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Severe Polyethylene Wear in The Uncemented Acetabular Cup System Associated with the use of 28mm Diameter Cobalt-Chrome Femoral Head Components, A Complication Previously Observed with 32mm Diameter Femoral Head Components, -A Case Series

*C R McLean MRCS(Glasg) AFRCSI, DPMSA, *J B Wood FRCS(Orth), *H Wynn-Jones MRCS ,*C White MRCS and  *A J Miller FRCS.

* Department of Orthopaedics
   Mayday University Hospital, London Road, Croydon CR7 7YE, 020 8401 3193

Address for Correspondence


 We report 10 cases of failure of the polyethylene liner at 3.5 to 11.75 years after total hip arthroplasty using the acetabular cup system (ACS).  In all cases the mode of failure was wear of the superior rim of the liner, through to the metal backing, with subsequent, localised liner fracture.  All of these cases were associated with the use of a 28mm head.  The design of the ACS is flawed as it lacks hemispherical geometry, causing rim loading on thin polyethylene.  All patients with this prosthesis should be monitored for evidence of polyethylene wear.

J.Orthopaedics 2004;1(2)e2


In 1999 Patel et al described the failure of 5 cases of the uncemented acetabular cup system as a result of excessive polyethylene wear [3].  In four of their five cases, the femoral head component diameter size was 32mm.  In 1994 Bono et al described failure in the same implant, by the same mechanism, in 15 cases – all of which were associated with the use of a 32mm diameter femoral head component [2].  In our series we describe failure of the same implant, by the same mechanism, however, in all 10 cases a 28mm diameter femoral head component was used.

Patients and method

Nine patients in this series underwent modular, uncemented, total hip arthroplasty, using the titanium alloy, porous coated, Trilock acetabular cup, with an ACS polyethylene liner designed to press-fit into the Trilock cup and uncemented AML femoral stem (DePuy, Leeds, Yorkshire, UK).  The liners were manufactured by ram extrusion and sterilised by gamma irradiation in air.  The femoral head components were made from cobalt-chrome.  All patients presented with symptoms of hip discomfort and episodes of “hip-squeaking” with radiographic evidence of excessive polyethylene wear.  Osteolysis around the acetabular component was radiographically evident in three of these cases.  One patient had a hybrid total hip arthroplasty using the Trilock uncemented cup with ACS polyethylene liner and a cemented MS-30 stem (Sulzermedica, Alton, Hampshire, UK).  In this case, in addition to the above symptoms, start-up pain was also a feature.  Radiographically there was gross osteolysis around the cemented femoral component. 

The mean age of the patients at the time of primary arthroplasty was 55 years (range 41 – 65); there were 5 males and 5 females.

Acetabular abduction angles and presence of osteolysis were recorded using anteroposterior pelvic x-ray.  At revision operation the mode of liner failure was noted.


The time to failure was between 3.5 and 11.75 years – mean 7 years.  Acetabular abduction angles were between 42 and 54 degrees – mean 44 degrees.  All patients had a 28mm diameter cobalt-chrome femoral head component.  At revision all polyethylene liners had evidence of excessive wear and fracture at the superior rim.  In nine cases the uncemented acetabular component was solidly fixed, in the remaining case the acetabular osteolysis was such that the acetabular component was uncovered and loose.  In three cases there was osteolysis of the acetabular component, morselised bone allograft was used to improve the bone stock, in one of these cases the loose acetabular component was removed and an uncemented stemmed acetabular component was inserted.  In the one case where a cemented femoral component was used this was found to be loose and easy to remove.  The remaining cement was removed and an uncemented revision stem was implanted.  Nine of the original ten Trilock acetabular components were retained and new liners were inserted.


Porous or hydroxy-apatite coating on metal-backed acetabular cups provides a metallic surface for biological fixation by bony in-growth.  Modularity of such components allows for removal and exchange of liners as and when required.  It should be noted that, as with polyethylene liners within a cement mantle, the diameter of the polyethylene is less than that of the cup that houses it.  The prosthetic femoral head size will also affect the thickness of the polyethylene liner.  Polyethylene thickness is an important factor in the determination of contact stresses that lead to surface damage [1].  Sterilisation of polyethylene by gamma irradiation in air may lead to oxidative degradation that may contribute to its failure [3].  In this series, of the nineteen uncemented components used, one required revision for aseptic loosening.  The only cemented component used, being a cemented femoral stem, was revised for aseptic loosening.  The remaining nine AML femoral stems remained solidly fixed to bone.  This may suggest that the uncemented AML femoral component is capable of withstanding the effects of polyethylene wear debris. We recommend that all patients with a Trilock acetabular component with an ACS liner be monitored – clinically and radiographically – for signs of excessive polyethylene wear.


[1] Bartel DL, Bicknell VL, Ithaca MS and Wright TM: The effect of conformity, thickness and material on stresses in ultra-high molecular weight components for joint replacement.  J Bone Joint Surg Am 68: 1041, 1986

[2] Bono JV, Sanford L and Toussaint MD: Severe polyethylene wear in total hip arthroplasty.  Journal of Arthroplasty 9: 119, 1994

[3] Patel J, Scott J, Radford JP: Severe polyethylene wear in uncemented acetabular cup system components.  Journal of Arthroplasty 14: 635, 1999



 This is a peer reviewed paper 

Please cite as :

Severe Polyethylene Wear in The Uncemented Acetabular Cup System Associated with the use of 28mm Diameter Cobalt-Chrome Femoral Head Components, A Complication Previously Observed with 32mm Diameter Femoral Head Components, -A Case Series
J.Orthopaedics 2004;1(2)e2





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