Michael D. Kurdziel

Analysis of retrieved agility total ankle arthroplasty systems.

Background: First generation total ankle arthroplasty (TAA) systems showed high rates of failure. The Agility™ (DePuy, Warsaw, IN) TAA system, a second generation design, had improved outcomes; however, implant failure due to loosening of the metallic components persisted. The purpose of this study was to analyze the damage modes and radiographic mode(s) of failure observed in retrieved Agility™ TAA. Materials and Methods: Ten devices were collected and each component was analyzed for common damage modes using microscopy. Clinical damage was analyzed with postoperative implant and preoperative revision procedure radiographs. Results: Analyses revealed damage/wear to retrieved components, including abrasion, dishing, and pitting. These third-body wear particles may be a precursor to wear debris induced osteolysis which could cause component loosening. Seven TAA systems were removed due to loosening or subsidence, suggesting component damage/wear may lead to clinically observed component loosening. Retrieval analysis indicated the polyethylene experiences edge loading, resulting in increased contact stresses to polyethylene in the primary articulation region and wear. Conclusion: Since poor clinical outcomes have been associated with component instability and osteolysis, analyzing retrieved components wear and damage may be an important step toward improving implant design, thereby decreasing wear debris induced osteolysis and improving clinical outcomes. Level of Evidence: IV, Case Series

Characterization of daptomycin-loaded antibiotic cement.

Antibiotics are commonly mixed with polymethylmethacrylate (PMMA) cement to suppress severe periprosthetic infections associated with total joint arthroplasty. The relationship between antibiotic concentration and the resulting elution kinetics remains unclear. The purpose of this study was to characterize the release of daptomycin from PMMA cement and the subsequent effects on mechanical properties.Varying concentrations of daptomycin and tobramycin were vacuum mixed in commercially available PMMA and subjected to an in vitro elution period. High-performance liquid chromatography was used to quantify the concentration of the amount of daptomycin eluted at predetermined time points. Samples were subjected to compressive loading to analyze the effect of antibiotic concentration on cement mechanical properties. Daptomycin elution increased when initial tobramycin concentration was increased. Furthermore, the addition of antibiotics increased the compressive strength of the cement in the postelution period. The binary addition of tobramycin with daptomycin antibiotics modifies the elution and mechanical properties of PMMA bone cement. Based on the findings of our study, 2 g of daptomycin and 3.6 g of tobramycin per 40-g packet of cement should be used to promote daptomycin elution without sacrificing PMMA mechanical properties.

Biomechanical Characterization of a Model of Noninvasive, Traumatic Anterior Cruciate Ligament Injury in the Rat

The onset of post-traumatic osteoarthritis (PTOA) remains prevalent following traumatic joint injury such as anterior cruciate ligament (ACL) rupture, and animal models are important for studying the pathomechanisms of PTOA. Noninvasive ACL injury using the tibial compression model in the rat has not been characterized, and it may represent a more clinically relevant model than the common surgical ACL transection model. This study employed four loading profiles to induce ACL injury, in which motion capture analysis was performed, followed by quantitative joint laxity testing. High-speed, high-displacement loading repeatedly induces complete ACL injury, which causes significant increases in anterior-posterior and varus laxity. No loading protocol induced valgus laxity. Tibial internal rotation and anterior subluxation occurs up to the point of ACL failure, after which the tibia rotates externally as it subluxes over the femoral condyles. High displacement was more determinative of ACL injury compared to high speed. Low-speed protocols induced ACL avulsion from the femoral footprint whereas high-speed protocols caused either midsubstance rupture, avulsion, or a combination injury of avulsion and midsubstance rupture. This repeatable, noninvasive ACL injury protocol can be utilized in studies assessing PTOA or ACL reconstruction in the rat.

The impact of rotator cuff deficiency on structure, mechanical properties, and gene expression profiles of the long head of the biceps tendon (LHBT): Implications for management of the LHBT during primary shoulder arthroplasty

The long head of the biceps tendon (LHBT) occupies a unique proximal intra‐articular and distal extra‐articular position within the human shoulder. In the presence of a rotator cuff (RC) tear, the LHBT is recruited into an accelerated role undergoing potential mechanical and biochemical degeneration. Intra‐articular sections of the LHBT were harvested during primary shoulder arthroplasty from patients with an intact or deficient RC. LHBTs were stained (H&E, Alcian Blue) and subjected to histologic analysis using the semiquantitative Bonar scale and measurement of collagen orientation. LHBTs (n = 12 per group) were also subjected to gene‐expression analyses via an RT2‐PCR Profiler Array quantifying 84 genes associated with cell‐cell and cell‐matrix interactions. LHBTs (n = 18 per group) were biomechanically tested with both stress‐relaxation and load‐to‐failure protocols and subsequently modeled with the Quasilinear Viscoelastic (QLV) and Structural‐Based Elastic (SBE) models. While no histologic differences were observed, significant differences in mechanical testing, and viscoelastic modeling parameters were found. PCR arrays identified five genes that were differentially expressed between RC‐intact and RC‐deficient LHBT groups. LHBTs display signs of pathology regardless of RC status in the arthroplasty population, which may be secondary to both glenohumeral joint arthritis and the additional mechanical role of the LHBT in this population.

Three-dimensional computed tomography measurement accuracy of varying Hill-Sachs lesion size

BACKGROUND The glenoid track concept has been proposed to correlate shoulder stability with bone loss. Accurate assessment of Hill-Sachs lesion size preoperatively may affect surgical planning and postoperative outcomes; however, no measurement method has been universally accepted. This study aimed to assess the accuracy and reliability of measuring Hill-Sachs lesion sizes using 3-dimensional (3D) computed tomography (CT). METHODS Nine polyurethane humerus bone substitutes were used to create Hill-Sachs lesions of varying sizes with a combination of lesion depth (shallow, intermediate, and deep) and width (small, medium, and large). Specimens were scanned with a clinical CT scanner for size measurements and a micro-CT scanner for measurement of true lesion size. Six evaluators repeated measurements twice in a 2-week interval. Scans were measured by use of 3D CT reconstructions for length, width, and Hill-Sachs interval and with use of 2D CT for depth. The interclass correlation coefficient evaluated interobserver and intraobserver variability and percentage error, and Student t-tests assessed measurement accuracy. RESULTS Interclass correlation coefficient reliability demonstrated strong agreement for all variables measured (0.856-0.975). Percentage error between measured length and measured depth and the true measurement significantly varied with respect to both lesion depth (P = .003 and P = .005, respectively) and lesion size (P = .049 and P = .004, respectively). DISCUSSION AND CONCLUSIONS The 3D CT imaging is effective and reproducible in determining lesion size. Determination of Hill-Sachs interval width is also reliable when it is applied to the glenoid track concept. Measured values on 3D and 2-dimensional imaging using a conventional CT scanner may slightly underestimate true measurements.

Neer Award 2017: wear rates of 32-mm and 40-mm glenospheres in a reverse total shoulder arthroplasty wear simulation model

BACKGROUND Larger glenosphere diameters have been used recently to increase prosthesis stability and impingement-free range of motion in reverse total shoulder arthroplasty. The goal of this study was to evaluate the rate of polyethylene wear for 32-mm and 40-mm glenospheres. METHODS Glenospheres (32 mm and 40 mm, n = 6/group) and conventional polyethylene humeral liners underwent a 5-million cycle (MC) wear simulation protocol. Abduction-adduction and flexion-extension motion profiles were alternated every 250,000 cycles. At each interval, mass loss was determined and converted to volume loss and wear rate. At 0, 2.5 MC, and 5 MC, liners were imaged using micro-computed tomography to determine surface deviation. White light interferometry was performed on liners and glenospheres at 0 and 5 MC to quantify surface roughness. Wear particle morphology was characterized by environmental scanning electron microscopy. RESULTS Total volume loss was significantly higher in 40-mm liners from 1.5 MC onward (P < .05). Overall, volumetric wear rate was significantly higher in 40-mm liners compared with 32-mm glenospheres (81.7 ± 23.9 mm3/MC vs. 68.0 ± 18.9 mm3/MC; P < .001). However, micro-computed tomography surface deviation results demonstrated increased linear penetration on 32-mm glenospheres compared with 40-mm glenospheres (0.36 ± 0.03 µm vs. 0.28 ± 0.01 µm; P = .002). Surface roughness measurements showed no difference for liners; however, increased roughness was noted for 40-mm glenospheres at 5 MC compared with 32 mm (P < .05). CONCLUSION Larger glenospheres underwent significantly greater polyethylene volume loss and volumetric wear rates, whereas smaller glenospheres underwent greater polyethylene surface deviations. The enhanced stability provided by larger glenospheres must be weighed against the potential for increased polyethylene wear.

Quantitative evaluation of retrieved reverse total shoulder arthroplasty liner surface deviation and volumetric wear: QUANTITATIVE EVALUATION OF HUMERAL LINER WEAR

Polyethylene wear is a known complication in total joint arthroplasty, however, in vivo wear rates in reverse total shoulder arthroplasty (RTSA) remain largely unknown. This study aimed to quantify volumetric and surface deviation changes in retrieved RTSA humeral liners using a novel micro‐computed tomography (μCT)‐based technique. After IRB‐approval, 32 humeral liners (single manufacturer and model) with term‐of‐service greater than 90 days were analyzed. Clinical demographics and surgical data were collected via chart review. Unworn liners were used as geometric controls. Retrieved and unworn liners underwent μCT scanning. Retrieved liner volumes were isolated, co‐registered to controls of matching geometry, and surface deviations of the articulation surface and rim were computed. Differences in total volume loss (TVL), volumetric wear rate (VWR), and surface deviation were reported. Semi‐quantitative grading evaluated rim damage presence and severity. Mean term‐of‐service for all liners was 2.07 ± 1.33 years (range: 0.30–4.73). Mean TVL and VWR were 181.3 ± 208.2 mm3 and 114.5 ± 160.3 mm3/year, respectively. Mean articulation and rim surface deviations were 0.084 ± 0.065 and 0.177 ± 0.159 mm, respectively. Articulation surface deviation was positively correlated to term‐of‐service. Rim damage was present on 63% of liners and correlated significantly to rim surface deviation. This study reports in vivo wear rates of retrieved RTSA implants. Our results demonstrate volumetric and articulation surface wear in select RTSA liners that is correlated to term‐of‐service. Calculation of in vivo wear rates can help bridge the gap between clinical outcomes and experimental models such as wear simulations and computational models.

Characterization of doxycycline-loaded calcium phosphate cement: implications for treatment of aneurysmal bone cysts

Percutaneous doxycycline for treatment for aneurysmal bone cysts (ABCs) has been shown to decrease recurrence rates, however, this requires multiple procedures, includes the risks soft tissue necrosis, and does not provide structural support. We propose utilizing curettage with doxycycline-loaded calcium phosphate cement. This study aimed to evaluate the elution profile of doxycycline from calcium phosphate cement. Calcium phosphate cement underwent an in vitro elution protocol evaluating doxycycline concentrations of 0, 5, 10, and 15 mg/mL. Eluted concentrations were quantified utilizing high performance liquid chromatography at predetermined time points over 96 h. Compressive strength was evaluated both pre- and post-elution and micro-computed tomography was utilized to assess changes in cement porosity. Cement with 15 mg/mL of doxycycline maintained a higher average concentration (mean, 95% confidence intervals) (14.5 µg/mL [9.2–19.9 µg/mL]) compared to both 5 mg/mL (5.8 µg/mL [3.1–8.6 µg/mL]; P < 0.001) and 10 mg/mL (8.4 ± µg/mL [6.0–10.9 µg/mL]; P < 0.001). Ultimate stress significantly decreased between pre- and post-elution samples for 10 mg/mL (P= 0.001) and 15 mg/mL (P = 0.004) groups. This study demonstrated a dose-dependent response in ultimate strength and compressive modulus with addition of doxycycline to calcium phosphate cement.

Exposure of articular chondrocytes to wear particles induces phagocytosis, differential inflammatory gene expression, and reduced proliferation

The production of wear debris particulate remains a concern due to its association with implant failure through complex biologic interactions. In the setting of unicompartmental knee arthroplasty (UKA), damage and wear of the components may introduce debris particulate into the adjacent, otherwise, healthy compartment. The purpose of this study was to investigate the in vitro effect of polymeric and metallic wear debris particles on cell proliferation, extracellular matrix regulation, and phagocytosis index of normal human articular chondrocytes (nHACs). In culture, nHACs were exposed to both cobalt-chromium-molybdenum (CoCrMo) and polymethyl-methacrylate (PMMA) wear debris particulate for 3 and 10 days. At 3 days, no significant difference in cell proliferation was found between control cells and cells exposed to both CoCrMo or PMMA particles. However, cell proliferation was significantly decreased for CoCrMo exposed nHACs at both 6 (P < 0.001) and 10 days (P < 0.001) and PMMA at 10 days (P < 0.001). Target gene expression displayed both a time- and material-dependent response to CoCrMo and PMMA particles. Significant differences in COL10A1, ACAN, VCAN, IL-1β, TNF-α, MMP3, ADAMTS1, CASP3, and CASP9 regulation were found between CoCrMo and PMMA exposed nHACs at day 3 with gene regulation returning to near baseline at 10 days. Results from our study indicate a role of wear debris induced cartilage degeneration after exposure to polymeric and metallic wear debris particulate, suggesting an additional pathway of cartilage breakdown, potentially manifesting in traditional clinical symptoms.Graphical Abstract

Complete dissociation of a dual mobility acetabular liner secondary to repeat dislocation

D islocation after total hip arthroplasty (THA) remains a challenging problem despite advances in implant design and surgical technique. Treatment options for this problem range from hip immobilization to revision of malpositioned components. Implants using dual mobility articulation have reported good outcomes while reducing the risk of prosthetic dislocation in higher risk patients. The concept of dual mobility THA was first introduced by Bousquet in 1974. It features a mobile polyethylene liner that is locked onto a ceramic or a metal head, articulating with an acetabular shell. Early patient outcomes from the use of dual mobility cups for both implant instability and during revision of failed metal-on-metal hip arthroplasty or resurfacing devices have been promising. Dislocation of a dual mobility hip is uncommon and typically occurs between the femoral head and the mobile liner. Recently, complete dissociation of a dual mobility liner from both the femoral head and the acetabular cup has been reported secondary to repeat dislocation, with dissociation of the mobile liner occurring only during attempted reduction. We report a patient who had complete dissociation of a mobile liner secondary to repeat dislocation in the setting of an infection, leading to the migration of the mobile liner out of the joint capsule. Prereduction radiographs confirmed that the mobile liner had completely dissociated before reduction. This is the first reported case in which complete dissociation of a mobile liner occurred independent of attempted reduction. The patient’s informed written consent was obtained for print and electronic publication of this case report. The authors report no actual or potential conflict of interest in relation to this article.