Progression of Hip Subluxation after Femoral Varization Osteotomy in Patients with Cerebral Palsy Sulis Bayu Sentono, M.D.†, Young Choi, M.D., Chin Youb Chung, M.D., Soon-Sun Kwon, Ph.D.*, Kyoung Min Lee, M.D., Moon Seok Park, M.D. †Department of Orthopaedic Surgery, Airlangga University Dr Soetomo Hospital, East Java, Indonesia. Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Kyungki, Korea. *Biomedical Research Institute, Seoul National University Bundang Hospital, Kyungki, Korea

Purpose To assess progression of hip subluxation after femoral varization derotation osteotomy (FVDO) in patients with cerebral palsy using a Linear Mixed Model (LMM) application and determined factors influence it

Background Hip subluxation and dislocation in children with spasticity resulting from CP may cause serious problems for affected patient Satisfactory short term results after FVDO or combined with Dega pelvic osteotomy for the treatment of hip subluxation and dislocation were reported by many authors There are only a few long term studies reporting recurrency after FVDO or combined with Dega pelvic osteotomy after some periodic follow-up.

Methods This study was a retrospective design Patients with CP, who visited our hospital and underwent FVDO or combined with Dega pelvic osteotomy between from 2003 Jun. to 2012 Oct. Investigate using X-ray in AP and Internal rotation view to assess Neck shaft angle(NSA), Head shaft angle (HAS), Migration percentage(MP) on pre-operative, immediate post operative and until last follow up

Methods For each of GMFCS level, the value of measurements (NSA, HSA, MP) was adjusted by multiple factors by using a Linear Mixed Model (LMM) with gender as the fixed effects and follow-up time (years) effect, laterality (side of hip) and each subject as the random effect

Operation Preop : FVDO + Dega

Operation Preop : FVDO + Dega

Methods (Measurement of NSA) Figure 1.:The angle between a line passing through the midway of the femoral shaft and another line connecting the femoral head center and midpoint of the femoral neck. The femoral head center was the center of best fitting outer circle of the femoral head. Pre Operative Post Operative

Methods (Measurement of HSA) Figure 1.:The head shaft angle was the angle between line passing through the femoral shaft midway and another line perpendicular to the proximal femoral physis. Pre Operative Post Operative

Methods (Measurement of MP) Figure 1.:The migration percentage was calculated by dividing the amount of the femoral head lateral to the Perkin’s line (A) with the total width of the femoral head (B) Pre Operative Post Operative

Results There were one hundreds and fourty-four hips in 76 bilateral spastic CP patients All were bilateral CP type with GMFCS II-III / IV / V were 12 / 30 / 34, respectively All got bilateral FVDO in equal amount and 80 hips combined with Dega pelvic osteotomy There were 57 males and 19 females with an average age at surgery was 8.5 ± 2.3 years (SD range from 4.5 to 16.5 years) and duration of follow up was 4.9±2.4 years

Results Parameters Values Patient’s Information No. of patients (M/F) 76(57/19) CP type (Uni/Bi) 0/76 GMFCS (II-III/IV/V) 12/30/34 Age at surgery (yr) 8.5 ± 2.3 Follow up duration 4.9±2.4 Type of surgery No. of Hips involved (Right/Left) 144(72/72) FVDO (Right/Left) Dega PO (Right/Left) 80(45/35)

Results Parameters Values Radiographic characteristics NSA (°) Preop 151.3±9.9 Immediate postop 129.0±14.6 Last F/U 129.1±15.3 HSA (°) 161.1±9.0 141.9±13.9 142.9±14.7 MP (%) 53.7±30.0 11.9±13.9 16.3±14.2

Estimate(%) 95% CI p GMFCS II-III (Intercept) 12.4 -0.8 to 25.5 0.062 Gender Male 11.4 -2.5 to 25.3 0.106 Side of hip Right -2.8 -8.3 to 2.7 0.285 Follow up Year 0.7 -4.1 to 5.5 0.742 GMFCS IV 18.7 10.5 to 26.9 <0.001 -7.1 -15.6 to 1.4 0.100 -0.8 -5.1 to 3.5 0.694 1.9 1.0 to 2.8 GMFCS V 11.2 0.2 to 22.1 0.046 -1.7 -13.2 to 9.8 0.774 -6.2 to 4.7 0.777 3.5 1.3 to 5.8 0.003

Results

Results

Results

Conclusions There is progression of hip subluxation after FVDO in patients with CP particularly in patients non-ambulatory (GMFCS level IV and V) Time of follow-up duration has main role in the occurency of this postulated

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