The influence of applied internal and external rotation on the pivot shift phenomenon

Effect of anterior cruciate ligament injury on acceleration response of knee joint

This study investigated the effect of anterior cruciate ligament (ACL) injury on relative acceleration of the tibia and femur during a number of tests/activities, in order to assess the feasibility of acceleration-based diagnosis of ACL injury using inertial sensors. First, a detailed finite element model of the knee joint was developed to simulate the target tests/activities, and identify those in which a large difference between the maximum acceleration peaks (MAPs) of the healthy and ACL injured knees is likely to be observed. The promising tests/activities were entered in an experimental study, where the relative accelerations of the tibiae and femurs of 20 individuals with unilateral ACL injury, allocated randomly to two groups of conscious and unconscious test conditions, were recorded. Model predictions indicated MAP ratios>1.5 for the ACL-injured to healthy knees, during the anterior drawer, Lachman, and pivot-shift tests, as well as the lunge activity. The experimental MAP results indicated acceptable test-retest reliabilities for all tests (coefficient of variation<0.25), and significant MAP differences (p < 0.05) in the anterior drawer and pivot-shift tests, in both coconscious and unconscious conditions. The individualized MAP results indicated side-to-side differences>2 m/s2 for all subjects during unconscious pivot shift tests, and >0.5 m/s2 for eight cases out of ten during conscious anterior drawer tests. It was concluded that the pivot shift test had a great repeatability and discriminative ability for acceleration-based diagnosis of ACL injury in unconscious condition. For the conscious condition, however, the anterior drawer test was appeared to be most promising.

Risk of overconstraining femorotibial rotation after anatomical ACL reconstruction using bone patella tendon bone autograft

INTRODUCTION

Numerous studies have focused on the anteroposterior stability after anterior cruciate ligament (ACL) reconstruction, with less emphasis on rotational stability. It has been hypothesized that bone patella tendon bone (BTB) autograft for ACL reconstruction restores knee rotation closely to normal due to its comparable fiber orientation to the native ACL.

MATERIALS AND METHODS

Twenty patients with unilateral ACL rupture and an uninjured contralateral knee were included in this study. The ACL was reconstructed using the medial third of the patellar tendon. Tunnel placement was controlled by fluoroscopy. Implant-free press-fit graft fixation was used on both femoral and tibial side. Bone blocks were carefully placed to restore fiber orientation of both the anteromedial and posterolateral bundle, similar to the native ACL. Rotatory laxity of both knees was measured at 0° and 25° of flexion pre- and post-surgery, using an active opto-electronical motion-analysis system (LUKOTRONIC AS 100^®). All measurements were performed under general anesthesia during surgery.

RESULTS

Knee rotation was reduced significantly in both 0°and 25° of flexion following ACL reconstruction (p < 0.001). The side to side difference (SSD) of the rotatory laxity in extension was greater in the ACL-deficient knee (14.9° ± 8.9°), but decreased significantly after ACL reconstruction (- 5.9° ± 7.7°, minus value means less than in the uninjured knee). There was a similar finding at 25° of knee flexion where greater rotation of the ACL-deficient knee (5.7° ± 10.3°) prior to surgery changed to lower degree of rotation after surgery (- 11.3° ± 8.4°) in comparison to the uninjured knee.

CONCLUSIONS

ACL reconstruction with a BTB graft in anatomical position using press-fit implant-free fixation is able to restore rotatory knee stability close to the intact contralateral knee. Despite the fact that the BTB graft offers fiber orientation close to the natural ACL, the surgeon should be aware of the potential risk of over-constraining the knee in terms of rotation.

LEVEL OF EVIDENCE

II.

Objectifying the Pivot Shift Test

The pivot shift test is utilized for assessment of rotatory instability in the anterior cruciate ligament (ACL) deficient knee. There are multiple reports of the pivot shift maneuver, and there is a lack of consensus among clinicians as to a standardized maneuver. Measurement devices are a feasible option to evaluate rotatory knee instability, objectively or quantitatively. Traditionally, measurement systems have been invasive systems. More recently, electromagnetic system, inertial sensor, or imaging analysis systems, specifically with the utilization of a tablet computer, have emerged as noninvasive, and more importantly, validated options. It is important to recognize that anatomic structures other than the ACL contribute to rotatory knee stability. Addressing the tibial slope, anterolateral structures of the knee, specifically the iliotibial band, and menisci during ACL surgery may decrease residual pivot shift in an attempt to improve clinical outcomes and prevent reinjury. This review article describes the pivot shift maneuver, objective measurement tools, and clinical applications of the pivot shift test.

The vancomycin soaking technique: no differences in autograft re-rupture rate. A comparative study

PURPOSE

The main aim of this study was to evaluate the re-rupture risk after an anterior cruciate ligament reconstruction (ACL-R) using the vancomycin soaking technique and to compare it with the re-rupture risk in patients on whom this technique was not utilized. The secondary purpose was to compare the functional outcomes of those two subsets of patients operated on for ACL-R. The hypotheses are that the vancomycin soaking technique does not affect the re-rupture risk or the functional outcomes.

MATERIAL AND METHODS

A retrospective historical cohort study was conducted. Two groups were compared in terms of the re-rupture rate (traumatic or atraumatic) and functional outcomes (International Knee Documentation Committee (IKDC), Tegner, and Lysholm). Group 1 consisted of patients that received pre-operative IV antibiotics. In group 2, the patients received pre-operative IV antibiotics along with a graft that had been presoaked in a vancomycin solution. A minimum follow-up of five years was required.

RESULTS

There were 17 patients that suffered a re-rupture in group 1 (4.7%) and 15 in group 2 (3.9%) (n.s.). IKDC was 82.0 in group 1 and 83.9 in group 2 (p = 0.049); Tegner scored 4 in both groups (n.s.) and Lysholm was 90.3 in group 1 and 92.0 in group 2 (p = 0.015).

CONCLUSION

The vancomycin soaking technique for ACL autografts is a safe procedure for the daily clinical practice, in terms of re-ruptures. Moreover, it does not impair functional outcomes after an ACL-R.

The Pivot Shift: Current Experimental Methodology and Clinical Utility for Anterior Cruciate Ligament Rupture and Associated Injury

PURPOSE OF REVIEW

The purpose of this manuscript is to (1) examine the history, techniques, and methodology behind quantitative pivot shift investigations to date and (2) review the current status of pivot shift research for its clinical utility for management of anterior cruciate ligament (ACL) rupture with associated injuries including the anterolateral complex (ALC).

RECENT FINDINGS

The pivot shift is a useful physical exam maneuver for diagnosis of rotatory instability related to ACL tear. Recent evidence suggests that the pivot shift is multifactorial and can be seen in the presence of ACL tear with concomitant injury to secondary stabilizers or with predisposing anatomical factors. The presence of a pivot shift post-operatively is associated with poorer outcomes after ACL reconstruction. Recent clinical and biomechanical investigations can help guide clinicians in utilizing pivot shift in diagnosis and surgical planning. Further research is needed to clarify optimal management of ALC in addition to ACL injury.