A novel method for accurate and reproducible functional cup positioning in total hip arthroplasty

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

BACKGROUND

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Lower 90-day inpatient readmission and 1-year reoperation in patients undergoing robotic versus manual total hip arthroplasty through an anterior approach

BACKGROUND

The value of robotic-assisted total hip arthroplasty (rTHA) has yet to be determined compared to conventional manual THA (mTHA).

OBJECTIVE

Evaluate 90-day inpatient readmission rates, rates of reoperation, and clinically significant improvement of patient-reported outcome measures (PROMs) at 1-year in a cohort of patients who underwent mTHA or rTHA through a direct anterior (DA) approach.

METHODS

A single-surgeon, prospective institutional cohort of 362 patients who underwent primary THA for osteoarthritis via the DA approach between February 2019 and November 2020 were included. Patient demographics, surgical time, discharge disposition, length of stay, acetabular cup size, 90-day inpatient readmission, 1-year reoperation, and 1-year PROMs were collected for 148 manual and 214 robotic THAs, respectively.

RESULTS

Patients undergoing rTHA had lower 90-day readmission (3.74% vs 9.46%, p= 0.04) and lower 1-year reoperation (0.93% vs 4.73% mTHA, p= 0.04). rTHA acetabular cup sizes were smaller (rTHA median 52, interquartile range [IQR] 50; 54, mTHA median 54, IQR 52; 58, p< 0.001). Surgical time was longer for rTHA (114 minutes vs 101 minutes, p< 0.001). At 1-year post-operatively, there was no difference in any of the PROMs evaluated.

CONCLUSION

Robotic THA demonstrated lower 90-day readmissions and 1-year reoperation rates than manual THA via the DA approach. PROMs were not significantly different between the two groups at one year.

Anatomical cup implantation assisted with dynamic 3D planning improves functional outcomes in primary total hip arthroplasty: A retrospective study

BACKGROUND

Anatomical cup implantation is a promising approach in primary total hip arthroplasty (THA) and improves functional outcomes.

OBJECTIVE

We aimed to evaluate the cup position and functional outcomes in primary THA with preoperative dynamic 3D planning.

METHODS

We retrospectively reviewed 54 hips in 48 patients who underwent primary THA with anatomical cup implantation (mean follow-up time: 52 months). Cup positions were evaluated based on patient-specific morphology, the acetabular fossa and the combined anteversion test. Functional outcomes were assessed after THA. The paired-sample t-test was performed for surgical and contralateral native hips among 42 patients who underwent unilateral THA.

RESULTS

Two hips suffered intraoperative trochanteric fracture, but no hip dislocations occurred. No patients reported groin or thigh pain, and all patients were capable of deep squatting and one-leg standing. The mean Harris hip score, WOMAC score, and physical SF-36 score were 94.46 ± 6.16, 10.41 ± 3.62, and 95.19 ± 8.74, respectively. Except for acetabular offset, THA restored biomechanics to those of contralateral native hip, including cup anteversion, abduction, femoral offset and acetabular height (P> 0.05).

CONCLUSION

This study provided evidence for the application of anatomical cup implantation assisted with dynamic 3D planning in primary THA, which restored morphology and improved functional outcomes.

"Koehlers teardrop is not a reliable landmark for assessing the centre of rotation after Total hip arthroplasty" - a retrospective radiological study

PURPOSE

Various anatomical landmarks have become established in radiography for the assessment of cup positioning after total hip arthroplasty (THA). The most important one is Koehler's teardrop figure (KTF). However, there is a lack of data on the validity of this landmark, which is widely used clinically for assessing the centre of rotation of the hip.

METHOD

A retrospective measurement of the lateral and cranial distance of the KTF to the centre of hip rotation was performed on the basis of 250 X-ray images of patients who had undergone THA. In addition, the dependence of these distances on pelvic tilt was determined in 16 patients by means of virtual X-ray projections based on pelvic CTs.

RESULTS

It was shown that the distance of the KTF from the centre of hip rotation in the horizontal plane is gender-dependent (men: 42.8 ± 6.0 mm vs. women: 37.4 ± 4.7 mm; p < 0.001) and age-dependent (Pearson correlation  - 0.114; p < 0.05). Furthermore, the vertical and horizontal distances are subject to variation depending on height (Pearson correlation 0.14; p < 0.05 and 0.40; p < 0.001, respectively) and weight (Pearson correlation 0.158; p < 0.05). The distance between the KTF and the centre of hip rotation varies slightly depending on pelvic tilt.

CONCLUSION

The KTF is not a sufficiently valid landmark for assessing the centre of rotation after THA. It is influenced by many different disturbance variables. However, it is largely robust against changes in pelvic tilt, so that it can be used as a reference point when comparing different intraindividual radiographs to assess the change in the centre of rotation due to implantation or to detect cup migration.

Creating Consensus in the Definition of Spinopelvic Mobility

INTRODUCTION

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

METHODS

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

RESULTS

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

DISCUSSION

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

The accuracy of component positioning during revision total hip arthroplasty using 3D optical computer-assisted navigation

INTRODUCTION

Despite the excellent outcomes associated with primary total hip arthroplasty (THA), implant failure and revision continue to burden the healthcare system. The use of computer-assisted navigation (CAN) offers the potential for more accurate placement of hip components during surgery. While intraoperative CAN systems have been shown to improve outcomes in primary THA, their use in the context of revision total hip arthroplasty (rTHA) has not been elucidated. We sought to investigate the validity of using CAN during rTHA.

METHODS

A retrospective analysis was performed at an academic medical institution identifying all patients who underwent rTHA using CAN from 2016-2019. Patients were 1:1 matched with patients undergoing rTHA without CAN (control) based on demographic data. Cup anteversion, inclination, change in leg length discrepancy (ΔLLD) and change in femoral offset between pre- and post-operative plain weight-bearing radiographic images were measured and compared between both groups. A safety target zone of 15-25° for anteversion and 30-50° for inclination was used as a reference for precision analysis of cup position.

RESULTS

Eighty-four patients were included: 42 CAN cases and 42 control cases. CAN cases displayed a lower ΔLLD (5.74 ± 7.0 mm vs 9.13 ± 7.9 mm, p = 0.04) and greater anteversion (23.4 ± 8.53° vs 19.76 ± 8.36°, p = 0.0468). There was no statistical difference between the proportion of CAN or control cases that fell within the target safe zone (40% vs 20.9%, p =  0.06). Femoral offset was similar in CAN and control cases (7.63 ± 5.84 mm vs 7.14 ± 4.8 mm, p = 0.68).

CONCLUSION

Our findings suggest that the use of CAN may improve accuracy in cup placement compared to conventional methodology, but our numbers are underpowered to show a statistical difference. However, with a ΔLLD of ~ 3.4 mm, CAN may be useful in facilitating the successful restoration of pre-operative leg length following rTHA. Therefore, CAN may be a helpful tool for orthopedic surgeons to assist in cup placement and LLD during complex revision cases.

Clinical Impact of Pelvic Malrotation on Radiograph-Based Preoperative Planning for Total Hip Arthroplasty: A Proof-of-Concept and Prudent Prediction of Acceptable Rotation

Introduction

Pelvic rotation (PR) on preoperative radiograph templating can affect various critical measured acetabular angles and potentially outcomes of successful total hip arthroplasty (THA). Optimising anatomical reconstruction of the joint is essential to achieve function, longevity and prevention of complications following surgery. There is limited literature that standardises the degree of acceptable PR on radiograph or its effects on the fitting of acetabular prostheses.

Objective

This study aimed to develop a proof-of-concept that quantifies how PR can affect various acetabular angles used in pre-operative THA templating and to formulate a practicable method of determining if the preoperative PR is acceptable.

Materials and methods

Computerised tomography (CT) models from three control and two THA patients were generated and manipulated in various degrees of PR. CT slices were thickened to simulate radiographs and acetabular angles measured.

Results

The acetabular anteversion distance (AAD) and lateral opening angle (LOA) demonstrated a linear and quadratic relationship with good correlation (R 2 = 0.923, R 2 = 0.710 respectively, p < 0.0001) in relation to PR. Change in area of prosthesis (AOP) demonstrated a good linear correlation (r 2 = 0.774 and r 2 = 0.875, p < 0.0001) with PR. Two novel measurements were used to estimate the degree of PR from a pelvic radiograph; the horizontal distance between pubic symphysis and middle of sacrococcygeal joint (PSSC) and the simplified pelvic rotation ratio (SPRR). A strong correlation between PSSC and SPRR with change in PR was observed (R 2 = 0.970, R 2 = 0.953, p < 0.001).

Conclusion

Preliminary result suggests that an SPRR > 2.0 correlates to PR > 20° with potential to have a clinical impact on preoperative measurements.

Anatomic Navigation Using the Transverse Acetabular Ligament for Acetabular Component Positioning in Total Hip Arthroplasty Through the Direct Anterior Approach

The transverse acetabular ligament (TAL) is a reliable native anatomic landmark that can be used to guide accurate acetabular implant positioning during total hip arthroplasty through the direct anterior approach. The accurate acetabular implant position is defined by the preoperative plan, which corresponds to the Lewinnek safe zone. This article describes the anatomy of the TAL , exposure of the TAL, and pearls and pitfalls for exposure of the acetabulum during total hip arthroplasty through the direct anterior approach. This article discusses how the TAL is used to guide acetabular implant positioning and describes pilot data from our single surgeon case series (n = 31).

Characterising acetabular component orientation with pelvic motion during total hip arthroplasty

INTRODUCTION

Suboptimal acetabular component position can result in impingement, dislocation, and accelerated wear. Intraoperative pelvic motion has led to surgeon error and acetabular cup malposition. This study characterises the relationship between pelvic rotation and postoperative acetabular cup orientation.

METHODS

A device was constructed to allow cadaveric pelvis rotation along three axes about an acetabular cup in fixed orientation. The acetabular cup was fixed in space at 40° of radiographic inclination and 15° of anteversion relative to the anterior pelvic plane to represent consistent surgeon intraoperative placement. Active marker clusters were fixed to surgical equipment while the cadaveric pelvis was cemented with passive reflective markers, both identified with the Optotrak Certus motion capture system. The reamed cadaveric pelvis was rotated along three axes from -45° to 45° of roll, -30° to 30° of tilt, and -35° to 35° of pitch. The change in component inclination and anteversion was recorded at each 5° interval. Using computed tomography 3D reconstruction, the experimental setup was duplicated computationally to assess against a greater range of pelvis and implant sizes.

RESULTS

Radiographic anteversion and inclination showed a non-linear relationship dependent on pelvic roll, tilt, and pitch. Radiographic anteversion changed -0.59°, 0.76° and 0.01° while radiographic inclination changed 0.23°, 0.18° and 1.00° for every 1° of pelvic roll, tilt and pitch, respectively. Computationally, anteversion changed -0.61°, 0.75° and 0.00° while inclination changed 0.22°, 0.19° and 1.00° for every 1° of pelvic roll, tilt and pitch, respectively. These results were independent of cup and pelvis size.

CONCLUSIONS

Intraoperative pelvic motion can significantly affect final cup position, and this should be accounted for when placing acetabular components during total hip arthroplasty. Based on this study, intraoperative adjustment of the acetabular component position based on pelvis motion may be implemented to improve postoperative component position.

Factors influencing knee valgus alignment in Crowe type IV hip dysplasia after total hip arthroplasty

Background

Valgus deformity of the knee remains a complaint after total hip arthroplasty (THA) among some patients with Crowe type IV hip dysplasia. We aimed to identify the knee alignment in these patients before and after surgery, and to explore the factors contributing to postoperative knee valgus alignment.

Materials and methods

We retrospectively reviewed a series of Crowe type IV patients who received THA between February 2010 and May 2019 in our hospital. The patients’ medical data were collected from the hospital information system. On both preoperative and postoperative full limb length standing radiographs, the following parameters were measured: hip–knee–ankle angle (HKA), mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle, anatomical tibiofemoral angle, anatomical lateral distal femoral angle, femoral neck-shaft angle, pelvic obliquity, limb length, height and lateral distance of hip center, and femoral offset. Univariate and multivariate binary logistic regression were used to identify the factors influencing postoperative knee valgus alignment.

Results

A total of 64 Crowe type IV patients (87 hips) were included in the study. Overall, HKA improved from 176.54 ± 3.52° preoperatively to 179.45 ± 4.31° at the last follow-up. Those hips were subdivided into non-valgus group (≥ 177.0°, n = 65) and valgus group (< 177.0°, n = 22) according to postoperative HKA. Only postoperative mLDFA was a significant factor in the multivariate regression model.

Conclusions

The postoperative mLDFA is a major factor related to knee valgus alignment after THA, which combines the preoperative anatomy and surgical reconstruction. Other factors previously published were found to have no significance.

Level of evidence

III.

Validation of a Novel Software Measurement Tool for Total Hip Arthroplasty

Background

Preoperative planning and postoperative evaluation of component position in total hip arthroplasty (THA) utilize specialized software that must be able to provide measurements that are both accurate and precise. A new software program for use in THA has recently been developed. We sought to evaluate the accuracy of this new software in comparison with two current, widely used software programs.

Methodology

Postoperative anteroposterior (AP) pelvic radiographs from 135 THA patients were retrospectively reviewed. Reference values for acetabular anteversion, inclination, and leg length were established using validated software programs (TraumaCad^® as the primary reference value [PRV] and OsiriX Lite^TM as the secondary reference value [SRV]). Measurements from the new software program (Intellijoint VIEW^TM) were compared with reference values using Student’s t-test and chi-square test.

Results

For anteversion, mean values for the PRV (27.34° ± 7.27°) and the new software (27.29° ± 7.21°) were not significantly different (p = 0.49). The new software differed from the PRV by a mean of 0.05° ± 0.93°. Similar results were noted for inclination, where the new software differed from the PRV and SRV by -0.13° ± 0.65° and 0.25° ± 1.26°, respectively (mean values: PRV: 43.62° ± 6.02°; SRV: 43.99° ± 6.27°; new software: 43.74° ± 6.17°; p = 0.87), and for leg length, where the new software differed from the PRV and SRV by 0.05 mm ± 0.46 mm and 0.22 mm ± 0.52 mm, respectively (mean values: PRV: 10.61 mm ± 11.60 mm; SRV: 10.77 mm ± 11.70 mm; new software: 10.56 mm ­ ± 11.61 mm; p = 0.98). Measurements were highly correlated across multiple reviewers (intraclass correlation coefficient ≥0.987).

Conclusions

The new software measurement tool is accurate and precise for assessing the acetabular component position and leg length measurements following THA in AP pelvic radiographs compared to currently used image measurement software.

Two year follow up of supercapsular percutaneously assisted total hip arthroplasty

BACKGROUND

Dislocation after primary total hip arthroplasty (THA) has an incidence of 2-3%. Approximately 77% of dislocations occur within the first year after surgery. The SuperPATH technique is a minimally invasive approach for THA that preserves soft tissue attachments. The purpose of this study is to describe the dislocation rate at 1 year after SuperPATH primary THA.

METHODS

All elective primary THAs performed by the senior author using the SuperPATH approach. Exclusion criteria were acute femoral neck fracture, revision surgery, or malignancy. There were 214 of 279 eligible patients available for telephone interviews (76.7%). Medical records were reviewed for secondary outcomes including early and late complications, cup positioning, distance ambulated on postoperative day one, discharge destination, and blood transfusions.

RESULTS

Mean age at surgery was 64 ± 10.8 years and mean time to telephone follow up was 773 ± 269.7 days. There were 104 female and 110 male patients. There were zero dislocations reported. Blood transfusions were performed in 3.7% of patients, and 75.7% were discharged to home at an average of 2.3 ± 1.0 days. Cup position averaged 43.6 ± 5.2° abduction and 20.9 ± 6.2° anteversion, with an average leg length discrepancy of 3.6 ± 3.32 mm. Complications included three intraoperative calcar fractures, one periprosthetic femur fracture, one early femoral revision, three superficial infections, and one instance of wound necrosis.

CONCLUSION

SuperPATH approach is safe for use in primary THA resulting in a low dislocation rate.

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.

Effect of postural changes on in vivo pelvic tilt and functional component anteversion in total hip arthroplasty patients with lumbar disc degenerations

Aims

The complex relationship between acetabular component position and spinopelvic mobility in patients following total hip arthroplasty (THA) renders it difficult to optimize acetabular component positioning. Mobility of the normal lumbar spine during postural changes results in alterations in pelvic tilt (PT) to maintain the sagittal balance in each posture and, as a consequence, markedly changes the functional component anteversion (FCA). This study aimed to investigate the in vivo association of lumbar degenerative disc disease (DDD) with the PT angle and with FCA during postural changes in THA patients.

Methods

A total of 50 patients with unilateral THA underwent CT imaging for radiological evaluation of presence and severity of lumbar DDD. In all, 18 patients with lumbar DDD were compared to 32 patients without lumbar DDD. In vivo PT and FCA, and the magnitudes of changes (ΔPT; ΔFCA) during supine, standing, swing-phase, and stance-phase positions were measured using a validated dual fluoroscopic imaging system.

Results

PT, FCA, ΔPT, and ΔFCA were significantly correlated with the severity of lumbar DDD. Patients with severe lumbar DDD showed marked differences in PT with changes in posture; there was an anterior tilt (-16.6° vs -12.3°, p = 0.047) in the supine position, but a posterior tilt in an upright posture (1.0° vs -3.6°, p = 0.005). A significant decrease in ΔFCA during stand-to-swing (8.6° vs 12.8°, p = 0.038) and stand-to-stance (7.3° vs 10.6°,p = 0.042) was observed in the severe lumbar DDD group.

Conclusion

There were marked differences in the relationship between PT and posture in patients with severe lumbar DDD compared with healthy controls. Clinical decision-making should consider the relationship between PT and FCA in order to reduce the risk of impingement at large ranges of motion in THA patients with lumbar DDD. Cite this article: Bone Joint J 2020;102-B(11):1505–1510.

Preoperative factors improving the prediction of the postoperative sagittal orientation of the pelvis in standing position after total hip arthroplasty

The aims of this study were to investigate if the sagittal orientation of the pelvis (SOP) in the standing position changes after total hip arthroplasty (THA) and evaluate what preoperative factors may improve the prediction of the postoperative standing SOP in the context of a patient-specific functional cup orientation. 196 primary THA patients from Japan were retrospectively selected for this study. Computed tomography imaging of the pelvis, EOS imaging of the lower body and lateral radiographs of the lumbar spine in the standing position were taken preoperatively. Common biometrics and preoperative Harris Hip Score were recorded. The EOS imaging in the standing position was repeated three months following THA. A 3D/2.5D registration process was used to determine the standing SOP. Thirty-three preoperative biometric, morphological and functional parameters were measured. Important preoperative parameters were identified that significantly improve the prediction of the postoperative standing SOP by using multiple linear LASSO regression. On average, the SOP changed significantly (p < 0.001) between the preoperative and postoperative standing position three months after THA by 3° ± 4° in the posterior direction. The age, standing lumbar lordosis angle (LLA) and preoperative supine and standing SOP significantly (p < 0.001) improve the prediction of the postoperative standing SOP. The linear regression model for the prediction of the postoperative standing SOP is significantly (p < 0.001) improved by adding the parameters preoperative standing SOP and LLA, in addition to the preoperative supine SOP, reducing the root mean square error derived from a leave-one-out cross-validation by more than 1°. The mean standing SOP in Japanese patients changes already three months after THA in comparison to the preoperative value. The preoperative factors age, LLA, supine and standing SOP can significantly improve the prediction of the postoperative standing SOP and should be considered within the preoperative planning process of a patient-specific functional cup orientation.

Effect of postural changes on in vivo pelvic tilt and functional component anteversion in total hip arthroplasty patients with lumbar disc degenerations

AIMS

The complex relationship between acetabular component position and spinopelvic mobility in patients following total hip arthroplasty (THA) renders it difficult to optimize acetabular component positioning. Mobility of the normal lumbar spine during postural changes results in alterations in pelvic tilt (PT) to maintain the sagittal balance in each posture and, as a consequence, markedly changes the functional component anteversion (FCA). This study aimed to investigate the in vivo association of lumbar degenerative disc disease (DDD) with the PT angle and with FCA during postural changes in THA patients.

METHODS

A total of 50 patients with unilateral THA underwent CT imaging for radiological evaluation of presence and severity of lumbar DDD. In all, 18 patients with lumbar DDD were compared to 32 patients without lumbar DDD. In vivo PT and FCA, and the magnitudes of changes (ΔPT; ΔFCA) during supine, standing, swing-phase, and stance-phase positions were measured using a validated dual fluoroscopic imaging system.

RESULTS

PT, FCA, ΔPT, and ΔFCA were significantly correlated with the severity of lumbar DDD. Patients with severe lumbar DDD showed marked differences in PT with changes in posture; there was an anterior tilt (-16.6° vs -12.3°, p = 0.047) in the supine position, but a posterior tilt in an upright posture (1.0° vs -3.6°, p = 0.005). A significant decrease in ΔFCA during stand-to-swing (8.6° vs 12.8°, p = 0.038) and stand-to-stance (7.3° vs 10.6°,p = 0.042) was observed in the severe lumbar DDD group.

CONCLUSION

There were marked differences in the relationship between PT and posture in patients with severe lumbar DDD compared with healthy controls. Clinical decision-making should consider the relationship between PT and FCA in order to reduce the risk of impingement at large ranges of motion in THA patients with lumbar DDD.

Clinical outcomes and complication profile of total hip arthroplasty after lumbar spine fusion: a meta-analysis and systematic review

BACKGROUND

Hip and spine pathology can alter the biomechanics of spino-pelvic mobility. Lumbar spine fusions can reduce the mobility of the lumbar spine and therefore result in compensatory femoral motion, contributing towards dislocations of THA.

PURPOSE

This meta-analysis aims to determine the effect of pre-existing spine fusions on THA outcomes, and complication profile including hip dislocations, all-cause revisions and all complications.

METHODS

A multi-database search was performed according to PRISMA guidelines. All studies that compared patients who underwent THA with and without prior SF were included in the analysis.

RESULTS

Ten studies were included in this review, consisting of 28,396 SF THA patients and 1,550,291 non-SF THA patients. There were statistically significant higher rates of hip dislocation (OR 2.20, 95% CI 1.71-2.85, p < 0.001), all-cause revision (OR 3.43, 95% CI 1.96-6.00, p < 0.001) and all complications (OR 2.83, 95% CI 1.28-6.24, p = 0.01) in SF than in non-SF THA patients. When registry data were excluded, these rates were approximately doubled. Subgroup analysis of revisions for dislocations was not statistically significant (OR 5.28, 95% CI 0.76-36.87, p = 0.09). While no meta-analysis was performed on clinical outcomes due to heterogeneous parameter reporting, individual studies reported significantly poorer outcomes in SF patients than in non-SF patients.

CONCLUSION

THA patients with SF are at higher risks of hip dislocations, all-cause revisions and all complications, which may adversely affect patient-reported outcomes. Surgeons should be aware of these risks and appropriately plan to account for altered spino-pelvic biomechanics, in order to reduce the risks of hip dislocations and other complications.

LEVEL OF EVIDENCE

II (Meta-analysis of non-homogeneous studies). These slides can be retrieved under Electronic Supplementary Material.

Modern cup alignment techniques in total hip arthroplasty: A systematic review

INTRODUCTION

A systematic review was conducted to assess the clinical and radiological outcomes of the alternative surgical techniques that consider the dynamic aspect of the acetabular orientation when aligning a cup (pelvic tilt-, lumbo-pelvic kinematics-, and spine-hip relationship-adjusted cup alignment techniques).

METHOD

Eight eligible articles reported the outcomes of total hip arthroplasty (THA) performed with alternative techniques. Clinical and radiological data were extracted. One study had a control group of patients who underwent conventional THAs (level III) while the seven other studies were level IV. Computer navigation system (CAS), Optimized Positioning System (OPS™), and manual instrumentation were used to align components in four, two, and two studies, respectively. A meta-analysis was not carried out because there was a lack of homogeneity between included articles regarding the method to position the cup and the nature of the reported data.

RESULTS

THA performed with alternative techniques had an early dislocation rate ranging from 0 to 1.9%, no unexpected catastrophic failure, and acceptable radiographic cup orientations. One study compared kinematically and mechanically aligned THAs and found no dislocation in either groups, similar patient reported outcome measures (43 Oxford-12 Score for both groups), and similar proportions of cup in the Lewinnek zone (respectively 65% and 70%).

DISCUSSION/CONCLUSION

Alternative methods accounting for the functional acetabular orientation seem to be clinically safe and effective in the early-term, and generate acceptable cup orientation on radiographs. Their values compare to those of more conventional techniques for cup implantation remain to be determined. We developed a classification of the multiple methods for aligning an acetabular component.

LEVEL OF EVIDENCE

IV, systematic review of level III and IV studies.

Kinematic alignment versus conventional techniques for total hip arthroplasty: A retrospective case control study

BACKGROUND

Residual complications of conventionally implanted hip components have only been partially reduced by improved implant design and higher surgical precision, and their occurrence is poorly predicted by the radiographic standing/supine cup orientation. This has raised awareness that conventional techniques may not aim for the correct component orientation target, and the lumbo-pelvic kinematics, which influences the functional acetabular orientation, may be of interest to further improve THA clinical outcomes. This has led to the development of the Lumbo-Pelvic kinematic alignment (KA) technique for THA that aims to anatomically position and kinematically align hip implants (acetabular and femoral, total and resurfacing components), in order to optimise prosthetic hip biomechanics and hopefully improve prosthetic function, patient satisfaction, and components' lifespan. Therefore, we conducted a case control investigation to assess the early-term safety and efficacy of this new technique by answering the following questions: does the KA technique for THA: (1) better restore the native hip anatomy, (2) generate a different radiographic supine cup position, and (3) improve clinical outcomes in comparison to the conventional mechanical alignment technique?

HYPOTHESES

Using KA technique allows there is no statistically significant difference between the pre to postoperative differential for acetabular medial and vertical offsets, femoral offset, and leg length.

METHODS

We led a case control retrospective study with prospectively collected clinical data. Forty-one consecutive unselected KA-THAs performed with manual instrumentation were paired with 41 mechanically aligned THAs. The 1-year clinical outcomes and radiographical measurements were compared.

RESULTS

Compared to the mechanical alignment technique, the KA technique resulted in a more anatomical restoration of the prosthetic hip centre of rotation with a lower delta pre- to post-operative horizontal acetabular offset (1.47mm for KA versus -5.1mm for MA, p=0.001), and with 74% of KA versus 50% of MA cups (p=0.044) being within 15% of native anatomy for the horizontal acetabular offset. In addition, the KA technique resulted in a higher cup anteversion (22°±7° vs 15°±8°, p<0.001) but similar cup inclination (41°±6° vs. 42°±7°, p=0.25), a similar proportion of cups within the Lewinnek zone (65% vs. 70%, p=0.8), similar excellent functional outcomes (delta Oxford score pre- to follow-up of 24.3 and 23.5 points for KA and MA groups, respectively, p=0.88), similar patient satisfaction scores of 95.4/100 and 89.5/100 for KA and MA groups, respectively, and the same absence of aseptic complications.

CONCLUSION

The KA technique for THA has been demonstrated to be safe, efficacious, and not inferior to the conventional MA technique at early-term. As the concept of the KA technique for THA is only at an early stage, its influence on mid to long-term clinical outcomes remains to be determined and further refinements of the concept are yet to be made.

LEVEL OF EVIDENCE

III; case-control retrospective study.

The effects of total hip arthroplasty in treating hip bony fusion in young and middle-aged patients with ankylosing spondylitis

Background

This study aims to investigate the curative effects of total hip arthroplasty (THA) in treating hip bony fusion for young and middle-aged patients with ankylosing spondylitis (AS).

Methods

The clinical data of 26 young and middle-aged patients with AS (31 coxae), who were treated with THA and followed-up for more than 3 years in the period between February 1998 and May 2013, were retrospectively analyzed. Among these patients, 22 patients were male (25 coxae) and 4 patients were female (6 coxae). Patients’ age ranged within 19–50 years old, with an average of 31.5 years old. The intervals from arthroplasty to the occurrence of hip joint lesions caused by AS ranged within 2–26 years, with an average of 11.2 years. The average Harris score before the surgery was 19.0 ± 11.5 points.

Results

Femoral proximal cleavage fracture occurred in one coxa during the surgery and was fixed by the steel wire cerclage. Sciatic nerve traction injury occurred in one coxa after the surgery, which recovered after 6 months. Posterior hip dislocation occurred in one coxa and was immediately treated with manual reduction. All patients were followed-up, and follow-up duration ranged within 36–123 months, with an average of 46.5 months. In the last follow-up, the average Harris score was 87.1 ± 13.1 points, total passive range of motion was 215.0 ± 22.0°, and passive range of flexion was 90.8 ± 9.3°. All these indexes significantly increased compared with pretreatment (P < 0.01). A periacetabular radiolucent line occurred in one coxa with a width of < 2 mm, and no femoral radiolucent line was found during follow-ups in any patient. Heterotopic ossification occurred in four coxae.

Conclusion

THA treatment for hip bony fusion caused by AS can achieve satisfactory hip function recovery and excellent prosthesis survival rate.

A Geometric Model to Determine Patient-Specific Cup Anteversion Based on Pelvic Motion in Total Hip Arthroplasty

Introduction

Cup position is critical to stability in total hip arthroplasty and is affected by pelvis motion during positions of daily life. The purpose of this study was to explicitly define the relationship between sagittal pelvic motion and resultant cup functional anteversion and create a tool to guide the surgeon to a patient-specific intra-operative anteversion.

Materials and Methods

10,560 combinations of inclination, anteversion, and pelvic tilt were generated using a geometric model. Resultant functional anteversion was calculated for each iteration and variables were correlated. An electronic mobile tool was created that compares inputted patient-specific values to population-based averages to determine pelvic positions and dynamics that may lead to instability.

Results

A third-degree polynomial equation was used to describe the relationship between variables. The freely downloadable mobile tool uses input from pre-operative plain radiographic measurements to provide the surgeon a quantitative correction to intra-operative cup anteversion based on differences in functional anteversion compared to population-based averages.

Conclusion

This study provides a geometric relationship between planned cup position, pelvic position and motion, and the resultant functional anteversion. This mathematical model was applied to an electronic tool that seeks to determine an individualized intra-operative cup anteversion based on measured patient-specific pelvic dynamics.

Optimum anatomic socket position and sizing for the direct anterior approach: impingement and instability

A comprehensive strategy is important for ensuring reproducible and safe acetabular component sizing and positioning. Presented here is our approach for anatomic acetabular component positioning in direct anterior total hip arthroplasty. This strategy has evolved with our understanding of the ramifications of socket sizing and positioning on instability and impingement. Data collected by a single surgeon (J.A.R.) between 2009 and 2011 influenced our current paradigm. We compare the sizing and positioning parameters of the anterior and posterior approach, thus demonstrating how the 2 are different. By highlighting these differences, we hope to provide a clear, defined approach to acetabular placement and sizing for direct anterior-approach total hip arthroplasty.

"Channel Lines": A Simple Surgical Technique to Aid in Achieving Patient-specific Ante-version During Implantation of Uncemented Acetabular Cups

Accurate acetabular cup placement is a crucial step for a successful total hip replacement. Transverse acetabular ligament is an important and reliable landmark that helps in determining the version during the placement of acetabular cups. However, the visualization of transverse acetabular ligament may not be easy as the view may be blocked by the implants and the instruments. We have devised a simple technique to aid in achieving patient-specific ante-version during implantation of uncemented acetabular cups by using "channel lines."

Can the use of an inclinometer improve the positioning of the acetabular component in total hip arthroplasty?

Aims

Accurate placement of the acetabular component is essential in total hip arthroplasty (THA). The purpose of this study was to determine if the ability to achieve inclination of the acetabular component within the 'safe-zone' of 30° to 50° could be improved with the use of an inclinometer.

Patients and Methods

We reviewed 167 primary THAs performed by a single surgeon over a period of 14 months. Procedures were performed at two institutions: an inpatient hospital, where an inclinometer was used (inclinometer group); and an ambulatory centre, where an inclinometer was not used as it could not be adequately sterilized (control group). We excluded 47 patients with a body mass index (BMI) of > 40 kg/m², age of > 68 years, or a surgical indication other than osteoarthritis whose treatment could not be undertaken in the ambulatory centre. There were thus 120 patients in the study, 68 in the inclinometer group and 52 in the control group. The inclination angles of the acetabular component were measured from de-identified plain radiographs by two blinded investigators who were not involved in the surgery. The effect of the use of the inclinometer on the inclination angle was determined using multivariate regression analysis.

Results

The mean inclination angle for the THAs in the inclinometer group was 42.9° (95% confidence interval (CI) 41.7° to 44.0°; range 29.0° to 63.8°) and 46.5° (95% CI 45.2° to 47.7°; range 32.8° to 63.2°) in the control group (p < 0.001). Regression analysis identified a 9.1% difference in inclination due to the use of an inclinometer (p < 0.001), and THAs performed without the inclinometer were three times more likely to result in inclination angles of > 50° (odds ratio (OR) 2.8, p = 0.036). The correlation coefficient for the interobserver reliability of the measurement of the two investigators was 0.95 (95% CI 0.93 to 0.97).

Conclusion

The use of a simple inclinometer resulted in a significant reduction in the number of outliers compared with a freehand technique. Cite this article: Bone Joint J 2018;100-B:862-6.

The Impact of Spino-Pelvic Alignment on Total Hip Arthroplasty Outcomes: A Critical Analysis of Current Evidence

BACKGROUND

In this review, we (1) evaluated the effect of adult spine deformity (ASD) and its surgical correction on patients who had a total hip arthroplasty (THA); (2) evaluated the outcomes of THA in patients who have had previous spinal fusion; and (3) we presented an algorithm on how to surgically address patients who simultaneously require THA and ASD correction.

METHODS

A comprehensive literature search was conducted. Our final analysis included 14 studies. Overall, there were 3 studies that reported on the impact of ASD on THA outcomes, 6 studies reported on the effect of ASD correction on THA outcomes, and 5 studies reported on the effect of spinal fusion on THA outcomes.

RESULTS

Patients with concurrent ASD and THA are at increased risk of THA dislocations and revisions with studies reporting a compiled 2.9% dislocation rate in 1167 patients. Patients who underwent ASD correction demonstrated a post-operative reduction of acetabular anteversion (mean reduction range 4.96°-11.2°, P < .001) and tilt (mean -7° ± 10°, P < .001). In THA patients with concurrent lumbosacral fusion, dislocation rates ranged between 3% at 1 year and 7.5% at 2 years compared to 0.4%-2.1% dislocation rates in matching cohorts (P < .001).

CONCLUSION

Spine balance can alter THA outcomes, but the exact mechanism is yet to be elucidated. We aimed at bridging the gap between hip and spine surgeons with an up-to-date analysis of the best available evidence and presented an algorithm for approaching patients who may simultaneously need ASD correction and THA.

Kinematic alignment technique for total hip and knee arthroplasty: The personalized implant positioning surgery

Conventional techniques for hip and knee arthroplasty have led to good long-term clinical outcomes, but complications remain despite better surgical precision and improvements in implant design and quality.

Technological improvements and a better understanding of joint kinematics have facilitated the progression to ‘personalized’ implant positioning (kinematic alignment) for total hip (THA) and knee (TKA) arthroplasty, the true value of which remains to be determined.

By achieving a true knee resurfacing, the kinematic alignment (KA) technique for TKA aims at aligning the components with the physiological kinematic axes of the knee and restoring the constitutional tibio-femoral joint line frontal and axial orientation and soft-tissue laxity.

The KA technique for THA aims at restoring the native ‘combined femoro-acetabular anteversion’ and the hip’s centre of rotation, and occasionally adjusting the cup position and design based on the assessment of the individual spine-hip relation.

The key element for optimal prosthetic joint kinematics (hip or knee) is to reproduce the femoral anatomy.

The transverse acetabular ligament (TAL) is the reference landmark to adjust the cup position.

Cite this article: EFORT Open Rev 2018;3:98-105. DOI: 10.1302/2058-5241.3.170022

Quantifying Pelvic Motion During Total Hip Arthroplasty Using a New Surgical Navigation Device

BACKGROUND

Accurate cup positioning is one of the most challenging aspects of total hip arthroplasty (THA). Undetected movement of the patient during THA surgery can lead to inaccuracies in cup anteversion and inclination, increasing the potential for dislocation and revision surgery. Investigations into the magnitude of patient motion during THA are not well represented in the literature.

METHODS

We analyzed intraoperative pelvic motion using a novel navigation device used to assist surgeons with cup position, leg length, and offset during THA. This device uses an integrated accelerometer to measure motion in 2 orthogonal degrees of freedom. We reviewed the data from 99 cases completed between February and September 2016.

RESULTS

The mean amount of pitch recorded per patient was 2.7° (standard deviation, 2.2; range, 0.1°-9.9°), whereas mean roll per patient was 7.3° (standard deviation, 5.5; range, 0.3°-31.3°). Twenty-one percent (21 of 99) of patients demonstrated pitch of >4°. Sixty-nine percent (68 of 99) of patients demonstrated >4° of roll, and 25% (25 of 99) of patients demonstrated roll of ≥10°.

CONCLUSION

Our findings indicate that while the majority of intraoperative motion is <4°, many patients experience significant roll, with a large proportion rolling >10°. This degree of movement has implications for acetabular cup position, as failure to compensate for this motion can result in placement of the cup outside the planned safe zone, thus, increasing the potential for dislocation. Further study is warranted to determine the effect of this motion on cup position, leg length, and offset.

Chronological changes in functional cup position at 10 years after total hip arthroplasty

PURPOSE

This study aims to clarify the chronological changes in functional cup position at a minimum follow-up of 10 years after total hip arthroplasty (THA), and to identify the risk factors influencing a significant difference in functional cup position during the postoperative follow-up period.

METHODS

We evaluated the chronological changes in functional cup position at a minimum follow-up of 10 years after THA in 58 patients with unilateral hip osteoarthritis. Radiographic cup position was measured on anteroposterior pelvic radiographs with the patient in the supine position, whereas functional cup position was recorded in the standing position. Radiographs were obtained before, 3 weeks after, and every 1 year after surgery.

RESULTS

Functional cup anteversion (F-Ant) increased over time, and was found to have significantly increased at final follow-up compared to that at 3 weeks after surgery (p<0.01). The maximum postoperative change in F-Ant was 17.0° anteriorly; 12 cases (21%) showed a postoperative change in F-Ant by >10° anteriorly. Preoperative posterior pelvic tilt in the standing position and vertebral fractures after THA were significant predictors of increasing functional cup anteversion.

CONCLUSIONS

Although chronological changes in functional cup position do occur after THA, their magnitude is relatively low. However, posterior impingement is likely to occur, which may cause edge loading, wear of the polyethylene liner, and anterior dislocation of the hip. We believe that, for the combined anteversion technique, the safe zone should probably be 5°-10° narrower in patients predicted to show considerable changes in functional cup position compared with standard cases.

A retrospective study on the relationship between altered native acetabular angle and vertical implant malpositioning

PURPOSE

Acetabular cup positioning in extreme angles of vertical position affects both stability and long-term survivorship of total hip arthroplasty. The purpose of this study is to determine whether native Sharp's angle is associated with an increased abduction angle of the acetabular component.

METHODS

Consecutive patients who underwent primary total hip replacement between February 2012 and August 2015 were included. Vertical positioning of acetabular implant in the antero-posterior post-operative radiographs were measured. The proportion of implants positioned outside the safe zone (40° ± 10°) was calculated and through a multivariate analysis, Sharp's angle and other factors possibly associated with cup malpositioning were evaluated.

RESULTS

Five hundred twenty-eight hip arthroplasties were analyzed. Prevalence of cup malpositioning was 7.6% and 25 patients had an altered native acetabular angle. An altered pre-operative Sharp's angle was associated with a higher risk of vertical malpositioning of the acetabular component (OR 2.51 IC 95%: 1.17-5.39) (p = 0.02). Body mass index, surgeon's volume, size of the implant, gender, pre-operative diagnose and age, were not associated with the position of the cup.

CONCLUSIONS

The alteration of the Sharp's angle as an indicator of hip dysplasia in native hips increases the odds of acetabular cup malpositioning. Other factors explored did not correlate with the position of the acetabular prosthesis. Systematic assessment of Sharp's angle should be included in the pre-operative planning of primary hip arthroplasty.

The influence of spine-hip relations on total hip replacement: A systematic review

Sagittal pelvic kinematics along with spino-pelvic angular parameters have recently been studied by numerous investigators for their effect on total hip replacement (THR) clinical outcomes, but many issue of spine-hip relations (SHR) are currently unexplored. Therefore, our review aims at clarifying the following questions: is there any evidence of a relationship between articular impingement/dislocation risk in primary THR and (1) certain sagittal pelvic kinematics patterns, (2) pelvic incidence, and (3) types of SHRs? A systematic review of the existing literature utilising PubMed and Google search engines was performed in January 2017. Only clinical or computational studies published in peer-reviewed journals over the last five years in either English or French were reviewed. We identified 769 reports, of which 12 met our eligibility criteria. A review of literature shows that sagittal pelvic kinematics, but not the pelvic incidence, influences the risk of prosthetic impingement/dislocation. We found no study having assessed the relationship between this risk and the types of SHRs. Sagittal pelvic kinematics is highly variable among individuals and certain kinematic patterns substantially influences the risk of prosthetic impingement/dislocation. Recommendations for cup positioning are therefore switching from a systematic to a patient-specific approach, with the standing cup orientation Lewinneck safe zone progressively giving way to a new parameter of interest: the functional orientation of the cup. Based on a recently published classification for SHRs, We propose a new concept of "kinematically aligned THR" for the purposes of THR planning. Further studies are needed to investigate the relevance of such a classification towards the assumptions and hypothesis we have made. Level of evidence,- Level IV, systematic review of level III and IV studies.

Pelvic Tilt Evaluation From Frontal Radiographs: The Validity, Interobserver Reliability and Intraobserver Reproducibility of the Sacro-Femoral-Pubic Parameter

BACKGROUND

The sacro-femoral-pubic (SFP) parameter, calculated using the SFP angle measured on a frontal pelvis radiograph, has previously been shown to have a strong correlation with sagittal pelvic tilt (PT) measured on a lateral x-ray. The purpose of this study is to assess the validity, interobserver reliability and intraobserver reproducibility of the SFP parameter in predicting the sagittal PT.

METHODS

This is a retrospective study of 100 patients with frontal and lateral radiographs of the pelvis. Two observers independently measured the SFP angle on frontal x-ray (midpoint of S1 end plate to centroid of acetabula to upper midpoint of the pubic symphysis) and PT on lateral x-ray (midpoint of sacral plate to the centroid of acetabula to vertical plane). The SFP parameter was defined using the equation: SFP parameter = 75 - SFP angle. The interobserver reliability and intraobserver reproducibility were calculated using interclass correlation coefficient (ICC). Validity of the SFP parameter was calculated using Pearson correlation coefficient.

RESULTS

The intraobserver reproducibility of the SFP parameter was excellent (ICC >0.90) for both observers. The interobserver reliability of all measurements was substantial for the SFP parameter (ICC >0.80) and PT (ICC >0.70). The concurrent validity of the SFP parameter was substantial (r = 0.70).

CONCLUSION

Calculating PT from a frontal radiograph using the equation for the SFP parameter is a valid, reliable, and reproducible formula that may be used to predict sagittal PT.

An Alternative Intraoperative Radiographic Method for Optimizing Cup Inclination during Total Hip Arthroplasty

OBJECTIVE

During total hip arthroplasty (THA), the location of the acetabular prosthesis is very important for guaranteeing successful surgery. However, this remains a challenge for many surgeons. This study aimed to investigate the feasibility of using the intraoperative fluoroscopic iliopubic tangential angle (IPTA) to determine the valgus angles of acetabular prostheses.

METHODS

In the first stage, the IPTA and valgus angles of native acetabula were defined and measured in 102 THAs obtained from the picture archiving and communication systems of our hospital. Obturator foramen morphology was also measured and divided into groups according to the axial length ratio. Correlations between obturator foramen morphology and IPTA and valgus angles of native acetabula were then determined. In the second stage, angular differences (angle θ) between the IPTA and valgus angles of native acetabula were measured during unilateral THA in 136 patients to determine whether this is a stable value that could be used as a reference for placement of acetabular prostheses. Postoperative data such as Harris Hip Score (HHS) scores and complications were collected and evaluated.

RESULTS

The average IPTA at the apex of the true acetabulum was 58.8° ± 4.1°. The average valgus angle of native acetabula was 43.1° ± 3.9° and angle θ was 15.7° ± 1.3°. Obturator foramen morphology was divided into five groups according to the axial length ratio. IPTA was closely related to obturator foramen morphology (Pearson r = 0.489, P ≈ 0.000). Angle θ was stable and independent of obturator foramen morphology. When the IPTA and angle θ were used as references for placing acetabular prostheses in 136 THAs, the average postoperative valgus angles of acetabular prostheses was 45.13° ± 4.07° and the good-to-excellent rate was 97.05%. There were no short-term complications such as fracture, dislocation or infection. The average HHS score 6 months after surgery was 37.2 higher than the preoperative score, this difference being significant (P < 0.01). Neither infection nor dislocation was found 6 months after surgery.

CONCLUSIONS

The IPTA (at the apex of the true acetabulum) and angle θ (obtained by intraoperative fluoroscopy) are consistent in determining the postoperative valgus angle of acetabular prosthesis during THA. Thus, IPTA and angle θ are of value in guiding placement of acetabular prostheses; in particular, this method can facilitate the learning of young surgeons.

ACETABULAR COMPONENT ORIENTATION IN TOTAL HIP ARTHROPLASTY: THE ROLE OF ACETABULAR TRANSVERSE LIGAMENT

Objective:

The aim of our study is to present the benefit of using the transvers acetabular ligament for intraoperative determination of the anteversion of acetabular component.

Methods:

Twenty-one total hip arthroplasties were performed. The transverse acetabular ligament was identified and used as a guide to position the acetabular component.

Results:

The mean anteversion angle was 16.9. None of the patients studied sustained a postoperative dislocation during this short follow-up period.

Conclusion:

We conclude from this preliminary study that the transverse acetabular ligament can aid positioning of the acetabular component of a THR. It defines the version of the acetabular component without the need for external instrumentation, and is independent of the position of the patient. Level of Evidence IV; Prospective Study.

The Transverse Acetabular Ligament as an Intraoperative Guide to Cup Abduction

BACKGROUND

The success of a total hip arthroplasty relies on optimal acetabular cup placement to ensure mating of the femoral head and acetabular cup throughout all positions of the hip joint. Poor cup placement is associated with dislocation, impingement, microseparation, component loosening, and accelerated wear due to rim loading. This study examined a novel method of using the transverse acetabular ligament (TAL) to guide cup inclination during primary total hip arthroplasty.

METHODS

A descriptive study using 16 hips from 9 cadavers. A computer navigation system measured inclination and version of the acetabular component in 3 positions with the lower edge of cup: (1) flush with, (2) 5 mm proximal to, and (3) 5 mm distal to free border of the TAL.

RESULTS

The median inclination angles were 44° in position (1), 30° in position (2), and 64° in position (3). The median anteversion angle for all positions was 19°.

CONCLUSION

Cup inclination was acceptable when the lower edge of the cup was flush or within 5 mm proximal to the TAL.

Effect of Spinal Deformity on Pelvic Orientation from Standing to Sitting Position

BACKGROUND

The effect of fixed spinal deformities on a functional pelvis from standing to sitting is not fully understood. We aimed to assess the change in preoperative sagittal pelvic tilt angle (SPTA) from standing to sitting in patients undergoing total hip arthroplasty, comparing flexible and fixed spinal deformities.

METHODS

Between July 2011 and October 2011, 68 consecutive unilateral total hip arthroplasties were implanted in 68 patients with a mean age of 71 ± 6 years. Fixed spinal deformity was defined as <10° of the change in SPTA from standing to sitting. Preoperative radiographic evaluation included standing (weight-bearing) anteroposterior and lateral pelvic and lumbosacral radiographs and a sitting lateral pelvic radiograph.

RESULTS

The mean standing and sitting SPTA was 3.7° of anterior tilt and 17.7° of posterior tilt, respectively (change of 21.4 ± 12.5°). Seventy-five percent had flexible pelvises, all of which had a posterior tilt from standing to sitting. One patient in the fixed pelvis (1.4%) had a loss of posterior tilt from standing to sitting. The mean change of SPTA from standing to sitting in the fixed and flexible pelvis groups was 5.9 ± 3.5° to 26.7 ± 9.6° of posterior tilt, which was statistically significant (P < .05).

CONCLUSION

There was a significant change in sagittal pelvic tilt from standing to sitting, especially in patients with a flexible spine, in which the functional anteversion increases with sitting. The patients with a fixed pelvis had significantly less SPTA in standing (less anteversion) with less posterior sagittal tilt in sitting, which should be incorporated in cup positioning.

Surgical technique and outcome of uncemented THR using HA coated stems in fused and deformed hips due to ankylosing spondylitis

BACKGROUND

Uncemented Total Hip Replacement (THR) is at present an accepted treatment in patients with severe deformity of the hip caused by advanced ankylosing spondylitis.

MATERIALS AND METHODS

We studied 20 patients, 2 female and 18 male, who had 29 THRs, all through a posterior approach. The patient's age at index surgery ranged from 20 to 47 years (mean 35.1). No trochanteric osteotomy was performed in any patient. A double cut of the femoral neck was performed for hips which were ankylosed in external rotation and flexion. Follow-up ranged from 18 to 46 months (mean 22.2 months).

RESULTS

The mean preoperative Harris Hip Score (HHS) was 34.6. At last follow-up all hips were considered excellent, with a mean HHS of 90. Radiographs revealed that the acetabular and femoral components were satisfactorily positioned with no radiographic evidence of loosening. No heterotrophic ossification was found.

CONCLUSIONS

1) Trochanteric Osteotomy was not found necessary to expose the hip through the posterior approach. 2) Uncemented THR using HA coated stem in the treatment of severe deformity of the hip caused by advanced ankylosing spondylitis allowed good lower limb function.

The Impact of Lumbar Spine Disease and Deformity on Total Hip Arthroplasty Outcomes

Concurrent spine and hip disease is common. Spinal deformities can restrict lumbar range of motion and lumbar lordosis, leading to pelvic obliquity and increased pelvic tilt. A comprehensive preoperative workup and component templating ensure appropriate compensation for altered pelvic parameters for implantation of components according to functional positioning. Pelvic obliquity from scoliosis must be measured to calculate appropriate leg length. Cup positioning should be templated on standing radiograph to limit impingement from cup malposition. In spinal deformity, the optimal position of the cup that accommodates pelvic parameters and limits impingement may lie outside the classic parameters of the safe zone.

Does stem design influence component positioning in total hip arthroplasty using a minimal invasive posterolateral approach?

PURPOSE

Limited data exist for the reconstructive potential of short bone-preserving stems in THA using a minimal invasive posterolateral approach. Our study aim was to assess the effect of stem design on the reconstruction of hip offset and leg length in MIS posterolateral THA.

METHODS

This retrospective consecutive single-surgeon study compares hip offset and leg length, as well as acetabular component positioning (cup anteversion; inclination) of 129 THAs with a cementless standard-length stem (Synergy®) and 143 THAs with a cementless short bone-preserving stem (Trilock®).

RESULTS

In reference to the contralateral side, the mean difference in hip offset was 0.9 mm (p = 0.067) for the standard stem and 0.1 mm (p = 0.793) for the short stem, respectively. Leg-length discrepancy was 0.7 mm (Synergy®) and 0.9 mm (Trilock®), respectively. A total of 233 (86 %) acetabular components fell within the target zone for anteversion and inclination.

CONCLUSION

Accurate component positioning in MIS posterolateral approach THA is possible and is not influenced by the type of stem.

The use of the transverse acetabular ligament for determining the orientation of the components in total hip replacement

The orientation of the acetabular component can influence both the short- and long-term outcomes of total hip replacement (THR). We performed a prospective, randomised, controlled trial of two groups, comprising of 40 patients each, in order to compare freehand introduction of the component with introduction using the transverse acetabular ligament (TAL) as a reference for anteversion. Anteversion and inclination were measured on pelvic radiographs.

With respect to anteversion, in the freehand group 22.5% of the components were outside the safe zone versus 0% in the transverse acetabular ligament group (p = 0.002). The mean angle of anteversion in the freehand group was 21° (2° to 35°) which was significantly higher compared with 17° (2° to 25°) in the TAL group (p = 0.004). There was a significant difference comparing the variations of both groups (p = 0.008).

With respect to inclination, in the freehand group 37.5% of the components were outside the safe zone versus 20% in the TAL group (p = 0.14). There was no significant difference regarding the accuracy or variation of the angle of inclination when comparing the two groups.

The transverse acetabular ligament may be used to obtain the appropriate anteversion when introducing the acetabular component during THR, but not acetabular component inclination.

Cite this article: Bone Joint J 2014;96-B:312–18.

Dislocation after total hip arthroplasty

Dislocation remains one of the most common complications after total hip arthroplasty, regardless of the surgical approach. While multiple reasons as laxity, implant position, improper implant choice, and impingement etc. might be leading factors for dislocation, an exact identification of the exact reason is of major importance, to plan for a proper surgical or nonsurgical correction. This article describes in detail the definition, etiology, reduction, and possible treatment options for dislocation after primary and revision total hip arthroplasty that are currently used at the Endo Klinik in Hamburg. It furthermore includes a distinct overview of possible surgical treatment options, based on the main pathology leading to dislocation.