Round ligament. (Ligament= teres capitis femoris .seu inter-articulare.) This ligament, which was first described by Vesalius, has very improperly received the epithet round, inasmuch as in point of fact it is a triangular fasciculus, about an inch and a half in length, having its base attached to the aceta bulum and its apex to the depression on the head of the femur. It is most advantageously placed for escaping injury in the various motions of the joint, as, independently of its corresponding to the soft cushion contained in the excavation of the acetabulum, its direction and attachments completely remove it from all danger on this score. It is attached by the superior portion of its base to the upper cornu of the notch, and to the external layer of the tranverse ligament; and by the inferior and larger portion of its base to the lower cornu, as well as to the external layer of the tranverse ligament; from these points of attachment its direction in the quiescent state of the limb, i. e. the femur being placed vertically under the pelvis, is upwards, outwards, and back wards, to its insertion into the head of the the joint is cut into in the recent state, there are processes seen extending from this ligament towards the circumference of the exca vation; these should not be mistaken for por tions or attachments of the ligamentum teres ; they are folds of the synovial membrane pro ceeding from that ligament over the surface of the acetabulum. Situated in the rough exca vation of the acetabulum, and forming a cushion for the ligamentum teres in the several motions and positions of the head of the femur, is the soft pulpy mass of fatty cellular tissue, covered by synovial membrane, already alluded to as the glands of Havers, first described and figured by that anatomist in his Osteologia Nova.
Capsular ligament.—The hip-joint is com pleted by a strong fibrous investment, termed capsular ligament (capsule jibrosu ossis fe moris). This is by far the strongest and largest capsular ligament in the body. How ever it is by no means uniform in its strength and thickness, these being greatly increased by super-imposed fibres in those situations upon which a considerable force is exercised in certain motions of the joint. It not only em braces the articulation, but also includes the neck of the femur, to the base of which it extends from the os innominatum. Its fibres are variously directed from the os innomi natum, to which they are firmly attached from the margin of the acetabulum to a considerable distance on the dorsum of that bone. Superiorly and externally they may be traced as far as the inferior anterior spinous process of the ilium in front, whilst posteriorly the great sciatic notch marks their boundary, and an arched line drawn from the inferior anterior spine of the ilium to the spine of the ischium denotes with tolerable exactness their attachment in this direction. Inferiorly and externally they are attached to that portion of the ischium situated between the cotyloid cavity and the external lip of the tuber ischii, and to this latter itself by very strong dense fibres.
Superiorly and internally they arise from that portion of the ilium situated between its an terior inferior spine and the ilio-pectineal eminence, and from the pubis as far as the superior cornu of the acetabulum. Inferiorly and internally the capsule is attached to the transverse ligament of the cotyloid cavity.
By this description we perceive that the cap sular ligament is firmly attached to the os inno minatum; that with the exception of the portion arising from the transverse ligament its origins at all points are from an inch to nearly two inches in extent. Passing in various directions, ac cording to their several situations, the fibres run to be inserted into the base of the neck of the femur, anteriorly into the anterior inter trochanteric line, superiorly and externally into the surface of the bone close to the digital fossa at the root of the great trochanter, inferi orly and internally to the line leading from the lesser trochanter to the anterior inter-trochan teric line, and posteriorly it is partly reflected upwards, so as to become continuous with the periosteum of the posterior part of the neck of the bone; this reflection taking place along the posterior inter-trochanteric line, and partly in serted into that line, especially at its internal and external extremities. The reflected portion is derived from the deep fibres of the capsule, which in passing upwards to be inserted into the bone at the circumference of the head, con tribute to form those hands of fibrous mem brane, which are manifest on the posterior aspect of the neck of the femur on opening the cap sule, being covered only by synovial membrane. These bands are sometimes of considerable strength, and they are well described and figured by Weitbrecht,. by whom they were designated retinacula.
We have already observed that the capsular ligament is not uniform in thickness at all points. At the outer part of its anterior sur face its thickness is very considerable, being strengthened and increased by a band of fibres of some magnitude (accessory ligament ), arising from the inferior anterior spine of the ilium and the space beneath, from which they descend, diverging to be inserted into the anterior inter trochanteric line ; these fibres are so much de veloped in some instances as almost to re semble a distinct ligament. At this point the capsule is nearly half an inch thick. Externally its thickness is considerable, though somewhat less than at the point last described. From the pubis a smaller and thinner band of acces sory fibres may be traced towards the lesser trochanter, strengthening the capsule in this situation ; between the two accessory bands in the centre of the anterior surface, the capsule is extremely thin, and sometimes wholly destitute of fibrous tissue, being altogether composed of synovial membrane, and a little cellular tissue, by which it is separated from the bursa that lies under the tendon of the psoas muscle: this bursa, moreover, sometimes communicates with the cavity of the joint through an opening in this situation.