THE AXKLE 1197 



outer surface of the calcaneum. It keeps the two peronei in place, and surrounds 

 them behind the fibula in one sheath with a single synovial sac, which extends 

 upwards into the leg for an inch and a half, and sends' two prtK-esses into the two 

 sheatlis in Avhich the tendons lie on the calcaneum. Farther on, while in relation 

 with the cul)oid, the peroneus longus has a second synovial sheath. 



( H) Internal. — This crosses from the internal malleolus to the inner surface of 

 the calcaneum. Beneath it are the following canals: (1) For the tibialis posticus. 

 This tendon-sheath is lined by a synovial memljrane extending from a point an 

 inch and a half above the malleolus to the scaphoid. (2) For the flexor longus 

 digitorum. The synovial sheath of this tendon is separate from that of the closely 

 contiguous til)ialis posticus. It extends upwards into the leg about as high as the 

 sheath just given. It reaches down into the sole of the foot; but where the tendon 

 subdivides to enter the thecse, each of these is lined by a se[)arate synovial sheath. 

 Next comes (3) a wide space for the posterior tibial vessels and nerve; and, lastlv, 

 (4) a canal, like the otlier two, with a separate synovial sheath, for the tendon of 

 the flexor longus hallucis. 



(Cj Anterior annular ligament. — This is a double structure. (1) Upper, 

 above the level of the ankle-joint, and tying the tendons down to the lower third 

 of the leg, it passes transversely between the anterior crest of the tibia and fibula. 

 Here is one sheath only, with a synovial membrane for the tibialis anticus. 

 (2) Lower, over the ankle-joint. This band is arranged like the letter •<, 

 placed thus (fig. 759;. It is attached by its root to the calcaneum, and by its 

 bifurcations to the internal malleolus and the fascia of the sole. This arrange- 

 ment of the branches of this ligament is not constant. In this, the lower annular 

 ligament, there are usually three sheaths with separate synovial membranes — the 

 innermost (the strongest in each) for the tibialis anticus, the next for the extensor 

 proprius hallucis, and the third common to the extensor cornnumis and peroneus 

 ti-rtius. 



Points in tenotomy and guides to the tendons. — The tendo Achillis 

 sliould be divided about an inch and a half above its insertion, its narrowest point, 

 which is about on a level with the internal malleolus. The knife should be intro- 

 duced on the inner side and close to the tendon, so as to avoid the posterior tiljial 

 artery (fig. 756). 



The tibialis anticus is often cut about an inch above its insertion into the 

 internal cuneiform, a point whicli is below the level of its synovial sheath. The 

 tendon has here the dorsalis pedis on its outer side, but scjiarated Ijy the tendon of 

 the extensor proprius hallucis. The knife is introduced on this side. 



The tibialis posticus. — The usual rule for dividing this tendon is to take a 

 spot two inches above the internal malleolus, and as accurately as possiljle midwav 

 between the anterior and internal borders of the leg. This point will give the inner 

 margin of the tibia, in close apposition to which the tendon is lying, and is a point 

 at which the tendon is rather farther from the artery than it is below, and is also 

 above the commencement of its synovial sheath. A sharp-pointed knife is used 

 first to open the sheath freely, and then a blunt-pointed one to divide the tendon. 

 The fiexor longus digitorum is usually cut at the same time. 



Owing to the great difficulty in making sure of dividing the tibialis posticus 

 tendon at this spot, and the risk of cutting the posterior tibial artery (fig. 756), it 

 has been advised of late years (Parker) to divide this tendon together with that of 

 the anticus simultaneously by an incision a little below and anterior to the tip of 

 the internal malleolus. Other guides are the position of the astragalf>-sca})hoid 

 joint, and, where the deformity is of gome standing, the crease wliich denotes the 

 inversion of the foot. The position of the two tibial arteries should be noted, and 

 also the lines along which the tendons are converging — the one across the lower 

 end of the tibia, the other from behind tlie tibia and below the sustentaculum tali 

 to the line of the scaphoid and internal cuneiform. Mr. R. W. Parker has nanu-d 

 this operation syndesmotomy, as he rightly considers that the astragalo-scaphoid 

 ligaments require division at the same time. 



Peronei. — The peronei, longus and brevis, may be divi<leti two inches above the 

 external malleolus, so as to be above the level of their synovial sheath. The knife 

 should be inserted verv close to the bone, so as to i)ass between the fibula and the 



