STANDING AND SITTING SAGITTAL PELVIC POSITION: OPTIMIZATION OF SACRAL SLOPE ANALYSIS USING THE RELATIVE PELVIC VERSION CONCEPT

J. Y. Lazennec; Y. W. Kim; J. Hani; A. Eslam Pour

doi:10.1302/1358-992X.2019.5.053

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General Orthopaedics

STANDING AND SITTING SAGITTAL PELVIC POSITION: OPTIMIZATION OF SACRAL SLOPE ANALYSIS USING THE RELATIVE PELVIC VERSION CONCEPT

International Society for Technology in Arthroplasty (ISTA) 31st Annual Congress, London, England, October 2018. Part 2.

J. Y. Lazennec
Y. W. Kim
J. Hani
A. Eslam Pour

STANDING AND SITTING SAGITTAL PELVIC POSITION: OPTIMIZATION OF SACRAL SLOPE ANALYSIS USING THE RELATIVE PELVIC VERSION CONCEPT

Lazennec JY, Kim YW, Hani J, Pour AE. STANDING AND SITTING SAGITTAL PELVIC POSITION: OPTIMIZATION OF SACRAL SLOPE ANALYSIS USING THE RELATIVE PELVIC VERSION CONCEPT. Orthop Procs. 2019;101-B(SUPP_5):53-53. doi:10.1302/1358-992X.2019.5.053

Lazennec, J. Y., et al. “STANDING AND SITTING SAGITTAL PELVIC POSITION: OPTIMIZATION OF SACRAL SLOPE ANALYSIS USING THE RELATIVE PELVIC VERSION CONCEPT.” Orthopaedic Proceedings, vol. 101-B, no. SUPP_5, 2019, pp. 53-53., https://doi.org/10.1302/1358-992X.2019.5.053

Lazennec, J. Y., Kim, Y. W., Hani, J., & Pour, A. E. (2019). STANDING AND SITTING SAGITTAL PELVIC POSITION: OPTIMIZATION OF SACRAL SLOPE ANALYSIS USING THE RELATIVE PELVIC VERSION CONCEPT. Orthopaedic Proceedings, 101-B(SUPP_5), 53-53. https://doi.org/10.1302/1358-992X.2019.5.053

Lazennec, J. Y., Kim, Y. W., Hani, J. and Pour, A. E. (2019) “STANDING AND SITTING SAGITTAL PELVIC POSITION: OPTIMIZATION OF SACRAL SLOPE ANALYSIS USING THE RELATIVE PELVIC VERSION CONCEPT.” Orthopaedic Proceedings, 101-B(SUPP_5), pp. 53-53. Available at: https://doi.org/10.1302/1358-992X.2019.5.053

Lazennec, J. Y., Y. W. Kim, J. Hani, and A. Eslam Pour. “STANDING AND SITTING SAGITTAL PELVIC POSITION: OPTIMIZATION OF SACRAL SLOPE ANALYSIS USING THE RELATIVE PELVIC VERSION CONCEPT.” Orthopaedic Proceedings 101-B, no. SUPP_5 (2019): 53-53. https://doi.org/10.1302/1358-992X.2019.5.053

Lazennec JY, Kim YW, Hani J, Pour AE. STANDING AND SITTING SAGITTAL PELVIC POSITION: OPTIMIZATION OF SACRAL SLOPE ANALYSIS USING THE RELATIVE PELVIC VERSION CONCEPT. Orthop Procs. 2019 Apr 1;101-B(SUPP_5):53-53. https://doi.org/10.1302/1358-992X.2019.5.053

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Abstract

Introduction

Spatial orientation of the pelvis in the sagittal plane is a key parameter for hip function. Pelvic extension (or retroversion) and pelvic flexion(or anteversion) are currently assessed using Sacral Slope (SS) evaluation (respectively SS decrease and SS increase). Pelvic retroversion may be a risk situation for THA patients. But the magnitude of SS is dependant on the magnitude of pelvic incidence (PI) and may fail to discriminate pelvic position due to patient's anatomy and the potential adaptation mechanisms: a high PI patient has a higher SS but this situation can hide an associated pelvic extension due to compensatory mechanisms of the pelvic area. A low PI patient has a lower SS with less adaptation possibilities in case of THA especially in aging patients. The individual relative pelvic version (RPV) is defined as the difference between « measured SS » (SSm) minus the « normal SS »(SSn) described for the standard population. The aim of the study was to evaluate RPV in standing and sitting position with a special interest for high and low PI patients.

Materials and Methods

96 patients without THA (reference group) and 96 THA patients were included. Pelvic parameters (SS and PI) were measured on standing and sitting EOS images. RPV standing (SSm-SSn) was calculated using the formula SSm – (9 + 0.59 × PI) according to previous publications. SSn in sitting position was calculated according to PI using linear regression: RPV sitting was calculated using the formula RPV = SS – (3,54+ 0,38 × PI). Three subgroups were defined according to pelvic incidence (PI): low PI <45°, 45°<normal PI<65° or high PI>65°.

Results

For THA patients, pelvic parameters were:

SSm standing 41° (SD 11°; 8°.73°)
SSm sitting 25° (SD 12°;−3°.54°)
SSm variation 16°(SD 11°; 9°.46°)
RPV standing −2°(SD 9°; −27°.21°)
RPV sitting 7° (SD 10; −15°.29°)

For non THA patients, pelvic parameters were:

SSm standing39° (SD 10°; 13°.63°)
SSm sitting 17° (SD 11°;−5°.48°)
SSm variation 27°(SD 13°; −27°.46°)
RPV standing −1°(SD 7°; −29°.12°)
RPV sitting 0° (SD 10,5; −29.35)

Standing-sitting SS variations and RPV were not correlated with PI.

Low PI incidence patients had very low RPV standing and sitting.

In non THA patients RPV standing and sitting were very low.

In THA patients standing-sitting SS variations and RPV were higher than for non THA patients. Sitting RPV was higher than in standing position.

Discussion, Conclusion

The overall analysis of SS has limitations: higher or lower SS may be linked to 2 factors: pelvic morphology (PI) and sagittal orientation of the pelvis. RPV and PI were not correlated: a higher or lower value of RPV directly represents the sagittal orientation of the pelvis. Low PI patients have a specific postural pattern with low pelvic adaptability. THA patients specificity for RPV needs further studies for understanding the impact on postoperative rebalancing and instability problems.

lazennec.jy@wanadoo.fr