Arthroscopic and o'pen Anatomy of the Hi p Michael B. Gerhardt, Kartik Logishetty, Morteza lV1eftah, and Anil S. Ranawat INTRODUCTION The hip joint is defined by the articulation between the head of the femur and the aeetahulum of the pelvis. It is covered by :l large soft -tissue envelop e and a complex array of neu rovascu- lar and musculotendinous str uctures. The joint's morphology anu orie ntation are complex, and th ere are wide ana to mic varia- tions seen amon g individuals. The joint's deep location makes both arthroscopic and open access challenging. To avoid iatro- genic injury while establishing functional and effic ient access, the hip surgeon should possess a sou nd ana to mic knowledge of the hip. T he human "hip" can be subdivided into three categories : I) the superficial surface anatomy; 2) the deep femo ro acetab u- la r Jo int and capsule; and 3) the ass ociated structur es, including the muscles, nerves, and vasculature, all of which directly affeet its function. Several bony landmarks defi ne tile surface anatomy of the hip. The anteros uperior iliac spine (ASIS) and anteroinferior i.liac spine (AIlS) are loca ted anteriorly, with the fo rm er being palpable. These structures serve as the insertion points for the sartorius ano the direct head of the rectus femoris, respectively. Pos ter olatera ll y, two bony ฀฀฀฀฀฀฀฀฀฀฀฀are paJpable: the greater troch, mt er and the posterosuperior ili ac spine. The greater trochanter serves as the insertion point of the tendon of the gluteus medius, the gluteus minimu s, the obtu rator externus, the o btura tor inte mus , tbe gemelli, and piriformis. The po sterosuperi or iliac spine serves as the attac hment point of tile oblique portion of the posterior sacroiliac ligaments a nd th e multifidus. During anhroscopic and open access to tile joi nt, both of these landm,lrks are uscf ul tools for incision planning, and, in combination with tile a nterior bony prominences, for initial orientation (Figure 2-1, A). Thc hip is a synovial, di art hrodial, ball-a nd-socket joint that is comprised of th e bony articulation b ctwcen the proxi- mal fe mur and the acetabulum. The acetabulum is formed at the cartilaginous confluence of the three bones of the pelvis: the ilium, the ischium, and th e pubis. vVhen aligned with the anterior pelvis plane, the acetabulum is inclined at ap pro xi- mately 55 degrees and anteverted at ap proximatel y 20 degre es, although there are gender variations. The ;lcetabular cup is roughly hemispheric in shape . It covers 70% of t he fem ora l he ad , and it has a wave-like profile of three peaks md thr ee troughs, including th e acetabular notch. The proxim al Fem ur consists of a femor al head, which articulates with th , acetah- ulum, 31ld a tape re d neck, which is angled ont o tIle Icmoral shaft. A normal femur has a neck-shaft angle of ap prox imllteiy 130 degrees. T here are a tot al of 27 mu scles that cross th e h ip ฀฀฀฀฀฀฀T hey can be categorized into six gro ups accordin g' to t he functiunal movements that they induce at the joint: 1) flexors; 2) extensors; 3) abductors; 4) adductors; 5) external rotators; and 6) interI12 I rotators. Althou gh some muscles have dual roles, their prim ary functions define their group placem(:)nt, and th ey all have ullique neurovascular supplies (TIt ble 2-1). The vascular supply of tbe hip stems from the external and internal iLiac ancries. An under s tandin g of the course of these vessels is critical fo r ,lVo iding catasu"ophic vascul ar inju ry. fn add ition, the blood supply to the fe l11()ral head is vulnerahle to both traumatic and iatro genic injury; the dis ruption of this sup- ply can resu lt in avasc ular n ecros is (Figure 2-2). HIP MUSCULATURE Hip Flexors The primary hip flexors are the rectus femo ri s, iliacus, psoas, iliocapsularis, and sartorius mu scles. The rectus fe moris mus- cle ha s two distinct origins proximally: t he direct head and the rd1 ected head. Th ey or iginate at the ATTS and thc a nterior acetabular rim (in cl ose proximity to the anterior hip capsule), respectively. The tendinous fibers of the rectus femoris coalesce distally and become confluellt witll the other qu adriceps mus- culature in tile thigh. The quadriceps consists of fo ur distinct muscles: 1) the vastus int er medius; 2) the vastus lateralis; 3) the vastus medi a li s; and 4) the rectus fem or is . T he rectus femoris is the only quadri ceps mu scle that traverses both the hip and the knee joint. The rectus femoris is a po werful hip fl exo r, but it is large ly dep endent on the po s ition of the knee and hip to ,lsse rt its influence. It is most p owerful when the knee is flexed, whereas sig nificant power is lost when the knee is extejlcled. T he rectu s femoris is innervated by the fem ora l nerve (i.e., the po s terior division of L2 to LA). The iliopsoas is another powerful hip fl exor that begins in two distinct region s proxima lly. T he iliac ll s has a brond origin, arising from th e inner t'lble of the ili ac wing, the sacral alae, and thc ili o lumb ar and sacroiliac li game n tS. T he psoas origi- nates at the lumbar trans verse processes, the intervertebral discs, amI the adjacent bodies from T I2 to L5, in addition to the tendinous arches between these points. Di sta lly, tile hvc> brge mu scalar boclies converge to become one distinct Su"ucture-the iliopsoas-a nd subsequently jointly insert at the less er tro- chanter of the proximal femur. The nerv e to th e ili opsoas (i.e., the ant er ior division of L I to L3) supplies the iliopsoas muscle. T he sarto r iu s o ri g in :! tes at tile ASIS and proceeds to tra- vcrse obliquely and laterally clown tile thigh to eventually in sert at the ante ri or surface of the tibia, JUSt inferomedial to the tibial 9