Surgical Management of Developmental Dysplasia of the Hip: A Comprehensive Masterclass

Comprehensive Introduction and Patho-Epidemiology

Developmental Dysplasia of the Hip (DDH) represents a complex, dynamic, and evolving spectrum of anatomic abnormalities involving the growing hip joint. It is not a static embryologic malformation but rather an unfolding developmental cascade ranging from mild capsular laxity and subtle acetabular dysplasia to frank, irreducible dislocation of the femoral head. The fundamental pathology lies in the loss of the concentric relationship between the femoral head and the acetabulum during the critical periods of fetal and infant growth. When the femoral head is not spherically seated within the acetabulum, the essential mechanical stimulus required for normal secondary acetabular remodeling is lost. This results in persistent dysplasia, characterized by a shallow, anteverted, and vertically oriented acetabulum, which inevitably leads to early-onset osteoarthritis, labral pathology, and severe biomechanical dysfunction if left untreated.

The epidemiology of DDH is multifaceted, reflecting a complex interplay of genetic predispositions and mechanical intrauterine factors. The overall incidence of neonatal hip instability is estimated to be 1 in 100 live births, while true dislocation occurs in approximately 1 in 1,000. Well-established risk factors include female sex, breech presentation, oligohydramnios, primiparity, and a positive family history. The female preponderance (ranging from 4:1 to 8:1) is largely attributed to the heightened sensitivity of female fetuses to maternal relaxin, resulting in exaggerated ligamentous laxity. Mechanical factors, such as the compressive forces of a breech position or oligohydramnios, restrict fetal lower extremity movement, forcing the hips into extreme flexion and adduction, which mechanically levers the femoral head out of the developing acetabulum. Postnatal environmental factors, particularly traditional swaddling practices that bind the lower extremities in extension and adduction, further exacerbate the risk of dislocation.

The pathophysiology of DDH centers on the concept of "biological plasticity." The infant hip possesses an extraordinary capacity for spontaneous remodeling, provided that a concentric, stable, and atraumatic reduction is achieved and maintained. The acetabular cartilage complex, particularly the triradiate cartilage, responds to the spherical presence of the femoral head by deepening and normalizing its version. However, this remodeling potential is highly time-dependent. It is maximal during the first few months of life and diminishes exponentially after 18 to 24 months of age. Consequently, delayed presentations or failures of conservative management (e.g., Pavlik harness or rigid abduction orthoses) necessitate definitive surgical intervention. In older children, soft-tissue procedures alone are insufficient; concomitant pelvic and femoral osteotomies become mandatory to mechanically correct the bony architecture, as the biological window for spontaneous remodeling has effectively closed.

The long-term consequences of untreated or inadequately managed DDH are devastating. A persistently dislocated hip results in a pseudoarthrosis within the iliac wing, leading to a profound limb length discrepancy, a pronounced Trendelenburg gait due to abductor insufficiency, and progressive lumbar hyperlordosis. Even subtle, residual dysplasia—often asymptomatic during childhood—manifests in the second or third decade of life as symptomatic labral tears and accelerated articular cartilage wear. The altered joint biomechanics, specifically the decreased weight-bearing surface area and the lateralized center of rotation, exponentially increase peak contact stresses across the chondral surfaces. Therefore, the ultimate goal of the orthopedic surgeon is not merely to reduce the hip, but to meticulously restore normal biomechanics to ensure the longevity of the native joint.

Detailed Surgical Anatomy and Biomechanics

A profound understanding of the surgical anatomy of the pediatric hip is the absolute prerequisite for safe and effective DDH surgery. The bony anatomy of the infant acetabulum is predominantly cartilaginous, anchored by the triradiate cartilage complex, which represents the confluence of the ilium, ischium, and pubis. In the dysplastic state, the acetabulum is characteristically shallow, deficient in anterolateral coverage, and excessively anteverted. The femoral head is often smaller than normal, and the proximal femur exhibits excessive anteversion and coxa valga. This bony mismatch creates a highly unstable articulation. The surgeon must recognize that the dysplastic acetabulum is not merely underdeveloped; it is actively misshapen by the abnormal forces exerted by the subluxated or dislocated femoral head.

The soft-tissue obstacles to concentric reduction are classically divided into intra-articular and extra-articular components, all of which must be systematically addressed during open reduction. Intra-articular obstacles include a hypertrophied ligamentum teres, which can become incredibly thick and act as a mechanical block within the acetabular fossa. The pulvinar, a pad of fibrofatty tissue, hypertrophies to fill the void left by the absent femoral head. The transverse acetabular ligament (TAL), which spans the acetabular notch, becomes contracted and pulled superiorly, effectively tethering the inferior aspect of the joint and preventing the femoral head from seating. Most critically, the labrum—specifically the superior portion—can become inverted into the joint space under the weight of the subluxating head, forming the so-called "limbus." The surgeon must carefully evert, rather than excise, this inverted limbus, as it contains essential chondrogenic potential for future acetabular roof development.

Extra-articular obstacles primarily involve the musculotendinous units that cross the hip joint. The iliopsoas tendon is perhaps the most significant extra-articular block. As the femoral head migrates superiorly and laterally, the iliopsoas tendon is drawn tightly across the anterior capsule, creating an "hourglass" constriction that physically prevents the femoral head from re-entering the true acetabulum. The adductor longus and brevis muscles also become severely contracted due to the chronically shortened position of the dislocated hip. Release of these contracted structures (psoas and adductor tenotomies) is mandatory not only to facilitate reduction but also to decompress the joint, thereby reducing the extreme pressure exerted on the capital femoral epiphysis when the hip is forced into abduction.

The vascular anatomy of the pediatric hip is of paramount importance, as iatrogenic injury leads to avascular necrosis (AVN), the most feared complication of DDH treatment. The primary blood supply to the capital femoral epiphysis in the infant and young child is derived almost exclusively from the deep branch of the medial circumflex femoral artery (MCFA). The MCFA courses posteriorly and superiorly along the femoral neck, penetrating the capsule at the base of the neck to form the subsynovial retinacular vessels. During the medial approach to the hip, the MCFA is highly vulnerable as it courses just inferior to the psoas tendon and medial capsule. Retractors placed carelessly over the inferior neck can easily crush these delicate vessels. Biomechanically, the dysplastic hip suffers from a superiorly and laterally displaced center of rotation. This displacement dramatically shortens the abductor moment arm, requiring the gluteus medius to generate massive forces to maintain a level pelvis during the single-leg stance phase of gait. This mechanical inefficiency leads to rapid abductor fatigue and the classic Trendelenburg lurch.

Exhaustive Indications and Contraindications

The decision-making process in the surgical management of DDH is highly nuanced, dictated by the patient's age at presentation, the severity of the pathoanatomy, the presence of underlying teratologic or neuromuscular conditions, and the failure of prior conservative modalities. Surgical intervention is absolutely indicated when a concentric, stable reduction cannot be achieved or maintained through closed means. In infants under 6 months of age, failure of a Pavlik harness—defined as a lack of clinical or ultrasonographic improvement after 3 to 4 weeks of strict compliance—mandates a transition to an examination under anesthesia, arthrogram, and attempted closed reduction with spica casting. If the "safe zone" of Ramsey (the arc of motion between the angle of extreme abduction where ischemia occurs and the angle of adduction where re-dislocation occurs) is less than 20 degrees, closed reduction is contraindicated, and open reduction is indicated.

Late-presenting DDH, typically defined as diagnosis after 6 months of age, frequently requires surgical intervention. Between 6 and 18 months, an initial attempt at closed reduction may be reasonable, but the likelihood of encountering insurmountable intra-articular obstacles is high. Open reduction via a medial or anterior approach becomes the standard of care in this cohort when closed reduction fails. For children presenting after 18 to 24 months of age, the biological potential for spontaneous acetabular remodeling is drastically reduced. In these patients, open reduction alone is insufficient and is virtually guaranteed to result in residual dysplasia or re-dislocation. Therefore, age greater than 18 months is a strict indication for combining an open reduction with a concomitant pelvic osteotomy (to improve anterolateral coverage) and often a femoral shortening varus derotation osteotomy (VDRO) to decompress the joint and correct excessive femoral anteversion.

Contraindications to surgical intervention in DDH are relatively few but critical to recognize. Active joint infection or systemic sepsis is an absolute contraindication to any elective reconstructive procedure. Severe medical comorbidities that preclude safe general anesthesia must be carefully weighed against the benefits of hip reduction. In the context of severe neuromuscular disease (e.g., spastic quadriplegic cerebral palsy with profound global developmental delay) or extreme teratologic syndromes (e.g., severe arthrogryposis multiplex congenita), the indications for surgical reduction are controversial. If the patient has no ambulatory potential and the dislocated hip is painless and mobile, aggressive surgical intervention may cause more harm (stiffness, pain, infection) than good. In such cases, surgical neglect or palliative procedures may be the most appropriate course of action.

Furthermore, age-specific contraindications dictate surgical approach. The medial approach (Ludloff or Ferguson) is strictly contraindicated in children older than 18 months, as it does not allow for a formal capsulorrhaphy or access to the superior acetabulum, both of which are required in older children. Similarly, redirectional osteotomies (like the Salter osteotomy) are contraindicated if the hip cannot be concentrically reduced, as redirecting the acetabulum over an unreduced or incongruous femoral head will rapidly destroy the articular cartilage.

Pre-Operative Planning, Templating, and Patient Positioning

Meticulous pre-operative planning is the absolute cornerstone of successful DDH surgery; the master surgeon wins the battle before the incision is ever made. The planning process begins with a comprehensive radiographic evaluation. In infants under 6 months, dynamic ultrasonography using the Graf method is the gold standard. The surgeon must critically evaluate the alpha angle (quantifying the bony roof) and the beta angle (quantifying the cartilaginous roof). However, once the capital femoral ossific nucleus appears (typically between 4 to 6 months of age), plain radiography becomes the primary imaging modality. A perfectly positioned anteroposterior (AP) pelvis and a frog-leg lateral are mandatory. The surgeon must draw and analyze the classic radiographic lines: Hilgenreiner's line (horizontal line through the triradiate cartilages), Perkin's line (vertical line from the lateral margin of the acetabulum), and Shenton's curve (the continuous arc formed by the medial femoral neck and the inferior border of the superior pubic ramus).

Advanced imaging plays a critical role in complex or revision cases. Intra-operative arthrography is an indispensable tool. By injecting radiopaque dye into the joint space, the surgeon can dynamically visualize the cartilaginous profile of the femoral head, the true depth of the acetabulum, and the presence of the classic "hourglass" capsular constriction or an inverted limbus (indicated by a pooling of dye medial to the femoral head, known as the "rose thorn" sign). Post-reduction, Magnetic Resonance Imaging (MRI) is increasingly utilized to confirm concentric reduction without subjecting the infant to the ionizing radiation of a CT scan. However, in older children requiring complex 3D pelvic osteotomies, a low-dose, fast-acquisition CT scan with 3D reconstruction is invaluable for precisely mapping the bony deficiency and templating the optimal osteotomy angles.

Surgical templating is a highly technical process, particularly when concomitant osteotomies are planned. For a femoral shortening VDRO, the surgeon must calculate the exact amount of femoral shortening required to decompress the joint. This is typically determined by measuring the distance of superior migration of the femoral head relative to the true acetabulum. The degree of derotation is calculated based on clinical examination (internal vs. external rotation arcs) and radiographic anteversion, aiming to restore a normal anteversion of 15 to 20 degrees. For pelvic osteotomies, the surgeon must template the exact hinge point. In a Salter osteotomy, the hinge is the pubic symphysis; the surgeon must template the size of the triangular bone graft required to achieve the desired degree of anterolateral rotation based on the preoperative Acetabular Index (AI).

Patient positioning and operating room setup must be executed with obsessive attention to detail. The patient is placed supine on a radiolucent operating table. For unilateral procedures, a bump is placed under the ipsilateral sacrum to elevate the hemipelvis slightly. The entire lower extremity, from the iliac crest to the toes, must be prepped and draped free to allow for unrestricted manipulation of the hip during the procedure. A sterile tourniquet may be applied to the proximal thigh for femoral procedures, though it is often omitted to allow for continuous assessment of perfusion. The fluoroscopy unit (C-arm) must be positioned to enter from the contralateral side, allowing for seamless, unobstructed AP and lateral imaging of the hip and pelvis throughout the operation. The surgeon must ensure that the C-arm can achieve a true AP of the pelvis without the table pedestal interfering.

Step-by-Step Surgical Approach and Fixation Technique

The Medial Approach (Ludloff and Ferguson)

The medial approach is an elegant, minimally invasive technique typically reserved for children under 12 to 18 months of age presenting with an isolated dislocation without severe bony dysplasia. Its primary advantage is direct, unimpeded access to the primary medial obstacles (the iliopsoas and adductors) while leaving the abductor musculature completely undisturbed.

1. Positioning and Incision: The patient is placed in the frog-leg position (hips flexed, abducted, and externally rotated). A longitudinal incision is made centered over the palpable adductor longus origin, extending distally for 3 to 4 centimeters.
2. Superficial Dissection: The deep fascia is incised. The adductor longus is isolated, taking care to protect the anterior branch of the obturator nerve. A formal tenotomy of the adductor longus is performed at its tendinous origin on the pubis.
3. Deep Dissection: The surgeon develops the internervous plane between the pectineus (innervated by the femoral nerve) anteriorly and the adductor brevis and magnus (innervated by the obturator nerve) posteriorly. Blunt dissection with a finger leads directly to the lesser trochanter.
4. Psoas Tenotomy: The lesser trochanter is palpated deep in the wound. The iliopsoas tendon is carefully isolated with a right-angle clamp and released directly at its insertion. This immediately releases the anterior tether on the capsule.
5. Capsulotomy and Protection of the MCFA: The medial joint capsule is now visible. This is the most critical step of the procedure. The medial circumflex femoral artery (MCFA) courses transversely just inferior to the capsule. Retractors must be placed strictly anterior and superior to the capsule. A longitudinal capsulotomy is performed parallel to the femoral neck.
6. Joint Clearance and Reduction: The ligamentum teres is identified, grasped, and excised at its base. The transverse acetabular ligament (TAL) is identified at the inferior margin of the acetabulum and radially incised to widen the entry to the true acetabulum. The femoral head is then gently reduced. Stability is assessed dynamically under fluoroscopy to define the safe zone. The capsule is left open, and the wound is closed in layers.

The Anterior Approach (Smith-Petersen)

The anterior approach is the definitive workhorse for DDH surgery. It is mandatory for children over 18 months of age, for teratologic dislocations, and for any case requiring a concomitant pelvic osteotomy or a formal capsulorrhaphy.

1. Incision and Superficial Dissection: A "bikini" incision is made parallel to the iliac crest, extending distally toward the anterior superior iliac spine (ASIS). The internervous plane between the sartorius (femoral nerve) and the tensor fasciae latae (superior gluteal nerve) is developed.
2. Deep Dissection and Apophyseal Split: The iliac apophysis is sharply split down to the bone. The iliacus muscle is elevated subperiosteally from the inner table of the ilium, exposing the sciatic notch. The direct head of the rectus femoris is detached from the ASIS, and the reflected head is detached from the anterior capsule.
3. Psoas Release and Capsulotomy: The psoas tendon is identified as it crosses the pelvic brim. It is isolated and tenotomized at the musculotendinous junction. A T-shaped or I-shaped capsulotomy is performed. The capsule must be meticulously preserved, as it is often redundant and will be required for the capsulorrhaphy.
4. Intra-articular Clearance: The femoral head is gently distracted. The ligamentum teres is excised. The fibrofatty pulvinar is removed from the acetabular fossa using a rongeur. The TAL is radially incised. The inverted limbus is carefully identified; a blunt hook is used to evert it out of the joint space. It must never be excised.
5. Capsulorrhaphy: Once concentric reduction is achieved and confirmed, the redundant capsule is managed. The inferior leaflet is pulled superiorly, and the superior leaflet is advanced distally and laterally (vest-over-pants repair). It is sutured tightly with heavy non-absorbable sutures to mechanically lock the femoral head within the acetabulum.

Concomitant Femoral Osteotomies (VDRO)

When reducing a high dislocation in an older child, the extreme tension placed on the joint can cause immediate ischemic necrosis of the femoral head. A subtrochanteric femoral shortening and varus derotation osteotomy (VDRO) is required to decompress the joint.

1. Approach: A standard lateral approach to the proximal femur is utilized, splitting the vastus lateralis.
2. Osteotomy: A transverse osteotomy is performed at the subtrochanteric level. A pre-calculated cylindrical segment of the femoral diaphysis (typically 1 to 3 cm) is resected to achieve the necessary shortening.
3. Realignment and Fixation: The proximal fragment is engaged with a pediatric blade plate or a locking proximal femoral plate. The distal fragment is externally rotated (to correct the excessive anteversion of the proximal segment) and abducted (to create varus at the osteotomy site). The plate is then rigidly fixed to the distal fragment with bicortical screws.

Pelvic Osteotomies (Salter, Pemberton, Dega)

Pelvic osteotomies are required to correct the deficient anterolateral coverage characteristic of the dysplastic acetabulum.

• Salter Innominate Osteotomy (Redirectional): A Gigli saw is passed through the greater sciatic notch and brought out anteriorly above the anterior inferior iliac spine (AIIS). The entire hemipelvis is cut. The distal fragment (containing the intact acetabulum) is levered laterally, anteriorly, and inferiorly, hinging on the pubic symphysis. A triangular bone graft, harvested from the anterior iliac crest, is impacted into the open wedge. The construct is rigidly stabilized with two threaded Kirschner wires driven from the proximal ilium, through the graft, into the distal fragment.
• Pemberton Pericapsular Osteotomy (Reshaping): An osteotome is driven through the outer and inner tables of the ilium, starting just above the AIIS and curving posteriorly and inferiorly parallel to the joint capsule, aiming precisely for the ilioischial limb of the triradiate cartilage. The osteotomy is incomplete; it hinges on the flexible triradiate cartilage. The acetabular roof is levered downward, reducing the volume of the acetabulum and improving anterolateral coverage. A bone graft is wedged into the defect. No internal fixation is typically required.
• Dega Transiliac Osteotomy (Reshaping): Similar to the Pemberton, but the inner cortex of the ilium is left intact posteriorly, creating a bony hinge. The osteotome is driven through the outer cortex and cancellous bone. This allows for significant lateral and posterior coverage, making it ideal for the posterior deficiency often seen in neuromuscular dysplasia (e.g., cerebral palsy).

Complications, Incidence Rates, and Salvage Management

The surgical management of DDH is fraught with potential complications, the most devastating of which is Avascular Necrosis (AVN) of the capital femoral epiphysis. AVN is almost entirely iatrogenic, resulting either from direct surgical trauma to the medial circumflex femoral artery (MCFA) during dissection or from vascular occlusion secondary to extreme mechanical pressure when the hip is immobilized in excessive abduction (the obsolete "frog-leg" cast position). The incidence of AVN varies widely in the literature, ranging from 5% to 30% depending on the severity of the dislocation and the techniques employed. The Kalamchi and MacEwen classification system is used to grade the severity of AVN. Type I involves transient changes limited to the ossific nucleus and carries an excellent prognosis. Type II involves damage to the lateral physis, leading to a progressive valgus deformity. Type III involves central physeal arrest, resulting in a short, broad neck (coxa brevis). Type IV is catastrophic, involving total damage to the epiphysis and physis, leading to severe coxa magna, brevis, and varus, ultimately resulting in early joint destruction.

Re-dislocation or persistent subluxation is another major complication, occurring in 2% to 8% of open reductions. This catastrophic failure is almost always due to technical errors: inadequate clearance of intra-articular obstacles (particularly a missed inverted limbus or unreleased TAL), failure to recognize and correct excessive femoral anteversion, or a lax, inadequate capsulorrhaphy. If a re-dislocation is identified on post-operative imaging, immediate return to the operating room for revision open reduction is mandatory. Delayed recognition often necessitates complex salvage procedures.

Nerve injury is a known risk, particularly to the femoral nerve during the anterior approach (due to excessive medial retraction) or the sciatic nerve during pelvic osteotomies (if the Gigli saw or osteotome breaches the sciatic notch indiscriminately). Infection rates are generally low (< 2%) but require aggressive surgical debridement if they occur. Premature physeal closure of the triradiate cartilage can occur following Pemberton or Dega osteotomies if the osteotome inadvertently violates the germinal zone of the cartilage, leading to a tethered, highly dysplastic acetabulum as the child grows.

When primary interventions fail or when patients present in late adolescence or adulthood with severe, symptomatic dysplasia, salvage management is required. If the joint is congruous but dysplastic, a Ganz Periacetabular Osteotomy (PAO) is the gold standard. The PAO involves a series of complex extra-articular cuts around the acetabulum, allowing massive reorientation of the joint while preserving the posterior column of the pelvis, enabling early weight-bearing. If the joint is incongruous or severely arthritic, salvage procedures such as the Chiari medial displacement osteotomy or a Shelf procedure are utilized. The Chiari osteotomy involves an extra-articular cut just superior to the capsule; the pelvis is displaced medially, and the joint capsule is interposed between the femoral head and the cancellous bone of the proximal iliac fragment. Over time, this capsule undergoes fibrocartilaginous metaplasia, forming a supportive "shelf" that mechanically prevents superior subluxation and increases the weight-bearing surface area.