The axial spondyloarthritis clinical phenotype in idiopathic hypoparathyroidism: critical review of concept that muscular hypercontractility can induce enthesopathy lesions.

Idiopathic hypoparathyroidism (iH-PoPT) is a rare condition infrequently associated with axial spondyloarthritis (SpA) which may mimic ankylosing spondylitis (AS). Axial SpA is a unifying clinical term for chronic inflammatory spinal disorders, although biomechanical factors may play a role. The primary objective of this review is to critically describe the iHPoPT/SpA phenotype defined by established criteria and its differentiation from AS. Five databases were comprehensively searched without time limit to retrieve 14 (11M, 3F) iH-PoPT/SpA cases. Their demographic, clinical, laboratory, radiographic, and HLA-B27 status were compared to two national series of AS patients. Mean (SD) onset age of musculoskeletal symptoms [32.5 (9.7)] was significantly older than 943 German AS patients [25.1 (8.5), (p=0.004)] and 842 Spanish AS patients [26.1 (9.7), (p=0.030)]. Radiographic lesions of iHPoPT/SpA differ morphologically from skeletal alterations in hyperparathyroid and hypophosphataemic syndromes which often have inadequate bone mineralisation and decreased bone mineral density (BMD). Clinical musculoskeletal manifestations were greater (p<0.001) in iHPoPT/SpA than AS patients at cervical (62 vs. 10%) and hip (85 vs. 22%) localisations, respectively. Typical AS sacroiliac joint structural lesions of erosions and bony bridging were reported in only 1 iHPoPT/SpA case and HLA-B27 was positive in 2 of 10 tested. The iHPoPT/SpA phenotype may be a natural experiment on the novel concept of how chronic hypocalcaemia of iHPoPT causes axial neuromotor hypercontractility and biomechanically induces the rare SpA association. In iHPoPT/SpA, neuromuscular hyper-contractility may predispose to axial radiographic enthesopathy lesions and contribute knowledge on biomechanical contributions and pathways for further research.

Quantified biomechanical properties of lower lumbar myofascia in younger adults with chronic idiopathic low back pain and matched healthy controls.

BACKGROUND: Non-specific chronic low back pain (LBP) is a prevalent condition that is poorly understood with respect to possible altered physical properties. Five biomechanical properties of stiffness, frequency, decrement, creep, and stress relaxation time of the L3-L4 myofascial tissue were quantified using the MyotonPro® in chronic idiopathic LBP and matched normal control subjects. METHODS: Measurements were obtained in the resting prone position on the left and right sides (initially and after 10 min rest) in 25 chronic LBP participants (16 female, 9 male) and 25 age- and sex-matched control subjects. Surface electromyography measurements were simultaneously conducted to ensure a resting state. FINDINGS: Female LBP had significantly greater median decrement (p < 0.001) and stiffness (p < 0.010) than female controls. In female LBP patients, BMI correlated with decrement (p < 0.010) and creep (p < 0.050); creep also correlated with decrement (p < 0.050). Significant male versus female differences were found in all five properties in both LBP and control subgroups, except decrement in control males versus females. INTERPRETATION: This study showed that greater median decrement was found in LBP female subjects suggesting decrease in elasticity in the lumbar myofascia. Most of the biomechanical properties differed significantly by gender. This study further documented that right-handed dominance might correlate with greater right-sided lumbar myofascial stiffness.