Risk Factors and Cup Protrusion Thresholds for Symptomatic Iliopsoas Impingement After Total Hip Arthroplasty: A Retrospective Case-Control Study

Determination of preoperative risk factors for iliopsoas tendonitis after total hip arthroplasty: A simulation study

This study aims to identify preoperative risk factors for iliopsoas tendonitis after total hip arthroplasty, a complication typically attributed to acetabular cup position and orientation, using a validated iliopsoas impingement detection simulation. Analyzing CT scans and X-rays of 448 patients using a validated preoperative planning protocol, patients were simulated for iliopsoas impingement and categorized into at-risk and not at-risk groups based on a prior validation study, with a 23% at-risk incidence. Implementing a propensity score matching algorithm to reduce covariate imbalance, we identified factors that may exacerbate risk of iliopsoas tendonitis. Parameters that were investigated included standing pelvic tilt, functional femoral rotation, and the difference between the planned acetabular cup diameter and native femoral head diameter (ΔC-NFH). Comparing pelvic tilt, we found a significant difference between the groups (at-risk: -6.0°, not at-risk: -0.7°; p << 0.01). A similar trend was noted for ΔC-NFH (at-risk: +5.7 mm, not at-risk: +5.1 mm; p = 0.01). Additional simulations of at-risk patients indicated increased anteversion of the acetabular cup reduces impingement risk more effectively than medialisation. These findings suggest that spinopelvic parameters may exacerbate iliopsoas irritation risk, underscoring their importance in preoperative planning and patient expectation management. Similar findings of a greater than 6 mm difference between cup size and native femoral head diameter being a significant risk for iliopsoas tendonitis have been observed before, underscoring its potential veracity. These results may provide surgeons with a simple threshold that can be used in determining a cup size to reduce the risk of iliopsoas tendonitis.

What happens in the medium-term to capsule-thickening plasties for iliopsoas impingement after total hip arthroplasty? Evaluation of 14 procedures at 4years' follow-up

INTRODUCTION

In 2015, we described a capsule-thickening technique via an anterior approach for iliopsoas cup impingement. To our knowledge, medium-term results have not been reported. We therefore retrospectively analyzed all cases in the initial series and those since 2015, to assess this original technique over a longer follow-up: (1) to analyze complications, and (2) to assess functional outcome.

HYPOTHESIS

The study hypothesis was that this surgical solution has a success rate sufficient for it to be included in the therapeutic armamentarium for iliopsoas impingement.

MATERIAL AND METHOD

Fourteen patients were included. Nine plasties were in first line, 3 after tenotomy, and 2 after cup exchange. The anterior Hueter approach was used, visualizing anterior cup overhang, sometimes associated with penetration of the anterior capsule, and enabling capsule-thickening by a folded Vicryl™ mesh. Functional results were analyzed.

RESULTS

At a median 4years' follow-up (IQR: 2-5; range: 1-9), change over baseline in Oxford score was 7 points (p=0.004), median Medical Research Council thigh flexion strength score was 5 (IQR: 5-5), and 50% of patients (7/14) were satisfied or very satisfied. The major complications rate was 7% (1/14), for 1 irrigation of infected hematoma, cured without recurrence; there was also 1 minor case of injury to the lateral cutaneous nerve of the thigh. Forty-three percent of patients (6/14) exhibited a minimal clinically important difference (MCID) and 64% (9/14) a patient-acceptable symptom state (PASS). Median anatomic overhang on anatomic CT transverse slice was 7mm (IQR: 3-8; range: 0-13). Four patients underwent secondary acetabular component exchange; their median overhang was 7.5mm (IQR: 7-8) compared to 5mm (IQR: 2-8) for the other patients (p-value non-calculable).

CONCLUSION

This surgical option seems interesting when acetabular overhang is not too great, especially as it does not affect flexion strength.

LEVEL OF EVIDENCE

IV.

Quantifying cup overhang after total hip arthroplasty: standardized measurement using reformatted computed tomography and association of overhang distance with iliopsoas impingement

OBJECTIVES

Currently, there is no standardized measurement method for evaluating cup overhang (CO) in patients undergoing total hip arthroplasty (THA). We propose a novel, standardized method of measuring overhang distance in patients following primary total hip arthroplasty (THA) on computed tomography (CT) images after multiplanar reformation and compare it to a previously proposed measurement method on sagittal CT images.

MATERIALS AND METHODS

This retrospective study included patients who underwent primary THA with an anterior approach. Patients with cup overhang (CO) and iliopsoas impingement (IPI) were identified by clinical and imaging data. Uncorrected overhang distance (ODu) was evaluated on orthogonal sagittal CT images while corrected overhang distance (ODc) was evaluated on reformatted sagittal CT images corrected for pelvic rotation and aligned with the plane of the cup face.

RESULTS

Out of 220 patients with THA, 23 patients (10.4%) with CO and 16 patients (7.3%) with IPI were identified. CO was significantly associated to IPI (p < 0.001). The inter- and intrareader agreement was almost perfect for ODc (κ = 0.822, κ = 0.850), whereas it was fair and moderate for ODu (κ = 0.391, κ = 0.455), respectively. The discriminative ability of ODc was excellent (area under the curve (AUC) = 0.909 (95% confidence interval (CI) 0.784-1.000)) in the receiver operating characteristic analysis. Conversely, AUC for ODu was poor, measuring 0.677 (95% CI 0.433-0.921).

CONCLUSION

We implemented a novel measurement method for CT images reformatted at the plane of the cup face to assess overhang distance in patients with CO following THA.

CLINICAL RELEVANCE STATEMENT

While further validation is necessary, the proposed method is characterized by its high reproducibility and might be used to predict the occurrence of iliopsoas impingement in patients with cup overhang following total hip arthroplasty.

KEY POINTS

• A novel, standardized method of measuring cup overhang distance in patients following primary total hip arthroplasty on CT images is proposed. • Cup overhang was associated to iliopsoas impingement. The proposed method was reproducible and showed excellent prediction of iliopsoas impingement in patients with cup overhang. • This method can be implemented in clinical practice when assessing CT images of patients with cup overhang for iliopsoas impingement.

Femoral anteversion change is associated with ischiofemoral impingement after total hip arthroplasty: a retrospective CT evaluation

OBJECTIVES

We evaluated the relationship between femoral anteversion (FA), FA change, and ischiofemoral impingement (IFI) and the relationship between FA, femoral offset (FO), and greater trochanteric pain syndrome (GTPS) after total hip arthroplasty (THA).

MATERIALS AND METHODS

In this retrospective study, two readers assessed FA and FO on CT images of 197 patients following primary THA with an anterior surgical approach between 2014 and 2021. FA change was calculated relative to preoperative CT, while FO change was calculated relative to preoperative radiographs and classified as decreased (≥-5 mm), increased (≥ + 5 mm), or restored (± 5 mm). Clinical and imaging data were analyzed for IFI and GTPS after surgery. Group differences were evaluated using Student's t-test, chi-square analysis, and receiver operating characteristic (ROC) analysis.

RESULTS

The change in FA was 3.6 ± 3.3° to a postoperative FA of 22.5 ± 6.8°, while FO increased by 1.7 ± 3.5 mm to a postoperative FO of 42.9 ± 7.1 mm. FA and FA change were higher in patients with IFI (p ≤ 0.006), while no significant difference was observed for patients with and without GTPS (p ≥ 0.122). IFI was more common in females (p = 0.023). In the ROC analysis, an AUC of 0.859 was observed for FA change to predict IFI, whereas the AUC value was 0.726 for FA alone. No significant difference was found for FO change in patients with and without IFI or GTPS (p ≥ 0.187).

CONCLUSION

Postoperative FA, FA change, and female sex were associated with IFI after anterior-approached THA. The change in FA was a better predictor of IFI than absolute postoperative FA alone.

CLINICAL RELEVANCE STATEMENT

The findings of this study suggest that preservation of the preoperative femoral anteversion may reduce postoperative ischiofemoral impingement in patients undergoing total hip arthroplasty.

KEY POINTS

• Higher postoperative femoral anteversion and anteversion change were associated with ischiofemoral impingement. • Femoral anteversion change was a better predictor of impingement than absolute postoperative anteversion. • No significant association was found between femoral offset and postoperative hip pain.

Arthroscopic Fractional Lengthening After Total Hip Arthroplasty Results in Improved Patient-Reported Outcomes and Low Rates of Revision Total Hip Arthroplasty

Purpose

To report the clinical outcomes and reoperation rates of arthroscopic and endoscopic iliopsoas release at short-term follow-up after ipsilateral total hip arthroplasty (THA) at 2 separate medical institutions and to evaluate whether demographic and radiographic parameters are associated with postoperative patient-reported outcomes (PROs).

Methods

Patients with iliopsoas tendinitis in the setting of prior THA who underwent arthroscopic iliopsoas fractional lengthening from 1988 to 2023 at 2 academic institutions were reviewed. Patients were included if they had 12 months of follow-up and underwent evaluation of preoperative anterior acetabular component overhang, surgery satisfaction, postoperative subjective hip flexion strength and anterior groin pain improvement, modified Harris Hip Score, Single Assessment Numeric Evaluation score, Tegner activity scale score, visual analog scale (VAS) score, and revision hip arthroplasty.

Results

Sixty hips in 58 patients (19 male and 39 female patients) were followed up for a mean of 39.3 months (range, 12.0-105.9 months) postoperatively. Of the patients, 77% reported feeling "much better" or "slightly better," 75% reported improved anterior groin pain, and 60% reported improved subjective hip flexion strength. The surgery satisfaction rating was 7.2 ± 3.3 (scale of 0 to 10). The mean postoperative modified Harris Hip Score, VAS score for pain at rest, VAS score for pain with use, and Single Assessment Numeric Evaluation score were 73.9 ± 19.4, 1.3 ± 2.4, 3.8 ± 2.9, and 71.9 ± 21.9, respectively. Preoperative anterior acetabular component overhang was 3.3 ± 6.5 mm and did not significantly correlate with postoperative PROs (P ≥ .45). The Tegner score improved from 2.5 ± 1.7 preoperatively to 2.9 ± 1.4 postoperatively (P = .0253). Three patients underwent revision arthroplasty at a mean of 25.3 months (range, 11.6-40.4 months) postoperatively, with an acetabular component revision rate of 3.3%.

Conclusions

Satisfactory outcomes and low revision arthroplasty rates were observed in patients undergoing arthroscopic iliopsoas lengthening after THA. There was no statistically significant relation between anterior acetabular component overhang and final PROs.

Level of Evidence

Level IV, therapeutic case series.

Morphological features of the acetabulum with coxa profunda in women: a retrospective observational study

BACKGROUND

The morphology of coxa profunda remains inadequately understood. However, knowledge about the characteristics of the acetabulum in coxa profunda can help to predict pelvic morphology in three dimensions based on radiographic findings, as well as help to diagnose and predict hip pathologies. Therefore, this study aimed to investigate the relationship between the morphological characteristics of the pelvis and coxa profunda.

METHODS

We conducted a retrospective analysis including women who had undergone unilateral total hip arthroplasty. Only those with normal hip joint morphology on the opposite side, as evidenced by anteroposterior pelvic radiography showing a distance of ≥ 2 mm between the ilioischial line and acetabular floor, were included. Five parameters related to acetabular anteversion, thickness, and the position of the ilioischial line were measured using axial computed tomography at the central hip joint. The coxa profunda group (n = 39) and control group (n = 34) were compared.

RESULTS

The mean acetabular anteversion angle was 12.5° ± 4° in the control group and 22.3° ± 5.6° in the coxa profunda group. The mean thickness from the acetabular fossa to the medial wall was 7.5 ± 1.7 mm in the control group and 3.9 ± 1.2 mm in the coxa profunda group. Furthermore, the bony region representing the ilioischial line was positioned more posteriorly in the coxa profunda group than it was in the control group.

CONCLUSION

Our findings suggest that coxa profunda in women is associated with anterior acetabular dysplasia and a thin acetabulum, in contrast to previous interpretations of excessive coverage. This insight suggests a conversion of coxa profunda from a finding of pincer-type femoroacetabular impingement to a finding of acetabular dysplasia, a revelation that also draws attention to cup positioning for total hip arthroplasty.

Satisfactory mid-term clinical outcomes of endoscopic tenotomy for iliopsoas tendinopathy following total hip arthroplasty

PURPOSE

To report 5-year outcomes of endoscopic iliopsoas tenotomy in patients with iliopsoas tendinopathy following total hip arthroplasty (THA) and determine whether clinical scores are associated with cup position.

METHODS

Patients who underwent endoscopic iliopsoas tenotomy for iliopsoas tendinopathy following THA (2014-2017) were contacted. Indications for endoscopic iliopsoas tenotomy after THA were groin pain during active hip flexion, exclusion of other causes of groin pain, and no pain relief after 6 months of conservative treatment. Pretenotomy cup inclination and anteversion were measured on radiographs; axial and sagittal cup overhang were measured on computed tomography (CT) scans. Oxford hip score (OHS), modified Harris hip score (mHHS), and groin pain were assessed.

RESULTS

The initial cohort comprised 16 men (17 hips) and 31 women (32 hips), aged 60.7 ± 10.6 years. Cup inclination and anteversion were, respectively, 46.2 ± 6.2° and 14.6 ± 8.4°, while axial and sagittal cup overhang were, respectively, 4.4 ± 4.0 mm and 6.9 ± 4.5 mm. At ≥5 years follow-up, four hips underwent cup and stem revision, two underwent isolated cup revision and one underwent secondary iliopsoas tenotomy. OHS improved by 23 ± 10 and mHHS improved by 31 ± 16. Posttenotomy groin pain was slight in 20.0%, mild in 17.5% and moderate in 12.5%. Regression analyses revealed that net change in mHHS decreased with sagittal cup overhang (β = -3.1; 95% confidence interval [CI] = -4.6 to -1.7; p < 0.001), but that there were no associations between cup position and net change in OHS.

CONCLUSIONS

Endoscopic iliopsoas tenotomy provides good mid-term clinical outcomes in patients with iliopsoas tendinopathy following THA. Furthermore, improvements in mHHS were found to decrease with increasing sagittal cup overhang, in cases for which adequate preoperative imaging was available.

LEVEL OF EVIDENCE

Level IV.

Editorial Commentary: For Post-Hip Arthroplasty Iliopsoas Tendonitis, Psoas Tenotomy Is the Preferred First-Line Treatment, Even in Cases of Cup Overhang

Iliopsoas impingement pathology is one of the causes of persistent pain after total hip arthroplasty. It is reported as occurring in approximately 4% of cases; this may be significantly greater (in cases of postarthroplasty pain of unknown etiology). Inflammation is a result of impingement of the tendon against the acetabular component. This may occur with anteroinferior prominence when the cup is properly positioned in anteversion or when the cup is oversized. Other causes of impingement include a cup-reinforcement ring or acetabular cage, a collared femoral component, screws penetrating through the ilium, cement extrusion, anterior wall hypoplasia, or increased femoral offset. When conservative treatment does not achieve the best outcome, the 2 main therapeutic options are psoas tenotomy or revision of the cup component. Tenotomy can be performed either arthroscopically or by an open approach and may be considered the best option for many patients, even in cases with anterior component prominence, as it is less invasive, presents fewer complications, and has faster recovery. The debate is open. The level of tenotomy remains controversial, with risks and benefits of both a lesser trochanter and transcapsular approach.

Selective laser melting of low-alloyed titanium based alloy with a large solidification range

In this work, thermodynamic calculations for α + β Type Ti-Fe-Cu-Sn alloy were carried out by the Thermo-Calc software. Powders from this alloy were obtained by plasma sputtering and used for subsequent 3D printing of experimental samples. The effect of various selective laser melting (SLM) parameters on porosity and hot cracking susceptibility as well as the electrochemical characteristics of the alloy have been studied. The optimal technological regime for the manufacture of samples by the SLM method was determined. It has been established that to obtain relatively dense samples without cracks, regimes with volumetric energy density Ev = 250-300 J/mm3 are required. It has been established that a change in the electrochemical behavior of the Ti94Fe1Cu1Sn4 alloy is related to the formation of a nonequilibrium Ti2Cu phase. Based on the findings we recomended directions for further research.

Anatomy of the iliopsoas notch and its relationship with morphology of the proximal femur

PURPOSE

Discrepancy between the morphology of the acetabular margin and the design of hemispheric acetabular cups used in total hip arthroplasty may produce postoperative hip pain due to an iliopsoas impingement at the iliopsoas notch. This study aimed to determine the anatomical features of the iliopsoas notch in the Central European sample, and to test whether the morphology of the proximal femur affects the size of the iliopsoas notch.

METHODS

The sample was composed of 40 matched pairs of dry hip bones and corresponding femora. The depth and length of the iliopsoas notch were measured and correlated with the available demographic data. The anthropometric parameters of the proximal femur were calculated using image-analysis software, and their association with the measurements of the iliopsoas notch was tested.

RESULTS

The iliopsoas notch was present in all specimens and featured four morphological configurations: curved (61.3%), angular (16.2%), irregular (16.2%), and straight (6.3%). Its size was found to be larger in males (P = 0.014 for depth, P < 0.001 for length). No significant difference existed between the sides. The height and age of the specimens did not correlate with the size of the iliopsoas notch. Furthermore, neither the femoral neck version, the lesser trochanteric version, nor the angle between the neck of the femur and the lesser trochanter influenced the dimensions of the iliopsoas notch.

CONCLUSION

The iliopsoas notch is a consistent landmark of the acetabulum, although its anatomical appearance is widely variable. The iliopsoas notch arrangement cannot be predicted perioperatively based on the morphology of the proximal femur. The various shapes and sex-related differences detected in this study could be used for designing new hip implants or could be utilized during cup positioning in total hip arthroplasty.

The Anterior Position of the Hip Center of Rotation Is Related to Anterior Cup Protrusion Length and Symptomatic Iliopsoas Impingement in Primary Total Hip Arthroplasty

BACKGROUND

Iliopsoas impingement (IPI) is an important complication after total hip arthroplasty (THA), and anterior cup protrusion is believed to be its main cause; however, the relationship between the hip center of rotation (COR) and symptomatic IPI or cup protrusion remains poorly understood. Therefore, the present study investigated these relationships.

METHODS

The medical records of 138 patients who underwent unilateral primary THA were retrospectively reviewed. There were 8 patients (5.8%) who had symptomatic IPI. The COR and cup protrusion length measured with 2 methods were assessed on computed tomography. Risk factors for symptomatic IPI and the relationship between the COR and protrusion length were evaluated.

RESULTS

Logistic regression analyses showed that anteroposterior position of the COR, sagittal cup protrusion length (SCPL) at the COR, and both axial and SCPLs at the most anterior margin of the cup were related to symptomatic IPI. Multivariable regression analyses showed that acetabular offset was related to axial protrusion length at the COR, and anteroposterior position of the COR was related to both axial and sagittal protrusion lengths at the most anterior margin of the cup.

CONCLUSION

Anterior position of the cup was related to symptomatic IPI and both axial and sagittal protrusion lengths at the most anterior margin of the cup. Anterior reaming and cup protrusion should be avoided as much as possible to prevent symptomatic IPI.

Increased hip flexion angle and protrusion of the anterior acetabular component can predict symptomatic iliopsoas impingement after total hip arthroplasty: a retrospective study

BACKGROUND

Iliopsoas impingement (IPI) is a known complication of total hip arthroplasty (THA). The aim of this study was to identify risk factors and the cut-off cup protrusion length for symptomatic IPI.

METHODS

We retrospectively reviewed 218 hips (46 men, 172 women) of 190 consecutive Japanese patients who underwent primary THA at our institution. Hips with IPI (n = 24) and control hips (n = 194) were compared according to age, body mass index, and clinical scores. We evaluated leg-length discrepancy, global offset, implant alignment angles, pelvic inclination, and anterior cup protrusion on plain radiographs and computed tomography scans.

RESULTS

Symptomatic IPI had an incidence of 11.0% and a predilection for hips with osteonecrosis. Pre- and postoperative hip flexion angles were significantly greater in hips with symptomatic IPI (p = 0.013 and p = 0.006, respectively). Cup protrusion length was significantly greater in hips with IPI (4.7 mm vs. 1.4 mm; p = 0.001). Receiver-operating characteristic curve analysis identified a threshold cup protrusion length of 3.9 mm (sensitivity 0.89, specificity 0.63) for symptomatic IPI. The incidence of symptomatic IPI tended to be lower in patients with greater posterior pelvic sagittal inclination despite the cup protrusion length being greater.

CONCLUSIONS

An increased hip flexion angle and protrusion of the anterior acetabular component predicted symptomatic IPI. The threshold cup protrusion length suggesting mild IPI might be about 3.9 mm and could be useful for identifying candidates for conservative treatment.

Does Augmented Reality-based Portable Navigation Improve the Accuracy of Cup Placement in THA Compared With Accelerometer-based Portable Navigation? A Randomized Controlled Trial

BACKGROUND

Previous studies reported good outcomes of acetabular cup placement using portable navigation systems during THA. However, we are aware of no prospective studies comparing inexpensive portable navigation systems using augmented reality (AR) technology with accelerometer-based portable navigation systems in THA.

QUESTIONS/PURPOSES

(1) Is the placement accuracy of the acetabular cup using the AR-based portable navigation system superior to that of an accelerometer-based portable navigation system? (2) Do the frequencies of surgical complications differ between the two groups?

METHODS

We conducted a prospective, two-arm, parallel-group, randomized controlled trial involving patients scheduled for unilateral THA. Between August and December 2021, we treated 148 patients who had a diagnosis of osteoarthritis, idiopathic osteonecrosis, rheumatoid arthritis, or femoral neck fracture and were scheduled to undergo unilateral primary THA. Of these patients, 100% (148) were eligible, 90% (133) were approached for inclusion in the study, and 85% (126) were finally randomized into either the AR group (62 patients) or the accelerometer group (64 patients). An intention-to-treat analysis was performed, and there was no crossover between groups and no dropouts; all patients in both groups were included in the analysis. There were no differences in any key covariates, including age, sex, and BMI, between the two groups. All THAs were performed via the modified Watson-Jones approach with the patient in the lateral decubitus position. The primary outcome was the absolute difference between the cup placement angle displayed on the screen of the navigation system and that measured on postoperative radiographs. The secondary outcome was intraoperative or postoperative complications recorded during the study period for the two portable navigation systems.

RESULTS

There were no differences between the AR and accelerometer groups in terms of the mean absolute difference in radiographic inclination angle (3° ± 2° versus 3° ± 2° [95% CI -1.2° to 0.3°]; p = 0.22). The mean absolute difference in radiographic anteversion angle displayed on the navigation screen during surgery compared with that measured on postoperative radiographs was smaller in the AR group than that in the accelerometer group (2° ± 2° versus 5° ± 4° [95% CI -4.2° to -2.0°]; p < 0.001). There were few complications in either group. In the AR group, there was one patient each with a surgical site infection, intraoperative fracture, distal deep vein thrombosis, and intraoperative pin loosening; in the accelerometer group, there was one patient each with an intraoperative fracture and intraoperative loosening of pins.

CONCLUSION

Although the AR-based portable navigation system demonstrated slight improvements in radiographic anteversion of cup placement compared with the accelerometer-based portable navigation system in THA, whether those small differences will prove clinically important is unknown. Until or unless future studies demonstrate clinical advantages that patients can perceive that are associated with such small radiographic differences, because of the costs and the unquantified risks associated with novel devices, we recommend against the widespread use of these systems in clinical practice.

LEVEL OF EVIDENCE

Level I, therapeutic study.

Endoscopic iliopsoas lengthening for treatment of recalcitrant iliopsoas tendinitis after total hip arthroplasty

Iliopsoas (IP) tendinitis from impingement upon the acetabular component after total hip arthroplasty (THA) has been treated with open and endoscopic IP tenotomy or acetabular component revision. This study describes the results of a consecutive series of patients treated with endoscopic IP tenotomy as a less invasive alternative. Twenty-eight patients with IP impingement after THA underwent endoscopic IP lengthening from 2012 to 2021 at a single-center academic institution. The follow-up of 24 of these patients was achieved with a mean follow-up of 7.6 months (range 1-28). Outcomes included the modified Harris Hip Score (mHHS), visual analog pain scale (VAS), satisfaction, component positioning and complications. Seventy-one percent of patients were satisfied or very satisfied after their operation. The median mHHS preoperatively was 57 (Interquartile range [IQR] 43-60) and postoperatively was 75 (IQR 66-92, P < 0.001). Clinically meaningful improvements in mHHS were seen in patients with VAS pain scores <5, cup prominence >8 mm, body mass index >30, and less than 2 years from their index THA. Two patients developed a deep infection 7 and 10 months postoperatively (neither related to the release), and one patient underwent open psoas release for persistent impingement. Endoscopic IP tenotomy is a safe and effective treatment for impingement after THA. Patients with cup prominence >8 mm, body mass index >30 and less than 2 years since their index THA may have more clinically meaningful improvements in pain and function.

A comparison of accuracy and safety between stem-first and cup-first total hip arthroplasty: a prospective randomised controlled trial

BACKGROUND

The combined anteversion theory to prevent impingement in total hip arthroplasty (THA) has been proposed. However, because stem-anteversion is influenced by the native femoral anteversion and the stem flexion/extension angle, it is often difficult to adjust stem anteversion during surgery. Therefore, the stem-first (combined anteversion) technique may be useful to adjust and achieve appropriate cup anteversion during surgery with respect to the implanted stem anteversion angle. However, the technique may adversely affect cup or stem angle accuracy and result in intra-operative bleeding, post-operative adverse events, and prolonged operative time. It is inconclusive whether either the stem-first or cup-first technique is safe or accurate. Therefore, this study assessed the accuracy and safety of stem-first THA compared to those of cup-first THA.

MATERIALS AND METHODS

This prospective randomised controlled trial analysed 114 patients who were randomly divided into 2 groups (stem-first group: n = 57, cup-first group (control group): n = 57). Primary outcomes included cup and stem angle, the discrepancies from the targeted angle and combined anteversion (evaluated via CT at 3 months postoperatively). Secondary outcomes included intraoperative blood loss, operative time, WOMAC, and adverse events.

RESULTS

There were no significant differences in age, gender, BMI or in the primary and secondary outcomes between the 2 groups.

CONCLUSIONS

Performing stem-first in THA did not adversely affect cup and stem angle accuracy, or result in intraoperative bleeding, prolongation of operative time, or postoperative adverse events. Thus, performing stem-first may be advantageous for achieving combined anteversion theory.

TRIAL REGISTRATION

University Hospital Medical Information Network (UMIN) registration number UMIN000025189.

Risk Factors for Iliopsoas Tendinopathy After Anterior Approach Total Hip Arthroplasty

BACKGROUND

Iliopsoas tendinopathy is a cause of groin pain following total hip arthroplasty (THA). With the anterior approach becoming increasingly popular, our aim was to determine the prevalence of iliopsoas tendinopathy following anterior approach THA, to identify risk factors and to determine an influence on patient-reported outcomes.

METHODS

This is a retrospective case-control study of prospectively recorded data on 2,120 primary anterior approach THA (1,815 patients). The diagnosis of iliopsoas tendinopathy was based on (1) persistent postoperative groin pain, triggered by hip flexion; (2) absence of dislocation, infection, loosening, or fracture; and (3) decrease of pain after fluoroscopy-guided iliopsoas tendon sheet injection with xylocaine and corticosteroid. Outcomes included hip reconstruction (inclination/anteversion and leg-length), complication rates, reoperation rates, and patient-reported outcomes including Hip disability and Osteoarthritis Outcome Score.

RESULTS

Forty four patients (46 THAs) (2.2%) were diagnosed with iliopsoas tendinopathy. They were younger than patients who did not have iliopsoas tendinopathy (51 years [range, 27-76] versus 62 years [range, 20-90]; P < .001). Logistic regression analyses demonstrated that younger age (P < .001) and presence of a spine fusion (P = .008) (odds ratio 4.6) were the significant predictors of iliopsoas tendinopathy. These patients had lower Hip disability and Osteoarthritis Outcome scores, reported more often low back pain (odds ratio 4.8), and greater trochanter pain (odds ratio 5.4).

CONCLUSION

We found an incidence of 2.2% of iliopsoas tendinopathy patients after anterior approach THA that compromised outcomes. Younger age and previous spine fusion were identified as most important risk factors. These patients were 5 times more likely to report low back pain and greater trochanter pain post-THA.

Relationship between iliopsoas muscle surface pressure and implant alignment after total hip arthroplasty: a cadaveric study

Iliopsoas impingement after total hip arthroplasty is caused by the implant irritating the iliopsoas muscle, but changes in the iliopsoas muscle have not been quantitatively evaluated. This study assessed changes in the surface pressure of the iliopsoas muscle when the implant alignment was varied. Total hip arthroplasty was performed in 10 fresh-frozen cadaveric hips. We evaluated the maximum and mean surface pressure of the iliopsoas muscle with the hip in 20° and 10° extension, the neutral position, and 10° flexion when the anterior cup protrusion length (ACPL), stem version, and stem offset were varied. When the ACPL was changed to 0, 3, and 6 mm in 20° extension, the maximum surface pressure was significantly increased for ACPL of 6 mm compared with 0 mm. Decreased stem anteversion resulted in a significant reduction in both the maximum and mean surface pressure compared with native anteversion from 20° extension to the neutral position. Increased stem offset resulted in significant increases in the maximum and mean surface pressure of the iliopsoas muscle compared with decreased stem offset in 20° extension. Not only large ACPL but also changes in stem version and offset affected the maximum surface pressure of the iliopsoas muscle.

Incidence and Risk Factors of Iliopsoas Tendinopathy After Total Hip Arthroplasty: A Radiographic Analysis of 1,602 Hips

BACKGROUND

Iliopsoas tendinopathy (IPT) can cause persistent groin pain and lead to dissatisfaction after total hip arthroplasty (THA). This study aimed to report the characteristics, incidences, risk factors, and treatment outcomes of IPT after THA.

METHODS

We reviewed primary THAs performed at a single institution between January 2012 and May 2018. Clinical and radiographic analyses were performed on 1,602 THAs (1,370 patients). Patient characteristics, component sizes, inclination and anteversion angles, and antero-inferior cup prominence (≥8 millimeters (mm)), were compared between the groups with and without IPT. Changes in teardrop to lesser trochanter distance were measured to estimate changes in leg length and horizontal offset caused by THA. Logistic regression models were used to identify the risk factors for IPT. IPT was identified in 53 hips (3.3%).

RESULTS

Patients with IPT had greater leg lengthening (12.3 versus 9.3 mm; P = .001) and higher prevalence of antero-inferior cup prominence (5.7 versus 0.4%; P = .002). There was no significant difference in inclination, anteversion, and horizontal offset change between the two groups. In multivariate analyses, greater leg lengthening, prominent acetabular cup, women, and higher body mass index were associated with IPT. All patients reported improvement in groin pain after arthroscopic tenotomy, while 35.7% with nonoperative management reported improvement (P < .001).

CONCLUSIONS

Symptomatic IPT occurred in 53 (3.3%) of the 1,602 primary THAs. Our findings suggest that leg lengthening as well as prominent acetabular cup in THAs can be associated with the development of IPT. Arthroscopic tenotomy was effective in relieving groin pain caused by IPT.

Localization of the ilioischial line on axial computed tomography images for preoperative planning of total hip arthroplasty

BACKGROUND

If the bony region indicating the ilioischial line is established on the preoperative axial computed tomography (CT) image, the distance between the simulated cup and the ilioischial line can be measured on this image so that the surgeon can use these data to define a more accurate preoperative two-dimensional (2D) template of total hip arthroplasty (THA). This study aimed to verify the hypothesis that on the CT axial image, the cortical bone area, indicated by the superimposition of a line (line α) with a perspective projection angle to the ilioischial line on radiography and tangent to the medial acetabular wall, is the cortical bone that represents the ilioischial line on radiography.

METHODS

Study 1: If the two measured distances (distance A' and distance B) are sufficiently equal, then the hypothesis can be supported. Distance A' was calculated by multiplying the distance A, between the ilioischial line and the medial margin of the metal cup after THA measured at the level of the hip joint center on the pelvic radiograph, by 0.91 to correct for radiographic magnification. Distance B was defined as the distance between the medial margin of the metal cup and line α on the axial CT image at the level of the hip joint center. These two distances were measured for all 51 hip joints included in the study. Study 2: The difference between distance A and distance A^# (distance A on the 2D template) was compared between the group containing 59 primary THAs in which distance B' was measured (distance B in the simulation) and the control group containing 59 primary THAs.

RESULTS

Study 1: The average distance for A' was 4.5 ± 2 mm, and the average distance for B was 4.7 ± 2.1 mm. The difference between distances A and B was 0.2 ± 0.2 mm. Study 2: The mean difference between distance A and distance A^# for the measurement and control groups was 1.8 ± 1.3 mm and 3.7 ± 2.4 mm, respectively (P < 0.001).

CONCLUSIONS

The ilioischial line is located in the bony region where line α intersects the medial acetabular wall with a maximum overlap on axial CT images.

Does intraoperative periprosthetic occult fracture of the acetabulum affect clinical outcomes after primary total hip arthroplasty?

INTRODUCTION

The frequency of intraoperative periprosthetic occult fracture of the acetabulum (IPOA) in primary total hip arthroplasty (THA) is relatively high. However, the effect of this fracture on clinical outcome and survival of primary THA remains unknown. This study aimed to determine the impact of IPOA on the outcomes of primary THA during a minimum follow-up of 5 years.

MATERIALS AND METHODS

This retrospective case-control study compared the outcomes of primary THA with or without IPOA during a minimum 5-year follow-up. Thirty-eight patients who underwent primary THA with IPOA (O group) were matched to 76 patients without IPOA (C group) between 2004 and 2013 based on age, sex, body mass index, primary diseases, cup diameter, cup design, and additional dome screw. Both groups underwent the same rehabilitation programs after surgery. We evaluated the Japanese Orthopaedic Association clinical outcomes score; postoperative complications, such as nerve injury, dislocation, heterotopic ossification, iliopsoas impingement, or infection; and radiographic outcomes. Additionally, we performed Kaplan-Meier survival analysis with cup aseptic loosening, cup failure revision, and all-cause revision as the endpoints.

RESULTS

There were no significant differences in the pre- and postoperative clinical scores, postoperative complication rates, and cup sagittal rotation between the two groups. Radiographic evaluations showed no aggravation of cases to overt fractures. Bone ingrowth was observed in all cases, and none of the acetabular cups had a progressive radiolucent line ≥ 2 mm in all the 3 acetabular zones. Ten-year survival rates for cup aseptic loosening and cup failure revision were 100% in both groups; those for all-cause revision were 97.4% (92.0-100%) and 100% in the O and C groups, respectively (p = 0.157).

CONCLUSIONS

Primary THA with IPOA provides favorable mid- to long-term outcomes. On IPOA diagnosis, although radiographic follow-up is necessary, additional treatments or rehabilitation programs are not required. Furthermore, postoperative computed tomography images for the detection of IPOA may be unnecessary.

Comparison of Preoperative Computed Tomography and Intraoperative Estimation in Predicting the Version of a Single-Wedge Femoral Stem

Objective

Early prediction of stem version aids in optimization of combined version during total hip arthroplasty (THA). This study aimed to analyze the discrepancy between stem version and native femoral version measured by different methods, and to explore which method can better predict the stem version.

Methods

We retrospectively reviewed 26 patients (39 hips) treated with robot‐assisted THA in our hospital between September 2019 and December 2019. A straight, single‐wedge, cementless stem (Accolade II) was used in all cases. Preoperative femoral version was measured at three levels on computerized tomography (CT) scan from the top to the middle level of femoral neck (Level 1 to Level 3). During THA, the version on cutting surface was measured prior to femoral broaching based on two reference lines: mid‐cortical line and T line (trochanteric fossa to the middle of medial cortex). After femoral broaching, stem version was measured based on the femoral neck trial using Mako system (Stryker). In the statistical analysis, the difference and absolute discrepancy between stem version and femoral version measured with various methods were examined using paired t‐test, and the relationship between stem version and various femoral versions were examined using correlation analysis.

Results

Mean femoral neck version (Level 1) was 9.5° ± 2.6° (range, −16.8°‐42.5°), while mean stem version measured by Mako system was 19.9° ± 2.0° (range, −8.0°‐49.0°). Femoral version measured with each method showed a moderate correlation with stem version (p < 0.05). There was a significant difference between stem version and femoral version except at Level 3, with a mean difference of 0.8° ± 13.6° (p = 0.729). With regard to the intraoperative estimation, stem version significantly increased compared to the value based on mid‐cortical line, with a mean difference of 8.4° ± 13.1° (p < 0.001). However, the mean value of stem version was a little smaller than that of femoral version measured by reference to T line, but without statistical significance (p = 0.156). No postoperative dislocations occurred during the study period. No revision was required for any component.

Conclusions

The middle level of femoral neck on CT scan and T line on cutting surface are better references to measure femoral version for predicting postoperative stem version. However, the relationship between stem version and predictive value was flexible. Therefore, further three‐dimensional studies of postoperative CT are needed to validate the press‐fit fixation and rotational freedom of the single‐wedge stem.

A Case of Iliopsoas Bursitis With Compressive Femoral Nerve Palsy Treated With Iliopsoas Tendon Release

Iliopsoas bursitis is a well-established cause of groin pain after total hip arthroplasty (THA), and it can become dramatically more complex when associated with neurovascular compression. Iliopsoas bursitis may be caused by a variety of pathologies in the setting of a THA but most frequently due to a prominent acetabular component or implant wear. Here we report a rare case of a female patient presenting with iliopsoas tendonitis, an accompanying femoral nerve palsy, and debilitating pain beginning 12 years after a previously successful primary THA without apparent implant wear. Ultimately, our patient was treated successfully with iliopsoas tendon release for anterior prominence of the acetabular component.

Augmented Reality- vs Accelerometer-Based Portable Navigation System to Improve the Accuracy of Acetabular Cup Placement During Total Hip Arthroplasty in the Lateral Decubitus Position

BACKGROUND

There have been no studies regarding the effectiveness of augmented reality (AR)-based portable navigation systems compared with accelerometer-based portable navigation systems in total hip arthroplasty (THA).

METHODS

We retrospectively compared THAs performed using an AR-based portable navigation system (n = 45) and those performed using an accelerometer-based portable navigation system (n = 42). All THAs were performed with the patient in the lateral decubitus position. The primary outcome was the absolute difference between cup placement angles displayed on the navigation screen and those measured on postoperative X-ray.

RESULTS

The mean absolute differences were significantly smaller in the AR-based portable navigation system group than the accelerometer-based portable navigation system group in radiographic inclination (2.5° ± 1.7° vs 4.6° ± 3.1°; 95% confidence interval 1.1°-3.2°, P < .0001). Similarly, the mean absolute differences were significantly better in the AR-based portable navigation system group in radiographic anteversion (2.1° ± 1.8° vs 6.4° ± 4.2°; 95% confidence interval 3.0°-5.7°, P < .0001). Neither hip dislocation, surgical site infection, nor other complications associated with use of the navigation system occurred in either group.

CONCLUSION

The AR-based portable navigation system may provide more precise acetabular cup placement compared with the accelerometer-based portable navigation system in THA.

Editorial Commentary: Iliopsoas Tenotomy for Pain After Total Hip: A Great Operation IF the Diagnosis Is Right

Iliopsoas tendon pain can be a frustrating condition for both patients and surgeons after total hip arthroplasty. It is difficult to diagnose definitively, as there is no imaging modality that offers reliable information and there are numerous causes of persistent groin pain in this patient population. The pain can ruin the results of an otherwise well-functioning total hip arthroplasty. Patients who respond best to arthroscopic iliopsoas tenotomy are those with isolated pain with hip flexion activities and reproducible pain with resisted hip flexion on examination or other provocative iliopsoas maneuvers. Patients with these symptoms in addition to more generalized pain findings (pain with weight-bearing, pain at night, pain with passive range of motion) tend not to respond as favorably to isolated iliopsoas tenotomy. In addition, optimal treatment for refractory cases has been controversial historically, as both acetabular component revision and iliopsoas tendon lengthening have been advocated. With the ever-increasing popularity of hip arthroscopy and recent clinical outcome reports, arthroscopic (or endoscopic) iliopsoas tenotomy has proven to be a very safe and effective treatment option for these patients, with one caveat: the diagnosis must be correct.

Endoscopic Tenotomy for Iliopsoas Tendinopathy Following Total Hip Arthroplasty Can Relieve Pain Regardless of Acetabular Cup Overhang or Anteversion

PURPOSE

To report outcomes of endoscopic iliopsoas tenotomy (EIT) in patients with iliopsoas tendinopathy following total hip arthroplasty (THA) and determine whether improvements in clinical scores are associated with acetabular cup anteversion measured on plain radiographs or overhang measured using established and alternative computed tomography (CT)-based methods.

METHODS

We evaluated patients who underwent EIT for iliopsoas tendinopathy after THA (2014-2017), performed between the lesser trochanter and psoas valley. Indications were groin pain during active hip flexion, exclusion of other complications, and no pain relief after 6 months of conservative treatment. Pretenotomy inclination and anteversion were measured on radiographs; sagittal and axial overhang were measured on CT scans on slices passing through: (Method 1) prosthetic head center and (Method 2) anterior margin of acetabular cup. Modified Harris hip score (mHHS), Oxford Hip Score (OHS), and level of groin pain were recorded at 12 or more months. Wilcoxon signed-rank tests were used to compare pre- and post-tenotomy scores, and intraclass correlation coefficients (ICCs) to assess intermethod agreement.

RESULTS

The cohort comprised 16 men (17 hips) and 32 women (33 hips), aged 60.8 ± 10.5 years at EIT. For the 30 (60%) hips that had pretenotomy CT scans, axial and sagittal overhang were, respectively, 3.4 ± 3.7 mm and 4.6 ± 4.6 mm, using Method 1, compared with 3.9 ± 3.9 mm and 6.9 ± 5.0 mm using Method 2. Intermethod agreement was good for axial (ICC, 0.67; P < .001) and sagittal (ICC, 0.68; P < .001) overhang. At a minimum 1 year after EIT, 3 hips had cup and stem revision and 1 hip had isolated cup revision, leaving 46 hips for clinical assessment. No complications were noted. mHHS improved by 26 ± 19 (P < .001) and OHS improved by 20 ± 11 (P < .001). Twenty-six hips (57%) achieved the patient acceptable symptom state for mHHS, whereas 42 hips (91%) achieved the patient acceptable symptom state for OHS. Post-tenotomy groin pain was slight in 15%, mild in 17%, and moderate in 11%. Regression analyses revealed no associations between clinical scores and overhang/anteversion.

CONCLUSIONS

For patients with iliopsoas tendinopathy following THA, endoscopic iliopsoas tenotomy granted clinically important improvements of mHHS in 76% and OHS in 89%, despite moderate residual groin pain in 11%. Improvements in clinical scores did not seem to be associated with the extent of cup overhang or anteversion in the cases for which adequate preoperative imaging was available.

LEVEL OF EVIDENCE

Level IV, retrospective cohort study.

Preliminary outcomes of the cementless UNITED hip system for primary total hip arthroplasty at a minimum 2-year follow-up

INTRODUCTION

This study aimed to report the initial results of the cementless UNITED hip system in primary total hip arthroplasty (THA) with a minimum follow-up of 2 years.

METHODS

We retrospectively studied a consecutive series of 203 cementless THAs in 180 patients operated between 2015-2017. We included 89 female and 91 male patients with a mean age of 67 (28 to 89) years. The mean follow-up was 40 (29 to 62) months. Clinical outcome scores and radiographs were measured. Survival was calculated defining failure as the need for any further femoral or acetabular revision, irrespective of the reason.

RESULTS

No femoral component loosening was detected. One patient had a Vancouver-B1 intraoperative periprosthetic femoral fracture treated with implant retention and cerclage wires. Two acetabular components were revised for aseptic loosening. Three patients suffered an acute infection treated with debridement, antibiotics, and implant retention. The mean Merle d'Aubigné et Postel scores improved from 13 (4 to 16) points preoperatively to 17 (12 to 18) points at the latest follow-up (p < 0.001). At a mean time of 40 months of follow-up, the survival was 99% and 100% for the acetabular and the femoral components, respectively.

CONCLUSION

This cementless design showed excellent preliminary outcomes in terms of fixation and patient satisfaction, comparable to that of other well-known similar systems.

Total Hip Arthroplasty Using a Hemispherical Uncemented Dual-Mobility Cup Results in Satisfactory Clinical Outcomes and No Dislocations at 2 years

BACKGROUND

The authors performed total hip arthroplasty (THA) using a novel hemispherical dual-mobility (DM) acetabular cup without a protrusive cylindro-spherical rim, intended to reduce risks of iliopsoas impingement without requiring changes to conventional intraoperative positioning as with unipolar cups. We aim to determine clinical scores and rates of dislocations, complications, and revisions of this hemispherical DM cup, with the hypothesis that this novel design would result in clinical scores and dislocation rates comparable to other contemporary DM cups with protrusive cylindro-spherical rims.

METHODS

We assessed 332 consecutive uncemented THAs performed using a hemispherical DM cup, at a minimum 2-year follow-up, using modified Harris Hip Score (mHHS) and Oxford Hip Score (OHS), and noting complications and revisions. Regression analyses were conducted to determine if mHHS and OHS depended on any independent factors.

RESULTS

At 2.8 ± 0.5 years (range, 2-5), 2 patients (0.6%) had stem and cup revisions, 3 patients (1%) had isolated stem revisions, 13 patients (4%) died, and none were lost to follow-up. No dislocations occurred. For the final cohort of 305 patients (314 hips) with their original implants in place, mHHS was 92 ± 12 (range, 46-100), and OHS was 57 ± 5 (range, 34-60). Multivariable analyses revealed that mHHS and OHS decreased significantly with age (β = -0.35, P < .001, and β = -0.15, P < .001, respectively).

CONCLUSIONS

With no dislocations and satisfactory clinical scores, this sizable cohort confirms that the novel hemispherical DM cup studied is effective at preventing dislocations, although longer-term follow-up remains necessary to ascertain the longevity of clinical outcomes and radiographic stability.

LEVEL OF EVIDENCE

Level IV, multicentric retrospective case series.

Anterior pelvic plane tilt poorly estimates the sagittal body alignment due to internal rotation of innominate bone

This study investigated the influence of the rotation of innominate bone on anterior pelvic plane (APP) tilt, the angle formed by the APP, and coronal plane of the body to determine whether the provision of proper information about the sagittal balance of the body by the value of the APP tilt (APPT). In total, 244 patients (171 females, 73 males) who were candidates for total hip or knee arthroplasty, periacetabular osteotomy, or shelf arthroplasty were included. The rotational angle of the innominate bone was quantified using computed tomography images at the level of the anterior superior, and anterior inferior iliac spine, and ischiopubic portion. Clustering analysis was performed to identify subtypes of innominate bone rotation. High, intermediate, and low internal rotational alignment groups were identified in females, characterized by rotational angles. Males were treated as one group, and no intergroup differences were observed in sacral slope (SS) and pelvic incidence. However, intergroup differences in APPT were found, indicating a variation in APPT irrespective of sagittal body balance. A negligible relationship between SS and APPT was observed in the high-internal-rotation group, intermediate-internal-rotation group, and male group, whereas a moderate correlation found in the low-internal-rotation group (r = .59). The results could suggest surgeons that the value of the APPT provides no information on the sagittal balance; therefore, it may be ignored for acetabular component positioning during preoperative planning for total hip arthroplasty.

Arthroscopic tendon release for iliopsoas impingement after primary total hip arthroplasty: a retrospective, consecutive series

INTRODUCTION

Aim of this study was to describe the clinical outcomes of 16 patients with iliopsoas (IP) impingement after primary total hip arthroplasty (THA), treated with an arthroscopic tendon release.

METHODS

16 patients (11 females/5 males), with a mean age of 57.8 ± 11.1 years (age at THA: 54.4 ± 11 years) and a diagnosis of IP impingement after primary THA, were treated with the Wettstein tenotomy. Preoperatively, every patient underwent a diagnostic ultrasonography guided peritendinous injection and a computed tomography (CT) scan. Every patient was clinically evaluated using WOMAC score. Subjective pain relief and active hip flexion strength were measured.

RESULTS

No complications related to arthroscopy were detected. Every cup was prominent with a mean axial overhang of 13 ± 4.8 mm (range 5-20 mm). At a mean follow-up of 27 ± 20.1 months (range 6-48 months), the WOMAC score was 83.7 ± 10.1 points. 13 patients out of 16 (81.3%) had a complete pain relief. 14 patients out of 16 (88%) regained full active hip flexion strength at the final follow-up. 1 patient was scheduled for cup revision after 6 months, due to persistent symptomatology. No demographic data or CT measurements about cup position statistically influenced the outcome.

CONCLUSIONS

When preceded by an appropriate diagnosis, arthroscopic tenotomy proved safe and effective for IP impingement, regardless the magnitude of cup protrusion.

Risk factors for iliopsoas impingement after total hip arthroplasty using a collared femoral prosthesis

Background

The relationship between collar design of a femoral component and iliopsoas impingement (IPI) after total hip arthroplasty (THA) is still underrecognized. The purpose of our study was to determine the possible risk factors for IPI related to the femoral component, when using a collared femoral prosthesis.

Methods

A total of 196 consecutive THA patients (206 hips) using a collared femoral prosthesis were reviewed retrospectively after exclusion of the factors related to acetabular component and femoral head. The patients were divided into +IPI and −IPI group according to the presence of IPI. Radiological evaluations were performed including femoral morphology, stem positioning, and collar protrusion length (CPL). Multivariate regression analysis was performed to assess the risk factors for IPI.

Results

At a minimum follow-up of 1 year, IPI was observed in 15 hips (7.3%). Dorr type C proximal femur was found in nine hips (60%) in the +IPI group and in 28 hips in the −IPI group (14.7%, p < 0.001). The mean stem anteversion in the +IPI group was significantly greater than that in the −IPI group (19.1° vs. 15.2°, p < 0.001), as well as the mean CPL (2.6 mm vs. − 0.5 mm, p < 0.001). The increased stem anteversion (OR = 1.745, p = 0.001) and CPL (OR = 13.889, p = 0.001) were potential risk factors for IPI.

Conclusions

The incidence of IPI after THA is higher than expected when using a collared femoral prosthesis. Among the factors related to collared femoral prosthesis, excessively increased stem anteversion and prominent collar protrusion are independent predictors for IPI. In addition, high risk of IPI should be carefully considered in Dorr type C bone, despite that femoral morphology is not a predictive factor.

Level of evidence

Level IV, clinical cohort study

Achievement of optimal implant alignment using taper wedge stems with cup-first THA through the MIS antero-lateral approach

PURPOSE

Combined anteversion (CA) technique (stem-first procedure) has become generally accepted as an ideal means to achieve optimal CA value in THA. However, we hypothesized that CA technique for patients with various native femoral anteversions could pose a risk of anterior or posterior cup protrusion. In the present study, we examined whether it is possible to use the taper wedge stem to change the stem version to achieve optimal CA while avoiding cup protrusions with the cup-first procedure through minimally invasive (MIS) antero-lateral approach.

METHODS

Eighty-one patients underwent cup-first THA with a taper wedge stem. The acetabular cup was placed following the preoperative planning of the cup alignment to avoid anterior cup protrusions using CT-based navigation. Following the CA theory, anteversion of the taper wedge stem was changed to the target anteversion from the patient's native femoral anteversion. The native femoral anteversion, the change in version angle of the stem, postoperative CA and the length of anterior cup protrusions were evaluated in postoperative CT measurements.

RESULTS

The native femoral anteversion averaged 25.7° ± 8.9° (range 8°-45°). Cases with increased and decreased stem anteversion were observed in 42 hips (51.8%) and 33 hips (40.7%), respectively. The amount of increased and decreased version angles averaged 7.7° ± 4.8° (range 2°-21°) and 7.8° ± 5.1° (range 2°-20°), respectively. Postoperative CA values averaged 36.7° ± 3.4° (range 29.4°-44.2°) and anterior cup protrusion length averaged 2.0 mm ± 2.6 mm (0 ~ 8.8 mm) in axial view and 0.4 mm ± 1.0 mm (0 ~ 3.6 mm) in sagittal view. Anterior cup protrusion of more than 10 mm was not observed in any hips.

CONCLUSION

This procedure can be considered as an option to achieve optimal CA anteversion while avoiding anterior cup protrusion in THA.

Association between total hip arthroplasty following periacetabular osteotomy and acetabular component overhang

BACKGROUND

There is limited understanding of anterior acetabular component overhang, which induces groin pain, in post-periacetabular osteotomy (PAO) hips during conversion to total hip arthroplasty (THA). The aim of the study were to determine the following: (1) the differences in the amount of acetabular component overhang among pre-PAO hips and post-PAO hips in simulating THA; (2) the factors associated with the amount of component overhang in THA following PAO; (3) whether high component placement with elevation of the hip center by 10 mm reduces the amount of component overhang compared to the anatomical component position in THA following PAO.

METHODS

Computer-based simulations of acetabular component implantation were performed using preoperative and postoperative CT data from 30 patients undergoing PAO. Implantation was performed thrice in each patient: in pre-PAO hips (anatomical component position) and post-PAO hips (anatomical and high component position). Component overhang was measured on the axial plane, which passes through the component center.

RESULTS

Overhang was greater in post-PAO hips [mean (SD) overhang: 5.2 (2.9) mm, pre-PAO hips: 10.2 (4.6) mm, post-PAO hips-mean difference, 5.0 mm; p < 0.001]. A smaller distance between the pubic osteotomy and the acetabulum, and greater overhang in pre-PAO hips was independent factors associated with increased overhang in post-PAO hips. Overhang was smaller with the high component position than with the anatomical component position in post-PAO hips [mean (SD) overhang-3.5 mm (2.9) with high component position among post-PAO hips; mean difference, 6.6 mm; p < 0.001). Ten post-PAO hips with the anatomical component position had overhang of at least 12 mm (the likely threshold for groin pain). Of these, 9 hips had reduced overhang (< 12 mm) with the high component position.

CONCLUSIONS

Acetabular component overhang was more severe in THA following PAO than in THA without prior PAO. Pubic osteotomy should be performed closer to the acetabular rim to prevent severe overhang in potential THA conversion cases. A high component position decreased the risk of severe overhang.

Patient-reported outcomes following primary total hip arthroplasty in Crowe type III or IV developmental dysplasia are comparable to those in Crowe type I: a case-control study of 96 hips with intermediate-term follow-up

BACKGROUND

A few previous studies have investigated patient satisfaction after total hip arthroplasty (THA) according to the degree of pelvic deformity. This study compared patient-reported outcomes after primary THA for Crowe types III, IV and I dysplasia.

METHODS

This retrospective, single-center, single-surgeon case-control study included patients who underwent primary THA between 2008 and 2016. We sent postal questionnaires to 38 patients with Crowe type III and IV dysplasia. Among the questionnaire respondents, 23 patients, excluding those with a follow-up period of < 1 year, were enrolled as the H group. The control group included 46 patients with Crowe type I, matched for sex, age, body mass index and surgical approach. To investigate the influence of femoral shortening osteotomy, the H group was divided according to whether femoral shortening osteotomy was performed. Ten patients underwent THA with femoral shortening osteotomy (FO group), while 12 patients underwent THA without femoral shortening osteotomy (N-FO group). Patient demographics, mean follow-up period, surgical information, pre- and postoperative leg length discrepancy (LLD), and perioperative complications were investigated. Clinical evaluations were performed using the Japanese Orthopaedic Association (JOA) scores, 36-item short-form survey (SF-36), net promotor score (NPS), visual analogue scale (VAS), and questionnaires. The VAS and SF-36 scores were determined only at final follow-up.

RESULTS

The H and control groups were not significantly different in the postoperative JOA scores and SF-36. In the H group, VAS at the final follow-up was significantly higher, and significantly more patients felt that postoperative rehabilitation was serious, expressing that they underwent THA for LLD correction. In addition, the VAS scores in the FO group was higher than those in the N-FO group. Postoperative LLD was significantly greater in the H group than in the control group. Each group had an NPS of > 50.

CONCLUSION

The postoperative VAS score was higher in Crowe type III and IV dysplasia than in Crowe type I dysplasia, but no significant differences were detected in the postoperative satisfaction, JOA score, and SF-36 score. These findings may help explain the effects of THA preoperatively to patients with Crowe type III and IV dysplasia.

LEVEL OF EVIDENCE

Therapeutic Level 3b.

Risk factors for pressure ulcers from the use of a pelvic positioner in hip surgery: a retrospective observational cohort study in 229 patients

Background

Intraoperatively acquired pressure ulcers are serious postsurgical complications requiring additional treatment, reoperation, and extended hospitalization. No study has investigated the frequency of the ulcers caused by compression with a pelvic positioner, which is used in hip surgeries to stabilize patients in the lateral decubitus position.

Methods

This retrospective study investigated the risk factors and the frequency of the ulcers caused by the use of pelvic positioners in hip surgeries. The records of patients who underwent surgical procedures under general anesthesia at our institution between January 1, 2016 and March 31, 2018 were reviewed. The inclusion criterion for the assessment of risk factors was hip surgery in the lateral decubitus position stabilized by a pelvic positioner. The exclusion criteria were patients with trauma, missing data, or a pre-existing pressure ulcer. Finally,.the study included 229 patients (265 hip surgeries). All the patients were positioned in the lateral decubitus position with the assistance of either a pelvic positioner, which had a single support fixture located over the pubic symphysis or a double support fixture located over the bilateral anterior superior iliac spine. Intraoperatively acquired pressure ulcers were diagnosed when ulcers were absent on admission and the redness that was observed immediately after surgery remained after 24 h. Multivariate analysis was used to identify factors associated with an increased risk for ulcers.

Results

Ulcers developed in 8 of 1810 (0.44%) patients who underwent orthopedic surgery. Seven of the 265 (2.64%) patients who underwent hip surgery in the lateral decubitus position stabilized by a pelvic positioner developed ulcers. All ulcers were located on areas of the body that were compressed by the pelvic positioner. After identifying controls for patient height (less than 154 cm), surgery duration (longer than 180 min), blood loss (more than 355 ml), and type of pelvic positioner used, we identified the independent risk factors for ulcers to be patient height < 154 cm (adjusted odds ratio, 12.8; p-value, 0.032) and the use of pelvic positioners with pubic bone support (adjusted odds ratio, 10.53; p-value, 0.047).

Conclusion

The use of pelvic positioners with pubic bone support should be avoided in patients with a height of < 154 cm to decrease the risk of ulcers.

New combined anteversion technique in hybrid THA: cup-first procedure with CT-based navigation

PURPOSE

Combined anteversion (CA) technique (stem-first procedure) is generally accepted as the optimal technique to attain an appropriate CA value in total hip arthroplasty (THA). However, cup anteversion is strongly influenced by the native femoral anteversion. Accordingly, anterior protrusion of the cup in the acetabulum might occur. The purpose of the present study is to investigate the achievement of the optimal CA while avoiding anterior cup protrusion and examine the significance of our new CA technique with cup-first procedure in hybrid THA.

METHODS

Seventy-nine hybrid THAs with the cup-first procedure used a CT-based navigation system for cup positioning. In the preoperative planning, cup anteversion was aimed at approximately 20°. However, in actuality, sufficient cup coverage in the original acetabulum based on individual anatomy is given priority over cup placement based on CT-based planning to ensure adequate cup coverage. The target stem anteversion was determined following Widmer's mathematical formula (37.3 = femoral stem anteversion × 0.7 + cup anteversion). Cemented stem was inserted according to the target stem anteversion angle.

RESULTS

Regarding the assessment of overall alignment, the calculated Widmer's CA values during surgery and postoperative CT evaluation were 34.1° ± 6.0° (range 20.7°-51.2°) and 35.1° ± 6.7° (range 21.6°-50.7°). There were 72 hips (91.1%) within 25°-50° of CA. Cup protrusion length averaged 2.0 mm ± 2.6 mm (0-8.8 mm) in the axial view and 0.4 mm ± 1.0 mm (0-3.6 mm) in the sagittal view. Cup protrusion length of more than 5 mm was indicated in 10 hips, and no hips observed more than 10 mm.

CONCLUSION

Our new CA technique (cup-first procedure) with hybrid THA was able to achieve optimal CA value while avoiding anterior cup protrusion.

The Accuracy of the Computed Tomography-Based Navigation System in Total Hip Arthroplasty Is Comparable With Crowe Type IV and Crowe Type I Dysplasia: A Case-Control Study

BACKGROUND

Clinical outcomes of total hip arthroplasty (THA) for Crowe type IV are poorer than for Crowe type I, because it is more difficult to accurately position the acetabular components. This study aimed to examine the accuracy of the computed tomography (CT)-based navigation system for acetabular component positioning in primary THA for Crowe type IV.

METHODS

From 2006 to 2018, 29 patients who underwent 34 primary THAs for Crowe type IV were enrolled in the "Type IV" group and 32 patients who underwent 34 THAs for Crowe type I were enrolled in the "Type I" group, formed by matching patients in the Type IV group on age, gender, body mass index, and surgical approach. We investigated (1) the accuracy of the cup size between that at preoperative planning and that actually implanted and (2) the mean deviation of the cup angle and 3-dimensional position of acetabular components between preoperative plan and postoperative records.

RESULTS

The accuracy of the cup size was 79.4% and 94.1% in the Type IV and Type I groups, respectively, without a statistically significant change detected (P = .075). The mean deviations of the cup angle and 3-dimensional position were comparable in both groups.

CONCLUSION

Using the CT-based navigation system, it was possible to accurately implant the acetabular component for Crowe type IV, and the accuracy was comparable to that for Crowe type I. The CT-based navigation system is a useful intraoperative tool to accurately implant the acetabular component, especially with severe pelvic deformities such as Crowe type IV.

Tilt-adjusted Cup Anteversion in Patients with Severe Backward Pelvic Tilt is Associated with the Risk of Iliopsoas Impingement: A Three-dimensional Implantation Simulation

BACKGROUND

Anterior overhang of the acetabular component is associated with iliopsoas impingement, which may cause groin pain and functional limitations after THA. However, little is known about the relationship between component overhang and functional alignment of the acetabular component. CT-based image simulation may be illuminating in learning more about this because CT images are more effective than radiographs for evaluating the component's overhang and position.

QUESTIONS/PURPOSES

Using CT simulations based on preoperative data of nondysplastic and dysplastic hips, we asked: (1) What are the differences in the amount of component overhang, defined as the mediolateral distance from the component's edge to the native acetabular bony boundary on axial images (axial overhang), and as the AP distance on sagittal images (sagittal overhang) among pelvises with neutral and posterior tilt (in which the cephalad portion of the pelvis is more posterior than the caudad portion in the sagittal plane) in patients with dysplastic hips and those with nondysplastic hips? (2) Are increments in the amount of component overhang associated with a difference in the likelihood that the iliopsoas tendon will impinge against the edge of the acetabular component, after controlling for native acetabular abduction and anteversion and the presence of dysplasia?

METHODS

A total of 128 hips (dysplastic group: 73 hips; nondysplastic group: 55 hips) were evaluated. We defined a dysplastic hip as one with a lateral center-edge angle of less than 20° on AP radiographs. Pelvic models with neutral (0°) and 10° and 20° of posterior tilt were created from CT data. In simulations, acetabular component models were implanted into the true acetabulum with a tilt-adjusted orientation angle that was defined as the component's angle based on a reference for the functional pelvic plane (coronal plane of the body) in each pelvic model. Axial and sagittal component overhang were measured on CT images. Axial overhang of at least 12 mm and sagittal overhang of at least 4 mm were defined as thresholds increasing the likelihood of iliopsoas impingement according to previous studies. When determining the amount of overhang of the acetabular component, we controlled for abduction and anteversion of the native acetabulum and the presence of dysplasia by performing a multivariable logistic regression analysis.

RESULTS

In dysplastic hips, axial overhang increased by a mean ± SD of 5 ± 1 mm (Bonferroni adjusted p < 0.001; 95% CI, 4.7-5.1) from 0° to 10° of posterior tilt and by 5 ± 1 mm (p < 0.001; 95% CI, 4.9-5.3) from 10° to 20° of posterior tilt. Sagittal overhang increased by 1 ± 0 mm (p < 0.001; 95% CI, 1.0-1.0) from 0° to 10° of posterior tilt and by 1 ± 0 mm (p < 0.001; 95% CI, 1.0-1.0) from 10° to 20° of posterior tilt. In nondysplastic hips, axial overhang increased by a mean of 5 ± 0 mm (p < 0.001; 95% CI, 4.7-5.0) from 0° to 10° of posterior tilt and by 5 ± 1 mm (p < 0.001; 95% CI, 4.6-5.0) from 10° to 20° of posterior tilt. Sagittal overhang increased by 1 ± 0 mm (p < 0.001; 95% CI, 1.0-1.1) from 0° to 10° of posterior tilt and by 1 ± 0 mm (p < 0.001; 95% CI, 1.0-1.1) from 10° to 20° of posterior tilt. After controlling for the presence of dysplasia, we found that native acetabular abduction and anteversion and posterior pelvic tilt, presence of dysplasia (p = 0.030; adjusted odds ratio [OR], 2.2; 95% CI, 1.1-4.6), native acetabular anteversion (p < 0.001; adjusted OR, 1.4; 95% CI, 1.3-1.5), and 10° and 20° of backward tilt compared with 0° of tilt (10° of posterior tilt: p < 0.001; adjusted OR, 15; 95% CI, 5.5-41; 20° of posterior tilt: p < 0.001; adjusted OR, 333; 95% CI, 96-1157) were independently associated with axial overhang of at least 12 mm; the model showed high goodness of fit (Nagelkerke's r = 0.68). In contrast, native acetabular anteversion (p < 0.001; adjusted OR, 1.2; 95% CI, 1.1-1.2) and 20° of backward tilt compared with 0° of tilt (p = 0.015; adjusted OR, 2.2; 95% CI, 1.2-4.0) were independently associated with sagittal overhang of at least 4 mm; the model had low goodness of fit (Nagelkerke's r = 0.20).

CONCLUSIONS

Acetabular component overhang is more severe when the pelvis tilts posteriorly. Moreover, posterior pelvic tilt, the presence of dysplasia, and higher native acetabular anteversion were independently associated with an increased risk of component overhang. When 20° of posterior tilt was adjusted, the risk of severe overhang was especially increased.

CLINICAL RELEVANCE

Based on these results, surgeons can attempt to prevent severe overhang in patients with posterior pelvic tilt by increasing component anteversion and abduction; when component anteversion is increased by 8° and abduction is increased by 2° from the target angle of 15° of anteversion and 40° of abduction in patients with posterior tilt of 20°, the risk of severe overhang is reduced to by approximately one-twentieth. However, it is still unclear how much the degree of component anteversion should be increased when surgeons attempt to prevent anterior prosthetic dislocation at the same time. Future studies such as prospective clinical trials evaluating both prosthetic dislocation and iliopsoas impingement in patients with posterior tilt might clarify this issue.

Outcomes of Nonoperative Management, Iliopsoas Tenotomy, and Revision Arthroplasty for Iliopsoas Impingement after Total Hip Arthroplasty: A Systematic Review

BACKGROUND

Nonoperative and operative management of iliopsoas impingement (IPI) is commonly performed following total hip arthroplasty (THA). The purpose of this systematic review is to compare patient-reported outcomes (PROs) following conservative treatment, iliopsoas (IP) tenotomy, and revision arthroplasty in patients presenting with IPI after THA.

METHODS

The PubMed and Embase databases were searched for articles regarding IPI following THA. Studies were included if (1) IPI after THA was treated with conservative management, an IP tenotomy, or acetabular component revision and (2) included PROs.

RESULTS

Eleven articles were selected for review and there were 280 hips treated for IPI following THA. Harris Hip Scores reported for the conservative group, the IP tenotomy group, and the cup revision group were 59.0 preoperatively to 77.8, 58.0 preoperatively to 85.4, and 58.1 preoperatively to 82.4 at latest follow-up, respectively. The IP tenotomy cohort also demonstrated superior postoperative functional outcomes using the Western Ontario and McMaster Universities Index, Medical Research Council score, Oxford Hip Score, and Merle d'Aubigné-Postel Pain Score. Patients who had a revision exhibited higher Oxford Hip Scores, higher Medical Research Council scores, and lower Visual Analog Scale Pain scores postoperatively.

CONCLUSION

Management of IPI following THA includes nonoperative measures, IP tenotomy, or acetabular component revision. Patients have been shown to experience favorable PROs at latest follow-up, with an apparent advantage for surgical treatment. Compared to revision arthroplasty, IP tenotomy resulted in a lower overall rate of complications with less severe complication types. Therefore, IP tenotomy should be considered as a second line of treatment for patients who failed conservative measures. Revision arthroplasty should be reserved for recalcitrant cases.

LEVEL OF EVIDENCE

IV.

Total hip arthroplasty using stem-first technique with navigation: the potential of achievement of the optimal combined anteversion being a risk factor for anterior cup protrusion

PURPOSE

In the combined anteversion (CA) technique for total hip arthroplasty (THA) with a cementless stem, cup anteversion is strongly influenced by the native femoral anteversion. It is hypothesized that in cases with large native femoral anteversion, cup anteversion can be decreased, and anterior cup protrusion from the anterior edge of the acetabulum could occur due to the achievement of optimal CA. In this study, the accuracy of CA in THA with the CA technique using imageless navigation and the relationship between the protrusion of the anterior edge of cup and optimum CA was retrospectively evaluated.

METHODS

Ninety-seven patients (104 hips) who underwent primary THA by the CA technique using image-free navigation were enrolled in the study. The femoral stem was placed following the individual femoral anteversion so that the target cup anteversion could be determined following a mathematical formula (37 = femoral stem anteversion × 0.7 + cup anteversion). Results The resulting CA values effectively achieved accurate CA with 39.49 ± 5.03° postoperatively. On the other hand, anterior cup protrusion was measured by computed tomography image. A cup protrusion length of more than 3 mm was indicated for 60 cases (57.7%). All included patients were divided into two groups: Group 1 as protrusion positive and Group 2 as protrusion negative. In Group 1, preoperative femoral anteversion and postoperative stem anteversion were significantly higher, while postoperative cup anteversion was significantly lower. However, the postoperative CA value indicated no significant difference between the groups.

CONCLUSIONS

The CA (stem-first) technique with image-free navigated THA could effectively achieve accurate CA. On the other hand, a large number of cases revealed anterior cup protrusion due to the low cup anteversion.