In Vivo Assessment of Skin Surface Pattern: Exploring Its Potential as an Indicator of Bone Biomechanical Properties.

The mechanical properties of bone tissue are the result of a complex process involving collagen-crystal interactions. The mineral density of the bone tissue is correlated with bone strength, whereas the characteristics of collagen are often associated with the ductility and toughness of the bone. From a clinical perspective, bone mineral density alone does not satisfactorily explain skeletal fragility. However, reliable in vivo markers of collagen quality that can be easily used in clinical practice are not available. Hence, the objective of the present study is to examine the relationship between skin surface morphology and changes in the mechanical properties of the bone. An experimental study was conducted on healthy children (n = 11), children with osteogenesis imperfecta (n = 13), and women over 60 years of age (n = 22). For each patient, the skin characteristic length (SCL) of the forearm skin surface was measured. The SCL quantifies the geometric patterns formed by wrinkles on the skin's surface, both in terms of size and elongation. The greater the SCL, the more deficient was the organic collagen matrix. In addition, the bone volume fraction and mechanical properties of the explanted femoral head were determined for the elderly female group. The mean SCL values of the healthy children group were significantly lower than those of the elderly women and osteogenesis imperfecta groups. For the aged women group, no significant differences were indicated in the elastic mechanical parameters, whereas bone toughness and ductility decreased significantly as the SCL increased. In conclusion, in bone collagen pathology or bone aging, the SCL is significantly impaired. This in vivo skin surface parameter can be a non-invasive tool to improve the estimation of bone matrix quality and to identify subjects at high risk of bone fracture.

Quantification of Microstructural Changes in the Dermis of Elderly Women Using Morphometric Indices of the Skin Surface.

OBJECTIVE: The main objective of this study was the development of a non-invasive mathematical marker of the skin surface, the characteristic length, to predict the microstructure of the dermis. This marker, at the individual level, is intended to provide the biological age of the patient in the context of personalised medicine for the elderly. STUDY DESIGN: To validate this hypothesis, a clinical study was conducted on 22 women over 60 years old from a population of osteoporotic subjects who sustained a femoral neck fracture: a morphological analysis of the skin surface was performed on the patient's forearm and quantitatively compared with microarchitectural parameters of the dermis. MAJOR RESULTS: The Elastin-to-Collagen ratio measured on dermis samples ranged between 0.007 and 0.084, with a mean of 0.035 ± 0.02. The surface characteristic length ranged between 0.90 and 2.621, with a mean of 0.64 ± 0.51. A very strong correlation was found between this characteristic length and the Elastin-to-Collagen ratio (r = 0.92). CONCLUSIONS: This study proposes an original diagnostic tool based on morphometric indices of the skin surface and shows a direct quantitative relationship with the dermis microarchitecture and its collagen and elastin content. The proposed method allows reliable and easy access to the intrinsic ageing of the dermis, which would be a strong biomarker in a personalised collagen treatment approach.

Correlation between skin and bone parameters in women with postmenopausal osteoporosis: A systematic review.

Skin and bone share similarities in terms of biochemical composition.Some authors have hypothesized that their properties could evolve concomitantly with age, allowing the estimation of the parameters of one from those of the other.We performed a systematic review of studies reporting the correlation between skin and bone parameters in women with postmenopausal osteoporosis.Fourteen studies - including 1974 patients - were included in the review.Three of these studies included two groups of participants - osteoporotic and non-osteoporotic - in order to compare skin parameters between them: two studies found a significant difference between the two groups and one did not.Eleven of these studies included one population of interest and compared its skin and bone parameters in a continuous manner: eight studies compared dermal thickness to bone mineral density (seven found a significant correlation [R = 0.19-0.486] and one did not); two studies compared skin elasticity to bone mineral density (both found a significant correlation [R = 0.44-0.57); and one study compared skin collagen to bone mineral density and found a significant correlation (R = 0.587).It can be assumed that the estimation of skin alterations from ageing could help in estimating concomitant bone alterations. Cite this article: EFORT Open Rev 2018;3:449-460. DOI: 10.1302/2058-5241.3.160088.

Mechanical alterations of the bone-cartilage unit in a rabbit model of early osteoarthrosis.

OBJECTIVE: The purpose of this study was to assess mechanical properties along with microstructural modifications of the hyaline cartilage (HC), calcified cartilage (CC) and cortical plate (Ct.Pt), in an anterior cruciate ligament transection (ACLT) model. Medial femoral condyles of six healthy rabbits (control group) and of six ACLT rabbits 6 weeks after OA induction were explanted. The zone of interest (ZOI) for all experiments was defined as the weight bearing areas of the samples. Biomechanical properties were measured using nanoindentation and morphological changes were evaluated using biphotonic confocal microscopy (BCM). RESULTS: All rabbits of the ACLT group displayed early PTOA. The results indicate an overall decrease in the mechanical properties of the HC, CC and Ct.Pt in the ACLT group. The average equilibrium modulus and elastic fraction of the HC decreased by 42% and 35%, respectively, compared with control group. The elastic moduli of the CC and Ct.Pt decreased by 37% and 16%, respectively, compared with control group. A stiffness gradient between CC and Ct.Pt appeared in the ACLT group. The irregularity of the cement line, quantified by its tortuosity in BCM images, was accentuated in the ACLT group compared with the control group. CONCLUSIONS: In the ACLT model, weight-bearing stress was modified in the ZOI. This disruption of the stress pattern induced alterations of the tissues composing the bone-cartilage unit. In term of mechanical properties, all tissues exhibited changes. The most affected tissue was the most superficial: hyaline cartilage displayed the strongest relative decrease (42%) followed by calcified cartilage (37%) and cortical plate was slightly modified (16%). This supports the hypotheses that PTOA initiates in the hyaline cartilage.

Contra-lateral hip fracture in the elderly: are decreased body mass index and skin thickness predictive factors?

PURPOSE: A correlation between soft tissue thickness and osteoporosis has been suggested. We aimed to estimate if a low body mass index (BMI) and/or a decrease of skin thickness could estimate the risk of contra-lateral hip fracture. METHODS: First, we performed a retrospective analysis of 1268 patients treated for a hip fracture. The 146 patients who had a contra-lateral hip fractures-study group-were compared with the 1078 patients who did not-control group. Four BMI categories were considered: obese, overweight, normal weight and low weight. Second, we enrolled prospectively 1000 consecutive patients in the emergency department. History of fractures, BMI, and skin aspect on the dorsum of both hands-classified as severe decrease thickness, moderate decrease thickness or normal-were recorded. RESULTS: pt?>In the first part, we found that patients with contra-lateral fractures had a significantly lower BMI than those in the control group (22.2 Vs 26.5 kg/m2, p = 0.01). In the second part, 48 on 1000 patients had a hip fracture. Among them, six had a contra-lateral fracture. BMI was 23.4 kg/m2 in bilateral hip fractures, 33.68 kg/m2 in the unilateral fracture group, and 28.04 kg/m2 in the non-fracture group (p = 0.04). Finally, patients with contra-lateral hip fractures had a severe decrease thickness of the skin. CONCLUSION: A low BMI and a decreased skin thickness increase independently the risk of fractures by three times. When associated, they increase the risk of fracture risk by five times. This combination had a sensitivity at 71 % and a specificity at 90 % for predicting hip fracture.