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SattAR Sattar Alshriyda Section Editor, Segment Author
  • Slipped upper femoral epiphysis (SUFE) involves slipping of the femoral head (epiphysis) relative to the neck through the growth plate (often called the physis) resulting in the head of the femur staying in the acetabulum and the neck slipping forward and outward.
  • Incidence varies from (2-7:100 000) with:
  1. Gender: It is more common in boys (3:1) and they tend to have their slip two years older than girls.
  2. Race:  more common in blacks and Polynesians
  3. Side: It is more common on the left side (Like DDH). It is bilateral in about 20% (one half present initially with both hips involved, the others developed it later, majority within 18 months of presentation of the first hip).
  • Although, the cause is poorly understood, several anatomical features and medical conditions have been implicated. These either increase shear forces and / or weaken the physis.

The followings increase the shear forces across the physis and can lead to slip:

  1. Overweight
  2. Femoral retroversion
  3. Increased  physis height
  4. More vertical slope of the physis
  5. Trauma

Weakness of the physis may be due to:

  1. Metabolic diseases: renal osteodystrophy-95% bilateral and rickets
  2. Endocrine disorders (65% bilateral): Hypothyroidism, growth hormone excess or deficiency, panhypopituitarism, hypogonadism, hyperparathyroidism, multiple endocrine neoplasia
  3. Iatrogenic: (radiotherapy, chemotherapy and GH.
  4. Genetic: (Turner's, Downs, Marfan’s and Kleinfelters syndromes)

fig 1.png

Plain radiograph shows bilateral SUFEs; the right has been treated with pinning in situ while the left has not been treated yet.

  • A child with SUFE usually presents with groin, thigh and/or knee pain and limping. It is not unusual for the child to be unnecessarily investigated (may be treated) for the knee before the real cause is discovered. The presentation can be gradual (60%) or acute.
  • The child may be able to weight bear and ambulate (stable slip) or may not be able to do so even with crutches (unstable).
  • Majority are overweight. The leg is short and externally rotated. There is usually restriction in hip abduction and internal rotation. Moreover, there is obligatory further abduction and external rotation when the hip is flexed (FABRE sign).

fig 2.png

A clinical photograph of a child with SUFE, The leg is short and externally rotated left leg (mimic fracture neck of femur). Patient was investigated (x-ray and ultrasound) and treated for knee pain (notice the knee immobiliser).

Radiological tests

Plain radiograph

This includes AP and true lateral view. Although, a frog lateral view is easier to obtain, it may displace the slip further and the slip severity may vary due to variations in positioning the limbs. The followings are useful signs:

  1. Widening and irregularity of the physeal line (early sign)
  2. Trethowan’s sign; lines (often called Klein’s lines) drawn on the superior borders of the femoral necks on the AP view should intersect femoral heads symmetrically.
  3. Decreased epiphyseal height as the head is slipped posteriorly behind the neck.
  4. Remodelling changes (callus behind the neck, smooth, rounded and sclerotic upper border- sometime this is called Herndon’s hump).
  5. Break in Shenton’s line and increased distance between the tear drop and the femoral neck metaphysis
  6. Capener's sign: The posterior acetabular margin normally cuts the medial corner of the metaphysis. In SUFE the whole metaphysis remains lateral to the acetabular margin.
  7. Steel’s blanch sign which is a crescent shape dense area in the metaphysic due to superimposition of the neck and the head.

CT-Scan

It is useful adjunct for preoperative planning as well as ruling out penetration of the hip joint by metalware postoperatively.

MRI

Valuable in detecting pre-slip and AVN. Postoperatively, the metalware can interfere with the quality of pictures and prevent accurate diagnosis. Bone scan is useful in this situation.

1. Break in Shenton’s line and increased distance between the tear drop and the femoral neck metaphysis

2. Capener's sign: The posterior acetabular margin normally cuts the medial corner of the metaphysis. In SUFE the whole metaphysis remains lateral to the acetabular margin.

3. Steel’s blanch sign which is a crescent shape dense area in the metaphysic due to superimposition of the neck and the head.

fig 3 real.jpg

fig 3 b.png

These x-rays show a positive Trethowan’s sign where the Klein’s intersect the right femoral head at a higher level than the left side, there is a widened and irregular physis, the epiphysis height is less on the right side, a positive Steel’s blanch and Capener’s signs.

Blood test

Endocrine disorders must be considered in every patient with SUFE. Loder (Loder and Greenfield 2001) studied the demographics of 433 patients (285 idiopathic, 148 atypical) and found that weight and age were predictors for atypical SUFE and he recommended the age-weight test to guide further investigation for underlying endocrine problems: the test was defined as negative when age younger than 16 years and weight > or = 50th percentile and positive when beyond these boundaries. The probability of a child with a negative test result having an idiopathic SUFE was 93%, and the probability of a child with a positive test result having an atypical SCFE was 52%.

Functional (Loder 1993); according to weight-bearing status into:

  1. Stable: patient is able to ambulate and bear their weight (see video link https://www.youtube.com/watch?v=7wxwU-7PgMc)
  2. Unstable: patient is unable to ambulate with or without crutches

Loder retrospectively reviewed 55 SUFEs and found that that AVN developed in 47% of patients who were not able to weight bear at presentation and he classied these slips as unstable slips. The other group who were able to weight bear and ambulated (called stable hips) developed no AVN. He was not able to demonstrate an association between early reduction and the development of AVN. Of note, unintentional reduction of the slip occurred in 26 unstable slips (out of 30) and in only 2 of the stable slips (out of 25).

Chronological- relating to the onset of symptoms;

  1. Pre-slip: patient has symptoms with no radiological evidence of displacement of the femoral head. Plan x-ray may show widening and irregularity of the physis.
  2. Acute: Symptoms and signs develop over a short period of time (<3 weeks)
  3. Chronic: Symptoms and signs develop over a longer period of time (>3 weeks), often months to years.
  4. Acute on chronic: Patients usually have features of chronic slip that suddenly increase in severity.

Morphological- majority of cases of SUFE, the epiphysis is displaced posteriorly and inferiorly (Also-called varus or posterior slip) relative to the femoral neck. In rare cases, the displacement is either superior or posterior (Also-called valgus or anterior slip).

fig 4.png

A clinical photograph of the same child (above), he walked in the clinic using crutches. Although he was not able to put any weight on left side, he was able to ambulate. This is stable slip. In contrast to patient with unstable slip who cannot ambulate and is brought in on a stretcher.

Two grading are in common use:

Wilson: This is based on the proportion of neck displacement from the femoral head; mild when the neck is displaced less than one-third of the diameter of the head, moderate when the neck is displaced between one-third and one-half of the diameter of the head  and severe when neck displacement of more than half the diameter of the head.

Southwick angle: (Southwick 1984). The angle is measured on the lateral view of the both hips. It is measured by drawing a line perpendicular to a line connecting the posterior and anterior tips of the epiphysis at the physis. The angle between the perpendicular line and the femoral shaft line is called the lateral epiphyseal shaft angle. The Southwick angle is the difference between the lateral epiphyseal shaft angle of the slipped and the non slipped sides. In patients with bilateral involvement, 12° is subtracted from each of the measured lateral epiphyseal angles.

  1. Mild slip (grade I) has an angle difference of less than 30 degrees
  2. Moderate slip (grade II) has an angle difference of between 30 and 50 degrees
  3. Severe slip has a difference of over 50 degrees.

In practice, most clinicians tend to use a combination of the Loder classification and one of the radiographic classifications. (Montgomery 2009).

fig 5.png

The aim of treatment is to prevent additional slippage by providing mechanical stability using screws or pins while avoiding the complications of AVN and chondrolysis. The choice of treatment depends on the type of slip, its severity, and surgical expertise. Figure 6 summarises the authors’ recommendations.

The recommend treatment of mild and moderate slip is by pinning-in-situ (PIS). However, there is significant controversy on treating severe slip, pinning in situ can be technically difficult if not impossible. Forceful reduction increases the risk of AVN and should be avoided. The options are either pinning in situ (if feasible) or corrective osteotomy as the primary treatment. The remodeling potential is not always predictable and a re-alignment procedure may be necessary with the former option. AVN is uncommon in stable slips, makes the latter option is not a popular choice in stable slips even when it is severe. In contrast to unstable slips where the risk of AVN is high (47%) and may justify open reduction and stabilisation.

fig 6.png

Flow chart of SUFE treatment. Courtesy of Cambridge University Press.

Several studies have tried to identify the best time to operate on SUFE, all suffer from flaws.

Loder in his classic paper (Loder 1993) noted more AVN in patients treated within 48 hours (7/8 versus 7/21). In contrast Peterson (Peterson, Weiner et al. 1997) showed stabilisation of SUFE within 24 hours led to less AVN (3/42=7%) in comparison with those stabilised after 24 hours (10/49=20%).

Phillip’s (Phillips, Griffiths et al. 2001) reported no single AVN in 16 unstable slips who were treated with 24 hours. In a study of 82 children (117 SUFEs), Kalogrianitis (Kalogrianitis, Tan et al. 2007) showed that AVN developed in 50% (8/16) of the unstable SUFEs. All but one were treated between 24 and 72 hours after symptom onset. They recommended the operation should be done within 24 hours or after 7 days but not in between.  

In a metanalysis of 5 studies, (Lowndes 2009) analysed data from 130 unstable SUFEs ; 56 were treated within 24 hours and 74 were treated after 24 hours of symptoms onset. They found that the odds for developing AVN if treatment occurs within 24 hours were half than those of developing AVN if treatment occurs beyond this point. (OR=0.50; 95% CI: 0.09–2.92; P: 0.441), a statistically non significant findings.

Four operations are in use for primary open reduction and fixation of the slip; Fish osteotomy (Fish 1984), Dunn’s Osteotomy (Dunn and Angel 1978),  Ganz surgical dislocation of the hip (Ganz, Gill et al. 2001) and Parsch technique (Parsch, Weller et al. 2009). Ganz surgical dislocation is also called modified Dunn’s osteotomy. They correct the slip at the subcapital level; however, they differ in the approaches.In Fish osteotomy and Parsch technique, Smith-Peterson anterior approach to the hip is used and it does not involve trochanteric osteotomy. Whereas in Dunn’s and Ganz osteotomy, lateral approach is used and the greater trochanter is osteotomised through the growth plate (Dunn’s osteotomy) or by flip trochanteric osteotomy (Ganz technique). The reported AVN rates are:

  • Fish osteotomy (3/66) (4%).
  • Dunn’s Osteotomy (9/73) (12%)
  • Ganz osteotomy (0/20) (0%).
  • Parsch technique (3/64)

The success of the above approaches is closely related to protecting (may be restoring) the blood supply to the femoral head which comes mainly from the posterior portion of the extra-capsular anastomotic ring. The incidences of AVN reported in the original reports are not comparable as the first two operations probably combined stable and unstable slips. Very few centres have reproduced Ganz results (Sankar, McPartland et al. 2010; Alves, Steele et al. 2013). Since it is publication, the Parish technique has become popular but comparable results from other centres remain to be seen.

Current recommendation for patients who are willing to accept a higher risk of AVN to correct a severe slip or slips which cannot be pinned, is the Parish technique for unstable one ( that does not reduce spontaneously) and Ganz osteotomy for stable ones.

fig 7.png

Severe SUFE in an overweight child treated with Dunn’s osteotomy. Notice the low uptake on the bone scan which is consistent with an AVN.

fig 8.tif.png

fig 8b.png

Severe SUFE with MRI evidence of AVN. There  is  high  STIR  signal within  the  left  femoral  head  consistent with AVN. This patient was treated with surgical dislocation and intra-operative pictures showed bleeding from the femoral head.

The risk of contralateral slip varies from 18 to 60% which could justify prophylactic PIS of the contralateral hip even if it is asymptomatic. However, this is not free of risk and it should be weighed against the benefit.

In a review of 50 children with unilateral SUFE, (Stasikelis, Sullivan et al. 1996) tried to identify predictors for future contralateral slip. They found the modified Oxford bone age strongly correlated with the risk of development of a contralateral slip; contralateral slip developed in 85% of patients with a score of 16, in 11% of patients with a score of 21, and in no patient with a score of 22 or more. The modified Oxford bone age is based on appearance and subsequent fusion of the iliac apophysis, femoral capital physis, greater and lesser trochanter.

The posterior slip angle (PSA) was proposed by  (Phillips, Phadnis et al. 2013) as a reliable predictor for contralateral slip. They examined 132 patients with SUFE and found the PSA was significantly higher in children who subsequently developed contralateral slip ( 17.2° ± 5.6°; N=42 vs. 10.8° ± 4.2°; N=90; P=0.001). If a posterior sloping angle of 14° were used as an indication for prophylactic fixation, 35 (of 42 = 83.3%) would have been prevented, and 19 ( of 90 = 21.1%) would have been pinned unnecessarily.

The followings may aid decision making (Alshryda, Jones et al. 2014):

  1. Age of the child (< 10 years is associated with a higher risk of bilaterality).
  2. Slips associated with renal osteodystrophy and endocrine disorders (a  high incidence of bilaterality)
  3. Poor compliance of the child and family.

The nature of current slip (very bad slip occurred over a very short period of time may justify pinning the other side)

Fig 10.png

The posterior sloping angle (PSA) measured by a line (A) from the center of the femoral shaft through the center of the metaphysis,. A second line (B) is drawn from one edge of the physis to the other, which represents the angle of the physis. Where lines A and B intersect, a line (C) is drawn perpendicular to line A. The PSA is the angle formed by lines B and C posteriorly as illustrated.

  1. AVN
  2. Chondrolysis: Chondrolysis is the rapid and progressive loss of articular cartilage seen in some SUFEs. The cause is unknown; however, few theories have postulated an autoimmune phenomenon or some interference with cartilage nutrition. Risk factors leading to chondrolysis include immobilisation in a cast, unrecognised pin penetration and severe SUFE rapid and progressive loss of articular cartilage after PIS. This may be due to pin penetration or protruded screw, but it has been also reported in other situations. Clinically patient develops increasing pain and stiffness and the x ray shows a decrease in the apparent joint space of more than two millimeters from that of the contralateral hip.
  3. Residual deformity and femoro-acetabular impingement
  4. Osteoarthritis (OA)
  5. Leg length discrepancy (LLD)
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References

  • 1. Alshryda, S., S. Jones, et al. (2014). Postgraduate Paediatric Orthopaedics: The Candidate's Guide to the FRCS (Tr and Orth) Examination. Cambridge, Cambridge University Press.
  • 2. Alves, C., M. Steele, et al. (2013). "Open reduction and internal fixation of unstable slipped capital femoral epiphysis by means of surgical dislocation does not decrease the rate of avascular necrosis: a preliminary study." J Child Orthop 6(4): 277-83.
  • 3. Dunn, D. M. and J. C. Angel (1978). "Replacement of the femoral head by open operation in severe adolescent slipping of the upper femoral epiphysis." J Bone Joint Surg Br 60-B(3): 394-403.
  • 4. Fish, J. B. (1984). "Cuneiform osteotomy of the femoral neck in the treatment of slipped capital femoral epiphysis." J Bone Joint Surg Am 66(8): 1153-68.
  • 5. Ganz, R., T. J. Gill, et al. (2001). "Surgical dislocation of the adult hip a technique with full access to the femoral head and acetabulum without the risk of avascular necrosis." J Bone Joint Surg Br 83(8): 1119-24.
  • 6. Kalogrianitis, S., C. K. Tan, et al. (2007). "Does unstable slipped capital femoral epiphysis require urgent stabilization?" J Pediatr Orthop B 16(1): 6-9.
  • 7. Loder, R. T. and M. L. Greenfield (2001). "Clinical characteristics of children with atypical and idiopathic slipped capital femoral epiphysis: description of the age-weight test and implications for further diagnostic investigation." J Pediatr Orthop 21(4): 481-7.
  • 8. Loder, R. T. R., B. S;Shapiro, P. S;Reznick, L. R;Aronson, D. D; (1993). "Acute slipped capital femoral epiphysis: the importance of physeal stability." J Bone Joint Surg Am 75(8): 1134-40.
  • 9. Lowndes, S. K., A.;Emery, D.;Sim, J.;Maffulli, N. (2009). "Management of unstable slipped upper femoral epiphysis: a meta-analysis." Br Med Bull 90: 133-46.
  • 10. Montgomery, R. (2009). "Slipped upper femoral epiphysis." Orthopaedic and Trauma 23:3(June): 169-183.
  • 11. Parsch, K., S. Weller, et al. (2009). "Open reduction and smooth Kirschner wire fixation for unstable slipped capital femoral epiphysis." J Pediatr Orthop 29(1): 1-8.
  • 12. Peterson, M. D., D. S. Weiner, et al. (1997). "Acute slipped capital femoral epiphysis: the value and safety of urgent manipulative reduction." J Pediatr Orthop 17(5): 648-54.
  • 13. Phillips, P. M., J. Phadnis, et al. (2013). "Posterior sloping angle as a predictor of contralateral slip in slipped capital femoral epiphysis." J Bone Joint Surg Am 95(2): 146-50.
  • 14. Phillips, S. A., W. E. Griffiths, et al. (2001). "The timing of reduction and stabilisation of the acute, unstable, slipped upper femoral epiphysis." J Bone Joint Surg Br 83(7): 1046-9.
  • 15. Sankar, W. N., T. G. McPartland, et al. (2010). "The unstable slipped capital femoral epiphysis: risk factors for osteonecrosis." J Pediatr Orthop 30(6): 544-8.
  • 16. Southwick, W. O. (1984). "Slipped capital femoral epiphysis." J Bone Joint Surg Am 66(8): 1151-2.
  • 17. Stasikelis, P. J., C. M. Sullivan, et al. (1996). "Slipped capital femoral epiphysis. Prediction of contralateral involvement." J Bone Joint Surg Am 78(8): 1149-55.