Outcomes of Dega osteotomy for developmental dislocation of hip in pre-school children

Abstract

Objective To explore the outcome of Dega osteotomy for developmental dislocation of the hip (DDH) in pre-school children aged 1.5-6 years and summarize the personalized application experience of acetabular arthroplasty. Methods A total of 34 involved hips of 28 pre-school DDH children with an average operative age of (28±10)(18-65)months from July 2007 to July 2012 were analyzed retrospectively.All 34 hips were dislocated and classified into 4 groups according to the shapes of false acetabula on preoperative radiography.Three hips of 3 children without false acetabula with conservative treatment previously were distributed into group A; 7 hips of 7 children with no false acetabula and without conservative treatment previously were distributed into group B; 9 hips of 6 children with obvious false acetabula pressing and eroding the true acetabula were distributed into group C; 15 hips of 12 children with extensive fusion of true and false acetabula(fused acetabula)were distributed into group D. Changes of morphologies and improvements of functions of involved hips and the incidence of avascular necrosis (AVN) were evaluated pre- and post-operation. Results Twenty-eight children with 34 involved hips were followed up successfully with an average period of(67±14)(48-96) months at an average age of(95±15)(73-126)months.Average acetabular index improved from 45°±6°(32°~57°) to 10°±7°(-6°~27°), average Reimer’s index improved from 0.95±0.12(0.53~1.00)to 0.15±0.11(-0.20~0.42)and average center edge angle was 23°±7°(11°~43°)postoperatively.All differences of changes were statistically significant pre- and postoperatively(t=26.375, 26.253 and -18.781, P<0.01). All Shenton lines of 34 hips were disrupted preoperatively and 31 of them became continuous at last with disruptions of 2 hips and reversed disruption of 1 hip.Modified Severin classification was applied for evaluating the radiographic improvement with 20 hips of type Ⅰ as excellent, 12 hips of type Ⅱ as good and 2 hips of type Ⅲ as moderate and the excellent-good rate was 94%(32/34 hips). Kalamchi & MacEwen classification was applied for evaluating the AVN of femoral heads with 9 hips of type Ⅱ and 25 hips without AVN and the incidence was 26%(9/34 hips). Modified McKay classification was applied for evaluating clinical functions with 29 hips as excellent, 4 hips as good and 1 hip as moderate.And the excellent-good rate was 97% (33/34 hips). No AVN was found in 5 hips of high-level Dega osteotomy in groups A & C, but 5/7 hips (71%) of low-level Dega osteotomy had AVN.The difference was statistically significant (P=0.028). AVN existed in all 3 hips of high-level Dega osteotomy in groups B & D, but only 1/19 hip (5%) of low-level Dega osteotomy had AVN.The difference was statistically significant (P=0.003). Conclusions The efficacy of Dega osteotomy is significant for pre-school DDH children.Such an operation is worth a wider clinical popularization.High-level Dega osteotomy with higher hinge and less range of suppressing of acetabular roof is applicable for correcting residual developmental dysplasia after conservative treatment and hips with obvious false acetabula.And low-level Dega osteotomy with lower hinge and greater range of suppressing of acetabular roof is applicable for true acetabula and fused acetabula.To acquire satisfactory coverage and forge matched containing femoral head with acetabulum are both basic requirements of acetabular arthroplasty.Corresponding operation may be performed according to different morphologies of acetabula to achieve personalized treatment for DDH.Each type of osteotomy has its own indication and should be applied discreetly. Key words: Dislocation of hip; Osteotomy; Ischemic necrosis of head of femur