title: Inadequate polyethylene thickness and osteolysis in cementless hip arthroplasty.
abstract: A matched series Porous Coated Anatomic (PCA), Howmedica, Rutherford, NJ) cementless hip arthroplasties comparing a 26-mm with a 32-mm head were reviewed. The 26-mm head was used in 63 hips of 56 patients (group 1), and the 32-mm head was inserted into 97 hips of 90 patients (group 2). The two groups were matched for age, sex, and primary diagnosis. The postoperative follow-up period ranged from 3 to 6.9 years (mean, 4.2 years) in group 1, compared with 3 to 7.9 years (mean, 4.5 years) for group 2. The mean clinical scores for pain, movement, and function were similar for the two groups. Erosive osteolytic lesions were encountered in 25.7% of the group 2 hips but in none of the group 1 cases. These lesions were not seen before 3 years after surgery and were present in Gruen zone 7 of all involved hips, although in two patients they were also noted in zone 1. Osteolysis was encountered only with the 32-mm head where the outer diameter of the metal backed cup was 52 mm or less. Therefore, inadequate polyethylene thickness, rather than head size, is implicated as the cause of plastic-particle mediated osteolysis.
authors.affiliation: Department of Orthopaedic Surgery, University of Bristol, United Kingdom.
authors.forename: I D
authors.initials: ID
authors.lastname: Learmonth
authors.forename: J G
authors.initials: JG
authors.lastname: Hussell
authors.forename: E J
authors.initials: EJ
authors.lastname: Smith
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000601:surgery; D010014:Osteolysis / Q000209:etiology*; D011095:Polyethylenes; D011183:Postoperative Complications / Q000209:etiology*; D011474:Prosthesis Design; D012189:Retrospective Studies
chemical_list: D011095:Polyethylenes