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INSIDE FEATURE Dr Jodi Richardson

Figuring out ACL puzzle A breakthrough by a Melbourne scientist may help reduce serious knee injuries in the AFL.

W

hen you think of football, lots of things come to mind, but I’m willing to bet mathematics isn’t one of them. But you might be surprised to consider the role it plays. Mathematics is a huge field and different elements are used when developing the fixture, drafting players, updating the ladder, line marking, allocating fantasy points, betting, stats, and GPS monitoring to name a handful. And now thanks to the lateral thinking of a Melbourne mechanical engineer, mathematical modelling has the potential to predict and ultimately reduce anterior cruciate ligament (ACL) injuries. The ACL is a major ligament inside the knee and is one of four ligaments joining the thigh bone (femur) to the shin bone (tibia). The ACL guards against excessive movement between these two bones. The ACL tightens as the leg straightens, so when you see a player’s knee straighten beyond the normal range of the joint (hyperextension), not only is it cringe worthy, it’s potentially damaging. The ACL is also at risk during landing, particularly as a player changes direction when the foot is planted in the turf and the knee twists. Damage to the ACL typically occurs without contact from another player. Next to hamstring strains, ACL injuries are responsible for the most games missed in the AFL, and this season saw plenty. The last victim was Sydney’s Rhyce Shaw, who snapped his ACL against Geelong in Round 22. He is one of a long list of players this year including

Alan Toovey, Anthony Morabito and Matt Suckling. The cost of an ACL injury to a player is high; they are typically season ending injuries requiring months of rehab after surgery. An ACL injury takes an emotional toll on players casting a shadow over their longevity in the game. The cost to clubs can’t be ignored either. Traditionally, and understandably, research around ACL prevention has centred on the muscles surrounding the knee joint. But during his PhD research in the Department of Mechanical Engineering at Melbourne University, Hossein Mokhtarzadeh was inspired to think out of the box. “When you look at an injury of any part of the body, you look at the muscles surrounding the joint and try to strengthen them,” Hossein explained. “Many people are trying to understand what is the role of the hamstrings, what is the role of the quadriceps? What I did was think about the role of the ankle muscles even though they do not wrap the knee joint.” Hossein initially followed through this idea by using mathematical models to calculate and predict the forces of the 92 lower limb muscles, after collecting ground reaction force data from male and female subjects jumping from a height and landing on one leg. “I could see the (activation) pattern of the muscles, which is not possible to do experimentally,” Hossein said. “You cannot put 92 sensors into someone’s body; it’s not practical and it’s not ethical.” Hossein identified that the soleus, a

Trigger point: The soleus muscle appears to play an important role in protecting the ACL.

Winged Crow: Taylor Walker.

powerful muscle forming part of the calf musculature, plays an important role in protecting the ACL. “Soleus starts at the foot and attaches (below the knee) on the shin, so it has nothing to do with the knee joint. When I calculated the force that it can apply backward on the shin to help protect the ACL, I realised that it is up to 30 per cent of the (force produced by the) hamstrings.” The new understanding that the soleus aids in the protection of the ACL changes the face of ACL injury prevention research for an injury that has been on the AFL’s injury radar for decades. In the late 1990s it was identified that more ACL injuries were sustained in warmer climates in Australia. This prompted investigations that led to the understanding that the weather and predominant grass types were

risk factors because of the way they trapped the foot. The management of AFL surfaces on northern grounds was changed and as a result ACL reconstruction rates began to fall. Over the past 10 years, however, ACL injury rates have remained fairly constant but these injuries were still responsible for an average of 13.5 missed games per club and 16 reconstructions in 2012. Hossein is now working closely with Carlton Football Club’s sports physiotherapist and Injury prevention co-ordinator Sam Rosengarten. Carlton’s world-class motion capture facility generates ground reaction forces as players land on the lab floor. This information combined with the measurement of joint angles enables the calculation of the force produced in joints such as the ankle, knee and hip. Using mathematical models, Hossein can take this force and joint motion information and calculate the muscle forces around each joint as well as calculating the force in the ACL itself. This data can then be shared with the club as a method for screening players who may be at risk of injury. “Understanding the contribution that the soleus muscle makes to protecting the ACL means that any deficits in the strength of these muscles in players can be identified and rectified, as a means of reducing ACL injury risk in these players,” Hossein explained. “If we prevent just half of the knee injuries in Australian football, it would protect players from serious injury and save the AFL millions of dollars.”

‘If we prevent just half of the knee injuries, it would save the AFL millions of dollars.’

Age related calf injuries in the AFL

T

he older you get, the older “old” is, but when it comes to calf muscle injuries, “older” is remarkably young. The AFL Injury Report has repeatedly shown that the risk of calf strain increases greatly for players over 26 years old. The report also showed that calf strains were higher in 2012 than in the previous 20 years of the survey. There was an average of three new calf strains per club last season, with an average of seven games missed per injury. The time out due to calf strain also increased, but this is likely due to more conservative injury management. And these stats are not unique to Aussie rules. A recent study of 1401 professional soccer players found that players 26 and older had almost double the rate of calf injury. Several studies have also shown this age related phenomena with hamstring strains.

AVERAGE MISSED GAMES PER CLUB PER SEASON

Snap: Rhyce Shaw ruptured his ACL in Round 22.

38 INSIDE FOOTBALL Wednesday October 30, 2013

ERA

1992-1998

1999-2005

2006-2012

AGE GROUPS

<=21 22-25 26+

<=21 22-25 26+

<=21 22-25 26+

CALF STRAINS

1.9 3.7 10.4

2.2 3.2 7.9

2.3 5.0 8.3

Source: AFL Injury Report 2012

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