Increased migration of the SHP prosthesis: radiostereometric comparison with the Lubinus SP2 design in 40 cases.
40 patients with primary arthrosis were randomized to receive either a cemented SHP (Scientific Hip Prosthesis) or Lubinus SP2 prosthesis. At 2 years radiostereometric measurements showed increased proximal migration (0.4/0.2 mm; p = 0.02) and more proximal wear (0.3/0.1 mm, p = 0.01) of the SHP socket. The SHP stem also subsided (-O.6/-0.1 mm, p<0.001) and rotated more into retroversion (2.6/0.3 degrees ) than did the SP2 design. This subsidence mainly occurred inside the cement mantle in 17 of 18 cases (13 SHP, 4 SP2), where this type of motion could be measured. The changes in bone mineral density evaluated with DEXA and the clinical results did not differ between the 2 groups. The subsidence of the SHP stem is the most pronounced so far recorded with radiostereometry in stems without a completely polished surface. This subsidence and the rotational instability imply a substantial risk of abrasive wear and increased stresses in the cement mantle.
Nivbrant
B
B
Department of Orthopedics, Northern University Hospital, Umeå, Sweden. Bo.Nivbrant@Orthop.umu.se
Kärrholm
J
J
Söderlund
P
P
D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D015519:Bone Density; D002484:Cementation; D005260:Female; D005500:Follow-Up Studies; D006621:Hip Joint / Q000000981:diagnostic imaging*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography