Orthopaedic Surgery/Bone Injury and Repair
|Bone Injury and Repair|
|<<Blood Supply of Long Bones||Bone Mineralisation>>|
Present day understanding of fracture healing has resulted in new approaches to fracture stabilization employing indirect reduction techniques and implant designs toward the goal of avoiding detrimental impact on the biology of the fracture hematoma. Intra-medullary rods and locking plates provide fixation for diaphyseal fractures without direct exposure of the fracture site. The goal is to restore length, correct angulation and malrotation and provide sufficient stability to enable early motion. Rigid fixation and anatomic reapproximation are no longer pursued when this can be expected to compromise the blood supply and soft tissue envelope of the fracture. Anatomic restoration of intra-articular fractures remains a priority, arthroscopic, computer navigation and fluoroscopic techniques continue to be developed to enable this to be accomplished in a less invasive fashion.
Damage to the microstructure of the skeleton occurs on a daily basis. Through the processes of remodeling the living skeleton of all large land based vertebrates is able to adapt to specific kinds of stress and repair fatigue failure of the microstructure occurring as a result of daily activity. From an evolutionary standpoint this is metabolically efficient as it enables a less robust skeleton be maintained to meet the needs of the organism. A lighter frame allows for lower energy demands for locomotion.
Consider a woman in east Africa who survives by preparing rice on a daily basis which she sells earning enough to have rice to eat and to buy rice for the next day. She must walk several miles to get water for cooking the rice, several more miles to gather firewood and several more to buy more rice. Her most valued possession is the aluminum pot in which she cooks the rice. The availability of plastic jugs has facilitated the process by allowing children to efficiently fetch water.
The demands on the skeleton for survival in this way are significantly greater than what is required to survive in modern society. Technology (the plastic jug) and collective enterprise (children with the help of the light weight jugs) enable productivity sufficient for survival with a lower net demand on the skeleton.
It is in this environment that we have evolved. Life in modern society in which the technology and collective existence has lead to a diminished role for the skeleton day to day, has also lead to an increased longevity.
The problems we encounter clinically therefore relate to the lack of daily triggers to skeletal remodeling and the long run result of skeletal insufficiency as we approach the limit of our longevity especially for women whose skeletal mass is smaller to begin with.
Osteocytes are the most abundant bone cell. They descend from osteoblasts and remain connected within the bone matrix by gap junctions within their canalicular network. Originally proposed by Frost in 1964 they are considered to have a mechanosensory role and thereby play an important role in functional adaptation