Document Type: RESEARCH PAPER
Rothman Institute of Orthopaedics, Thomas Jefferson University, Philadelphia, PA, USA
Rothman Institute of Orthopaedics, Thomas Jefferson University, Philadelphia, PA, USA----- Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran
Department of Orthopaedic Surgery, Hospital for Special Surgery, Weill Medical College at Cornell University, New York, NY, USA
Background: Hip osteoarthritis (OA) is a major cause of pain and disability that results in considerable social and medical costs. Mechanics such as posture, alignment and orientation of the hips and the spinal column and the relationship between these factors have been implicated in the development of both hip and spine pathologies. This study aims to test the hypothesis if pelvic incidence varies in patients with and without osteoarthritis. We assessed the relationship between spinopelvic alignment as measured by pelvic incidence (PI) and the presence of hip OA.
Methods: We collected supine pelvis CT scans of 1,012 consecutive patients not known to have hip OA. Our first group consisted of 95 patients with moderate to severe hip OA as per radiology reports. The second group included 87 patients with no evidence of hip OA. Power analysis revealed the need for 77 patients per group to find a mean difference in PI of 5º or less between both groups. Two trained physicians independently measured the PI to account for inter-observer reliability.
Results: Patients with moderate to severe hip OA had a mean PI of 56.5º±12.8º. The mean PI for patients without hip OA was 57.2º±7.5º. An independent samples t-test revealed no significant difference between the PI values of the two groups. Spearman’s correlation coefficient of 0.754 demonstrated a high inter-observer reliability.
Conclusion: There was no difference in PI angle of hip OA patients and "healthy" patients. Our measurements of patients without OA were almost identical to the reported normal PI values in the literature. It appears that hip OA is not associated with PI angle, refuting the hypothesis made in previous studies, stating that elevated PI contributes to the future development of hip arthritis. CT scan seems to be a reliable and accurate way of assessing pelvic incidence.
- Cooper C, Inskip H, Croft P, Campbell L, Smith G, McLaren M, et al. Individual risk factors for hip osteoarthritis: obesity, hip injury, and physical activity. Am J Epidemiol. 1998; 147(6):516-22.
- Lanyon P, Muir K, Doherty S, Doherty M. Assessment of a genetic contribution to osteoarthritis of the hip: sibling study. BMJ. 2000; 321(7270):1179-83.
- Matsuyama Y, Hasegawa Y, Yoshihara H, Tsuji T, Sakai Y, Nakamura H, et al. Hip-spine syndrome: total sagittal alignment of the spine and clinical symptoms in patients with bilateral congenital hip dislocation. Spine. 2004; 29(21):2432-7.
- Fogel GR, Esses SI. Hip spine syndrome: management of coexisting radiculopathy and arthritis of the lower extremity. Spine J. 2003; 3(3):238-41.
- Yoshimoto H, Sato S, Masuda T, Kanno T, Shundo M, Hyakumachi T, et al. Spinopelvic alignment in patients with osteoarthrosis of the hip: a radiographic comparison to patients with low back pain. Spine. 2005; 30(14):1650-7.
- Vialle R, Levassor N, Rillardon L, Templier A, Skalli W, Guigui P. Radiographic analysis of the sagittal alignment and balance of the spine in asymptomatic subjects. J Bone Joint Surg Am. 2005; 87(2):260–7.
- Offierski CM, MacNab I. Hip-spine syndrome. Spine. 1983; 8(3):316-21.
- Parvizi J, Pour AE, Hillibrand A, Goldberg G, Sharkey PF, Rothman RH. Back pain and total hip arthroplasty: a prospective natural history study. Clin Orthop Relat Res. 2010; 468(5):1325-30.
- Ben-Galim P, Ben-Galim T, Rand N, Haim A, Hipp J, Dekel S, et al . Hip-spine syndrome: the effect of total hip replacement surgery on low back pain in severe osteoarthritis of the hip. Spine. 2007; 32(19):2099-102.
- Legaye J, Duval-Beaupere G, Hecquet J, Marty C. Pelvic incidence: a fundamental pelvic parameter for three-dimensional regulation of spinal sagittal curves. Eur Spine J. 1998; 7(2):99-103.
- Lazennec JY, Brusson A, Rousseau MA. Hip-spine relations and sagittal balance clinical consequences. Eur Spine J. 2011; 20(Suppl 5):686–98.