title: Unicompartmental knee replacement: a comparison of constrained and unconstrained designs.
abstract: Seventy-six patients who had eighty-seven unicompartmental knee replacements were followed for an average of fifty-three months (range, two to twelve years). The operation was on the medial side in eighty-two knees and on the lateral side in five. Fifty replacements were unconstrained and thirty-seven were constrained. Of the fifty knees that had an unconstrained replacement, forty-nine (98 per cent) had a good or excellent result, compared with only twenty-six (70 per cent) of the knees that had a constrained replacement; the difference is significant (p = 0.0007). No knee that had an unconstrained replacement had a poor result, compared with nine (24 per cent) of the knees that had a constrained replacement (p = 0.0009). Four (8 per cent) of the fifty knees that had an unconstrained replacement later had a revision total knee arthroplasty, compared with ten (27 per cent) of the thirty-seven knees that had a constrained replacement; the difference is significant (p = 0.04). Noteworthy degenerative changes in the opposite compartment occurred in only one of the eighty-seven knees (a knee in which an unconstrained prosthesis had been inserted).
authors.affiliation: Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston.
authors.forename: W A
authors.initials: WA
authors.lastname: Hodge
authors.forename: H P
authors.initials: HP
authors.lastname: Chandler
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D010014:Osteolysis / Q000000981:diagnostic imaging; D011474:Prosthesis Design; D011859:Radiography; D012086:Reoperation; D012189:Retrospective Studies