Excessive posterior pelvic tilt from preoperative supine to postoperative standing after total hip arthroplasty.

Aims: Excessive posterior pelvic tilt (PT) may increase the risk of anterior instability after total hip arthroplasty (THA). The aim of this study was to investigate the changes in PT occurring from the preoperative supine to postoperative standing position following THA, and identify factors associated with significant changes in PT. Methods: Supine PT was measured on preoperative CT scans and standing PT was measured on preoperative and one-year postoperative standing lateral radiographs in 933 patients who underwent primary THA. Negative values indicate posterior PT. Patients with > 13° of posterior PT from preoperative supine to postoperative standing (ΔPT ≤ -13°) radiographs, which corresponds to approximately a 10° increase in functional anteversion of the acetabular component, were compared with patients with less change (ΔPT > -13°). Logistic regression analysis was used to assess preoperative demographic and spinopelvic parameters predictive of PT changes of ≤ -13°. The area under receiver operating characteristic curve (AUC) determined the diagnostic accuracy of the predictive factors. Results: PT changed from a mean of 3.8° (SD 6.0°)) preoperatively to -3.5° (SD 6.9°) postoperatively, a mean change of -7.4 (SD 4.5°; p < 0.001). A total of 95 patients (10.2%) had ≤ -13° change in PT from preoperative supine to postoperative standing. The strongest predictive preoperative factors of large changes in PT (≤ -13°) from preoperative supine to postoperative standing were a large posterior change in PT from supine to standing, increased supine PT, and decreased standing PT (p < 0.001). Flexed-seated PT (p = 0.006) and female sex (p = 0.045) were weaker significant predictive factors. When including all predictive factors, the accuracy of the AUC prediction was 84.9%, with 83.5% sensitivity and 71.2% specificity. Conclusion: A total of 10% of patients had > 13° of posterior PT postoperatively compared with their supine pelvic position, resulting in an increased functional anteversion of > 10°. The strongest predictive factors of changes in postoperative PT were the preoperative supine-to-standing differences, the anterior supine PT, and the posterior standing PT. Surgeons who introduce the acetabular component with the patient supine using an anterior approach should be aware of the potentially large increase in functional anteversion occurring in these patients.

Modular dual-mobility articulations in patients with adverse spinopelvic mobility.

AIMS: Adverse spinal motion or balance (spine mobility) and adverse pelvic mobility, in combination, are often referred to as adverse spinopelvic mobility (SPM). A stiff lumbar spine, large posterior standing pelvic tilt, and severe sagittal spinal deformity have been identified as risk factors for increased hip instability. Adverse SPM can create functional malposition of the acetabular components and hence is an instability risk. Adverse pelvic mobility is often, but not always, associated with abnormal spinal motion parameters. Dislocation rates for dual-mobility articulations (DMAs) have been reported to be between 0% and 1.1%. The aim of this study was to determine the early survivorship from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) of patients with adverse SPM who received a DMA. METHODS: A multicentre study was performed using data from 227 patients undergoing primary total hip arthroplasty (THA), enrolled consecutively. All the patients who had one or more adverse spine or pelvic mobility parameter had a DMA inserted at the time of their surgery. The mean age was 76 years (22 to 93) and 63% were female (n = 145). At a mean of 14 months (5 to 31) postoperatively, the AOANJRR was analyzed for follow-up information. Reasons for revision and types of revision were identified. RESULTS: The AOANJRR reported two revisions: one due to infection, and the second due to femoral component loosening. No revisions for dislocation were reported. One patient died with the prosthesis in situ. Kaplan-Meier survival rate was 99.1% (95% confidence interval 98.3 to 100) at 14 months (number at risk 104). CONCLUSION: In our cohort of patients undergoing primary THA with one or more factor associated with adverse SPM, DM bearings conferred stability at two years' follow-up. Cite this article: Bone Joint J 2022;104-B(7):820-825.

Does Prosthetic or Bony Impingement Occur More Often in Total Hip Arthroplasty: A Dynamic Preoperative Analysis.

BACKGROUND: Impingement is a leading cause for instability resulting in revision total hip arthroplasty (THA). Impingement can be prosthetic, bony, or soft tissue. The purpose of this study is to investigate, using a virtual simulation, whether bony or prosthetic impingement presents first in well-positioned THAs. METHODS: Twenty-three patients requiring THA were planned for a ceramic-on-poly cementless construct using dynamic planning software. Cups were orientated at 45° inclination and 25° anteversion when standing. Femoral components and neck lengths were positioned to reproduce native anteversion and match contralateral leg length and offset. The type and location of impingement was then recorded with recreation of anterior and posterior impingement during standard and extreme ranges of motion (ROM). RESULTS: In standard ROM, flexion produced both prosthetic and bony impingement and extension resulted in prosthetic impingement in models with lipped liners. In extreme ROM, anterior impingement was 78% bony in 32-mm articulations, and 88% bony in 36-mm articulations. Posterior impingement was 65% prosthetic in 32-mm articulations, and 55% prosthetic in 36-mm articulations. Dual mobility cups showed the greatest risk of posterior prosthetic impingement in hyperextension (74%). CONCLUSION: In standard ROM, both bony and prosthetic impingement occurred in flexion, while prosthetic impingement occurred in extension in models with lipped liners. In hyperextension, prosthetic impingement was more common than bony impingement, and was exclusively the cause of impingement when a lip was used. In flexion, impingement was primarily bony with the use of a 36-mm head. The risk of posterior prosthetic impingement was greatest with dual mobility cups. LEVEL OF EVIDENCE: 3.

Variation in femoral anteversion in patients requiring total hip replacement.

BACKGROUND: Optimal implant alignment is important for total hip replacement (THR) longevity. Femoral stem anteversion is influenced by the native femoral anteversion. Knowing a patient's femoral morphology is therefore important when planning optimal THR alignment. We investigated variation in femoral anteversion across a patient population requiring THR. METHODS: Preoperatively, native femoral neck anteversion was measured from 3-dimensional CT reconstructions in 1215 patients. RESULTS: The median femoral anteversion was 14.4° (-27.1-54.5°, IQR 7.4-20.9°). There were significant gender differences (males 12.7°, females 16.0°; p < 0.0001). Femoral anteversion in males decreased significantly with increasing age. 14% of patients had extreme anteversion (<0° or >30°). CONCLUSIONS: This is the largest series investigating native femoral anteversion in a THR population. Patient variation was large and was similar to published findings of a non-THR population. Gender and age-related differences were observed. Native femoral anteversion is patient-specific and should be considered when planning THR.

Prevalence of Sagittal Spinal Deformity Among Patients Undergoing Total Hip Arthroplasty.

BACKGROUND: The important relationship between sagittal spinal alignment and total hip arthroplasty (THA) is becoming well recognized. Prior research has shown a significant relationship between sagittal spinal deformity (SSD) and THA instability. This study aims at determining the prevalence of SSD among preoperative THA patients. METHODS: A multicenter database of preoperative THA patients was analyzed. Radiographic parameters measured from standing radiographs included anterior pelvic plane tilt, spinopelvic tilt, and lumbar lordosis (LL); pelvic incidence (PI) was measured from computed tomography scans. Lumbar flatback was defined as PI-LL mismatch >10°, balanced as PI-LL of -10° to 10°, and hyperlordosis as PI-LL <-10°. RESULTS: A total of 1088 patients were analyzed (mean, 64 years; 48% female). And 59% (n = 644) of patients had balanced alignment, 16% (n = 174) had a PI-LL > 10°, and 4% (n = 46) had a PI-LL > 20° (severe flatback deformity). The prevalence of hyperlordosis was 25% (n = 270). Flatback patients tended to be older than balanced and hyperlordotic patients (69.5 vs 64.0 vs 60.8 years, P < .001). Spinopelvic tilt was more posterior in flatback compared to balanced and hyperlordotic patients (24.7° vs 15.4° vs 7.0°) as was anterior pelvic plane tilt (-7.1° vs -2.0° vs 2.5°) and PI (64.1° vs 56.8° vs 49.0°), all P < .001. CONCLUSION: Only 59% of patients undergoing THA have normally aligned lumbar spines. Flatback SSD was observed in 16% (4% with severe flatback deformity) and there was a 25% prevalence of hyperlordosis. Lumbar flatback was associated with increasing age, posterior pelvic tilt, and larger PI. The relatively high prevalence of spinal deformity in this population reinforces the importance of considering spinopelvic alignment in THA planning and risk stratification.

Effects of Sagittal Spinal Alignment on Postural Pelvic Mobility in Total Hip Arthroplasty Candidates.

BACKGROUND: Recent research has demonstrated that patients with reduced pelvic mobility from standing to sitting have higher rates of dislocation after total hip arthroplasty (THA). This study evaluates the effect of sagittal spinal deformity, defined by pelvic incidence-lumbar lordosis mismatch (PI-LL), on postural changes in pelvic tilt (PT). METHODS: A multicenter database of 1100 preoperative THA patients was queried. Anterior-pelvic-plane tilt (APPt), spinopelvic tilt (SPT), and LL were measured from radiographs of patients in supine, standing, flexed-seated, and stepping-up postures; PI was measured from computed tomography. Patients were separated into 3 groups based on PI-LL (<-10°, -10° to 10°, >10°) and propensity-score matched by PI. Lumbar flatback-deformity was defined as PI-LL > 10°, hyperlordosis: PI-LL < -10°. SPT/APPt, including changes between each posture were compared across PI-LL groups using analysis of variance, with post-hoc Tukey tests. Pearson correlations were reported when testing associations between SPT/APPt change and PI-LL. RESULTS: After propensity-score matching, 288 patients were analyzed (mean 65 y; 49% F). SPT and APPt change differed across all PI-LL categories from standing to seated, supine, and stepping-up with less SPT/APPt recruitment among hyperlordotic vs flatback patients (all P < .001). Greater PI-LL correlated with greater SPT recruitment from standing to seated (R = 0.294), supine (R = 0.292), and stepping-up (R = 0.207) (all P < .001). Smaller LL changes from standing to seated were associated with greater SPT recruitment (R = 0.372, P < .001). CONCLUSIONS: Postural changes in SPT/APPt are associated with spinopelvic measures in THA candidates. Hyperlordotic patients tend to utilize their spines more compared with flatback patients who were more likely to recruit PT. Increased focus on patients with lumbar flatback and hyperlordosis may help in reducing prosthetic dislocation prevalence following THA.

Prevalence of Anterior Femoral Neck Osteophyte in a Total Hip Arthroplasty Population: Analysis of Preoperative Surgical Plans.

Despite strongly positive results of total hip arthroplasty (THA), patients remain at risk for complications including dislocation. Spinopelvic motion and the hip-spine relationship have been recognized as important factors in surgical planning and implant positioning in THA. Periarticular osteophytes are one of the hallmark pathoanatomic features of osteoarthritis and may influence implant positioning and joint stability; residual osteophytes at the anterior femoral neck may cause anterior impingement and posterior instability. No studies have been identified which establish the prevalence of anterior femoral neck osteophyte for incorporation into THA planning. 413 consecutive patients scheduled for THA underwent preoperative planning taking into account spinopelvic motion to establish optimal component position. Each surgical plan was reviewed retrospectively by four independent raters who were blinded to other imaging and intraoperative findings. Anterior femoral neck osteophytes were rated as being absent, minor, or extensive for each case. A single outlying rater was excluded. Inter-rater reliability was calculated manually. The patient group comprised 197 male and 216 female hips, with a mean age of 63 years (range 32-91). The presence of anterior femoral neck osteophytes was identified in a mean of 82% of cases (range 78-86%). A significant number of patients were found to have large or extensive osteophytes present in this location (mean 27%; range 23-31%). Inter-rater reliability was 70%. A large majority of our THA patients were found to have anterior femoral neck osteophytes. These must be considered during preoperative planning with respect to the spinopelvic relationship. Failure to identify and address osteophytes intraoperatively may increase the risk of impingement in flexion and/or internal rotation, leading to decreased range of motion, joint instability, and possibly dislocation. Planned future directions include incorporation of an impingement and instability model into preoperative planning for THA.