METHOD OF DETERMINING MINIMAL SIZE OF SKIN CUT IN MINI-INVASIVE KNEE JOINT ENDOPROSTHETICS Russian patent published in 2015 - IPC A61B17/56 

FIELD: medicine.

SUBSTANCE: invention relates to medicine, in particular to traumatology and orthopaedics. Patient's body type is determined: brachymorphic (B), dolichomorphic (D), mesomorphic (M). X-ray examination of knee joint in frontal and lateral projections and patella in Merchant axial projection are performed. X-ray images are used to calculate patella length (Lp), width (Wp), thickness (Tp) by means of ruler or calliper. Model and size of endoprosthesis, anterior-posterior and medial-lateral dimension of its components, which must correspond to maximal extensibility (E) of wound, are determined by means of fitting templates with application of X-ray images. Angle of bending in knee joint (Ab), angle of patella rotation angle (Ap), value of maximal horizontal patella displacement in lateral direction (Pp) are specified. Obtained data are substituted into formula for calculation of sum of values of influencing factors R_m, R_b, R_d for each body type: for people of mesomorphic body type: R_m=(0.001385Ab+0.01032Ap+0.95102Pp-0.7712Tp+1.7949Wp-0.8902Lp+0.22803); for people of brachymorphic body type: R_b=(-0.00228Ab+0.0116Ap+0.072Pp-0.232Tp+0.2298Wp+1.1696Lp+0.4631); for people of dolichomorphic body type: R_d=(-0.001351Ab+0.01625Ap+0.968Pp-0.3574Tp+0.603Wp-0.1554Lp+2.809), where Ab is angle of bending in knee joint, degrees; Ap is angle of patella rotation, degrees; Pp is displacement of patella horizontally in lateral direction, cm; Tp is thickness of patella, cm; Wp is width of patella, cm; Lp is length of patella, cm; after which minimal value of skin cut is calculated: for people of mesomorphic body type P"з"m=(R-R_m)/0.1726; for people of brachymorphic type P"з"b=(R-R_b)/-0.1495; for people of dolichomorphic body type P"з"d=(R-R_d)/0.0533, where P"з"m, P"з"b, P"з"d is minimal value of skin cut for each body type, R is maximal extensibility of operation wound, R_m, R_b, R_d is sum of values of influencing factors for each body type, and mini-invasive endoprosthetics of knee joint with minimal traumatic cut is realised, if ratio of preliminarily determined parameters, satisfying given mathematical expression, is fulfilled for each body type.

EFFECT: method makes it possible to reduce complications due to determination and implementation of minimally traumatic and sufficient for operation performance access.

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