Lumbosacral Transitional Vertebrae Influence on Acetabular Orientation and Pelvic Tilt

Lumbosacral transitional vertebrae (LSTV) are common congenital variances with a prevalence found in the population up to 35.6%. The literature demonstrates an influence of LSTV on bony pelvic anatomy. The influence on the anatomical acetabular orientation, which is important for cup positioning in total hip arthroplasty, has not yet been described for patients with LSTV. A total of 53 patients with LSTV were identified from a CT Database including 819 subjects. Fifty patients with LSTV could be included and were matched for age and sex against a control group. We examined the influence of LSTV, classified according to Castellvi, on acetabular orientation and pelvic tilt in the supine position. Functional acetabular anteversion and inclination, assessed against the table plane, were compared against anatomical acetabular anteversion and inclination, assessed against the anterior pelvic plane. The anatomical acetabular inclination correlated with the pelvic tilt (r = 0.363, p < 0.001). The anatomical acetabular inclination was significantly larger than the functional acetabular inclination in the supine position (p < 0.001). Castellvi grading of LSTV correlated negatively with pelvic tilt (ρ = −0.387, p = 0.006). Castellvi grading correlated significantly with functional acetabular anteversion (ρ = 0.324, p = 0.022) and anatomical acetabular anteversion (ρ = 0.306, p = 0.022). A higher Castellvi grading was accompanied by a reduced pelvic tilt in the supine position. The functional acetabular anteversion and anatomical acetabular anteversion increased in parallel to the higher Castellvi grading. Therefore, LSTV and Castellvi grading might be assessed on pre-operative X-rays prior to hip arthroplasty and surgeons might consider adjusting cup positioning accordingly.

Acetabular Morphology and Spinopelvic Characteristics: What Predominantly Determines Functional Acetabular Version?

Background:

In addition to the relative size of the acetabular rim and how the pelvis is positioned in space, the plane in which the acetabular version is calculated also affects its measurement.

Purpose:

To determine the relative contribution of pelvic and acetabular characteristics on morphological version (measured relative to the anterior pelvic plane angle [APPA]) and functional version (measured relative to the horizontal table).

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Included were 50 acetabular dysplasia patients and 109 asymptomatic controls. Using image analysis software, morphological parameters of the pelvis and acetabulum were determined from 2-dimensional computed topography: pelvic incidence, pelvic tilt angle, sacral slope, APPA, morphological and functional acetabular versions, and subtended angles (measure of acetabular rim prominence relative to the femoral head center) around the acetabular clockface in 30° increments. Correlation and multivariable regression analyses were performed with morphological and functional version as dependent variables and spinopelvic and acetabular parameters as independent variables.

Results:

Morphological version was moderately associated with differences between anterior and posterior subtended angles (R = 0.68 [P < .001] and R = 0.57 [P < .001] for differences at 165° and 15° and 135° and 45°, respectively). Functional version was moderately associated with pelvic tilt angle (R = 0.56; P <.001) and the difference in subtended angles between anterior and posterior rims (R = 0.61 [P < .001] and R = 0.50 [P < .001] for differences at 165° and 15° and 135° and 45°, respectively). Multivariate analysis revealed a good model for predicting morphological version (R² = 0.44; P < .01) and functional version (R² = 0.58; P < .01). Subtended angle difference between 165° and 15° (B = 0.36 [95% CI, 0.24-0.49]; P < .001) was most strongly related to morphological version, and pelvic tilt angle (B = 0.57 [95% CI, 0.46-0.68]; P < .001) was most strongly related to functional version.

Conclusion:

Functional acetabular version was influenced most strongly by pelvic tilt angle rather than the relative prominence of the acetabular rims. Before determining surgical management for version abnormalities, it would be prudent to assess pelvic mobility and characteristics in different functional positions. In patients with minimal pelvic tilt change dynamically, corrective osteotomy would be the treatment of choice to improve functional version.

[Effect of acetabular tilt angle on acetabular version in adults with developmental dysplasia of the hip]

Objective

To investigate the difference in acetabular tilt angle (ATA) between adults with deve-lopmental dysplasia of the hip (DDH) and normal adults and the effect of ATA on acetabular version.

Methods

Between February 2009 and October 2015, 31 adult female patients with DDH (39 hips) (DDH group) and 31 female patients with osteoarthritis of the knee (31 hips) who had no history of hip disease (control group) were included in this study. The average age was 39 years (range, 18-59 years) in the DDH group, and was 69 years (range, 52-79 years) in control group. The morphometric parameters of the acetabulum including ATA, acetabular anteversion angle (AAA), acetabular inclination angle (AIA), acetabular cranial anteversion angle (ACAA), and acetabular sector angle (ASA) were mea- sured by CT reconstruction; The ASA was used as an index for acetabular coverage of the femoral head. The correlation between ATA and other parameters was analyzed using Pearson correlation analysis.

Results

The values of ATA, AAA, and AIA of the DDH group were significantly larger than those of the control group ( P<0.05). The ASA in all directions was significantly decreased in the DDH group when compared with the values in the control group ( P<0.05). There was no significant difference in ACAA between two groups ( t=1.918, P=0.523). The ATA was positively correlated with AAA and ACAA in the DDH group ( r=0.439, P=0.001; r=0.436, P=0.002), but there was no correlation between ATA and AIA ( r=0.123, P=0.308). In the control group, the ATA was not correlated with AAA, ACAA, and AIA ( r=-0.004, P=0.724; r=-0.079, P=0.626; r=-0.058, P=0.724). Regarding acetabular coverage of the femoral head, the ATA and AAA were correlated negatively with anterior ASA ( P<0.05) and positively with posterior ASA ( P<0.05), but had no correlation with superior ASA ( P>0.05) in the DDH group; AIA was correlated negatively with anterior ASA and superior ASA ( P<0.05) and had no correlation with posterior ASA ( r=-0.092, P=0.440). In the control group, there was no correlation between ATA and ASA in any direction ( P>0.05). In the DDH group, defects of the acetabular anterior wall, lateral wall, and posterior wall were observed in 18 hips (46.2%), 15 hips (38.5%), and 6 hips (15.3%), respectively. ATA value of the posterior wall defect [(15.70±10.00)°] was significantly smaller than those of the acetabular anterior wall and lateral wall defects [(22.91±5.06)° and (21.59±3.81) °] ( P<0.05), but no signficant difference was found between anterior wall and lateral wall defects ( P>0.05).

Conclusion

ATA will influence acetabular version in DDH. The anterior rotation of the acetabular fragment during periacetabular osteotomies is an anatomically reasonable maneuver for hips with anterolateral acetabular defect, while the maneuver should be avoided in hips with posterior acetabular defect.

Prevalence of Femoral and Acetabular Version Abnormalities in Patients With Symptomatic Hip Disease: A Controlled Study of 538 Hips

BACKGROUND

Variations in femoral and acetabular version are becoming increasingly recognized as contributing factors to the development of hip pain in patients with femoroacetabular impingement (FAI) and hip dysplasia. It is still unknown what the true prevalence of these rotational abnormalities is in this patient population.

PURPOSE

To determine (1) the prevalence of femoral version abnormalities in symptomatic hips with FAI and hip dysplasia, (2) the prevalence of combined abnormalities of femoral and acetabular version in these patients, and (3) which specific hip morphologies are associated with abnormalities of femoral version.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 462 symptomatic patients (538 hips) were included who had hip pain attributed to FAI or hip dysplasia and who presented to our tertiary referral center for hip preservation surgery between 2011 and 2015. We retrospectively examined femoral and acetabular version among 11 subgroups with predefined hip morphologies and compared findings with a control group. The allocation to each subgroup was based on morphologic reference values for femoral head coverage, lateral center edge angle, alpha angle, and neck-shaft angle calculated on plain radiographs.

RESULTS

Of the 538 hips included, 52% were found to have abnormal femoral version; severe abnormalities were found in 17%. Severely decreased femoral version (<0°) was found in 5%; moderately decreased femoral version (0°-10°), in 17%; moderately increased femoral version (26°-35°), in 18%; and severely increased femoral version (>35°), in 12%. The most frequent abnormal combination was increased femoral version combined with normal acetabular version (22%). We found significantly lower mean femoral version for the cam-type FAI group (15°) and significantly higher mean femoral version for the Perthes hips (32°; ie, Legg-Calvé-Perthes disease) as compared with the control group (22°). The mean femoral version of the study group was 19°; for male patients, 15°; and for female patients, 22°.

CONCLUSION

Abnormalities in femoral version are highly prevalent in patients with hip pain who are eligible for hip preservation surgery, and severe abnormalities are prevalent in 1 of 6 patients (17%). Based on these results, the evaluation of young patients with hip pain should always include an assessment of femoral version and acetabular version to best decide what treatment approach should be undertaken to optimize outcomes.

Effect of changes in pelvic tilt on range of motion to impingement and radiographic parameters of acetabular morphologic characteristics

BACKGROUND

The current understanding of the effect of dynamic changes in pelvic tilt on the functional acetabular orientation and occurrence of femoroacetabular impingement (FAI) is limited.

PURPOSE

To determine the effect of changes in pelvic tilt on (1) terminal hip range of motion and (2) measurements of acetabular version as assessed on 2- and 3-dimensional imaging.

STUDY DESIGN

Controlled laboratory study.

METHODS

Preoperative pelvic computed tomographic scans of 48 patients (50 hips) who underwent arthroscopic surgery for the treatment of FAI were analyzed. The mean age of the study population was 25.7 years (range, 14-56 years), and 56% were male. Three-dimensional models of the hips were created, allowing manipulation of the pelvic tilt and simulation of hip range of motion to osseous contact. Acetabular version was measured and the presence of the crossover sign, prominent ischial spine sign, and posterior wall sign was recorded on simulated plain radiographs. Measurements of range of motion to bony impingement during (1) hip flexion, (2) internal rotation in 90° of flexion, and (3) internal rotation in 90° of flexion and 15° adduction were performed, and the location of bony contact between the proximal femur and acetabular rim was defined. These measurements were calculated for -10° (posterior), 0° (native), and +10° (anterior) pelvic orientations.

RESULTS

In native tilt, mean cranial acetabular version was 3.3°, while central version averaged 16.2°. Anterior pelvic tilt (10° change) resulted in significant retroversion, with mean decreases in cranial and central version of 5.9° and 5.8°, respectively (P < .0001 for both). Additionally, this resulted in a significantly increased proportion of positive crossover, posterior wall, and prominent ischial spine signs (P < .001 for all). Anterior pelvic tilt (10° change) resulted in a decrease in internal rotation in 90° of flexion of 5.9° (P < .0001) and internal rotation in 90° of flexion and 15° adduction of 8.5° (P < .0001), with a shift in the location of osseous impingement more anteriorly. Posterior pelvic tilt (10° change) resulted in an increase in internal rotation in 90° of flexion of 5.1° (P < .0001) and internal rotation in 90° of flexion and 15° adduction of 7.4° (P < .0001), with a superolateral shift in the location of osseous impingement.

CONCLUSION/CLINICAL RELEVANCE

Dynamic changes in pelvic tilt significantly influence the functional orientation of the acetabulum and must be considered. Dynamic anterior pelvic tilt is predicted to result in earlier occurrence of FAI in the arc of motion, whereas dynamic posterior pelvic tilt results in later occurrence of FAI, which may have implications regarding nonsurgical treatments for FAI.