Our purpose was to compare the clinical wear performance of highly cross-linked (Crossfire) polyethylene with conventional (N2Vac) polyethylene total hip bearings. We implanted 56 hips (47 patients) with Crossfire acetabular bearing liners and compared their wear performance with 53 conventional polyethylene inserts. Wear and clinical data were collected retrospectively at a minimum 4-year and average 5-year followup. The linear femoral head penetration rate measured from plain radiographs was 0.055 mm/year +/- 0.022 mm/year for the Crossfire polyethylene and 0.138 mm/year +/- 0.073 mm/year for the control, a reduction of 60% for the Crossfire components. Calculated annual wear was 0.036 mm/year for the Crossfire components and 0.131 mm/year for the controls, a reduction of 72%. Radiographic review at most recent followup showed a reduction in erosive osteolytic lesions of the proximal femur for the Crossfire components compared with controls, also suggesting a reduction in debris release for the Crossfire components. Complications leading to revision were not seen in the Crossfire or control groups. These clinical findings suggest that this particular highly cross-linked polyethylene can provide wear reduction and an alternate bearing surface for active patient populations. Level of Evidence: Therapeutic study, Level III (retrospective comparative study). See the Guidelines for Authors for a complete description of levels of evidence.
"Highly crosslinked polyethylenes (HXLPEs) have been developed to improve the wear performance of UHMWPE. Previous investigations have shown that crosslinking of the polymer chains through irradiation significantly reduces the wear rate of UHMWPE  . However, it has been shown that the mechanical properties of polyethylene, such as impact toughness and fatigue, are compromised after crosslinking . "
"Polyethylenes (PEs) with elevated crosslinking for improved wear resistance have been in clinical use for more than 10 years. Wear measurements based on clinical radiographs have indicated wear rates substantially lower than for historical PEs [3, 4, 8, 10, 11, 15–18, 23, 28, 42], with a corresponding reduction in the incidence and severity of debris-induced osteolysis. The promising clinical performance of the crosslinked PEs has led to their use in hips with larger-diameter balls to provide additional resistance to dislocation . "
[Show abstract][Hide abstract] ABSTRACT: The low wear rates of crosslinked polyethylenes provide the potential to use larger diameters to resist dislocation. However, this requires the use of thinner liners in the acetabular component, with concern that higher contact stresses will increase wear, offsetting the benefits of the crosslinking.
We asked the following questions: Is the wear of conventional and crosslinked polyethylene liners affected by ball diameter, rigidity of backing, and liner thickness? Are the stresses in the liner affected by thickness?
Wear rates were measured in a hip simulator and stresses were calculated using finite element modeling.
Without crosslinking, the wear rate was 4% to 10% greater with a 36-mm diameter than a 28-mm diameter. With crosslinking, wear was 9% lower with a 36-mm diameter without metal backing and 4% greater with metal backing. Reducing the thickness from 6 mm to 3 mm increased the contact stress by 46%, but the wear rate decreased by 19%.
The reduction in wear with 5 Mrad of crosslinking was not offset by increasing the diameter from 28 mm to 36 mm or by using a liner as thin as 3 mm.
The results indicate, for a properly positioned 5-Mrad crosslinked acetabular component and within the range of dimensions evaluated, neither wear nor stresses in the polyethylene are limiting factors in the use of larger-diameter, thinner cups to resist dislocation.
Clinical Orthopaedics and Related Research 02/2011; 469(2):395-404. DOI:10.1007/s11999-010-1555-6 · 2.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Osteolytic lesions are common radiological findings behind acetabular prosthetic cups. If the cup is well-fixed, the management is quite controversial. Although implant exchange is the most reliable procedure, in most cases it could be considered overtreatment, with the potential for further morbidity and bone loss. Liner exchange associated with lesion debridement and grafting represents an alternative option that is less invasive. Here we present our experiences from a small pilot study of minimally invasive osteolysis treatment without bearings exchange in patients with no evidence of liner wear.
Inclusion criteria: retroacetabular osteolytic lesions in ceramic-on-polyethylene or metal-on-polyethylene cementless total hip arthroplasties, affecting more than 50% of the bone-prosthesis interface on anteroposterior radiography. Exclusion criteria: head penetration into the liner, suspected loosening or infection. Six patients were selected, two asymptomatic and four symptomatic. Only the symptomatic patients accepted the proposed treatment (performed between June 2004 and March 2006). All of them received fluoroscopy-assisted lesion debridement through an iliac cortical window, morcellized bone allograft mixed with autologous platelet-rich plasma, joint exploration for culture and lavage through a small capsular window. Patients were followed up clinically and radiologically at six months, 12 months, and then yearly.
Three patients out of four showed clinical and radiological improvement. One showed radiological improvement only, and recently underwent cup exchange for subsequent loosening. The visual analog scale (VAS) values for pain decreased on average, but not significantly. No major complications occurred. No recurrence was noted at 2.25-4 years' follow-up.
Although the small series does not allow any absolute conclusions to be drawn, the reported results seem to justify further, wider studies. It is still unclear if osteolytic lesions associated with no wear of the poly liner would progress to implant failure if left untreated. Until the problem is better understood, this procedure might represent an interesting way to prevent potential loosening and severe bone loss in intact sockets.
Journal of Orthopaedics and Traumatology 01/2009; 9(4):225-31. DOI:10.1007/s10195-008-0031-5
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