Which muscles are critical for abnormal posture, balance and gait in patients with FSHD?

Facioscapulohumeral dystrophy (FSHD) is the third most common inherited
neuromuscular disorder. It is an autosomal dominant slowly progressive myopathy
with a variable age of onset, mostly in the second or third decade of life
(Kissel, 1999). The pattern of muscle weakness is often asymmetrical, and the
rate and extent of progression may vary considerably with sudden periods of
unexplained rapid disease progression. FSHD may eventually lead to serious
disabilities of speech, swallowing, reaching, standing and walking, even in
early adulthood. Twenty percent of the patients become wheelchair bound
(Padberg 1982; Lunt & Harper, 1991; Tawil & van der Maarel, 2006).
The semimembraneous, tibialis anterior, biceps femoris, medial gastrocnemius
muscles and adductor group appeared to be most affected, whereas the psoas,
vasti, gluteal and peroneal muscles were relatively unaffected (Olsen et al.
2006). As a result, patients develop specific problems with posture, balance
and gait.
Lastly, several case reports of infantile FSHD indicate the importance of
excessive lumbar lordosis for losing the capacity to ambulate. Excessive
lordosis would be related to weakness of the pelvic extensors, in particular
gluteus maximus (Shapiro et al., 1991; Dorobek & Kabzinska, 2004; Lee et al.,
2009). Hyperlordosis is often attributed to weak abdominal muscles and
relatively strong back extensor muscles (Padberg 1982; Shapiro at al., 1991),
but this notion has not yet been substantiated with quantitative data.
In general, one can conclude that the typical hyperlordotic posture and the
marked balance and gait abnormalities in FSHD are poorly understood, which
makes it difficult to develop effective intervention strategies such as bracing
(Shapiro et al., 1991) or fall prevention programmes (Horlings et al., 2009).
It is expected that with a better understanding of the mechanisms that are
responsible for the balance and gait disabilities, it should be possible to
improve rehabilitation strategies.

The primary aim of this study is to identify the muscles that are most critical
to the abnormal standing posture, standing balance and gait in FSHD patients
and to elucidate the most important mechanisms of falls. The ultimate goals are
(1) to establish novel hypotheses that can be tested in larger groups of
patients and (2) to find clues to improve bracing and training strategies in
order to optimize individual functioning and prevent falls in FSHD patients.

Cross-sectional, explorative patient-control study with laboratory assessments
of posture, balance and gait in combination with structural magnetic resonance
imaging (MRI).

The extent of the burden for a person in time is about 6 hours, distributed
over 3 sessions. After the measurements there might be a risk of fatique, which
depends on the physical limitations of the person.