Page 92 - Adams and Stashak's Lameness in Horses, 7th Edition

58 Chapter 1

artery is detached from the cranial wall of the femoral Flexor muscles of the hip joint are the gluteus super­
artery. In the distal third of the thigh, the descending genicu­ ficialis, tensor fasciae latae, rectus femoris, iliopsoas,
VetBooks.ir the adductor, supplying these muscles and terminating in joint are the gluteus medius, biceps femoris, semitendi­
sartorius, and pectineus. Extensor muscles of the hip
lar artery courses distocraniad between the sartorius and
nosus, semimembranosus, adductor, and quadratus fem­
branches to the stifle.
The femoral artery gives off its last branch, the (dis­ oris. Muscles adducting the thigh include the gracilis,
tal) caudal femoral artery, and continues between the sartorius, adductor, pectineus, quadratus femoris, and
medial and lateral heads of the gastrocnemius as the obturatorius externus. Slight abduction is exerted on the
popliteal artery (Figure 1.46). The caudal femoral artery thigh by all three gluteal muscles. The thigh is rotated
pursues a short course caudad, giving off muscular laterad by the iliopsoas, external and internal obtura­
branches to the superficial digital flexor and gastrocne­ tors, and the gemelli. Medial rotation is accomplished
mius. Ascending branches from this substantial artery through the combined action of the adductor and glu­
supply thigh and calf muscles. A descending branch of teus profundus muscles.
the caudal femoral artery runs distocaudad over the lat­
eral head of the gastrocnemius along with the lateral
saphenous vein. The many branches of the caudal femo­ Pelvis
ral artery make anastomotic connections between the The equine pelvis, like that of other animals, com­
obturator artery proximally and the saphenous artery prises ilium, ischium, and pubis; these bones are individ­
distally. ually identifiable in the young but have fused by 10–12
16
months of age. The acetabulum is formed through con­
tributions from all three bones of the pelvis.
Hip (Coxofemoral) Joint
The wing‐shaped ilium presents two prominences,
The acetabulum of the os coxae is formed where the visible landmarks on the horse. The dorsally directed
ilium, ischium, and pubis meet. The lunate surface of the tuber sacrale inclines mediad toward its fellow, so
acetabulum, a cup‐shaped cavity arcing around a deep that the two sacral tubers come within 2–3 cm over
nonarticular fossa, articulates with the head of the the first sacral spinous process. The ilial wing sweeps
femur. A fibrocartilaginous rim, the acetabular labrum, ventrolaterad as the tuber coxae, creating the point of
increases the articular surface of the acetabulum. The the hip. Caudally, the ischial tuberosity presents as a
transverse acetabular ligament bridges the labrum across laterally directed ridge to which muscles of the thigh
the medially located acetabular notch, binding two liga­ attach.
ments as they emerge from the fovea capitis of the femo­ The pubis and ischium from each side meet ventrally
ral head (Figure 1.51). The ligament of the head of the at the pelvic symphysis. In the young animal fibrocarti­
femur comes from the fovea and attaches in the pubic lage joins the bones. Later in life, a synostosis is formed
groove on the ventral aspect of the pubis. The thick as the cartilage ossifies in a cranial to caudal sequence.
accessory femoral ligament passes out through the
acetabular notch to blend into the prepubic tendon. It Lymphatic Drainage
provides partial origin to the gracilis and pectineus
muscles. Two lymphocenters are involved in the lymphatic
The capacious joint capsule of the hip attaches to the drainage of the pelvic limb. The popliteal lymphocenter
acetabular labrum and on the neck of the femur a few consists of 3–12 small popliteal lymph nodes embedded
millimeters from the margin of the femoral head about 5 cm deep between the biceps femoris and
(Figure 1.51). The synovial membrane within the joint semitendinosus muscles adjacent to the tibial nerve
wraps around the intracapsular ligaments. An outpock­ (Figure 1.44). They may be absent in some horses. The
eting of the synovium passes out through the acetabular popliteal lymph nodes receive afferent lymphatics
notch to lie between the accessory femoral ligament and from the distal pelvic limb. Efferents drain to the deep
the pubic groove. The fibrous joint capsule is intimately inguinal lymphocenter.
attached to the fascia of the external obturator and deep The deep inguinal lymphocenter is a mass of lymph
gluteal muscles. Fat covers the capsule dorsally. The nodes 8–12 cm long within the femoral canal. It consists
articularis coxae muscle is related to the lateral aspect of of 16–35 individual lymph nodes. In addition to receiv­
the hip joint, detaching some fibers to the joint capsule. ing lymphatic vessels from the popliteal lymphocenter,
During flexion of the hip joint, the articularis coxae the lymph nodes of the deep inguinal lymphocenter
tense the joint capsule. (Figure 1.50) receive vessels from the caudal abdominal
wall and superficial inguinal lymph nodes. Efferent ves­
sels from the deep inguinal lymphocenter are afferent to
Movements of the Hip Joint
the medial iliac lymph nodes, located retroperitoneally
While the hip joint is a ball‐and‐socket joint, it is near the origin of the external iliac arteries. 16
capable only of very limited movement beyond flexion
and extension. Abduction of the thigh is restricted by the Stay Apparatus of the Pelvic Limb
ligament of the head of the femur and the accessory fem­
oral ligament. Adduction is checked by the attachments The quadriceps femoris muscle and the tensor fasciae
of the gluteal muscles on the femur. In the normal stand­ latae act to pull the patella, parapatellar cartilage, and
ing position, the caudolateral part of the head of the medial patellar ligament proximad to the locked position
femur lies outside the acetabulum. The hip joint is over the medial trochlear ridge of the femur when the limb
slightly flexed in this position. The range of motion is positioned to bear weight at rest (Figure 1.52). Through
between extreme flexion and extension is only 60°. 16 the components of the reciprocal apparatus (cranially,