Hip — Surgical Anatomy and Approaches

Introduction

The hip joint, the deepest and most constrained ball-and-socket articulation in the body, presents the orthopedic surgeon with multiple operative approaches, each with characteristic advantages, disadvantages, and risks. The approaches range from the anterior (Smith-Petersen) with its claim to muscle-sparing access, through the anterolateral (Watson-Jones) and direct lateral (Hardinge) approaches that balance access with abductor preservation, to the workhorse posterior approach with its complete exposure but greater dislocation risk, and the trochanteric flip osteotomy (Ganz) with its access to the entire femoral head while preserving the vascular supply. The fundamental anatomical consideration governing approach selection is the blood supply to the femoral head through the medial femoral circumflex artery and its retinacular branches — disruption of these vessels produces avascular necrosis, a substantial concern in fracture management and increasingly in joint-preserving surgery. This chapter draws on Orthopaedic Surgical Approaches, Operative Hip Arthroscopy (Byrd), Netter’s Concise Orthopaedic Anatomy, and Gray’s Anatomy.

Bony and Articular Anatomy

The hip joint comprises the femoral head (covered by approximately 70 percent articular cartilage in the typical adult) articulating with the acetabulum (the cup formed by the fused ilium, ischium, and pubis). The detailed anatomy was addressed in Topics Trauma-20 (acetabulum) and Orth-7 (DDH). Key surgical landmarks include: Greater trochanter: The principal lateral landmark, insertion of the gluteus medius (lateral facet), gluteus minimus (anterior facet), piriformis (superior facet), and other short rotators. Lesser trochanter: Medial; insertion of the iliopsoas. Femoral head and neck: With the typical neck-shaft angle of 130 degrees and anteversion of 10 to 15 degrees. Intertrochanteric line (anteriorly) and intertrochanteric crest (posteriorly): The hip capsule attaches along these lines. ASIS and AIIS: The anterior landmarks for anterior approaches. The hip capsule is a strong fibrous structure with thickenings forming the iliofemoral (Y- ligament of Bigelow), pubofemoral, and ischiofemoral ligaments. The iliofemoral ligament is the strongest ligament in the body and the principal anterior restraint.

Blood Supply to the Femoral Head

The blood supply to the femoral head is the central anatomical concern of hip surgery:

Medial femoral circumflex artery (MFCA): A branch of the deep femoral artery. The principal supply to the femoral head (approximately 70 to 80 percent in most specimens). Courses posteriorly around the femoral neck and gives off retinacular branches that ascend within the capsular reflection along the posterior aspect of the femoral neck to enter the femoral head near the cartilage-bone junction. Surgical approaches that disrupt these retinacular vessels (particularly the posterior approach with disruption of the obturator internus and gemelli insertion) produce AVN risk. Lateral femoral circumflex artery (LFCA): Provides smaller anterior contribution. Artery of the ligamentum teres: A branch of the obturator artery (variable). Of importance in children but generally inadequate as the sole blood supply in adults. The Ganz trochanteric flip osteotomy preserves the deep branch of the medial femoral circumflex artery by maintaining the obturator externus insertion and the posterior capsular reflection, providing safe surgical hip dislocation without AVN.

Muscular Anatomy

The principal hip muscles include: Anterior compartment: Iliopsoas (hip flexion), rectus femoris (hip flexion, knee extension), sartorius (hip flexion, knee flexion), pectineus. Lateral compartment: Gluteus medius and minimus (abduction, internal rotation in flexion), tensor fasciae latae. Posterior compartment: Gluteus maximus (extension, external rotation), piriformis (external rotation), short external rotators (gemelli, obturator internus and externus, quadratus femoris). Medial compartment: Adductor longus, brevis, magnus; gracilis. The gluteus medius and minimus are critical for normal gait (Trendelenburg gait develops with their dysfunction); their preservation is paramount in any approach.

Neurovascular Anatomy

Femoral nerve, artery, vein: Pass beneath the inguinal ligament. The femoral artery is the principal vascular concern in anterior hip approaches. Sciatic nerve: Exits the pelvis through the greater sciatic foramen, typically below the piriformis. The principal neurological concern in posterior hip approaches. Lateral femoral cutaneous nerve: Crosses near the ASIS. At risk in anterior approaches (Smith-Petersen) with meralgia paresthetica as a common complication. Superior gluteal nerve: Runs between gluteus medius and minimus. At risk in lateral approaches (Hardinge) with abductor weakness as the principal concern.

Anterior Approach (Smith-Petersen)

The Smith-Petersen anterior approach uses the internervous interval between the sartorius (femoral nerve) medially and the tensor fasciae latae (superior gluteal nerve) laterally, and the deep interval between the rectus femoris (femoral nerve) medially and the gluteus medius (superior gluteal nerve) laterally. Indications The approach has historically been used for hip arthrodesis, open reduction of femoral head fractures, biopsy, tumor procedures, and pelvic osteotomies. In recent years, it has gained substantial popularity as the direct anterior approach (DAA) to total hip arthroplasty with reduced soft-tissue disruption and lower dislocation rates. Technique Patient supine, often on a specialized table (Hana table) with traction. Incision from approximately 2 cm distal to the ASIS, extending distally for 8 to 15 cm in the line between the sartorius and the tensor fasciae latae. The interval is developed; the lateral femoral cutaneous nerve is identified and protected. The interval between rectus femoris and gluteus medius is developed. The hip capsule is opened, with reflection or excision of the capsule providing joint access. Complications Lateral femoral cutaneous nerve injury (meralgia paresthetica) is common (20 to 80 percent transient, 5 to 10 percent persistent). Wound complications at the proximal incision (with creases and skin folds). Femoral fracture during stem insertion (more common in DAA than in posterior approach because of the more difficult femoral exposure). Stem malposition because of more limited visualization of the proximal femur.

Anterolateral Approach (Watson-Jones)

The Watson-Jones approach uses the interval between the gluteus medius posteriorly and the tensor fasciae latae anteriorly, with reflection of the gluteus medius from the anterior aspect of the greater trochanter. Indications Total hip arthroplasty, open reduction internal fixation of certain proximal femur fractures, hemiarthroplasty. Technique Patient supine or lateral decubitus. Incision over the greater trochanter, extending proximally and distally for the desired length. The fascia lata is incised. The interval between gluteus medius and tensor fasciae latae is developed. The anterior portion of the gluteus medius is partially detached from the trochanter (with later repair). The hip capsule is opened anteriorly.

Complications Abductor dysfunction with partial detachment of the gluteus medius; meticulous repair is essential. Superior gluteal nerve injury with deeper proximal dissection.

Direct Lateral Approach (Hardinge)

The Hardinge approach splits the gluteus medius in line with its fibers, with anterior reflection of the anterior portion (including the gluteus minimus) attached to a flap of the vastus lateralis. The approach provides good anterior exposure of the hip joint while preserving the posterior capsule and structures. Indications Total hip arthroplasty, hemiarthroplasty, femoral neck fracture fixation. Technique Patient supine or lateral decubitus. Longitudinal lateral incision over the trochanter. Fascia lata opened. Gluteus medius split in line with its fibers (only as far proximal as 5 cm from the trochanter to protect the superior gluteal nerve). The anterior portion of the gluteus medius (with the gluteus minimus) is reflected anteriorly as a single flap, often in continuity with the vastus lateralis. The hip capsule is opened anteriorly. Complications Superior gluteal nerve injury with extended proximal dissection (limiting the abductor split to 5 cm from the trochanter is critical). Abductor weakness even with appropriate technique; trochanteric pain and persistent limp are recognized concerns.

Posterior (Southern, Kocher-Langenbeck modification, Moore) Approach

The posterior approach is the workhorse for total hip arthroplasty in many centers and the standard for posterior pelvic and acetabular surgery (the Kocher-Langenbeck variant addressed in Topic Anatomy-7).

Indications Total hip arthroplasty, hemiarthroplasty, open reduction of posterior hip dislocations, posterior wall and posterior column acetabular fracture fixation, sciatic nerve exploration. Technique Patient in lateral decubitus with the affected side up. Curved incision from the PSIS region, over the greater trochanter, extending distally into the proximal thigh. Fascia lata and gluteus maximus aponeurosis opened. Gluteus maximus split in line with its fibers (biased to avoid the inferior gluteal nerve). The short external rotators (piriformis, gemelli, obturator internus, quadratus femoris) are identified at their trochanteric insertions; the sciatic nerve is identified inferior to the piriformis. The short external

rotators are detached from the trochanter and reflected medially to expose the posterior capsule. The capsule is opened and the joint is accessed. Complications Sciatic nerve injury (1 to 3 percent in elective procedures, higher in posterior dislocation reduction). Posterior hip dislocation after total hip arthroplasty (the principal concern; historical rates of 3 to 5 percent, reduced by careful soft-tissue repair and modern implant positioning). Heterotopic ossification. Abductor preservation (an advantage of this approach — the gluteus medius and minimus are not disturbed).

Trochanteric Flip Osteotomy (Ganz)

The Ganz trochanteric flip osteotomy (Ganz, 2001) provides comprehensive access to the entire femoral head and acetabulum with preservation of the medial femoral circumflex artery and consequently of the femoral head blood supply. Technique Patient in lateral decubitus. Posterior incision similar to the Kocher-Langenbeck. The greater trochanter is osteotomized (typically with a stepwise cut) and reflected anteriorly with the attached gluteus medius and minimus. The capsular reflection containing the medial femoral circumflex artery is preserved by keeping the obturator externus insertion intact. The hip capsule is opened (typically Z-shaped or H-shaped), and the femoral head is dislocated anteriorly out of the acetabulum. Indications Femoral head fracture fixation, FAI surgery, femoral head osteochondritis dissecans treatment, Perthes residual deformity correction, tumor resection of the femoral head, comprehensive surgical hip dislocation procedures. Complications Trochanteric nonunion (1 to 5 percent), heterotopic ossification, abductor weakness.

Hip Arthroscopy

Hip arthroscopy has emerged as the platform for management of FAI, labral tears, and other intra-articular hip pathology. The principal portals include: Anterolateral portal: Approximately 1 to 2 cm anterior and 2 cm distal to the greater trochanter tip. The principal viewing portal. Anterior portal: Established under fluoroscopic guidance, with attention to the lateral femoral cutaneous nerve. Posterolateral portal: Posterior to the trochanter. Mid-anterior portal: An accessory portal for specific procedures.

The arthroscopic examination of the central compartment (within the joint) and the peripheral compartment (between the capsule and the femoral neck) requires hip distraction (typically with a traction table) for central compartment access.

Summary and Take-Home Points

The hip offers multiple surgical approaches, each with characteristic advantages and risks centered on the muscular envelope, the neurovascular structures, and the blood supply to the femoral head through the medial femoral circumflex artery. The Smith-Petersen anterior approach uses the internervous intervals between sartorius/tensor (superficial) and rectus/gluteus medius (deep) and has gained popularity as the direct anterior approach to THA. The Watson-Jones anterolateral approach uses the interval between gluteus medius and tensor fasciae latae with anterior gluteus medius reflection. The Hardinge direct lateral approach splits the gluteus medius and reflects the anterior portion with the gluteus minimus and a flap of vastus lateralis. The posterior approach through gluteus maximus split and short external rotator detachment is the workhorse for THA, with sciatic nerve injury and posterior dislocation as the principal concerns. The Ganz trochanteric flip osteotomy provides comprehensive access to the femoral head while preserving the medial femoral circumflex artery. The principal neurovascular structures at risk include the lateral femoral cutaneous nerve (anterior approaches, meralgia paresthetica), the femoral nerve and vessels (deep anterior dissection), the sciatic nerve (posterior approach), and the superior gluteal nerve (between gluteus medius and minimus, at risk with extended proximal lateral dissection). The choice of approach depends on the surgeon’s training and preference, the planned procedure (THA, fracture fixation, joint-preserving surgery, tumor resection), and the patient’s anatomy and comorbidities. The chapter that follows turns to the thigh and knee, completing the proximal-to-distal lower extremity sequence.