TY - JOUR
T1 - Examination of ten fractured Oxford unicompartmental knee bearings
AU - Pegg, Elise
AU - Pandit, H.
AU - Gill, H. S.
AU - Keys, G. W.
AU - Svard, U. G.
AU - O'Connor, J. J.
AU - Murray, D. W.
PY - 2011
Y1 - 2011
N2 - Since the Oxford knee was first used unicompartmentally in 1982, a small number of bearings have fractured. Of 14 retrieved bearings, we examined ten samples with known durations in situ (four Phase 1, four Phase 2 and two Phase 3). Evidence of impingement and associated abnormally high wear (> 0.05 mm per year) as well as oxidation was observed in all bearings. In four samples the fracture was associated with the posterior radio-opaque wire. Fracture surfaces indicated fatigue failure, and scanning electron microscopy suggested that the crack initiated in the thinnest region. The estimated incidence of fracture was 3.20% for Phase 1, 0.74% for Phase 2, 0.35% for Phase 3, and 0% for Phase 3 without the posterior marker wire. The important aetiological factors for bearing fracture are impingement leading to high wear, oxidation, and the posterior marker wire. With improved surgical technique, impingement and high wear should be prevented and modern polyethylene may reduce the oxidation risk. A posterior marker wire is no longer used in the polyethylene meniscus. Therefore, the rate of fracture, which is now very low, should be reduced to a negligible level.
AB - Since the Oxford knee was first used unicompartmentally in 1982, a small number of bearings have fractured. Of 14 retrieved bearings, we examined ten samples with known durations in situ (four Phase 1, four Phase 2 and two Phase 3). Evidence of impingement and associated abnormally high wear (> 0.05 mm per year) as well as oxidation was observed in all bearings. In four samples the fracture was associated with the posterior radio-opaque wire. Fracture surfaces indicated fatigue failure, and scanning electron microscopy suggested that the crack initiated in the thinnest region. The estimated incidence of fracture was 3.20% for Phase 1, 0.74% for Phase 2, 0.35% for Phase 3, and 0% for Phase 3 without the posterior marker wire. The important aetiological factors for bearing fracture are impingement leading to high wear, oxidation, and the posterior marker wire. With improved surgical technique, impingement and high wear should be prevented and modern polyethylene may reduce the oxidation risk. A posterior marker wire is no longer used in the polyethylene meniscus. Therefore, the rate of fracture, which is now very low, should be reduced to a negligible level.
UR - http://www.scopus.com/inward/record.url?scp=83455170804&partnerID=8YFLogxK
UR - http://dx.doi.org/10.1302/0301-620X.93B12.27408
UR - http://www.ncbi.nlm.nih.gov/pubmed/22161922
U2 - 10.1302/0301-620X.93B12.27408
DO - 10.1302/0301-620X.93B12.27408
M3 - Article
SN - 0301-620X
VL - 93
SP - 1610
EP - 1616
JO - Journal of Bone and Joint Surgery - British Volume
JF - Journal of Bone and Joint Surgery - British Volume
IS - 12
ER -