Pelvic incidence and hip disorders

Sacroiliac joint fusion in patients with ankylosing spondylitis is associated with hip involvement

OBJECTIVE

Ankylosing spondylitis (AS) is a progressive inflammatory disease that affects the axial skeleton, and often associated with hip involvement. However, the causative factors for radiological hip involvement in patients with AS are not well characterized. This study aimed to investigate the factors associated with hip involvement in patients with AS.

METHODS

Sixty-seven patients (134 hips) diagnosed with AS who qualified the modified New York criteria at our institution between January 2005 and June 2022 were enrolled. Patients were divided into two groups: the hip involvement group (BASRI-hip score ≥2 points) and the normal group (BASRI-hip score <2 points). Demographic, clinical and radiographic characteristics were compared between the two groups.

RESULTS

Twenty-six patients (38.8%) had radiological hip involvement, of which 23 (88.5%) patients were male. There were significant between-group differences with respect to sacroiliac joint fusion, crossover sign, high centre edge angle and low sharp angle (P < 0.05). On logistic regression analysis, older age, sacroiliac joint fusion and pincer type were identified as independent risk factors for hip involvement.

CONCLUSION

AS with hip involvement was significantly more likely to involve sacroiliac joint fusion, which suggested that mechanical stress in adjacent joints and reduced spinopelvic range of motion may influence hip involvement.

Effect of spinal fusion on joint space narrowing of the hip: comparison among non-fusion, short fusion, and middle or long fusion

BACKGROUND

Lumbar fusion corrects spinal deformities and improves spinal complications. Hip osteoarthritis (OA) is strongly correlated with spinal mobility, and joint space narrowing of the hip after spinal fusion has gained attention. This study aimed to elucidate the effect of spinal fusion on hip joint space narrowing.

MATERIALS AND METHODS

We retrospectively examined 530 hips of 270 patients who underwent spinal surgery. All the patients underwent whole-spine radiography before and at the final follow-up. Patients were divided into three groups (N group: non-spinal fusion, S group: up to three interbody fusions, and L group: more than four interbody fusions). The rates of joint space narrowing, spinal parameters (sagittal vertical axis, thoracic kyphosis, lumbar lordosis, sacral slope, pelvic tilt, and pelvic incidence), and limb length discrepancy at the final follow-up were compared. A multilinear regression analysis was performed to identify the risk factors for the rate of joint space narrowing.

RESULTS

The rate of joint space narrowing was significantly higher in the L group than in the N and S groups (P < 0.001). No significant difference in the rate of joint space narrowing was observed between the N and S groups. Multiple linear regression analysis revealed that the number of fusion levels (p < 0.05) and follow-up period (p < 0.001) were independent risk factors for joint space narrowing. Spinal parameters at the final follow-up were not independent risk factors.

CONCLUSIONS

Long spinal fusion (more than four levels) led to significantly greater joint space narrowing of the hip than short (up to three levels) or no fusion. Spinal alignment did not affect joint space narrowing of the hip. Surgeons should be aware that more than four interbody fusions may result in worse joint space narrowing of the hip.

LEVEL OF EVIDENCE

IV, retrospective study.

Unravelling the hip-spine dilemma from the CHECK-cohort: is sagittal pelvic morphology linked to radiographic signs of femoroacetabular impingement?

INTRODUCTION

To date the aetiology of femoroacetabular impingement (FAI) is still not completely understood. There are mechanical theories that suggest symptomatic FAI is linked to sagittal pelvic morphology and spinopelvic-femoral dynamics. The aim of this study is to evaluate the relation of sagittal pelvic morphology and orientation to radiographic signs of FAI. Additionally, we test whether the relation between FAI and spinopelvic parameters differs in osteoarthritic hips.

METHODS

From a prospective, observational cohort study, 1002 patients between 45 and 65 years old with a first episode of knee or hip pain were followed for 8 years. All patients who had lateral lumbar radiographs and clinical and radiographic follow-up of the hips were included in the present study. Range of internal rotation of the hip as well as radiographic signs of FAI (alpha and Wiberg angle) and presence of hip osteoarthritis (Kellgren and Lawrence) were systematically measured at baseline. Pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS)) were measured at 8-year follow-up. Associations between PI, PT, SS and FAI parameters were tested using generalised estimating equations.

RESULTS

421 subjects, 842 hips, were included. No significant relations between PI, PT or SS and alpha or Wiberg angle were found. Comparison of hips with and without radiological sign(s) of FAI showed no differences in PI, PT or SS. There was no relation between range of internal rotation of the hip and spinopelvic parameters.

CONCLUSION

Sagittal pelvic morphology and orientation are not related to the presence of radiological signs of FAI in this study population.

Revealing the Effect of Spinopelvic Alignment on Hip Disorders

Background

Hip osteoarthritis (HOA) is a growing burden and one of the leading causes of hip pain. The relationship between the HOA and the alignment of the spinopelvic region has been intensively studied, however the issue remains controversial. Spinopelvic imbalance, HOA, and dysplasia were investigated in relation to sagittal spinopelvic parameters in this study.

Methods

We collected computerized tomography (CT) topograms of the pelvis or abdomen from 380 patients. In antero-posterior (AP) topograms, Tonnis grading, center-edge angle (CEA) and Sharp's acetabular angle (AA) measurements were performed on each patient. Lateral topograms were used to evaluate the following spinopelvic parameters for each patient: pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), sacral table angle (STA), lumbar lordosis (LL), proximal lumbar lordosis (PLL), distal lumbar lordosis (DLL), and PI-LL difference. Initially, the cohort was divided into two subgroups based on whether or not they had HOA. Then, they were divided into two subgroups based on whether or not they had dysplasia. Ultimately, it was divided in half based on the PI-LL imbalance. Statistical analyses were conducted to determine the likely correlations between the spinopelvic parameters of these subgroups. In addition, the correlations between spinopelvic parameters were investigated.

Results

There were 380 patients evaluated. We found no association between HOA or dysplasia and spinopelvic parameters. In addition, there was no association between PI-LL imbalance and HOA or dysplasia.

Conclusion

There was no difference in constant PI and STA angle, besides other variable parameters, between groups having HOA and dysplasia or not. PI-LL imbalance has no effect on HOA and dysplasia.

Lumbosacral fusion increases the risk of hip osteoarthritis

OBJECTIVE

There may be biomechanical changes in the adjacent hip joint after lumbosacral fusion. The literature has limited information on how these biomechanical changes may result in hip joint space.

MATERIAL

METHOD: Our retrospective study examined hip joint space narrowing in patients who underwent lumbosacral fusion between 2020 and 2022. In addition, spinopelvic parameters such as sacral slope, the sagittal vertical axis, pelvic incidence, lumbar lordosis, and pelvic tilt were compared in patients who underwent short-segment (up to three levels, S group) and long-segment (4 and higher levels, L group) fusions.

RESULTS

Our study found no significant relationship between spinopelvic parameters and joint space narrowing in the S and L groups. In addition, it was determined that there was more narrowing in the hip joint space in the long-segment group, and there was a positive correlation between the segment length and the narrowing in the hip joint space.

CONCLUSION

After lumbosacral fusion, narrowing of the hip joint space was observed. Particularly patients with long-segment lumbosacral fusion should be followed closely regarding hip osteoarthritis risk.

Modified unilateral iliac screw fixation with partial reduction in the treatment of high-grade spondylolisthesis at L5/S1 in adult patients: introduction of key technique, report of clinical outcomes and analysis of spinopelvic parameters

BACKGROUND

Management of high-grade spondylolisthesis (HGS) remains challenging. Spinopelvic fixation such as iliac screw (IS) was developed to deal with HGS. However concerns regarding constructs prominence and increased infection-related revision surgery have complicated it's use. We aim to introduce the modified iliac screw (IS) technique in treating high-grade L5/S1 spondylolisthesis and it's clinical and radiological outcomes.

METHODS

Patients with L5/S1 HGS who underwent modified IS fixation were enrolled. Pre- and postsurgical upright full spine radiographs were obtained to analyze sagittal imbalance, spinopelvic parameters, pelvic incidence-lumbar lordosis mismatch (PI-LL), slip percentage, slip angle (SA), and lumbosacral angle (LSA). Visual analogue scale (VAS), Oswestry disability index (ODI) were evaluated pre- and postoperatively for clinical outcomes assessment. Estimated blood loss, operating time, perioperative complications and revision surgery were documented.

RESULTS

From Jan 2018 to March 2020, 32 patients (15 males) with mean age of 58.66 ± 7.77 years were included. The mean follow-up period was 49 months. The mean operation duration was 171.67 ± 36.66 min. At the last follow-up: (1) the VAS and ODI score were significantly improved (p < 0.05), (2) PI increased by an average of 4.3°, the slip percent, SA and LSA were significantly improved (p < 0.05), (3) four patients (16.7%) with global sagittal imbalance recovered a good sagittal alignment, PI-LL within ± 10° was observed in all patients. One patient experienced wound infection. One patient underwent a revision surgery due to pseudoarthrosis at L5/S1.

CONCLUSION

The modified IS technique is safe and effective in treating L5/S1 HGS. Sparing use of offset connector could reduce hardware prominence, leading to lower wound infection rate and less revision surgery. The long-term clinical affection of increased PI value is unknown.

From the Spinopelvic Parameters to Global Alignment and Proportion Scores in Adult Spinal Deformity

In the last 20 years, sagittal alignment and balance of the spine have become one of the most important issues in the field of spine surgery. Recent studies emphasize that sagittal balance and alignment are more important for health-related quality of life. The understanding of normal and abnormal sagittal alignment of the spine is necessary for the diagnosis and appropriate treatment of adult spinal deformity (ASD), and we will discuss the currently used classification of ASD, the parameters of sagittal alignment that are essential for the diagnosis of spinal deformity, compensatory actions to maintain sagittal balance, and the relationship between sagittal alignment and clinical symptoms. Furthermore, we will also discuss the recently introduced Global Alignment and Proportion scores. The Korean Spinal Deformity Society is publishing a series of review articles on spinal deformities to help spine surgeons better understand spinal deformities.

Hip-Spine Syndrome: A Focus on the Pelvic Incidence in Hip Disorders

Since Offierski and MacNab reported a close association between the hip and spine as hip-spine syndrome in 1983, many studies on spinal alignment in hip disorders have been conducted. Notably, the pelvic incidence angle (PI) is the most important parameter and is determined by the anatomical variations in the sacroiliac joint and hip. Studies on the association of the PI with hip disorders can help in understanding the pathophysiology of hip-spine syndrome. A PI increase has been observed during the evolution of bipedal locomotion in humans and in the acquisition of gait during child development. Although the PI is a fixed parameter that is stable and unaffected by posture from adulthood onwards, it has become clear that it increases in the standing position in older people. While it may be associated with a greater risk of developing or progressing to spinal disorders, the association between the PI and hip disorders remains controversial because of the multifactorial nature of hip osteoarthritis (HOA) and the wide range of PIs in HOA (18-96°), making the interpretation of results difficult. However, several hip disorders (i.e., femoroacetabular impingement and rapid destructive coxarthrosis) have been shown to be associated with the PI. Further investigation on this topic is, therefore, warranted.

Wide anatomical variability of PI normative values within an asymptomatic population: a systematic review

PURPOSE

Studies on sagittal alignment parameters have solely focused on patients with preexisting spinal deformity. Limited data in the literature have analyzed pelvic incidence (PI) values in an asymptomatic patient population. The purpose of this study was to: (1) systematically review the literature to analyze normative PI values in asymptomatic patients; and (2) provide a more definitive geometric measurement guide for determining surgical interventions.

METHODS

A systematic review of retrospective studies was performed by searching PubMed to identify studies that analyzed PI measurements in asymptomatic subjects. The following search phrases were used: (pelvic incidence, pelvic tilt, sacral slope, sagittal alignment, radiograph, asymptomatic, normative values, and adults) using Boolean operators AND, OR and NOT. Patients with pathology involving the osseous pelvic anatomy (including fracture, infection, tumor, previous surgery, and lumbosacral fusion) that would prevent measurement of the selected parameters were not included. Pelvic incidence (PI) values were analyzed.

RESULTS

A total of 29 studies met inclusion criteria, including 3629 asymptomatic subjects who underwent standing lateral radiographs (mean age, 41.1 years; range, 24-69 years) for the purposes of analyzing pelvic incidence values. Overall, the mean PI value was 50.0° (range, 24-69) which is consistent with reported values in the literature.

CONCLUSION

Wide anatomical variability and broad clinical interpretation of PI normative values do little to guide surgical planning for successful outcomes. However, this systematic review has presented PI-stratified normative values in a large sample of asymptomatic subjects which can serve as a grounded geometric reference for spine surgeons when considering surgical intervention approaches.

Functional implant positioning in total hip arthroplasty and the role of robotic-arm assistance

INTRODUCTION

Accurate implant positioning, tailored to the phenotype and unique biomechanics of each patient is the single most important objective in achieving stability in THA and maximise range of motion. The spine-pelvis-hip construct functions as a single unit adapting to postural changes. It is widely accepted in the literature that no universaltarget exists and variations in spinopelvic mobility mandate adjustments to the surgical plan; thus bringing to the fore the concept of personalised, functional component positioning.

METHODS

This manuscript aims to outline the challenges posed by spinopelvic imbalance and present a reproducible, stepwise approach to achieve functional-component positioning. We also present the one-year functional outcomes and Patient Reported Outcome Measures of a prospective cohort operated with this technique.

RESULTS AND CONCLUSION

Robotic-arm assisted Total Hip Arthroplasty has facilitated enhanced planning based on the patient's phenotype and evidence suggests it results in more reproducible and accurate implant positioning. Preservation of offset, avoiding leg-length discrepancy, accurate restoration of the centre of rotation and accomplishing the combinedversion target are very important parameters in Total Hip Arthroplasty that affect post-operative implant longevity, patient satisfaction and clinical outcomes.

Errors in the radiographic measurement of pelvic incidence

Pelvic incidence (PI) is often quantified in patients undergoing total hip arthroplasty. Errors in radiographic PI measurements can affect clinical outcomes. The purposes of this study were (1) to evaluate the error in radiographic PI measurement in patients with hip osteoarthritis (OA) and (2) to analyze the factors related to the error. Radiographs and computer tomography (CT) images of 100 patients (24 men and 76 women; mean age 63.7 years) with unilateral OA were reviewed. The error in radiographic PI measurement was defined as the difference between the radiographic measurement of the PI (rPI) and the accurate value of PI measured using CT images (cPI). Factors related to the error in the rPI were analyzed, including the coronal and axial rotation of the pelvis on lateral radiographs. The degree of coronal and axial rotation was expressed as the angle of rotation around the anteroposterior and craniocaudal axes. The mean rPI was significantly larger than the cPI (57.8° and 54.1°, p < 0.01). The error in the rPI was 3.6° on average and 15.8° at maximum. The mean coronal and axial rotation of the pelvis was 9.6° and 4.4°, respectively. The error in the rPI positively correlated with coronal pelvic rotation and rPI, and negatively correlated with axial pelvic rotation (p < 0.01, r = 0.35, 0.43, and -0.45, respectively). The rPI was 3.6° larger on average than the cPI in patients with hip OA. Coronal and axial rotation of the pelvis and a large PI were related to the error in the rPI.

Hip-Spine Syndrome in the Nonarthritic Patient

Hip-spine syndrome refers to concurrent hip and spine pathology with overlapping symptoms. Most of the literature has studied it in relation to total hip arthroplasty literature and has been shown to increase dislocation risk. Lumbar spine and pelvic mobility have been studied less frequently in relation to nonarthritic pathologic hip states. Understanding the biomechanical relationship between the lumbar spine, pelvis, and hip can help elucidate how hip-spine syndrome affects the nonarthritic hip and how it impacts outcomes of hip arthroscopy. Changes in lumbar spine motion may be the reason certain predisposed patients develop symptomatic femoroacetabular impingement (FAI) or ischiofemoral impingement. Some athletes may be "hip users" with a low pelvic incidence, making them more reliant on hip motion due to less-intrinsic lumbopelvic motion. When these patients have FAI morphology, their increased reliance on hip motion makes them prone to experiencing femoroacetabular contact and concurrent symptoms. Other athletes may be "spine users," with larger pelvic incidence and more baseline lumbopelvic motion, making them less reliant on hip motion and therefore less prone to experiencing hip impingement even with hip FAI morphology. Hip-spine syndrome also appears to have an impact on patient selection, role of nonoperative treatment, and hip arthroscopy surgical outcomes. Identifying patients with concurrent pathology may allow surgeons to recommend targeted physical therapy or counsel patients better on their expectations after surgery.

The Impact of Spinopelvic Parameters on Hip Degeneration After Spinal Fusion

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

This study aimed to investigate the effects of spinopelvic alignment parameters after spinal fusion on the rate of joint space narrowing in nonarthritic hips.

SUMMARY OF BACKGROUND DATA

Spinal fusion affects the forces on the adjacent hip joint. Therefore, hip joint narrowing may be increased after spinal fusion surgery. However, the relationship between spinal alignment and hip degeneration remains unclarified.

METHODS

We retrospectively reviewed data from patients who underwent lumbar spinal fusion from 2011 to 2018 at our institute. Patients with hip osteoarthritis (Kellgren-Lawrence grade ≥II) or hip dysplasia were excluded. The rate of hip joint space narrowing after spinal fusion was measured in 191 patients (382 hips). We assessed the effects of the following spinopelvic alignment parameters on the joint narrowing rate: pelvic tilt, sacral slope (SS), pelvic incidence (PI), lumbar lordosis (LL), PI-LL, sagittal vertical axis, and distance between the C7 plumb line, and the central sacral vertical line (C7-CSVL).

RESULTS

The hip joint narrowing rate was greater when four or more levels were fused compared with single-level fusion. After adjusting for the effects of patient-related factors, the alignment parameters significantly associated with the hip joint narrowing rate were the PI ( P = 0.0002), SS ( P = 0.047), and PI-LL ( P = 0.0022). A subgroup analysis of patients who underwent long fusion (four or more levels combined with iliac screws) also indicated that the PI ( P = 0.013), SS ( P = 0.0054), and PI-LL ( P = 0.046) were associated with the hip joint narrowing rate.

CONCLUSION

The PI, SS, and PI-LL were associated with the progression of hip joint narrowing after spinal fusion, especially after fusion of four or more levels. Surgeons need to be aware of the risk of increased hip joint narrowing in patients with a large PI, SS, and PI-LL after fusion surgery.

Acetabular labral tear is associated with high pelvic incidence with or without femoroacetabular impingement morphology

PURPOSE

The aim of this study was to investigate the association between pelvic sagittal parameters and acetabular labral tears.

METHODS

Three-hundred and sixty-five patients (449 hips) who underwent magnetic resonance imaging (MRI) or magnetic resonance arthrogram (MRA) for hip pain were enrolled in this study. Pelvic sagittal parameters, including the pelvic incidence, pelvic tilt, and sacral slope, were measured with a standing lumbosacral lateral radiograph. All subjects were divided into two groups according to the presence or absence of radiologic acetabular labral tears and compared. Furthermore, the two groups were divided into subgroups according to whether femoroacetabular impingement (FAI) morphology was present or not and compared.

RESULTS

Pelvic incidence was greater in the labral tear group than in the non-labral tear group (52.3° ± 8.2° versus 47.1° ± 6.8°, p < 0.001). After accounting for potentially confounding variables, we found that higher age (odds ratio 1.04, 95% confidence interval [CI] 1.02 to 1.06, p = 0.001), FAI (odds ratio 15.11, 95% CI 7.43 to 30.75, p < 0.001), and high pelvic incidence (odds ratio 1.13, 95% CI 1.09 to 1.17, p < 0.001) were independently associated with acetabular labral tear. When only the patients without FAI (308 hips) were divided into groups with and without acetabular labral tear, we found that higher age (odds ratio 1.03, 95% CI 1.01 to 1.06, p = 0.008) and high pelvic incidence (odds ratio 1.15, 95% CI 1.11 to 1.19, p < 0.001) were independently associated with acetabular labral tear.

CONCLUSION

Acetabular labral tear is associated with high pelvic incidence with or without FAI morphology.

LEVEL OF EVIDENCE

III.

Pelvic incidence is not associated with the development of hip osteoarthritis

AIMS

Pelvic incidence (PI) is considered an important anatomical parameter for determining the sagittal balance of the spine. The contribution of an abnormal PI to hip osteoarthritis (OA) remains controversial. In this study, we aimed to investigate the relationship between PI and hip OA, and the difference in PI between hip OA without anatomical abnormalities (primary OA) and hip OA with developmental dysplasia of the hip (DDH-OA).

METHODS

In this study, 100 patients each of primary OA, DDH-OA, and control subjects with no history of hip disease were included. CT images were used to measure PI, sagittal femoral head coverage, α angle, and acetabular anteversion. PI was also subdivided into three categories: high PI (larger than 64.0°), medium PI (42.0° to 64.0°), and low PI (less than 42.0°). The anterior centre edge angles, posterior centre edge angles, and total sagittal femoral head coverage were measured. The correlations between PI and sagittal femoral head coverage, α angle, and acetabular anteversion were examined.

RESULTS

No significant difference in PI was observed between the three groups. There was no significant difference between the groups in terms of the category distribution of PI. The DDH-OA group had lower mean sagittal femoral head coverage than the other groups. There were no significant correlations between PI and other anatomical factors, including sagittal femoral head coverage, α angle, and acetabular anteversion.

CONCLUSION

No associations were found between mean PI values or PI categories and hip OA. Furthermore, there was no difference in PI between patients with primary OA and DDH-OA. From our evaluation, we found no evidence of PI being an independent factor associated with the development of hip OA. Cite this article: Bone Joint J 2021;103-B(11):1656-1661.

Greater trochanteric pain syndrome in women: Analysis of magnetic resonance, sagittal alignment, muscular strength and endurance of the hip and trunk

INTRODUCTION

There are many studies on the Greater Trochanteric Pain Syndrome (GTPS), however its relationship with radiographic and biomechanics parameters is not established.

OBJECTIVE

To compare the magnetic resonance images (MRI) of the hip, radiographic parameters of sagittal alignment (pelvic incidence, sacral slope and lumbar lordosis), muscular strength and endurance in women with and without GTPS.

METHODS

Forty women, age over 45, IMC <30 Kg/m2 and sedentary, were recruited and distributed in two groups: GTPS group (GTPSG, n = 20) and Control group (CG, n = 20). All participants underwent MRI scans and X-ray for sagittal alignment analysis in the hip and performed tests for muscular strength and endurance of the hip and trunk.

RESULTS

No differences were found between the GTPSG and CG for the frequency of tendinopathy (P = .30), peritendinitis (P = .10), bursitis (P = .68) and enthesitis (P = .15), however the gluteus medius tendon tear was more prevalent in GTPSG (P = .05). There were no differences in radiographic parameters for pelvic incidence (P > .05), sacral slope (P > .05) and lumbar lordosis (P > .05). The GTPSG showed lower strength of all hip muscle groups (abductors, adductors, flexors, extensors and rotators; P < .01 for all), as well as lower endurance in the Supine Bridge test and Prone bridge test (P < .01).

CONCLUSION

The results of the MRI and radiographic parameters did not differentiate women with and without GTPS. However, the evaluation of muscle strength and endurance can establish the difference between groups.

Automatic Characterization of Pelvic and Sacral Measures from 200 Subjects

BACKGROUND

An understanding of pelvic and acetabular morphology and orientation is required for accurate surgical reconstruction of the hip and spine, as well for component placement in a total hip arthroplasty. Our objectives were to develop an automated system for measuring pelvic and sacral orientations utilizing computed tomographic (CT) scans and to characterize these measures across 200 asymptomatic subjects.

METHODS

An automated feature recognition algorithm was created to identify acetabular and pelvic orientation across 200 scans generated for non-musculoskeletal conditions. Three-dimensional models were generated from CT data to serve as inputs to the algorithm. Acetabular orientation was defined by comparing a plane fit to the acetabular rim with the anterior pelvic plane. Pelvic inclination, pelvic tilt, and sacral slope were defined as the angles between landmarks identified across the pelvis: pubic tubercles, acetabular center, left and right anterior superior iliac spines, and sacral plate.

RESULTS

The mean sacral slope was 36.49°, the mean pelvic tilt was 15.60°, and the mean pelvic incidence was 52.05°. The mean sacropubic angle was 32.48° and the mean pelvic-Lewinnek angle was 8.93°. Significant differences between male and female subjects were observed in the sacral slope (mean difference, 4.72°; p < 0.05), pelvic tilt α (mean difference, 4.17°; p < 0.05), pelvic tilt γ (mean difference, 3.06°; p < 0.05), and the pelvic-Lewinnek angle (mean difference, 1.76°; p < 0.05). The comparison of acetabular orientation measures with those in a prior study of the same cohort yielded intraclass correlation coefficients (ICCs) all above 0.97. The validation of sacral orientation via manual measurement also yielded ICC values all at or above 0.97.

CONCLUSIONS

Our algorithm showed a high degree of consistency in acetabular orientation measures with respect to a prior study of the same cohort. The measures of pelvic orientation were found to be accurate and reliable when compared with manual measurements of the same data set. All measurements of pelvic orientation were consistent with the means reported in the literature.

CLINICAL RELEVANCE

An accurate and reproducible, automated technique for determining pelvic and acetabular orientation provides a way to characterize these measures as an aid in clinical diagnosis and preoperative planning.

Femoroacetabular Impingement and Acetabular Labral Tears - Part 2: Clinical Diagnosis, Physical Examination and Imaging

The clinical diagnosis of femoral acetabular impingement (FAI) continues to evolve as the understanding of normal and pathological hips progresses. Femoral acetabular impingement is currently defined as a syndrome in which the diagnosis consists of the combination of a previously-obtained comprehensive clinical history, followed by a consistent and standardized physical examination with specific orthopedic maneuvers. Additionally, radiographic and tomographic examinations are used for the morphological evaluation of the hip, and to ascertain the existence of sequelae of childhood hip diseases and the presence of osteoarthritis. The understanding of the femoral and acetabular morphologies and versions associated with images of labral and osteochondral lesions obtained through magnetic resonance imaging (MRI) contributes to the confirmation of this syndrome in symptomatic patients, and helps in the exclusion of differential diagnoses such as iliopsoas tendon snaps, subspine impingement, ischiofemoral impingement, and other hip joint pathologies.

Unravelling the knee-hip-spine trilemma from the CHECK study

AIMS

The aetiologies of common degenerative spine, hip, and knee pathologies are still not completely understood. Mechanical theories have suggested that those diseases are related to sagittal pelvic morphology and spinopelvic-femoral dynamics. The link between the most widely used parameter for sagittal pelvic morphology, pelvic incidence (PI), and the onset of degenerative lumbar, hip, and knee pathologies has not been studied in a large-scale setting.

METHODS

A total of 421 patients from the Cohort Hip and Cohort Knee (CHECK) database, a population-based observational cohort, with hip and knee complaints < 6 months, aged between 45 and 65 years old, and with lateral lumbar, hip, and knee radiographs available, were included. Sagittal spinopelvic parameters and pathologies (spondylolisthesis and degenerative disc disease (DDD)) were measured at eight-year follow-up and characteristics of hip and knee osteoarthritis (OA) at baseline and eight-year follow-up. Epidemiology of the degenerative disorders and clinical outcome scores (hip and knee pain and Western Ontario and McMaster Universities Osteoarthritis Index) were compared between low PI (< 50°), normal PI (50° to 60°), and high PI (> 60°) using generalized estimating equations.

RESULTS

Demographic details were not different between the different PI groups. L4 to L5 and L5 to S1 spondylolisthesis were more frequently present in subjects with high PI compared to low PI (L4 to L5, OR 3.717; p = 0.024 vs L5 to S1 OR 7.751; p = 0.001). L5 to S1 DDD occurred more in patients with low PI compared to high PI (OR 1.889; p = 0.010), whereas there were no differences in L4 to L5 DDD among individuals with a different PI. The incidence of hip OA was higher in participants with low PI compared to normal (OR 1.262; p = 0.414) or high PI (OR 1.337; p = 0.274), but not statistically different. The incidence of knee OA was higher in individuals with a high PI compared to low PI (OR 1.620; p = 0.034).

CONCLUSION

High PI is a risk factor for development of spondylolisthesis and knee OA. Low pelvic incidence is related to DDD, and may be linked to OA of the hip. Level of Evidence: 1b Cite this article: Bone Joint J 2020;102-B(9):1261-1267.

High Pelvic Incidence Is Associated with Disease Progression in Nontraumatic Osteonecrosis of the Femoral Head

BACKGROUND

Although several factors exacerbate osteonecrosis of the femoral head (ONFH), little is known about whether pelvic sagittal parameters are associated with a greater risk of ONFH progression.

QUESTIONS/PURPOSES

The purpose of this study was to investigate the association between pelvic sagittal parameters and disease progression (collapse of the femoral head) in patients with nontraumatic ONFH.

METHODS

From March 2010 through December 2016, we saw 401 patients with unilateral ONFH diagnosed at an outpatient clinic using plain radiography and MRI that were retrospectively reviewed. Of those, 276 patients met our inclusion criteria: Association Research Circulation Osseous (ARCO) Stage I or II nontraumatic unilateral ONFH without femoral head collapse, older than 18 years, and no prior surgical treatment. In all, 74% (203 of 276) of hips had complete follow-up (clinical and radiographic) at a minimum of 2 years. The pelvic sagittal parameters (pelvic incidence, pelvic tilt, and sacral slope) of all patients were measured with standing radiographs by two observers. Progression of disease and potential collapse of the femoral head of all patients (ARCO Stage ≥ III) was examined using radiography every 2 to 3 months after the first outpatient clinic visit. If patients with intractable pain associated with collapse of the femoral head did not respond to nonoperative treatment, THA was performed during the follow-up period. The patients were divided into two groups for comparison: those whose femoral head collapsed within 12 months (rapid progression group) and those whose femoral head did not collapse (nonrapid progression group). The rapid progression group consisted of 49 men and 55 women with a mean age of 55 years; the nonrapid progression group consisted of 60 men and 39 women with a mean age of 56 years. Factors such as age, sex, BMI, size of necrotic lesions, location of necrosis, necrosis risk factor associated with the rapid progression of disease were analyzed using an exploratory univariate analysis followed by a multivariate analysis.

RESULTS

Pelvic incidence (53° ± 9° versus 49° ± 7°; p < 0.01) and sacral slope (38° ± 9° versus 33° ± 7°; p < 0.01) were greater in the rapid progression group than in the non-rapid progression group. After accounting for potentially confounding variables like age, sex, BMI, size of necrotic lesions, location of necrosis, and necrosis risk factors, the only variable we found that was independently associated with more rapid disease progression was high (> 55°) pelvic incidence (odds ratio, 0.95 [95% CI 0.91 to 0.99]; p = 0.03).

CONCLUSIONS

After controlling for potential confounders such as age, sex, BMI, size of necrotic lesions, location of necrosis, and necrosis risk factors, we found that a high pelvic incidence was associated with a greater likelihood of femoral head collapse in patients with nontraumatic ONFH. Assessing pelvic sagittal parameters in patients with early nontraumatic ONFH may help anticipate which patients are at risk for femoral head collapse, but future prospective studies are needed to confirm these findings.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Reliability of hip range of motion measurement among experienced arthroscopic hip preservation surgeons

The aim of this study was to determine (i) the reliability of hip range of motion measurement among experienced arthroscopic hip preservation surgeons and (ii) the magnitude of hip flexion change with posterior pelvic tilt. Five experienced arthroscopic hip preservation surgeons (5–18 years of hip surgery experience) performed passive hip range of motion (internal and external rotation), flexion (contralateral hip extended) and flexion with posterior pelvic tilt (contralateral hip maximally flexed) on five young healthy asymptomatic volunteers (three males, two females; 34.4 ± 10.7 years of age). Motion was measured via digital photography and goniometry. Inter-observer reliability was calculated via two-way mixed, single measures, intra-class correlation coefficient. Paired t-test was utilized to compare hip flexion (with contralateral hip extended) to hip flexion with posterior pelvic tilt (with contralateral hip in forced flexion). The reliabilities of measurements of hip flexion with posterior pelvic tilt and external rotation were excellent, that of hip flexion was fair, and that of hip internal rotation was poor. The magnitude of hip flexion increase with posterior pelvic tilt was 17.0° ± 3.0° (P < 0.001). The reliability of hip range of motion measurement by five experienced arthroscopic hip preservation surgeons was excellent for measures of hip flexion with posterior pelvic tilt and external rotation. Contralateral maximal hip flexion significantly increased ipsilateral hip flexion (approximately 17°).

Level of Evidence: Diagnostic, level III (without consistently applied reference standard)

Iliopsoas snapping hip: improving the diagnostic value of magnetic resonance imaging with a novel parameter

OBJECTIVE

To illustrate an advanced imaging parameter that describes the course of the iliopsoas tendon, and evaluate its correlations with iliopsoas internal hip snapping syndrome.

METHODS

This retrospective cohort study reviewed hip MRI images of all patients seen by a single surgeon between January 2015 and March 2016. The comparison group included all patients with clinical internal hip snapping, versus the control group that did not. MRI images were processed using minimum intensity projection. Measurements obtained of the pelvis and course of the iliopsoas tendon included: pelvic incidence, coronal angle, and sagittal opening angle (SOA). Comparison of measurements between the groups was performed with Mann-Whitney U analysis and receiver operator curve (ROC) plotting, with a significance cutoff of p = 0.05.

RESULTS

The control group (n = 85) and comparison group (n = 48) demonstrated no difference in age or gender. Pelvic incidence was similar [51.3 (± 10.7) degrees control versus 52.2 (± 7.7) degrees comparison (p = 0.36)], as was coronal angle [13.9 (± 4.6) degrees control versus 14.8 (±4.8) degrees comparison (p = 0.15)]. There was a significant difference in SOA [137.0 (± 5.9) degrees control versus 141.9 (± 6.5) degrees comparison (p < 0.01)]. ROC analysis revealed SOA threshold of 140 degrees for clinical IP hip snapping (p < 0.01), with odds ratio 5.2 (2.4-11.3) for SOA > 140 degrees.

CONCLUSIONS

Iliopsoas hip snapping is often part of a more complex disease process. While challenging to diagnose, advanced imaging parameters, like the sagittal opening angle, relate with clinical pathology. The SOA offers diagnostic value, with a threshold of greater than 140 degrees significantly correlating with clinical presentation.