Relation of Musculoskeletal Strength and Function to Postural Stability in Ambulatory Adults With Cerebral Palsy

Five-year risk of fracture and subsequent fractures among adults with cerebral palsy

Background

Epidemiologic evidence documenting the incidence of fracture and subsequent fractures among adults with cerebral palsy (CP) is lacking, which could inform fracture prevention efforts. The objective was to characterize the 5-year rate of initial and subsequent fragility fractures among adults with CP.

Methods

This retrospective cohort study used Medicare claims from 01/01/2008–12/31/2019 from adults ≥18 years old with CP (n = 44,239) and elderly ≥65 years old without CP (n = 2,176,463) as a comparison. The incidence rate (IR), IR ratio (IRR), and site distribution were estimated for the initial and subsequent fragility fractures over 5-years by sex and age.

Results

The IR of fragility fracture at any site over the 5-year follow-up was similar for 18–30-year-old men with CP (IR = 5.2; 95%CI = 4.4–5.9) and 30–34-year-old women with CP (IR = 6.3; 95%CI = 5.3–7.2) compared to the same sex youngest-old (65–74 years old) without CP (IRR = 1.09 and 0.94, respectively, both P > 0.05), and increased with older age for those with CP. The number of fragility fractures and IR of subsequent fragility fractures was similar for young men and middle-aged women with CP compared to elderly without CP, and increased with older age for those with CP. The proportion of fragility fracture at the tibia/fibula decreased while the vertebral column and multiple simultaneous sites (most involved hip/lower extremities) increased with older age.

Conclusion

Young and middle-aged adults with CP had similar-to-worse initial and subsequent fragility fracture profiles compared to the general elderly population- a well characterized group for bone fragility. Findings emphasize the need for fracture prevention efforts at younger ages for CP, possibly by ~5 decades younger.

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Fracture prevention efforts are focused on the elderly and postmenopausal women.

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Fragility fracture risk is elevated for those with CP across the adult lifespan.

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For men, the risk for 18–29 year olds (CP) was on par with 65–74 year olds (no CP).

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For women, risk for 30–34 year olds (CP) was on par with 65–74 year olds (no CP).

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CP had a higher risk of subsequent fragility fractures that was also premature.

Clinical bone health among adults with cerebral palsy: moving beyond assessing bone mineral density alone

AIM

To understand associations among bone mineral density (BMD), bone mineral content (BMC), and bone area, and their association with fractures in adults with cerebral palsy (CP).

METHOD

This retrospective cohort study included 78 adults with CP with a hip dual energy X-ray absorptiometry (DXA) from 1st December 2012 to 3rd May 2021 performed at the University of Michigan. Data-driven logistic regression techniques identified which, if any, DXA-derived bone traits (e.g. age/sex/ethnicity-based z-scores) were associated with fracture risk by sex and severity of CP. BMC-area associations were examined to study the structural mechanisms of fragility.

RESULTS

Femoral neck area was associated with lower age-adjusted odds ratios (ORs) of fracture history (OR 0.72; 95% confidence interval [CI] 0.49-1.06; p=0.098), while higher BMD was associated with higher odds of incident fracture (OR 3.08; 95% CI 1.14-8.33; p=0.027). Females with fracture had lower area than females without fracture but similar BMC, whereas males with fracture had larger area and higher BMC than males without fracture. The paradoxical BMD-fracture association may be due to artificially elevated BMD from BMC-area associations that differed between females and males (sex interaction, p˂0.05): males had higher BMC at lower area values and lower BMC at higher area values compared to females.

INTERPRETATION

BMD alone may not be adequate to evaluate bone strength for adults with CP. Further research into associations (or integration) between BMC and area is needed.

Methods and Strategies for Reconditioning Motor Output and Postural Balance in Frail Older Subjects Prone to Falls

In frail older subjects, the motor output of the antigravity muscles is fundamental in resisting falls. These muscles undergo accelerated involutions when they are inactive and the risk of falling increases during leisure and domestic physical activity. In order to reduce their risk of falling, frail older subjects limit their physical activities/exercises. The problem is that the less they exercise, the less they are able to exercise and the greater the risk in exercising. Hence, a vicious circle sets up and the antigravity muscles inevitably continue to deteriorate. This vicious circle must be broken by starting a reconditioning program based on developing the strength of antigravity muscles (especially lower-limb muscles). To begin with, for each increase in muscle strength, postural balance is improved. Once this increase reaches the threshold beyond which postural balance no longer improves, it seems appropriate to implement exercises aimed at concomitantly improving motor output and postural balance in order to counteract or even reverse the involution process of the postural balance system. Methods and strategies toward this end are proposed in this present communication. However, the transfer effects between strength increase and postural balance ability are not yet totally known and future research should evaluate the relationship between muscle strength and postural balance throughout rehabilitation programs (i.e., program follow-ups) in frail older subjects in order to advance knowledge of this relationship.