In bone physiology, the bone remodeling period describes the temporal duration (i.e. lifespan) of the basic multicellular unit (BMU) that is responsible for bone turnover. Historically, this was referred to as the sigma (σ) or sigma period,[1] but the terminology is now outdated.
Although bone may appear superficially as a static tissue, it is actually very dynamic, undergoing constant remodeling throughout the life of the vertebrate organism. This occurs with the synchronized action of osteoclasts and osteoblasts, cells that resorb and deposit bone, respectively.
The remodeling period
The remodeling period consists of the combined duration of the resorption, the osteoclastic reversal (the phase marked by shifting of resorption processes into formative processes) and the formation periods of bone growth and development.[2] This period refers to the average total duration of a single cycle of bone remodeling at any point on a bone surface.[3]
Remodeling duration (in wks)
Resorption
Reversal
Formation
Total
Rabbits
1
0.5
4.5
6
Dogs
1.5
0.5
10
12
Humans
2
2
13
17
For the remodeling to occur, appropriate cell signaling occurs to trigger osteoclasts to resorb the surface of the bone, followed by deposition of bone by osteoblasts. Together, the cells in any given particular region of the bone surface that are responsible for bone remodeling are known as the basic multicellular unit (BMU), and it is the average lifespan of the BMU that is referred to as the remodeling period.[4] The size of a BMU is roughly 200μm in diameter, defined by the 100μm diffusion capability in bone.
Determining the bone remodeling period
In calculating the bone remodeling period, a two-dimensional model is examined, referring to the time it takes for the area in question to be eroded and then filled in with new bone (sigma will be used here for simplicity's sake). The bone formation portion (σf) of the bone remodeling period is calculated as follows:[5]
in which MWT refers to the mean wall thickness of the completed bone unit and Mf refers to the prevailing mean effective bone appositional rate. In other words, what this formula means is that the bone remodeling period is equivalent to the thickness of the microscopic segment of bone being formed divided by the rate at which it forms. If the mean linear rate of bone resorption is known, the bone resorption portion (σr) can be similarly calculated:[5]
Consequently, the entire bone remodeling period (σr + f, equivalent to σ) can be represented by the following formula:[5]
The linear bone resorption rate (Mr) cannot be measured directly, but it approximates a third of σf.[6]
Interspecies differences
Each vertebrate species exhibits a distinct duration of bone regeneration and remodeling, and it appears as though there is an inversely proportional relationship between the rate of bone regeneration and the phylogenetic evolution of the animal.[7] Each remodeling period lasts 3–6 months in humans, 3 months in dogs, and 6 weeks in rabbits.[8]
References
^Frost, HM. Tetracycline-based histological analysis of bone remodeling. Calc Tiss Res 1969;3:211-237.
^Burr, DB. The effects of altered strain environments on bone tissue kinetics. Bone 1989;10:215-221.
^Parfitt, AM, et al. Bone histomorphometry: standardization of nomenclature, symbols, and units. J Bone Miner Res 1987;2:595-610.
^Doll, B; et al. Overview of fracture repair. In Pietrzak, WS; editor: Musculoskeletal tissue regeneration: biological materials and methods, New Jersey: Humana Press, 2008. ISBN1-58829-909-0 page 48
^ abcJaworski, ZFC: Bone histomorphometry: Outline of theory and practice. In Simmons, OJ; Kunin AS; editors: Skeletal Research, Volume 2. New York: Academic Press, 1983. ISBN0-12-429002-7 pages 237-276.
^Frost, HM. "Only dynamics in osteoporosis and in osteomalacia." Thomas, Springfield, Illinois - 1966.
^Martınez-Gonzalez, JM, et al. Evaluation of minipigs as an animal model for alveolar distraction. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2005;99:11-6
^Roberts WE, et al. Fisiologia y metabolismo oseo. In: Misch C, editor: Implantologia contemporanea. Madrid: Mosby, 1995. ISBN84-8086-384-6 pages 324-350.
May 05, 2023
bone, remodeling, period, bone, physiology, bone, remodeling, period, describes, temporal, duration, lifespan, basic, multicellular, unit, that, responsible, bone, turnover, historically, this, referred, sigma, sigma, period, terminology, outdated, contents, b. In bone physiology the bone remodeling period describes the temporal duration i e lifespan of the basic multicellular unit BMU that is responsible for bone turnover Historically this was referred to as the sigma s or sigma period 1 but the terminology is now outdated Contents 1 Bone remodeling 2 The remodeling period 2 1 Determining the bone remodeling period 3 Interspecies differences 4 ReferencesBone remodeling EditAlthough bone may appear superficially as a static tissue it is actually very dynamic undergoing constant remodeling throughout the life of the vertebrate organism This occurs with the synchronized action of osteoclasts and osteoblasts cells that resorb and deposit bone respectively The remodeling period EditThe remodeling period consists of the combined duration of the resorption the osteoclastic reversal the phase marked by shifting of resorption processes into formative processes and the formation periods of bone growth and development 2 This period refers to the average total duration of a single cycle of bone remodeling at any point on a bone surface 3 Remodeling duration in wks Resorption Reversal Formation TotalRabbits 1 0 5 4 5 6Dogs 1 5 0 5 10 12Humans 2 2 13 17 For the remodeling to occur appropriate cell signaling occurs to trigger osteoclasts to resorb the surface of the bone followed by deposition of bone by osteoblasts Together the cells in any given particular region of the bone surface that are responsible for bone remodeling are known as the basic multicellular unit BMU and it is the average lifespan of the BMU that is referred to as the remodeling period 4 The size of a BMU is roughly 200mm in diameter defined by the 100mm diffusion capability in bone Determining the bone remodeling period Edit In calculating the bone remodeling period a two dimensional model is examined referring to the time it takes for the area in question to be eroded and then filled in with new bone sigma will be used here for simplicity s sake The bone formation portion sf of the bone remodeling period is calculated as follows 5 s f M W T M f displaystyle sigma f frac MWT M f in which MWT refers to the mean wall thickness of the completed bone unit and Mf refers to the prevailing mean effective bone appositional rate In other words what this formula means is that the bone remodeling period is equivalent to the thickness of the microscopic segment of bone being formed divided by the rate at which it forms If the mean linear rate of bone resorption is known the bone resorption portion sr can be similarly calculated 5 s r M W T M r displaystyle sigma r frac MWT M r Consequently the entire bone remodeling period sr f equivalent to s can be represented by the following formula 5 s r f M W T M r M W T M f displaystyle sigma r f frac MWT M r frac MWT M f The linear bone resorption rate Mr cannot be measured directly but it approximates a third of sf 6 Interspecies differences EditEach vertebrate species exhibits a distinct duration of bone regeneration and remodeling and it appears as though there is an inversely proportional relationship between the rate of bone regeneration and the phylogenetic evolution of the animal 7 Each remodeling period lasts 3 6 months in humans 3 months in dogs and 6 weeks in rabbits 8 References Edit Frost HM Tetracycline based histological analysis of bone remodeling Calc Tiss Res 1969 3 211 237 Burr DB The effects of altered strain environments on bone tissue kinetics Bone 1989 10 215 221 Parfitt AM et al Bone histomorphometry standardization of nomenclature symbols and units J Bone Miner Res 1987 2 595 610 Doll B et al Overview of fracture repair In Pietrzak WS editor Musculoskeletal tissue regeneration biological materials and methods New Jersey Humana Press 2008 ISBN 1 58829 909 0 page 48 a b c Jaworski ZFC Bone histomorphometry Outline of theory and practice In Simmons OJ Kunin AS editors Skeletal Research Volume 2 New York Academic Press 1983 ISBN 0 12 429002 7 pages 237 276 Frost HM Only dynamics in osteoporosis and in osteomalacia Thomas Springfield Illinois 1966 Martinez Gonzalez JM et al Evaluation of minipigs as an animal model for alveolar distraction Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2005 99 11 6 Roberts WE et al Fisiologia y metabolismo oseo In Misch C editor Implantologia contemporanea Madrid Mosby 1995 ISBN 84 8086 384 6 pages 324 350 Retrieved from https en wikipedia org w index php title Bone remodeling period amp oldid 1126648923, wikipedia, wiki, book, books, library,
