ARTROMOT -S2 PRO Biomécanique...CPM devices.The first in Sept./Oct. 2000 examined the movement...

Biomechanical Study

ARTROMOT®-S2 PRO

1. Instruction, aim 3

2. The study sublect: the motor-drivenCPM ARTROMOT®-S2 PRO 7

3. Measurements on testpersons 9

3.1. Movement in abduction / adduction 9

3.2. Elevation (flexion) movements 16

3.3. Rotation movements 18

4. Summary 21

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Table of contents

The aim of this biomechanical study was to investigate theextent to which the motor-driven shoulder CPM deviceARTROMOT®-S2 PRO is capable of imparting a physiolo-gically appropriate and safe passive motion to the shoulderjoint in various degrees of motion range. The measure-ments of the kinematics of the CPM device were carried outon three healthy test persons. The use of the CPM devicedepends greatly on the injury in question. Certain move-ments have to be excluded, others facilitated. Particularcare has been taken to ensure that the specified movementremains limited to the rotary axis selected and is not trans-mitted to other freedom of movement degrees of the shoul-der joint, thoracic girdle or even the vertebral column.

The essential condition for fulfilling this objective is to matchthe setting options of the CPM device rotary axes with thepatient's joint axis, especially the setting of the shoulderCPM rotary axis with the patient's shoulder, with the highestpossible degree of accuracy. Any deviation in the position ofthe axes causes rotary movements also in relation to otheraxes or displacement of the thoracic girdle to the rump inthe course of the cyclical movement program. This canresult in tension and pressure on the shoulder joint (alsoreferred to as coercive forces due to the externally determi-ned - forced - movement curves which deviate from thejoint movements provided for physiologically).

The flexibility of the human shoulder joint is greater thanthat of any other joint. In addition to the different gyratoryand rotary motions, the shoulder joint can also be shiftedon the chest with relative ease, especially if the patient'smuscles are relaxed, as in the application of the CPM devi-ce. Inversely, this also means that, if the adjustment of theCPM is not quite correct, unwanted movements interminglewith the intended movements without, however, resulting inmajor coercive forces acting on the shoulder. These forceswill increase in intensity only in case of very rough andimmediately identifiable maladjustments. The rigid fixationof the test person's shoulder and arm on the CPM device isnot envisaged in the ARTROMOT®-S2 PRO. Even then, thetest person's thoracic girdle would reposition toward a mini-mum of the external coercive forces. Even in the most unfa-vorable case, the forces created are lower than in normaluse of the shoulder e.g. when carrying objects. However,the patient’s injured or diseased shoulder is probably highlysensitive to pain. Treatment is often carried out under localanaesthetic.

The shoulder is particularly vulnerable to stiffening whenimmobilized, leading to pain. The reason for this is in theanatomical construction of the shoulder. Reserve folds ofthe joint capsule and bulging of the mucous bursa quicklyconglutinate and harden, especially following blood seepa-ge caused by a trauma, and become immobile when notused. Calcifications may even form. Moreover, the shoulderjoint is the joint which is stabilized to the greatest extent bymuscles and ligaments and is most dependent on these.

This study is the second on motor-driven ARTROMOT®

CPM devices. The first in Sept./Oct. 2000 examined themovement performance of the knee joint CPMARTROMOT®-K2 PRO. The movement pattern of the shoul-der joint with its many degrees of freedom of movement isfar more complex than that of the knee joint, which, as agood approximation (at least as far as the requirements of

the CPM device are concerned), is a simple hinged jointwith only one degree of motion range, in which the move-ment remains largely restricted to one plane. In the shoul-der joint none of the movement is solely restricted to onesection of a joint or to movement in only one plane.

In addition to these difficult movement patterns of theshoulder, the measurability of the movements externally isalso a problem if invasive methods of measurement are notused. Movements within the thoracic girdle, e.g. the displa-cement and rotation of the shoulder blade, are in part scar-cely identifiable externally. The skin slides relatively freelyover the structure of the joints, therefore marks on the skinof the test person only partially reflect the movements inthe joint. However, in this study it was only possible tomeasure movements using non-invasive methods, withmarks on the test persons´ skin. The spatial movementswere analyzed from video recordings. The precision of themeasurement results in this study is therefore less than inthe study on motor-driven CPM knee joint movementsplints.

Application and indication of shoulder joint CPM devices:

Motor-driven CPM devices are used for continual, if initiallyonly passive, mobilization, not only in the early functionalfollow-up treatment in post-operative therapy but also in therehabilitative field of conservative therapy. This treatmentmethod is referred to as CPM treatment - continuous passi-ve motion. Studies have shown that long-term movementtherapy of joints accelerates healing even through purelypassive mobilization. This can prevent subsequent stret-ching or bending deficits which would require complicatedtreatment. The CPM device can also lead to rapid remobi-lization when stiffening of the joints has already set in.Clinical users even speak of the pain-reducing effects of theCPM device after operations and the reduction in swellingin the operated area as a result of improved drainage of thetissue fluid. Application of the splints even take place underlocal anaesthetic of the injured joint, particularly in the treat-ment of the shoulder which is especially sensitive to painand also highly vulnerable to stiffening. Treatment is there-fore possible at an early stage despite the patient’s highsensitivity to pain.

The duration of clinical applications are normally fromseveral hours a day to continuous applications. However,the motor-driven splint should on no account be usedinstead of regular physiotherapy, rather as supplementarytreatment. Breaks can be programmed between the move-ment cycles on the device. The motor-driven splint shouldenable a slow, steady movement of the joint to be treated,in this case the shoulder, with freely selectable maximumangle. In the course of the healing process, the speed ofmovement of the splint and the angle range are thenincreased. When setting the size and speed of the angle,attention is paid to the patient’s freedom from pain. Themotor power of the splint is not intended to stretch joints byforce.

The factors examined in the following are:■ the adjustability and handling of the splint,■ the display accuracy of the control section of the

motor-driven splint,■ the angle speed of the movements in the shoulder joint,■ the alignment of the shoulder joint of the test person with

the splint,■ monitoring of undesirable accompanying movements at

other points of the thoracic girdle.

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1. Instruction, Aim

This study is not designed to examine questions rela-ting to the technical safety of the splint, such as thereliability of the angle-limit stop of the motors, thesafety reversal switch in the event of blockages of thejoint (spasmodic switching) and similar safety-relevantcharacteristics.

The natural degree of freedom of movement of theshoulder joint and the thoracic girdle The shoulder joint is not only the most mobile of all joints inthe human body, but is also a particularly complex joint inits construction, consisting of several part-joints which forma joint complex (cf. Fig. 1a). The main joint is the actualshoulder joint itself, articulatio humeri, the rotary joint of thehumerus in the glenoid cavity of the shoulder blade. As is tobe expected in a ball-and-socket joint, the head of thehumerus is formed as a ball joint (with deviations from theideal ball form). The counter-piece, the socket, is located inthe upper outer angle of the body of the shoulder blade (thescapula), but is significantly smaller than the area of thehead.A fibrous cartilage ring, labrum glenoidale, the acetabular

lip, extends the area of the glenoid cavity and adapts it tothe head of the humerus (cf. Fig.1b). This cartilage ring isone of the most vulnerable points of the shoulder joint.Damage leads to a permanently instable shoulder joint,susceptible to dislocation. Injury to the labrum glenoidale isusually caused traumatically by dislocation of the shoulder.

Fig. 1a, the thoracic girdle comprising humerus, shoulder-blade (scapula), clavicula (only partly visible in the dia-gram), thorax and thoracic spine.

(These and following figures 1 from:I.A.Kapandji, Funktionelle Anatomie der Gelenke,Band 1 - Obere Extremität, Bücherei desOrthopäden Band 40, Ferdinand Enke Verlag,(1984))

Fig. 1b, the shoulder joint articulatio humeri.This is the pivot joint of the humerus (a) in the glenoid cavi-ty of the shoulder-blade (b). A fibrous cartilage ring (c),labrum glenoidale, forms part of the socket.

Further true pivot joints of the thoracic girdle or physiologi-cal joints in which two bone surfaces shift in relation toeach other are the acromial secondary joint, the acromio-clavicular joint, the sternoclavicular joint between the clavi-cula and sternum and finally the shoulder-blade which canbe moved in relation to the thorax.

The basic anatomical positioning of the shoulder joint isdefined as the position with freely dropping arm. Thevarious angles in this position are defined as 0°. All rotati-ons of the shoulder joint are given relative to this position:a) Rotation of the upper arm to the three spatial axes:

1. Flexion (anteversion, forward pendular movement of thehanging arm, possible to 180° from the basic position) andextension (retroversion, backward pendular movement ofthe hanging arm, maximum 45°) around the transversalaxis (transverse axis through both shoulders).

Flexion is carried out on the splint with the lower arm ang-led at the elbow. This is referred to as an elevation move-ment by the manufacturer of the splint and in the followingstudy. (Often only anteversion exceeding 90° is referred toas elevation). Extension movements cannot be practicedwith the motor-driven splint.

Fig. 1c, Flexion and extension movements of the shoulderjoint.

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2. Abduction (sideways abduction of the arm) and adduc-tion (sideways pendular movement of the arm to the body)around the frontal oriented axis. The increasing abductionposition of the arm to approx. 60° takes place exclusively inthe articulatio humeri shoulder joint. From 60° to 120° theshoulder-blade also moves. From 120° onwards the trunkbegins to tilt to the opposite side.

This accompanying movement of the thoracic girdle isshown in its typical form in this study. The ARTROMOT®-S2PRO is designed to carry out adduction movements to175°, involving the entire thoracic girdle including the spinein the movement. However, any patient able to move theirshoulder with this degree of freedom would be unlikely tostill receive treatment on such a CPM device.

Most everyday abduction movements take place at an ante-version position of approx. 30°.

Fig. 1d, Abduction and adduction movements of the shoul-der joint.

3. Forward and backward rotation of the abducted arm aro-und the vertical axis, forward movement of the arm in thehorizontal to 140°, backward movement to 30°.

ARTROMOT®-S2 PRO is not designed to carry out movement in relation to this axis. However, angle settingsfor the ante/retroposition may be selected and set on the device.

Fig. 1e, Forward and backward rotation of the shoulderjoint.

b) Rotation of the upper arm along its longitudinal axis,possible in any position of the shoulder joint:

The basic position 0° is defined as the position in (a), al-though this does not represent the physiological basic posi-tion. Outward rotation to approx. 80° (b) and inward rotationto 100° (c) are possible. With angled elbow, a continualinward rotation of more than 30° is only possible in conjunc-tion with an abduction position as the movement of thelower arm is otherwise blocked by the trunk. A certaindegree of abduction positioning of the arm is thereforenecessary in treatment with the ARTROMOT®-S2 PROCPM splint. The angling of the lower arm is alsoa precondition as there is otherwise no lever available toinduce the rotary movement.

Fig. 1f, Rotation of the humerus in the shoulder joint aroundthe longitudinal axis.

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Most everyday movements take place between the physio-logical basic position of 30° inward rotation and the definedbasic position of 0°.

A further reason also makes the shoulder joint an unusualjoint: it is not joined directly to the trunk but to the shoulder-blade, which in turn moves against the trunk. The degreesof freedom of movement of the scapula on the thorax musttherefore be added in addition to the degrees of freedom ofmovement of the shoulder joint.- The shoulder-blade can be shifted by about 15 cm bet-ween the maximum medial and maximum lateral horizontalpositions, see (b) in adjacent Fig. 1g. at the same time arotation of up to 40° to the vertical axis (a) occurs. (Fig. (a)is the plan view of the cross-section through the thorax).- In the vertical, the shoulder-blade can be shifted by 10 cmto 12 cm, always accompanied by a certain amount of rota-tion as in (d).- The shoulder-blade can be rotated by about 60° in thevertical in relation to its area (d).

Any movement in the shoulder-blade does not remain limi-ted solely to an individual degree of movement freedom,rather it is accompanied by more or less large rotations orshifts in other degrees of freedom of movement.

Fig. 1g, the degrees of freedom of movement of the shoul-der-blade

The most common injuries to the shoulder joint are

- Rupture of the rotation cuffs (tendon ruptures to total rupture of rotation cuffs as cause of shoulder pain and stiffness of the shoulder; result of trauma, commonly due to degenerative changes - especially in the elderly)

- dislocation of the shoulder, often accompanied by injuriesto the bones, labrum lesions and Hill-Sachs impression (impression on dorsolateral edge of the head of the humerus in habitual dislocation of the shoulder joint)

- Rupture of the capsule- Subcapitla fracture of the humerus- Bankart lesion (rupture of the labrum glenoidale in

anterior dislocation of the shoulder joint).

The shoulder joint stiffens most rapidly with relation toabduction movements, followed by outward rotation. Thejoint stiffens in its basic position (adduction and inward rota-tion).Due to the high mobility of the shoulder joint, the joint cap-

sule and the synovial bursa have large reserve folds andbulges which are stretched and pulled flat by large-scalemovements. These structures are at particularly high risk ofconglutination and stiffening from immobilization, leading topain. Purely passive movement of the joint and the associa-ted regular stretching of these structures avoids these risks.

Fig. 1h, frontal section through the shoulder region, on theleft adducted joint, on the right abducted to 90°. Marked:the area of the joint capsule which is folded in the adductedjoint and quickly conglutinates on lack of abduction activity.

Course of the study and evaluation of measurement data:

The ARTROMOT®-S2 PRO executes single movementexercises i.e. one motor is activated, the other switched off,or combined movements in which both motors run simultaneously, synchronously or asynchronously. Singlemovements only have been analyzed in the measurementsfor this study.

The movements transmitted from the splint to the test per-son and any undesirable accompanying movements ofother areas of the shoulder region are evaluated in thisstudy.

The scope of the movements measured in this study is lar-ger than those which would usually be carried out on aninjured patient.

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The motor-driven CPM ARTROMOT®-S2 PRO is designedfor continuous passive movement of the shoulder joint. Thetherapy aims of CPM treatment are the avoidance of immo-bilization damage (joint stiffness) and the promotion ofrapid healing, accompanied by improvement in joint meta-bolism.

The manufacturer’s indication list includes the treatment ofmost injuries, postoperative conditions and diseases of theshoulder joint.

Examples:- shoulder distortions- operative measures in the shoulder joint e.g. operatively

treated impingement syndrome and endoprosthesis,- soft-tissue interventions in the region of the thoracic

girdle.

As contraindications, the manufacturer lists acute inflamedchanges in the joint, spastic paralysis and instable osteo-synthesis.

Fig. 2a shows the motor-driven shoulder movement splintand its degrees of setting freedom. The adjustment optionswhich must be firmly adjusted for each patient are markedin red e.g. the height of the shoulder joint above the seat(SH), the angle of the seat back (LW), angle of the elbow(EW), the angle setting for ante- / retro-positioning (ARW)and other parameters.

The height of the pivotal axis of the shoulder joint above theseat and the length of the upper and lower arm splints of theARTROMOT®-S2 PRO can be infinitely adjusted in lengthand adapted to suit the individual patient. The back of theseat can also be adjusted in stages. The precise adjustmentof the height of the shoulder joint axis (SH in Fig.3) to theindividual patient is especially important.

The lower arm shell can be adjusted by a rod so that lowerarms of varying strengths are still positioned exactly parallelto the splint. If the axis is too far above or below the lowerarm axis, the actual abduction angle in the shoulder jointwould be permanently increased or decreased in compari-son to the angle set on the control unit. Incorrect move-ments and force (at a minor level, however) would onlyresult from a movement of motor B.

Only the lower arm of the patient is held in the lower armsplint by a Velcro strap, the patient is otherwise free tochose his sitting position and posture himself. Of course,the therapist needs to instruct the patient about what isrequired of him.

Both the seat and the back of the chair are flat. The patientis free to sit in the middle of the seat, or to the left or right.In order to reproduce the same position of the patient in thechair, the arm rest on the side not being treated shouldalways be set at the same height. There is no scale provi-ded for this. An anatomically formed bucket seat wouldmake positioning of the patient clearer and more easilyreproducible, but would make it difficult for the patient toavoid any defective positions or forced movements whichmay arise during treatment.

The movement of the patient is effected by two motors onthe shoulder splint. Motor A in the area of the shoulderjoint in abduction / adduction (when the angle setting forante- / retro-positioning is about 0° or in elevation for ante- /retro-positioning of about 90°). Motor B in the region of theelbow is responsible for rotation of the upper arm in theshoulder joint.

The angle movement area, that is the upper and lowerlimits of the angle, are set on the hand control of the motor-driven splint. For motor A angles of between 30° (adduction)and 175° (abduction and elevation / flexion) can be selec-ted, for motor B angles between 90° inward rotation to 90°outward rotation. The manually adjustable range for ante /retroversion is 0° (retroversion) to 120° (anteversion).

The angle speed can be set between 1% and 100% of themaximum speed. In contrast to the knee joint CPM deviceof the previous study in which the percentages were only tobe seen as reference values, in the shoulder CPM devicethe speeds between 100% and 10% are in the expectedrelation. The speed decreases more slowly only in the caseof smaller percentages. The maximum speed of 100% wasselected for the tests. A movement cycle between adduc-tion of the shoulder joint (30%, motor A) and maximumabduction (175%) and back to adduction again takesapprox. 1 minutes. The movement cycles of motor B bet-ween 90° inward rotation and 90° outward rotation andback again take about the same time.

In any maximum angle setting, a pause of up to 30 secondscan be set between the stretching phase and the bendingphase. The splint does not move in this time. The splintdoes not start to move abruptly from the resting position,but starts gradually, until reaching the full movement speedafter a few seconds. This was found to be pleasant by thetest persons. Although devices which start to move abruptlyand quickly from the standing position do not harm patientsin any way, they can be irritating for patients with pain.

The rotations can be restricted to motor A or B, the othermotor remaining in a fixed pre-selected position. However,both motors may be moved at the same time, synchronously,both reaching the limit of the movement range set simulta-neously, or they may be operated asynchronously. Notevery such combination is suitable or even geometricallypossible. The manufacturer recommends caution and carefulmonitoring when the splint is operated asynchronously.

The settings chosen may be recorded in a chip card andread again later, making adjustment and setting easier forrepeat treatments.

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2. The study subject: the motor-driven CPM ARTROMOT®-S2 PRO

Fig. 2a, the motor-driven shoulder CPM device ARTROMOT®-S2 PRO.

Red: Values which have to be adjusted to the patient onetime and that stay unchanged during the whole treatment:OL: Length of the upper armUL: Length of the forearmSH: Height of motor A above the seatHU: Height of the forearm splint; has to be adjusted so thatthe axis of the forearm has the same level as the upper-and forearm of the splintHL: Height of the arm rest for the other armARW: Adjustment of the angles for ante-/retroposition, adjustable between 0° and 120°, shown with 20°EW: Angle of the elbow, most of the time 90° as shownLW: Angle of the back of the chair, gradually adjustableYellow: Swivelling zones of the motors during the treatment,Motor A (max. 30° to 175°)Motor B (max. 90°- 0°- 90°).

Fig. 2b, hand programming unit of the ARTROMOT®-S2 PRO.This setting moves the patient´s arm in ab-/adduction.Motor A swivels the upper arm between 30° (left figure inthe display) and 80° abduction (right figure).Right now it is located at 75° (middle figure in the display).Fig. 2a was taken by lower abduction, ca. 60°.Motor B at the elbow is turned off at this treatment program.

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Fig. 3, Adjustment of the shoulder CPM to the patient.The axis of rotation of motor A should point to the centre ofthe patient´s shoulder joint during the whole movement.Deviations of the axes should be as small as possible.Deviations of the axle bearings from each other can lead totractive and pressure forces during the movement.Moreover the movement is potentially not limited to the sel-ected degree of freedom of the joints.

There´s no direct holding fusion between shoulder bent ofthe patient and the motor splint. The patient is not fastenedat the chair, only his forearm is fixed in the splint.A posture change of the patient at the chair - e.g. a soakingduring a treatment which tooks a long time - leads to a non-compliance between motor A and the shoulder jointaxis of the patient.Because of this an exact and lasting conformation of thesplint to the patient cannot be expected.Even this undefined positioning of the patient due to themobility of the trunk is the main problem of the applicationof the shoulder CPM in practise.However, a very precise conformation is not really neces-sary from medical sight. The posture of the joint rotationaxes is very hard to determine without any measuringmethods from outside, the more so as the shoulder jointwith its lots of degrees of freedom.Bad postures about few cm´s between the rotation axesfrom splint and shoulder of the patient have to be expected,but also to be tolerated.Because of the big natural mobility the shoulder belt canevade such caused bad postures as long as the displace-ments are small enough.

In all the following measurements the speed of the CPMdevice was set at 100%. The splint was adjusted as closelyas possible to the anatomical proportions of the test person.Adjustment was checked during the first test cycle andcorrected as necessary.

The angle range was selected in each case so that theangle maximum and minimum still appeared to be realistic.Smaller ranges would normally be selected in clinicalpractice. The splint allows for even larger ranges ofmovement.

3.1. Movement in abduction / adduction

In the following figures 9a to 9b an abduction movement of30° to 140° was carried out. In fact, the splint allows settingsof up to 175°. Following the majority of shoulder injuries,abduction movements are carried out over a relatively widerange (except for complicated fractures of the shoulder jointwhich are initially immobilized). It is precisely this freedomof movement which is most commonly restricted due toconglutination of the joint capsule.

The light-reflecting markers are colored in the first picture(Fig. 9a) (the markers on the test person are red, those onthe splint are green). In subsequent photos of later move-ment phases these marker dots are copied onto the positionas shown in picture 1. Any shift of the markers is thenevident (shown additionally by black arrows).

The abduction angle is defined between the upper armsplint or the upper arm of the test person and the verticalrod of the splint. In the event that the upper arm of thepatient is oriented identically with the upper arm rod of theCPM device, the measured angle value is also the same.This is to be taken into consideration when interpreting thejoint angle of the test person. The angle does not refer tothe longitudinal body axis of the test person. If the testperson were to sit tilting slightly to one side, this would notbe taken into consideration in this joint angle definition.

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3. Measurements on testpersons

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Fig. 9a to 9b, four photographs taken during abduction /adduction movements of the test person RO. Red dots:marker positions on the skin of the test person in first pic-ture, 9a, green dots: markers on the movement splints. Theabduction angle is defined as between the upper arm splintor the upper arm of the test person and the vertical rod ofthe splint. This is to be taken into consideration in the inter-pretation of the angle of the joint of the test person.

No significant shift in markers can be identified up to about90° abduction position. At the extreme angle of 140° theshift is obvious. This is precisely the behavior expectedaccording to the description in Chap. 1, Fig. 1d, accordingto which, with increasing abduction, only the shoulder jointis initially involved, then the thoracic girdle and, with extre-me angles, the entire thorax and the spinal column. Thepivotal axes of the shoulder joint of the test person and thesplints also diverge more and more.

On closer examination of the picture, the inexact positioningof the shoulder joint of the test person relative to motor A isnoticeable. After several abduction / adduction cycles thetest person has been permanently pushed slightly to theright on the chair. Therefore the upper arm in Fig. 9a(Picture 1) is not parallel to the upper arm axis of the splint.This is similarly evident in the diagram of the progress ofthe angle in the following. This permanent shift is not evi-dent in the other two test persons.

Comparison of the measured shoulder joint angle ofthe motor-driven splint and the test person

A complete movement cycle per test person is analyzed ineach case. In the following figures 10a to 10c, the measure-ments from the video analysis of the shoulder joint angle ofthe CPM device and the shoulder joint angle of the test per-son are presented using examples. The second diagramshows the angle difference of the shoulder joint angleminus the splint joint angle. For a definition of the shoulderjoint angle compare Fig. 1.

Fig. 10a, abduction / adduction movement, test person RO.Comparison of shoulder joint angle of CPM device and testperson.

Angle speed 100%, set abduction range 30° to 140°.

Above: the two angles over the period of the test time.Possible systematic measuring errors of the splint jointangle may be in the region of ±1°, those of the shoulderjoint angle of the test person ±2°.

Below: the difference of the two angles (splint joint angle -shoulder joint angle).

The accuracy of the difference angle is between ±2° and±3°.

Outside the possible measurement errors (shaded area),any angular differences deviating from zero are certain tobe genuine defective angle positions with small and largeabduction.

The shoulder joint of test person RO cannot fully executethe prescribed angle movement of the splint. The deviationfor high abduction angles is understandable in the light ofthe functional anatomy described. The angle deviation forsmaller abduction is due to the gradual shift to the right onthe treatment chair during previous movement cycles.

The increase in the angle curve of the test person is lowerthan that of the splint throughout the entire angle range.This fact above all indicates the deviation in position of thetest person and the chair from the outset.

In the case of the other two test persons, this deviation inangle and the incorrect positioning of the shoulder joint insmall abduction is not identifiable, as the following diagramsshow. For larger abduction angles of over 90° deviations inangles are also evident in these test persons:

Test person CH:

Fig. 10b, abduction / adduction movement, test person CH,set abduction range 30° to 140°.

Above: both angles over the period of the test time.

Below: the difference between the two angles (splint jointangle - shoulder joint angle).

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Abduction/Adduction, test person RO,Abduction range to 140o

Abduction/Adduction, test person RO,Abduction range to 140o

______ angle of splint______ angle of shoulder joint

curves have different gradi-ents because of deviationsof the shoulder position

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______ angle difference

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Abduction/Adduction, test person CH,Abduction range to 140o

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at this area same anglesand same gradients

Significant angle deviations in excess of possible measure-ment errors only occur with abduction angles larger thanapprox. 90°, then increasing rapidly. For an abduction anglesetting of the splint the difference amounts to approx. 20°.The shoulder joint of the test person is then abducted byonly 120°.The increase in the curve is also the same for the test per-son and the splint up to 90° (cf. Fig. 10a).

Test person ST:

Fig. 10c, abduction / adduction movement, test person ST,set abduction range 30° to 140°.



Up to approx. 90° abduction, the splint angle and the shoul-der joint angle of the test person are exactly identical. Over90° the deviation increases rapidly to approx. 15°. Theincrease in curve is also identical to 90°.

The shoulder joint angle and the difference between thetest person and the splint for the two extremes of abductionangle (30° and 140°) and the angle of 80° are summarizedin the following table.

Table: Deviations in abduction angleRO CH ST

Angle / Angle difference

at 30° abduction 40° 10° 30° 0° 30° 0°


at 80° abduction 83° 3° 78° -2° 30° 0°


at 140° abduction 128°-12° 120°-20 125°-15°

Accuracy of measured angle at ±2° to ±3°.

At 80° abduction there is practically no angle deviation forthe two test persons, CH and ST. This is also evident in thefollowing measurements. In further tests the abductionrange was set at 30° to 80° for the two test persons. Noangle deviations were found during the movement cycles.(As a result of the small scale of the movements, a completemovement cycle now only takes about 45 seconds ratherthan approx. 70 seconds. In order to facilitate comparison,the same time scale of up to 70 seconds has been used inthe diagrams):

Test person CH:

Fig. 10d, abduction / adduction movement, test person CH,set abduction range 30° to 80°.



No angle deviations between the splint and the test personare evident throughout the entire movement cycle.

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Abduction/Adduction, test person ST,Abduction range to 140o

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at this area same anglesand same gradients


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Test person ST:

Fig. 10e, abduction / adduction movement, test person ST,set abduction range 30° to 80°.



No angle deviations between the splint and the test personare evident throughout the entire movement cycle.

Summary: If abduction treatment is restricted to the rangefrom 30° to approx. 80° (possibly also to 90° or 100°), virtually no angle deviation is to be expected between thesplint and the patient as long as the shoulder joint of thetest person was set exactly to the motor axis A at thebeginning and did not shift significantly during treatment.The humerus joint is only capable by nature of carrying outapprox. 90° abduction movement, any movement above thisis a sliding movement in the shoulder-blade and othermovements.

In addition to the angle correspondence, the question stillarises of possible unwanted movements in the thoracicgirdle.

First a possible sideways list of the thoracic girdle is in-vestigated. To this end the axis of the markers on the shoulderof the test person ("shoulder axis 1") are examined for tilting,as is the axis through the two markers on the shoulder- blades ("shoulder axis 2").

Fig. 11a, tilting of the thoracic girdle axis during abductionmovement, test person RO.

The transverse axis of the thoracic girdle shows virtually no tilting within the framework of test accuracy, althoughdefective positioning between the test person and the splintand deviations in the abduction angle were previouslyidentified. As shown in Fig. 9a to 9d, the test person is only evading the movement horizontally.

Fig. 11b, tilting of the thoracic girdle during abduction movement, test person CH.

No sideways tilting can be identified in the thoracic girdle upto 110°. In contrast to the previous test person, from thispoint onwards the thoracic girdle and the thorax begin to tiltto the side by up to 10°. This test person not only evadeshigh abduction horizontally but also through sideways tilting.

If the abduction movement is limited to smaller angles up to80°, as in the lower diagram, no sideways tilting takesplace.

(In both diagrams the course of the abduction angle is alsoshown, using the scale on the right.)

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angl

e


Abduction/Adduction, test person RO,Abduction range to 140o ,

tilt of shoulder axis

time

angl

e

______ shoulder axis 1______ shoulder axis 2

Abduction/Adduction, test person CH,Abduction range to 140o ,


time

angl

e

______ shoulder axis 1______ shoulder axis 2______ splint angle

Abduction/Adduction, test person CH,Abduction range to 80o ,


time

angl

e

______ shoulder axis 1______ shoulder axis 2______ splint angle

The sideways tilting of the thoracic girdle for the two extre-mes of abduction angle (30° and 140°) and the angle of 80°is summarized in the following table.

Table: Sideways tilting of the thoracic girdle in abduction

RO CH ST

Tilting axis 1 / axis 2

at 30° abduction 0° 0° 0° 0° 0° 0°


at 80° abduction 1° 1° 0° 0° 0° 0°


at 140° abduction 2° 2° 10° 10 5° 4°

Axis 1 through the markers on the shoulders, axis 2through the markers on the shoulder-blades.

Accuracy of measured angle at ±2° to ±3°.

At up to 80° abduction, a sideways list of the thorax doesnot occur in any of the three test persons. In the case ofmore extreme abduction, they take greatly varying evasionthrough sideways listing, ranging from not at all in test per-son RO, to 10° in test person CH. A pure sideways shiftoccurs in test person RO, as shown in Fig. 12a, whilst side-ways tilting occurs in test person CH (Fig. 13a).

On the shifting and tilting of the thorax, shifting of theshoulder-blade to the thorax:

The metric spatial positions of the markers are evaluatedfrom the video. The movement of the markers in the follo-wing diagram:

Fig. 12a, movement in the region of the thoracic girdle, spinal column, test person RO.

Numbering of markers for the following diagram:

All markers shift to a greater or lesser degree to the right asthe abduction angle increases. The movement scope of theshoulder joint treated (left) is the largest. This means thatthe treated shoulder - the shoulder-blade - shifts in relationto the thorax. The varying shifts of the marker on the shoulder(maximum 5.5 cm) and the shoulder-blade (3 cm) alsoindicate an additional rotation of the shoulder-blade than

would be expected from the functional anatomy. The thoraxshifts by approx. 1 cm to 2 cm to the right, the shoulder-blade therefore approx. 3 cm to 4 cm in relation to the thorax. (Due to the possible skin movement of the marker,the actual movement of the shoulder-blade may be evenlarger).

In the following diagram the absolute shift distances of themarkers are summarized:

Fig. 12b, movements in the region of the thoracic girdle,spinal column. Absolute movement of the markers in cm.The black curve represents the course of the abductionangle (with the scale on the right). Measurement accuracyis approx. ±1 cm. Shoulder marker No. 6 is the first markeron the treated shoulder to move, at approx. 80° abductionits movement exceeds the measurement accuracy limit of1 cm. The other markers only follow at higher abductionangles from about 110° onwards.

In addition to the total shift of the thoracic girdle and thorax,the movement of individual markers relative to each othermay also be investigated. A reduction in spacing betweenmarkers on both shoulders or shoulder-blades result, asmentioned, from a medial shift of the shoulder-blades on thetreated side. A stronger shift in the marker on the shoulderthan the markings in the middle of the shoulder-blade isdue to an additional rotation of the shoulder-blade in relationto the axis vertical to its surface. Detailed analysis of thismatter should not be taken too far.

The essential statement is: no movement can be identifiedin the shoulder joint up to 80° abduction, at up to 110°movement takes place in the shoulder blade and, via theshoulder-blade, the entire thorax.

In test person CH a clear sideways list of the trunk takesplace at abduction angles of 120° and over.

14

marker on theshoulder

marker on the shoulder-blade

spinal marker

time

______ absolute movement marker 6______ absolute movement marker 7______ absolute movement marker 8______ absolute movement marker 9______ absolute movement marker 10______ absolute movement marker 11______ absolute movement marker 12______ absolute movement marker 13______ absolute movement marker 14______ angle of splint

y (c

m)

x (cm)

(cm

)

Absolute shift distances of the markers during the abduction/adduction, test person RO,

Abduction range to 140o

Fig. 13a, Movement in thoracic girdle, spinal column regi-ons, test person CH.

Numbering of markers:

As the abduction angle increases, all markers shift to agreater or lesser degree to the right, in a declining curve tothe right. The test persons leans to the right. The shift orsideways listing of the trunk is not desirable, but not reallyharmful in a patient only injured in the shoulder.

Fig. 13b, Movements in the region of the thoracic girdle,spinal column. Absolute movement of the markers in cm.The black curve represents the course of the abductionangle (with the scale on the right). Shoulder marker No. 6 isthe first marker on the treated shoulder to move, movingthe most. The other markers only follow at higher abductionangles from about 110° to 120° onwards. The lower themarker on the spinal column, the less it is affected by themovement. This is due to the rotation movement of thetrunk. The rotation center is located in the area of the lum-bar vertebra / seat.

For smaller abduction movements to 80° practically nounwanted movements take place, as the following diagramshows:

Fig. 13c, as Fig. 13b, now with smaller abduction range.

In test person ST the relationships are more like those oftest person RO. The corresponding diagrams are not shownseparately here. Shifts in the shoulder occur at approx. 90°,movement of the thorax only from approx. 120° onwards.

15

time


y (c

m)

x (cm)



spinal marker

(cm

)

time


(cm

)

Absolute shift distances of the markers during the abduction/adduction, test person CH,


Absolute shift distances of the markers during the abduction/adduction, test person CH,


Elevation (flexion) movements

For most shoulder injuries, elevation up to 90° is practiced,care should be taken with shoulder luxation above thisangle.

Figures 15a to d show a course of movements in four indi-vidual pictures again. The movement range set was 30° to130°. As in figure 9, the marker positions of the initial set-ting in the first picture are copied in the subsequent pictu-res. Photographs of the test persons taken from the sideare shown, perendicular to the movement plane of the rota-tion movement. Analyses were also made with the camerafocused on the back of the test person.

Fig. 15a to d, four photographs taken during elevationmovement, test person RO.Red dot: marker on the shoulder and shoulder-blade of thetest person and on the auxilliary extension bar of the upperarm, position in each case as in first picture, green dot:marker on the movement splint. The elevation angle is defined as being between the upper arm splint or upperarm of the test person and the vertical bar of the splint.

16

Similar factors apply to the measurement of the elevationangle as for abduction. Incorrect adjustment of the splint tothe test person is noticeable in the angle deviations, aboveall in differing increases in the angle curves:

Fig. 16a, Elevation movement, test person RO, elevationrange set 30° to 130°.



At an angle setting of 70° (the splint was originally set atthis position) both test values agree. At other angles thedeviation increases linearly to a maximum of approx. 12° at130° elevation. The deviating curve increases of the anglecurves are an indication of deviating rotational joint axes ofthe splint and the test person, that is slightly inaccurateadjustment of the splint to the test person.

Fig. 16b, Elevation movement, test person ST, elevationrange set 30° to 130°.



The angle curves deviate less than in the previous case fortest person RO. The angle difference of maximum - 7° islarger than the possible measurement error in angle meas-urement (±2° to ±3°) only for higher elevation. The increas-es in the angle curves also deviate to a lesser degree, theadjustment of the splint to the test person was obviouslybetter than in the previous case.

Table RO CH ST


at 30° elevation 35° 5° 37 7 33° 3°


at130° elevation 118° -12° 117° -13 123° -7°

The three test persons do not follow the elevation move-ment of the shoulder joint to the extent predefined by themotor-driven splint. The largest deviations in angle occur atthe highest elevations. For all three test persons, therefore,the total scope of movement of the shoulder joint is smallerthan that of the splint. This difference is approx. 17° for testperson RO and about 20° and 10° for the other two testpersons. The cause is a deviation in the rotational axis ofthe splint and test person. Whether this misalignment arosewhen the splint was adjusted to the test person, or whetherit occurred in the course of elevation through a shift in theshoulder cannot be precisely determined. Measuring theangle of the upper arm via the "cantilever rod" may alsocontribute to the error.

17

Elevation, test person RO,elevation range 30o to 130o

time

angl

e

______ elevation splint______ elevation shoulder

Elevation 30o to 130o, test person RO,angle difference splint-test person

time

angl

e

______ angle difference ______ elevation splint

Elevation, test person ST,elevation range 30o to 130o

time

angl

e

______ elevation splint______ elevation shoulder

Elevation 30o to 130o, test person ST,angle difference splint-test person

time

angl

e

______ angle difference ______ elevation splint

The absolute movements of the markers on the thoracicgirdle and spinal column are determined as in the previouschapter on abduction movement. This time a differentiationis drawn between a rotary movement of the shoulder mar-ker viewed from a camera perspective from the side (due torotation and lowering of the shoulder-blade) and the shiftingof marker dots in the plane of the back, viewed from theback camera.

Fig. 17a, Movement of markers on the shoulder of the testperson RO, elevation 30o to 130o.

Viewed from the side, the markers on the shoulder make arotary movement around an angle a (approx. 35° of mar-kers on the shoulder, about 20° of markers on the shoulder-blade) and a shift by the length r (approx. 2 cm).

From the back perspective:

Fig. 17, Movement of markers on the back of the test personRO, elevation 30o to 130o.

The marker on the shoulder gradually shifts with increasingelevation by a maximum of about 2 cm medial and 2.5 cmdownwards. The marker on the shoulder-blade shifts onlydownwards by about 4 cm.

All other markers remain practically unaffected. The mostsignificant values are summarized in the following table.The data relating to the side-view camera, above all, is onlyto be considered with reservation. It is not possible to clear-ly distinguish whether the skeleton of the thoracic girdlemakes the movement or the muscles and skin are pulledalong by the elevation movement. The differences in anglewith relation to the rotation of shoulder marker and markeron the shoulder-blade suggest this interpretation.

Table RO CH ST

Rotation of thoracic girdle

from side perspective

(shoulder / shoulder-blade

in degrees) 35° 20° 15° 10° 40° 10°

Shift in shoulder

from the side-perspective 2 cm 4 cm 2 cm

Shift of shoulder marker

in cm (1st number vertical

shift., negative values

downwards, 2nd number

medial shift) -2.5 2.0 0 3 0 2

Shift of shoulder-blade

marker in cm (1st number

vertical shift., negative values

downwards, 2nd number

medial shift) 4.0 0 -2 2 0 2

3.3. Rotation movements

In the treatment of some injury patterns of the shoulder, inparticular injuries to the ligaments, dislocated shoulderjoints and after operations in the m. subscapularis region,outward rotation is less commonly practiced, and in theinitial stages avoided completely. Dislocation of the shoul-der occurs most easily precisely through outward rotation,outward rotation is luxation provocation.

A certain degree of abduction of the arm is required tocarry out rotation on the splint. Measurements were carriedout at 70° and 85° abduction. Small degrees of rotationmovement can also be carried out with smaller abduction.The decisive factor is that the splint rods do not collide withthe patient at any point. This is particularly difficult whenexercising with a slight forward rotation of the shoulder.Outward rotation can be carried out more easily in abduc-tion positions.

As in the two previous chapters, individual photographstaken during a movement cycle by a camera directed at theback of the test person are presented first. The test involvedoutward and inward rotations of up to 60° each.

18

y (c

m)

x (cm)



spinal axis, motor A

y (c

m)

x (cm)



spinal marker

Fig. 18a to d, four photographs taken during rotation move-ment, test person RO.Rotation range -60° to 60°. Abduction angle setting 85°(measurements were taken at 70° abduction in a furthertest series). Red dot: marker on the shoulders, shoulder-blades and spinal column of the test person’s position ineach case as in first picture, green dot: marker on themovement splint. The rotation angle is determined from the direction of the camera to the side next to the splint.

Figures 18a to 18d immediately show that unwanted movements in the thoracic girdle during rotation are limitedto approx. 1 cm.

19

The following diagrams show the angle curves and angledifferences determined from the camera shots taken fromthe side of the test person. In order to carry out the rotationmovement, the arm also has to be abducted.Measurements were taken in two series at 70° and 85°abduction.

Fig. 19a, Rotation movement, test person RO, set rotationrange 60° inward rotation (interpreted as a positive angle)to 60° outward rotation (interpreted as negative angle -60°).

The splint is set at 85° abduction.



The angle curves do not measurably deviate. The possibleangle measurement error is ±2°to ±3°.

Fig. 19b, as for Fig. 14a, rotation movement, test personRO, this time the splint is set at 85° abduction.



In none of the cases, including the other two test persons,is the angle deviation more than 1° to 2°, that is larger thanany possible error in angle measurement. A table summari-zing the results is therefore dispensed with.

Shifts in the markers in the region of the thoracic girdle andthe spinal column are scarcely identifiable and are all under1 cm and therefore within measurement accuracy5. Furtherdetails are therefore also dispensed with here.

20

time

angl

e

______ rotation splint______ rotation arm

Rotation movement at 85o, test person RO,angle difference

time

angl

e


time

angl

e

______ rotation splint______ rotation arm

Rotation movement at 70o, test person RO,angle difference

time

angl

e


The motor-driven shoulder CPM device ARTROMOT®-S2PRO is designed for the continuous passive mobilization(CPM) of the shoulder joint in conjunction with physiothera-py. This biomechanical study investigates whether the kine-matics of the splint are transferred to the patient withoutunwanted movement and stress. Are the prescribed move-ments of the machine reproduced by the test person andare other movements unintentionally induced? Tests werecarried out on three test persons with healthy, fully mobileshoulder joints. The kinematic parameters were taken fromvideo analysis of the movements.

The study did not investigate questions relating to the tech-nical safety of the splint, such as the reliability of the angle-limit stop of the motors, the safety reversal switch in theevent of blockages of the joint and similar safety-relevantcharacteristics.

The applications of shoulder joint CPM splints for passivemobilization (CPM) and their positive benefits in avoidingstiffening of joints after injuries or operations are indisputa-ble. The shoulder joint is particularly vulnerable to stiffeningwhen immobilized, the use of movement splints is thereforeindicated. Similar movement splints are also available forthe mobilization of other joints such as the knee, elbow andfinger joints.

The adjustment of the splint to fit the test person was car-ried out using several setting sizes on the splint. In princi-ple, this is not complicated, but is made more difficult by thevery high degree of mobility of the human thoracic girdleand spinal column. None of the test persons sat in exactlythe same position on the treatment chair on any two conse-cutive tests. Moreover, there is no direct firm connectionbetween the thoracic girdle of the patient and the motor-driven splint. With the exception of the lower arm, the pati-ent is not firmly attached to the chair of the movementsplint during treatment, but is free to move when sitting.

The patient’s cooperation is a precondition for treatment with the shoulder CPM splint.

A change in position of the patient e.g. sinking down duringlonger treatment sessions, causes motor axis A to be defo-cused in relation to the shoulder joint axis of the patient.However, the setting of motor axis A on the center of thepatient’s shoulder joint is vital for the exact setting of thesplint to the patient. A certain degree of deviation betweenthe splint pivotal axes and the pivotal axes of the shoulderjoint of the patient is therefore to be expected despite everycare being taken. These deviations are easily tolerated wit-hin the scope defined for this study. Due to the naturallyhigh mobility of the shoulder joint, a misalignment and theforces produced can be avoided, as long as the repositio-ning required is not too great. The patient’s injured or disea-sed shoulder joint is, however, especially sensitive to pain.The angle range of the CPM splint should therefore alwaysbe selected according to the painfree options of the patient.

The display accuracy of the hand control unit for bothmotor-driven degrees of freedom of movement was deter-mined in an initial test.

The display for motor A showed an angle which was toosmall by about 3° to 4° throughout the majority of the move-ment range. However, the deviation is not significant. In theoperating instructions the manufacturer states explicitly that

differences may occur between the angle displayed on thedevice and the angle setting of the patient’s joint. Painfree,relaxed movement of the extremities is the most importantfactor. The deviation measured on motor B was within thetest accuracy range of approx. ±1°.

The angular velocity of the motorized splint under investiga-tion is infinitely variable between 100% and 1%.

Motorized splints are often applied very soon after injuriesor operations. The velocity of the splint must therefore beadjustable and reduced far enough to move the patient slo-wly and without causing any pain. The movement velocity ofthe splint and the range of movement are then graduallyincreased in the course of the healing process. In the slo-west setting, the maximum angular velocities of theARTROMOT®-S2 PRO are far less than 1° per second. Thisslow speed is unlikely to damage or impair even a newlyoperated patient.

Before the preselected limits of the range of movement arereached, the ARTROMOT®-S2 PRO gradually deceleratesthe velocity. The slow restart after a pause at the reversalpoint of the movement was perceived as pleasant by thetest persons. In most cases, the extreme angular positionsare likely to be quite painful and stressful for the patients.Reducing the speed at this point is therefore a very sensi-ble and appropriate concept.

The trials involving test persons extended over severalcomplete movement cycles. One movement cycle (not oneof the first) was analyzed in each case. Continuous patientapplications are quite common in practice.

Three separate consecutive tests recorded the three anglemovement options of the splint, abduction / adduction(moved by motor A), elevation (also referred to as flexion,caused by motor A, with changed ante / retroversion of thesplint) and outward / inward rotation (induced by motor B).

Movements of the shoulder CPM splint in abduction /adduction

With abduction treatment limited to the range of 30° toapprox. 80° (perhaps even to 90° or 100°), the coincidenceof the shoulder joint angle of the test person and the shoul-der joint angle of the motor-driven splint is highly exact.Practically no angle deviation was calculated between thesplint and the patient as long as the shoulder joint of thetest person was accurately positioned on motor axis A anddid not shift significantly during treatment. Angle discrepan-cies increase rapidly in abduction angles exceeding approx.100°. The humerus joint can, from its nature, only carry outabduction movements of about 90°, any movement abovethis is a sliding movement in the shoulder-blade and othermovements.

The movement patterns of the three test persons proved tobe exactly as is to be expected from medical literature onfunctional anatomy: at up to 80° abduction none of thethree test persons displayed unwanted movements at otherpoints in the thoracic girdle or thorax regions. The firstmovements (shifting and rotation) in the shoulder regionoccur with stronger abduction up to 110° or 120°. Abovethis the test persons start to make involuntary evasivemovements, varying from person to person, through side-ways shifting and tilting of the thorax.

The main statement is: no movement is evident in theshoulder joint (except the abduction, naturally) up to 80°

21

4. Summary

abduction, up to 110° the shoulder-blade moves and abovethis level the shoulder-blade and the entire thorax.

Movements of the shoulder CPM splint in flexion / elevation

The correct adjustment of the movement splint to the shoul-der axis of the test person proved most difficult for thismovement pattern. Incorrect adjustments of the pivotal axisof the shoulder for the splint and joint were evident to agreater or lesser extent in all three test persons. As a result,the range of the angle movement of the shoulder was lessthan that prescribed by the splint. With the angle movementlimited to 90° elevation, (the upper arm points forward hori-zontally), the angle deviations were maximum 5° for onetest person and below 3° for the other two test persons i.e.insignificant in all cases.

The shoulder-blade appears to follow the increasing elevati-on of the joint to a certain degree by a downwards shift androtation on the thorax. This causes a shift in the pivotal jointof the shoulder of the test person. This explains the fact thatcoincidence was not exact throughout the entire movementcycle between the pivotal joint of the splint and the test per-son, a fact which was evident in the analysis of the anglecurves.

No significant movements were induced at other points inthe region of the thoracic girdle and the thorax.Here again the findings are: if the range of movement is

limited to realistic levels for an injured patient, in this caseto approx. 90° elevation, only small deviations occur in theangle movement of the shoulder joint and the splint and noother unwanted movements occur at other points in theregion of the thoracic girdle and the thorax.

Movements of the shoulder CPM splint in outward andinward rotation

No angle deviations larger than 1° to 2°, that is larger thanany possible test errors, could be identified in any of thethree test persons. Unwanted movements in the region ofthe thoracic girdle and spinal column are not evident. Allmovements lie within the test accuracy.

Summary: if the range of movements selected are restric-ted to normal, everyday shoulder movements, there are noor only small deviations between the prescribed movementsof the splint and the movements made by the shoulder.Hardly any unwanted movements occur at other points inthe thoracic girdle and thoracic region. At greater extremesin angle, certain deviations and incorrect movements occurto approximately the extent which is to be expected takingthe functional anatomy into consideration. However, pati-ents would not carry out such extensive movements untilthe later stages of convalescence, when the shoulder is nolonger as sensitive and painful. Even then the forces on theshoulder joint would not be very great, certainly far lessthan those experienced in everyday use, e.g. when carryingobjects.

Conclusion

The motorized movement splint "Ormed ARTROMOT®-S2PRO" for the passive motion of the shoulder joint, investiga-ted under the aspects of biomechanics, meets the require-ments of a motor-driven movement device. The deviceimparts to the patient's shoulder joint a physiologicallyappropriate and non-hazardous passive movement. If themotorized splint is adjusted properly to fit the patient, the

movement is largely restricted to the pivotal axis selectedand no forces and torques which may be damaging canoccur in the shoulder joint. To a certain extent, errors inadjusting the splint to the patient have no serious negativeeffects on the results. However, the device should alwaysbe carefully adjusted to the patient's bodily dimensions.

However, the higher movement range of the splint shouldnot normally be used to the full extent on patients. Eventest persons without injuries found the extreme angle set-tings to be exaggerated and unpleasant.

The three test persons reported the support on the motori-zed splint to be good and in no way unpleasant.

The delay in the start-up and stopping of the splint wereperceived as being particularly positive.

The therapeutic benefits of the motorized splint, undisputedin medical terms, by far exceed any drawbacks caused byan inexact setting of the splint.

The physiological coincidence of movement between theshoulder joint to be treated and the kinematics of the moto-rized splint is good for movements within the normal rangeof movements for the shoulder joint. The use of the motori-zed splint can be recommended for clinical use and, afterthe appropriate setup and instructions given by the thera-pist, also for use at home.

Veit Senner, Head of Institute

Jürgen Mitternacht, Project Supervisor

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Ormed GmbH & Co. KG • Merzhauser Straße 112 • D-79100 Freiburg • Phone ++49(0)761/45 66-01 • Fa x ++49 (0 ) 761 /45 66 - 55 01www. o rmed . d e • e -ma i l : i n f o @ o rmed . d e • Madras/India, Phone 0 44-8 11 14 94, Fax 0 44 - 8 11 27 52 • St. Paul/USA,Phone 001-800-4402784, Fax 001-651-4157405 • Prague/CR, Phone 02-84094650, Fax 02-84094660 • Vienna/A, Tel 01-53 20 83 40,Fax 01-53 20 83 431

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