Functional Pelvic Orientation Measured from Lateral Standing and Sitting Radiographs

138

144

Appropriate anatomic concepts for surgery to treat femoroacetabular impingement require a precise appreciation of the native acetabular anatomy. We therefore determined (1) the spatial acetabular rim profile, (2) the topography of the articular lunate surface, and (3) the 3-D relationships of the acetabular opening plane comparing 66 bony acetabula from 33 pelves in female and male pelves. The acetabular rim profile had a constant and regular wave-like outline without gender differences. Three prominences anterosuperiorly, anteroinferiorly and posteroinferiorly extended just above hemispheric level. Two depressions were below hemispheric level, of 9°at the anterior wall and of 21°along the posterosuperior wall. In 94% of all acetabula, the deepest extent of the articular surface was within 30°of the anterosuperior acetabular sector. In 99% of men and in 91% of women, the depth of the articular surface was at least 55°along almost half of the upper acetabular cup. The articular surface was smaller in women than in men. The acetabular opening plane was orientated in 21°± 5°for version, 48°± 4°for inclination and 19°± 6°for acetabular tilt with no gender differences. We defined tilt as forward rotation of the entire acetabular cup around its central axis; because of interindividual variability of acetabular tilt, descriptions of acetabular lesions during surgery, CT scanning and MRI should be defined and recorded in relation to the acetabular notch. Acetabular tilt and pelvic tilt should be separately identified. We believe this information important for surgeons performing rim trimming in FAI surgery or performing acetabular osteotomies.

Section: Discussionmentioning

confidence: 99%

“…Apart from variations in pelvic tilt [2,10,12,32,33,41,48,57], this can now be explained by variations of acetabular tilt, which influences spatial positions of peaks and depressions along the rim. The results of our measurements for version are comparable to other anatomical studies (Table 8).…”

Section: Discussionmentioning

confidence: 99%

Acetabular Morphology: Implications for Joint-preserving Surgery

Köhnlein¹,

Ganz

Impellizzeri³

et al. 2009

138

144

“…However, more recently a topic of considerable discussion is dynamic sagittal pelvic tilt and its role in deciding the optimal position of the acetabular component to avoid instability [21,30]. Variability in pelvic tilt can change acetabular component orientation after THA, and hip replacement surgeons have investigated pelvic tilt in sitting posture [11,19,20], because posterior dislocations often occur when a patient is rising from a chair. Sitting pelvic tilt dictates the proximity of the rim of the acetabulum to the proximal femur and, therefore, the risk of impingement.…”

Section: Introductionmentioning

confidence: 99%

“…Sitting pelvic tilt dictates the proximity of the rim of the acetabulum to the proximal femur and, therefore, the risk of impingement. Although some studies have described pelvic tilt during postural changes [11,41], few have considered pelvic tilt as a function of the hip-spine relationship [23,24], because it is difficult to view the entire lumbar spine (L1-S1) and hips on a conventional lateral radiograph.…”

Section: Introductionmentioning

confidence: 99%

Does Degenerative Lumbar Spine Disease Influence Femoroacetabular Flexion in Patients Undergoing Total Hip Arthroplasty?

Esposito

Miller

Kim

et al. 2016

202

177

Background Sitting pelvic tilt dictates the proximity of the rim of the acetabulum to the proximal femur and, therefore, the risk of impingement in patients undergoing total hip arthroplasty (THA). Sitting position is achieved through a combination of lumbar spine segmental motions and/or femoroacetabular articular motion in the lumbarpelvic-femoral complex. Multilevel degenerative disc disease (DDD) may limit spine flexion and therefore increase femoroacetabular flexion in patients having THAs, but this has not been well characterized. Therefore, we measured standing and sitting lumbar-pelvic-femoral alignment in patients with radiographic signs of DDD and in patients with no radiographic signs of spine arthrosis.Questions/purposes We asked: (1) Is there a difference in standing and sitting lumbar-pelvic-femoral alignment before surgery among patients undergoing THA who have no radiographic signs of spine arthrosis compared with those with preexisting lumbar DDD? (2) Do patients with lumbar DDD experience less spine flexion moving from a standing to a sitting position and therefore compensate with more femoroacetabular flexion compared with patients who have no radiographic signs of arthrosis? Methods Three hundred twenty-five patients undergoing primary THA had preoperative low-dose EOS spine-toankle lateral radiographs in standing and sitting positions. Eighty-three patients were excluded from this study for scoliosis (39 patients), spondylolysis (15 patients), not having five lumbar vertebrae (7 patients), surgical or disease fusion (11 patients), or poor image quality attributable to high BMI (11 patients). In the remaining 242 of 325 patients (75%), two observers categorized the lumbar spine as either without radiographic arthrosis or having DDD based on defined radiographic criteria. Sacral slope, lumbar lordosis, and proximal femur angles were measured, and these angles were used to calculate lumbar spine flexion and femoroacetabular flexion in standing and sitting positions. Patients were aligned in a standardized sitting position so that their femurs were parallel to the floor to achieve approximately 90°of apparent hip flexion. Results After controlling for age, sex, and BMI, we found patients with DDD spines had a mean of 5°more posterior pelvic tilt (95% CI, À2°to À8°lower sacral slope angles; p \0.01) and 7°less lumbar lordosis (95% CI, À10°to À3°; p \ 0.01) in the standing position compared with patients without radiographic arthrosis. However, in the sitting position, patients with DDD spines had 4°less posterior pelvic tilt (95% CI, 1°-7°higher sacral slope angles; p = 0.02). From standing to sitting position, patients with DDD

“…Although the omega zone addresses all hip morphology parameters relevant for FAI, postural factors such as pelvic tilt and lumbosacral lordosis also influence femoral head position in the acetabulum. Nevertheless, for persons positioned supine in a CT scanner, there is a fairly robust correlation with their standing posture [6,7]. Finally, the analysis of the omega zone was performed with steps of 30°of flexion.…”

Section: Discussionmentioning

confidence: 99%

Can Combining Femoral and Acetabular Morphology Parameters Improve the Characterization of Femoroacetabular Impingement?

Bouma

Hogervorst

Audenaert

et al. 2015

Background Femoroacetabular impingement (FAI) presupposes a dynamic interaction of the proximal femur and acetabulum producing clinical symptoms and chondrolabral damage. Currently, FAI classification is based on alpha angle and center-edge angle measurements in a single plane. However, acetabular and femoral version and neck-shaft angle also influence FAI. Furthermore, each of these parameters has a reciprocal interaction with the others; for example, a shallow acetabulum delays impingement of the femoral head with the acetabular rim. Questions/purposes We introduce the new parameter ''omega zone,'' which combines five parameters into one: the alpha and center-edge angles, acetabular and femoral version, and neck-shaft angle. We sought to determine whether the omega zone could differentiate patients with FAI from (1) normal control subjects (alpha \ 55°), but also from (2) control subjects with elevated alpha angles (C 55°). Methods We evaluated CT data of 20 hips of male patients with symptomatic cam-type FAI and of 35 male hips extracted from 110 anonymized CT scans for vascular diagnosis. We excluded hips with osteoarthritis, developmental dysplasia, or coxa profunda (center-edge angle 20°-45°on AP pelvic view or corresponding coronal CT views). With dedicated software, femoral and pelvic orientation was standardized; we tested the omega zone in four hip positions in three distinct groups: patients with cam-type FAI (alpha [ 60°) and control subjects with normal (\ 55°) and high alpha angles (C 55°). Results The omega zone was smaller in patients with cam-type FAI than normal control subjects (alpha angle \ 55°) at 60°and 90°of flexion (mean, 12%; 95% confidence interval [CI], 7-17; p = 0.008; Cohen's d = 9%; 95% CI, 4-13; p = 0.003). Furthermore, the omega zone was smaller in all positions in patients with cam-type FAI than control subjects with high alpha angles (0°p = 0.017, 30°p = 0.004, 60°p = 0.004, 90°p = 0.007). In contrast, the omega zone did not differ between control subjects with normal or high alpha angles. In all hips, the omega zone decreased with flexion, corresponding to a decrease in remaining impingement-free motion with flexion.