Sports Injuries

Chiropractic injury specialist, Dr. Alexander Jimenez examines a preventive injury approach based on the very best of what's known.

In sports medicine, there's not any tougher challenge than hamstrings -- often our most commonly seen injury, as well as uncomfortably significant re-injury rates. With a growing amount of research in this area(6), this is a good time to bring the literature together and invent an evidence-based method of preventing hamstring injury and recurrence.

Risk Factors

The logic of identifying risk factors is to modify these so as to decrease injury levels. We will need to know not just which factors are risky, but just how they influence harm.

Modifiable Factor 1): The Hamstrings

Powerful recent evidence implicates strength shortages as a pre-disposing factor for hamstring injury. The imbalances usually analyzed are: hamstring to quad (H:Q); eccentric to concentric (E:C); and side to side (S:S). By comparison, the demand for hamstring flexibility is much less apparent in the signs.

Since 2008 a number of isokinetic strength studies, such as a very large one, have shown isokinetic strength shortages to be predictive of hamstring injury. Back in Hong Kong, athletes using a diminished H:Q had 17 times increased risk of hamstring injury (8) and in elite Japanese sprinters S:S weakness has been correlated with hamstring injury(two).

One of 462 Belgian soccer players, the injury rate was considerably higher among gamers with isokinetic power imbalances, compared to those without(6).

Past injury is an integral factor (see below), and a study may help us to understand why. It reports that optimum length (ie, the best muscle length for active stress) has been found to be briefer in formerly injured muscles. Reduced/shorter 'optimal span' could perhaps predispose the hamstring to injury during eccentric loading in its outer variety (ie, once the muscle is nearing full stretch)(16).

The role of hamstring flexibility remains unclear: one study (Aussie Rules) revealed that sit-and-reach evaluation results didn't correlate with cerebral muscle injury(11). In a bigger Belgian soccer study, nevertheless, those injured had previously had considerably bad hamstring flexibility(17).

Modifiable Factor 2): Other Structures

One of Aussie rules players, too little flexibility in quadriceps(18) and hip flexors(19) has been predictive of hamstring injury. The same studies investigated restricted ankle dorsiflexion and concluded that this could have some relevance(19). I discuss this below.

Weak gluteals are implicated due to their job as concentric hip extensors. It has been proven that sprinters with S:S fatigue in concentric hip expansion were more prone to hamstring injury on the weak side(two). Equally all pelvic muscles help to maintain pelvic stability and hence reduce injury threat(41).

Non-Modifiable Risk Factors

Although the following factors are unalterable, it makes great sense to consider these when targeting particular players for preventive programs, especially in the event that you don't have access to expensive and time consuming isokinetic testing.

Two studies found the best risk factor for a previous posterior thigh injury (12) or a past history of hamstring injury (19). This goes some way to describing recurrence rates touching 40% in 1 study(3).

Some studies confirm that age is a factor, with older players at elevated risk(12,19,18,1). Players of black cultural origin(1) and Aboriginal descent(12) have been demonstrated to be more than averagely vulnerable.

If, for instance, you're responsible for a black 29-year-old participant with a hamstring injury background, you'll have both rationale and evidence to direct your use of a preventive program with that individual.

Mechanism Of Injury

To examine more precisely the mechanism of harm, we must consider the part of the hamstring muscle. Injury generally occurs in a sprinting scenario. Quick active extension of the knee requires the hamstrings to act eccentrically to decelerate the late swing-phase; but then they have instantly to change to concentric loading during early stance phase, where they behave as hip extensors(20). This stage sets the hamstrings in their outer range, in the very moment they have to make the greatest effort. Fig 1 (below) helps illustrate how these risk factors interact.

The eccentric action of the sprint creates very high intrinsic forces at the hamstring muscles(8). If at any stage the load exceeds the mechanical limit tolerated from the muscular unit, this will cause collapse(6) -- probably to be the result of excessive fibre stretch during a lengthening contraction(15). And the faster the exercise speed, the higher the eccentric torque created (22). Therefore it appears that hamstrings are hurt during eccentric contraction at the late swing phase of sprinting(48).

Most injuries include the biceps femoris muscle(1,47). This might be because at sprints of 80 percent to 100% of high speed, summit lengths are significantly longer and occur later than in another hamstring muscles(23). In this last period of gait, a high-force stretch-shortening cycle happens, and the hamstring unit relies on its non-contractile component to absorb, then generate force(22,24).

We can now start to learn the way the reduced isokinetic strength profile could cause hamstring overload and injury.

Hamstring flexibility becomes an issue if you regard that harm happens in late swing/early posture stage, once the muscle is lengthened. Logically, a short muscle must invest additional time in its outer range (ie, slightly lengthened under pressure) so as to come up with a typical powerful stride length. This places the lengthened hamstring under more stress and might explain why short hamstrings can be prone to trauma(17). In the exact same way that 'optimum length' (the muscle's optimal length for active tension) is found to be shorter in previously injured muscles (see above), this decreased length could also predispose the hamstring to injury in the exact situation(16).

The Fatigue Factor

And here is something you may discover surprising: there's a strong rationale and a few evidential back-up to imply that both general aerobic and particular hamstring endurance operate are strongly implicated in injury.

Hamstring injuries are most frequent during rivalry(1), even when effort should be at its highest. It is well known that in football a significant increase in injury is observed toward the end of each half(1). This may well be explained by the reduction in bizarre hamstring torque generation and operational power ratio -- caused by fatigue -- which players tend to suffer from at the conclusion of football halves. The angle of peak torque generation increases significantly (ie, the best length gets shorter) as every half goes on(42). Other factors include:

• Muscle elasticity (which buffers the muscle fibers) reduces with length(48)
• Fatigued muscles consume less energy before they fail(26)
• Hamstrings fatigue comparatively faster than their antagonist, which will affect the H:Q ratio adversely(27).

Place this lot together in plain English and also you get a hamstring muscle that, as exercise duration raises, is weakening relative to its antagonist, and getting unable to create and absorb as much pressure in its own exposed selection. We know that sprint times slow and stride lengths shorten as exhaustion sets in(43). Therefore any athlete lacking endurance will put their hamstring at a compromised position. To now demand high rates and stride lengths can only risk injury.

It's A Multi-Factorial Thing

Fatigue is not likely to be the sole factor in play. Here are some other prime contributors to injury:

Hip flexor length is as important as hamstring length(48). The two rectus femoris and hip flexors can anteriorly rotate the pelvis. In late-stance stage, brief contralateral (opposite side) hip flexors will rotate the anus relatively anteriorly; and in late-swing phase the ipsilateral (same-side) leg will need to stride somewhat further to generate a normal powerful stride length. This will place the hamstring further into its vulnerable outer range.

Similarly, a lack of dorsiflexion in the contralateral ankle during mid- to late-stance phase may limit a normal stride length -- again, causing the ipsilateral leg to over-stride. I've seen this in a young player with no history of hamstring injury who returned to play after a significant ankle injury, which had left him having significantly reduced dorsiflexion. On his return, this player, once worried (two matches in four days, as needs must), proceeded to severely rip his contralateral hamstring.

The glutes play a twofold function. Primarily, neuromuscular control of the pelvis may permit the hamstrings to operate at safe spans(41). As posterior rotators of their pelvis, contralateral gluts control (ie, limit) anterior rotation in late stance phase, thereby helping to normalize ipsilateral stride length.

Secondly, the glutes can act as synergists to the concentrically behaving hamstrings during early stance phase. It's been shown that concentric hip extensor weakness could induce a player to hamstring injury (two). So it can be that more powerful and more effective glutes will float the hamstrings at this point.

Abdominal muscles are rarely mentioned from the hamstring injury literature, but no doubt that they play a part. As controls of pelvic rotation (combined with glutes), they could reduce anterior pelvic tilt and the negative effect of tight hip flexors and low back muscles.

In summary, whatever regulates anterior pelvic rotation will help normalize stride length in late swing phase, which shields the hamstrings by maintaining them functioning inside a positive range (41). And conversely, any compromise or compensation to attain, 'normal strong stride length' will place the hamstrings at a mechanical disadvantage, raising the probability of damage.

Interventions

Prevention is also, as always, the best medicine. And the key to an effective intervention would be to direct it to the right athletes, which means screening. There's both strong rationale and evidence to guide the screening procedure, which will in turn, guide your prescription. The time you save in not needing to train inappropriate players can then be spent with the 'at risk' players. Hamstring strength will be the mainstay of a prevention program.

One out of both match athletes will have significant isokinetic strength shortages(6). I talk below where to 'set the bar' for isokinetic screening, a 'poor man's' algorithm/rationale for strengthening, and the rationale for exercise selection.

Setting The Bar For Isokinetic Testing

How do you determine that athletes require a preventive intervention? Reports give a fairly confusing variety of outcomes. Most predictive studies indicate that a conventional (concentric: concentric) H:Q ratio of over 0.6 predicts injury. Actual figures include 0.6 , 0.61, 0.55, 0.47 and 0.57 or 0.55 (8,11,35,36,6).

Logically, the operational H:Q ratio (bizarre hams: concentric quads) should best reflect injury risk, provided that it examines the ability of the eccentrically acting hamstrings to decelerate the concentrically acting quadriceps in late swing phase(8), where trauma typically happens(48). It appears that if cut-off is put at 0.98 (biodex), athletes under this are 'in danger'(8,6). The Croisier study (level of evidence 1) also showed that using only the 0.6 conventional ratio can miss as many as 30 percent of imbalances. Croisier also showed that a functional ratio higher than 1.40 eliminated risk of trauma, so get your athlete on the weights!

The Croisier study used an imbalance of higher than 5% (between the 2 sides), though it accounts 10% and 20 percent being used in different research studies. 1 key point is that the further steps you use, the less chance of missing an in danger athlete. Consequently, if you place your cut-offs as follows...

• Conventional ratio 0.6
• Functional ratio 0.98
• Side-to-side gap 5%

...you need to catch your at-risk athletes. Two cautionary notes: optimal isokinetic ratios differ between sports, so every individual game might have to set its own cut-off points(29). And keep in mind that the modest but real danger of injury involved with isokinetic testing(30,6).

Poor Man's Assumption Algorithm

Without isokinetic testing, you could be able to reason (evidence-based) or make some assumptions about who to include in preventative strengthening applications, following the algorithm in Fig 2.

Testing Effectiveness

A study of English rugby players found that Nordic hamstring exercises reduced the incidence and severity of hamstring injuries(5). Two more research in football successfully utilized the same exercise to greatly reduce hamstring injuries in contrast to controls(3,34).

It appears that measuring the efficacy of the program does more than just demonstrate progress -- it may actually play a substantial part in consolidating advancement. Back in 2008 Croisier et al showed that by adjusting imbalances (as quantified by successive sessions of isokinetic testing) that they could decrease injury levels to people of players with no imbalances. However, if the isokinetic testing sessions were omitted, and the players were therefore unable to get objective feedback about attaining 'normalization' in their rehab attempts, their subsequent reductions in re-injury rates were not statistically significant.

These favorable studies simply looked at strength parameters. Is it possible that by fixing other particular individual risk factors, as mentioned above, we can yield even more beneficial effects?

Rehabilitate The Injury

Even the very best prevention approaches can't altogether banish hamstring injuries. With recurrence levels being so high(3,1,2,5), successful rehabilitation is an integral part of a prevention program. In most athletes with a history of injury, even when matched, the injured hamstring is still poorer(40,38)and 'optimal span' is shorter(16). So, again, it comes down to strengthening.

Thus, in 26 previously injured athletes, 18 were found to possess a power deficit; those 17 who successfully bolstered the hamstrings to rigorous parameters prevented any further injury during the next season(40).

Evidence of effective rehab also lends weight to the argument that hamstring span(17) and also poor spinal management(2,41,48) are risk factors. Athletes who did more stretching were discovered to have shorter rehabilitation times(39); apps that focused on improving neuromuscular control of the lumbopelvic region were more effective than conventional rehab alone (41).

Alongside rehabilitation, it needs to be ensured that the athlete is back to decent levels of fitness. As there are no consensus guidelines for this(45), it is useful to refer to this athlete's previous aerobic and rate testing scores. Early exhaustion arising from bad aerobic fitness can compromise hamstring muscle functioning(42,43) and place the hamstrings at a physiological disadvantage. Not only should an athlete test ordinary for speed, but as injuries occur at top speed (21), They should have trained at full speed to gain this specific training impact. Lastly, if at all possible, hamstrings should be tested isokinetically to make sure that sensible strength parameters have been reached(38).

The timing of return to competition must be the collectively agreed decision of all parties involved. When analyzing the risk/benefit profile of a recurrence, you want to think beyond simply the likelihood of a repeat accident. In a study of Aussie Rules players, participant performance upon return to game from hamstring injury (as assessed by the team coach) has been substantially reduced(44). It is very important that an athlete reach complete normal function when they should be expected to work well in competition.

And Another Thing...

We haven't yet mentioned the lumbar spine, sacroiliac joint, or adverse neural tension (ANT) as preceding and potentially predisposing a player to hamstring injury. A history of lumbar spine injury doesn't correlate to hamstring injury risk(12). After the concept, however, that anything which interrupts standard powerful stride length increases injury risk, a rigid or rotated pelvis (SIJ lumbar spine) or ANT leading to lack of flexibility in late-swing stage could be responsible.

Equally, any source of pain or aggravation of neural interfaces (by way of instance nerve roots, neural foramen, piriformis) that raised hamstring muscle tone would again set the hamstrings in a mechanical disadvantage. According to this understanding, one of our athletes went to Germany, where they had been exposed to 43 injections, therefore I for one hope the rationale holds good. With this luxury (and possibly even with it), the best expectation would be to improve lumbopelvic control, not only to safeguard the lumbar spine structures but also to unload the hamstrings.

Conclusion

Following this tour around the pelvis, to describe hamstring injury as multi-factorial seems understated. All players should undergo the identical screening and identification processes. But all prevention/rehab interventions need to be tailored to the patient so they target appropriate risk factors.

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BFR, or blood flow restriction training, has been utilized throughout a range of exercise modes. These include cycling, walking and strength training. When doing resistance training with blood flow restriction therapy, tight cuffs or pliers are commonly utilized.

Virtually, blood flow restriction training is most frequently employed when utilizing resistance training with low loads of around 20 to 30 percent of 1RM and with wraps that are wrapped at a perceived tightness of 7 out of 10.

When compression of the vasculature proximal to the muscles is achieved via other means, the expression blood flow restriction training is more commonly used. An alternative way of employing this pressure is through the usage of knee bends. This sort of blood flow restriction therapy can be termed blood flow restriction training that was sensible to distinguish it from the method in which inflated cuffs are utilized to produce a strain.

Chiropractor, Dr. Alexander Jimenez explores the advantages of using eccentric strengthening in rehab for a faster Return-to-play following severe hamstring injuries.

Sporting activities involving high demands of sprinting or excessive stretching (kicking, slipping, split positions) are found to affect the incidence of severe hamstring injuries. Hamstring injuries are varied in character comprising differing injury types, location and size. This makes recommendations concerning rehabilitation and prognosis about healing time plus return-to-play notoriously difficult. It's been suggested that reunite- to-play timescales change between 28-51 days after acute hamstring injuries based upon the biomechanical cause, site, and evaluation of soft tissue injury(1). However, this is a controversial issue, which this report will explore.

After a return to game, the probability of re-injury is high within the first 2 weeks(2). The causes are linked with first hamstring weakness; fatigue; a lack of flexibility, and a strength imbalance between the hamstrings (bizarre) and also the quadriceps (concentric)(2). The greatest contributory factor however, is believed to be an inadequate rehabilitation program, which coincides with a premature return to sport(3). More proof is now highlighting the advantage of mostly using eccentric strengthening exercises at hamstring rehab performed at large loads at more musculotendon lengths(1,4).

Semitendinosus (ST), they're involved with extension of the hip, flexion of the knee as well as providing multi-directional equilibrium of the tibia and pelvis. All 3 muscles cross the posterior component of the two hip and the knee joints which makes them biarticular. As a result, they need to continuously react to large mechanical forces created by upper limb, trunk and lower limb locomotion via concentric and eccentric contractions. These forces are greatly improved during athletic activity, which is a likely culprit due to their high injury frequency.

In a study at the University of Melbourne, biomechanical analysts quantified the biomechanical load (ie musculotendon strain, speed, force, power, and operate) experienced by the hamstrings across a full stride cycle during over-ground sprinting, as well as the biomechanical load across each person hamstring muscle(4).

Firstly, the hamstrings undergo a stretch-shortening cycle through sprinting, with the lengthening phase happening during the terminal swing and shortening phase commencing before foot attack, and ongoing throughout the stance. Secondly, the biomechanical load on the biarticular hamstring muscles has been found to be best during the terminal swing.

BFLH had the biggest peak musculotendon strain, ST demonstrated the best musculotendon lengthening velocity, and SM produced the greatest musculotendon force as well as absorbing and generating the maximum musculotendon power. This has ties in with other similar research, which divides peak musculotendon strain as a large contributor to eccentric muscle damage, ie hamstring injury, instead of peak muscle power(1); hence the recommendation of bizarre strengthening for acute hamstring rehabilitation.

Site Of Injury & Grading Classification

In a randomised controlled trial Professional Swedish footballers(1), the primary injury was situated in BFLH (69%). This contrasted with 21% of those players that sustained their principal harm within SM. It was common to maintain a secondary harm to ST in addition to BFLH (80\%) or SM (44%). A clear majority (94\%) of the most important injuries were discovered to be of the sprinting-type and were located in the BFLH, whereas, SM was the very common (76 percent) location because of the stretching- kind of harm. These findings were supported in another similar post(5).

Typically (see Table 1), classification for Acute soft tissue injury, such as hamstrings, has depended on a grading system of I (moderate), II (mild), or III (severe) (2,6,7). This classification is useful concerning coherent descriptions between different medical staff members during clinical diagnosis and prognosis following severe injury.

The British Athletics Medical Team Suggests a new injury classification system for improved diagnostic precision and prognostication based on MRI attributes (see Table 2 and figure below revealing 'letter classification) (5).

Discovering true return-to-play Timescales following a severe hamstring injury has proven difficult. Injuries involving an intramuscular tendon or aponeurosis with adjoining muscle fibers (BF during high-speed running) typically require a shorter recovery period compared to those involving a proximal free limb or MTJ (SM during dancing or kicking)(2).)

Additionally, There Are connections between MRI Findings as well as the area of injury, and return-to-play. Likewise, the length of oedema indicates a similar effect on healing period -- ie the longer the length, the more the retrieval(1). In addition, the place of peak pain on palpation following severe injury can also be linked with increased healing intervals(1).

Moreover, there have been efforts To explain the link between grading of acute hamstring injury and return-to-play. In a prospective cohort study on 207 professional footballers with severe hamstring injuries, 57 percent were grade I, 27 percent were grade II, and 3 percent were grade III. Grade I injuries returned to perform inside a mean of 17 days. Grade II was 22 days, and grade III was 73 days. Eighty four percent of those accidents affected the BF, 11\% SM, and 5\% ST, however there was no substantial difference in lay-off time for injuries to the 3 different muscles(5). This has been compared to 5-23 times with regular I-II injuries, and 28-51 times for grade I-III in other research respectively (1,8).

Several researchers have contended the Advantages of eccentric strengthening after an acute hamstring injury versus concentric when aiming to reduce timeframes for return-to-play(1-5,9). The crux of this debate is that together with the vast majority of acute hamstring injuries occurring throughout eccentric loading (terminal swing or stretching), the rehabilitation 'should reflect the specific situation that lead to the harm'(1). This quote was obtained from a research study, which showed a significant difference between an eccentric and concentric rehabilitation program following severe hamstring injuries in elite and non-elite footballers.

Clinical trial on 75 footballers at Sweden, which noted that using eccentric strengthening versus the time to return-to-play was decreased by 23 days. This was irrespective of the sort of injury or the website of injury. The outcome measure was the amount of days to come back to full-- team training and availability of match choice. This article will now research this study in greater depth.

Two rehab protocols were utilized, And initiation began five days after injury. All players had sustained a sprinting-type (top speed jogging/ speed) or stretching-type injury (high kicking, split places, slide handling). Exclusion criteria included previous hamstring injuries, injury to anterior thigh, continuing history of low back problems, and pregnancy.

Evaluation 5 days after the accident, to expose the severity and site of injury. A participant was judged to be fit to return to full-team training using the energetic 'Askling H-test' (see below). A positive test is when a participant experiences any insecurity or apprehension when performing the test. The test ought to be completed without full dorsiflexion of the ankle.

Seventy two percent of gamers sustained sprinting-type accidents, whilst 28 percent were stretching-type. Of these, 69\% continuing injury to BFLH, whereas 21\% was located from the SM. Injuries to ST were just continued as secondary injuries (48\% with BFLH, and 44\% with SM). Ninety four percent of sprinting-type injuries were located in the BFLH, while SM was the most common (76\%) location for the stretching-type injury.

The two rehabilitation protocols utilized were labelled L-protocol and the C-protocol. One aimed at loading hamstrings through lengthening (L-protocol), and the other consisted of exercises with no focus on lengthening (C). Each consisted of three exercises that could be carried out anywhere and were not dependent of complex gear. They also geared toward controlling flexibility, trunk/pelvic equilibrium as well as specific strength training to the hamstrings. All were played in the sagittal plane with speed and load improved throughout.

Findings

The Opportunity to reunite was significantly shorter in the L-protocol compared with the C-protocol, averaging 28 times and 51 days respectively. Time to come back was also significantly shorter in the L-protocol than in the C-protocol for injuries of the two sprinting-type and stretching-type, as well as for injuries of different injury classification.

BFLH is involved more often in sprinting-type injuries as a consequence of terminal swing. This is possibly because of its absorption of the most significant summit musculotendon strain across all four hamstring muscles.

Injuries can be classified from Grade I-III or maybe more specifically Grade 1-4 for severity and a-c depending on site of injury. This according to MRI findings. The closer the site of injury is into the proximal hamstring tendon, the longer the recurrence- to-play period. Employing eccentric strengthening exercises in rehabilitation programs will promote a quicker return- to-play.

To enable a thorough rehab procedure, clinicians will need to take into account the first hamstring weakness, Any lack of flexibility, previous hamstring accidents, age, exhaustion, and intensity and strength imbalances between hamstring (eccentric) and quadriceps (concentric) contraction.

References
1. Br J Sports Med 2013; 47: 953-959
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Muscle strains are a common injury among athletes, together with the hamstrings being susceptible to injury in sports which involve high speed running. As an example, musculotendon strains accounted for almost half of accidents in the National Football League team throughout pre-season practice, with hamstring strains being the most common and requiring the most time (average of 8.3 days) apart from game.

From the Australian Football League, hamstring strains are the most frequent injury with approximately six accidents per club a year, and 33 percent of those being recurrent injuries. The susceptibility of the hamstrings to harm during high speed running is linked to the biomechanical demands put on the muscle, although debate continues regarding whether injury occurs through the stance or swing phase of a gait cycle.

This problem is applicable for designing the type of resistance training which may be effective for preventing recurrent or first hamstring injuries, among others. Specifically, injury prevention programs would ideally incorporate aspects (e.g. lower extremity positions, muscle lengths, contraction type) that are most similar to the conditions related to injury, such that the athlete could maximize the gains in functional strength and minimize the risk of future damage or injury.

Chiropractor, Dr. Alexander Jimenez details the relevant anatomy and biomechanics of the hamstring, common mechanisms of injury, the clinical signs and symptoms and management in the kind of surgical repair.

Introduction

Hamstring injuries in athletes are re-injury and typical to the hamstring is a reasonably frequent occurrence. Orchard and Seward (2002) found that at elite-level Australian Rules football, hamstring injuries were the most common kind of injury requiring time off from competition. Muscle strains are the most frequent, followed by more significant myotendinous junction tears. These respond well to rehab. Total ruptures of the muscle are uncommon as are complete ruptures of the hamstring origin (Steinbruck 1987), and accidents like these can be very painful.

Hamstring muscle origin ruptures in the kind of avulsions of the growth plate are more frequent in younger populations due to the immature epiphyseal growth plate (apophysis) found to the ischial tuberosity in older children and adolescents (Wootton et al 1990). Avulsions in adults with ischial tuberosities that are fully-fused have a tendency to be ruptures of the proximal hamstring tendon or complete avulsion fractures of the ischial tuberosity.

Prompt diagnosis and proper treatment of ischial tuberosity avulsions/ tendon ruptures is critical due to the residual loss of power persistent in non-operatively treated instances of hamstring ruptures (Birmingham et al 2011). The ongoing complications with chronic non-repaired complete hamstring tendon avulsions are pain, weakness and cramping during locomotion and pain with sitting (Wood et al 2008, Harris et al 2001). As with most tendon avulsions repair leads than delayed repair. Repair within four weeks of injury resulted in better outcome compared with those repaired after four weeks (Harris et al 2011)

Relevant Anatomy & Biomechanics

The hamstring muscles comprise the biceps femoris (long head and short head), semitendinosus and semimembranosus. All muscles (except biceps short head) attach onto the ischial tuberosity. The head biceps starts on the femur along the linea aspera.

At the origin, the head attach to the ischial tuberosity and of the semitendinosus and bicep form a conjoined tendon and the semimembranosus with its tendon attaches. Figure 2 above shows the attachments of the two individual heads.

At puberty there appears at the ischial tuberosity a secondary ossification centre and this doesn't fuse until the late teens or early twenties. In this time frame between the appearance of the apophysis and its fusion, a force traction on the hamstring may avulse the apophysis as this forms the weak link between the muscle and the bone. After skeletal maturity, injury is more likely to take place at the junction.

The hamstring origin is intimately connected to the sciatic nerve's passage during the upper posterior thigh. Serious injury to the muscle that produces a large hematoma may create adhesions in the vicinity of the sciatic nerve that may complicate the athlete's performance when recovered, or the nerve may be injured due to a grip neuritis as the muscle belly retracts away from the nerve (Chakravarthy et al 2005) or due to compression from a tight fibrotic band directly to the ischial tuberosity. Diligent treatment of sciatic nerve mobility is a significant element in hamstring rupture direction (see below in conversation on management).

It is not unusual for the hamstring origin rupture to involve only two heads of not all three and the hamstring. These are classified as partial avulsions. It is more common if the avulsion is partial that it involves the conjoined tendon of the biceps femoris and semitendinosis (Heinamen 2013).

Mechanism Of Injury (MOI)

The hamstrings are vulnerable to trauma due to the anatomical arrangement and on account of the leverage that acts through the hip during functional movements.

The most frequent MOI is forced knee extension in a position of hip flexion and as the muscle is placed below a rapid and large eccentric load. The force is directed to the junction. This is sometimes due to a sudden and forceful landing from a jump with the knee locked in extension, or during foot contact in sprinting, or in excessive and uncontrolled hip flexion such as when the leg slips out from underneath the body and moves into hip flexion with the knee extended (forward splits, water skiing and bull riding).

However, it is thought that in order for tendons to rupture, a degree of degenerative change needs to be present in the tendon prior to rupture. This has been observed that rupture and supraspinatus tendons that rupture. This possible clarifies why myotendinous ruptures in the hamstrings of young athletes almost never happens, they fail at the growth plate and might also explain the rising frequency at middle aged recreational athletes (Cohen and Bradley 2007).

The hallmark of classic tendon degeneration is an anatomical and biochemical change in tendon tissue. Collagen fibers become disorganized, the intracellular matrix changes foci develop in the tendon, hypervascularity of the tendon is present. The forces which create this effect that is degenerative tend to be both compressive and tensile . As the hip is rapidly flexed the force is applied due to rapid eccentric loading on the hamstring tendon. The force is a result of the unique anatomy of the ischial tuberosity bone that 'pushes' into the tendon and makes a compression zone. Due to repeat episodes of tensile and compressive force, the tendon gradually degenerates and may eventually rupture as it's weakened (Docking et al 2013).

Signs & Symptoms

The usual mechanism of injury has been described above, and the pain can be severe and debilitating once the hamstring origin ruptures. The athlete describes it as 'being shot by a sniper'. An audible 'pop' may be heard. The athlete will be guarded on the affected limb and will be reluctant to weight bear on a loaded limb.

On examination, a palpable defect may be felt below the ischial tuberosity and a loss of the contour of the hamstring may be observed, however these will be dependent on the size of the gluteals and any intervening adipose tissue that may make direct palpation and visualization difficult. A discolouration may be seen throughout the muscle, if the athlete is examined following the incident.

The athlete will demonstrate a painful weakness in both knee flexion and hip extension that is isolated. Range of motion is going to be as they'll be unwilling to weight bear pain functionally and restricted they may walk with a limp.

Presentation to the practice has been delayed, generally because the athlete assumes the injury is purely muscle-related and will heal, if, then the patient may show atrophy of the hamstring muscle due to disuse.

Imaging

CT imaging and plain x-rays supply little use unless an avulsion of the hamstring tendon from the ischial tuberosity has happened.

Ultrasound imaging may be helpful; however, its sensitivity and specificity has not yet been reported.

As the delicate tissue detail is visualized in an MRI, MRI is the investigation of choice in a suspected rectal origin rupture and it can highlight tendon retraction's level in addition to any interference with the nerve. Furthermore, MRI can be used in through all phases of recovery to appraise the therapeutic capacity of the tendon.

Management

The treatment of hamstring origin injuries is contentious; fix or not fix. A number of standards have been suggested that can help the practitioner decide if the hamstring injury requires surgery (Domb et al 2013):

However, some and complete incomplete ruptures of the hamstring origin will require treatment in the vast majority of athletes on account of the concerns regarding loss of strength and power.

The case for operative management of partial hamstring origin rupture is not as clear-cut. It may be that some of these can rehabilitate well following a partial rupture; however, if pain and dysfunction persist after a lengthy rehabilitation process, then repair of a partial rupture can result in good clinical outcomes (Aldridge et al 2012). However, Lempainen et al (2006) presented a series of partial hamstring ruptures that responded well to surgical intervention.

Surgery

The hamstring is approached with a posterior incision starting at the gluteal fold. The incision may extend over a distance to completely access the hamstring tendon that is retracted. The posterior cutaneous nerve and the sciatic nerve is going to be visualized and any adhesions can carefully be resected (neurolysis). A neurolysis will be necessary if the surgery was delayed due to failure or a delayed surgery following treatment. This will be evacuated, if there is a hematoma observed.

The proximal tendon stump on the ischial tuberosity will be found as will the retracted tendon and these will be approximated with the knee in flexion (to decrease the hamstring stretch). They will be repaired with Ethibond sutures and Merselene tapes. This will be anchored tapping screw if the tendon has avulsed of the tuberosity.

By flexing the knee to 45 degrees to create tension the integrity of the repair will be tested. This enables the surgeon to check the 'safe' available range of motion intra- operatively so that physiotherapy can start early (at two weeks) in the safe ranges. This will avoid a prolonged immobilisation that's been demonstrated to lead to range and strength loss and significant atrophy in hamstring repairs.

Then the demand for a postoperative knee flexion brace is not required, if the injury is reasonably new. However, if the surgery was delayed due to failed conservative management a knee flexion brace post-operative may be required.

Some authors have attempted endoscopic repair of the hamstring tendon and state that this procedure offers more benefits like minimal scar tissue, superior visualisation of the hamstring tendon, decreased bleeding and better protection of the neurovascular bundle (Domb et al 2013).

Post-Surgical Outcomes

Almost all studies conducted on the outcomes of hamstring tendon repair in return and strength return to function show that it is unreasonable to expect that the athlete returns to full strength in the hamstring following a hamstring tendon. Although the strength of the hamstring is still diminished, the athlete can return typically to a pre-injury amount of competition.

Wood et al (2008) found that in those with repaired hamstring tendons, 80% returned to pre-injury heights of sports. What's more, hamstring strength returned to a level of 89% to a mean of 84% and hamstring endurance. Konan and Haddad (2010) found that 90% of the hamstring injuries they tracked returned to pre-injury levels of sport. Isokinetic testing and all reported functional outcome showed that the hamstring strength returned to 83% at six months compared with 56% at the pre-surgery level. Finally, Cohen and Bradley (2007) reported on seven patients who underwent operative repair and found that average time to return to function (and sports) was 8.5 months. To pre-operative levels of function, six of the seven had returned by post-operative six months.

References

• Aldridge, S.E., Heilpern, G.N., Carmichael, J.R., Sprowson, A.P., Wood, D.G. Incomplete avulsion of the proximal insertion of the hamstring: outcome two years following surgical repair. Journal of Bone and Joint Surgery. 2012. 94(5); p. 660-662.
• Birmingham, P., Muller, M., Wickiewicz, T., Cavanaugh, J., Rodeo, S., Warren, R. Functional outcome after repair of proximal hamstring avulsions. The Journal of Bone and Joint Surgery. 2001. 93-A(19):p. 1819-1826.
• Chakravarthy, J., Ramisetty, N., Pimpalnerker, A., Mohtadi, N. Surgical repair of complete proximal hamstring tendon ruptures in water skiers and bull riders: a case report of four cases and review of the literature. British Journal of Sports Medicine. 2005. 39; p. 569-572.
• Cohen, S., Bradley, J. Acute proximal hamstring rupture. J Am Acad Orthop Surg. 2007. 15(6); p. 350-355.
• Docking, S., Samiric, T., Scase, E. Purdham, C. Cook, J. Relationship between compressive loading and ECM changes in tendons. Muscle Ligaments Tendons J. 2013. 3(1); p. 7-11
• Domb, B.G., Linder, D., Sharp, K.G., Sadik, A., Gerhardt, M.B. Endoscopic repair of proximal hamstring avulsion. Arthrosc Tech. 2013. 2(1); p. e35-e39.
• Harris, J.D., Griesser, M.J., Best, T.M., Ellis, T.J. Treatment of proximal hamstring ruptures: a systematic review. Int Journal of Sports Med. 2011. 32(7); p. 390-495.
• Heinanen, M. Proximal Hamstring Avulsion – Anatomy, Cause of Injury, Surgical treatment and Post-operative Treatment Protocol. Suomen Ortopedia ja Traumatologia. 2013. 36: p. 104-110.
• Konan S, Haddad F. Successful return to high level sports following early surgical repair of complete tears of the proximal hamstring tendons. Int Orthop. 2010; 34:119-23.
• Lempainen, L., Sarimo, J., Heikkila, J., Mattila, K., Orava, S. Surgical treatment of partial tears of the proximal origin of the hamstring muscles. British Journal of Sports Medicine. 2006. 40; p. 688-691.
• Orchard, J. and Seward, H. Epidemiology of injuries in the Australian Football League, seasons 1997–2000. British Journal of Sports Medicine, 2002. 36; p. 39-45.
• Pombo, M., Bradley, J.P. Proximal hamstring avulsion injuries: A technique note on surgical repairs. Sports Health. 2009. 1(3); p. 261-264.
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• Wood, D.G., Packham, I., Trikha, S.P., Linklater, J. Avulsion of the proximal hamstring origin. Journal of Bone Joint Surgery (Am), 2008. 90-A; p. 2365-2374
• Wootton J.R., Cross, M.J., Holt, K.W.G. Avulsionof the ischial apophysis. The case for open reduction and internal fixation. Journal of Bone and Joint Surgery. 1990. 72; p. 625-627