Tantalum Beads Research Articles

Greater Postoperative Biceps Tendon Migration Following Biceps Tenodesis Correlates with Lower Patient Reported Outcomes Scores

To assess the relationship between tendon migration, as measured by radiostereometric analysis (RSA), and patient-reported outcome measures (PROMs) following biceps tenodesis (BT); to determine the likelihood of achieving clinically significant outcomes (CSOs) following BT; and to identify factors that impact CSO achievement. Patients undergoing arthroscopic suprapectoral or open subpectoral BT at a single, high-volume academic medical center were prospectively enrolled. A tantalum bead sutured to the tenodesis construct was utilized as a radio-opaque marker. Biceps tendon migration was measured on calibrated radiographs at 12 weeks postoperatively. PROMs (Constant-Murley score [Constant], Single Assessment Numeric Evaluation [SANE], and Patient-Reported Outcomes Measurement Information Systemic-Upper Extremity [PROMIS-UE]) were collected preoperatively and at ≥2 years follow-up. Of 115 patients enrolled, 94 (82%) patients were included (median age=52 years and BMI=31.4 kg/m2). At a mean follow-up of 2.9 years, median Constant, SANE, and PROMIS-UE were 33 (interquartile range [IQR]=26-35), 90 (IQR=80-99), and 47 (IQR=42-58), respectively. Median tantalum bead migration was 6.5 mm (IQR 1.8-13.8). There was a significant correlation between migration and Constant (r2 = 0.222, beta= -0.554, 95% CI -1.027- [-0.081], P=0.022), SANE (r2 = 0.238, beta= -0.198, 95% CI -0.337 - [-0.058], P=0.006) and PROMIS-UE (r2 = 0.233, beta= -0.406, 95% CI -0.707 - [-0.104], P=0.009). In univariable analysis, higher BMI was associated with achievement of substantial clinical benefit (SCB, unadj-OR=1.078, 95%CI 1.007-1.161, P=0.038). Greater bead migration was negatively associated with achievement of minimal clinically important difference (MCID, unadj-OR=0.969, 95% CI 0.943-0.993, P=0.014) and patient acceptable symptomatic state (PASS, unadj-OR 0.965, 95% CI 0.937-0.989, P=0.008) on all 3 instruments. A 1 cm-increase in tenodesed biceps tendon migration was associated with a decrease in Constant, SANE, and PROMIS-UE of 6, 2, and 4 points, respectively, at a mean of 2.9 years after surgery. Most patients achieved clinically significant outcomes (CSOs) for these PROMs by latest follow-up, and greater biceps tendon construct migration was negatively associated with the likelihood of CSO achievement. IV, retrospective case series.

Fully automated determination of robotic pedicle screw accuracy and precision utilizing computer vision algorithms

Historically, pedicle screw accuracy measurements have relied on CT and expert visual assessment of the position of pedicle screws relative to preoperative plans. Proper pedicle screw placement is necessary to avoid complications, cost and morbidity of revision procedures. The aim of this study was to determine accuracy and precision of pedicle screw insertion via a novel computer vision algorithm using preoperative and postoperative computed tomography (CT) scans. Three cadaveric specimens were utilized. Screw placement planning on preoperative CT was performed according to standard clinical practice. Two experienced surgeons performed bilateral T2–L4 instrumentation using robotic-assisted navigation. Postoperative CT scans of the instrumented levels were obtained. Automated segmentation and computer vision techniques were employed to align each preoperative vertebra with its postoperative counterpart and then compare screw positions along all three axes. Registration accuracy was assessed by preoperatively embedding spherical markers (tantalum beads) to measure discrepancies in landmark alignment. Eighty-eight pedicle screws were placed in 3 cadavers’ spines. Automated registrations between pre- and postoperative CT achieved sub-voxel accuracy. For the screw tip and tail, the mean three-dimensional errors were 1.67 mm and 1.78 mm, respectively. Mean angular deviation of screw axes from plan was 1.58°. For screw mid-pedicular accuracy, mean absolute error in the medial–lateral and superior–inferior directions were 0.75 mm and 0.60 mm, respectively. This study introduces automated algorithms for determining accuracy and precision of planned pedicle screws. Our accuracy outcomes are comparable or superior to recent robotic-assisted in vivo and cadaver studies. This computerized workflow establishes a standardized protocol for assessing pedicle screw placement accuracy and precision and provides detailed 3D translational and angular accuracy and precision for baseline comparison.

Stable polyethylene inlay fixation and low polyethylene wear rate in fixed-bearing total knee arthroplasty at five to six years' follow-up.

Micromotion of the polyethylene (PE) inlay may contribute to backside PE wear in addition to articulate wear of total knee arthroplasty (TKA). Using radiostereometric analysis (RSA) with tantalum beads in the PE inlay, we evaluated PE micromotion and its relationship to PE wear. A total of 23 patients with a mean age of 83 years (77 to 91), were available from a RSA study on cemented TKA with Maxim tibial components (Zimmer Biomet). PE inlay migration, PE wear, tibial component migration, and the anatomical knee axis were evaluated on weightbearing stereoradiographs. PE inlay wear was measured as the deepest penetration of the femoral component into the PE inlay. At mean six years' follow-up, the PE wear rate was 0.08 mm/year (95% confidence interval 0.06 to 0.09 mm/year). PE inlay external rotation was below the precision limit and did not influence PE wear. Varus knee alignment did not influence PE wear (p = 0.874), but increased tibial component total translation (p = 0.041). The PE inlay was well fixed and there was no relationship between PE stability and PE wear. The PE wear rate was low and similar in the medial and lateral compartments. Varus knee alignment did not influence PE wear.

Enhancing Single-Plane Fluoroscopy: A Self-Calibrating Bundle Adjustment for Distortion Modeling.

Single-plane fluoroscopy systems with image intensifiers remain commonly employed in a clinical setting. The imagery they capture is vulnerable to several types of geometric distortions introduced by the system's components and their assembly as well as interactions with the local and global magnetic fields. In this study, the application of a self-calibrating bundle adjustment is investigated as a method to correct geometric distortions in single-plane fluoroscopic imaging systems. The resulting calibrated imagery is then applied in the quantitative analysis of diaphragmatic motion and potential diagnostic applications to hemidiaphragm paralysis. The calibrated imagery is further explored and discussed in its potential impact on areas of surgical navigation. This work was accomplished through the application of a controlled experiment with three separate Philips Easy Diagnost R/F Systems. A highly redundant (~2500 to 3500 degrees-of-freedom) and geometrically strong network of 18 to 22 images of a low-cost target field was collected. The target field comprised 121 pre-surveyed tantalum beads embedded on a 25.4 mm × 25.4 mm acrylic base plate. The modeling process resulted in the estimation of five to eight distortion coefficients, depending on the system. The addition of these terms resulted in 83-85% improvement in terms of image point precision (model fit) and 85-95% improvement in 3D object reconstruction accuracy after calibration. This study demonstrates significant potential in enhancing the accuracy and reliability of fluoroscopic imaging, thereby improving the overall quality and effectiveness of medical diagnostics and treatments.

ACCURACY OF MEASURING IN VIVO SYNDESMOSIS JOINT KINEMATICS DURING LEVEL GAIT

AbstractObjectivesThe syndesmosis joint, located between the tibia and fibula, is critical to maintaining the stability and function of the ankle joint. Damage to the ligaments that support this joint can lead to ankle instability, chronic pain, and a range of other debilitating conditions. Understanding the kinematics of a healthy joint is critical to better quantify the effects of instability and pathology. However, measuring this movement is challenging due to the anatomical structure of the syndesmosis joint. Biplane Video Xray (BVX) combined with Magnetic Resonance Imaging (MRI) allows direct measurement of the bones but the accuracy of this technique is unknown. The primary objective is to quantify this accuracy for measuring tibia and fibula bone poses by comparing with a gold standard implanted bead method.MethodsWritten informed consent was given by one participant who had five tantalum beads implanted into their distal tibia and three into their distal fibula from a previous study. Three-dimensional (3D) models of the tibia and fibula were segmented (Simpleware Scan IP, Synopsis) from an MRI scan (Magnetom 3T Prisma, Siemens). The beads were segmented from a previous CT and co-registered with the MRI bone models to calculate their positions. BVX (125 FPS, 1.25ms pulse width) was recorded whilst the participant performed level gait across a raised platform. The beads were tracked, and the bone position of the tibia and fibula were calculated at each frame (DSX Suite, C-Motion Inc.). The beads were digitally removed from the X-rays (MATLAB, MathWorks) allowing for blinded image-registration of the MRI models to the radiographs. The mean difference and standard deviation (STD) between bead-generated and image-registered bone poses were calculated for all degrees of freedom (DOF) for both bones.ResultsThe absolute mean tibia and fibula bone position differences (Table 1) between the bead and BVX poses were found to be less than 0.5 mm for both bones. The bone rotation differences were found to be less than 1° for all axes except for the fibula Z axis rotation which was found to be 1.46°. One study1 has reported the kinematics of the syndesmosis joint and reported maximum ranges of motion of 9.3°and translations of 3.3mm for the fibula. The results show that the accuracy of the methodology is sufficient to quantify these small movements.ConclusionsBVX combined with MRI can be used to accurately measure the syndesmosis joint. Future work will look at quantifying the accuracy of the talus to provide further understanding of normal ankle kinematics and to quantify the kinematics across a healthy population to act as a comparator for future patient studies.Declaration of Interest(b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

QUANTIFICATION OF THE ACCURACY OF IN VIVO TIBIOFEMORAL KINEMATICS CALCULATED USING MAGNETIC RESONANCE IMAGING AND BIPLANE VIDEO X-RAY

AbstractObjectivesInvestigate Magnetic Resonance Imaging (MRI) as an alternative to Computerised Tomography (CT) when calculating kinematics using Biplane Video X-ray (BVX) by quantifying the accuracy of a combined MRI-BVX methodology by comparing with results from a gold-standard bead-based method.MethodsWritten informed consent was given by one participant who had four tantalum beads implanted into their distal femur and proximal tibia from a previous study. Three-dimensional (3D) models of the femur and tibia were segmented (Simpleware Scan IP, Synopsis) from an MRI scan (Magnetom 3T Prisma, Siemens). Anatomical Coordinate Systems (ACS) were applied to the bone models using automated algorithms1. The beads were segmented from a previous CT and co-registered with the MRI bone models to calculate their positions. BVX (60 FPS, 1.25 ms pulse width) was recorded whilst the participant performed a lunge. The beads were tracked, and the ACS position of the femur and tibia were calculated at each frame (DSX Suite, C-Motion Inc.). The beads were digitally removed from the X-rays (MATLAB, MathWorks) allowing for blinded image-registration of the MRI models to the radiographs. The mean difference and standard deviation (STD) between bead-generated and image-registered bone poses were calculated for all degrees of freedom (DOF) for both bones. Using the principles defined by Grood and Suntay2, 6 DOF kinematics of the tibiofemoral joint were calculated (MATLAB, MathWorks). The mean difference and STD between these two sets of kinematics were calculated.ResultsThe absolute mean femur and tibia ACS position differences (Table 1) between the bead and image-registered poses were found to be within 0.75mm for XYZ, with all STD within ±0.5mm. Mean rotation differences for both bones were found to be within 0.2º for XYZ (Table 1). The absolute mean tibiofemoral joint translations (Table 1) were found to be within ±0.7mm for all DOF, with the smallest absolute mean in compression-distraction. The absolute mean tibiofemoral rotations were found to be within 0.25º for all DOF (Table 1), with the smallest mean was found in abduction-adduction. The largest mean and STD were found in internal-external rotation due to the angle of the X-rays relative to the joint movement, increasing the difficulty of manual image registration in that plane.ConclusionThe combined MRI-BVX method produced bone pose and tibiofemoral kinematics accuracy similar to previous CT results3. This allows for confidence in future results, especially in clinical applications where high accuracy is needed to understand the effects of disease and the efficacy of surgical interventions. Acknowledgements: This research was supported by the Engineering and Physical Sciences Research Council (EPSRC) doctoral training grant (EP/T517951/1).Declaration of Interest(b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

A combined experimental and finite element analysis of the human elbow under loads of daily living

Elbow trauma is often accompanied by a loss of independence in daily self-care activities, negatively affecting patients’ quality of life. Finite element models can help gaining profound knowledge about native human joint mechanics, which is crucial to adequately restore joint functionality after severe injuries. Therefore, a finite element model of the elbow is required that includes both the radio-capitellar and ulno-trochlear joint and is subjected to loads realistic for activities of daily living. Since no such model has been published, we aim to fill this gap.For comparison, 8 intact cadaveric elbows were subjected to loads of up to 1000 N, after they were placed in an extended position. At each load step, the displacement of the proximal humerus relative to the distal base plate was measured with optical tracking markers and the joint pressure was measured with a pressure mapping sensor.Analogously, eight finite element models were created based on subject-specific CT scans of the corresponding elbow specimens. The CT scans were registered to the positions of tantalum beads in the experiment. The optically measured displacements were applied as boundary conditions.We demonstrated that the workflow can predict the experimental contact pressure distribution with a moderate correlation, the experimental peak pressures in the correct joints and the experimental stiffness with moderate to excellent correlation. The predictions of peak pressure magnitude, contact area and load share on the radius require improvement by precise representation of the cartilage geometry and soft tissues in the model, and proper initial contact in the experiment.

A Radiostereometric Analysis of Tendon Migration After Arthroscopic and Mini-Open Biceps Tenodesis: Interference Screw Versus Single Suture Anchor Fixation.

Studies suggest that similar clinical results are achieved via arthroscopic and open biceps tenodesis (BT) techniques. To quantify the postoperative migration of the BT construct between arthroscopic suprapectoral BT (ASPBT) and open subpectoral BT (OSPBT) techniques via interference screw (IS) or single-suture suture anchor (SSSA) fixation using radiostereometric analysis. Cohort study; Level of evidence, 2. Distal migration of the biceps tendon after OSPBT with a polyetheretherketone IS, OSPBT with 1 SSSA, ASPBT with polyetheretherketone IS, and ASPBT with 2 SSSAs was measured prospectively. Patients with symptomatic biceps tendinopathy and preoperative patient-reported outcome measures (PROMs) including Constant-Murley subjective, Single Assessment Numeric Evaluation, or Patient-Reported Outcomes Measurement Information System-Upper Extremity scores were included. A tantalum bead was sutured on the proximal end of the long head of the biceps tendon before fixation of tendon tissue. Anteroposterior radiographs were performed immediately postoperatively, at 1 week, and at 3 months. Bead migration was measured, and preoperative PROMs were compared with those at latest follow-up. Of 115 patients, 94 (82%) were available for final follow-up. IS fixation yielded the least tendon migration with no difference between the open and arthroscopic approaches (4.31 vs 5.04 mm; P = .70). Fixation with 1 suture anchor demonstrated significantly greater migration than that achieved with an IS at both 1 week (6.47 vs 0.1 mm, 6.47 vs 1.75 mm, P < .001;) and 3 months (14.76 vs 4.31 mm, 14.76 vs 5.04 mm, P < .001) postoperatively. Two-suture anchor fixation yielded significantly greater migration than IS fixation at 1 week (7.02 vs 0.1 mm, P < .001; 7.02 vs 1.75 mm, P = .003) but not 3 months postoperatively (8.06 vs 4.31 mm, P = .10; 8.06 vs 5.04 mm, P = .07). Four patients with suture anchor fixation (3 patients in the OSPBT 1 SSSA group, 9.4%, and 1 patient in the ASPBT 2 SSSAs group, 3.8%) developed a Popeye deformity, whereas no Popeye deformities occurred in the IS groups. Mean 3-month bead migration in patients with and without a Popeye deformity was 60.8 and 11.2 mm, respectively (P < .0001). PROMs did not differ among groups at final follow-up. Interference screw fixation yielded the least tendon migration whether achieved arthroscopically or open. The available data indicated that fixation with 1 SSSA but not 2 SSSAs resulted in significantly greater migration than that achieved with an IS. Despite variations in tendon migration, PROMs were similar among all groups. When SSSAs are used, tendon migration may be minimized by using ≥2 anchors.

A prospective radiostereometric analysis of the stability of a metal-backed glenoid component/autograft composite in reverse shoulder arthroplasty.

Reverse total shoulder arthroplasty (rTSA) can be used in complex cases when the glenoid requires reconstruction. In this study, a baseplate with composite bone autograft and a central trabecular titanium peg was implanted, and its migration was assessed for two years postoperatively using radiostereometric analysis (RSA). A total of 14 patients who underwent a rTSA with an autograft consented to participate. Of these, 11 had a primary rTSA using humeral head autograft and three had a revision rTSA with autograft harvested from the iliac crest. The mean age of the patients was 66 years (39 to 81). Tantalum beads were implanted in the scapula around the glenoid. RSA imaging (stereographic radiographs) was undertaken immediately postoperatively and at three, six, 12, and 24 months. Analysis was completed using model-based RSA software. Outcomes were collected preoperatively and at two years postoperatively, including the Oxford Shoulder Score, the American Shoulder and Elbow Score, and a visual analogue score for pain. A Constant score was also obtained for the assessment of strength and range of motion. RSA analysis showed a small increase in all translation and rotational values up to six months postoperatively, consistent with settling of the implant. The mean values plateaued by 12 months, with no evidence of further migration. In four patients, there was significant variation outside the mean, which corresponded to postoperative complications. There was a significant improvement in the clinical and patient-reported outcomes from the preoperative values to those at two years postoperatively (p < 0.001). These findings show, using RSA, that a glenoid baseplate composite of a trabecular titanium peg with autograft stabilizes within the glenoid about 12 months after surgery, and reinforce findings from a previous study of this implant/graft with CT scans at two years postoperatively, indicating that this type of structural composite results in sound early fixation.

Migration Characteristics of a Proximally Coated Collarless Femoral Stem: A Prospective 2-Year Radiostereometric Analysis Study.

Collared femoral stems have been considered to reduce the risk of early subsidence over collarless stems. However, with advances in material technology, new surface treatments have been introduced into cementless stem design to enhance primary fixation and long-term stability. This study aims to analyze the early migration behaviors of a proximally coated collarless femoral stem and cementless acetabular component and compare the outcomes with commercially available cementless stems and acetabular cups. A total of 24 patients (25 hips) undergoing total hip arthroplasty were recruited and followed up for 2years. All patients received a Masterloc femoral stem (Medacta International SA, Castel San Pietro, Switzerland) and an Mpact acetabular component (Medacta International SA, Castel San Pietro, Switzerland) with tantalum beads embedded during the operation. Radiographs for radiostereometric analysis were taken immediately postsurgery, 6-months, 1-year, and 2-years postoperatively. The median condition number for this study was 59. The median stem subsidence was-0.08 mm (-2.47 to 0.40) at 2 years. The median cup subsidence was-0.03 mm (-0.38 to 0.57) at 2 years. The migration of the Masterloc stem was less than that of other cementless collarless, as well as collared stems, as reported in literature. This study has demonstrated the high stability and fixation provided with the use of a collarless cementless stem. The subsidence seen in both this cementless femoral stem and acetabular cup at 2 years postoperative was below the range reported in literature for cementless collarless and collared stems.

Paper 51: A Radiostereometric Analysis of Tendon Migration following Arthroscopic and Mini-Open Biceps Tenodesis: Interference Screw confers Greater Construct Stability than All-Suture Suture Anchor Fixation, with No Difference in Patient-Reported Outcomes

Objectives: To quantify the postoperative migration of the BT construct between arthroscopic suprapectoral (ASPBT) and open subpectoral (OSPBT) techniques via interference screw (IS) or all-suture anchor with a single suture (SSSA) fixation with radiostereometric analysis (RSA). Methods: Distal migration of the biceps tendon following OSPBT with a Polyetheretherketone (PEEK) IS, OSPBT with one SSSA, ASPBT with PEEK IS, and ASPBT with two SSSAs was measured prospectively. Patients with symptomatic biceps tendinopathy and preoperative Patient-Reported Outcome Measures (PROMs) including CMS, SANE, or PROMIS-UE scores were included. A tantalum bead was sutured on the proximal end of the long head biceps tendon before fixation. AP radiographs were performed immediately postoperatively, 1 week, and 3 months. Bead migration was measured, and PROMs were compared. Results: Of 115 patients, 94 were available for final follow-up (82%). Average age was 52.1±10.5 years, and BMI was 30.8±5.4 kg/m2. There was no difference in tendon migration between OSPBT and ASPBT performed with an IS (P=0.70). OSPBT performed with one SSSA (21.70 mm) demonstrated significantly greater migration than ASPBT with IS (4.31mm, P&lt;0.001) and OSPBT with IS (5.04 mm, P&lt;0.001). Three patients (9.4%) who had OSPBT with one SSSA and one who had ASPBT with two SSSAs (3.8%), developed a Popeye deformity; none occurred in the IS groups. Mean 12-week bead migration in patients with versus without Popeye deformity was 60.8 mm and 11.2 mm, respectively (P&lt;0.0001). PROMs did not differ at final follow-up. Conclusions: ASPBT and OSPBT with IS fixation demonstrated the least tendon migration, while OSPBT with one SSSA yielded the most. Compared to IS, fixation with one, but not two, SSSAs resulted in significantly greater migration. Average bead migration following a Popeye deformity was 6.1cm. To minimize migration when using SSSAs, at least 2 sutures should be used with an interlocking pattern within the tendon. [Table: see text]

X‐Ray Visualized Synovial Fluid Carbon Dioxide Sensor for Early Detection of Prosthetic Hip Infections

AbstractA radiographically visualized implantable dissolved carbon dioxide (CO2) sensor is developed to non‐invasively detect and monitor hip infections. The sensor is based on a pH‐responsive hydrogel as the sensing material, immersed in a carbonate buffer contained in a capsule with a CO2‐permeable membrane. Dissolved CO2 decreases the buffer pH causing the polyacrylic acid‐based hydrogel to shrink. The hydrogel length is determined using plain radiography by measuring the movement of a radiodense tantalum bead embedded in the hydrogel with respect to a metal wire in the casing. The sensor shows a clear response in the range of 15–115 mm Hg CO2, with a 4.3 mm Hg precision at 15 mm Hg CO2 level and a 6.4‐hour response time. The hydrophobic CO2‐permeable membrane is impermeable to aqueous molecules rendering the CO2 measurement independent of the external solution pH, which can be measured with a separate X‐ray visualized sensor. Separating the sensor from the aqueous environment is also expected to reduce the potential for biofouling and increase longevity. In summary, the first dissolved gas sensor that can be visualized radiographically is described; it has potential applications in detecting and studying implant infection and local carbon tissue CO2 levels.

Low dose CT-based spatial analysis (CTSA) to measure implant migration after ceramic hip resurfacing arthroplasty (HRA): A phantom study.

Implant migration is a predictor of arthroplasty survivorship. It is crucial to monitor the migration of novel hip prostheses within premarket clinical investigations. RSA is the gold standard method, but requires calibrated radiographs using specialised equipment. A commercial computed tomography micromotion analysis solution is a promising alternative but is not yet available for use with monobloc ceramic implants. This study aimed to develop and validate a CT-based spatial analysis (CTSA) method for use with ceramic implants. A phantom study was undertaken to assess accuracy and precision. A ceramic hip resurfacing arthroplasty (HRA) and 20 tantalum beads were implanted into a synthetic hip model and mounted onto a 6-degree of freedom motion stage. The hip was repeatedly scanned with a low dose CT protocol, with imposed micromovements. Data were interrogated using a semiautomated technique. The effective radiation dose for each scan was estimated to be 0.25 mSv. For the head implant, precision ranged between 0.11 and 0.28 mm for translations and 0.34°-0.42° for rotations. For the cup implant, precision ranged between 0.08 and 0.11 mm and 0.19° and 0.42°. For the head, accuracy ranged between 0.04 and 0.18 mm for translations and 0.28°-0.46° for rotations. For the cup, accuracy ranged between 0.04 and 0.08 mm and 0.17° and 0.43°. This in vitro study demonstrates that low dose CTSA of a ceramic HRA is similar in accuracy to RSA. CT is ubiquitous, and this method may be an alternative to RSA to measure prosthesis migration.

FIVE-YEAR RSA RESULTS ASSESSING SUBSIDENCE AND ROTATION OF THE PARAGON HIP SYSTEM CONFIRMING IMPLANT STABILITY

Roentgen Stereophotogrammetric Analysis (RSA) is the gold standard for measuring implant micromotion thereby predicting implant loosening. Early migration has been associated with the risk of long-term clinical failure. We used RSA to assess the stability of the Australian designed cementless hip stem (Paragon TM) and now report our 5-year results.Fifty-three patients were prospectively and consecutively enrolled to receive a Paragon hip replacement. Tantalum beads were inserted into the bone as per RSA protocol and in the implant. RSA x-rays were taken at baseline 1–4 days post-surgery, at 6 weeks, 6 months, 12 months, 2 years, and 5 years. RSA was completed by an experienced, independent assessor.We reported the 2-year results on 46 hips (ANZJS 91 (3) March 2021 p398) and now present the 5-year results on 27 hips. From the 2-year cohort 5 patients had died, 8 patients were uncontactable, 1 patient was too unwell to attend, 5 patients had relocated too far away and declined. At 5 years the mean axial subsidence of the stem was 0.66mm (0.05 to 2.96); the mean rotation into retroversion was 0.49˚ (−0.78˚ to 2.09˚), rotation of the stem into valgus was −0.23˚ (−0.627˚ to 1.56˚). There was no detectable increase in subsidence or rotation between 6 weeks and 5 years. We compared our data to that published for the Corail cementless stem and a similar pattern of migration was noted, however greater rotational stability was achieved with the Paragon stem over a comparable follow-up period.The RSA results confirm that any minor motion of the Paragon cementless stem occurs in the first 6 weeks after which there is sustained stability for the next 5 years. The combination of a bi-planar wedge and transverse rectangular geometry provide excellent implant stability that is comparable to or better than other leading cementless stems.

Dynamic Radiographs Are Unreliable to Assess Arthrodesis Following Cervical Fusion: A Modeled Radiostereometric Analysis of Cervical Motion.

In vitro study. The purpose of the present study was to utilize an idealized cervical spine model to determine whether the parallax effect or changes in the position of the spine relative to the x-ray generator influence intervertebral motion parameters on dynamic cervical spine radiographs. The utility of flexion-extension radiographs in clinical practice remains in question due to poor reliability of the parameters utilized to measure motion. A cervical spine model with tantalum beads inserted into the tip of each spinous process was utilized to measure interspinous process distance (IPD) on plain radiographs. The model was then manipulated to alter the generator angle and generator distance, and the IPD was measured. The impact of individual and combined changes in these parameters on IPD was assessed. Multivariate analysis was performed to identify independent drivers of variability in IPD measurements. Isolated changes in the generator distance and generator angle and combined changes in these parameters led to significant changes in the measured IPD at each intervertebral level in neutral, flexion, and extension, which, in many instances, exceeded an absolute change of >1mm or >2mm. Multivariate analysis revealed that generator distance and generator angle are both independent factors impacting IPD measurements that have an additive effect. In an idealized cervical spine model, small clinically feasible changes in spine position relative to the x-ray generator produced substantial variability in IPD measurements, with absolute changes that often exceeded established cutoffs for determining the presence of pathologic motion across a fused segment. This study further reinforces that motion assessment on dynamic radiographs is not a reliable method for determining the presence of an arthrodesis unless these sources of variability can be consistently eliminated. 3.

Early Tensile Loading in Nonsurgically Treated Achilles Tendon Ruptures Leads to a Larger Tendon Callus and a Lower Elastic Modulus: A Randomized Controlled Trial

Background: Early tensile loading improves material properties of healing Achilles tendon ruptures in animal models and in surgically treated human ruptures. However, the effect of such rehabilitation in patients who are nonsurgically treated remains unknown. Hypothesis: In nonsurgically treated Achilles tendon ruptures, early tensile loading would lead to higher elastic modulus 19 weeks after the injury compared with controls. Study Design: Randomized controlled trial; Level of evidence, 2. Methods: Between October 2015 and November 2018, a total of 40 nonsurgically treated patients with acute Achilles tendon rupture were randomized to an early tensile loading (loaded group) or control group. Tantalum bead markers were inserted percutaneously into the tendon stumps 2 weeks after the injury to allow high-precision measurements of callus deformation under mechanical testing. The loaded group used a training pedal twice daily to produce a gradual increase in tensile load during the following 5 weeks. Both groups were allowed full weightbearing in an ankle orthosis and unloaded range of motion exercises. Patients were followed clinically and via roentgen stereophotogrammetric analysis and computed tomography at 7, 19, and 52 weeks after the injury. Results: The mean ± standard deviation elastic modulus at 19 weeks was 95.6 ± 38.2 MPa in the loaded group and 108 ± 45.2 MPa in controls (P = .37). The elastic modulus increased in both groups, although it was lower in the loaded group at all time points. Tendon cross-sectional area increased from 7 weeks to 19 weeks, from 231 ± 99.5 to 388 ± 142 mm2 in the loaded group and from 188 ± 65.4 to 335 ± 87.2 mm2 in controls (P < .001 for the effect of time). Cross-sectional area for the loaded group versus controls at 52 weeks was 302 ± 62.4 mm2 versus 252 ± 49.2 mm2, respectively (P = .03). Gap elongation was 7.35 ± 13.9 mm in the loaded group versus 2.86 ± 5.52 mm in controls (P = .27). Conclusion: Early tensile loading in nonsurgically treated Achilles tendon ruptures did not lead to higher elastic modulus in the healing tendon but altered the structural properties of the tendon via an increased tendon thickness. Registration: NCT0280575 (ClinicalTrials.gov identifier).

Paper 66: Radiostereometric Analysis of Biceps Tenodesis: A Prospective Comparison of All-Suture Anchor vs. Interference Screw, Arthroscopic and Mini-Open Techniques

Objectives:Recent studies suggest that similar results can be achieved via arthroscopic and open biceps tenodesis techniques. The purpose of this investigation was to quantify and compare the behavior of the biceps tenodesis construct in arthroscopic suprapectoral (ASPBT) and open subpectoral (OSPBT) techniques performed with either interference screw or suture anchor fixation, with radiostereometric analysis (RSA).Methods:A prospective cohort study was performed comparing migration of the biceps tendon after suprapectoral and subpectoral biceps tenodesis (BT) with Polyetheretherketone (PEEK) interference screw vs. all-suture suture anchor (ASSA) fixation. Patients with symptomatic biceps tendinopathy, anterior intertubercular groove tenderness, and positive biceps tension tests were included in the investigation. A tantalum bead, functioning as a radiostereometric marker, was sutured to the biceps tendon before final fixation of tendon tissue with either an interference screw or suture anchor. Following final fixation, AP radiographs were obtained intraoperatively. Follow up single view AP radiographs were obtained at one week and 3-months post-operatively. The distance from the center of the tantalum bead to the most proximal aspect of the humeral head was measured.Results:Of 128 patients enrolled, 120 (93.8%) were available for follow-up. The average age was 52.05±10.5 years, average BMI 30.8±5.4, and 29% of the patients were females. Groups were similar concerning patient demographics and concomitant procedures. At final follow up, there was no difference in distal migration between the OSPBT and ASPBT performed with an interference screw (4.31 vs. 4.02 mm, respectively, P=0.418). BT performed with a single ASSA demonstrated significantly more migration than BT performed with double ASSA (27.24 vs. 9.73 mm, respectively, P=0.005) and significantly more migration than the interference screw (27.24 26 vs. 4.31 mm, respectively, P<0.001). BT performed with the double ASSA technique demonstrated significantly more migration than the interference screw (9.73 vs. 4.02 mm, respectively, P=0.041). Three patients (11.1%) in the open single ASSA group, one patient in the arthroscopic double ASSA group (4.0%) suffered Popeye deformities. None of the patients in the interference screw cohorts experienced Popeye deformities.Conclusions:OSPBT and ASPBT demonstrate similar construct stability with use of interference screws as assessed by RSA. BT performed with single ASSA fixation resulted in more distal migration compared to double ASSA and interference screw fixation. Interference screw fixation provided more construct stability compared to a single and double ASSA, whether performed arthroscopically or with an open approach. These findings are the first in vivo results to characterize and quantify the biceps tenodesis construct in the post-operative period.Table 1.Patient Demographics and Other Characteristics.Table 2.Intraoperative Findings.Table 3.Tantalum bead migration at 1 week, 3 months and between 1 week and 3 months for arthroscopic and open techniques.Figure 1.Comparison of postoperative construct migration for the four studied techniques of biceps tenodesis measured by radiostereometric analysis.

Poster 143: Variation in Postoperative Tendon Migration Does Not Result in Significant Differences in Patient Reported Outcomes in Patients Undergoing Arthroscopic or Open Biceps Tenodesis Using All-Suture Suture Anchor and Interference Screw

Objectives:It is unknown whether the degree of biceps tendon migration influences patient outcomes following biceps tenodesis (BT). We aimed to assess the relationship between in vivo tendon migration and patient reported outcomes (PROs) following arthroscopic and open BT using suture anchor (SA) and interference screw (IS) constructs.Methods:One hundred twenty patients undergoing arthroscopic and open BT with SA or IS fixation at a single academic center were prospectively enrolled. Postoperative biceps tendon migration was measured via RSA, using a tantalum bead as a radio-opaque marker for tendon migration, with radiographs at 3- and 12-weeks postoperatively. PROs (Constant, SANE and PROMIS) were collected preoperatively, and at 6 months, 1 year, and 2 years. A Bonferroni correction was made for multiple comparisons.Results:Preoperative PRO completion was as follows: 20 (16.7%) ASES, 64 (53.3%) Constant, 96 (80.0%) SANE, and 108 (90.0%) PROMIS-UE. Patients with an open SA had a younger median age (48.4, IQR 38-55.4, P=0.014) and fewer dominant-sided surgeries (8/33 patients or 24.2%, P=0.003). PRO scores did not differ by groups for any questionnaire at all timepoints. There were no significant differences in likelihood of achieving MCID for ASES (P>0.99), Constant (P=0.87), SANE (P=0.68), or PROMIS-UE (P>0.99) between groups. In univariable analysis, no patient- or surgery-related factors served as significant predictors of achieving MCID at 6 months. Notably, neither RSA bead migration>3cm (Constant: OR= -0.54, 95%CI -2.53-1.45, P=0.60; SANE: collinear; PROMIS-UE: collinear) nor Popeye deformities (Collinear for all PROs) were negatively associated with likelihood of achieving MCID.Conclusions:Patient-reported outcomes are similar for patients undergoing arthroscopic BT via IS and SA, and open BT via IS and SA. No significant predictors of achieving MCID at 6 months were identified, including migration of the RSA bead. Biceps tendon migration was not significantly correlated with patient reported outcomes.Table 1.Demographics and PROs in Patients with biceps tenodesisFigure 1.Scatter plot of 6-Month change in Constant and Tantalum bead migration (R⁁2=0.03,P=0.38)Figure 2.Scatter plot of 6-Month change in SANE and Tantalum bead migration (R⁁2 = 0.004, P=0.78)Figure 3.Scatter plot of 6-Month change in PROMIS UE and Tantalum bead migration (R⁁2 = 0.01, P=0.42)

Full and Hollow Metal–Ceramic Beads Based on Tantalum and Alumina Produced by Alginate Gelation

Metal–ceramic composite beads containing different amounts of tantalum and alumina, particularly 100 vol% tantalum and 60–40 vol% tantalum/alumina, are produced by the alginate gelation process. Sodium alginate is used as gelling agent in the metal–ceramic suspension, while a calcium chloride solution is prepared to trigger the consolidation process. As in the previous study, different nozzles are used in order to obtain beads of three different sizes. The largest beads result to be hollow, and hence require a freeze‐drying step in order to prevent their collapse. After debinding in air, the composite beads are sintered at 1600 °C under inert atmosphere. Samples in green and sintered state are analyzed by digital light microscopy and scanning electron microscopy. Investigations by mercury intrusion porosimetry reveal that composite beads feature smaller pores compared to pure tantalum beads, as well as lower open porosity. The fracture strength is evaluated on single beads. Despite the high metallic content, both composite and pure tantalum beads show a brittle behavior. X‐ray powder diffraction (XRD) analyses reveal the presence of , , and alongside pure Ta in the samples prepared from pure tantalum. The impurities are due to reactions with Na, C, and Ca from the used additives.

Skull‐Brain Biomechanics of Headbutting. An XROMM Pilot Study on Goats

In humans, the coup‐contrecoup injury occurs opposite the site of impact when the brain meets the skull, causing intracerebral hemorrhage. It makes up a significant portion of traumatic brain injuries (TBI) and can often lead to neurodegeneration. Bighorn sheep and related bovids are known for their impressive headbutting rituals performed during the rut, the general belief being that these animals come away unharmed from these encounters. However, a recent immunohistochemical study revealed TBI in bighorn sheep and muskoxen in relation to headbutting. With a large gyrencephalic brain, repetitive headbutting, and a pathology pattern resembling early chronic traumatic encephalopathy in humans, bovids present themselves as a significant model for TBI. It is, however, uncertain whether bovids sustain coup‐contrecoup injury due to the oblong shape of their braincase and tight fit to the brain. We aimed to investigate whether cranial and neuroanatomical aspects of the bovid head anatomy contribute to TBI reduction, using goats as a model to measure brain movement independent of the skull upon impact.Four cadaveric goat heads were implanted with radiodense tantalum beads in the skull and brain. A weight‐drop system was used to create an impact within the field of view of a biplanar fluoroscopy system. The heads were CT scanned and the recording was reconstructed as an animated 3D model using x‐ray reconstruction of moving morphology (XROMM). The brain markers were tracked relative to each other to account for soft tissue deformation and marker migration and relative to the skull markers to account for brain movement. We were able to visualize how the brain moves in relation to the skull for the first time in bovids, providing a better understanding of skull‐brain biomechanics.