The Journal of Arthroplasty xxx (2013) xxx–xxx
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Spinal Factors Influencing Change in Pelvic Sagittal Inclination From Supine Position to Standing Position in Patients Before Total Hip Arthroplasty Satoru Tamura, MD a, Masaki Takao, MD, PhD b, Takashi Sakai, MD, PhD b, Takashi Nishii, MD, PhD a, Nobuhiko Sugano, MD, PhD a a b
Department of Orthopaedic Medical Engineering Osaka University Graduate School of Medicine Suita, Japan Department of Orthopaedic Surgery Osaka University Graduate School of Medicine Suita, Japan
a r t i c l e
i n f o
Article history: Received 30 September 2013 Accepted 24 November 2013 Available online xxxx Keywords: pelvic sagittal inclination total hip arthroplasty compression fracture age lumbar spondylolisthesis
a b s t r a c t In some atypical patients, pelvic sagittal inclination (PSI) changes posteriorly by N10° from supine to standing position before total hip arthroplasty (THA). Several studies have suggested PSI in standing position is related to lumbar degeneration. The purpose of this study was to investigate spinal factors influencing changes in PSI from supine to standing position before THA. Participants comprised 163 consecutive patients who had undergone THA. Presence of compression fractures, presence of lumbar spondylolisthesis, thoracic kyphosis angle, lumbar lordosis angle, S1 anterior tilt angle and T4 plumb line position were investigated as spinal factors. Presence of compression fractures, age, presence of lumbar spondylolisthesis and small S1 anterior tilt angle were independently associated with posterior change in PSI from supine to standing position in patients before THA. © 2013 Elsevier Inc. All rights reserved.
In total hip arthroplasty (THA), cup alignment is one of the most important factors related to impingement, dislocation and wear [1–3]. Cup alignment is affected by the inclination of the pelvis and, in particular, cup anteversion is drastically changed by pelvic sagittal inclination (PSI) when cup orientation is less than 45° [4]. Lembeck et al reported that a 1° decrease in PSI (reclination) resulted in approximately 0.7° of increase in radiographic cup anteversion [4]. Nonetheless, PSI in a supine position has been reported to offer a good reference pelvic position for aiming cup orientation to avoid implant impingement and dislocation [5,6]. PSI does not usually change more than 10° from supine to standing position either preoperatively or after THA [7–9]. However, there are some ‘atypical’ patients whose PSI changes of N10° posteriorly from supine to standing position [7–9]. In those atypical patients the risk of posterior implant impingement during hip extension and/or external rotation may increase during standing activities when cup is placed by using PSI in supine position as the reference plane. One study suggested that the anterior pelvic plane (APP) through the most anterior aspect of the pubic tubercle and bilateral anterior superior iliac spines (ASISs) is often tilted posteriorly even when these atypical patients are supine, and that these patients were older than the other “typical” patients whose PSI change from supine to standing position was within 10° [9]. Several studies have also suggested
The Conflict of Interest statement associated with this article can be found at http:// dx.doi.org/10.1016/j.arth.2013.11.014. Reprint requests: Nobuhiko Sugano, MD, PhD-Department of Orthopaedic Medical Engineering Osaka University Graduate School of Medicine 2-2 Yamadaoka, Suita 5650871, Japan.
that PSI in standing position is affected by lumbar degeneration such as degenerative disc diseases and degenerative spondylolisthesis [10–12]. But, it has been unclear whether age and spinal degenerative changes are related, dependently or independently, to PSI in standing position or the PSI change from supine to standing position. If we can identify major influencing factors related to large PSI changes from supine to standing position, we may find a prophylactic method for the prevention of large PSI changes from supine to standing position. However, no reports have evaluated factors related to PSI change N 10° from supine to standing position in consideration of THA. The purpose of this study was therefore to investigate spinal factors influencing the PSI change from supine to standing position in patients who underwent THA, using standing lateral radiographs of the whole spine. Materials and Methods Participants in this study comprised 163 consecutive patients who underwent primary THA in our hospital between January 2010 and December 2011. Institutional review board approval was obtained for this study. Mean age at the time of THA was 61.8 ± 12.4 years (range, 26 to 86 years). There were no patients with neurologic diseases such as Parkinson’s disease, brain infarction, or multiple sclerosis. Anteroposterior (AP) radiographs of the pelvis in standing position were taken preoperatively with the line between bilateral ASISs perpendicular to the central beam of X-ray. The target for the central X-ray was over the superior margin of the pubic symphysis. Standing lateral radiographs of the whole spine were taken preoperatively. Each
0883-5403/0000-0000$36.00/0 – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.arth.2013.11.014
Please cite this article as: Tamura S, et al, Spinal Factors Influencing Change in Pelvic Sagittal Inclination From Supine Position to Standing Position in Patients Before Total..., J Arthroplasty (2013), http://dx.doi.org/10.1016/j.arth.2013.11.014
2
S. Tamura et al. / The Journal of Arthroplasty xxx (2013) xxx–xxx
patient was standing in a comfortable posture while the hands were placed on an antero-lateral support bar to avoid overlap of the upper extremities and spine. Computed tomography (CT) of the pelvis was also performed preoperatively for navigation THA. Preoperative PSI in a supine position was measured on CT using 3D Template software (Kyocera Medical, Osaka, Japan). On multi-planar reconstructions (MPRs), the pelvis was rotated to make the line between bilateral ASISs parallel to the horizontal axis. Digitally reconstructed radiographs (DRRs) of the lateral view of the pelvis were generated and the angle between APP and vertical axis was defined as PSI in the supine position. A positive value for the angle indicated anterior tilting of the pelvis. The ratio of the vertical diameter (A) to the horizontal diameter (B) (VH ratio) of the pelvic foramen on standing radiographs (Fig. 1) was measured to calculate PSI in the standing position. To match the VH ratio on a DRR to that on standing radiographs, the pelvis was sagittally rotated on the lateral MPR and the sagittal inclination of APP represented PSI in the standing position (Fig. 1). In some patients with sagittal inclination of APP in the standing position tilted strongly posteriorly, the pelvic foramen was not identifiable on standing radiographs. In those cases, VH ratio of the right obturator foramen was used to calculate PSI in the standing position. Some authors measured PSIs on lateral radiographs
[13–15]. However, soft tissue noise can make landmark localization difficult and failure to observe landmarks could introduce large errors of measurement [13]. The technique of matching the CT images and radiographs used in this study has often been used to measure PSI in standing position [7–9,16,17]; a high degree of PSI measurement accuracy using this method has been reported [7]. When the PSI change from supine to standing position was N10° posteriorly, the patient was classified as showing atypical posterior pelvic tilt on standing (Group P). The remaining patients were classified as the control group (Group C). In all 163 patients, mean change of PSI from supine to standing position was − 6.9 ± 5.7° (range, − 25.3° to 8.6°). Forty-one patients (25%) were in Group P and 122 patients (75%) were in Group C. On standing lateral radiographs of the whole spine, presence of compression fracture and lumbar spondylolisthesis was evaluated. Presence of compression fracture was defined when wedge, biconcave, or compression deformities as described by Eastell et al were present [18]. Presence of lumbar spondylolisthesis was diagnosed when a lumbar vertebra showed N 10% of anterior translation compared to the adjacent lower vertebra. The following radiographic parameters were also measured: thoracic kyphosis angle, defined as the angle between lines drawn along the inferior endplate of the T12 vertebrae and the superior endplate of T4; lumbar lordosis angle, defined as the angle between lines drawn along the superior endplate of S1 and the superior endplate of L1; S1 anterior tilt angle, defined as the angle between a line along the superior endplate of S1 and the horizontal line; and T4 plumb line position, defined as the distance between the anterior tip of the superior endplate of S1 and the plumb line through the centroid of T4 (positive value indicates the T4 plumb line was located anterior to the anterior tip of S1). Although the C7 plumb line is often used as a parameter of sagittal spinal balance in the literature [19,20], the T4 plumb line was used in this study because of the unclear contour of the C7 vertebra on lateral radiographs of the whole spine. Parameters including age, PSI in supine position, thoracic kyphosis angle, S1 anterior tilt and T4 plumb line were compared between Groups P and C by non-parametric Mann–Whitney U test. Parameters including gender, presence of compression fracture and presence of lumbar spondylolisthesis were compared between Groups P and C using Fisher’s exact test. Hip diagnosis was compared between Groups P and C using the chi-square test. Multiple regression analyses were performed to compare the relationship between degree of change in PSI from supine to standing position and all the above parameters. Values of P b 0.05 were considered to indicate statistical significance. Statistical analyses were performed using SPSS version 19 software (SPSS, Chicago, IL, USA). Results The characteristics of patients in Groups P and C are shown in Table 1. Significant differences between Groups P and C were evident in age, PSI in supine position, presence of compression fracture, presence of lumbar spondylolisthesis, lumbar lordosis angle, S1 anterior tilt angle and T4 plumb line position. In multiple linear regression analysis, the parameters that independently influenced the change in PSI from supine to standing position were presence of compression fracture (standard partial regression coefficient (β) = − 0.20, P = 0.005), age (β = − 0.15, P = 0.038), presence of lumbar spondylolisthesis (β = − 0.15, P = 0.033) and S1 anterior tilt angle (β = 0.34, P b 0.001) (Table 2). The multiple correlation coefficient (r) was 0.543.
Fig. 1. Measurement of PSI in a standing position. (A) On AP radiographs of the pelvis in a standing position, vertical diameter of the pelvic foramen (A) divided by horizontal diameter of the pelvic foramen (B) was calculated as VH ratio. (B) The pelvis was rotated sagittally until VH ratio of the pelvic foramen on DRR became similar to that of standing AP radiographs. (C) On sagittal DRR, the angle between APP and the vertical axis was measured as PSI in a standing position.
Discussion This study is the first to report relationships between spinal radiographic parameters and the change in PSI from supine to standing position. The parameters that multiple linear regression
Please cite this article as: Tamura S, et al, Spinal Factors Influencing Change in Pelvic Sagittal Inclination From Supine Position to Standing Position in Patients Before Total..., J Arthroplasty (2013), http://dx.doi.org/10.1016/j.arth.2013.11.014
S. Tamura et al. / The Journal of Arthroplasty xxx (2013) xxx–xxx
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Table 1 Characteristics of Patients. Parameters Patients Age (years) Gender (male/female) Hip diagnosis (patients) Osteoarthritis Osteonecrosis of the femoral head Others PSI in supine position (°) Presence of compression fracture (patients) Presence of lumbar spondylolisthesis (patients) Thoracic kyphosis angle (°) Lumbar lordosis angle (°) S1 anterior tilt angle (°) T4 plumb line position (mm)
Group P
Group C
41 67.2 ± 12.8 (34–85) 3/38
122 60.0 ± 11.8 (26–86) 19/103
34 3 4 2.0 ± 9.0 (−27–17.8) 6 (15%) 13 (32%) 28.6 ± 11.7 (−12.8–48.5) 38.5 ± 19.2 (−2.8–85.5) 30.2 ± 14.6 (0.0–73.5) −20.5 ± 36.9 (−75.1–63.7)
108 11 3 6.4 ± 5.7 (−12.2–20.2) 3 (2%) 12 (11%) 29.1 ± 8.7 (7.2–57.6) 48.8 ± 12.0 (6.6–77.2) 38.8 ± 10.2 (2.1–64.9) −31.0 ± 24.8 (−102.6–23.2)
P 0.001a 0.28b
0.13c b0.001a b0.01b b0.01b 0.79a b0.001a b0.001a 0.04a
Mean ± standard deviation (range). a Mann–Whitney U test. b Fisher’s exact test. c Chi-square test.
analysis identified as significantly associated with change in PSI were presence of compression fracture, age, presence of spondylolisthesis and S1 anterior tilt angle. Presence of compression fracture was one of the independent factors related to reclination of the pelvis from supine to standing position. To the best of our knowledge, no previous studies have shown this correlation. Compression fracture changed the spinal alignment with the increase in kyphosis angle and the anterior shift of the T4 plumb line in standing position. To compensate for the change in spinal alignment, the pelvis rotated posteriorly. Treatment of osteoporosis before the occurrence of compression fractures may be one of a number of methods to prevent the large posterior change of PSI from supine to standing position. Several reports have described changes in PSI from supine to standing position. Nishihara et al and Miki et al reported that the maximum change in PSI was − 21° [7,9], while Babisch et al reported a value of − 14° [8]. In the present study, the maximum PSI change from supine to standing position was −25.3°. Subjects in Group P of this study could thus have included the most atypical patients, showing marked posterior PSI changes in standing position. On the other hand, the proportion of Group P to the total population in this study was higher (25%) than in the previous study (8%) [7]. In this study, age was one of the factors related to posterior change in PSI from supine to standing position. The difference in mean age could have contributed to the higher proportion of Group P in this study (mean age, 62 years) compared to the previous study (mean age, 56 years) [7]. Several reports have examined correlations between age and whole sagittal spinal alignment in the standing position. Gelb et al and Hammerberg et al suggested age was positively correlated with anterior positioning of the C7 plumb line, while anterior positioning of the C7 plumb line correlated negatively with lumbar lordosis angle [21,22]. Hirano et al suggested that age showed a significant negative correlations with back muscle strength and with lumbar lordosis angle in Japanese N50 years old [23]. Aging thus influences spinal alignment and back
Table 2 Results of Multiple Linear Regression Analysis. Parameters Presence of compression fracture Age Presence of lumbar spondylolisthesis S1 anterior tilt
Standard Partial Regression Coefficient (β)
P
−0.2 −0.15 −0.15 0.34
b0.01 0.04 0.03 b0.001
muscle strength. In this study, age independently influenced the change in PSI from supine to standing position, although spinal parameters including lumbar lordosis angle, thoracic kyphosis angle and T4 plumb line position did not. Weakness of back muscles might thus have influenced the large posterior change in PSI from supine to standing position. Exercise to maintain muscle strength of the trunk may be one of a number of methods to prevent the large posterior change of PSI from supine to standing position. In this study, lumbar spondylolisthesis was a factor that independently influenced the change in PSI from supine to standing position. Although the correlation between PSI in the supine position and lumbar spondylolisthesis was not examined, this might be explained by the mechanism for compensation of lumbar spondylolisthesis as described by Barrey et al, who suggested that PSI in the standing position rotated posteriorly when lumbar lordosis angle was small and C7 plumb line was located anteriorly in patients with lumbar spondylolisthesis [11]. Concerning S1 anterior tilt angle, the sacroiliac joint is nearly fixed from supine to standing position [24] and S1 anterior tilt represents PSI in the standing position. S1 anterior tilt was reasonably considered as the factor most strongly influencing the large posterior change in PSI from supine to standing position. Several limitations to this study must be considered when interpreting the results. First, assessment of the lower extremities such as flexion angle of the hip and knee was not performed. These factors could also show significant contributions. As Offierski and Macnab suggested, flexion contracture of the hip rotated the pelvis anteriorly, leading to hyperextension of the lumbar spine, particularly in patients with hip osteoarthritis [25]. To investigate the relationship between hip contracture and PSI in supine and standing positions, further studies are required. Second, we only evaluated the existence of compression fractures. The type of vertebral deformities due to fractures, such as wedge deformity, biconcavity deformity and compression deformity, might correlate with changes in PSI from supine to standing position [18]. However, due to the small sample size of patients, the correlation was not evaluated in this study. Third, we did not consider coronal alignment of the pelvis and the spine. Large changes in pelvic coronal inclination from supine to standing position may occur in patients with compression fractures and lumbar degenerative disease. So the change in pelvic coronal inclination from supine to standing position and the magnitude of impact on the risk of impingement need to be studied in the future. Fourth, we only measured change in PSI from supine to standing position before THA. Even optimal cup alignment based on the preoperative pelvic position could become suboptimal after THA due to further postoperative PSI
Please cite this article as: Tamura S, et al, Spinal Factors Influencing Change in Pelvic Sagittal Inclination From Supine Position to Standing Position in Patients Before Total..., J Arthroplasty (2013), http://dx.doi.org/10.1016/j.arth.2013.11.014
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change. Because the previous study suggested that the mean difference between preoperative PSI and PSI at 1 year after THA was within 5° in both supine and standing positions [7], the assessment of preoperative PSI change could reflect PSI change in the early postoperative period and may be useful for predicting the risk of implant impingement during standing activities. However, whether the preoperative change of PSI from supine to standing position is maintained long after THA has remained unclear. The present study suggested that aging and spinal degeneration including compression fractures and lumbar spondylolisthesis are related to PSI. Longitudinal studies are needed to clarify whether those factors influence PSI in both supine and standing positions after THA. In conclusion, the presence of compression fracture, aging, presence of lumbar spondylolisthesis and small S1 anterior tilt angle were factors independently associated with posterior change in PSI from supine to standing position in patients before THA. References 1. Barrack RL. Dislocation after total hip arthroplasty: implant design and orientation. J Am Acad Orthop Surg 2003;11:89. 2. Widmer KH. Containment versus impingement: finding a compromise for cup placement in total hip arthroplasty. Int Orthop 2007;31(Suppl 1):S29. 3. Malik A, Maheshwari A, Dorr LD. Impingement with total hip replacement. J Bone Joint Surg Am 2007;89:1832. 4. Lembeck B, Mueller O, Reize P, et al. Pelvic tilt makes acetabular cup navigation inaccurate. Acta Orthop 2005;76:517. 5. Sugano N, Nishii T, Miki H, et al. Mid-term results of cementless total hip replacement using a ceramic-on-ceramic bearing with and without computer navigation. J Bone Joint Surg Br 2007;89:455. 6. Sugano N, Tsuda K, Miki H, et al. Dynamic measurements of hip movement in deep bending activities after total hip arthroplasty using a 4-dimensional motion analysis system. J Arthroplasty 2012;27:1562. 7. Nishihara S, Sugano N, Nishii T, et al. Measurements of pelvic flexion angle using three-dimensional computed tomography. Clin Orthop Relat Res 2003;411:140.
8. Babisch JW, Layher F, Amiot LP. The rationale for tilt-adjusted acetabular cup navigation. J Bone Joint Surg Am 2008;90:357. 9. Miki H, Kyo T, Sugano N. Anatomic hip range of motion after implantation during total hip arthroplasty with a large change in pelvic inclination. J Arthroplasty 2012;27:1641. 10. Labelle H, Roussouly P, Berthonnaud E, et al. The importance of spino-pelvic balance in L5-s1 developmental spondylolisthesis: a review of pertinent radiologic measurements. Spine 2005;30:S27. 11. Barrey C, Jund J, Noseda O, et al. Sagittal balance of the pelvis–spine complex and lumbar degenerative diseases. A comparative study about 85 cases. Eur Spine J 2007;16:1459. 12. Barrey C, Jund J, Perrin G, et al. Spinopelvic alignment of patients with degenerative spondylolisthesis. Neurosurgery 2007;61:981. 13. Eckman K, Hafez MA, Ed F, et al. Accuracy of pelvic flexion measurements from lateral radiographs. Clin Orthop Relat Res 2006;451:154. 14. DiGioia AM, Hafez MA, Jaramaz B, et al. Functional pelvic orientation measured from lateral standing and sitting radiographs. Clin Orthop Relat Res 2006;453: 272. 15. Imai N, Ito T, Suda K, et al. Pelvic flexion measurement from lateral projection radiographs is clinically reliable. Clin Orthop Relat Res 2013;471:1271. 16. Steppacher SD, Tannast M, Zheng G, et al. Validation of a new method for determination of cup orientation in THA. J Orthop Res 2009;27:1583. 17. Murphy WS, Klingenstein G, Murphy SB, et al. Pelvic tilt is minimally changed by total hip arthroplasty. Clin Orthop Relat Res 2013;471:417. 18. Eastell R, Cedel SL, Wahner HW, et al. Classification of vertebral fractures. J Bone Miner Res 1991;6:207. 19. Le Huec JC, Charosky S, Barrey C, et al. Sagittal imbalance cascade for simple degenerative spine and consequences: algorithm of decision for appropriate treatment. Eur Spine J 2011;20(Suppl 5):699. 20. Morvan G, Mathieu P, Vuillemin V, et al. Standardized way for imaging of the sagittal spinal balance. Eur Spine J 2011;20(Suppl 5):602. 21. Gelb DE, Lenke LG, Bridwell KH, et al. An analysis of sagittal spinal alignment in 100 asymptomatic middle and older aged volunteers. Spine 1995;20:1351. 22. Hammerberg EM, Wood KB. Sagittal profile of the elderly. J Spinal Disord Tech 2003;16:44. 23. Hirano K, Imagama S, Hasegawa Y, et al. Effect of back muscle strength and sagittal spinal imbalance on locomotive syndrome in Japanese men. Orthopedics 2012;35: e1073. 24. Sturesson B, Uden A, Vleeming A. A radiostereometric analysis of the movements of the sacroiliac joints in the reciprocal straddle position. Spine 2000;25:214. 25. Offierski CM, MacNab I. Hip–spine syndrome. Spine 1983;8:316.
Please cite this article as: Tamura S, et al, Spinal Factors Influencing Change in Pelvic Sagittal Inclination From Supine Position to Standing Position in Patients Before Total..., J Arthroplasty (2013), http://dx.doi.org/10.1016/j.arth.2013.11.014
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Spinal Factors Influencing Change in Pelvic Sagittal Inclination From Supine Position to Standing Position in Patients Before Total Hip Arthroplasty Satoru Tamura, MD a, Masaki Takao, MD, PhD b, Takashi Sakai, MD, PhD b, Takashi Nishii, MD, PhD a, Nobuhiko Sugano, MD, PhD a a b
Department of Orthopaedic Medical Engineering Osaka University Graduate School of Medicine Suita, Japan Department of Orthopaedic Surgery Osaka University Graduate School of Medicine Suita, Japan
a r t i c l e
i n f o
Article history: Received 30 September 2013 Accepted 24 November 2013 Available online xxxx Keywords: pelvic sagittal inclination total hip arthroplasty compression fracture age lumbar spondylolisthesis
a b s t r a c t In some atypical patients, pelvic sagittal inclination (PSI) changes posteriorly by N10° from supine to standing position before total hip arthroplasty (THA). Several studies have suggested PSI in standing position is related to lumbar degeneration. The purpose of this study was to investigate spinal factors influencing changes in PSI from supine to standing position before THA. Participants comprised 163 consecutive patients who had undergone THA. Presence of compression fractures, presence of lumbar spondylolisthesis, thoracic kyphosis angle, lumbar lordosis angle, S1 anterior tilt angle and T4 plumb line position were investigated as spinal factors. Presence of compression fractures, age, presence of lumbar spondylolisthesis and small S1 anterior tilt angle were independently associated with posterior change in PSI from supine to standing position in patients before THA. © 2013 Elsevier Inc. All rights reserved.
In total hip arthroplasty (THA), cup alignment is one of the most important factors related to impingement, dislocation and wear [1–3]. Cup alignment is affected by the inclination of the pelvis and, in particular, cup anteversion is drastically changed by pelvic sagittal inclination (PSI) when cup orientation is less than 45° [4]. Lembeck et al reported that a 1° decrease in PSI (reclination) resulted in approximately 0.7° of increase in radiographic cup anteversion [4]. Nonetheless, PSI in a supine position has been reported to offer a good reference pelvic position for aiming cup orientation to avoid implant impingement and dislocation [5,6]. PSI does not usually change more than 10° from supine to standing position either preoperatively or after THA [7–9]. However, there are some ‘atypical’ patients whose PSI changes of N10° posteriorly from supine to standing position [7–9]. In those atypical patients the risk of posterior implant impingement during hip extension and/or external rotation may increase during standing activities when cup is placed by using PSI in supine position as the reference plane. One study suggested that the anterior pelvic plane (APP) through the most anterior aspect of the pubic tubercle and bilateral anterior superior iliac spines (ASISs) is often tilted posteriorly even when these atypical patients are supine, and that these patients were older than the other “typical” patients whose PSI change from supine to standing position was within 10° [9]. Several studies have also suggested
The Conflict of Interest statement associated with this article can be found at http:// dx.doi.org/10.1016/j.arth.2013.11.014. Reprint requests: Nobuhiko Sugano, MD, PhD-Department of Orthopaedic Medical Engineering Osaka University Graduate School of Medicine 2-2 Yamadaoka, Suita 5650871, Japan.
that PSI in standing position is affected by lumbar degeneration such as degenerative disc diseases and degenerative spondylolisthesis [10–12]. But, it has been unclear whether age and spinal degenerative changes are related, dependently or independently, to PSI in standing position or the PSI change from supine to standing position. If we can identify major influencing factors related to large PSI changes from supine to standing position, we may find a prophylactic method for the prevention of large PSI changes from supine to standing position. However, no reports have evaluated factors related to PSI change N 10° from supine to standing position in consideration of THA. The purpose of this study was therefore to investigate spinal factors influencing the PSI change from supine to standing position in patients who underwent THA, using standing lateral radiographs of the whole spine. Materials and Methods Participants in this study comprised 163 consecutive patients who underwent primary THA in our hospital between January 2010 and December 2011. Institutional review board approval was obtained for this study. Mean age at the time of THA was 61.8 ± 12.4 years (range, 26 to 86 years). There were no patients with neurologic diseases such as Parkinson’s disease, brain infarction, or multiple sclerosis. Anteroposterior (AP) radiographs of the pelvis in standing position were taken preoperatively with the line between bilateral ASISs perpendicular to the central beam of X-ray. The target for the central X-ray was over the superior margin of the pubic symphysis. Standing lateral radiographs of the whole spine were taken preoperatively. Each
0883-5403/0000-0000$36.00/0 – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.arth.2013.11.014
Please cite this article as: Tamura S, et al, Spinal Factors Influencing Change in Pelvic Sagittal Inclination From Supine Position to Standing Position in Patients Before Total..., J Arthroplasty (2013), http://dx.doi.org/10.1016/j.arth.2013.11.014
2
S. Tamura et al. / The Journal of Arthroplasty xxx (2013) xxx–xxx
patient was standing in a comfortable posture while the hands were placed on an antero-lateral support bar to avoid overlap of the upper extremities and spine. Computed tomography (CT) of the pelvis was also performed preoperatively for navigation THA. Preoperative PSI in a supine position was measured on CT using 3D Template software (Kyocera Medical, Osaka, Japan). On multi-planar reconstructions (MPRs), the pelvis was rotated to make the line between bilateral ASISs parallel to the horizontal axis. Digitally reconstructed radiographs (DRRs) of the lateral view of the pelvis were generated and the angle between APP and vertical axis was defined as PSI in the supine position. A positive value for the angle indicated anterior tilting of the pelvis. The ratio of the vertical diameter (A) to the horizontal diameter (B) (VH ratio) of the pelvic foramen on standing radiographs (Fig. 1) was measured to calculate PSI in the standing position. To match the VH ratio on a DRR to that on standing radiographs, the pelvis was sagittally rotated on the lateral MPR and the sagittal inclination of APP represented PSI in the standing position (Fig. 1). In some patients with sagittal inclination of APP in the standing position tilted strongly posteriorly, the pelvic foramen was not identifiable on standing radiographs. In those cases, VH ratio of the right obturator foramen was used to calculate PSI in the standing position. Some authors measured PSIs on lateral radiographs
[13–15]. However, soft tissue noise can make landmark localization difficult and failure to observe landmarks could introduce large errors of measurement [13]. The technique of matching the CT images and radiographs used in this study has often been used to measure PSI in standing position [7–9,16,17]; a high degree of PSI measurement accuracy using this method has been reported [7]. When the PSI change from supine to standing position was N10° posteriorly, the patient was classified as showing atypical posterior pelvic tilt on standing (Group P). The remaining patients were classified as the control group (Group C). In all 163 patients, mean change of PSI from supine to standing position was − 6.9 ± 5.7° (range, − 25.3° to 8.6°). Forty-one patients (25%) were in Group P and 122 patients (75%) were in Group C. On standing lateral radiographs of the whole spine, presence of compression fracture and lumbar spondylolisthesis was evaluated. Presence of compression fracture was defined when wedge, biconcave, or compression deformities as described by Eastell et al were present [18]. Presence of lumbar spondylolisthesis was diagnosed when a lumbar vertebra showed N 10% of anterior translation compared to the adjacent lower vertebra. The following radiographic parameters were also measured: thoracic kyphosis angle, defined as the angle between lines drawn along the inferior endplate of the T12 vertebrae and the superior endplate of T4; lumbar lordosis angle, defined as the angle between lines drawn along the superior endplate of S1 and the superior endplate of L1; S1 anterior tilt angle, defined as the angle between a line along the superior endplate of S1 and the horizontal line; and T4 plumb line position, defined as the distance between the anterior tip of the superior endplate of S1 and the plumb line through the centroid of T4 (positive value indicates the T4 plumb line was located anterior to the anterior tip of S1). Although the C7 plumb line is often used as a parameter of sagittal spinal balance in the literature [19,20], the T4 plumb line was used in this study because of the unclear contour of the C7 vertebra on lateral radiographs of the whole spine. Parameters including age, PSI in supine position, thoracic kyphosis angle, S1 anterior tilt and T4 plumb line were compared between Groups P and C by non-parametric Mann–Whitney U test. Parameters including gender, presence of compression fracture and presence of lumbar spondylolisthesis were compared between Groups P and C using Fisher’s exact test. Hip diagnosis was compared between Groups P and C using the chi-square test. Multiple regression analyses were performed to compare the relationship between degree of change in PSI from supine to standing position and all the above parameters. Values of P b 0.05 were considered to indicate statistical significance. Statistical analyses were performed using SPSS version 19 software (SPSS, Chicago, IL, USA). Results The characteristics of patients in Groups P and C are shown in Table 1. Significant differences between Groups P and C were evident in age, PSI in supine position, presence of compression fracture, presence of lumbar spondylolisthesis, lumbar lordosis angle, S1 anterior tilt angle and T4 plumb line position. In multiple linear regression analysis, the parameters that independently influenced the change in PSI from supine to standing position were presence of compression fracture (standard partial regression coefficient (β) = − 0.20, P = 0.005), age (β = − 0.15, P = 0.038), presence of lumbar spondylolisthesis (β = − 0.15, P = 0.033) and S1 anterior tilt angle (β = 0.34, P b 0.001) (Table 2). The multiple correlation coefficient (r) was 0.543.
Fig. 1. Measurement of PSI in a standing position. (A) On AP radiographs of the pelvis in a standing position, vertical diameter of the pelvic foramen (A) divided by horizontal diameter of the pelvic foramen (B) was calculated as VH ratio. (B) The pelvis was rotated sagittally until VH ratio of the pelvic foramen on DRR became similar to that of standing AP radiographs. (C) On sagittal DRR, the angle between APP and the vertical axis was measured as PSI in a standing position.
Discussion This study is the first to report relationships between spinal radiographic parameters and the change in PSI from supine to standing position. The parameters that multiple linear regression
Please cite this article as: Tamura S, et al, Spinal Factors Influencing Change in Pelvic Sagittal Inclination From Supine Position to Standing Position in Patients Before Total..., J Arthroplasty (2013), http://dx.doi.org/10.1016/j.arth.2013.11.014
S. Tamura et al. / The Journal of Arthroplasty xxx (2013) xxx–xxx
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Table 1 Characteristics of Patients. Parameters Patients Age (years) Gender (male/female) Hip diagnosis (patients) Osteoarthritis Osteonecrosis of the femoral head Others PSI in supine position (°) Presence of compression fracture (patients) Presence of lumbar spondylolisthesis (patients) Thoracic kyphosis angle (°) Lumbar lordosis angle (°) S1 anterior tilt angle (°) T4 plumb line position (mm)
Group P
Group C
41 67.2 ± 12.8 (34–85) 3/38
122 60.0 ± 11.8 (26–86) 19/103
34 3 4 2.0 ± 9.0 (−27–17.8) 6 (15%) 13 (32%) 28.6 ± 11.7 (−12.8–48.5) 38.5 ± 19.2 (−2.8–85.5) 30.2 ± 14.6 (0.0–73.5) −20.5 ± 36.9 (−75.1–63.7)
108 11 3 6.4 ± 5.7 (−12.2–20.2) 3 (2%) 12 (11%) 29.1 ± 8.7 (7.2–57.6) 48.8 ± 12.0 (6.6–77.2) 38.8 ± 10.2 (2.1–64.9) −31.0 ± 24.8 (−102.6–23.2)
P 0.001a 0.28b
0.13c b0.001a b0.01b b0.01b 0.79a b0.001a b0.001a 0.04a
Mean ± standard deviation (range). a Mann–Whitney U test. b Fisher’s exact test. c Chi-square test.
analysis identified as significantly associated with change in PSI were presence of compression fracture, age, presence of spondylolisthesis and S1 anterior tilt angle. Presence of compression fracture was one of the independent factors related to reclination of the pelvis from supine to standing position. To the best of our knowledge, no previous studies have shown this correlation. Compression fracture changed the spinal alignment with the increase in kyphosis angle and the anterior shift of the T4 plumb line in standing position. To compensate for the change in spinal alignment, the pelvis rotated posteriorly. Treatment of osteoporosis before the occurrence of compression fractures may be one of a number of methods to prevent the large posterior change of PSI from supine to standing position. Several reports have described changes in PSI from supine to standing position. Nishihara et al and Miki et al reported that the maximum change in PSI was − 21° [7,9], while Babisch et al reported a value of − 14° [8]. In the present study, the maximum PSI change from supine to standing position was −25.3°. Subjects in Group P of this study could thus have included the most atypical patients, showing marked posterior PSI changes in standing position. On the other hand, the proportion of Group P to the total population in this study was higher (25%) than in the previous study (8%) [7]. In this study, age was one of the factors related to posterior change in PSI from supine to standing position. The difference in mean age could have contributed to the higher proportion of Group P in this study (mean age, 62 years) compared to the previous study (mean age, 56 years) [7]. Several reports have examined correlations between age and whole sagittal spinal alignment in the standing position. Gelb et al and Hammerberg et al suggested age was positively correlated with anterior positioning of the C7 plumb line, while anterior positioning of the C7 plumb line correlated negatively with lumbar lordosis angle [21,22]. Hirano et al suggested that age showed a significant negative correlations with back muscle strength and with lumbar lordosis angle in Japanese N50 years old [23]. Aging thus influences spinal alignment and back
Table 2 Results of Multiple Linear Regression Analysis. Parameters Presence of compression fracture Age Presence of lumbar spondylolisthesis S1 anterior tilt
Standard Partial Regression Coefficient (β)
P
−0.2 −0.15 −0.15 0.34
b0.01 0.04 0.03 b0.001
muscle strength. In this study, age independently influenced the change in PSI from supine to standing position, although spinal parameters including lumbar lordosis angle, thoracic kyphosis angle and T4 plumb line position did not. Weakness of back muscles might thus have influenced the large posterior change in PSI from supine to standing position. Exercise to maintain muscle strength of the trunk may be one of a number of methods to prevent the large posterior change of PSI from supine to standing position. In this study, lumbar spondylolisthesis was a factor that independently influenced the change in PSI from supine to standing position. Although the correlation between PSI in the supine position and lumbar spondylolisthesis was not examined, this might be explained by the mechanism for compensation of lumbar spondylolisthesis as described by Barrey et al, who suggested that PSI in the standing position rotated posteriorly when lumbar lordosis angle was small and C7 plumb line was located anteriorly in patients with lumbar spondylolisthesis [11]. Concerning S1 anterior tilt angle, the sacroiliac joint is nearly fixed from supine to standing position [24] and S1 anterior tilt represents PSI in the standing position. S1 anterior tilt was reasonably considered as the factor most strongly influencing the large posterior change in PSI from supine to standing position. Several limitations to this study must be considered when interpreting the results. First, assessment of the lower extremities such as flexion angle of the hip and knee was not performed. These factors could also show significant contributions. As Offierski and Macnab suggested, flexion contracture of the hip rotated the pelvis anteriorly, leading to hyperextension of the lumbar spine, particularly in patients with hip osteoarthritis [25]. To investigate the relationship between hip contracture and PSI in supine and standing positions, further studies are required. Second, we only evaluated the existence of compression fractures. The type of vertebral deformities due to fractures, such as wedge deformity, biconcavity deformity and compression deformity, might correlate with changes in PSI from supine to standing position [18]. However, due to the small sample size of patients, the correlation was not evaluated in this study. Third, we did not consider coronal alignment of the pelvis and the spine. Large changes in pelvic coronal inclination from supine to standing position may occur in patients with compression fractures and lumbar degenerative disease. So the change in pelvic coronal inclination from supine to standing position and the magnitude of impact on the risk of impingement need to be studied in the future. Fourth, we only measured change in PSI from supine to standing position before THA. Even optimal cup alignment based on the preoperative pelvic position could become suboptimal after THA due to further postoperative PSI
Please cite this article as: Tamura S, et al, Spinal Factors Influencing Change in Pelvic Sagittal Inclination From Supine Position to Standing Position in Patients Before Total..., J Arthroplasty (2013), http://dx.doi.org/10.1016/j.arth.2013.11.014
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change. Because the previous study suggested that the mean difference between preoperative PSI and PSI at 1 year after THA was within 5° in both supine and standing positions [7], the assessment of preoperative PSI change could reflect PSI change in the early postoperative period and may be useful for predicting the risk of implant impingement during standing activities. However, whether the preoperative change of PSI from supine to standing position is maintained long after THA has remained unclear. The present study suggested that aging and spinal degeneration including compression fractures and lumbar spondylolisthesis are related to PSI. Longitudinal studies are needed to clarify whether those factors influence PSI in both supine and standing positions after THA. In conclusion, the presence of compression fracture, aging, presence of lumbar spondylolisthesis and small S1 anterior tilt angle were factors independently associated with posterior change in PSI from supine to standing position in patients before THA. References 1. Barrack RL. Dislocation after total hip arthroplasty: implant design and orientation. J Am Acad Orthop Surg 2003;11:89. 2. Widmer KH. Containment versus impingement: finding a compromise for cup placement in total hip arthroplasty. Int Orthop 2007;31(Suppl 1):S29. 3. Malik A, Maheshwari A, Dorr LD. Impingement with total hip replacement. J Bone Joint Surg Am 2007;89:1832. 4. Lembeck B, Mueller O, Reize P, et al. Pelvic tilt makes acetabular cup navigation inaccurate. Acta Orthop 2005;76:517. 5. Sugano N, Nishii T, Miki H, et al. Mid-term results of cementless total hip replacement using a ceramic-on-ceramic bearing with and without computer navigation. J Bone Joint Surg Br 2007;89:455. 6. Sugano N, Tsuda K, Miki H, et al. Dynamic measurements of hip movement in deep bending activities after total hip arthroplasty using a 4-dimensional motion analysis system. J Arthroplasty 2012;27:1562. 7. Nishihara S, Sugano N, Nishii T, et al. Measurements of pelvic flexion angle using three-dimensional computed tomography. Clin Orthop Relat Res 2003;411:140.
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Please cite this article as: Tamura S, et al, Spinal Factors Influencing Change in Pelvic Sagittal Inclination From Supine Position to Standing Position in Patients Before Total..., J Arthroplasty (2013), http://dx.doi.org/10.1016/j.arth.2013.11.014
