588 A MANUAL OF ANATOMY 



supply from the dorsalis pedis artery and its metatarsal branch, 

 the internal plantar artery, and the plantar arch. 



Nerve-supply. — ^The dorsalis pedis, internal plantar, and external 

 plantar nerves. 



Movements at the Tarso-metatarsal Joints. — The movements allowed are 

 flexion and extension. At the internal tarso-metatarsal joint flexion is 

 associated with a certain amount of abduction, whilst extension is accom- 

 panied by sUght adduction. At the middle tarso-metatarsal joint flexion 

 and extension are allowed, but no lateral movement. At the cubo-metatarsal 

 joint flexion and extension, combined with abduction and adduction, are 

 allowed, lateral movement being tolerably free in the case of the fifth meta- 

 tarsal. A certain amount of gliding or to-and-fro movement is also per- 

 missible at the tarso-metatarsal joints in the following manner : the third 

 metatarsal base can glide upwards, whilst the pair on either side of it can glide 

 downwards, the effect being to diminish the span of the transverse arch of the 

 foot. When the reverse movement takes place the span of the arch is increased. 



The portion of the transverse arch which is formed by the bases of the 

 metatarsal bones has the following muscles attached to its various parts : 

 tibialis posticus, adductor obliquus hallucis, peroneus longus, flexor brevis 

 minimi digiti, and tibialis anticus. The first three muscles diminish the 

 span, and so deepen the arch, whilst the tibialis anticus increases the span, 

 and so renders the arch wider. 



Surgical Anatomy of the Tarso-metatarsal Joints. — It is in this situation 

 where Lisfranc's and Hey's amputations are performed. The guide to the 

 line of articulation on the outer border of the foot is the tuberosity on the 

 outer side of the base of the fifth metatarsal, which can always be felt 

 without difficulty. The joint between the cuboid and the fifth metatarsal 

 is situated immediately behind this tuberosity. The guide to the line of 

 articulation on the inner border of the foot is a point i^ inches in front of the 

 tuberosity of the navicular bone. The line of articulation is in no sense 

 transverse, its inner part being about i inch further forwards than the outer 

 part. The tarso-metatarsal joints are remarkable for their irregularity, which 

 is due to two causes. In the first place, the anterior surfaces of the three 

 cuneiform bones do not present an even frontage. The internal and external 

 cuneiform project further forwards than the middle cuneiform, and so a 

 recess is formed which receives the base of the second metatarsal as that 

 extends backwards to articulate with the middle cuneiform. The base of 

 the second metatarsal thus becomes locked between the internal and external 

 cuneiform. In the second place, the external cuneiform extends a Uttle 

 further forwards than the cuboid. The line of the tarso-metatarsal articula- 

 tions, from the inner border of the foot to the outer border, is as follows : 

 (i) outwards, between the internal cuneiform and first metatarsal ; (2) back- 

 wards, for about ^ inch (at this stage a very strong interosseous ligament has 

 to be divided, as it passes between the internal cuneiform and the inner side 

 of the base of the second metatarsal ; (3) outwards, between the middle 

 cuneiform and second metatarsal ; (4) forwards, for about | inch ; (5) outwards, 

 between the external cuneiform and third metatarsal ; (6) backwards, for 

 about J inch ; and (7) outwards and backwards, between the cuboid and the 

 fourth and fifth metatarsals. 



The Intermetatarsal Joints. 



The basal intermetatarsal joints belong to the class diarthrosis, 

 and to the subdivision arthrodia. The bones concerned are the 

 outer four metatarsals. The first metatarsal bone does not usually 

 articulate with the second, but sometimes it does. The ligaments 

 are dorsal, plantar, and interosseous. . 



