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Acetabular Canal. Part 3.

 

Acetabular CanalPart 3

S.V. Arkhipov, Independent Researcher, Joensuu, Finland


Abstract

This article describes the space where the ligamentum capitis femoris (LCF) attaches and functions. See also Part 1 and Part 2.

 

The Significance of the Acetabular Canal

The acetabular canal contains the main areas of attachment for the LCF (ligamentum capitis femoris). Its distal end attaches to the femoral head, while the proximal end connects to the fossa and notch of the acetabulum. The primary purpose of the acetabular canal is to ensure the normal functioning of the LCF. Normally, the LCF should not come into contact with the joint surfaces. Therefore, the length of the LCF should not exceed the diameter of the acetabular fossa, i.e., the diameter of the central section of the acetabular canal Its depth should be less than the thickness of the LCF.



Figure 1. Lateral wall of the acetabular canal and LCF; the bottom of the acetabulum is removed (from 1908GrayH). 

The diameter and depth of the acetabular fossa, and thus the acetabular canal, are critical dimensions for the LCF. A reduction in depth results in the bottom of the acetabular fossa approaching the articular surface of the femoral head, which has been observed by us and other authors in the older age group (1972ПодрушнякЕП; 2012АрхиповСВ). In this case, the LCF becomes compressed between the lateral wall of the acetabular canal—the cartilage surface of the femoral head—and the medial wall, the bottom of the acetabular fossa, covered by synovial and adipose tissue. Figuratively speaking, even in a normal state, the LCF is constantly caught "between Scylla and Charybdis." Continuing with this analogy, it can be said that the compressed LCF within the acetabular canal will inevitably be destroyed, much like the ships destroyed by the clashing rocks of the Symplegades in Greek mythology. The gradual compression of the LCF leads to its flattening and thinning due to abrasion, as well as histological transformation. As the LCF becomes fragile, it tears under what were previously normal stretching loads.


Visualization of the Acetabular Canal

Due to the deep location of the hip joint, it is impossible to palpate the entrance to the acetabular canal, let alone see it with the naked eye. The acetabular canal only exists when the femoral head and the acetabulum are in articulation. In ancient times, the contents of the acetabular canal were studied during post-mortem dislocation of the femoral head. It was first observed during the preparation of a deceased body for burial. The first post-mortem arthrotomy of the hip joint with hip disarticulation is presumed to have occurred in Morocco 15,000-12,500 years ago (2016MariottiV_CondemiS). Remains of a human aged 8,000-4,500 years with signs of hip disarticulation were discovered in southern China (2024YeZ_LiFJ). The acetabular canal was also examined during the preparation of bodies for mummification. The oldest embalmed body discovered in Chile is approximately 7,900±180 years old (1984AllisonMJ_LowensteinJM).

It seems that the first physicians to observe the acetabular canal were Herophilus of Chalcedon and Erasistratus of Ceos. These anatomists, in the 3rd-2nd century BCE, conducted hundreds of dissections in Alexandria (1831CelsusAC). The first to propose access to the acetabular canal by removing the anterior wall of the acetabulum was P.N. Gerdy (1833). The first successful penetration into the acetabular canal from the pelvic side was performed by W. Weber and E. Weber, who drilled a hole in the bottom of the acetabular fossa (1836WeberW_WeberE). The contents of the acetabular canal were first observed from the medial side by J. Struthers and G.M. Humphry. They made an opening in the bottom of the acetabular fossa (1858StruthersJ; 1858HumphryGM).


 Figure 2. Lateral wall of the acetabular canal and LCF; the bottom of the acetabulum is removed (from 1904FickR). 

Today, the study of the acetabular canal is inconceivable without the use of instrumental methods. Its visualization is available radiologically, for example, via plain radiography of the hip joint.


Figure 3. The acetabular canal (indicated by an arrow) in a radiograph; top – fragment of a standard anteroposterior X-ray of the hip joint; bottom – X-ray of the hip joint in the axial projection by Launstein (personal observation).


In radiography, the transverse ligament in the outer segment of the peripheral part of the acetabular canal is indistinguishable. As a result, this segment appears larger in cross-section on the X-ray than in reality. In children, the contents of the acetabular canal can be visualized using ultrasound.

Radiography allows visualization of the medial and lateral walls of the acetabular canal. A detailed view of its shape and dimensions can be obtained using computed tomography (CT) of the hip joint.


Figure 4. The acetabular canal (indicated by an arrow) visualized by computed tomography; top – fragment of a horizontal scan of the hip joint; bottom – fragment of a frontal scan of the hip joint (personal observation).


Three-dimensional reconstruction of CT scans of the hip joint enables visualization of the "entrance" to the acetabular canal, specifically the external opening of the acetabular notch.


Figure 5. External opening of the acetabular canal ("entrance" indicated by an arrow), 3D reconstruction of computed tomography; top – hip joint, front view; bottom – hip joint, bottom view (personal observation).


Viewed from below during X-ray tomography, the "entrance" to the acetabular canal has a pear-shaped form. It is wider at the back and narrower at the front. In cases of hip joint trauma, the configuration of the external opening leading to the acetabular canal may change.


Figure 6. Change in the configuration of the entrance to the acetabular canal (indicated by an arrow) in case of a fracture of the acetabular fossa with dislocation of the femoral head outward (3D reconstruction from computed tomography, bottom view, personal observation).


In some cases, CT of the hip joint reveals a shadow of the LCF in the acetabular canal. More detailed visualization of the contents of the acetabular canal can be achieved using magnetic resonance imaging (MRI) of the hip joint.


Figure 7. The acetabular canal on magnetic resonance imaging, the shadow of the LCF indicated by an arrow; top – fragment of a horizontal scan of the hip joint; bottom – fragment of a frontal scan of the hip joint (personal observation).


MRI, especially with contrast, allows differentiation of the contents of the acetabular canal: LCF, adipose tissue accumulation, cartilage surfaces, synovial fluid, synovial membrane folds, and the transverse ligament of the acetabulum.

As age increases, the depth of the acetabular fossa decreases and may even disappear entirely (1972ПодрушнякЕП). We observed the absence of the acetabular canal in the fourth stage of osteoarthritis. 


Figure 8. View of a hip joint affected by osteoarthritis of the fourth degree; area of the acetabular canal filled with newly formed bone tissue indicated by an arrow (fragment of a standard anteroposterior X-ray, personal observation).


The fossa and notch of the acetabulum usually disappear in protrusion coxarthrosis. Additionally, the acetabular canal may become filled with fibrous tissue, osteophytes, chondral bodies, and cartilage fragments. Newly formed bone and scar tissue, a deformed acetabular fossa, free joint bodies, as well as osteophytes from the deformed femoral head and the internal edges of the lunate surface, lead to damage of the LCF during movement (see Pathology of the Acetabular Canal). We believe this is one of the reasons for the disappearance of the LCF.


References

Allison MJ, Focacci G, Arriaza B, Standen V, Rivera M, Lowenstein JM. Chinchorro, momias de preparación complicada: métodos de momificación. Chungara: Revista de Antropología Chilena. 1984;13:155-73.

Celsus AC. On medicine, in eight books, Latin and English. Translated from L. Targa's edition, the words of the text being arranged in the order of construction. To which are prefixed, a life of the author, tables of weights and measures, with explanatory notes, etc. designed to facilitate the progress of medical students. By Alex. Lee, A.M., Surg. In two volumes. London: E. Cox, MDCCCXXXI [1831].

Gerdy PN. Physiologie médicale, didactique et critique. T. 1. Paris: Librairie de Crochard, 1833.

Gray H. Anatomy, descriptive and surgical; 17th ed. Philadelphia, New York: Lea & Febiger, 1908. 

Fick R. Handbuch der Anatomie und Mechanik der Gelenke: Erster Teil: Anatomie der Gelenke. Jena: G. Fischer, 1904. 

Humphry GM. A Treatise on the Human Skeleton including the Joints. Cambridge: MacMillan and Company, 1858.

Mariotti V, Belcastro MG, Condemi S. From corpse to bones: funerary rituals of the Taforalt Iberomaurusian population. Bulletins et Memoires de la Societe d'Anthropologie de Paris. 2016;28(1-2)60-5. 

Struthers J. Demonstration of the use of the round ligament of the hip joint. Edinburgh Med J. 1858;4(5)434-42. 

Weber W, Weber E. Mechanik der menschlichen Gehwerkzeuge: eine anatomisch-physiologische Untersuchung. Gottingen: Dietrichsche Buchhandlung, 1836.

Ye Z, Wang M, Stock JT, Li FJ. Disarticulation, evisceration and excarnation: Neolithic mortuary practices at Dingsishan, southern China. Antiquity. 2024;98(399)616-35. 

Архипов СВ. Роль связки головки бедренной кости в патогенезе коксартроза: дис. … канд. мед. наук. Москва, 2012. 

Подрушняк ЕП. Возрастные изменения суставов человека. Киев: Здоров‘я, 1972. 


Keywords

ligamentum capitis femoris, ligamentum teres, ligament of head of femur, acetabular canal, anatomy, attachment


                                                                     

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