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Residual acetabular dysplasia is known as the most frequent cause of osteoarthritis of the hip, leading to joint destruction in 25% to 50% of cases by the age of 50 years [1]. In the classic pathomorphology, the degeneration starts early with overload of

1 Department of Orthopaedic Surgery, Balgrist University Hospital, Forchstr. 340, CH-8008 Enrich, Switzerland

2 Department of Orthopaedics Surgery, Schulthess Clinic Lengghalde 2, CH-8008, Zürich, Switzerland the anterolateral joint, visible by the increased subchondral sclerosis on standard anteroposterior (AP) X-rays [2].

It is well accepted today [3] that surgical increase of the local transmission area and a more even load transmission can slow the process of destruction and postpone total hip replacement substantially. Among the different techniques available, reorientation procedures allow for the most physiological correction of the joint mechanics. We have performed most of the described techniques. Based on limitations with several of the former techniques (Table 1), we defined in 1983 the aspects to be achieved with a new technique as follows: optimal correction including version and medialization of the acetabular fragment; a single approach to avoid repositioning of the patient during the procedure; easy fixation of the fragment allowing for early ambulation; and unlimited access to the joint to treat intracapsular pathologies without the potential risk of avascular necrosis of the acetabular fragment. Finally, the new technique should allow major bilateral correction without narrowing of the birth canal because most of the patients are females of reproductive age.

The new technique, which was tested on 25 cadavers and performed for the first time in March 1984 (Fig. 1), consists of five osteotomy steps beginning with an

Table 1. Characteristics of reorientation procedures

Author(s)

Type of osteotomy

Incisions

Possible intracapsular surgery

Relationship to acetabulum

Perfusion of fragment

Salter [34] Sutherland [35]

Single Double

Distant Distant

LeCoeur [37]

Double

Triple

Triple Triple

Distal intraarticular Juxtaarticular

Distant Juxtaarticular

Carlioz [40]

Triple

Juxtaarticular

Nishio [ 41 ] Ninomiya [42] Eppright [43] Wagner [ 44] Kuznenko [45] Ganz [5]

Spherical

Spherical

Spherical

Spherical

Translation

Periacetabular

Close Close Close

Close ?

Juxtaarticular

incomplete cut of the ischium followed by the complete osteotomy of the pubis. For the supra- and retroacetabular chevron-type osteotomy, we abandoned early the detachment of the abductor muscles from the ilium for a complete intrapelvic execution. The last osteotomy is to combine the incomplete cuts (1 and 4 on Fig. 1) and is again performed from the inside of the pelvis [4] (Fig. 2). For the execution, a set of special retractors and osteotomes is needed. Intraoperative fluoroscopy is not necessary, although it is used by most surgeons. Although the execution of the osteotomies becomes easy with time, the precise special orientation of the fragment remains challenging (Fig. 3). For the fixation of the standard correction, 3 x 3.5 mm screws 50 to 80 mm in length are sufficient. Postoperative treatment consists of toe-touch weight-bearing for 6 to 8 weeks. Ninety percent of the hips are consolidated by then for full weight-bearing. Over the following years, several vascular studies have been performed to confirm the intact perfusion of the acetabular fragment [5-8].

The technique and our own results have been published on several occasions [5,9-11]. The procedure has gained popularity, especially in North America [12-19]. Our own experience is based on more than 1500 operated hips over the years.

Possibility of correction

Limiting factors

Narrowing of

Osteotomy

Anterior

Lateral

Mediali-

Version

for reorientation

birth canal

crossing

cover

cover

sation

growth plate

+(+)

+(+)

Symphysis

++

+ +

+

?

Sacrospinal+

sacrotubular

ligament

?

?

?

?

Sacrospinal +

?

+

sacrotubular

ligament

+ +(+)

+ +(+)

+

?

Sacrospinal +

?

sacrotubular

ligament

+ +(+)

+ +(+)

+

?

Sacrospinal +

?

sacrotubular

+ + + +

+ + + +

+ +

?

Periosteum on

With large

quadrilateral

bilateral

surface

correction

+ + +

+ + +

+ +(+)

?

Sacrospinal

With large

ligament

bilateral

correction

+ + +

+ + +

(+)

?

Capsule

+ + +

+ + +

(+)

?

Capsule

+

+ + +

+ + +

(+)

?

Capsule

+

+ + +

+ + +

++

?

Capsule

+

?

?

?

?

?

?

?

+ + + +

+ + + +

+ + + +

+ + +

Capsule +

+

attached

abdominal

muscle

Knee Joint Ray Mp1

Fig. 1. First case of periace-tabular osteotomy (PAO). a Anteroposterior (AP) pelvic radiograph of a 13-year-old girl with a proximal femoral focal deficiency (PFFD) of the left side and a functional hip. Previous surgery was a valgus intertrochanteric osteotomy and a femoral shaft lengthening procedure. The acetabu-lum is very shallow and retroverted; the proximal femur shows a hypoplastic epiphysis on a thick and short femoral neck. b Postoperative radiograph after PAO and intertrochanteric revalgiza-tion osteotomy. In 1984, the retroversion of the acetabu-lum was not recognized as part of the pathomorphology and has therefore not been corrected. Eight weeks later, a posterior subluxation was recognized and treated with a posterosuperior shelfplasty using a plate for fixation. c The left hip, 21 years after periacetabular surgery, with a reasonably good clinical result (no pain, relative abductor weakness) and a congruent and rather large joint space

Fig. 2. Schematic drawing of the various osteotomy steps for the periacetabular osteotomy. Osteotomy of the anterosuperior iliac spine (0) is required for a sufficient approach. The first osteotomy is the "blind" partial ischial cut (1), followed by the pubic osteotomy (2); this is followed by the supraacetabular (3) and retro-acetabular osteotomy (4), before the controlled fracture is induced

Fig. 3. Orthograde intraoperative AP pelvic radiograph. Orthograde means that the tip of the os coccyx points toward the middle of the symphysis and the distance between the tip of the sacrococcygeal joint and the symphysis ranges between 2 (men) and 4 (women) cm [33]. With such an intraoperative tray, several parameters are controlled: the distance between femoral head and ilioischial line, the inclination of the supraacetabular sclerosis over the femoral head (acetabular index), the anterior and posterior border of the acetabulum, and finally the Menard-Shenton line, which in an ideal condition should be normalized after the periacetabular osteotomy

One of the earlier experiences was the phenomenology of acetabular rim pathologies before the cartilage itself becomes affected. Although it was known that the labrum can become avulsed in hip dysplasia [20], the incidence of such lesions was seen to be much more frequent with radial magnetic resonance (MR) arthrography [21] and potentially accompanied by other rim pathologies as ganglion formation in the labrum, the surrounding tissue, and the periacetabular bone. Rim fractures could be identified as part of a labrum rupture and as such are mostly seen in rather congruent hips [22]. Using MRI, we also could see that some labral ruptures showed the disconnection deep in the acetabular cartilage, indicating a clearly reduced prognosis for a reorientation procedure when compared with a case having avulsion of the labrum alone (Fig. 4).

Our 10 years of results with periacetabular osteotomy (PAO) finally show that cases without labral lesions do better in the long run, indicating that the labrum lesion is a precursor or even the first step of osteoarthritis of a dysplastic hip because it takes part in the load transmission and, when it fails, the head migrates further out of the socket with substantial deterioration of the load transmission and the beginning of rapid joint destruction [22]. The observation that the labrum in acetabular dysplasia is hypertro-phic has added a further argument in borderline morphologies where it may be unclear whether the hip suffers from dysplasia or impingement from another patho-morphology such as retroversion [21]. Whether rim pathologies should be treated or left alone while performing a periacetabular osteotomy is the subject of ongoing dis-

Fig. 4. a Magnetic resonance imaging (MRI) shows an avulsion of the labrum from the osseous rim with a substantial gap between the two structures. The femoral head is migrating out of the joint after the labrum as last resistance has failed. b Frontal MR image shows that the avulsed labrum comes with a substantial flap of acetabular cartilage (arrow indicates level of separation)

cussion. It is a general observation that hips with a small labral avulsion normally become asymptomatic even without an attempt to resect or refix this structure. It may be possible with smaller rim fragments that become unloaded in a similar way after osteotomy and may eventually consolidate. Intraosseous ganglia also can disappear spontaneously after a redirection of the acetabulum. However, as soon as these lesions surpass a certain size, an attempt to treat the lesion is justified or even recommended. This conclusion is especially true for large and floating bucket-handle lesions of a degenerated labrum (Fig. 5) and for large supraacetabular ganglion formation.

We further learned over the years that acetabular dysplasia is not uniform antero-lateral insufficiency of coverage of the femoral head but shows a multitude of pure and combined anterior, lateral, and posterior dysplasias. Li and Ganz [23] showed that one of six dysplastic hips were retroverted (Fig. 6). Mast et al. [24] found, with one of three, an even higher number. Although the classic anterolateral dysplasia remains the most common, pure lateral deficiency of coverage is rare and the pure posterior deficiency is an exception, and then is seen in functional hips of proximal

Fig. 5. Intraoperative view of a bucket-handle avulsion of a degenerated labrum (arrow)

Fig. 6. AP-pelvic radiograph of the dysplastic acetabulum of an Asian woman shows retroversion of the superior one-third of the acetabulum

Fig. 5. Intraoperative view of a bucket-handle avulsion of a degenerated labrum (arrow)

femoral focal deficiency (PFFD) [25] or posttraumatic dysplasia [26]. One important group of a posterior insufficiency of coverage or anterior overcoverage consists of hips with Salter or triple osteotomies in childhood [27] in which a correct version of the acetabulum was difficult to establish in the presence of an unossified acetabular rim. If a retroverted dysplastic acetabulum is redirected in the same way as an anterolateral^ dysplastic acetabulum, the problem of this hip may be increased and further treatment even more difficult. Surgery then becomes necessary (Fig. 7).

Fig. 7. aAP-pelvic radiograph of a 14-year-old girl after three attempts of acetabular redirection and two attempts of proximal femoral osteotomy. The acetabulum is extremely retroverted (arrows show the anterior border; the posterior border is hidden behind the inner acetabular wall). On the femoral side the head is deformed, the neck is short, and there is subtrochanteric abduction with medialization of the femoral shaft. The hip showed impingement with 40° flexion, creating severe problems with sitting on a chair. b Postoperative radiograph of the pelvis after 40° internal rotation of the acetabulum. To bridge the displacement necessary for such a correction, the plate had to be prebended stepwise. Fixation was then only possible on the inside of the stable ilium and on the outside of the acetabular fragment. On the femoral side, femoral neck lengthening, trochanteric advancement, and subtrochanteric alignment were necessary to regain an anatomical morphology

Fig. 7. aAP-pelvic radiograph of a 14-year-old girl after three attempts of acetabular redirection and two attempts of proximal femoral osteotomy. The acetabulum is extremely retroverted (arrows show the anterior border; the posterior border is hidden behind the inner acetabular wall). On the femoral side the head is deformed, the neck is short, and there is subtrochanteric abduction with medialization of the femoral shaft. The hip showed impingement with 40° flexion, creating severe problems with sitting on a chair. b Postoperative radiograph of the pelvis after 40° internal rotation of the acetabulum. To bridge the displacement necessary for such a correction, the plate had to be prebended stepwise. Fixation was then only possible on the inside of the stable ilium and on the outside of the acetabular fragment. On the femoral side, femoral neck lengthening, trochanteric advancement, and subtrochanteric alignment were necessary to regain an anatomical morphology

Our first 75 cases with a minimum of 10 years' follow-up (10-13.8 years) showed good to excellent results in 88% when only hips without signs of osteoarthritis were considered. Taking all hips, the success rate dropped to 73% with good or excellent results [28]. The higher early failure rate was in the group with grade III osteoarthritis [29], an observation that caused us to exclude most of such hips from the indication for a reorientation. A standard AP X-ray, however, may be misleading when the joint space narrowing is rather the result of an anterolateral subluxation and does not represent cartilage loss. Such hips can be an acceptable indication and may lead to a good result for years, helping to postpone an artificial joint for a prosthesis lifetime (Fig. 8). Very early failures were observed also in reoriented hips with a secondary acetabulum.

With our 10-year follow-up study we had unexpectedly found that 30% of the patients had developed impingement symptoms over the years [28]. These symptoms were in most of the patients not severe enough, very severe, or only detectable with the impingement test [30], but in this small group hips were included with perfect corrections of the acetabulum. Further studies showed that the anterolateral head-neck junction in dysplastic hips frequently had no waist, producing a decreased clearance for flexion/internal rotation after correction of the acetabular roof [31].

Hip Sclerosis

Fig. 8. a AP radiograph of the left hip of a 37-year-old woman with subchondral sclerosis and ganglion (cyst) formation and marked joint space narrowing with advanced osteoarthritis. b Lateral radiograph of the same day (false profile view) shows fewer secondary signs of arthrosis but anterosuperior migration of the head. c Postoperative radiograph of the pelvis immediately after periacetabular osteotomy shows a normal joint space. d Ten years later: result with good clinical function. e Fifteen years after PAO. The patient has now problems with the left hip and is ready for total hip replacement (THR)

Fig. 8. a AP radiograph of the left hip of a 37-year-old woman with subchondral sclerosis and ganglion (cyst) formation and marked joint space narrowing with advanced osteoarthritis. b Lateral radiograph of the same day (false profile view) shows fewer secondary signs of arthrosis but anterosuperior migration of the head. c Postoperative radiograph of the pelvis immediately after periacetabular osteotomy shows a normal joint space. d Ten years later: result with good clinical function. e Fifteen years after PAO. The patient has now problems with the left hip and is ready for total hip replacement (THR)

Fig. 8. Continued

As an intraoperative consequence we check routinely this motion and perform an anterolateral osteochondroplasty of the head-neck junction in seven of ten hips to improve the offset (Fig. 9). The necessary capsulotomy allows further treatment of any additional intraarticular pathology, which surprisingly often escapes preopera-tive evaluation. So far, the clinical follow-up of our more recent cases seems to support this additional treatment step.

Retroversion of the acetabulum is not only a phenomenon in residual acetabular dysplasia but is common in nondysplastic hips as well; some of these idiopathic retroversions have a substantial degree. Such hips become symptomatic in early adulthood as a result of impingement of the anterior overcoverage against the head-neck

Fig. 9. a Coronal MRI section of the symptomatic dysplastic right hip of a 30-year-old woman. The anterior head-neck contour rim is out of sphericity with the risk of impingement after redirection of the acetabulum. b The periacetabular osteotomy was executed via an anterior capsulotomy, and the anterior head-neck contour was shaped to avoid impingement and to improve the limited internal rotation in flexion

Fig. 9. a Coronal MRI section of the symptomatic dysplastic right hip of a 30-year-old woman. The anterior head-neck contour rim is out of sphericity with the risk of impingement after redirection of the acetabulum. b The periacetabular osteotomy was executed via an anterior capsulotomy, and the anterior head-neck contour was shaped to avoid impingement and to improve the limited internal rotation in flexion junction in flexion/internal rotation. Such acetabular morphologies can be treated with a periacetabular osteotomy, reestablishing an anteversion by internal rotation of the acetabular fragment around a vertical axis. The limitation of such a correction is a posterior acetabular rim at or lateral of the center of the femoral head. With such a morphology, rotation of the acetabular fragment would have the risk of posterior impingement [32]. The second limitation is the quality of the acetabular cartilage in the area of anterior overcoverage. Preoperative MRI must show a normal cartilage; otherwise, it is better to trim the anterior overcoverage and refix the labrum. However, one has to take into consideration that some of these hips do not have a reasonable size of acetabular roof to allow complete trimming of the anterior coverage without the risk of producing a dysplasia-like lateral coverage. In general, we prefer to perform the reorientation of the retroverted nondysplastic acetabulum in patients under the age of 20 and do the trimming with refixation of the labrum in older patients with severe retroversion.

Some of the nondysplastic but severely retroverted acetabuli, but also some of the dysplastic acetabuli, show in addition a substantial deformity of the proximal femur, making a surgical step at this level, such as a capsulotomy, necessary.

Because surgery for the acetabular correction and substantial surgery of the proximal femur are hardly possible via a Smith-Peterson approach, we reevaluated the possibility of a posterolateral approach. It is well known that a rotational acetabular osteotomy (RAO) can successfully be performed via a posterolateral approach when the hip joint capsule is left intact. We first studied again the periacetabular blood supply [8]. The fact that the inferior branch of the superior gluteal artery, which runs in a rather mobile periosteal tissue along the distal border of the gluteus minimus and provides the perfusion of the supraacetabular bone together with arcades of the anastomosing supraacetabular artery and branches of the iliolumbar artery [7], can be mobilized and lifted from the bone to be osteotomised offers the possibility of a lateral acetabular reorientation together with a substantial capsulotomy with preserved perfusion of the acetabular fragment [8].

This osteotomy is in its supraacetabular course slightly more proximal to preserve the vessel arcade (Fig. 10). We have successfully performed seven cases so far, all with conditions necessitating a lateral approach (Fig. 11). We will certainly increase the

Acetabular Rim Fracture Muscles
Fig. 10. Anatomical dissection of the lateral iliac wing with the superior gluteal artery (A. glut. sup) providing a vascular branch to the superior acetabular rim. The ramus supraacetabularis follows the course of the piriformis muscle (MPi) and crosses the line of the osteotomy

Fig. 11. a Intraoperative photograph of a woman who had significant intraarticular pathology and simultaneously an acetabular dysplasia. b The periacetabular osteotomy was performed through a trans-trochanteric lateral approach

V Jfe a

a indication with increasing experience; the execution via a Smith-Peterson approach, however, will remain the standard.

In conclusion, in our armamentarium of surgical techniques to preserve the natural hip joint, periacetabular osteotomy is the operation that leads to the most predictable results. The technical execution is demanding, and even more so is orientation of the acetabulum, which must be individualized. The correction must be exact in all parameters, including a normal version of the acetabulum. In addition, one has to consider that the proximal femur may be dysplastic as well, which has to be corrected if possible at the same time.

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