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

Hip-Spine Relationship in Femoroacetabular Impingement: Does Hip Arthroscopy Affect Pelvic Mobility?

BACKGROUND

Femoroacetabular impingement (FAI) is a well-recognized cause of hip pain in adults. The hip-spine relationship between the femur, pelvis, and lumbosacral spine has garnered recent attention in hip arthroplasty. However, the hip-spine relationship has not been well described in patients with FAI.

QUESTIONS/PURPOSES

The goal of this study was to determine whether lumbopelvic mobility is altered after hip arthroscopy. Does lumbopelvic motion, defined as the difference between standing and sitting measurements for sacral slope (SS), pelvic tilt (PT), and pelvic-femoral angle (PFA), change after hip arthroscopy for FAI?

METHODS

Between June 2019 and March 2020, one surgeon performed 43 arthroscopic hip labral repair surgeries for FAI in active-duty military servicemembers. The diagnosis of FAI was made clinically and with standing AP pelvis, Dunn lateral, and false-profile radiographs. All patients underwent advanced imaging, including 3T MRI to identify labral tears and three-dimensional CT to characterize bony morphology. The musculoskeletal radiologist measured alpha angle, lateral center-edge angle, anterior center-edge angle, neck-shaft angle, femoral version, and acetabular version at 1200, 1300, 1400, and 1500 using CT. Patients also underwent a diagnostic fluoroscopic-guided injection with local anesthetic and corticosteroids; > 50% pain relief was considered a positive response to injection. During the study period, the operative surgeon did not perform any open procedures for FAI; all surgical treatment was performed arthroscopically. Preoperative sitting and standing radiographs were obtained from all patients. Ninety-five percent (41 of 43) of the cohort underwent adequate postoperative sitting and standing radiographs obtained 2 months after surgery, which were used for analysis in this retrospective study. The cohort was 71% male (29 of 41) and 29% female (12 of 41), with a mean age of 33 years. Within this military population undergoing primary hip arthroscopy, 30 were enlisted servicemembers and 11 were officers. SS, PT, and PFA were measured by four observers on sitting and standing lateral pelvic radiographs. Interclass correlation statistics indicated high reliability for SS, PT, and seated PFA (κ range 0.75 to 1.00) compared with lower reliability for standing PFA measurements (κ range 0.59 to 0.65). The delta between standing and sitting SS, PT, and PFA was compared perioperatively. Student t-test analysis was used for comparisons (p < 0.05).

RESULTS

Lumbosacral motion in the sitting position changed after hip arthroscopy. Measurements of the standing lumbopelvic mobility did not change with hip arthroscopy: ΔSS = 1.8° (p = 0.13), ΔPT = -0.56° (p = 0.50), ΔPFA = 0.54° (p = 0.50). However, measurements of sitting lumbopelvic mobility did change with hip arthroscopy. SS diminished (Δ = -4.3°; p = 0.008), PT increased (Δ = +3.9°; p = 0.03), and PFA increased (Δ = +4.3°; p = 0.03) when patients were seated. These data may indicate that in the sitting position, less motion occurs at the spine and more motion occurs at the hip after hip arthroscopy.

CONCLUSION

This radiographic study suggested that lumbopelvic mobility in the seated position is affected by hip arthroscopy for FAI. The clinical significance of this observation remains unknown but warrants further investigation. Future studies should seek to determine whether changes in lumbopelvic mobility after hip arthroscopy have clinically relevant effects, either positive or negative.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Hip-spine syndrome from the perspective of radiology: correlations between hip joint disease and lumbar spine MRI findings

BackgroundHip joint (HJ) pain, which may be caused by lumbar disease, is a common complaint.PurposeTo investigate the prevalence and specific correlations between various HJ diseases and lumbar spine magnetic resonance imaging (MRI) findings in patients with HJ pain.Material and MethodsPatients with the chief complaint of HJ pain who had both HJ MRI and lumbar MRI were retrospectively included. According to the existence of HJ disease, patients were divided into the following groups: non-HJ disease; osteoarthritis (OA); femoroacetabular impingement (FAI); ischiofemoral impingement (IFI); greater trochanter pain syndrome (GTPS); and other diseases. The prevalence of major lumbar MRI findings was compared. Correlations between HJ disease and major lumbar MR findings were explored.ResultsA total of 585 patients were included, of which 566 (96.8%) had major findings on lumbar MRI. The HJ disease group was more likely to be female and had more spondylolisthesis, while the non-HJ disease group had more low back or leg pain. The OA group was older and correlated with lumbar spinal stenosis (contingency coefficient = 0.164) and spondylolisthesis (contingency coefficient = 0.095). The FAI group was younger, had more male patients, and correlated with lumbosacral transitional vertebrae (contingency coefficient = 0.122). The IFI group was older, had more female patients, and correlated with facet joint osteoarthritis (contingency coefficient = 0.168). The GTPS group was older, had more female patients, and correlated with spondylolisthesis (contingency coefficient = 0.097).ConclusionMajor lumbar MRI findings were frequently observed in patients with hip pain, even in patients without HJ disease. Specific lumbar MRI finding correlated with different HJ disease.

Achieving cup target as per spinopelvic assessment is associated with improved THA outcome: a prospective, multicentre study

BACKGROUND

Different methods can help to optimise sagittal cup orientation in total hip arthroplasty (THA) based on individual spinopelvic characteristics. This study aimed to: (1) assess how often combined sagittal index (CSI) and hip-spine-classification targets were achieved post THA; (2) compare anteversion/inclination between cups in-/outside optimal CSI zone; and (3) determine association with outcome.

METHODS

This is a multicentre, prospective, case-cohort study of 435 primary THA for osteoarthritis (53% females; age: 65 ± 12 years; follow-up: 2.4 ± 0.6 years) (58% lateral, 29% anterior, 13% posterior approach). No robotics or dual-mobility were used. Patients underwent spinopelvic radiographs to measure parameters including lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), pelvic femoral angle (PFA), and ante-inclination (AI) on lateral spinopelvic radiographs. Unbalanced spine was defined as PI - LL ⩾ 10° (PI: pelvic incidence; LL: lumbar lordosis), stiffness as ∆LL < 20°. Optimal cup orientation was based on CSI targets: 205-245° for balanced spine (n = 327), or 215-235° for unbalanced spine (n = 108), hip-spine classification targets (±5°), and conventional inclination/anteversion (40/20° ± 10°) target. Patient-reported outcome was measured using Oxford Hip Score (OHS).

RESULTS

CSI targets were achieved in 60% (n = 261/435), whilst 44% had cup position within hip-spine classification targets (n = 125/284). Anteversion was higher among cups within CSI targets (26° ± 8° vs. 22° ± 10°; p < 0.001). Overall dislocation rate was 0.9% (n = 4/435), without difference whether CSI targets were achieved (0.4% vs. 1.7%; p = 0.178). Postoperative OHS was better among those within CSI targets (42 ± 8 vs. 40 ± 9; p = 0.003) or within hip-spine-classification targets (p = 0.028), but not according to conventional orientation (p = 0.384).

CONCLUSIONS

Awareness of adverse spinopelvic characteristics and using sagittal characteristics (especially CSI) can help surgeons to achieve optimal cup orientation, improving outcome and reducing dislocation risk post-THA.

Hip Arthroscopy Patients with Concomitant Low Back Pain Show Clinical Improvement and Time-Dependent Survivorship Comparable to Those Without Low Back Pain: A Propensity Matched Study at Long-Term Follow-Up

PURPOSE

The purpose of this study was to evaluate patient-reported outcomes (PROs), achievement of clinically significant outcomes (CSOs), and reoperation-free survivorship at long-term follow-up following primary hip arthroscopy (HA) for femoroacetabular impingement syndrome (FAIS) in patients with and without preoperative lower back pain (LBP).

METHODS

A repository was reviewed to identify patients who underwent primary HA for FAIS between 1/2012-5/2014 with 10-year follow-up. Exclusion criteria included prior ipsilateral hip surgery, concomitant procedures, congenital hip disorders, non-FAIS hip pathologies, Tönnis grade >1, history of platelet-rich plasma injections, and missing 10-year follow-up. Patients that self-reported preoperative, concomitant LBP were propensity-matched 1:1 to non-LBP patients by age, sex, and body-mass-index (BMI). PROs collected included Hip Outcome Score-Activities of Daily Living and Sports Subscale (HOS-ADL/HOS-SS), 12-item International Hip Outcome Tool (iHOT-12), modified Harris Hip Score (mHHS), and Visual Analog Scale (VAS) for Pain and Satisfaction. Minimal clinically important difference (MCID) and patient acceptable symptom state (PASS) were compared. Subgroup analysis was conducted comparing females and males with LBP. Reoperation-free survivorship was compared with Kaplan-Meier analysis. An a priori power analysis determined sample size.

RESULTS

Overall, 69 hips in 67 LBP patients were matched to 69 hips in 67 non-LBP patients. Demographics were similar between groups, including age (39.22±10.3 vs. 38.99±10.7 years, P=0.90), sex (55.1% vs. 55.1% female, P=1.0), and BMI (26.15±4.6 vs. 26.36±5.1 kg/m2, P=0.80). Average follow-up duration was 10.43±0.4 years. The most common cause of LBP was degenerative lumbar or sacral conditions, including degenerative disc disease (DDD), degenerative joint disease (DJD), or spondylosis, accounting for 38.8% (26/69) of the cohort. Mean preoperative HOS-ADL (62.38±18.7 vs. 64.45±21.1, P=0.57), HOS-SS (37.83±22.6 vs. 45.67±24.7, P=0.09), mHHS (53.63±14.6 vs. 57.01±14.6, P=0.22), iHOT-12 (33.29±19.0 vs. 39.49±15.8, P=0.27), and VAS Pain (71.88±18.3 vs. 71.87±19.1, P=1.0) were similar between LBP and non-LBP patients. Additionally, the mean 10-year follow-up HOS-ADL (81.48±21.2 vs. 79.57±22.0, P=0.66), HOS-SS (66.87±31.3 vs. 67.36±30.4, P=0.94), mHHS (74.15±18.8 vs. 73.19±17.7, P=0.79), iHOT-12 (77.77±23.3 vs. 69.63±29.3, P=0.13), VAS Pain (23.98±25.0 vs. 32.19±28.4, P=0.11), and VAS Satisfaction (83.47±25.3 vs. 81.43±29.7, P=0.73) were similar between LBP and non-LBP patients. LBP and non-LBP patients had comparable MCID achievement for HOS-ADL (72% vs. 56%, P=0.13), HOS-SS (74% vs. 50%, P=0.06), mHHS (74% vs. 65%, P=0.47), iHOT-12 (83% vs. 72%, P=0.67), VAS Pain (89% vs. 75%, P=0.10), and any PRO (98% vs. 93%, P=0.32). Similarly, LBP and non-LBP patients had comparable PASS achievement for HOS-ADL (64% vs. 65%, P=1.0), HOS-SS (66% vs. 69%, P=0.83), mHHS (64% vs. 60%, P=0.84), iHOT-12 (65% vs 61%, P=0.84), VAS Pain (55% vs. 50%, P=0.71), and any PRO (76% vs. 80%, P=0.81). Subgroup analysis revealed no significant differences between females and males with LBP in preoperative or 10-year follow-up PROs as well as MCID and PASS achievement rates. Reoperation-free survivorship was comparable (P=1.0).

CONCLUSIONS

Patients undergoing primary HA for FAIS with concomitant LBP may achieve comparable PROs, CSOs, and reoperation-free time-dependent survivorship to patients without LBP at long-term follow-up.

LEVEL OF EVIDENCE

Retrospective, Matched Case-Control Study, Level III.

Lewinnek zone not "the be-all and end-all" functional planning for acetabular component positioning in total hip arthroplasty

BACKGROUND

Proper positioning of a total hip arthroplasty (THA) plays a crucial role in the success and long-term survivorship of the implant. Cup positioning within the Lewinnek Safe Zone (LSZ) does not, however, avoid implant dislocation. Thus, the concept of a functional cup position has been introduced. The purpose of this study was to assess the discrepancy between LSZ and the acetabular cup position suggested by the patient's specific functional planning. The hypothesis was that a mismatch does exist.

METHODS

One hundred consecutive patients with primary hip osteoarthritis undergoing primary THA with a personalized functional preoperative planning and patient-specific cup implantation system were enrolled. Anatomical and spino-pelvic functional parameters were recorded and, for each patient, a "safe cup orientation" was suggested. The suggested functional safe zone was compared to the LSZ.

RESULTS

The mean suggested inclination was 39° ± 3° (range 32°-45°). The mean suggested anteversion was 21° ± 3° (range 12°-28°). The patient's functional acetabular inclination (AI) corresponded to the LSZ in one of the 100 patients, whereas the acetabular anteversion (AV) was outside the LSZ in 8 of the 100 patients. The mean pelvic tilt while standing and sitting were 0.5° ± 7° (range 21°-45°) and -6° ± 16.7° (range -63°-33°), respectively. The mean pelvic incidence was 52° ± 9.7° (range 33°-83°).

CONCLUSION

When a functional patient's specific preoperative planning is performed, the LZS does not correspond to the patient's functional safe zone in about 8% of patients. The concept of a universal safe zone should be revisited, and a functional personalized safe zone may have to be more widely considered.

Hip-lumbar mobility loss affects quality of life in patients undergoing both lumbar fusion and total hip arthroplasty

Aims

Overall sagittal flexion is restricted in patients who have undergone both lumbar fusion and total hip arthroplasty (THA). However, it is not evident to what extent this movement is restricted in these patients and how this influences quality of life (QoL). The purpose of this study was to determine the extent to which hip-lumbar mobility is decreased in these patients, and how this affects their QoL score.

Methods

Patients who underwent primary THA at our hospital between January 2010 and March 2021 were considered (n = 976). Among them, 44 patients who underwent lumbar fusion were included as cases, and 44 THA patients without lumbar disease matched by age, sex, and BMI as Control T. Among those who underwent lumbar fusion, 44 patients without hip abnormalities matched by age, sex, and BMI to the cases were considered as Control F. Outcome and spinopelvic parameters were measured radiologically in extension and flexed-seated positions. Hip, lumbar, and hip-lumbar mobility were calculated as parameter changes between positions.

Results

There were 20 male and 112 female patients in the case and control groups, with a mean age of 77 years (5 to 94) and a mean BMI of 24 kg/m2 (15 to 34). QoL score and hip-lumbar mobility were reduced in cases compared to Control T and F, and were further reduced as the number of fused levels increased. Hip-lumbar mobility was associated with reduction in activity-related QoL, mostly for those activities requiring sagittal flexion.

Conclusion

This study confirmed that hip-lumbar mobility is a factor that influences activity, most of all those requiring overall sagittal flexion. Clinicians should focus on hip-lumbar mobility and counteract disability by suggesting appropriate assistive devices.

Impact of Supine, Standing, and Sitting Postures on Acetabular Component Orientation in Total Hip Arthroplasty

INTRODUCTION

Total hip arthroplasty (THA) is a highly effective surgical procedure aimed at relieving pain and restoring function in patients with severe hip joint disorders, such as osteoarthritis, osteonecrosis, and developmental dysplasia of the hip (DDH). The primary goals of THA are to alleviate pain, improve joint function, and enhance the quality of life by providing a stable and well-functioning hip joint. Accurate orientation of the acetabular component is critical for the success of THA, ensuring optimal joint mechanics, reducing the risk of complications such as dislocation and wear, and enhancing implant longevity. Postural changes significantly influence the orientation and stability of the acetabular component. Traditional supine evaluations may not accurately reflect the functional alignment during daily activities, necessitating more dynamic assessment methods.

MATERIALS AND METHODS

The study was conducted at a tertiary care hospital in Chennai, Tamil Nadu, India, from March 2018 to October 2019. It was a prospective study involving 27 patients who underwent primary THA. Exclusion criteria included bilateral or revision THA, a history of spine or hip surgery, neurological or musculoskeletal disorders, or lower limb deformities. Computed tomography scans were performed in supine, simulated standing, and sitting postures. Pre-operative and post-operative evaluations included standing and sitting lateral lumbosacral spine radiographs. Measurements at the spinopelvic junction evaluated spinal balance and pelvic compensation. The anatomical acetabular anteversion (AAA) was determined in supine, standing, and sitting positions using CT scans.

RESULTS

The study included 27 patients aged 19 to 66 (mean age 37). Most patients (17, 63%) were between 21-40 years old. Osteoarthritis was the most common indication for THA (15, 55.6%), followed by osteonecrosis (six, 22.2%), DDH (four, 14.8%), and post-traumatic arthritis (two, 7.4%). Spinopelvic mobility assessment showed 15 (55.6%) participants with normal mobility, eight (29.6%) who were hypermobile, three (11.1%) stiff, and one (3.7%) who were severely stiff. Significant variability in acetabular component orientation was observed across postures: mean supine AAA was 11.04° (SD 14.44°), standing AAA was 13.07° (SD 14.38°), and sitting AAA was 30.93° (SD 14.28°). The mean difference between sitting and standing AAA was 17.85° (SD 11.83°). Statistical analysis revealed significant differences in acetabular component orientation across different postures (p < 0.05).

CONCLUSION

This study highlights the critical need for dynamic and individualised approaches in THA. The findings underscore the importance of dynamic pre-operative assessments, including standing and sitting radiographs, to optimise component placement. Clinical recommendations include tailoring surgical techniques based on individual spinopelvic mobility, utilising advanced intraoperative tools for precise placement, and developing customised post-operative rehabilitation programs.

En bloc resection of the ligamentum flavum for bilateral decompression in unilateral biportal endoscopic transforaminal lumbar interbody fusion: a 2-year follow-up study

BACKGROUND

Unilateral biportal endoscopic transforaminal lumbar interbody fusion (UBE-TLIF) is a minimally invasive procedure for treating lumbar degenerative diseases. However, the use of endoscopic lumbar interbody fusion does not completely eliminate the risk of dural and nerve root injuries. This study has refined UBE-TLIF to incorporate en bloc resection of the ligamentum flavum for bilateral decompression and aim to detail the surgical procedure and evaluate the clinical outcomes of this modification.

METHODS

This study analyzes the outcomes of 109 consecutive patients treated by a single surgeon for lumbar degenerative disease using UBE-TLIF. Patients were divided into two groups: Group A (51 patients) underwent en bloc resection of the ligamentum flavum, while Group B (58 patients) underwent routine piecemeal resection. Assessed outcomes included surgery-related complications, operation time, estimated blood loss, postoperative stay, visual analogue scale (VAS) score, and Oswestry Disability Index (ODI). The surgical technique is detailed within the study.

RESULTS

In Group A, no nerve root or dura injuries were observed, whereas Group B reported one case of nerve root injury and three dura tears. The average operation time for Group A was shorter than that for Group B; however, the difference was not statistically significant (P > 0.05). No significant differences were found in the VAS score, ODI, estimated blood loss, or postoperative stay between the groups during follow-up.

CONCLUSIONS

En bloc resection of the ligamentum flavum for bilateral decompression in UBE-TLIF demonstrates satisfactory clinical outcomes and low perioperative complications rates, offering a safe and innovative alternative for the treatment of lumbar degenerative disease.

Patient-Specific Acetabular Safe Zones in Total Hip Arthroplasty: External Validation of a Quantitative Approach to Preoperatively Templating Spinopelvic Parameters

Background

Spinopelvic mechanics are critical in total hip arthroplasty; however, there is no established consensus for adjusting acetabular component positioning based on spinopelvic parameters. This study aimed to (1) validate a recently developed Patient-Specific acetabular safe-zone calculator that factors in spinopelvic parameters and (2) compare differences with hip-spine classification targets.

Methods

A total of 3750 patients underwent primary total hip arthroplasty across 3 academic referral centers, with 33 (0.88%) requiring revision for instability. Spinopelvic parameters were measured before initial total hip arthroplasty, and acetabular component position was measured following the index and revision procedures. Most operations employed either computer navigation or robotic assistance (94%). Surgical approaches included both anterior and posterior techniques. Utilizing our recently developed patient-specific safe-zone calculator, theoretical intraoperative positions were calculated and compared to true component positions before and after revision.

Results

Among 33 patients who underwent revision, none dislocated at an average follow-up of 5.1 years. In the external validation cohort, the average absolute differences between the patient-specific safe-zone and the median hip-spine classification recommendation were 3.8° ± 2.1° inclination and 5.0° ± 3.2° version. For the pooled cohort, the absolute differences between the patient-specific safe-zone targets and the prerevision component positions were 7.9° ± 5.1° inclination and 11.4° ± 6.9° version. After revision, the mean absolute differences decreased to 3.6° ± 3.1° inclination and 5.8° ± 3.5° version (P < .001).

Conclusions

A patient-specific approach improved acetabular component positioning accuracy within 6° of version and 4° of inclination of stable, revised hips. Patient-specific safe zones provide quantitative targets for nuanced spinopelvic preoperative planning that may mitigate risk of instability and may indicate use of assisted technologies.

Can we identify abnormal pelvic tilt using pre-THA anteroposterior pelvic radiographs?

BACKGROUND

Patients with increased pelvic tilt (PT) are at risk for instability following total hip arthroplasty (THA). Identification of increased PT using anteroposterior (AP) pelvic radiographs could avoid additional spinopelvic radiographs. This study aimed to (1) describe which AP pelvic parameters most accurately estimate sagittal PT, and (2) determine thresholds for these parameters that can identify patients with increased PT.

METHODS

This was a retrospective, consecutive, cohort study in a tertiary referral hospital on 225 patients (age: 66 ± 12 years-old; 52% female) listed for THA. Patients underwent pre-operative standing AP pelvic radiographs to measure distance- and angular- based parameters from several anatomical landmarks. Sagittal PT was measured on a standing lateral spinopelvic radiograph and considered high when ≥ 20°.

RESULTS

No AP pelvic parameters correlated strongly with sagittal PT. Ratio between horizontal and vertical diameter of the pelvic foramen (C/D ratio) (rho - 0.341; p < 0.001); and vertical distance between trans-SIJ and trans-ASIS line (SITA) (rho 0.307; p < 0.001) correlated moderately with sagittal PT. Sacro-femoral-pubic (SFP) angle < 60° had highest sensitivity (85%), but lowest specificity (52%) to differentiate between patients with and without increased PT. If SITA > 62 mm, C/D ratio < 0.5 and SFP < 60°, specificity increased (88%), but sensitivity was low (49%).

CONCLUSION

In the absence of computerized models, AP pelvic parameters cannot accurately predict sagittal PT. However, an SFP < 60° should alert a hip surgeon that a patient may have an increased PT, and would benefit from additional lateral spinopelvic imaging prior to THA.

LEVEL OF EVIDENCE

Level II, diagnostic study.

Kinematic-kinetic compliant acetabular cup positioning based on preoperative motion tracking and musculoskeletal modeling for total hip arthroplasty

The invention of the surgical robot enabled accurate component implantation during total hip arthroplasty (THA). However, a preoperative surgical planning methodology is still lacking to determine the acetabular cup alignment considering the patient-specific hip functions during daily activities such as walking. To simultaneously avoid implant edgeloading and impingement, this study established a kinematic-kinetic compliant (KKC) acetabular cup positioning method based on preoperative gait kinematics measurement and musculoskeletal modeling. Computed tomography images around the hip joint and their biomechanical data during gait, including motion tracking and foot-ground reaction forces, were collected. Using the reconstructed pelvic and femur geometries, the patient-specific hip muscle insertions were located in the lower limb musculoskeletal model via point cloud registration. The designed cup orientation has to be within the patient-specific safe zone to prevent implant impingement, and the optimized value selected based on the time-dependent hip joint reaction force to minimize the risk of edgeloading. As a validation of the proposed musculoskeletal model, the predicted lower limb muscle activations for seven patients were correlated with their surface electromyographic measurements, and the computed hip contact force was also in quantitative agreement with data from the literature. However, the designed cup orientations were not always within the well-known Lewinnek safe zone, highlighting the importance of KKC surgical planning based on patient-specific biomechanical evaluations.

Influence of Contralateral Hip Status on Pelvic Tilt After Total Hip Arthroplasty

Background

Every degree of change in pelvic tilt (PT) leads to a 0.7° change in anteversion and a 0.3° change in inclination. This study aimed to determine the significance of contralateral hip arthritis on changes in PT using preoperative and postoperative anteroposterior radiographs.

Methods

There were 193 primary total hip arthroplasties done by 2 surgeons at a single academic tertiary referral center reviewed between September 2021 and January 2023. PT was calculated as Tilt = -(ln[(B/A) × (1/0.483)]) / 0.051. Value A is the distance from the base of the SI joint to the superior margin of the obturator foramen; value B is the height of the obturator foramen. After exclusions, contralateral hips were identified as being normal (n = 75), arthritic (n = 39) (Tönnis grade 3/4), replaced (n = 34), or having undergone simultaneous bilateral total hip arthroplasty (n = 5) on postoperative films. Difference in PT was measured between preoperative and postoperative films taken 1-3 months after surgery. Analyses for statistical significance were calculated using t-tests and one-way analysis of variance.

Results

Average change in PT in patients with normal contralateral hips was -5.2° with an absolute mean difference of 7.6°, -1.5° for arthritic contralateral hips with an absolute mean difference of 5.0°, -1.6° for replaced contralateral hips with a mean absolute difference of 4.3°, and 2.2° for bilateral hips with a mean absolute difference of 2.6° (P < .01).

Conclusions

Differences in postoperative PT changes between healthy, arthritic, and replaced contralateral hip study groups were significant. Changes in preoperative to postoperative tilt may have implications for optimal cup placement.

Previous lumbar spine fusion increases the risk of dislocation following total hip arthroplasty in patients with hip-spine syndrome: a systematic review and meta-analysis

BACKGROUND

With life expectancy on the rise, there has been an increase in patients with concomitant degenerative hip and spine pathology, defined as hip-spine syndrome (HSS). Patients affected by HSS may require both total hip arthroplasty (THA) and lumbar spinal fusion (LSF), although there is a paucity of data regarding how the sequential timing of these procedures may influence clinical outcomes. This study aims to compare complications and spinopelvic parameters in patients with HSS who underwent either LSF first or THA first.

METHODS

A systematic search of PubMed and Scopus was conducted for randomized and nonrandomized studies investigating complications and spinopelvic parameters in patients with HSS who had undergone THA and LSF. The Methodological Index for Non-Randomized Studies (MINORS) tool was utilized to assess the risk of bias in included studies. Relevant outcomes were pooled for meta-analysis.

RESULTS

Eleven articles were included in this study. There was a significantly higher THA dislocation rate in patients who had undergone LSF first compared to those who had THA first (OR: 3.17, 95% CI 1.23-8.15, P = 0.02). No significant difference was found in terms of THA aseptic loosening (OR: 0.86; 95% CI 0.32-2.32, p = 0.77) and revision rate (OR: 1.18, 95% CI: 0.53-2.62) between these two groups. Individuals who received THA only showed a significantly lower risk of hip dislocation (OR: 0.14, 95% CI: 0.08-0.25, P < 0.00001) and THA revision (OR: 0.22, 95% CI: 0.14-0.36, P < 0.00001) compared to patients with a previous LSF.

CONCLUSIONS

In HSS patients who underwent both LSF and THA, those who received LSF first displayed an increased risk of hip dislocation after subsequent THA. Additionally, the relative risks of dislocation and revision rate appeared significantly lower in patients who had undergone THA only when compared to THA patients with a history of previous LSF. Due to the impact of LSF on spinopelvic biomechanics, caution must be exercised when performing THA in individuals with instrumented spines.

PROSPERO ID

CRD42023412447.

LEVEL OF EVIDENCE

LL.

How Do Spinopelvic Characteristics Change Post-Total Hip Arthroplasty? A Longitudinal Assessment Raising Awareness of the Postoperative Period

BACKGROUND

Spinopelvic characteristics, including sacral slope (SS), are commonly evaluated in different positions pre-total hip arthroplasty (THA). This study aimed to: 1) investigate the change in spinopelvic parameters at 7 days (early) and 1-year post-THA; and 2) identify patient characteristics associated with a change in SS of more than 7° post-THA.

METHODS

We prospectively studied 250 patients who underwent unilateral THA [132 women, age 66 years (range, 32 to 88)] and underwent biplanar images preoperatively and at 7 days and 1-year post-THA. Parameters measured included pelvic incidence, standing lumbar lordosis, SS, and proximal femoral angle (PFA). A SS change ≥ 7° was considered the threshold as it would result in more than a 5° change in cup orientation.

RESULTS

Early post-THA SSstanding remained within ± 6º from preoperative measurements in 75% of patients, reduced by ≥ 7° in 9%, and increased by ≥ 7° in 16%. Those that showed a reduction in SS had the lowest PFA and the highest SS pre-THA (P = .028, .107, and < 0.001, respectively). From 7 days until the 1-year mark, pelvic tilt increased, SS reduced (mean: -4º, range: -29 to 17º, P < .001), and patients stood with greater hip extension ΔPFAstanding (mean 7°, range: -34 to 37°, P < .001). At 1 year, SSseated had remained within ± 6º, relative to the pre-THA value, in 49% of patients.

CONCLUSIONS

Standing spinopelvic characteristics, especially SSstanding, remain within ±6° in three-quarters of patients both early- and at 1-year post-THA. In the remaining cases, pelvic tilt changes significantly. In 9% of cases, SS reduces ≥ 7° early THA, probably due to the alleviation of fixed-flexion contractures. The SSseated changes by ≥ ± 7° in almost 50% of cases in this study, and its clinical value as a preoperative planning tool should be questioned.

LEVEL OF EVIDENCE

Level II, diagnostic study.

Patients with Hip Osteoarthritis Have a Higher Rate of Spinal Reoperation Following Lumbar Spinal Fusion

BACKGROUND

Lumbar spinal pathology is known to affect outcomes following total hip arthroplasty (THA). However, the effect of hip osteoarthritis (OA) on outcomes following lumbar fusion has not been well studied. The purpose of this study was to determine the association between hip OA and spinal reoperation following lumbar spinal fusion.

METHODS

The 5% Medicare Part B claims database was queried for all patients who underwent primary elective lumbar fusion from 2005 to 2019. Patients were divided into 2 groups: those who underwent elective THA within 1 year after primary lumbar fusion, indicating that they had severe hip OA at the time of lumbar fusion, and those who underwent lumbar fusion with no diagnosed hip OA and no THA during the study period. Exclusion criteria included THA as a result of trauma, revision THA or primary THA in the 5-year period before primary lumbar fusion, <65 years of age, and no enrollment in the database for 5 years before and 1 year after primary lumbar fusion. The primary outcome was spinal reoperation within 1, 3, and 5 years. Multivariable Cox regression was performed with age, sex, diabetes, heart disease, obesity, smoking status, osteoporosis, number of levels fused, use of posterior instrumentation, use of an interbody device, use of bone graft, and surgical approach as covariates.

RESULTS

Overall, 1,123 patients (63.4% female; 91.3% White; mean age, 76.8 ± 4.1 years) were included in the hip OA group and 8,893 patients (56.2% female; 91.3% White; mean age, 74.8 ± 4.9 years) were included in the control group. After multivariable analysis, patients with severe hip OA had significantly greater rates of revision surgery at 3 years (odds ratio [OR], 1.61; p < 0.001) and 5 years (OR, 1.87; p < 0.001) after the index lumbar fusion.

CONCLUSIONS

Patients with severe hip OA at the time of primary lumbar fusion had a significantly increased risk of spinal reoperation at 3 and 5 years postoperatively. These data provide further evidence to support performing THA prior to lumbar fusion in the unsettled debate regarding which surgery should be prioritized for patients with simultaneous degenerative diseases of the hip and lumbar spine.

LEVEL OF EVIDENCE

Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Hip-spine parameters change with increasing age

Aims

Spinopelvic pathology increases the risk for instability following total hip arthroplasty (THA), yet few studies have evaluated how pathology varies with age or sex. The aims of this study were: 1) to report differences in spinopelvic parameters with advancing age and between the sexes; and 2) to determine variation in the prevalence of THA instability risk factors with advancing age.

Methods

A multicentre database with preoperative imaging for 15,830 THA patients was reviewed. Spinopelvic parameter measurements were made by experienced engineers, including anterior pelvic plane tilt (APPT), spinopelvic tilt (SPT), sacral slope (SS), lumbar lordosis (LL), and pelvic incidence (PI). Lumbar flexion (LF), sagittal spinal deformity, and hip user index (HUI) were calculated using parameter measurements.

Results

With advancing age, patients demonstrate increased posterior APPT, decreased standing LL, decreased LF, higher pelvic incidence minus lumbar lordosis (PI-LL) mismatch, higher prevalence of abnormal spinopelvic mobility, and higher HUI percentage. With each decade, APPT progressed posteriorly 2.1°, LF declined 6.0°, PI-LL mismatch increased 2.9°, and spinopelvic mobility increased 3.8°. Significant differences were found between the sexes for APPT, SPT, SS, LL, and LF, but were not felt to be clinically relevant.

Conclusion

With advancing age, spinopelvic biomechanics demonstrate decreased spinal mobility and increased pelvic/hip mobility. Surgeons should consider the higher prevalence of instability risk factors in elderly patients and anticipate changes evolving in spinopelvic biomechanics for young patients.

Accuracy of intraoperative approximation of pelvic tilt using preoperative standing radiographs

Background

Anterior approach surgeons who utilize intraoperative fluoroscopy often try to match a preoperative radiograph as a reference for intraoperative cup position. Every degree of inaccuracy in tilt leads to a roughly 0.7° change in anteversion. This study aimed to determine how closely pelvic tilt (PT) is approximated intraoperatively when compared to preoperative anteroposterior (AP) radiographs.

Methods

This was a retrospective review of 193 primary THA's done by 2 surgeons at an academic tertiary referral center between September 2021-January 2023. There were 24 patients excluded for distorted anatomy, post-traumatic arthritis, insufficient x-rays, or a sacroiliac joint that could not be visualized on film. Data collected included age and BMI. PT was calculated using the formula, Tilt = -(ln((B/A) x (1/0.483)))/0.051. Value A is the distance from the base of the SI joint to the superior margin of the obturator foramen; value B is the height of the obturator foramen.

Results

Mean preoperative PT was 0.2° versus intraoperative PT was 3.4° (p < 0.001). Mean absolute difference was 6.5°. 48% of patients (n = 81) had an absolute difference less than 5°, 31% (n = 52) between 5° and 10°, 14% (n = 24) between 10° and 15°, and 7% (n = 12) greater than 15°. There was no correlation between BMI or age and PT discrepancy.

Conclusion

Of the patients, 21% had a discrepancy of 10° or greater between their preoperative radiographs and intraoperative fluoroscopic images. Surgeons should be aware of potential errors in cup positioning and be particularly diligent in high-risk cases.

Influence and Relationship of Pain on Lumbar Biomechanics in a Young Adult Population with Non-Specific Low Back Pain

The therapeutic actions indicated for low back pain, in addition to physiotherapy, include mobilization of the affected segment, as it is assumed that a loss of mobility may contribute to a patient's pain. The aim of this study was to investigate the influence of back pain on the degrees of spinal mobility in young adults. Eighty-six volunteers participated in the study. Fingertip-to-floor distance, Schöber's test, the fingertip-to-floor lateral flexion test, GHQ-12, the Fear-Avoidance Beliefs Questionnaire and the STarT Back Screening Tool were used. There were statistically significant differences between the two groups (pain and no pain) in degrees of spinal flexion (Schöber's test and side flexion) showing greater mobility in the group with pain. However, the group with low back pain showed less rotational mobility. The presence or absence of back pain had an impact on the individual's sporting practice and perception of pain, and they were able to carry out their sporting activities normally. Young adults with idiopathic low back pain showed some statistically significant differences in relation to the mobility of the spine in the different planes of movement (flexion and side flexion), conditioning their quality of life and sports practice.

Spinopelvic interactions in total hip arthroplasty: 295 patients followed for a minimum follow-up of 10 years

BACKGROUND

Concurrent spinal pathology is frequent in patients undergoing total hip arthroplasty (THA). In this study we examined whether spinopelvic interactions affect THA outcomes at a minimum follow-up of 10 years.

PATIENTS AND METHODS

295 patients with a mean age of 63.3 (range 56‒80) years receiving a THA between 2006 and 2009 were assessed. Of these, 195 had mild lumbar disc degeneration and 100 had advanced lumbar spondylosis. We analysed the changes in the Harris Hip Score (HHS) and the survival rate for postoperative low back pain (LBP) and dislocation. Changes in acetabular component position, sacro-femoral-pubic (SFP) and pelvic obliquity (PO) angles were assessed with radiological images.

RESULTS

The mean HHS was lower in female patients (p = 0.009), patients >65 years of age (p < 0.001) and those with advanced lumbar spondylosis (p = 0.002). 52 (71.2%) of the patients reporting preoperative LBP experienced improvement after THA while 47 (21.1%) of those without preoperative LBP postoperatively reported new onset LBP. Female patients (p = 0.025; hazard ratio [HR]: 1.831; 95% CI, 1.081-3.101) and those with preoperative LBP (p = 0.007; HR 2.068; 95% CI, 1.221-3.504) were at a higher risk of developing postoperative LBP at 10 years. 4 out of 9 THA dislocations were late and had shown decreasing SFP angle values over time. Acetabular component inclination and anteversion angles increased over time, whereas the SFP angle was associated with sex and age and the PO angle with age and the severity of any preoperative lumbar degeneration.

CONCLUSIONS

Concurrent spinal pathology influences THA outcomes at a minimum follow-up of 10 years. Sex, age, and associated lumbar degeneration can affect clinical and radiological changes over time. A decrease in SFP angle values over time was found in patients sustaining late dislocation.

Effect of lumbosacral transitional vertebra on developmental alterations of the hip: a quantitative investigation of the lumbo-pelvic-hip complex via whole-body computed tomography

Background

Lumbosacral transitional vertebra (LSTV) is a common spinal variant, with the reported prevalence varying from 8.1% to 36%. LSTV has been shown to alter the lumbo-pelvic parameters and reduce the benefits of total hip arthroplasty, but the specific effects of LSTV on hip development remain unclear. The aim of this study was thus to investigate the impact of LSTV on developmental alterations of the hip.

Methods

A total of 310 individuals were categorized into three groups according to whole-body computed tomography (CT) imaging: a group with sacralization of 23 presacral vertebrae (PSV) (n=102), a group with lumbarization of 25 PSV (n=108), and a normal control group with 24 PSV (n=100). Quantitative parameters of the lumbo-pelvic-hip complex (LPHC) including lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), axial and sagittal acetabular anteversion angle (AAA), center-edge (CE) angle, Sharp angle, and femoral neck-shaft angle (FNSA) were measured and analyzed. Statistical analyses were used to compare the differences of these quantitative parameters among the three groups and to assess the relationship between hip and lumbar-pelvic parameters.

Results

Significant differences between each pair of three groups and the LSTV subgroups were only found in the sagittal AAA (left side: P=0.008; right side: P<0.001), with no differences found for the other parameters. Compared to the normal group (24 PSV), both the 23 PSV and 25 PSV groups exhibited increased values in the sagittal AAA, especially in the right side of the 23 PSV group. Only the sagittal AAA showed low-to-moderate positive correlations with pelvic parameters of PI (r=0.195-0.429; P=0.001-0.08) and PT (r=0.239-0.605; P=0.001-0.03).

Conclusions

Variations of LSTV are correlated with the hip anatomical development via LPHC transmission and may potentially reduce the sagittal acetabular coverage, particularly in the 23 PSV subtype on the right side.

Decrease in pelvic incidence after adult spinal deformity surgery is a predictive factor for progression of hip joint osteoarthritis

BACKGROUND

This study aimed to evaluate the association between spinopelvic alignment parameters and hip osteoarthritis progression after spinal alignment correction surgery for adult spinal deformity, focusing on the preoperative to postoperative change in spinopelvic alignment.

METHODS

This retrospective study enrolled 100 adult spinal deformity patients (196 hip joints) who underwent spinal fusion surgery, after excluding four joints with previous total hip arthroplasty. Acetabular roof obliquity (ARO), center edge angle (CE) and Kellgren and Lawrence (KL) grade were measured in the hip joint. Spinopelvic alignment parameters were measured preoperatively and 1-month postoperatively and the changes (Δ) during this period were calculated. Patients were followed-up for ≥ 5 years and factors associated with KL grade progression at 5-years postoperatively were determined by logistic regression analysis.

RESULTS

In the analysis with all cases, KL grade progressed in 23 joints. Logistic regression analysis revealed age (OR: 1.098, 95% CI: 1.007-1.198, p = 0.019), ARO (OR: 1.176, 95% CI: 1.01-1.37, p = 0.026), and Δ PI (OR: 0.791, 95% CI: 0.688-0.997, p < 0.001) as parameters significantly associated with KL grade progression. On the other hand, in the analysis limited to 185 cases with 1-month postoperative KL grade of 0, KL grade progressed in 13 joints. Logistic regression analysis revealed PI-LL (OR: 1.058, 95% CI: 1.001-1.117, p = 0.04), ΔPI (OR: 0.785, 95% CI: 0.649-0.951, p < 0.001), and ΔCobb (OR: 1.127, 95% CI: 1.012-1.253, p = 0.009) as parameters significantly associated with progression.

CONCLUSIONS

Both the overall and limited analyzes of this study identified preoperative to postoperative change in PI as parameters affecting the hip osteoarthritis progression after spinal fusion surgery. Decrease in PI might represent preexisting sacroiliac joint laxity. Patients with this risk factor should be carefully followed for possible hip osteoarthritis progression.

Spinopelvic Motion: A Simplified Approach to a Complex Subject

Knowledge of the relationship between the hip and spine is essential in the effort to minimize instability and improve outcomes following total hip arthroplasty (THA). A detailed yet straightforward preoperative imaging workup can provide valuable information on pelvic positioning, which may be helpful for optimum placement of the acetabular cup. For a streamlined preoperative assessment of THA candidates, classification systems with a capacity for providing a more personalized approach to performance of THA have been introduced. Familiarity with these systems and their clinical application is important in the effort to optimize component placement and reduce the risk of instability. Looking ahead, the principles of the hip-spine relationship are being integrated using emerging innovative technologies, promising further streamlining of the evaluation process.

A novel imageless accelerometer-based navigation system improves acetabular cup placement accuracy during total hip arthroplasty in the lateral decubitus position

INTRODUCTION

The accuracy of acetabular cup placement using conventional portable imageless navigation systems in total hip arthroplasty (THA) in the lateral decubitus position remains challenging. Several novel portable imageless navigation systems have been developed recently to improve cup placement accuracy in THA. This study compared the accuracy of acetabular cup placement using a conventional accelerometer-based portable navigation (c-APN) system and a novel accelerometer-based portable navigation (n-APN) system during THA in the lateral decubitus position.

MATERIALS AND METHODS

This retrospective cohort study compared 45 THAs using the c-APN and 45 THAs using the n-APN system. The primary outcomes were the absolute errors between the intraoperative and postoperative values of acetabular cup radiographic inclination and anteversion angles and the percentage of cases with absolute errors within 5°. Intraoperative values were shown on navigation systems, and postoperative measurements were conducted using computed tomography images.

RESULTS

The median absolute errors of the cup inclination angles were significantly smaller in the n-APN group than in the c-APN group (3.9° [interquartile range 2.2°-6.0°] versus 2.2° [interquartile range 1.0°-3.3°]; P = 0.002). Additionally, the median absolute errors of the cup anteversion angles were significantly smaller in the n-APN group than in the c-APN group (4.4° [interquartile range 2.4°-6.5°] versus 1.9° [interquartile range 0.8°-2.7°]; P < 0.001). Significant differences were observed in the percentage of cases with absolute errors within 5° of inclination (c-APN group 67% versus n-APN group 84%; P = 0.049) and anteversion angles (c-APN group 62% versus n-APN group 91%; P = 0.001).

CONCLUSIONS

The n-APN system improved the accuracy of the cup placement compared to the c-APN system for THA in the lateral decubitus position.

The Impact of Pelvic Incidence on Spinopelvic and Hip Alignment and Mobility in Asymptomatic Subjects

BACKGROUND

The influence of pelvic incidence (PI) on spinopelvic and hip alignment and mobility has not been well investigated. The aim of this study was to evaluate the influence of PI on spinopelvic and hip alignment and mobility, including the pelvic-femoral angle (PFA) and motion (ΔPFA), in functional positions in a cohort of asymptomatic volunteers.

METHODS

This was a single-center, prospective, cross-sectional study. We included 136 healthy volunteers (69% female; mean age, 38 ± 11 years; mean body mass index, 22 ± 3 kg/m2) divided into 3 subgroups on the basis of their PI: PI < 45° (low PI), 45° ≤ PI ≤ 60° (medium PI), and PI > 60° (high PI). We made full-body lateral radiographs in free-standing, standing with extension, relaxed-seated, and flexed-seated positions. We measured the sacral slope (SS), lumbar lordosis (LL), and PFA. We calculated lumbar (∆LL), pelvic (∆SS), and hip (∆PFA) mobilities as the change between the standing (i.e., standing with or without extension) and sitting (i.e., relaxed-seated or flexed-seated) positions.

RESULTS

There were significant differences between some of the 3 subgroups with respect to the LL, SS, and PFA in each of the 4 positions. There were no significant differences in ΔLL, ΔSS, or ΔPFA between the 3 groups when moving from a standing to a sitting position. PI had an inverse linear correlation with PFAextension (R = -0.48; p < 0.0001), PFAstanding (R = -0.53; p < 0.0001), PFArelaxed-seated (R = -0.37; p < 0.0001), and PFAflexed-seated (R = -0.47; p < 0.0001). However, PI was not correlated with ΔPFAstanding/relaxed-seated (R = -0.062; p = 0.48) or ΔPFAextension/flexed-seated (R = -0.12; p = 0.18). Similarly, PI was not significantly correlated with ΔLL or ΔSS in either pair of positions.

CONCLUSIONS

This study confirmed that spinopelvic and hip parameters in functional positions were affected by PI, whereas lumbar, pelvic, and hip mobilities did not depend on PI. These findings suggest that hip surgeons should consider the PI of the patient to determine the patient's specific functional safe zones before and after total hip arthroplasty.

LEVEL OF EVIDENCE

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Functional assessment of component positioning in patients with groin pain after total hip arthroplasty as a tool to guide management

BACKGROUND

Persisting groin pain post total hip arthroplasty (THA) is a common and complex issue that can be difficult to diagnose and manage. Acetabular component positioning is often implicated.

AIMS AND METHODS

We used a previously well described and validated functional positioning protocol to determine if functional acetabular malpositioning was a factor in groin pain post THA and hence to determine if acetabular revision would be indicated. We compared patient-specific functional acetabular positioning to traditional CT evaluation of cup position and assessment of anterior cup overhang.

RESULTS

39 patients with groin pain post-THA were investigated. Functional acetabular malpositioning was diagnosed in 31% (12/39). Revision THA was performed in those 12 patients, resulting in resolution of functional malpositioning (100%), with an overall accuracy of 5.6° (range 1-12), and resolution of groin pain in 67% (8/12). 33% (4/12) of the revised implants had functional positioning located outside the traditional "40/20 zone". Comparison with CT indicated that 40% (4/10) of implants with anterior overhang were well positioned, however only 50% (6/12) of functionally malpositioned implants had CT evidence of anterior cup prominence. Of the 8/12 revision patients who had resolution of their groin pain, only 1 had cup prominence.

CONCLUSIONS

This study suggests that the utilisation of a patient specific functional positioning algorithm in the analysis of persistent groin pain following THA can assist in identifying the underlying cause of pain and help to guide treatment. For a functionally malpositioned acetabulum, revision surgery offers a potential resolution of groin pain.

Mobility of the lumbo-pelvic-hip complex (spinopelvic mobility) and sagittal spinal alignment - implications for surgeons performing hip arthroplasty

INTRODUCTION

The optimal positioning of the hip prosthesis components is influenced by the mobility and balance of the spine. The present study classifies patients with pathology of the spino-pelvic-hip complex, showing possible methods of preventing hip dislocations after arthroplasty.

HYPOTHESIS

Hip-Spine Classification helps arthroplasty surgeons to implant components in more patient-specific position.

MATERIALS AND METHODS

The group of 100 patients treated with total hip arthroplasty. Antero-posterior (AP) X-rays of the pelvis in a standing position, lateral spine (standing and sitting) and AP of the pelvis (supine after the procedure) were analyzed. We analyzed a change in sacral tilt value when changing from standing to sitting (∆SS), Pelvic Incidence (PI), Lumbar Lordosis (LL) Mismatch, sagittal lumbar pelvic balance (standing position). Patients were classified according to the Hip-Spine Classification. Postoperatively, the inclination and anteversion of the implanted acetabular component were measured.

RESULTS

In our study 1 A was diagnosed in 61% of all cases, 1B in 18%, 2 A in 16%, 2B in 5%. 50 out of 61 (82%) in group 1 A were placed within the Levinnek "safe zone". In 1B, 2 A, 2B, the position of the acetabular component was influenced by both the spinopelvic mobility and sagittal spinal balance. The mean inclination was 43.35° and the anteversion was 17.4°.

CONCLUSIONS

Categorizing patients according to Hip-Spine Classification one can identify possible consequences the patients at risk. Pathology of the spino-pelvic-hipcomplex can lead to destabilization or dislocation of hip after surgery even though implanted according to Lewinnek's indications. Our findings suggest that Lewinnek safe zone should be abandoned in favor of the concept of functional safe zones.

What patient parameters influence lumbar stiffness in patients with hip pathology?

Lumbar stiffness leads to greater hip dependence to achieve sagittal motion and increases instability after total hip arthroplasty (THA). We aimed to determine parameters that influence lumbar stiffness among patients with hip pathology. We hypothesized that modifiable (degenerative changes, spinal canal stenosis, facet orientation) and nonmodifiable factors (muscle condition) would be associated with lumbar spine stiffness. In this retrospective case-cohort study from a tertiary referral center, consecutive patients presenting at a hip specialist clinic underwent standing and deep-seated radiographic assessment to measure lumbar lordosis (∆LL) (stiffness: ∆LL < 20°), hip flexion (∆PFA: pelvic femoral angle), and degree of degenerative-disc-disease (DDD) (facet osteoarthritis, disc height, endplate proliferative changes). Of these, 65 patients were selected with previous lumbar spine magnetic resonance imaging, allowing to determine lumbar facet orientation, spinal canal stenosis (Schizas classification), and flexor- and extensor-muscle atrophy (Goutallier classification). Mean ∆LL was 45° (range: 11°-72°) and four patients (6%) exhibited spine stiffness. Patients with multilevel DDD (n = 22) had less ∆LL than those with no/single level (n = 43) DDD (34° [range: 11°-53°] vs. 51° [21°-72°]; p < 0.001). Number of DDD levels correlated strongly with ∆LL (ρ = -0.642; p < 0.001). Spinal stiffness was only seen in patients with ≥4 DDD levels. There was no correlation between ∆LL and facet orientation (p > 0.05). ∆LL correlated strongly with extensor atrophy at L3-L4 (ρ = -0.473), L4-L5 (ρ = -0.520), and L5-S1 (ρ = -0.473) and poorly with flexors at L4-L5 (ρ = -0.134) and L5-S1 (ρ = -0.227). Lumbar stiffness is dependent on modifiable (muscle atrophy) and nonmodifiable (extend of DDD) factors. This can guide nonoperative management of hip pathology, emphasizing the relevance of core muscle rehabilitation to improve posture and stiffness. Identification ≥4 DDD levels should alert surgeons of increased THA instability risk. Level of evidence: level IV, cohort series.

Instability in Patients With Lumbar Spine Disease Undergoing Posterior Approach and Lateral Approach Primary Total Hip Arthroplasty

INTRODUCTION

Dislocation rates in patients who have fixed spinopelvic motion have been reported up to 20%. Few studies have directly compared dislocation rates in patients who have spine pathology undergoing total hip arthroplasty (THA) through different surgical approaches. This study compared postoperative dislocation rates in patients who had lumbar spine disease and underwent primary THA using a posterior or direct lateral approach.

METHODS

Between 2011 and 2017, consecutive cohorts of primary THAs were retrospectively reviewed. One surgeon routinely used a posterior approach, while the other used a direct lateral approach. Chart and radiographic review were conducted to identify patients who had lumbar spine disease. Dislocations among cohorts with and without lumbar spine disease were compared by posterior and direct lateral approaches.

RESULTS

The overall dislocation rate was 1.3% (15/1,198). The top four predictors of dislocation were presence of lumbar spine disease (odds ratio [OR] 5.0; P = 0.014), posterior surgical approach (OR, 6.5; P = 0.074), cases performed for fracture (OR, 4.4; P = 0.035), and women (OR, 4.6; P = 0.050). Dislocation rates among direct lateral approach patients who had lumbar spine pathology were significantly lower than posterior approach patients who had lumbar spine pathology (0.0% versus 3.6%; P = 0.011).

DISCUSSION

Although dislocation rates were low in both groups, study results suggest that a direct lateral approach for primary THA may reduce postoperative dislocations for patients who have limited spinopelvic motion due to lumbar spine pathology. Furthermore, surgeons using the posterior approach might consider optimizing the femoral head to acetabular cup ratio in patients who have lumbar spine disease.

Hip-spine relationship: clinical evidence and biomechanical issues

The hip-spine relationship is a critical consideration in total hip arthroplasty (THA) procedures. While THA is generally successful in patient, complications such as instability and dislocation can arise. These issues are significantly influenced by the alignment of implant components and the overall balance of the spine and pelvis, known as spinopelvic balance. Patients with alteration of those parameters, in particular rigid spines, often due to fusion surgery, face a higher risk of THA complications, with an emphasis on complications in instability, impingement and dislocation. For these reasons, over the years, computer modelling and simulation techniques have been developed to support clinicians in the different steps of surgery. The aim of the current review is to present current knowledge on hip-spine relationship to serve as a common platform of discussion among clinicians and engineers. The offered overview aims to update the reader on the main critical aspects of the issue, from both a theoretical and practical perspective, and to be a valuable introductory tool for those approaching this problem for the first time.

The Empty Ischial Fossa Sign: A Visual Representation of Relative Inadequate Anteversion in the Posteriorly Tilted Pelvis

Background

Instability is a known complication following total hip arthroplasty (THA) and is influenced by spinopelvic alignment. Radiographic markers have been investigated to optimize the acetabular cup position. This study evaluated if the empty ischial fossa (EIF) sign and the position of the trans-teardrop line were predictive of postoperative instability.

Methods

All patients who underwent THA from 2011 to 2018 at a single institution were retrospectively reviewed. Pelvic tilt was measured using a trans-teardrop line compared to the superior aspect of the pubic symphysis on standing anteroposterior pelvis radiographs. Postoperative dislocations were identified through chart review and radiographic review. The EIF sign was determined by the presence of uncovered bone below the posterior inferior edge of the acetabular component at the level of the native ischium and posterior wall on standing postoperative anteroposterior radiographs.

Results

One thousand seven hundred fifty patients (952 anterior approach and 798 posterior approach) were included. The EIF sign was present in 458 patients (26.2%) and associated with an increased dislocation rate (3.9% vs 0.9%, P < .0001). Patients with spondylosis/instrumented fusion, and positive EIF sign had a dislocation risk of 5.1% vs 1.3% (P = .001). A postoperative outlet pelvis was not significant for increased dislocation risk (odds ratio 2.16, P = .058). Patients with combined spondylosis/fusion, posterior approach, outlet pelvis, and EIF sign had a dislocation rate of 14.5%.

Conclusions

The EIF sign was an independent risk factor for postoperative instability and may represent failure to account for pelvic tilt. Avoidance of the EIF sign during cup positioning may help reduce dislocations following THA.

The Hip-spine Assessment of a Novel Surgical Planning Software Provides Acetabular Component Targets That Are Reliable and in Agreement With Current Clinical Recommendations

Background

Spinopelvic immobility has been reported to increase dislocation risk following total hip arthroplasty. Surgically placing acetabular components in a functional orientation has been shown to mitigate risk. The aim of this study was to evaluate the validity and reliability of novel surgical planning software to generate clinically recommended cup targets.

Methods

Hip-spine assessments were performed retrospectively on 40 patients. Five reviewers, including 3 arthroplasty-trained surgical fellows and 2 clinical research scientists performed the assessments. Hip-spine assessments consisted of measuring anterior pelvic plane tilt, sacral slope, pelvic incidence, and lumbar lordosis on standing anteroposterior pelvis and lateral standing and seated hip-spine images. Generated cup targets and a control group (40°/20° relative to the anterior pelvic plane) were compared to clinically recommended cup targets. Agreement was defined as a cup position within the recommended range or within 3° of a specific target (eg, 40° inclination) when no range was provided. Intraclass correlation coefficients were used to assess interrater and intrarater reliability, and McNemar's chi-square test was used to measure success relative to the control group.

Results

The intraclass correlation coefficient was 0.88 for delta sacral slope and 0.92 for pelvic incidence-lumbar lordosis mismatch. For patients with spinopelvic risk factors, the generated targets matched the clinical recommendations in 81% of patients compared to only 16% in the control group.

Conclusions

Excellent interrater and intrarater reliability was achieved using the novel surgical planning software. The resultant target values agreed with clinical recommendations to a greater extent than the control group.

Hip-Spine Relationship between Sagittal Balance of the Lumbo-Pelvi-Femoral Complex and Hip Extension Capacity: An EOS Evaluation in a Healthy Caucasian Population

STUDY DESIGN

A prospective study of healthy volunteers.

OBJECTIVES

The influence of the sagittal alignment of the spine and its influence on the extension reserve have been reported in the literature. However, specific analysis of the intrinsic coxofemoral and extrinsic pelvic component in subjects without any spinal or hip pathologies remains poorly reported. The aim of this study was to categorize the hip extension capacity, or extension reserve (ER), in relation to spinal sagittal alignment whilst standing, in a young healthy population. We hypothesized that the global extension reserve (GER) of the hip joint was influenced by the sagittal spinopelvic alignment.

METHODS

We evaluated the ER of 120 healthy Caucasian volunteers (56 females (46.7%), 74 males (53.3%); mean age 25.6 years), using low dose radiographs from an EOS® X-ray imaging system in 2 functional positions; neutral standing position and in a forward lunge position. The GER is defined as the sum of the intrinsic (hip) extension reserve (IER) and the extrinsic (pelvic) extension reserve (EER). Cases were grouped into 4 sagittal alignment subtypes according to the Roussouly classification, and analyzed.

RESULTS

Global extension reserve values were not significantly different between the 4 Roussouly subtypes (P = .094), nor between patients with a sacral slope (SS) <35° (types 1/2) and ≥ 35° (type 3/4) (P = .837). Statistically significant differences were seen between IER in each subtype (P = .015), and EER (P = .006). No difference in ER was seen between subtypes regarding pelvic incidence (PI).

CONCLUSION

An inverse relationship was found between IER and EER among Roussouly subtypes. The range of motion of the pelvis and the hip joint was higher in patients with a greater sacral slope.

How to Screen for Lumbar Spine Stiffness in Patients Awaiting Total Hip Arthroplasty

BACKGROUND

This study aimed to (1) define the prevalence of spinopelvic abnormalities among patients who have hip osteoarthritis (OA) and controls (asymptomatic volunteers) and (2) identify factors that reliably predict the presence of lumbar spine stiffness.

METHODS

This is a prospective, cross-sectional, case-cohort study of patients who have end-stage primary hip OA, who underwent primary total hip arthroplasty (THA). Patients were compared with a cohort of asymptomatic volunteers, matched for age, sex, and body mass index (BMI), serving as a control group. Spinopelvic pathologies were defined as: lumbar spine flatback deformity (difference of 10 or more degrees for pelvic incidence minus lumbar lordosis angle), a standing sagittal pelvic tilt of 19° or more and lumbar spine stiffness (lumbar flexion of less than 20° between both postures).

RESULTS

The prevalence of spinopelvic pathologies was similar between patients and controls (flatback deformity: 16% versus 10%, P = .209; standing pelvic tilt >19°: 17% versus 24%, P = .218; lumbar spine stiffness: 6% versus 5%, P = .827). Age over 65 years-old and standing lumbar lordosis angle less than 45° were associated with high sensitivity and specificity for identifying lumbar spine stiffness (age >65 years: 82% and 66%; standing lumbar lordosis angle <45°: 85% and 73%).

CONCLUSION

The presence of end-stage hip osteoarthritis was not associated with increased prevalence of adverse spinopelvic characteristics compared to matched, asymptomatic volunteers. Age and LLstanding are the strongest predictors of lumbar spine flexion and can guide clinical practice on when to obtain additional radiographs for patients who have hip OA before arthroplasty to identify at-risk patients.

LEVEL OF EVIDENCE

II (prospective, cohort study).

Effect of Lumbar Fusion and Pelvic Fixation Rigidity on Hip Joint Stress: A Finite Element Analysis

STUDY DESIGN

This study compared hip stress among different types of lumbopelvic fusion based on finite element (FE) analysis.

OBJECTIVE

We believe that the number and placement of S2 alar iliac (AI) screws and whether the screws loosen likely influence hip joint stress in the FE model.

SUMMARY OF BACKGROUND DATA

Spinopelvic fixation has been shown to increase the risk of progression for hip joint osteoarthritis. The biomechanical mechanism is not well understood. We hypothesize that the rigid pelvic fixation may induce stress at adjacent joints.

MATERIALS AND METHODS

A three-dimensional nonlinear FE model was constructed from the L4 vertebra to the femoral bone. From the intact model, we made four fusion models, each with different lower vertebrae instrumentation: (1) intact, (2) L4-S1 fusion, (3) L4-S2 AI screw fixation, (4) L4-S2 AI screw fixation with S2 AI screw loosening, and (5) L4-S1 and dual sacral AI screw fixation. A compressive load of 400 N was applied vertically to the L4 vertebra, followed by an additional 10 Nm bending moment about different axes to simulate either flexion, extension, left lateral bending, or right axial rotation. The distal femoral bone was completely restrained. The von Mises stress and angular motion were analyzed across the hip joints within each fusion construct model.

RESULTS

Hip joint cartilage stress and range of motion increased for all postures as pelvic fixation became more rigid. The dual sacral AI screw fixation model increased stress and angular motion at the hip joint more than intact model. Our results suggest that more rigid fixation of the pelvis induces additional stress on the hip joint, which may precipitate or accelerate adjacent joint disease.

CONCLUSIONS

Dual sacral AI fixation led to the highest stress while loosening of S2 AI decreased stress on the hip joint. This study illustrates that more rigid fixation among lumbosacral fusion constructs increases biomechanical stress on the hip joints.

Outcomes of Hip Arthroscopy in the Setting of Concomitant Symptomatic Lumbosacral Spine Pathology: A Matched Control Study With Minimum 24-Month Follow-up

BACKGROUND

The overlapping biomechanical relationship between the lumbosacral spine and pelvis poses unique challenges to patients with concomitant pathologies limiting spinopelvic range of motion.

PURPOSE

To assess the influence of concomitant, symptomatic lumbosacral spine pathology on patient-reported outcome measures (PROMs) after hip arthroscopy for the treatment of femoroacetabular impingement (FAI) and symptomatic labral tears.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A retrospective query of prospectively collected data identified patients aged ≥18 years with a minimum 24-month follow-up who underwent hip arthroscopy by a single surgeon for the treatment of symptomatic labral tears secondary to FAI. Patients were stratified into cohorts based on the presence (hip-spine [HS]) or absence (matched control [MC]) of symptomatic lumbosacral spine pathology. Inclusion within the HS cohort required confirmation of lower back pain/symptoms on preoperative surveys plus a diagnosis of lumbosacral spine pathology verified by radiology reports and correlating clinical documentation. Patients with previous spine surgery were excluded. PROMs were compared between groups, along with rates of achieving minimal clinically important difference (MCID) thresholds, Patient Acceptable Symptom State (PASS) thresholds, revision arthroscopy, and conversion to total hip arthroplasty (THA).

RESULTS

A total of 70 patients with lumbosacral pathology were coarsened exact matched to 87 control patients without spinal pathology. The HS cohort had preoperative baseline scores that were significantly worse for nearly all PROMs. Follow-ups at 3, 6, 12, and 24 months displayed similar trends, with the HS cohort demonstrating significantly worse scores for most collected outcomes. However, at every time point, HS and MC patients exhibited similar magnitudes of improvement across all PROM and pain metrics. Furthermore, while significantly fewer HS patients achieved PASS for nearly all PROMs at 12- and 24-month follow-ups, MCID thresholds were reached at similar or greater rates across all PROMs relative to the MC cohort. Finally, there were no significant differences in rates of revision or THA between cohorts at maximum available follow-up.

CONCLUSION

After hip arthroscopy to address labral tears in the setting of FAI, patients with symptomatic lumbosacral pathologies and no history of spine surgery were found to exhibit inferior pre- and postoperative PROMs but achieved statistically similar clinical benefit and rates of PROM improvement through 24-month follow-up compared with the MC cohort with isolated hip disease. These findings aid in providing a realistic recovery timeline and evidence that coexisting hip and spine disorders are not a contraindication for arthroscopic hip preservation surgery.

An Analysis of the Preoperative Factors, Spinopelvic Mobility and Sagittal Spinal Alignment in Pre-THA Patients

Hip arthroplasty is a very effective medical procedure. The optimal positioning of the components and the functioning of the endoprosthesis are influenced, among other things, by the mobility and balance of the spine. The aim of the study was to analyze the factors influencing the mobility of the lumbar-pelvic-iliac complex (spinopelvic mobility) together with the assessment of sagittal spinal alignment in patients prior to THA (total hip arthroplasty). Patients who underwent hip replacement surgery due to advanced osteoarthritis of the hip were enrolled in the study (n = 103). The sociodemographic characteristics, BMI, radiological advancement of the degenerative disease, quality of life, and range of joint mobility were completed using a proprietary questionnaire, the EQ-5D-5L questionnaire, and a clinical examination. X-ray images were analyzed: AP of the pelvis standing up, lateral of the spine standing and sitting. Key parameters were measured as ∆SS-change in sacrum angle value when changing from standing to sitting position and pelvic incidence (PI)-lumbar lordosis (LL) mismatch-sagittal lumbar pelvic balance measured in standing position. The patients were assigned to the appropriate groups according to the Hip-Spine Classification: normal group: 1A (n = 65; 63.1%), abnormal groups: 1B (n = 17; 16.5%), 2A (n = 16; 15.5%), 2B (n = 5; 4.9%). A correlation was shown between the abnormal groups and the individual components of PROMs in the scope of the self-service and normal activities categories (EQ-5D and EQ-VAS). However, the strength of the relationship turned out to be moderate, and the remaining components of the survey were statistically insignificant. The remaining factors analyzed, i.e., age, BMI, the range of hip motion, the presence of contracture in the joint in a clinical examination, and the radiological advancement of osteoarthritis on the Tonnis scale, do not predict abnormal relationships between the spine and the pelvis in our patients waiting for THA. Therefore, further investigations are needed to evaluate the correlation between preoperative factors and the lumbar-pelvic-iliac complex in patients prior to planned hip arthroplasty.

The Outcome of Hip Arthroscopy in the Setting of Lumbar Spine Disease Is Beneficial, Yet Limited: A Systematic Review of Existing Evidence

PURPOSE

To compare hip arthroscopy outcomes in femoroacetabular impingement (FAI) patients with concurrent symptomatic lumbar spine disease to the outcomes of arthroscopic FAI patients without spine disease.

METHODS

A systematic review was performed according to PRISMA guidelines via PubMed, Cochrane, Embase, and Google Scholar databases. Studies were valid for inclusion if they had an average follow-up ≥12 months and compared patient-reported outcome measures (PROMs) in hip arthroscopy patients with and without concurrent spinal disease. Data collected included study characteristics, patient demographics, follow-up intervals, surgical indications, spinal pathology, PROMs, and reoperation rates.

RESULTS

Twelve studies were included in this systematic review. 3,107 patients who underwent hip arthroscopy were evaluated: 1,056 with coexisting lumbar spine disease (spine cohort) and 2,051 control subjects without spine disease (control cohort). The average follow-up period was 24 months. Across included studies, there were 35 instances wherein postoperative PROM scores reported by each cohort were compared. In all 35 instances, the spine cohort reported inferior postoperative PROM scores with the difference being significant (P < .05) on 23 PROMs. Collectively, 23 cases were available contrasting the proportion of each cohort to achieve the minimal clinically important difference (MCID). In 22 (95.65%) of these cases, the spine cohort achieved the MCID at a lower rate than the control cohort. There were 14 PROMs, wherein intragroup analyses were reported that compared the preoperative and postoperative score reported by the spine cohort. On all 14 PROMs, the spine cohort reported significant (P < .05) improvement after arthroscopic intervention.

CONCLUSION

FAI patients with coexisting lumbar spine pathology experience significant improvement from baseline state after arthroscopic intervention. However, the postoperative outcomes reported are inferior, and the improvement from arthroscopy was limited when compared to surgical control subjects with FAI and normal spinal anatomy.

LEVEL OF EVIDENCE

Level IV: systematic review of Level II, III, and IV studies.

Creating Consensus in the Definition of Spinopelvic Mobility

INTRODUCTION

The term "spinopelvic mobility" is most often applied to motion within the spinopelvic segment. It has also been used to describe changes in pelvic tilt between various functional positions, which is influenced by motion at the hip, knee, ankle and spinopelvic segment. In the interest of establishing a consistent language for spinopelvic mobility, we sought to clarify and simplify its definition to create consensus, improve communication, and increase consistency with research into the hip-spine relationship.

METHODS

A literature search was performed using the Medline (PubMed) library to identify all existing articles pertaining to spinopelvic mobility. We reported on the varying definitions of spinopelvic mobility including how different radiographic imaging techniques are used to define mobility.

RESULTS

The search term "spinopelvic mobility" returned a total of 72 articles. The frequency and context for the varying definitions of mobility were reported. 41 papers used standing and upright relaxed-seated radiographs without the use of extreme positioning, and 17 papers discussed the use of extreme positioning to define spinopelvic mobility.

DISCUSSION

Our review suggests that the definitions of spinopelvic mobility is not consistent in the majority of published literature. We suggest descriptions of spinopelvic mobility independently consider spinal motion, hip motion, and pelvic position, while recognizing and describing their interdependence.

Anteroposterior pelvic radiograph findings correlate with sagittal spinopelvic motion

It has been well documented in the arthroplasty literature that lumbar degenerative disc disease (DDD) contributes to abnormal spinopelvic motion. However, the relationship between the severity or pattern of hip osteoarthritis (OA) as measured on an anteroposterior (AP) pelvic view and spinopelvic biomechanics has not been well investigated. Therefore, the aim of the study is to examine the association between the severity and pattern of hip OA and spinopelvic motion. A retrospective chart review was conducted to identify patients undergoing primary total hip arthroplasty (THA). Plain AP pelvic radiographs were reviewed to document the morphological characteristic of osteoarthritic hips. Lateral spine-pelvis-hip sitting and standing plain radiographs were used to measure sacral slope (SS) and pelvic femoral angle (PFA) in each position. Lumbar disc spaces were measured to determine the presence of DDD. The difference between sitting and standing SS and PFA were calculated to quantify spinopelvic motion (ΔSS) and hip motion (ΔPFA), respectively. Univariate analysis and Pearson correlation were used to identify morphological hip characteristics associated with changes in spinopelvic motion. In total, 139 patients were included. Increased spinopelvic motion was observed in patients with loss of femoral head contour, cam deformity, and acetabular bone loss (all p < 0.05). Loss of hip motion was observed in patients with loss of femoral head contour, cam deformity, and acetabular bone loss (all p < 0.001). A decreased joint space was associated with a decreased ΔPFA (p = 0.040). The presence of disc space narrowing, disc space narrowing > two levels, and disc narrowing involving the L5-S1 segment were associated with decreased spinopelvic motion (all p < 0.05). Preoperative hip OA as assessed on an AP pelvic radiograph predicts spinopelvic motion. These data suggest that specific hip osteoarthritic morphological characteristics listed above alter spinopelvic motion to a greater extent than others.

Sacral Slope Change From Standing to Relaxed-Seated Grossly Overpredicts the Presence of a Stiff Spine

BACKGROUND

Several authors propose that a change in sacral slope of ≤10° between the standing and relaxed-seated positions (ΔSS_{standing→relaxed-seated}) identifies a patient with a stiff lumbar spine and has suggested the use of dual-mobility bearings for such patients undergoing a total hip arthroplasty (THA). The aim of this study was to assess how accurately ΔSS_{standing→relaxed-seated} can identify patients with a stiff spine.

METHODS

A prospective, multicentre, consecutive cohort series of 312 patients had standing, relaxed-seated, and flexed-seated lateral radiographs prior to THA. ΔSS_{standing→relaxed-seated} was determined by the change in sacral slope between the standing and relaxed-seated positions. Lumbar flexion (LF) was defined as the difference in lumbar lordotic angle between standing and flexed-seated. LF ≤20° was considered a stiff spine. The predictive value of ΔSS_{standing→relaxed-seated} for characterizing a stiff spine was assessed.

RESULTS

A weak correlation between ΔSS_{standing→relaxed-seated} and LF was identified (r² = 0.13). Eighty six patients (28%) had ΔSS_{standing→relaxed-seated} ≤10° and 19 patients (6%) had a stiff spine. Of the 86 patients with ΔSS_{standing→relaxed-seated} ≤10°, 13 had a stiff spine. The positive predictive value of ΔSS_{standing→relaxed-seated} ≤10° for identifying a stiff spine was 15%.

CONCLUSION

In this cohort, ΔSS_{standing→relaxed-seated} ≤10° was not correlated with a stiff spine. Using this simplified approach could lead to a 7-fold overprediction of patients with a stiff lumbar spine and abnormal spinopelvic mobility, unnecessary use of dual-mobility bearings, and incorrect component alignment targets. Referring to patients with ΔSS_{standing→relaxed-seated} ≤10° as being stiff is misleading. The flexed-seated position should be used to effectively assess a patient's spine mobility prior to THA.

Functional Component Positioning in Total Hip Arthroplasty and the Role of Robotic-Arm Assistance in Addressing Spinopelvic Pathology

Hip, spine, and pelvis function as a unified kinetic chain. Any spinal pathology, results in compensatory changes in the other components to accommodate for the reduced spinopelvic motion. The complex relationship between spinopelvic mobility and component positioning in total hip arthroplasty presents a challenge in achieving functional implant positioning. Patients with spinal pathology, especially those with stiff spines and little change in sacral slope, are at high instability risk. In this challenging subgroup, robotic-arm assistance enables the execution of a patient specific plan, avoiding impingement and maximizing range of motion; especially utilizing virtual range of motion to dynamically assess impingement.

The Correlation Between Pelvic Motion and Lumbar Motion in Patients Presenting With a Lumbar Spinal Pathology: Implications for Assessing Dislocation Risk in Total Hip Arthroplasty

Background

Arthroplasty surgeons use the change in sacral slope (ΔSS) from sitting to standing as a measure of spinal motion. The relationship between ΔSS and the change in lumbar lordosis (ΔLL), an established spinal motion measure, has not been well studied. This study aims to determine the correlation between ΔSS and ΔLL.

Methods

Consecutive patients presenting to a spine clinic from 2020 to 2021 at a single institution were retrospectively studied. Standing and sitting lateral radiographs were measured for SS and LL. Patients were divided using ΔSS and ΔLL into stiff (0°-9°), normal (10°-30°), or hypermobile (>30°) category. Patients with a ΔSS-determined normal or hypermobile spine but a ΔLL-determined stiff spine were compared to the rest of the cohort.

Results

Overall, 100 patients were included. Of these patients, 47% had the same classification when looking at ΔSS and ΔLL, whereas 53% had conflicting classifications. Twenty percent of patients had a ΔSS-determined normal or hypermobile spine but ΔLL-determined stiff spine. The correlation between ΔSS and ΔLL was 0.510 (P < .001). When isolating patients who underwent lumbar fusion, the correlation between ΔSS and ΔLL was 0.345 (P < .001).

Conclusions

ΔSS has a moderate correlation with ΔLL in patients presenting for evaluation of their lumbar spine but low correlation in patients with lumbar fusion. In our cohort, 20% of patients had a ΔSS-determined normal or hypermobile spine but a ΔLL-determined stiff spine, representing a potential high-risk dislocation cohort not captured by ΔSS alone. Arthroplasty surgeons should revisit classifying spinal motion based solely on ΔSS.

The Top Three Burning Questions in Total Hip Arthroplasty

Total hip arthroplasty (THA) for end-stage osteoarthritis is one of the most effective surgical treatments in medicine. Impressive outcomes have been well documented in the literature with patients gaining ambulation and recovery of hip joint function. Nevertheless, there are still debatable issues and controversies that the orthopedic community has not been able to provide a definitive answer for. This review is focused on the current three most debatable issues surrounding the THA procedure: (1) new cutting-edge technology, (2) spinopelvic mobility, and (3) fast-track protocols. The scope of the herein narrative review is to analyze the debatable issues surrounding the three aforementioned topics and conclude the best contemporary clinical approaches regarding each issue.

Prosthetic Hip Dislocations in Direct Anterior versus Posterior Approach in Patients with Instrumented Lumbar Fusion

BACKGROUND

Instrumented Posterior Lumbar Spinal Fusion (IPLSF) has been demonstrated to contribute to instability following Total Hip Arthroplasty (THA). It is unclear whether a supine Direct Anterior (DA) approach reduces the risk of instability.

METHODS

A retrospective review of 1,773 patients who underwent THA through either a DA approach or a posterior approach at our institution over a 7-year period. Radiographic and chart review were then used to identify our primary group of interest comprised of 111 patients with previous IPLSF. Radiographic review, chart review, and phone survey was performed. Dislocation rates in each approach group were then compared within this cohort of patients with IPLSF.

RESULTS

Within the group of patients with IPLSF, 33.3% (n=37) received a DA approach while 66.6% (n=74) received a posterior approach. None of the 9 total dislocations in the DA group had IPLSF, whereas 4 of the 16 total dislocations in the posterior approach group had IPLSF (p=0.78). When examining the larger group of patients, including those without IPLSF, patients undergoing a DA approach had a lower BMI and were likely have a smaller head size implanted (p<0.001 for both). Using Fischer's exact test, fusion was associated with dislocation in the posterior approach group (p<0.01), whereas fusion was not associated with dislocation in the anterior approach group (p=1.0).

CONCLUSIONS

While there was no significant difference in dislocation rates between posterior and anterior approach groups, in patients with IPLSF, the anterior approach had a lower percentage of dislocation events compared to the posterior approach.

Dislocation Rates of Primary Total Hip Arthroplasty in Patients With Prior Lumbar Spine Fusion and Lumbar Degenerative Disk Disease With and Without Utilization of Dual Mobility Cups: An American Joint Replacement Registry Study

INTRODUCTION

Patients undergoing primary total hip arthroplasty (THA) with a previous history of lumbar spine fusion (LSF) are at increased risk of dislocation. The purpose of this study was to compare the 90-day and 1-year dislocation rates of patients with LSF or lumbar degenerative disk disease who underwent primary THA with and without dual mobility (DM) constructs.

METHODS

An American Joint Replacement Registry data set of patients aged 65 years and older undergoing primary THA with minimum 1-year follow-up with a history of prior LSF or a diagnosis of lumbar degenerative disk disease was created. DM status was identified, and dislocation and all-cause revision at 90 days and 1 year were assessed.

RESULTS

A total of 15,572 patients met study criteria. The overall dislocation rates for the non-DM and DM groups were 1.17% and 0.68%, respectively, at 90 days, and 1.68% and 0.91%, respectively, at 1 year ( P = 0.005). The odds of 90-day (OR = 0.578, [ P = 0.0328]) and 1-year (OR = 0.534, [ P = 0.0044]) dislocation were significantly less with DM constructs, compared with non-DM constructs. No statistically significant difference was observed in revision rates between groups.

DISCUSSION

This large registry-based study identified a reduced risk of dislocation in patients at risk for spinal stiffness when a DM compared with non-DM construct was used in primary THA at 90-day and 1-year follow-up intervals. Our data support the use of DM constructs in high-risk patients with stiff spines and altered spinopelvic mobility as a promising option to mitigate the risk of postoperative hip instability after primary THA.

LEVELS OF EVIDENCE

Level III. Therapeutic retrospective cohort.

Failure of a Highly Cross-Linked Polyethylene Liner After Spine Fusion

A 73-year-old woman, 11 years after total hip arthroplasty and 2 years after a multilevel lumbar spine fusion, presented with a 2-month history of anterior hip and gluteal pain. She was diagnosed with an acetabular liner fracture that occurred through the high wall, likely related to repetitive impingement on the neck of the femoral implant, as notable burnishing was observed on the explanted femoral head. The acetabulum was successfully revised to a dual-mobility articulation. Spinal fusion after total hip arthroplasty can alter the acetabular implant position and was seen in our patient whose previously functional high-walled liner failed. Surgeons may consider alternative techniques, including a change in acetabular implant's anteversion to mitigate the need for a high-walled liner or the use of a dual-mobility bearing.

Association of age and spinopelvic function in patients receiving a total hip arthroplasty

Restricted spinopelvic mobility received attention as a contributing factor for total hip arthroplasty (THA) instability. However, it is still unknown, how the spinopelvic function is influenced by age. In identifying the patients at highest risk for altered spinopelvic mechanics the study aimed to determine the association of age on the individual segments of the spinopelvic complex and global spinal sagittal alignment in patients undergoing THA. 197 patients were included in the prospective observational study conducting biplanar stereoradiography (EOS) in standing and sitting position pre-and postoperatively. Two independent investigators assessed C7-sagittal vertical axis (C7-SVA), cervical lordosis (CL), thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), anterior plane pelvic tilt (APPT), and pelvic femoral angle (PFA). Key segments of the spinopelvic complex are defined as lumbar flexibility (∆ LL = LL_standing - LL_sitting), pelvic mobility (∆ SS = SS_standing - SS_sitting) and hip motion (∆ PFA = PFA_standing - PFA_sitting). Pelvic mobility was further defined based on ∆ SS = SS_standing - SS_sitting as stiff (∆ SS < 10°), normal (∆ SS ≥ 10°-30°) and hypermobile (∆ SS > 30°). The patient collective was classified into three groups: (1) < 60 years (n = 56), (2) ≥ 60-79 years (n = 112) and (3) ≥ 80 years (n = 29). Lumbar flexibility (∆ LL) was decreased with increasing age between all groups (36.1° vs. 23.1° vs. 17.2°/p₁₊₂ < 0.000, p₂₊₃ = 0.020, p₁₊₃ < 0.000) postoperatively. Pelvic mobility (∆ SS) was decreased in the groups 2 and 3 compared to group 1 (21.0° and 17.9° vs. 27.8°/p₁₊₂ < 0.000, p₂₊₃ = 0.371, p₁₊₃ = 0.001). Pelvic retroversion in standing position (APPT) was higher in group 2 and 3 compared to group 1 (1.9° and - 0.5° vs 6.9°/p₁₊₂ < 0.000, p₂₊₃ = 0.330, p₁₊₃ < 0.000). Global sagittal spinal balance (C7-SVA) showed more imbalance in groups 2 and 3 compared to group 1 (60.4 mm and 71.2 mm vs. 34.5 mm/p₁₊₂ < 0.000, p₂₊₃ = 0.376, p₁₊₃ < 0.000) postoperatively. The preoperative proportion of patients with stiff pelvic mobility in group 1 was distinctly lower than in group 3 (23.2% vs. 35.7%) and declined in group 1 to 1.8% compared to 20.7% in group 3 after THA. Changes after THA were reported for groups 1 and 2 representing spinopelvic complex key parameter lumbar flexibility (∆ LL), pelvic mobility (∆ SS) and hip motion (∆ PFA), but not for group 3. This is the first study to present age-adjusted normative values for spinopelvic mobility. The subgroups with increased age were identified as risk cohort for altered spinopelvic mechanics and enhanced sagittal spinal imbalance and limited capacity for improvement of mobility after THA. This valuable information serves to focus in the preoperative screening on the THA candidates with the highest risk for abnormal spinopelvic function.

Complications following total hip arthroplasty and hemiarthroplasty for femoral neck fractures in patients with a history of lumbar spinal fusion

INTRODUCTION

The purpose of this study was to examine whether previous lumbar spinal fusion (LSF) was an independent risk factor for complications in patients undergoing total hip arthroplasty (THA) or hemiarthroplasty for displaced femoral neck fractures.

METHODS AND MATERIALS

An administrative database was queried from 2010 to Q2 of 2019 to analyze and compare complications in patients undergoing either THA or hemiarthroplasty for femoral neck fracture with a history of LSF versus no history of LSF. Joint complications including periprosthetic fracture, prosthetic joint infection (PJI), prosthetic joint dislocation (PJD), aseptic loosening, and prosthetic revision were examined at 90 days and 1 year post-operatively.

RESULTS

In the THA cohort, patients with prior LSF had significantly higher likelihood of aseptic loosening at 90 days and 1 year post-operatively in comparison to those without prior LSF (90-day: OR 2.22; 1-year: OR 1.95). Patients in the hemiarthroplasty cohort with prior LSF had significantly higher likelihood of PJI (90-day: OR 2.18; 1-year: OR 2.37), aseptic loosening (90-day: OR 3.42; 1-year: OR 4.68), and prosthetic revision (90-day: OR 2.27; 1-year: OR 2.25) in both the 90-day and 1-year postoperative period in comparison to those without prior LSF. Additionally, for the same cohort, periprosthetic fracture (1-year: OR 2.32) and PJD (1-year: OR 2.31) were significantly higher at 1-year postoperative.

CONCLUSION

Presence of LSF was found to be an independent risk factor for increased joint complications in patients undergoing either a THA or hemiarthroplasty for displaced femoral neck fractures.

Influence of kinematics of the lumbopelvic complex in hip arthroplasty dislocation: from assessment to recommendations

INTRODUCTION

In total hip arthroplasty (THA), misplacement of the implant can provide instability. Adequate orientation of the acetabular cup is a challenge due to variations in inter-individual anatomy and kinematics of the pelvis in everyday life. The aim of this study was to characterize the kinematic factors influencing the risk of dislocation in order to give recommendations for optimal placement of the cup. We hypothesized that the lack of pelvic adaptation would influence the risk of prosthetic instability and motivate adapted.

MATERIALS AND METHODS

Eighty patients with primary unilateral THA were included in a matched case-control study. Seventy-four patients were divided into two groups: group 1 (G1) consisting of patients with postoperative THA dislocation (37 patients) and group 2 (G2), without episodes of dislocation within two years postoperatively (37 patients). In both groups, spino-pelvic parameters and cup orientation were measured in standing and sitting positions with EOS^® X-ray imaging and compared to each other between 12 and 24 months post-operatively.

RESULTS

No significant difference between the two groups was found for static parameters. In a sitting position, a lack of pelvic retroversion with a significant lower variation in sacral slope was observed in group 1 (8.0° ± 9.3 for G1 versus 14.7° ± 6.2 for G2, p < 0.01). Twenty-two (59%) patients with THA instability had sacral slope variations of less than 10° versus eight (21% of patients) with stable THA (p < 0.01). Cup orientation in the Lewinnek safe zone was not significantly different (59% vs 67%, p = 0.62), and the spino-pelvic parameters and cup orientation measured did not change between the standing and sitting positions. However, only 14 (37%) cups in G1 were in the functional safe zone versus 24 (67%) in G2 (p = 0.03).

CONCLUSION

Static parameters of the sagittal spinopelvic balance have a low predictive value for prosthetic instability. Dynamic analysis is essential. Kinematic parameters must be taken into account in determining the ideal position of the cup or stem. Stiffness with locked standing or sitting pelvis must be integrated in order to determine a personalized safe zone.

LEVEL OF EVIDENCE

Level III (matched case-control study).