The Journal of Bone & Joint Surgery

The Journal of Bone & Joint Surgery, Volume 86, Issue 10

Scientific Articles | October 01, 2004

Advancement and Separation of Apex Hole Eliminators with Cementless Duraloc 100 Cups: A Report of Nineteen Cases

Tim A. Walde, MD¹; Alexandra M. Claus, MD, PhD²; Vivek Mohan, MD³; Robert H. HopperJr., PhD³; C. Anderson EnghJr., MD³; Charles A. EnghSr., MD³

¹ Abteilung fuer Unfallchirurgie, Plastische und Wiederherstellungschirurgie der Georg-August-Universitaet, Goettingen, Germany
² Fakultaet fuer Klinische Medizin der Universitaet Heidelberg, Klinikum Mannheim gGmbH, Orthopaedische Universitaetsklinik, Mannheim, Germany
³ Anderson Orthopaedic Research Institute, 2501 Parker's Lane, Suite 200, Alexandria, VA 22306. E-mail address: research@aori.org

View Disclosures and Other Information

General research funding for this study was provided by Inova Health System, Falls Church, Virginia. Two of the authors receive royalties and serve as consultants for DePuy, a Johnson and Johnson company. One author owns Johnson and Johnson stock.

Investigation performed at the Anderson Orthopaedic Research Institute, Alexandria, Virginia

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J Bone Joint Surg Am, 2004 Oct 01;86(10):2251-2256

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Abstract

Background: From 1992 to 1996, we performed 541 cementless total hip arthroplasties using a Duraloc 100 acetabular component with an apex hole eliminator that did not have a positive stop design. During routine follow-up radiographic evaluation, we noted several hips with advanced or separated hole eliminators. This study presents the clinical consequences of this occurrence and its relationship to polyethylene wear and osteolysis.

Methods: A total of 541 hips (358 with a minimum duration of follow-up of five years) were evaluated clinically with use of the method of Merle D'Aubigné and Postel. Anteroposterior pelvic and iliac oblique radiographs were used to evaluate polyethylene wear, osteolysis, hole eliminator position, and component stability.

Results: Nineteen hips that had been followed for an average of eighty-nine months showed advancement or complete separation of the hole eliminator on radiographic evaluation. In most hips, advancement of the hole eliminator was visible on only the iliac oblique radiograph. In all but one hip with separation of the hole eliminator, complete plug separation was detectable on both the iliac oblique and anteroposterior pelvic radiographs. No association was found between polyethylene wear and either advancement or separation of the hole eliminator. No osteolysis was visible radiographically in the hips with hole eliminator advancement, but osteolysis was always visible in the hips that had complete separation of the hole eliminator.

Conclusions: The hole eliminator has been redesigned since November 1995 to prevent possible advancement. However, patients with earlier designs should be followed carefully because advancement or separation can be expected in about 5% of the patients who have been followed for a minimum of five years. Despite this complication, which is seen radiographically, all patients were satisfied with the function of the hip. We do not recommend surgery solely to remove or replace the hole eliminator.

Level of Evidence: Therapeutic study, Level IV (case series [no, or historical, control group]). See Instructions to Authors for a complete description of levels of evidence.

Figures in this Article

Central or dome holes are designed to facilitate accurate insertion of cementless acetabular components by allowing direct visualization of component seating. However, the hole exposes the retroacetabular region to joint fluid that contains polyethylene particles¹, and this may facilitate retroacetabular osteolysis². To minimize this problem, manufacturers added a hole eliminator to seal the effective joint space. In one early design, there was no mechanical block to prevent either overinsertion or advancement of the hole eliminator. As a result, we have observed hole eliminator advancement and, in some instances, complete separation of the hole eliminator from the acetabular component. Although the design was changed in November 1995 to prevent advancement and separation (Fig. 1), we report the cases of these patients to alert the orthopaedic community to our finding.

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Fig. 1: Photographs of two hole eliminators retrieved at the time of revision surgery. The images on the left show the old hole eliminator without a positive stop (upper left) and the product number 1246-01 (lower left). The images on the right show the redesigned hole eliminator with a variable terminal thread pitch (upper right) and the new product number D1246-03 (lower right).

Our study describes the clinical sequelae and timing of hole eliminator advancement and/or separation with this acetabular cup design. We also describe the relationship of this finding to the occurrence of osteolysis.

Materials and Methods

Materials and Methods | Results | Discussion | References

Between 1992 and 1996, the two senior authors (C.A.E. Jr. and C.A.E. Sr.) performed 1110 primary total hip arthroplasties. Of those arthroplasties, 541 were performed with use of a Duraloc 100 cup (DePuy, Warsaw, Indiana) and a central hole eliminator without a positive stop. The 541 hips were identified retrospectively by the product numbers of the hole eliminator. A total of 442 hips (82%) had a minimum duration of radiographic and clinical follow-up of two years, and 358 (66%) had a minimum duration of radiographic and clinical follow-up of five years.

In the clinical evaluation, pain and the ability to walk were graded according to the scoring system of Merle D'Aubigné and Postel³ as modified by Charnley⁴. In addition, the patients completed a questionnaire for the evaluation of their satisfaction with the function of the hip.

According to our radiographic protocol, anteroposterior and iliac oblique radiographs of the pelvis were made after the arthroplasty. The femoral components were evaluated with use of the criteria described by Engh et al.⁵. Acetabular stability was defined as the absence of cup migration and circumferential radiolucencies at the implant-bone interface.

In nineteen hips in which hole eliminator advancement or separation was identified, the immediate postoperative radiographs were evaluated to determine the initial position of the apical hole eliminator. In thirteen hips, the eliminator was seated flush to the shell on the oblique radiograph made six weeks postoperatively. In the remaining six hips, the eliminator was found to be 1 to 3 mm overinserted (Table I). In subsequent follow-up radiographs, any change in plug position from these baseline values was measured in millimeters and recorded as advancement. If separation occurred, the time-interval between the identification of plug advancement and separation was recorded. Additionally, other radiographic views made at the same examination were scrutinized to see if hole eliminator advancement could be detected.

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TABLE I Data on the Nineteen Hips

										Merle D'Aubigné and Postel Score
Case	Type and Size of Liner*(mm)	Wear Rate (mm/yr)	Initial Plug Position†	Time to Diagnosis for Initial Advancement/Separation (mo)	Diagnosis	Total Duration of Follow-up (mo)	Hole Eliminator Migration (mm)	Osteolysis at Time of Last Follow-up	Size of Osteolytic Lesion (cm²)	Pain	Walking
1	E 26	0.05	1	14/-	Advanced	92	-	N	-	6	6
2	H 28	0.16	F	17/-	Advanced	53‡	-	N	-	2	2
3	E 28	0.14	F	65/-	Advanced	100	-	N	-	6	6
4	H 28	0.09	F	69/-	Advanced	96	-	N	-	6	6
5	E 28	0.06	1	78/-	Advanced	78	-	N	-	6	6
6	E 28	0.13	F	89/-	Advanced	89	-	N	-	6	6
7	H 28	0.18	F	90/-	Advanced	90	-	N	-	5	6
8	H 28	0.08	F	91/-	Advanced	106	-	N	-	6	6
9	H 32	0.03	3	-/37	Separated	130	15.6	Y	4.75	6	6
10	E 28	0.18	F	25/46	Separated	75	8.5	Y	1.92	6	6
11	E 28	0.29	F	-/46	Separated	81	9.3	Y	3.1	6	6
12	E 28	0.25	2	-/56	Separated	68	15.6	Y	4.62	6	6
13§	H 28	-	F	-/62	Separated	62	-	Y	5.2	-	-
14	E 28	0.05	F	48/70	Separated	70	4.2	Y	4.23	4	6
15	H 28	0.32	F	-/75	Separated	102	12.5	Y	2.57	6	6
16	H 28	0.12	F	-/80	Separated	80	39.9	Y	7.36	6	6
17	H 28	0.16	F	66/88	Separated	88	9.8	Y	2.24	6	6
18	E 28	0.08	1	-/90	Separated	102	2.5	Y	0.85	5	6
19	H 28	0.14	1	-/107	Separated	107	57.3	Y	6.85	6	6

E = Enduron and H = Hylamer. †The plugs were either flush (F) or overinserted, with the values given in millimeters. ‡Components revised at fifty-three months because of infection. §Components retrieved at autopsy.

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TABLE I Data on the Nineteen Hips

										Merle D'Aubigné and Postel Score
Case	Type and Size of Liner*(mm)	Wear Rate (mm/yr)	Initial Plug Position†	Time to Diagnosis for Initial Advancement/Separation (mo)	Diagnosis	Total Duration of Follow-up (mo)	Hole Eliminator Migration (mm)	Osteolysis at Time of Last Follow-up	Size of Osteolytic Lesion (cm²)	Pain	Walking
1	E 26	0.05	1	14/-	Advanced	92	-	N	-	6	6
2	H 28	0.16	F	17/-	Advanced	53‡	-	N	-	2	2
3	E 28	0.14	F	65/-	Advanced	100	-	N	-	6	6
4	H 28	0.09	F	69/-	Advanced	96	-	N	-	6	6
5	E 28	0.06	1	78/-	Advanced	78	-	N	-	6	6
6	E 28	0.13	F	89/-	Advanced	89	-	N	-	6	6
7	H 28	0.18	F	90/-	Advanced	90	-	N	-	5	6
8	H 28	0.08	F	91/-	Advanced	106	-	N	-	6	6
9	H 32	0.03	3	-/37	Separated	130	15.6	Y	4.75	6	6
10	E 28	0.18	F	25/46	Separated	75	8.5	Y	1.92	6	6
11	E 28	0.29	F	-/46	Separated	81	9.3	Y	3.1	6	6
12	E 28	0.25	2	-/56	Separated	68	15.6	Y	4.62	6	6
13§	H 28	-	F	-/62	Separated	62	-	Y	5.2	-	-
14	E 28	0.05	F	48/70	Separated	70	4.2	Y	4.23	4	6
15	H 28	0.32	F	-/75	Separated	102	12.5	Y	2.57	6	6
16	H 28	0.12	F	-/80	Separated	80	39.9	Y	7.36	6	6
17	H 28	0.16	F	66/88	Separated	88	9.8	Y	2.24	6	6
18	E 28	0.08	1	-/90	Separated	102	2.5	Y	0.85	5	6
19	H 28	0.14	1	-/107	Separated	107	57.3	Y	6.85	6	6

Pelvic osteolysis was defined as an area of localized bone loss that had not been present on the immediate post-operative radiographs and that had an osteosclerotic margin that could be clearly delineated. Osteolysis was graded by a single observer; however, it was impossible to blind the observer to the presence of hole eliminator advancement or complete separation.

Linear polyethylene wear rates and the size of the osteolytic lesion were calculated according to the edge detection method of Martell and Berdia⁶. Linear head penetration was measured on the anteroposterior pelvic radiograph. Measurement of the size of the osteolytic lesion was performed on the image providing the best view of the lesion. The reviewer measuring polyethylene wear was blinded to the occurrence of hole eliminator advancement and osteolysis.

Results

Materials and Methods | Results | Discussion | References

Nineteen hips had advanced or completely separated hole eliminators. In eighteen hips (seventeen patients), the advancement or separation of the hole eliminators was detected during routine radiographic evaluation at an average of eighty-nine months (range, fifty-three to 130 months) postoperatively. One additional hip was noted to have separation of the hole eliminator in a component retrieved at autopsy from a patient (Case 13) who died sixty-two months postoperatively (Table I).

The preoperative diagnosis for the eighteen patients (nineteen hips) was primary osteoarthritis (eleven hips), osteonecrosis (three hips), arthritis secondary to hip dysplasia (three hips), rheumatoid arthritis (one hip), and inflammatory arthritis (one hip). There were eight men and ten women who had an average age of fifty-two years (range, thirty-five to seventy-two years) at the time of surgery.

All nineteen femoral components were extensively porous-coated and had been inserted without cement. The outer diameters of the acetabular components were 52 mm (seven hips), 54 mm (three hips), 56 mm (five hips), 58 mm (three hips), and 60 mm (one hip). The diameters of the modular femoral heads were 28 mm in seventeen hips, 26 mm in one hip, and 32 mm in one hip. Ten hips had a Hylamer acetabular liner (DePuy), and nine had an Enduron liner (DePuy).

Timing

Evidence of advancement or separation was observed at a mean of sixty-three months (range, fourteen to 107 months) postoperatively (Table I). Eight of the nineteen hips showed advancement without separation of the eliminator from the shell. The total mean duration of follow-up for these eight hips was eighty-eight months (range, fifty-three to 106 months), and the mean time from the diagnosis of advancement to the most recent follow-up evaluation was twenty-four months (range, zero to seventy-eight months). The hole eliminators had advanced between 1 and 3 mm during this time.

In eleven hips (Cases 9 through 19), complete separation of hole eliminator from the shell was observed at a mean of sixty-nine months (range, thirty-seven to 107 months) (Table I). The mean duration of follow-up for these eleven hips was eighty-eight months (range, sixty-two to 130 months). The mean length of follow-up since separation was nineteen months (range, zero to ninety-three months). Four hips had been followed for more than two years. Eight of the eleven hips presented with a complete separation, although no previous advancement of the hole eliminator had been diagnosed. In the other three hips (Cases 10, 14, and 17), the time-interval from the first evidence of advancement to the diagnosis of separation was twenty-one months for one hip and twenty-two months for two hips. The distance of migration of the separated hole eliminators from their original position was measured on the iliac oblique radiographs and averaged 17.5 mm (range, 2.5 to 57.3 mm) (Table I).

Function

In all but one hip (the one in the patient who died), the finding of hole eliminator advancement or separation was an incidental radiographic finding at the time of a routine follow-up visit. Excluding the patient (Case 13) who died and the patient (Case 2) who had a revision because of infection after fifty-three months, the mean modified Merle D'Aubigné and Postel score for the remaining seventeen hips at the last follow-up evaluation was 5.8 points for pain and 6 points for walking.

One patient with a wear rate of 0.29 mm/yr felt a snapping sensation of the hip in maximum flexion. Another patient who was able to walk an unlimited distance complained of mild pain on the ipsilateral side on weight-bearing at the last follow-up evaluation. There were no dislocations. All patients were satisfied with the function of the hip.

One hip was revised because of infection; otherwise, there were no reoperations. There was no significant difference in the activity level (scored with a 5-point system by the physician), body weight, or cup abduction angle when the nineteen hips with hole eliminator advancement were compared with the remaining 522 hips.

Radiographic Evaluation

All femoral components were graded as stable and bone ingrown. All acetabular components were stable, and none had a circumferential radiolucency radiographically. Two acetabular components had nonprogressive radiolucencies of <2 mm in zone 1⁷.

No osteolysis was observed in the eight hips that showed only advancement, but all of the hips with complete separation of the hole eliminator had osteolytic lesions. All of the lesions were adjacent to or appeared to originate from the apical hole of the acetabular component. The lesion size ranged from 0.85 to 7.36 cm² (Fig. 2).

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Fig. 2: An anteroposterior pelvic radiograph of a hip (Case 16), made eighty months postoperatively, with an outline around an area of osteolysis (zones 2 and 3) and a separated hole eliminator lying at the medial aspect of the cup (arrow).

We also evaluated which was the best radiograph to use for the diagnosis of hole eliminator advancement or separation. For all fifteen hips that showed evidence of advancement or overinsertion of the hole eliminator (Figs. 3-A and 3-B), the diagnosis was made on the basis of the iliac oblique radiograph; for only four of them could the diagnosis have been made on the basis of an anteroposterior radiograph. For the ten hips with clinical radiographs demonstrating separation of the hole eliminator, separation was seen in nine on both the anteroposterior and iliac oblique radiographs. In one hip, separation of the hole eliminator was seen on only the iliac oblique radiograph.

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Figs. 3-A and 3-B: Case 6. Fig. 3-A An iliac oblique radiograph made immediately postoperatively, showing the hole eliminator flush to the shell. Fig. 3-B An iliac oblique radiograph made eighty-nine months postoperatively, showing advancement of the hole eliminator. The radiographic beam is almost tangential to the cup surface in the iliac oblique radiograph.

Excluding the hip that had the hole eliminator separation detected at the time of autopsy, the average wear rate per year seen radiographically was 0.14 mm/yr (0.14 mm/yr for the Enduron group and 0.14 mm/yr for the Hylamer group) for the eighteen hips (Table I). Seven hips had <0.1 mm/yr, eight had between 0.1 and 0.2 mm/yr, and three had >0.2 mm/yr. There was no relationship between wear and advancement or separation of the hole eliminator.

Discussion

Materials and Methods | Results | Discussion | References

In our experience, advancement of the acetabular hole eliminator is a complication that can be detected radiographically if serial iliac oblique radiographs are carefully observed. In this view, the radiographic beam is tangential to the dome of the cup, allowing the area of the hole eliminator to be easily seen. In contrast to advancement, complete separation of the hole eliminator from the shell is a sign that there may be retroacetabular osteolysis. Complete separation of the eliminator can almost always be diagnosed on either anteroposterior or iliac oblique radiographs.

In this series, hole eliminator advancement and separation were not necessarily a sign of increased polyethylene wear. The wear rates in this series are comparable with the reported wear rates from another study with the same implants⁸.

We speculate that a pressure gradient between the polyethylene liner-cup interface and the retroacetabular region could contribute to advancement of the hole eliminator. We also speculate that retroacetabular bone adjacent to it probably prevents separation of the hole eliminator from the shell. However, if joint fluid leaked around it, leading to retroace-tabular osteolysis, then the hole eliminator could be free to migrate into the osteolytic defect. We believe this is a possible explanation of our findings and implies that this version of the hole eliminator did not completely eliminate the occurrence of retroacetabular osteolysis as it was designed to do.

To correct the problem of advancement and separation, the manufacturer redesigned the hole eliminator (Fig. 1). Initially, the pitch of the terminal threads remained constant, thereby allowing for advancement. To counteract this possibility, a variable terminal thread pitch was introduced on the eliminator to allow for seating and locking. Surgeons who used this cup and hole eliminator prior to 1996 can expect to see hole eliminator advancement or separation in about 5% of the hips that have been followed for five years or more.

Our experience suggests that the occurrence of hole eliminator advancement and separation is infrequent and has not influenced patient outcomes. All instances were detected as incidental findings, and no patient had surgery to retrieve the hole eliminator. All but one of the patients in the present study were clinically asymptomatic. Therefore, we recommend that orthopaedists should continue to follow such asymptomatic patients, and, if an advancement of the hole eliminator is diagnosed, the patient should be informed of the increased risk of osteolysis that is associated with complete separation. We do not recommend surgery solely to remove or replace the hole eliminator.

References

Materials and Methods | Results | Discussion | References

SchmalzriedTP, Jasty M, Harris WH. Periprosthetic bone loss in total hip arthroplasty. Polyethylene wear debris and the concept of the effective joint space. J Bone Joint Surg Am.1992;74: 849-63.74849 1992 [PubMed]

ClausAM, Sychterz CJ, Hopper RH Jr, Engh CA. Pattern of osteolysis around two different cementless metal-backed cups: retrospective, radiographic analysis at minimum 10-year follow-up. J Arthroplasty.2001;16(8 Suppl 1): 177-82.16177 2001 [PubMed][CrossRef]

Merle D'AubignéR, Postel M. Functional results of hip arthroplasty with acrylic prosthesis. J Bone Joint Surg Am.1954;36: 451-75.36451 1954

CharnleyJ.Low friction arthroplasty of the hip: theory and practice. New York: Springer; 1979. 1979

EnghCA, Massin P, Suthers KE. Roentgenographic assessment of the biologic fixation of porous-surfaced femoral components. Clin Orthop.1990;257: 107-28. Erratum in: Clin Orthop. 1992;284:310-2.257107 1990 [PubMed]

MartellJM, Berdia S. Determination of polyethylene wear in total hip replacements with use of digital radiographs. J Bone Joint Surg Am.1997;79: 1635-41.791635 1997 [PubMed]

DeLeeJG, Charnley J. Radiological demarcation of cemented sockets in total hip replacement. Clin Orthop.1976;121: 20-32.12120 1976 [PubMed]

OrishimoKF, Claus AM, Sychterz CJ, Engh CA. Relationship between polyethylene wear and osteolysis in hips with a second-generation porous-coated cementless cup after seven years of follow-up. J Bone Joint Surg Am.2003; 85: 1095-9.851095 2003 [PubMed]

Topics

hip joint ; osteolysis ; apex hole eliminator ; diastasis

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Tim A. Walde, Alexandra M. Claus, Vivek Mohan, Robert H. HopperJr., C. Anderson EnghJr., Charles A. EnghSr.; Advancement and Separation of Apex Hole Eliminators with Cementless Duraloc 100 CupsA Report of Nineteen Cases. The Journal of Bone & Joint Surgery. 2004 Oct;86(10):2251-2256.

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