Pelvic incidence: a predictive factor for three-dimensional acetabular orientation-a preliminary study

How the hip-spine relationship influences total hip arthroplasty

INTRODUCTION

Motion in the spine, pelvis and hips which make up the spinopelvic femoral complex (SPFC) implies mechanical relationships that help maintain trunk balance and optimize hip functionThe aim of this study was to understand the physiology of the SPFC and evaluate the dysfunctions of the SPFC and their implications for total hip arthroplasty considering the hip-spine relationship.

METHODS

A review of relevant and comprehensive studies on this subject is reported in order to highlight a pathophysiology that integrates the description of the evaluations of the spine-pelvic and hip parameters and recommendations for the kinematic planning of the THA procedure. The primary objective was to determine which type of hip-spine relationship has the highest risk for THA complications and to become proficient in selecting the priority surgical intervention when both the hip and spine are affected. Finally, this review attempted to assist hip surgeons with surgical technique, tools, implant selection, and goals of planning a THA that requires personalized kinematic alignment. Determine the influence of THA on these kinematics and the effect of stiffness of the lumbopelvic complex on the risk of THA failure.

RESULTS

When a person sits, the pelvis goes into retroversion and the acetabulum opens forward. This frees the femoral head and neck to allow hip flexion. The opposite - pelvic anteversion - occurs when a person stands. When pelvic mobility is limited, the hip must increase its range of motion to accommodate these posture changes. Disturbances in spinal and pelvic kinematics lead to abnormal hip function, which may contribute to complications following total hip arthroplasty (THA).

CONCLUSION

A precise evaluation of the parameters governing the SPFC must be taken into account in order to best optimize the placement and choice of THA implants.

LEVEL OF EVIDENCE

IV.

Radiological signs of femoroacetabular impingement are linked to pelvic version in asymptomatic subjects

INTRODUCTION

With the recent interest in hip-spine relationship, the link between femoroacetabular impingement (FAI) and the lumbar-pelvic-femoral complex (LPFC) appears decisive. The objectives of this study were (1) to compare the pelvic version, as well as (2) all the parameters of the LPFC between two populations of healthy subjects, comparing those with radiological signs of FAI to those without and finally, (3) to evaluate the LPFC parameters according to the type of FAI.

HYPOTHESIS

Asymptomatic subjects with radiological signs of FAI had superior pelvic anteversion.

MATERIALS AND METHOD

This retrospective study was based on a prospective cohort of 118 voluntary asymptomatic patients including 62 men (52.5%) with a mean age of 25.6 years±4.4 (19-39). The following parameters: pelvic version (PV), pelvic incidence (PI), lumbar lordosis (LL), sacral slope (SS), hip flexion, intrinsic (IER) and extrinsic (EER) extension reserve were measured using EOS imaging™ in the reference standing position and the lunge position. The radiological signs of FAI (cam, pincer, mixed) were identified on these acquisitions then separated into 2 groups. The first was the group presenting with one or more images of FAI (FAI+) and the second group with no images of FAI (FAI-).

RESULTS

There were 143 hips in the FAI+ group compared to 93 hips in the FAI- group. There were 36.4% cams and 45% pincers. With an average of 9.08°±7.81 (-11.0; 27.0) versus 12.33°±8.94 (-5.0; 55.0), the PV was significantly lower (p=0.022) in the FAI+ group compared to the FAI- group. A post-hoc power analysis on the primary outcome (PV) confirmed sufficient power (1-β=0.809). Compared to the FAI- group, the cam group presented a significantly lower IER and EER (respectively p=0.014 and p=0.047). The comparative analysis between the FAI- and pincer groups found a significant difference in PI (p=0.001), PV (p<0.001), IER (p=0.017) and hip flexion (p<0.001), SS in lunge position (p=0.031) and EER (p=0.039).

CONCLUSION

Asymptomatic subjects with radiographic signs of FAI present with weak pelvic version when standing. This pelvic hyper-anteversion is mainly found in the event of a radiological pincer sign.

LEVEL OF EVIDENCE

III, retrospective comparative study.

Is there a correlation between pelvic incidence and orientation of the acetabulum? An analysis based on a three-dimensional statistical model of the pelvic ring

The pelvic ring is a complex anatomical structure building up the connection between the trunk and the legs. Whilst there is a broad discussion in the literature about the dynamic interaction between spine, pelvis and the hip joints, there is still little information about the relation and interaction of the constant pelvic parameters. Based on a three‐dimensional (3D) statistical model consisting of 150 uninjured and bony healthy pelves (100 Europeans, 50 Japanese; 81 males, 69 females; average age 74.3 years ± 17.5 years) an evaluation of pelvic incidence (PI) and acetabular orientation in anteversion and inclination was performed and potential correlations of these intraindividual constant parameters were investigated. Pelvic incidence is defined as the angle between the perpendicular to the sacral plate at its midpoint and the line connecting this point to the middle axis of the femoral heads. Acetabular anteversion is defined as the angle between the perpendicular to the best‐fit plane on the acetabular rim and the coronal plane measured in strict lateral view. Acetabular inclination is defined as the angle between the perpendicular to the best‐fit plane on the acetabular rim and the sagittal plane in strict frontal view. Data were further analysed with regard to different subgroup's age, sex and ethnicity. A positive correlation between PI and acetabular anteversion could be demonstrated. Further, PI and also the acetabular parameters anteversion and inclination were found to be significantly higher in the European individuals than in the Asian. The results of the present study demonstrate a relation between the anatomical configuration of the constant pelvic parameters building up the connection points to the next proximal respectively caudal skeleton section. The findings might lead to more comprehensive treatment strategies in case of trauma or degenerative pathologies of the pelvis in the future.

A Transfer Learning Approach for Lumbar Spine Disc State Classification

Recently, deep learning algorithms have become one of the most popular methods and forms of algorithms used in the medical imaging analysis process. Deep learning tools provide accuracy and speed in the process of diagnosing and classifying lumbar spine problems. Disk herniation and spinal stenosis are two of the most common lower back diseases. The process of diagnosing pain in the lower back can be considered costly in terms of time and available expertise. In this paper, we used multiple approaches to overcome the problem of lack of training data in disc state classification and to enhance the performance of disc state classification tasks. To achieve this goal, transfer learning from different datasets and a proposed region of interest (ROI) technique were implemented. It has been demonstrated that using transfer learning from the same domain as the target dataset may increase performance dramatically. Applying the ROI method improved the disc state classification results in VGG19 2%, ResNet50 16%, MobileNetV2 5%, and VGG16 2%. The results improved VGG16 4% and in VGG19 6%, compared with the transfer from ImageNet. Moreover, it has been stated that the closer the data to be classified is to the data that the system trained on, the better the achieved results will be.

Effect of Spinal Alignment Changes on Lower Back Pain in Patients Treated with Total Hip Arthroplasty for Hip Osteoarthritis

Background and objectives: The influence of changes in spinal alignment after total hip arthroplasty (THA) on improvement in lower back pain (LBP) remains controversial. To evaluate how changes in spinal malalignment correlate with improvement in preoperative LBP in patients who underwent THA for hip osteoarthritis. Materials and Methods: From November 2015 to January 2017, 104 consecutive patients who underwent unilateral THA were prospectively registered. Whole spine X-rays and patient-reported outcomes (PROs) were obtained preoperatively and 12 months postoperatively. The PROs used were the Numerical Rating Scale (NRS) for back pain, EuroQol 5 Dimension, and Short Form-12. Results: Seventy-four (71%) patients with complete data were eligible for the analysis. The sagittal parameters changed slightly but significantly. Coronal alignment significantly improved. Twenty-six (37%) patients had LBP preoperatively. These patients had smaller lumbar lordosis (LL), larger PT, and larger PI minus LL than the patients without LBP. Fourteen (54%) of the 26 patients with preoperative LBP showed pain improvement, but there were no significant differences in the radiographic parameters. Conclusions: Although preoperative LBP was likely to be resolved after THA, there were no significant correlations between alignment changes and LBP improvement. The cause of LBP in patients with hip osteoarthritis (OA) patients might be multifactorial.

The evolution of pelvic canal shape and rotational birth in humans

BACKGROUND

The human foetus typically needs to rotate when passing through the tight birth canal because of the complex shape of the pelvis. In most women, the upper part, or inlet, of the birth canal has a round or mediolaterally oval shape, which is considered ideal for parturition, but it is unknown why the lower part of the birth canal has a pronounced anteroposteriorly oval shape.

RESULTS

Here, we show that the shape of the lower birth canal affects the ability of the pelvic floor to resist the pressure exerted by the abdominal organs and the foetus. Based on a series of finite element analyses, we found that the highest deformation, stress, and strain occur in pelvic floors with a circular or mediolaterally oval shape, whereas an anteroposterior elongation increases pelvic floor stability.

CONCLUSIONS

This suggests that the anteroposterior oval outlet shape is an evolutionary adaptation for pelvic floor support. For the pelvic inlet, by contrast, it has long been assumed that the mediolateral dimension is constrained by the efficiency of upright locomotion. But we argue that the mediolateral elongation has evolved because of the limits on the anteroposterior diameter imposed by upright posture. We show that an anteroposteriorly deeper inlet would require greater pelvic tilt and lumbar lordosis, which compromises spine health and the stability of upright posture. These different requirements of the pelvic inlet and outlet likely have led to the complex shape of the pelvic canal and to the evolution of rotational birth characteristic of humans.

No linear correlation between pelvic incidence and acetabular orientation: Retrospective observational study

Links between sagittal spinal alignment and acetabular orientation attract considerable research attention with the goal of understanding “hip-spine syndrome.” However, whether pelvic incidence (PI) is related to acetabular orientation remains debatable. The purpose of the present study was to determine: 1. whether the correlation between PI and acetabular orientation is present in pelvises of young healthy adults, and 2. whether the correlation is present in subgroups of sex, or between the left and right pelvis. We analyzed 100 abdominopelvic computed tomography (CT) scans of skeletally healthy young adults. We measured PI and acetabular orientation with three-dimensional (3D) measurements. The orientation of 200 acetabula was measured using 3D reconstructed models of 100 pelvises in the coordinate system based on the anterior pelvic plane (APP). To quantify the acetabular orientation, the radiographic definitions of anteversion and inclination were used. To examine the correlation between acetabular orientation and PI, Pearson's correlation was used. The mean PI was 46.9° ± 10.2°, and the mean acetabular orientation 15.3° ± 5.7° anteverted and 37.5° ± 3.9° inclined. While no significant difference in the PI was observed, the average acetabular orientation of female pelvises (anteversion, 17.5° ± 5.6°; inclination, 36.7° ± 3.7°) was more anteverted and less inclined compared to that of male pelvises (anteversion, 13.2° ± 4.9°; inclination, 38.3° ± 3.9°, respectively; P values < .05). The correlation between PI and acetabular orientation was statistically not significant. After division of study group by sex, the linear correlation between PI and acetabular orientation was not statistically supported. The asymmetry of the acetabular orientation between the left and right sides was not significant. The linear relationship between anatomical acetabular orientation and PI was not evident in the normal population. Our finding thus proves the absence of a linear relationship between the upper and lower articular orientation of the pelvic segment and deepens the understanding of the characteristics of acetabular orientation and PI.

The relationship between pelvic incidence and anatomical acetabular anteversion in female Japanese patients with hip osteoarthritis: a retrospective iconographic study

PURPOSE

This study aimed (1) to investigate the relationship between pelvic incidence (PI) and the anatomical acetabular anteversion (AA) relative to the spino-pelvic tilt (SPT) plane (anatomical AA_SPT), relative to the anterior pelvic plane (anatomical AA_APP), and functional standing AA; and (2) to compare AA and the sagittal spino-pelvic parameters of lumbo-pelvic complex types 1 (PI ≤ 30°) and 2 (PI > 30°), in Japanese females with hip osteoarthritis.

METHODS

We conducted a retrospective study on 110 Japanese females with unilateral hip osteoarthritis. PI, standing lumbar lordosis (LL), standing SPT, anatomical AA_SPT, anatomical AA_APP, and functional standing AA were measured and calculated using radiographs and computed tomography. The PI-LL difference was defined as the mathematical difference between the PI and standing LL angles. Pearson's correlation test was used to measure the relationship between the PI and AA. Student's t test was used to compare spino-pelvic parameters between lumbo-pelvic complex type 1 (n = 24) and type 2 (n = 86).

RESULTS

There was a significant relationship between the PI and anatomical AA_SPT (r =  -0.532, p < 0.001), but no significant relationship between the PI and anatomical AA_APP (r =  -0.021, p = 0.824) or functional standing AA (r = 0.104, p = 0.299). Lumbo-pelvic complex type 1 had a higher anatomical AA_SPT (22.4° ± 9.1° vs. 5.4° ± 15.1°, p < 0.001), similar anatomical AA_APP (15.0° ± 10.6° vs. 15.1° ± 15.3°, p = 0.981) and functional standing AA (12.4° ± 8.0° vs. 15.0° ± 14.1°, p = 0.254), a lower standing SPT (- 14.3° ± 11.0° vs. 13.7° ± 12.6°, p < 0.001), and a lower PI-LL difference (- 14.4° ± 18.5° vs. 6.4° ± 17.1°, p < 0.001) in comparison to lumbo-pelvic complex type 2.

CONCLUSION

Our findings will help to improve the understanding of hip anatomy and its relationship with the standing spino-pelvic alignment in Japanese females with hip osteoarthritis.

The severity of developmental dysplasia of the hip does not correlate with the abnormality in pelvic incidence

Background

The purpose of this study was to investigate the association between the severity of Developmental dysplasia of the hip (DDH) and the abnormality in pelvic incidence (PI).

Methods

This was a retrospective study analyzing 53 DDH patients and 53 non-DDH age-matched controls. Computed tomography images were used to construct three-dimensional pelvic model. The Crowe classification was used to classify the severity of DDH. The midpoint of the femoral head centers and sacral endplates were projected to the sagittal plane of the pelvis. The PI was defined as the angle between a line perpendicular to the sacral plate at its midpoint and a line connecting this point to the axis of the femoral heads. Independent sample t-tests were used to compare the differences between the PI of DDH group and the non-DDH controls group. Kendall’s coefficient of concordance was used to determine the correlation between the severity of DDH and PI.

Results

Patients with DDH had a significantly (p = 0.041) higher PI than the non-DDH controls (DDH 47.6 ± 8.2°, normal 44.2 ± 8.8°). Crowe type I patients had a significantly (p = 0.038) higher PI (48.2 ± 7.6°) than the non-DDH controls. No significant difference between the PI in Crowe type II or III patients and the PI in non-DDH controls were found (Crowe type II, 50.2 ± 9.6°, p = 0.073; Crowe type III, 43.8 ± 7.2°, p = 0.930). No correlation was found between the severity of DDH and the PI (r = 0.091, p = 0.222).

Conclusions

No correlation was found between the severity of DDH and the PI. The study confirmed that the PI in DDH (Crowe type I) group was higher than that of the non-DDH control group, while the PI does not correlate with the severity of DDH.

The characteristics of the whole pelvic morphology in slipped capital femoral epiphysis: A retrospective observational study

Slipped capital femoral epiphysis (SCFE) is a very common disorder affecting the adolescent hip. The etiology of SCFE is multifactorial and mechanical force associated with the characteristic morphology of the hip is considered one of the causes of SCFE. We investigated the characteristics of whole pelvic morphology including pelvic incidence (PI) in patients with SCFE and compared it with pelvic morphology in healthy children. We retrospectively assessed the whole pelvic morphology of 17 patients with SCFE and 51 healthy children using their pelvic computed tomography data. We measured superior iliac angle, inferior iliac angle, and ischiopubic angle as the parameters of pelvic rotation. Additionally, we measured acetabular anteversion of the superior acetabulum (AVsup) and of the center of the acetabulum (AVcen), and measured anterior acetabular sector angle (AASA), posterior acetabular sector angle, and the superior acetabular sector angle (SASA) as parameters of acetabular coverage and PI. Each measurement was compared between the 2 groups. AASA and SASA of patients with SCFE were significantly greater than that of controls, and AVsup of patients with SCFE was significantly smaller. There were no significant differences in pelvic rotation, PI, or AVcen between the 2 groups. This is the 1st report to evaluate SCFE patients' whole pelvic morphology including PI and pelvic rotation. Our results showed that patients with SCFE have excessive coverage of the anterior and superior acetabulum, and a more retroverted cranial acetabulum as compared with healthy control subjects. Such characteristic pelvic morphology may be involved in the onset of SCFE. To clarify the mechanical forces involved in SCFE onset, further investigations of pelvic morphology and alignment, including the femur and spine, are needed.

Variation in pelvic shape and size in Eastern European males: a computed tomography comparative study

Background

The significantly accelerated development of human society in the last millennium has brought about changes in human behavior and body mass that may have influenced human bone morphology. Our objective was to analyze the variation in pelvic shape and size in males from modern and medieval populations.

Methods

We obtained 22 pelvic girdles of adult males from a medieval cemetery located in Cedynia, Poland. The control group comprised 31 contemporary male pelves from individuals inhabiting the same region. The analyzed parameters were: interspinous distance (ISD), intercristal distance (ICD), intertuberous distance (ITD), anatomic conjugate of the pelvis, height of the pelvis (HP), iliac opening angle (IOA), iliac tilt angle (ITA), and ISD/ITD/HP ratio. Geometric morphometrics was used to analyze differences in shape in the pelves. All analyses were carried out on three-dimensional CT reconstructions of pelves.

Results

ISD, ICD, and IOA were significantly greater in modern pelves than in those from Cedynia, but no significant differences were seen between the two groups in ITD, anatomical conjugate, HP, or ITA. ISD/ITD/HP ratios were significantly lower in the Cedynia group. Geometric morphometrics revealed significant differences in pelvic shape between the analyzed groups.

Discussion

The pelves of modern males are larger, wider, and flatter than those of medieval males. Changes in the set of daily activities that produce mechanical loading and estimated body mass may constitute the main factors explaining pelvic variability. However, differences in ontogenesis should also be taken into consideration, especially since growth in past populations is often found to be reduced relative to modern populations.

Postoperative changes in sacropelvic junction in short-segment angular kyphosis versus Scheuermann kyphosis

PURPOSE

To comparatively evaluate the biomechanical alterations those occur in the sagittal plane of sacropelvic junction in angular kyphosis (AK) and Scheuermann kyphosis (SK) patients after surgery.

METHODS

The spine radiographs of 52 patients operated for short-segment AK (n = 20) or SK (n = 32) were studied. Main outcome measures were sacral slope, pelvic incidence, pelvic tilt, lumbar lordosis, and thoracic kyphosis angles.

RESULTS

In AK group, local and thoracic kyphosis angles, as well as lumbar lordosis angle, showed statistically significant reduction with surgery. Thoracic kyphosis and lumbar lordosis angles were reduced significantly in SK group. Postoperatively, there were significant differences between groups in lumbar lordosis, pelvic tilt angle, and sacral slope (p = 0.021, p = 0.001, and p = 0.027, respectively). Thoracic kyphosis angle and sacral slope were increased, and there was a remarkable correlation between thoracic kyphosis and lumbar lordosis values in the AK group.

CONCLUSIONS

The results of this study suggest that a significant sacropelvic improvement can be achieved by balanced sagittal vertical axis and T1 spinopelvic leading to a good sagittal alignment of spine in patients with AK and SK. Changes seen in morphological parameters after surgery may be closely related with baseline biomechanics and structure of the spine and pelvis. Therefore, further clinical and scientific trials are necessary both to elucidate the biomechanics, their clinical implications, and to develop new techniques and models for spine and pelvis surgery.

Does hemipelvis structure and position influence acetabulum orientation?

Background

Although acetabulum orientation is well established anatomically and radiographically, its relation to the innominate bone has rarely been addressed. If explored, it could open the discussion on patomechanisms of such complex disorders as femoroacetabular impingement (FAI). We therefore evaluated the influence of pelvic bone position and structure on acetabular spatial orientation. We describe this relation and its clinical implications.

Methods

This retrospective study was based on computed tomography scanning of three-dimensional models of 31 consecutive male pelvises (62 acetabulums). All measurements were based on CT spatial reconstruction with the use of highly specialized software (Rhinoceros). Relations between acetabular orientation (inclination, tilt, anteversion angles) and pelvic structure were evaluated. The following parameters were evaluated to assess the pelvic structure: iliac opening angle, iliac tilt angle, interspinous distance (ISD), intertuberous distance (ITD), height of the pelvis (HP), and the ISD/ITD/HP ratio. The linear and nonlinear dependence of the acetabular angles and hemipelvic measurements were examined with Pearson’s product − moment correlation and Spearman’s rank correlation coefficient. Correlations different from 0 with p < 0.05 were considered statistically significant.

Results

Comparison of the axis position with pelvis structure with orientation in the horizontal plane revealed a significant positive correlation between the acetabular anteversion angle and the iliac opening angle (p = 0.041 and 0.008, respectively). In the frontal plane, there was a positive correlation between the acetabular inclination angle and the iliac tilt angle (p = 0.025 and 0.014, respectively) and the acetabular inclination angle and the ISD/ITD/HP ratio (both p = 0.048).

Conclusions

There is a significant correlation of the hemipelvic structure and acetabular orientation under anatomic conditions, especially in the frontal and horizontal planes. In the anteroposterior view, the more tilted-down innominate bone causes a more caudally oriented acetabulum axis, whereas in the horizontal view this relation is reversed. This study may serve as a basis for the discussion on the role of the pelvis in common disorders of the hip.

An accurate method of radiological assessment of acetabular volume and orientation in computed tomography spatial reconstruction

Background

Two-dimensional (2D) measurements of acetabular morphology and orientation are well known; there is less information on these acetabular characteristics in three dimensions. One important reason is the lack of standardized reference planes for the pelvis, especially in relation to the spinopelvic unit; another is that no method precisely assesses the acetabulum in three-dimensional (3D) orientation based on its axis rather than on the directions of the edges of the acetabular rim. We present an objective, highly reliable and accurate, axis-based approach to acetabular anthropometry in the measurement of acetabular volume and spatial orientation in both normal and pathologic hips. This was done using reference planes based on the sacral base (SB) and true acetabular axis in 3D computed tomography (CT) pelvic reconstruction.

Methods

Radiological examinations of 30 physiologic pelves (60 acetabula) were included in the study. Reliability and accuracy of the method were verified by comparing acetabular angles in 2D pelvic scans with 3D reconstructions. We also applied the method to two pathologic acetabula.

Results

Comparison of axis position in the horizontal plane revealed significant positive correlations between 2D angle measurements (acetabular anteversion angle [AAA] and anterior acetabular index [AAI]) and 3D measurement of anteversion angle (p < 0.001 and p = 0.012, respectively). In the frontal plane, there was no difference between abduction angle, measured on topogram, and inclination angle, obtained from a 3D model (p = 0.517). In the sagittal plane, there was a significant negative correlation between AAA and acetabular tilt (p < 0.001). Inter- and intra-observer reproducibility was excellent for determination of the sacral-base plane and assessment of volume, with Fleiss κ coefficients of 0.850 and 0.783, respectively, and intraclass correlation coefficients of 0.900 and 0.950, respectively. Inter-observer reproducibility for evaluation of acetabular axis ranged from 0.783 to 0.883, and intra-rater reliability ranged from 0.850 to 0.900 for all 3D angles.

Conclusions

Our method is a new, reliable diagnostic tool for assessing the acetabula in both normal and pathologic hip joints. The sacral-base plane can be used as a stable reference that takes the relationship of the acetabulum to the spinopelvic unit into consideration.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-015-0503-8) contains supplementary material, which is available to authorized users.