A comparative study of "plasmacup" and "porous-coated" acetabular components: survival after 10 to 12 years of follow-up.
OBJECTIVE
Our primary aim was to compare the long-term survivorship rates and the rates of successful osseointegration between two different types of uncemented acetabular components.


BACKGROUND
Two types of alloys have primarily been used for the manufacture of the uncemented acetabular components: titanium-based and cobalt-based alloys. A titanium-based alloy appears to be more effective with regard to interface stress transfer to the host bone because of its lower elastic modulus relative to a cobalt-based alloy. This supposed mechanical advantage of a titanium-based alloy component motivated this comparative study.


METHODS
Two uncemented acetabular components, a porous-coated acetabulum and a Plasmacup®, were compared with a focus on long-term prosthesis survivorship and the development of acetabular osseointegration. Five radiographic signs of osseointegration were evaluated at the last follow-up appointment: (1) absence of radiolucent lines, (2) presence of a superolateral buttress, (3) medial stress-shielding, (4) radial trabeculae, and (5) an inferomedial buttress. We considered the presence of any three of these radiographic signs, in the absence of acetabular dislocation or symptoms, to be indicative of successful acetabular osseointegration.


RESULTS
Among 70 patients implanted with the porous-coated acetabulum, 80% achieved osseointegration over a mean follow-up time of 11.9 years versus 75.3% of the 73 patients who received a Plasmacup insert over a mean of 10.7 years. Prosthesis survivorship rates were not different between the two groups. Revision surgery due to mild or severe acetabular osteolysis, polyethylene wear, and aseptic loosening occurred in eight patients (11.4%) with a PCA versus nine (12.3%) with a Plasmacup.


CONCLUSIONS
We conclude that, during the first ten years after surgery, there is no significant difference between these two types of uncemented cups with regard to either prosthesis survivorship or successful osseointegration.
Department of Orthopedics, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil. rrnegreiros@gmail.com
José Ricardo Negreiros
JR
Vicente
Carlos Antonio Soares
CA
Ulhoa
Marcio
M
Katz
Renato Dainesi
RD
Addeo
Alberto Tesconi
AT
Croci
D000077:Acetabulum / Q000601:surgery*; D000328:Adult; D000368:Aged; D019544:Equipment Failure Analysis; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D016348:Osseointegration; D020959:Polyethylene; D011474:Prosthesis Design / Q000379:methods; D012086:Reoperation; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult
D020959:Polyethylene
J Orthop Res. 1987;5(4):548-61
3681529
J Arthroplasty. 2003 Jan;18(1):16-22
12555177
Clinics (Sao Paulo). 2008 Aug;63(4):509-14
18719763
J Bone Joint Surg Am. 1998 Aug;80(8):1175-85
9730127
J Arthroplasty. 2002 Oct;17(7):856-63
12375243
J Bone Joint Surg Br. 1993 Sep;75(5):835-6
8376454
Can J Surg. 1998 Feb;41(1):48-52
9492747
Z Orthop Unfall. 2007 Sep-Oct;145 Suppl 1:S9-S12
17939101
J Bone Joint Surg Am. 1995 May;77(5):760-6
7744901
J Bone Joint Surg Am. 1979 Jan;61(1):15-23
365863
J Bone Joint Surg Am. 2003 Jun;85(6):1079-83
12784006
J Arthroplasty. 1997 Feb;12(2):133-48
9139095
J Bone Joint Surg Br. 1972 Feb;54(1):61-76
5011747
Z Orthop Unfall. 2007 Sep-Oct;145 Suppl 1:S20-4
17939093
Clin Orthop Relat Res. 2006 Mar;444:176-83
16523139
J Bone Joint Surg Am. 2001 Sep;83(9):1333-8
11568195
J Arthroplasty. 1999 Aug;14(5):538-48
10475551
J Bone Joint Surg Br. 2009 Apr;91(4):447-50
19336802
J Bone Joint Surg Br. 1998 May;80(3):396-403
9619925
J Bone Joint Surg Am. 1991 Apr;73(4):587-92
2013598