Prevalence and Risk Factors for Stiffness Following Open Reduction for Developmental Dysplasia of the Hip.

Objective: Most prior investigations on adverse outcomes after open reduction (OR) for developmental dysplasia of the hip (DDH) have focused on avascular necrosis, redislocation, and residual dysplasia. To our knowledge, no previous study has investigated risk factors for stiffness, an underappreciated source of postoperative morbidity. The goals of this study were to define the entity more clearly and evaluate the prevalence and risk factors for arthrofibrosis after OR for DDH.

Methods: A retrospective study was conducted, including all open hip reductions for DDH performed by a single surgeon from 2009 to 2022. Preoperative anteroposterior pelvic radiographs were used to calculate superior displacement, which was defined as the distance from the highest point of the proximal femoral metaphysis to the Hilgenreiner line, normalized by pelvic width. Cases treated with premature postoperative bracing cessation and/or referral to physical therapy with a resolution of stiffness within 6 months were categorized as mild arthrofibrosis. Cases that required >6 months of formal physical therapy for persistent range of motion concerns, manipulation under anesthesia, and/or inpatient rehabilitation admission were categorized as significant arthrofibrosis.

Results: This study included 170 hips with a mean age of 21.6 months (range: 6.1 to 93.6 mo) and a mean follow-up of 46.8 months. 156 ORs (91.8%) were done through an anterior approach. Sixty-four patients (37.6%) had a concomitant isolated pelvic osteotomy, and 34 (20.0%) had both pelvic and femoral osteotomies. During the postoperative course, 109 patients (64.1%) had no arthrofibrosis, 38 (22.4%) had mild stiffness, and 23 (13.5%) had significant arthrofibrosis. On multivariable analysis, older age, superior displacement, and concomitant pelvic osteotomy were associated with any degree of arthrofibrosis ( P < 0.05). Children older than 18 months or with dislocations higher than 16% of pelvic width had a 4.7 and 2.7 times higher risk, respectively, of experiencing some degree of stiffness postoperatively.

Conclusions: Older age, high dislocations, and concomitant pelvic osteotomy without femoral shortening are risk factors for stiffness after OR for DDH. Surgeons should counsel families about the risk of postoperative stiffness, which occurred to some degree in 36% of our patients.

Level of evidence: Level IV.