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3. Knee
1. Functional anatomy and characteristics of the deformities
Muscle Functions
Antigravity Muscles
Flexors:
-Biceps femoris (short head)
(See the clause of "Hip joint; functional anatomy and
characteristic of the deformity")
-Semimembranosus (Muscle fibers
with short distal tendon fibers)
-Muscular origins of the gastrocnemius (lateral and medial
heads)
These muscles flex the knee, stabilize it in the stance phase
and prevent its hyperextension. During the swing phase, they lift
the leg upwards against gravity, and assist to clear the foot from
the ground.
Extensors:
-Vastus medialis
-Vastus lateralis
-Vastus intermedius
These muscles extend the knee joint, keep it in extended
position, stabilize it in semiflexed position, and prevent the
collapse of the knee during stance phase.
Non-antigravity Muscles
Flexors:
-Biceps femoris (Long head)
This portion flexes the knee, and participates in the
propelling movements of the body.
-Semitendinosus
It flexes the knee, and participates in the propelling
movements of the body.
-Gastrocnemius (lateral and medial head with tendinous origin)
They flex the knee and propel the body in various activities
such as rolling, crawling, walking and running.
Extensors:
-Rectus femoris
This muscle extends the knee, and participates in propelling
the body forwards in the activities of rolling, crawling. walking
and running.
-Sartorius
This muscle extends the knee and propels the body forwards.
- Gluteus maximus and tensor fascia lata)
These muscles extend the knee, as a supplemental extensor.
Development of the Knee Joint and Its Characteristics
Characteristics of the knee in the human body are observed
in its extended position at upright standing. In the phylogenetic
development to attain the upright posture, humans have developed
an elaborate extending mechanism, which mostly depends on the
well-developed quadriceps, and enabled them to stand upright with
extended knees. Development of the skeletal system is also needed
to achieve stability and to prevent lateral instability of the knee.
So, in order to provide stability, the femoral condyles and tibial
plateaus are well developed, providing a large contact area between
the femur and tibia. The development of the patella in front of the
joint, and the semilunar cartilages in the medial and lateral joint
spaces, is another elaborate mechanism. Ligamentous enforcement
with the anterior and posterior cruciate ligaments and medial and
lateral collateral ligaments are also important.
The muscular body-supporting mechanism is also
elaborately developed. Antigravity activities of the vastus
lateralis, medialis and intermedius give anterior stability, through
muscular fixation of the patella to the floor of the patellar groove
on the femur. The gluteus maximus and tensor fascia lata also
support the lateral side of the knee through iliotibial tract. The
sartorius supports the medial wall of the knee. Posterior wall is
supported with activities of the monoarticular biceps femoris,
popliteus, semimembranosus and muscular origins of the medial
and lateral heads of the gastrocnemius. With these elaborate
skeletal, ligamentous and muscular support mechanisms, extended
posture of the knee in upright walking posture can be achieved,
and consequently, energy loss can be minimized in these erect
postures of the human body. In the knee joint, excessive stress
against the joint surfaces can be minimized and effective weight
bearing made feasible by keeping the knee in a slightly flexed
posture.
In cerebral palsy, however, the monoarticular body
supporting muscles such as the vastus medialis, lateralis and
intermedius are mostly weakened, and consequently, flexion
deformity of the knee results, with decreased weight bearing
ability. Here, the knee joint cartilage is exposed to excessive
stresses in various directions, and can cause rapid degeneration
affecting the activities and the quality of life in humans.
The extension deformity due to the excessive hypertonicity
of the quadriceps which is called as recurvatum, or stiff-legged
knee is another serious problem. In this deformity, the patient does
not have an effective antigravity stance phase with the knee
flexed during gait, thereby losing the protective and flexible
mechanism of the knee, causing early degenerative changes in
older patients.
2. Historical reviews
Flexion deformity is the most common deformity observed in
the knee. This deformity is originally caused by hypertonicity of
the hamstrings and the gastrocnemius, and fixed ligamentous
contracture of the posterior capsule is induced as a result of long
lasting flexed-posture. To correct this deformity, control of
hypertonicity of the flexors by selective muscle release is essential,
and secondly, correction of the fixed ligamentous and capsular
contractures in the posterior popliteal region is also needed. Many
approaches have been proposed for this correction.
Distal Hamstrings Transfer
Eggers in 1952 reported hamstrings transfer, from the tibial
condyle to the femoral condyle to correct flexion deformity, by
converting the biarticular hamstrings to monoarticular hip
extensors, thereby preserving the extension activity of these muscle
in the hip.189 This consideration seems to be reasonable, since
only hypertonicity of the hamstrings as flexors of the knee is
selectively relieved, and activity of the hamstrings as extensors of
the hip is preserved. This approach may be used only in older
patients with the capsular contracture for correction of some fixed
flexion deformity of the knee, because the postoperative
recurvatum deformity due to predominant hypertonicity in knee
extensors can be prevented by the ligamentous contracture.
However, when indications are broadened to the dynamic
and moderate deformity where the fixed ligamentous contractures
have not developed, reverse deformity such as stiff-legged-knee or
recurvatum might be caused. Bleck stated that the total transfer
often resulted in a straight knee in which the flexors could not
function and so stability and flexible weight bearing posture with
slightly flexed knee was lost.67 Difficulty in flexing the knee in
ADL also presents serious problems. In order to prevent these
serious complications, various considerations have been proposed.
Sutherland and associates in 1969, reported lateral transfer of
the semitendinosus and semimembranosus, to the lateral aspect of
distal end of the femur, for correction of internal rotation of the hip
and crouched posture. Here, the preserved biceps femoris can be
considered to prevent hyperextension of the knee.146 Ray and
associates in 1979, reported the same lateral transfer, preserving
other flexors to prevent occurrence of stiff legged knee.151
However, importance of the semimembranosus as supporter and
stabilizer of the medial and posterior side of the knee should be
considered. Bleck stated that he abandoned transfer of the
hamstrings, to avoid postoperative extension tendency of the knee.
67
Hamstrings Lengthening
Lengthening of the hamstrings are also commonly used for
correction of flexion deformity of the knee. Selective lengthening
of the medial hamstrings is recently advocated.
Thometz and associates presented an approach in
which they lengthened tendons of the gracilis and semitendinosus,
by using the Z plasty lengthening, and also lengthened the musculo
tendinous insertion of the semimembranosus and biceps femoris,
by using the intramuscular tenotomy technique.59 This procedure
is more reasonable, as the semimembranosus and biceps femoris
have very short tendons at their insertions, and therefore they are
considered to be posterior supporters of the knee, preventing its
collapse to recurvatum posture.
Similarly, Hsu and associates reviewed49 patients in whom
the semitendinosus and gracilis tendons were elongated by Z-plasty
and the semimembranosus and biceps femoris were elongated by
section of intramuscular tendon for correction of crouched posture.
190 They reported that 40 of 49 patients had significant
improvements in gait pattern and 18 had improvements in motor
function level.
In 1992, Dhawlikar and associates presented 126 CP patients
who had been treated with tenotomy of the semitendinosus and
gracilis and aponeurotomy of the semimembranosus and biceps
femoris with excellent results in walking ability and straight leg
raising test.191
Thus, in the correction of knee flexion deformity, new
considerations have been introduced recently. Differences in form
and function of each of the hamstrings have been carefully noticed,
and applied in the surgical treatment. The semimembranosus and
biceps femoris are defined, as stabilizers of the posterior aspect of
the knee, and some of their activities have been preserved, by
using the intramuscular lengthening. On the other hand, the
semitendinosus and gracilis tendon can be lengthened by using the
sliding technique, as they are the main contributors of knee flexion
deformity. We also have carried out a similar approach since 1983,
with excellent results.192
Proximal Lengthening of the Hamstrings
Silverskiold in 1923 recommended the transfer of the
proximal origin of the hamstrings to the posterior region of the
femur for correction of flexion deformity of the knee. He was the
first to consider the proximal tendon of hamstrings in the treatment
of knee flexion deformity.166
Proximal myotomy of the hamstrings was then proposed by
Seymour and Sharrad, for reduction of tightness of the hamstrings
with limited flexion of the hip, a short stride length, and limited
straight leg raising.161 Drumond and associates applied this
procedure for correction of flexion deformity of the knee, and for
short stride-length. He reported postoperative excessive lumbar
lordorsis and genu recurvatum, and described that total proximal
release was no longer recommended.193 Reimer also stated
various advantages of the proximal release.194
Serious concerns regarding proximal lengthening of the
hamstrings are the postoperative excessive hip-flexion, followed by
excessive lumbar lordosis and anterior tilt of the pelvis. Hip flexion
can be caused more directly by the proximal release than by the
distal release, as the hyperactive extensors are directly released at
the hip. There is general agreement that in the cases of proximal
lengthening of the hamstrings, postoperative flexion of the hip can
present serious problems of anterior pelvic tilt and excessive
lordosis. Therefore, distal lengthening has been considered for
correction of the knee flexion deformity.
Proximal Release of the Gastrocnemius
The gastrocnemius is an another factor causing flexion
deformity of the knee. There are some severely contractured knees
in which simple flexor release or transfer of the hamstrings such as
Eggers procedure is not effective. In spite of aggressive release of
the hamstrings, correction will not be achieved, leaving residual
hypertonicity and contracture. This is because there remains
hypertonicity of gastrocnemius as a knee flexor. So for achieving
sufficient and satisfactory correction in the knees, releases of the
ligamentous contracture in the posterior capsule and the proximal
tendons of the gastrocnemius should be considered. However,
release of the gastrocnemius has been rarely mentioned in the
literature. In 1958, Banks and associates reported proximal
aponeurosis lengthening of the gastrocnemius for correction of
equinus deformity, in the patients with flexion deformity of the
knee. However, their attention was focused only on correction of
equinus deformity and not on correction of flexion in the knee.195
In 1921, Putti described posterior capsulotomy for correction
of fixed flexion deformity of the knee in paralytic conditions and
also introduced release of proximal-heads of the gastrocnemius.196
This proximal release of the gastrocnemius provides us with a
strong weapon, for correction of fixed flexion contracture of the
knee in older patients more than 20 years old. We are convinced
that tendinous insertion of the gastrocnemius to the femoral
condyle as well as all hamstrings are hyperactive knee flexors in
cerebral palsy and that they cause the knee flexion deformity.
Here, at our institute, severe flexion more than 50 degrees has
been appropriately corrected with combined approach of distal
lengthening of the hamstrings and proximal intramuscular
lengthening of the gastrocnemius (Fig. 6AB, 99AB).35,61,192
A. Before OSSCS
B. After OSSCS
Fig. 99AB: Effect of posterior release of the knee
15-year-old boy, Spastic diplegia
Flexion deformity with capsular contracture cannot be corrected by
just lengthening of the hamstrings alone, if hypertonicity of the
gastrocnemius is overlooked and its proximal origin is not
lengthened. In moderate fixed deformity, intramuscular
lengthening of the proximal head of the gastrocnemius combined
with hamstrings release is most useful for achieving correction.
Releases of the proximal tendinous origins of the gastrocnemius
correct the deformity quite effectively, while the preserved
muscular origin can act, as a protector and restraint of the back of
the knee, preventing recurvatum deformity.
For severely flexed deformity with fixed capsular and
ligamentous contractures, total posterior capsulotomy with section
of proximal tendinous and muscular origins of the gastrocnemius is
required.
Release of the iliotibial tract and sartorius
In severely flexed knee with fixed contracture, the tightened
and shortened iliotibial tract and sartorius are obstacles for
correction. It is not well known if these two muscles are flexors or
extensors. There seems to be some controversy on this matter.
However, clinically, these two muscles become tightened in the
process of operative procedure when all the flexor factors are
released and the knee is forcefully extended. Therefore, they can be
recognized as contributing factors in severe flexion deformity more
than 60 degrees. For correction, release of these two structures
could be considered.
Posterior capsulotomy
Capsular and ligamentous contractures in popliteal region are
an another factor causing flexion deformity. Release of these
structures is most effective. We have done this procedure in the
knee with fixed flexion contracture and achieved correction with
excellent results (Fig. 102AB, 103AB).61,192
Extensor Release (Genu Recurvatum Deformity)
(Overactivity of the Rectus Femoris)
Extension deformity of the knee is another problem causing
stiff-legged knee with decreased clearance of the foot during gait
and inhibited flexion of the knee during turnover, crawling, sitting,
and kneeling activities. The genu recurvatum after distal
hamstrings release presents a serious disaster with detrimental
effects at the knee, inhibiting normal swing and causing toe
dragging, circumduction and vaulting. Many authors are concerned
that the genu recurvatum deformity has resulted after some kind of
flexor release and have discussed how to prevent this hazardous
problem.197,198 Gage stated that full knee extension is mandatory, if
ambulation is the goal,57,58 and that Perry was the first to suggest a
transfer of the distal end of the rectus femoris, so that the muscle
can actually augment knee flexion during swing.
Gage documented that co-contractions of the biarticular
muscles limit range of motion at the knee joint, and that extensor
hypertonicity inhibits clearance of the foot. So, he recommended
concomitant surgery, including transfer of the rectus femoris and
release of the hamstrings. 57,58 Nene and associates used distal
transfer of the rectus femoris in their simultaneous multiple
operations for spastic diplegic and reported an improvement of
knee flexion from a mean of 28.3 degrees to 45.2 degrees during
gait.199 Patrick in 1996, described techniques of psoas tenotomy
and rectus femoris transfer, although no information about the
results is available.200
We also noticed the fact that overactivity of the rectus
femoris causes extended knee, and have developed an
intramuscular lengthening technique of the rectus femoris at the
distal musculotendinous region.35,36,192 This operation has been
carried out in 63 knees of 57 patients with stiff-legged knees or
genu recurvatum deformity. In most of these cases, excessively
extended knee has been corrected, and the dexterity of the knee
was restored (Fig. 6AB, 13AB, 18AB, 20AB, 23AB, 25AB,
100AB)).
A
B
Fig. 100AB. Effect of OSSCS for stiff-legged knee
5-year-old boy. mixed quadriplegia
(Spastic and ataxic)
The contracture of the iliotibial tract could be another
causative factor of extension deformity of the knee, although this
factor has been least documented in literature. Release of the
iliotibial tract proximal to the knee joint could be considered to be
effective for correction of fixed extension deformity of the knee in
totally involved patients with externally rotated hip.
3. Surgical Approaches
Considerations
Extension Deformity
Flexion Deformity
(Fig. 101AB)
A. Before OSSCS
B. After OSSCS
Fig. 101AB: Effect of OSSCS for correction of
flexion deformity of the knee
Patella Alta
(Fig. 101AB, 102AB).
Extent of Release
(Decision-making)
A
B
Fig. 102AB: Effect of OSSCS for correction of
flexion deformity of the knee
By concomitant release of the flexors and extensor,
rigidity of the knee was lessened, and flexibility restored.
Surgical Techniques
Fig. 103AB: technigues of release of the knee flexors
A: Muscle release
B: Posterior capsulotomy
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Fig. 104: technigues of release of the knee extensor
(Distal tendon of the rectus femoris)
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