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Slipped upper femoral epiphysis (SUFE) FRCS

Terms in this set (50)

location
left hip is more commonly affected
bilateral in 17% to 50% (~25%) 1/4
slipped capital femoral epiphysis (SCFE)
is an condition of the proximal femoral physis that leads to slippage of the metaphysis relative to the epiphysis, and is most commonly seen in adolescent obese males
incidence
10 to 10x5
demographics
more common in
1) obese children
2) males (male to female ratio is 2:1.4)- almost double
3) specific ethnicities - African Americans, Pacific islanders, Latinos
during the period of rapid growth (10-16 years of age)
Mean age of rapid growth?
girls: 11-13,
boys: 14-16
What are the two primary risk factors?
- Obesity (single greatest risk factor)
- acetabular retroversion and femoral retroversion
- history of previous radiation therapy to the femoral head region
What two other disorders are
associated with SCFE development?
- Hypothyroidism ( most common etiology of nonidiopathic SCFE
labs: elevated TSH)
- growth hormone deficiency
- General deficiency of the puitary gland
- Renal disease ( renal osteodystrophy)
Aetiology
- For those presenting in teenage years, the
underlying cause appears to be mechanical.
- For the younger children, the endocrine imbalance leads to weakening of the physis allowing the slip.
mechanical theory
slippage occurs though the hypertrophic zone of the physis (similar to Salter-Harris type I fracture)
in adolescence perichondrial ring thins and weakens
What four SCFE patient groups ought
to have an endocrine evaluation ( hormone work-up)?
<10 years old (young age)
>16 years old ( older age)
<50th percentile for weight
Bilateral involvement of hips
Most common endocrine disorders related with SCFE?
- Hypothyreodism (most common)
- Hyperparathyroididm
- Growth hormon deficiency
- panhypopituitarism
- Renal osteodystrophy
In which two directions does the
femoral neck (metaphysis) slip?
Anterior
Superior & extrenal rotation
In which two directions does the
epiphysis slip?
Posterior
Inferior
What does a biopsy of zone of
provisional calcifcation show?
Granulation tissue between columns
Renal SCFE from renal osteodystophy where it occurs?
through the secondary spongiosa (metaphysis)
What key physical exam finding is suggestive of SCFE?
Obligatory external rotation with hip flexion (Dremnan sign)

This produces a varus, retroverted deformity. Hence, physical examination of an affected hip classically demonstrates loss of internal rotation, flexion, and abduction
physical examination signs
- Obligatory external rotation with hip flexion
- loss of internal rotation of the hip
- decreased flexion
- abduction restricted
- limping, able to weight bear?
- shortening of the leg / trendeleburg gait
x-ray work up for SCFE
request pelvis X-ray (AP and cross-table lateral views of both hips)

I do not prefer frog lateral as it may worsen the severity in unstable slips; however, it is reasonable to request in a stable slip
What are the six radiographic features of
a SUFE?
(A) Steel sign: on anteroposterior radiography, a double density is found at the metaphysis (caused by the posterior lip of the epiphysis being superimposed on the metaphysis);
(B) widening of the growth plate (physis) compared with the uninvolved side;
(C) decreased epiphyseal height compared with the uninvolved side;
(D) Klein's line: on anteroposterior radiography, a line drawn along the superior edge of the femoral neck should normally cross the epiphysis; the epiphysis will fall below this line in slipped capital femoral epiphysis; and (
E) lesser trochanter prominence, which is caused by external rotation of the femur.
F) schams sign ( Loss of the normal overlap of the femoral neck metaphysis and the ischium) - Shenton's line break
What is Trethowan's sign?
Klein's line: line drawn along the superior surface of the neck in AP view. It should dissect the epiphysis.
In case it does not, which indicates a slip and a positive Trethovan's sign
What if this child's X-ray was normal?
Normal X-ray does not exclude SUFE (it may be in the preslip stage); therefore, I would request an MRI scan but also, I would consider other possible diagnoses.
Classification
SUFE can be classified according to :
1) stability (ability to weight-bear),
2) duration of symptoms
3) the severity of the slip
Loder classification ( The Loder classification divided slips into stable or unstable)- based on ability to bear weight
- Children with stable slips are mobile and weight-bearing to some degree.
- A child with an unstable slip is said to be in so much pain that they are unable to mobilize / stand even with crutches
The relevance of the stability of the slip is with regards to AVN risk prediction.
Loder described 96% good results in those with stable slips,
47% AVN occurring in those with unstable slips.
More recent studies have confirmed that AVN is more
common in unstable cases
SUFE may also be classified according to the duration of the symptoms:
Acute slips - <3 weeks duration of symptoms
Acute on chronic - Acute exacerbation of symptoms following a chronic slip
Chronic slips - >3 weeks duration
Those with chronic slips will have
remodelling changes on the posterior and inferior border of the femoral neck in an attempt to stabilise the head.
As the
blood supply to the epiphysis travels along the posterior aspect of the neck if the surgeon attempts to reduce a chronic slip they can stretch the vessel over the callus leading to AVN.
SUFE is classified according to the severity of the slip using
Southwick's angle
This is the angle between a line perpendicular to the epiphysis and the femoral neck line on a frog-leg lateral view
3 lines are drawn on the lateral hip radiograph.
1: a line connecting the two corners of the epiphysis;
2: a perpendicular line is drawn to 1 through the middle of the neck;
3:line is drawn along the axis of the femoral shaft.
The angle between line 2 and 3 is measured.
Southwick Slip Angle Classification - based on femoral epipyseal-diaphyseal angle difference
Mild - <30 difference from the other side
Moderate - 30 to 60 difference from the other side
Severe - >60 difference from the other side
Southwick Slip Angle Classification
- Epiphyseal-diaphyseal angle can be measured on both AP and frog lateral pelvis radiographs
- Slip angle classification is based on the degree of difference between the affected and unaffected hip
- If bilateral hips are involved, use 145° as "unaffected" hip reference for AP and 10° as "unaffected" hip reference for lateral
Classification of the degree of displacement of the head relative to the neck(Wilson) AP view
- mild slip (grade I) is one where the displacement of the head as a proportion of neck (physis) width <1/3
- moderate slip (grade II), displacement is between a 1/3 - 1/2 of the neck width
- severe slip (grade III) has displacementof > 1/2 of the neck width
Areas of controversy regarding the SCFE
- Prophylactic pinning of the contralateral hip
- 2 VS 1 pin for fixation
- partial threaded vs full threaded screws
- reduction of the slip
- traction fracture table vs radiolucent
- time for an intervention
- routine removal of the implants
traction fraacture table vs radiolucent controversy
The patient is positioned supine on a fracture table (without traction). The other limb can be placed in abduction or flexed and abducted on stirrup to allow for imaging.
Optimum visualization of the femoral head before the procedure is essential.

(In bilateral stable slip, a radiolucent table is preferred over the fracture table because it reduces the chance of worsening the contralateral slip by overenthusiastic positioning.
This also reduces the time for re-positioning and re-draping the contralateral side.
2 VS 1 screw for fixation controversy
double screws offer 66% stiffer construct- good for unstable, high grade slips

the risk of intra-articular penetration increases from 4% to 20% with double screws
partial threaded vs full threaded screws controversy
Although there were no differences between screw types in an in vitro model, bone healing around the fully threaded screw may eventually provide greater stability.

The use of fully threaded screw remains a reasonable option in the treatment of SCFE, and implant removal may be easier with such a system.
Management
The goals of operative management in SUFE are:
- to prevent any further progression of the slip,
- avoid avascular necrosis (AVN)
- convert a acute unstable slip into chronic stable
- provide the best long-term outcome possible for the child
Pinning-in-situ (PIS)
Indications :both stable and unstable slips
manipulation of the slip to provide an anatomical reduction
commonly resulted in AVN, particularly true in chronic
slips. This is because the posterior blood supply for the
epiphysis becomes tented over the remodeling changes from
the SUFE and the vessels contract to accommodate their new
position. By forcing the epiphysis back to an anatomical
position the vessel is overstretched compromising the blood
supply. The exception to this rule is the acute on chronic slip
the acute on chronic slip
It is acceptable in this circumstance, with very gentle positioning, to reduce the head to the chronic slip position prior to PIS
The modern technique for PIS
- use a single cannulated screw (6.5 or 7.3 mm) placed in the centre of the epiphysis on both AP and lateral views,
- perpendicularly to physis
- The screw typically requires an anterior entry point on the femoral neck to allow a clear shot at the centre of the epiphysis ( This also protects the vessels located at the inferoposterior aspect of the neck)
- avoid the entry point medially to the intertrochanteric line to avoid impingement
- The goal is to place at least five threads (=/> 5 ) into the epiphysis
- screws should be at least 5mm from the subchondral bone in all views
- confirm that pin is not penetrating the hip joint
Management of the contralateral hip / prophylactic pinning of the contralateral hip
contralateral hip prophylactic fixation controversial
current indications are :
high-risk patients for contralateral slip(~ 40-80%)
- initial slip at a young age (< 10 years-old)
- open triradiate cartilage
- obese males
- endocrine disorders (e.g. hypothyroidism), - renal disease- renal osteodystrophy
- Poor compliance of the child and family
- The nature of the current slip (a very bad slipoccurring over a very short period of time mayjustify pinning the other side)
Buzzphrase: I would discuss this with the family and advise on prophylactic pinning.
radiological markers have been proposed to aid decision-making about pinningthe other asymptomatic side in patients withSUFE
- the posterior sloping angle
- the modified Oxford bone age

Both of these markers are not perfect and do not have 100% positive or negative predictive value
posterior slip angle
is measured by a line (A) from the centre ofthe femoral shaft through the centre of themetaphysis;
a second line (B) is drawn fromone edge of the physis to the other, whichrepresents the angle of the physis. Wherelines A and B intersect, a third line (C) isdrawn perpendicular to line A.

The PSA is the angle formed by lines B andC posteriorly
Critical posterior slope angle for prophylactic fixation
I would have a low threshold to prophylactically pin the other side if the posterior slopingangle > 14° as research has shownthat the risk of contralateral slip would 83%.
Acute severe slips management
In this circumstance, there is no remodelling posteriorly to endanger the vasculature. There is a general consensus that open reduction of these slips is advisable.
After this stage, they advised placing the child on traction for a few weeks to convert the situation to a chronic severe slip and then
manage appropriately
The timing of surgery is controversial
Work from Southampton, amongst others, has
suggested that the risk of AVN in acute severe slips is related
to the timing of surgery10. They found that the risk of AVN
increased substantially past 24 hours of presentation
Late procedures
The two main late treatment plans to consider for SUFE are
- osteoplasty and
- corrective proximal femoral osteotomy
Osteoplasty
can be performed either open or arthroscopically. Shaving the extra bone of the metaphyseal hump prevents cam-type impingement as the hip is flexed and abducted.
Corrective proximal femoral SHORTENING osteotomy
The aim is to realign the proximal femur to improve the range of movement and prevent impingement and progression to osteoarthritis
Multiple osteotomies have been described for correction of
the deformity. The location of the osteotomy ranges from the
intertrochanteric region to the physis itself
- The closer the osteotomy comes to the physis the greater the possible correction that can be achieved.
- Unfortunately, the closer that the surgery is performed to the physis the greater is the risk of AVN.
Compare postoperative weightbearing status with stable and
unstable SCFE
Stable: weight-bearing as tolerated
(WBAT)
Unstable: non-weight-bearing
(NWB)
Follow-up until
Follow-up until there is a complete closure of the physis
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