Investigating Biomechanical Causes of Slipped Capital Femoral Epiphysis - Case Study Example

The Investigation of the Biomechanical Causes of Slipped Capital Femoral Epiphysis. Introduction Diagram to show the difference between a normal hip and one with a slipped femoral epiphysis in an older child , patient.co.uk, 2016 This essay will consider the biomechanical cause of slipped femoral capital using a literature search to investigate this, looking at various appropriate pieces of academic and scientific writing. The topic, sometimes referred to as ‘Slipped capital femoral epiphysis ( SCFE) , may otherwise be described as a slipped upper femoral epiphysis, (SUFE). Either term can be used to refer to a fracture passing through the growth plate or physis of the femoral head, which then leads to a slippage of the epiphysis. According to Thacker and Clarke ( 2015) the phenomenon is misnamed, as the epiphysis is held in place within the bowl of the acetabulum by the ligamentum teres. The metaphysis actually moves both anteriorly and proximally, while the epiphysis stays within the acetabulum. Slipped capital femoral epiphysis (SCFE) was described firstly by Ernst Müller ( 1926). He referred to it as ‘Schenkelhalsverbiegungen im Jungesalter’, which can be translated as “bending or bowing of the femoral neck in adolescence”. The growth plate is still actively present into late adolescence, a time when the body is developing. In this condition, the difficulty occurs in the upper area (MedLinePLus, 2016). At its most basic the epiphysis and the diaphysis of the femur, the areas above and below the growth plate, have moved, or slipped, from their normal position in relation to each other ( Patient, page 1, 2013). The femoral epiphysis remains in its usual place within the acetabulum, while the metaphysis, the end of the femur, rotates externally and moves, most often, in an anterior direction. Patient ( 2013) gives the epidemiology of this condition in some detail, and state that it occurs in only 1 in 10,000 people each year. Loder (1998) states that he found it occurring bilaterally in 40 % of cases. Later, in 2003, Loder et al linked the condition to having a deeper acetabulum. These researchers state that it has been postulated that having a deeper acetabulum leads to an increase in the shearing forces placed on the proximal femoral physis and so results in a higher incidence of SCFE. Song et al , ( 2009) writing about the situation in Korea, state that it occurs much less frequently in non-western countries ( Amara et al, page 1, 2015), although this situation is changing, as childhood obesity rates rise. The increased weight causes an abnormally high mechanical load across the proximal femoral physis. It most commonly affects boys aged between 11 and 17, with a peak at the age of 13, although (Rajan et al, 2003) it can occur as early as only three years of age. Some researchers claim that three times as many boys as girls are affected. In girls it tends to occur at a slightly younger age, with a peak at 11 years 6 months, often two years earlier than in their male peers ( Rajan et al, 2003), presumably because this is when they experience their adolescent growth spurt, as described by Loder ( 1998). Amara et al ( page 1, 2015), looking at the more severe slips, give an average age of 13 among the 186 patients they followed up, with only slightly more males than females (58.7 %). For some as yet unknown reason the left hip is affected more often than the right, although in up to 40% of cases it can be both sides which are affected, although one side may develop problems before the other. Paulis et al (2013), who looked at more than 40 different studies of children, found clear links between childhood obesity, even in quite young children, and a number of skeletal problems. There was a clear association between increased BMI and musculo=skeletal problems in this very large cohort. Krul et al ( 2009) were among a number of research groups who came up with similar findings. Among young people in adolescence SCFE is the commonest of hip disorders, especially among overweight males, and is commoner in black males, and in Pacific Islanders than in white ones, perhaps possibly because of increased body weight among these populations ( Peck, 2010). Walter and Young ( 2016), would agree, but also report a higher rate among Hispanics in America, than among the white population. It can occur without any history of trauma. The result of such a slip is a painful limp, often developing gradually and progressively. There is a limitation to hip movement, stretching is difficult and the problem becomes worse if there is strenuous activity, and abnormal movement of the limb becomes obvious. According to Patient (2013) in 90% of cases the joint remains stable and the affected person can still walk. In 10% of cases the injury is unstable and the person cannot walk, even if crutches are used. Also (Loder 1998) they have a higher chance of developing avascular necrosis, than in those whose slips are stable. Amara et al ( 2015) who looked at the most severe cases, found in their research that only 50.5% of the joints were stable, and 49.5% were unstable, so it seems that the likelihood of stability can be linked to the degree of severity. Patient ( 2013) go on to list a number of factors which increase the risk of occurrence. These include mechanical reasons such as localised trauma and obesity, these being commoner causes, but would also include non-bio-mechanical causes such as having inflammatory conditions such as septic arthritis or having one of a number of conditions which affect hormonal levels such as hypothyroidism, growth hormone deficiency, hypopituitarism pseudohypoparathyroidism or a vitamin D deficiency. Earlier radiation of the pelvic area may be a precipatory factor, as may having renal osteodystrophy-induced bone dysplasia. Presentation will to some extent depend upon the degree of the slippage. There will be discomfort in the region of the hip, the groin, the medial thigh or even the knee, as this has been referred to from the hip ( Loder (1998). Pain occurs when walking. Failure of the proximal femoral physis brings about an obvious deformity, with both posterior and medial displacement of the proximal femoral epiphysis. If the person involved can carry out more extensive exercise, such as running or jumping, or carrying out movements which include pivoting, the result will be increased pain. Pre-slip there may be slight discomfort. In cases of acute slippage pain may be severe enough to prevent walking, or even standing on the affected leg. Alterations in the gait, with a limp on the side which is affected, will be accompanied by external rotation of the leg, and a trunk shift. Hip motion will be limited, especially if the child tries to rotate his leg internally or to abduct this leg. In other cases, described as ‘Acute-on-chronic’ ( Patient, page 2, 2013) there may have been some pain, an alteration in gait and a limp for some time, perhaps over several months. The degree of pain experienced will suddenly increase considerably. In chronic cases symptoms are mild, although there may be changes in the gait. In a few cases the only symptom reported is knee pain, and there is a degree of external rotation when walking. When the leg is flexed up, the hip tends to move towards an externally rotated position. On examination some shortening of the leg can be observed, and a degree of atrophy of the thigh muscle may be noted. This is a relatively rare condition, possibly only once in 100,000 young people, so few general doctors will see more than one or two patients during their working lives, (Upglow and Clarke, 2004,page 631), so the more that is known about it the better, including such things as how it can be diagnosed and treated, so that these doctors will know how to intervene and their patient’s problems can be relieved appropriately. This essay will consider research into the condition and its treatment, but seeks to see if obesity, or some other cause, is the major factor in its development. A number of causes for slipped capital femoral epiphysis have been suggested, but the causes are not entirely understood. A literature search will be carried out, using relevant search terms such as slipped capital femoral, SCFE, and SUFE. Articles will be in English as far as possible, or are an accurate translation, and will be considered for their relevance, and the scientific rigour of the data. Articles will be topical as far as possible, although at times it is necessary to cite earlier research. The data in such articles will be considered together with the various arguments, and whether the researchers agree with each other, or perhaps come up with different ideas. The condition can occur in other mammals, but this essay will in the main consider human situations. It will at times be necessary to cite older papers as these are cited by various authors, as well as showing how there are measurable differences over time as some countries become more westernised, including in dietary terms. In considering a wide variety of texts it was found there were a variety of emphasises in many papers. Some concentrated upon causes, while others looked at the processes involved and yet other papers were mostly concerned with treatment. It is clear from considering their various reports that the condition is still not clearly understood ( Rajan et al , 2003). Some papers considered the results from only one centre, whereas others looked at those from many different centres, so considering many hundreds of cases. Because there is no one agreed and definitive cause, this can make it harder to diagnose the condition, or to prevent it worsening or occurring in the other hip. Amare et al (page 1, 2015) point out how there are a variety possible treatments, many of which are linked to perceived causes, and that some of these could be considered controversial, perhaps unproven, by some members of the medical fraternity. Thacker and Clarke ( 2015) concluded that in the vast majority of patients, the exact cause is unknown, though having a deep acetabulum is mentioned by some authors such as Podeszwa et al (2012) , but there are also atypical slips which can be associated with such things as non-mechanical causes such as known endocrine disorder, with osteodystrophy, with renal failure, or which occur in those who had previously undergone radiation therapy. In the main this essay will concentrate upon biomechanical causes . Song et al ( 2009) looked at data from 19 hospitals across Korea ,considering such things as the person’s age at the onset of the condition, their sex and their past medical history as well as their height and weight and the type of slippage experienced. These researchers describe how the condition was almost unknown in Korea before 1979, but has been increasing slowly in rates of occurrence ever since that time, although the rate remains lower than in western countries and that reported from Japan. They do however add the caveat that in 1988 national health insurance became open to all Koreans, and also state that better access to care and more accurate diagnosis were also to be considered. Despite this they link the rise in numbers with increased body mass index, as BMI was higher in the group with the condition than the mean for their peer group. In 2004 Upglow and Clarke considered the management of this condition. They state that there is some controversy about which treatment which is the most effective in the more extreme cases, although for most a simple cannulated screw can be used to fix the problem. The controversy arises as to when in the process is the optimum timing for such an intervention. They discuss the problem of missed or late diagnosis, as a child may complain of pain elsewhere in their limb, rather than actually in the hip joint.. This means that a correct diagnosis is initially missed, which results not only in delays in treatment, but in many cases also means that the condition worsens in the meantime. If causes were better understood this would presumably be less likely to occur. Kendig et al ( 1993) had described how accurate diagnosis could be difficult, and it is true that many papers have been written about missed diagnosis in this condition, something which can often result in a greater degree of slippage ( Causey et al, 1995) . Upglow and Clarke ( 2004) state that delay in diagnosis brings about the worst outcomes, whether the fracture is stable or unstable, that is whether or not the patient can bear weight on the joint. Yet it seems that some delay happens in the majority of cases according to the figures supplied by Upglow and Clarke ( 2004, p231). Patient ( 2013) give statistics on the final outcome or prognosis ,which depends upon the initial degree of slippage and early diagnosis. In 94-96% of cases outcomes are good if there is less than one third of the diameter of the femoral neck involved in the displacement. As the degree of displacement increases complications are more likely to occur and can happen in as many as 45 % of cases. Another consideration is making a differential diagnosis in order to arrive at the correct one, , so excluding conditions such as osteomyelitis; septic arthritis; an acute fracture of the hip; Perthes’ disease (a condition in which the head of the femur becomes soft and its tissues break down) and conditions such as acute transient synovitis. The differentiation into various degrees of slippage , as described by Southwick (1967), is mentioned. Patient ( 2013, page 1) classifies four types: -Pre-slip, that is where there is a wide epiphyseal line without slippage; Acute form, where slippage occurs suddenly, normally occurring apparently spontaneously.; Acute-on-chronic is when slippage happens acutely in cases where there is an existing chronic slip;. Chronic ,with a steadily progressive slippage is the commonest type. Upglow and Clarke( 2004, page 235) conclude that screw fixation in situ is the commonest procedure for most people, but the rarer unstable ,and also more severe, slips can be problematic. Zilkins et al ( 2010) however describe how avascular necrosis of the epiphysis and other complications can occur if patients are operated upon. They also describe long term problems such as loss of function and degenerative disease of the affected joint. Zilkins et al ( 2010, p. 1009) mention a number of possible surgical interventions which depend to a large extent upon the degree of slip experienced. Walter and Craig ( 2015) point out that this is not a condition, however slight it is considered to be, in which there is a case for merely observing it , or for attempting closed reduction. Mozzanum et al ( 2012) concentrate not so much on solutions as the causes. They looked at up to date radiographic studies which showed that, despite earlier studies which seemed to show normal acetabulas, many cases showed retroversion of the acetabulum and also an increase in superolateral coverage of the femoral head, as supported by the findings of Chung et al as long ago as 1976. Despite these findings however Mozzanum et al state that it is still not clear as to whether this situation is because of ‘primary abnormal morphology’ ( Mozzanum et al,page 2145, 2012), or is the cause some secondary pathology as a response to an as yet unknown cause. In 1976 for instance Chung et al concluded that the causes were mechanical in obese children stating that :- The forces necessary to cause slipping were found to be within the physiological range of the force that would be generated in overweight children, suggesting that purely mechanical factors may play a major role in the etiology of slipped capital femoral epiphysis. Since 1976 the rate of children with obesity aged 12 or more has tripled ( NIH, 2013) despite attempts to prevent this by various governments , such as that in the U.K. (Gov UK, 2013 onwards) . Such obesity, once established, is highly likely to continue and remain in adult life, and leads to an increased risk of developing heart disease, becoming diabetic, and is linked to several other conditions, including certain types of cancer. This interest by Mozzanum et al ( 2012) in the retroverted acetabulum as a possible cause is also reflected in the paper by Bauer et al ( 2013). These authors also looked at problems with the femoral head and they concluded that a deformity of the neck of the femur after a SCFE results in a decrease in the angle of the in the head neck junction. Such changes cause articular cartilage damage, as well as labral pathology. They go on to say that any retroversion of the acetabulum has been linked to hip pain . This means that the alignment of the mouth of the acetabulum is not within the parameters of the normal anterolateral direction, but slopes more posterolaterally (Reynolds et al, 1999), and also mentioned by Podeszwa et al (2012) among others, including Gelberman et al in 1986. Bauer et al ( page 91, 2013) found that in 82 % of unilateral cases the involved hips showed at least one indication of retroversion. The opposite, uninvolved hips also, in 76% of cases, demonstrated one or more indications of retroversion or tipping backwards from what is considered the normal position. These authors cite research by Leunig et al ( 2000), who showed that the femoral metaphysis after a SCFE closely borders the acetabular rim, and causes a degree of damage to both the acetabular cartilage and also the labrum, a ring of cartilage which goes around the outside rim of the hip socket. Such findings mean that, when treatment is considered, it is necessary that clinicians are aware of any acetabular morphology, as a result of biomechanical action, which may be present, both in the involved and in the opposite uninvolved hips. Dodds et al ( 2009) attempted to determine whether or not the severity of the slip which has occurred would go on to determine the likelihood of such damage from impingement in later life. They concluded that, because there are no radiographic indicators which could predict the future onset of femoroacetabular impingement, then hips which had not been pinned prophylactically should be followed up into adulthood and monitored for any impingement. They felt that the severity or not of the slip could not be accurately be used as a predictive tool for the later onset of femoroacetabular impingement. In their particular study, which involved 49 Irish patients ( 65 hips) , considering these cases retrospectively , these researchers found that in no pre-slips or in prophylactically pinned hips, there was an absence of clinical impingement at the time of their review. Podeszwa et al (2012) were concerned in the main with causes, and looked at another aspect of this problem, considering how the depth of the acetabulum had an effect upon physeal or growth plate stability in cases of slipped capital femoral epiphysis. A deep acetabulum was defined by these authors as one in which:- The medial edge of the acetabulum (coxa profunda) or the medial edge of the femoral head (acetabular protrusio) was touching or crossed the ilioischial line. (Podeszwa et al (page 2152, 2012). This group of researchers considered the following questions:- • What is the prevalence of a deep acetabulum in cases of slipped capital femoral epiphysis? • Is the presence of a deep acetabulum associated with physeal instability? • Is the presence of a deep acetabulum associated with the occurrence of a contralateral, slipped capital femoral epiphysis? That is to say, is the presence of a deep acetabulum in one hip linked to the occurrence of a slipped capital femoral epiphysis on the other hip? They attempted to answer these questions by considering retrospectively some 232, mostly male, patients who presented in the first instance with a unilateral slipped capital femoral epiphysis, and who later developed a problem on the other side. They point out that, although causes are not entirely understood, abnormal mechanical forces, such as obesity, which act across the femoral epiphysis have been shown to be potentially a contributory factor, as described by Bhatia et al in 2006. Podeszwa et al ( 2012) found that on the whole females tended to have deeper acetabula. These researchers considered preoperative radiographic parameters; the stability of any slip, the progress towards a contralateral SCFE. Also taken into account were demographic factors such as age and sex which were then compared between patients with and without deep acetabula. They concluded that having a lower body mass index and a higher degree of lateral centre-edge angle and slip angle were found to be associated with a deep acetabulum, and that a deep acetabulum was commoner among those patients with an unstable SCFE. Rajan et al ( 2003) state that:- The shape of the physis lends a certain amount of stability to resist sheer forces across it, including the interlocking effect of the zone of provisional ossification, the concave shape of the epiphysis and the perichondral fibrocartilaginous ring complex around the physis itself. It seems that, in a high number of cases, obesity overcomes this natural stability. Obesity in young people is of course associated with a number of possible co-morbidities. Public Health England (2016) lists these as :- • Type 2 diabetes • Asthma • Obstructive sleep apnoea • Cardiovascular problems • Psychological risks as well as musculo -skeletal problems which would of course include hip problems. Yamaki et al ( 2011) would extend this list to as many as 15 issues, which they say are related to childhood obesity. Riad et al ( page 411, 2007) were concerned with preventing contralateral slips. They had the aim of determining significant predictors for the later development of a contralateral slip in young patients presenting with an already established unilateral SCFE. They were also seeking to study the incidence of complications such as avascular necrosis, because the slippage has resulted in the blood supply to the bone being cut off, and also chondrolysis, that is the breakdown and then eventual disappearance of the articular cartilage ( Painpump.net, 2016). If this occurs it will then lead to a narrowing of the joint space, which can be seen radiographically, and an accompanying restriction of motion in the joint, as well as considerable pain. Riad et al, (2007) saw the chronological age of patients as being a definite factor when considering it as a predictor of having a second slip on the other side in patients presenting with unilateral SCFE. They felt that this was such a strong link that they recommended strongly consideration of prophylactic treatment, using screw fixation, of the as yet unaffected hip in girls who present when still under 10 years old, and in the case of males, in those who present when still under 12 years old. This is done widely throughout Europe, despite the possible risk of a surgical intervention for something which has not yet occurred ( Riad et al, page 411, 2007), but Walter and Craig, ( 2015) suggest a more individualised treatment, which considers both the risks and the benefits of treating a ,as yet unaffected, hip. Riad et al ( 2007) concluded that a number of factors could be involved in any slippage, and that these factors:- sex; age; race, bone age ( that is the maturity of the bones); obesity and atypical slips, could be used for predicting the risk of contralateral involvement. Of these age was one of the strongest predictors for the development of a contralateral slip, as they found that among girls aged less than 10 and boys of 12 and under, if one hip was affected then they invariably would also have problems with the second hip. There could be other problems as a result, as Amara et al ( 2015) point out, linking it to the development of necrosis and osteoarthritis, although Walter and Young, ( 2015) consider that treatment carried out effectively could present these problems from occurring . In 2010 Shank et al considered valgus slipped capital femoral epiphysis, that is ones in which the slip is turned outwards, away from the central line of the body. Such cases were identified radiographically to show an increase in the prominence of the lateral femoral epiphysis in relation to the lateral femoral neck. This was accompanied by an increase in the anteroposterior physis shaft angle. In most young people with SCFE, the capital femoral epiphysis undergoes posterior and medial displacement relative to the femoral neck. Muller ( 1926) was the first clinician who described a patient who was found to have posterior and lateral displacement, and it was he who introduced the term valgus SCFE, the opposite of varus, which is when the displacement is turned inwards towards the centre line of the body, the more common occurrence according to Rajan et al (2003).Muller describes the situation of valgus in young people who already had acetabular dysplasia, that is some abnormality of the hip joint anatomy This particular version of the condition was found by Shank et al ( 2010) in 4.7% of their patients, so it affects only a tiny minority, usually of slightly younger patients. Of the 12 patients found ( out of 258 ) , with some having both hips affected, despite the mechanical problems which result, four of them were found to have a dysfunction of the pituitary gland and of the production of growth hormone. Another patient was found to have Stickler syndrome, a rare genetic condition which, among other symptoms, can cause joint problems, but which affects only one in 9,000 new born infants ( Genetic Home Reference, 2016) . Loder et al ( 2006) stated that it was necessary to be aware of the presence of valgus, both in order to diagnose accurately, and also in order to decide and carry out the most suitable treatment for each patient. Among 105 children diagnosed these researchers found some cases where the amount of slippage could not be ascertained , but they did find 91 mild slippages, 34 moderate, and 8 with severe SCFEs The type of SCFE was known in 12 instances - there were 85 chronic, 28 acute, 3 children were asymptomatic bilaterally, and 9 still in preslip. 122 slips were stable and 12 unstable. Four children were found to have 7 stable valgus SCFEs. Other groups would find slightly different figures. Shank et al ( 2010) also link this particular condition to childhood obesity, as do other researchers looking at other versions of SCFE. So we have a number of possible mechanical causes related to higher than average B.M.I., sex; age; race, bone age, valgus which is associated with an increase in the anteroposterior physis shaft angle, which has been linked to an abnormality of the hip joint. In some cases it is a hormonal or genetic condition which has caused the changes which then result in a mechanical slippage. This condition, although still relatively rare, especially in non-westernised societies, is found in increasing numbers as time goes on. Although a large number of papers were considered , from many sources, including non-western ones, not all parameters were included for each patient in each paper, which at times makes valid comparisons difficult, or even impossible to arrive at with great accuracy. As Amara et al said ( 2015) the conclusions of the various studies cited above are varied. On the other hand, as modern imaging techniques have developed it has become easier for the medical fraternity to see and to understand the mechanics of this condition. This then should make it easier for them to work out the best ways to deal with it in individual cases. Although mainly occurring in young people who are overweight, this is obviously a very variable condition, which has a number of causes, mechanical and otherwise, as well as a variety of solutions, as can be seen in the descriptions detailed above. In some cases the cause can be linked to the most appropriate treatment for individuals. It is clear however that it still is not always possible to be exact as to causal factors, although in many cases the condition is definitely linked to childhood obesity, an increasing problem in westernised societies. This , adversely affects the body’s mechanics, as well as causing other comorbidities, which may be very serious. In some cases there are hormonal or other causes, including genetic ones, but it is clear that obesity is the overruling link, that is having a BMI in the top 5 % (Centers for Disease Control and Prevention, 2015). So it seems clear that this not just a surgical problem. There needs to be a concerted effort by wider society to deal with the increasing problem of childhood obesity, which has many other negative effects which could affect the individual’s health adversely throughout their life, limiting their opportunities, costing large amounts and resulting in a poorer life style. This will involve changes on both an individual and family level, but also will involve such things as education on healthy eating, government policies, and agencies such as schools which provide meals for pupils, some of which is already ongoing. References Images. 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