Table 11.
Previous retrieval studies evaluating the influence of conformity on tibial polyethylene surface damage
| Study | Designs* | Number | Implantation duration (years) | UHMWPE type† | Damage scores‡,§ | Comments/Conclusions | ||
|---|---|---|---|---|---|---|---|---|
| Delamination | Pitting | Deformation | ||||||
| Collier et al. [11] (1991) | Fully conforming: LCS® rp (DP), LCS® mb (DP), Insall-Burstein® II (Z1) | 38 | Not specified | 0.4 | 1.6 | 1.1 | There was a positive correlation between the intensity of wear and the level of contact stress Noncongruent designs had greater wear than fully congruent ones Greater wear in the thinner inserts was observed for the noncongruent design |
|
| Moderately conforming curved-on-curved: Synatomic® (DP), Kinemax® (H), PCA® II (H) | 42 | Not specified | 1.0 | 1.8 | 1.3 | |||
| Moderately conforming flat-on-flat: MG® (Z1), MG® II (Z1), PCA® I, Ortholoc® III (DC), Natural Knee® (I), Kinematic® (H) | 42 | Not specified | 0.9 | 1.5 | 1.1 | |||
| Blunn et al. [8] (1997) | Minns Meniscal® TKA (Z2) | 30 | 4.4 | Not specified | 5.6 | 3.0 | 3.5 | Delamination was the principal wear type In medium- and long-term retrieved specimens of the designs with moderately high conformity, delamination wear was associated with restriction of rotational movement of the femoral component or with abrupt changes in the radius of the tibial component Wear attributed to cement abrasion or entrapment occurred on the more conforming designs |
| Kinematic® TKA (H) | 60 | 5.1 | Not specified | 7.0 | 4.7 | 1.7 | ||
| PCA® TKA (H) | 17 | 5.1 | Not specified | 9.0 | 3.4 | < 1.0 | ||
| Total Condylar® TKA (H) | 22 | 3.8 | Not specified | 3.3 | 3.6 | < 1.0 | ||
| Attenborough® TKA (Z2) | 15 | 8.4 | Not specified | 11 | < 1.0 | < 1.0 | ||
| Willie et al. [47] (2008) | 10 congruent 8 ultracongruent (knee system was not specified) |
18 | GUR 1020, slab consolidation molded, gamma-in-air | 5 (11) E 3 (6) O |
0 (0) E 0 (0) O |
The focus was on comparing the highly crosslinked polyethylene to the conventional polyethylenes | ||
| 3 congruent 7 flat (knee system was not specified) |
10 | GUR 4150, ram extruded, gamma-in-air | 32 (28) E 35 (25) O |
2 (2) E 1 (2) O |
Used melt technique to distinguish between plastic deformation and actual wear damage Premelt: conformity did not have an effect on surface damage for both polyethylenes Postmelt: the flat geometry was associated with higher damage for conventional polyethylene |
|||
| 8 ultracongruent 5 congruent (knee system was not specified) |
13 | Durasul® | 0 (0) E 0 (0) O |
0 (0) E 0 (0) O |
||||
| Current study | Conforming: CCK/PS Insall-Burstein® II (Z1) | 38 | GUR 4150, ram extruded, gamma-in-air | 2.3 (2.4) | 4.4 (3) | 0.21 (0.47) | Conforming design was associated with more delamination, pitting, edge loading, and embedded bone cement | |
| Less conforming: MG® II (Z1) | 31 | Same | 1.1(2.4) | 2.2 (2) | 0.15 (0.32) | |||
* Manufacturer code in parentheses: DP = DePuy (Warsaw, IN, USA); H = Howmedica (Rutherford, NJ, USA); R = Richards (Memphis, TN, USA); W = Waldemar Link (Hamburg, Germany); Z1 = Zimmer, Inc (Warsaw, IN, USA); Z2 = Zimmer UK (Swindon, UK); †Durasul®: GUR 1050, slab compression molded, ~95-kGy electron beam, melted, ethylene oxide); ‡values are expressed as mean, with SD in parentheses; §E = premelt surface damage area (%) and O = postmelt surface damage area (%) for Willie at al. [47]; PS = posterior-stabilized; CCK = constrained condylar knee.