Hip Pain in Patients With Spinal Muscular Atrophy: Prevalence, Intensity, Interference, and Factors Associated With Moderate to Severe Pain

Abstract

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. Level of Evidence: Level III.

Hip Pain in Nonambulatory Children with Type-I or II Spinal Muscular Atrophy

“…Our institution's aggressive multidisciplinary treatment of these medically frail children over the past 2 decades, prior to the widespread use of DMTs, allowed this to be the largest, most homogeneous, nonambulatory SMA cohort to be assessed for hip pain. Previous studies have increased sample sizes by combining patients who had SMA with those with other neuromuscular disorders [22][23][24] or have mixed both ambulatory and nonambulatory patients with SMA 25,26 , which may have confounded their results. Sporer and Smith, who combined ambulatory patients with type-III and nonambulatory patients with type-II SMA (n = 41), reported that 45% of the subjects had radiographic hip pathology and only 2 (5%) reported hip pain at a mean follow-up of 14 years 26 .…”

“…Sporer and Smith, who combined ambulatory patients with type-III and nonambulatory patients with type-II SMA (n = 41), reported that 45% of the subjects had radiographic hip pathology and only 2 (5%) reported hip pain at a mean follow-up of 14 years 26 . In addition, Xu et al, who also combined ambulatory and nonambulatory patients (n = 104), found that 58% of patients reported hip pain 25 . Given the more functionally uniform (nonambulatory), but medically frail, patients in our study, our mean follow-up of 10.4 years and sample size compare favorably with these studies and are larger and longer than those in other published studies describing hip pain in patients with SMA 14,20,23,26 .…”

Bilateral Dega and Varus Derotational Osteotomies for Painful Hip Subluxation in Acute Flaccid Myelitis: A Case Report

“…Anecdotally, we understand a subset of these populations to still experience painful hip displacement that interferes with daily activities. A recent study demonstrated that hip dislocation, as determined clinically or radiographically, is an independent predictor of moderate-to-severe hip pain in patients with SMA [ 9 ]. In the present case, we illustrate that patients with AFM can similarly experience symptomatic hip dislocation related to their low muscle tone and weakness.…”

“…Due to this, some physicians question the value of operative treatment for painless hip displacement in these populations, as patients are privy to perioperative complications while potentially achieving only transient benefits. Yet, it must be noted that pain relief following reconstruction can be substantial and improve quality of life, highlighting the value of such procedures in symptomatic cases refractory to more conservative measures [ 9 ].…”

Hip Displacement in Spinal Muscular Atrophy: The Influences of Genetic Severity, Functional Level, and Disease-modifying Treatments

“…With the advent of diseasemodifying agent (DMA) treatments, 9 including those targeting SMN2 gene splicing (nusinersen, risdiplam) or replacing the defective SMN1 gene (onasemnogene abeparvovec), improvements in function and life expectancy for all SMA types have renewed interest in the impact of hip displacement on the development of hip pain and arthrosis and whether or not it should be surgically treated. 10,11 Although newer DMAs have improved function and overall health in SMA, their effects on the prevention of hip displacement are unknown. The purpose of this study was to determine risk factors for the development of hip displacement in SMA.…”