Biomechanics in orthopedics

Biomehanika u ortopediji je široko područje koje se bavi primjenom zakona mehanike na čovjekov lokomotorni sustav. Za shvaćanje osnovnih pravila potrebno je imati znanja fizike, osnovna znanja matematike, te znanja iz područja medicine, prvenstveno anatomije lokomotornog sustava i ortopedije. Zglobove, u biomehaničkom smislu, možemo promatrati kao središta osi vrtnje, a udove kao poluge. Uzglobljena tijela nalazit će se u stanju ravnoteže ako im momenti sila s obje strane budu jednaki, gdje najčešće s jedne strane djeluje težina promatranog dijela tijela, a s druge mišićna sila koja se protivi toj težini u cilju održavanja ravnoteže. Na zglobu kuka se počela primjenjivati suvremena biomehanika. U biomehaničkom smislu zglob kuka najjednostavnije je promatrati kod uspravnog stajanja na dvije noge gdje je sila jednako raspodijeljena na oba zgloba, te težišnica prolazi kroz središte zdjelice, duž kralježnice. Kod zgloba kuka postoje dvije poluge na koje djeluju sile, a to su lateralna, mjesto djelovanja mišićne sile, i medijalna poluga, mjesto djelovanja težine tijela. Opterećenje zgloba je mnogo veće kod stajanja na jednoj nozi ili kod hoda. Održavanje stabilnosti u zglobu kuka bitno je zbog održavanja stabilnosti tijela u prostoru, te kretanja. Zajedno sa zglobom kuka u tome sudjeluje i koljenski zglob, kao najveći zglob u tijelu. I zglob kuka i koljenski zglob trajno su pod opterećenjem i biomehanika u ortopediji se bavi upravo shvaćanjem utjecaja sila na neke promjene koje se događaju u zglobovima, te utjecaj nekih promjena na nastanak poremećaja u biomehaničkim odnosima. Glavni klinički znak kojim se očituje poremećaj na razini zgloba kuka ili koljenskog zgloba je šepanje. Jedan od razloga poremećaja u hodu, uz neke uzroke koji nisu vezani za biomehaniku, je upravo poremećaj u djelovanju sila na zglob, zbog čega često dolazi do kompenzacijskog patološkog hoda u svrhu održavanja ravnoteže. Utjecaj nošenja razne vrste obuće, nošenje cipela s visokom petom kod žena na promjene u zglobovima koljena, područja su kojima se bavi biomehanika. Nošenje štapa na strani suprotnoj od strane bolesnog kuka u cilju smanjenja momenata sile, smanjenjem težine tijela, isto je područje kojim se bavi biomehanika u ortopediji. Proučavanjem djelovanja sila na koljenski zglob kod čučnjeva, također.Biomechanics in orthopaedics is a wide field which deals with the application of laws of mechanics on the human locomotor system. Understanding its fundamental rules calls for knowledge of physics, basic mathematics and diverse fields of medicine, particularly the anatomy of the locomotor system and orthopaedics. From a biomechanical perspective joints can be viewed as centres of the rotation axis, and limbs as levers. Jointed bodies achieve equilibrium if moments of force on both of the sides are equal, whereby mostly on one side there is the effect of weight of the examined body part, and on the other there is muscular force opposed to that weight in order to keep the balance. Contemporary biomechanical approaches are now used on the hip joint. Biomechanically, the hip joint is best examined when standing up straight on both legs, whereby the force is equally divided between both joints and the median runs through the centre of the pelvis, along the spine. In the case of the hip joint, there are two levers on which forces are exerted – the lateral, which is the place where the muscular force is exerted, and the medial lever, which is where the body’s weight acts. Joint stress is significantly higher when standing on one leg or when walking. Maintaining stability of the hip joint is important for keeping the body stable in space and for moving. In addition to the work of the hip joint, this is also accomplished by the knee joint, the largest joint in the human body. Both the hip and the knee joints are under constant pressure. Orthopaedic biomechanics focuses on the effect of forces on particular changes taking place in the joints and the impact these changes have on the development of biomechanical dysfunctions. The principal clinical sign of dysfunctional hip joint or knee joint is limping. Apart from some causes not related to biomechanics, one of the causes of deviations from the normal gait pattern is abnormal exertion of forces on the joint, often leading to a compensatory pathological gait so as to keep the balance. The effects of wearing various types of footwear, such as high heels by women, on changes in the knee joints are problems focused on by biomechanics. In addition to this, it deals with the issue of using a walking cane held contralateral to the affected hip so as to reduce the torque by reducing the body’s weight, and analyzes the acting of forces on the knee joint when performing squats