Biomechanical investigation of pelvic stability in developmental dysplasia of the hip: unilateral salter osteotomy versus one-stage bilateral salter osteotomy

Abstract

Background: Developmental dysplasia of the hip (DDH) is a common disease in infants and children, and the treatment of bilateral DDH remains controversial. This study aimed to evaluate the stability of one-stage bilateral Salter pelvic osteotomy for bilateral DDH in patients of walking age.

Methods: In total, nine child cadavers aged 2-6 years were included. A universal mechanical testing machine was used for stability test. We performed two different surgical procedures on the specimens: nine child cadavers underwent unilateral Salter pelvic osteotomy, and six child cadavers were randomly selected to undergo Salter pelvic osteotomy again to simulate one-stage bilateral Salter pelvic osteotomy. The stability of the bilateral sacroiliac joints, local stability of the operation area, ultimate load test, and axial stiffness were evaluated.

Results: Both unilateral and bilateral Salter osteotomy could destroy the integrity of the pelvic ring and increase the risk of pelvic instability. In this study, compared with unilateral Salter osteotomy, bilateral Salter osteotomy had similar pelvic stability, and there was no significant difference between unilateral and bilateral Salter osteotomy in sacroiliac joint stability (p > 0.05), local stability (p = 0.763), ultimate load (p = 0.328), and axial stiffness (p = 0.480).

Conclusions: One-stage bilateral Salter pelvic osteotomy as a potential surgical method is viable and stable for children with bilateral DDH.

Keywords: Developmental dysplasia of the hip; One-stage; Salter osteotomy; Unilateral.

Fig. 1

Intact pelvis and marked point. a The intact pelvis before treated with different operation. b The marked point of M1, M2, M3, L1, L2, R1, and R2. M1 and M3 were marked on the iliac side of the sacroiliac joint, respectively, and M2 was marked at the same level on the sacrum. L1(R1) and L2(R2) were marked on both sides of Salter osteotomy, respectively. The blue arrow refers to the broken end of the osteotomy

Fig. 2

Different osteotomy for pelvis and the displacement of marked point was acquired by sophisticated camera. a The intact pelvis. b The unilateral salter pelvic osteotomy. c One-stage bilateral Salter pelvic osteotomy. The red arrow refers to M1 or M2 or M3, and green arrow refers to L1(R1) and L2(R2)

Fig. 3

The movement locus of marked point when a force added to the pelvis on the top of the fifth lumber from 0 to 400 N. a The marked point in pink rectangle were analyzed. b The yellow line represents the movement locus of marked point in pink rectangle. c The blue and red line represents displacement of X-axis direction and Y-axis direction respectively when the force added from 0 N to 400 N

Fig. 4

Assessment of stability of bilateral sacroiliac joints. a Stability comparison of intact pelvis and pelvis treated with unilateral salter pelvic osteotomy. b Stability comparison among intact pelvis, pelvis treated with unilateral Salter pelvic osteotomy and one-stage bilateral Salter pelvic osteotomy (^⋆p < 0.05, ^⋆⋆p < 0.01)

Fig. 5

Assessment of stability of local stability of operation area, ultimate load test and axial stiffness. a The RVD of local stability of operation area for different operation sites. b comparison of axial stiffness among non-operation group, unilateral salter pelvic osteotomy group and one-stage bilateral Salter innominate osteotomy group. c Comparison of ultimate load for unilateral salter pelvic osteotomy and one-stage bilateral Salter innominate osteotomy (^⋆⋆p < 0.01)