Reconstruction of the posterior cruciate ligament for isolated injuries of the posterior cruciate ligament: A myth or reality?

Reconstruction of the posterior cruciate ligament for isolated injuries of the posterior cruciate ligament: A myth or reality?

                                         Dr KS Dhillon FRCS, LLM

Posterior cruciate ligament (PCL) injuries result from a posteriorly directed force applied to the proximal tibia, unlike anterior cruciate ligament (ACL) injuries which result from non-contact rotational forces. Injuries to the PCL are believed to be rare as compared to ACL injuries. The true incidence of PCL injuries is unknown partly because these injuries are easily missed and some patients may not seek treatment because symptoms associated with PCL injuries are less disabling as compared to symptoms associated with ACL injuries. However the incidence of PCL injuries has been reported to vary from 1% to 47% of all ligament injuries of the knee (1). There have been suggestions that only about 40% of PCL injuries are isolated injuries and rest are usually combined ligamentous injuries (2). The ideal treatment of PCL injuries according several authors remains controversial (2-4).

Is treatment of PCL injuries controversial or are there some conflicts of interest involved in the treatment of patients with PCL injuries which makes surgeons promote surgical reconstruction of the PCL for such injuries?

Treatment of isolated PCL injuries

There is no controversy about the treatment of PCL avulsion fractures, which are ideally treated by open reduction and internal fixation when the fragment is large enough to be fixed with a screw. Isolated injuries of the PCL usually produce a grade I to II posterior laxity of the knee while a grade III laxity is produced by a combined PCL and posterior lateral corner injuries. What is the best method of treatment of isolated PCL injuries?

An acute mid-substance tear of the PCL may heal (5) unlike ACL mid-substance injuries which do not heal. Logically such injuries should be treated conservatively. The long term natural history of isolated PCL injuries suggests that there is no indication for surgical treatment of such injuries because the outcome of conservative treatment is good. There are no studies to show that surgical treatment is better than conservative treatment for isolated tear of the PCL. Neither is there any evidence that surgical treatment reduces the incidence of osteoarthritis of the knee after PCL injuries (4).

Natural history of isolated PCL injuries

One of the earlier studies of the long term outcome of non-operatively treated isolated PCL injuries was done by Parolie and Bergfeld in 1986 (6). They studied 25 patients who were treated conservatively for isolated PCL injuries and followed-up for a mean of 6.2 years (2.2 to 16 years). They found that 80% of the patients were satisfied their knee and 84% had returned to their previous sport, with 68% at same level of performance and 16% at a reduced level of performance. Patients who were satisfied with their knee and had returned to sports had quadriceps strength of more than 100% of the contralateral uninvolved knee and those who were dissatisfied with their knee and not returned to sports had less than 100% strength of the quadriceps as compared to the contralateral knee.

Selbourne et al (7) prospectively studied the natural history of acute, isolated, non-operatively treated PCL injuries in athletically active patients. The study included 133 patients all of whom completed a yearly questionnaire for an average of 5.4 years (2.3 to 11.4 years) and 51% of the patients (68 out of 133) returned for long-term clinical and radiological examination. The functional outcome was good with a mean modified Noyes knee score of 84.2 points, a mean Lysholm score of 83.4 and a mean Tegner activity score of 5.7.The grade of laxity had no correlation with subjective functional outcome. Fifty percent of the patients returned to the same sport at the same or higher level of performance, one third (33.3%) returned to same sport at a lower level and one-sixth (16.6%) did not return to the same sport.

The authors concluded that ‘athletically active patients with acute isolated posterior cruciate ligament tears treated nonoperatively achieved a level of objective and subjective knee function that was independent of the grade of laxity’.

The longest follow-up study of patients with acute, isolated PCL injuries treated non-operatively was reported by Shelbourne et al in 2013 (8). The study included 68 patients who had a subjective follow-up at a mean of 17.6 years and 44 of the patients had a subjective and objective follow-up at a mean of 14.3 years (10-21 years). The mean quadriceps strength was 97% of the contralateral side and the range of knee motion was normal in all patients.

Fifty percent of the patients had no osteoarthritis (OA) of the knee, 30% had mild OA, 9% (4 patients) had moderate and 2% (1 patient) had severe OA of the knee at a mean follow-up 14.3 years. The mean IKDC (International Knee Documentation Committee) and modified CKRS (modified Cincinnati Knee Rating System) subjective scores were 73.4 ± 21.7 and 81.3 ± 17.4, respectively at 17 years follow-up and the subjective scores did not correlate with the degree of PCL laxity.
The authors concluded that long term follow-up of patients, with isolated PCL injuries treated non-operatively, shows that patients remain active, have good muscle strength, full range of knee motion and they report good subjective scores and that the incidence post-traumatic OA is low.

In 2007 Patel et al (1) published a study involving 57 patients with acute isolated PCL injuries who were treated non-operatively with a mean follow up of 6.9 years (2 to 19.3 years). Seventeen patients (29.8%) had a grade I and 41 patients (71.9%) had a grade II laxity of the PCL. The functional outcome at 7 years was good with a mean Lysholm-II knee score of 85.2 points (range 51 to 100 points) and a mean Tegner activity level of 6.6 (range 3 to 10). The Lysholm-II knee scoring system, showed excellent results in 40%, good in 52%, fair in 3%, and poor in 5% of the knees. The incidence of mild medial compartment OA was 12% and moderate medial compartment OA 5% and none of the patients had severe OA.

These medium and long term studies of the natural history of isolated PCL injuries reveal that the subjective functional outcome is good, without surgical intervention, with majority of the patients returning to their pre-injury activity level. Are the results of PCL reconstruction better than conservative treatment?

Surgical treatment of isolated PCL injuries

Most of the published studies reporting the outcome of PCL reconstruction for isolated PCL injuries are small case series with a short follow-up, and the heterogeneity of the patients studied and the technique used make it difficult to judge outcome in these patients(3).
However there are two studies that have reported the long term outcome of PCL reconstruction in patients with isolated PCL injuries.

Herman et al (9) studied 25 patients (22 male, 3 female) with an average age of 30.8 years who underwent single bundle PCL reconstruction for pain and functional instability of the knee. The mean follow-up was 9.1 years (6.5 to 12.6 years). Twenty two patients were evaluated clinically and 3 patients provided telephone interviews.

The final mean IKDC score was 65, Lysholm score was 75 and the VAS (visual analogue score) was 8. The functional scores were fair to good and were significantly better than the pre-operatively scores. The final Tegner score was 5.7. The functional results were significantly better in patients with no cartilage damage at the time of surgery and in those who underwent surgery within 1 year post injury.

Jackson et al (10) evaluated the long term outcome of PCL reconstruction in 26 patients after failed conservative treatment. At 10 years follow-up the IKDC score was 87 and the Lysholm score improved from 60 to 90 post-operatively. Twenty two patients had radiological examination and 18% of the patients had grade II OA changes and another 18% had grade III OA changes.
A careful analysis of the subjective outcome reported by Shelbourne (7) and Patel (1) for non-operative treatment and that by Herman (9) and Jackson (10) for surgical treatment of PCL injuries appears to be very similar.

Complications of PCL surgery

PCL injuries are rare and the indications for surgery of the PCL are limited since conservative treatment has good outcome, therefore the number of PCL surgeries carried out by surgeons per year are small. This limited experience with such complex surgery can lead to a higher incidence of complications especially when there are vital neurovascular structures at the back of the knee. Furthermore catastrophic complications usually never get reported which can give surgeons a false sense of relative risks involved when undertaking such procedures.

Besides the standard complications, such as those associated with anaesthesia and complication of surgery such as infections and thromboembolic complications which can occur with any orthopaedic procedure, there are specific complications associated with PCL surgery, some of which includes neurovascular injury, osteonecrosis, fractures, stiffness, residual laxity and anterior knee pain.
A survey of frequency of complications associated with arthroscopic surgical procedures of the knee reported by Salzler et al (11), where the data was obtained from the ABOS (American Board of Orthopaedic Surgery) data base, showed that the complication rate was the highest for PCL surgery as compared with other arthroscopic procedures. The complication rate for PCL surgery was 20.1%, ACL surgery 9.7%, meniscal repair 7.7%, menisectomy 2.8% and chondroplasty 3.5%. The overall pulmonary embolism rate was 0.11% and the infection rate 0.84%. These were self-reported complication rates and the authors believe that the actual rates may be higher.

Conclusion

The outcome of non-operative treatment for isolated mid-substance PCL injuries is good as has been revealed by long term studies of the natural history of such injuries. The results of surgical reconstruction of the PCL are not superior to that of non-operative treatment and PCL surgery can be associated with complications which would not be seen with conservative treatment. Hence there appears to be no indication for PCL reconstruction for intra-substance tears of the PCL.

References

1. Patel DV, Allen AA, Warren RF, Wickiewicz TL, Simonian PT. The Nonoperative Treatment of Acute, Isolated (Partial or Complete) Posterior Cruciate Ligament-Deficient Knees: An Intermediate-term Follow-up Study. HSS J. 2007 Sep; 3(2): 137–146.

2. Clancy WG Jr, Sutherland TB. Combined posterior cruciate ligament injuries. Clin Sports Med 1994; 13(3):629–647.

3. Montgomery SR, Johnson JS, McAllister DR, Petrigliano FA. Surgical management of PCL injuries: indications, techniques, and outcomes. Curr Rev Musculoskelet Med. 2013 Jun; 6(2): 115–123.

4. Dowd GSE. Reconstruction of the posterior cruciate ligament: Indications and results. J Bone Joint Surg [Br] 2004; 86-B: 480-91.

5. Shelbourne KD, Jennings RW, Vahey TN. Magnetic resonance imaging of posterior cruciate ligament injuries: assessment of healing. Am J Knee Surg 1999; 12:209-13.

6. Parolie JM, Bergfeld JA: Long-term results of nonoperative treatment of isolated posterior cruciate ligament injuries in the athlete. Am J Sports Med 1986; 14:35-38.

7. Shelbourne KD, Davis TJ, Patel DV. The natural history of acute, isolated, nonoperatively treated posterior cruciate ligament injuries. A prospective study. Am J Sports Med. 1999 May-Jun; 27(3):276-83.

8. Shelbourne KD, Clark M, and Gray T. Minimum 10-Year Follow-up of Patients after an Acute, Isolated Posterior Cruciate Ligament Injury Treated Nonoperatively. Am J Sports Med July 2013 vol. 41 no. 7 1526-1533.

9. Hermans S, Corten K, Bellemans J. Long-term results of isolated anterolateral bundle reconstructions of the posterior cruciate ligament: a 6- to 12-year follow-up study. Am J Sports Med. Aug 2009; 37(8):1499-507.

10. Jackson WF, van der Tempel WM, Salmon LJ, Williams HA, Pinczewski LA. Endoscopically-assisted single-bundle posterior cruciate ligament reconstruction: results at minimum ten-year follow-up. J Bone Joint Surg Br. 2008 Oct; 90(10):1328-33.

11. Salzler MJ, Miller CD, Lin A, Irrgang JJ, Harner CD. Complications Following Arthroscopic Knee Surgery. Orthopaedic Journal of Sports Medicine, September 2013 vol. 1 no. 4 suppl 2325967113S00044.