title: Dislocations and the femoral head size in primary total hip arthroplasty.
abstract: The dislocation rate of 3197 Charnley prostheses with 22 mm head in which the surgery was done between 1979 and 1991 in 2 orthopaedic centers was compared with that of 2875 Lubinus prostheses with 32 mm head in which the surgery was done between 1980 to 1991 in 3 other centers. A 1-year followup showed an equal rate of dislocation (2.4%-2.5%) in the 2 groups and included 75% of the 201 dislocated hips. Almost all of the late dislocations occurred with the Charnley prosthesis, resulting in a total dislocation rate of 3.7% compared with 2.9% with the Lubinus prosthesis. Regardless of the type of prosthesis used, there was a higher risk of dislocation in patients with nonhealed hip fractures and in arthroplasties performed by less experienced surgeons. When these 2 variables were removed, the small femoral head was not associated with an increased risk of dislocation. However, there were 77 of 118 (65%) recurrent dislocations in the Charnley group, compared with 37 of 83 (45%) in the Lubinus group, and the relative risk of a dislocated hip arthroplasty becoming recurrent increased by 2.3 times if the small femoral head was used. The number of reoperations also were doubled in this group. Almost 4 times as many dislocations were documented within 2 weeks after surgery after any type of prosthesis inserted through a posterior approach compared with the transtrochanteric approach, but there was no increase in rate of recurrence or revision.
authors.affiliation: Department of Orthopaedics, Malmö University Hospital, Sweden.
authors.forename: U
authors.initials: U
authors.lastname: Hedlundh
authors.forename: L
authors.initials: L
authors.lastname: Ahnfelt
authors.forename: C H
authors.initials: CH
authors.lastname: Hybbinette
authors.forename: L
authors.initials: L
authors.lastname: Wallinder
authors.forename: J
authors.initials: J
authors.lastname: Weckström
authors.forename: H
authors.initials: H
authors.lastname: Fredin
mesh_terms: D000368:Aged; D005260:Female; D005270:Femur Head / Q000033:anatomy & histology*; D006622:Hip Prosthesis; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D011474:Prosthesis Design; D012189:Retrospective Studies