture, which in turn can be lead through the drill tunnel, thereby “hitching” the damaged ligament back onto bone. In the under 16 year olds PCL repair and the use of small diameter tunnels to provide fixation for the retaining sutures, can be effective, and should not be disregarded. Whenever possible repair and/or hitching of any reasonable PCL material during acute reconstruction should be attempted, in adults as well.
Chronic PCL Reconstruction
This is the commonest category of surgery in my practice. About 10% of the PCL reconstructions are isolated. About 90% of the PCL reconstructions are combined operations involving the PLC and a wide range of associated damaged structures. From my experience it is the multi-directional (combined) instability which is virtually always symptomatic. In the complex injured knee it is essential to stabilise the rational instability. From my first series (1982-1992) of 63 chronic PCL interventions, reconstruction only of the PCL (then with a “laterally” placed tibial tunnel) failed to control postero-lateral rotatory instability (PLRI) due to PLC damage. These injuries are probably primarily a PLC injury with a secondary PCL component. It is interesting that in every PLC injury there was associated PCL ALB rupture. The optimal stabilisation demands combined PLC and PCL reconstruction. It is my preference to use synthetics using a dedicated “Y” ligament design.
The use of autologous, allograft or synthetic materials all have their proponents and opponents! I have seen success and failures in many types of reconstruction, including my own. One contra-indication to “synthetics” is the “naked” notch. It seems that either due to synovial fluid exposure, or minimal collagenisation that the “naked” synthetic will fail. Fortunately most of the PCL is extra-articular and retrosynovial but it is mandatory to gain some form of tissue cover. This is the reason that synthetics are more suitable in the “acute” situation.
Adjustment of Graft Tension
Whatever the type of graft reconstruction the flexion/extension arc of the joint must be “obeyed”. A strict part of the surgical technique relates to graft “tensioning”. The ALB is adjusted with the knee in full flexion. In this position the graft is made taut and then fixed. The PMB is adjusted in full extension, in a similar manner. The CB is adjusted in full extension as well. It is much better to have a knee joint with a little laxity – or even grade 1 instability – than a tight joint lacking some flexion, or worse extension, due to “over-tensioning”. If adjustment is carried out at flexion angles other than “full”, perhaps the joint should then be “checked out” to ensure the flexion/extension arc has a “full” range of movement.
The Role of Osteotomy
The varus knee, especially with medial compartment osteoarthritis and an element of PLRI from PLC damage stabilises poorly. A valgising osteotomy is recommended under these circumstances three months prior to reconstruction. In about 50% of my patients the osteotomy itself provided adequate comfort and function to such an extent that ligament reconstruction was not required. The osteotomy not only loads and stabilises the lateral compartment but also provides amelioration of the medial compartment osteoarthritis.
Previous ACL Surgery
One of the problems encountered in the “chronic knee” relates to previous ACL surgery. The presence of a torn PCL in an obviously torn “ACL knee” is easily overlooked more often than generally appreciated. An excellent ACL reconstruction, in the presence of PCL damage, usually “fixes” the tibia with an element of posterior sag. In order to gain a reasonable expectation of improvement from PCL surgery, the posterior translational “fault” should be corrected. Suffice to say that some form of adjustment of the “graft” or release of even reconstruction of the ACL graft is necessary and desirable.
The present “state of the art” of PCL surgery remains challenging. The lessons learnt, seem to take a long time to evolve. Each surgeon has his own philosophy and idiosyncratic surgical tricks. That which works in one surgeons hands may not in anothers.
In order to progress it is essential that open and objective discussion takes place. This should always be of a constructive dialogue as it is through the interchange of ideas that real advances are made, and lead to patient benefit.
