DIAGNOSIS By Mr Andy Williams, FRCS (Orth)

OPTIMAL MANAGEMENT OF ACL INJURY IN 2007 – PART 1

Anterior cruciate ligament (ACL) injury is relatively common. The incidence is increasing, partly due to the growing competitive nature of sport and participation of individuals in sport. and particularly involvement among women who have a significantly higher instance of ACL rupture compared to males. Despite the increase in profile of this injury the diagnosis is often missed on first presentation and even when correctly diagnosed, management is not necessarily as good as one would expect.

PRE-DISPOSING FACTORS TO ACL INJURY As already mentioned, women have an extremely high risk of ACL rupture. Their relative risk is around sevenfold compared to that of men. There are a number of theories as to why this may be. It may be related to the relatively narrow dimension of the female intercondylar notch thereby allowing less excursion of the ligament within it before it impinges and tears. Alternatively it might be related to women having more ligament laxity as a rule. There is considerable interest in the patterns of limb movement in women compared with men and in particular the 'jump/land' patterns which tend to be different between the two sexes. Women tend to land with feet closer together and the knees bend towards each other accompanied by tibial external rotation and hip internal rotation. Considerable work, in the USA especially, has been put into teach- ing girls the more male pattern of movement but it remains to be

THE LACHMAN TEST Test purpose: ACL rupture Description: Start position - it is important that the proximal hand holds the thigh from the lateral side and is motionless in space. The distal hand grasps the leg below the knee with the knee at 20-300

flexion and applies an anterior force (arrow). To

aid this, externally rotate the limb a little so that the examin- er’s hand is largely supporting under the thigh. In addition it can be helpful for the examiner to rest the elbow of their prox- imal upper limb on their adjacent iliac crest for support. Both these manoevres help stop the hand shaking with fatigue and so help the patient relax. They are especially helpful in a large subject. If it is really impossible to grasp the thigh well, an alternative technique is to place the subjects knee over the examiner’s knee flexed 20-300

. The examiner’s proximal hand

then ‘clamps’ the thigh against the examiner’s knee so fixing it. The tibia can then be subject to an anteriorly directed force by the examiner’s other hand. Significantly more anterior translation, as in this case, compared to the uninjured side represents a positive test for ACL laxity.

6

seen whether or not this translates to a reduced incidence of ACL rupture. Hormonal changes during the menstrual cycle have also been implicated as a possible factor in predisposition to ACL rupture due to their effects on ligament laxity. These studies remain very unclear as to how real, or otherwise, this is (see reference at end of this article for a review of this topic).

There is no doubt that predisposition occurs since the instance of ACL ruptures in both a subject’s knees is higher than one would expect if an ACL tear was simply related to bad luck. In addition, there are families who have more ruptures than is likely to be just coincidence. There does also seem to be a racial variation. In par- ticular, Arabic patients seem to have a peculiarly high level of ACL rupture. This could be related to a steeper tibial slope in their knees.

THE PIVOT SHIFT TEST Test purpose: ACL rupture Description: This test involves holding the limb out straight and applying internal rotation which will sublux the lateral tibial condyle anteriorly off the lateral femur. The knee is then flexed, whereupon around 200

knee flexion, mediated by ten-

sion in the ilio-tibial band, the tibia reduces on the femur with a characteristic 'clunk'. Since the joint subluxation/ reduction occurs laterally the phenomenon is exaggerated by simultaneously applying a valgus force.

With internal rotation (red arrow) applied with the knee close to extension, anterior subluxation of the lateral tibia (white arrow) occurs in ACL deficiency. Further flexion leads to the 'pivot shift' whereby sudden posterior reduction (white arrow) of the subluxed tibia occurs. This test can be hard for many examiners to achieve.

sportex medicine 2007:33(Jul):6-9