Upper Limb Dislocations Frequent in McEDS, Small Study Reports

Shoulder dislocations were most frequent in group of 13 patients in study

Steve Bryson, PhD avatar

by Steve Bryson, PhD |

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Researchers detailed the upper limb motion, occurrence of dislocations, and bone health of children and adults with musculocontractural Ehlers-Danlos syndrome (mcEDS).

Shoulder dislocations were the most frequent dislocations, while two or more upper limb dislocations occurred in the majority of study participants. Children, more than adults, had hyperextended elbow joints, while all finger joints were significantly limited in their range of motion.

X-rays showed bone structural abnormalities were also common, including narrowing of the finger bones with age, suggesting the defects associated with mcEDS may also affect bone formation, the researchers noted.

The study, “Clinical Presentation and Characteristics of the Upper Extremity in Patients with Musculocontractural Ehlers–Danlos Syndrome,” was published in the journal Genes.

EDS is a group of 13 inherited conditions affecting connective tissue that provides structure to joints throughout the body. All EDS subtypes are generally marked by fragile tissue, joints that extend beyond the normal range of motion (hypermobile), and skin that stretches more than normal (hyperextensible).

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mcEDS is a rare EDS subtype caused by variants in the CHST14 or DSE genes, both leading to the insufficiency production of dermatan sulfate, a complex sugar molecule that provides support and stability to connective tissue.

Newborns with mcEDS have adducted thumbs, where the thumb lies across the palm, and clubfoot, where the foot is twisted out of shape. Other symptoms include abnormal facial and head features, long slender fingers, developmental motor delays, muscle weakness with low muscle tone (hypotonia), and eye, heart, kidney, and digestive tract involvement.

Although the clinical signs of mcEDS-DSE are similar to those of mcEDS-CHST14, joint- and skin-related features, hypotonia, and developmental motor delays are less common than in mcEDS-CHST14.

There are, however, no detailed reports specifically examining motor function and joint structure of the upper limbs in people with mcEDS.

Study in Japan included 13 mcEDS patients

To learn more, researchers at the Shinshu University School of Medicine, in Japan, conducted detailed examinations of the upper limbs of 13 mcEDS patients, ages 4–45 years, of whom seven were women. Among them, 12 were diagnosed with mcEDS-CHST14, and one had mcEDS-DSE.

Medical assessments revealed 12 participants (92.3%) had a history of dislocations, and one patient had a history of bone fractures.

Shoulder dislocations were the most frequent upper limb dislocations, occurring in 11 patients (84.6%), followed by two (15.4%) with elbow dislocations. Seven patellar (knee cap) dislocations also were reported. Two or more dislocations occurred in 10 individuals (76.9%). The mcEDS-DSE patient had no dislocation history.

Tendon dislocations in the knuckle of the hand were seen in eight patients (61.5%), and four (30.8%) had swan neck deformity of the middle joint of the finger.

Although none reported pain, motion pain occurred in the elbows of two participants and the hand of one patient. Tenderness of the elbow was reported in two cases, and one had difficulty lifting their shoulder.

Participants younger than 18 showed a tendency toward hyperextension of the elbow joint. In comparison, adults showed a more limited range of elbow extension. Range of wrist motion was normal regardless of age. However, all fingers, including the thumb, index, middle, ring, and little finger, were significantly limited in the range of motion.

Grip strength

The mcEDS-DSE patient had no severe loss of grip, but the adults with mcEDS-CHST14 had a mean grip strength of 8.2 kg, below the mean grip strength of healthy Japanese adults, reportedly to be 25.5 kg for women and 42.0 kg for men.

“Grip strength of patients with this disease was clearly reduced compared with the healthy adult population,” the researchers noted.

X-ray examinations showed six patients (46.2%) had a sustained dislocation of the radial head, where the shorter radius bone of the lower arm meets the elbow joint. Five (38.5%) had deformities of the ulnar head, where the longer ulna bone of the lower arm connects to the elbow, while two had wrist bone fusions.

Osteoarthritis, a joint disease, was observed in four cases (30.8%) and only in adults, while hand osteoarthritis was not recorded.

The length of the finger bones (phalanges) and hand bones (metacarpals) of mcEDS adults was similar to that of the general population, but the width of these bones tended to be narrower. The ratio of the metacarpal width to the medullary cavity, the hollow part of the bone that contains bone marrow, decreased with age.

Because the narrowing of the medullary cavity progressed with bone growth, researchers suggested “dermatan sulfate may be associated with bone formation.”

QuickDASH scores

Lastly, the QuickDASH questionnaire (disability of the arm, shoulder, and hand), a subjective tool to evaluate upper limb disorders, was applied, whereby higher scores out of 100 reflect more severe disability. The mean QuickDASH score was 34.5, indicating that “the majority of mcEDS-CHST14 patients demonstrated reduced upper extremity function,” the researchers wrote.

Although children were unable to perform certain QuickDASH tasks, such as household chores and washing their backs, adults were able to carry out these tasks to some extent. Pain domain questions were reportedly higher in adults. The QuickDASH score of the mcEDS-DSE patient was 15.9, lower (less severe disability) than the mean score of mcEDS-CHST14 patients, the team noted.

“In patients with elbow hyperextension, the use of braces that limit elbow extension may prevent elbow dislocation,” the authors concluded. “Due to the dislocation of the radial head and morphological abnormality of the [ulna], deformity of the elbow and wrist joints may progress and lead to further deterioration of upper extremity motor function. The findings of the present study also suggest an important role for dermatan sulfate in the maintenance of the skeletal system.”