Monthly Archives: April 2016

Anterior Cruciate Knee Ligament Injuries – The End Of The Affair For Most Sports Careers Despite The Injury Unlocking Exquisite Redundant Neuromuscular Protective Mechanisms

I was watching a rugby game recently and saw a player land wrongly in a tackle and immediately collapse to the ground clutching his knee joint, and heard later that he had suffered a ruptured anterior cruciate ligament injury that would require nine months post-injury before he would be able to return to his chosen sport. Many years ago in my student days, after a few too many beers at a party, I jumped off a low wall, landed wrongly, and tore the meniscus in my left knee. The next day it had swollen up, but I did not think much of it and tried to drive to University, and always remember the horror I felt when getting to the bottom of the road and I tried to push in the clutch with my left leg to allow use of the brake at the stop street, and my leg would not react at all, and I only avoided an accident by turning off the car while working the brake pedal with my right foot. It always puzzled me afterwards why my leg would not respond at all despite my ‘command’ for it to do so, as even with the injury, I expected, while perhaps it might be painful to do so, that I would still have reasonable control over my leg movements, which appeared okay when walking slowly to the car and taking my weight on my uninjured leg. Perhaps this triggered a ‘deep’ interest in what controlled our muscles and other body functions, and when I started a PhD degree with Professors Tim Noakes, Kathy Myburgh and Mike Lambert as my supervisors at the University of Cape Town in the early 1990’s, I chose to look at neural reflexes and brain control mechanisms regulating lower limb function after anterior cruciate ligament knee injury. So what happens when the knee joint suffers a major injury, and can one ever ‘come back’ from it?

The knee joint is one of the most precarious joints in the body, and as compared to the hip and shoulder joints, which have quite a degree of stability generated by their ‘ball and socket’ design, it is simply made up of three individual bones (the femur, tibia and patella) moving ‘over’ each other while being attached to each other with a number of ligaments and muscles, which are pretty much all that creates stability in and around the knee joint. The knee mostly moves in a backwards / forwards (in medical terms flexion and extension) plane, and has a small degree of rotation inwards and outwards, but is basically a ‘hinge’ type joint that moves in one plane only. The major ligaments of the knee joint preventing too much flexion and extension are the anterior cruciate ligament (ACL), which prevents hyper-extension (the lower limb calf region moving too far ‘forwards’ relative to the upper thigh) and the posterior cruciate ligament (PCL), which prevents hyper-flexion of the knee joint. There are also relatively strong ligaments on each side of the knee joint (the medial and lateral collateral ligaments), as well as several ligaments and tendons securing the patella in place in the front of the knee. Two large pieces of cartilage, the medial and lateral menisci, ‘sit’ on the tibia and allow smooth movement to occur across the entire range of movement between the two big bones (femur and tibia) of the knee joint and protect each of these from damage which would occur if they ‘rammed’ into each other each time the bone moved without the protection of the two menisci.

While these ligaments (and there are several others in the knee joint beyond those I have described above), tendons and menisci provide the majority of support to maintain the fidelity of the knee joint, the surrounding muscles – particularly the quadriceps and hamstrings muscles – also provide important secondary support to the knee joint during active movement such as walking or running, when a greater degree of dynamic stability beyond the static stability the ligaments and tendons supply, is needed. So muscles are not just creators of movement, they are also important stabilisers of the body’s joints, and there needs to be a high degree of dynamic control of them by the central nervous system during movement to ensure things work ‘just right’ with not too much and not too little force being applied to the joint at any one time during any movement. The hamstring muscles have been shown to be agonists (assistants) of the ACL, and when they fire they ‘pull back’ the lower part of the knee joint so as to reduce pressure on the ACL when the knee extends to its limits, while the quadriceps muscles similarly assist the PCL from having too much pressure on it associated with too much flexion of the knee joint (though only at certain angles of the knee joint and not through its entire range of movement). Interestingly, the quadriceps muscles are not just agonists of the PCL, but also are ‘antagonists’ of the ACL, and their activation can also increase hyper-extension pressure on the knee joint (and therefore on the ACL) when the quadriceps contracts particularly when the knee is in an extended position. So the quadriceps muscles can be the ‘friend’ of the ACL and knee joint, but can also be its ‘foe’.

What is fascinating in this process is the structure and function of the nerve pathways both from and to all of the knee joint, ACL and muscles around them, and how these nerve pathways act differently in an intact ACL as compared to the damaged ACL state. In the intact ACL are mechanoreceptors (receptors which pick up mechanical pressure) which fire when the ACL is put under pressure / moves, and they send information back via nerves to the spinal cord, and cause increased firing of the hamstring muscles, in order to protect both the ACL and integrity of the entire knee joint. When the ACL is ruptured, receptors called free nerve endings in the surrounding capsule of the knee joint fire in response to movement of the entire knee joint, which would happen to a greater degree in the absence of the ACL after it ruptures, and importantly, these injury associated capsular free nerve ending reflexes don’t just increase the firing to the hamstrings muscles, they at the same time reduce firing to the quadriceps muscle, in order to protect the knee from further damage which could occur if the quadriceps were active maximally in the absence of the ACL. This free nerve ending pathway is known as a redundant pathway, as it only ‘fires’ when the ACL is damaged, and does not do so normally. Interestingly, the redundant free nerve ending related pathway does not seem to stop working even if the ACL is repaired or replaced, which means that even if one fixes the ligament materially, one cannot ever completely repair the sensitive neuronal control pathways as part of the operation.

While these redundant neural firing pathways are protective and are designed to help the knee from incurring further damage, they are unfortunately not helpful in allowing athletes who suffer ACL injuries from getting back to their full strength and a return to sport with the one hundred percent function they had prior to suffering the injury. The quadriceps muscles inhibitory firing pathway is particularly a problem from a return to sport perspective, as it means that the quadriceps muscles will always be weaker than before the ACL injury, and this is born out from most studies of quadriceps strength after injury, which show a continued deficit of at least 5-10 percent injured limb compared to the unaffected limb, and that is when rehabilitation of the injured limb is done post-injury or operation, and is even higher when it is not. Furthermore, the altered firing synergies, even those of the increased hamstring firing, appear to be sub-optimal from a functional pattern of movement perspective, even if they are protective, and there even appears to be whole body / both limb firing pattern changes, with athletes favouring the injured leg and taking more weight on the uninjured limb even if they are unaware of themselves doing this (though some folk speculate that using crutches for a prolonged period of time after ACL injury may be in part a cause of these whole limb and gait changes). These changes surely are at least to a degree responsible for the high rate of re-injury of the damaged ACL observed in those athletes who return to competitive sport after ACL injury, and potentially the high rate of ACL or other knee joint injury in the unaffected limb which some folk suggest occurs with return to sport after ACL injury.

So therefore, sadly for those who suffer ACL (and other) knee injuries and want to return to competitive sport, or to their pre-injury level of sport, redundant neural mechanisms between the knee joint and the surrounding muscles, while functionally being designed to give a measure of protection to the knee joint in the case where the ACL is damaged or absent, paradoxically ensures by its very activity that the function of the surrounding muscles is attenuated, particularly in the quadriceps muscle, and they will never have ‘full’ functional activity of the knee joint after the injury, despite them having a brilliant surgeon who performs a perfect mechanical replacement of the ACL surgically, and despite the best rehabilitative efforts of either the athlete or those assisting them with their rehabilitation. An athlete has two choices after suffering an ACL injury (and other associated ligament injuries which worsen the prognosis even more). Firstly, they can attempt to return to their sport as they did it before their injury but with changing how they perform it by ‘compensating’ for their injury – if in team sports by improving other aspects of their game so that their reduced capacity for agility and speed after injury is not ‘noticed’, and in individual sports by altering pacing strategy or style of performing their sport (though particularly in individual sports this is not really an option and the loss of competitive capacity is ‘painfully obvious’), and with the awareness that that they have a good chance of re-injuring themselves. Secondly, they can downgrade their expectations and level of sport, either retiring from their sport if competitive or changing the level of intensity they routinely perform their sport to a lower level, as hard as it is for athletes to come to terms with having to do this. But there is no ‘going back’ to what life was like before the injury, and this creates a potential ethical dilemma for those involved in rehabilitating athletes after ACL injury – if one works on increasing for example their quadriceps strength, one is ‘going against’ a natural protective mechanisms ‘unlocked’ by the ACL injury, and one may be paradoxically increasing the chances of future damage to the athlete by the very rehabilitation one is trying to help them by doing it, and one should perhaps rather be ‘rehabilitating’ them by working on their psychological mindset so that they are able to come to terms with the concept of permanent loss of some function of their injured knee and the need to potentially look for alternative sporting outlets or methods of earning their salaries.

The wonderful period of my life as a PhD student back in the early 1990’s, learning about these exquisite neuromuscular protective mechanisms surrounding the knee joint that are ‘activated’ after knee ligament injury (and potentially meniscal injury too), started a lifelong work ‘love affair’ with the brain and the regulatory mechanisms controlling the different and varied functions of the body, that has lasted to this day, and ‘unlocked’ a magical world for me of neural pathways and complex control processes that has ensured for me a lifetime without boredom and never a moment when I don’t have something to ponder on, apart from initiating an amazing ‘journey’ trying to understand how ‘it all works’. But this scientific exploration has not helped me fix my knee joint after the injury all those years ago – my left leg has never been the same again after that injury which required a full meniscectomy eventually as treatment, and still swells up if I run at all and even if my cycle rides are too long, and the muscles around the affected knee have never been as strong as they were no matter how much gym I do for them. So by understanding more about the nature of the mechanisms of response to something as major as anterior cruciate ligament knee injury, I have also come to understand more about the concepts of fate and acceptance of things, and that a single bad landing (or indeed having one beer too many leading to that bad landing) can create consequences that there are no ‘going back’ from, and that will change one’s life forever. After a bad knee injury, nature has given us the capacity for a ‘second chance’ by having these redundant protective mechanisms, but that second chance is designed to work at a slower and more relaxed pace, and with the caution of experience and the conservatism the injury engenders, rather than with the freedom of expression that comes with youth and the feeling of invincibility associated with it. Rivers do not flow upstream, and we don’t get any younger as each day passes, and our knee joints sadly will never be the same again after major injury, despite the best surgery and rehabilitation that one gets and does for them. Nature ensures this ‘reduction in capacity’ happens paradoxically for our own ‘good’, and the biggest challenge for clinicians is to understand this and convey that message to the athletes they treat, and for athletes it is to accept this potential ‘truism’ too, and let go of their sporting ambitions and find a quieter, more sedate life sitting on the bank of the river they used to ride the flow of prior to suffering their knee injury. But please left knee, let me have a few more good bike rides in the cool morning air far from the madding crowd, before you pack up completely!


Athlete Pre-Screening For Cardiac And Other Clinical Disorders – Is It Beneficial Or A Classic Example Of Screening And Diagnostic Creep

Last week the cycling world was rocked by the death of an elite cyclist, who died competing in a professional race of an apparent heart attack. A few years ago when living in the UK, the case of a professional football player who collapsed in the middle of a game as a result of having a heart attack, and only survived thanks to the prompt intervention of pitch-side Sports Medicine Physicians and other First Aid folk received a lot of media attention, and there were calls for increased vigilance and screening of athletes for heart disorders. Many years ago, one of my good friends from my kayaking days, Daniel Conradie, who apart from being a fantastic person won a number of paddling races, collapsed while paddling in the sea and died doing what he loved best of an apparent heart attack. Remembering all of these incidents got me thinking of young folk who die during sporting events, and if we clinical folk can prevent these or at least pick up potential risk factors in them before they do sport, which is known as athlete screening, or pre-screening of athlete populations, and which is still a controversial concept and is not uniformly practiced across countries and sports for a variety of reasons.

Screening as a general concept is defined as a strategy used in populations to identify the possible presence of an ‘as-yet-undiagnosed’ disorder in individuals who up to the point of screening have not presented or reported either symptoms (what one ‘feels’ when one is ill) or signs (what one physically ‘presents with’ / what the clinician can physically see, feel or hear when one is ill). Most medicine is about managing patients who present with a certain disorder or symptom complex who want to be cured or at least treated to retain an optimal state of functioning. Screening for potential disorders is as described a strategic method of pre-emptively diagnosing a potential illness or disorder, in order to treat it before it manifests in an overt manner, in the hope of reducing later morbidity (suffering as a result of an illness)and mortality (dying as a result of the illness) in those folk being screened. It is also enacted to reduce the cost and burden of clinical care which would be the result of the illnesses not being picked up until it is too late to treat them conservatively with lifestyle related or occupational changes, and costly medical interventions are needed which put a drain on the resources of the state or organizing body which consider the need for screening in the first place. Universal screening involves screening all folk in a certain selected category (such as general athlete screening), while case finding screening involves screening a smaller group of folk based on the presence of identified risk factors in them, such as if a sibling is diagnosed with cancer or a hereditary disorder.

For a screening program to be deemed necessary and effective, it has to fulfil what are known as Wilson’s screening criteria – the condition should be an important health problem, the natural history of the condition should be understood, there should be a recognisable latent or early symptomatic stage, there should be a test which is easy to perform and interpret and is reliable and sensitive (not have too many false positive or false negative results), the resultant treatment of a condition diagnosed by the condition should be more effective if started early as a result of screening-related diagnosis, there should be a policy on who should be treated if they are picked up by the screening program, and diagnosis and treatment should be cost-effective, amongst other criteria. Unfortunately, there are some ‘side-effects’ of screening programs. Overscreening is when screening occurs as a resultant of ‘defensive’ medicine (when clinicians screen patients simply to prevent themselves being sued in the future if they miss a diagnosis) or physician financial bias, where physicians who stand to make financial gain as a result of performing screening tests (sadly) advocate large population screening protocols in order to make a personal profit from them. Screening creep is when over time recommendations for screening are made for populations with less risk than in the past, until eventually the cost/benefit ration of doing them becomes less than marginal, but they are continued for the same reasons as for overscreening. Diagnostic creep occurs when over time, the requirements for making a diagnosis are lowered with fewer symptoms and signs needed to classify someone as having either an overt disease, or when folk are diagnosed as having a ‘pre-clinical’ or ‘subclinical’ disease. Patient demand is when patients push for screening of a disease or disorder themselves after hearing about them and being concerned about their own or their family’s welfare. All of these contribute to making the implementation of a particular screening program to be almost always a controversial process which requires careful consideration and an understanding of one’s own personal (often subconscious) biases when making decisions related to screening or not screening populations either as a clinician, health manager or member of the public.

Regarding specifically athlete screening, there is still a lot of controversy regarding who should be screened, what they should be screened for, how they should be screened, and who should manage the screening process. Currently, to my knowledge, Italy is the only country in the world where there is a legal requirement for pre-screening of athlete populations and children before they start playing sport at school (including not just physical examination but also ECG-level heart function analysis). In the USA, American Heart Association guidelines (history, examination, blood pressure and auscultation – listening to the heart with a stethoscope – of heart sounds) are recommended but practice differs between states. In the UK, athlete screening is not mandatory, and the choice is left up to different sporting bodies. In the Nordic countries, screening of elite athletes is mandated at the government level, but not all athlete populations as per what happens in Italy. There is ongoing debate about who should manage athlete screening in most countries, with some folk feeling it should be controlled at government level and legislated accordingly, other folk suggesting it should be controlled by professional medical bodies such as the American Heart Association in the USA or the European Society of Cardiology in Europe, while other folk believe it should be controlled by the individual sporting bodies which manage each different sporting discipline or even separately by the individual teams or schools that want to protect both the athletes and themselves by doing so. Obviously who pays for the screening factor is a large factor in these debates, and perhaps there is no unanimity in policy across countries, clinical associations and sporting bodies as described above, because of this.

The fact that there is no clear world-wide policy on athlete screening is on the one hand surprising, given the often emotional calls to enact it each time a young athlete dies, and also because the data from Italian studies has shown that the implementation of their all-population screening programs has reduced the incidence of sudden death in athletes from around 3.5/100 000 to around 0.4/100 000 (for those interested these data are described in a great study by Domenico Corrado and colleagues in the journal JAMA). But, the data described also suggests that there is a relatively low mortality rate to start with – from the above figures of 100 000 folk playing sport, only 3.5 of these died when playing sport before the implementation of screening, and a far higher number of folk die each day from a variety of other clinical disorders. The number of folk ‘saved’ is also very small in relation to the cost – a study by Amir Halkin and colleagues calculated that based on cost-projections of the Italian study, a 20 year program similar to that conducted by the Italians over 20 years of ECG testing of young competitive athletes would cost between 51 and 69 billion dollars and would save around 4800 lives, and the cost therefore per life saved was likely to range between 10 and 14 million dollars. While each life lost is an absolute tragedy both for that person and their family and friends, most lawmakers and government / governing bodies would surely think very carefully before enacting such expensive screening trials, with such low cost/benefit ratios, again with high burdens of other diseases that require their attention and funds on a continuous basis to be managed in parallel with athlete deaths. So from this ‘pickup’ rate and cost/benefit ratio perspective one can see there is already reason for concern regarding the implementation of broad screening trials for athlete populations.

Of equal concern is that of the level of both false negative and false positive tests associated with athlete screening. False negatives occur when tests do not pick up underlying abnormalities or problems, and in the case of heart screening, if one does not include ECG evaluation in the testing ‘battery’ there is often a high rate of false negative results described for athlete testing. Even using ECG’s are not ‘fail-proof’, and some folk advocate that heart-specific testing should include even more advanced testing than ECG can offer, including ultrasound and MRI based heart examination techniques, but these are very expensive and even less cost effective than those described above. False positives occur when tests diagnose a disorder or disease in athletes that is not clinically relevant or indeed does not exist. In athletes this is a particular problem when screening for heart disorders, as doing exercise routinely is known to often increase heart size to cope with the increased blood flow requirements which are part of any athletic endeavour, and this is called ‘athlete’s heart’. One of the major causes of sudden death is a heart disorder known as hypertrophic cardiomyopathy, where the heart pathologically enlarges or dilates, and it is very difficult to tell the difference on most screening tests between athletes heart and hypertrophic cardiomyopathy, with several folk diagnosed as having the latter and prevented from doing sport, when their heart is ‘normally’ enlarged rather than pathologically as a result of their sport participation. A relevant study of elite athletes in Australia by Maria Brosnan and colleagues found that when testing them using ECG level heart test, of 1197 athletes tested, 186 of these were found to have concerning ECG results (in their studies using updated ECG pathology criteria this number dropped to 48), but after more technically advanced testing of these concerning cases, only three athletes were found to have heart pathology that required them to stop their sport participation, which are astonishing figures from a potential false positive perspective. Such false-positive tests can result in potential loss of future sport related earnings or other sport participation related benefits.

Beyond false-negative and false-positive tests, there are a number of other factors which ensure that mass athlete screening remains controversial. For example, Erik Solberg and colleagues reported that while the majority of athletes were happy to undergo ECG and other screening, 16% of football players were scared that the pre-screening would have consequences to their own health, while 13% of them were afraid of losing their licence to play football, and 3% experienced overt distress during pre-screening itself because of undergoing the tests per se. The issue of civil liberties versus state control therefore needs to come into consideration in debates such as screening of athletes as a ‘blanket’ requirement if it is enacted. While most athlete screening programs and debate focusses on heart problems, there are a number of other non-cardiac causes of sudden death in athletes, such as exercise-induced anaphylaxis (an acute allergic response exacerbated by exercise participation), exercise-associated hyponatremia, exertional heat illness, intracranial aneurysms and a whole lot of other clinical disorders, and the debate is further complicated by whether these ‘other’ disorder should be included in the screening process. Furthermore, most screening programs focus on young athletes, while a large number of older folk begin doing sport at a later age, often after a long period of sedentary behaviour, and these older ‘new’ or returning sport enthusiasts are surely at an even higher risk of heart-related morbidity or mortality during exercise, and therefore one needs to think of whether screening should incorporate such folk too. However, whether there should be older age specific screening for a variety of clinical disorders is as hotly debated and controversial as it is young athlete screening, and adding screening of them for exercise specific potential issues surely complicates the matter to an even greater degree, even if an argument can be made that it is surely needed.

In summary therefore, screening of athletes for clinical disorders that may harm or even kill them during their participation in the sport they perform is still a very controversial area of both legislation and practice. There is an emotional pain deep in the ‘gut’ each time one hears of someone dying in a race, and a feeling that as a clinician or person that one should do more, or more should be done to ‘protect them from themselves’ using screening as the tool to do so. But given the low cost/benefit ratio from both a financial and ‘pickup’ perspective, it is not clear if making a country-wide decision to conduct athlete screening is not an example of both screening and diagnostic creep, or if athlete screening satisfies Wilson’s criteria to any sufficient degree. If I was a government official, my answer to whether I would advocate country-wide screening would be no based on the low cost/benefit ratio. If I was a member of a medical health association, to this same question I would answer yes, both from an ethical and a regulatory perspective, as long as my association did not have to foot the bill for it. If I was head of a sport governing body, I would say yes to protect the governing body’s integrity and to protect the athletes I governed, as long as I did not have to foot the bill for it. If I was a clinical researcher, I would say no, as we do not know enough about the efficacy of athlete screening and because there is a too high level of false-positive and false-negative results. If I was a sports medicine doctor I would say yes, as this would be my daily job, and I would benefit financially from it. If I was an athlete, I would be ambivalent, saying yes from a self-protection perspective, but saying no from a job and income protection perspective. If I was the father of a young athlete, I would say yes, to be sure my child is safe and would not be harmed by playing sport, but I would also worry about the psychological and social aspects if he or she was prohibited from playing sport as a result of a positive heart or other clinical screening test. It is in these conflicting answers I myself give when casting myself in these different roles, to which I am sure if each of you reading this article answered yourself would also similarly give a wide array of different responses, is perhaps where the controversy in athlete screening originates and what will make it always contentious. I do think that if as a newly qualified clinician back then in our paddling days, if I had tested my great friend Daniel Conradie’s heart function and found something that was worrying and suggested he stop paddling because of it, he would probably have told me to ‘take a hike’ and continued paddling even with such knowledge. I am sure as a young athlete I would have done similar if someone had told me they were worried about something in my health profile back then but were not one hundred percent sure of it having a negative future consequence on my sporting activity and future life prospects. Athlete screening tests and decisions related to them will almost always be about chance and risk, rather than certainty and conclusive determination of outcomes. To race or not race, based on a chance of perhaps being damaged by racing, or even dying, given the outcome of a test that warns you, but may be either false-positive or false-negative, that is the question. What would you do in such a situation, as an athlete, as a governing body official, or as a legislator? That’s something to ponder that doesn’t seem to have an easy answer, no matter how tragic it is to see someone young dying while doing what they love doing best.


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