Article by Walmsley T. A note on the retinacula of Weitbrecht (1916). The author discusses the embryonic development and relationships of the ligamentum capitis femoris (LCF) in humans and animals.
A NOTE ON THE
RETINACULA OF WEITBRECHT.
By THOMAS WALMSLEY, M.B., Senior Demonstrator in Anatomy, University of Glasgow.
The synovial membrane of the hip-joint is in extent
and attachment similar to that of other diarthroses, but the retinacula of
Weitbrecht (or ligaments of Stanley) lend to it a special interest. These
retinacula are readily recognized on the interior of the capsule as flattened
bands passing inwards towards the margin of the head of the femur from the
attachment of the peripheral capsule. The following description of their
constitution may be selected as expressive of current opinion. The retinacula
are arranged in three groups, superior, middle, and inferior: structurally,
they are synovial covered capsular reflections: morphologically, the inferior
set is said to represent the persistent retinaculunm of the invaginated
ligamentum teres (Keith), while the superior set has been described by Frazer
as being entirely due to medially directed reflections of the tendon of the M.
pyriformis: functionally, they are developed either to prevent intracapsular fracture
of the neck of the femur in the infant (Fawcett) or, if that has already
occurred, as a means of fixation of the fragments (Hepburn in Cunningham).
These descriptions form the bases of this study of these bands.
The blood-vessels which perforate the capsular
attachment and pass along the superficies of the neck of the femur to enter the
foramina towards the articular margin of the head may be shown by X-ray photographs
of mercury-injected specimens to terminate in the metaphysis of the neck and
the epiphysis of the head. From the points where they perforate the capsule
these vessels derive and carry inwards indefinite fibrous prolongations of the
capsule wall which are covered over or are completely invested by reflections
of synovial membrane. These elements constitute the retinacula of Weitbrecht.
The fibrous prolongations terminate by fusion with the superficial structures
of the neck at varying and indefinite distances from their origin, while the
synovial reflections pass onwards to the cartilaginous margin of the head where
they form the coverings of the " synovial pads of fat." In Haver's
definition the term synovial pad is applied to a mass of vascularised fat
invested by synovial membrane locally modified for the production of synovia.
In addition, however, to the glandular function of the covering membrane, these
masses act as movable pads, which are drawn into and occupy the more obvious
peripheral spaces which would otherwise occur between the articular surfaces of
organic joints during their action.
This separation of the articular surfaces, as I shall
show in a forthcoming publication, is peculiar to organic joints, and to fill
the potential intervals movable and yielding structures are required: and such
are found in two modifications (Goodsir). If space alone is to be occupied
synovial pads fulfil the requirements, and associated with each pad is a
synovial mechanism for the regulation of its movements; but if resistance to
pressure is an additional function fibrocartilaginous tissue is necessary.
In connection with the hip-joint there are three
synovial pads: two are in relation to the articular margin of the head of the
femur, and the third is situated in the acetabular fossa. The femoral pads are
placed in the superior and inferior concavities of the articular margin of the
head at the medial ends of the synovial retinacula. Both are freely movable on
the underlying tissues of the neck, so that on semi-flexion of the limb, when
the whole peripheral capsule, and therefore the synovial retinacula, are
relaxed, these pads react to the suction action generated in the joint within
the cotyloid ligament, and move so that the inferior comes to lie on the pubic portion
of the acetabular margin and occupies an interval which would otherwise be
created between that part of the acetabular surface and the femoral neck
adjacent to the receding margin of the head. When the inferior retinacula are
stretched, as occurs in the tightening of the capsule in extension or
hyperflexion, they pull on the synovial pad and flattening it on the neck of
the bone remove it from any possible intervention between the articular surface
of the acetabulum and the advancing margin of the femoral head. These pads,
then, are placed so as to equalise the uneven articular margin of the head of
the femur in its varying position on the uniform margin of the acetabulum, and
their synovial mechanisms are the retinacula of Weitbrecht. The acetabular pad
is placed in the acetabular fossa superficial to its thin easily detached
periosteum, to which it is movably united by weak ligamentous connections and
fine vascular channels. The amount of the mass varies in individual cases and
may here and there seem to be deficient, especially in the upper part of the
fossa, but normally is of volume more than sufficient to fill the acetabular
fossa, the excess being necessary in its function. The movements of this pad
are such that on semi-flexion of the limb it passes into the acetabulum under
the action of the suction force within the joint and controlled by the synovial
covering of the lig. teres, and abolishes the interval which would otherwise be
produced by the apical displacement of the head of the femur: and this movement
is visible from the peripheral aspect of the joint as an "indrawing"
of the structures superficial to the "acetabular gap." On extension
of the limb the excessive portion of the pad is visibly protruded through the
acetabular gap, and reaches that position not by an expulsive action of the
advancing apical part of the femoral head but by being actively withdrawn by
its peculiar synovial retinaculum attached to the superficial part of the lig.
teres.
The suction action generated within the joint is
entirely within the cotyloid ligament, and is obtained because of the
atmospheric vacuum within that part of the articulation in which the joint surfaces
undergo separation from one another. Between the articular surfaces, however, there
will be at no time any interval unoccupied by synovial fluid or unobliterated
by the movable walls of the containing cavity or of the contained femoral head,
since the induction of a vacuum interval by separation of the surfaces would
determine the onset of a force active in the re-establishment of surface
contact, but detrimental, since in direct opposition, to the working of the
contracting muscles. In the lateral movement of the head of the femur which
accompanies its rotation to semi-flexion from the extended position the apical
interval is avoided by the movement of the acetabular pad, which falls into the
acetabulum and diminishes its cubic content. The cotyloid ligament, on the
other hand, is expanded by the lateral movement of the head and thus the volume
of the cavity is increased, but the movements of the femoral pads avoid the appearance
of any marginal interval.
We have determined these facts in the adult human
subject, and after consideration of the retinacula in some of the domestic
carnivore, (1) certain of the ungulata, (l) and in one of the apes, feel that
the following conclusions are justified: That the incidence of the retinacula
is coincident with the blood-vessels of the epiphysis of the head and
metaphysis of the neck as determined by dissection of the recent specimen or by
analysis of the vascular foramina in the macerated bone: that they are
reflections of the synovial membrane over the fibrous sheaths of these vessels,
and the sheaths are indefinite prolongations of the capsule wall: that they
serve as an active mechanism in the function of the femoral synovial pads. Further,
we would believe that none of them possesses any peculiar morphological
significance, but that they are developed and are retained permanently where
they will be free from direct capsular pressure and are associated with the
blood-vessels and synovial pads purposively and precisely in those situations.
(1) In these groups there is no superior retinaculum,
nor superior femoral synovial pad, owing to the shape and articular incidence
of that area of the femoral head.
In denying the morphological significance of the
inferior retinaculum it seems reasonable to conclude that the view advanced by
Keith is in itself insufficient to account for the persistent retention of a
structure, of importance only at so remote a stage in phylogeny: nor is it in
agreement with the facts of comparative embryology. In the human embryo the lig.
teres is completely free at the first appearance of the joint cleft: in the
embryo tapir a synovial mesentery binds the ligament to the capsule wall, while
in the adult the ligament is invested as in the human subject (Welcher): in the
walrus, where the limb pertains to the reptilian type, the ligament arises
within the joint cavity permanently enfolded in a synovial reflection from the
capsule (Moser). We believe these facts to indicate that the inferior femoral
retinaculum does not represent, in whole at least, the persistent remains of
the mesentery of the invaginated lig. teres, but that this mesentery would, and
possibly does occur, as the retinaculuin of the acetabular pad of fat (also
described by Weitbrecht) which arises in relation to the extra-acetabular part
of the lig. teres and invests the blood-vessels passing through the acetabular
gap to the acetabular synovial pad. As regards the superior group being the
direct prolongation of the tendon of the M. pyriformis, we believe this to be
the seeming result of the fusion of that tendinous expansion with the capsule,
and that it is from the capsule that the fibrous elements of the retinaculum
are derived. In the majority of mammalian groups (of all we have examined) the
superior retinaculum is absent, and this we have associated with the shape of
the articular femoral head.
In the infant the retinacula are of relatively larger
size than in the adult, and we would relate the fact to the relatively larger
blood-vessels which pass to the head at that period.
External
links
Walmsley T. A note on the retinacula of Weitbrecht. Journal
of Anatomy. 1916;51(Pt 1)61-4. ncbi.nlm.nih.gov
Authors
& Affiliations
Thomas Walmsley (1889-1951) was a Scottish anatomist, Professor
of Anatomy at Queen's University, Belfast. wikipedia.org
Keywords
ligamentum
capitis femoris, ligamentum teres, ligament of head of femur, anatomy,
embryology, development, animals
NB! Fair practice / use: copied for the purposes of criticism, review, comment, research and private study in accordance with Copyright Laws of the US: 17 U.S.C. §107; Copyright Law of the EU: Dir. 2001/29/EC, art.5/3a,d; Copyright Law of the RU: ГК РФ ст.1274/1.1-2,7
Comments
Post a Comment