Staying Out of Trouble with the Hip: Legg-Calvé-Perthes, Slipped Capital Femoral Epiphysis, and Transient Synovitis vs. Septic Arthritis

Legg-Calvé-Perthes is an idiopathic avascular necrosis
(AVN) of the capital femoral epiphysis in a young child. The condition
tends to run a fairly predictable time course. It affects both hips in
about 10% of cases and is much more common in boys (about 4 to 1).
Children with Legg-Calvé-Perthes disease most commonly present between
the ages of 4 and 8 years, but the condition may be seen in children
less than 2 years old and as old as skeletal maturity. Most of the
trouble with Legg-Calvé-Perthes disease revolves around making the
diagnosis, dealing with the parents, and being selective about surgical
treatment. Without careful selection, the orthopaedist can get into
trouble by overtreating the young or the mildly affected, or the
untreatable severe cases, or conversely, get into trouble by missing
the more involved older child who would really benefit from surgical
management (Fig. 22-1).

The key to staying out of trouble and making the
diagnosis of Legg-Calvé-Perthes is to recognize that the presentation
can be very subtle and may be mistaken for transient synovitis in the
early stages.¹ The most common experience of

the orthopaedist at diagnosis is a mom who says “I notice a slight limp
at the end of the day, but he wasn’t complaining of pain.”

Another source of trouble with Perthes is being fooled by conditions that imitate it (see box).

On physical examination, the only sign of a problem may
be a subtle asymmetry in hip motion, typically a loss of hip abduction
and/or internal rotation. In a young child in the early stages of the
disease, the examiner should carefully control the pelvis during
examination to avoid missing subtle asymmetry between the hips.

In later stages of the disease, the child may have a
flexion contracture and a positive Thomas test. Contracture or spasm of
the adductor tendon can also be seen. Just as it is easy to miss a
subtle loss of hip motion, it is easy to miss gait abnormalities early
in the condition. If there is a subchondral fracture or a hip effusion,
the child may walk with either an antalgic gait or with the foot
somewhat externally rotated. Later in the condition, the child may
develop a Trendelenburg gait and have a Trendelenburg sign.

To stay out of trouble, order an anterior/posterior and
frog lateral plain radiograph at the first visit for any child who
presents complaining of hip or thigh pain.

Dr. Crawford will look for the “Catawampus sign,” a
pelvic shift to obliquity on frog lateral. If there is no synovitis,
the pelvis will be level. If there is a synovitis, the pelvis is
shifted to the affected side because the x-ray technician is trying to
abduct that side but since the hip won’t abduct, the child elevates
that pelvis and it appears “catawampus,” or out of line. Beware of the
appearance of joint effusion, which might be evidence of early growth
failure or growth of the femoral head. Be aware that even high-quality
plain radiographs may be normal at the first visit.

On initial radiographs, look for the extent of
involvement of the femoral epiphysis, paying particular attention to
the lateral pillar, which increasingly has been shown to be a key for
prognosis. Advanced imaging, such as technician 99 bone scan or MRI,
are not typically ordered when a child presents with Perthes. If the
differential diagnosis is concerning and the physician needs to search
for the source the hip or thigh pain, a bone scan, especially with pin
hole views, can be a good locator.

MRI is sometimes used to assess the extent of femoral
head involvement early in the disease process. However, some believe
that the MRI will exaggerate the involvement without contributing
significantly to the treatment decision.

The treatment of Legg-Calvé-Perthes disease remains
controversial, and has been dominated in the past more by personal
preference and local customs than good

data.
There are several keys to staying out of trouble when treating Perthes.
First, it is important to understand how much the concept of a “dead
hip” terrifies parents. Parents who present to you, especially for a
second opinion, can be bewildered by information on the Internet and
the multiple varying opinions that they get from experienced “experts.”
To stay out of trouble, you will need more time with these families to
explain the pathophysiology of the condition, the expected time course,
and the limited amount of long-term natural history and treatment data.
It is disconcerting to families to learn how little we know about this
condition. The recent publication of better studies²,³
has shown us that staying out of trouble means more than adhering to
the time-honored principles of just motion and containment.

It is clear that the orthopaedic surgeon should focus
attention on children 8 years and older, and on those with moderate hip
involvement (Herring B, or B/C). Surgeons and children get in trouble
when a complication occurs in the process of overtreating one of the
60+% of children who would do perfectly well without ever seeing a
doctor.

Trying to rest the hip of an active (often hyperactive)
boy or girl with Legg-Calvé-Perthes can create trouble for the family
and the doctor. Children less than 6 or 7 years are usually not
coordinated enough to be able to use crutches. Even children old enough
to use crutches cannot be expected to be completely compliant with
them. Therefore, when resting the hip seems important, many prefer to
use abduction (Petrie casts) (Fig. 22-2) for a
period of 6 weeks, followed by physical therapy to work on hip and knee
range of motion. To stay out of trouble with Petrie casts, be careful
to pad carefully around the Achilles tendon, as this is a common site
of cast pressure sores. Also, prepare the family for a child who is
difficult to transport and move around the house.

Should the orthopaedist choose a surgical option, there
are certainly several areas that can be sources of trouble for any of
the operations: shelf arthroplasty, Salter osteotomy, or varus
derotational osteotomy (VDRO). Each of these surgical options has one
or more champions who promote it as the best option for most kids. Each
method has pros and cons and sources of trouble (see next page). A
common theme for any procedure is to avoid surgery on a very stiff hip.

The orthopaedist should learn to diagnose hinge abduction, as it alters the operative approach.⁴

Slipped capital femoral epiphysis (SCFE) is the number
one adolescent hip disease, estimated at 1 per 10,000 in the United
States, and is probably increasing with the epidemic of pediatric
obesity. About 80% of the cases occur during the adolescent growth
spurt (at approximately 12 years old for girls and 13.5 years old for
boy). The condition is said to be more common in obese African American
boys, and more common on the left side. One key to staying out of
trouble with SCFE is to recognize the child who is an outlier in terms
of these demographic criteria. If the child is not in the typical age
range, consider a possible underlying cause such as renal
osteodystrophy, hypothyroidism, panhypopituitarism, and hypogonadal
conditions.

About 25% of the cases of SCFE are bilateral, although
some experts believe that up to 60 to 80% are bilateral, many being
silent cases that are not discovered until much later. Perhaps the
greatest source of trouble with SCFE is a delay in diagnosis (Fig. 22-4). In one series, the mean time from first seeing a physician until the correct diagnosis was nearly 4 months.⁶ Remember that in SCFE associated with renal failure, the SCFEs are bilateral in 95% of cases.⁷
It is also important to remember that the age at the time of
presentation of SCFE is predictive of whether a contralateral SCFE will
occur.⁸,⁹

At presentation, the child will usually have hip, groin, or thigh pain, often for a long time.¹⁰ A recent study¹¹ was published in the journal Pediatrics
to target the primary care audience. The authors determined that
patients who present with primarily knee or distal thigh pain, patients
with Medicaid coverage, and patients with stable slips have longer
delays in diagnosis of SCFE.

Although quite a bit of research has been done on missed SCFE by primary care doctors,⁶
there are plenty of anecdotal stories about orthopaedic surgeons
missing the diagnosis. These include stories in which the surgeon first
thinks of SCFE while trying to get the externally rotated hip into the
leg holder for a knee arthroscopy, or worse, discovering a SCFE at one
of the knee arthroscopy postop visits (Fig. 22-5).
On physical examination, these children will often have an abductor
lurch or an antalgic gait. The foot is usually externally rotated. On
the table-top exam, the patient will demonstrate obligate external
rotation and abduction with attempts to flex the hip (Fig. 22-6). To stay out of trouble, recognize

the signs of an acute unstable SCFE. Children will not be able to walk
and may have pain just with gentle log rolling of the hip. This is
considered by many to be an orthopaedic emergency.

Poor imaging, or the misreading of good imaging, can be
a source of trouble with SCFE. An AP and frog lateral of both hips
should be obtained. Although some believe that the true lateral
radiograph is more sensitive, it is much harder to obtain in a morbidly
obese adolescent with hip pain. Often, the AP view will show important
signs of a mild SCFE for the careful observer, such as subtle physeal
widening, a break in Klein’s line (Fig. 22-7) or a decrease in femoral epiphyseal height of the involved side compared to the opposite side.

More advanced imaging, such as bone scan or MRI, is
rarely necessary in SCFE. In some select cases, when there is a very
high clinical suspicion, but no confirming evidence on good quality
plain radiographs, an MRI can be helpful to

make the diagnosis¹² (Fig. 22-8).
The surgeon should look for edema on either side of the physes. Other
signs on MRI may be slight widening of the physes and a hip effusion.
Beware, however, that an obese adolescent with a hip effusion could
certainly have some other condition.

The goals of treatment of SCFE are to stabilize the
physis before more epiphyseal displacement occurs and avoid AVN or some
procedure or hardware-related complication. There is general agreement
that an unstable SCFE should be treated as an emergency, and admitted
and operated on as soon as possible. Stable SCFEs should be treated
promptly as well. Every institution has stories about mild stable SCFE
patients who went home for the weekend and had significant progression.

In stabilizing a slipped capital femoral epiphysis, the
surgeon should aim to have a screw (7 mm or bigger) into the center of
the femoral head on every radiographic view, perpendicular to the
physis, stopping about 5 mm from the subchondral bone of the epiphyseal
articular cartilage. To stay out of trouble, avoid the posterior,
superior portion of the femoral head where the blood supply enters the
epiphysis. If you are going to miss in one direction or another, miss
with your screw inferior to the center of the head.

Good intraoperative imaging is essential to staying out
of trouble. You should be able to clearly visualize the femoral head on
both the AP and lateral views. Many surgeons have discovered that it is
easier to obtain good visualization of the

femoral head on the lateral view in an obese adolescent using a radiolucent table.¹³
The same visualization can be very difficult on the fracture table.
Using the radiolucent table is a somewhat more demanding technique,
because it is easy to bend the guide pin as the hip is taken into the
frog lateral position. In very obese kids, an arthrogram can help to
keep you out of trouble.¹⁴

Classic descriptions of the surgical technique recommend
entering the anterior femoral neck as proximal as is necessary in order
to place the guide in perpendicular to the physes. If you use the same
technique as for pinning an adult hip fracture, you may not be
perpendicular to the physis and you risk subtrochanteric fracture (Fig. 22-9).
Such recommendations, however, can lead to several sources of trouble
in severe SCFEs. As the entry site for the screw gets closer and closer
to the physis, there is less metaphyseal bone of the femoral neck to
hold the screw. This can lead to cut out of the screw, progression of
the slip after pinning, or femoral neck fracture.¹⁵ Likewise, the anterior screw can also abut against the edge of the acetabulum (Fig. 22-10) during flexion and extension, leading to damage. Hard bone can be a problem as well (Fig. 22-11).
In chronic SCFE, the bone just distal to the physes can become very
dense, as the region is subjected to high shear forces during the
progression of the slip. When drilling your guide pin, don’t allow it
to stop in this dense bone: it can be very difficult to restart the
guide pin. Judicious use of live fluoroscopic imaging and continuous
drilling can avoid this problem. In most cases, it is unnecessary to
overdrill the guide pin. However, if you like to overdrill, be very
alert that any bend in the pin could lead to shearing of the pin during
over drilling. Robb, et al.¹⁶ described six cases in which the guidewire was damaged by the cannulated drill (Fig. 22-12).
In five of those cases, the wire broke off within the femur. The broken
wire was retrieved in two of the cases but not in the remaining three.
Although there is controversy about how far the screw should be across
the physis, most experts and studies recommend 4 to 5 threads into the
epiphysis. One recent study¹⁷ found
that slip progression is inversely related to the number of screw
threads engaging the epiphysis on the postoperative frog-leg lateral
radiograph. Finally, after the screw is in place, it is essential to be
certain that the most proximal tip of the screw is not in the joint
itself. Use of the approach and withdrawal technique can assure proper
screw positioning at the end of the case (Fig. 22-13).

Special considerations may be necessary to stay out of
trouble in atypical SCFEs. If the SCFE is related to renal
osteodystrophy, the keys are combined medical management and surgery
with custom-machined pins preventing slip progression while allowing
continued physeal growth.¹⁸ Warn
parents of children with Down syndrome that there is a much higher
incidence of AVN in Down kids, and look for hypothyroidism.¹⁹,²⁰

After surgery, partial weight bearing is recommended, although most adolescents will stop using crutches within about 2 weeks. Persistent hip pain that lasts more than 2 weeks after surgery should be a red flag!
Because most patients experience a rapid relief of their preoperative
symptoms, the surgeon should carefully look for problems if the patient
returns for a followup visit and there is persistent hip pain.

It is helpful to advise the family prior to treatment
that screw removal is generally not indicated. Because symptoms are
rare, and will probably not complicate a total hip in the future, the
removal procedure can be a major source of problems. Another important
counseling discussion regards whether the asymptomatic side should be
stabilized with a screw. A recent study showed that in cases in which
the probability of contralateral SCFE exceeds 27%, or in cases in which
reliable followup is not feasible, pinning of the contralateral hip is
favored.²¹ Another study showed that
the triradiate cartilage was a good clue: if it is closed, there is
only a 4% chance of contralateral slip.²²
The decision as to whether to pin one or both hips thus depends heavily
on the interaction between the surgeon and the parents. To stay out of
trouble, if the child is from a typical demographic group and followup
will be reliable, observation is generally preferred to the risk of
creating a complication on the asymptomatic side (which is uniformly
unappreciated by families and exploited by plaintiff attorneys). On the
other hand, if the child has renal osteodystrophy, hypothyroidism or
some other endocrine problem, cannot be relied on for followup, or has
parents who aggressively want both hips fixed, it is probably best to
offer bilateral internal fixation at the time of the initial
presentation.

Although only about 5 to 10% of SCFEs are unstable (Fig. 22-15),
they certainly cause more than 5 to 10% of the problems. To stay out of
trouble, an unstable SCFE should be treated as an emergency, and the
family should be counseled at the time of presentation about the high
risk of AVN. A second screw for additional internal fixation may be
considered, and the child should be followed very closely in the
postoperative period. At the time of fixation, “inadvertent” reduction
is the standard practice at many centers. Many believe that “the damage
is

done” to the blood supply to the epiphysis, so reduction (to unkink the vessels and create a more physiologic hip) is performed.²³ Such empiric beliefs and observations have been supported by a recent angiographic study.²⁴ There is also some evidence that a capsulotomy may decrease the risk of AVN after reduction.²⁵ Unfortunately, the trial lawyers have evidence in the literature to condemn reduction,²⁶ and thus many surgeons feel the need to use the words “inadvertent reduction” in the operative note.

Internal fixation of a valgus slipped capital femoral
epiphysis presents certain challenges. The perfect trajectory for a pin
may put the neurovascular bundle at risk²⁷ (Fig. 22-16).

Transient synovitis is the most common cause of hip pain
in school-age children. Conversely, septic arthritis of the hip is rare
but is a potentially crippling disaster if the diagnosis is delayed or
not made at all. Distinguishing transient synovitis from septic
arthritis is an essential skill for staying out of trouble in pediatric
orthopaedics. Although recent studies have provided some clinical
predication rules,³¹, ³², ³³ they are no substitute for experience, good judgment, and a careful history and physical examination.

In septic arthritis, the child is usually sick, getting
worse by the hour, and will not bear weight on the involved side. There
is usually pain with simple log-rolling of the hip. Usually the CRP is
up even early in the condition. Erythrocyte sedimentation rate (ESR)
may not be elevated in the first 24 hours of infection.³⁴

The key to diagnosis is history and physical examination
followed by an aspiration of any hip that is suspicious for septic
arthritis. Beware of the possibility of a false-negative ultrasound,
especially if the symptoms have been present for less than 24 hours.³⁵

To stay out of trouble, the surgeon should be fairly
aggressive in the indications for irrigation/debridement. Most authors
recommend that if the white count is higher than 50,000 in the fluid,
the rest of the clinical picture suggests septic arthritis; a formal
open irrigation and debridement of the hip through an anterior approach
is then recommended.

To stay out of trouble, it is best to err on the side of
irrigation and debridement than to miss a case of septic arthritis. In
this way, it is much like the philosophy the general surgeons have for
treating appendicitis.

The surgical technique for draining septic arthritis is
familiar to most pediatric orthopaedists. To stay out of trouble, it is
important to avoid the blood supply, which comes in posteriorly. For
this reason, the approach is anteriorly through the tensor fascia
lata/sartorius interval. It is important to have a very definite
capsulotomy. Many surgeons recommend actually taking a small piece of
the capsule out to be certain that the joint has been decompressed. It
is important to irrigate the joint aggressively and decompress the
femoral neck if there is associated femoral neck osteomyelitis. A drain
is usually placed around the femoral neck and pulled a few days later.
Without a drain, the hip arthrotomy can close quickly and there can be
a reaccumulation of the fluid, necessitating repeat surgery. The child
should rest in bed for a couple of days to keep the drain in and allow
the hip to quiet down. Antibiotic management lasts 4 to

6
weeks, based on the organism that is cultured and the recommendation of
the infectious disease experts. CRP is the most valuable test to follow
in the postoperative period.

To stay out of trouble, beware when C-reactive protein
does not rapidly normalize in the first week after surgery. In the face
of either persistent symptoms or an elevated CRP, the surgeon reflect
on these questions: Could there be another collection in another area?
Could the fluid have reaccumulated? Is the diagnosis right? Are the
antibiotics right?

After septic arthritis, followup for at least a few
years is valuable, to study growth and the risk of AVN. For neonates
who experience sepsis, it is the orthopaedist’s job to prove that there
are not two septic hips or septic arthritis elsewhere. Multifocal
septic arthritis is very common in the neonate and can be a major
source of trouble. It is best to aspirate both hips and perhaps other
joints in order to make the diagnosis as soon as possible.