Hamstring

COMPARISON BETWEEN HAMSTRING
LENGTHENING TENDON AND HAMSTRING
TENDON TRANSFER ON CHILD’S CROUCH KNEE
CEREBRAL PALSY WITH GAIT OUTCOME

Table of Contents
Introduction................................................................................................................................2
Normal Gait Analysis ................................................................................................................2
The types of Gait Analyses........................................................................................................3
Abnormal kinetic pattern of crouch knee...................................................................................4
Biomechanics differences between hamstring tendon lengthening and transfer.......................5
Clinical Implication ...................................................................................................................8
Conclusion .................................................................................................................................9
References................................................................................................................................10

Introduction
Cerebral Palsy (CP) is defined as a non-progressive brain lesion and has many disorders that
may affect both movement and posture (Bobath 1991). Spastic cerebral palsy influence 70%
of child population with CP and happen when white matter tracks damage between the cortex
and the spinal cord. Moreover, a key problem for children with spastic CP is their feet and leg
muscles, which might shorten or tighten around certain joints (Bjorklund 2006). Crouch knee
is one of many gait pattern for spastic cerebral palsy. This condition of crouch knee is
described as walking with severe knee flexion during stance phase associated with other
problems such as hip and knee flexion (Flynn and Wiesel 2012). Therefore, orthopaedic
surgery is necessary for children who are in worse condition in order to enhance their
mobility (Bjorklund 2006). The main objective of surgery is to improve or regain function by
treating deformities of bone or muscle shortening, such as the hamstring (Kocher and Millis
2011). Hamstring tendon lengthening and hamstring tendon transfer are two main surgeries
that could improve crouch knee especially in mid-stance that require full knee extension
(Dreher et al. 2013). However, Lengthening tendon of hamstring by the technique of surgery
is considered as the standard intervention to enhance crouch knee (Chang et al. 2004).
Therefore, there are some arguments and contradictions about which has more positive
impact on crouch knee when compared with the two types of surgeries (Dreher et al. 2013).
There had been an identification of 4 articles that supported the comparison of both the
surgeries considered in this essay. The comparison of the two surgeries will be conducted in
kinematic with less attention upon kinetic parameters that are the key elements creating gap.
Hence, this gap has increased the need of conducting scrutiny investigation to answer the key
question for this research. The research question is “Which has a significant improvement
between hamstring tendon lengthening or hamstring tendon transfer surgery in the
biomechanics aspect of gait after correcting crouch knees of children with cerebral palsy and
how that reflect on physiotherapy clinic?
Normal Gait Analysis
Gait analysis provides a larger picture that helps to understand normal and abnormal pattern
of gait and aims to assist movement diagnosis regarding which intervention is more suitable
for certain condition. The gait cycle illustrates gait in two parameters that are distance
(spatial) and time (temporal). The gait cycle starts with contact of heel on the ground and
ends when the same heel comes in contact with the surface again. There are two phases of

gait cycle that are stance (heel strike, foot flat, midstance, heel-off, and toe off) and swing
phase (acceleration, midswing, and deceleration). First, stance phase is defined as the time
consumed in the phase when the foot is on the ground and this represents 60% of the overall
gait cycle. Second, swing phase is defined as the time consumed in the phase when the foot
does not come in contact with the floor and this represents 40% of the overall gait cycle.
In addition, there are two periods of double support that means the contact of two legs with
the ground at the same time in order to shift body weight from one leg to another during two
different phases. Moreover, the other parameters that can help understanding better gait
analysis are steps and stride. There are two steps, right and left that lead to a stride the overall
gait cycle. The distance between heel contact of one foot to the opposite foot heel point can
be defined in terms of step length while stride length is a point from heel contact of one
extremity to heel contact again for the same limb.
(Fig: Different Phases of Gait Cycle)
The types of Gait Analyses
The gait analysis is divided into two parts: Kinematic, which illustrates movement angle
without force consideration and Kinetic, which illustrates movement with force involved.
Considering kinematic of knee that is related to topic question in two different phases. First,
knee stance phase in heal contact to foot flatten the angle of knee bend from 0-15 degree in
flexion position and quadriceps contracts first to hold knee in extension and then
eccentrically to reduce flexion and control movement. Second, when the foot is flat to mid-
stance, the knee extends from 15-5 degree with the start of movement from flexion towards
extension and quadriceps just working at the beginning of movement. Third, mid-stance to
heel off the knee continues to extend from 5 degree of flexion to 0 degree (neutral) and there

is no requirement of muscle activity. Finally in stance phase, from heel off to toe off, the knee
starts flexing from 0 to 40 degree of flexion and quadriceps with the need to control knee
flexion.
However, in the knee swing phase there are three stages involved. First, from acceleration to
mid-swing, the knee becomes flex from 40 to 60 degree and the muscle performing activities
are biceps femoris (short head), gracilis and sartorious by contracting concentrically. Second,
in the mid-swing phase, the knee moves from flexion at an angle of 60 to 30 degree of
extension. Finally, in the deceleration phase, the knee continuous to extend until 0 degree and
quadriceps contracts concentrically to stabilize knee in extension position (O’Sullivan and
Schmitz 2007).
The second type of gait analysis is kinetic that focuses on movement with force and torque
consideration. First, force is a fundamental element of kinetic that helps to distinguish
between normal and abnormal gait pattern. This is the force that is applied under the ground
of leg when the subject walks also referred to as foot force. In contrast, the force that is
applied to the leg by the surface is referred to as reaction force. To describe the ground
reaction force, there are three orthogonal axes: vertical, anterior-posterior and medial-lateral
force. Second important element in kinetic is joint torque that focuses on ground reaction
force which is applied under leg during walking with the generation of external torque
(Neumann 2013).
Abnormal kinetic pattern of crouch knee
Crouch knee can be referred to as more knee flexion in the stance period, with variation of
range of motion during the swing period (Sutherland and Davids 1993). A child with spastic
cerebral palsy will be suffering from anterior knee pain because the great amount of loading
on the patellofemoral joint may result in affecting gait and function (Ganjwala 2011). First,
the hip joint angel in crouch gait persistently increases in hip flexion through gait cycle and
the hip joint was large extensor moment within initial contact and mid-stance by -0.8 Nm/kg
because of the contracture of flexor knee muscle.
Second, the Knee in initial stance increased flexion by 50-degree more than normal gait (0-15
degree) and continually increased flexion through the stance period (Lin et al. 2000). Thus,
more knee flexion will create a high extensor moments in knee (Matjačić et al. 2006).
However, the knee extension moment will decrease when ankle planter-flexion moment

increases in mid stance because of soleus firing to accelerate knee extension (Neptune et al.
2001). The vertical ground reaction force passes behind knee joint and creates internal
extension moment. Furthermore, the ankle is an excessive dorsiflexion and ground reaction
force moving forward and generating external Doris-flexor and internal planter-flexor
moment. In EMG, hamstring muscles activate in initial stance and terminal swing. To sum
up, stance period is the main issue of crouch group especially in mid-stance when body is
unable to shift weight because of excessive knee flexion. Another issue is excessive ankle
dorsiflexion that leads to generate internal planter flexor because the ground reaction force
moves anteriorly (Lin et al. 2000).
Biomechanics differences between hamstring tendon lengthening and
transfer
To treat the pervious crouch knee complication, there are two main operation that may
improve crouch gait if the hamstring contracture is the reason. First, distal hamstring
lengthening surgery that procedure is tenderized or there is an elongated tendon by
intramuscular tendon release (Feng et al. 2012). The advantages of distal hamstring
lengthening is improved range of motion of hip and knee especially in knee extension in mid-
stance as well as power transferred to the knee and the hip (Rethlefsen and Tolo 1999).
However, the disadvantages of distal hamstring lengthening are hyper lordosis. This is the
condition of increased anterior pelvic tilt and recurrent knee flexion (Baumann et al. 1980).
The second operation technique that may enhance crouch knee dysfunction is a hamstring
tendon transfer that involves transfer of both, semitendinosus and gracilize tendons to the
adductor tubercle in distal part of femur (Flynn and Wiesel 2012). Therefore, this process of
tendon transfer will change middle hamstring from bi-articular into mono-articular muscle
(Fitoussi and Bachy 2015). The advantages of hamstring transfer are more than hamstring
lengthening tendon in kinematic as well as kinetic with the additional benefit of peak hip
power (Feng et al. 2012). However, the disadvantages are loss of knee flexion in swing phase
and increased pelvic tilt (Dreher et al. 2013).
The research by Chang et al. (Chang et al. 2004), which included 83 limbs, and by Feng et al
(Feng et al. 2012), which included 20 limbs, tend to investigate distal hamstring lengthening
that helps in correcting crouch knee dysfunction. They found that in primary hamstring
lengthening the popliteal angel decreased by approximately 15 degree, the knee flexion at
foot contact was decreased by approximately 10 degree and pelvic tilt was increased by about

2 degree from pre to post-operative. In comparison, the research by Feng et al (Feng et al.
2012), which included 18 limbs, and by De Mattos et al (De Mattos et al. 2014), which
included 32 limbs, investigate the post one year outcome of hamstring tendon transfer
surgery. The result was an improvement in popliteal angel that decreased by approximately
10 degree, the knee flexion at foot contact was decreased by 15 degree and pelvic tilt was
increased by approximately 6 degree after the surgery. Both surgeries have the similar
outcome on kinematic elements with slight difference in anterior pelvic tilt in hamstring
tendon transfer group.
On the other hand, when there is a comparison between two surgeries on kinetic elements,
there is an obvious result of peak power in the hip and knee decreased by approximately 0.5
w/kg in hamstring lengthening group, the peak hip power was increased significantly by 0.4
w/kg in hamstring transfer group. Thus, there is some improvement in short time that may
end up taking place after hamstring tendon lengthening. This might increase knee extension
at mid-stance phase, but increase pelvic tilt and reduce power of hip and knee supporting the
idea that elongate muscle tendon may lead to the loss of muscle contractibility as a result of
which the muscle becomes weak (Fitoussi and Bachy 2015). However, there are two
misassumptions that the anterior pelvic tilt does not have clinical significance even though
there is a statistical difference in both types of surgery (Feng et al. 2012). The second
misassumption is about the peak hip power not being deteriorated in hamstring tendon
lengthening group over time (De Mattos et al. 2014). However, both studies that have
perceive these misassumptions show small sample size that may effect on result and hence,
there is a contradiction of the study that include large power size (Rosenthal et al. 2011).
Furthermore, the drawbacks of hamstring tendon lengthening surgery, which are anterior
pelvic tilt and hamstring weakness, may increase chance of re-crouch knee in the longer run
because of vertical ground reaction force that cause more knee extension movement during
loading response and mid-stance (Matjačić et al. 2006). This concern was agreed by Chang et
al (Chang et al. 2004) who noticed the recurrence crouch knee in 18 children among those
who underwent hamstring lengthening tendon.
Investigating the long-term follow up of hamstring tendon lengthening and transfer will help
to know the effect of surgery is consistent or may result in having deterioration effect. Thus,
it can be stated (De Mattos et al. 2014) that the comparison of hamstring transfer with
hamstring elongation in long-term follow up, provide the impact of hamstring elongation and
transfer in the longer run. The research study included 18 limbs that showed similar

improvement in the previous studies conducted on popliteal angel, minimum knee flexion in
stance phase, average of pelvic tilt and worsened peak hip power in stance phase pre and
post-operative. However, when compared between post-operative and long-term, there lies an
obvious improvement in popliteal angel by about 6 degree in long-term, minimum knee
flexion increases slightly from 0.5 degree, with an average pelvic tilt decrease by 1 degree
and peak hip improved by approximately 0.2 w/kg in long term follow-up. Therefore,
decreasing pelvic tilt degree and improving peak hip power in long term might contradict
previous assumption about recurrence of crouch knee after hamstring lengthening surgery,
but this finding needs more investigation to confirm the long-term effect of hamstring tendon
lengthening while referring to a number of sample sizes. In contrast, the group of hamstring
tendon transfer in the longer run slightly increased in popliteal angel of 4 degree, with the
average pelvic tilt dealing with slight deterioration by 1 degree and minimum knee flexion in
stance was almost increased being double by 5 degree in long term follow up.
Although, all parameters indicate the long term hamstring tendon transfer become
deteriorated slightly and indicate the potential recurrence of crouch knee, the hip power
surprisingly improved by approximately 0.2 w/kg in long-term follow up. Thus, this
improvement in peak hip power raise may be a major concern and encouraging to investigate
why hip power improved while all parameters decreased. The answer that may solve this
concern is hamstring tendon transfer may have the ability to stabilize the pelvis and generate
hip extension power that will move pelvic posteriorly because the hamstring moment arm
become greater when this muscle become monoarticular rather than bi- articular (Dreher et
al. 2013). Moreover, another explanation is spastic children cerebral palsy suffering from
different muscle not just a specific single muscle, but all muscles rather than hamstring that
has enough power for attributing the crouch knee (Flynn and Wiesel 2012).
Related to the articles referred to conclude this essay, comparison between hamstring tendon
lengthening and transfer increases the curiosity to understand what has more positive impact
on child’s gait. Therefore, the hamstring tendon transfer shows a positive impact on pelvic tilt
degree and popliteal angle dealing with better improvement. Moreover, the result of
hamstring tendon transfer, which would change hamstring muscle from bi-articular muscle
into monoarticular muscle, results in creating large movements of the arm that generate high
hip power as a consequence and reflects on kinematic of knee positively to correct crouch
gait. However, lengthening hamstring tendon will lose hip and knee power. To support the
claim, one study depicted long-term improvement because of the relative small power size in

that study comparing with other studies. Other studies depicted large power size and
recurrence crouch knee. In general, the hamstring tendon transfer show a positive impact on a
child’s knee being kinematical and kinetical that may enhance the quality of the gait.
Clinical Implication
The hamstring tendon lengthening has some drawbacks that may influence a child’s gait
negatively such as anterior pelvic tilt, decrease hip and knee power and may lead towards
recurrence crouch knee (Dreher et al. 2013). The reason for that is elongated muscle that will
result in the loss of contractibility that lead to weakness (Jozsa et al. 1990) and muscle
implanted in pelvic also may contribute to increase pelvic tilt (De Mattos et al. 2014).
Focusing on hamstring and qudercips flexibility and strengthened knee will stabilize knee
joint and prevent recurrent crouch knee (Tecklin 2008). One of the best exercise that may
improve muscle strength and coordination for both hamstring and qudercips can be
considered as a cycling therapy (Rimmer 2001). Fowler et al (Fowler et al. 2010) did
randomized control trail study on 68 child with spastic cerebral palsy and the result was
significant improvements in, gross motor function, and some measures of strength such
hamstring in the cycling group. Therefore, the cycling therapy will be recommended to
include in rehabilitation protocol after hamstring tendon lengthening operation to maximize
knee and hip power. Another concern about hamstring tendon lengthening is increase pelvic
tilt because of weakness of hip extensor that show in hip power and hip flexor contracture
that may lead to recurrent flexed knee (Dreher et al. 2012).
Thus, stretching exercise for hip flexor and strength hip extensor should be considered to
minimize the side effect of hamstring tendon lengthening surgery (Sahrmann 2013). On the
other hand, hamstring tendon transfer has more advantages than hamstring tendon
lengthening in pelvic tilt and great hip power that reflect on hamstring strength, but the main
issue in hamstring tendon transfer is decrease knee flexion during swing phase because of the
hamstring tendon was changed into distal femur side (Dreher et al. 2013). To increase knee
flexion in swing phase strength gastrocnemius, which acts as a knee flexion and ankle planter
flexion, should be included in treatment plane after hamstring tendon transfer surgery (Rha et
al. 2015). The reason of anterior pelvic tilt in transfer group is different in lengthening group
that because the unequal force between hip flexor and extensor muscle that illustrate in peak
hip power (Dreher et al. 2013). Therefore, strengthening exercise in hip flexor might
equalization pelvic power and reduce anterior pelvic tilt (Mansfield and Neumann 2014). In

general, the hamstring tendon transfer surgery shows significant difference in hip power and
not even a single article had been found to conclude recurrence of flex knee, while the
hamstring tendon surgery shows the opposite effect. The plane of treatment is different
between two types of surgery in tendon transfer group the gastrocnemius should be strength,
while hamstring should be strength in lengthening group. Both groups should strength and
stretches selective muscle group hip flexor or extensor depend on cause of the anterior pelvic
tilt and cycling will be best training for both groups.
Conclusion
The cerebral palsy child, who has crouch knee, faces difficulties in walking such as hip and
knee flexion because of hamstring contracture (De Mattos et al. 2014). The surgery aims to
enhance increase knee extension in mid-stance rather than knee flexion ((Feng et al. 2012).
The types of surgery that could help improving crouch knee is hamstring tendon lengthening
and hamstring tendon transfer. Both surgeries show significant difference in kinematic
parameter that provides scientific evidence to enhance children’s gait. However, hamstring
tendon transfer shows a great positive impact on both kinematic and kinetic parameters that
would be more beneficial than hamstring tendon lengthening. In addition, the treatment plane
is different in both groups because of variation that cause the problem, but the cycling
therapy should be included as a treatment for both groups to improve muscle power for
different muscle. To sum up, these findings may assist both physiotherapist and pediatric
surgeon to decide which treatment and surgery most appropriate for crouch knee gait in CP
child.

References
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