Hamstring injuries are considerably common in
athletes and the chances of re-injury are fairly frequent. Researchers determined that in elite-level Australian football, hamstring injuries were the most widespread type of sports injury requiring time away from competition. Researchers also found that low-grade muscle strains occur most frequently, followed by more
substantial myotendinous junction tears. Fortunately, these have shown a
positive response to conservative rehabilitation. Complete ruptures of the
muscle are significantly rare, same as complete ruptures originating at the
hamstring. Such type of sports injuries can be impairing.
Muscle ruptures in the form of hamstring
avulsions have been reported more frequently in the younger population due to
an immature epiphyseal growth plate found on the ischial tuberosity in older
children and adolescents. Hamstring avulsions in adults with fully fused
ischial tuberosities are contributed to be ruptures of the proximal hamstring
tendon or complete avulsion fractures of the ischial tuberosity.
An immediate diagnosis following proper
treatment methods for ischial tuberosity avulsions or tendon ruptures is essential
at this point because several individuals whom were treated non-operatively for
hamstring ruptures experienced residual loss of power. Further complications
for hamstring avulsions include pain, weakness, cramping during locomotion and
pain while sitting. As with the majority of tendon avulsions, treating the
injury as soon as possible can present better outcomes than delaying treatment.
According to research, receiving treatment within four weeks of injury resulted
in better recovery outcomes as compared to those which received treatment after
four weeks of injury.
Hamstring Anatomy and Biomechanics
The hamstring muscles consist of the biceps
femoris, both the long head and the short head, the semitendinosus and the
semimembranosus. All of these muscles, excluding the biceps short head, attach
onto the ischial tuberosity. The short head biceps begin along the femur simultaneously
with the linea aspera.
At the proximal origin, the long head of the
biceps and the semitendinosus form a combine to create the tendon which
attaches to the ischial tuberosity and the semimembranosus.
When an individual undergoes puberty, a
secondary ossification center at the ischial tuberosity develops without fusing
until the individual’s late teens or early twenties. Within the period of time
between the fusion of the apophysis, an increased force traction may cause a
hamstring avulsion along the apophysis as a result of a weakened connection
between the bone and the muscle. After the bones begin to mature, injuries at
the myotendinous junction become more common.
The structures of the hamstring greatly associate
with the passage of the sciatic nerve along the upper posterior thigh. A severe
injury to the muscle that causes a large hematoma may develop adhesions in and
around the sciatic nerve which may create complications towards an athlete’s
overall performance after the rehabilitation process. Also, the nerve may
become damaged or injured as a result of a traction neuritis when the muscle
belly retracts away from the nerve. Furthermore, compression or impingement due
to a tight fibrotic band distal to the ischial tuberosity may also cause
complications for many athletes. Managing hamstring avulsions and other types
of injuries relating to the proper function and mobility associated with the
sciatic nerve is an important factor towards overall recovery.
It is not uncommon for hamstring avulsions to involve only two heads of
the hamstring and not all three. These are identified as partial avulsions. It
is more common if the hamstring avulsions are partial to where it involves the
combined tendon of the biceps femoris and the semitendinosus.
Mechanism of Injury
Due to the anatomical structure of the hamstrings, these can be highly vulnerable
to suffer trauma or injury in the regions where the muscles and other tissues
cross both the hip and knee, primarily because of its large leverage to
function with the hip during movements.
The most common mechanism of injury involves forced knee extensions in a
position of hip flexion while the muscle is placed under a large and rapid
eccentric load. The force is conducted to the myotendinous junction. This often
results due to a sudden and forceful landing from a jump where the knee was
locked in extension, 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 during sports or
physical activities like forward splits, water skiing and bull riding.
Nonetheless, it’s been considered that in order for tendons to rupture,
some level of degenerative alterations must have developed in the tendon before
the rupture occurred. This hypothesis has been identified in athletes where the
Achilles tendons rupture and the supraspinatus tendons rupture. Researchers
have associated these findings with why myotendinous ruptures in the hamstrings
of young athletes almost never occur, how they fail at the growth plate as well
as explaining its increasing frequency in middle aged, recreational athletes.
The degeneration of the tendon occurs throughout the anatomical and
biochemical change in the tissue of the tendon. The collagen fibers become disorganized,
the intracellular matrix changes, cystic foci develop in the tendon and
hypervascularity within the tendon becomes present. Tension and compression forces
being applied against the body can often create these degenerative effects. The
forces of tension occur as a result of a rapid, eccentric loading against the
hamstring tendon as the hip is rapidly flexed. The forces of compression occur
when the singular anatomy of the ischial tuberosity bone presses against the
tendon and creates a zone of impingement. Repetitive and constant tension and
compression forces then progressively degenerate, eventually becoming weaker
and rupturing.
Furthermore, because of the proximity of the hamstring muscles to the
sciatic nerve which runs down each leg from the lower back, a hamstring rupture
could also affect this crucial nerve. As a result, the inflammation and
swelling caused by an injury to the hamstring muscles and other surrounding
tissues may compress the sciatic nerve, leading to symptoms of sciatica. Sciatica
is commonly referred to as a series of symptoms rather than a single injury and
condition. Therefore, athletes with hamstring avulsions may additionally
experience symptoms of sciatica.
The affected athlete must seek immediate medical attention not only to
effectively treat hamstring injuries but also to determine the presence of
sciatica and properly diagnose whether another type of injury or underlying
condition may be causing the sciatic nerve pain besides the hamstring rupture.
Symptoms of Hamstring Avulsions
Athletes with hamstring avulsions commonly describe experiencing severe
and debilitating symptoms after the injury. Many athletes report the pain as a
sudden shot along with an audible pop. A majority of individuals faced with
hamstring avulsions are guarded on the affected limb and are reluctant to bear
full weight on a loaded limb. Hamstring ruptures causing sciatica may
experience pain along with numbness and tingling sensations, radiating along
the lower back, buttocks and thighs. Also, in some cases of injury, an athlete
may develop myofascial pain syndrome, a disorder causing muscle pain in
seemingly unrelated areas of the body.
When the affected athlete visits a healthcare professional, such as a
chiropractor, physical therapist or other specialist, on examination, a
palpable defect may be felt below the ischial tuberosity and a loss of the
contour of the hamstring can often be observed. These, however, generally
depend on the size of the gluteals and any intervening adipose tissue which
could make direct palpation and visualization difficult. Healthcare specialists
usually describe a significant discoloration throughout the hamstring muscle a
few days after the injury occurred.
Further evaluation of athletes with hamstring avulsions show
weakness in both isolated knee flexion and isolated hip extension along with
reported pain. The individual’s range of motion is greatly restricted due to
the symptoms and walking with a limp may be common as they may be unable to
bear weight through the injured muscle.
If proper medical attention is delayed because the injury appears to be
muscle related and the athlete believes it could heal on its own, the individual
may experience hamstring muscle atrophy due to disuse.
Imaging
Basic X-rays and CT scans won’t provide beneficial results unless the
hamstring avulsions occurred from the ischial tuberosity.
Ultrasound imaging may be useful, however, further research regarding its
sensitivity and specificity requires more research.
MRI is the preferred method when the presence of a hamstring rupture is
suspected because the details of the soft tissues are well displayed on an MRI,
highlighting the level of tendon retraction as well as any interference with
the sciatic nerve. Furthermore, MRI can be utilized throughout all stages of
rehabilitation to evaluate the healing capacities of the tendon.
Hamstring Injury: Common Sports Injuries
Treatment for Hamstring Ruptures
The treatment procedures for hamstring injuries have long been considered
controversial, whether they effectively repair or don’t repair the damage or
injury. A large number of criteria has been suggested to help healthcare
professionals, such as chiropractors and physical therapists, among others, to
help determine if athletes faced with hamstring avulsions may require surgery.
First, the osseous avulsion must have more than a 2 cm retraction.
Second, there must be complete tears in all 3 tendons with or without
retraction, and last, partial tears reporting painful and symptomatic despite
prolonged conservative treatment, are some of the criteria an individual must
meet to signal the need for surgery.
However, some partial or complete ruptures of the hamstring generally
requires some form of operative treatment among the vast majority of athletes,
primarily due to concerns regarding residual loss of strength and power.
Instances where partial hamstring ruptures may require operative
treatment still remain fully unclear. In some cases, partial ruptures may
rehabilitate properly through conservative procedures but if pain and other
symptoms continue after a prolonged period of rehabilitation, then repairing a
partial rupture through operative measures may lead to positive outcomes.
Surgery for Hamstring Ruptures
The surgical procedure for repairing hamstring avulsions is as follows:
First, the hamstring muscle is contacted with a posterior incision beginning at
the gluteal fold. The incision may extend over a 10 cm distance in order for
the specialist to be able to fully access the retracted hamstring tendon. The placement
of the posterior cutaneous nerve and the sciatic nerve in relation to the
individual will be visualized and any adhesions at this point can be carefully
resected, a process known as neurolysis. Neurolysis is almost always essential
if surgery has been delayed due to misdiagnosis or following unsuccessful
conservative treatment procedures. If a hematoma is detected, then this will be
cleared.
The end piece of the proximal tendon on the ischial tuberosity is then
located, as is the retracted tendon, and these will be closely located with the
knee in flexion to reduce the hamstring stretch. Then, they will be repaired
with Ethibond sutures and Merselene tapes. If the tendon has avulsed, then this
will be anchored with a titanium self-tapping screw.
The stability of the surgical repair is evaluated by passively flexing
the knee 45 degrees to create tension in the muscle and tendon. This allows the
specialist to analyze the safety of the individuals range of motion throughout
the course of surgery so that rehabilitation exercises and stretches can being
early within safe ranges. Furthermore, this will avoid prolonged immobilization
which have been shown to lead to considerable amounts of atrophy as well as
loss of strength and range in post-operative hamstring repairs.
If hamstring injuries are effectively treated early, the need for a
post-operative knee flexion brace is generally not necessary but, if the
surgery was delayed, then a post-operative knee flexion brace may be required.
Several researches have attempted endoscopic repairs of hamstring
avulsions, stating that this procedure can offer more benefits, such as
minimizing scar tissue, superior visualization of the hamstring tendon,
decreasing the amount of bleeding and better protection of the neurovascular
bundle.
Post-Surgical Outcomes
A majority of studies regarding the outcomes of hamstring tendon repairs
through surgery providing the return of the individual’s strength and function
have demonstrated that it may be unreasonable to expect an athlete to return to
full strength in the hamstring following a surgically repaired hamstring
tendon. Although the strength and function of the hamstring may be reduced, the
athlete can successfully return to a pre-injury level of competition in most
cases.
Researchers concluded that among those individuals who underwent surgical procedures to repair injured hamstring tendons, 80 percent of them returned to participate in
pre-injury levels of sports and/or physical activities. Moreover, the individual’s
hamstring isotonic strength returned to an average of 84 percent while
hamstring endurance returned to an average of 89 percent. Additionally, the
researchers found that 90 percent of the hamstring injuries they followed had
returned to pre-injury levels of sport or physical activity. All of these
reported excellent outcomes in function and isokinetic tests demonstrated that
the strength of the hamstring returned to 83 percent at six months as compared
to 56 percent at the pre-surgery level. Finally, the researchers reported the
evaluated results of seven individuals who underwent operative repair and
concluded that the average time they experienced a restoration of function was
8.5 months. By six months of port-operative procedures, six of the seven
individuals had returned to pre-operative levels of function.
By Dr. Alex Jimenez
