Cementation of Cross-linked Polyethylene Liner Into Well-Fixed Acetabular Shells

The Journal of Arthroplasty Vol. 25 No. 3 2010

Cementation of Cross-linked Polyethylene Liner Into Well-Fixed Acetabular Shells Mean 6-Year Follow-Up Study Jung-Pan Wang, MD, Wei-Ming Chen, MD,* Cheng-Fong Chen, MD, Chao-Ching Chiang, MD, Ching-Kuei Huang, MD, and Tain-Hsiung Chen, MD

Abstract: The purpose of this study was to evaluate retrospectively the outcomes of cementation of cross-linked polyethylene (PE) liner in a well-fixed metal shell in 23 hips with an average follow-up period of 6 years. The mean Harris hip score was 69.6 ± 12 (range, 46-83) points preoperatively. The average postoperative follow-up was 72.3 months (range, 56-100 months). At the final follow-up, the mean Harris hip score was 95.5 ± 3 (84-100) points. There was no change in the bone-shell interface. No new osteolytic lesions were identified. The lesions impacted with bone graft had united completely. The remaining osteolytic lesions had decreased in size. There was no recurrent osteolysis, hip dislocation, component migration, and failure at the cement-metal interface. The results of the current study revealed that cementation of cross-linked PE liner into a well-fixed shell provided good midterm durability. Keywords: cement, well-fixed acetabular shell, cross-linked polyethylene liner, revision total hip arthroplasty. © 2010 Elsevier Inc. All rights reserved.

With the increasing popularity of surgical treatment of revision total hip arthroplasty, the orthopedists are faced with a well-fixed cementless acetabular shell with debris-induced osteolysis, which requires the exchange of a polyethylene (PE) liner and bone graft. Unfortunately, the locking mechanism may be damaged, the shell may be malpositioned severely, or a replacement liner may not be available. Hence, some clinical reports suggested that cup revision is unavoidable for a wellfixed shell [1,2]. Removal of a well-fixed shell is associated with bone loss and increasing morbidity [3-6]. An alternative technique has been introduced, involving cementation of a PE liner in a well-fixed metal shell [3,5,7-13]. There are some clinical short-term results for fixation of a conventional PE liner [9,11,14] or metal-inlay PE liner cemented into an existing shell [15]. There are currently

From the *Department of Orthopaedics and Traumatology, Taipei Veterans General Hospital, Taipei, Taiwan; and Department of Surgery, School of Medicine, National Yang-Ming University, Taipei, Taiwan. Submitted May 15, 2008; accepted December 18, 2008. No benefits or funds were received in support of the study. Reprint requests: Wei-Ming Chen, MD, Department of Orthopaedic and Traumatology, Taipei Veterans General Hospital, 201, Sec 2, ShihPai Road, Taipei 112 Taiwan. © 2010 Elsevier Inc. All rights reserved. 0883-5403/08/2503-0015$36.00/0 doi:10.1016/j.arth.2008.12.003

no data available for midterm and long-term results. The purpose of this study was to evaluate retrospectively the midterm outcomes of cementation of cross-linked PE liner into a well-fixed metal shell with an average of 6-year follow-up period.

Materials and Methods Eight hundred thirteen revision total hip arthroplasty were done at our institution from December 1996 to May 2003. In 23 of the 813 cases, well-fixed shells were retained in situ with cementation of cross-linked PE liner into shells of which 18 cases had no available new liners, and the remaining 5 cases had dysfunction of locking mechanism of shells. The group comprised 12 male and 9 female patients, whom were collected and retrospectively reviewed. Two females had bilateral hip revision at different time. Demographic data of all 23 cases are shown in Table 1. The average duration from the last procedure to revision was 9.7 ± 3 years (5-20 years). The average diameter of the initial shell was 55.3 mm (48-64 mm). The mean age at the time of the revision surgery was 61.0 years (range, 43-75 years). The mean preoperative Harris hip score was 69.6 ± 12 (46-83) points. All the cases had well-fixed shells, but either the new PE liner was not available or locking mechanisms were damaged. Seventeen cases with acetabular osteolysis were treated only with cementation of cross-linked PE liner. Six cases with stem loosening and liner wear were

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Cementation of Cross-linked Polyethylene Liner Into Well-Fixed Acetabular Shells  Wang et al

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Table 1. General Information of the 23 Patients Age/sex/ side

Initial diagnosis

Initial shell

Initial size

Duration (y)

PE liner

Size

59/F/L 64/M/R 64/M/L 74/M/L 68/M/R 68/M/L 46/F/R 57/F/R 56/F/L 60/F/R 43/F/R 59/F/L 60/M/R 74/F/L 68/M/R 44/F/L 44/M/L 68/F/L 48/M/L 71/M/R 75/M/L 65/F/L 70/M/R

DDH Trauma OA Trauma OA OA DDH INFH DDH SLE Traumatic OA SLE OA OA, DM OA SLE SLE OA, DM INFH OA OA, DM INFH OA

PCA PCA AML ABG ABG ABG ABG AML ABG HG HG HG HG ABG AML AML AML AML AML HG ABG AML ABG

50 52 58 54 54 54 48 62 58 54 64 54 56 54 54 54 58 58 62 56 50 52 58

12 20 13 13 8 8 5 6 11 15 7 14 6 10 8 8 8 9 12 8 8 9 7

Longevity Marathon Longevity Crossfire Marathon Marathon Marathon Marathon Longevity Longevity Longevity Longevity Longevity Longevity Marathon Marathon Marathon Marathon Marathon Longevity Crossfire Marathon Crossfire

46 50 56 52 52 50 44 60 56 50 60 52 54 50 50 50 56 54 60 54 48 50 56

Revision stem Y

Y Y Y Y

Y

Allograft Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y

Preoperative Harris score 74 67 68 48 47 47 81 66 83 46 82 83 77 77 60 83 80 71 74 71 80 77 60

Postoperative Harris score 97 93 93 84 94 94 96 96 100 93 100 96 100 96 97 96 94 97 100 93 98 94 97

DDH indicates developmental dysplasia of the hip; OA, osteoarthritis; INGH, ischemic necrosis of femoral head; DM, diabetes mellitus; PCA, porouscoated anatomic; ABG, Anatomique Benoist Girard; F, female; M, male; L, left; R, right.

treated with revision of stem and cementation of crosslinked PE liner. All 23 cases were operated by a single surgeon (WMC). The original manufacturer of existing implant and the implant manufacturer of new liner used were recorded (Table 1). Of the 23 cross-linked PE liner, 9 were Marathon liners (DePuy, Warsaw, Ind), 6 were Crossfire liners (Stryker, Kalamazoo, Mich), and 8 were Longevity liners (Zimmer, Warsaw, Ind). The average diameter of new cross-linked PE liner size was 52.6 mm (44-60 mm). Basically, most of the new liners and heads corresponded to the implant manufacturer of the original shell (Marathon liner for anatomic medullary locking [AML; Depuy, Warsaw, Ind], Longevity liner for HarrisGalante [HG; Zimmer, Warsaw, Ind]). However, some cases were not corresponded for some reasons. These 3 cases (fifth, sixth, and seventh case) were combined with AML stem revision and new heads; hence, Marathon liners were used (Fig. 1B). For the other 2 cases (third and ninth case), there were no liners of original implant manufacturer available; therefore, we had to use other implant manufacturers, which was readily available in the operation room. We did not use the constrained liner because of no previous history of dislocation and also good stability when we checked on the table. In our cases, the same sizes of new heads were used, even if the stem needed revision. Morselized allografts were impacted into the osteolytic defect over acetabular and femoral area after debridement in 19 patients. For prevention of infection after revision surgery, the vancomycin-impregnated cement was used to fix the liner to the shell in all cases as well as to fill the lytic areas

in 4 patients with systemic lupus erythematosus (SLE) and 3 patients with diabetes. The patients were assessed with radiographs and the Harris hip score [16] taken at the preoperative assessment and the most recent follow-up. There was accessible and adequate documentation in all 23 cases such as initial operative notes and discharge summaries and radiographs. Immediate full weight bearing was allowed in all patients postoperatively because the shells remained well fixed. Surgical Technique Intraoperative assessment must be done to make the decision of whether the acetabular metal shell should be either retained or removed. Patients with a malpositioned metal shell and a metal shell damaged secondary to head penetration were performed by cup revision. The stability of the shell was confirmed by both preoperative x-ray and intraoperative examination. We used needle nosed locking pliers or bone rongeur to catch the rim of the shell and move as hard as possible to see if there was any motion of the shell. The acetabular and femoral osteolysis was identified preoperatively. Careful debridement and grafting of the lesions were done for the 19 cases with osteolytic lesions, which we can approach. The morselized allografts were impacted into the acetabular areas (mostly zones 1 and 2) through screw holes and the areas around the rim and the stem. All of the existing cups had screw holes present. The screws were not removed if there was no radiolucency around the screw on preoperative x-ray, and the screws were tightly fixed without loosening.

422 The Journal of Arthroplasty Vol. 25 No. 3 April 2010

Fig. 1. (A) A 43-year-old male patient was operated for stem loosening. The well-fixed shell was planned to be retained to preserve his bone stock after considering his age. (B) Cementation of new liner and long-stem revision. (C) Harris hip score was 95 points at 6 years postoperatively.

The downsized liner trials 2 to 4 mm smaller than the inner diameter of the existing shell were chosen to fit against the metal rim of the fixed shell, and then we decided the size of new liners. A high-speed bur was used to score the inner surface of the shell and outer surface of PE liner to ensure good cement interdigitation, which is essential for firm fixation. The new downsized 2- to 4-mm cross-linked PE liners were cemented into the existing shell under early doughy phase. The desired thickness of cement mantle will be 1 to 2 mm. Great attempt was made

during the pressurization process to ensure the liner was fully seated within the shell. Immediately, weight bearing was allowed to all the patients because the shells remained well fixed.

Results All patients had complete functional assessments. The average follow-up period was 72.3 months (range, 56100 months). The data for this analysis were obtained from the hospital charts, telephone interviews, detailed

Fig. 2. (A) A 59-year-old female patient with SLE was operated for liner wear and osteolysis. (B) Cementation of liner and impacted allograft. (C) Harris hip score was 97 points at 7 years postoperatively.

Cementation of Cross-linked Polyethylene Liner Into Well-Fixed Acetabular Shells  Wang et al

questionnaire, and clinical records. The postoperative Harris hip score was 95.5 ± 3 (84-100) points on average. All Harris hip scores improved after surgery (Table 1). Of the 23 patient, one who was treated with stem revision and PE liner cementation had a superficial wound infection and was successfully treated with local debridement and intravenous antibiotics. Fortunately, there was no neurovascular injury, hip dislocation, liner dislodgement, or other complications associated with the revision. At the most recent follow-up, there was no change in the bone-shell interface and no new osteolytic lesions were identified. The osteolytic lesions filled with bone graft were shown to be union (Fig. 2C). The average durability of 6 years is excellent in this series.

Discussion Springer et al [14] reported a series of cemented PE liner in 16 patients with at least 2-year follow-up, and their Mayo Hip Scores improved from 52.8 preoperatively to 76.6 at the final follow-up. No case of acetabular liner loosening or prosthesis failure has been noted. Haft et al [9] reported a series of cemented PE liner in 17 patients with a follow-up of 2.5 years. Only one case failed at the cement-liner interface because of the liner being too large. Yoon et al [15] reported a series of cemented metalinlay PE liner in 39 patients with a follow-up of 2.8 years. Mean Harris hip scores improved from 65 preoperatively to 86.9 at the final follow-up. Thirty-five (92%) of the 38 cases (except a single failure) showed excellent or good results. The only one failed case was also owing to the liner being too large. In our series, cross-linked PE liner was done in 23 cases, with an average follow-up of 6 years. The Harris hip score improved from 69.6 preoperatively to 95.5 at the final follow-up. No case of acetabular liner loosening or dislocation has been noted. Although favorable outcome with high successful rate was shown at the above series, the use of this cement technique and selection of patients should be carried out with great caution. Moreover, the patient should be fully informed of the potential risks such as dislodgement of liner, infection, and hip dislocation. Evaluation of the preoperative radiographs is critical in determining whether the new PE liner is available or not. It is also important to determine various factors including the exchangeability of the liner, the locking mechanism, the position and damage of the shell, adequate thickness of the liner, and some types of hydroxyapatite (HA)-coated shells. Cup revision was performed for patients with a malpositioned metal shell and a metal shell damaged secondary to head penetration. In our 23 cases, the inclination of our retained shell was, on average, between 40° and 45°, and there was no history of dislocation or impingement before revision of liners. After revision of liners, hip stability checked on table was good. Until now, there was no dislocation noted. We will need more patients with longer follow-up

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period for further study. In the future, larger heads and constrained liner or adjustment of liner during cementing could then be considered as alternatives when we see cases with acceptable cup position, but with history of dislocation or impingement, or cases with mild malpositioned cup. Cementation of a PE liner cannot be performed for all well-fixed cups. In Maloney series, the HA-coated pressfit cup made by Osteonics (Allendale, NJ) is removed routinely regardless of implant stability because of its poor performance record [17]. Because of poor outcome of HA-coated Omnifit prosthesis (Stryker Howmedica Osteonics) from our clinical experience and other clinical reports [18,19], Omnifit HA cup was also routinely removed during revision at our institute even if the cup was well fixed. Poor performance of Landos Atoll HAcoated cup was also mentioned [20]; therefore, routine cup revision will be carried out in the case of these cups even though they are well-fixed. The cement techniques in a metal shell varied [5,710,12,21], and the optimal thickness of a cement mantle has not been determined. Some authors stated that 2-mm optimal mantles are based on cemented femoral and preliminary bench testing [5,7-9,21]. Bonner et al [8] reported that cementation of a PE liner into a metal shell can be stronger than a conventional locking mechanism if the liner is undersized. Oversized liner should be used carefully because failure from oversized liner was reported in some clinical results [9,15]. We used a 2- to 4-mm undersized liner for adequate liner positioning to maximize containment of the liner within the shell and at least minimal cement mantle thickness. The desired thickness of cement mantle will be 1 to 2 mm. In the case where the smallest liner cannot be fully seated into the shell, the liner could be minimized by burring or downsizing to head 22 mm to obtain smaller liner. In our series, we did not use downsized heads and remained the same size (range, 26-32 mm), because we did not encounter any problem with the size of the liner. In the future, we may meet some cases in which the size of the head cannot be downsized. The thickness of liner less than 8 mm is acceptable because the thickness of the crosslinked PE liner was 5 mm at a minimum, which was recommended by Muratoglu et al [22]. Some authors stated that the addition of circumferential grooves in the PE liner was able to increase the fixation strength of the liner [5,8,9,12]. Haft et al [21] stated that the liners should have vertical grooves to increase torsion strength at the cement-liner interface and circumferential grooves to increase the lever-out strength. In our cases, the turtle shell-like grooves were made on the outer surface of the cross-linked PE liner. Apart from additional grooves, to improve pressurization into the shell, we prefer to use pressurize into a cement mantle in the early doughy phase. We must try to make the liner be fully centrally seated within the shell as possible when we keep pressurization.

424 The Journal of Arthroplasty Vol. 25 No. 3 April 2010 Using the technique of cementation of cross-linked polyethylene liner into well-fixed acetabular shells, we have successfully treated 23 patients who experienced wearing of the liner but no loosening of cup. The midterm follow-up showed a favorable and satisfactory outcome. Long-term follow-up is ongoing. The potential advantages of this technique include less surgical time and surgical morbidity such as pelvic bone loss or discontinuity, restoration of bone stock, earlier functional recovery, and access for the use of antibiotics-impregnated cement. On the basis of our data, cementation of a cross-linked PE liner into a well-fixed metal shell could be an acceptable alternative option in acetabular revision surgery if no suitable liner is available.

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