Acromegaly: Balance, Falls and Fracture Risk

HR-pQCT is a 3-dimensional imaging modality that can be applied to bone and joints in vivo, in order to non-invasively assess the quantity and quality of trabecular and cortical bone compartments separately. HR-pQCT will be applied to peripheral skeletal sites, namely the distal radius and tibia, where image slices equivalent to 9 mm of bone will be acquired. From this, parameters such as volumetric bone mineral density (vBMD), cortical density, cortical porosity, trabecular density, trabecular thickness, trabecular spacing and others will be calculated using specialized software. In the same scanning session, images of the wrist and ankle joints will be produced and analyzed for features of arthrosis, such as erosions, osteophytosis and others.

Through DXA scans, we will obtain information regarding body composition, hip and spine bone mineral density, as well as examine any previous vertebral fractures using vertebral fracture assessment (VFA). VFA is a function of DXA scanners which allows for visualization of thoracic and lumbar vertebrae (usually T4-L4) in order to detect vertebral fractures34. Vertebral fractures can then be classified as either mild, moderate or severe using the method described by Genant et al35.

Using the OsteoProbe®, we will by microindentation measure the bone material strength index (BMSi), an in vivo surrogate measure of the fracture resistance of the cortical bone in the tibia. The participant is placed in a supine position with the examined leg rotated slightly outward. After identifying the site of interest, located midway between the medial tibial plateau and the medial malleolus, disinfectant is applied to the skin of the tibia being examined. Finally, under local anesthesia and fully sterile conditions, a test probe is inserted through the skin and onto the midshaft of the tibia, and the fracture resistance of the bone tissue is measured.

Hand grip strength will be assessed using a digital hand dynamometer as a measure of peripheral muscle strength. Leg extensor strength will be examined using the peak torque measured by an isometric dynamometer mounted on a fixed chair. 3 attempts will be given for each method, and the maximum value recorded.

The TUG test is a functional test frequently used to assess balance in older individuals and is performed by measuring the time it takes for an individual to go from sitting to standing position, walk 3 meters, turn around and return to sitting position. A TUG score of \>13,5 seconds is associated with an increased risk of falls.

Postural control will be assessed by means of a force platform that registers Center of Pressure (CoP) as a measure of postural stability. Measurements are performed under a variety of conditions, including eyes open/closed and on different surfaces. From the CoP measurements, parameters such as CoP range and CoP velocity in both antero-posterior and medial-lateral directions will be calculated using specialized software.

To fully examine all components of balance, nerve conduction will be tested using a handheld device called NC-stat DPN-Check in order to assess any peripheral neuropathy.

Visual acuity will be tested using an automated refractometer (KR-800S Auto-kerato-refractometer, Topcon Healthcare, The Netherlands).