Department

Human Biomechanics I Course Project

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Dateof submission:

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.

Fig1: Pictorial diagram of the extended fore arm handling a variablemass.

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. Fmis the effort in the system or tension that is experienced at thebiceps attached to radius. Mcis the load at the palm which is supinated. The weight of theforearm, mbat 21.0cm from O, is also included in the system since it will exertsome tension on the tendon. Point O is a fixed pivotal point at theelbow and a = 5.7 is the distance between the point O and the pointat which 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 betweenFmand the forearm with respect to the horizontal, then the finalexpression 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 and a change in the angle iseffected by adjusting the upper arm and maintaining the foreman in ahorizontal position.

Usingthe expression above, the effort and tension exerted by a given 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 300to 400,500,600and 700. Results obtained from the calculations summarized in the table belowwere used to plot graphs on which the limit of 500N 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

GraphsofFmplotted 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 clear fromthe table and the graphs that the mass should never get to 60N andthe 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 direction.It is also not possible for the forearm to overlap the upper arm andcalculations for a case where the forearm is parallel to the upperarm are also limited.

Conclusionand recommendations

Basedon these calculations, the injured employee should undergo on-the-jobrehabilitation strictly following the parameters given and keepingwithin the limits of tendon force or effort as recommended by thespecialist. The most favorable parameters for rehabilitation basedon these computations would be alternating between a force 50N at300,40N at 400,30N at 500and 20N at 600or other combinations below these values.