KNEE

Rotatory knee laxity tests and the pivot shift as toolsfor ACL treatment algorithm

Volker Musahl • Sebastian Kopf • Stephen Rabuck •

Roland Becker • Willem van der Merwe • Stefano Zaffagnini •

Freddie H. Fu • Jon Karlsson

Received: 29 November 2011 / Accepted: 19 December 2011 / Published online: 30 December 2011

� Springer-Verlag 2011

Abstract The goal of anterior cruciate ligament (ACL)

reconstruction surgery is to eliminate the pivot shift phe-

nomenon. Different injury mechanisms and injury patterns

may lead to specific knee laxity patterns. Computer navi-

gation is helpful for the surgeon during examination under

anesthesia. Surgical treatment may have to be altered if

high-grade laxity is detected preoperatively for example by

utilizing a computer navigation that is a helpful adjunct for

surgeons during examination under anesthesia. A typical

case for revision ACL reconstruction is presented. This

article describes several techniques of laxity assessments.

Based on the type and degree of pathologic laxity, a

treatment algorithm has been developed.

Level of evidence V.

Keywords Anterior cruciate ligament � Treatment �Pivot shift � Clinical examination

Introduction

During the past decade, a large body of research has focused

on the function of the two functional bundles of the anterior

cruciate ligament (ACL). The posterolateral (PL) bundle is

taut and locks the knee in full extension by inhibiting anterior

tibial translation [2, 38, 42, 43]. During knee flexion, the PL

bundle relaxes and allows the tibia to internally rotate while

the quadriceps muscle contracts. This supports function of

knee weight bearing in extension and allowing movement

during knee flexion [38]. This physiologic movement pattern

is disrupted during knee injuries involving rupture of the

ACL leading to rotatory knee laxity [28, 38, 43].

The resultant pivot shift phenomenon is a shift of the knee

pivot from the medial tibial spine centrally (intact knee) to

produce an anterior and medial subluxation (ACL-deficient

knee). Therefore, the anterior tibial translation in the lateral

compartment is exaggerated, but it is still anterior tibial

translation, and not rotation [11, 24]. The cause of the pivot

shift phenomenon is not only injury of the ACL, but also

injury to secondary restraints, such as collateral ligaments,

especially the lateral collateral ligament, capsule, meniscus

roots, meniscotibial ligaments, and shape of the bones

(compression fractures of posterolateral tibial plateau and/or

anterolateral femur) [11, 18, 31, 33, 35, 36, 54]. Any

meaningful treatment algorithm would have to address these

factors to achieve a successful clinical outcome.

V. Musahl (&) � S. Rabuck � F. H. Fu

Department of Orthopaedic Surgery, Center for Sports Medicine,

University of Pittsburgh, 3200 S Water Street,

Pittsburgh, PA 15203, USA

e-mail: musahlv@upmc.edu

S. Kopf

Center for Musculoskeletal Surgery, Charite,

University Medicine, Berlin, Germany

R. Becker

Department of Orthopaedic and Traumatology,

City Hospital Brandenburg, Brandenburg, Germany

W. van der Merwe

The Sports Science Orthopaedic Clinic,

Cape Town, South Africa

S. Zaffagnini

Sports Traumatology Department and Biomechanics

Laboratory, Instituti Ortopedici Rizzoli,

Bologna University, Bologna, Italy

J. Karlsson

Department of Orthopaedics, Sahlgrenska University Hospital,

Goteborg, Sweden

123

Knee Surg Sports Traumatol Arthrosc (2012) 20:793–800

DOI 10.1007/s00167-011-1857-6

The elimination of the pivot shift is one of the goals in

ACL reconstruction surgery (B. Clancy, August 25, 2011,

What have we learnt over the last 30 years of ACL

reconstruction, Personal Communication) [19]! Studies of

simulated pivot shift or simulated combined rotatory

loading conditions have shown variable magnitudes of

increased tibial rotation following ACL deficiency [29, 37].

However, in vivo, and in numerous clinical outcome

studies, the pivot shift has been shown to persist in a

considerable number of patients, even following anatomic

ACL reconstruction [32]. The question is, what exactly are

the factors contributing to this persistent rotational insta-

bility, and how can this be avoided?

The success of ACL reconstruction should be considered

in short term but also in a long-term aspect. The short-term

goal of ACL reconstruction is to return the athlete to sport as

quickly and safely as possible [15, 46, 47]. While the long-

term goal is to avoid further injury or re-injury as well as

avoid chronic pain and the development of osteoarthritis

(OA) [7]. Therefore, ACL healing and recovery of muscle

function would be predictors of short-term outcome, while

meniscal injury and chondral damage are the most accurate

predictors of long-term knee function [1, 8, 41].

Clinical scenario

A typical scenario may be a patient presenting with a

history of an acute non-contact knee injury and a ‘‘pop’’. A

clinical examination may or may not have been obtained,

but the MRI reveals a bone bruise pattern and torn ACL.

The patient is indicated for surgery. Autograft ACL

reconstruction is performed, and a concomitantly present

medial meniscus tear is treated with partial resection [36].

The outcome of this patient is good, but mild rotatory

instability persists over the years. We all know the fate of

this patients’ ACL reconstructed knee in the medium-term,

i.e., OA [8, 12].

An alternate, and preferred, diagnostic procedure for the

same patient would include a specifically history of pre-

vious or contralateral knee injury, generalized ligamentous

laxity, and injury mechanism. The evaluation of each

patient should focus on identifying the unique character-

istics of that patient’s injury pattern. Anatomic ACL

reconstruction has demonstrated significant variability in

the anatomy of the ACL and a resultant variability in ACL

injuries. As a result, when anatomically reconstructing the

ACL, the goal should be to individualize the surgical

procedure to the unique characteristics of that patient

[20–22, 40, 45, 48]. Clinical examination should consist of

several tests for rotatory knee laxity, e.g., pivot shift test,

varus–valgus (VV) laxity test, internal–external (IE) rota-

tion dial tests, and exclusion of further ligamentous knee

injuries such as PCL rupture. It is preferred that clinical

examination is performed on at least two different occa-

sions. At the time of surgery, a useful preoperative plan-

ning tool is examination under anesthesia (EUA) [35, 49].

Case example

An 18-year-old division I football player underwent ACL

reconstruction at the end of his junior year in high school.

Following surgery, he played his senior year denying pain or

any symptoms of instability. His college pre-season physical

examination 18 months later revealed near-symmetric

quadriceps strength, no loss of motion, but a moderate

effusion. Laxity examination demonstrated a 2B Lachman

test, a 2? opening on varus stress with a strong end point. The

pivot shift test was a 2? with a ‘‘clunk’’ and at least 10 mm of

noticeable translation in the lateral compartment.

MRI revealed a vertical and slightly anterior femoral

tunnel of the ACL reconstruction. The tibial tunnel is

posteriorly located within the native footprint. The ACL

graft is absent (Figs. 1, 2). The medial meniscus is status

post partial posterior horn resection. A vertical split is

present in the vascular zone at the junction of meniscus and

posteromedial capsule (Fig. 3). The lateral meniscus is

intact. The lateral collateral ligament and posterolateral

corner complex are intact.

The assessment following EUA was a chronic, recur-

rent, high-grade ACL insufficiency with associated medial

meniscus capsule separation. Existing tunnels are non-

Fig. 1 Sagittal fat suppressed MRI of failed ACL reconstruction.

ACL graft is deficient/absent

794 Knee Surg Sports Traumatol Arthrosc (2012) 20:793–800

123

anatomic (femur) and partially anatomic (tibia; Fig. 2). The

pathologic opening of the knee on varus stress testing in

extension was felt to be secondary to medial meniscus

insufficiency. The lack of subjective instability of the

patient was judged to be secondary to the well-functioning

quadriceps muscle.

Based on the high-grade positive pivot shift test, the

surgical plan was for (1) revision ACL reconstruction,

utilizing autologous BTB graft, (2) anatomic single-bundle

technique (Fig. 4), and (3) medial meniscus repair. If the

meniscus is found to be irreparable (4), staged medial

meniscus reconstruction with allograft or collagen menis-

cus implant would be recommended.

The resolution for this case was revision ACL recon-

struction as planned and medial meniscus repair. The

medial meniscus capsule separation was repaired utilizing

an accessory posteromedial portal and all-inside suture

repair with two braided sutures using a 70�-curved suture

passer (Fig. 5). The medial meniscus vertical split of mid

body to posterior horn junction was repaired utilizing an

all-inside suture-passing device.

Information gained from pivot shift test

The pivot shift test is the most important and most specific

test during EUA [4]. Clinical grading is complicated.

However, from controlled laboratory studies, it is known

that lateral compartment translation predicts the grade of

the pivot shift [3]. The surgeon should therefore attempt to

focus on the movement of the lateral compartment and try

Fig. 2 Flexion posteroanterior weight bearing and lateral radiograph

of the left knee demonstrating preserved joint spaces and vertical

tunnel architecture. The angle of the femoral tunnel in the coronal

plane is \15�

Fig. 3 Axial fat suppressed MRI demonstrating vertical split tear of posterior horn medial meniscus (arrow) in vascular zone

Knee Surg Sports Traumatol Arthrosc (2012) 20:793–800 795

123

to understand if there is more or less than *10 mm of

translation present. For example, a grade I pivot shift

(*6 mm of lateral compartment translation) usually rep-

resents an isolated ACL injury. A grade II pivot shift or

higher ([12 mm of lateral compartment translation) usu-

ally indicates concomitant injury to secondary restraints,

most commonly the medial meniscus [35]. Therefore, a

grade II? pivot shift on EUA should leave the surgeon

suspicious for concomitant injuries. A medial meniscus

tear in this case scenario should be repaired, because its

integrity will contribute to the elimination of excess rota-

tory knee laxity [36].

What if a grade II pivot shift is present and no con-

comitant meniscus or collateral ligament injury can be

found? Here, it may be an injury or permanent strain of the

capsule, generalized ligamentous laxity, or underlying

morphologic abnormalities. Zaffagnini et al. [53] have

shown that in those cases, a concomitant lateral tenodesis

may be indicated. The goal of this review paper is to

present methods to assess and treat different injury

patterns.

Anterior–posterior laxity

When intra-operative laxity data were analyzed pre- and

postoperatively, a significant reduction in all knee laxities

was shown after ACL reconstruction [49]. The navigation

system was also validated for the use of anterior–posterior

laxity tests, by direct comparison with commercial

arthrometer testing systems [25, 34]. These systems have

been proven for evaluating and detecting different laxity

patterns following anatomic double-bundle ACL recon-

struction [10, 16, 44, 51].

Kinematic analysis of the knee

Navigation technology allows for a complete kinematic

analysis of the limb. These systems have been used to

evaluate not only the AP translation during Lachman and

anterior drawer testing, but also IE and VV rotations of the

tibia under different stress tests at fixed flexion angles.

Several studies quantitatively report the effect of ACL

reconstruction on controlling global knee laxity. Intra-

observer reliability was \1 mm/1.5� and an inter-observer

repeatability \1.2 mm/2.3� [30].

Combined ACL and extraarticular tenodesis

A very useful application of navigation systems is the

evaluation of laxity patterns following different surgical

reconstruction procedures. Isolated single-bundle and sin-

gle-bundle reconstruction with lateral plasty were com-

pared [6, 49]. The extra-articular procedure controlled

lateral tibial compartment during the Lachman testing,

reducing translation by 1.6 mm, whereas during drawer

Fig. 4 Arthroscopic image of

the notch demonstrating a

malplaced and high original

femoral tunnel (a) and anatomic

center of the ACL for planned

tunnel in revision surgery (b)

Fig. 5 Arthroscopic image of

the posterior compartment (with

70� arthroscope through

Gillquist portal) demonstrating

a vertical split of posterior horn

to posteromedial capsule

junction (a). Image b is taken

after all-inside repair with 2 no.

2 braided sutures

796 Knee Surg Sports Traumatol Arthrosc (2012) 20:793–800

123

testing, the control was about 1 mm in both compartments.

Additional lateral tenodesis was shown to result in

improved static laxity reduction in VV stress test at full

extension and in IE rotation at 90� of flexion [53].

Combined ACL and MCL injury

Computer navigation was shown to be able to detect the

presence of additional ligamentous lesions. Combined

ACL/MCL lesions result in greater AP laxity and greater

VV laxity. It has been shown that residual laxity remains

when ACL reconstruction is performed in patients with

combined ACL and MCL lesions [50].

Dynamic laxity testing

While AP laxity testing of the knee has been demonstrated

to be effective, rotational laxity testing is less consistent.

Variability in rotational laxity measurements may be

related to the fact that other structures of the knee joint can

be involved, while the constitutional laxity of the patient

must be considered.

Recent studies have focused on the analysis of the pivot

shift test. However, it has been difficult to describe and

quantify dynamic laxity of the knee joint utilizing the pivot

shift. Preliminary results demonstrate good intra-tester

reliability of pivot shift test performed before and after

ACL reconstruction [17, 26].

Clinical grading, which has been historically inconsis-

tent, can be correlated with different parameters by means

of navigation [3, 24]. The clinical grade correlated well

with the dynamic behavior (AP translation and IE rotation)

of the joint, specifically the lateral compartment [5, 26].

Additional tenodesis may improve static laxity as reported

above; however, anatomic double-bundle reconstruction

presented better results in controlling the dynamic laxity of

the knee joint, especially when the acceleration during

reduction is considered [53].

Preoperative high laxity

Preoperative laxity measurements have been taken recently

in a study in order to define the threshold for pathological

knee condition. For this study, laxity data from 115 patients

who underwent ACL reconstruction were analyzed.

Patients were divided into 4 groups (A, B, C, and D)

according to their preoperative laxity, determined with a

surgical navigation system. Patients with higher preopera-

tive laxity (group C and D) maintained higher values for all

laxity tests also following ACL reconstruction (Fig. 6). The

findings from this study can be used to further analyze and

stratify the presence of peripheral soft-tissue injuries, such

as MCL and meniscal lesions. In the future, treatment

algorithms may be modified to be more injury-specific

(Zaffagnini et al., personal communication).

Treatment algorithm

The main focus of the treatment algorithm is the amount of

laxity that dictates treatment. A low-grade pivot shift and

negative findings of additional laxity tests would indicate

ACL augmentation or primary ACL reconstruction. How-

ever, in cases where the pivot shift is 2? and greater on

preoperative EUA ([12 mm lateral compartment transla-

tion), additional surgical repair or reconstruction may be

necessary (Fig. 7). In this scenario, meniscus deficiency

would mandate surgical repair. Low-grade opening with a

good end point on VV stress testing can sometimes indicate

chronic meniscus deficiency. Treatment could consist of

meniscus reconstruction and/or biplanar osteotomy [9, 13].

High-grade medial laxity should be treated with MCL

surgery, lateral laxity with posterolateral corner surgery.

Some data exist to support extra-articular tenodesis

[39, 53].

The unique presentation of each patient’s injury and

anatomy requires an individualized approach. Suboptimal

outcomes following ACL reconstruction may be a result of

a surgical plan that incompletely addresses the patient’s

injury or anatomy. By improving the ability to detect the

Fig. 6 Pre- and Postoperative

knee laxities according to

defined preoperative laxity

groups (A, B, C, and D).

*P \ 0.05 for one-way

ANOVA analysis with all pair

wise contrast, from Zaffagnini

et al. [53]

Knee Surg Sports Traumatol Arthrosc (2012) 20:793–800 797

123

subtleties of each injury, the patient’s anatomy may be

better restored. However, the anatomy of the ACL is var-

iable. An individualized approach, whereby the graft and

surgical technique are chosen based on the patient’s unique

anatomy, may be necessary to restore the native kinematics

of the knee. Ultimately, the goal of anatomic ACL recon-

struction is to achieve improved clinical outcomes and

avoidance of the development of OA [20–22, 40, 45, 48].

Conclusion

Navigation systems have demonstrated feasibility in cus-

tomizing the surgical strategy to be patient-specific. The

focus is on evaluation and comparison of laxity parameters

between injured and healthy knee. The philosophy of

computer navigation as an intra-operative tool for treat-

ment algorithm is changing. Surgeons are ready to accept

the quantitative information on static and, above all,

dynamic behavior of the joint, as provided by computer

navigation. This approach may be able to aid in improving

ligament reconstruction surgery. In the future, the intro-

duction of hard- and soft-tissue modeling into navigation

may also improve the knowledge of patient-specific

parameters, leading toward a predictive planning of the

surgery itself based both on anatomy and joint function.

Recently, noninvasive methodologies based on electro-

magnetic or acceleration sensors have been shown to

quantitatively evaluate the pivot shift test [14, 23, 27, 52].

In the future, quantitative dynamic laxity testing can be

performed in the office. Together with imaging modalities

and patient-specific parameters of joint laxity and mor-

phology, quantitative pivot shift testing will enable sur-

geons to modify their treatment plans based on the

requirements of each individual patient.

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