Rama Ramakrishnan

Five-Year Comparative Study of Highly Cross-Linked (Crossfire) and Traditional Polyethylene

The purpose of this study was to compare the linear penetration rates of a highly cross-linked ultra-high-molecular-weight polyethylene to traditional polyethylene. Twenty-seven highly cross-linked components were matched to 27 traditional polyethylene components with respect to age, sex, body mass index, and activity level. Each group was followed up for a mean of approximately 6 years. Linear penetration was measured using Martells computerized technique (J Bone Joint Surg Am 1997;79:1635). The mean total penetration was 0.283 mm (SD, 0.253) for the highly cross-linked group. The mean total penetration for the traditional polyethylene was 0.696 mm (SD, 0.402). This difference was highly significant (P < or = .001). Our experience demonstrates a 59% reduction in total penetration of highly cross-linked polyethylene when compared with traditional polyethylene at a minimum of 5 years.

Metal-on-Metal Hip Resurfacing

Hip resurfacing devices require a new radiographic evaluation technique owing to femoral components with short or no stems. Fourteen US surgeons implanted 1148 metal-on-metal hip resurfacing (HR) devices in a US-FDA-IDE clinical trial, which began in 2001. In this multi-center, prospective study, 337 patients (mean age, 50.1 years) were enrolled as a study group of unilateral HR arthroplasties. Radiographs of 292 HR arthroplasties at a minimum 2-year follow-up (maximum 3 years) were reviewed. There were 10 patients with radiographic evidence of femoral component instability beyond 2 years, as evidenced by subsidence > or = 5mm. Of these, 7 did not have clinical symptoms associated with femoral component instability. In the study group, 24 revisions were reported, of which 8 were due to femoral neck fractures, 4 were due to acetabular component loosening, 11 were due to femoral component loosening, and 1 due to dislocation.

Once annealed highly cross-linked polyethylene exhibits low wear at 9 to 15 years

A once annealed highly cross-linked polyethylene (HXLPE) was introduced in 1998. Concerns regarding its long-term performance and oxidative resistance exist because of the presence of retained free radicals. The authors studied 48 patients with 50 hip implants having an average age of 62 years. They were followed for 9 to 15 years. The purpose of this study was to determine linear wear rate and the incidence of osteolysis and/or mechanical failure. At an average follow-up of 12.2 years, the annual linear wear rate was 0.018 mm (SD, 0.024 mm). No mechanical failures or osteolysis have been found to date. The clinical performance of this HXLPE continues to meet expectations despite the presence of free radicals. [Orthopedics. 2016; 39(3):e565-e571.].

Long-term Wear Data From a Prospective Multicenter Study of Second-Generation Highly Cross-linked Polyethylene Inserts in Total Hip Arthroplasty

In a prospective multicenter trial on highly cross-linked polyethylene inserts in patients undergoing total hip arthroplasty, 118 patients consented to 10-year follow-up. Medium-term follow-up results showed low wear at 5 and 7 years after surgery. The current study focuses on long-term data at 10 years. Patients were followed up by either phone or office visit to collect long-term clinical data including Harris hip score and adverse events. There were 2 deaths and 2 revisions, 1 at 6.5 years for pelvic cyst and severe pain and another at 8.0 years for recurrent dislocation. For wear analysis, suitable radiographic images for 48 patients (52 hips) at minimum 10-year follow-up were available. Mean age of the cohort was 62.5 years (62% female). Femoral head penetration was measured using Martells method from the radiographic images between the 6-week and the subsequent follow-ups. Polyethylene wear rate was calculated from the penetration data. Descriptive statistics were performed. There was no evidence of significant oxidation or locking mechanism failure. Mean Harris hip score of the group was 94.3. No osteolysis was noted by an independent radiographic reviewer. The slope of the bestfit regression line to the femoral head penetration data, which represents the overall linear wear rate of the polyethylene, was 0.014 mm/y. The wear rate was significantly below the 0.100 mm/y critical threshold for development of osteolysis. Volumetric wear rate was calculated to be 11.6 mm3/y. The second-generation highly cross-linked polyethylene acetabular inserts had low wear in the long term (10.3 years) with no incidence of osteolysis. [Orthopedics. 2018; 41(4):e529-e533.].