Innominate Osteotomy of Salter

Chapter 70

Innominate Osteotomy of Salter

Richard E. Bowen and Norman Y. Otsuka

DEFINITION

The Salter innominate osteotomy is commonly performed in conjunction with an open reduction for the dislocated hip in developmental dysplasia of the hip (DDH).
The osteotomy can also be performed to treat acetabular dysplasia in the child with a concentrically reduced hip.7

ANATOMY
The Salter innominate osteotomy rotates around an axis running from the posterior cortex of the sciatic notch to the midpoint of the symphysis pubis.
The osteotomy rotates the acetabulum to improve anterior and lateral femoral head coverage.
The distal fragment of the osteotomy undergoes slight distal, posterior, and medial displacement in addition to rotation.5
An up-to-30-degree bone wedge inserted in the osteotomy site increases anterior and lateral femoral head coverage in a proportion of about 2:1 (the practical limit of correction).5

PATHOGENESIS
Acetabular dysplasia is caused by the following:
- Lack of a reduced, spherical head within the growing acetabulum
- Abnormal interstitial or appositional growth within the acetabular and triradiate cartilage
- Abnormal development of the secondary centers of ossifi-cation of the ilium, pubis, and ischium
In the developmentally dislocated hip, the acetabular labrum is flattened and hypertrophied, referred to as the “neolimbus.”
The acetabular dysplasia in the infant and young child with DDH is predominantly anterior and lateral.8

NATURAL HISTORY
The natural history of the dysplastic hip with hip subluxation is worse than the hip with acetabular dysplasia alone.
- Patients with subluxated dysplastic hips develop pain and disability and radiographic evidence of osteoarthrosis. The age of onset of symptoms depends on the degree of subluxation, with severe subluxation leading to symptoms in the third decade of life.10
- Patients with acetabular dysplasia without subluxation develop radiographic evidence of osteoarthrosis in the sixth decade of life, and some will develop pain and disability, depending on the degree of dysplasia.10
  
  PATIENT HISTORY AND PHYSICAL FINDINGS
Patients with developmental hip dislocation may have a positive family history and are usually female and first-born children.

There can be a history of breech presentation at birth.
Children with a dislocated hip usually meet their gross motor milestones within the appropriate timeframe.
The pertinent physical examination findings in the walking child (the timeframe when this operation is typically performed) are listed below.
Hamstring tightness test: Normally, the hamstrings will tighten with passive knee extension, and no knee hyperexten-sion should be possible. A positive test implies hip dislocation or flaccid paralysis of the hamstring muscles.
Gluteus medius lurch: Trunk lean over the stance phase leg signifies a positive test, which is a nonspecific sign of hip pathology caused by dislocation, coxa vara, or painful hip conditions.
Galeazzi sign: Knees at different levels signify a positive test, which indicates hip dislocation or congenital shortening of the femur.
Limitation of hip abduction: Normal abduction range of motion is 80 degrees tested in flexion in the newborn and infant. Asymmetric abduction suggests unilateral hip dislocation. Bilaterally decreased abduction suggests bilateral hip dislocation.
Trendelenburg sign: If the pelvis dips away from the affected leg during single limb stance, the test is positive. Like the gluteus medius lurch, a positive test is a nonspecific sign of hip pathology caused by dislocation, coxa vara, or painful hip conditions.
Inspection of inguinal skin fold: Normal inguinal skin folds are symmetric and stop short of the anal aperture posteriorly. Asymmetric skin folds are a relatively nonspecific finding in the dislocated hip.

IMAGING AND OTHER DIAGNOSTIC STUDIES
Standing anteroposterior (AP) and supine frog-leg lateral pelvis radiographs
- On the AP film, the acetabular index should be measured to diagnose acetabular dysplasia. Normal values are 35 degrees at birth, 25 degrees at 1 year of age, and 20 degrees at 2 years of age (FIG 1).9
- Also on the AP film, the line of Shenton is inspected for discontinuity, which represents hip subluxation (FIG 1).
A false-profile view of the hip can identify more subtle cases of acetabular dysplasia, particularly in the walking child.
Advanced imaging studies (3D CT scanning of the acetabulum, MRI of the hip) may be of value in older children to assess acetabular morphology.

DIFFERENTIAL DIAGNOSIS
Proximal femoral focal deficiency
Congenitally short femur
Developmental coxa vara
Legg-Calvé-Perthes disease

1517

Acetabular index

Hilgenreiner's line

Shenton's line

FIG 1 • Measurement of the acetabular index and location of the line of Shenton. This schematic of an AP pelvis radiograph demonstrates a dislocated right hip. Line of Hilgenreiner is drawn through the top of the triradiate cartilages. A second line is drawn from the line of Hilgenreiner at the inferior edge of the ossified margin of the acetabulum to the lateral edge of the ossified margin of the acetabulum. The angle between these two lines is the acetabular index. The line of Shenton should be a continuous arc between the medial femoral neck and the superior aspect of the obturator foramen in the normal hip. It is not continuous in the dislocated hip.

NONOPERATIVE MANAGEMENT

The acetabular index should be observed for improvement over 12–18 months after successful closed reduction in the child less than 18 months of age.
- If residual acetabular dysplasia exists, a Salter innominate osteotomy can be performed at that time.2
Whether the osteotomy should be performed concurrently with an open reduction or as a staged procedure is controversial.
- A child less than 18 months old who fails closed reduction can be treated with an isolated open reduction of a dislocated hip and observed for improvement in the acetabular index into the normal range over 12 to 18 months.
  
  FIG 2 • Patient positioning. The patient is placed with a gel roll longitudinally under the right thorax, elevating the right hemipelvis. The area of sterile preparation is from the rib cage proximally, the midline anteriorly and posteriorly, and the entire leg distally.
- A subsequent Salter innominate osteotomy should be performed if acetabular development is deficient after observation.4
  
  SURGICAL MANAGEMENT
Surgical indications:
- Age 18 months to 6 years6
- Concentric hip reduction (either preoperatively or intra-operatively with an open reduction)6
- No or minimal osteoarthrosis of the hip
- At least 100 degrees of hip flexion and 30 degrees of hip abduction
- Anterior and lateral acetabular dysplasia
  
  Preoperative Planning
A hip arthrogram is first performed in cases of hip dysplasia before patient positioning to confirm a concentric reduction.
- If there is not a concentric reduction, other procedures (open reduction, proximal femoral osteotomy) are performed to achieve a concentric reduction before performing a Salter innominate osteotomy.
For the dislocated hip, a closed reduction is attempted.
- If a gentle concentric closed reduction is achieved and the patient is over 18 months old, a Salter innominate osteotomy including intramuscular psoas lengthening without open hip reduction can be performed.
An estimation of femoral anteversion with fluoroscopy before patient positioning is used to decide if a concurrent femoral derotational osteotomy is necessary.
- We perform a femoral derotational osteotomy if femoral anteversion is greater than 45 degrees.
  
  Positioning
The patient is placed supine on the operating table with a gel roll under the thoracolumbar spine on the affected side (but not under the affected pelvis), raising the affected side into an oblique position.
The hip is prepared from the midline anterior and posterior, to the inferior rib cage proximally, and the entire extremity distally (FIG 2).

Approach

An anterior Smith-Peterson approach to the hip is used, with the incision modified as described in Chapter PE-67 (FIG 3).

FIG 3 • Surgical incision. The incision is placed obliquely over the anterior aspect of the hip and is centered about 2 cm below the anterior superior iliac spine.

Proximally, the incision curves to follow the contour of the iliac crest but is distal to it. Distally, the incision curves to lie in the intermuscu-lar interval between the sartorius and tensor fascia lata muscles.

Because the skin is mobile in the child, the incision can be easily moved to complete the exposure of the iliac crest and the anterior aspect of the hip without having it rest directly on the iliac crest.

EXPOSURE OF THE ANTERIOR HIP AND ILIUM

and medial, the iliac apophysis is split with a no. 15 blade ■ An intramuscular psoas tendon lengthening is per-scalpel from the iliac tubercle to the anterior inferior iliac formed at the pelvic brim.

spine (AIIS).

TECHNIQUES

SALTER INNOMINATE OSTEOTOMY

tractor in the notch. ■ The operating room table is lowered, and with hands as

TECH FIG 1 • A. Gigli saw on top of subperiosteal retractors in the sciatic notch. B. Location of the Salter innominate os-

B teotomy.

HARVESTING BONE GRAFT

FIG 2C).

A C

TECH FIG 2 • A,B. Location of bone graft harvest. C. Bone graft shaped into 30-degree wedge.

The exposure of the anterior hip is the same as for an ■ The inner and outer tables of the ilium are subpe-open reduction of the hip in Chapter PE-67. riosteally dissected with Crego periosteal elevators to the
While retracting the external oblique muscle proximal sciatic notch.

Curved Crego or Rang retractors are placed subpe- ■ The Gigli saw is placed into the right angle clamp later-riosteally in the sciatic notch from the medial and lateral ally and pulled around the sciatic notch (TECH FIG 1A). sides. ■ The right-angled clamp is rotated into the notch on top
The medial retractor is placed on top of the lateral re- of the medial retractor.
The tip of a right-angled clamp is placed on top of the re- wide as possible, the Gigli saw is used to make the os-tractors from the medial side of the sciatic notch. teotomy, exiting just above the AIIS (TECH FIG 1B).

The iliac wing is removed with an oscillating saw laterally or bone-biting forceps from the AIIS to the iliac tubercle (TECH FIG 2A,B).
The graft is shaped in to a 30-degree bone wedge (TECH

TECHNIQUES

PLACING THE GRAFT

Towel clamps are used to stabilize the proximal fragment and hinge the distal fragment anterior and lateral. The distal fragment is pulled anteriorly to prevent posterior slipping, and the posterior part of the osteotomy is kept apposed (TECH FIG 3A).
If done as an isolated procedure, opening the osteotomy site can be facilitated by placing the leg in the figure 4 position.
The graft is placed in the osteotomy gap concave side medial, with the medial cortex flush with the medial cortex of the proximal and distal fragments (TECH FIG 3B).
The graft is secured with two threaded Steinmann pins placed from proximal across the graft into the medial and posterior portion of the distal fragment up to the triradiate cartilage (TECH FIG 3C).
The acetabulum is palpated (if done with an open reduction) or the hip taken through full range of motion (if done as an isolated procedure) to ensure pins are extra-articular.
An intraoperative obturator oblique radiograph is taken with the pins in place to ensure they do not enter the triradiate cartilage (TECH FIG 3D).

A B C

TECH FIG 3 • A. Hinging open the osteotomy. Towel clamps are used to grasp the proximal and distal osteotomy fragments. The proximal fragment is stabilized and the distal fragment is pulled anterior and hinged anterior and lateral. B. The graft is placed in the osteotomy site with the concave side facing medial. The medial cortex of the proximal fragment, graft, and distal fragment are flush with each other. The proximal, and particularly the distal, osteotomy fragments are wider than the graft, meaning that the lateral cortex of the graft is significantly more medial than the lateral cortices of the proximal and distal fragments. C. Two threaded Steinmann pins are drilled from the proximal fragment across the posterior half of the graft to the distal fragment. The pins are placed just deep to the medial cortices. The surgeon is looking from proximal-lateral to distal-medial along the Steinmann pin path in this figure. D. Intraoperative obturator oblique pelvic radiograph shows the Steinmann pins holding the graft in

D place and stopping short of the triradiate cartilage.

WOUND CLOSURE
- The iliac apophysis is closed with absorbable suture in a figure 8 fashion.
  - The first loop of the figure 8 is circumferential around the entire apophysis, and the second loop captures only the superficial half of the apophysis.
The pins are cut above the apophysis, coming to lie in the subcutaneous fat, for easy future removal.
The common head of the rectus femoris tendon is repaired to its insertion.
Subcutaneous tissue and skin are closed in the standard fashion.

PEARLS AND PITFALLS

Indications ■ The osteotomy should be performed only for anterior and lateral acetabular deficiency in the concentrically reduced hip.
- The surgeon should avoid performing the osteotomy in conditions with known posterior hip dysplasia, such as myelomeningocele or cerebral palsy.
  
  Iliac exposure ■ Retracting the external oblique muscle away from the iliac apophysis avoids unnecessary bleeding when cutting it.
- Raytec sponges placed subperiosteally on the inner and outer tables of the ilium aid in dissection and decrease bleeding.
- Strict subperiosteal exposure of the sciatic notch is essential.
  
  Performing the ■ Twisting the retractors in opposite directions facilitates Gigli saw passage.
  
  osteotomy ■ The anterior inferior iliac spine needs to be fully exposed to determine the proper osteotomy exit position.
  
  Opening the ■ The osteotomy should be hinged open, pulling the distal fragment anterior and keeping the osteotomy posterior cortex of the osteotomy opposed.
  
  Fixation ■ Proper pin length can be estimated by holding a second identical pin along the medial cortex at the desired problems depth (FIG 4).
- It is imperative to obtain an intraoperative radiograph showing that the pins stop short of the triradiate cartilage.
- Extra-articular pin placement should be ruled out by direct palpation if concomitant hip open reduction is being performed, or by placing the hip through a full range of motion and feeling and listening for crepitus.
- Aiming pins just deep to the medial cortex in the proximal and distal fragments and the graft aids in proper medial pin placement.
- Aiming pins in the posterior half of the graft aids in proper posterior pin placement.

FIG 4 • Estimating Steinmann pin length. The Steinmann pin can be held along the medial surface of the osteotomy and graft to estimate the depth of pin insertion and marked with a pen.

POSTOPERATIVE CARE

The patient is placed in a one-and-a-half hip spica cast with the affected hip in the position of maximal hip stability and, if possible, close to the position of weight bearing (about 30 degrees of flexion, 20 degrees of abduction, and 20 degrees of internal rotation).
When performed as an isolated procedure, young children should be immobilized in a single-leg spica cast for about 6 weeks, when early radiographic evidence of healing is evident.
Older children who are reliable may be allowed to use crutches and perform touch-down weight bearing on the affected side without the use of a single-leg spica cast.

OUTCOMES
Patients with concentrically reduced hips and corrected acetabular dysplasia with a Salter innominate osteotomy, in the absence of avascular necrosis, have good to excellent functional outcomes scores at over 30 years after the index procedure.
Functional outcomes are best when the acetabular dysplasia is initially corrected to near-normal radiographic values.1,4

COMPLICATIONS
Neurovascular injury to structures in the sciatic notch
Lateral femoral cutaneous nerve injury during surgical exposure
Inadequate correction of acetabular dysplasia due to inadequate patient selection preoperatively or inadequate acetabular rotation intraoperatively3
Injury to the femoral nerve due to prolonged retraction of the psoas muscle or incorrect identification of the psoas tendon during intramuscular tenotomy
Pin penetration into the hip joint or triradiate cartilage
Nonunion at the osteotomy site
Migration of the graft due to inadequate fixation3
Avascular necrosis of the femoral epiphysis3
Growth arrest of the triradiate cartilage

REFERENCES

Barrett WP, Staheli LT, Chew DE. The effectiveness of the Salter innominate osteotomy in the treatment of congenital dislocation of the hip. J Bone Joint Surg Am 1984;68A:79–87.
Gillingham BL, Sanchez AA, Wenger DR. Pelvic osteotomies for the treatment of hip dysplasia in children and young adults. J Am Acad Orthop Surg 1999;7:325–337.
Gur E, Sarlak O. The complications of Salter innominate osteotomy in the treatment of congenital dislocation of the hip. Acta Orthop Belg 1990;56:257–261.
Macnicol MF, Bertol P. The Salter innominate osteotomy: should it be combined with concurrent open reduction? J Pediatr Orthop B 2005;14:415–421.
Rab GT. Biomechanical aspects of Salter osteotomy. Clin Orthop Relat Res 1978;132:82–87.
Salter RB. Innominate osteotomy in treatment of congenital dislocation of the hip. J Bone Joint Surg Br 1961;43B:518–539.
Salter RB. Role of innominate osteotomy in the treatment of congenital dislocation and subluxation of the hip in the older child. J Bone Joint Surg Am 1966;48:1413–1439.
Sarban S, Ozturk A, Tabur H, et al. Anteversion of the acetabulum and femoral neck in early walking age patients with developmental dysplasia of the hip. J Pediatr Orthop B 2005;14:410–414.
Scoles PV, Boyd A, Jones PK. Roentgenographic parameters of the normal infant hip. J Pediatr Orthop 1987;7:656–663.
Weinstein SL. Natural history of congenital hip dislocation (CDH) and hip dysplasia. Clin Orthop Relat Res 1987;225:62–76.