Overview Ball-and-socket type of diarthrodial joint Stability conferred by bony architechture augmented by acetabular labrum and hip capsule Acetabulum formed from three ossification centers ilium ischium pubis posterosuperior portion has thicker cartilage for weightbearing purposes Osteology Acetabulum anteverted 15 degrees abducted 45 degrees (caudal tilt) divided into four quadrants line drawn from ASIS through center of acetabulum anterior and posterior quadrants line perpendicularly bisecting previous line superior and inferior quadrants posterior-superior contains superior gluteal nerve and vessels and sciatic nerve safest zone for screw placement posterior-inferior contains inferior gluteal nerve and internal pudendal vessels second safest zone for screw placement anterior-inferior contain the obturator vessels unsafe for screws anterior-superior contains external iliac artery and vein unsafe for screws Proximal femur femoral head center of femoral head should be at the level of the tip of the greater trochanter femoral neck anteverted 15 degrees (in relation to femoral condyles) neck shaft angle of 125 degrees greater trochanter lesser trochanter Capsule & Ligaments Hip joint capsule attaches anteriorly along the intertrochanteric line attaches posteriorly along the intertrochanteric crest basicervical and intertrochanteric regions are extracapsular three ligaments iliofemoral ligament (Y ligament of Bigelow) strongest ligament attaches to the AIIS and intertrochanteric line taut in full hip extension prevents anterior dislocation / hyperextension ischiofemoral reinforces posterior capsule pubofemoral Ligamentum teres cotyloid notch to fovea of femoral head Transverse acetabular ligament located in the most inferior portion of labrum provides anatomic landmark to assess acetabular version during reaming for THA Blood Supply Blood supply to femoral head changes with age birth to 4 years of age medial and lateral circumflex and ligamentus teres 4 years of age to adult posterosuperior and posteroinferior retinacular vessels from medial femoral circumflex piriformis start nails damage posterosuperior retinacular vessels can cause AVN of femoral head adult age medial femoral circumflex avoid transection the quadratus during posterior approach and damaging the MFC artery Ligamentum teres arterial branch of the posterior division of the obturator artery to the femoral head not significant in adults Abdominal aorta external iliac artery common femoral artery at risk during screw placement in anterosuperior quadrant during THA profunda femoris lateral femoral circumflex ascending branch at risk during the direct anterior approach medial femoral circumflex major blood supply to femoral head at risk during psoas tenotomy femoral artery perforators supply vastus lateralis internal iliac artery obturator (posterior branch) supplies transverse acetabular ligament at risk with screw placement and acetabular retractors in the anteroinferior quadrant superior gluteal inferior gluteal supplies short external rotators and gluteus maximus runs along the piriformis after it exits the greater sciatic notch internal pudendal re-enters pelvis via lesser sciatic notch Corona Mortis vascular connection between inferior epigastric branch of the external iliac vessels obturator vessels Neurologic Lumbosacral plexus T12-S4 nerve roots lies posterior to psoas muscle Sciatic nerve posterior division peroneal lateral in comparison to tibial division most commonly injured neural structure during THA runs deep to long head of biceps femoris superior gluteal inferior gluteal piriformis posterior femoral cutaneous anterior division tibial nerve to quadratus femoris nerve to obturator internus pudendal coccygeus Obturator nerve innervates medial compartment all hip adductors except hamstring portion of adductor magnus Femoral nerve between iliacus and psoas branches to muscle, overlying skin, and hip joint Lateral femoral cutaneous nerve L2-L3 nerve roots; branch of the lumbar plexus deep to inguinal ligament near ASIS Genitofemoral nerve L1-L2 nerve roots; branch of the lumbar plexus two terminal branches femoral branch genital branch pierces iliopsoas and runs on its anteromedial surface Musculature Hip flexors iliopsoas rectus femoris sartorius pectineus iliacus Hip adductors adductor magnus (adductor portion) adductor longus adductor brevis adductor minimus gracilis External rotators gluteus maximus piriformis obturator externus obturator interus superior gemellus inferior gemellus quadratus femoris Hip abductors gluteus medius gluteus minimus tensor fasciae latae Hip extensors gluteus maximus hamstring tendons semitendinosis semimembranosus long head of the biceps femoris adductor magnus (hamstring portion) Approaches to the hip 5 main approaches Anterior - Smith-Petersen Anterolateral - Watson-Jones Medial Direct lateral - Hardinge Posterior - Southern or Moore