Efficacy of Drug-Coated Balloon Angioplasty in Pulmonary Vein Stenosis or Total Occlusion.

BACKGROUND: Current therapies for pulmonary vein stenosis (PVS) or pulmonary vein total occlusion (PVTO) involving angioplasty and stenting are hindered by high rates of restenosis. OBJECTIVES: This study compares a novel approach of drug-coated balloon (DCB) angioplasty and stenting with the current standard of care in PVS or PVTO due to pulmonary vein isolation (PVI). METHODS: A retrospective single-center study analyzed patients with PVS or PVTO due to PVI who underwent either angioplasty and stenting (NoDCB group; December 2012-December 2016) or DCB angioplasty and stenting (DCB group; January 2018-January 2021). Multivariable Andersen-Gill regression analysis assessed the risk of restenosis and target lesion revascularization (TLR). RESULTS: The NoDCB group comprised 58 patients and 89 veins, with a longer median follow-up of 35 months, whereas the DCB group included 26 patients and 33 veins, with a median follow-up of 11 months. The DCB group exhibited more PVTO (NoDCB: 12.3%; DCB: 42.4%; P = 0.0001), with a smaller reference vessel size (NoDCB: 10.2 mm; DCB: 8.4 mm; P = 0.0004). Follow-up computed tomography was performed in 82% of NoDCB and 85% of DCB, revealing lower unadjusted rates of restenosis (NoDCB: 26%; DCB: 14.3%) and TLR (NoDCB: 34.2%; DCB: 10.7%) in the DCB group. DCB use was associated with a significantly lower risk of restenosis and TLR (HR: 0.003: CI: 0.00009-0.118; P = 0.002). CONCLUSIONS: The novel approach of DCB angioplasty followed by stenting is effective and safe and significantly reduces the risk of restenosis and reintervention compared with the standard of care in PVS or PVTO due to PVI.

True Confessions of Neutral Mechanical Disciple-How I Learned to Love a Patient-Specific Target.

INTRODUCTION: Classical neutral mechanical alignment in total knee arthroplasty (TKA) has been a standard paradigm, while more recently, other alignment schemas, such as kinematic, individualized, and functional, have been explored. This study aimed to investigate the effect of three-dimensional (3D) computed tomography (CT)-based surgical robotics inputs on a classically trained surgeon's TKA component positions and alignment targets over time. MATERIALS AND METHODS: Data from 1,394 consecutive robotically-assisted TKAs by a single surgeon from 2016 to 2020 were analyzed. Metrics collected included pre-balance planned implant component positions, final planned implant component positions after soft tissue balancing, and constitutional alignment from CT scans. Joint line obliquity was plotted against the arithmetic hip-knee angle (aHKA) using coronal plane alignment of the knee (CPAK). Three categories of alignment strategy were defined: true mechanical alignment (tMA), adjusted mechanical alignment (aMA), and no mechanical alignment (noMA). RESULTS: A shift to overall varus component positioning was observed over the years. Joint line obliquity according to CPAK showed a wider spread in later years, and the distribution of tibial and femoral coronal alignment angles expanded over time. CONCLUSION: The study revealed a change in alignment targets and final positioning of components away from neutral biomechanical axes in a large volume of TKAs by a single, classically trained surgeon over five years of using a robotic arm-assisted TKA system with CT-based planning. The most dominant factor for this change was the use of 3D CT planning, allowing the surgeon to assess patient-specific anatomy and plan accordingly. Outcome data is needed to determine if this change in behavior and surgical technique was beneficial. In summary, using a CT scan-based robotically assisted technique led to a gradual and complete shift from tMA to predominantly a non-mechanically aligned philosophy in TKA.

Multi-Planar Expansion of the Coronal Plane Alignment of the Knee Classification? A Computed Tomographic Study Indicates No Significant Correlation With Alignment Parameters in Other Planes.

BACKGROUND: The Coronal Plane Alignment of the Knee (CPAK) classification categorizes knee phenotypes based on constitutional limb alignment (arithmetic hip-knee-ankle angle or aHKA) and joint line obliquity (JLO). This study aimed to determine if sagittal and rotational knee alignments vary among CPAK types in order to establish whether this classification should be expanded beyond coronal plane assessment. METHODS: Coronal, sagittal, and rotational alignment measurements were made and CPAK types were calculated from computed tomographic data of 437 patients (509 knees) who underwent robotic-assisted total knee arthroplasty (TKA). Differences in femoral, tibial, and tibio-femoral angular measurements were compared across CPAK types, and correlations were made to aHKA and JLO. Nonparametric and linear regression tests were used to analyze between-type differences. RESULTS: There were no differences in tibial slope or femoral rotational measures across CPAK phenotypes. However, CPAK Type III knees had a greater tibio-femoral rotation mean difference than CPAK Type I, II, IV, and V knees (P < .05). We also found increased femoral flexion in Type I knees when compared to Type VI knees (P = .01). The aHKA had a weak correlation with femoral flexion angle, and JLO had a weak correlation with femoral posterior condylar axis to tibial antero-posterior axis angle. CONCLUSION: Few clinically important differences in sagittal and rotational alignments were found between CPAK types, indicating that CPAK phenotype has little correlation to 3-dimensional alignment characteristics. Need for an expansion of the CPAK classification beyond coronal plane alignment is not supported from these results.

The Effect of Minor Adjustments to Tibial and Femoral Component Position on Soft Tissue Balance in Robotic Total Knee Arthroplasty.

BACKGROUND: Ideal goals for alignment and balance in total knee arthroplasty (TKA) remain controversial. We aimed to compare initial alignment and balance using mechanical alignment (MA) and kinematic alignment (KA) techniques and to analyze the percentage of knees that could achieve balance using limited adjustments to component position. METHODS: Prospective data on 331 primary robotic TKAs (115 MAs and 216 KAs) were analyzed. Medial and lateral virtual gaps were recorded in both flexion and extension. A computer algorithm was used to calculate potential (theoretical) implant alignment solutions to achieve balance within 1 millimeter (mm) without soft tissue release given an alignment philosophy (MA or KA), angular boundaries (±1, ±2, or ±3°), and gap targets (equal gaps or lateral laxity allowed). The percentage of knees that could theoretically achieve balance was compared. RESULTS: Less than 5% of TKAs were initially balanced. Limited adjustments to component position increased the percentage of TKAs that could be balanced in a graduated manner, with no difference between MA and KA start points: adjustments of ±1 (10% versus 6%, P = .17), ±2 (42% versus 39%, P = .61), or of ±3 (54% versus 51%, P = .66). A higher percentage of TKAs could be balanced when a greater range for lateral gap laxity was allowed. Balancing from KA resulted in increased joint line obliquity in the final implant alignment. CONCLUSION: A high percentage of TKAs can be balanced without soft tissue release using minor adjustments to component position. Surgeons should consider the relationship between alignment and balance goals when optimizing component positioning in TKA.

The trochlear sulcus of the native knee is consistently orientated close to the sagittal plane despite variation in distal condylar anatomy.

PURPOSE: The aim of this study was to describe the native trochlear orientation of non-arthritic knees in three planes and to quantify the relationship between trochlear and distal condylar anatomy across race and sex. METHODS: Computed tomography scans of 1578 femora were included in this study. The mediolateral position of the trochlear sulcus, the distal trochlear sulcus angle (DTSA) the medial sulcus angle (MSA) and the lateral sulcus angle (LSA) as well as the mechanical lateral distal femoral angle (mLDFA) were measured relative to a standard reference coordinate system. Multiple linear regression analyses were performed to account for potential confounding variables. RESULTS: The mediolateral position of the trochlear sulcus had minimal mean deviation of the sagittal femoral plane. The mean DTSA was 86.1° (SD 2.2°). Multilinear regression analysis found mLDFA, sex, and age all influence DTSA (p < 0.05), with mLDFA having by far the greatest influence (r2 = 0.55). The medial facet of the trochlear sulcus was found to be flat proximally and more prominent distally. The lateral facet was relatively uniform throughout the arc. CONCLUSION: In non-arthritic knees, due to a strong positive correlation between the DTSA and the mLDFA, the trochlear sulcus is consistently orientated in the sagittal femoral plane regardless of distal condylar anatomy. Minor deviations from the sagittal plane occur in a lateral direction in the middle part and in a medial direction at the proximal and distal part of the trochlea. These findings have relevance regarding the biomimetic design of total knee implants.

Relationships among Clinical Factors and Patient-reported Outcome Measures in Adults with Convergence Insufficiency.

SIGNIFICANCE: When exploring relationships among clinical measures and patient-reported outcome measures in adults with convergence insufficiency, worse symptoms (Convergence Insufficiency Symptom Survey [CISS] score) seemed to be correlated with worse reading function domain score (Adult Strabismus-20 quality-of-life questionnaire). After treatment, improved symptoms were associated with improved reading function quality of life. PURPOSE: This study aimed to explore relationships between clinical measures and patient-reported outcome measures in adults undergoing treatment for symptomatic convergence insufficiency. METHODS: In a prospective multicenter observational study, we evaluated adults with symptomatic convergence insufficiency (i.e., clinical measures of near exodeviation, receded near point of convergence, reduced near positive fusional vergence; CISS score ≥21). Fifty-seven participants treated with vision therapy/exercises (n = 35) or base-in prism (n = 22) were analyzed. Spearman correlation coefficients ( R ) were used to assess associations among the three clinical measures and patient-reported outcome measures (CISS, Diplopia Questionnaire, four Adult Strabismus-20 quality-of-life domains) before treatment (baseline) and after 10 weeks and 1 year. Associations were interpreted to be present when the lower limit of the 95% confidence interval (CI) was moderate to strong ( R ≥ 0.4). RESULTS: Among multiple exploratory analyses, the only moderate to strong baseline correlation was between worse CISS and worse Adult Strabismus-20 reading function scores ( R = 0.62; 95% CI, 0.43 to 0.76). Regarding change in measures with treatment, the only moderate to strong correlations were between improved CISS and improved Adult Strabismus-20 reading function scores for prism at 10 weeks ( R = 0.78; 95% CI, 0.52 to 0.91) and 1 year ( R = 0.85; 95% CI, 0.65 to 0.94) and for vision therapy/exercises at 1 year ( R = 0.78; 95% CI, 0.57 to 0.89). CONCLUSIONS: In exploratory analyses, we found positive correlations between CISS symptom scores and reading function quality-of-life scores. The absence of correlations between symptoms and individual clinical measures is consistent with clinical experience that, in convergence insufficiency, symptoms and clinical findings can be discordant.

A prospective randomised controlled trial of mechanical axis with soft tissue release balancing vs functional alignment with bony resection balancing in total knee replacement-a study using Stryker Mako robotic arm-assisted technology.

BACKGROUND: Improving the functional outcome following total knee arthroplasty (TKA) by using different alignment techniques remains controversial. The surgical techniques and technologies used so far to obtain these alignments have all suffered from inaccuracies. The use of robotic technology to plan and execute the bony resection provides increased accuracy for these various alignment techniques and may determine which will deliver superior function. Functional alignment (FA) is a newer surgical technique that aims to position the prosthesis with respect to each patients' specific bony anatomy whilst minimising disruption to the soft tissue envelope. This trial aims to compare the patient and surgical outcomes of FA to the current gold standard surgical technique, mechanical alignment (MA), under randomised and blinded conditions. METHODS: Patients with symptomatic knee osteoarthritis will be prospectively recruited. Following informed consent, 240 patients will be randomised to either a MA surgical technique (the control group) or a FA surgical technique (the intervention group) at a ratio of 4:1 using a random number generator. All patients will undergo computer tomography (CT) based robotic arm-assisted surgery to execute planned implant positioning and alignment with high levels of accuracy. The primary outcome is the forgotten joint score (FJS) at 2 years post-operation. Secondary outcome measures include patient reported outcome measures of post-operative rehabilitation, pain, function and satisfaction, as well as limb alignment, implant revisions and adverse events. Intention-to-treat and per-protocol population analysis will also be conducted. Standardisation of the surgical system and care pathways will minimise variation and assist in both patient and physiotherapist blinding. Ethical approval was obtained from the Northern B Health and Disability Ethics Committee (20/NTB/10). DISCUSSION: Currently, MA remains the gold standard in knee replacement due to proven outcomes and excellent long-term survivorship. There are many alternative alignment techniques in the literature, all with the goal of improving patient outcomes. This study is unique in that it leverages an advanced analytics tool to assist the surgeon in achieving balance. Both alignment techniques will be executed with high precision using the CT-based robotic arm-assisted surgery system which will minimise surgical variation. This trial design will help determine if FA delivers superior outcomes for patients. TRIAL REGISTRATION: Australia and New Zealand Clinical Trials Registry (ANZCTR), ACTRN12620000009910 . Registered on 9 January 2020. CLINICALTRIALS: gov, NCT04600583 . Registered on 29 September 2020.

The impact of functional combined anteversion on hip range of motion: a new optimal zone to reduce risk of impingement in total hip arthroplasty.

AIMS: Pelvic tilt (PT) can significantly change the functional orientation of the acetabular component and may differ markedly between patients undergoing total hip arthroplasty (THA). Patients with stiff spines who have little change in PT are considered at high risk for instability following THA. Femoral component position also contributes to the limits of impingement-free range of motion (ROM), but has been less studied. Little is known about the impact of combined anteversion on risk of impingement with changing pelvic position. METHODS: We used a virtual hip ROM (vROM) tool to investigate whether there is an ideal functional combined anteversion for reduced risk of hip impingement. We collected PT information from functional lateral radiographs (standing and sitting) and a supine CT scan, which was then input into the vROM tool. We developed a novel vROM scoring system, considering both seated flexion and standing extension manoeuvres, to quantify whether hips had limited ROM and then correlated the vROM score to component position. RESULTS: The vast majority of THA planned with standing combined anteversion between 30° to 50° and sitting combined anteversion between 45° to 65° had a vROM score > 99%, while the majority of vROM scores less than 99% were outside of this zone. The range of PT in supine, standing, and sitting positions varied widely between patients. Patients who had little change in PT from standing to sitting positions had decreased hip vROM. CONCLUSION: It has been shown previously that an individual's unique spinopelvic alignment influences functional cup anteversion. But functional combined anteversion, which also considers stem position, should be used to identify an ideal THA position for impingement-free ROM. We found a functional combined anteversion zone for THA that may be used moving forward to place total hip components. Cite this article: Bone Jt Open 2021;2(10):834-841.

Variability of pelvic axial rotation in patients undergoing total hip arthroplasty.

BACKGROUND: Pelvic axial rotation affects the functional orientation of an acetabular component. Every 1° of axial rotation changes functional acetabular anteversion by 1°. There is limited information on pelvic rotation in THA patients, since it is difficult to measure on routine radiographs. Therefore, we used spine-to-ankle biplanar radiography to investigate variability in pelvic rotation in patients before and after THA. METHODS: In 156 patients undergoing primary unilateral THA, we measured preoperative, 6 weeks and 1 year postoperative pelvic rotation in both standing and sitting positions using a biplanar radiography system. Patients with fixed pelvic rotation had a similar magnitude and direction of pelvic rotation in all standing or sitting images. We further identified patients with position-independent or position-dependent fixed pelvic rotation. RESULTS: Pelvic rotation was common in THA patients, with 82 patients (53% of 156 patients) having at least 1 image with > 7° of rotational deformity. 12 patients (8% of 156 patients) had fixed rotation, 6 patients (4%) had position-independent fixed axial rotation and 6 patients (4%) had position-dependent fixed axial rotation. CONCLUSIONS: It may be important to recognise whether a THA patient has a fixed pelvic axial rotational deformity, where 1 hip is consistently forward or backward in functional imaging. Fixed rotation will increase or decrease the functional anteversion of an acetabular component depending on THA side. Further research might better characterise associations and predictors of fixed axial rotation and its impact on patient outcomes after THA.

Treatment of Recurrent Dislocation after Total Hip Arthroplasty Using Advanced Imaging and Three-Dimensional Modeling Techniques: A Case Series.

BACKGROUND: Surgical treatment options for addressing recurrent dislocation after total hip arthroplasty (THA) vary. Identifying impingement mechanisms in an unstable THA may be beneficial in determining appropriate treatment. QUESTIONS/PURPOSES: We sought to assess the effectiveness of developing pre-operative plans for treating hip instability after THA. We used advanced imaging and three-dimensional modeling techniques to perform impingement analyses in patients with unstable THA. METHODS: We evaluated a series of eight patients who would require revision THA to treat recurrent dislocation. Using a pre-operative algorithmic approach, we built patient-specific models and evaluated hip range of motion with computed tomographic scanning and biplanar radiography. This information was used to determine a surgical treatment plan that was then executed intra-operatively. Patients were followed for 2 years to determine whether they experienced another hip dislocation following treatment. RESULTS: Pre-operative kinematic modeling showed four of the eight patients had limited hip range of motion during flexion and internal rotation; a prominent anterior inferior iliac spine (AIIS) was found to limit hip range of motion in some of these cases. In the other four patients, range of motion was acceptable, suggesting soft-tissue causes of dislocation. No patients in this series experienced dislocation after undergoing revision THA. CONCLUSION: Advanced modeling techniques may be useful for identifying the impingement mechanisms responsible for instability after THA. Once variables contributing to limited hip range of motion are identified, surgeons can develop treatment plans to improve patient outcomes. Resecting a hypertrophic AIIS may improve hip range of motion and may be an important consideration for hip surgeons when revising unstable THAs.

Biplanar Low-Dose Radiography Is Accurate for Measuring Combined Anteversion After Total Hip Arthroplasty.

BACKGROUND: Acetabular component position alone has not been predictive of stability after total hip arthroplasty (THA). Combined anteversion of the acetabulum and femur has the potential of being more predictive of stability. Unfortunately, femoral component position is difficult to measure on plain radiographs. Computed tomography (CT) is the gold standard for measuring implant position post-operatively, but CT exposes patients to a substantial amount of radiation. QUESTIONS/PURPOSES: We sought to determine whether biplanar low-dose radiography can be used to accurately measure both acetabular and femoral implant position after THA. METHODS: Twenty patients underwent standing low-dose biplanar spine-to-ankle radiographs and supine CT scans 6 weeks after THA. Measurements of acetabular inclination, acetabular anteversion, and femoral anteversion were performed by two blinded observers and compared. RESULTS: The average absolute differences between biplanar radiographs and CT scans were 2° ± 2° for acetabular inclination, 3° ± 2° for acetabular anteversion, and 4° ± 4° for femoral anteversion between EOS measurements and CT measurements. Interobserver agreement was good for acetabular inclination, acetabular anteversion, and femoral anteversion (Cronbach's α = 0.90) using biplanar low-dose imaging. CONCLUSION: Biplanar radiography is a reliable low-radiation alternative for measuring acetabular inclination, acetabular anteversion, femoral version, and thus combined anteversion compared to CT. Femoral anteversion had the most variability but is still clinically relevant.

Zirconia Phase Transformation in Zirconia-Toughened Alumina Ceramic Femoral Heads: An Implant Retrieval Analysis.

BACKGROUND: Zirconia-toughened alumina ceramic was introduced as a femoral head material for total hip arthroplasty. The material combines the stability of alumina with the toughness of zirconia. Despite inherent benefits for bearing surfaces, concern exists in the medical field that phase transformation of the zirconia grains could worsen wear resistance and lower the strength of the head. We examined these concerns in retrieved and artificially aged ceramic heads. METHODS: Twenty-eight ceramic composite heads retrieved at revision surgery were combined with 5 pristine heads (as negative controls for phase transformation) and 5 artificially aged pristine heads (as positive controls). The extent of zirconia phase transformation at the bearing surfaces was examined through confocal Raman spectroscopy and X-ray diffraction. Burst testing was conducted on all pristine and aged heads and the 4 retrieved implants with the longest lengths of implantation. RESULTS: Retrieved heads had higher maximum average volume fractions of the monoclinic phase compared to pristine or aged heads. Length of implantation was not correlated to the volume fraction of the monoclinic phase. All the heads achieved a burst load far above the 46 kN Food and Drug Administration acceptance criterion; 3 of the 4 retrieved heads had burst strengths exceeding 100kN. CONCLUSION: Our results showed that phase transformation occurs in vivo in ceramic composite femoral heads, but the amount transformed did not increase with the length of time the head had been implanted. The negligible effect upon burst strength of the retrieved and artificially aged heads is reassuring. These results support continued clinical use of this alumina-zirconia composite material as a head material.

MRI of THA Correlates With Implant Wear and Tissue Reactions: A Cross-sectional Study.

BACKGROUND: MRI is predictive of adverse local tissue reactions (ALTRs) after THA but how MRI directly relates to implant surface wear, fretting, and trunnion corrosion at different articulations between implant components remains unclear. MRI generates high-contrast images to display soft tissues around arthroplasty and may provide a surgeon the means to distinguish and differentiate host-related synovial patterns as a response to either polyethylene wear or metal wear and corrosion products. QUESTIONS/PURPOSES: The purposes of this study were (1) to correlate findings from MRI in patients who have undergone THA with direct assessment of implant wear, corrosion, and fretting from retrieved components; and (2) to distinguish the unique synovial responses on MRI in patients who have undergone THA based on bearing materials. METHODS: In this prospective study, patients undergoing THA (181 patients, 187 hips) with metal-on-metal (MoM), hip resurfacing (HRA), metal-on-polyethylene (MoP), ceramic-on-polyethylene, ceramic-on-ceramic, or modular neck designs having revision surgery (between October 2013 and June 2017) underwent preoperative MRI. A single reader blinded to the bearing surface made an assessment of the synovial response (Gwet's AC1, 0.65-0.97); these data were compared with semiquantitative histology of tissue samples by a single reader (Gwet's AC1, 0.92) and semiquantitative wear, corrosion, and fretting analysis of retrieved components using Goldberg scoring (Gwet's AC1, 0.60-0.79). Direct noncontact measurements of implant wear were also made. Correlations and analyses of variance were used to assess associations between metrics and differences by implant type, respectively. RESULTS: Correlations were found between MRI synovial thickness with severity of fretting and corrosion damage of the female head-neck trunnion of femoral stems in modular designs (ρ = 0.26 [95% confidence interval {CI}, 0.12-0.39]; p = 0.015, n = 185) and ALTR grade and volumetric wear in MoM bearings (ρ = 0.93 [95% CI, 0.72-0.98]; p < 0.001, n = 10). MRI synovial thickness was highest in patients identified with aseptic lymphocyte-dominated vasculitis-associated lesions and diffuse tissue necrosis. On MRI, MoP hips demonstrated a distinct polymeric synovial response, whereas HRA, MoM, and modular hips more commonly demonstrated ALTR. Hips classified as having a polymeric synovial response on MRI had a greater number of particles present in tissue samples. CONCLUSIONS: In this study, we demonstrated that MRI of THA can distinguish synovial responses that reflect the bearing type of the implanted THA and correlate to direct measurements of implant wear, corrosion, and fretting and histologic assessment of wear particles in periprosthetic tissues. MRI provides a means of direct, noninvasive visualization of the host-generated synovial response. Patients presenting with painful arthroplasties may be evaluated for the cause of their discomfort, specifically highlighting any concerning synovial reactions that would warrant more prompt surgical intervention. Future studies would benefit from a prospective evaluation of different implants to assess the natural longitudinal history of arthroplasty complications, including the development and prevalence of ALTR across bearing constructs. LEVEL OF EVIDENCE: Level III, diagnostic study.

Polyethylene Wear Increases in Liners Articulating With Scratched Oxidized Zirconium Femoral Heads.

BACKGROUND: Oxidized zirconium (OxZr) femoral heads were introduced in hip arthroplasty to reduce wear of the polyethylene compared with metallic heads and to reduce fracture risk compared with ceramic heads. Severe scratches have been reported on OxZr heads in patients undergoing revision for instability, but whether these scratches contribute to increased acetabular polyethylene wear remains unclear. QUESTIONS/PURPOSES: (1) How is the polyethylene of the acetabular liner affected by damage on the opposing OxZr head? (2) How does damage to the head affect the degree of polyethylene wear? METHODS: We assessed damage and deformation on all retrieved highly crosslinked liners that had articulated against OxZr heads collected at one institution between 2006 and 2013. Two observers used a visual subjective scoring system to assess polyethylene damage on the surface of the 42 retrieved liners. Polyethylene components were also laser scanned to measure dimensional changes to the liner. These outcomes were compared with the severity of scratching on the surface of the articulating OxZr head. We also used a 12-station hip simulator to measure wear over five million cycles (MCs) of pristine liners articulating against nine retrieved OxZr heads with varying degrees of scratching representing a spectrum of little to severe damage and three retrieved ceramic heads with severe metal transfer. RESULTS: Seventeen of the OxZr heads showed severe damage, of which 14 heads had been revised for dislocation. The retrieved liners that had articulated with these heads had greater damage scores for abrasion (mean score 0.4 versus 1.6; p = 0.008) and embedded debris (mean score 0.4 versus 1.4; p = 0.006) compared with liners that had articulated with less damaged heads. Four severely damaged OxZr heads wore at a higher rate than the others in the study with weight loss of 37.7 mg, 30.0 mg, 14.4 mg, and 2.6 mg after the first MC and a steady increase through testing to 5 MCs. Conversely, neither OxZr heads with less damage nor ceramic heads with severe metal transfer produced appreciable wear. CONCLUSIONS: Surface scratching of OxZr heads from recurrent dislocation and reduction maneuvers leads to increased wear of the crosslinked polyethylene used as a bearing surface. CLINICAL RELEVANCE: Patients in whom such instability occurs in the presence of an OxZr head should be followed closely for the possibility of more severe wear.

Total Hip Arthroplasty Patients With Fixed Spinopelvic Alignment Are at Higher Risk of Hip Dislocation.

BACKGROUND: Sitting radiographs have been used as a pre-operative tool to plan patient-specific total hip arthroplasty (THA) component position that would improve hip stability. Previous work has demonstrated that spinal mobility may impact functional acetabular position when seated. We sought to determine whether patients who dislocate following THA have different sitting spinopelvic alignment or acetabular component orientation compared to patients who did not dislocate. METHODS: A consecutive series of 1000 patients underwent post-operative low-dose biplanar spine-to-ankle lateral radiographs in standing and sitting positions 1 year following THA. Twelve patients (1% of all patients) experienced hip dislocation. Patients were categorized as having normal lumbar spines (without radiographic arthrosis) or as having lumbar multi-level degenerative disc disease. Measurements of spinopelvic alignment parameters (including sacral slope, lumbar lordosis, and proximal femur angles) and acetabular component orientation in sitting position (functional inclination and functional anteversion) were performed. RESULTS: Patients who dislocated had significantly less spine flexion, less change in pelvic tilt, and more hip flexion from standing to sitting positions compared to patients with normal spines. In sitting position, dislocators had acetabular components with less functional inclination and less functional anteversion. CONCLUSION: This study demonstrates that patients with fixed spinopelvic alignment from standing to sitting position are at higher risk of hip dislocation. Imaging patients from standing to sitting position using this technique can provide valuable information on whether a patient has fixed spinopelvic alignment with postural changes and is therefore at higher risk of dislocation.

Failure After Modern Total Knee Arthroplasty: A Prospective Study of 18,065 Knees.

BACKGROUND: We sought is to determine the mechanism of failure among primary total knee arthroplasties (TKAs) performed at a single high-volume institution by asking the following research questions: (1) What are the most common failure modes for modern TKA designs? and (2) What are the preoperative risk factors for failure following primary TKA? METHODS: From May 2007 to December 2012, 18,065 primary TKAs performed on 16,083 patients at a single institution were recorded in a prospective total joint arthroplasty registry with a minimum of 5-year follow-up. We retrospectively reviewed patient charts to determine a cause of failure for primary TKAs. A cox proportional hazard model was used to determine the risk of revision surgery following primary TKA. RESULTS: The most common reasons for failure within 2 years after TKA were infection and stiffness. The multivariable regression identified the following preoperative risk factors for TKA failure: history of drug abuse (hazard ratio [HR] 4.68; P = 0.03), deformity/mechanical preoperative diagnosis (HR 3.52; P < .01), having a constrained condylar knee implant over posterior-stabilized implant (HR 1.99; P < .01), post-traumatic/trauma preoperative diagnosis (HR 1.78; P = .03), and younger age (HR 0.61; P < .01) CONCLUSION: These findings add to the growing data that primary TKAs are no longer failing from polyethylene wear-related issues. This study identified preoperative risk factors for failure of primary TKAs, which may be useful information for developing strategies to improve outcomes following TKA.

Polyethylene Damage Increases With Varus Implant Alignment in Posterior-stabilized and Constrained Condylar Knee Arthroplasty.

BACKGROUND: Implant malalignment in primary TKA has been reported to increase stresses placed on the bearing surfaces of implant components. We used a longitudinally maintained registry coupled with an implant retrieval program to consider whether preoperative, postoperative, or prerevision malalignment was associated with increased risk of revision surgery after TKA. QUESTIONS/PURPOSES: (1) What is the relative polyethylene damage on medial and lateral compartments of the tibial plateaus from revised TKAs? (2) Does coronal TKA alignment affect implant performance, such that TKAs aligned in varus are predisposed to experience increased polyethylene damage? (3) Does TKA alignment differ between postoperative and prerevision radiographs, and if so, what does this difference suggest about the mechanical contact load placed on a knee with a TKA? METHODS: Between 2007 and 2012, we performed 18,065 primary TKAs at our institution. By March 2016, 178 of those TKAs (1%) were revised at our center at least 2 years after primary surgery at our institution. Eighteen of those TKAs were excluded from this analysis because the tibial insert was not explanted during revision surgery, and four more were excluded because the inserts were lost or returned to the patient before the study was initiated, leaving 156 retrieved polyethylene tibial inserts (in 153 patients) revised at greater than 2 years after the primary TKA for this retrospective study. Patients who underwent revision surgery elsewhere were not considered here, since this study depended on having retrieved components. Polyethylene damage modes of burnishing, pitting, scratching, delamination, surface deformation, abrasion, and third-body debris were subjectively graded on a scale of 0 to 3 to reflect the extent and severity of each damage mode. On preoperative, postoperative, and prerevision radiographs, overall alignment, femoral alignment, and tibial alignment in the coronal plane were measured according to the protocol recommended by the Knee Society. RESULTS: Knees with more overall varus alignment after TKA had increased total damage on the retrieved tibial inserts (Spearman's rank correlation coefficients of -0.3 [95% CI, -0.4 to -0.1; p = 0.001]). We also found revised TKAs tended to drift back into greater varus before revision surgery, with a mean (SD) of 3.6° ± 4.0° valgus for postoperative alignment compared with 1.7° ± 6.4° prerevision (p = 0.04). CONCLUSIONS: Despite surgical efforts to achieve neutral mechanical alignment, remaining varus alignment places an increased contact load on the polyethylene articular surfaces. The drift toward further varus alignment postoperatively is consistent with the knee adduction moment remaining high after surgery. CLINICAL RELEVANCE: While we found a predisposition toward recurrence of the preoperative varus deformity, we did not find increased medial as opposed to lateral polyethylene damage, which may be explained by the curve-on-curve toroidal design of the articulating surfaces of the TKA implants in this study.

MRI, Retrieval Analysis, and Histologic Evaluation of Adverse Local Tissue Reaction in Metal-on-Polyethylene Total Hip Arthroplasty.

BACKGROUND: The severity and location of adverse local tissue reaction (ALTR) seen in metal-on-polyethylene total hip arthroplasty (THA) is not well described. METHODS: We retrospectively reviewed the records of patients who underwent a revision THA using our biomechanics database. We included all patients who underwent revision surgery for the diagnosis of ALTR with THA implants that had modularity solely at the head-neck junction and excluded patients with implant modularity at sites other than the head-neck junction. Magnetic resonance imaging (MRI) was evaluated by a fellowship-trained radiologist who specializes in evaluating metal artifact reducing MRI sequences to quantify the ALTR lesions. Histology was evaluated for findings of ALTR using the Campbell score. RESULTS: We identified 11 patients in the database. Eight patients had an MRI ALTR grade of severe and 7 did based on the histology score. The mean synovial volume was 218,658 mm3 (range 23,461-451,435 mm3) with a mean maximal synovial thickness of 15.3 mm (range 3-34.3 mm). A disruptive infiltration of the abductors due to pseudocapsule invasion was seen in 67% of the patients with 3 not having abductor involvement. Mean preoperative cobalt and chromium levels were 5.4 ppb (range 1-12.3 ppb) and 1.1 ppb (range 0.6-2.4 ppb), respectively. CONCLUSION: Patients with ALTR from head-neck junction corrosion in metal-on-polyethylene THA may present with large pseudotumors that have previously been under appreciated. Mean preoperative serum cobalt and chromium ion levels remained relatively low, and MRI was an effective way to characterize the size and location of these lesions.

Crosslink Density Is Reduced and Oxidation Is Increased in Retrieved Highly Crosslinked Polyethylene TKA Tibial Inserts.

BACKGROUND: The wear resistance of highly crosslinked polyethylene depends on crosslink density, which may decrease with in vivo loading, leading to more wear and increased oxidation. The relationship among large and complex in vivo mechanical stresses, breakdown of the polyethylene crosslinks, and oxidative degradation is not fully understood in total knee arthroplasty (TKA). We wished to determine whether crosslink density is reduced at the articular surfaces of retrieved tibial inserts in contact areas exposed to in vivo mechanical stress. QUESTIONS/PURPOSES: (1) Does polyethylene crosslink density decrease preferentially in regions of the articular surface of thermally stabilized crosslinked polyethylene tibial components exposed to mechanical stress in vivo; and (2) what is the ramification of decreased crosslink density in TKA in terms of accompanying oxidation of the polyethylene? METHODS: From May 2011 to January 2014, 90 crosslinked polyethylene tibial components were retrieved during revision surgery as a part of a long-standing implant retrieval program. Forty highly crosslinked polyethylene tibial inserts (27 posterior-stabilized designs and 13 cruciate-retaining designs) retrieved for instability (15 cases), stiffness (11), infection (six), aseptic loosening (four), pain (two), and malposition (two) after a mean time of 18 months were inspected microscopically to identify loaded (burnished) and unloaded (unburnished) regions on the articular surfaces. Swell ratio testing was done according to ASTM F2214 to calculate crosslink density and infrared spectroscopy was used according to ASTM F2102 to measure oxidation. RESULTS: The region of the tibial insert influenced crosslink density. Loaded surface regions had a mean crosslink density of 0.19 (95% confidence interval [CI], 0.18-0.19) mol/dm3, lower than the other three regions (loaded subsurface, unloaded surface, and unloaded subsurface), which had crosslink densities of 0.21 (95% CI, 0.21-0.22; p < 0.01) mol/dm3. Peak oxidation levels were higher in loaded regions with a mean oxidation index (OI) of 0.67 (95% CI, 0.56-0.78) versus unloaded regions with a mean OI of 0.36 (95% CI, 0.27-0.45; p < 0.01). Peak oxidation levels were higher in annealed samples with a mean OI of 0.66 (95% CI, 0.52-0.81) versus remelted samples with a mean OI of 0.40 (95% CI, 0.34-0.47; p < 0.01). CONCLUSIONS: The results suggest that the crosslink density decreases and accompanying oxidation is driven predominantly by contact stress conditions. If crosslink density continues to decrease with continued loading over time, crosslinked polyethylene may not provide a clinical advantage over conventional polyethylene in the long term for TKA. Therefore, we will continue to collect longer term retrievals to evaluate mechanical property changes in crosslinked polyethylenes. CLINICAL RELEVANCE: Although we found a decrease in crosslink density and increase in oxidation in the tibial inserts, the degree of oxidation does not suggest, for now, a reason for concern in these early retrievals. The OI values of the tibial inserts in this study were lower than the critical oxidation level (OI > 3) reported in the literature where polyethylene may lose mechanical properties and have the compromised ability to withstand mechanical loading.