Summary

A pre-operative high-grade pivot shift in anterior cruciate ligament deficient knees is associated with time from injury and the magnitude of injured soft-tissue structures, thereby suggesting a gradual decompensation of secondary restraints over time in chronic ACL-deficient knees.

Abstract

Background

The pivot shift (PS) test is a clinical sign to assess the rotational instability occurring in Anterior Cruciate Ligament (ACL) injured patients. The exact origin and the evolution over time of a pre-operative high-grade PS is still controversial and incompletely understood. Recently, a multifactorial background involving different anatomical structures and more specifically the menisci has been discussed.

Purpose

The purpose of this study was to reveal associations between pre-operative PS test and patient and injury characteristics in a series of ACL injured knees. The hypothesis was that a pre-operative high-grade PS is associated with the magnitude of structural soft-tissue damage (type of ACL injury and number of injured menisci) and with the time between injury and surgery.

Methods

The study cohort involved 376 patients from a center-based registry receiving primary ACL reconstruction surgery (239 males/137 females; median age 26, IQR 19-34). All patients were clinically examined under anaesthesia before surgery by grading the PS test. During arthroscopy, the type of ACL tear (complete/partial) as well as the presence of associated meniscus lesions including ramp lesions were documented. Structural soft tissue damage in the injured knee was classified as follows: (1) partial ACL tear, (2) complete isolated ACL tear, (3) complete ACL tear with injury of one meniscus and (4) complete ACL tear with lesions of the 2 menisci. Cartilage damage and associated ligament injuries were not considered. Chi-square and Mann-Whitney-U tests were used to evaluate whether gender, age, body mass index, sport at injury, mechanism of injury, time between injury and surgery and structural damage were associated with a high-grade PS (grade III) when compared with low-grade PS (grade 0-II). Significance was set at p<0.05.

Results

A high-grade PS test was observed in 26% (n=98) of cases. A significant association with PS grading was shown for age (p<0.05) and time between injury and surgery (p<0.05). The degree of PS was also associated with the magnitude of structural soft-tissue damage (p=0.01). A high PS was observed in 9% of partial ACL tears, 25% of complete isolated ACL tears, 26% of complete ACL tears with injury of one meniscus and 36% of complete ACL tears with damage of the 2 menisci.

Conclusion

Younger age, time from injury to surgery and the magnitude of structural soft-tissue damage are associated with grade III pre-operative PS. A high-grade PS in chronic ACL-deficient knees may thus suggest a gradual decompensation of secondary soft tissue restraints over time.