Two stage cementation and screw augmentation of large acetabular defects in low demand patients: Early results and surgical technique

Abstract

Introduction

The reconstruction of large acetabular defects in revision hip arthroplasty represents a challenge to the surgeon and increases the complexity of the case. There are different options to overcome the problem of acetabular deficiency. In the elderly low demand patients, the main objective of revision surgery is to provide pain relief, allow immediate full weight bearing, and an early return to function.

Methods

This article presents our experience in acetabular revision surgery using a novel technique of two stage cementation and screw augmentation in low demand patients. We report on the surgical technique and present the early results in 10 patients.

Results

There were 6 females and 4 males with average age of 83.8 years. Patients were followed up for an average of 18.1 months. All patients were pain free and full weight bearing at the time of the final follow up with radiographs showing maintenance of implant position. None of the patients underwent revision surgery and there were no radiographic signs of failure detected in the early follow-up period.

Conclusion

This is a suitable technique in the management of large acetabular defects in revision hip arthroplasty, especially in the low demand patient population. It is a simple cost-effective technique that reduces the complexity of the acetabular revision, operative time, and morbidity associated with prolonged complex revision surgery.

1. Introduction

Revision of loose acetabular components presents a major challenge due to the loss of bone stock caused by wear and implant loosening.¹ The acetabular osteolysis and bone deficiency often means that there is insufficient amount of bone to cement a new implant and achieve stability. Loose cemented cups often leave combined defects with bone that has a sclerotic surface that is resistant to cement pressurisation and penetration using conventional techniques. The surgical aim of revising a failed acetabular component is to implant a stable component restoring the hip center and joint biomechanics. The use of cancellous bone grafting with cementless or cemented acetabular cups is a suitable option in dealing with simple acetabular defects.² Impaction bone grafting (IBG) in contained defects has provided good midterm results but the long-term results have been unfavourable, possibly due to graft non-union or resorption.³

Large acetabular defects, on the other hand, represent a complex problem. The combination of contained as well as segmental defects increases the complexity of the revision. There have been various reconstruction techniques used in the past to deal with major acetabular defects. These include the use of cages, implantation of components at a high hip centre,^4,5 jumbo cups, trabecular metal augmentation, impaction bone graft, and structural bone grafting.^5,6 These techniques are often complex and increase the length of surgery with subsequent increase the risk to the patients.

In the elderly low demand patients, the main objective of revision surgery is to provide pain relief and restoration of function.⁷ These frail patients often have significant co-morbidies that increase the risk of revision surgery. This article presents our experience in acetabular revision surgery using a novel technique of two stage cementation and screw augmentation in the low demand elderly patients. We discuss our surgical technique and present our early short-term results.

2. Methods

The technique we describe is suitable for one stage revision of aseptic loosening of acetabular implants therefore the presence of infection should be excluded. As part of the preoperative workup, all patients were assessed clinically by the senior author with detailed history, clinical examination, and laboratory investigations. The clinical assessment included gait assessment, leg length, muscle function, and hip range of motion (active flexion and abduction). Radiological investigation included anteroposterior pelvis and lateral hip plain radiographs. Judet views or CT scans are sometimes required to aid surgical planning.

2.1. Surgical technique

2.1.1. Acetabular preparation

Patients are positioned in the lateral decubitus position following administration of general or spinal anaesthetic ± sedation. Tranexamic acid is administered at the start of surgery but antibiotics are withheld until tissue specimens are taken (3–5 specimens). We utilize the posterior approach to the hip joint⁸ providing an adequate acetabular exposure by placing a Charnley pin proximally and elevating gluteus medius and minimus off the iliac bone. Releasing part of the gluteus maximus tendon distally facilitates the placement of an angled Hohman's retractor displacing the femur anteriorly improving visualisation of the acetabulum. Adequate exposure of the entire periphery of the acetabulum is necessary.

The hip joint capsule is aspirated and the fluid sent for microbiological examination to rule out infection. Tissue specimens are obtained from capsule, femur, and acetabular tissues. Following the dislocation of the hip, the femoral component is examined for loosening and the femoral head is inspected for any signs of wear. If the stem is to be retained, the femoral head is retracted proximal and anterior to the acetabulum. The acetabular component is removed preserving as much bone as possible. A meticulous debridement of the socket is carried out clearing all granulation tissue from the bone surface and the extent of the acetabular defect is assessed. Formal reaming is often not appropriate due to lack of bone but can be used to gently roughen the bone surface. The transverse acetabular ligament (TAL) is an important landmark to aid acetabular cup placement and should be preserved if found intact.^9,10 The teardrop (at the same level as the TAL) is almost always present and is a very helpful landmark for the inferior aspect of the socket at a normal hip centre. Stage one of the revision is completed following thorough washout of the acetabular defect using pulse lavage.

2.1.2. Two stage cementation ± screw augmentation

The technique of screw augmentation has been largely adopted from the technique of structural bone grafting in order to reinforce acetabular cement fixation.¹¹ In dental surgery metal pegs are used to reinforce restorations where large amounts of amalgam are required. Following acetabular preparation as described above, 2 × 3.2 mm drill holes are made in the superior acetabulum angled posteriorly and medially and 2 × 6.0 mm cancellous screws are then inserted. The screws are angled to avoid impingement on the acetabular component and deliberately left prominent to engage the subsequent cement mantle acting as anchors for the cement and strengthening the cement-bone interface. A Wroblewski drill is used to insert multiple drill holes into the acetabular bone where possible to aid cement penetration and fixation (Fig. 1).

Fig. 1.

A; Acetabulum following preparation, B; Direction of the drill holes (posterior and medial), C; Two 6 mm cancellous screws in the posterior-superior quadrant of the acetabulum with one third of the screw length left outside the bone, D; position of the socket following 2 stage cementation technique.

This technique requires the use of two separate mixes of cement. Patients generally have significant segmental acetabular defects resulting in a lack of containment rendering conventional methods of cement pressurisation ineffective. The use of high viscosity rapid-setting cement is recommended to achieve better cancellous bone penetration (Depuy, CMW2). The bone surface is prepared with saline pulsed lavage and the defect packed with ribbon gauze (soaked in hydrogen peroxide 1.5% solution and then squeezed out). The first cement mix is thumb pressurized into the acetabular bony defects and around the shafts of the 2 screws. This layer of cement should be thin and must not obstruct the acetabular component. Once the cement has cured, a second mix of cement is then introduced and a cemented polyethylene socket is pressurized onto the first cement layer. Excellent bonding is known to occur between layers of cement.12, 13, 14 The hip is reduced and stability tested. Closure of the wound is performed in a standard manner for the posterior approach.

Postoperatively, the patients are allowed full weight bearing as tolerated and intravenous antibiotic cover is continued for 24 h.

3. Methods

Ten consecutive acetabular revisions using the technique described were included in this study. All revisions were performed by the senior author in a single institution. Clinical notes were retrospectively reviewed. Data recorded included; patient's demographics, clinical assessment, mobility status, comorbidities, classification of acetabular defects using American Academy of Orthopaedic Surgeon (AAOS)¹⁵ and Paprosky classification,¹⁶ rehabilitation protocol, and radiographic results. The mean follow-up in this study was 18.1 months (range 10–28). Table 1 is a summary of the 10 consecutive acetabular revisions included in this study.

Table 1.

Summary of the 10 consecutive acetabular revisions included in the study.

Case	Age	Gender	ASA grade	Femoral stem revised?	Clinical assessment at last follow up			Follow up duration
					Trendelenburg test	Range of hip flexion	Range of hip abduction
1	78	Female	3	No	Negative	50	30	14
2	85	Male	3	No	Negative	80	35	11
3	81	Female	3	No	Negative	70	25	15
4	87	Male	4	No	Negative	50	40	17
5	93	Female	4	Yes	Negative	70	30	17
6	78	Female	3	No	Negative	75	35	27
7	80	Male	3	No	Negative	60	35	10
8	86	Male	3	Yes	Positive	40	30	18
9	84	Female	3	No	Negative	70	40	24
10	86	Female	3	No	Negative	60	40	28
Mean	83.8					63	34	18.1

3.1. Case example (1) revision of both components

A 93-year-old female presented with a painful left total hip replacement that was performed 35 years ago. She presented with 14 months history of atraumatic trochanteric and proximal thigh pain on weight bearing. Her mobility gradually deteriorated until she became reliant on a wheel chair. Plain pelvis radiographs revealed a loose Charnley total hip replacement with a femoral head penetrating the bone superiorly. This started as progressive superior cup wear which eventually broken through the superior aspect of the socket. The femoral head resulted in severe bone loss and a defect extending to the level of the sciatic notch. The femoral stem also showed signs of loosening. Clinical and laboratory investigations revealed normal inflammatory markers and the patient underwent a single stage revision for aseptic loosening. Intra-operatively, there was massive bone loss in the acetabulum both superiorly and posteriorly. A stable cemented acetabular implant was inserted utilising the two-stage cementation and cement augmentation technique. The femoral stem was also revised for aseptic loosening. Fig. 2 shows pre and postoperative radiographs of the patient's pelvis. The immediate postoperative pelvis radiographs showed restoration of the hip center and leg length. At 17 months follow up review, the patient was mobilising with 2 sticks and had pain free active left hip flexion and abduction of 70 and 30° respectively. The latest pelvis radiograph showed no signs of loosening or implant failure.

Fig. 2.

A; Anteroposterior radiograph of the pelvis showing right sided Austine-Moore hemiarthroplasty and a left loose Charnley total hip replacement. The left femoral head has worn through the polyethylene socket and is lying in the pelvic bone superiorly, B; Postoperative pelvis radiograph showing revised acetabular and femoral components with restoration of the hip center and leg length.

3.2. Case example (2) acetabular revision

A 78-year-old female underwent a left Charnley total hip replacement 22 years ago. She presented with progressively worsening left groin and knee pain for 8 months. Radiographs showed a loose acetabular cemented socket with a large acetabular bony defect with a very thin rim of bone medially indicating a possibility of medial wall deficiency or acetabular discontinuity. Intraoperatively, the acetabular walls were very thin, ballooned but intact with no pelvic discontinuity. The femoral stem was not loose and the femoral head was not scratched. Fig. 3 shows pre and postoperative radiographs of the patient's pelvis.

Fig. 3.

A; Anteroposterior radiograph showing left Charnley total hip replacement with significant loosening of the acetabular component and thin ballooned medial wall, B; Postoperative pelvis radiograph showing revised acetabular component with restoration of the hip centre and leg length.

4. Results

A total of 10 total hip replacements with aseptic loosening and large acetabular deficiencies underwent revision using 2 stage cementation and screw cementation technique. There were 6 females and 4 males with mean age of 83.8 years (range 78–93). Eight patients were ASA grade III and 2 patients were ASA grade IV. Six hips had American Academy of Orthopedic Surgeons (AAOS) type 2 (Paprosky type 2C) deficiency and four had AAOS type 3 (Paprosky type 3A) defects of the acetabulum. Two patients were found to have loose femoral stems and were revised. No drains were used in any of the patients. All 10 patients were wheelchair bound preoperatively owing to the severe pain they experienced from the loose acetabular components. Revisions were performed on an average of 21.3 years after the index procedure. Operative time for acetabular revision was less than 2 h.

Postoperatively, the average active hip flexion was 63 (range 40–80) while the average active hip abduction was 34 (range 25–40) as highlighted in Table 1. There were no dislocations encountered and all patients were allowed to fully weight bear postoperatively. There were no cases of wound infection or periprosthetic fractures.

5. Discussion

Revision of failed acetabular components may present a challenge as is it often associated with large areas of osteolysis and bone loss. There are many different reconstruction techniques with varying levels of success and complexity. Structural allografts and reconstruction cages have been reported to be associated with early loosening and high failure rate.¹⁷ Failure rates of 45% have been reported at 7 years following the use of allografts¹⁸ with revision rates of 25% at 12 years of follow-up.¹⁹ The use of allografts is also associated with the risk of disease transmission, the requirement for tissue bank infrastructure, graft preparation difficulty, and the possibility of reabsorption.²⁰ Bilobed acetabular components are designed to fill only superior segmental defects and it is difficult to obtain good bony apposition without gaps.²¹ Trabecular metal wedges have been used with encouraging short and medium term results.²² however, some of its disadvantages include the potential for generating debris at the wedge-cement-acetabulum interface, high cost of implant, and lack of long-term data.²² Mohaddes et al.²³ reports on 2460 revisions from the Swedish Hip Arthroplasty Register and found that one third of all uncemented first-time acetabular revisions were performed using a trabecular metal cup. They concluded that the short-term survival of the trabecular metal design is about equal to that of the cemented cup design, so the high cost of trabecular metal needs to be taken into consideration.

We have utilised this novel technique in the revision of failed acetabular components associated with acetabular bone loss. We have restricted the use of this technique to the low demand elderly patient population with the aim of providing a pain-free stable acetabular component and immediate full weight-bearing. The technique is only suitable in cases of aseptic loosening and thus infection needs to be ruled out in every case.

The use of two stage cementation is similar in principal to the cement-in-cement technique widely used in revision of cemented femoral implants. Several biomechanical and clinical studies^12,14,24 have provided strong evidence to support the use of cement-in-cement technique in femoral stem revisions. A study by the Exeter group²⁵ in 2012 reported on the use of cement-in-cement technique in acetabular revisions. They reported on 60 acetabular cement-in-cement revisions with a 92.2% survival rate at 5 years. They concluded in their study that the use of this technique provides a durable method of fixation due to the bonding of the two layers of cement. Our technique of two stage cementation utilises the same principal by using two mixes of cement, the first thin cement layer provides cement bone penetration enhancing the overall implant fixation. The second layer of cement would bond to the first layer provided that the interface between them is dry from blood and debris. The two cancellous screws function as anchors for the cement and further enhance the cement bone interface.

The main weakness of our study is the short-term follow up. None of the postoperative radiographs showed any signs of acetabular implant loosening or migration, however, longer follow up is necessary to be able to assess the long-term results of this new technique. Limitations of this study also include small sample size and the retrospective nature of data collection.

6. Conclusion

Our experience with this novel two stage cementation technique has been favourable with no implant failures, dislocations, or re-revisions at mean follow up of 18.1 months. Our early results have encouraged us to continue to use this technique as a salvage option for large acetabular defects. We believe that this is a suitable technique in the management of large acetabular defects in revision hip arthroplasty, especially in the low demand patient population. We recommend the use of this technique in reconstruction of Paprosky type 2 and 3A defects. It is a simple technique that reduces the complexity of the acetabular revision, operative time, cost of surgery, and the morbidity associated with prolonged complex revision surgery. However, more data and longer follow up are needed to determine whether this technique does indeed provide a good long-term outcome and could be considered as an effective way in dealing with large acetabular defects in revision hip surgery.

Funding

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

Declarations of interest

None.

Appendix A. Supplementary data

The following is the Supplementary data to this article: