The Results of Surgical Repair of Acute Tears of the Posterior Cruciate Ligament JOHN POURNARAS, M.D., AND PANP. SYMEONIDES, M.D. In 20 patients, the torn posterior cruciate ligament (PCL) was repaired without reinforcement within two weeks after injury. Fourteen patients had a midsubstance tear, and in six the ligament was avulsed from the femur without bone. There were 11 isolated and nine combined injuries. The followup period ranged from two to 10.5 years. Postoperatively, all had posterior instability graded from 1 + to 2+. Nevertheless, the subjective results were good in 15 patients, fair in five, and poor in none. Posterior instability did not produce significant functional impairment of the knee for a considerable number of years. Suture alone cannot restore the PCL and is not strong enough to withstand the applied forces on the knee. The significance of the posterior cruciate ligament (PCL) in the stability of the knee and the necessity for surgical repair of its tears are still controversial. There are reports in the literature based on clinical and biomechanic studies in which the PCL is considered a prime stabilizer of the Furthermore, it has been stated that posterior instability will often lead to the development of articular cartilage changes.* On the contrary, Dandy and Pusey3 questioned the importance of the PCL for good function of the knee. In addition, in experimental work in dogs it was found that sectioning the PCL produced fewer changes in From the Orthopaedic Department, Aristotelian University of Thessaloniki, G. Papanikolaou Hospital, Thessaloniki, Greece. Reprint requests to John Pournaras, M.D., Orthopaedic Department, Aristotelian University of Thessaloniki, 54006 Thessaloniki, Greece. Received: July 3 I , 1989. the joint, e.g.,meniscal tears, osteophyte formation, or articular cartilage changes, than did sectioning of the anterior cruciate ligament (ACL)." Because there is a direct relationship between the amount of change and the degree of instability, it was concluded that in dogs, at least, the PCL was less important than the ACL in the stability of the knee. It should also be mentioned that in reported cases of PCL rupture, the subjective and objective results after surgical repair are not equally good. Thus in the series of Hughston et aL6 of 20 cases with acute tears of the PCL, the subjective results were good in 18 (90%) and the objective results were good in I3 (65%).Moore and Larson' also found that of 18 surgically repaired cases of PCL tears with or without dynamic reinforcement, 15 (83%)had residual instability; however, in 14 (77.7%)the functional result was excellent or good. From these reports it is obvious that there is a disparity between the presence of postsurgical posterior instability and the function of the knee. It is also assumed that surgical treatment of acute tears of the PCL is not always successful. The latter does not apply to the avulsion injuries from the tibia with bone. The purpose of this paper is to present the results of surgical repair in 20 cases with acute rupture of the PCL. MATERIALS AND METHODS Twenty patients with an acute PCL rupture were surgically treated during the last 10.5 years. In 14 patients, the ligament had a midsubstance 103 104 Pournaras and Syrneonides tear and in six it was avulsed without bone from its femoral attachment. Avulsion injuries of the ligament with a piece of bone from the tibia were excluded from this study. Seventeen of the patients were men and three were women, ranging in age from 18 to 41 years (average, 26 years). The causes of the knee injuries were traffic accidents in 12 (most involving a motorcycle), falls from a height to the ground in five, and sports injuries in three (long jump in two and skiing in one). It was difficult for the patients to describe precisely the exact position ofthe knee at the moment of injury, particularly for those involved in motorcycle accidents. However, forcible posterior displacement of the tibia in a flexed knee with or without rotation was the most common mechanism of injury. In one patient only, the rupture was the result of a hyperextension injury of the knee. In 1 1 patients, the injury of the PCL was isolated. In four it was combined with a tear of the medial collateral ligament, in three with a tear of the lateral collateral ligament and the posterola- Clinical Orthopaedics and Related Research teral corner, in one with rupture ofthe medial collateral ligament and ACL, and in another one with injury to the ACL. In all knees a positive posterior drawer test or sag of the tibia of from 2 t to 3+ was present with the knee in 90" flexion. This sag could also be demonstrated roentgenographically (Figs. 1 and 2). A mild to moderate degree of effusion of the knee existed in all patients. In the cases in which the tear of the PCL was combined with a tear of the medial or lateral structures, there was a positive abduction or adduction test in extension. All patients were operated on within the first two weeks after injury. The midsubstance tears were repaired with an end-to-end suture using silk No. 1 (Ethicon, Somerville, New Jersey). A technique similar to the Bunnel method of suturing tendons was used, i.e., one suture was passed through the proximal part and the other through the distal portion of the torn ligament. The two sutures were tightened together until good approximation is achieved. No other structures were used to reinforce this suture. In the avulsion injuries from the femur without bone, two tunnels were opened from the medial FIG. I A and 1 B. Preoperative lateral roentgenograms of (A) the normal left knee and (B) the right knee with the PCL tear. The posterior displacement of the tibia (posterior sag) is evident. Number 267 June. 1991 Acute PCL Tears 105 FIG.2A and 2B. Lateral roentgenograms from another patient with a PCL tear. (A) The posterior sag of the tibia (right knee) is clearly shown compared to the (B) normal left knee. side ofthe medial femoral condyle directed toward the lateral side in the intercondylar notch at the point where the PCL is normally attached. A No. I silk stitch attached to the end of the avulsed ligament was passed through these tunnels and tightened. In 12 cases, the posterior approach described by ODonoghue" was used. Care was taken to restore the posterior capsule, which was significantlytraumatized in three cases. In six patients, the suture of the torn ligament was performed through the same medial or lateral approach that was used for repairing the medial or lateral structures. In the remaining two cases in which the ligament was avulsed from the femur, it was reattached through an anteromedial approach. At the end of the operation, a Steinmann pin was inserted through the upper end ofthe tibia and incorporated in an above-knee plaster-of-paris cast applied with the knee in 20" flexion. The Steinmann pin was used to prevent posterior displacement of the tibia in the plaster, reducing the stress on the sutured ligament. The plaster was removed after six to eight weeks, following which the rehabilitation program commenced. RESULTS The patients were followed for two to 10.5 years (average, five years). All patients re- turned to their previous normal daily activities and were able t o participate in recreational sports. None of the operated patients took part in competitive sports either before or after surgical intervention. They had no pain after their usual activities. No episodes of locking were reported. Five patients complained of occasional mild swelling after prolonged activity. Two had a feeling of knee instability. In both of these patients, there was a combined tear of the ACL that had not been repaired. The subjective results following the criteria of Hughston el aL6 could be graded as good in I5 patients and fair in five. No patient had a poor subjective result. Even in the two patients with a feeling of instability, the result was evaluated as fair when the other parameters were taken into consideration. Four of the six patients with avulsion of the ligament from its femoral attachment had good results. Objectively, all 20 patients had a positive posterior drawer sign of 1+ to 2+, which was manifested with posterior sag of the tibia. None had restriction of knee movement of 106 Pournaras and Symeonides more than 10”-15”. In five patients, there was a mild effusion of the knee. No medial or lateral instability was detected in the patients with repaired rupture of the medial or lateral structures. Muscle power of the quadriceps was restored in all patients after prolonged physiotherapy. Slight crepitus was palpable in two. In one patient who had an unrepaired combined tear of the ACL, this crepitus was present one year after the operation. If the objective results in these patients are evaluated with the criteria put forth by Hughston et a/.,6 taking particularly into consideration posterior instability, there were 12 fair and eight poor results. In no patient could the objective result be graded as good because in this category the posterior drawer test should be negative. DISCUSSION The number of patients diagnosed with rupture of the PCL has significantly increased over the last 20 years. This is because of the increased number of traffic accidents, particularly those of motorcyclists, the increased participation of people in competitive or recreational sports, and the improved knowledge concerning the diagnosis of posterior instability of the knee. The mechanism of injury is not always clearly described, particularly for patients involved in traffic accidents who cannot remember the exact position of the knee at the moment of the accident. Trickey” proposed three mechanisms that could produce a tear ofthe PCL: (1) an anteroposterior forceat the front of the flexed knee (only the PCL is usually injured); (2) hyperextension of the knee, that will produce a tear of the ACL as well; and (3) a posteriorly directed rotatory injury which will also produce a tear of the collateral ligament or the posterior corners of the capsule. The first and third of the abovementioned mechanisms were the most common in the patients described in this report. The posterior drawer sign or posterior sag of the tibia is often considered the most reli- Clinical Orthopaedics and Related Research able sign in diagnosing tears of the PCL, either isolated or combined. Some investigators state that it is always positive in acute tears of this ligament or in chronic posterior i n ~ t a b i l i t y . ~ , ~In , ~ ,1980, ’’ Hughston et a/.,6 believed that the posterior drawer sign was not a reliable test for acute ruptures. They found it positive in only 30% of their cases of acute tear of the PCL, all associated with rupture of the medial or lateral collateral ligament. They considered a more reliable sign to be the abduction or adduction test with the knee in extension and the anterior drawer sign with the tibia in internal rotation. In all patients reported here there was a positive posterior drawer sign of 2+ to 3+- with the tibia in neutral position. In one half of the patients, the posterior displacement decreased when the tibia was held in internal rotation. Clancy et a/.’ attributes this to the presence of Humphry’s or Wrisberg’s ligament. These ligaments are tightened when the tibia is internally rotated, preventing posterior displacement of the tibia. It is interesting to note that all these patients had a positive posterior drawer sign despite the repair of the PCL and the insertion of a Steinmann pin in the upper tibia to prevent posterior displacement until the ligament was healed. It seems that sutures alone are not strong enough to resist the forces applied on the repaired PCL, which ultimately fails and cannot provide static stability. It has been previously reported that patients with posterior instability after a repaired or unrepaired tear of the PCL retain good function of the k r ~ e e .Even ~ . ~ Hughston el a/.,6who strongly support the view that the PCL is a main stabilizer, found that in their seven patients with poor or fair objective results, the subjective result was good in six. In six of the seven there was a positive drawer sign or unreducible posterior subluxation rated 1 + to 2+. In all patients of this report, the subjective results were good or fair. On the contrary, objectively, the results were evaluated fair or poor. It should be pointed out again that none of these patients was partici- Number 267 June, 1991 Acute PCL Tears pating in competitive athletic activities. From the aforementioned, one may conclude that a failed PCL repair does not lead to significant functional impairment in everyday activities, probably because it produces single-plane and not rotatory instability. REFERENCES 1. 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