Improvements in muscle-tendon properties are beneficial to balance in multiple sclerosis

Morphological and Mechanical Properties of the Human Patella Tendon in Adult Males With Achondroplasia

Achondroplasia is a genetic mutation of fibroblast growth factor receptor resulting in impaired growth plate development in long bones due to lower collagen turnover. Despite the characteristic shorter stature and lower strength in Achondroplasic groups, little is known of the tendon mechanical properties under loading. The aim of this study was therefore to conduct a between measure design of patella tendon (PT) mechanical properties (stress, strain, stiffness and Young's Modulus) in 10 men with Achondroplasia (22 ± 3 years) and 17 male controls (22 ± 2 years). PT mechanical properties were measured during isometric maximal voluntary contraction (iMVC) of the knee extensors using ultrasonography. The Achondroplasic group produced 54% less stress at iMVC than controls (29.4 ± 8.0 v 64.5 ± 14.0 MPa, P < 0.001, d = 3.12). Maximal excursion of the Achondroplasic PT was 22% less than controls at iMVC (7.4 ± 2.1 v 5.5 ± 1.7 mm, P < 0.001, d = 0.99), but there was no difference in strain between groups (13 ± 4 v 13 ± 3%, P > 0.05). Achondroplasic PT were 47% less stiff (748 ± 93 v 1418 ± 101 N·mm⁻¹, P < 0.001, d = 6.89) and had a 51% lower Young's modulus (0.39 ± 0.09 v 0.77 ± 0.14 GPa, P < 0.001, d = 3.46) than controls at iMVC. Achondroplasic PT are indeed more compliant than controls which may contribute to lower relative force production. The causes of higher Achondroplasic PT compliance are unclear but are likely due to the collagen related genetic mutation which causes Achondroplasia.

Muscle and Myotendinous Tissue Properties at the Distal Tibia as Assessed by High-Resolution Peripheral Quantitative Computed Tomography

High-resolution peripheral quantitative computed tomography (HR-pQCT) quantifies bone microstructure and density at the distal tibia where there is also a sizable amount of myotendinous (muscle and tendon) tissue (M_T); however, there is no method for the quantification of M_T. This study aimed (1) to assess the feasibility of using HR-pQCT distal tibia scans to estimate M_T properties using a custom algorithm, and (2) to determine the relationship between M_T properties at the distal tibia and mid-leg muscle density (MD) obtained from pQCT. Postmenopausal women from the Hamilton cohort of the Canadian Multicenter Osteoporosis Study had a single-slice (2.3 ± 0.5 mm) 66% site pQCT scan measuring muscle cross-sectional area (MCSA) and MD. A standard HR-pQCT scan was acquired at the distal tibia. HR-pQCT-derived M_T cross-sectional area (M_TCSA) and M_T density (M_TD) were calculated using a custom algorithm in which thresholds (34.22-194.32 mg HA/cm³) identified muscle seed volumes and were iteratively expanded. Pearson and Bland-Altman plots were used to assess correlations and systematic differences between pQCT- and HR-pQCT-derived muscle properties. Among 45 women (mean age: 74.6 ± 8.5 years, body mass index: 25.9 ± 4.3 kg/m²), M_TD was moderately correlated with mid-leg MD across the 2 modalities (r = 0.69-0.70, p < 0.01). Bland-Altman analyses revealed no evidence of directional bias for M_TD-MD. HR-pQCT and pQCT measures of M_TCSA and MCSA were moderately correlated (r = 0.44, p < 0.01). Bland-Altman plots for M_TCSA revealed that larger MCSAs related to larger discrepancy between the distal and the mid-leg locations. This is the first study to assess the ability of HR-pQCT to measure M_T size, density, and morphometry. HR-pQCT-derived M_TD was moderately correlated with mid-leg MD from pQCT. This relationship suggests that distal M_T may share common properties with muscle throughout the length of the leg. Future studies will assess the value of HR-pQCT-derived M_T properties in the context of falls, mobility, and balance.

[Interferon-β1b in multiple sclerosis therapy: more than 20 years clinical experience]

The introduction of interferon-β1b in 1993 in the USA and 2 years later in Europe made it possible for the first time to alter the course of the disease in patients with relapsing-remitting multiple sclerosis (MS). Subsequently, interferon-β1b was approved for the treatment of patients with active secondary progressive MS (1999) and early relapsing-remitting MS following a first demyelinating event (clinically isolated syndrome, CIS) (2006). Here we provide an overview of the clinical experience gathered during more than 20 years of interferon-β use focusing on long-term efficacy and safety and the impact of early initiation of treatment. Furthermore, the following aspects will be discussed: putative mechanisms of action of interferon-β, indications for a disease-modifying therapy, clinical relevance of neutralizing antibodies, importance of adherence in MS therapy, high versus low frequency therapy, combination therapies with interferon-β and safety of interferon-β in children and adolescents with MS and during pregnancy.

Strong tendon repair using SLLS technique for traumatic disruption of tibialis anterior tendon and extensor hallucis longus tendon to enable early rehabilitation after surgery

Level of Evidence: V, Expert Opinion

Effect of foot and ankle immobilization on leg and thigh muscles' volume and morphology: a case study using magnetic resonance imaging

Our aim was to determine the time course of any changes in muscle volume and shape in the lower limbs following immobilization. A healthy young woman (29 years) had suffered a fracture of the fifth metatarsal of the right foot. MRI scanning of her right thigh and calf muscles had been performed 1 month before the injury (Pre) during a scan initially planned as a teaching tool, 2 days following a 4-week immobilization period (Post), and after a 2-month recovery period (Post+2). The results show muscle volume decrements in the triceps surae (TS), quadriceps (Quad), and hamstring (Ham) of 21.9%, 24.1%, and 6.5%, respectively, between the Pre and Post measurements. At Post+2, the Quad and TS muscle volumes were still 5.2% and 9.5% lower, compared with the Pre data. The Ham muscle volume, however, was 2.7% greater than at the Pre phase. Following recovery, the increase in individual TS muscles volume was limited to both proximal and medial (with respect to the knee joint) segments of the muscles. These results indicate very substantial and rapid losses in muscle volumes, both proximally and distally to the immobilization site. The results also show that recovery is far from complete up to 2 months post cast removal. The results have implications for the requirements for rehabilitation for orthopedic patients.