Department

Biomechanics

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Biomechanicsand particularly biostatics analysis can be used in designingrehabilitation parameters for a patient with torn distal bicepstendon. The diagram below depicts the forearm of a human being interms of force and an angle between the forearm on a horizontal basisand Fm. the purpose of this project is to conduct biostatics analysis aimedat developing a rehabilitation programmme for an employee with a torndistal biceps tendon. The employee has been advised by a specialistnot to subject the tendon to a force exceeding 500N duringrehabilitation.

Diagramof the forearm system.

Inthis system, Force is given in Newtons as the unit of measure. Weshall also assume that a 1kg mass gives a force of 10N due togravitational pull. Fm is the effort in the system or tension thatis experienced at the biceps attached to radius. Mc is the loadatthe palm which is supinated. The weight of the forearm, mb at 21.0cmfrom O, is also included in the system since it will exert sometension on the tendon. Point O is a fixed pivotal point at the elbowand a = 5.7 is the distance between the point O and the point atwhich the tendon attaches to the radius.

Anexpression for the magnitude Fmcan be derived from the following equilibrium equation:-

Fmx 5.7 = (21 x 16.6) + (40.6 x mc)

Fm= {(21 x 16.6) + (40.6 x mc)/ 5.7}

Sincethe force will also depend on the angle between Fm and the forearmwith respect to the horizontal, then the final expression for Fmin this system is

Fm= {(21 x 16.6) + (40.6 x mc)/ 5.7}/ Cosθ

Cosθis a factor that checks the motion of the effort since in thissystem, the forearm is held horizontally.

Usingthe expression above, the effort and tension exerted by a give forceat the palm of a supinated hand was calculated. The force was thenvaried from 20N to 30N, 40N, 50N and 60N. correspondingly, the anglebetween the long axis of the upper arm was varied from 30 to 40, 50,60 and 70 degrees. Results obtained from the calculations summarizedin the table below were used to plot graphs on which the limit of500N was indicated.

Dataand results

Table1 below shows values of Fmobtained using the expression above with varying values of θ and mc.

Table1: values of Fmfor the arm

&nbsp

Θ

&nbsp

300

400

500

600

700

mc (N)

20

235

266

317

407

595

30

317

359

428

550

804

40

400

452

538

692

1013

50

481

545

649

834

1221

60

563

638

760

977

1430

Thefirst column gives values of mcin N while the first row gives the angle between the forearm and Fm. the values highlighted have exceeded the value advised by the injuryspecialist.

Thegraphs below show the relationship obtained when Fm is plottedagainst values of mc and θ respectively. The red line in the graphsindicates the limit as advised by the specialist.

Graphof Fmagainst θ when mc= 20N

Graphof Fmagainst θ when mc= 30N

Graphof Fmagainst θ when mc= 40N

Graphof Fmagainst θ when mc= 50N

Graphof Fmagainst θ when mc= 60N

Graphsof Fmplotted against mcaregiven below

Graphof Fmagainst mcwhen θ = 300

Graphof Fmagainst mcwhen θ = 400

Graphof Fmagainst mcwhen θ = 500

Graphof Fmagainst mcwhen θ = 600

Graphof Fmagainst mcwhen θ = 700

Discussion

Itis evident from the table and the graphs that the force exerted onthe tendon increases as with an increase in angle θ and an increasein Fm. To keep the force within the recommended limits, it is clearfrom the table and the graphs that the mass should never get to 60Nand the angle should never go beyond 700. When θ approaches zero, the tension on the tendon will approach amaximum. However, this analysis is limited in that it is not easy tomake calculations when the effort compliments the mass in directionand it is also not possible for the forearm to overlap the upper arm.

Conclusionand recommendations

Basedon these calculations, the injured employee should undergo on-the-jobrehabilitation strictly following the parameters and keeping withinthe limits recommended by the specialist. The most favorableparameters for rehabilitation based on these computations would bealternating between a force 50N at 300,40N at 400,30N at 500and 20N at 600or other combinations below these values.