Salters’ osteotomy

Patient in supine position with 1L bag of saline under buttock. This will need to be removed prior to closure of wound to check position with image intensifier. Prior to formal skin preparation the perineum should be prepped with non alcoholic prep and covered with opsite or similar adhesive.

The operative limb is draped free. A ‘U’ drape is ideal ensuring that the medial limb of the drape passes along the midline to the umbilicus. The lateral limb should be as posterior as possible and there should be access to the whole iliac crest.
The iliac crest and anterior superior iliac spine should be marked and the incision placed 1-2cm below and parallel to the crest.

The length of the incision will vary depending on the age and size of the child.In a small infant 6-8cm should be sufficient. It is important that the incision should extend 2-3cm beyond the ASIS. A straight incision is used rather than a Smith Peterson approach since cosmoses is much better. The posterior extent of the incision should not extend beyond the level of the greater trochanter.

Sharp dissection continues through subcutaneous fat until the iliac crest is identified. Distally in the wound the lateral cutaneous nerve will need to be identified. It will be underneath the fascia running obliquely over sartorius to lie along the medial border of TFL. The nerve can be difficult to identify until the superficial fascia has been opened. Small blood vessels invariably run across the top of the nerve and may give a clue to its location.

The anterior approach to the hip is continued between TFL (lateraly) and sartorius medially. The lateral cutaneous nerve will need to be retracted medially (with sartorius) using Langenbach retractors.

The external oblique muscle folds over the top of the iliac crest. It should be carefully ‘feathered’ off the apophysis using diathermy. This should be done over a distance of 3-4cm and care should be taken to avoid damage to the apophysis.

The apophysis palpated between thumb and index finger. It is split in its midline using a size 15 blade. The apophysis is thick in young children and it is easy to veer off at an angle.

The apophysis and then has to be reflected off the iliac bone. This is easily accomplished by using a periosteal elevator or small spinal cobb to find the plane between the apophysis and the bone. The abductors will be in continuation with the apophysis and together with the periosteum will easily elevate off the outer table of the ileum. The process is repeated on the inner table of the bone.

Elevation of the periosteum is facilitated by using a swap which also achieves haemostasis. The iliac wing has to be visualised as far as the Anterior inferior iliac spine and also as far as the sciatic notch. The latter can be difficult and spinal cobb elevator is ideal for elevating periosteum off the quadrilateral plate and inner table of ischium. On the inner table there will be one or two feeder vessels running from periosteum to bone. These should be cauterised and bone wax applied to the bone.

The muscle belly of iliopsoas lies on the medial aspect of the iliac wing and runs down over the pelvic brim towards the lesser trochanter. The classic description of Salter osteotomy requires release of psoas. This should be done at the level of the pelvic brim and the tendon should be divided within the muscle belly. This avoids weakening hip flexion too much.
The muscle is easiest to identify on the inside of the iliac wing and then followed distally.
If a window is created in the periosteum after it has been elevated off the inner table of the ileum the muscle belly is easily visualised.

If the hip is flexed this will release tension in psoas. The tendon can be felt on the undersurface of the muscle belly and a right angle retractor pass around it. It is critical to ensure that the femoral nerve has not been mistaken for the tendon. Case reports of neurectomy have been described! On close inspection one can see muscle fibres running into the tendon.
The tendon is divided with diathermy. If the muscle twitches do not proceed.
Sometimes the tendon will be in 2 or more strands. Both should be divided.

The next step is to isolate the ilem with retractors. The aim will be to divide the bone from the sciatic notch to the anterior inferior iliac spine with the cut just above the acetabulum.
A sciatic notch retractor (Rang) has a distal lip that can be ‘hooked’ under the sciatic notch. The first retractor is placed medially. Extreme care is needed to ensure that the retractor is sub periosteal and that there are no soft tissues between the retractor and the bone.

A second retractor is then similarly placed into the sciatic notch from the lateral surface of the ilium. The tip of one retractor should fit inside the other. One should then ensure that there are no soft tissues between the retractors and the bone of the sciatic notch.

The ilium is divided with a gigli saw. It is easiest to pass the saw through the sciatic notch by first passing a nylon tape loaded onto a right angle retractor. This is passed from the medial side.

The tape is retrieved from the lateral side and the free end tied to the gigli saw which is then passed through the sciatic notch.

Once the gigli saw has been passed through the sciatic notch the handles are applied. A cobb elevator or similar long instrument is placed across the front of the ilium. There is a tendency for the gigli wire to suddenly exit the bone and the retractor will protect surgeon/assistent from receiving a face full of gigli wire!

The wire tends to bind and get stuck in the bone as the ileum is divided. To mitigate against this it is important to keep ones hands as wide apart as possible. The aim is to exit at the level of the anterior inferior iliac spine.

The distal fragment is displaced laterally and anteriorly thus increasing anterior and lateral cover of the femoral head. Displacement is facilitated by placing the leg in the figure of 4 position. By pressing backwards on the knee the osteotomy will open up anteriorly.

The distal fragment is rotated further using pointed towel clip. The aim is to achieve an opening wedge osteotomy, The huge point is posteromedially at the sciatic notch.

The anterolateral extreme of the osteotomy is opened and this can be achieved with a laminar spreader.

Autologous iliac crest bone graft is next harvested from the ipsilateral side. A blunt Homan retractor is inserted on the inner table of the pelvis and the soft tissues retracted to allow access with a small oscillating saw.

It is usually possible to harvest two triangular grafts from the iliac crest. The size of the graft should match the gap created when the distal fragment is displaced forwards and opened anteriorly.
The final radiological correction at 6 weeks will generally be 50% of the size of the graft inserted. For example if the pre operative acetabular index is 40 degrees and a 30 degree graft is inserted the final actebular index will be approximately 25 degrees.

This photograph is taken from the assistants side of the operating table. The osteotomy gap is held open using towel clip to hold the distal fragment. The graft is then held and inserted with Kocher forceps.

The position of the leg has to be maintained until the graft has been stabilised. Failure to do so will result in tendency for osteotomy to open up posteriorly. Two threaded K wires (2.0-2.5mm) are usually sufficient.
The bolster is removed from behind the operative hip so that the patient is in a supine position and the image intensifier brought in from the assistants side of the operating table.
The K wires should both engage the graft being passed between the inner and outer tables. The anterior K wire is easier to insert. The posterior K wire should be aimed down the posterior column of the pelvis but should not be passed across the triradiate cartilage. This photograph is taken from the assistants side of the operating table.

Once the first graft has been inserted and stabilised the leg can be extended from the ‘figure of four’ position and stability of the osteotomy checked. A second graft can then be inserted either medial or lateral (as in this case). This graft should not require stabilisation.

The iliac apophysis is approximated using a towel clip and repaired with several interrupted 1 vicryl sutures.

Once the apophysis has been repaired the K wires are divided with bolt cutters leaving them approximately 5mm proud so that they can be removed at a later stage (typically 3-6 months).

The wound is closed in layers, fat and subcutaneous absorbable sutures. Although the aim is for the osteotomy to be stable without supplementary casts it has to be remembered that the majority of cases will be in children less than 5 years old. Such patients may be a little unreliable and have a tendency to mobilise once the post operative pain settles. For this reason a hip spice cast should be considered.

Pre operative radiograph of 2 year old child having had previous closed reduction of left DDH. Note the acetabular index raised at 42 degrees. Femoral head is enlocated. This would be suitable for Salter osteotomy or acetabuloplasty.

Per operative imaginig. Acetabular index has been reduced and 2 threaded 2.5mm K wires are holding osteotomy. Note how the obturator foramen is asymmetrical. The left side appears to be “squinting” due to the fact that the acetabular fragment has displaced laterally and anteriorly.The distal fragment has also been displaced slightly laterally. The osteotomy is hinging rather than opening medially.