Pcl Jurnal

RUPTURE OF THE POSTERIOR CRUCIATE LIGAMENT OF THE KNEE

E. L. TRICKEY, LONDON, ENGLAND

From the Edgware General Hospital and the Royal National Orthopaedic Hospital, Stanmore

Injury to the posterior cruciate ligament of the knee joint is believed to be uncommonexcept in association with severe general ligament rupture and dislocation of the knee joint.The isolated injury has been described in the literature, however, in particular by Abbott,Saunders, Bost and Anderson (1944), though no large series has been reported. This paperis based on seventeen cases seen from 1960 to 1965 in which rupture of the posterior cruciateligament was the predominant feature of the knee joint injury.

The injury is often not diagnosed and it is more common than is realised. Usually surgicalrepair is not done for a number of reasons, such as the belief that conservative treatment isalways satisfactory, or because the injury is not diagnosed, or because it is thought that theligament is too inaccessible for satisfactory repair.

MECHANISM OF INJURY

The commonest cause of injury is a motor cycle accident (Table I). A less common causeis a car accident in which the knee strikes the dashboard. The posterior cruciate ligament isruptured as a result of a backward force on the front of the flexed knee. The ligament maybe torn from its bony attachment or a fragment of bone may be detached with the ligament(Table II). In all the knees in this series that were explored the ligament was avulsed at its

TABLE I

CAUSE OF INJURY IN SEVENTEEN CA.SES

Motor cycle accident . 12

Car accident. . . 4

Bicycle . . . 1

TABLE II

TYPE OF LIGAMENT RUPTURE IN SEVENTEEN CASES

Avulsion of ligament with a fra gmen t of b one fr om th e tibia . 13

Avulsion of ligament from tibia . . . . . . 4

tibial attachment, and when a bony fragment was avulsed with the ligament it was detachedfrom the back of the intercondylar region of the tibia. The capsule at the back of the jointwas also torn to an extent dependent on the force of the injury. The posterior cruciate ligamentcan be completely torn without significant injury to other knee ligaments. Even after posteriordislocation of the knee, as in Case 17, there may be only very slight laxity of the collateralligaments after reduction of the dislocation (Fig. I).

PHYSICAL SIGNS

The patient presents with a painful, swollen knee after a road accident. Pain in the jointis severe and there is usually much limitation of movement. Abnormal mobility cannot be

334 THE JOURNAL OF BONE AND JOINT SURGERY

Figure 1-Case 1. Radiographs showing posterior dislocation of the knee. After reduction of the dislocationthe only significant ligament damage was of the posterior cruciate. Figure 2-Case 2. Radiograph to show the

slight displacement of the bone fragment from the tibia.

Case 11. Figure 5-Radiograph to show the large bone fragments avulsed with the ligament from theintercondylar region and the back of the lateral condyle of tibia. Figure 6-Radiograph after screw fixation ofthe bony attachment of the posterior cruciate ligament and removal of the loose fragment from the lateral

tibial condyle.

RUPTURE OF THE POSTERIOR CRUCIATE LIGAMENT OF THE KNEE 335

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336 E. L. TRICKEY

tested accurately because ofpain. The amount ofswelling is variable, though it is not necessarilyvery great. The front of the knee or the upper part of the shin is contused or lacerated. Thisphysical sign is seldom absent. Other injuries caused by the same mechanism may be found,such as a fracture of the tibia or patella or a serious injury in the region of the hip. Althoughboth knees may be injured at the same time bilateral posterior cruciate ligament damage hasnot been seen (Table III).

The classical physical sign of a ruptured posterior cruciate ligament is the posteriordrawer sign-abnormal posterior subluxation of the tibia on the femur. Abnormal antero-posterior mobility must be tested with the knee in flexion, preferably at 90 degrees, becauselaxity ofeither cruciate ligament is not detectable unless thejoint is flexed more than 20 degrees.

TABLE III

ASSOCIATED INJURIES IN SEVENTEEN CASES

Bruising, abrasions or lacerations on front of knee or shin . I 16

Fracture of the tibial plateau . . . . . . I

Fracture of the tip of fibula . . . . . . 2

Posterior dislocation of the hip . . . . . . ] I

Transverse midshaft fractures of the tibia and fibula . . 1

Fracture of the patella . . . . . . . 1

Double fracture of the femur . . . . . . 1

Posterior hypermobility must be distinguished from anterior hypermobility by a comparisonofthe bony points ofboth knees in a similar position offlexion. Too often all such hypermobilityis labelled as cruciate laxity without distinction and assumed to be due to damage to theanterior ligament. Often there is doubt as to the type and extent of suspected ligament damagebecause pain inhibits the relaxation necessary for a complete examination. When examinationis incomplete for this reason it must be carried out under a general anaesthetic. Mistakes indiagnosis are made because this step is not taken.

Radiographic examination will show no abnormality if the ligament is avulsed from bone.If the ligament is detached with a fragment of bone this fragment is seen at the back of theintercondylar space. It may be only slightly displaced (Fig. 2), or it may be pulled upwardsand rotated (Figs. 3 and 5). The injury is more likely to be missed when bone is not detached.

TREATMENT

There is a difference of opinion amongst orthopaedic surgeons concerning the place ofsurgical repair of torn knee ligaments. The view taken here is that if a ligament, or more

than one ligament, is completely torn surgical repair should be done as soon as possible, andpreferably within seven days of injury. This applies whether or not there is avulsion of bone.A partially torn ligament should be treated conservatively.

The degree of damage is assessed by examination under general anaesthesia. It is thedegree of damage that determines the result of conservative treatment and not the presence orabsence of bone avulsion. Abrasions and lacerations on the front of the knee do not contra-indicate immediate surgery; in fact they are an indication for surgical repair within twelvehours. If this line of action is not taken it is possible that the delay may be longer than theoptimum time for surgical intervention because the abrasions are not healed. Surgical repair

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VOL. 50B, NO. 2, MAY 1968

after three weeks is not usually worth while. I believe that this principle applies as much toinjuries of the posterior cruciate as to other ligaments.

SURGICAL APPROACH AND REPAIR

This should follow the recommendations ofAbbott and Carpenter (1945) and ODonoghue(1960). A general anaesthetic is given, a high thigh tourniquet is applied and the patient isplaced in the prone position.

An S-shaped incision is made across the popliteal fossa (Fig. 7). The inferior limb of theincision is on the medial side unless examination has indicated that there is some significant

P--.-- T

INCISI( kt SEMIMEM-BRANOSUS-

LINE OF ----IDIVISION OF

MEDIALHEAD OF

. GASTROCNEMIU . MUSCLE -

FIG. 7 FIG. 8 FIG. 9Figures 7 to 9-Diagrams to show the surgical approach to the right posterior cruciate ligament.

damage to the lateral side of the back of the joint. The deep fascia is divided in the line of theskin incision. The posterior cutaneous nerve ofthe calfis identified and preserved. If necessarythis can be used as a guide to the neurovascular bundle. The medial head of gastrocnemiusis defined clearly up to its attachment on the back of the femoral condyle. It is then dividedacross its muscle fibres close to its attachment to bone, and well above the point of entry of itsnerve and blood supply (Fig. 8). In this region it is partly tendinous and the tendon is usuallyattached to the capsule ofthe knee joint. The medial edge of the muscle is cleared of its deepattachment for about 75 centimetres (3 inches) distal to its upper end and then the medialhead can be turned over to the lateral side with its nerve and blood supply. The surgeon willfind that this stage of dissection is more easily undertaken if he stands on the medial side ofthe affected knee. The posterior capsule and the posterior oblique ligament are now clearlyseen.

Attention should be paid now to blood vessels. The medial superior geniculate vesselslie above the point of division of the gastrocnemius muscle but may require division andligation for adequate mobilisation. The middle geniculate vessels are very short, passingfrom the popliteal vessels straight forward into the knee joint through the posterior obliqueligament. It is nearly always necessary to divide and ligate these and this should be donecarefully. The medial inferior geniculate vessels run along the upper border of the popliteusmuscle and need not be disturbed.

A vertical incision is made through the capsule and posterior oblique ligament near tothe midline and the posterior cruciate ligament is now readily seen (Fig. 9). If a fragment ofbone has been detached with it, this will be rotated into the intercondylar region and caneasily be extracted.

338 E. L. TRICKEY


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FIG. 10Radiograph of the knee of a man of 55 injured in amotor-cycle accident thirty years previously. There isan ununited avulsion fracture of the posterior cruciateligament. His complaint was that the knee would

give way.

FIG. 11 FIG. 12Case 6. Figure 1 l-Radiographs of a slightly displaced avulsion fracture. Figure 12-Appearance two years

later. The injury was not treated. The fragment has not united and has become displaced.

340 E. L. TRICKEY


This is a better exposure than that which was described by Lee (1937) and Smillie (1962)of approaching the ligament between the two heads of gastrocnemius, and is preferable tothat described by Brennan (1960) of a postero-medial incision with removal of the meniscus;

it is a pity to remove a normal meniscusmerely to obtain a good view of the pos-tenor cruciate ligament.

The method of repair depends onwhether or not a fragment of bone has beenavulsed. Ifa fragment has been avulsed thisis usually about one to two centimetres in

diameter; despite its small size it can alwaysbe screwed back into its bed (Figs. 4 and6). If an attempt is made to suture it tosurrounding soft tissues the repair is un-satisfactory because they are not strongenough.

If a ligament has been torn above thebone it must be sutured back into bone. Itis impossible to suture the ligament to theremains of the ligament or to soft tissues.The method of repair recommended is

that described by ODonoghue (1960) and Smillie (1962). A figure-of-eight stitch of numberI black silk is passed through the torn end of the ligament leaving two long ends of suturematerial. Two separate and parallel drill holes are made through the tibia from the regionof the normal attachment of the ligament to the subcutaneous anterior border near the tibia!tubercle, where a small skin incision is made. The ends of the silk are each passed througha drill hole with a straight needle and the suture is tied on the front of the tibia.

The incision in the capsule is repaired. The medial head of gastrocnemius is suturedback into position; this is easily done because the muscle does not retract. The deep fasciaand skin are sutured. The leg is immobilised in a long plaster. It is important that the kneeis not flexed more than 5 degrees. With more flexion than this a rocking strain on the ligamentis possible. It does not seem to matter whether or not the foot is included in plaster, but ifit is the leg is more comfortable.


The plaster is changed at two weeks, when the sutures are removed and a new plaster isapplied, with a similar amount of knee flexion, and weight-bearing is permitted. Plasterimmobilisation is continued for a total of six to eight weeks and thereafter full knee movementis permitted.

A similar approach can be made through the lateral head of gastrocnemius but the viewof the back of the joint is not quite so good. During such an exposure the common peronealnerve should be identified and displaced laterally.

RESULTS OF TREATMENT

Details of the patients in this series are given in Tables IV and V. There was some posteriorcruciate laxity in the more severe cases treated conservatively, but there was none in thosetreated surgically. About an equal number of cases in each group had a loss of 10 degrees ofknee flexion one year after injury.

It is not intended to compare the results of conservative treatment with those of surgicalrepair. It is difficult to assess the true results of conservative treatment because a number ofcases pass undiagnosed. Enough late cases have been seen in the past to show that persistentposterior cruciate laxity can be as severe a disability as untreated rupture of the anteriorcruciate ligament, and this laxity can be present whether or not there has been bone avulsion(Fig. 10).

From these cases it is shown that the repair of acute rupture of this ligament can becarried out quite easily and that the repair is successful.

SUMMARY

1 . Seventeen cases of knee injury are described in which the predominant lesion was ruptureof the posterior cruciate ligament. Seven were treated conservatively and ten by surgical repair.2. Most cases occurred in motor cyclists.3. The extent of the rupture should be determined by examination under anaesthesia.4. Early surgical repair is indicated for complete rupture.5. An effective method of repair is described.

It is with pleasure that I acknowledge the help of the Photographic Department of the Institute of Orthopaedicsat the Royal National Orthopaedic Hospital, Stanmore, and in particular of Mrs T. A. Holland. I am indebtedto Mr R. H. Ansell for the drawings in Figures 7 to 9.

REFERENCES

ABBOTT, L. C., and CARPENTER, W. F. (1945): Surgical Approaches to the Knee Joint. Journal of Bone andJoint Surgery, 27, 277.

ABBOTT, L. C., SAUNDERS, J. B. de C. M., BO5T, F. C., and ANDERSON, C. E. (1944): Injuries to the Ligamentsof the Knee Joint. Journal of Bone and Joint Surgery, 26, 503.

BRENNAN, J. J. (1960): Avulsion Injuries of the Posterior Cruciate Ligaments. Clinical Orthopaedics, 18, 157.LEE, H. G. (1937): Avulsion Fracture of the Tibial Attachments of the Cruciate Ligaments. Journal of Bone and

Joint Surgery, 19, 460.ODONOGHUE, D. H. (1960): Surgical Treatment of Injuries to the Knee. Clinical Orthopaedics, 18, 11.SMILLIE, I.S. (1962): Injuries of the Knee Joint. Third edition. Edinburgh and London: E. & S. Livingstone Ltd.

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