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 Table of Contents  
CLINICAL ARTICLE
Year : 2015  |  Volume : 1  |  Issue : 1  |  Page : 28-34

One stage soft tissue release, open reduction, femoral shortening, osteotomy and peri acetabular augmentation for spastic dislocated hip-early results


Swami Vivekanand National Institute of Rehabilitation Training and Research, Olatpur, Bairoi, Cuttack, Orissa, India

Date of Web Publication21-Apr-2015

Correspondence Address:
Sakti Prasad Das
SV NIRTAR Olatpur, Bairoi, Cuttack , Orrisa
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2395-4264.153562

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  Abstract 

Objectives: The goals of hip surgery in cerebral palsy are to maintain adequate reduction of the femoral head, prevent pain, improve sitting balance and maintain motion and the ambulatory status of the patient. It is now well accepted that soft tissue release, open reduction and femoral shortening were necessary for a stable hip along with some type of pelvic osteotomy. We evaluated the clinical and radiological results of one-stage correction of hip dislocation for cerebral palsy patients.
Materials and Methods: We reviewed clinical outcomes and radiologic indices of 32 dislocated hips in 24 children with cerebral palsy (13 males, 11 females; mean age, 8.6 years). All 32 hips had dislocation. Preoperative Gross Motor Function Classification System (GMFCS) scores of the patients were as follows; level V (13 patients), level IV (9), and level III (2). The combined surgery included release of contracted muscles, (adductors, rectus femoris, iliopsoas) open reduction of the femoral head, femoral shortening varusderotation osteotomy and the modified Dega osteotomy along with shelf procedure. Hip range of motion, GMFCS level, acetabular index, center- edge angle, migration percentage, neck shaft angle, Sharp's angle was measured before and after surgery. The mean follow-up period was 38.1 months.
Results: Hip abduction (median, 40°), sitting comfort and GMFCS level were improved after surgery, and pain was decreased. There were no femoral head avascular necrosis, no infection or nonunion. There was no redislocation. All radiologic indices showed improvement after surgery.
Conclusions: So, we believe that a combined approach of muscle releases, open reduction, femoral shortening varus-derotation osteotomy, Dega osteotomy and penicapsularacetabular augmentation was a highly effective method for the treatment of spastic dislocated hips in our patients.

Keywords: Acetabular augmentation, cerebral palsy, dega osteotomy, hip dislocation, pericapsular osteotomy


How to cite this article:
Das SP, Pradhan S, Sahoo P K, Ganesh S, Mohanty R N, Das S K. One stage soft tissue release, open reduction, femoral shortening, osteotomy and peri acetabular augmentation for spastic dislocated hip-early results. Indian J Cereb Palsy 2015;1:28-34

How to cite this URL:
Das SP, Pradhan S, Sahoo P K, Ganesh S, Mohanty R N, Das S K. One stage soft tissue release, open reduction, femoral shortening, osteotomy and peri acetabular augmentation for spastic dislocated hip-early results. Indian J Cereb Palsy [serial online] 2015 [cited 2017 Apr 24];1:28-34. Available from: http://www.ijcpjournal.org/text.asp?2015/1/1/28/153562


  Introduction Top


Subluxation and dislocation of the hip is a major source of disability for children with cerebral palsy, with the incidence ranging between 3% and 75%. [1],[2],[3],[4] Hip dislocation and subluxation are caused by multiple factors including contraction of muscles, a deformed proximal femur and acetabular deficiency. [5],[6] Contraction of the adductor and flexor muscles leads to disturbances of the muscular balance of the hip joint region, to deformation of the acetabulum and proximal femur such as coxavalga, [7] increase of ante version and to subsequent hip subluxation and dislocation. [8] These issues gradually worsen the acetabular deformity and deficiency, aggravating the hip dislocation and subluxation. Dislocation of the hip is associated with poor sitting balance, pelvic obliquity, scoliosis and difficulty in perineal care. [1],[9],[10],[11],[12] Therefore, preventive treatment for dislocation of the hip is important, and if the hip is dislocated, treatment of the cause and stable reduction of the dislocated femoral head are necessary. [1],[11],[12],[13] It has been suggested that all these problems can be improved with one-stage correction. [9],[10] We have done open reduction in all our cases along with capsulorrhaphy due to high resubluxation in high Reimer's migration percentage cases reported previously. [10]

Due to the global deficiency of acetabulum in long standing dislocated cases, and reported subluxation post operatively by various authors, we have combined the Dega osteotomy with acetabular augmentation.

We evaluated the results of spastic hip dislocation which included soft tissue release, open reduction, femoral varusderotation osteotomy and the modified Dega osteotomy along with Staheli type acetabular augmentation. [9],[10]


  Materials and Methods Top


From October 2006 to March 2012, we performed soft tissue release, open reduction, femoral derotationvarus osteotomy and pericapsularacetabular augmentation along with Dega osteotomy for dislocation of 32 hips in 24 patients. The mean age at the time of surgery was 8.6 years (range, 2-13 years) and the mean follow-up period was 38.1 months (range, 12 to 45 months). There were 13 males and 11 females; 21 of these patients had quadriplegic and 3 had diplegic type of cerebral palsy. All 32 hips were having dislocation and we have excluded cases having subluxation. Eight cases were bilateral. Preoperative Gross Motor Function Classification System (GMFCS) was level V in 13 patients, level IV in 9, and level III in 2. One patient with level III could walk for short distances with hip pain with a hand-held mobility device. Nine patients who were scored at GMFCS level IV could walk for short distances with a walker before onset of hip problems, but all these patients had difficulty in walking after hip dislocation. All of the other patients (13 in level V) were unable to walk because of muscle contracture and hip discomfort associated with instability, and had difficulty in maintaining a seated position [Figure 1].
Figure 1: Clinical photograph of a quadriplegic cp child (GMFCS V) prone for dislocation

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All patients were treated with single event surgery including open reduction of the dislocated femoral head, release of contracted muscles, varus-derotation-shortening femoral osteotomy and the modified Dega osteotomy along with acetabular augmentation. For the patients with bilateral involvement, the more painful and deformed side was treated first, except that release of contracted muscles was performed for both legs in the first operation. After application of a hip spica cast for 6 weeks and rehabilitation with physical therapy for 2-4 weeks, surgery was then performed on the contra lateral hips.

Following surgery, a hip spica cast applied. Physical therapy was started after removal of cast and union of osteotomy site which is approximately 6-8 weeks. We evaluated the improvement in hip range of motion (ROM), the degree of pain, comfort while sitting and complications such as postoperative infection during follow-up. For assessing comfort while sitting, we checked whether patients could maintain a seated position without body support; for estimating discomfort or pain, the patients' parents were asked whether the pain had decreased worsened or remained about the same. We also evaluated changes in the acetabular index, center-edge angle, migration percentage, neck shaft angle, redislocation, and nonunion on a postoperative anteroposterior radiograph of the pelvis.

Soft tissue release and open reduction

After the assessment of contracture in the adductors, iliopsoas, rectus femoris, hamstrings, and achilles tendon during preoperative physical examinations, lengthening procedures for contracted soft tissues were performed selectively. Among the adductors, tenotomy was first performed in the adductor longus, next in the adductor brevis and finally in the gracilis in sequence until the hip could be abducted normally. The second incision is made parallel to the iliac crest with use of salter's variation of the smith-petersen approach; the iliac apophysis is divided and the iliac wing is stripped subperiosteally down to the sciatic notch both medially and laterally, for better visualization of the notch during the osteotomy. The medial exposure allows visualization of the anterior inferior iliac spine where the osteotomy will be done and appreciation of the thickness of the iliac wall during the osteotomy. Straight head of rectusfemoris was released and attached temporarily to silk then reflected head of rectus released from capsule retaining its superior attachment. Then fractional lengthening of the tendinous portion of the iliopsoas at the pelvic brim is done 14 then capsule is opened through a t-shaped incision after exposure from anterior, superior and posterior aspects. Next, the ligamentum teres is removed, the contracted transverse acetabular ligament is cut, and the acetabulum is cleared of any remaining obstructions (fatty tissue or additional capsular adhesions).

Before proceeding, the femoral head is carefully inspected to assess deformity and loss of articular cartilage. If there are severe changes in the shape of the femoral head and loss of more than 50% of the articular cartilage, reduction of the hip is not carried out. Instead valgus osteotomy was performed. Then femoral head is reduced and capsular repair done.

Varus derotation shortening osteotomy

With a lateral approach to the proximal femur, femoral shortening and a varus derotational osteotomy (VDRO) was performed at the level of subtrochantericregion and fixed with 4.5 mm thick recon plate. The amount of femoral shortening was equivalent to the overlapped distance of the proximal and distal portions of the osteotomized femur during slight traction of the leg. The femoral neck-shaft angle was corrected to 115-120° and the ante version was corrected to 15-20°.

Modified dega osteotomy along with acetabular augmentation

Bicortical cuts were made anteriorly over the anterior inferior iliac spine and posteriorly at the greater sciatic notch with the osteotome. A unicortical cut was then made through the outer cortex of the ilium between these two points passing approximately 1-2 cm above the lateral margin of the acetabulum. Under image-intensifier control, the curved osteotome was directed halfway between the inner and outer iliac cortices. Care was taken to stop the osteotome above the triradiate cartilage. Then the acetabulum was rotated laterally and downward using a lamina spreader, hinging on the triradiate cartilage to correct the dysplasia until the acetabular angle was decreased to 15°. The bone graft (usually obtained from the femoral shortening osteotomy) was then placed into the osteotomy site. The placement of the bone graft corresponded to where the major acetabular deficiency was found. In this manner, we could decrease the acetabular angle, increase the coverage of the femoral head and reshape a trough-like deformed acetabulum. Then slice of bone taken from ilium and pushed in the trough created above the supra acetabular area. Gouged out cancellous bone taken from ilium was placed on the graft. Then graft was fixed by joining both heads of rectus femoris above it. Wounds were closed in layers after application of romovac negative pressure drain.

Post operative management

After closure of the operative wounds, a hip spica cast was applied for 6 weeks.


  Results Top


CLINICAL-The median postoperative range of abduction of the hip improved from 21.8° (range, 5-35°) to 40.0° (range, 30-50°) Following surgery, 12 (75%) out of the 16 patients who could not maintain a seated position preoperatively were able to sit without a body supporter. Nineteen patients (83%) reported a decrease in pain, 4 (17%) experienced about the same level of pain pre- and postoperatively, and one reported a worsening of pain following treatment which was for 2 months and relieved by physiotherapy. The 6 (26%) patients who were scored at GMFCS level V preoperatively almost improved to level 4 postoperatively. The GMFCS levels of the other 18 patients stayed the same. There was no infection or wound problems after surgery.

RADIOLOGICAL-The median acetabular index improved from 35.7° before surgery to 19.0° postoperatively; the median center- edge angle changed from 1.1° to 31.5°; and the migration percentage improved from 74.2-10.6% after surgery. All radiologic results improved significantly. There were no hip redislocation and no nonunion of the osteotomy site were observed. Avascular necrosis (AVN) of the femoral head was not observed [Figure 2] [Figure 3] [Figure 4] [Figure 5].
Figure 2: Preop. case 8. X Ray - Spastic quadriplegic had Right side hip dislocation

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Figure 3: Post operative x-ray- case No 8 after a follow up of two years. There is improvement of radiological indices

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Figure 4: Preop X Ray of case 2. This spastic quadriplegic cerebral palsy had bilateral hip dislocation

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Figure 5: Post operative x-ray after two and half years showing improvement of radiological indices

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  Discussion Top


Early acetabuloplasty, in addition to soft tissue lengthening and VDRO of the proximal femur greatly improves the chances for prolonged hip stability for patients with spastic dislocated hips. [6],[9],[14],[15],[16],[17],[18] Many acetabular indices are difficult to measure in cerebral palsy due to hip flexion contracture and the resulting increases in pelvic tilting. Therefore, many authors believe the migration percentage is the most accurate way to monitor hip instability in such patients. It has been recommended that acetabular correction should be performed when the migration percentage is over 50-70%, because the more serious the dislocation of the femoral head, the more likely it is accompanied by acetabular deficiency. [19],[20] McNerny et al., [10] found resubluxation rate of 60% in hips that did not undergo open reduction in migration percentage of 70% in comparison to 3% in hips that had got open reduction with capsulorrhaphy. So, they recommend open reduction with capsulorrhaphy in patients with migration percentage of Reimer's more than 70%. Our cases include all dislocations when presented to us. So, we have done open reduction along with capsulorrhaphy in all our cases.

Apart from the Dega osteotomy, pelvic osteotomies for the treatment of the dysplastic hip in cerebral palsy include the Salter innominate osteotomy [21] Pemberton acetabuloplasty. [17] C hiari osteotomy [22],[23] and the shelf procedure. [18] However, the Salter innominate osteotomy and Pemberton acetabuloplasty are not suitable for all dysplastic hips in cerebral palsy because they are designed mainly to correct anterolateral acetabular deficiency [9] while acetabular deficiency in cerebral palsy exists in various locations. With 3D CT, Kim and Wenger [5] demonstrated the variable locations of acetabular deficiency in cerebral palsy: Anterior in 29%, superolateral in 15%, posterior in 37%, and mixed in 19%. They reported that the acetabulum showed a trough-like elongated deformity. The Chiari osteotomy and shelf procedure do not use the articular cartilage of the acetabulum to cover the femoral head, [9],[10] and do not correct the elongated, trough-like deformity of the acetabulum. The modified Dega osteotomy is ideal for these hips by providing selectively improved coverage based on the main area of deficiency (anterior, superiolateral, or posterior) and by reshaping the elongated acetabulum directly. We have added the shelf procedure after Dega to increase the coverage which prevents redislocation.

Since the Dega osteotomy [24],[25] was first introduced in 1969, many studies have been conducted using this technique [25],[26],[27] However, the procedure as originally described did not sufficiently increase coverage of the femoral head, because the posteromedial cortex of the ilium and the greater sciatic notch were not cut. [25],[26],[27] To produce better results, Mubarak et al., [9] and McNerney et al., [10] described the modified Dega osteotomy in which bicortical cuts were made in the anterior inferior iliac spine and the greater sciatic notch. With this modified procedure, posterior coverage of the femoral head is increased by placing a larger bone graft in the posterior part of the osteotomy. Moreover, while other pelvic osteotomies require internal fixation, more stability is obtained without internal fixation by inserting autologous bone fragments from the the proximal femoral shortening osteotomy into the osteotomy site. Elasticity of the osteotomized iliac bone with a hinge at the triradiate cartilage enhances the stability of the bone graft. Chung et al., [28] demonstrated the morphometric changes in the acetabulum after Dega osteotomy which is similar to the osteotomy we used. They reported that the anterosuperior, superolateral and posterosuperior covers had improved significantly and the mean acetabular volume increased after the osteotomy. Ostercamp et al., [23] performed Chiari osteotomy in 12 CP patients in a series of 13 hips and concluded that it is effective in mild and moderately subluxated hips but insufficient in global deficiency. They concluded that the dislocated cases to be treated by combined Chiari and shelf procedure. Because the location of the acetabular deficiency is variable, we believe that our combined acetabuloplasty is ideal.

Open reduction helps us in visually inspecting the acetabular deficiency and cartilage damage in the femoral head. Cases having damage to articular cartilage of femoral head were excluded from our study and treated with some other procedures.

Although the variation of the proximal femur itself naturally introduces a shortening component and relieves tension around the hip in many cases. Still, we added a shortening osteotomy in cases of dislocation in order to avoid excessive varization of the femur and to reduce the pressure caused by the Dega osteotomy. Harvested material from the shortening procedure was used for the bone graft in the Dega pelvic osteotomy. Open reduction with capsulorrhaphy was performed in all the cases. In all cases, the hamstrings were lengthened because the soft tissue procedure was conducted before the proximal femoral procedure.

The current concept in correction of unstable hips in cerebral palsy maintains bilateral procedures, especially including the contralateral femoral side, to prevent eventual contralateral hip instability and windswept hip. With our approach, usually involving no more than soft tissue correction in the less severely affected hip, we have not observed significant suluxation on the contralateral side to date. When further subluxation occurs, a femoral side procedure may be required without delay. All patients in this study showed a coxavalga deformity and increased anteversion of the proximal femur by soft tissue contracture from the first visit. All of them were treated with single event multilevel surgery. Simultaneous correction of multiple problems could extend the operation time, increasing the likelihood of complications. However, if the surgeons are experienced, patients would benefit from the shortened hospitalization and rehabilitation times.

In our patients, stable reduction of the femoral head was followed by a remarkable improvement in abduction. Furthermore, this was achieved without increased pain because of the release of contracted muscles and the increased stability of the hip joint as well as improved comfort in the seated position. The four patients who failed to achieve comfortable sitting experienced the same degree of pain as they had preoperatively.

However, all of them were GMFCS level V and were considered to have an abnormal sense of balance caused by the cerebral palsy apart from the problems in their hips. Some of them had scoliosis with fixed pelvic obliquity. The patients who could not maintain a stable seated position solely due to contracted muscles and hip pain, were able to sit comfortably after the operation. As it was difficult to determine the degree of pain or discomfort quantitatively (for example with a VAS score) for our young patients, we interviewed parents about the patients' pain (decreased, maintained or increased). The pain that patients complained of in this study may be considered to be irritability caused by hip motion when the hip is unstable. We believe that this irritability and the contracted soft tissues are the major causes preventing ambulation and of comfort in the seated position. After stable reduction of the hip joint, some of the patients were able to walk again with a walker for short distances, and most could sit comfortably.

We had noted no AVN of the femoral head in hips.


  Conclusions Top


In summary, we believe that a combined approach of muscle releases, open reduction, femoral-shortening varus-derotation osteotomy, and penicapsularacetabular augmentation was a highly effective method for the treatment of spastic dislocated hips in our patients.

 
  References Top

1.
Samilson RL, Tsou P, Aamoth G, Green WM. Dislocation and subluxation of the hip in cerebral palsy. Pathogenesis, natural history and management. J Bone Joint Surg Am 1972;54:863-73.  Back to cited text no. 1
[PUBMED]    
2.
Boldingh EJ, Jacobs-van der Bruggen MA, Bos CF, Lankhorst GJ, Bouter LM. Determinants of hip pain in adult patients with severe cerebral palsy. J Pediatr Orthop B 2005;14:120-5.  Back to cited text no. 2
    
3.
Hodgkinson I, Jindrich ML, Duhaut P, Vadot JP, Metton G, Berard C. Hip pain in 234 non-ambulatory adolescents and young adults with cerebral palsy: A cross-sectional multicentre s tudy. Dev Med Chi ld Neurol 2001;43:806-8.  Back to cited text no. 3
    
4.
Noonan KJ, Jones J, Pierson J, Honkamp NJ, Leverson G. Hip function in adults with severe cerebral palsy. J Bone Joint Surg Am 2004;86:2607-13.  Back to cited text no. 4
    
5.
Kim HT, Wenger DR. Location of acetabular deficiency and associated hip dislocation in neuromuscular hip dysplasia: Three-dimensional computed tomographic analysis. J Pediatr Orthop 1997;17:143-51.  Back to cited text no. 5
    
6.
Gamble JG, Rinsky LA, Bleck EE. Established hip dislocations in children with cerebral palsy. Clin Orthop Relat Res 1990:90-9.  Back to cited text no. 6
    
7.
Minear WL, Tachdjian MO. Hip dislocation in cerebral palsy. J Bone Joint Surg Am 1956;38:1358-64.  Back to cited text no. 7
[PUBMED]    
8.
Fabry G, MacEwen GD, Shands AR Jr. Torsion of the femur: A follow-up study in normal and abnormal conditions. J Bone Joint Surg Am 1973;55:1726-38.  Back to cited text no. 8
[PUBMED]    
9.
Mubarak SJ, Valencia FG, Wenger DR. One-stage correction of the spastic dislocated hip. Use of pericapsular acetabuloplasty to improve coverage. J Bone Joint Surg Am 1992;74:1347-57.  Back to cited text no. 9
    
10.
McNerney NP, Mubarak SJ, Wenger DR. One-stage correction of the dysplastic hip in cerebral palsy with the San Diego acetabuloplasty: Results and complications in 104 hips. J Pediatr Orthop 2000;20:93-103.  Back to cited text no. 10
    
11.
Pritchett JW. The untreated unstable hip in severe cerebral palsy. Clin Orthop Relat Res 1983;169-72.  Back to cited text no. 11
    
12.
Hoffer MM. Management of the hip in cerebral palsy. J Bone Joint Surg Am 1986;68:629-31.  Back to cited text no. 12
[PUBMED]    
13.
Baker LD, Dodelin R, Bassett FH 2 nd . Pathological changes in the hip in cerebral palsy: Incidence, pathogenesis, and treatment: A preliminary report. J Bone Joint Surg Am 1962;44-A: 1331-411.  Back to cited text no. 13
    
14.
Kay RM, Rethlefsen SA, Ryan JA, Wren TA. Outcome of gastrocnemius recession and tendo-achilles lengthening in ambulatory children with cerebral palsy. J Pediat Orthop B 2004;13:92-8.  Back to cited text no. 14
    
15.
Gordon JE, Capelli AM, Strecker WB, Delgado ED, Schoenecker PL. Pemberton pelvic osteotomy and varus rotational osteotomy in the treatment of acetabular dysplasia in patients who have static encephalopathy. J Bone Joint Surg Am 1996;78:1863-71.  Back to cited text no. 15
    
16.
Root L, Laplaza FJ, Brourman SN, Angel DH. The severely unstable hip in cerebral palsy. Treatment with open reduction, pelvic osteotomy, and femoral osteotomy with shortening. J Bone Joint Surg Am 1995;77:703-12.  Back to cited text no. 16
    
17.
Shea KG, Coleman SS, Carroll K, Stevens P, Van Boerum DH. Pemberton pericapsular osteotomy to treat a dysplastic hip in cerebral palsy. J Bone Joint Surg Am 1997;79:1342-51.  Back to cited text no. 17
    
18.
Zuckerman JD, Staheli LT, McLaughlin JF. Acetabular augmentation for progressive hip subluxation in cerebral palsy. J Pediatr Orthop 1984;4:436-42.  Back to cited text no. 18
[PUBMED]    
19.
Noonan KJ, Walker TL, Kayes KJ, Feinberg J. Varus derotation osteotomy for the treatment of hip subluxation and dislocation in cerebral palsy: Statistical analysis in 73 hips. J Pediatr Orthop B 2001;10:279-86.  Back to cited text no. 19
    
20.
Song HR, Carroll NC. Femoral varusderotation osteotomy with or without acetabuloplasty for unstable hips in cerebral palsy. J Pediatr Orthop 1998;18:62-8.  Back to cited text no. 20
    
21.
Salter RB. Innominate osteotomy in the treatment of congenital dislocation and subluxation of the hip. J Bone Joint Surg Br 1961;43:518-39.  Back to cited text no. 21
    
22.
Dietz FR, Knutson LM. Chiari pelvic osteotomy in cerebral palsy. J Pediatr Orthop 1995;15:372-80.  Back to cited text no. 22
    
23.
Osterkamp J, Caillouette JT, Hoffer MM. Chiari osteotomy in cerebral palsy. J Pediatr Orthop 1988;8:274-7.  Back to cited text no. 23
    
24.
Dega W. Selection of surgical methods in the treatment of congenital dislocation of the hip in children. Chir Narzadow Ruchu Ortop Pol 1969;34:357-66.  Back to cited text no. 24
[PUBMED]    
25.
Grudziak JS, Ward WT. Dega osteotomy for the treatment of congenital dysplasia of the hip. J Bone Joint Surg Am 2001;83-A: 845-54.  Back to cited text no. 25
    
26.
Jozwiak M, Marciniak W, Piontek T, Pietrzak S. Dega's transiliac osteotomy in the treatment of spastic hip subluxation and dislocation in cerebral palsy. J Pediatr Orthop B 2000;9:257-64.  Back to cited text no. 26
    
27.
Reichel H, Hein W. Degaacetabuloplasty combined with intertrochanteric osteotomies. Clin Orthop Relat Res 1996:234-42.  Back to cited text no. 27
    
28.
Chung CY, Choi IH, Cho TJ, Yoo WJ, Lee SH, Park MS. Morphometric changes in the acetabulum after Dega osteotomy in patients with cerebral palsy. J Bone Joint Surg Br 2008;90:88-91.  Back to cited text no. 28
    


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