Hip pain in patients with spinal muscular atrophy: Prevalence, intensity, interference, and factors associated with moderate to severe pain

Background: A subset of patients with spinal muscular atrophy (SMA) develop hip pain. We analyzed (1) the characteristics of hip pain in patients with SMA (prevalence, intensity, interference with activities, and responsiveness to treatment) and (2) factors (patient, clinical, and radiographic) associated with moderate to severe pain. Methods: We performed a retrospective record review and telephone survey of 104 patients with SMA (77% response rate; 44% female; mean age, 22 ± 13 y) who presented for treatment between 2010 and 2020. Patient, clinical, and radiographic characteristics (when available) were recorded. Patients with current or past hip pain were asked about pain characteristics. Pain intensity and interference were assessed with the Brief Pain Inventory, modified for SMA (scale, 0 to 10 with 0 indicating no pain/interference). We used univariate analysis and ordered logistic regression to determine associations between patient factors and hip pain (α = 0.05). Results: Hip pain occurred in 60/104 patients (58%), with 15 (14%) indicating moderate to severe pain. Compared with patients with normal body mass index values, patients who were obese had 5.4 times the odds [95% confidence interval (CI), 1.3-23] of moderate to severe pain. Hip contractures [adjusted odds ratio (aOR), 3.2; 95% CI, 1.2-8.8] and dislocations (aOR, 2.9; 95% CI, 1.1-7.9) were associated with greater odds of pain compared with hips without these presentations. Surgical correction for scoliosis (aOR, 2.6; 95% CI, 1.1-6.5) was also associated with greater odds of moderate to severe pain. Femoral head migration percentage was the only radiographic parameter associated with pain. Mean modified Brief Pain Inventory pain intensity was 2.1 ± 2.3. Prolonged sitting, sleep, and transfers (eg, bed to wheelchair) were the activities most affected by pain. Conclusions: Hip pain was moderate to severe in 14% of patients with SMA. Obesity, hip contractures, surgical correction of scoliosis, and hip dislocations were independently associated with pain. Although mean pain intensity was low, hip pain interfered with daily activities, including prolonged sitting, sleep, and transfers.