The Journal of Arthroplasty Vol. 24 No. 1 2009

Case Report

Delayed Catastrophic Failure of a Ceramic Head inHybrid Total Hip Arthroplasty

Imran Anwar, MRCSEd, MSc, Gauraang Bhatnagar, MRCS, BSc, andSalah Atrah, FRCS, MSc (Orth)

Abstract: Catastrophic failure of ceramic implants is a rare but known complicationof total hip arthroplasty where such implants have been used. We report an unusualcase of a 67-year-old woman who underwent bilateral hybrid total hip arthroplastyusing ceramic-on-polyethylene bearings. Seven years later, she presented with left-sided hip pain in the absence of any trauma. She was found to have a completelyshattered ceramic head, with subsequent erosion of the metal taper of the femoralstem through the polyethylene insert, its metal shell, and into the pelvis. Thiscomplicated subsequent revision surgery, as removal of the acetabular componentresulted in a large pelvic defect that required an acetabular reinforcement ring andbone grafting. She recovered well after the revision procedure. Key words: ceramic,failure, fracture, polyethylene, total hip arthroplasty.© 2009 Elsevier Inc. All rights reserved.

Case Report

A 67-year-old woman underwent bilateral totalhip arthroplasties in 1999. On the right side, she hada hybrid procedure with an Omnifit metal-on-polyethylene system (Stryker Howmedica Osteo-nics, Mahwah, NJ). Six months later, she underwenta hybrid procedure on the left side, using a 28-mmceramic (aluminium oxide) head on a 10-mmstandard Muller stem for the femoral componentand a 28/50-mm Hedrocel elliptical, metal-backedpolyethylene (nonmodular) cup (all implants fromStratec Medical, Oberdorf, Switzerland). She made

From the Department of Trauma and Orthopaedics, The HillingdonHospital NHS Trust, Uxbridge, Middlesex, UK.

Submitted April 24, 2007; accepted January 21, 2008.No benefits or funds were received in support of the study.Reprint requests: Imran Anwar, MRCSEd, MSc, Flat 5, 56

Claremont Road, N6 5BY Highgate, London, UK.© 2009 Elsevier Inc. All rights reserved.0883-5403/08/2401-0026$36.00/0doi:10.1016/j.arth.2008.01.310

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an uneventful recovery and subsequently remainedsymptom-free for 6 years.

In October 2005, she was reviewed in clinic anddescribed an episode when she heard an audible“crack” in her left groin while sitting on her bed. Shedenied any history of trauma. After this event, shebegan to experience pain in her upper medial leftthigh, resulting in difficulty mobilizing. Clinicalexamination in the outpatient clinic at the timewas unremarkable. An anteroposterior (AP) pelvisradiograph was taken, but no adverse features wereidentified (Fig. 1). Blood tests including inflamma-tory markers were also normal. An isotope bonescan was performed, and the results excluded anyinfective process occurring in the hip. No specifictreatment was prescribed, but she continued to befollowed up in the outpatient clinic.

On subsequent follow-up in June 2006, there hadbeen a deterioration in her symptoms after a courseof physiotherapy. Repeat radiographs demonstrateddisintegration of the ceramic head and proximalmigration of the femoral stem. The taper had eroded

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Fig. 1. An AP radiograph of the pelvis at 6 years and3months after the bilateral total hip arthroplasty. Note theceramic head on the left side is intact.

Fig. 3. Extracted prosthesis. Note perforated metal-backedpolyethylene cup, medial pelvic wall bone still attached.Four large fragments of the shattered ceramic head havebeen retrieved.

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through not only the polyethylene but also themetal back of the acetabular cup and was protrudinginto the pelvis (Fig. 2A and B).

Fig. 2. A, An AP radiograph of the pelvis taken at 6 yearsand 11 months after the primary procedures. B, A lateraradiograph of the left hip taken preoperatively—beforerevision procedure. The ceramic head had shattered, withsubsequent erosion through the polyethylene and metacup by the metal femoral stem taper.

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The patient was scheduled for revision hiparthroplasty, which was briefly delayed due to herhaving an unrelated medical illness, and wasperformed in December 2006. At operation, a lateral(Hardinge) approach was used. Several large frag-ments of the shattered ceramic head were retrieved(Fig. 3), and a thorough lavage was carried out. Noevidence of implant loosening or infection wasfound, but there was extensive metallosis surround-ing both the acetabular and proximal part of thefemoral components. The stem and cement wereremoved, and the femoral canal was reamed. Theacetabular component was found to have a defect inits central superior aspect, with the defect penetrat-ing through the polyethylene cup and its metal backinto the pelvis.

During removal of the acetabular component, itwas noted that the anterior and medial pelvic wallshad become osteointegrated with the metal acet-abular back, and on retrieval of the implant, thisarea of the pelvis was left deficient. The defect wasconsistent with Paprosky classification type IIIa [1].The area of bone loss was filled with morsellizedbone graft, and a titanium graft augmentationprosthesis (GAP) acetabular reinforcement ringwas inserted and secured with 4 cancellous screws.A 48-mm polyethylene cup was cemented. Anuncemented distal femoral stem measuring 155 ×16 mmwith a +20-mm hydroxyapatite (HA)-coatedproximal body (23 mm) was used for the femoralstem. A 28-mm (+4 mm) metal modular head wasused. All implants were part of the Restoration

Fig. 4. Postoperative AP radiograph of the pelvis followingrevision procedure.

Delayed Catastrophic Failure of a Ceramic Head in Hybrid Total Hip Arthroplasty � Anwar et al 158.e7

modular system (Stryker Howmedica Osteonics).The postoperative radiograph is shown in Fig. 4. Thepatient required transfusion postoperatively butrecovered and is now mobilizing well.

Discussion

Ceramic components were first used in hiparthroplasty in the 1970s. Their smooth surfacemakes them less susceptible to wear compared withmetal. However, ceramics are also brittle, and thismakes them more prone to fracture. Early ceramicfemoral heads suffered from fracture rates whichmay have been as high as 13.4% [2]. Thanks todevelopments in materials, science, and manufac-turing, catastrophic failure of modern ceramicprostheses is now a rare event, with a fracture rateof 0.004% in one study [3]. Many factors have beensuggested as contributing to the risk of ceramic headfracture, including trauma, obesity, small balldiameter, poor manufacturing techniques, andsurgical error [4].The underlying cause of the ceramic head

fracture in this particular case can only bespeculated upon. We propose that the most likelymechanism is that an episode of minor, seeminglyinsignificant trauma may have initiated a fracturein the ceramic head, which was not identifiable onthe radiograph taken in October 2005 (Fig. 1) whenshe first presented with symptoms. This, in turn, ledto formation of hoop stresses within the compo-nent, resulting in eventual catastrophic failure.Such a mechanism has been demonstrated invitro, and an in vivo case of delayed fracture ofthe femoral head following trauma has also beendescribed [4,5]. In the case presented here, con-tinued weight-bearing on the affected hip led to

gradual erosion of the polyethylene acetabularinsert and eventually of the metal back of theacetabular component by the metal femoral stemtaper. To our knowledge, this is the first describedcase where this has occurred.

The case demonstrates the importance of thor-ough evaluation and investigation in a patient withceramic implants presenting with sudden onsetgroin pain and an audible crack. In such cases,asymmetry of the femoral head component is oneearly radiological sign which may indicate failure.In this particular case, initial radiographs taken afterthe onset of symptoms failed to identify any causefor the patient's symptoms. Had ceramic headfailure been possible to diagnose at an earlierstage, revision would have been less complicatedas a new cup could have been cemented into theHedrocel. There may also have been limited damageto the stem taper at that stage, allowing replacementof the failed ceramic head with a metal one withoutthe need for stem revision.

Several factors complicated subsequent revisionsurgery. Erosion of the stem taper through both thepolyethylene insert and its metal shell meant that asimple exchange of the polyethylene insert was notan option. It also made intraoperative dislocation ofthe hip and subsequent retrieval of the acetabularcomponent more difficult. The stem taper haderoded into pelvic bone, and its subsequent move-ment created a small defect superiorly. During itsmigration through the acetabulum, the femoralstem taper had become damaged and eroded,necessitating revision of the whole femoral com-ponent as opposed to replacement of the modularhead alone. Furthermore, bone ingrowth aroundthe Hedrocel metal acetabular component compli-cated its removal, resulting in a much larger pelvicdefect, which required bone grafting and use of aGAP ring implant. Removal of uncemented acet-abular components often results in large pelvicdefects, as in this case, due to osteointegration ofbone at its interface with the implant. Specializedtechniques have now been developed, whichreduce the amount of bone loss at the boneimplant interface. These include use of the Explantdevice (Zimmer, Warsaw, Ind), which uses shortfollowed by long blades to break the bone implantinterface with minimal resection of surroundingbone [6].

Revision total hip arthroplasty after fracture of aceramic femoral head is a challenging procedure.Retrieval of as many ceramic particles as possibleis crucial to the survivorship of the revision, as anyremaining fragments may cause subsequent abra-sive wear and lead to osteolysis and loosening. A

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study looking at the outcome of revision proceduresfollowing ceramic femoral head fracture gave asurvival rate of 63% at 5 years [7]. The mostfrequent cause of failure necessitating rerevisionwas implant loosening. Factors identified as con-tributing to longer survival rates included exchangeof any components, which may contain embeddedceramic particles, and extensive synovectomy, toremove as much ceramic debris as possible.

References

1. Paprosky WG, Perona PG, Lawrence JM. Acetabulardefect classification and surgical reconstruction inrevision arthroplasty. A 6-year follow-up evaluation.J Arthroplasty 1994;9:33.

2. Fritsch EW, Gleitz M. Ceramic femoral head fracturesin total hip arthroplasty. Clin Orthop Relat Res 1996;328:129.

3. Willmann G. Ceramic femoral head retrieval data. ClinOrthop Relat Res 2000;379:22.

4. Michaud RJ, Rashad SY. Spontaneous fracture of theceramic ball in a ceramic-polyethylene total hiparthroplasty. J Arthroplasty 1995;10:863.

5. McLean CR, Dabis H, Mok D. Delayed fracture of theceramic femoral head after trauma. J Arthroplasty2002;17:503.

6. Burns AWR, McCalden RW. Current techniques andnew developments in acetabular revision surgery. CurrOrthop 2006;20:162.

7. Allain J, Roudot-Thoraval F, Delecrin J, et al. Revisiontotal hip arthroplasty performed after fracture of aceramic femoral head. A multicenter survivorshipstudy. J Bone Joint Surg Am 2003;85-A:825.