Introduction

Hip dysplasia in the adult can lead to pain and limping. Unfavorable leverages are responsible for the fatiguing of the abductors, whereas an insufficient coverage of the femoral head causes overload at the acetabular rim with shearing forces that result in lesions of the labrum and acetabular cartilage that eventually lead to osteoarthrosis (OA) of the hip.

The natural history of the dysplastic hip without subluxation is not well known, but it is estimated that 40% to 50% of patients with dysplasia develop OA before the age of 50 years and that approximately 50% have their first reconstructive surgeries before the age of 60 years. It appears that hips with a lateral center-edge angle (LCE angle) of less than 16 degrees or an acetabular index of more than 15 degrees will ultimately develop end-stage OA. Alternatively, it is well known that all dysplastic hips with subluxation evolve into OA during the second to third decade of life. Surgical interventions aim to alter the natural course of this degeneration.

Reorientation procedures include single, double, and triple osteotomies as well as spheric and periacetabular osteotomies. The inherent drawbacks of these osteotomies are a limited range of displacement; the potential narrowing of the pelvic cavity; and the need for a substantial internal fixation, because some techniques create a discontinuity of the pelvic ring. The medialization of the joint is difficult to achieve, and some osteotomies have an intra-articular course, because the radiologically visible teardrop remains in situ. To avoid these disadvantages, the Bernese periacetabular osteotomy (PAO) was developed in 1984. The polygonally shaped juxta-articular osteotomy respects the vascular blood supply to the acetabular fragment. It also facilitates extensive acetabular reorientation, including the correction of the version and mediolateral displacement. The posterior column remains intact, which protects the sciatic nerve and enables minimal internal fixation. The dimensions of the true pelvis remain unchanged, thus permitting unimpaired vaginal delivery. All steps of the acetabular osteotomy are performed with the use of the modified Smith-Petersen approach. During the early stages of this technique, some centers preferred the ilioinguinal approach; however, this was abandoned after several cases of thrombosis of the femoral artery, with serious consequences in some patients. In addition, the Smith-Petersen approach allows for an anterior capsulotomy for the inspection and correction of labral pathology and of potential femoroacetabular impingement. Initially, PAO was designed for the treatment of the dysplastic hip. With the recognition of orientation problems of the acetabulum—particularly retroversion—as a cause of impingement, the technique was also applied for the correction of acetabular pathologies other than dysplasia. It is currently used for the treatment of acetabular retroversion and for selected cases of protrusio.

Basic science

The insufficient coverage of the femoral head by a too-small acetabulum leads to high loads at the acetabular roof. Most often, coverage is not only insufficient, but it is also maloriented with a steep acetabular roof. This results in a small inclined plane and leads to instability and the migration of the femoral head, thus further increasing load and shear stresses at the acetabular rim. The acetabular labrum initially hypertrophies to maintain the femoral head within the joint. If the chronic shear stresses persist, the labral soft-tissue compensation fails, and the labrum is torn off of the acetabular rim, sometimes with an osseous fragment. Acetabular rim fractures usually occur only in the presence of bone cysts, which have weakened the bony rim.

Histomorphologically, the labrum shows myxoid degeneration of its fibrocartilage structure and adjacent ganglion formation within the bone or soft tissues. In addition to increased femoral head instability, the joint-sealing function, which is required for cartilage lubrication and the distribution of joint pressures, is also lost. In this mechanically adverse situation, an increase of joint contact pressures at the acetabular rim is directly related to the onset of cartilage degeneration. As an adaptation to the increased load transmission, an increase in the subchondral bone density at the anterolateral acetabular rim can be observed.

Indications

In the presence of severe dysplasia or aspheric congruency, simultaneous femoral osteotomy for optimal positioning of the femoral head has to be evaluated.

Contraindications

A definite upper age limit does not exist. However, patients who are more than 50 years old are rarely treated with an acetabular osteotomy. In contrast with distant pelvic osteotomies, the Bernese PAO crosses the posterior line of the triradiate cartilage. Therefore, this osteotomy is not indicated if substantial growth potential remains within this physis.

Brief history and physical examination

Imaging and diagnostic studies

Surgical technique

The patient is in a supine position with the lower limb draped free. The iliac crest and the proximal half of the thigh should be accessible. Surgery is performed through a modified Smith-Petersen approach with osteotomy of the anterosuperior iliac spine (ASIS). The first part of the dissection is performed with the hip in extension. The incision starts at the gluteal tubercle of the iliac crest, curves just lateral to the ASIS, and continues in a curved way to the lateral aspect of the proximal thigh. The subcutaneous tissue is incised in line, and a lateral skin flap is developed until the fat layer between the fascia of the sartorius and the tensor fasciae latae becomes visible. The main branch of the lateral femoral cutaneous nerve lies in this fatty tissue. The muscle belly of the tensor fasciae latae is identified, and its fascia is split lengthwise. The dissection follows the fascia medially into the interval between the tensor fasciae latae and the sartorius muscle. The tensor is pulled laterally with a narrow Langenbeck retractor. Slight abduction of the lower limb helps to relax this muscle. The floor of the muscle compartment is incised longitudinally, and the lateral border of the muscle belly and the tendon of the rectus femoris, including its reflected part, are visualized. The fascia between the rectus and the tensor can be of quite variable thickness, and, in the distal part of the incision, the ascending branch of the lateral femoral circumflex artery runs within this fascial layer between the rectus and the tensor fasciae latae. These blood vessels represent an important source of vascularization of the tensor fasciae latae and therefore have to be protected. The blood vessels are mobilized from the fasciae to allow for the spread of the deep layers of the approach.

The origin of the external oblique muscle that overhangs the iliac crest is lifted and detached subperiosteally from the iliac crest to about 1.5 cm from the ASIS. The ASIS is osteotomized about 1.5 cm to 2 cm proximal to the palpable tip of the ASIS. The osteotomized ASIS is mobilized medially together with the origin of the sartorius and the inguinal ligament. The dissection of the inner table of the iliac wing is continued strictly subperiosteally down to the pelvic brim. In approximately half of patients, the nutrient artery of the iliolumbar artery enters the iliac wing lateral to the pelvic brim. This blood vessel has to be visualized carefully and coagulated. There may be considerable backflow from the bone; if this happens, hemostasis can be performed with the use of bone wax to obstruct the blood vessel. In the other half of patients, the nutrient artery enters the bone medial to the pelvic brim and cannot be controlled. In these cases, blood loss through the supra-acetabular osteotomy can be substantial and can only be controlled by bone wax after the mobilization of the acetabular fragment. The periosteal and muscle connection with the osteotomized ASIS should be preserved, thus preventing a stretching of the femoral cutaneous nerve, even if the wound is considerably spread. The intact periosteum that covers the iliac muscle protects this muscle during the entire operation. The exposure of the inside of the pelvis is continued by detaching the origin of the iliac muscle along the interspinous crest until the origins of the direct and reflected heads of the rectus become visible. At this time, it is advantageous to hold the hip in 40 degrees of flexion with the leg holder to relax the medial soft tissues.

The direct head of the rectus is detached from the anteroinferior iliac spine (AIIS), and the indirect head is divided. The rectus femoris then is retracted medially with a Langenbeck retractor, and the lateral limit of iliocapsularis muscle becomes visible. Particularly among patients with dysplastic hips, the iliocapsular muscle (i.e., the capsular part of the iliac muscle) can be hypertrophic and well visible lying on the joint capsule. The main site of origin lies at the distal border of the AIIS.

The iliocapsular muscle is detached from the capsule by sharp dissection going from lateral to medial until the iliopectineal bursa is opened and the psoas tendon becomes visible. The psoas tendon is undermined and retracted medially with the use of a pointed Hohmann retractor driven into the pubic ramus 1 cm to 1.5 cm medial to the iliopectineal eminence. The psoas tendon protects not only the femoral nerve but also the femoral vessels from overstretching; therefore, it should never be divided. The iliocapsularis muscle is now completely detached from the capsule, thus exposing the anteroinferior part of the capsule around the calcar. Any accidental opening of the capsule should be closed, because a closed capsule being put under tension facilitates the dissection of the ischial ramus. During this stage, a large, curved pair of scissors with rounded ends is advanced along the anteroinferior capsule, and the space between the capsule and the obturator externus is enlarged by spreading the scissors (Figure 26-1). The transversely running muscle belly of the obturator externus can often be seen. Because the medial femoral circumflex artery that supplies the femoral head runs distal to the muscle belly, scissors and other instruments must stay strictly proximal to the muscle belly. If visualization is impossible, it is safe to keep the instruments in close contact with the capsule.

Figure 26–1 The completed approach. The osteotomy of the anterosuperior iliac spine allows for the preparation of the inner pelvis. A Hohmann retractor sits on the pubis. The iliocapsularis is detached from the capsule, and the scissors are placed around it. With the tip of the scissors, the ischium is palpated.

All osteotomies are performed with the patient’s hip in 45 degrees of flexion. The first cut is the partial osteotomy of the ischium (Figure 26-2). The scissors follow the capsule in a posterior direction until the ischial ramus is reached in the area of the infracotyloid notch. With the tip of the scissors, one can palpate the posterior and inferior border of the facies lunata of the acetabulum. The width of the ischium is assessed by gliding the scissors medially into the obturator foramen and then laterally until a soft resistance prevents further dissection. The soft-tissue resistance is formed by the tendinous origins of the ischiocrural muscles, which exceed the lateral border of the ischium when the hip is flexed. Respecting this resistance helps to avoid the lateral slipping of an instrument and thus protects the sciatic nerve. A large periosteal elevator or a Cobb elevator can be used to assist with the introduction of a 15-mm curved pelvic osteotome. The infracotyloid notch is palpated with the osteotome. The osteotome should point in the direction of the contralateral shoulder to avoid exiting through the lateral cortex and putting the sciatic nerve in danger. The handle of the osteotome points in a posteroinferior direction. The entry point of the osteotome is carefully made, and it is then driven slowly to a depth of 20 mm to 25 mm while the direction of the handle is gradually changed so that, at the end of the insertion, the handle points posterosuperiorly. At this stage, it is important to remember that the posterior column is not osteotomized completely. With wiggling motions, the osteotome is pulled back to the entry point, but the blade remains in contact with the bone. By doing this, one can feel whether the medial and lateral cortical borders are still intact. At the level of the entry point, the osteotome is moved carefully onto the remaining medial bone bridge and advanced with the same technique as used previously. The same technique is then applied to the lateral side. To relax and protect the sciatic nerve, the flexed hip has to be abducted and externally rotated. Of special importance is the fact that the medial cortex should be cut, whereas the lateral cortex should only be notched for the protection of the sciatic nerve. To determine whether the osteotomy is sufficiently deep and especially to be sure that the medial cortex is included in the osteotomy, the osteotomy is carefully repeated. The orientation as well as the depth of the partial osteotomy can be checked with the image intensifier. A sufficiently deep cut is the most important prerequisite for the problem-free displacement of the acetabulum at the end of all osteotomies.

Figure 26–2 Osteotomy of the ischium.

The second cut is the osteotomy of the superior pubic ramus, which is made just medial to the iliopectineal eminence. To ease visualization, the flexed hip is slightly adducted. A 16-mm Hohmann retractor is placed 1 cm to 1.5 cm medial to the eminence. The periosteum of the superior pubic ramus is incised, and the base of the pubic ramus is exposed subperiosteally; two blunt retractors are inserted around it to protect the obturator nerve and vessel. With the use of a 15-mm Lexer osteotome, a complete osteotomy is made that starts medial to the iliopubic eminence and perpendicular to the long axis of the pubic ramus, with the osteotome pointed medially at a 45-degree angle. One of the blunt retractors is placed into the osteotomy of the superior pubic ramus.

For the remaining three osteotomy steps, the approach to the quadrilateral plate is completed, and the abductors have to be tunneled. For the approach to the quadrilateral plate, the periosteum along the anterior surface of the anterior wall of the acetabulum, starting at the iliopectineal eminence, is incised and stepwise detached medially and inferiorly. Beyond the pelvic brim, the use of a curved periosteal elevator is recommended. To improve the stability of the reversed blunt Hohmann retractor positioned on the ischial spine, the dissection should not be carried out into the greater sciatic foramen. Having cleared the entire surface of the medial acetabular wall, the reversed blunt Hohmann retractor is inserted and levered against the ischial spine. The entire space up to the sacroiliac ligaments can now be viewed. Adduction of the flexed leg allows for the reduction of the soft-tissue tension (Figure 26-3).

Figure 26–3 The abductors are tunneled, and a reversed Hohmann retractor is placed into the greater sciatic notch to protect the sciatic nerve. A second reversed Hohmann retractor is placed medially onto the sciatic spine to retract the intrapelvic musculature medially to allow for the wide exposure of the quadrilateral plate.

Only limited subperiosteal tunneling is necessary at the outer wall of the ilium; all that is needed is just enough to insert a reversed blunt Hohmann retractor down to the greater sciatic foramen to protect the muscles and the sciatic nerve during the supra-acetabular and retroacetabular osteotomies. Halfway between the ASIS and AIIS and starting just distal to the osteotomy of the ASIS, the gluteus minimus is detached by sharp dissection over a distance of 3 cm and then freed with a curved periosteal elevator until the tip of a blunt reversed Hohmann retractor can reach the greater sciatic foramen. The tunneling proximally should not involve the remaining fibers of origin of the tensor fasciae latae; distally, an area approximately 3 cm wide should be left at the origin of the gluteus minimus. In this latter area, the supra-acetabular branch of superior gluteal artery is embedded to ensure the blood supply to the supra-acetabular region.

The supra-acetabular and retroacetabular osteotomies (i.e., the third and fourth steps) are performed in two parts. First, the planned line of osteotomy is marked on the inside of the ilium with a straight 10-mm Lexer osteotome. The marking starts on the lower border of the osteotomized ASIS and continues perpendicularly in a posterior direction, stopping short of the pelvic brim by 1.5 cm. The mark then continues, usually at an angle of 110 degrees to 120 degrees distally in the direction of the ischial spine. The determination of the apex and the degree of the angle can vary, depending on the patient’s anatomy. It is important that the retroacetabular cut be made at a distance of at least 1 cm away from the greater sciatic notch. With an oscillating saw, the first step—the supra-acetabular osteotomy—is performed (Figure 26-4). Second, with a curved Simal osteotome, the remaining distance to the pelvic brim is osteotomized at an angle of 110 degrees to 120 degrees to the first cut. The purpose of this cut is to osteotomize the bone completely; therefore, it is important that the curved retractor introduced on the external side of the pelvis remains in situ to protect the abductors and the sciatic nerve (Figure 26-5). With a straight Simal osteotome, the cortical bone of the quadrilateral plate is cut at a distance of approximately 1.5 cm anterior to the greater sciatic notch (Figure 26-6). Only the first 20 mm to 30 mm must be osteotomized; the remaining bony bridge in the direction of the sciatic spine will be broken later on in a controlled fashion. Because the subchondral bone of the joint and the rim of the greater sciatic notch are very hard, this controlled fracture always succeeds without extending into the joint or the greater sciatic notch.

Figure 26–4 The supra-acetabular osteotomy starts at the distal end of the osteotomy of the anteroinferior iliac spine and runs in a perpendicular direction to a point approximately 1 cm lateral to the iliopectineal line.

Figure 26–5 With a curved osteotome, the remaining distance to the pelvic brim is osteotomized. The osteotome is aimed at the lateral cortex. The soft tissues and the sciatic nerve are protected by the lateral retractor.

Figure 26–6 With a straight Simal osteotome, the cortical bone of the quadrilateral plate is cut at distance of approximately 1.5 cm anterior to the greater sciatic notch.

A 15-mm Lexer osteotome is introduced into the second posterior part of the osteotomy. By pulling the handle forward, a lever movement is exerted against the acetabulum until the bridge toward the sciatic spine breaks. If this maneuver does not succeed with moderate force, then the posterior part of the osteotomy should be extended more distally. The acetabulum is still attached to the pelvis at the posterior and caudal corner through a bone bridge between the first ischial cut and the posterior part of the supra-acetabular osteotomy. A Schanz screw is inserted through the AIIS into the supra-acetabular bone and parallel to the inner wall. The remaining bone bridge is now put under tension. With a spreader inserted into the posterior part of the supra-acetabular osteotomy and pulled through at the Schanz screw in a distal and lateral direction, the acetabulum is tilted distally and laterally; this allows for a better view of the quadrilateral plate. A 20-mm-wide angled pelvic osteotome is advanced 4 cm below the pelvic brim at an angle of 50 degrees to the quadrilateral plate in the direction of the endpoint of the first ischial osteotomy (Figure 26-7). The osteotome is advanced with careful hammer blows until resistance ceases. This is repeated two to three more times with more distal positioning of the osteotome. A decrease in tension is felt by less resistance at the Schanz screw and by a loosening of the spreader. Under no conditions should the chisel be advanced beyond the point at which no more resistance is felt because of the risk of injury to the sciatic nerve. The complete mobilization of the acetabular fragment is done by opposing the forces of the Schanz screw and the spreader: the Schanz screw is rotated forcefully medially, whereas the spreader is rotated externally to the outside of the pelvis. By doing this, the last part of the posteroinferior bone bridge is fractured.

Figure 26–7 With a large spreader, the remaining bone bridge between the ischial osteotomy and the supra-acetabular osteotomy is put under tension. The osteotomy propagates more distally and is completed with the large special osteotome, and the fragment then is mobilized. The Schanz screw is rotated forcefully medially, whereas the spreader is rotated externally to the outside of the pelvis. By doing this, the last part of the posteroinferior bone bridge is fractured.

The acetabular fragment is now freely movable and thus can be reoriented. Because there is a tendency of the dysplastic joint to lateralize, the fragment must be correspondingly medialized. If the center of rotation is in a proper position, the correction is achieved by rotating the acetabular fragment around the femoral head. A supra-acetabular gap that appears during correction is always the result of hinging caused by incomplete posterocaudal mobilization or a persisting bone bridge (Figure 26-8). The correction depends on the area of deficient cover. The preoperative assessment of the anteroposterior pelvic radiograph includes an analysis of the lateral, anterior, and posterior coverage. Anterolateral deficiency is most commonly present, but one has to be aware that approximately 15% of these hips have a posterior deficiency (i.e., acetabular retroversion). For the most common type, the main correction is an anterior rotation in combination with some internal rotation. In general, this leads to sufficient lateral coverage. The correction is provisionally stabilized with two 2.5-mm threaded Kirschner wires advanced from the iliac crest into the fragment. The checking of the correction is performed with an anteroposterior radiograph of the entire pelvis that permits for a comparison with the opposite hip. The inclination of the weight-bearing area of the acetabulum should not go beyond the horizontal plane. The edges of the anterior and posterior wall should meet at the lateral edge of the sourcil. The center of the femoral head should lie neither too lateral nor too medial as measured by the distance between the medial border of the femoral head and the ilioischiatic line. Novices in particular run the risk of overcorrection, either by exaggerating the lateral coverage or by creating retroversion of the acetabulum. Overcorrection of the acetabulum may lead to a pincer type of femoroacetabular impingement. Even for the experienced surgeon, several adjustments and corresponding radiographs are necessary.

Figure 26–8 Schematic images of the different locations of hinging. A, If the acetabulum is rotated around an inferior hinge (i.e., an incomplete osteotomy of the ischium), the hip joint is lateralized. B, A completely free fragment allows for rotation around the center of the femoral head. C, Conversely, if the fragment is not mobilized completely cranially or in the area of the pubis, the correction will medialize the center of the rotation.

Occasionally, after preceding femoral osteotomies or in the presence of aspheric deformities of the femoral head, a simultaneous varus or extension osteotomy of the femur is necessary to stabilize the femoral head and to improve congruency. Intraoperative radiographs in abduction as well as abduction and flexion will supply the necessary information.

While waiting for the intraoperative radiographs, the joint is opened with a “T”-shaped incision, and the labrum is inspected. Only free-floating flaps or intralabral ganglia are removed. Should a large acetabular rim fragment be present, the pseudarthrosis is freshened, and the fragment is fixed with a mini screw. With the joint opened, the head–neck junction is evaluated for potential causes of impingement. If necessary, a bulge at the anterolateral transition between head and neck is shaped so that a normal neck diameter results and neither flexion nor flexion and internal rotation interfere with the acetabular rim. Flexion of up to 95 degrees and a balanced rotation to either side in 90 degrees of flexion is desirable.

The definite fixation is achieved with two 3.5-mm cortex screws of 60 mm to 80 mm in length that are introduced from the iliac crest into the acetabular fragment. An additional screw is inserted from the AIIS through the fragment and aimed at the sacroiliac joint. Occasionally a 3.5-mm reconstruction plate at the inner side of the pelvis is needed, particularly for patients with osteoporosis or after a substantial correction. The bone of the acetabular fragment that exceeds anteriorly is removed and inserted into the osteotomy cleft.

The capsule is closed loosely with resorbable sutures. The direct and reflected heads of the rectus are reinserted with the use of transosseous, nonresorbable sutures. The osteotomized ASIS is fixed with a 2.7-mm cortical screw. The abdominal muscles are reattached back to the iliac crest and the fascia of the proximal thigh is closed with absorbable sutures. Suction drains are placed subcutaneously (but not intrapelvicly), if necessary; because of the large cancellous osteotomy surfaces, the patient could be exsanguinated.

Figure 26-9 shows the preoperative and postoperative radiographs of a patient with bilateral dysplasia.

Figure 26–9 A, Preoperative radiograph of a 35-year-old female patient with bilateral dysplasia. The left side shows already some mild joint space narrowing. B, The same patient 10 years (left side) and 9 years (right side) after periacetabular osteotomy. The joint spaces are stable without further signs of degeneration, and excellent results are seen on both sides.

Postoperative rehabilitation

The leg is positioned in a foam splint with the hip in extension and the foot in a neutral position. After 1 to 2 days, the suction drains are removed, and the dressing is changed. Mobilization is started on the first or second postoperative day with two crutches. Touch-down weight bearing of approximately 15 kg is allowed for 8 weeks. At this time, physiotherapy is limited to instruction in and surveillance of proper gait and partial weight bearing. The lifting of the extended lower limb while in a supine position is not allowed for 6 weeks so as not to disturb the reattached hip flexors. After 8 weeks, the progression of the union is checked radiographically. If signs of bony union are present, progressive weight bearing and strengthening exercises of the hip abductors are started. Physiotherapy is now directed to gain back normal strength and coordination. Three months postoperatively, walking without a limp and a cane should be possible. Before allowing the patient to discontinue the use of crutches, the Trendelenburg sign should be negative and normal abductor strength should be present when the patient is tested in the lateral decubitus position.

Results and outcomes

Siebenrock and colleagues reported about 75 symptomatic dysplastic hip joints in 63 patients treated with the Bernese PAO. This group included the first series of PAOs performed between 1984 and 1987. The mean patient age was 29 years (range, 13 to 56 years), and the female-to-male ratio was 3.4 to 1. Fifty percent of the hips were Severin grade III, and 44% were Severin grade IV with signs of subluxation. Osteoarthrosis was present in 51% of the patients. Twenty-three patients (31%) had previous acetabular (14 hips) and femoral (9 hips) surgery for the treatment of the dysplastic hip. The average follow up time was 11.3 years (range, 10 to 13.8 years) in 71 hip joints (95%). In 58 patients (82%), the hip joint was preserved at the last follow up, with good to excellent results in 73% of these patients. Unfavorable outcomes were significantly associated with an older age of the patient, moderate to severe joint degeneration at the time of surgery, labral lesions, less anterior coverage correction, and a suboptimal acetabular index. The presence of joint degeneration was correlated with a significantly worse outcome. The analysis of the hip joints with only Tönnis grade 0 or 1 degeneration showed good to excellent outcomes in 88% of patients.

Major complications were encountered in the first 18 patients, including an intra-articular cut in 2 patients, excessive lateralization in 1 patient, a secondary loss of correction in 2 patients, and femoral head subluxation in 3 patients.

Steppbacher and colleagues reevaluated the initial study group after 20 years. Four patients (5 hips) were lost to follow up, and 1 patient (2 hips) had died. The remaining 58 patients (68 hips) were followed for a minimum of 19 years (mean, 20.4 years; range, 19 to 23 years), and 41 hips (60%) were preserved at the final follow up. Forty-one hips (60%) had a preserved hip joint at 20 years, which corresponds with a cumulative Kaplan-Meier survivorship rate of 60.5% (range, 48.7% to 72.2%; 95% confidence interval). Twenty-six hip joints (38%) were converted to total hip arthroplasty, and one had a hip fusion at a mean time of 11.7 ± 5.9 years (range, 0.9 to 19.3 years). The 41 surviving hips (60%) had a mean Merle d’Aubigné score of 15.8 ± 2.1 at the final follow up. Of these, 81% (33 hips) were graded as good to excellent, 15% (6 hips) were graded as fair, and 5% (2 hips) were considered poor. No major changes in any of the radiographic parameters were observed during the 20-year postoperative period, except for the osteoarthrosis score. Six factors that are predictive of poor outcome were identified: 1) age at surgery; 2) preoperative Merle d’Aubigné score; 3) positive anterior impingement test; 4) limp; 5) osteoarthrosis grade; and 6) postoperative extrusion index.

In general, there is only very limited long-term experience with other reorienting acetabular osteotomies; in fact, there is only the study of Schramm and colleagues that involved 22 patients who underwent Wagner osteotomy for the treatment of the dysplastic hip. The mean age at surgery was 24.4 ± 9.7 years, and 19 women and 3 men were treated. Seventeen hips had no signs of osteoarthrosis. The authors reported a survivorship of 68% for the first 22 cases of spheric periacetabular osteotomy after a minimum follow up of 20 years. The remaining 15 hips had an average Harris Hip Score of 86 points (range, 50 to 100 points), and the clinical results were rated as good or excellent for 11 of the 15 patients. Risk factors for failure were the incongruency of the joint and a poor preoperative Harris Hip Score. The Kaplan-Meier survival rate estimate with conversion to total hip replacement as the endpoint was 86.4% at 20 years.

In a study that was specifically designed to assess the influence of osteoarthrosis on outcome, Trousdale and colleagues retrospectively reviewed 42 patients after PAO with and without intertrochanteric osteotomy performed between January 1984 and December 1990. There were 8 male and 34 female patients. The average age of the patients at the time of the operation was 47 years (range, 11 to 56 years). Ten patients had combined PAO and intertrochanteric osteotomies. Osteoarthrosis was graded according to the Tönnis classification: it was grade I in 15 patients, grade II in 18 patients, and grade III in 9 patients. Follow up averaged 4 years (range, 2 to 8 years). The Harris Hip Score improved significantly (P < .0001) from an average of 62 points preoperatively to an average of 86 points postoperatively. Results were excellent or good for 32 of the 33 patients with grade I or II osteoarthrosis. Eight of the 9 patients who had grade III osteoarthrosis had a Harris Hip Score of less than 70 points at the final follow up. Six patients subsequently underwent total hip arthroplasty, and 3 patients had an additional intertrochanteric osteotomy. Reported complications included heterotopic ossification in 14 patients (33%), nonunion of the pubic osteotomy in 2 patients (5%), and pain related to the hardware that led to its removal in 9 patients (21%). Overall, the study showed that the amount of preoperative arthrosis correlated with postoperative outcome.

There are several short-term outcomes reported from various centers. The results are remarkably consistent and can be summarized as follows: patients with minimal to moderate arthritic changes usually achieve pain relief and improved function after surgery. However, patients with advanced radiographic degenerative changes have less predictable success (Table 26-1).

Complications

In addition to the usual surgical risks of bleeding, thrombophlebitis, embolism, and infection, there are some additional risks related to the surgical approach, the osteotomy, and the things that occur after treatment.

Risks associated with the approach include the avulsion of the reattached muscles (i.e., musculus sartorius, musculus rectus femoris); injury to vessels (i.e., obturator vessels, medial femoral circumflex artery) and nerves (i.e., lateral femoral cutaneous nerve, obturator nerve, femoral nerve, sciatic nerve); and heterotopic ossification. Most commonly, some damage to the lateral femoral cutaneous nerve is observed. The course of the nerve in the area of the ASIS is highly variable. To avoid damage to the main branch, the fascia over the tensor should be incised lateral to the fatty streak, including the nerve. The patient has to be advised that numbness of the proximal lateral thigh may occur. However, other nerve lesions are rare. In the series of the senior author, 7 of more than 1000 PAOs result in the permanent loss of sciatic nerve function. Damage to the femoral nerve is very uncommon, but the nerve may become overstretched after a Sharrard procedure in which the iliopsoas muscle is transferred and thus no longer protecting the femoral nerve. The nerve may also incur damage during corrections that include substantial medial tilting of the acetabular fragment during the correction of acetabular retroversion. Heterotopic ossification is observed around the origin of the rectus femoris muscle; this ossification may cause extra-articular impingement with a painful limitation of flexion.

Complications associated with the osteotomy include intra-articular osteotomy, fracture of the posterior column, undercorrection, overcorrection, a loss of fixation, delayed union, and nonunion. Nonunion of the pubic ramus is rarely seen (it is more often seen with major corrections). In general, the condition is not painful, and it necessitated a revision in only one of our patients. A fracture through the posterior column may result in a nonunion of the ischium. In three of our patients, this was painful and required revision with bone grafting and plating.

Proud screw heads at the iliac crest may cause tenderness and may have to be removed. During the postoperative course, a loss of correction can result from weight bearing that occurs too early; surgical revision to realign the acetabular fragment should occur as soon as possible. Additional supra-acetabular fixation with a 3.5-mm reconstruction plate from the inside of the pelvis has to be considered. Avulsion of the reattached ASIS after a straight-leg raise has to be revised as well.

A consequence of the increased coverage of the femoral head—and not really a complication—is a slight decrease in the overall range of motion.