Hughes
G, Watkins J. Sports Medicine, 2006; 36 (5), 411 – 428.
Amount
of non – contact ACL injuries is reported to be higher among females. There is
lack of scientific evidence to support why. To answer question why someone
might be more susceptible to suffer an injury, number of risk factors are
frequently presented. Usually, these are divided into intrinsic and extrinsic.
Authors of this review find that categorization limited due to its inability to
show how these risk factors interact, which might be crucial in case of ACL
injury aetiology. This paper presents a risk – factor model for ACL injuries in
female based on analysis of key elements of the passive and dynamic stability support
mechanisms.
In
regards to passive stability of the knee joint, which may play role in etiology
of ACL injury is ligament laxity and geometry of articular surfaces. Q – angle
is reported to be greater in females and since greater q- angle means greater
knee valgus angle which is said to place ACL at higher stress, one could state
that females might be at greater risk of sustaining ACL tear. Authors indicate
that some papers found relationship between greater Q –angle and higher risk of
ACL ruptures, but others studies refute that notion. Congruence between
articular surfaces of the femur and tibia is another factor potentially having
an importance here. It might be affected by damaged menisci but there is no
evidence that meniscal injury increases the risk of ACL tear (at least up to
2006 when the current paper was published). Tibio – femoral congruence also
depends on width of the intercondylar notch (INW): the wider the notch, the
lower the congruence. However, some studies reported that females have a
smaller INW than males and again some research confirm that those having
smaller INW are more susceptible to torn their ACL but other studies do not
confirm that, therefore no strong evidence exists to support association
between smaller INW and higher ACL rupture incidence among females. Finally,
increased knee joint laxity has been proposed to result in higher risk of ACL
injury and some studies indicate that females exhibit greater ligamentous
laxity than males. It might be in relation to phases of menstrual cycle which
possibly affect length and tensile stiffness of ACL, however authors indicate
that these findings are inconsistent therefore it cannot be determined whether
it plays major role in higher ACL tear occurrence among women.
Dynamic
stability risk factors reviewed by authors included the patellar tendon – tibia
shaft angle (PTTSA), muscle activity pattern, muscle reaction time, time to
peak torque and muscle stiffness. The more knee is extended the greater PTTSA
and the greater strain on ACL. Indeed, studies show that ACL injuries occur
most frequently when the knee is more extended rather than flexed. Also, some
papers note that PTTSA is on average greater in female than male. Given that,
authors suggest that higher PTTSA can be regarded as a significant risk factor
for ACL rupture in female. Activity of quadriceps and hamstring in dynamic movements
should ideally result in zero shear loads on the proximal tibia. Research has
found that females exhibit greater quadriceps dominance compared to males
therefore place higher anterior shear load on their proximal tibia and
subsequently increase ACL strain. Ability of muscles to resist movement in
particular joint is called muscle stiffness. Number of studies has found that
females demonstrate reduced knee joint muscle stiffness in comparison to males
potentially placing their ACL on increased load. Another factor possibly
contributing to greater incidence of ACL tears among females is fatigue. Some
papers found that fatigued women tended to increase their knee valgus angle as
well as tended to decrease their knee flexion angle during landing and other
dynamic activities. These factors have been previously suggested to place
greater stress on ACL.
In
conclusion, authors state that available evidence suggests that greater
incidence of ACL ruptures in women may account for sex differences in the
dynamic stabilizing structures rather than the passive stability system,
although more research is needed to figure out how these factors interact.
Do
you treat more women with torn ACL than men? Do you see any other explanation
why female might be more susceptible to ACL injury? Are there any differences
in yours treatment programs for women and men?
All rights reserved to the Sports Medicine.
All rights reserved to the Sports Medicine.
No comments:
Post a Comment