Hip subluxation and dislocation are common in children with cerebral palsy (CP) and have been reported in up to 45% of these patients 1–4. The risk of hip displacement is related to the gross motor functional level as graded by the Gross Motor Function Classification System (GMFCS) 5–7. In 50–70% of CP patients, hip displacement can make perineal care difficult, alter sitting balance, and be a source of pain 2,3,8, and most clinicians agree that surgical treatment is indicated for progressive hip subluxation in this patient population 2–4,8–21.
The goal of any treatment is to create a reduced, stable, mobile hip with reduction of existing pain. Once a hip develops significant subluxation, reduction and stabilization can be achieved with a varus derotational, shortening femoral osteotomy (VDRSO) to decrease anteversion and the tension on the surrounding hip musculature, including hamstrings 14. If acetabular dysplasia is present, acetabular osteotomy may also be required. Different surgical procedures to reshape, redirect, or augment the acetabulum have been described by many authors in the past few decades 8–14,16–34.
The aim of this study was to evaluate the outcome of severely involved, nonambulatory CP patients (GMFCS levels IV and V) with hip subluxation or dislocation treated by simultaneous VDRSO osteotomy and percutaneous pelvic osteotomy (PPO) 22–24,30,32 performed by a minimally invasive surgical approach.
Patients and methods
A retrospective review was carried out of all patients with the diagnosis of CP and hip subluxation or dislocation treated surgically by simultaneous soft-tissue release, VDRSO, and PPO between 2002 and 2011. Twenty-eight nonambulatory children and adolescents (17 boys and 11 girls) with CP, GMFCS levels IV and V, fulfilled the inclusion criteria, and a total of 34 hips were identified. Of these, 18 (64%) were classified as GMFCS level IV and 10 (36%) as GMFCS level V. Four GMFCS 6 level IV patients (four hips) were lost to follow-up and were excluded from the study (Table 1). Finally, 30 hips in 24 patients (15 boys and 9 girls) were available for inclusion in the study. At the time of chart and radiograph review, the mean age of the patients was 9.4 years (5–16.5 years) and the mean follow-up was 35.9 months (6–96 months).
Demographics, orthopedic manifestations, and age at surgery are shown in Table 1.
Age, sex, GMFCS level, side(s) of operated hip, total duration of follow-up, immediate postoperative immobilization, complications, and the need for revision surgery were recorded for all patients. Clinical information and follow-up data were obtained from medical records. Eligible patients included those with a diagnosis of spastic quadriplegia or CP GMFCS level IV or V with unilateral or bilateral hip subluxation or dislocation and surgical treatment of the deformity by simultaneous soft-tissue release, VDRSO, and PPO. From 2002 onwards, all severely involved CP patients were treated by this technique. All surgical procedures were performed by the two main authors of the present study, jointly or individually.
All anterior–posterior (AP) radiographs of the pelvis were reviewed and the Reimers’ 25,26 migration percentage (MP) and acetabular angle (AA) 26,27 were measured to provide an objective assessment of the relationship of the proximal femur with the acetabulum and the effects of surgery.
MP and AA were measured for each time point. Evidence of progressive, postoperative hip displacement, and/or graft failure or dislodgement was also recorded.
The patient was placed in a supine position.
Under an image intensifier, a straight line, corresponding to the axis of the acetabular roof, was drawn 5–10 mm proximal to the roof of the acetabulum. A second line starting off at the tip of the greater trochanter was traced between the anterior iliac spine (AIS) and the posterior iliac spine. The intersection between the first and the second line indicates where to make the skin incision. The skin incision should measure about 2–3 cm in length and be parallel to the femoral shaft (Fig. 1a and b).
The subcutaneous tissue, the proximal portion of the tensoris fascia lata muscle, the gluteus medius, and minor muscles must be dissected bluntly to reach the outer table of the iliac bone. Using a Cobb dissector, the muscle tissue must be scraped off the outer table of the iliac bone from the sciatic notch to the AIS.
The osteotomy should be performed between 5 and 10 mm proximal to the acetabular roof 24. The pelvic osteotomy must be performed under an image intensifier and the osteotome should appear as a straight line during the complete procedure, meaning that it is perpendicular to the bone and parallel to the source of radiation.
Only the outer table of the iliac bone from the AIS to the sciatic notch was cut with a straight osteotome (Fig. 2a and b). The osteotome was always directed toward the triradiate cartilage. A curved osteotome can then be inserted to complete the osteotomy. At this point, two straight osteotomes can be inserted and used to lever open the osteotomy. Alternatively, a laminar spreader can be used instead of the osteotomes.
Bone graft insertion
The maximum opening of the osteotomy was measured. The graft obtained from the femoral shortening was wedged on the basis of this measurement. A 2 mm Kirschner wire was inserted into the graft to help push it into the opened space (Fig. 2a and b). Spreading the two osteotomes opens the space created by the osteotomy and favors the bone graft to slide into it, without having the graft rotate around the wire. As soon as the graft passes the outer table of about 40% of its length, the upper osteotome can be removed. At this point, the graft can be advanced further by hitting the tip of the Kirschner wire. If required, a bone impactor can be used to impact the graft further. Immediately before closure, an AP radiograph of the pelvis and a lateral radiograph of the operated hip should be carried out to assess the coverage of the femoral head and good positioning of the bone graft (Fig. 3a and b).
This procedure is indicated for severely involved, nonambulatory, GMFCS IV and V, CP patients with unilateral or bilateral hip subluxation or dislocation.
If the hip does not reduce after soft-tissue release and VDRSO, an open reduction should be considered. Hips that have been displaced for several years are most likely to be associated with capsular retraction and PPO should therefore not be performed.
Moreover, this surgical procedure should not be carried out in ambulatory patients as the impact of cutting through the abductor muscles mass is not known.
The results were analyzed using a paired Student’s t-test to assess preoperative and postoperative differences. The level of significance was set at P value less than 0.05.
The mean Reimers’ MP improved from 67.1 (42–100) preoperatively to 7.7 (0–70) at the last follow-up (P<0.05) and the mean AA improved from 31.8° (22–48°) preoperatively to 15.7° (5–27°) (P<0.05). Twenty-eight out of 30 hips had an MP lower than 30% at the last follow-up. Twenty-six out of 30 hips had an AA equal to or lower than 25° at the final follow-up. Table 2 shows the variation in MP and AA from presentation until the last follow-up in all patients.
The PPO osteotomy was carried out as part of a combined procedure including femoral osteotomy (VDRSO) and soft-tissue release. Six patients (25%) underwent bilateral PPO and bilateral soft-tissue release and VDRSO; 13 patients (54%) underwent unilateral PPO and bilateral soft-tissue release and VDRSO; five patients (21%) were subjected to unilateral PPO and unilateral soft-tissue release and VDRSO. The four excluded patients underwent unilateral PPO and bilateral soft-tissue release and VDRSO (Table 1).
PPO lasted on average 30 min/patient per side (25–40) and was always carried out through a skin incision of 2–3 cm.
Immobilization was accomplished postoperatively with a spica cast for 12 weeks in two patients with bilateral VDRSO and unilateral PPO (7%) (Table 2). The postoperative complications are shown in Table 3.
This retrospective study aimed to evaluate the outcome of pelvic osteotomy using a minimally invasive approach combined with VDRSO and soft-tissue release in nonambulatory children with severe CP. It is a preliminary report on 30 consecutively operated hips with 35.9 months’ average follow-up (Fig. 4a and b). All hips except one remained located and MP and AA improved from 67.1 to 7.7 and from 31.8 to 15.7, respectively (Fig. 4a and b). Three cases of avascular necrosis of the femoral head and one case of bone graft dislodgement were observed. All operated hips were pain-free at the time of the last follow-up, although four patients (12%) had pain for 6–12 months after surgery (Table 3).
Acetabular dysplasia can be addressed with surgical procedures redirecting (e.g. Salter osteotomy), reshaping (e.g. Albee, Dega, Pemberton, or San Diego osteotomy) and salvaging/augmenting the depth of the acetabulum, such as the shelf and Chiari osteotomies. Reshaping osteotomies reduce the volume and shape of the acetabulum by increasing its lateral coverage without a significant reduction in the posterior coverage 16,17,19,22–25,29–31.
Using a standard technique to reshape the acetabulum, Roposch and Wedge 32, Robb and Brunner 33, and Inan et al. 34 showed that a stable, painless, and concentric reduction of the hip could be achieved in most of their patients. All authors reported good results, with improvement in MP and AA 31–34. In our patients, MP and AA also improved, although the Albee-like acetabuloplasty 30 was performed by a less invasive surgical technique.
The skin incision, 2–3 cm in length, is wide enough to allow the straight and curved osteotomes to perform the pelvic osteotomy without damaging the skin and the subcutaneous tissues. The osteotome can be displaced upward and downwards toward the AIS and the sciatic notch, respectively.
We did not find radiographic evidence of premature closure of the triradiate cartilage in any patient of our series. To avoid this complication, the osteotomy should extend down to the triradiate cartilage, without crossing it. Bucholz et al. 35 found that premature closure of the triradiate cartilage did not affect the stability of the hip if it occurred after 10 years of age. Twelve patients (50%) in our group were 10 years or older at the time of surgery.
We found that this technique could also be successfully performed in CP patients with closed triradiate cartilage. In patients with closed triradiate cartilage, the osteotomy has to be extended to the original site of the cartilage and takes advantage of the reduced resistance of the porous iliac bone 33,34,36–39. In this subgroup of patients, broader osteotomes should be used to open the osteotomy to avoid collapse of the porotic iliac bone 33,34,36–39 under the pressure exerted by the osteotome during the opening maneuver.
In our series, all except one hip remained located, and three hips developed avascular necrosis 40. The only hip that dislocated after the surgical procedure did not concentrically reduce after soft-tissue release and VDRSO, and an open reduction should have been carried out at that time. Two patients with associated movement disorders were casted after surgery to reduce uncontrolled movements and postoperative pain. Avascular necrosis was not observed in casted patients. Two patients developed distal femur fractures. Both fractures occurred at the distal metaphysis and were not directly related to the surgical procedure (Table 3).
We observed only one case of bone graft dislodgement. Our hypothesis is that soft tissues contribute toward maintaining the bone graft in place by pushing it against the iliac bone as the surgical dissection is reduced compared with standard techniques. This is further supported by the findings that 92% of our patients did not require cast immobilization, irrespective of the age at surgery. Moreover, surgical time is reduced compared with standard techniques. However, because the osteotomy is performed under image intensifier guidance, the amount of exposure may be higher compared with standard open techniques. One possible complication, although not yet encountered by the authors of this study, is a lesion of the superior gluteal artery, which runs about 3 cm proximal to the skin incision. Therefore, we recommend performing the skin incision not too proximal and only after the identification of adequate reference points.
In their long-term follow-up study, Song and Carroll 41 reported a hip dislocation or a subluxation rate of 26% after VDRSO alone and 12% after VDRSO and pelvic osteotomy. Recent studies suggest that soft-tissue procedures for the management of hip displacement in children at GMFCS levels IV and V have a high failure rate but the best form of bony reconstruction is yet to be determined. In their group of severe CP patients with unilateral hip surgery, Canavese and colleagues found that more than 50% had an MP over 50%, or redislocation of the operated hip, or displacement of the contralateral hip at skeletal maturity 14,22,41.
Although longer follow-up studies are required to draw definitive conclusions, our findings indicate that a combined approach of soft-tissue releases, VDRSO, and PPO is an effective, reliable, and minimally invasive method for the treatment of spastic dislocated hips in severely involved CP patients. Also, patients with relative incongruity, closed triradiate cartilage, and some deformity of the femoral head can benefit from this combined approach. However, if the hip does not reduce after soft-tissue release and VDRSO, an open reduction should be considered. In conclusion, pelvic osteotomy through a less invasive surgical approach seems to be a valid alternative with an outcome similar to that of standard techniques and allows less muscle stripping and a shorter operating time.
Conflicts of interest
There are no conflicts of interest.
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