Marker Placements

Marker Placement Protocols

LifeMOD™ uses four standard marker placement protocols for the incorporation of Motion Capture (MOCAP) data from an external source into the model. If one of the four configurations are used, LifeMOD™ will automatically create all the motion agents on the model.

Plug-in-Gait Marker Placement

Figure 1 displays where Plug-in-Gait markers should be placed on the subject. Where left side markers only are listed, the positioning is identical for the right side.

Figure 1: Plug-in-Gait Marker Placement Protocol

Upper Body

Head Markers

LFHD	Left front head	Located approximately over the left temple
RFHD	Right front head	Located approximately over the right temple
LBHD	Left back head	Placed on the back of the head,roughly in a horizontal plane of the front head markers
RBHD	Right back head	Placed on the back of the head, roughly in a horizontal plane of the front head markers

The markers over the temples define the origin and the scale of the head. The rear markers define its orientation. If they cannot be placed level with the front markers, and the head is level in the static trial, tick the "Head Level" check box under options on "Run static model" in the pipeline when processing the static trial. Many users buy a headband and permanently attach markers to it.

Torso Markers

C7	7th Cervical Vertebrae	Spinous process of the 7th cervical vertebrae
T10	10th Thoracic Vertebrae	Spinous Process of the 10th thoracic vertebrae
CLAV	Clavicle	Jugular Notch where the clavicles meet the sternum
STRN	Sternum	Xiphoid process of the Sternum
RBAK	Right Back	Placed in the middle of the right scapula. This marker has no symmetrical marker on the left side. This asymmetry helps the auto-labeling routine determine right from left on the subject.

C7, T10, CLAV, STRN define a plane hence their lateral positioning is most important.

Arm Markers

LSHO	Left shoulder marker	Placed on the Acromio-clavicular joint
LUPA	Left upper arm marker	Placed on the upper arm between the elbow and shoulder markers. Should be placed asymmetrically with RUPA
LELB	Left elbow	Placed on lateral epicondyle approximating elbow joint axis
LFRA	Left forearm marker	Placed on the lower arm between the wrist and elbow markers. Should be placed asymmetrically with RFRA
LWRA	Left wrist marker A	Left wrist bar thumb side
LWRB	Left wrist marker B	Left wrist bar pinkie side

The wrist markers are placed at the ends of a bar attached symmetrically with a wristband on the posterior of the wrist, as close to the wrist joint center as possible.

LFIN

Left fingers

Actually placed on the dorsum of the hand just below the head of the second metacarpal

Lower Body

Pelvis

LASI	Left ASIS	Placed directly over the left anterior superior iliac spine
RASI	Right ASIS	Placed directly over the right anterior superior iliac spine

The above markers may need to be placed medially to the ASIS to get the marker to the correct position due to the curvature of the abdomen. In some patients, especially those who are obese, the markers either can't be placed exactly anterior to the ASIS, or are invisible in this position to cameras. In these cases, move each marker laterally by an equal amount, along the ASIS-ASIS axis. The true inter-ASIS Distance must then be recorded and entered on the subject parameters form. These markers, together with the sacral marker (LPSI and RPSI markers), define the pelvic axes.

LPSI	Left PSIS	Placed directly over the left posterior superior iliac spine
RPSI	Right PSIS	Placed directly over the right posterior superior iliac spine

LPSI and RPSI markers are placed on the slight bony prominences immediately below the dimples (sacro-iliac joints), at the point where the spine joins the pelvis.

SACR

Sacral wand marker

Placed on the skin mid-way between the posterior superior iliac spines (PSIS). An alternative to LPSI and RPSI.

SACR may be used as an alternative to the LPSI and RPSI markers to overcome the problem of losing visibility of the sacral marker (if this occurs), the standard marker kit contains a base plate and selection of short "sticks" or "wands" to allow the marker to be extended away from the body, if necessary. In this case it must be positioned to lie in the plane formed by the ASIS and PSIS points.

Leg Markers

LKNE

Left knee

Placed on the lateral epicondyle of the left knee

To locate the "precise" point for the knee marker placement, passively flex and extend the knee a little while watching the skin surface on the lateral aspect of the knee joint. Identify where knee joint axis passes through the lateral side of the knee by finding the lateral skin surface that comes closest to remaining fixed in the thigh. This landmark should also be the point about which the lower leg appears to rotate. Mark this point with a pen. With an adult patient standing, this pen mark should be about 1.5 cm above the joint line, mid-way between the front and back of the joint. Attach the marker at this point.

LTHI

Left thigh

Place the marker over the lower lateral 1/3 surface of the thigh, just below the swing of the hand, although the height is not critical.

The thigh markers are used to calculate the knee flexion axis location and orientation. Place the marker over the lower lateral 1/3 surface of the thigh, just below the swing of the hand, although the height is not critical. The antero-posterior placement of the marker is critical for correct alignment of the knee flexion axis. Try to keep the thigh marker off the belly of the muscle, but place the thigh marker at least two marker diameters proximal of the knee marker. Adjust the position of the marker so that it is aligned in the plane that contains the hip and knee joint centers and the knee flexion/extension axis. There is also another method that uses a mirror to align this marker, allowing the operator to better judge the positioning.

LANK	Left ankle	Placed on the lateral malleolus along an imaginary line that passes through the transmalleolar axis
LTIB	Left tibial wand marker	Similar to the thigh markers, these are placed over the lower 1/3 of the shank to determine the alignment of the ankle flexion axis

The tibial marker should lie in the plane that contains the knee and ankle joint centers and the ankle flexion/extension axis. In a normal subject the ankle joint axis, between the medial and lateral malleoli, is externally rotated by between 5 and 15 degrees with respect to the knee flexion axis. The placements of the shank markers should reflect this.

Foot Markers

LTOE	Left toe	Placed over the second metatarsal head, on the mid-foot side of the equinus break between fore-foot and mid-foot
LHEE	Left heel	Placed on the calcaneous at the same height above the plantar surface of the foot as the toe marker

Helen Hayes (Davis) Marker Placement

The following describes in detail where the Helen Hayes markers should be placed on the subject. Where left side markers only are listed, the positioning is identical for the right side.

Figure 2: Helen Hayes (Davis) Marker Placement Protocol

Lower Body

Pelvis

14	L ASIS	Placed directly over the left anterior superior iliac spine
7	R ASIS	Placed directly over the right anterior superior iliac spine

Sarum

Placed on the skin mid-way between the posterior superior iliac spines (PSIS).

Leg Markers

L Fem. Epicondyl

Placed on the lateral epicondyle of the left knee

Marker placement follows the same process as the plug-in-gait marker placement.

L Fem. Wand

A 4 inch wand is placed on the left leg over the lower lateral 1/3 surface of the thigh, just below the swing of the hand.

The antero-posterior placement of the marker is critical for correct alignment of the knee flexion axis. Adjust the position of the marker so that it is aligned in the plane that contains the hip and knee joint centers and the knee flexion/extension axis.

10	Left Malleolus	Placed on the lateral malleolus along an imaginary line that passes through the transmalleolar axis
11	Left tibial wand	Similar to the thigh markers, these are placed over the lower 1/3 of the shank to determine the alignment of the ankle flexion axis

Foot Markers

8	Left Metatarsal Head	Placed over the second metatarsal head, on the mid-foot side of the equinus break between fore-foot and mid-foot
9	Left Heel	Placed on the calcaneous at the same height above the plantar surface of the foot as the toe marker

Body Segment CG Marker Placement

The following describes in detail where the body segment CG markers should be placed on the subject. Where left side markers only are listed, the positioning is identical for the right side.

Figure 3: Body Segment CG Marker Placement Protocol

For this method, markers are never really placed at the CG locations. Software furnished with the motion capture system is used to resolve a marker cluster to the segment CG. The data consists of a time history of marker locations (X, Y, Z) and orientations (Xang, Yang, and Zang Euler angles).

This represents the most general method to incorporate motion capture data. Data for all marker locations listed above is not necessary and would depend on the application and body configuration.

Golfer Full-Body Marker Placement

The following describes in detail where the Golfer Full-Body Marker set should be placed on the subject.

Figure 4: Golfer marker placement protocol - 3D view.

Figure 5: Golfer marker placement protocol - Front view.

Figure 6: Golfer marker placement protocol - Back view.

Upper Body

Torso Markers

Thoracic 4th

Spinous process of the 4th thoracic vertebrae

Right Arm Markers

RSHO	Right Shoulder	flat portion of the acromion
RHUW	Right Humeral Wand	A 4 inch wand is placed on the upper arm between the elbow and shoulder. Should be placed symmetrically with LHUW
REPI	Right Epicondyle	Placed on lateral epicondyle approximating elbow joint axis
RFOW	Right Forearm Wand	A 4 inch wand is placed on the lower arm between the elbow and the wrist. Should be placed symmetrically with LROW
RWRI	Right Wrist	Right wrist center

Left Arm Markers

LSHO	Left Shoulder	flat portion of the acromion
LHUW	Left Humeral Wand	A 4 inch wand is placed on the upper arm between the elbow and shoulder. Should be placed symmetrically with RHUW
LEPI	Left Epicondyle	Placed on lateral epicondyle approximating elbow joint axis
LFOW	Left Forearm Wand	A 4 inch wand is placed on the lower arm between the elbow and the wrist. Should be placed symmetrically with RROW
LWRI	Left Wrist	Right wrist center

Golf Shaft Marker

SHFT

Golf Shaft Marker

Marker placed on the golf shaft 10 inches from the center of the right hand. See Figure 7.

Placement of shaft marker
Figure 7: Placement of the shaft marker with respect to the right hand. (front view left, side view right)

Lower Body

Pelvis

LASIS	L ASIS	Placed directly over the left anterior superior iliac spine
RASIS	R ASIS	Placed directly over the right anterior superior iliac spine

SACRU

Sarum

Placed on the skin mid-way between the posterior superior iliac spines (PSIS).

Leg Markers

RFEMC	R Fem. Epicondyle	Placed on the lateral epicondyle of the left knee
LFEMC	L Fem. Epicondyle	Placed on the lateral epicondyle of the left knee

RFEMW	R Fem. Wand	A 4 inch wand is placed on the left leg over the lower lateral 1/3 surface of the thigh, just below the swing of the hand.
LFEMW	L Fem. Wand	A 4 inch wand is placed on the left leg over the lower lateral 1/3 surface of the thigh, just below the swing of the hand.

LLATM	Left Malleolus	Placed on the lateral malleolus along an imaginary line that passes through the transmalleolar axis
RLATM	Right Malleolus	Placed on the lateral malleolus along an imaginary line that passes through the transmalleolar axis
LTIBW	Left Tibial Wand	Similar to the thigh markers, these are placed over the lower 1/3 of the shank to determine the alignment of the ankle flexion axis
RTIBW	Right tibial wand	Similar to the thigh markers, these are placed over the lower 1/3 of the shank to determine the alignment of the ankle flexion axis

Foot Markers

L2MET	Left Metatarsal Head	Placed over the second metatarsal head, on the mid-foot side of the equinus break between fore-foot and mid-foot
R2MET	Right metatarsal Head	Placed over the second metatarsal head, on the mid-foot side of the equinus break between fore-foot and mid-foot
RHEEL	Right Heel	Placed on the calcaneous at the same height above the plantar surface of the foot as the toe marker
LHEEL	Left Heel	Placed on the calcaneous at the same height above the plantar surface of the foot as the toe marker