Quantification of polyethylene degradation in mobile bearing knees: A retrieval analysis of the Anterior-Posterior-Glide (APG) and Rotating Platform (RP) Low Contact Stress (LCS) knee

Figures & data

Figure 1. Measurement methodology (APG bearing left, RP right; shaded area worn). Arrows indicate direction of movement.

Table 1. Summary of patient demographics and retrieval cases

	Anterior-posterior glide	Rotating platform
No. of tibial inserts	10	7
Women:men	6:4	5:2
Mean age (range)	63 (52–78)	56 (36–73)
Mean weight (range)	83 (70–112)	96 (90–100)
Mean time in situ (range)	31 (10–51)	36 (9–70)
Activity level (LM:MH)	6:3	3:3
Pain and loosening	7	4
Cemented:uncemented	1:9	1:6

LM: low to medium activity level

MH: medium to high activity level.

Table 2. Intended bearing radii compared to measured values (mm)

Size	Intended value	Measured value a
Small +	32.7	32.8
Large	41.4	41.0
New RP	35.7	35.8 b
New APG	41.4	41.4 b

^aMeasured value: the bearing radii were calculated from unworn areas on retrieved devices.

^bThe method and model was verified using new inserts.

Figure 2. Average linear penetration for the seventeen inserts

Table 3. Average penetration rate and volume loss for APG and RP LCS inserts

Insert type	Penetration rate (mm/year) mean (range)	Volume loss (mm3/year) mean (range)
APG superior	0.052 (0.007–0.110)	49 (6.2–109)
APG backside	0.039 (0.001–0.097)	36 (1.9–52)
Total wear		85
RP superior	0.054 (0.015–0.089)	44 (25–72)
RP backside	0.037 (0.014–0.051)	33 (1.7–91)
Total wear		77

Figure 3. Severity of wear of the superior LCS bearing surface.

Figure 4. Severity of wear of the inferior LCS bearing surface.

Table 4. Measurement of wear in total knee arthroplasty

TKA	Bearing	Wear (mm/year)	Reference
Rotaglide	Mobile	0.046	Polyzoides 1999
Oxford Bi-compartmental	Fixed	0.026–0.043	Argenson 1992
AMK, PFC Synatomic	Fixed	0.35	Benjamin 2001
Freeman Samuelson	Fixed	0.025	Plante-Bordeneuve 1993
Porous Coated Anatomic	Fixed	0.13	Lavernia 2001
Interax	Fixed	0.23	Hoshino 2002
Oxford Unicompartmental	Mobile	0.02	Price et al. 2005
AGC	Fixed	0.1	Gill et al. 2006
LCS	Mobile	0.053	Present study

Polyzoides A J, Tsakonas A, Brooks S, Pickford M. Design characteristics experimental studies and ten years of clinical experience with a fully conforming mobile bearing knee prostheses. Proc of the Intl Symp on the Knee. Inst Mech Eng London. 1999

 Google Scholar

Argenson J N, O’Connor J J. Polyethylene wear in meniscal knee replacement. A one to nine-year retrieval analysis of the Oxford knee. J Bone Joint Surg (Br) 1992; 74: 228–32

 PubMedGoogle Scholar

Benjamin J, Szivek J, Dersam G, Persselin S, Johnson R. Linear and volumetric wear of tibial inserts in posterior cruciate retaining knee arthroplasties. Clin Orthop 2001, 392: 131–8

 PubMedGoogle Scholar

Plante-Bordeneuve P, Freeman M A. Tibial high density polyethylene wear in conforming tibiofemoral prosthesis. J Bone Joint Surg (Br) 1993; 75: 630–6

 PubMedGoogle Scholar

Lavernia C J, Sierra R J, Hungerford D S, Krackow K. Activity level and wear in total knee arthroplasty. J Arthroplasty 2001; 16(4)446–53

 PubMed Web of Science ®Google Scholar

Hoshino A, Fukuoka Y, Ishida A. Accurate in vivo measurement of polyethylene wear in total knee arthroplasty. J Arthroplasty 2002; 17(4)490–6

 PubMedGoogle Scholar

Price A J, Short A, Kellert C, Beard D, Gill H, Pandit H, Dodd C A, Murray D W. Ten-year in vivo wear measurement of a fully congruent mobile bearing unicompartmental knee arthroplasty. J Bone Joint Surg (Br) 2005; 87(11)1493–7

 PubMedGoogle Scholar

Gill H S, Waite J C, Short A, Kellert C F, Price A J, Murray D W. In vivo measurement of volumetric wear of a total knee replacement. The Knee 2006; 13: 312–7

 PubMed Web of Science ®Google Scholar