Lesions of the jaw bone are well known to the laity as well as to the professions.  The mechanics of these lesions will serve as a very clear illustration of the lesions of other joints less well known.  They occur when the jaw has been opened beyond the limit of its normal motion, has invaded new territory, become entangled in the tissue there, and going back tries to carry this with it; making a wrinkle and being held there by it.  It  may even be that it passes beyond the dead center of the ligaments that hold it, so that their tension now holds the jaw out, instead of holding it in.  This mechanical principle should be studied in connection with all lesions.

    Irregularities in the movement of the jaw, falsely called lesions, may be due to irregular contractures of the muscles that move the jaw.  Thrusting the jaw forward on one side, one observes that only one tooth touches the jaw above; contractures of the muscle that produces this motion will bring about this result and other such results in varying degrees.  Thickening of the tissues of the joint also may give the appearance of slight lesions.

    The technic for true lesions of the jaw bone is in principle the same as in other lesions.  Using one side as a fulcrum, the other side is lifted over the catch; or putting a fulcrum (a cork or spool) between the jaws, pressure is exerted on the tip so as to stretch the tissues and lift the bone over the point engaged.
 
 
CLAVICLE

    The motion of the sterno-clavicular joint is wide as to direction, narrow as to range.  It bends forward or back or up as the shoulder blade is driven forward or drawn back or up; it rotates as the shoulder rotates.  It may slide in and out on the manubrium.  The size of the end of the bone indicates the amount of pressure it sustains, and the size of the ligaments indicates the amount of tensile strain they bear.

    Warp lesions of the clavicle are very frequent.  Real lesions doubtless occur, but it is not easy to distinguish between the two.

 
DIAGNOSIS

    Diagnosis of lesions of the clavicle is made by comparing the two sides, and is by no means positive.  The two sides differ much in size.  It may be assumed, however, that the less prominent side is in lesion if either side is.  There are few forces drawing the clavicle forward.
 

TECHNIC

    Patient supine.  Operator half sits on corner of table facing foot of table, with thigh resting on it opposite patient’s shoulder; lifts patient’s shoulder of affected side on to thigh so that shoulder-blade rests on thigh; presses down on shoulder or arm, to stretch ligaments of clavicle.  Then placing fingers under clavicle and lifting he draws elbow backward and up to limit of rotation in that direction, and then forward and up and out, and down, using thigh as a fulcrum.  Clavicle is thus lifted forward.

    Caution.  The tissues under the clavicle are very sensitive and easily bruised.  It is necessary to find the point at which pressure with the fingers will cause least pain.  This point is usually at the juncture of the inner third with the middle third.  The fingers must be neither pressed too far in—barely enough to produce upward pressure—nor lifted with too much power.  The leverage over the thigh, the drawing of the joint out, up, and rotating it backward, does most of the work of restoration.

    Lesions of the cartilages of the ribs are found.  These cases are probably surgical.

    Lesions of the acromial end of the clavicle are occasionally found.  One end of the joint may be used as a lever to adjust the other, and then the technic reversed if necessary.  The articulation is parallel to the saggital axis of the body, at right angles to the articulation at the sternal end, to permit those motions of the shoulder-blade not permitted at the sternal end.

 
TECHNIC

    Patient seated, operator standing behind, puts foot on table and knee under patient’s axilla, moves knee with axilla away from body of patient until part of weight is resting on knee and there is tension away from median line (the knee under the axilla presses equally against the humerus, tending to gap lesions and against scapula, tending to close it; and to pry open merely shoulder joint).  Lifting on shoulder and shoulder-blade gaps acromio-clavicular joint.  If posterior end is in lesion, turn knee to point toward median line, carrying with it scapula.  This makes a fulcrum of anterior end and gaps open the posterior end.  Then pressing down on acromial process or clavicle as needed, move arm and scapula as needed to reduce lesion.  If anterior end is in lesion, turn knee to point outward from median line, so as to gap anterior end, and press down on acromial process or clavicle as needed with rotation of arm and scapula to reduce lesion.
 

BICIPITAL TENDON

    The long bicipital tendon is often found to have slipped from its groove, stretching or rupturing its retaining ligaments, and llying close to the coracoid tendon of the biceps.

 
DIAGNOSIS

    Inability to raise the arm in front or behind back or laterally, beyond a certain point; soreness over bicipital groove; relaxed state of outer half of biceps muscle.

    Differential diagnosis:  This condition must be distinguished from inflammation of various portions of the shoulder, and from rheumatoid neuritis, which commonly shows itself first in this area and simulates this lesion often very closely.  Other symptoms of rheumatism, or of diseases allied to rheumatism, aid the diagnosis.

 
TECHNIC

    The problem is to bring the groove as close to the present position of the tendon as possible, to lift the tendon into the groove, to hold it there by fixing the shoulder in an inverted position until the tissues have resumed their normal tone.  Patient seated operator standing at side, grasps arm at elbow, forearm flexed to relieve tension on biceps; lifts arm to about forty-five degrees, rotates forearm down as far as possible, then with fingers of other hand locates tendon and lifts into groove, then rotates arm backward with forearm lift.  An adhesive bandage may be applied to hold the shoulder back and the arm everted as much as possible, and kept there for a week or ten days, longer if the lesion has persisted for some time.

 
FEMUR

DIAGNOSIS
 
    Dislocations of the hip and of other joints of the extremities are surgical cases, and are well known and thoroughly described.  The principle of correction is traction.  A point in the diagnosis of dislocations of the hip is well worth while here.  Patient supine, an assistant standing at foot of table grasping toes prepared to rotate them out and down, then up and in (both feet out and down at the same time); operator places thumbs on anterior superior spines of ilium and lays hands over greater trochanter; as assistant rotates toes, each greater trochanter describes an arc whose center is the center of the acetabulum in normal hips.  This arc is very quickly determined by the curve of the palms.  Its position with reference to the anterior superior spine is instantly defined.  In dislocations of the hip, the trochanter describes an arc which points immediately to the position of the head of the bone.  The normal arc is slightly more down than up.  If the position of the head is on the dorsum of the ilium, the arc will be altogether up and in; if the position be in the thyroid notch, the trochanter of that side will be correspondingly lower than its fellow, and the rotation will be up and in.  If the arc be shorter and more sharply curved than its fellow, it points to a fracture of the neck or a tubercular destruction of the head of the bone.  As soon as the arc is defined under the palm, the position of the head and the length of the neck is instantly defined.

    Lesions of the ligamentum teres are believed to occur.  The tendon becomes curled the wrong way and cramped on itself.

    The diagnosis is obscure; a catch in walking; pains on the inner side of the knee without other lesions of the hip joint (the tendon is a development from the transverse ligament, and originally connected with certain muscles of the thigh, whence probably the pain in the inner side of the knee).

 
TECHNIC

    The problem is to stretch the ligament in all directions, relying on the tendency to the normal to restore it to normal position; is therefore to carry the head of the bone around the rim of the acetabulum at the limit of normal tension, from the anterior edge of the notch, the lower anterior corner, up, back and around and down to the other side of the acetabular notch.  If this does not give relief, rotation in the opposite direction may be tried.

    Patient supine; thigh is raised to forty-five degrees, abducted, and leg is also abducted; this brings head of bone to anterior edge of notch; leg is then abducted; this brings head to anterior edge of acetabulum; foot and knee are then abducted together; this carries head to almost the top of notch; foot is then abducted as knee is lowered always at limit of tension centrally; this carries head around upper third of acetabulum; maintaining foot in abduction, the knee is then carried up, out, down, and to normal position.

 
SESAMOID BONES

    Lesions of the sesamoid bones under the big toe are found.  Diagnosis rests on pain, cramps, and shallowness of the corresponding side under the first joint of the big toe.

 
TECHNIC

    The problem is to locate the bone, relax the tendon, pull it down to the level of the joint, slide it into place and hold it there while the ligaments regain tone.

    Sharply flex toe; rotate affected side down; move to opposite side with traction; assisting the sesamoid bone with fingers if possible.  Adhesive tape or plaster casts may be used to maintain fixity as long as seems desirable.