Tibia Fibula | Gross Anatomy | Anjani Mishra

GROSS STUDY OF TIBIA-FIBULA(LEG)                

Written By Anjani Mishra

THE TIBIA(OX)

Type: It is long and massive bone.

Shape: It is distinctly curved; three sided above and smaller & flattened below.

Direction: Placed obliquely downward and backward.

Relation: It is related with the the femur above and tarsus below.

Articulation: It articulates proximally with the distal extrimity of femur forming a stiffle joint and distally with tarsal bones forming a hock joint.

Location: Present in hind limb at leg position.

Composition: 1 shaft & 2 extremities.

Shaft:

     It presents 3 surfaces & 3 borders.
 

Surfaces:

Lateral surface:

• It is slightly spiral in its direction.
• The surface is concave above, convex in middle and nearly flat below.
• Lodges tibialis anterior muscle. 

Posterior Surface:

• It is flattened from side to side.
• Towards the medial border there is a narrow triangular area for the insertion of the popliteus muscle.
• The remaining part of this surface is marked by a number of rough lines, the linea muscularis, which serve for the origin of flexor muscle. 

Medial Surface:

• It is slightly convex.
• It is rough at upper part for the attachment of sartorious, gracilis and semi-membranous muscles and medial ligament of the femor-tibial articulation.
• Below it is narrower, smooth and subcutaneously placed.

Borders:

Anterior Border:

•  It is very prominent in upper third and constitutes the tibial crest.
• The rest of its extent is rounded and indistinct.
• The crest, at its extent is rounded and indistinct.
• The crest, at its medial aspect, presents a rough prominence for the insertion of semitendinosous and a part of biceps femoris. 

Lateral Border:

• It is concave lengthwise.
• There is a space between fibrous cord and the lateral border of the tibia, through which anterior tibial vessel passes outward and forward. 

Medial Border:

•  It is thicker and rounded in its dorsal half and gives attachment to the popliteus muscle.

Extremities:

Proximal Extremity:

•  It is large and consists of 3 tuberosities and 2 condyles.
• The anterior tuberosity is non-articular prominence placed in front of the proximal extremity.
• It continues below with the tibial crest and gives attachment to the three straight ligaments of patella.
• Between anterior tuberosity and lateral condyle, there is a deep, smooth semicircular notch called sulculus muscularis, for the passage of common tendon of the proneus tertius, common digital extensor and medial digital extensor.
• The condyles are medial and lateral, and they stand on top of the medial and lateral tuberosities.
• Each condyles is swaddle-shaped articular surface, which is prolonged on the spine for articulation with the corresponding condyle of the femur, through the medium of an inter-articular fibro-cartilage.
• The three tuberosities are separated by inter tuberal fossa.
• The tibial spine is a central articular eminence divided into a medial higher and lateral lower part.
• The rudimentary fibula is attached to the lateral tuberosity.

Distal Extremity:

• It is much smaller than the proximal extrimity and articulates with the tibial and fibular tarsal.
• The surface is compounded of two deep antero-posterior grooves separated by an articular ridge.
• The medial groove is bounded by the medial malleolus, while the lateral groove is separated by a sharp border which articulates with the lateral malleolus.
• The anterior part of the medial malleolus is prolonged downward and is pointed. 
• The lateral malleolus is a separate piece of bone which articulates with the tibia to complete the lateral groove. 
• This small piece of bone is placed between the proximal ends of the tibial tarsal and the distal end of the fibular tarsal at their lateral aspect.

Comparison with:

A) Tibia of Horse:

•  Comparatively larger and longer.
• Ridges on posterior surface are more.
• The posterior surface is divided into two by an oblique popliteal line.
•   Nutrient foramen is either on or near to the popliteal line.
• The anterior tuberosity is vertically grooved.
•   Sulcus muscularis is wider.
• There is a face on outerside of the lateral tuberosity for the articulation with the fibula
• The grooves and ridge on the distal extremity are directed obliquely downward and outward.
• The lateral groove is wider but shallower than the medial.
• The lateral malleolus is not a separate piece but is wider than that of ox while the medial malleolus is more prominent of the two.

B) Tibia of Dog:

• Tibia is as long as the fibula.
• Shaft forms a double curve, the proximal part is convex medially and distal part is convex laterally.
• The tibial crest is more prominent but short.
• Nutrient foramen is usually found in the upper third of the lateral border.
• The anterior tuberosity is not grooved.
• The distal extremity is small and four sided.
• The lateral malleolus is not fused with the distal extremity.

C) Tibia of Pig:

•  More similar with than that of ox.
• The tuberosity is grooved in front, and a narrow sulcus separates it from lateral condyle.
• The posterior part of the crest is very prominent and curves outwards.
• The sulcus is narrow.
• It presents a proximal and distal facet for articulation with the fibula at lateral aspect.

D) Tibia of Goat:

• It is long and slender, but otherwise resembles to that of ox.

E) Tibia of Fowl:

 Fig: The skeleton of fowl showing tibia fibula

  30. Fibula, 31. Tibia, 32. Metatarsus

• The tibia in reality is tibio-tarsus because the bone of the proximal row of the tarsus are fused with the distal end of tibia.
•   Shaft is nearly straight.
• Tibial crest is prominent.
• Distal end is condyloid.
• This is the largest bone of the body.

         THE FIBULA

• The fibula is rudimentary bone.
• In young it is in the form of fibrous cord extending from the lateral tuberosity of the  tibia to the lateral maleolus.
• In adult, the proximal end of this fibrous cord becomes ossified, and the head of the fibula is fused with lateral tuberosity of tibia.
• The distal extremity also ossifies but remains separate as the lateral maleolus.
• The body later gets reduced to a small, short blunt and elongated prolongation of the fibrous cord.
• The body and the distal end remain as the blunt prolongation.

Comparison with:

A) Fibula of Horse:

• Better developed than in the ox.
• It is an aborted long bone and looks like a splint bone.
• It presents a body and two extremities.
• Fibula is placed along the lateral border of tibia.
• Proximal extremity or the head is the thickest portion of the bone.
• Distal extremity forms a sharp pointed end and terminates in the lower third of the tibia.
• Anterior and posterior borders are thick and blunt.

B) Fibula of Dog:

• Fibula is as long as tibia and is slender, slightly twisted and larger at either extremities.
• The proximal part of the shaft is separated form the tibia by a large interosseous space, but the middle and the lower parts are flattened and closely attached to the tibia by interosseous ligament. 
• The distal extremity forms the lateral maleolus which articulates with the tibia and the tibial tarsal medially.
  

C) Fibula of Pig:

•  Fibula is thin bone and extends the entire length of tibia, separated by a wide interosseous space.
• The shaft is flattened from side to side.
• The proximal part is wide and deeply grooved laterally.
• The distal part is narrower and thicker.

D) Fibula of Goat:

• The fibula has no shaft, and its proximal end is represented by small prominence below the lateral margin of the lateral tuberosity of the tibia.
• The distal end forms the lateral maleolus, as in the ox.

 

E) Fibula of Fowl:

• Fibula is much reduced long bone.
• The articular head is massive and is flattened from side to side.
• The body is slender and tapers to a point one-half way down the tibia. 
• The proximal extrimity is enlarged and is flattened transversally. It articulates with the lateral condyles of the femur and tibia.

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