1 Introduction

Periacetabular lesions with intraarticular pathology are not uncommon in the setting of metastatic disease.¹ In situations where the associated lesion has resulted in persistent functional decline, uncontrollable pain, or (impending) fracture, operative reconstruction has become standard of care. In circumstances with extensive periacetabular and intraarticular involvement, as is the case with Harrington class 3 lesions, surgical technique is critical to optimize joint function, minimize complications, and allow for immediate postoperative weightbearing and mobilization.^1–4

Harrington's original 1981 technique involved a cemented acetabular cup reinforced with Steinmann pins fanned out from the acetabulum into the intact ilium.⁴ His technique, and modified versions thereof, have shown good results for many patients, however the reported complication rate has been alarmingly high, with some series approaching 30%.^1,2,4–10 In response, others have developed alternative treatment strategies including either cage reconstruction, custom triflange reconstruction, screw/pin acetabular reinforcement in different configurations, or resection arthroplasty.^{2,6,7,9,10,12,13} Bishop and Routt classically described the “osseous fixation pathways (OFP)” for the treatment of pelvic and acetabular fractures.¹⁴ Until recently, the periacetabular OFPs had not been utilized in the treatment of periacetabular metastatic lesions. Lozano-Calderon et al. first described reconstruction of the posterior column with a retrograde ischioacetabular Steinmann pin combined with cemented total hip arthroplasty.¹² Geller et al. described a novel technique of utilizing 3 OFPs without arthroplasty for the stabilization of mostly pathologic fractures of the acetabulum without articular or quadrilateral surface involvement.³

The purpose of this study is to describe a combined technique utilizing a combination, single stage, OFP screw reinforcement of a cemented total hip arthroplasty for the treatment of metastatic periacetabular intraarticular lesions. The goals are to determine safety and efficacy of this treatment modality and to demonstrate that it allows for early stable weightbearing and mobilization. We hypothesized that this treatment modality would provide functional pain relief and an stable hip construct for immediate weight bearing in patients with periacetabular metastatic disease.

2 Methods

After institutional review board approval, the electronic medical records of 15 patients (16 cases) who received this combined technique for periacetabular intraarticular metastatic lesions were reviewed. Procedural indications include the above pathology with uncontrollable pain and functional debilitation secondary to metastatic disease involving the periacetabular region of the pelvis. No patients were excluded from review. All patients underwent periacetabular bone reinforcement via a combination of anterior column (superior ramus), posterior column, and supra-acetabular screws. All hip replacements were performed via the direct anterior approach with a cemented all polyethylene liner.

Patient demographics including age, gender, and American Society of Anesthesiologists (ASA) score were reviewed. Pre and postoperative ambulatory status, pain medication utilization, and visual analog scale (VAS) pain scores were evaluated and compared. Preoperative radiographs and computed tomography (CT) scans were reviewed by two fellowship trained orthopaedic surgeons for classification. Operative details including estimated blood loss, surgical duration, the need for blood transfusion, and complications were reviewed.

2.1

2.1 Operative technique

Patients are placed supine on a flat radiolucent table. The C-arm is positioned contralateral to the operative extremity. Appropriate radiographic views including the anterior posterior (AP), pelvic inlet (PI), pelvic outlet (PO), combined obturator oblique outlet (COOO), combined obturator oblique inlet (COOI), and Iliac oblique (IO) views are obtained and marked before draping for ease of imaging during the operation. The patient's operative extremity, flank, and entire lower abdomen and pelvis are prepped and draped in standard sterile fashion (Fig. 1).

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Fig. 1 Image of patient positioning in operating room.

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The decision for screw placement corresponds with disease location: antegrade superior ramus screw for anterior wall/pubic root involvement, antegrade posterior column screw for posteromedial acetabular and ischial involvement, and supra-acetabular screw for anterior column/articular dome involvement. Screw augmentation is provided with either a 4.5 mm cortical screw or 7.3 mm fully threaded cannulated screw, based on the size of the OFP.

As previously described in the literature, all OFPs are identified and subsequently instrumented via a combination of standard radiographic views.¹² The superior ramus OFP is identified via the COOO and PI views and is either drilled for insertion of a 4.5 mm cortical screw or first instrumented with a guide wire followed by cannulated drill and 7.3 mm screw insertion (Fig. 2). The starting point is typically 1–2 cm cranial and in line with the acetabulum on the gluteus medius pillar. Trajectory of the drill/wire should hug the posterior and cranial cortexes of the superior ramus on fluoroscopy to minimize violation of the articular surface.

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Fig. 2 Superior ramus screw placement.

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For posterior column reinforcement, a part of the lateral window of the ilioinguinal approach is utilized for access to the inner table of the ilium, lateral to the pelvic brim. A 5 cm incision is made along the border of the iliac crest. Dissection is carried down to the deep fascia. The tendinous junction between the abdominal obliques and the origin of the tensor fascia lata is identified. The tendinous structure is divided, and the abdominal oblique tendon is elevated subperiosteally. Once along the inner table, the iliacus muscle is elevated subperiosteally with a cobb elevator to the pelvic brim. The starting point for the posterior column OFP is identified via the IO and AP views. On the IO view the starting point and trajectory should be posterior to the joint surface. On the AP view, the starting point and trajectory should run along the ilioischial line. The posterior column OFP is then stabilized with a cortical or cannulated screw (Fig. 3).

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Fig. 3 Posterior column screw placement.

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The start point for the supra-acetabular OFP is identified by the tear drop on the COOO view representing the anterior inferior iliac spine. Screw trajectory towards the posterior superior iliac spine is evaluated via the COOI and IO views (Fig. 4). On the COOI view, drill trajectory should be centered between the inner and outer table. On the IO view, the drill should aim just superior to the greater sciatic notch. After satisfactory positioning of the drill, the pathway is stabilized with either a cortical or cannulated screw. Once all required percutaneous reinforcement is finalized, the incisions are irrigated and closed in standard layered fashion. Next, attention is turned to the hip replacement component of the procedure, which does not require a secondary setup or patient repositioning.

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Fig. 4 Supra-acetabular screw placement.

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The approach to the hip is determined based on femoral metastases. If the disease burden warrants a cemented long stem prosthesis, then a direct lateral (Hardinge) approach is used. Otherwise, direct anterior is the preferred approach. In this series, a standard direct anterior approach was used to access the hip in all cases. Once the hip approach is performed and the acetabulum is exposed, it is then prepared in the standard fashion with the exception of acetabular reaming. Reaming is either performed until standard component positioning is obtained or until the stabilization screws prevent further medial and/or proximal progression. When tumor is encountered, it is thoroughly debrided via curette and high-speed burr and irrigated with hydrogen peroxide. Once debridement is completed, argon beam ablation may be used for adjuvant therapy of the lesion if deemed necessary. Cup stability is assessed based on degree and location of tumor burden, as well as intraoperative assessment. If additional stability is required, screws may be placed in a retrograde fashion into the ilium or a high-speed burr can be used to create additional pockets for cement interdigitation within the acetabulum in areas uninvolved by tumor. After thorough irrigation and drying of the defect, polymethylmethacrylate (PMMA) bone cement is mixed and injected into the acetabulum and pressurized prior to cup insertion. A liner impactor is used to seat the cup while a tamp may be used to adjust anteversion and abduction. Attention is then turned to the femur. Standard operative technique is employed to deliver and prepare the femur. The stem is chosen based on femoral bone quality or tumor involvement. In patients with good bone quality and no femoral lesions, a tapered-wedge stem is preferred. If metastatic disease is present at or above the lesser trochanter or in osteoporotic bone, a cemented stem is chosen. For diffuse femoral metastasis, a cemented long stem is utilized through a direct lateral approach.¹⁵ Once the hip is deemed stable with trial components, final components are placed, the wound is irrigated and closed in a standard fashion (Fig. 5).

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Fig. 5 Superior ramus, Post Column, and Supra-acetabular Screws with a Cemented Acetabulum Total Hip Replacement.

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3 Results

In total, 15 patients underwent 16 of the procedures outlined above [1 bilateral (Fig. 6)]. Patient demographics, including ASA score, primary cancer type, Harrington classification, and metastatic acetabular classification (MAC) score can be seen in Table 1. Thirteen cases were classified as having Harrington class 3 pathology, defined as a periacetabular metastases with an acetabular dome defect. Breast cancer was the most common primary pathology (n = 5).

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Fig. 6 Bilateral superior ramus and supra-acetabular screw fixation with a cemented acetabulum total hip replacement.

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Information pertaining to each patient's hospital and postoperative course can be seen in Table 2. The mean postoperative hospital length of stay was 5.8 days (range: 1–22 days). Eleven patients (12 cases) were discharged to home and four were discharged to a rehabilitation facility. Fourteen of 16 cases were permitted to weight bear as tolerated on the operative extremity following surgery. The two cases given restrictions were allowed 50% weightbearing because of oncologic disease burden compromising lumbopelvic stability. Eleven patients (12 cases) required a blood transfusion during the postoperative period. Low-molecular-weight heparin and Aspirin 81 mg twice a day were the most common form of deep venous thromboembolism (DVT) prevention. All patients received postoperative radiation therapy. Four patients died on their oncologic disease burden during the study course of this study. Mean follow up time from the date of surgery, excluding those patients who died, was 309 days (range: 75–560 days).

Outcome data can be found in Table 3. Mean improvement in VAS pain scores [0–10] from the day prior to surgery compared to the 24 h prior to discharge was 1.0 (range: -4 - 6). Fifteen of 16 cases ambulated on postoperative day 1. Mean maximum distance walked in the hospital prior to discharge was 100 feet (range: 15–250). At the last follow up visit, 2 patients required a cane for ambulation, 7 required a walker, and 6 were ambulating without assistance. There have been no postoperative complications, including wound complications, deep venous thromboembolism, radiographic loosening, dislocations, or hardware failures to date.

Operative details can be seen in Table 4. The average operative time was 167 min (range: 132–217 min). Average estimated blood loss was 619 mL (range: 200 mL–3550 mL). There were no intraoperative complications. No patients underwent preoperative embolization. All patients required at least 2 percutaneous screws for acetabular stabilization. All cases received a cemented all polyethylene cup, of which, three were augmented with supplemental screw fixation.

4 Discussion

Metastatic disease involving the pelvis can be a devastating process.¹ Although a well-recognized challenge, the treatment options for periacetabular metastasis that have been described come with significant morbidity.^1–11 When Harrington first proposed his treatment technique in 1981, he attempted to restore the weightbearing axis with a cemented cup arthroplasty with reinforced Steinmann pins inserted retrograde from the cup to the into the intact ilium as the stable OFPs recognized today were not yet described.⁴ Modifications to his technique have evolved over time to include antegrade pin placement, replacing pins for threaded screws, supplementing with acetabular cups with flange antiprotrusio shells, and custom cages.^{1,2,6,7,9–11} These different techniques were proposed in an attempt to reduce the high rate of mechanical failure reported in the literature, with some series reporting as high as 29%.¹⁰ Recently, others have experimented with isolated pelvic reinforcement utilizing screws in alternative configurations.^3,11 Bishop and Routt outlined all the pelvic OFPs for fixation of pelvic and acetabular fractures.¹² By adapting these methods for the treatment of metastatic disease, periacetabular OFPs offer an opportunity for acetabular reinforcement different from that originally described by Harrington. Screws positioned along the superior ramus, supra-acetabulum, and ischium completely surround the acetabulum and add reinforcement/anchorage to the cement that is more analogous to actual reinforcement bars or “rebar” in modern building construction. The mechanical properties of concrete and PMMA make them ideal to withstand compressive forces, but prone to failure from bending and tension forces.¹⁴ Therefore, in construction, concrete is often reinforced with steel “rebar” to combat bending and tension forces. The same has been done in orthopaedics, such as with steel wires, which have been shown to significantly improve the tensile, bending, and shear properties of PMMA.^16,17 In Harrington's construct, the pins fan out from the cup following the lines of compression, which may not be as mechanically advantageous. Our belief, based on the mechanical properties of reinforced bone cement, is that screws oriented along the periacetabular OFPs, provide better mechanical “rebar” support from the tension, bending, and shear forces of a cemented cup.

Lozano-Calderon et al., in 2016 were first to describe reinforcement of the ischium with a retrograde screw through the posterior column OFP in combination with a cemented cup arthroplasty for metastatic disease involving the posterior column.¹¹ They found improved quality of life and functional outcomes, adequate cup stability, and minimal complications.¹¹ They had one mechanical failure and one surgical site infection, however their long-term follow up was limited by a high mortality rate at 10 months, 5/11 patients.¹¹

More recently, Geller et al. published an acetabular fixation technique that utilized the three periacetabular OFPs without arthroplasty and demonstrated encouraging outcomes for patients with primarily Harrington class 3 lesions.³ Although their study was mostly for pathologic acetabular fractures and excluded patients with intraarticular or quadrilateral surface pathology, it serves as a proof of concept study for alternative stabilization and reinforcement strategies. In our series of patients, we combined periacetabular reinforcement, via screws in these OFPs, with cemented acetabular cup fixation. Advantages of the combined technique include location specific “rebar” reinforcement for a cemented cup and avoidance of a second surgery in patients who have disease progression, articular surface involvement, or progressive pain. In addition, every patient in our series received adjuvant radiation therapy. Therefore, a single stage procedure has the added benefit of avoiding the possible wound complications associated with an arthroplasty performed further down the road following radiation therapy. Some may argue that combining the procedures may be too much of a surgical insult in one setting, particularly in a high-risk patient population. However, the acetabular stabilization procedure is done mostly percutaneously, with minimal blood loss or added dissection. While our average EBL was 619 mL, one of our patients had an EBL of 3550 mL which heavily skewed the data, as without this data point the average EBL was the average EBL was 423 mL. Furthermore, with our technique, our EBL and rate of transfusion compare favorably with historical numbers, and our operative time, which included both screw placement and hip arthroplasty, was on average only about 20 min longer than what was reported by Geller et al.³

In terms of efficacy, the primary goal of this procedure was to provide pain relief and a stable hip for immediate weight bearing mobilization. In our series, the majority of patients experienced pain improvement before hospital discharge. All but one patient was ambulating on postoperative day 1. No loosening, hardware failure, or migration was seen on the most recent radiographic evaluation. As for safety, there were no complications in the immediate postoperative period or at the most recent follow up. With that being said, it should be emphasized that safely performing this technique relies on an intimate understanding of pelvis osteology and a firm grasp of each patient's underlying osseous disease.

There were several limitations associated with this limited case series. First and foremost, this is a retrospective evaluation of a small number of patients and is therefore subject to the standard associated biases. Although the follow up in our study is relatively limited, which unfortunately can be an inherent limitation of oncologic studies, all but four of our patients were still alive at final follow up which approached 1 year. While this is a clear limitation and studies with longer follow up will be required, the purpose of this case series was to highlight a safe, effective strategy for addressing a challenging problem. The third limitation of this case series pertains to our ability to accurately quantify postoperative outcomes because of the heterogeneity of each patient's clinical situation. For example, in our patient who underwent bilateral procedures, in the week prior to her hip reconstructions, she also underwent a caesarian section and an anterior-posterior cervical spine stabilization procedure for widespread metastatic disease. Therefore, our outcome data is confounded by each patient's unique oncologic clinical situation.

Although our experience lacks a large patient population or long term follow up, our current data suggests that simultaneous percutaneous acetabular reinforcement and cemented total hip arthroplasty is safe and provides effective pain relief for immediate stable mobilization. Further long-term and prospective comparative trials will be required to elucidate our findings.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.