The acetabular anteversion and inclination were not statistically different in the group demonstrating CT evidence of osteolysis compared with those with no evidence of lysis (p = 0.49 and 0.72, respectively). There was no difference in postoperative Harris hip and UCLA scores in those exhibiting osteolysis and those with no evidence of lysis (Table 2). Assuming a two-sided test and an alpha of 0.05, the study had sufficient power to detect a 5° or greater between-group difference in anteversion and inclination and a 1.2-point or greater between-group difference in UCLA scores.
The goal of alternative bearing surfaces in THA is to reduce the wear to a degree that minimizes osteolysis and prevents aseptic loosening over time. The clinical elimination of both wear and osteolysis could potentially allow indefinite survivorship of THAs, providing an excellent option for young patients with hip disease not amenable to other hip preservation procedures. Several studies have demonstrated improved wear properties with HXLPE liners; however, the goal of this study was to determine whether HXLPE could also reduce the incidence of osteolysis compared with conventional polyethylene in a younger patient population. Other goals of this study were to determine the effectiveness of radiographs in evaluating the presence of and size of osteolytic lesions. Also, we wanted to determine the effects of wear, acetabular position, head size, and Harris hip and UCLA scores on the presence of lysis.
We acknowledge limitations to our study. First is the lack of randomization. The patient populations are slightly different. Second, the conventional liner group had longer followup and had smaller average head size. We statistically adjusted for the length of followup and found no changes in our results or conclusions. Smaller heads were used along with conventional polyethylene before the availability of HXLPE. Likely, both factors contributed to greater wear and development of lysis. Third, only patients who volunteered for the CT scan were included in the study and might not represent the entire population; however, all patients who fit the inclusion criteria were offered the opportunity to have a CT scan evaluation. Fourth, because lateral radiographs were not part of the standard postoperative protocol at the initiation of this study, we were unable to perform three-dimensional wear analysis. Nonetheless, two-dimensional wear analysis demonstrates good correlation with three-dimensional analysis and may be more reproducible [24, 34]. The HipAnalysis software does not account for pelvic tilt and rotation when calculating the anteversion and coronal inclination, which can introduce some error into these measurements despite our use of strict imaging protocols. Our data in fact document radiographs are not ideal for identifying lytic lesions. The same would hold true for cysts, and because we do not have preoperative CT scans on all patients, there is a possibility that lesions identified as osteolysis could have been present preoperatively as osteoarthritic cysts. We believe using our screening method prevented many false-positive cases of osteolysis; however, because CT scans miss up to 25% of osteolytic lesions , we cannot determine the true incidence of osteolysis.
Osteolysis was identified on CT in 12 of 50 (24%) hips with conventional liners and only one of 48 (2%) hips with HXLPE, representing a 92% reduction in the incidence of osteolysis. This is slightly less than previously reported incidences  of osteolysis, which may be a function of the rigorous definition of osteolysis and methodology of filtering out arthritic cysts. Also, we used 10 MRad irradiated HXLPE, whereas other studies evaluating wear and incidence of osteolysis used 5 to 7.5 MRad irradiated HXLPE [18, 38, 39] (Table 4). Experimentally, the degree of crosslinking alters the wear profile of the polyethylene, but its effect on osteolysis is still unknown .
Only seven of the 13 hips with osteolysis evident on CT had lesions visualized on radiographs. CT scans and MRIs detect over 80% of clinically relevant osteolytic lesions with MRIs being more sensitive for detecting lesions but less accurate for measuring volume of lytic lesions , which may be more clinically relevant . The sensitivity of plain radiographs in determining the true incidence of osteolysis has yielded poor results [4, 30, 46, 47]. When lytic lesions are evident on radiographs, the size is often underestimated ; however, some authors believe radiographs may be adequate for detection of clinically relevant volumes of lysis [28, 42]. We found no difference in the volume of osteolysis in those patients with radiographic evidence of osteolysis compared with those without lytic lesions on plain radiographs, indicating even large lesions can easily be missed on plain radiographs . This is similar to the results demonstrated in another study, which showed no difference in the volume of lysis when seen on radiographs compared with those seen on CT only .
In this study, the average head penetration rate in patients demonstrating osteolysis on CT scan was greater than those with no evidence of osteolysis This is consistent with the results of other studies evaluating the incidence of osteolysis [31, 38, 39], indicating dose of wear debris most likely plays some role in the osteolysis process (Table 4). However, after excluding the patient with massive lysis, we found no correlation between the amount of radiographic head penetration and volume of osteolytic lesions. Previous literature investigating the association between wear and volume of osteolysis has been varied. Puri et al.  found no correlation between linear wear rate and volume of osteolysis; however, Leung et al.  found larger lesions in the group with the most wear but did not comment specifically on correlation values. The lack of correlation found in this study seems appropriate because osteolysis is multifactorial and lesion size likely depends both on the amount of wear and how vigorous each individual’s response is to the particles created.
The group with osteolysis had a smaller average head size than those without lysis. Several studies show smaller heads create more linear wear [32, 37], which could increase the incidence of lysis. Recent studies, however, have contradicted this thought, demonstrating larger head sizes have increased both linear and volumetric wear [12, 22, 44]. Another study found no difference in linear wear but increased volumetric wear with larger heads; however, this was with HXLPE liners only .
We found no difference in the anteversion or inclination of the acetabulum in those with and without lysis. It is well known that malpositioned components can increase wear [7, 16]; however, because these groups were similar, it is unlikely that this contributed to the wear or lysis in the two groups. Harris hip scores between the groups with lysis and without lysis were similar. This indicates osteolysis is a silent process that remains asymptomatic until catastrophic failure occurs. This makes it a particularly hard problem to treat as well, because surgeons must convince asymptomatic patients to undergo surgery when they are not having pain.
Longevity HXLPE liners are highly effective at reducing the incidence of osteolysis during 5- to 9-year followup. We also demonstrated radiographs are not sufficient for identifying the incidence of osteolysis. We found no difference in the size of lesions seen on CT and radiographs compared with those only seen on CT scans, which negates some authors’ claims that radiographs can detect clinically relevant osteolysis. Pre- or immediate postoperative radiographs, along with a strict definition of osteolysis, are essential for making the diagnosis of osteolysis on CT. The low incidence in the HXPLE group does not support CT screening examinations during intermediate-term followup.
We thank Kirk E. Smith for his work with CT scan processing and measurement of these CT examinations.
1. Abu-Amer, Y., Darwech, I. and Clohisy, JC. Aseptic loosening of total joint replacements: mechanisms underlying osteolysis and potential therapies. Arthritis Res Ther
2007; 9: (Suppl 1):S6. 10.1186/ar2170
2. Ayers, D., Hayes, P., Drew, J., Eskander, M., Osuch, D. and Bragdon, C. Two-year radiostereometric analysis evaluation of femoral head penetration in a challenging population of young total hip arthroplasty patients. J Arthroplasty
2009; 24: (6 Suppl):9-14. 10.1016/j.arth.2009.05.027
3. Beaule, PE., Dorey, FJ., Hoke, R., Leduff, M. and Amstutz, HC. The value of patient activity level in the outcome of total hip arthroplasty. J Arthroplasty.
2006; 21: 547-552. 10.1016/j.arth.2005.09.004
4. Cahir, JG., Toms, AP., Marshall, TJ., Wimhurst, J. and Nolan, J.CT and MRI of hip arthroplasty. Clin Radiol.
2007; 62: 1163-1171.
5. Clohisy, JC., Calvert, G., Tull, F., McDonald, D. and Maloney, WJ. Reasons for revision hip surgery: a retrospective review. Clin Orthop Relat Res.
2004; 429: 188-192. 10.1097/01.blo.0000150126.73024.42
6. D’Antonio, JA., Manley, MT., Capello, WN., Bierbaum, BE., Ramakrishnan, R., Naughton, M. and Sutton, K. Five-year experience with Crossfire highly cross-linked polyethylene. Clin Orthop Relat Res.
2005; 441: 143-150. 10.1097/00003086-200512000-00024
7. Del Schutte, H, Jr, Lipman, AJ., Bannar, SM., Livermore, JT., Ilstrup, D. and Morrey, BF. Effects of acetabular abduction on cup wear rates in total hip arthroplasty. J Arthroplasty.
1998; 13: 621-626. 10.1016/S0883-5403(98)80003-X
8. Digas, G., Karrholm, J., Thanner, J., Malchau, H. and Herberts, P. The Otto Aufranc Award. Highly cross-linked polyethylene in total hip arthroplasty: randomized evaluation of penetration rate in cemented and uncemented sockets using radiostereometric analysis. Clin Orthop Relat Res.
2004; 429: 6-16. 10.1097/01.blo.0000150314.70919.e3
9. Dorr, LD., Wan, Z., Shahrdar, C., Sirianni, L., Boutary, M. and Yun, A. Clinical performance of a Durasul highly cross-linked polyethylene acetabular liner for total hip arthroplasty at five years. J Bone Joint Surg Am.
2005; 87: 1816-1821. 10.2106/JBJS.D.01915
10. Dowd, JE., Sychterz, CJ., Young, AM. and Engh, CA. Characterization of long-term femoral-head-penetration rates. Association with and prediction of osteolysis. J Bone Joint Surg Am.
2000; 82: 1102-1107.
11. Dumbleton, JH., Manley, MT. and Edidin, AA. A literature review of the association between wear rate and osteolysis in total hip arthroplasty. J Arthroplasty.
2002; 17: 649-661. 10.1054/arth.2002.33664
12. Elfick, AP., Hall, RM., Pinder, IM. and Unsworth, A. Wear in retrieved acetabular components: effect of femoral head radius and patient parameters. J Arthroplasty.
1998; 13: 291-295. 10.1016/S0883-5403(98)90174-7
13. Endo, M., Tipper, JL., Barton, DC., Stone, MH., Ingham, E. and Fisher, J. Comparison of wear, wear debris and functional biological activity of moderately crosslinked and non-crosslinked polyethylenes in hip prostheses. Proc Inst Mech Eng. [H]
2002; 216: 111-122.
14. Engh, CA, Jr, Stepniewski, AS., Ginn, SD., Beykirch, SE., Sychterz-Terefenko, CJ., Hopper, RH, Jr, and Engh, CA. A randomized prospective evaluation of outcomes after total hip arthroplasty using cross-linked marathon and non-cross-linked Enduron polyethylene liners. J Arthroplasty
2006; 21: (Suppl 2):17-25.
15. Fisher, J., McEwen, HM., Tipper, JL., Galvin, AL., Ingram, J., Kamali, A., Stone, MH. and Ingham, E. Wear, debris, and biologic activity of cross-linked polyethylene in the knee: benefits and potential concerns. Clin Orthop Relat Res.
2004; 428: 114-119. 10.1097/01.blo.0000148783.20469.4c
16. Gallo, J., Havranek, V. and Zapletalova, J. Risk factors for accelerated polyethylene wear and osteolysis in ABG I total hip arthroplasty. Int Orthop.
2010; 34: 19-26. 10.1007/s00264-009-0731-3
17. Glyn-Jones, S., Isaac, S., Hauptfleisch, J., McLardy-Smith, P., Murray, D. and Gill, H. Does highly cross-linked polyethylene wear less than conventional polyethylene in total hip arthroplasty? A double-blind, ransomized, and controlled trial using roentgen stereophotogrammetric analysis. J Arthroplasty.
2008; 23: 337-343. 10.1016/j.arth.2006.12.117
18. Gomez-Barrena, E., Puertolas, JA., Munuera, L. and Konttinen, YT. Update on UHMWPE research: from the bench to the bedside. Acta Orthop.
2008; 79: 832-840. 10.1080/17453670810016939
19. Harris, WH. Traumatic arthritis of the hip after dislocation and acetabular fractures: treatment by mold arthroplasty. An end-result study using a new method of result evaluation. J Bone Joint Surg Am.
1969; 51: 737-755.
20. Heisel, C., Silva, M., dela Rosa, MA. and Schmalzried, TP. Short-term in vivo wear of cross-linked polyethylene. J Bone Joint Surg Am.
2004; 86: 748-751.
21. Heisel, C., Silva, M. and Schmalzried, TP. Bearing surface options for total hip replacement in young patients. Instr Course Lect.
2004; 53: 49-65.
22. Hermida, JC., Bergula, A., Chen, P., Colwell, CW, Jr, and D’Lima, DD. Comparison of the wear rates of twenty-eight and thirty-two-millimeter femoral heads on cross-linked polyethylene acetabular cups in a wear simulator. J Bone Joint Surg Am.
2003; 85: 2325-2331.
23. Howie, DW., Neale, SD., Stamenkov, R., McGee, MA., Taylor, DJ. and Findlay, DM. Progression of acetabular periprosthetic osteolytic lesions measured with computed tomography. J Bone Joint Surg Am.
2007; 89: 1818-1825. 10.2106/JBJS.E.01305
24. Hui, AJ., McCalden, RW., Martell, JM., MacDonald, SJ., Bourne, RB. and Rorabeck, CH. Validation of two and three-dimensional radiographic techniques for measuring polyethylene wear after total hip arthroplasty. J Bone Joint Surg Am.
2003; 85: 505-511.
25. Kawamura, H., Dunbar, MJ., Murray, P., Bourne, RB. and Rorabeck, CH. The porous coated anatomic total hip replacement. A ten to fourteen-year follow-up study of a cementless total hip arthroplasty. J Bone Joint Surg Am.
2001; 83: 1333-1338.
26. Kitamura, N., Leung, SB. and Engh, CA, Sr, Characteristics of pelvic osteolysis on computed tomography after total hip arthroplasty. Clin Orthop Relat Res.
2005; 441: 291-297. 10.1097/01.blo.0000192359.12573.15
27. Kitamura, N., Naudie, DD., Leung, SB., Hopper, RH, Jr, and Engh, CA, Sr, Diagnostic features of pelvic osteolysis on computed tomography: the importance of communication pathways. J Bone Joint Surg Am.
2005; 87: 1542-1550. 10.2106/JBJS.D.02882
28. Kitamura, N., Pappedemos, PC., Duffy, PR, III, Stepniewski, AS., Hopper, RH, Jr, Engh, CA, Jr, and Engh, CA. The value of anteroposterior pelvic radiographs for evaluating pelvic osteolysis. Clin Orthop Relat Res.
2006; 453: 239-245. 10.1097/01.blo.0000246554.41058.8d
29. Lachiewicz, PF., Heckman, DS., Soileau, ES., Mangla, J. and Martell, JM. Femoral head size and wear of highly cross-linked polyethylene at 5 to 8 years. Clin Orthop Relat Res.
2009; 467: 3290-3296. 10.1007/s11999-009-1038-9
30. Leung, S., Naudie, D., Kitamura, N., Walde, T. and Engh, CA. Computed tomography in the assessment of periacetabular osteolysis. J Bone Joint Surg Am.
2005; 87: 592-597. 10.2106/JBJS.D.02116
31. Leung, SB., Egawa, H., Stepniewski, A., Beykirch, S., Engh, CA, Jr, and Engh, CA, Sr, Incidence and volume of pelvic osteolysis at early follow-up with highly cross-linked and noncross-linked polyethylene. J Arthroplasty
2007; 22: (Suppl 2):134-139. 10.1016/j.arth.2007.04.006
32. Livermore, J., Ilstrup, D. and Morrey, B. Effect of femoral head size on wear of the polyethylene acetabular component. J Bone Joint Surg Am.
1990; 72: 518-528.
33. Martell, JM. and Berdia, S. Determination of polyethylene wear in total hip replacements with use of digital radiographs. J Bone Joint Surg Am.
1997; 79: 1635-1641.
34. Martell, JM., Berkson, E., Berger, R. and Jacobs, J. Comparison of two and three-dimensional computerized polyethylene wear analysis after total hip arthroplasty. J Bone Joint Surg Am.
2003; 85: 1111-1117.
35. McCalden, R., MacDonald, S., Rorabeck, C., Bourne, R., Chess, D. and Charron, K. Wear rate of highly cross-linked polyethylene in total hip arthroplasty. A randomized controlled trial. J Bone Joint Surg Am.
2009; 91: 773-782. 10.2106/JBJS.H.00244
36. Olyslaegers, C., Defoort, K., Simon, JP. and Vandenberghe, L. Wear in conventional and highly cross-linked polyethylene cups: a 5-year follow-up study. J Arthroplasty.
2008; 23: 489-494. 10.1016/j.arth.2007.02.013
37. Oonishi, H., Tsuji, E. and Kim, Y. Retrieved total hip prostheses. Part 1: The effects of cup thickness, head sizes, and fusion defects on wear. J Mater Sci Mater Med
1998; 9: 393-401. 10.1023/A:1013283513509
38. Orishimo, KF., Claus, AM., Sychterz, CJ. and Engh, CA. Relationship between polyethylene wear and osteolysis in hips with a second-generation porous-coated cementless cup after seven years of follow-up. J Bone Joint Surg Am.
2003; 85: 1095-1099.
39. Puri, L., Wixson, RL., Stern, SH., Kohli, J., Hendrix, RW. and Stulberg, SD. Use of helical computed tomography for the assessment of acetabular osteolysis after total hip arthroplasty. J Bone Joint Surg Am.
2002; 84: 609-614.
40. Schmalzried, TP., Shepherd, EF., Dorey, FJ., Jackson, WO., dela Rosa, M., Fa’vae, F., McKellop, HA., McClung, CD., Martell, J., Moreland, JR. and Amstutz, HC. The John Charnley Award. Wear is a function of use, not time. Clin Orthop Relat Res.
2000; 381: 36-46. 10.1097/00003086-200012000-00005
41. Shia, DS., Clohisy, JC., Schinsky, MF., Martell, JM. and Maloney, WJ.THA with highly cross-linked polyethylene in patients 50 years of age or younger. Clin Orthop Relat Res.
2009; 467: 2059-2065. 10.1007/s11999-008-0697-2
42. Shon, WY., Gupta, S., Biswal, S., Han, SH., Hong, SJ. and Moon, JG. Pelvic osteolysis relationship to radiographs and polyethylene wear. J Arthroplasty.
2009; 24: 743-750. 10.1016/j.arth.2008.02.012
43. Soto, MO., Rodriguez, JA. and Ranawat, CS. Clinical and radiographic evaluation of the Harris-Galante cup: incidence of wear and osteolysis at 7 to 9 years follow-up. J Arthroplasty.
2000; 15: 139-145. 10.1016/S0883-5403(00)90022-6
44. Tarasevicius, S., Robertsson, O., Kesteris, U., Kalesinskas, RJ. and Wingstrand, H. Effect of femoral head size on polyethylene wear and synovitis after total hip arthroplasty: a sonographic and radiographic study of 39 patients. Acta Orthop.
2008; 79: 489-493. 10.1080/17453670710015472
45. Udomkiat, P., Dorr, LD. and Wan, Z. Cementless hemispheric porous-coated sockets implanted with press-fit technique without screws: average ten-year follow-up. J Bone Joint Surg Am.
2002; 84: 1195-1200.
46. Walde, TA., Mohan, V., Leung, S. and Engh, CA, Sr, Sensitivity and specificity of plain radiographs for detection of medial-wall perforation secondary to osteolysis. J Arthroplasty.
2005; 20: 20-24. 10.1016/j.arth.2004.04.010
47. Walde, TA., Weiland, DE., Leung, SB., Kitamura, N., Sychterz, CJ., Engh, CA, Jr, Claus, AM., Potter, HG. and Engh, CA, Sr, Comparison of CT, MRI, and radiographs in assessing pelvic osteolysis: a cadaveric study. Clin Orthop Relat Res.
2005; 437: 138-144. 10.1097/01.blo.0000164028.14504.46