Hospital Pequeno Príncipe, Curitiba, PR, Brazil
Introduction
Hip dislocation or subluxation in non-ambulatory patients with spastic cerebral palsy can lead to pain, difficulties to perform perineal hygiene, pressure ulcers, lower limb fractures, and loss of balance to sit, especially in unilateral or asymmetric cases.1,2 Prevention and early treatment are recommended.2,3 In cases of subluxation/dislocation, reconstructive surgery is indicated, usually consisting of femoral varus osteotomy, with or without acetabuloplasty and soft tissue release.4–6
In unilateral dislocations, there is controversy regarding treatment for the contralateral hip. Some studies indicate bilateral reconstruction due to the risk of progression to subluxation and the asymmetry that may result from unilateral reconstruction.7 Conversely, performing surgery in a normal hip increases the operative time and bleeding, and may lead to complications.8
This study aimed to assess the evolution of the contralateral hip after unilateral reconstructive procedure with varus osteotomy of the proximal femur and Dega transiliac osteotomy (with or without the release of soft tissue) and the possible factors associated with the development (or not) of subluxation.
Material and methods This was a retrospective study based on the analysis of charts of non-ambulatory patients with spastic cerebral palsy and functionally classified by the Gross Motor Functional Classification System (GMFCS) as levels IV and V. Patients underwent unilateral hip reconstruction surgery due to dislocation or subluxation in this hospital, from March 1999 to April 2009. Theis study was approved by the Research Ethics Committee of this department.
For inclusion in the study, patients with cerebral palsy needed to have undergone unilateral hip reconstruction surgery (varus osteotomy of the femur, Dega transiliac osteotomy with or without soft tissue release), and present a minimum follow-up period of 30 months and clinical and radiographic documentation to enable analysis in three time-points: at the time of surgery (immediate pre- and postoperative periods), approximately two years after surgery, and at last follow-up visit.
Clinical parameters evaluated were: sex, previous surgery or botulinum toxin application, age at surgery, follow-up time after surgery, and abduction at the three time-points. Regarding the procedure, it was assessed whether femoral shortening associated with varus osteotomy was performed.
Radiographic evaluation was done on the anteroposterior pelvic incidence and consisted of femoral head migration percentage (Reimer’s extrusion index [RI]), acetabular angle (AC), and Shenton’s line (SL) continuity.
To evaluate the associated factors, patients were divided into two groups: those who showed progression of the RI in the contralateral hip (group I), and those who did not present such progression (group II). Progression was considered when RI was 40% in the last follow-up.
Statistical analysis was performed with tests selected based on the type of variable studied.
Results Seventeen patients met the inclusion criteria. Eight evolved with contralateral hip subluxation (group I), while nine did not (group II).
Group I had three males and five females; group II had one male and eight females (non-significant difference)
The mean age at time of surgery in group I was 62 months (28–110) and mean follow-up time was 62 months (31–125). Group II had mean age at time ofsurgery of98 months (64–159) and mean follow-up time of 83 months (32–150). These differences were not significant.
Regarding interventions prior to the reconstructive procedure, three patients from group I and two from group II had already undergone botulinum toxin application in adductor and/or flexor muscles. Previous soft tissue release surgery was observed in two (25%) patients from group I and in four (44%) from group II. Femoral shortening during reconstructive procedure was performed in five (63%) patients from group I and in seven (78%) from group II. These differences were not significant.
In the immediate postoperative period, 50% (4/8) of the Xrays from group I showed SL discontinuity; in turn, this finding was observed in 33% of cases in group II (non-significant difference). In the second evaluation (two years after surgery), SL discontinuity was observed in 100% (8/8) of patients from group I and in 22% (2/9) of those from group II.This difference was statistically significant.
Mean abduction in group I was 28? in the immediate preoperative period, 36? in the assessment at two years postoperative, and 24? on the last visit. In group II, these values were 27?, 36?, and 34?, respectively. There was no statistical difference between groups.
Mean AC in group I was 23?, 26?, and 29? at the three above mentioned periods. Group II showed 18?, 15?, and 17?, respectively. These differences were not significant. RI in the immediate postoperative period, two years after surgery, and at the last visit was 34%, 68%, and 84%, respectively, in group I; it was 20%, 17%, and 13% in group II. The difference in the last two evaluations was significant. Combining the data from RI and AC, we observed that, out of nine hips that presented RI < 30 and AC < 25 in the immediate postoperative period, only one evolved to contralateral subluxation ( p < 0.05).
Discussion Hip subluxation or dislocation in non-ambulatory patients with spastic cerebral may cause pain, difficulty in positioning and hygiene, and contribute to the development of scoliosis and contractures in the lower limbs.9 Therefore, when diagnosed in skeletally immature patients, surgical reconstruction is indicated. In this institution, the adductor muscles are released (and usually, the iliopsoas muscles), and femoral varus osteotomy and Dega acetabuloplasty are performed.4–6 When unilateral, some authors recommend soft tissue procedure and varus osteotomy in the contralateral hip. This indication would be justified by the increased risk of subluxation and the possible asymmetry as a result of the unilateral procedure, which would cause difficulties in positioning and would change the spinal alignment.7
The risk of impairment of the contralateral side ranges from 4% to 75%. Noonan et al.7 studied 35 patients, 33 nonambulatory, who underwent unilateral surgery. Of these, 26 (74.3%) developed subluxation. They recommended that the procedure should be performed bilaterally, especially if some degree of acetabular dysplasia is observed. Despite believing that the bilateral bone procedure is justified, Carr and Gage10 found only 20% of progression to subluxation. Park et al.8 developed a decision analysis model with data from the literature and concluded that the bilateral procedure has superior outcomes.
In the present study, approximately half of the patients developed contralateral subluxation. The authors understand that this finding does not make a prophylactic procedure mandatory for all patients, as it is a major procedure with some risks. This study also aimed to identify factors associated with the occurrence (or not) of contralateral subluxation. As hip dislocation is known to be associated with patients with more severe impairment, this study only included nonambulatory patients (GMFCS IV or V).11,12
Surgery in younger patients may be associated with increased risk for development of contralateral subluxation.9,12 Although no significant associations were observed, there was a tendency for hip contralateral subluxation in operated patients under 8 years of age (62; ±25 months).
Individually, none ofthe measures – either clinical or radiological, in the immediate pre- and post-operative periods – was able to indicate the evolution of the contralateral hip in the present study. The most significant finding was that hips that showed RI < 30% associated with AC < 25? had lower probability of future dislocation. This finding somewhat corroborates those by Noonan et al., who observed that hips with dysplastic changes were at higher risk for subluxation.7
An important factor is that the hips that developed subluxation presented it within the first two years of the procedure. Therefore, the contralateral hip should be closely monitored in this postoperative period in case of unilateral surgery
The present study had some limitations. In addition to the retrospective design, the mean follow-up period was 73 months, and not all patients had reached skeletal maturity at the last assessment. The multitude of surgeons who performed these procedures over the ten years of the study may have affected the results. The small sample size also decreases the statistical strength of the various factors studied
Conclusion
The study suggests that prophylactic surgery in the contralateral hip is not justified for all patients, especially in those older than 8 years of age with RI < 30% and AC < 25?. Contralateral subluxation occurs in the first two postoperative years; parents should be advised about this risk, and patients should be closely monitored during this time.
Conflicts of interest
The authors declare no conflicts of interest.
1. Terjesen T. The natural history of hip development in cerebral palsy. Developmental medicine and child neurology. Dev Med Child Neurol. 2012;54(10):951–7. 2. Phelps WM. Prevention of acquired dislocation of the hip in cerebral palsy. J Bone Joint Surg Am. 1959;41(3):440–8. 3. Hägglund G, Lauge-Pedersen H, Wagner P. Characteristics of children with hip displacement in cerebral palsy. BMC Musculoskelet Disord. 2007;8:101. 4. Bagg MR, Farber J, Miller F. Long-term follow-up of hip subluxation in cerebral palsy patients. J Pediatr Orthop. 1993;13(1):32–6. 5. Hoffer MM, Stein GA, Koffman M, Prietto M. Femoral varus-derotation osteotomy in spastic cerebral palsy. J Bone Joint Surg Am. 1985;67(8):1229–35. 6. 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(12):1863–71. 7. Noonan KJ, Walker TL, Kayes KJ, Feinberg J. Effect of surgery on the nontreated hip in severe cerebral palsy. J Pediatr Orthop. 2000;20(6):771–5. 8. Park MS, Chung CY, Kwon DG, Sung KH, Choi IH, Lee KM. Prophylactic femoral varization osteotomy for contralateral stable hips in non-ambulant individuals with cerebral palsy undergoing hip surgery: decision analysis. Dev Med Child Neurol. 2012;54(3):231–9. 9. Bleck EE. The hip in cerebral palsy. Orthop Clin North Am. 1980;11(1):79–104. 10. Carr C, Gage JR. The fate of the nonoperated hip in cerebral palsy. J Pediatr Orthop. 1987;7(3):262–7. 11. Cooperman DR, Bartucci E, Dietrick E, Millar EA. Hip dislocation in spastic cerebral palsy: long-term consequences. J Pediatr Orthop. 1987;7(3):268–76. 12. Shukla PY, Mann S, Braun SV, Gholve PA. Unilateral hip reconstruction in children with cerebral palsy: predictors for failure. J Pediatr Orthop. 2013;33(2):175–81.
