Background: There is considerable controversy regarding whether a double-bundle reconstruction of the posterior cruciate ligament is superior to single-bundle techniques. The purpose of this study was to compare posterior tibial translation and external rotation following double and single-bundle tibial inlay reconstruction of the posterior cruciate ligament in both a posterolateral corner-deficient and a repaired cadaver model.
Methods: Posterior drawer testing, dial testing, and stress radiography were performed on nine cadaver knees. The intact knees served as controls. The posterior cruciate ligament and the posterolateral corner structures were resected, and each knee then underwent a double-bundle reconstruction of the posterior cruciate ligament. Following testing, both with and without the posterolateral corner repaired, the posteromedial bundle was released and the knee was retested with a single-bundle reconstruction.
Results: With dial testing, external rotation measured a mean (and standard error) of 7.6° ± 0.4° at 30° of knee flexion and 9.0° ± 0.8° at 90° after the double-bundle reconstruction with posterolateral corner repair, and it measured 11.2° ± 1.4° at both 30° and 90° after the single-bundle reconstruction with posterolateral corner repair. When dial testing was performed after the double-bundle reconstruction without posterolateral corner repair, external rotation measured a mean of 15.8° ± 1.9° at 30° and 16.9° ± 2.0° at 90°; after the single-bundle reconstruction without posterolateral corner repair, it measured 20.1° ± 1.8° at 30° and 20.3° ± 1.7° at 90°. Without posterolateral corner repair, the double-bundle reconstruction permitted significantly less external rotation than did the single-bundle reconstruction at 30° (p = 0.03). Stress radiography showed the mean posterior displacement after the double-bundle reconstruction with posterolateral corner repair to be 3.3 ± 1.4 mm. This value was not significantly different from the mean posterior displacement of 4.8 ± 1.0 mm after the single-bundle reconstruction with posterolateral corner repair, and both values were similar to that for the intact control (2.9 ± 0.5 mm) (p = 0.254). However, the single-bundle reconstruction without posterolateral corner repair was associated with significantly increased posterior displacement when compared with the intact controls (p = 0.039) and with the double-bundle reconstruction without posterolateral corner repair (p = 0.026).
Conclusions: Double-bundle reconstruction of the posterior cruciate ligament offers measurable benefits in terms of rotational stability and posterior translation in the setting of an untreated posterolateral corner injury. With the posterolateral corner intact, at time zero, the double-bundle reconstruction used in this study provided more rotational constraint to the knee at 30° and it did not further reduce posterior translation.
Clinical Relevance: Compared with single-bundle reconstruction, double-bundle reconstruction provided increased rotational and posterior control, which was most pronounced in the setting of an untreated posterolateral corner injury. This increased stability may be beneficial in the common clinical setting, in which these reconstructions tend to stretch over time. On the other hand, the persistence of the rotational overconstraint at 30° of knee flexion seen with the double-bundle reconstruction in this study may be a risk factor for osteoarthritis.