LIVRE JDG 2016

SECONDARY RESTRAINTS TO INTERNAL ROTATION…

There is evidence of ITB injury occurring with

ACL injury and contributing to the spectrum of

instability seen. At operation, Terry found that

injury to the deep and capsulo-osseous layers

occurred in 84 and 71% of ACL ruptures

respectively, and that injury to these structures

correlated with the pivot shift findings [42].

The majority of these injuries occurred at the

femoral insertion.

THE MENISCI

The role of the medial meniscus as a secondary

stabilizer to anterior translation is well

documented [43, 44]. Much less has been

published regarding the role of the menisci in

controlling rotation.

Musahl examined the effect of medial and

lateral meniscectomy in the ACL deficient knee

using navigation and a mechanized pivot

shifter [7]. Medial meniscectomy significantly

increased anterior tibial translation during the

Lachman test, but did not increase lateral

compartment translation during the pivot shift.

Lateral meniscectomy, on the other hand,

caused a significant increase in lateral

compartment translation during the pivot shift

but had no effect on the Lachman examination.

Petrigliano reported increased rotational

instability after uni- and bi-compartmental

meniscectomy, although they did not

differentiate in their report which compartment

was meniscectomized first [45].

Shybut investigated the impact of tears of the

posterior root of the lateral meniscus on

stability in the ACL deficient knee [8]. Using

an infrared motion analysis system, loss of the

meniscal root was shown to increase lateral

compartment translation during the pivot shift.

Lording and Getgood examined the role of the

ALL and posterior lateral meniscal root on

internal rotation in the ACL deficient knee [33].

Loss of the meniscal root significantly

increased internal rotation in extension and at

knee flexion angles under 30°, while the ALL

significantly controlled rotation only at higher

degrees of flexion (fig. 3).

Some medial meniscal lesions may also play a

role in rotational instability. Peltier investigated

the effect of very peripheral medial medial

meniscal tears, termed “ramp” lesions [9]. He

found increased anterior translation after

creation of a ramp lesion in the ACL deficient

knee, but also increased internal rotation after

division of the meniscotibial ligament of the

posterior horn. It seems likely that this

measured

internal

rotation

represents

posteromedial rotation, and the relevance of

this finding to clinical instability in the ACL

deficient knee is unclear.

DISCUSSION

The anterolateral ligament, iliotibial band and

lateral meniscus all contribute to the restraint

of anterolateral rotatory instability at the knee.

Considered together, these structures could be

considered to constitute the “anterolateral

corner” of the knee. As outlined above,

biomechanical studies suggest the contribution

of these structures is dependent on knee flexion

angle, with the lateral meniscus being more

important near extension and the anterolateral

ligament exerting greater control at deeper

flexion angles above 30°.

The indications for surgical management for

the anterolateral extra-articular structures are

yet to be fully determined. The results of intra-

articular reconstruction are satisfactory for the

majority of patients, and as such extra-articular

reconstruction should be reserved for those

most likely to benefit from the additional

intervention. This may include those at higher

risk of failure, such as younger patients [46]

and those returning to pivoting sports [47], and

those undergoing revision procedures.

Excessive tibial rotation in the non-injured

knee is a risk factor for both ACL injury and

poor outcomes after ACL surgery [48, 49], and

may also be an indication for an extra-articular

procedure.

The degree of clinical laxity has also been

proposed as an indication; however, it seems

likely that the severity of this laxity reflects