The clinical and radiographic indications for a combined PAO/PFO are similar to those for an isolated PAO. Patients should have clinical symptoms and signs directly related to the deformity, such as inguinal and/or trochanteric pain, abductor weakness, or limited hip motion secondary to a high-riding greater trochanter. These can improve following a combined PAO and PFO [5
] and, we believe, justify such a complex surgery. On the other hand, globally limited and painful range of motion, osteoarthritis of Tönnis Grade 2 [35
] or worse, and older age generally represent contraindications for a combined procedure. However, in well-selected cases, improvement in Harris Hip (60 to 90) and WOMAC (8.7 to 3) scores have been reported 5 years after PAO in those over the age of 40 [20
The majority of abnormalities requiring a PFO in addition to a PAO can be categorized as either intraarticular or extraarticular. Intraarticular causes can be divided into inadequate improvement of coverage (lateral center-edge angle < 25°, acetabular index > 10°, extrusion index > 30%) [36
], containment (distance between ilioischial line and femoral head > 5 to 7 mm), or congruency (nonconcentric joint space with a width > 3 mm) following an isolated PAO. Intraarticular pathologies represent not only the largest but also the most challenging group with respect to decision-making (Fig. ). Extraarticular causes include a high-riding greater trochanter with a short neck, a deformity not infrequently seen as sequelae of Perthes disease or following the treatment of hip dysplasia in early childhood (Fig. ), and prior varus ITO.
Fig. 1A–B (A) This algorithm applies to hips with insufficient coverage and normal joint space. If an abduction view shows good coverage and congruency, PAO alone is indicated. If not, the abduction view is repeated with the hip internally rotated. If congruency (more ...)
Fig. 2 Hips with Perthes or Perthes-like deformities and secondary acetabular dysplasia may be governed by extraarticular impingement. When abduction over 20° is possible, the PAO is performed first. The final decision regarding a PFO is determined by (more ...)
Standard anteroposterior pelvic, false profile, and functional views (commonly abduction and occasionally adduction) have been the basic imaging modalities used to predict coverage, containment, and congruency following PAO. Differentiation between joint space narrowing caused by anterolateral migration and that caused by cartilage loss can be made with abduction views. Clear improvement of the joint space with abduction indicates that anterolateral subluxation is the cause of the incongruency, and that PAO alone will likely be sufficient (Fig. ). If the abduction view fails to produce widening of a narrowed joint space, it may be repeated with the hip flexed 10° to 15° and/or internally rotated in the presence of high femoral antetorsion. Joint improvement with this combined view indicates that a PFO may be required in addition to the PAO. An abduction view is also helpful for assessing the adequacy of an isolated PAO for hips with a high fovea. With coxa magna or coxa valga, the high degree of abduction necessary for better containment may indicate that a PAO alone would result in a negative roof angle. Similar to how anterolateral migration can be assessed by abduction radiographs, anterior migration of the head can be estimated by a loss of congruency on the false profile view. These functional views may be repeated intraoperatively to confirm the need for a varus ITO, and to define the necessary angle of correction and amount of derotation, which depends on the clinical range of external and internal rotation (Fig. ).
Fig. 3A–D (A) This AP pelvic radiograph shows acetabular dysplasia of the left hip with severe joint space narrowing and subchondral sclerosis mimicking advanced OA. (B) However, the false profile view shows normal superior joint space width, indicating anterior (more ...)
Fig. 4A–C (A) This AP pelvic radiograph of a 12 year-old girl shows coxa valga and magna with acetabular dysplasia of the right hip. (B) An abduction view of the right hip shows acceptable congruency but marginal containment, indicating that PFO should (more ...)
In Perthes and Perthes-like deformities with secondary acetabular dysplasia, the high-riding trochanter may prevent adequate acetabular correction and may lead to the persistence of restricted hip abduction (Fig. ). This limits the information obtained from abduction radiography and may prevent the detection of concomitant intraarticular impingement. A MR arthrogram may allow further assessment of intraarticular pathology, including possible FAI that may remain after acetabular correction. Additionally, an adduction radiograph can provide information regarding the benefit of a valgus osteotomy, especially for hips with a congruent but nonspherical joint (Fig. ). With such pathomorphology, a classic trochanteric advancement may be insufficient, but RFNL through a surgical dislocation approach may substantially enhance hip motion [7
Fig. 5A–B (A) This AP pelvic radiograph shows bilateral sequelae of Perthes disease. A high acetabular index, mushroom-shaped femoral head, short neck and high-riding greater trochanter are apparent on the left side, although the joint space remains fairly congruent. (more ...)
For hips previously treated with a varus osteotomy, acetabular correction during the PAO may not be restricted but hip motion following the PAO may be limited and become painful over time (Fig. ). Preoperative drawings with both acetabular reorientation and revalgization of the proximal femur can demonstrate the need for a combined approach. With unilateral varus, the femoral correction may be accomplished by a revalgization ITO with increases in both leg length and abductor lever arm. However, with bilateral varus deformity and unilateral symptoms, relative neck lengthening and trochanteric advancement may be a more effective approach.
Fig. 6 A history of previous varus ITO can be a particular problem when a PAO is indicated for the treatment of residual acetabular dysplasia. Paper drawings made from functional abduction and adduction views are completed with the desired position of the acetabulum (more ...)
If the surgeon presumes cartilage destruction is the primary reason for persistent joint space narrowing in the abduction view, an MR arthrogram may give further information regarding the thickness and structure of the acetabular cartilage. MR can also suggest impending migration by showing a gap between cartilage surfaces. Additionally, the cartilage of the femoral head may be assessed in the anticipation of joint space normalization by a varus osteotomy. If the MR arthrogram shows substantial articular damage, we do not believe joint preservation surgery should be offered, even to patients in their twenties.
In the majority of patients, clinical assessment of hip range of motion, conventional radiographs, and MR arthrography in cases with questionable cartilage will provide adequate information to determine whether we will recommend a PFO. However, the definitive decision for a PFO usually depends on intraoperative and/or postoperative functional views (Fig. ). Therefore, we obtain patient consent for additional procedures whenever a PFO is considered. The possibility that a varus or extension ITO may lead to subsequent impingement [10
] must be considered during surgical planning and managed with appropriate osteochondroplasty.
Fig. 7A–E (A) This AP pelvic radiograph shows bilateral acetabular dysplasia with marked subluxation and lateral joint space narrowing. (B) An intraoperative AP radiograph after left PAO shows residual lateral joint space narrowing. (C) The intraoperative abduction (more ...)
Historically, PFOs have been intertrochanteric or subtrochanteric osteotomies, which have been used extensively [9
] and are accepted as techniques that effectively alter proximal femoral anatomy with low rates and severity of complications. However, since these osteotomies are performed at a distance from the deformity, they produce several side effects. They either medialize or lateralize the femoral shaft and alter the mechanical axis of the lower extremity.
They also shorten or lengthen the limb depending on whether a varus or valgus osteotomy is implemented.
The more distal these osteotomies are executed, the larger these side effects. In certain circumstances these may be desired effects; however, in the majority of cases, they are undesired consequences. Although most of these side effects can be minimized by choosing an appropriate implant and modifying the surgical technique, unilateral shortening of the femur by varus ITO remains a major problem, especially for female patients.
Recently, osteotomies have been performed at the femoral head and neck levels through the surgical dislocation approach [6
]. The key element in executing a RFNL, FNO, or FHRO is the extended retinacular soft-tissue flap, which provides sustained and reliable protection of the blood supply to the femoral head throughout the procedure [7
]. To develop the retinacular flap, the posterosuperior portion of the stable trochanter is resected subperiosteally to the level of the femoral neck. In the presence of an open physis, this piece can be mobilized as a single unit. However, with a closed physis, piece-meal resection is necessary. Following resection of the stable trochanter, the retinaculum and posterior periosteum are carefully elevated from the proximal femur to develop a single sleeve of tissue comprised of the retinaculum and external rotators. This flap extends from the lesser trochanter distally to the level at which the retinacular vessels enter the femoral head proximally. A similar subperiosteal dissection, including elevation of Weitbrecht’s ligament, is performed around the medial and posteromedial neck producing one contiguous semi-tubular periosteal sleeve, which contains the blood supply to the epiphysis and allows circumferential access to the neck. The extended length of the flap allows for forces, particularly tension, on the vessels to be better distributed.
One osteotomy performed through this approach is RFNL [7
]. This technique effectively treats extraarticular and intraarticular impingement caused by a high-riding greater trochanter and/or a short femoral neck and normalizes muscular and joint biomechanics (Fig. ). Again, the key element of this osteotomy is the extended retinacular soft-tissue flap, although the flap does not have to be developed circumferentially as with the neck osteotomy (Fig. ) [7
]. RFNL can be performed in combination with osteochondroplasty of the head-neck junction to reduce FAI. This technique has decreased the need for true femoral neck lengthening [40
Fig. 8A–B (A) This AP radiograph of the left hip of a 12 year-old patient shows a deformity of unknown etiology with necrosis of the medial portion of the femoral head. Severe subluxation, a short neck and high-riding greater trochanter are apparent, along (more ...)
Fig. 9A–B (A) This schematic drawing shows the first step of the extended retinacular soft-tissue flap during the surgical hip dislocation approach. After Z-shaped capsulotomy, the posterosuperior portion of the stable trochanter is trimmed down to the level of (more ...)
Another intracapsular osteotomy, FNO, produces corrections that are closer to the deformity, more effective in influencing the superior joint space and result in less medialization/lateralization of the femoral shaft and less alteration of limb-length than an ITO. Also, the heads of the screws used for fixation of the femoral neck osteotomy are less noticeable and irritating to the patient compared to the lateral plating used for fixation of an ITO (Fig. ). The presence of a previous ITO reportedly does not influence the long-term survival of THA [2
]. We expect that FNO will also not decrease subsequent THA survival and will, additionally, lessen the technical difficulty of total hip conversion compared to that following an ITO [2
Fig. 10A–C (A) This AP pelvic radiograph of a patient with multiple exostoses demonstrates bilateral complex hip dysplasia characterized by shallow acetabula marked coxa valga and exostoses of the posterior neck. On the left side, the exostosis was impinging against (more ...)
Certain hips with marked residual DDH are associated with deformities of the femoral head that cannot be corrected by a classic PFO since the head itself must be reshaped. The deformity may involve the medial or the lateral contour of the head or exhibit coxa plana with medial and lateral convexity, complicated by subluxation or severe extrusion. These complex deformities may benefit from the addition of a FHRO [7
]. Once again, the key element of this osteotomy is the extended retinacular flap that allows preservation of the blood supply to the medial and lateral portions of the head while a central section is resected. Although the femoral head can be sufficiently perfused by the superior retinacular branches of the medial femoral circumflex artery alone, there is a constant branch of the medial femoral circumflex artery that runs within Weitbrecht’s ligament and supplies a medial sector of the epiphysis [7
]. Therefore, the blood supply to the femoral head can be preserved while a central segment of the head is resected. While the medial epiphyseal pillar remains connected with the metaphysis, the lateral pillar, supplied by vessels within the retinacular flap, is osteotomized from the metaphysis to allow the resection gap to be closed and the cartilage surfaces to be adjusted. This procedure produces a smaller and rounder head that can stably be reduced into the reoriented socket (Fig. ).
Fig. 11A–E (A) Coronal CT cut of a 15 year-old with Perthes disease showing an enlarged femoral head with central necrosis hinging on the acetabular rim. Also seen are a short neck, high-riding greater trochanter and partially convex and dysplastic acetabulum. (more ...)
As previously mentioned, preoperative radiographic evaluation of obtainable coverage, containment, and congruency will identify the majority of hips in need of an adjunctive PFO in addition to PAO [12
]. When performing a combined PAO/PFO, we previously completed the PAO first unless the proximal femoral deformity prevented acetabular reorientation. The reasoning was that the amount of acetabular correction is predetermined by the need to achieve a nearly horizontal roof and a neutral version, both of which can be estimated with an intraoperative orthograde radiograph of the pelvis. In contrast, the correction on the femoral side does not have such defined limits and can more easily be adjusted to the conditions of each case. Recently, we have adhered less strictly to this guideline. When using the surgical dislocation approach to make intracapsular corrections, the ischial cut at the infracotyloid groove can be made under direct visualization by developing the interval between the inferior gemellus and obturator externus muscles. Simultaneously, the sciatic nerve can be visualized and appropriately retracted (Fig. ). Performing the incomplete osteotomy of the ischium at this point adds very little time. The patient can be positioned and prepped in a way that both the lateral and anterior incisions are included and, therefore, reprepping is not needed when changing from the lateral to supine position. If necessary, the surgeon can return to the lateral approach after performing the PAO. For these reasons, it is preferable to perform the femoral and acetabular corrections under one general anesthetic.
Fig. 12A–B (A) This drawing shows the approach to the ischium through a lateral incision for performing the first ischial osteotomy of the PAO. The gap between inferior gemellus and obturator externus/quadratus femoris muscles is identified by palpation before it (more ...)
In some cases, a PAO may be indicated for hips with lateral joint space narrowing and MR evidence of acetabular cartilage damage, but with a widened and congruent joint space in the abduction view. For these patients it is wise to obtain preoperative consent for a PFO in case the intraoperative AP radiograph after PAO does not show a sufficiently widened and congruent joint space but the abduction film does. In this rare instance, the PFO is performed after the PAO under the same anesthesia (Fig. ). Likewise, hips with acceptable acetabular morphology but a pronounced femoral deformity are a special challenge, for which preoperative evaluation may indicate a femoral procedure only. However, residual problems may be encountered which would lead to the recommendation of a PAO at a later time (Fig. ). Although such rare exceptions for performing the PAO and PFO as staged procedures do exist, the general goal should be to perform both osteotomies under one anesthesia.
Fig. 13A–E (A) This AP pelvic radiograph of a 19 year-old patient shows marginal acetabular dysplasia, acetabular retroversion, nonspherical extension of the femoral epiphysis and a short neck. MR indicated that the femoral reshaping required would exceed (more ...)