Marco Teloken, David Gusmao, and Marcus Crestani
DEFINITION
According to the prefix peri (meaning “around”), a periacetabular osteotomy (PAO) is defined as an osteotomy that involves dislodging the hip socket from its bony bed in the pelvis without distorting the normal pelvic anatomy. The socket is then reoriented in a more appropriate position, reducing the deleterious effects of some unfavorable conditions.
Closure of the acetabular growth plate is a precondition.
Although the purpose of all reconstructive pelvic osteotomies is the same, the PAO modifies only the orientation of the acetabulum.
Ideally, the site of the periacetabular osteotomy should be as close to the acetabulum as needed to mobilize it, to preserve the blood supply, and to avoid joint penetration.
By definition, PAOs include the spherical or rotational osteotomies described by Eppright,6 Nynomiya, and Wagner,24,25the polygonal Bernese osteotomy as described by Ganz,8 and their modifications.
The osteotomy described by Eppright is barrel-shaped and is oriented along an anteroposterior axis. This osteotomy allows for excellent lateral coverage, but only a limited amount of anterior coverage can be achieved.
The Wagner type I osteotomy is a single, spherical osteotomy that provides simple rotatory displacement without lengthening, shortening, medialization, or lateralization. The relative disadvantage, which involves simple acetabular realignment, is that the intact medial buttress of the quadrilateral plate prevents medialization of the joint.
The Wagner type II osteotomy is a spherical acetabular osteotomy that combines rotation of the isolated acetabular fragment with a lengthening effect. It is accomplished by placing an iliac bone graft in the cleft between the rotated acetabular fragment and the overlying ilium.
The Wagner type III osteotomy is a spherical acetabular osteotomy that involves both acetabular realignment and medialization. It is achieved by the creation of the initial basic spherical acetabular osteotomy followed by an additional Chiari-like cut proximally. Fixation usually is obtained with a special construct of tension Kirschner wires connected by a semitubular plate.
The Bernese osteotomy8 involves a series of straight cuts to separate the acetabulum from the pelvis. It is the preferred acetabular procedure at many centers for several reasons:
It can be done through one incision with a series of straight, relatively reproducible, extra-articular cuts.
It allows for large corrections of the osteotomized fragment in all directions that are needed, including lateral rotation, anterior rotation, medialization of the hip center, and version correction.
It is inherently stable, in part because the posterior column remains intact.
Minimal internal fixation is required.
Early ambulation with no external immobilization is possible.
The vascularity of the acetabular fragment through the inferior gluteal artery is preserved.
Arthrotomy can be done without risk of further devascularization of the osteotomized fragment.
The shape of the true pelvis is not markedly changed, allowing women who become pregnant after the procedure to have normal vaginal delivery.
It can be done without violation of the abductor mechanism, facilitating a relatively rapid recovery.
ANATOMY
The basic anatomy around the hip consists of the superficial surface anatomy and deep bony, muscular, and neurovascular anatomy.
The clinically relevant surface anatomy of the hip consists of several superficial bony prominences.
The anterior landmarks consist of the prominent anterosuperior iliac spine and anterior inferior iliac spine, which serve as insertion points for the sartorius and direct head of the rectus femoris, respectively.
The greater trochanter and the posterior superior iliac spine also are easily identified on the posterolateral aspect of the hip.
The proximal femur and the acetabulum constitute a very stable and constrained bony articulation, which can be classified with regard to:
Histology: synovial (diarthrodial)
Morphology: enarthrodial (ball and socket)
Axes of movement: polyaxial
The acetabulum is formed by the confluence of the ischium, ilium, and pubis, which usually are fused by 15 to 16 years of age.
It is oriented approximately 45 degrees caudally and 15 degrees anteriorly. It is hemispherical in shape and covers 170 degrees of the femoral head.
The articular surface is horseshoe-shaped and is lined with hyaline cartilage, except at the acetabular notch.
The acetabular labrum is a fibrocartilaginous structure that runs circumferentially around the periphery of the acetabulum. It increases the depth of the bony acetabulum and contributes to its stability. It is attached to the acetabular articular cartilage via a thin transition zone of calcified cartilage on the articular side. The nonarticular side of the labrum is attached directly to bone. Only the peripheral one third or less of the labrum has a rich blood supply, provided by branches from the obturator, superior gluteal, and inferior gluteal arteries. Pain fibers are most concentrated anteriorly and anterosuperiorly.
The transverse acetabular ligament connects the anterior and posterior portions of the labrum.
The ligamentum teres originates from the transverse ligament over the acetabular notch and inserts into the fovea of the femoral head.
The proximal femur is formed by the femoral epiphysis and the trochanteric apophysis, both of which ossify by 16 to 18 years of age. The femoral head is approximately two thirds of a sphere and is covered with hyaline cartilage, except at the foveal notch.
The angle between the shaft and the neck is approximately 125 degrees, with 15 degrees of anteversion related to the posterior femoral condyles.
The joint capsule attaches to the margins of the acetabular lip as well as the transverse ligament and extends like a sleeve to the base of the femoral neck. Three major ligaments reinforce it.
The iliofemoral ligament of Bigelow lies anteriorly and has an inverted Y-shape. It tightens with hip extension.
The pubofemoral ligament, which covers the inferior and medial aspect of the hip joint capsule, tightens with hip extension and abduction.
The ischiofemoral ligament lies posteriorly, and its fibers spiral upward to blend with the zona orbicularis, a band that courses circumferentially around the femoral neck. It also tightens with extension, which explains why some degree of hip flexion increases capsular laxity.
The hip joint is least stable in the flexed position, in which the capsular ligaments slacken.
Normal hip range of motion includes the following (FIG 1):
Abduction and adduction (50/0/30 degrees)
Internal and external rotation (40/0/60 degrees)
Flexion and extension (15/0/120 degrees)
The muscular attachments surrounding the hip are extensive: a total of 27 muscles cross the joint.
The primary flexors are the iliacus, psoas, iliocapsular, pectineus, rectus femoris (direct and indirect heads), and sartorius muscles.
FIG 1 • The axis and the movements of the hip.
The extensors are the gluteus maximus, semimembranosus, semitendinosus, biceps femoris (short and long heads), and adductor magnus (ischiocondyle part) muscles.
The abductors are the gluteus medius and minimus muscles, the tensor fascia lata, and the iliotibial band.
The adductors are the adductor brevis, adductor longus, and gracilis muscles and the anterior part of the adductor magnus muscle.
The external rotators are the piriformis, quadratus femoris, superior gemellus, inferior gemellus, obturator internus, and obturator externus muscles.
The blood supply originates from the common iliac arteries, which diverge and descend lateral to the common iliac veins and slightly posterior and medial to the common iliac veins. At the pelvic brim, the common iliac artery divides into the internal and external iliac arteries.
From the internal iliac system, the superior and inferior gluteal arteries and the obturator artery supply the psoas major and quadratus lumborum muscles, the pelvic viscera, and parts of the bony pelvis.
The acetabulum receives its blood supply from branches of the superior and inferior gluteal arteries, the pudendal artery, and the obturator anastomoses, all of which are branches of the internal iliac artery.
The external iliac artery continues to follow the iliopsoas muscle, first medially, then anteriorly. It exits the pelvis under the inguinal ligament and becomes the femoral artery.
The iliopectineal arch divides the space between the inguinal ligament and the coxal bone. The lacuna musculorum, which is lateral to the iliopectineal arch, contains the iliopsoas muscle and femoral nerve. The lacuna vasorum, which is medial to the iliopectineal arch, contains the femoral artery and vein.
From the external iliac system, the medial and lateral femoral circumflex artery anastomoses around the proximal femur.
The medial femoral circumflex artery has three main branches: ascending, deep, and trochanteric.
The deep branch is the primary blood supply to the femoral head. Its course starts between the pectineus and iliopsoas tendon along the inferior border of the obturator externus.
The trochanteric branch sprouts off at the proximal border of the quadratus femoris to the lateral trochanter.
Posteriorly, the deep medial femoral circumflex artery enters between the proximal border of the quadratus femoris and inferior gemellus, then travels anterior to the obturator internus and superior gemellus, where it perforates the capsule. It then gives rise intracapsularly to two to four superior retinacular vessels. The deep branch of the medial femoral circumflex artery has several anastomoses: with the descending branch of the lateral femoral circumflex artery at the base of the femoral neck; with the deep branch of the superior gluteal artery at the insertion of the gluteus medius; with the inferior gluteal artery along the inferior border of the piriformis, posterior to the conjoined tendon; and with the pudendal artery near the retroacetabular space.
The lateral femoral circumflex artery, the metaphyseal artery, and the medial epiphyseal artery contribute little to the vascularity of the femoral head.
Pelvic innervations of the lumbar plexus: L1, L2, L3, L4
The femoral nerve, located on the anteromedial side of the iliopsoas muscle, passes under the inguinal ligament as it enters the thigh.
The lateral cutaneous nerve emerges from the lateral border of the psoas major at about its middle, and crosses the iliacus muscle obliquely, toward the anterosuperior iliac spine. It then passes under the inguinal ligament and over the sartorius muscle into the thigh, where it divides into an anterior and a posterior branch.
The anterior branch becomes superficial about 10 cm below the inguinal ligament, and divides into branches that are distributed to the skin of the anterior and lateral parts of the thigh, as far as the knee. The terminal filaments of this nerve often communicate with the anterior cutaneous branches of the femoral nerve and with the infrapatellar branch of the saphenous nerve—forming, with them, the patellar plexus.
The posterior branch pierces the fascia lata and subdivides into filaments, which pass backward across the lateral and posterior surfaces of the thigh, supplying the skin from the level of the greater trochanter to the middle of the thigh.
The obturator nerve is located in the fascia directly under the pubic bone. The femoral and obturator nerves also travel with their arteries anteriorly and medially, respectively.
Pelvic innervations of the lumbosacral plexus: L4, L5, S1, S2, S3
The sciatic nerve travels without any significant arterial counterpart out to the greater sciatic foramen, with the posterior femoral cutaneous and other small nerves, to the short external rotators.
The superior gluteal nerve exits the pelvis via the suprapiriform portion of the sciatic foramen along with the superior gluteal vessels.
Palsy results in abductor lurch, also known as a Trendelenburg gait.
The inferior gluteal nerve exits the pelvis via the infrapiriform portion of the sciatic foramen along with the superior gluteal vessels.
Palsy results in difficulty in rising from a seated position and climbing stairs due to weakness of hip extension.
PATHOGENESIS
The mechanical cause of osteoarthritis is secondary to several conditions, including:
Developmental dysplasia of the hip. A maloriented articular surface with deficient anterior or global coverage of the femoral head and decreased contact area leads to excessive and eccentric loading of the anterosuperior portion and subsequently promotes the development of early osteoarthritis of the hip.10,17,26
Acetabular retroversion can result from posterior wall deficiency or excessive anterior coverage, or both, and contributes to osteoarthritis.1,2,20,22
Abnormal contact between the proximal femur and the acetabular rim during terminal motion of the hip leads to lesions of the acetabular labrum or the adjacent acetabular cartilage. This phenomenon is more common in young and physically active adults. The early chondral and labral lesions continue to progress, resulting in degenerative disease. It has been found in a variety of hip conditions more commonly than has been previously noted, including dysplasia, Legg-Calvé-Perthes disease, and post-pelvic osteotomies.
The posterior aspect of the acetabulum is subjected to high loads during the activities of daily living. With acetabular retroversion, theoretically greater unit loads are imposed on the available posterior cartilage, which may be responsible for the development of osteoarthritis of the hip.7
Joint hyperlaxity, as in Down syndrome
These patients have hips with a substantial structural deformity that predisposes the hip to dynamic instability, localized joint overload, impingement, or a combination of these factors, which results in intra-articular disease and premature secondary osteoarthritis.
NATURAL HISTORY
The anatomy of the hip joint and the development of degenerative joint disease are related.
Femoroacetabular impingement is caused by overcoverage of the acetabulum (ie, retroversion). The repeated insult leads to degenerative arthritis, rendering a joint-preserving procedure much less predictable and quality of the results dependent on the extent of cartilage damage.
Developmental dysplasia of the hip
Dysplasia without subluxation. Patients usually present because of an incidental finding of dysplasia on a radiograph or because they become symptomatic. Evidence supports the idea that dysplasia will result in degenerative joint disease in adults, particularly in women.4 Increased contact stresses at the joint interface are postulated to be the cause of articular degeneration.
Dysplasia with hip subluxation usually is accompanied by significant degenerative changes around the third or fourth decade of life.
The prevalence of osteoarthritis by the age of 50 years has been reported to be 43%3 to 50%26 in patients who have dysplasia and 53%15 in those who have Perthes disease.
Using a technique that respects the blood supply to the acetabular fragment and promotes adequate reorientation can modify the natural history of the osteoarthritis. Improvement of the insufficient coverage of the femoral head, reduction of mediolateral displacement, and correction of the version of the fragment are the main approaches to correcting malalignments of the hip.
PATIENT HISTORY AND PHYSICAL FINDINGS
Determining the etiology of hip pain can be difficult. Both extra- and intra-articular hip structures can give rise to pain, which can be referred to the groin, the lateral trochanteric region, or the lateral, medial, or anterior thigh, as well as the posterior pelvis, buttock, and lower back.
The history for patients with intra-articular hip pathology can range from an acute twisting or falling episode to the insidious onset of pain that increases over months to years. Many important symptoms may not be readily volunteered by the patient, but must be sought by the orthopedist.
The mechanically abnormal hip can either be asymptomatic or present with pain, limping, a sense of weakness, or feelings of instability, snapping, and locking.
The pain from arthritis occurs with weight bearing, with the first few steps after a period of immobilization, and is localized to the groin.
The pain from abductor fatigue is localized to the posterior iliac crest or over the abductor muscles. It may radiate as far distally as the knee.
Earlier stages of osteoarthritis secondary to dysplasia
Imbalance due to overgrowth of the greater trochanter: coxa breva and coxa vara, Legg-Calvé-Perthes disease
The pain caused by osteocartilaginous impingement depends on the activity and on the position of the limb.
May be exacerbated by combining flexion, adduction, and internal rotation
Occurs after the person has been sitting for a long period
The “C sign” is diagnostic: the patient places the index finger over the anterior aspect of the hip and the thumb over the posterior trochanteric region to indicate the location of their pain.
The acute pain related to acetabular rim syndrome12 is a sharp, sudden pain in the groin, often associated with a strong sense of instability or locking.
Instability is described as a feeling that the joint is unstable.
Snapping, locking, and clicking are common symptoms. A true locking of the hip is a sign of labral disease. Painless clicking can occur as the iliopsoas tendon snaps over the uncovered anterior femoral head, an occurrence that may be associated with dysplasia.
The physical examination includes the evaluation of stance, gait, limb lengths, strength, and range of motion, and special tests.
Patients with intra-articular pathology may stand with the hip flexed and walk with an antalgic gait with a shortened stance phase and shortened stride length.
In the presence of acetabular dysplasia, internal rotation of the hip often is increased because of excessive anteversion of the femoral neck.
If internal rotation is decreased, the patient may have secondary osteoarthritis.
The Trendelenburg test
Specific tests include:
The impingement test. The hip is rotated internally as it is flexed to 90 degrees and adducted 15 degrees. This brings the anterior femoral neck in contact with the anterior rim of the acetabulum, which is the usual site of overload in acetabular dysplasia. The test is positive in patients with acetabular rim syndrome. The patient's pain typically is in the groin.
The apprehension test. The hip is extended and externally rotated. This produces a feeling of discomfort and instability in patients who have anterior uncovering of the femoral head.
Moving the hip from full flexion, external rotation, and abduction to a position of extension, internal rotation, and adduction can recreate pain and snapping in patients with anterolateral labral tears and iliopsoas snapping hip.
Pain with supine log-rolling of the hip is the most specific test for intra-articular pathology.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Plain radiography includes an AP view of the pelvis, a falseprofile view, a cross-table view, and a functional view in abduction of the affected hip (FIG 2).
The AP radiograph of the pelvis is the view that gives the most information.
It is taken with the patient standing, allowing an assessment of the hip during load-bearing.
It must be in neutral rotation and without any pelvic tilt.
Shenton's line is assessed, because discontinuity suggests hip subluxation secondary to hip dysplasia (FIG 3).
The presence of an acetabular rim fracture may suggest rim overload.
The hip space and the presence of any degenerative changes also are assessed.
The degree of dysplasia is assessed by the following measurements:
The center-edge angle of Wiberg26: an angle subtended by a line from the center of the femoral head to the lateral acetabular margin, and a vertical line from the center of the femoral head. It also is known as the lateral center edge angle, and is greater than 25 degrees in nondysplastic hips.
The Tonnis angle14,21: the inclination of the weightbearing zone of the acetabulum. In normal hips, it should be less than 10 degrees (see Fig 3).
FIG 2 • AP (A), false-profile (B), cross-table (C), and functional (D) radiologic views of the hip.
CEA FIG 3 • Shenton's line (SL), center-edge angle (CEA), and inclination of the weight-bearing zone of the acetabulum (TA).
Acetabular version: assessed by identifying the anterior and posterior rims of the acetabulum. If the anterior line crosses the posterior line (the cross-over sign), the acetabulum is retroverted.
The false-profile view of Lequesne and de Sèze13 is obtained with the patient standing with the affected hip on the cassette, with the pelvis rotated 65 degrees from the plane of the radiographic film and with the ipsilateral foot parallel to the film. The beam is centered on the femoral head perpendicular to the cassette.
This view allows assessment of the anterior coverage of the femoral head. The ventral inclination angle can be measured by a line from the center of the femoral head to the anterior acetabular margin, and a vertical line from the center of the femoral head. It also is known as the anterior center edge angle. In normal hips the angle will be greater than 25 degrees.
The functional view in abduction is taken with the hip in maximal abduction.
It simulates the potential correction for osteotomy.
The hip should be congruent, reduced, and covered.
CT scans provide three-dimensional information with a clearer indication of the lack of coverage than plain radiographic indices.
The ideal position of the hip is full extension and 15 degrees of external rotation.
MRI
MR arthrography helps to analyze the acetabular labrum and the features related to abnormal loading.
Hypertrophy, dysplasia
Degeneration
Tears
Findings such as cartilage loss, labral lesions, and cyst formation can be predicted based on preoperative radiographic findings.
These findings may be useful in alerting the surgeon to the location and nature of intra-articular disorders that could be addressed at the time of arthrotomy.
SURGICAL MANAGEMENT
Indications for PAO
Symptomatic severe acetabular dysplasia (grade IV or V) according to Severin's classification
Symptomatic anterior femoroacetabular impingement due to acetabular retroversion20
Minimal or no secondary osteoarthritis
Young, healthy patient
Adequate congruency of the hip joint
Adequate hip flexion (100 degrees) and abduction (30 degrees)
Contraindications for PAO
Moderate to advanced secondary osteoarthritis—grade 2 or 3
Older age
Major hip joint incongruity
Obesity
Major restriction of hip motion (hip flexion of less than 100 degrees or abduction of less than 30 degrees, unless a proximal femoral procedure is planned to address femoroacetabular impingement)
For rotational osteotomy
CE angle lower than 40 degrees
Acetabular roof inclination greater than 60 degrees
Femoral head deformity inaccessible for correction
Major medical comorbidities
Patient noncompliance
Preoperative Planning
A complete history is obtained, and a physical examination is performed.
The location of, quality of, and activities associated with hip pain are recorded.
Gait pattern, leg length, and range of motion are documented.
Appropriate medical and anesthetic evaluation is performed.
Preoperative neurovascular status is documented.
Radiographic examination
AP view of the pelvis
True lateral: Dunn views, 45 and 90 degrees
False-profile: Lequesne and de Sèze view
The functional view in abduction with internal rotation may indicate the amount of correction possible.
Positioning
Bernese Periacetabular Osteotomy
The patient is positioned supine on a radiolucent table.
A footrest is secured to the table to assist in holding the extremity in a position of hip flexion.
The ipsilateral upper limb rests over the chest.
The limb is prepared and draped from above the iliac crest to the foot to allow wide access to the hemipelvis.
If needed, nerve-monitoring leads are placed and secured on the involved extremity, over-wrapped with stockinette and an adhesive wrap.
Approach
The Bernese PAO is a modified Smith-Petersen approach, a direct anterior approach that combines the iliofemoral and ilioinguinal approaches, preserving the abductor muscle attachments.
TECHNIQUES
BERNESE PERIACETABULAR OSTEOTOMY
Incision, Dissection, and Iliac Spine Osteotomy
The Bernese PAO is a modified Smith-Petersen approach that starts with a skin incision that describes a gentle medial curve from 3 cm proximally to 10 cm distally to the anterosuperior iliac spine (TECH FIG 1A).
Subcutaneous flaps are raised medially and laterally, aiming to identify the fascia over the tensor fasciae latae muscle belly.
The interneural space between the tensor fasciae and the sartorius is developed by incising the fascia in line with the muscle fibers, protecting the lateral femoral cutaneous nerve, which stays within the sartorius fascia.
The aponeurosis of the external oblique muscle is reflected medially off the iliac crest.
The anterosuperior iliac spine is osteotomized about 15 mm proximally on the iliac crest, preserving the origin of the sartorius and the ilioinguinal ligament (TECH FIG 1B).
Proximally to the osteotomized site, the periosteum on the medial edge of the iliac crest is incised and reflected medially with the origin of the iliacus muscle.
The conjoint tendon of the rectus muscle is transected and reflected distally, leaving a stump of tendon in the anterior inferior iliac spine for later repair.
A plane over the anterior hip capsule and under the psoas tendon is developed by reflecting off the iliocapsularis muscle fibers.
The hip capsule is exposed anteriorly and inferomedially, with the exposure facilitated by hip flexion.
Ischial Osteotomy
Following the capsule posteriorly, the anterior aspect of the ischium is palpated with scissors that dissect the infracotyloid groove and identify the limits:
Hip capsule, superiorly
TECH FIG 1 • A. The skin incision for the modified Smith-Petersen approach to the pelvis and the hip. B. Osteotomy of the anterior superior iliac spine preserving the attachments of the sartorius muscle and the ilioinguinal ligament.
Obturator foramen, medially
Origin of the ischiotibial muscles, laterally
The scissors are used to protect and favor the entrance of a curved (or angled), pronged, 1.27-cm osteotome.
The osteotome is positioned in the infracotyloid groove and is checked with AP and 45-degree oblique fluoroscopy views.
The infra-acetabular osteotomy starts just distal to the inferior lip of the acetabulum and aims toward the middle of the ischial spine.
At the same AP plane, the osteotome progresses as follows:
Through the medial cortex up to approximately 1 cm anterior to the posterior cortex
Through the central part of the ischium
Onto the lateral cortex, which is the least deep portion and needs no more than 20 mm of penetration (TECH FIG 2). Abduction of the hip minimizes the risk of sciatic nerve injury during this cut. Superior iliac spine Sartorius Ilioinguinal ligament Iliopsoas tendon
Pubic, Iliac, and Posterior Column Cuts
Hip flexion and adduction now facilitate exposure of the pubic ramus.
The periosteum is incised along the superior cortex, and a pair of narrow curved retractors are placed around the anterior and posterior aspects of the pubic ramus, protecting the obturator nerve. A third spiked retractor is impacted into the superior cortex at least 1 cm medial to the medial-most extent of the iliopectineal eminence, retracting the iliopsoas and the femoral neurovascular bundle medially.
The pubic cut is oriented from anterosuperior and lateral to posteroinferior and medial, avoiding creating a bony spike in the mobile fragment (TECH FIG 3A). It can be initiated with a small oscillating saw or a burr into the anterosuperior cortical, just lateral to the spiked retractor.
The posteroinferior cortical cut is completed with a straight or angled osteotome.
The periosteum must be released all around, allowing the correction.
To make the iliac cut, the ileum and the quadrilateral surface of the pelvis are stripped subperiosteally. The sciatic notch is identified with a large Hohmann retractor.
The lateral cortex of the ileum is assessed from its crest by detaching a small portion of the periosteum, allowing the insertion of a blunt retractor to protect the abductor muscles during the iliac osteotomy.
A high-speed burr is used to make a target hole approximately 1 cm superolateral to the pelvic brim.
The iliac cut is then made with an oscillating saw, first along the medial cortex and then, with the lower extremity abducted, into the lateral cortex (TECH FIG 3B).
For the posterior column cut, the column is exposed with the straight cobra retractor along the inner aspect of the true pelvis toward the ischial spine.
TECH FIG 2 • Incomplete osteotomy of the ischium should be achieved in three steps: at the medial cortex (A), at the central portion (B), and at the lateral cortex (C).
The cut into the medial cortex is made by a straight osteotome at an angle of 120 degrees to the iliac cut (TECH FIG 3C) under fluoroscopic monitoring.
The cut is then completed with a straight osteotome that extends 5 to 6 cm down or an angled osteotome that goes from medial to lateral in three or four steps (TECH FIG 3D).
Mobilization and Correction
A Schanz pin is placed in the supra-acetabular region, and the mobility of the fragment is tested (TECH FIG 4).
Lack of full mobility indicates the need to review three sites:
The periosteum around the pubic ramus
The posterior cortex at the 120-degree pivot point
The infra-acetabular cut
A bone spreader inserted into the iliac cut can be used as an auxiliary to the Schanz pin.
The correction is then carried out in whatever plane, aiming for a suitable position.
The superior pubic ramus is accessed, and the acetabular fragment is tilted anterolaterally to ensure that it can be completely unlocked.
The acetabulum is then repositioned with internal rotation and some forward tilt extension.
Translation of the fragment should be:
Medially, as desired. This can be achieved with some direct pressure from the lateral side with a pointed Hohmann retractor. Care is taken to maintain or restore anteversion.
Superiorly, in an attempt to achieve bone-to-bone contact with the overlying ilium and to minimize lengthening of the extremity with extensive corrections.
TECH FIG 3 • A. The pubic cut. B. The iliac cut is performed from the anterior superior iliac spine directly toward the sciatic notch and stops approximately 1 cm superolateral to the pelvic brim. C. The posterior column cut is directed at a 120-degree angle from the iliac cut. The orientation of this cut can be assessed with a 45-degree iliac oblique fluoroscopic view. D. The posterior column cut is completed with a 45-degree angled osteotome.
TECH FIG 4 • The acetabular fragment is mobilized with a Schanz pin.
Fixation
A provisional fixation is performed using three or four 2.5-mm Kirschner wires. An AP radiograph of the pelvis, centered over the symphysis pubis, is obtained to confirm the correction. The symphysis pubis must be in line with the sacrococcygeal joint, with the obturator foramen symmetric and the pelvis horizontal.
Meanwhile, arthrotomy is carried out to evaluate the integrity of the labrum and the femoral head-neck junction.
Large, unstable labral tears are repaired with suture anchors.
Degenerative labral tears are removed.
Lack of femoral head–neck offset is a common deformity in dysplastic hips and a cause of femoroacetabular impingement. Osteoplasty using a curved osteotome and a burr should be done.
AP radiographs must be evaluated for the lateral center edge angle, the acetabular inclination, the medial translation of the hip-joint center, the position of the teardrop, and the version of the acetabulum.
Slight undercorrection is preferred to excessive correction.
TECH FIG 5 • The definitive fixation is performed with three 4.5-mm screws and one 3.5-mm screw for the anterosuperior iliac spine.
The definitive fixation is carrying out using three or four 4.5-mm cortical screws (TECH FIG 5).
One screw is placed into the anterolateral aspect of the acetabular fragment to act as a “blocking” screw.
Two or three additional screws are placed progressively more medially.
Fluoroscopic images are made again to confirm the acetabular reduction and the position of fixation hardware.
Range of motion is assessed to rule out secondary femoroacetabular impingement and instability.
Hip flexion must be greater than 90 degrees.
Joint stability is assessed by extension, abduction, and external rotation.
Wound Closure
The prominent aspect of the anterior acetabular fragment is trimmed with an oscillating saw; the trimmings are used to fill up the iliac gap.
The anterior hip capsule is approximated with absorbable suture.
The rectus tendon origin is repaired with nonabsorbable suture.
The anterosuperior iliac spine fragment is repositioned and fixed with a small-fragment screw or nonabsorbable suture through drill-holes in the ilium.
Deep and superficial wound drains are placed. The remainder of the superficial wound is closed in a routine fashion.
POSTOPERATIVE CARE
Pain control
The hip is placed in neutral position in a soft splint.
Pain control should be compatible with the perioperative regimen.
A multimodal analgesic regimen utilizing regional blockade, nonsteroidal anti-inflammatory drugs, and other peripheral and centrally acting analgesics, including α-2 agonists, ketamine, α-2δ ligands, and opioids is one of the most efficacious strategies for reducing pain following the surgery.19
Use pain-rating scales—visual or color analogues—before discharging the patient at the 5th or 6th day.
The suction drains are removed after 48 hours.
Thromboembolism prophylaxis follows many protocols.
Chemoprophylaxis
Low-molecular-weight heparin during hospitalization
Mechanical prophylaxis
Intermittent pneumatic compression to the calves7
Heterotopic ossification prophylaxis–facultative
Not necessary when preserving the soft tissue around the hip
For at-risk situations: indomethacin, 25 mg three times per day
Physical therapy
Should be simple, emphasizing function more than strengthening or range of motion
The patient is out of bed on the third postoperative day.
Partial weight bearing (10 kg) is begun with crutches.
Active movements that could jeopardize the reinsertion of the musculature are discouraged for 6 weeks.
Resistive exercises are avoided for 12 weeks.
After 8 to 10 weeks, walking is allowed with a cane, which should be used until the abductors are strong enough to stabilize the hip.9
Consolidation
Radiographs should be taken and analyzed immediately postoperatively, at 6 weeks, and again at 12 weeks.
OUTCOMES
Reduction in pain and preoperative limp has been universal, though the degree of reduction has depended on the amount of preoperative osteoarthritis.23
The amount of acetabular redirection possible is approximately equivalent, but medialization of the joint center is achieved easily with the Bernese osteotomy.
Patients with spherical femoral heads and spherical but dysplastic acetabula can be expected to have long-lasting or permanent relief of symptoms and prevention of osteoarthritis.16
COMPLICATIONS
Complications can be classified as trivial, moderate, or major4:
Trivial–those of little clinical importance that require no treatment
Pubic non-union
Reduced lateral femoral cutaneous sensation
Asymptomatic heterotopic ossification
Moderate
Minor wound complications
Minor medical complications
Peroneal nerve neuropraxis
Fractures not requiring treatment
Major–those with the potential for significant morbidity
Nerve palsy with permanent impairment
Major bleeding
Reflex sympathetic dystrophy
Loss of fixation
Deep venous thrombosis
Deep infection
Complications, and their severity, are commonly linked with the surgeon's learning curve.4,11
Technical complications have been analyzed and correlated with some specific steps of the procedure.11
Surgical approach
Nerve injury: the lateral femorocutaneous is most commonly injured (30% of patients).
Acetabular necrosis: inferior branch of the superior gluteal artery and the acetabular branches, from inferior gluteal artery injuries
Previous procedures increase the risk.
Osteotomy
Intra-articular osteotomy
Ischium: most common on superolateral femoral head migration
Posterosuperior segment: excess of verticalization or insufficient extension of the iliac osteotomy
Posterior column discontinuity
Sciatic nerve at risk
Ischial cut
Posterior column cut
Fragment positioning
Insufficient correction
Resubluxation
Excessive correction
Resubluxation
Lateralization: stress fracture of the lateral lip
Overmedialization: progressive protrusio
Retroversion: impingement
Fragment fixation
Nonunion
Pubic—not uncommon, no treatment required Interposition of the iliopsoas muscle must be ruled out before closure.
Ischium—clinical symptoms uncertain, may need grafting
Supra-acetabular—not common, treatment required
Acetabular fragment migration
Prominent screw heads can be minimized by using 3.5mm instead of 4.5-mm screws
Postoperative period
Patient noncompliance
Lack of instructions
Routine changing
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