eChapters

Sites for surgical interventions

Luxation of patella in cattle and horses

The luxation of patella is a condition wherein the patella of the stifle joint (femoropatellar articulation) is locked above the medial ridge of the trochlea of the femur.

Anatomy of femoropatellar articulation of the stifle joint

The stifle joint is a composite joint formed in two parts. One of these is an articulation between the condyles of distal extremity of femur and the condyles of the proximal extremity of tibia (femoro-tibial articulation) and the other is the articulation between the trochlea of the distal extremity of the femur and the articular surface of the patella (femoro-patellar articulation).

The trochlea of the femur consists of two asymmetrical ridges separated by a groove. The medial ridge is more prominent, wider and a little more extended dorsally than the lateral ridge. The two ridges converge ventrally. The articular surface of the patella is more or less quadrilateral or triangular with the base above and apex below. It has a vertical ridge in the middle and it separates the two concave areas of which the medial one is larger than the lateral. The patella is fastened against the trochlea with the help of three types of ligaments. One of these is the capsular ligament which is attached to the periphery of the articular areas of the two segments of the joint. The other one is the medial and lateral collateral ligaments. The third set of ligaments is the patellar (straight) ligaments.

Horse

The lumbosacral plexus in horse is formed by last three lumbar and first two sacral nerves, similar to that in ox. The caudal gluteal nerve divides into two branches. The medial branch supplies the superficial gluteal muscle in addition to the middle and deep gluteal and biceps femoris muscles. The lateral branch reaches the level of tuber ischii and terminates into the semitendinosus muscle at the perineal region. The sciatic nerve is almost similar to that of ox in the disposition and distribution of its branches. The superficial and deep peroneal nerves are also similar to those of ox. The tibial nerve divides at the distal third of the leg into medial and lateral plantar nerves. Each plantar nerve divides at the fetlock into cranial, middle and caudal digital nerves.

Dog

The lumbosacral plexus in dog is formed by the last four or five lumbar and first two or three sacral nerves. The cranial gluteal nerve receives fibres from sixth and seventh lumbar and first and second sacral nerves. The caudal gluteal nerve arises from sixth and seventh lumbar and first sacral nerves. The sciatic nerve derives fibres from sixth and seventh lumbar and first and second sacral nerves. The lateral cutaneous nerve arises either from sciatic or from the peroneal nerve. The peroneal nerve divides into superficial and deep branches, similar to those of ox. The tibial nerve divides into medial and lateral plantar nerves at the level of distal third of the leg. The medial plantar nerve divides at the metatarsus into medial and lateral branches. The medial branch becomes the first plantar common digital nerve. It divides to form the plantar proper digital nerves of the first and second digits. The lateral branch divides into three plantar metatarsal nerves which unite, in the intermetatarsal space with the three plantar common digital nerves of the lateral plantar nerve. Each of these united plantar common digital nerves descends and after reaching at the metatarso-phalangeal articulation into three plantar proper digital nerves. The lateral plantar nerve, divides into three plantar common digital nerves which join the three plantar metatarsal nerves and form the plantar (caudal) proper digital nerves. The united proper digital nerves supply the second to fifth digit and terminate into the corresponding intermetatarsal space.

Pelvic (Lumbosacral) plexus

The hind limb is supplied by the nerve branches extending from the Pelvic (lumbosacral) plexus (Fig. 6-4 A and B) which is formed by the convergence of the ventral divisions of the last three lumbar and first two sacral nerves. It is formed in two parts, the cranial and caudal. The two parts are connected by anastomotic branches. The cranial (lumbar) part is formed by the fourth and fifth lumbar nerves and lies between the psoas major and psoas minor muscles while the caudal (sacral) part is formed by the sixth lumbar and first and second sacral nerves. Some times a root from third sacral also joins this part. It lies on the pelvic surface of the sacrosciatic (ischial) ligament. The nerves extending from the cranial part of the plexus are the lateral cutaneous femoral, the femoral and the obturator. The nerves extending from the caudal part are the cranial gluteal, caudal gluteal and the sciatic (ischiatic).

Lateral cutaneous femoral nerve

The lateral cutaneous femoral nerve while leaving the cranial part of the plexus, receives fibres from the fourth lumbar nerve, passes caudally between the psoas major and psoas minor muscles and reaches the tuber coxae. Here it perforates the obliquus abdominis externus muscle in company with the circumflex iliac artery and reaches the skin of the lateral aspect of the thigh. In this course, the nerve supplies the psoas major, psoas minor, iliacus and external oblique muscles of the abdomen and the skin and cutaneous muscle on the lateral face of the thigh.

Horse

The arteries of the hind limb of horse have in general similar architecture as that of ox except the special features mentioned below.

The deep circumflex iliac artery which is a branch of the external iliac artery in ox has a variable origin in horse. It may originate directly from the aorta or the common iliac trunk just prior to the origin of the external iliac artery. The prepubic and deep femoral arteries arise either by a common trunk or separately from the femoral artery. The obturator artery is a well developed independent branch of the femoral artery in horse as against its origin as a branch of deep femoral artery in ox. The saphenous artery is a small branch of femoral artery and it supplies the skin on the medial aspect of the thigh and leg. The popliteal artery terminates by its division into cranial and caudal tibial arteries at a lower level in horse than that in ox. The caudal tibial artery is larger and longer in horse than that in ox. From the proximal plantar arch extend four caudal metatarsal arteries instead of four, two of them are superficial and the other two deep branches. The large metatarsal artery descends along the groove between the large and lateral small metatarsal bone and divides just above the fetlock into lateral and medial digital arteries. Each digital artery divides at the middle of the wing of the third phalanx into preplantar and plantar digital arteries. The preplantar digital arteries supply the sensitive laminae of the sole. The plantar digital arteries of the opposite sides form anastomosis. Small laminar branches from the anastomosis form the circumflex artery of the toe which supplies branches to the sole.

The lymphatics of hind limb is comprised of four lymph nodes namely the deep inguinal, epigastric, coxal and popliteal lymph nodes and the afferents and efferent ducts joining and leaving these lymph nodes.

Deep inguinal lymph node

The deep inguinal lymph node is located in the region of deep femoral artery near the origin of the caudal epigastric and the pudic branches from it. The lymph node receives afferents from the muscles in the prepubic and the thigh regions. The efferent vessel from this lymph node joins and opens in the medial iliac lymph node.

Epigastric lymph node

The epigastric lymph node is inconstant. When present, it is located on the course of the caudal epigastric artery near the pubis on the medial surface of the rectus abdominis muscle. The afferents for this lymph node are received from the abdominal muscles and the peritoneum in the vicinity. The efferent vessel of this lymph node joins the medial iliac lymph node.

The venous drainage of hind limb begins from two digital venous plexuses, one for each digit, situated in the corium of the foot. From each of these plexuses extend three digital veins namely the dorsal common digital vein, the medial digital vein and the lateral digital vein. The digital veins in their upward course converge and form the metatarsal veins which in their turn continue upward in the leg region as tibial and popliteal veins and then in the thigh region as femoral vein which finally joins the external iliac vein as the chief vein of the hind limb.

Digital veins

The dorsal common digital vein arises from the corresponding digital plexus in the form of proper digital vein.The two proper digital veins ascend along the medial face of the corresponding digit and unite at about the middle of the interdigital space below the metatarso-phalangeal articulation (fetlock joint) and form the dorsal common digital vein. The later, thus formed, ascends through the interdigital space, crosses vertically the metatarso-phalangeal articulation and after reaching the distal extremity of the metatarsal bone continues upward as dorsal metatarsal vein.

The medial digital vein after arising from the digital venous plexus ascends along the caudomedial aspect of the medial digit in company with the satellite artery, shares a branch each from the dorsal common digital and lateral digital veins, ascends the medial face of the fetlock joint and is then continued up as the medial plantar metatarsal vein.

The lateral digital vein after arising from the digital venous plexus of the lateral digit passes upward in the interdigital space, communicates a branch to the dorsal common digital and medial digital veins and then ascends the lateral face of the fetlock joint and then is continued up as the lateral plantar metatarsal vein.

The main arterial trunk that supplies blood to the hind limb is the external iliac artery. As this trunk passes down through different segments (regions) of the limb it is differently named according to that segment or the region. In the abdomen it is named as iliac, in the thigh region as femoral, in the leg region as tibial and popliteal and down that the metatarsal artery and lastly the digital.

External iliac artery

The external iliac artery arises from the abdominal aorta ventral to the fifth or sixth lumbar vertebra. It descends at the side of the pelvic inlet ventrally and caudally along the tendon of psoas minor, crosses the tendon, reaches the cranial border of the pubis, gains the space between the sartorius and pectineus muscles and then continues in the thigh (femoral region) as the femoral artery. In this course it is covered by peritoneum and is related laterally to the psoas minor, sartorius and iliacus muscles, medially to the common iliac vein and caudally to the external iliac vein. The following are the collateral branches of the external iliac artery.

Horse

The tensor fasciae latae is less extensive.

The superficial gluteus exists separately. It is ‘V’ shaped. It originates from the lateral angle of ilium (tuber coxae) and gluteal fascia and is inserted to the third trochanter. The middle gluteus is the largest of the three gluteal muscles and is very extensive. It originates from the aponeurosis of the longissimus dorsi, extends as far forwards up to first lumbar vertebra and is inserted in three heads, to the trochanter major, the crest ventral to trochanter major and the trochanteric ridge. The deep gluteus is smaller than the middle gluteus and is inserted to the convexity of the trochanter major.

The biceps femoris has an additional insertion to the femur on the rough surface near the trochanter tertius.

The semitendinosus arises from the transverse processes of the first two or three coccygeal vertebrae. The semimembranosus is larger and arises from the sacrosciatic ligament also.

The sartorius does not arise from the shaft of the ilium. The gracilis is not so extensively fused to its fellow at the origin.

The obturator internus has an iliac part- the pisiformis. Its tendon passes through the lesser sciatic foramen and hence does not unite with that of the obturator externus.

Articularis genu is absent

The fascia covering the hind limb is the superficial and deep fascia. The superficial fascia is very scanty lies beneath the skin. It has the same general disposition as in other regions of the body. The deep fascia is in the form of a thick strong sheet covering the superficial layer of muscles over the medial aspect of the hind limb. From this sheet extend several septa that pass between different muscles or muscle groups in the thigh region. The deep fascia of the leg region continues cranially with the fascia of the thoracolumbar region. Caudally it is attached to the aponeurotic tendon of insertion of sartorius and gracilis muscles. The part of the deep fascia that continues on the lateral aspect of the thigh is the fascia lata which is continuous with the gluteal fascia dorsally.

The muscles of the hind limb (Fig. 6-3 A and B) are arranged into different regional, positional as well as functional groups. The muscles of hip and thigh region are arranged in the lateral, medial and cranial groups. The muscles of leg and foot are arranged in dorsolateral and plantar groups. The dorsolateral muscles are generally the extensors of tarsus and digits while the plantar muscles are the flexors of tarsus and digits.

Horse

The hip joint has an additional ligament called the pubio-femoral ligament. It arises from the prepubic tendon, passes dorsally and laterally and then caudally and lodges into the subpubic (pubio-femoral) groove, penetrates the capsular ligament, passes through the acetabular notch and is inserted into the fovea capitis behind the round ligament on the head of femur. This ligament is peculiar to solipeds and it prevents the side kicking. The absence of this ligament in ruminants allows them abduction freely and that is how the ruminants can kick sideways. As against this, the equines can kick only back way. The other difference about the hip joint in horse is that the cotyloid ligament is narrower because of the deeper acetabulum.

The stifle joint of horse in general resembles that of ox except that the middle patellar ligament is not so prominent as that in ox.

The tibio-fibular articulation in horse is a diarthrosis and an amphiarthrosis. The diarthrosis is formed between the lateral condyle of tibia and the head of the fibula. It has intimate capsular ligament. The amphiarthrosis is formed between the shafts of the tibia and the fibula. The shafts of the two bones are binded by the proximal and distal interosseous ligaments.

The hock joint of horse has minor differences with those of ox owing to the difference in the number of tarsal bones and their arrangement. The synovial membrane is supported everywhere except at the dorsomedial (craniomedial) aspect where it bulges out in the cases of bog-spavin. If there is a distension of tarsal sheath, it bulges out as two rounded swellings on either sides of the tendon of deep digital flexor. The movements at the hock joint are very limited.

The articulations of hind limb (pelvic limb) comprises the joints of pelvic region which include the sacro-iliac articulation, pelvic symphysis and the hip joint; the articulation of thigh region named as stifle joint; the articulation of tarsal or hock joint and the articulations of digits which include the metatarso-phalangeal joint (fetlock) joint, the proximal interphalangeal joint (pastern joint) and the distal interphalangeal joint (coffin joint). The joints of pelvic region especially the sacro-iliac joint and the pelvic symphysis have been described with the articulations of abdomen and pelvis.

Horse

The femur of horse is more massive than that in ox. The proximal third of the caudal surface of shaft of femur presents a rough eminence for attachment of biceps femoris muscle. The trochanter minor is a rough ridge like structure. The proximal third of the lateral border of shaft presents trochanter tertius for attachment of superficial gluteus muscle. The trochanter major is comprised of a convexity, a summit and a crest. The trochanteric ridge is vertical and it connects the trochanter major with the third trochanter. The lateral supracondyloid crest and the supracondyloid fossa are better developed in horse than that in ox. The patella of horse is wider and longer than that of ox.

The tibia in horse is relatively longer than that in ox. The popliteal line is prominent. It extends from the proximal third of the medial border, obliquely crosses the caudal surface and ends at the middle of the lateral border of the shaft of tibia. The medial border in its proximal third bears a small popliteal tubercle for attachment of popliteus muscle. The lateral border is attached to the shaft of the fibula and encloses an interosseous tibiofibular arch with the fibula. At the proximal extremity, the cranial tuberosity is vertically grooved. The lateral condyle on its lateral side presents facet for articulation with the proximal extremity of fibula. At the distal extremity, the grooves are oblique. The lateral malleolus is fused with the distal extremity of tibia, The medial malleolus is more prominent than the lateral one.

The hind limb (Fig. 6-1) is termed as pelvic limb and it consists of four segments-the pelvic or hip region, thigh, leg and the pes region. The skeleton of pelvic region is formed by the pelvic girdle (os coxae). The skeleton of thigh region is mainly formed by a long bone (thigh bone) the femur and at its lower extremity is a short sesamoid bone, the patella. The leg region is formed by two long bones, the larger one the tibia and the smaller one the fibula. The last segment, the pes has three subdivisions as tarsus, metatarsus and digits. The tarsus has five short bones arranged in two rows on par with the carpus of fore limb. The metatarsus is constituted by two bones of which one is a long bone called the large metatarsal and the other a short small rudimentary bone the small metatarsal bone. The last part of the hind limb is the digits which are constituted by six phalanges and six sesamoids like those of the forelimb.

Site for nerve block

Brachial plexus block

The brachial plexus is the key source of nerve supply to the fore limb. Loss of sensation below the elbow is achieved by blocking the nerve roots contributing to this plexus. In ox it is formed by the ventral branches of 6th to 8th cervical and 1st and 2nd thoracic spinal nerves. These nerve roots pass over the lateral aspect of the middle third of the first rib before anastomosing to form the plexus. All these nerve roots can be blocked by injecting anaesthetic solution on these nerves at the middle third of the lateral surface of the first rib. To reach this site, the needle is inserted between the thoracic wall and the medial face of the shoulder at the level of acromion process of the scapula about 12 to 14 cm cranial to it horizontally in the caudal direction.

The blocking of brachial plexus is indicated for operations for reducing the fractures of the bones of fore arm and manus.

Horse

The brachial plexus in horse is formed by ventral branches of the last three thoracic and first two thoracic spinal nerves similar to that in ox. The disposition and distribution of nerve branches extending from the plexus is almost similar to that of the ox except the following two.

The radial nerve after reaching the musculospiral groove gives out a cutaneous branch that passes through the lateral head of triceps and is distributed to the skin on the lateral aspect of forearm.

The main trunk of the radial nerve after crossing the carpus descends along the medial aspect of the palmer surface of metacarpus as palmer medial metacarpal nerve and further down on the medial digit as palmer medial digital nerve.

The ulnar nerve descends the carpus and after reaching the metacarpal region joins the lateral branch of the median nerve, descends first along the lateral aspect of the palmer surface of metacarpus as palmer lateral metacarpal nerve and then along the lateral (abaxial) aspect of the lateral digit as palmer lateral digital nerve.

Brachial plexus (FIG. 5-5 A)

The fore limb is supplied by nerves that extend from the brachial plexus. The brachial plexus is a large wide, flat and thick fascicular anastomosis of nerves formed by the convergence of ventral branches of last three cervical and first two thoracic spinal nerves in ox. It is placed between the scalenus muscle on the lateral wall of thorax and subscapularis and deep pectoral muscles on the costal (medial) surface of the scapula. From this plexus extend the following eleven branches (nerves) which are distributed mainly to the fore limb (thoracic limb) and most of the muscles of the thoracic girdle.

Horse

The arteries of fore limb of horse are more or less similar in their course and distribution. However, there are some special features in respect of some of these arteries as described below.

The brachial artery descends vertically on the medial aspect of humerus to its distal extremity, crosses it obliquely and descends along the joint capsule and medial lateral ligament of elbow joint, gives off common interosseous artery at the proximal third of the forearm and then continues distally as median artery.

The median artery descends along the caudomedial aspect of the radius covered by flexor carpi radialis muscle and divides just proximal to medial condyle into radial and collateral ulnar (ulnar) arteries.

The collateral ulnar artery is smaller of the two terminal branches of median artery. It descends along the cranial surface of radius under cover of the extensor carpi radialis and terminates a little above the carpus by anastomosing with a branch of radial artery.

The lymph from the fore limb is collected and carried into the circulation through two main lymph nodes, the prescapular and the axillary lymph nodes. There may be two more lymph nodes in fore limb but those are inconsistent and only occasionally found in ox. These include the accessory axillary lymph node and infraspinous lymph nodes and their afferents are mostly from the thoracic wall.

The venous drainage of the fore limb of ox is conducted by two independent routes, the superficial and deep routes, in the fore limb. The major vein of the superficial route is the cephalic vein and that of the deep route is the axillary vein. The venous drainage of the fore limb begins at the digits and is carried by branches of both the routes intermingling or confluent with each other up to the level of elbow joint. From the elbow upwards the journey of the two paths is completely independent of each other. The superficial veins join the cephalic vein while the deep veins join the axillary vein to open into the cranial vena cava.

Superficial veins

The superficial veins begin in the form of distal deep and distal superficial palmer arch just above the fetlock joint. These venous arches are formed by the union of axial and abaxial digital veins. From these venous arches extend the dorsal metacarpal vein ascending first through the interdigital space and then winding around the large metacarpal bone. In this course it anastomoses with the branches of radial vein on the dorsomedial aspect of the carpometacarpal region and passes further upward as accessory cephalic vein.

Subclavian artery

The fore limb is chiefly supplied by the subclavian artery (Fig. 5-4 A). It originates from the brachiocephalic trunk within the thoracic cavity. The left subclavian detaches from the brachiocephalic trunk opposite the second rib, passes craniodorsally towards the thoracic inlet winds around the cranial border of the first rib and then courses caudoventrally through the axillary space between the subscapular and teres major muscles as the axillary artery. It gives off the subscapular branch and continues as the brachial artery. The right subclavian is the direct continuation of the brachiocephalic trunk after the later gives off the bicarotid trunk opposite the first rib. It gets exit through the thoracic inlet, winds around the cranial border of the first rib and then continues as the right axillary artery and thereafter as the brachial artery similar to the artery of the left side.