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Section I: SYMPOSIUM: Tribute to Dr. G. Dean MacEwen

A New Modified Technique of Triple Osteotomy of the Innominate Bone for Acetabular Dysplasia

Lipton, Glenn E MD*; Bowen, J Richard MD*†

Editor(s): Guille, James T MD, Guest Editor; Kumar, S Jay MD, Guest Editor

Author Information
Clinical Orthopaedics and Related Research: May 2005 - Volume 434 - Issue - p 78-85
doi: 10.1097/01.blo.0000163484.93211.94
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Abstract

Persistent acetabular dysplasia and hip subluxation in children leads to arthritis of the hip.7,17,19,20 The treatment of acetabular dysplasia and hip subluxation remain challenging because the normal biomechanical relationships in the hip have been altered.9 If after conservative treatment there continues to be residual symptomatic subluxation and/or acetabular dysplasia, surgical treatments must be considered. The goals of surgery are to reorient the biomechanical relationships such that the development of degenerative hip disease is delayed or prevented. To achieve these goals various pelvic osteotomies have been used. Reshaping osteotomies, such as the Pemberton and Dega osteotomies, reshape the acetabulum in order to restore the normal biomechanical relationship between the femoral head and acetabulum in children with open triradiate cartilage.1,10,11 The problems with the reshaping osteotomies are that they primarily are indicated for the capacious acetabulum (Pemberton) and they only provide lateral or posterior acetabular coverage when doing the osteotomies (Dega ).1,3,10,11

Redirectional osteotomies, including the single innominate Salter osteotomy and the triple innominate Steel osteotomy, shift the position of acetabulum to a position that gives improved coverage of the femoral head with out changing the shape of the acetabulum.13,14,16 The Salter osteotomy is a single innominate osteotomy used to treat deficiencies of the acetabulum that cause failure of coverage of the anterolateral femoral head. A triangular wedge of bone from the iliac crest is placed and fixed in the osteotomy site (Fig 1). This procedure has best results when done in children up to 4 years old13,14 and shouldn’t be done after age 7 because of the pubic symphysis closure that limits mobility of the fragment. Therefore, the Salter osteotomy is limited in that its best results are seen in children younger than 4 years with anterolateral acetabular deficiencies.

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Fig 1.:
A single innominate Salter osteotomy is illustrated from the AP view. A triangular wedge of bone from the iliac crest is placed and fixed in the osteotomy site.

The Steel osteotomy is a triple osteotomy of the innominate bone which consists of a Salter osteotomy with additional osteotomies of the ischium and the pubis (Fig 2).16 Although this osteotomy allows for great ability to redirect the acetabulum in older children and young adults, it is limited in its ability to maintain postoperative stability of the hip joint. With that lack of stability, the rehabilitation of the patient is affected.

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Fig 2.:
A triple innominate Steel osteotomy is illustrated from the AP view.

Our purpose is to describe the technique developed by the senior author (JRB) and present preliminary results of a new variation of a triple osteotomy of the innominate bone, which allows for better coverage of the femoral head by articular cartilage of the acetabulum and gives the hip joint better stability for weightbearing.

The prerequisites and indications for the described modified triple osteotomy are the following: a child with acetabular dysplasia in which the acetabulum is maldirected; a child with the capacious acetabular dysplasia; obtaining a concentric reduction of the hip joint with 25° to 30° of abduction and neutral rotation as demonstrated on an anteroposterior pelvis roentgenogram; and adequate range of motion at the hip with no more than 15° loss of motion in any plane.

The contraindications to the described triple osteotomy are the following: previous diseases of the hip that have resulted in destruction of the femoral head or acetabulum; degenerative arthritis of the hip; ankylosis of the hip; and the hip being irreducible, with abduction of the thigh.

The advantages of the described modified triple osteotomy are the following; better coverage of the femoral head by articular cartilage of the acetabulum, better hip joint stability for weightbearing and no need for spica cast immobilization. The disadvantages of the described triple osteotomy are the following: the procedure is technically demanding; it does not change the joint capacity of a capacious acetabulum; and it causes distortion of the pelvis, which may affect passage of a fetus during natural child birth if the procedure is done bilaterally.

MATERIALS AND METHODS

Between 1998 and 2002 the senior author (JRB) did 13 modified triple osteotomies in 11 patients. There were 3 boys and 8 girls in the study. Medical records, operative records, and radiographs were reviewed. All surgeries were done in patients with residual acetabular dysplasia who had previous developmental dysplasia of the hip and symptoms of mild-to-moderate hip pain. Nine patients had unilateral procedures and two patients had bilateral procedures for a total of 13 modified triple osteotomies. There were five hips on which previous bony hip surgery had been done. On physical examination, all patients had decreased abductor strength.

Radiographic evaluation included preoperative, postoperative, and followup assessments with AP radiographs. The vertical center edge angle of Weiberg and acetabular angle of Sharp were measured. The acetabulum was considered dysplastic if the vertical center edge angle was less than 20° or if the acetabular angle was greater than 43°.15,21

The procedure is done using two incisions: an ischial incision and a bikini-type iliofemoral incision. The patient should be positioned prone on a radiolucent spine table with the hips flexed 90° for the ischial approach as described by Tonnis.18 Somatosensory evoked potentials are used to monitor the sciatic nerve. The operative area is scrubbed, prepared and draped into a sterile field. To identify the bony landmarks, palpate the ischial tuberosity. A 4-cm to 5-cm horizontal incision should be made to approach the ischial tuberosity. The incision should begin 1 cm proximal to the gluteal crease and should extend perpendicular to the axis of the femoral shaft. The hamstrings and biceps femoris muscles are exposed at their origins on the ischial tuberosity. Next, blunt dissection down to and between the semitendinosus and semimembranosus muscles is done. A curved hemostat is placed behind the ischium into the obturator foramen. It is important to note the sciatic nerve is lateral to the semimembranosus and lies deep in the medial and inferior aspect of the gluteus maximus. The sciatic nerve should not be exposed. The sciatic nerve and the semimembranosus muscle, which is tendinous near its origin, have a similar appearance and care should be taken in this area. Next, the periosteum of the ischium is elevated just medial to the ischial tuberosity and protective retractors are placed medially and laterally around the ischium. The ischial osteotomy is now done. As described by Kumar et al,6 about 1 to 1.5 cm of bone is removed with a rongeur (Fig 3). This wound is then closed and dressed.

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Fig 3.:
A–B. (A) The AP view of the hip is shown with the ischial osteotomy illustrated by the cross hatched area in the ischium. Approximately 1 to 1.5 cm of bone is removed. (B) The lateral view is shown with the ischial osteotomy illustrated by the cross-hatched area in the ischium.

The iliofemoral approach part of procedure is done with the patient in the supine position and on a radiolucent table as above. It is our preference to change gowns and gloves and use a different set of instruments for this part of the procedure. The affected lower limb, hemipelvis, and lower part of the chest are scrubbed, prepared, and draped into a sterile field. The anterior part of the iliac crest and the anterior-superior iliac spine are palpated to identify bony landmarks. A bikini skin incision then is made, beginning just inferior to the anterior-superior iliac spine and continuing laterally to a point just beyond the middle of the iliac crest. This incision provides for a satisfactory cosmetic appearance. Next, the anterior part of the iliac crest is exposed. The lateral origins of the gluteus medius and minimus muscles are subperiosteally reflected from the outer ala cortex of the ilium to the greater sciatic notch. The sartorius muscle is detached from its origin at the anterior superior iliac spine and is reflected medially. The iliacus and psoas muscles subperiosteally are reflected from the inner ala cortex of the ilium to the greater sciatic notch. The femoral nerve, artery, and vein, which lie anteriorly to these muscles, should be protected. The psoas muscle and tendon are retracted medially and the pectineal eminence is exposed. Expose the pubic ramus adequately, elevating subperiosteally the pectineous muscle, approximately 1 cm from the pectineal eminence. A curved hemostat is introduced superiorly to the pubic ramus into the obturator foramen. Then, a second curved forceps should be introduced inferiorly to the pubic ramus, to make contact with the upper forceps. The placement of the forceps will serve to protect the obturator artery, vein, and nerve, which are located medially. The pubic osteotomy then is done with an osteotome (Fig 4). After the pubic osteotomy is complete, the iliac osteotomy is done as in the Salter technique using a Gigli saw from the greater sciatic notch to the midpoint between the anterior-superior and anterior-inferior iliac spines (Fig 5).13 Next, a triangular wedge of bone with the base along the line of the osteotomy from the proximal part of the ilium is resected from the outer cortex with an osteotome and curette. The resected triangle should be from the outer cortex only (Fig 6). This is similar to the modification described by Kalamchi for the Salter osteotomy, except that the inner cortex is left intact.5 The triangular wedge is typically between one and one and a half centimeters in height. The resection of the triangular wedge of bone from the outer cortex alone creates a slot, which will later serve as an abutment which the distal posterior aspect of the ilium will fit. Next, a bone clamp should be attached to the acetabular segment. The acetabular segment is the mobilized distally, anteriorly and laterally to cover the femoral head. The distal-posterior part of the ilium then is drawn and rotated into the slot created in the lateral cortex of the ilium (Fig 7). If necessary a bone graft may be obtained from the wing of the ilium and placed in site of the iliac osteotomy; however, bone grafting may not be been necessary. The iliac osteotomy then is fixed with two 7.3-mm cannulated screws from the inner aspect of the proximal ilium to the distal segment taking care to avoid the hip joint. The rectus femoris muscle should be reattached to the anterior inferior iliac spine. The sartorius muscle and the lateral end of the inguinal ligament should be attached to the anterior-superior iliac spine. After the pectineal and iliopsoas muscles have been allowed to fall back into place, the wound should be closed in layers. To evaluate stability, the hip should be ranged under fluoroscopy. No movement of the fixed osteotomy should occur with range of motion. If adequate fixation is not obtained with the cannulated screws, a spica cast should applied with the affected hip at 20° of abduction, 5° of flexion, and neutral rotation. Finally, an AP radiograph should be obtained to verify the position of the acetabulum.

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Fig 4.:
A–B. (A) The AP view of the hip is shown with the pubic osteotomy illustrated by the cross-hatched area. (B) The lateral view is shown with the pubic osteotomy illustrated by the dashed line.
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Fig 5.:
A–B. (A) The AP view of the hip is shown with the iliac osteotomy illustrated by the dashed line. (B) The lateral view of the hip is shown with iliac osteotomy illustrated by the dashed line. The triangular wedge of bone from the proximal part of the ilium to be resected from the outer cortex is illustrated by the dotted line. The triangular wedge is approximately 1 to 1.5 cm high.
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Fig 6.:
A–B. (A) The AP view of the hip is shown with all three innominate osteotomies complete. (B) The lateral view of the hip is shown with all three innominate osteotomies complete.
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Fig 7.:
A–B. (A) The AP view of the hip is shown after the distal-posterior part of the ilium has been drawn and rotated into the slot created in the lateral cortex of the ilium. (B) The lateral view of the hip is shown after the distal-posterior part of the ilium has been drawn and rotated into the slot created in the lateral cortex of the ilium.

Postoperatively, the patient is allowed ambulation with crutches with minimal toe-touch weightbearing on the involved side. Radiographs are obtained at 3 and 6 weeks after surgery. When early callous formation is noted, weightbearing is advanced. Typically after 8 weeks, most patients are able to ambulate with the occasional use of one crutch for comfort. Physical therapy then is started for gait training and muscle strengthening. The physical therapy should direct attention toward strengthening the hip abductor muscles. Patients typically have a pronounced Trendelenburg gait with the initiation of ambulation and by 4 to 5 months postoperatively the Trendelenburg gait resolves.

RESULTS

The mean age at surgery was 14.9 years (range, 10.7–16.3 years). The mean patient weight at surgery was 49.8 kg (range, 25–92.4 kg). The mean patient height at surgery was 156.6 cm (range, 132–170 cm). The mean followup was 2.1 years (range, 1.3–3.0 years). Preoperatively, all 11 patients had a limp, eight had a constant limp and three had a limp after exercise or at the end of the day. At followup, the limp had resolved in all patients except one in which the limp worsened. Preoperatively, all 11 patients (13 hips) had painful hips; patients reported two hips as being severely painful, nine hips as being moderately painful, and two hips as being mildly painful. At followup, all patients except one had complete resolution of hip pain. Iliac crest bone graft was used in one patient, and no patient had a shelf or other concomitant bony procedure at the time of surgery. Postoperatively, no patient required a spica cast. The mean operative time was 141.5 minutes (range, 108–179 minutes). The mean estimated blood loss was 342 mL (range, 150–800 mL).

The mean preoperative center edge angle of Weiberg was 8.9° (range, 5°–17°). This improved postoperatively to a mean of 45.6° (range, 31°–58°) when measured to the edge of the redirected acetabulum. The mean center edge angle at followup was 44.9° (range, 29°–58°).

The mean preoperative acetabular angle of sharp was 53° (range, 48°–61°). This improved postoperatively to a mean of 25.4° (range, 19°–40 °). The acetabular angle of sharp at followup was 28° (range, 18°–41°).

All hips went on to bony union of their innominate osteotomies and there was no implant failure or loss of initial correction. Complications included excessive intraoperative blood loss of 800 mL in one patient. The patient received 1 unit of packed red blood cells and her operative and postoperative courses were uneventful.

One patient (one hip) was considered to have a failed procedure. This patient had continued moderate hip pain. The patient had a leg-length inequality and a worsened limp. At 26 months after his triple innominate osteotomies he had bilateral femoral valgus osteotomies that resolved his pain and leg-length inequalities. Currently, the patient remains pain free without any restriction of activities.

DISCUSSION

This new modified triple osteotomy of the innominate bone is a technically demanding procedure and requires careful operative planning. The technique and its difficulty is similar to that described by Steel.16 However, three changes to Dr Steel’s surgical technique were used. The first change was previously described by Kumar et al,6 which recommended the resection of 1 to 1.5 cm of bone after the ischial osteotomy in order to facilitate medialization and rotation of the acetabulum. The second change is to resect a triangular wedge of bone from the outer cortex of the proximal part of the ilium creating a slot, which will later serve as an abutment that the distal posterior aspect of the ilium will fit. The third and final change is to fix the iliac osteotomy with two 7.3-mm cannulated screws instead of Steinman pins. With that, the osteotomy provides excellent intraoperative mobility of the acetabular fragment and subsequent coverage of the femoral head. Although the previously described versions of the triple osteotomy give extensive coverage of the femoral head they achieve this through osteotomies that sacrifice stability of the reconstruction. In order to restore stability to the hip and maintain the ability to achieve the correction afforded by the traditional triple osteotomy, the described modifications to the procedure were devised.

The review of clinical data shows the center edge angle increasing to a mean of 44.9° and the acetabular angle decreasing to a mean of 28°. This is a correction of 36 and 25°, respectively. The correction achieved by this new modification to the triple osteotomy is similar to the previous reports.2,4,6,16,12 Therefore, the described modification does not adversely affect the correction achieved by prior versions of the triple osteotomy; however, it provides greater stability. With greater stability, we are able to allow immediate postoperative crutch walking and we avoid the use of a spica cast. Furthermore, no cases of pseudarthrosis have occurred with this technique, whereas other investigators report up to 4 %.12,16

No immediate complications have occurred in our patients except for excess blood loss in one patient. However, we are unable to comment on the long-term outcome of these procedures. We currently have successful resolution of symptoms in 12 of the 13 hips (92%) that we treated with the described procedure, and further long-term evaluation is needed. Still, concerns exist regarding the effects of this procedure on our female patients and their ability to have natural childbirth. This is especially of note in female patients having bilateral procedures. Loder et al8 evaluated the triple osteotomy as described by Steel and found a borderline decrease in the mid-pelvis and a markedly decreased pelvic outlet. However, the authors concluded the birth canal was unaffected because the mid-pelvis is the narrowest plane and is not markedly affected.

We have described a new modification of the triple osteotomy of the innominate bone. The ischium, pubis, and iliac bones are osteotomized, with resection of a triangular wedge of bone from the outer cortex of the proximal part of the ilium. The resection of the triangular wedge of bone from the outer cortex alone creates a slot with the intact inner cortex serving as a stabilizing abutment where the distal posterior aspect of the ilium fits. We have shown through our preliminary results that there is similar or better correction with the modification and it affords greater stability. The rigid construct of the osteotomy and pelvic fixation facilitates early weightbearing. Further followup is necessary to determine the long-term effects and outcome of this procedure.

References

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