Reliability and validity of measuring acetabular component orientation by plain anteroposterior radiographs

The accuracy of cup anteversion measurement on postoperative pelvic radiographs: A comparative retrospective cohort study between DDH and non-DDH patients

Rationale and objectives

Postoperative pelvic radiographs remain a vital tool for assessing cup orientation after total hip arthroplasty (THA), with the accuracy influenced by various factors. The objective of this study is to investigate the accuracy of cup anteversion measurement in developmental dysplasia of the hip (DDH) patients and others based on postoperative pelvic radiographs conducted under the current heavy workload conditions.

Materials and methods

Patients who underwent THA at our hospital with both postoperative X-ray and CT images from January 2020 to December 2022 were included in this retrospective cohort study. Virtual X-ray films were generated using digitally reconstructed radiographs (DRR) technology from CT images, with pelvic position perfectly controlled. Radiographic anteversion (RA) was measured on 3D-CT, virtual X-rays, and actual postoperative X-rays, abbreviated as RA_3D, RA_DRR, and RA_Xray, respectively. A repeated-measures analysis of covariance (ANCOVA) was utilized to evaluate the variations in RA within and between different groups across three methods. The Bland-Altman plot analysis showed the variations among methods in DDH and non-DDH patients, setting a clinically acceptable limits of agreement (LOA) at ±5°.

Results

This study included 154 hip cases, with 63 DDH and 91 other diseases. Repeated-measures ANCOVA revealed a descending trend in RA across three methods, with differences of 2.64° (DDH) vs. 2.74° (others) from 3D to DRR, and 4.89° (DDH) vs. 1.07° (others) from DRR to X-ray. The group by methods interaction effect were significant (p = 0.002). Significant statistical differences in RA_Xray (P = 0.035) were observed between DDH and non-DDH patients, but not in RA_3D and RA_DRR. Bland-Altman plots showed 71.4 % of DDH patients exceeded the clinically acceptable LOA, compared to 36.3 % of other patients.

Conclusion

Our study indicated that under the current intense workload, the reliability of assessing cup anteversion using postoperative pelvic radiographs is challenged, especially in patients with DDH.

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

INTRODUCTION

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

HYPOTHESIS

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Functional outcome of direct anterior versus posterior approach in total hip arthroplasty: a propensity-matched Asian study

INTRODUCTION

The direct anterior approach (DAA) to total hip arthroplasty (THA) is a surgical approach that minimises soft tissue trauma, resulting in faster rehabilitation when compared to a posterior approach (PA). This study aimed to evaluate the difference between the two groups in an Asian cohort using propensity score matching.

METHODS

A retrospective review of prospectively collected registry data of 794 primary THAs was performed. The effects on patients with DAA THA versus patients with PA THA were investigated. Propensity scores were generated using logistic regression to adjust for confounding variables of age, gender, body mass index and diagnosis. Data analysis was performed, and statistical significance was defined as a P value < 0.05.

RESULTS

The average length of stay (LOS) for the PA group and DAA group was 5.4 days and 2.9 days, respectively (P < 0.001). One (1.9%) patient from the PA group suffered a posterior dislocation 6 months after surgery and subsequently underwent revision surgery 2 years later. No dislocations were detected in the DAA group. The DAA group had better functional outcome, satisfaction and expectation scores at 6 months and 2 years.

CONCLUSION

In this study, patients who underwent DAA THA had better functional outcome at 2 years and almost 2 days shorter overall LOS than those who underwent PA THA. Therefore, the DAA to THA is a novel technique that has shown improved functional outcomes, with fewer complications compared to PA THA.

Is the Acetabular Cup Orientation Different in Robot-Assisted and Conventional Total Hip Arthroplasty With Right-Handed Surgeons Using an Anterolateral Approach?

Introduction Total hip arthroplasty (THA) is one of the most successful orthopaedic procedures. Survival rates from 90% at 10 years to 93% at 20 years have been reported in different studies. Differences in implant and patient characteristics can undoubtedly explain some of this variability observed in prosthesis durability, but the effect of surgical technique and implant orientation cannot be ignored. Therefore, many intraoperative methods (anatomic landmarks, intraoperative x-ray, fluoroscopy, navigation, and robotic surgery) have been attempted to avoid acetabular component malpositioning. Although postoperative computed tomography (CT) is accepted as the gold standard for the measurement of acetabular anteversion, it remains controversial in respect of costs and radiation exposure. The aim of this study was to examine how acetabular component orientation was affected in robotic and conventional THA operations performed by two surgeons with right-hand dominance. Material and methods The study included 113 primary THA operations performed on 113 patients between 2017 and 2022 in two groups: (i) robotic THA (Mako, Stryker Corporation, Kalamazoo, Michigan, United States) (55 patients) and (ii) conventional THA (58 patients). The patients comprised 51 males and 62 females. THA was performed on 54 right-side hips and 59 left-side hips. The operations were performed by two orthopaedic surgeons, each with 20 years of arthroplasty experience, on all the patients in the lateral decubitus position with an anterolateral approach. In all the cases, the orientation of the acetabular component was 40° inclination and 20° anteversion.  Difficult THA procedures (patients with developmental dysplasia of the hip (DDH), a history of hip surgery, revision THA, defect or deformity of the acetabulum, a history of scoliosis or lumbar posterior surgery, or those requiring proximal femoral osteotomy) were excluded from the study. Using the Liaw and Lewinnek methods, the acetabular component anteversion was measured on the radiographs taken in the optimal position postoperatively and the acetabular cup inclination angles were measured on the pelvis radiographs. The groups were compared using the Kolmogorov-Smirnov, Pearson Chi-square and Mann-Whitney U statistical tests. The limits were accepted as 40±5° for inclination and 20±5° for anteversion. Results No statistically significant difference was determined between the groups in respect of age, gender, or operated side. No statistically significant difference was determined between the optimal acetabular cup inclination angles of the robotic and conventional THA groups (p = 0.79). No statistically significant difference was determined between the optimal acetabular cup anteversion angles of the left and right conventional THA groups. Statistically significantly better results were determined in the robotic group in respect of acetabular cup anteversion (p<0,001).  Conclusion The optimal orientation of the acetabular component is a key factor for successful THA. Otherwise, revision surgery is inevitable for reasons such as instability, impingement, or increased wear. The results of this study demonstrated that robotic surgery was superior to the conventional method in the placement of the acetabular component in the desired orientation.

Artificial Intelligence Autonomously Measures Cup Orientation, Corrects for Pelvis Orientation, and Identifies Retroversion From Antero-Posterior Pelvis Radiographs

BACKGROUND

Measuring cup orientation is time consuming and inaccurate, but orientation influences the risk of impingement and dislocation following total hip arthroplasty (THA). This study designed an artificial intelligence (AI) program to autonomously determine cup orientation, correct for pelvis orientation, and identify cup retroversion from an antero-posterior pelvic radiographs.

METHODS

There were 2,945 patients between 2012 and 2019 identified to have 504 computed tomographic (CT) scans of their THA. A 3-dimensional (3D) reconstruction was performed on all CTs, where cup orientation was measured relative to the anterior pelvic plane. Patients were randomly allocated to training (4,000 x-rays), validation (511 x-rays), and testing (690 x-rays) groups. Data augmentation was applied to the training set (n = 4,000,000) to increase model robustness. Statistical analyses were performed only on the test group in their accuracy with CT measurements.

RESULTS

AI predictions averaged 0.22 ± 0.03 seconds to run on a given radiograph. Pearson correlation coefficient was 0.976 and 0.984 for AI measurements with CT, while hand measurements were 0.650 and 0.687 for anteversion and inclination, respectively. The AI measurements more closely represented CT scans when compared to hand measurements (P < .001). Measurements averaged 0.04 ± 2.21°, 0.14 ± 1.66°, -0.31 ± 8.35°, and 6.48° ± 7.43° from CT measurements for AI anteversion, AI inclination, hand anteversion, and hand inclination, respectively. AI predictions identified 17 radiographs as retroverted with 100.0% accuracy (total retroverted, n = 45).

CONCLUSION

The AI algorithms may correct for pelvis orientation when measuring cup orientation on radiographs, outperform hand measurements, and may be implemented in a timely fashion. This is the first method to identify a retroverted cup from a single AP radiograph.

Medial wall reconstruction using metal disc augments in revision total hip arthroplasty

PURPOSE

Medial acetabular bone defects are frequently encountered in revision total hip arthroplasty (THA), but few studies have focused on their reconstruction. This study aimed to report the radiographic and clinical results after medial acetabular wall reconstruction using metal disc augments in revision THA.

METHODS

Forty consecutive revision THA cases using metal disc augments for medial acetabular wall reconstruction were identified. Post-operative cup orientation, the centre of rotation (COR), stability of acetabular components and peri-augments osseointegration were measured. The pre-operative and post-operative Harris Hip Score (HHS) and Western Ontario and McMaster Universities Arthritis Index (WOMAC) were compared.

RESULTS

The mean post-operative inclination and anteversion were 41.88 ± 6.70° and 16.73 ± 5.35°, respectively. The median vertical and lateral distance between the reconstructed CORs and the anatomic CORs were -3.45 mm (interquartile range [IQR]: -11.30 mm, -0.02 mm) and 3.18 mm (IQR: -0.03 mm, 6.99 mm). Thirty-eight cases completed the minimum two year clinical follow-up, whereas 31 had a minimum two year radiographic follow-up. Acetabular components were radiographically stable with bone ingrowth in 30 cases (30/31, 96.8%) while one case was classified as radiographic failure. Osseointegration around disc augments was observed in 25 of 31 cases (80.6%). The median HHS improved from 33.50 (IQR: 27.50-40.25) pre-operatively to 90.00 (IQR: 86.50-96.25) (p < 0.001), whereas the median WOMAC significantly improved from 38.02 (IQR: 29.17-46.09) to 85.94 (IQR: 79.43-93.75) (p < 0.001).

CONCLUSION

In revision THA with severe medial acetabular bone defect, disc augments could provide favorable cup position and stability, peri-augments osseointegration, with satisfactory clinical scores.

Three-Dimensional Morphometry of the Canine Pelvis: Implications for Total Hip Replacement Surgery

OBJECTIVES

 Two-dimensional measurements of acetabular geometry are widely used for the assessment of acetabular component orientation following total hip replacement (THR). With the increasing availability of computed tomography scans, there is an opportunity to develop three-dimensional (3D) planning to improve surgical accuracy. The aim of this study was to validate a 3D workflow for measuring angles of lateral opening (ALO) and version, and to establish reference values for dogs.

METHODS

 Pelvic computed tomography scans were obtained from 27 skeletally mature dogs with no radiographic evidence of hip joint pathology. Patient-specific 3D models were built, and ALO and version angles were measured for both acetabula. The validity of the technique was determined by calculating intra-observer coefficient of variation (CV, %). Reference ranges were calculated and data from left and right hemipelves were compared using a paired t-test and symmetry index.

RESULTS

 Measurements of acetabular geometry were highly repeatable (intra-observer CV 3.5-5.2%, inter-observer CV 3.3-5.2%). Mean (± standard deviation) values for ALO and version angle were 42.9 degrees (± 4.0 degrees) and 27.2 degrees (± 5.3 degrees) respectively. Left-right measurements from the same dog were symmetrical (symmetry index 6.8 to 11.1%) and not significantly different.

CONCLUSIONS

 Mean values of acetabular alignment were broadly similar to clinical THR guidelines (ALO of 45 degrees, version angle of 15-25 degrees), but the wide variation in angle measurements highlights the potential need for patient-specific planning to reduce the risk of complications such as luxation.

High varus stem alignment in short-stem total hip arthroplasty: a risk for reconstruction of femoro-acetabular offset, leg length discrepancy and stem undersizing?

PURPOSE

Short stems are increasingly used in in total hip arthroplasty (THA) because of advantages in bone and soft tissue preservation and reconstruction of hip geometry. Short stems can be inserted in a more varus position compared to conventional straight stems. This poses the risk of final varus misplacement of the femoral component, which is not intended in all femoral short stems.

METHODS

We wanted to evaluate the effect of a high varus stem positioning in MIS THA on hip offset, leg length and femoral canal fill index. A series of 1052 consecutive THAs with a singular cementless femoral short stem and press-fit cup was retrospectively screened for inclusion. One hundred six patients with unilateral THA and a contralateral healthy hip met the inclusion criteria. Measurements were carried out on preoperative and 3 months anterior-posterior postoperative radiographs. Patients were divided into Group A (varus stem alignment ≤ 3°) and Group B (varus stem alignment > 3°).

RESULTS

Hip offset (HO) increased significantly in Group B by 4 mm (p = 0.013). No influence on leg length difference was detected in both groups. Preoperative CCD angle was significantly lower in Group B (p < 0.001). Canal Fill Indices (CFI) were significantly lower in Group B (CFI I: p < 0.001; CFI II p = 0.003; CF III p = 0.002).

CONCLUSION

High varus stem alignment > 3° leads to a statistically significant but minor increase in HO and poses the risk of stem undersizing. A preoperatively low genuine CCD angle pose a risk for varus stem positioning.

Assessing component orientation of total hip arthroplasty using the low-dose bi-planar radiographs

Background

Three-dimensional computed tomography (3D CT) reconstruction is the reference standard for measuring component orientation. However, functional cup orientation in standing position is preferable compared with supine position. The low-dose bi-planar radiographs can be used to analyze standing cup component orientation. We aimed to assess the validity and reliability of the component orientation using the low-dose bi-planar radiographs compared with the 3D CT reconstruction, and explore the differences between the functional cup orientation in standing radiographs and supine CT scans.

Methods

A retrospective study, including 44 patients (50 hips) with total hip arthroplasty (THA), was conducted. CT scans were taken 1 week after surgery and the low-dose bi-planar radiographs were taken in the follow-up 6 weeks later. Component orientation measurement was performed using the anterior pelvic plane and the radiographic coronal plane as reference, respectively.

Results

The study showed no significant difference in cup anteversion (p = 0.160), cup inclination (p = 0.486), and stem anteversion (p = 0.219) measured by the low-dose bi-planar radiographs and 3D reconstruction. The differences calculated by the Bland–Altman analysis ranged from − 0.4° to 0.6° for the three measured angles. However, the mean absolute error was 4.76 ± 1.07° for functional anteversion (p = 0.035) and 4.02 ± 1.08° for functional inclination (p = 0.030) measured by the bi-planar radiographs and supine CT scans.

Conclusions

The low-dose bi-planar radiographs are the same reliable and accurate as 3D CT reconstruction to assess post-THA patients’ component orientation, while providing more valuable functional component orientation than supine CT scans.

A single-surgeon experience in reconstruction of femoro-acetabular offset and implant positioning in direct anterior approach and anterolateral MIS approach with a curved short stem

PURPOSE

Minimally invasive surgery using short stems in total hip arthroplasty gained more popularity. The differences in change of hip offset and implant positioning in minimally invasive approaches are not fully known. Therefore, this study was conducted to evaluate the difference in reconstruction of hip offset and implant positioning in direct anterior approach (DAA) and minimally invasive anterolateral approach (AL MIS).

METHODS

A single surgeon series of 117 hips (117 patients; mean age 65.54 years ± 11.47; index surgery 2014-2018) were included and allocated into two groups: group A (DAA) with 70 hips and Group B (AL MIS) with 47 patients operated. In both groups the same type of cementless curved short hip stem and press fit cup was used.

RESULTS

Both groups showed an equal statistically significant increase of femoral (p < 0.001) and decrease of acetabular offset (p < 0.001). Between both groups no statistically significant difference in offset reconstruction, leg length difference or implant positioning could be found. Leg length increased in both groups significantly and leg length discrepancy showed no difference (group A: - 0.06 mm; group B: 1.11 mm; p < 0.001). A comparable number of cups were positioned outside the target zone regarding cup anteversion.

CONCLUSION

The usage of a curved short stem shows an equal reconstruction of femoro-acetabular offset, leg length and implant positioning in both MIS approaches. The results of this study show comparable results to the existing literature regarding change of offset and restoration of leg length. Malposition of the acetabular component regarding anteversion poses a risk.

Conversion of the Sagittal Functional Safe Zone to the Coronal Plane Using a Mathematical Algorithm: The Reason for Failure of the Lewinnek Safe Zone

BACKGROUND

Ante-inclination (AI) of the cup is a key component of the combined sagittal index (CSI) for predicting joint stability after total hip arthroplasty (THA). We aimed to (1) validate a mathematical algorithm relating AI to radiographic anteversion (RA), radiographic inclination (RI), and pelvic tilt (PT); (2) convert the AI criterion of the CSI into the coronal functional safe zone (CFSZ) and explore the influences of standing-to-sitting pelvic motion (PM) and pelvic incidence (PI) on the CFSZ; and (3) attempt to locate a universal cup orientation that always fulfills the AI criterion of the CSI for all patients.

METHODS

In the first phase, a phantom pelvis was designed to simulate a range of PT values, and an acetabular cup was implanted with different RA, RI, and PT settings using a robot-assisted technique and scanned using the EOS imaging system. The second phase involved patient radiographs. We enrolled 100 patients who underwent robot-assisted THA from April 2019 to December 2019, and EOS images before THA and at the 12-month follow-up were recorded. The AI was measured on a lateral radiograph; this angle was used as the reference and compared with the calculated AI to assess the accuracy of the algorithm. Linear regression was conducted to explore the relationship between the size of the CFSZ and the values of PM and PI. We calculated the intersection of the CFSZs of the patients to find a universal cup orientation (RA and RI) for the CSI.

RESULTS

The algorithm was accurate according to both the phantom study and patient radiographs using PT at the time of follow-up, with mean absolute errors (MAEs) of 1.5° (width of 95% confidence interval [CI], 2.2°) and 2.8° (width of 95% CI, 3.0°), respectively. However, the preoperatively predicted AI had an MAE of 9.0° (width of 95% CI, 10.5°). In patient subgroups with lower PM or PI, the sizes of the CFSZ and of its intersection with the Lewinnek safe zone were significantly smaller (p < 0.017). No universal cup orientation existed to fulfill the CSI criteria for all patients or for any of the PM or PI subgroups.

CONCLUSIONS

The target orientation for the cup in THA should be individualized. Our validated algorithm may serve as a quantitative tool for the patient-specific optimization of cup AI on the basis of the functional safe zone.

CLINICAL RELEVANCE

The Lewinnek safe zone fails because it cannot predict the functional orientation of the cup. The concept of a universal safe zone of cup orientation should be abandoned and replaced by a patient-specific surgical target.

An Updated Meta-Analysis of Randomized Controlled Trials on Total Hip Arthroplasty through SuperPATH versus Conventional Approaches

The object was to conduct a systematic review and meta‐analysis of randomized controlled trials (RCTs) up to the present to draw reliable conclusions in the comparison between short‐term outcomes of total hip arthroplasty (THA) through supercapsular percutaneously assisted approach in THA (supercapsular percutaneously‐assisted total hip (SuperPATH)) versus conventional approaches (CAs). A systematic literature search was performed to identify RCTs comparing primary and secondary outcomes of THA through SuperPATH vs. CAs. Mean differences (MDs) were calculated for continuous outcomes and odds ratios (ORs) for dichotomous outcomes, using the DerSimonian and Laird method, the Mantel–Haenszel method and random effects model. A total of 14 RCTs involving 1021 patients met the inclusion criteria. Primary outcomes: SuperPATH reduced intraoperative blood loss (MD = −61.4, 95% CI −119.1 to −3.8). SuperPATH increased Harris hip score (HHS) 3, 6 and 12 months postoperatively (MD = 2.4, 95% CI 0.6–4.2; MD = 2.1, 95% CI 0.6–3.6; MD = 0.7, 95% CI 0.1–1.3; resp.). Both approaches did not differ in postoperative complication rates (OR = 0.7, 95% CI 0.2–3.3). Secondary outcomes: SuperPATH reduced pain visual analogue scale (VAS) 1 day and 3 days postoperatively (MD = −1.0, 95% CI −1.8 to −0.2; MD = −1.2, 95% CI −1.8 to −0.5; resp.). SuperPATH reduced incision length (MD = −5.2, 95% CI −7.0 to −3.4). SuperPATH increased operation time (MD = 14.3, 95% CI 3.7–24.8). Both approaches did not differ relevantly in acetabular cup inclination (MD = −1.8, 95% CI −3.8–0.2) and acetabular cup anteversion (MD = −0.6, 95% CI −1.2 to −0.1) angles. The overall findings of this meta‐analysis (Meta‐SuCAs‐2) suggested that the short‐term outcomes of THA through SuperPATH were superior to CAs. In the primary outcome, SuperPATH had a lower intraoperative blood loss and a higher HHS. Both approaches did not differ in postoperative complications. In the secondary outcome, SuperPATH had a lower pain VAS and a shorter incision length. Both approaches showed sufficient results in acetabular cup positioning. CAs had a shorter operation time than SuperPATH.

Acetabular cup position differs in spinopelvic mobility types: a prospective observational study of primary total hip arthroplasty patients

INTRODUCTION

Spinopelvic mobility was identified as a contributing factor for total hip arthroplasty (THA) instability. The influence of spinopelvic function on acetabular cup positioning has not yet been sufficiently investigated in a prospective setting. Therefore, our study aimed (1) to assess cup inclination and anteversion in standing and sitting based on spinopelvic mobility, (2) to identify correlations between cup position and spinopelvic function, (3) and to determine the influence of the individual spinal segments, spinal sagittal balance, and spinopelvic characteristics on the mobility groups.

MATERIALS AND METHODS

A prospective study assessing 197 THA patients was conducted with stereoradiography in standing and sitting position postoperatively. Two independent investigators determined cup anteversion and inclination, C7-Sagittal vertical axis, cervical lordosis (CL), thoracic kyphosis (TK), lumbar lordosis (LL), sacral slope, pelvic tilt (PT), anteinclination (AI), and pelvic femoral angle (PFA). Spinopelvic mobility is defined based on ∆PT = PT_standing - PT_sitting as ∆PT < 10° stiff, ∆PT ≥ 10-30° normal, and ∆PT > 30° hypermobile. Pearson coefficient represented correlations between the cup position and spinopelvic parameters.

RESULTS

Significant differences were demonstrated for cup anteversion (stiff/hypermobile 29.3°/40.1°; p < 0.000) and inclination (stiff/hypermobile 43.5°/60.2°; p < 0.000) in sitting, but not in standing position. ∆ (standing/sitting) of the cup anteversion (stiff/neutral/hypermobile 5.8°/12.4°/19.9°; p < 0.000) and inclination (stiff/neutral/hypermobile 2.3°/11.2°/18.8°; p < 0.000) revealed significant differences between the mobility groups. The acetabular cup position in sitting, was correlated with lumbar flexibility (∆LL) and spinopelvic mobility. Significant differences were detected between the mobility types and acetabular orientation (AI sit:stiff/hypermobile 47.6°/65.4°; p < 0.000) and hip motion (∆PFA:stiff/hypermobile 65.8°/37.3°; p < 0.000). Assessment of the spinal segments highlighted the role of lumbar flexibility (∆LL:stiff/hypermobile 9.9°/36.2°; p < 0.000) in the spinopelvic complex.

CONCLUSION

The significantly different acetabular cup positions in sitting and in the ∆ between standing and sitting and the significantly altered spinopelvic characteristics in terms of stiff and hypermobile spinopelvic mobility underlined the consideration for preoperative functional radiological assessment. Identifying the patients with altered spinopelvic mechanics due to a standardized screening algorithm is necessary to provide safe acetabular cup positioning. The proximal spinal segments appeared not to be involved in the spinopelvic function.

Does obesity affect acetabular cup position, spinopelvic function and sagittal spinal alignment? A prospective investigation with standing and sitting assessment of primary hip arthroplasty patients

Background

Total hip arthroplasty (THA) instability is influenced by acetabular component positioning, spinopelvic function and sagittal spinal alignment. Obesity is considered as a risk factor of THA instability, but the causal relationship remains unknown. This study aimed to investigate the influence of BMI on (1) spinopelvic function (lumbar flexibility, pelvic mobility and hip motion), (2) sagittal spinal alignment pre- and postoperatively and (3) acetabular cup position postoperatively in primary THA patients in a prospective setting.

Methods

One hundred ninety patients receiving primary total hip arthroplasty were enrolled in a prospective cohort study and retrospectively analysed. All patients received stereoradiography (EOS) in standing and relaxed sitting position pre-and postoperatively. C7-sagittal vertical axis (C7-SVA), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), anterior plane pelvic tilt (APPT), and pelvic femoral angle (PFA) were assessed. Key parameters of the spinopelvic function were defined as lumbar flexibility (∆ LL = LL_standing − LL_sitting), pelvic mobility (∆ PT = PT_standing − PT_sitting) and hip motion (∆ PFA = PFA_standing − PFA_sitting). Pelvic mobility was further defined based on ∆ PT as stiff, normal and hypermobile (∆ PT < 10°; 10°–30°; > 30°). The patients were stratified to BMI according to WHO definition: normal BMI ≥ 18.5–24.9 kg/m² (n = 68), overweight ≥ 25.0–29.9 kg/m² (n = 81) and obese ≥ 30–39.9 kg/m² (n = 41). Post-hoc analysis according to Hochberg's GT2 was applied to determine differences between BMI groups.

Results

Standing cup inclination was significant higher in the obese group compared to the normal BMI group (45.3° vs. 40.1°; p = 0.015) whereas standing cup anteversion was significantly decreased (22.0° vs. 25.3°; p = 0.011). There were no significant differences for spinopelvic function key parameter lumbar flexibility (∆ LL), pelvic mobility (∆ PT) and hip motion (∆ PFA) in relation to BMI stratified groups. The obese group demonstrated significant enhanced pelvic retroversion compared to the normal BMI group (APPT − 1.8° vs. 2.4°; p = 0.028). The preoperative proportion of stiff pelvic mobility was decreased in the obese group (12.2%) compared to normal (25.0%) and overweight (27.2%) groups. Spinal sagittal alignment in C7-SVA and PI-LL mismatch demonstrated significantly greater imbalance in the obese group compared to the normal BMI group (68.6 mm vs. 42.6 mm, p = 0.002 and 7.7° vs. 1.2°, p = 0.032, respectively) The proportion of patients with imbalanced C7-SVA was higher in the obese (58.5%) than in the normal BMI group (44.1%).

Conclusions

The significantly increased spinal sagittal imbalance with altered pelvic mechanics is a potential cause for the reported increased risk of THA dislocations in obese patients. Consequently, the increased spinal sagittal imbalance in combination with normal pelvic mobility need to be taken into account when performing THA in obese patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-021-02716-8.

Interobserver and Intraobserver Reliabilities of Three-Dimensional Postoperative Evaluation Software in Total Hip Arthroplasty

BACKGROUND

In primary and revision total hip arthroplasty, to prevent perioperative complications, the prediction of the optimal implant size is essential. Using three-dimensional computed tomography-based postoperative evaluation software, we explored the accuracy and the precision of measurement of the size, alignment, and position of the prosthetic components after total hip arthroplasty.

METHODS

Using postoperative evaluation software, the postoperative computed tomography data from 20 hips in 20 patients were evaluated. The component size, alignment, and three-dimensional positioning of the cup and stem were assessed. The concordance rates of the component, repeatability (intraobserver reliability), and reproducibility (interobserver reliability) of postoperative evaluation were calculated. The radiographic inclination and radiographic anteversion of the cup, anteversion, varus-valgus angle, and flexion-extension angles of the stem were measured for alignment. The implant positioning was measured along three axes, namely, X-axis (transverse), Y-axis (sagittal), and Z-axis (longitudinal).

RESULTS

The concordance rates of all parts are above 94%. The intraobserver and interobserver intraclass correlation coefficients of alignment measurement were very good for both cup (0.879-0.964) and stem (0.973-0.996). The intraobserver and interobserver intraclass correlation coefficients of cup positioning were very good (0.961-0.987) for all axes. The intraobserver and interobserver intraclass correlation coefficients of implant positioning were very good for the stem (0.879-0.995) for all axes.

CONCLUSIONS

Computed tomography-based postoperative evaluation software was able to evaluate the size and position of total hip implants with high reproducibility.

Assessment of Acetabular Component Anteversion after Total Hip Arthroplasty: Comparison of Anteroposterior and Cross-Table Lateral Radiographs with Computed Tomography Scans

Background

Several methods of measurement of anteversion of acetabular components after total hip arthroplasty (THA) have been described in the literature using plain radiographs or computed tomography (CT) scans. None of these have proved to be the gold standard. We aimed to study the correlation between the CT and radiographic methods of calculation of acetabulum anteversion.

Methods

CT scans of the pelvis, anteroposterior (AP) and cross-table lateral (CL) radiographs were obtained in 60 patients who underwent THA two weeks after surgery. Anteversion was measured using Widmer method and Liaw method on AP radiographs, and the ischiolateral method on CL radiographs. Anteversion measured on the CT scan was taken as the reference anteversion and the above measurements were analysed for correlation with the measurements on CT scan. Intraclass correlation coefficients (ICCs) were calculated for both intra- and interobserver reliability.

Results

Mean acetabular version on CL radiographs was 53.1 ± 10.7. Mean version on AP radiographs by Widmer method was 21.4 ± 3.6 and by Liaw method was 20.3 ± 4.8. Mean version on CT scans was 26.02 ± 6.8. There was a good correlation between the acetabular version on CT scans with the version on AP radiographs by Widmer method (r = 0.78, p < 0.001) and Liaw method (r = 0.87, p < 0.001). Good correlation was seen between the acetabular version on CL radiographs and CT scans (r = 0.91, p < 0.001). Also, a good correlation was observed between the acetabular version measurements on CL radiographs and AP radiographs by Widmer method (r = 0.81, p < 0.001) or Liaw method (r = 0.70, p < 0.001). Excellent inter- and intraobserver reliability were seen for all the measurements.

Conclusions

Calculation of acetabular component version on AP views as well as CL views of plain radiographs showed a strong correlation with the version measurements on CT scans. Good correlations were observed between different techniques of measurement on radiographs. Therefore, all these measurements can be valid methods for assessment of anteversion.

MRI Assessment of Muscle Damage After the Posterolateral Versus Direct Anterior Approach for THA (Polada Trial). A Randomized Controlled Trial

BACKGROUND

There is controversy in literature whether the direct anterior approach (DAA) results in less muscle damage compared with the posterolateral approach (PLA) for total hip arthroplasty. The aim of this randomized controlled trial was to assess muscle damage between these two approaches.

METHODS

Forty-six patients were included. Muscle atrophy, determined with the Goutallier classification, and muscle surface of twelve muscles were analyzed on magnetic resonance imaging images made preoperatively and one year postoperatively. Differences in component placement after DAA or PLA were assessed on radiographs. Harris hip scores and Hip disability and Osteoarthritis and Outcome Score were used as functional outcomes.

RESULTS

External rotator musculature was damaged in both approaches. After PLA, the obturator muscles showed significantly more atrophy and a decrease in muscle surface. After DAA, the tensor fascia latae showed an increased muscle atrophy and the psoas muscle showed a decreased muscle surface. An increase in muscle surface was seen for the rectus femoris, sartorius, and quadratus femoris after both approaches. The muscle surface of the gluteus medius and iliacus was also increased after PLA. No difference in muscle atrophy was found between the approaches for these muscles. The inclination angle of the cup in PLA was significantly higher. No differences were found in functional outcomes.

CONCLUSION

Different muscle groups were affected in the two approaches. After PLA, the external rotators were more affected, whereas the tensor fascia latae and psoas muscles were more affected after DAA.

Direct anterior approach (DAA) vs. conventional approaches in total hip arthroplasty: A RCT meta-analysis with an overview of related meta-analyses

OBJECTIVES

Several systematic reviews and meta-analyses on short-term outcomes between total hip arthroplasty (THA) through direct anterior approach (DAA) compared to THA through conventional (including anterior, anterolateral, lateral transgluteal, lateral transtrochanteric, posterior, and posterolateral) approaches (CAs) in treatment of hip diseases and fractures showed contradicting conclusions. Our aim was to draw definitive conclusions by conducting both a fixed and random model meta-analysis of quality randomized controlled trials (RCTs) and by comparison with related meta-analyses.

DESIGN

We performed a systematic literature search up to May 2020 to identify RCTs, comparing THA through DAA with THA through CAs and related meta-analyses. We conducted risk of bias and level of evidence assessment in accordance with the Cochrane's Risk of Bias 2 tool and with the guidelines of the Centre for Evidence-Based Medicine. We estimated mean differences (MD) with 95% confidence intervals (CI) through fixed and random effects models, using the DerSimonian and Laird method. Heterogeneity was assessed using tau-square (τ2). Our conclusions take into account the overall results from related meta-analyses.

RESULTS

Nine studies on THA through DAA met the criteria for final meta-analysis, involving 998 patients. Three studies were blinded RCTs with a level I evidence, the other 6 studies were non-blinded RCTs with a level II evidence. We came to the following results for THA through DAA compared to THA through CAs: operation time (I2 = 92%, p<0.01; fixed: MD = 15.1, 95% CI 13.1 to 17.1; random: MD = 18.1, 95% CI 8.6 to 27.5); incision length (I2 = 100%, p<0.01; fixed: MD = -2.9, 95% CI -3.0 to -2.8; MD = -1.1, 95% CI -4.3 to 2.0); intraoperative blood loss (I2 = 87%, p<0.01; fixed: MD = 51.5, 95% CI 34.1 to 68.8; random: MD = 51.9, 95% CI -89.8 to 193.5); VAS 1 day postoperatively (I2 = 79%, p = 0.03; fixed: MD = -0.8, 95% CI -1.2 to -0.4; random: MD = -0.9, 95% CI -2.0 to 0.15); HHS 3 months postoperatively (I2 = 52%, p = 0.08; fixed: MD = 2.8, 95% CI 1.1 to 4.6; random: MD = 3.0, 95% CI -0.5 to 6.5); HHS 6 months postoperatively (I2 = 0%, p = 0.67; fixed: MD = 0.9, 95% CI -1.1 to 2.9; random: MD = 0.9, 95% CI -1.1 to 2.9); HHS 12 months postoperatively (I2 = 0%, p = 0.79; fixed: MD = 0.7, 95% CI -0.9 to 2.4; random: MD = 0.7, 95% CI -0.9 to 2.4). We compared our findings with 7 related meta-analyses.

CONCLUSIONS

Considering the results of our meta-analysis and the review of related meta-analyses, we can conclude that short-term outcomes of THA through DAA were overall better than THA through CAs. THA through DAA had a shorter incision length, a tendency towards a lower pain VAS 1 day postoperatively and better early postoperative functional outcome than THA through CAs. The intraoperative blood loss showed indifferent results. THA through DAA had a longer operation time than THA through CAs.

Can a simple iPad app improve C-arm based component position in anterior THA?

INTRODUCTION

Correct acetabular component positioning improves hip biomechanics, impingement free range of motion and may lead to a reduced risk of postoperative dislocation. The C-arm is a simple and cost-effective tool for THA in a supine position, however, evaluation of the images can be challenging due to parallax. The current study aimed to investigate whether a software app-based measurement technique can control acetabular component position and leg length in anterior THA.

MATERIALS AND METHODS

Ninety-three patients with end-stage osteoarthritis aged 65.2 ± 9.6 years (range 30-86 years) were included in this prospective study. All patients underwent direct anterior THA using a Hana orthopedic surgery table. C-arm imaging and an iPad software app were used to determine intraoperative acetabular anteversion, inclination and leg length discrepancy. The app provides a measuring tool that is applied to intraoperative c-arm images. The intraoperative measurements were compared to the measurements of standard postoperative AP-pelvis radiographs.

RESULTS

Intraoperative software app-based anteversion measurements averaged 20.5° (range 16.0° to 24.0°) compared to 20.9° (range 14.7° to 25.6°) postoperatively. Mean intraoperative inclination was 40.5° (range 35° to 48°) compared to postoperative 40.7° (range 35° to 49°). Mean intraoperative leg length discrepancy was 0.9 mm (range - 4-5 mm) compared to postoperative 0.6 mm (range - 5-6 mm). A strong Pearson's correlation was observed between the intraoperative and postoperative measurements for anteversion (r = .701; P < .0001), inclination (r = .816; P < .0001) and leg length discrepancy (r = .542; P < .0001).

CONCLUSIONS

The software app used in the current study allowed for a simple and accurate measurement of intraoperative cup position and leg length in direct anterior THA.

Spinopelvic mobility affects accuracy of acetabular anteversion measurements on cross-table lateral radiographs

AIMS

Cross-table lateral (CTL) radiographs are commonly used to measure acetabular component anteversion after total hip arthroplasty (THA). The CTL measurements may differ by > 10° from CT scan measurements but the reasons for this discrepancy are poorly understood. Anteversion measurements from CTL radiographs and CT scans are compared to identify spinopelvic parameters predictive of inaccuracy.

METHODS

THA patients (n = 47; 27 males, 20 females; mean age 62.9 years (SD 6.95)) with preoperative spinopelvic mobility, radiological analysis, and postoperative CT scans were retrospectively reviewed. Acetabular component anteversion was measured on postoperative CTL radiographs and CT scans using 3D reconstructions of the pelvis. Two cohorts were identified based on a CTL-CT error of ≥ 10° (n = 11) or < 10° (n = 36). Spinopelvic mobility parameters were compared using independent-samples t-tests. Correlation between error and mobility parameters were assessed with Pearson's coefficient.

RESULTS

Patients with CTL error > 10° (10° to 14°) had stiffer lumbar spines with less mean lumbar flexion (38.9°(SD 11.6°) vs 47.4° (SD 13.1°); p = 0.030), different sagittal balance measured by pelvic incidence-lumbar lordosis mismatch (5.9° (SD 18.8°) vs -1.7° (SD 9.8°); p = 0.042), more pelvic extension when seated (pelvic tilt -9.7° (SD 14.1°) vs -2.2° (SD 13.2°); p = 0.050), and greater change in pelvic tilt between supine and seated positions (12.6° (SD 12.1°) vs 4.7° (SD 12.5°); p = 0.036). The CTL measurement error showed a positive correlation with increased CTL anteversion (r = 0.5; p = 0.001), standing lordosis (r = 0.23; p = 0.050), seated lordosis (r = 0.4; p = 0.009), and pelvic tilt change between supine and step-up positions (r = 0.34; p = 0.010).

CONCLUSION

Differences in spinopelvic mobility may explain the variability of acetabular anteversion measurements made on CTL radiographs. Patients with stiff spines and increased compensatory pelvic movement have less accurate measurements on CTL radiographs. Flexion of the contralateral hip is required to obtain clear CTL radiographs. In patients with lumbar stiffness, this movement may extend the pelvis and increase anteversion of the acetabulum on CTL views. Reliable analysis of acetabular component anteversion in this patient population may require advanced imaging with a CT scan. Cite this article: Bone Joint J 2021;103-B(7 Supple B):59-65.

Iliopsoas Impingement After Direct Anterior Approach Total Hip Arthroplasty: Epidemiology, Risk Factors, and Treatment Options

BACKGROUND

The objective of this study is to evaluate the incidence, natural history, response to treatment, and risk factors for anterior iliopsoas impingement (AIPI) after direct anterior approach (DAA) total hip arthroplasty (THA).

METHODS

Between January 1, 2009 and January 4, 2014, 600 patients (655 hips) who underwent primary DAA THA were retrospectively reviewed. AIPI incidence was calculated. Natural history and response to a stepwise treatment approach was assessed. Radiographic anterior acetabular component overhang was measured. Asymptomatic controls were used to identify risk factors for the development of AIPI.

RESULTS

In total, 518 patients (559 hips) met the inclusion criteria. The incidence of AIPI was 32/559 (5.7%). Symptom resolution occurred in 22/32 (68.8%) patients at final follow-up. Nonoperative management was successful in 15/32 (46.9%) patients. Operative intervention resulted in symptom resolution in 5/8 (62.5%) patients. On univariate analysis, female gender (odds ratio [OR] 2.79), acetabular component to native femoral head diameter ratio above 1.1 (OR 3.85), and any measurable overhang (OR 7.07) significantly raised the risk of AIPI, while increasing native femoral head diameter was protective for AIPI (OR 0.83).

CONCLUSION

AIPI is a cause of groin pain after DAA THA, which often improves with conservative measures. Significant predisposing factors for AIPI include female gender, small native femoral head diameter, increased acetabular component to femoral head diameter ratio, and most notably, any measurable acetabular component overhang.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Does using the direct anterior approach with a standard table for total hip arthroplasty reduce leg length discrepancies? Comparative study of traction table versus standard table

INTRODUCTION

Primary total hip replacement (THR) comes with a risk of leg length discrepancy (LLD), which occurs in 25 % of cases, especially when the surgery is done using an anterior approach on a traction table, since it is not easy to verify the lengths of the legs. By doing the anterior approach on a standard table an intraoperative visual evaluation of leg lengths can be done after the trial implants are in place. As far as we know, the ability to set the leg length has not been compared between procedures done on a standard table or a traction table. This led us to carry out a retrospective comparative study to determine whether using a standard table for anterior THR will 1) allow better control over leg length, 2) increase the risk of incorrect implant positioning, 3) increase the surgical complication rate.

HYPOTHESIS

Anterior THR on a standard table will allow better control over leg length than anterior THR on a traction table.

MATERIAL AND METHODS

This single center retrospective study included 266 THRs done between January 1, 2018 and November 2, 2019 for primary (n=219) or secondary (n=47) hip osteoarthritis. The 137 cases done with a traction table were compared to the 129 cases with a standard table. The two groups were comparable in terms of age, sex, body mass index, indication and bilateral implants. They were not comparable in the surgeon experience (more junior surgeons in the standard table group [p<0.001]) and types of implants used (more cementless cups and stems in the standard table group [p=0.001]). Radiographs were used to measure the LLD, cup inclination, and femoral stem placement in the frontal plane. Any early complications were documented. The target was for the operated leg to be the same length as the contralateral leg, which was defined as within 10mm of each other.

RESULTS

The mean postoperative LLD was comparable between the traction table group 1.56±7.32 mm (min -15.6 max 17.2) and the standard table group 0.53±6.93 mm (min -16.4 max 13.7) (p=0.24). In the traction table group, 81 % (111/137) of patients had legs of the same length, versus 84 % (109/129) in the standard table group (p=0.7). Cup inclination was comparable with a mean of 40.4±7.1 degrees (min 23.4; max 58.5) in the traction table group versus 39.3±7.5 degrees (min 19.9; max 60.9) in the standard table group (p=0.21). The frontal position of the femoral stem was comparable between groups with a mean of 0.09±0.45 degrees (min -1; max 3.98) in the traction table group versus 0.08±0.59 degrees (min -4.97; max 1.93) in the standard table group (p=0.86). There were 5 complications (3.7 %) in the traction table group versus 11 (8.5 %) in the standard table group (p=0.16).

CONCLUSION

Use of a standard table to carry out THR by the direct anterior approach does not provide better control over leg length than using a traction table, subject to preoperative planning. When doing the procedure on a standard table, the implant placement is at least comparable, with a similar risk of complications.

LEVEL OF EVIDENCE

III; case matched study.

Lewinnek Safe Zone References are Frequently Misquoted

BACKGROUND

Optimal acetabular component orientation in total hip arthroplasty (THA) is a necessity in achieving a stable implant. Although there has been considerable debate in the literature concerning the safe zone, to date, there has not been any review to determine if these references are consistent with the definition applied by Lewinnek et al. in 1978. Therefore, this article aims to examine the available literature in the PubMed database to determine how often a correct reference to the safe zone as defined by Lewinnek was applied to discussions regarding THA.

METHODS

A search for literature in the PubMed database was performed for articles from 1978 to 2019. Search criteria included terms 'Lewinnek,' 'safe zone,' and 'total hip arthroplasty.' Exclusions included abstract-only articles, non-English articles, articles unrelated to THA, and those lacking full content.

RESULTS

A review of literature yielded 147 articles for inclusion. Overall, only 11% (17) cited the Lewinnek article correctly. Forty-five percent (66) of articles referenced measurements in the supine position, 18% (26) referenced other positions, and 37% (55) did not specify. Nineteen percent (28) reported measurements of the acetabular cup orthogonal to the anterior pelvic plane, while 73% (108) did not, and 7% (11) did not specify. Twenty-three percent (34) measured from computed tomography scans instead of other methods.

CONCLUSIONS

In the discussion of the safe zone regarding THA, only 11% of articles listed are consistent with the definition established by Lewinnek. This warrants further investigation into a consistent application of the term and its implications for THA implant stability and dislocation rates.

Ceramic-on-metal bearing in short stem total hip arthroplasty: ions, functional and radiographic evaluation at mid-term follow-up

INTRODUCTION

The aim of this study is to evaluate clinical, radiographic and laboratory results of ceramic-on-metal (CoM) (hybrid hard bearing) in total hip arthroplasty (THA), associated with a short stem implant.

METHODS

From a cohort of 37 patients suffering from primary or secondary hip osteoarthritis who underwent THA using CoM bearing, 19 were suitable for this study. All procedures were performed by the same surgeon using a posterior-lateral approach. All patients were compared clinically using the Harris Hip Score (HHS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), visual analogue scale (VAS), 12-item Short Form Health Survey (SF12F/M), and radiographically (offset, CD angle, limb length discrepancy, cup inclination and anteversion, subsidence, osseointegration, heterotopic ossification). Blood samples were collected in order to evaluate chromium (Cr) and cobalt (Co) ions level. Radiographic evaluations were carried out by 3 different blinded surgeons. A statistical analysis was performed.

RESULTS

At a mean follow-up of 97 (73-125) months all implanted stems were well-positioned and osseointegrated. Clear improvements were observed for clinical scores comparing preoperative and postoperative values. Radiographic evaluation showed a good ability to restore proper articular geometry. Cr ion analysis revealed values below the safety threshold except for 1 case. Serum levels of Co were below the threshold in all patients. There was a statistically significant correlation only between Cr metal ions and length of follow-up.

CONCLUSIONS

CoM bearing has proven to be reliable and safe at a mean 8-year follow-up for patients in whom the components were correctly implanted. The rise of blood metal ions was minimal and involved neither systemic or local toxicity nor influenced clinical results.

False profile view is independently associated with serum metal levels in patients with metal-on-metal hip arthroplasty

PURPOSE

Elevated levels of serum metal ions can be found in some patients with metal-on-metal (MoM) hip replacements. This study seeks to identify whether there is a significant association between the contact patch to rim distance (CPRD) and the anterior center edge angle (ACEA), respectively, and serum cobalt (Co) and chromium (Cr) levels in patients treated with unilateral MoM hip replacements by using standing anteroposterior and false profile view radiographs.

METHODS

This is a retrospective analysis on 53 patients with either unilateral ReCap or M2a-Magnum MoM hip replacements operated in 2006 or 2007. Univariate linear regression and multivariable linear regression (MLR) analyses were performed using the CPRD and ACEA along with risk factors for elevated serum levels of Co and Cr previously suggested in the literature as explanatory variables. Serum Co and Cr were measured using inductively coupled plasma mass spectrometry.

RESULTS

The MLR model showed that the same three variables (gender, CPRD and ACEA) were significantly associated with serum levels of both Co and Cr explaining approximately half of the variation. A univariate analysis showed a polynomial association between both anteversion angle and the ACEA with serum levels of Co and Cr. The vertex of the polynomial function was located at approximately 20° and 40°, respectively.

CONCLUSION

Gender, CPRD and ACEA are independently associated with serum levels of Co and Cr. Both ACEA and anteversion angles have optimae associated with low serum metal levels which may be useful for post-surgery evaluation of cup positioning.

Retention of metals in periprosthetic tissues of patients with metal-on-metal total hip arthroplasty is reflected in the synovial fluid to blood cobalt transfer ratio in the presence of a pseudotumour

Background

Modern metal-on-metal (MOM) arthroplasties were performed for over a decade before alarming reports of adverse metal reactions dramatically reduced their use. Failures are seen more often with high-wearing implants, but also well-positioned components with more favourable wear patterns can cause problems. There are no specific clinical indicators that could help us to predict the prognosis of these implants. For this reason, we still need more information on the effect of underlying factors that contribute to this process.

Methods

In this prospective cohort study, we investigated how cup orientation and type of pseudotumour determined by the Hart classification effect the distribution of metals in blood, synovial fluid and tissues surrounding the metal-on-metal hip prosthesis in revision surgery patients. One thousand two hundred twenty-nine metal-on-metal hip patients were screened and of those, 60 patients that had a revision surgery due to adverse metal reaction were included. Whole blood, synovial fluid and synovial/pseudotumour tissue samples were analysed for metal ion concentrations (Co, Cr, Mo and Ti).

Results

The lowest metal concentrations were found when both cup anteversion and inclination were optimal, and the highest when both were suboptimal. Suboptimal anteversion alone raised Cr-ion concentrations more than suboptimal inclination. The concentrations of metals in blood, synovial fluid or synovial soft tissue were the same in patients with and without a pseudotumour, but the relative transfer percentage of cobalt from synovial fluid to blood was higher in patients with a pseudotumour.

Conclusions

The implant orientation alone does not explain the metal concentrations found in tissues or distribution of metals between different tissues. The accumulation of metals in periprosthetic soft tissues increase the total metal load, and in the presence of a pseudotumour this is reflected in the transfer ratio of Co from synovial fluid to the blood. The total metal load of the pseudotumour tissue should be defined in future studies to determine if this will provide new insights for clinical practice.

Total hip arthroplasty and lumbar spine disorders: Plain co-existence or mutual influence?

Lumbar spine disorders (LSD) might influence the outcome after total hip arthroplasty (THA). Despite a known common prevalence of LSD and degenerative hip disorders, this study investigates their mutual influence in case of co-existence with the purpose to advance surgeons planning and patient’s prognosis. Patients with and without LSD were compared before and at the one-year postoperative examination. For clinical evaluation the WOMAC was assessed. The radiological analysis focused on cup anteversion and inclination. The total group included 203 consecutive patients. The overall incidence of LSD was 51.0%. Patients with LSD were on average 4.3 years older and had a 1.8 higher BMI than non-LSD patients (P<0.05). The cup positioning and the clinical results were comparable between both groups before and at the last time of follow up (P>0.05). No hip dislocations nor clinical signs of impingement were seen.We can conclude that there is a high degree of co-existence of LSD and hip disorders. However, a strong negative impact of LSD to clinical or radiologic results could not be confirmed in our study.

A Surgeon's handedness in direct anterior approach-hip replacement

BACKGROUND

The impact of handedness on clinical outcomes was easily overlooked in hip replacement. This study aimed to find whether the component positioning and hip function were affected by the handedness in total hip arthroplasty (THA) through direct anterior approach (DAA).

METHODS

Total 102 patients who underwent bilateral DAA-THAs simultaneously between May 2016 and November 2018 in our institute were reviewed. All surgeries were operated by one right-handed surgeon. Their demographic, cup positioning, stem alignment, femoral stem fit, Harris hip score (HHS), intraoperative and postoperative complications were used to evaluate the role of handedness in DAA.

RESULTS

The inclination of left cups was significantly larger than that of right cups (42.61 ± 7.32 vs 39.42 ± 7.19, p = 0.000). The stem fit of left femur was significantly larger than that of right femur (84.34 ± 4.83 vs 82.81 ± 6.07, p = 0.043). No significant differences in safe zone ratio, HHS and complications between bilateral hips were found.

CONCLUSIONS

A surgeon's handedness had significant impact on cup's inclination and femoral stem fit in DAA-THA. However, there were no significant differences of cup malpositioning, stem alignment, hip function scores and complications between bilateral DAA-THAs.

Robot-Assisted Total Hip Arthroplasty for Arthrodesed Hips

Background

Conversion of arthrodesed hips to total hip arthroplasty (THA) remains technically demanding. This study aims to evaluate the safety and efficacy of robot-assisted THA in arthrodesed hips.

Methods

We retrospectively analyzed 45 ankylosing spondylitis patients with hip arthrodesis in the Chinese PLA General Hospital between August 2018 and August 2019. All surgeries were carried out by one single surgeon. The patients were followed at 3 months after surgery. Gender, body mass index, angle of hip arthrodesis, operating time, intraoperative fluoroscopic times, postoperative length of hospitalization, cup positioning, postoperative leg length discrepancy, offset discrepancy, intraoperative and postoperative complications, and postoperative Harris Hip Score were collected for all patients.

Results

Twenty-two patients (35 hips) who underwent robot-assisted THA and 23 patients (37 hips) who underwent manual THA were enrolled in this study. There were no significant differences in demographics and arthrodesed angles between the two groups. The fluoroscopic times during manual THA were significantly higher than those during robot-assisted THA (2.16±1.61 vs 0.47±0.61, respectively, p=0.000). In the robotic group, the percentage of acetabular cups within the safe zone was significantly greater than in the manual group (94.29% vs 67.56%, respectively, p=0.042). For manual THA, the anteversions were significantly different between the left and right sides (21.14±7.86 vs 16.00±6.32, respectively, p=0.042); however, no such significant difference was found in robot-assisted THA.

Conclusion

Compared with manual THA for arthrodesed hips, robot-assisted THA had significant advantages in improving the frequency of achieving cup positioning within the target zone with diminished radiation dose and no increase in operating time.

Early Polyethylene Failure in a Modern Total Hip Prosthesis: A Note of Caution

BACKGROUND

Historically, there has been excellent survivorship of total hip arthroplasty with newer implants expected to outperform prior generations. Review of our institutional database identified problems with one particular cross-linked polyethylene liner in mid-term follow-up, which has not been reported in the literature. We report on the technical aspects of this liner, as well as the clinical and radiographic factors associated with early failure of this bearing in our practice.

METHODS

A retrospective review of our institutional database was performed from January 2009 to June 2019 of patients who presented with significant osteolysis in the setting of prior total hip arthroplasty with a contemporary polyethylene liner. Demographic and radiographic measures were collected for all patients.

RESULTS

Twelve patients were identified, with nine undergoing revision surgery. All patients demonstrated radiographic osteolysis at the time of revision surgery. The average time to diagnosis of failure was 55.9 months (range: 12-120 months). Average cup position preoperatively was 44 degrees inclination (range: 36-53 degrees) and 21 degrees anteversion (range: 10-34 degrees). Nine patients underwent revision of the acetabular component, with two also undergoing femoral component revision. The Manufacturer and User Facility Device Experience database revealed 22 reported cases of wear-related failure from 2009 to 2019.

CONCLUSIONS

Considering that no identifiable risk factors related to patient demographics or implant position were identified, the Exactech Connexion GXL liner may be prone to a high rate of early failure from wear and severe secondary osteolysis. We recommend close surveillance of patients with this bearing surface.

Hip resurfacing arthroplasty for osteonecrosis of the femoral head: Implant-specific outcomes and risk factors for failure

Background

Hip resurfacing arthroplasty (HRA) may be a suitable option for treating osteonecrosis of the femoral head (ONFH). However, concerns regarding the extent of osteonecrosis, amount of defect under the prosthesis, and implant-related complications remain. This study aimed to report implant-specific outcomes and risk factors for failure of HRA in ONFH.

Methods

A total of 202 HRAs (166 patients) performed by a single surgeon were investigated. The stage, size, and location of ONFH were evaluated using preoperative radiographs and magnetic resonance images. Clinical, radiographic results, and serum metal concentrations of articular surface replacement (ASR) and non-ASR devices were compared. Logistic regression analysis was performed to identify the contributors of failures. The mean follow-up duration was 10.6 years.

Results

Twenty-six hips (12.9%) were operated with Birmingham Hip Resurfacing (BHR), 99 (49.0%) with ASR, and 77 (38.1%) with Conserve Plus. The mean Harris Hip Score improved from 52.1 to 93.2 at the final follow-up (P < 0.001). Revision-free survivorships of non-ASR and ASR implants were 99.0% and 82.4%, respectively (P < 0.001). In multivariate analysis, the use of ASR prosthesis, greater combined necrotic angle, and smaller head size were associated with revision surgery. A large combined necrotic angle was the only independent risk factor for mechanical failure at the femoral side (P = 0.029).

Conclusion

HRA for ONFH using BHR and Conserve Plus implants demonstrated favourable clinical outcomes with high revision-free survival rates at 10 years. However, care should be taken for large necrotic lesions that can lead to femoral neck fracture or aseptic femoral loosening.

The translational potential of this article

This study suggests HRA performed for appropriately selected patients with ONFH can show excellent long-term clinical results. Therefore, HRA should remain as one of the treatment options for ONFH, and further development of HRA implants should be continued.

Radiographic assessment of the cup orientation after total hip arthroplasty: a literature review

Optimal acetabular cup orientation is of substantial importance to good long-term function and low complication rates after total hip arthroplasty (THA). The radiographic anteversion (RA) and inclination (RI) angles of the cup are typically studied due to the practicability, simplicity, and ease of interpretation of their measurements. A great number of methods have been developed to date, most of which have been performed on pelvic or hip anteroposterior radiographs. However, there are primarily two influencing factors for these methods: X-ray offset and pelvic rotation. In addition, there are three types of pelvic rotations about the transverse, longitudinal, and anteroposterior axes of the body. Their effects on the RA and RI angles of the cup are interactively correlated with the position and true orientation of the cup. To date, various fitted or analytical models have been established to disclose the correlations between the X-ray offset and pelvic rotation and the RA and RI angles of the cup. Most of these models do not incorporate all the potential influencing parameters. Advanced methods for performing X-ray offset and pelvic rotation corrections are mainly performed on a single pelvic AP radiograph, two synchronized radiographs, or a two-dimensional/three-dimensional (2D-3D) registration system. Some measurement systems, originally developed for evaluating implant migration or wear, could also be used for correcting the X-ray offset and pelvic rotation simultaneously, but some drawbacks still exist with these systems. Above all, the 2D-3D registration technique might be an alternative and powerful tool for accurately measuring cup orientation. In addition to the current methods used for postoperative assessment, navigation systems and augmented reality are also used for the preoperative planning and intraoperative guidance of cup placement. With the continuing development of artificial intelligence and machine learning, these techniques could be incorporated into robot-assisted orthopaedic surgery in the future.

Proceeding from direct lateral to anterolateral approach in total hip arthroplasty: A closer look on radiological and clinical aspects

Introduction

Since less invasive approaches for total hip arthroplasty (THA) are promoted, our aim was to compare direct lateral (DLA) and anterolateral approach (ALA) under otherwise identical conditions.

Methods

Pre - and postoperative x-rays from 200 propensity matched patients (DLA vs. ALA) were evaluated for anatomical reconstruction.

Results

Overall, the cup position was within the safe zone in both group while the mean center of rotation (COR) was placed more medial and cranial in both groups compared to preoperative anatomy (p > 0.05). The mean leg elongation was comparable between both approaches (p > 0.05). Postoperatively the WOMAC improved about 90%.

Conclusion

This study confirmed that the ALA can be safely used for THA in minimal invasive setting.

Intraoperative evaluation of acetabular cup position during anterior approach total hip arthroplasty: are we accurately interpreting?

INTRODUCTION

Intraoperative radiographic evaluation during total hip arthroplasty (THA) has shown to improve the accuracy of acetabular component placement, however, differences in interpretation based on radiographic technique has not been established. This study aims to determine if differences exist in the interpretation of acetabular component abduction and anteversion between different radiographic projections.

METHODS

55 consecutive direct anterior THAs in 49 patients were prospectively enrolled. Target anteversion and abduction was defined by the Lewinnek zone. Fluoroscopy was used to direct acetabular component placement intraoperatively. After final cup implantation, fluoroscopic posterior-anterior hip and pelvis images were obtained for analysis. After completion of the procedure, an anterior-posterior plain pelvis radiograph was obtained in the operating room. Acetabulum component abduction and anteversion were postoperatively determined using specialised software on each of the 3 image acquisition methods.

RESULTS

Average acetabular cup abduction for intraoperative fluoroscopic posterior-anterior hip (FH), intraoperative fluoroscopic posterior-anterior pelvis (FP), and postoperative, standard, anteroposterior pelvis radiographs (PP) was 40.95° ± 2.87°, 38.87° ± 3.82° and 41.73° ± 2.96° respectively. The fluoroscopic hip and fluoroscopic pelvis tended to underestimate acetabular cup abduction compared to the postoperative pelvis (p < 0.001). Average acetabular cup anteversion for FH, FP, and PP was 19.89° ± 4.87°, 24.38° ± 5.31° and 13.36° ± 3.52° respectively. Both the fluoroscopic hip and fluoroscopic pelvis overestimated anteversion compared to the AP pelvis, with a 6.38° greater mean value measurement for FH (p < 0.001), and an 11° greater mean value measurement for FP (p < 0.001).

CONCLUSIONS

Fluoroscopic technique and differences between radiographic projections may result in discrepancies in component position interpretation. Our results support the use of the fluoroscopic posterior-anterior hip as the choice fluoroscopic imaging technique.

Total Hip Arthroplasty With Subtrochanteric Shortening Osteotomy in Patients With High Hip Dislocation Secondary to Childhood Septic Arthritis: A Matched Comparative Study With Crowe IV Developmental Dysplasia

BACKGROUND

Total hip arthroplasty (THA) with subtrochanteric shortening osteotomy (SSO) is performed to manage hips with high dislocations. We compared outcomes of THA with SSO in patients with high hip dislocation resulting from childhood septic arthritis and Crowe IV developmental dysplasia of the hip (DDH).

METHODS

We reviewed 60 THAs with SSO performed between May 1996 and December 2013. Thirty-one cases were classified as sequelae of childhood infection and 29 as DDH. Twenty-five hips were selected for each group after the propensity score was matched with preoperative demographics and leg length discrepancy (LLD). Clinical scores, complication and reoperation rates, radiographic results, and survivorships were compared. The mean duration of follow-up was 12.3 (range 5-22) years.

RESULTS

The average correction in LLD was 2.5 cm for childhood infection and 3.6 cm for DDH (P = .002). The infection group received more transfusions (mean 3.3 vs 2.0 units, P = .002), required more time for union of osteotomy site (mean 6.8 vs 5.2 months, P = .042), and reported lower Harris Hip Score (mean 85.1 vs 91.3, P = .017). Reoperations were performed in 11 (44%) previously infected hips and 3 (12%) DDHs (P = .012). Kaplan-Meier survivorship with an endpoint of revision for any reason was lower in the infection group (83.6%) than in the DDH group (100%) at 10 years (log rank, P = .040).

CONCLUSION

THA with SSO in high hip dislocation secondary to childhood septic arthritis demonstrated less favorable clinical outcomes with increased risks of complication, compared with those performed in Crowe IV DDH with similar degree of chronic dislocation.

Accuracy of planar anteversion measurements using anteroposterior radiographs

Background

Several methods using simple anteroposterior (AP) radiographs have been suggested for the measurement of anteversion of the cup component after total hip arthroplasty. Herein, we compared six widely used anteversion measurement methods using two different types of AP radiograph, the conventional pelvis AP and hip-centered AP radiographs, to identify the measurement method and the type of radiograph that would provide the highest accuracy and reliability.

Methods

We developed two custom-made bi-planar anteversion measurement models for the validation test. The models were designed for pelvis AP and hip-centered AP radiographs, respectively. The radiographs were acquired using the inclination angles of both models, changing from 10° to 70° at 10° increments. For each inclination angle, anteversion was changed from 0° to 30° at 5° increments. The measurements were obtained independently by two orthopedic surgeons blinded from each other’s measurements, using the methods of 1) Pradhan et al., 2) Lewinnek et al., 3) Widmer et al., 4) Liaw et al., 5) Hassan et al., and 6) Ackland et al. The measurements were repeated after 2 months. The accuracy, compared with that of the reference angle, and intra-observer and inter-observer reliabilities of each method were calculated.

Results

The highest accuracy was found when the method of Liaw et al. was used with hip-centered AP radiographs, which showed a difference of 1.37° ± 1.73 from the reference angle. Moreover, regardless of the type of radiograph, the methods by Pradhan et al., Lewinnek et al., and Liaw et al. showed excellent correlations with the reference anteversion. However, substantial differences were found when the methods by Widmer et al., Hassan et al., and Ackland et al. were used, regardless of the type of radiograph used. When anteversion was measured in an inclination between 30° and 50°, the method of Pradhan et al., when used with pelvis AP radiographs, showed the highest accuracy (1.23° ± 0.92°). We also found no significant difference in anteversions between the measurements made on pelvic and hip-centered AP radiographs. Both interobserver and intraobserver reliabilities were high for all the measurements tested.

Conclusions

The methods by Pradhan et al., Liaw et al., and Lewinnek et al. may provide relatively accurate anteversion measurements with high reliability, regardless of the type of radiograph.

Intraoperative measurement of cup inclination using fluoroscopy requires a correction factor

INTRODUCTION

Malpositioning of the cup in total hip arthroplasty (THA) is associated with dislocation, early polyethylene wear, and impingement. The direct anterior approach (DAA) THA allows for intraoperative fluoroscopy imaging (IF). The current study investigates the following research hypotheses: (1) intraoperative measurements of radiographic cup inclination (RI) are reliable and reproducible. (2) A correction factor can compensate for the complex parallax effects when using IF.

METHODS

In 2016, 100 consecutive hips underwent primary THA utilizing DAA and IF for cup placement. RI was measured on intraoperative fluoroscopy images and postoperative AP pelvis radiographs.

RESULTS

Determination of RI on IF images is reliable and reproducible (ICC 0.851-0.950). RI measurement on IF images had a good correlation with the corresponding postoperative RI on AP pelvis radiographs (r = 0.538, p < 0.001). However, intraoperative RI measurements are on average 4.9° lower compared to postoperative measurements (SD 2.5°).

CONCLUSION

Intraoperative fluoroscopy is a reliable tool to measure RI during DAA THA. The surgeon needs to apply a 5°. correction factor to the intraoperative measurements to adjust for parallax.

A precise method for determining acetabular component anteversion after total hip arthroplasty

AIMS

Several radiological methods of measuring anteversion of the acetabular component after total hip arthroplasty (THA) have been described. These are limited by low reproducibility, are less accurate than CT 3D reconstruction, and are cumbersome to use. These methods also partly rely on the identification of obscured radiological borders of the component. We propose two novel methods, the Area and Orthogonal methods, which have been designed to maximize use of readily identifiable points while maintaining the same trigonometric principles.

PATIENTS AND METHODS

A retrospective study of plain radiographs was conducted on 160 hips of 141 patients who had undergone primary THA. We compared the reliability and accuracy of the Area and Orthogonal methods with two of the current leading methods: those of Widmer and Lewinnek, respectively.

RESULTS

The 160 anteroposterior pelvis films revealed that the proposed Area method was statistically different from those described by Widmer and Lewinnek (p < 0.001 and p = 0.004, respectively). They gave the highest inter- and intraobserver reliability (0.992 and 0.998, respectively), and took less time (27.50 seconds (sd 3.19); p < 0.001) to complete. In addition, 21 available CT 3D reconstructions revealed the Area method achieved the highest Pearson's correlation coefficient (r = 0.956; p < 0.001) and least statistical difference (p = 0.704) from CT with a mean within 1° of CT-3D reconstruction between ranges of 1° to 30° of measured radiological anteversion.

CONCLUSION

Our results support the proposed Area method to be the most reliable, accurate, and speedy. They did not support any statistical superiority of the proposed Orthogonal method to that of the Widmer or Lewinnek method. Cite this article: Bone Joint J 2019;101-B:1042-1049.

Evaluation of the spine is critical in the workup of recurrent instability after total hip arthroplasty

AIMS

While previously underappreciated, factors related to the spine contribute substantially to the risk of dislocation following total hip arthroplasty (THA). These factors must be taken into consideration during preoperative planning for revision THA due to recurrent instability. We developed a protocol to assess the functional position of the spine, the significance of these findings, and how to address different pathologies at the time of revision THA.

PATIENTS AND METHODS

Prospectively collected data on 111 patients undergoing revision THA for recurrent instability from January 2014 to January 2017 at two institutions were included (protocol group) and matched 1:1 to 111 revisions specifically performed for instability not using this protocol (control group). Mean follow-up was 2.8 years. Protocol patients underwent standardized preoperative imaging including supine and standing anteroposterior (AP) pelvis and lateral radiographs. Each case was scored according to the Hip-Spine Classification in Revision THA.

RESULTS

Survival free of dislocation at two years was 97% in the protocol group (three dislocations, all within three months of surgery) versus 84% in the control group (18 patients). Furthermore, 77% of the inappropriately positioned acetabular components would have been unrecognized by supine AP pelvis imaging alone.

CONCLUSION

Using the Hip-Spine Classification System in revision THA, we demonstrated a significant decrease in the risk of recurrent instability compared with a control group. Without the use of this algorithm, 77% of inappropriately positioned acetabular components would have been unrecognized and incorrect treatment may have been instituted. Cite this article: Bone Joint J 2019;101-B:817-823.

A Minimum of 15-Year Results of Cementless Total Hip Arthroplasty Using a 28-mm Metal-On-Metal Articulation

BACKGROUND

We previously reported unexpected early failures of total hip arthroplasty (THA) utilizing a 28-mm Ultima metal-on-metal (MoM) articulation. However, long-term results of small-diameter MoM THAs still remain unclear. The purpose of this study was to evaluate the clinical and radiographic outcomes of the previously reported cohort at a minimum follow-up of 15 years.

METHODS

The original cohort consisted of 171 primary THAs (167 patients) using a 28-mm MoM articulation performed between April 2000 and March 2002. Of these, 130 hips (126 patients) were reviewed at an average follow-up of 17.1 (range, 15-18) years. Clinical score, complications, presence of osteolytic lesion, serum metal ion concentrations, and implant survivorships were evaluated.

RESULTS

The mean Harris Hip Score improved from 44.9 points preoperatively to 90.5 points at the latest follow-up. During the entire period since the original surgery, a total of 5 revisions (3.8%) were associated with adverse reaction to metal debris (ARMD). The last revision surgery for symptomatic ARMD was performed at 6 years postoperatively. The implant survivorships with an end point of revision for aseptic failure and for any reason were 95.4% and 93.8%, respectively. Radiographic osteolytic lesions were detected in 27 hips (20.8%). The average serum metal concentration was 2.50 (range, 0.12-9.86) μg/L for cobalt and 2.81 (range, 0.82-12.3) μg/L for chromium.

CONCLUSIONS

THA using a 28-mm MoM articulation showed favorable long-term outcomes with a relatively high revision-free survival rate. There was no significant symptomatic ARMD after the last acetabular revision performed at 6 years postoperatively.

Can some early revision total hip arthroplasties be avoided?

Aims

Studying the indications for revision total hip arthroplasty (THA) may enable surgeons to change their practice during the initial procedure, thereby reducing the need for revision surgery. The aim of this study was to identify and describe the potentially avoidable indications for revision THA within five years of the initial procedure.

Patients and Methods

A retrospective review of 117 patients (73 women, 44 men; mean age 61.5 years (27 to 88)) who met the inclusion criteria was conducted. Three adult reconstruction surgeons independently reviewed the radiographs and medical records, and they classified the revision THAs into two categories: potentially avoidable and unavoidable. Baseline demographics, perioperative details, and quality outcomes up to the last follow-up were recorded.

Results

A total of 60 revision THAs (51.3%) were deemed potentially avoidable and 57 (48.7%) were deemed unavoidable. The following were identified as avoidable factors: suboptimal positioning of the acetabular component (29; 48%), intraoperative fracture or a fracture missed on an intraoperative radiograph (20; 33%), early (less than two weeks) aseptic loosening (seven; 11.7%), and symptomatic leg length discrepancy of > 1 cm (four; 6.7%).

Conclusion

A surprisingly large proportion of acute revision THAs are potentially avoidable. Surgeons must carefully evaluate the indications for revision THAs in their practice and identify new methods to address these issues. Cite this article: Bone Joint J 2019;101-B(6 Supple B):97–103.

Fourth-generation ceramic-on-ceramic THA results in improvements in midterm outcomes compared to third-generation THA but does not resolve noise problems: a cohort study of a single-hip system

BACKGROUND

Using data from the Korean Hip Registry, we aimed to investigate mid-term clinical and radiographic outcomes, including the prevalence of periprosthetic joint infection (PJI), osteolysis, and component loosening or dislocation, and to analyze the incidence of bearing-related complications following modern ceramic-on-ceramic (COC) total hip arthroplasty (THA) using a single cementless hip system.

METHODS

Four hundred eighty-two patients (602 hips) who underwent Forte or Delta COC THAs with a single hip system and had a minimum 5-year follow-up were identified. The sample included 243 (50.4%) women and 239 (49.6%) men with a mean age of 50.6 years (range: 18-83 years). The Forte group comprised 310 hips, and the Delta group comprised 292 hips. The mean follow-up was 6.1 years (range: 5-10.2 years).

RESULTS

Cup orientation did not differ between groups. No hip had a PJI or osteolysis in either group. All acetabular components and all but two femoral components (in the Delta group) were well fixed. Dislocations occurred in six (1.9%) hips in the Forte group and one (0.3%) hip in the Delta group (p = 0.124). A total of nine (1.5%) revisions were performed. The 5-year survival rates for all-cause revisions were 98.4 and 98.6%, respectively. One (0.3%) ceramic head fracture occurred in the Forte group. Sixteen (5%) hips exhibited clicking and 6 (2%) hips had squeaking in the Forte group; 16 (6%) hips exhibited clicking and 5 (2%) hips had squeaking in the Delta group. Multiple regression analysis revealed that noise generation was unassociated with any factor.

CONCLUSIONS

From the Korean Hip Registry data, THA with modern ceramic bearings showed encouraging results, with lower risks of PJI, osteolysis, and component loosening. In particular, Delta COC THA resulted in no PJI or ceramic fracture and had a reduced dislocation risk. However, associated noise remains a concern.

Assessment of acetabular version in total hip arthroplasty: an application of Widmer's technique in a regional setting

BACKGROUND

Acetabular prosthesis positioning in total hip arthroplasty is important in reducing the risk of dislocation. Assessment of version by computed tomography scan is expensive and involves a large radiation dose. We wished to assess the value of Widmer's technique, utilizing readily available radiographs, to determine cup anteversion.

METHODS

Patients who underwent primary total hip arthroplasty by the senior author (AGS) at a single regional hospital over a 5-year period were eligible for inclusion. Measurements were performed using the technique described by Widmer, utilizing standard post-operative radiographs. Statistical analysis was undertaken in SPSS v22. Significance was accepted at P < 0.05.

RESULTS

Assessment included 109 hips in 99 patients; 63 hips with cemented cups and 46 hips with uncemented cups. Mean acetabular anteversion in the cemented group was 11.9° (0-27.7, SD: 7) and in the uncemented group was 14.1° (10.3-32.7, SD: 7.1); this difference trended towards statistical significance (P = 0.09). Test-retest measurements showed high degree of correlation (Pearson test: 0.927, P < 0.001). There were 96 of 109 hips positioned in the Lewinnek safe zone of 5-25° anteversion. The crude dislocation rate in our cohort was 6.4% (7 of 109 hips) with all dislocations occurring in hips placed in the safe zone.

CONCLUSION

Widmer's technique is a reliable method for calculating acetabular version in a regional hospital setting and offers the individual surgeon a ready technique of personal quality control. Cup version was not a significant factor contributing to dislocation rates in our series.

A Prospective, Randomized Study of Surgical Positioning Software Shows Improved Cup Placement in Total Hip Arthroplasty

Several technologies are available to assist surgeons with acetabular component positioning in total hip arthroplasty. The purpose of this study was to determine whether surgical positioning software would improve cup position compared with fluoroscopy. This prospective, randomized study compared 200 primary total hip arthroplasty cups placed with and without surgical positioning software. All cases were performed by a single surgeon using the direct anterior approach with fluoroscopy. The target abduction and anteversion angles were set at 40° and 20°, respectively, and measured postoperatively. Cup placement time, total fluoroscopy time, and cup position were compared between groups. Mean abduction was 40.4° (range, 32.7°-49.0°) in the software group compared with 42.3° (range, 33.7°-51.1°) in the control group. The cups placed using software were significantly closer to the target abduction angle (P<.001) with fewer outliers. Mean anteversion was 20.8° (range, 11.2°-31.7°) in the software group compared with 21.8° (range, 11.3°-34.3°) in the control group (P=.063). Eighty-seven percent of cups in the software group fell within 5° of the abduction target, compared with only 68% in the control group (P<.01). Cup placement took longer in the software group (7:04 minutes vs 4:58 minutes, P<.001), and 2 seconds more total fluoroscopy time was used in that group as well (12.9 seconds vs 11.1 seconds, P<.001). The software improved both the accuracy and the precision of cup placement, with only modest increases in surgical time and fluoroscopy time. [Orthopedics. 2019; 42(1):42-47.].

Three-dimensional assessment of the influence of juvenile pubic symphysiodesis on the pelvic geometry of dogs

OBJECTIVE To evaluate the 3-D geometry of canine pelves and to characterize the long-term effects of juvenile pubic symphysiodesis (JPS) on pelvic geometry by comparing the pelvic configuration between littermates that did and did not undergo the procedure. ANIMALS 24 Labrador Retriever, Golden Retriever, or Labrador Retriever-Golden Retriever crossbred service dogs from 13 litters. PROCEDURES At 16 weeks old, puppies with a hip joint distraction index ≥ 0.5 were randomly assigned to undergo thermal JPS (n = 9), mechanical JPS (7), or a sham (control) surgical procedure (8). Ten years later, each dog underwent a CT scan of the pelvic region. Modeling software was used to create 3-D reconstructions from the CT scans, and various pelvic measurements were made and compared among the 3 treatments. RESULTS Compared with the control treatment, thermal and mechanical JPS increased the hemipelvis acetabular angle by 4°, the acetabular angle of lateral opening by 5°, and the orientation of the medial acetabular wall in a transverse plane by 6°, which indicated that JPS increased dorsal femoral head coverage by the acetabulum. Both JPS procedures decreased the pelvic canal area by approximately 20% and acetabular inclination by 6° but did not alter acetabular retroversion. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that thermal and mechanical JPS were equally effective in altering the 3-D pelvic geometry of dogs. These findings may help guide future studies of alternatives for optimizing canine pelvic anatomy to minimize the risk of hip dysplasia and associated osteoarthritis.

The Hip Morphology Changes with Ageing in Asian Population

Objectives

This study aims to determine the changing in hip anatomy parameters with age and reveals the reason for the extorsion of lower extremity in the aged.

Design

Retrospective study.

Participants

One hundred and forty patients who had received imaging check of the femur and acetabulum between October 2013 and October 2016 were included in this study.

Main Outcome Measures

The femoral neck torsion angle (FNTA), neck-shaft angle (NSA), and acetabular anteversion angle (AVA) were measured by an experienced orthopedic surgeon. All the patients' demographic and physical characteristics including age, sex, body laterality, height, and weight were recorded. The Student t-test, two-way ANOVA, Pearson correlation, and multiple linear regression were used for the statistical analysis.

Results

The mean age for male and female was 45.01±15.38 and 49.30±17.63 years, respectively. Outcomes revealed that the NSA on the right side of the body, 133.46±4.46° in male and 134.36±4.71° in female, was statistically higher than the left side. Female FNTA had significantly higher values than male (P<0.01). Two-way ANOVA reveals that FNTA and AVA were correlated with age (P<0.05) but not weight, height, or BMI. NSA was correlated with age, weight, and BMI (P<0.05) but not height. Multiple linear regression analysis showed that only age made an independent contribution to NSA.

Conclusions

The NSA and FNTA of Asian population may have an obvious decrease whereas AVA increases with ageing, which reveals the reason for the extorsion of lower extremity with elderly. During hip-related surgery in elderly patients, more attention should be paid to these lower extremity anatomic changes.

The reliability of measuring acetabular component position on radiographs using everyday diagnostic imaging software

BACKGROUND

It is standard practice for total hip arthroplasty (THA) patients to have post-operative imaging, and one of the reasons is to assess the adequacy of acetabular component position. Correct positioning of the acetabular component is important for successful outcome in THA. Acetabular component position can be measured from either computed tomography (CT) or plain radiographs. While CT is the gold standard for accurately measuring acetabular component position, radiographs are routinely used for post-operative evaluation. However, measurement of acetabular component position from plain radiographs is not straightforward and numerous methods have been proposed. As most imaging is now digital, the aim of this study was to investigate the reliability of one method to measure acetabular component position using a basic diagnostic imaging software program that is readily available to orthopaedic surgeons.

METHODS

We investigated the reliability Lewinnek's method using a basic Picture Archiving and Communication System program, InteleViewer ™ . We measured 69 post-operative anteroposterior (AP) radiographs of patients who underwent primary THA. Intra-observer and inter-observer reliability for Lewinnek's method was calculated using the intraclass correlation coefficient.

RESULTS

Our results showed excellent intra- and inter-observer reliability for both inclination (0.99, 95% confidence interval (CI): 0.99-1.0; and 0.97, 95% CI: 0.95-0.99) and anteversion (0.99, 95% CI: 0.98-0.99; and 0.93, 95% CI: 0.89-0.96) measurements.

CONCLUSION

This study has shown that using Lewinnek's method, acetabular component position can be reliably measured on post-operative AP digital radiographs using readily available software tools.

The direct anterior minimal invasive approach in total hip replacement: a prospective departmental study on the learning curve

INTRODUCTION

Introduction of new surgical techniques is normal, but seldom monitored in real time. The purpose of this study was to monitor the learning curve when introducing a new surgical technique to a department. We did a prospective evaluation of the learning curve when introducing the minimally invasive direct anterior approach in total hip arthroplasty. We wish to investigate whether there is a learning curve for the direct anterior minimal invasive approach in total hip replacement and what are the early complications to this approach.

METHODS

The department changed from the direct lateral approach to the minimally invasive direct anterior approach. We monitored the first 522 patients operated using this approach with regards to patient outcome scores and complications 6 months postoperatively.

RESULTS

The last 250 patients operated all had significantly better results with regard to patient outcome scores and cup placement. We investigated 100 patients at a time and compared them with the rest of the patient and found the same pattern. This pattern ends when we reach patients somewhere between 200-300.

DISCUSSIONS

We established the learning curve on a departmental level with regards to introduction of the minimal invasive direct anterior approach. We see a steady improvement in scores with regards to patient outcome scores and cup positioning until we reach a steady-state. The learning curve here flattens out. Departments must understand that one should expect early complications and somewhat less than optimal results at first when introducing this new surgical technique.