The Journal of Arthroplasty xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Standing Versus Supine Radiographs to Evaluate Femoral Head Penetration in the Polyethylene Liner After Total Hip Arthroplasty Masaaki Maruyama, MD, PhD a, Keiji Tensho, MD b, Shinji Wakabayashi, MD, PhD c, Kenji Hisa, MD d a
Department of Orthopedic Surgery, Shinonoi General Hospital, Shinonoi, Nagano 388–8004, Japan Department of Orthopedic Surgery, Shinshu University School of Medicine, Matsumoto, Nagano 390–8621, Japan Department of Orthopedic Surgery, Chushin Matsumoto Hospital, Matsumoto Medical Center, Matsumoto, Nagano 399–0021, Japan d Department of Orthopedic Surgery, IMS Miyoshi General Hospital, Miyoshi-cho, Iruma-gun Saitama 354–0041, Japan b c
a r t i c l e
i n f o
Article history: Received 14 October 2013 Accepted 5 February 2014 Available online xxxx Keywords: standing radiograph femoral head penetration polyethylene liner wear total hip arthroplasty
a b s t r a c t The linear penetration rates for ceramic femoral heads on conventional and highly cross-linked polyethylene were measured and compared with radiographs taken in the standing and supine position taken three weeks postoperatively and at final follow-up. Seventy-five patients (83 hips) with conventional polyethylene (group-1) and two hundred and seventy five patients (300 hips) with highly cross-linked polyethylene (group-2) were studied. Follow-up periods were 14.5 years in group-1 and 8.6 years in group-2. The average penetration rates in group-1 were 0.17 mm/year in supine position and 0.18 mm/year in standing position (P b 0.05). On the other hand, the rates in group-2 were 0.03 mm/year and 0.04 mm/year respectively (P b 0.05). Although there were statistical differences between groups, 0.01 mm differences are probably not clinically relevant. © 2014 Elsevier Inc. All rights reserved.
Highly cross-linked polyethylene (XLP) introduced and showed 60% or more wear reduction compared with conventional ultra high molecular weight polyethylene (CON) in total hip arthroplasty (THA) [1–6], except for extremely large (36- and 40-mm) prosthetic femoral head [7] and metal-backed XLP liner [8]. The highly cross-linked allpolyethylene cemented cups showed lower proximal penetration in both supine and standing positions [1]. Although most radiographs used for polyethylene wear measurements have been taken with the patient in the supine position in order to assess penetration by the femoral head into the acetabular polyethylene socket, regardless of XLP or CON, we have questioned the effect of weight-bearing on the position of the head within the socket because the polyethylene wear must occur in the weight bearing area of the socket. In addition, posterior pelvic tilt in standing position might occur due to increased kyphosis with lumbar spondylosis during follow-up periods. It seemed that the measuring points for wear in the socket were different between supine and standing position. This might be one of causes of discrepancy in socket wear between supine and standing position (Fig. 1). In the literature, however, there was no evidence that radiographs must be made with the patient bearing weight in order to accurately measure the position of the femoral head within the polyethylene liner [9]. Bragdon et al [10] found no difference
The Conflict of Interest statement associated with this article can be found at http:// dx.doi.org/10.1016/j.arth.2014.02.010. Reprint requests: Masaaki Maruyama, MD, PhD, Department of Orthopedic Surgery, Shinonoi General Hospital, 666–1 Ai, Shinonoi, Nagano 388–8004, Japan.
between the average total femoral head penetration when using supine or standing radiographs. The current study aimed to determine the effect of weight-bearing, i.e. standing on the two-dimensional radiographic penetration of the femoral head within the socket. Wear and creep deformity of the polyethylene was defined as femoral head penetration in THA. Patients and Methods All patients were given informed consent to participate in this clinical study, and our hospital institutional review board approved the study. Between March 1, 1997 and October 28, 1999, ninety primary and one revision cemented total hip arthroplasties (81 patients) with conventional (non cross linked) ultra high molecular weight polyethylene (CON) cemented socket combined zirconia (group-1) head were performed at our hospital, and between October 29, 1999 and June 30, 2007, three hundred and twenty six primary and three revision cemented or reverse hybrid total hip arthroplasties (300 patients) with highly cross-linked polyethylene (XLP) socket combined zirconia or alumina head (group-2) were also performed at our hospital. All of the operations were performed by the senior author (M.M.) with the clean air enclosure and with the surgeon wearing a total-body exhaust suit. Surgical Technique and Postoperative Care All operations were performed with the patient in the lateral decubitus position and stabilized on an air-fluidized body fixation
http://dx.doi.org/10.1016/j.arth.2014.02.010 0883-5403/© 2014 Elsevier Inc. All rights reserved.
Please cite this article as: Maruyama M, et al, Standing Versus Supine Radiographs to Evaluate Femoral Head Penetration in the Polyethylene Liner After Total Hip Arthroplasty, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.02.010
2
M. Maruyama et al. / The Journal of Arthroplasty xxx (2014) xxx–xxx
system (Magic bed TM Nikko Fines Industries Co. Ltd., in Japan same as Vac-Pac TM Surgical Positioning System, Olympic Medical Co. Ltd., Seattle, WA, USA). A posterolateral approach to the hip is used for exposure without osteotomy of the greater trochanter. In case of severe dysplastic hip, the bulk bone derived from the resected femoral head is grafted to manage the lateral acetabular roof defect located proximally at the rim of the acetabulum. An all-polyethylene socket (manufactured by KYOCERA Medical Corporation, Osaka Japan: the company was named as Japan Medical Materials Corporation between September, 2004 and March, 2012) was cemented in the acetabulum (Figs. 1 and 2). Polyethylene was sterilized using ethylene oxide gas for CON and gamma radiation for XLP (Table 1). Femoral stems (manufactured by the same company) were cemented for elderly patients (most of them were 70 years old or more) or fixed without bone cement in younger patients with good bone quality. All prosthetic heads were ceramic (zirconia or alumina) and were attached to the stem with a taper lock. All patients with alumina head had implantation of a straight collarless Ti-6Al-4V femoral component (cemented or cementless) and those with zirconia head had a cemented straight collarless Co-Cr femoral component. Deep venous thrombosis prophylaxis was routinely done with oral medication, Warfarin, with a few patients recognized as higher risk given low-molecular-weight Heparin for two weeks. On the third postoperative day the patients were allowed to use a wheelchair with
touch-down weight-bearing following passive and assisted active range of motion (ROM) exercises as instructed by our physiotherapists. The use of crutches for ambulation was begun on the 10th to 14th postoperative day, with progressive weight-bearing as tolerated. Time to full weight bearing was 3–4 weeks postoperatively. Follow-Up and Review The patients were semiannually examined in outpatient clinic after operation. Death from causes unrelated to the operation or lost to follow-up for long term of minimum six year was excluded from the wear measurement study. In addition, the hips with augmentation device, such as support ring, which interfered to determine a boundary part with polyethylene and cement, were also excluded from the study. As a result, six patients (eight hips) in the group-1 and twenty-five patients (twenty nine hips) in the group-2 were excluded from the wear measurement study due to these exclusion criteria. The follow-up rate was 91.2% (83/91 hips) for the group-1 and 91.2% (300/329 hips) for the group-2, respectively. As a result, a total of three hundred and fifty patients (three hundred and eighty three hips) who had had a total hip arthroplasty had been examined with digital radiographs with a set of anteroposterior (AP) radiographs and lateral radiograph (Lauenstein) for each patient: one AP radiograph was made with the patient supine and another AP was made with the patient standing in full weight bearing on the replaced hip. The radiographs were taken at three weeks postoperatively and at the time of follow-up. The average ceramic femoral head penetration was measured with radiographs taken in the supine and standing position at the final follow-up and compared with those of three weeks postoperatively. In case of patient with obesity, it may became difficult to determine a boundary part with polyethylene and cement because of thickness of abdominal fat hanging down the hip joint in standing position. In such cases, the abdominal fat should be lifted at the time of taking radiograph in standing position. The follow up periods were 14.5 ± 1.0 (range, 12.0–16.5) years in group-1 and 8.6 ± 2.1 (range, 6.0–13.6) years in group-2. In addition, group-2 was divided into two groups such as subgroup-Z with the use of Zirconia head and subgroup-A of Alumina head. Patient demographics and diagnoses of the hip joint disease or causes for THA were demonstrated in the Tables 2 and 3. Radiographic Assessments
Fig. 1. (A) Radiograph in supine position at 14 years postoperatively of a 60-year-old female at the time of surgery. The paired arrows indicate measuring points for polyethylene wear. (B) Radiograph in standing position at 14 years postoperatively of a 60-year-old female at the time of surgery. The paired arrows indicate measuring points for polyethylene wear. In this case, the pelvis was tilted posteriorly in standing position. Therefore, the measuring points for wear were different between supine and standing radiographs. Evaluation in supine position might lead to underestimation of polyethylene wear, as the wear occurred in weight bearing area of the socket.
All measurements on the radiographs of the two-dimensional position of the head were performed by a single researcher with use of a computerized measurement system which had a computerized digitizer with an accuracy of ± 0.01 mm. Only the anteroposterior radiographs of the bilateral hip joints were used for the measurements, because the lateral radiographs were often of inadequate quality. The thickness of polyethylene was measured in the proximal part of the socket in each radiograph. The penetration rate was determined by comparing the thickness in the follow-up radiograph with the thickness in the initial three-week postoperative radiograph at the same locations [11]. The thickness of the socket was measured along a line connecting the center of the prosthetic femoral head to the outer border of the socket at its shortest distance in at least three points. The socket-cement interface could be used to identify the proximal border of the socket in some cases that the wire marker took an ellipsoid form on the follow-up radiograph due to anteversion or retroversion or polar rotation of the cup (Fig. 2). Loosening on the radiographs was defined as the presence of a continuous (100%) radiolucent zone at the bone-cement interface with the width increased progressively or a change in position, i.e. migration or subsidence, of the prosthesis. Migration of the socket on
Please cite this article as: Maruyama M, et al, Standing Versus Supine Radiographs to Evaluate Femoral Head Penetration in the Polyethylene Liner After Total Hip Arthroplasty, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.02.010
M. Maruyama et al. / The Journal of Arthroplasty xxx (2014) xxx–xxx
3
Fig. 2. Methods for measurement of femoral head penetration rates to polyethylene socket. Radiograph in supine position at 3 weeks (A) and 14 years (B) postoperatively of a 61year-old female at the time of surgery. The wire marker was often rotated due to posterior tilt of the pelvis correlated with spondylosis of the lumbar spine. In the case, polyethylene wear was measured at the socket-cement interface (bold arrows). The wear rates for each case were measured at least three points indicated by a pair of a solid arrow and a dotted arrow respectively, and defined with maximum wear rate. Diagram of the radiological measurements used: T = inter-teardrop line; M = 15–35° medial to vertical; N = perpendicular to the inter-teardrop line; and L: =15–35° lateral to vertical.
the radiographs was defined as the presence of a change in position of 2 mm or more, or rotation. The change in position of the stem on the radiographs was defined as the presence of a progressive subsidence of 2 mm or more, or any change of position, such as varus or valgus. Results We have 14 hips (11 sockets and 1 stem in the group-1 and 2 sockets in the group-2) with radiological loosening. Eleven hips of the socket loosening cases had conventional polyethylene socket and six of them were revised. Two hips of the socket loosening cases had XLP socket and one of them was revised. A case with the stem loosening had fractured stem without bony support due to massive osteolysis caused by heavy conventional polyethylene wear. Linear penetration rates of the ceramic head in group-1 (CON) were 0.172 ± 0.069 (range, 0.044–0.350) mm/year in supine position and 0.178 ± 0.069 (range, 0.023–0.358) mm/year in standing position (P b 0.05, paired t-test), and linear regression analysis showed that the two measurements were highly correlated (r 2 = 0.88) (Fig. 3). On the other hand, the rates in group-2 (XLP) were 0.029 ± 0.023 (range, 0–0.110) mm/year and 0.035 ± 0.026 (range, 0–0.117) mm/year respectively (P b 0.05, paired t-test) but linear regression analysis showed that the two measurements were not correlated (r 2 = 0.19)
(Fig. 4). The mean ceramic head penetration rate in XPL socket showed 80.3% (standing) and 83.1% (supine) reduction compared with those in CON. There was significant increase of the rates measured in the standing position compared with those in the supine position. Linear penetration rates of the ceramic head in subgroup-Z were 0.028 ± 0.023 (range, 0–0.110) mm/year in supine position and 0.033 ± 0.026 (0–0.117) mm/year in standing position (P b 0.05, paired t-test), and those in subgroup-A were 0.030 ± 0.023 (range, 0–0.110) mm/year and 0.038 ± 0.026 (range, 0–0.104) mm/year respectively (P b 0.05, paired t-test) (Table 4). Discussion Supine radiograph is commonly used to measure femoral head penetration rate into polyethylene socket [4,5,11,12]. There was no evidence that radiographs must be made with the patient bearing weight in order to accurately measure the position of the femoral head within the polyethylene liner because of a nearly perfect relationship between the measurements of the position of the head on radiographs made with the patient standing and bearing weight and those on radiographs made with the patient standing but not bearing weight [9]. Bragdon et al [10] found no difference between the average total femoral head penetration when using supine or standing radiographs.
Table 1 Comparison of Cross-Linked and Conventional Polyethylene.
Brand Name of Polyethylene
Manufacturer
Resin
Aeonian (Highly Cross-Linked UHMWPE) ConventionalUHMWPE
Kyocera Medical
GUR 1050
Molding Method
Radiation Temperature
Radiation Dose (kGy)
Radiation Type
Postirradiation Thermal Treatment
Sterilization Method
Sheet Molded
RT
35
Gamma
Annealed 110°C 10 hours
Gamma (25 kGy) in Nitrogen EtO
RT: Room temperature. EtO: Ethylene oxide gas. UHMWPE: Ultra high molecular weight polyethylene.
Please cite this article as: Maruyama M, et al, Standing Versus Supine Radiographs to Evaluate Femoral Head Penetration in the Polyethylene Liner After Total Hip Arthroplasty, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.02.010
4
M. Maruyama et al. / The Journal of Arthroplasty xxx (2014) xxx–xxx
Table 2 Patient Demographics. THA Hips With (Patients) CON XLP
Age at Surgery (y) F/U Periods (y) Female:Male (Average ± SD, Range) (Average ± SD, Range)
83 (75) 72:3 300 (275) 259:16
58.1 ± 8.6 (26–83) 62.2 ± 10.0 (24–81)
14.5 ± 1.0 (12.0–16.5) 8.6 ± 2.1 (6.0–13.6)
CON: Conventional polyethylene, XLP: Cross linked polyethylene.
Both in the group-1 and group-2, however, linear penetration rates of the prosthetic femoral head in the current study were significantly larger in standing position than in supine position (P b 0.05, paired t-test). The materials of the femoral head such as Zirconia and Alumina had no influence on the wear rates measured in supine or in standing position. Data in the group-1 revealed that measurements of the position of the head on radiographs made with the patient supine were significantly correlated with measurements of the position of the head on radiographs made with the patient bearing weight, but not in the group-2. Since the polyethylene wear occurs in the patient bearing weight position including ambulation, we consider that real wear point should be identified in standing position. In addition, posterior tilting of the pelvis occurred in some cases at standing position due to kyphosis or decrease of lordosis of the lumbar spine with spondylosis (Fig. 1). In such cases, measuring point in supine radiograph for polyethylene wear may be inadequate because it does not reflect the point with greatest wear. This results in underestimation of the penetration rate including polyethylene wear. Because the prosthetic head moves three-dimensionally after THA, Hamaji et al [13] reported that linear penetration rates in the frontal and sagittal planes, and three-dimensional linear penetration rates were calculated from the penetration vectors based on standing anteroposterior and lateral radiographs obtained at follow-up. This is reasonable method, but it is difficult to take lateral radiograph in standing position and to obtain adequate quality for wear measurement routinely. In addition, Sychterz et al [14] showed that for most patients (95%) head penetration can be measured sufficiently from anteroposterior radiographs alone. Vandenbussche et al [15] reported that measurement of femoral head penetration in polyethylene using a 3-dimensional CT-scan technique was accurate, and had repeatability for low wear cases associated with highly cross linked polyethylene. They mentioned that CT, using a slice thickness of 0.0625 mm, estimated femoral head penetration in both all-poly and metal-backed acetabular components with accuracy ranging from 0.009 to 0.245 mm (mean 0.080; SD 0.067). This was a good measuring method in supine position based on the use of a high quality CT which might be settled in very few institutions in the world, except for our hospital. However, CT evaluation cannot be carried out in standing position. This is the first report which shows cemented all polyethylene acetabular components comparing wear of conventional polyethylene versus cross-linked polyethylene without metal backed acetabular or modular acetabular components. Concerning prosthetic materials, Wroblewski et al mentioned that relatively low polyethylene wear rate (0.03 mm/year) was performed in Zirconia head on conventional polyethylene socket in THA and that Ceramic-UHMWPE is the next
Fig. 3. Linear femoral head penetration rates of conventional ultra-high molecular weight polyethylene cases in supine and standing position. There was positive correlation between the average total penetration rates when using supine or standing radiographs.
Fig. 4. Linear femoral head penetration rates of cross linked ultra-high molecular weight polyethylene cases in supine and standing position. There was no correlation between the average total penetration rates when using supine or standing radiographs.
stage in the evolution of total hip arthroplasty [16]. However, the polyethylene wear rates were not reduced in THA with Zirconia head on conventional polyethylene in our series [17]. Therefore, we focused on XLP to reduce the wear rates and used this polyethylene for THA after October, 1999. The highly cross-linked polyethylene decreased the penetration rate mainly after one year probably reflecting less wear [2]. GlynJones et al [18] mentioned that the penetration in the first 3 months
Table 3 Diagnoses of the Hip Joint Disease or Causes for THA. THA With
Dysplastic
Dislocated
Primary
Traumatic
RA
RDC
AVN
Revision
Ankylosed
Total
CON XLP Total (%)a
70 249 319 (83.3)
0 6 6 (1.6)
3 29 32 (8.4)
2 4 6 (1.6)
2 2 4 (1.0)
1 3 4 (1.0)
3 3 6 (1.6)
2 2 4 (1.0)
0 2 2 (0.5)
83 300 383
CON: Conventional polyethylene, XLP: Cross linked polyethylene, Dysplastic/Dislocated/Primary/Traumatic: Osteoarthritis of the hip joint, RA: Rheumatoid Arthritis, RDC: Rapidly Destructive Coxarthrosis, AVN: Avascular Necrosis of the Femoral Head. a Values are expressed as total number, with percentage in parentheses.
Please cite this article as: Maruyama M, et al, Standing Versus Supine Radiographs to Evaluate Femoral Head Penetration in the Polyethylene Liner After Total Hip Arthroplasty, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.02.010
M. Maruyama et al. / The Journal of Arthroplasty xxx (2014) xxx–xxx
5
Table 4 Demographics and Penetration of the Head to Polyethylene Socket (Creep Plus Wear): Zirconia vs Alumina Ceramics—Only XLP Cases.
Ceramics
Hips: THAs Female: (Patients) Male
Age at Surgery (y) F/U Periods (y) Supine Xp (mm/y) Standing Xp (mm/y) Paired t-Test (Average ± SD, Range) (Average ± SD, Range) (Average ± SD, Range) (Average ± SD, Range) (Supine vs. Standing)
Zirconia subgroup-Z
194 (178)
171:7
64.0 ± 10.0 (24–81)
9.3 ± 2.2 (6.0–13.6)
88:9
58.2 ± 8.6 (33–77)
7.1 ± 1.0 (6.0–8.9)
P b 0.05
P b 0.05
Alumina subgroup-A 106 (97) unpaired t-test
0.028 ± 0.023 (0–0.110) 0.030 ± 0.023 (0–0.110) N.S.* (P = 0.392)
0.033 ± 0.026 (0–0.117) 0.038 ± 0.026 (0–0.104) N. S.* (P = 0.151)
P b 0.05 (P = 0.0013) P b 0.05 (P = 0.0248)
Zirconia heads were used in all cases with the cemented stem and some cases with the Ti-6Al-4V cementless stem. Alumina heads were mainly used in the rest cases of the cementless stem. F/U: Follow up.
was probably caused by creep or bedding in; from 3 months onward, much of the penetration was probably caused by wear. Therefore, the penetration is mainly contributed by polyethylene wear after 3 months postoperatively. They also reported that the femoral head penetration rate was creep-dominated in the first 6 months and was probably caused by wear from one year after THA [3]. As it is impossible to distinguish creep and wear of polyethylene liner clinically, penetration of the prosthetic femoral head into polyethylene socket has been usually used for expression of both creep and wear. Digas et al [1] reported that at 2 years the highly cross-linked polyethylene liner showed 62% lowered proximal penetration and 31% lowered total (three-dimensional) penetration when the patients were examined in supine position, whereas showing an 80–90% wear reduction in hip simulator testing. After this report, there were a lot of reports that the highly cross-linked polyethylene liner reduced 60–94% of polyethylene wear rates including creep as compared with those of conventional polyethylene [3–6]. In the current study, we had similar results that XLP showed 80–83% reduction as compared with conventional polyethylene. In our series, polyethylene sockets without metal shell were cemented in all cases. In metal backed XLP acetabular liner, however, Moor et al reported a case with early failure of the liner [8]. Longer follow-up time is, therefore, needed to evaluate whether highly cross-linked polyethylene in hip arthroplasty has any advantages over all-cemented and uncemented THA. Conclusions We found significant difference between the average total ceramic femoral head penetration between supine and standing radiographs in using both CON and XPL socket. The measurement in supine radiograph might result in maximum 20% underestimation of penetration rate. Acknowledgements The authors wish to thank Mrs. Kinue Kobayashi, Ms. Kumie Miyamoto, and Mrs. Aya Higashijo for their excellent clinical and technical assistance. References 1. Digas G, Kärrholm J, Thanner J, et al. 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.
2. Digas G. New polymer materials in total hip arthroplasty. Evaluation with radiostereometry, bone densitometry, radiography and clinical parameters. Acta Orthop Suppl 2005;76(315):3. 3. Glyn-Jones S, McLardy-Smith P, Gill HS, et al. The creep and wear of highly crosslinked polyethylene: a three-year randomised, controlled trial using radiostereometric analysis. J Bone Joint Surg Br 2008;90(5):556. http://dx.doi.org/10.1302/ 0301-620X.90B5.20545. 4. D'Antonio JA, Manley MT, Capello WN, et al. Five-year experience with Crossfire highly cross-linked polyethylene. Clin Orthop Relat Res 2005;441:143. 5. Capello WN, D'Antonio JA, Ramakrishnan R, et al. Continued improved wear with an annealed highly cross-linked polyethylene. Clin Orthop Relat Res 2011;469(3):825 [Epub 2010 Sep 16]. 6. McCalden RW, MacDonald SJ, Rorabeck CH, et al. Wear rate of highly cross-linked polyethylene in total hip arthroplasty. A randomized controlled trial. J Bone Joint Surg Am 2009;91(4):773. http://dx.doi.org/10.2106/JBJS.H.00244. 7. Lachiewicz PF, Heckman DS, Soileau ES, et al. Femoral head size and wear of highly cross-linked polyethylene at 5 to 8 years. Clin Orthop Relat Res 2009;467(12):3290. http://dx.doi.org/10.1007/s11999-009-1038-9. [Epub 2009 Aug 19]. 8. Moore KD, Beck PR, Petersen DW, et al. Early failure of a cross-linked polyethylene acetabular liner. A case report. J Bone Joint Surg Am 2008;90(11):2499. http://dx. doi.org/10.2106/JBJS.G.01304. 9. Moore KD, Barrack RL, Sychterz CJ, et al. The effect of weight-bearing on the radiographic measurement of the position of the femoral head after total hip arthroplasty. J Bone Joint Surg Am 2000;82(1):62. 10. Bragdon CR, Thanner J, Greene ME, et al. Standing versus supine radiographs in RSA evaluation of femoral head penetration. Clin Orthop Relat Res 2006;448:46. 11. Maruyama M., Terayama K. Socket wear of Charnley low friction arthroplasty. Fifteen year follow-up. Bulletin Hospital for Joint Diseases 1993–1995;53(4):37– 42. 12. Maruyama M, Capello WN, D’Antonio JA, et al. Effect of low friction ion treated femoral heads on polyethylene wear rates. Clin Orthop Relat Res 2000;370:183. 13. Hamaji H, Yamamoto S, Ishibashi H, et al. Novel method to evaluate femoral head penetration in the polyethylene liner after total hip arthroplasty: three-dimensional evaluation on standing radiographs. J Orthop Sci 2008;13(5):425. http://dx. doi.org/10.1007/s00776-008-1263-1. [Epub 2008 Oct 9]. 14. Sychterz CJ, Yang AM, McAuley JP, et al. Two-dimensional versus threedimensional radiographic measurements of polyethylene wear. Clin Orthop Relat Res 1999;365:117. 15. Vandenbussche E, Saffarini M, Hansen U, et al. Measurement of femoral head penetration in polyethylene using a 3-dimensional CT-scan technique. Acta Orthop 2010;81(5):563. http://dx.doi.org/10.3109/17453674.2010.519163. 16. Wroblewski M, Siney PD, Nagai H, et al. Wear of ultra-high-molecular-weight polyethylene cup articulating with 22.225 mm zirconia diameter head in cemented total hip arthroplasty. J Orthop Sci 2004;9(3):253. 17. Maruyama M, Wakabayashi S, Tensho K, et al. Usefulness of standing anteroposterior radiograph of the hip for socket wear measurement in total hip arthroplasty: Comparative study of conventional with highly cross linked polyethylene. Presented in 12eme Association Franco-Japonaise d'Orthopedie 2013, Kyoto, Japan. 18. Glyn-Jones S, Isaac S, Hauptfleisch J, et al. Does highly cross-linked polyethylene wear less than conventional polyethylene in total hip arthroplasty? A double-blind, randomized, and controlled trial using roentgen stereophotogrammetric analysis. J Arthroplasty 2008;23(3):337. http://dx.doi.org/10.1016/j.arth.2006.12.117.
Please cite this article as: Maruyama M, et al, Standing Versus Supine Radiographs to Evaluate Femoral Head Penetration in the Polyethylene Liner After Total Hip Arthroplasty, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.02.010
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Standing Versus Supine Radiographs to Evaluate Femoral Head Penetration in the Polyethylene Liner After Total Hip Arthroplasty Masaaki Maruyama, MD, PhD a, Keiji Tensho, MD b, Shinji Wakabayashi, MD, PhD c, Kenji Hisa, MD d a
Department of Orthopedic Surgery, Shinonoi General Hospital, Shinonoi, Nagano 388–8004, Japan Department of Orthopedic Surgery, Shinshu University School of Medicine, Matsumoto, Nagano 390–8621, Japan Department of Orthopedic Surgery, Chushin Matsumoto Hospital, Matsumoto Medical Center, Matsumoto, Nagano 399–0021, Japan d Department of Orthopedic Surgery, IMS Miyoshi General Hospital, Miyoshi-cho, Iruma-gun Saitama 354–0041, Japan b c
a r t i c l e
i n f o
Article history: Received 14 October 2013 Accepted 5 February 2014 Available online xxxx Keywords: standing radiograph femoral head penetration polyethylene liner wear total hip arthroplasty
a b s t r a c t The linear penetration rates for ceramic femoral heads on conventional and highly cross-linked polyethylene were measured and compared with radiographs taken in the standing and supine position taken three weeks postoperatively and at final follow-up. Seventy-five patients (83 hips) with conventional polyethylene (group-1) and two hundred and seventy five patients (300 hips) with highly cross-linked polyethylene (group-2) were studied. Follow-up periods were 14.5 years in group-1 and 8.6 years in group-2. The average penetration rates in group-1 were 0.17 mm/year in supine position and 0.18 mm/year in standing position (P b 0.05). On the other hand, the rates in group-2 were 0.03 mm/year and 0.04 mm/year respectively (P b 0.05). Although there were statistical differences between groups, 0.01 mm differences are probably not clinically relevant. © 2014 Elsevier Inc. All rights reserved.
Highly cross-linked polyethylene (XLP) introduced and showed 60% or more wear reduction compared with conventional ultra high molecular weight polyethylene (CON) in total hip arthroplasty (THA) [1–6], except for extremely large (36- and 40-mm) prosthetic femoral head [7] and metal-backed XLP liner [8]. The highly cross-linked allpolyethylene cemented cups showed lower proximal penetration in both supine and standing positions [1]. Although most radiographs used for polyethylene wear measurements have been taken with the patient in the supine position in order to assess penetration by the femoral head into the acetabular polyethylene socket, regardless of XLP or CON, we have questioned the effect of weight-bearing on the position of the head within the socket because the polyethylene wear must occur in the weight bearing area of the socket. In addition, posterior pelvic tilt in standing position might occur due to increased kyphosis with lumbar spondylosis during follow-up periods. It seemed that the measuring points for wear in the socket were different between supine and standing position. This might be one of causes of discrepancy in socket wear between supine and standing position (Fig. 1). In the literature, however, there was no evidence that radiographs must be made with the patient bearing weight in order to accurately measure the position of the femoral head within the polyethylene liner [9]. Bragdon et al [10] found no difference
The Conflict of Interest statement associated with this article can be found at http:// dx.doi.org/10.1016/j.arth.2014.02.010. Reprint requests: Masaaki Maruyama, MD, PhD, Department of Orthopedic Surgery, Shinonoi General Hospital, 666–1 Ai, Shinonoi, Nagano 388–8004, Japan.
between the average total femoral head penetration when using supine or standing radiographs. The current study aimed to determine the effect of weight-bearing, i.e. standing on the two-dimensional radiographic penetration of the femoral head within the socket. Wear and creep deformity of the polyethylene was defined as femoral head penetration in THA. Patients and Methods All patients were given informed consent to participate in this clinical study, and our hospital institutional review board approved the study. Between March 1, 1997 and October 28, 1999, ninety primary and one revision cemented total hip arthroplasties (81 patients) with conventional (non cross linked) ultra high molecular weight polyethylene (CON) cemented socket combined zirconia (group-1) head were performed at our hospital, and between October 29, 1999 and June 30, 2007, three hundred and twenty six primary and three revision cemented or reverse hybrid total hip arthroplasties (300 patients) with highly cross-linked polyethylene (XLP) socket combined zirconia or alumina head (group-2) were also performed at our hospital. All of the operations were performed by the senior author (M.M.) with the clean air enclosure and with the surgeon wearing a total-body exhaust suit. Surgical Technique and Postoperative Care All operations were performed with the patient in the lateral decubitus position and stabilized on an air-fluidized body fixation
http://dx.doi.org/10.1016/j.arth.2014.02.010 0883-5403/© 2014 Elsevier Inc. All rights reserved.
Please cite this article as: Maruyama M, et al, Standing Versus Supine Radiographs to Evaluate Femoral Head Penetration in the Polyethylene Liner After Total Hip Arthroplasty, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.02.010
2
M. Maruyama et al. / The Journal of Arthroplasty xxx (2014) xxx–xxx
system (Magic bed TM Nikko Fines Industries Co. Ltd., in Japan same as Vac-Pac TM Surgical Positioning System, Olympic Medical Co. Ltd., Seattle, WA, USA). A posterolateral approach to the hip is used for exposure without osteotomy of the greater trochanter. In case of severe dysplastic hip, the bulk bone derived from the resected femoral head is grafted to manage the lateral acetabular roof defect located proximally at the rim of the acetabulum. An all-polyethylene socket (manufactured by KYOCERA Medical Corporation, Osaka Japan: the company was named as Japan Medical Materials Corporation between September, 2004 and March, 2012) was cemented in the acetabulum (Figs. 1 and 2). Polyethylene was sterilized using ethylene oxide gas for CON and gamma radiation for XLP (Table 1). Femoral stems (manufactured by the same company) were cemented for elderly patients (most of them were 70 years old or more) or fixed without bone cement in younger patients with good bone quality. All prosthetic heads were ceramic (zirconia or alumina) and were attached to the stem with a taper lock. All patients with alumina head had implantation of a straight collarless Ti-6Al-4V femoral component (cemented or cementless) and those with zirconia head had a cemented straight collarless Co-Cr femoral component. Deep venous thrombosis prophylaxis was routinely done with oral medication, Warfarin, with a few patients recognized as higher risk given low-molecular-weight Heparin for two weeks. On the third postoperative day the patients were allowed to use a wheelchair with
touch-down weight-bearing following passive and assisted active range of motion (ROM) exercises as instructed by our physiotherapists. The use of crutches for ambulation was begun on the 10th to 14th postoperative day, with progressive weight-bearing as tolerated. Time to full weight bearing was 3–4 weeks postoperatively. Follow-Up and Review The patients were semiannually examined in outpatient clinic after operation. Death from causes unrelated to the operation or lost to follow-up for long term of minimum six year was excluded from the wear measurement study. In addition, the hips with augmentation device, such as support ring, which interfered to determine a boundary part with polyethylene and cement, were also excluded from the study. As a result, six patients (eight hips) in the group-1 and twenty-five patients (twenty nine hips) in the group-2 were excluded from the wear measurement study due to these exclusion criteria. The follow-up rate was 91.2% (83/91 hips) for the group-1 and 91.2% (300/329 hips) for the group-2, respectively. As a result, a total of three hundred and fifty patients (three hundred and eighty three hips) who had had a total hip arthroplasty had been examined with digital radiographs with a set of anteroposterior (AP) radiographs and lateral radiograph (Lauenstein) for each patient: one AP radiograph was made with the patient supine and another AP was made with the patient standing in full weight bearing on the replaced hip. The radiographs were taken at three weeks postoperatively and at the time of follow-up. The average ceramic femoral head penetration was measured with radiographs taken in the supine and standing position at the final follow-up and compared with those of three weeks postoperatively. In case of patient with obesity, it may became difficult to determine a boundary part with polyethylene and cement because of thickness of abdominal fat hanging down the hip joint in standing position. In such cases, the abdominal fat should be lifted at the time of taking radiograph in standing position. The follow up periods were 14.5 ± 1.0 (range, 12.0–16.5) years in group-1 and 8.6 ± 2.1 (range, 6.0–13.6) years in group-2. In addition, group-2 was divided into two groups such as subgroup-Z with the use of Zirconia head and subgroup-A of Alumina head. Patient demographics and diagnoses of the hip joint disease or causes for THA were demonstrated in the Tables 2 and 3. Radiographic Assessments
Fig. 1. (A) Radiograph in supine position at 14 years postoperatively of a 60-year-old female at the time of surgery. The paired arrows indicate measuring points for polyethylene wear. (B) Radiograph in standing position at 14 years postoperatively of a 60-year-old female at the time of surgery. The paired arrows indicate measuring points for polyethylene wear. In this case, the pelvis was tilted posteriorly in standing position. Therefore, the measuring points for wear were different between supine and standing radiographs. Evaluation in supine position might lead to underestimation of polyethylene wear, as the wear occurred in weight bearing area of the socket.
All measurements on the radiographs of the two-dimensional position of the head were performed by a single researcher with use of a computerized measurement system which had a computerized digitizer with an accuracy of ± 0.01 mm. Only the anteroposterior radiographs of the bilateral hip joints were used for the measurements, because the lateral radiographs were often of inadequate quality. The thickness of polyethylene was measured in the proximal part of the socket in each radiograph. The penetration rate was determined by comparing the thickness in the follow-up radiograph with the thickness in the initial three-week postoperative radiograph at the same locations [11]. The thickness of the socket was measured along a line connecting the center of the prosthetic femoral head to the outer border of the socket at its shortest distance in at least three points. The socket-cement interface could be used to identify the proximal border of the socket in some cases that the wire marker took an ellipsoid form on the follow-up radiograph due to anteversion or retroversion or polar rotation of the cup (Fig. 2). Loosening on the radiographs was defined as the presence of a continuous (100%) radiolucent zone at the bone-cement interface with the width increased progressively or a change in position, i.e. migration or subsidence, of the prosthesis. Migration of the socket on
Please cite this article as: Maruyama M, et al, Standing Versus Supine Radiographs to Evaluate Femoral Head Penetration in the Polyethylene Liner After Total Hip Arthroplasty, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.02.010
M. Maruyama et al. / The Journal of Arthroplasty xxx (2014) xxx–xxx
3
Fig. 2. Methods for measurement of femoral head penetration rates to polyethylene socket. Radiograph in supine position at 3 weeks (A) and 14 years (B) postoperatively of a 61year-old female at the time of surgery. The wire marker was often rotated due to posterior tilt of the pelvis correlated with spondylosis of the lumbar spine. In the case, polyethylene wear was measured at the socket-cement interface (bold arrows). The wear rates for each case were measured at least three points indicated by a pair of a solid arrow and a dotted arrow respectively, and defined with maximum wear rate. Diagram of the radiological measurements used: T = inter-teardrop line; M = 15–35° medial to vertical; N = perpendicular to the inter-teardrop line; and L: =15–35° lateral to vertical.
the radiographs was defined as the presence of a change in position of 2 mm or more, or rotation. The change in position of the stem on the radiographs was defined as the presence of a progressive subsidence of 2 mm or more, or any change of position, such as varus or valgus. Results We have 14 hips (11 sockets and 1 stem in the group-1 and 2 sockets in the group-2) with radiological loosening. Eleven hips of the socket loosening cases had conventional polyethylene socket and six of them were revised. Two hips of the socket loosening cases had XLP socket and one of them was revised. A case with the stem loosening had fractured stem without bony support due to massive osteolysis caused by heavy conventional polyethylene wear. Linear penetration rates of the ceramic head in group-1 (CON) were 0.172 ± 0.069 (range, 0.044–0.350) mm/year in supine position and 0.178 ± 0.069 (range, 0.023–0.358) mm/year in standing position (P b 0.05, paired t-test), and linear regression analysis showed that the two measurements were highly correlated (r 2 = 0.88) (Fig. 3). On the other hand, the rates in group-2 (XLP) were 0.029 ± 0.023 (range, 0–0.110) mm/year and 0.035 ± 0.026 (range, 0–0.117) mm/year respectively (P b 0.05, paired t-test) but linear regression analysis showed that the two measurements were not correlated (r 2 = 0.19)
(Fig. 4). The mean ceramic head penetration rate in XPL socket showed 80.3% (standing) and 83.1% (supine) reduction compared with those in CON. There was significant increase of the rates measured in the standing position compared with those in the supine position. Linear penetration rates of the ceramic head in subgroup-Z were 0.028 ± 0.023 (range, 0–0.110) mm/year in supine position and 0.033 ± 0.026 (0–0.117) mm/year in standing position (P b 0.05, paired t-test), and those in subgroup-A were 0.030 ± 0.023 (range, 0–0.110) mm/year and 0.038 ± 0.026 (range, 0–0.104) mm/year respectively (P b 0.05, paired t-test) (Table 4). Discussion Supine radiograph is commonly used to measure femoral head penetration rate into polyethylene socket [4,5,11,12]. There was no evidence that radiographs must be made with the patient bearing weight in order to accurately measure the position of the femoral head within the polyethylene liner because of a nearly perfect relationship between the measurements of the position of the head on radiographs made with the patient standing and bearing weight and those on radiographs made with the patient standing but not bearing weight [9]. Bragdon et al [10] found no difference between the average total femoral head penetration when using supine or standing radiographs.
Table 1 Comparison of Cross-Linked and Conventional Polyethylene.
Brand Name of Polyethylene
Manufacturer
Resin
Aeonian (Highly Cross-Linked UHMWPE) ConventionalUHMWPE
Kyocera Medical
GUR 1050
Molding Method
Radiation Temperature
Radiation Dose (kGy)
Radiation Type
Postirradiation Thermal Treatment
Sterilization Method
Sheet Molded
RT
35
Gamma
Annealed 110°C 10 hours
Gamma (25 kGy) in Nitrogen EtO
RT: Room temperature. EtO: Ethylene oxide gas. UHMWPE: Ultra high molecular weight polyethylene.
Please cite this article as: Maruyama M, et al, Standing Versus Supine Radiographs to Evaluate Femoral Head Penetration in the Polyethylene Liner After Total Hip Arthroplasty, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.02.010
4
M. Maruyama et al. / The Journal of Arthroplasty xxx (2014) xxx–xxx
Table 2 Patient Demographics. THA Hips With (Patients) CON XLP
Age at Surgery (y) F/U Periods (y) Female:Male (Average ± SD, Range) (Average ± SD, Range)
83 (75) 72:3 300 (275) 259:16
58.1 ± 8.6 (26–83) 62.2 ± 10.0 (24–81)
14.5 ± 1.0 (12.0–16.5) 8.6 ± 2.1 (6.0–13.6)
CON: Conventional polyethylene, XLP: Cross linked polyethylene.
Both in the group-1 and group-2, however, linear penetration rates of the prosthetic femoral head in the current study were significantly larger in standing position than in supine position (P b 0.05, paired t-test). The materials of the femoral head such as Zirconia and Alumina had no influence on the wear rates measured in supine or in standing position. Data in the group-1 revealed that measurements of the position of the head on radiographs made with the patient supine were significantly correlated with measurements of the position of the head on radiographs made with the patient bearing weight, but not in the group-2. Since the polyethylene wear occurs in the patient bearing weight position including ambulation, we consider that real wear point should be identified in standing position. In addition, posterior tilting of the pelvis occurred in some cases at standing position due to kyphosis or decrease of lordosis of the lumbar spine with spondylosis (Fig. 1). In such cases, measuring point in supine radiograph for polyethylene wear may be inadequate because it does not reflect the point with greatest wear. This results in underestimation of the penetration rate including polyethylene wear. Because the prosthetic head moves three-dimensionally after THA, Hamaji et al [13] reported that linear penetration rates in the frontal and sagittal planes, and three-dimensional linear penetration rates were calculated from the penetration vectors based on standing anteroposterior and lateral radiographs obtained at follow-up. This is reasonable method, but it is difficult to take lateral radiograph in standing position and to obtain adequate quality for wear measurement routinely. In addition, Sychterz et al [14] showed that for most patients (95%) head penetration can be measured sufficiently from anteroposterior radiographs alone. Vandenbussche et al [15] reported that measurement of femoral head penetration in polyethylene using a 3-dimensional CT-scan technique was accurate, and had repeatability for low wear cases associated with highly cross linked polyethylene. They mentioned that CT, using a slice thickness of 0.0625 mm, estimated femoral head penetration in both all-poly and metal-backed acetabular components with accuracy ranging from 0.009 to 0.245 mm (mean 0.080; SD 0.067). This was a good measuring method in supine position based on the use of a high quality CT which might be settled in very few institutions in the world, except for our hospital. However, CT evaluation cannot be carried out in standing position. This is the first report which shows cemented all polyethylene acetabular components comparing wear of conventional polyethylene versus cross-linked polyethylene without metal backed acetabular or modular acetabular components. Concerning prosthetic materials, Wroblewski et al mentioned that relatively low polyethylene wear rate (0.03 mm/year) was performed in Zirconia head on conventional polyethylene socket in THA and that Ceramic-UHMWPE is the next
Fig. 3. Linear femoral head penetration rates of conventional ultra-high molecular weight polyethylene cases in supine and standing position. There was positive correlation between the average total penetration rates when using supine or standing radiographs.
Fig. 4. Linear femoral head penetration rates of cross linked ultra-high molecular weight polyethylene cases in supine and standing position. There was no correlation between the average total penetration rates when using supine or standing radiographs.
stage in the evolution of total hip arthroplasty [16]. However, the polyethylene wear rates were not reduced in THA with Zirconia head on conventional polyethylene in our series [17]. Therefore, we focused on XLP to reduce the wear rates and used this polyethylene for THA after October, 1999. The highly cross-linked polyethylene decreased the penetration rate mainly after one year probably reflecting less wear [2]. GlynJones et al [18] mentioned that the penetration in the first 3 months
Table 3 Diagnoses of the Hip Joint Disease or Causes for THA. THA With
Dysplastic
Dislocated
Primary
Traumatic
RA
RDC
AVN
Revision
Ankylosed
Total
CON XLP Total (%)a
70 249 319 (83.3)
0 6 6 (1.6)
3 29 32 (8.4)
2 4 6 (1.6)
2 2 4 (1.0)
1 3 4 (1.0)
3 3 6 (1.6)
2 2 4 (1.0)
0 2 2 (0.5)
83 300 383
CON: Conventional polyethylene, XLP: Cross linked polyethylene, Dysplastic/Dislocated/Primary/Traumatic: Osteoarthritis of the hip joint, RA: Rheumatoid Arthritis, RDC: Rapidly Destructive Coxarthrosis, AVN: Avascular Necrosis of the Femoral Head. a Values are expressed as total number, with percentage in parentheses.
Please cite this article as: Maruyama M, et al, Standing Versus Supine Radiographs to Evaluate Femoral Head Penetration in the Polyethylene Liner After Total Hip Arthroplasty, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.02.010
M. Maruyama et al. / The Journal of Arthroplasty xxx (2014) xxx–xxx
5
Table 4 Demographics and Penetration of the Head to Polyethylene Socket (Creep Plus Wear): Zirconia vs Alumina Ceramics—Only XLP Cases.
Ceramics
Hips: THAs Female: (Patients) Male
Age at Surgery (y) F/U Periods (y) Supine Xp (mm/y) Standing Xp (mm/y) Paired t-Test (Average ± SD, Range) (Average ± SD, Range) (Average ± SD, Range) (Average ± SD, Range) (Supine vs. Standing)
Zirconia subgroup-Z
194 (178)
171:7
64.0 ± 10.0 (24–81)
9.3 ± 2.2 (6.0–13.6)
88:9
58.2 ± 8.6 (33–77)
7.1 ± 1.0 (6.0–8.9)
P b 0.05
P b 0.05
Alumina subgroup-A 106 (97) unpaired t-test
0.028 ± 0.023 (0–0.110) 0.030 ± 0.023 (0–0.110) N.S.* (P = 0.392)
0.033 ± 0.026 (0–0.117) 0.038 ± 0.026 (0–0.104) N. S.* (P = 0.151)
P b 0.05 (P = 0.0013) P b 0.05 (P = 0.0248)
Zirconia heads were used in all cases with the cemented stem and some cases with the Ti-6Al-4V cementless stem. Alumina heads were mainly used in the rest cases of the cementless stem. F/U: Follow up.
was probably caused by creep or bedding in; from 3 months onward, much of the penetration was probably caused by wear. Therefore, the penetration is mainly contributed by polyethylene wear after 3 months postoperatively. They also reported that the femoral head penetration rate was creep-dominated in the first 6 months and was probably caused by wear from one year after THA [3]. As it is impossible to distinguish creep and wear of polyethylene liner clinically, penetration of the prosthetic femoral head into polyethylene socket has been usually used for expression of both creep and wear. Digas et al [1] reported that at 2 years the highly cross-linked polyethylene liner showed 62% lowered proximal penetration and 31% lowered total (three-dimensional) penetration when the patients were examined in supine position, whereas showing an 80–90% wear reduction in hip simulator testing. After this report, there were a lot of reports that the highly cross-linked polyethylene liner reduced 60–94% of polyethylene wear rates including creep as compared with those of conventional polyethylene [3–6]. In the current study, we had similar results that XLP showed 80–83% reduction as compared with conventional polyethylene. In our series, polyethylene sockets without metal shell were cemented in all cases. In metal backed XLP acetabular liner, however, Moor et al reported a case with early failure of the liner [8]. Longer follow-up time is, therefore, needed to evaluate whether highly cross-linked polyethylene in hip arthroplasty has any advantages over all-cemented and uncemented THA. Conclusions We found significant difference between the average total ceramic femoral head penetration between supine and standing radiographs in using both CON and XPL socket. The measurement in supine radiograph might result in maximum 20% underestimation of penetration rate. Acknowledgements The authors wish to thank Mrs. Kinue Kobayashi, Ms. Kumie Miyamoto, and Mrs. Aya Higashijo for their excellent clinical and technical assistance. References 1. Digas G, Kärrholm J, Thanner J, et al. 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.
2. Digas G. New polymer materials in total hip arthroplasty. Evaluation with radiostereometry, bone densitometry, radiography and clinical parameters. Acta Orthop Suppl 2005;76(315):3. 3. Glyn-Jones S, McLardy-Smith P, Gill HS, et al. The creep and wear of highly crosslinked polyethylene: a three-year randomised, controlled trial using radiostereometric analysis. J Bone Joint Surg Br 2008;90(5):556. http://dx.doi.org/10.1302/ 0301-620X.90B5.20545. 4. D'Antonio JA, Manley MT, Capello WN, et al. Five-year experience with Crossfire highly cross-linked polyethylene. Clin Orthop Relat Res 2005;441:143. 5. Capello WN, D'Antonio JA, Ramakrishnan R, et al. Continued improved wear with an annealed highly cross-linked polyethylene. Clin Orthop Relat Res 2011;469(3):825 [Epub 2010 Sep 16]. 6. McCalden RW, MacDonald SJ, Rorabeck CH, et al. Wear rate of highly cross-linked polyethylene in total hip arthroplasty. A randomized controlled trial. J Bone Joint Surg Am 2009;91(4):773. http://dx.doi.org/10.2106/JBJS.H.00244. 7. Lachiewicz PF, Heckman DS, Soileau ES, et al. Femoral head size and wear of highly cross-linked polyethylene at 5 to 8 years. Clin Orthop Relat Res 2009;467(12):3290. http://dx.doi.org/10.1007/s11999-009-1038-9. [Epub 2009 Aug 19]. 8. Moore KD, Beck PR, Petersen DW, et al. Early failure of a cross-linked polyethylene acetabular liner. A case report. J Bone Joint Surg Am 2008;90(11):2499. http://dx. doi.org/10.2106/JBJS.G.01304. 9. Moore KD, Barrack RL, Sychterz CJ, et al. The effect of weight-bearing on the radiographic measurement of the position of the femoral head after total hip arthroplasty. J Bone Joint Surg Am 2000;82(1):62. 10. Bragdon CR, Thanner J, Greene ME, et al. Standing versus supine radiographs in RSA evaluation of femoral head penetration. Clin Orthop Relat Res 2006;448:46. 11. Maruyama M., Terayama K. Socket wear of Charnley low friction arthroplasty. Fifteen year follow-up. Bulletin Hospital for Joint Diseases 1993–1995;53(4):37– 42. 12. Maruyama M, Capello WN, D’Antonio JA, et al. Effect of low friction ion treated femoral heads on polyethylene wear rates. Clin Orthop Relat Res 2000;370:183. 13. Hamaji H, Yamamoto S, Ishibashi H, et al. Novel method to evaluate femoral head penetration in the polyethylene liner after total hip arthroplasty: three-dimensional evaluation on standing radiographs. J Orthop Sci 2008;13(5):425. http://dx. doi.org/10.1007/s00776-008-1263-1. [Epub 2008 Oct 9]. 14. Sychterz CJ, Yang AM, McAuley JP, et al. Two-dimensional versus threedimensional radiographic measurements of polyethylene wear. Clin Orthop Relat Res 1999;365:117. 15. Vandenbussche E, Saffarini M, Hansen U, et al. Measurement of femoral head penetration in polyethylene using a 3-dimensional CT-scan technique. Acta Orthop 2010;81(5):563. http://dx.doi.org/10.3109/17453674.2010.519163. 16. Wroblewski M, Siney PD, Nagai H, et al. Wear of ultra-high-molecular-weight polyethylene cup articulating with 22.225 mm zirconia diameter head in cemented total hip arthroplasty. J Orthop Sci 2004;9(3):253. 17. Maruyama M, Wakabayashi S, Tensho K, et al. Usefulness of standing anteroposterior radiograph of the hip for socket wear measurement in total hip arthroplasty: Comparative study of conventional with highly cross linked polyethylene. Presented in 12eme Association Franco-Japonaise d'Orthopedie 2013, Kyoto, Japan. 18. Glyn-Jones S, Isaac S, Hauptfleisch J, et al. Does highly cross-linked polyethylene wear less than conventional polyethylene in total hip arthroplasty? A double-blind, randomized, and controlled trial using roentgen stereophotogrammetric analysis. J Arthroplasty 2008;23(3):337. http://dx.doi.org/10.1016/j.arth.2006.12.117.
Please cite this article as: Maruyama M, et al, Standing Versus Supine Radiographs to Evaluate Femoral Head Penetration in the Polyethylene Liner After Total Hip Arthroplasty, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.02.010
