Distal Stem Research Articles

A SCARECROW-based regulatory circuit controls Arabidopsis thaliana meristem size from the root endodermis.

Main conclusionSCARECROW controls Arabidopsis root meristem size from the root endodermis tissue by regulating the DELLA protein RGA that in turn mediates the regulation ofARR1levels at the transition zone.Coherent organ growth requires a fine balance between cell division and cell differentiation. Intriguingly, plants continuously develop organs post-embryonically thanks to the activity of meristems that allow growth and environmental plasticity. In Arabidopsis thaliana, continued root growth is assured when division of the distal stem cell and their daughters is balanced with cell differentiation at the meristematic transition zone (TZ). We have previously shown that at the TZ, the cytokinin-dependent transcription factor ARR1 controls the rate of differentiation commitment of meristematic cells and that its activities are coordinated with those of the distal stem cells by the gene SCARECROW (SCR). In the stem cell organizer (the quiescent center, QC), SCR directly suppresses ARR1 both sustaining stem cell activities and titrating non-autonomously the ARR1 transcript levels at the TZ via auxin. Here, we show that SCR also exerts a fine control on ARR1 levels at the TZ from the endodermis by sustaining gibberellin signals. From the endodermis, SCR controls the RGA REPRESSOR OF ga1-3 (RGA) DELLA protein stability throughout the root meristem, thus controlling ARR1 transcriptional activation at the TZ. This guarantees robustness and fineness to the control of ARR1 levels necessary to balance cell division to cell differentiation in sustaining coherent root growth. Therefore, this work advances the state of the art in the field of root meristem development by integrating the activity of three hormones, auxin, gibberellin, and cytokinin, under the control of different tissue-specific activities of a single root key regulator, SCR.Electronic supplementary materialThe online version of this article (doi:10.1007/s00425-016-2471-0) contains supplementary material, which is available to authorized users.

CORR Insights(®): Is There a Benefit to Modularity in 'Simpler' Femoral Revisions?

Where Are We Now? Cementless distal fixation for femoral revision is an established and effective surgical technique [1, 3]. Failure of these femoral revisions at 10 years is typically less than 10%. However, the failure rate is correlated with the extent of femoral bone loss. When the femoral diaphyseal bone is damaged or of poor quality, failure of distal fixation increases [3]. Modular body femoral stems were developed to facilitate reconstruction of the most difficult femoral revisions. The modular construct allows surgeons to improve distal fixation with a wide range of distal implant sizes and shapes. After the distal segment is secured, the modular proximal body is attached; this step typically offers the surgeon many options in terms of lengths as well as the ability to control rotation independently from the distal stem portion. Potential advantages of modular-body revision stems include easier surgery, better restoration of leg length, and a lower likelihood of hip dislocation. The disadvantages include the potential for mechanical failure of the modular junction and increased cost. Some surgeons use modular body stems for femoral revisions that show only mild or moderate femoral bone loss. We must recognize that the present healthcare environment places a major emphasis on value-based care. In light of that, and given the disadvantages of modular body stems, should surgeons continue to use these components for milder femoral bone loss when nonmodular body stems have been proven to be effective for these defects? The authors addressed this question with a retrospective multicenter study. In their study, the authors also determined the relative value of modular and monoblock femoral components. While rerevisions were less common in patients treated with modular stems, intraoperative fractures were more common in this group. Modular stems also failed to show benefits in terms of the risk of dislocation or the likelihood of osseointegration. Because the authors could not conclude superiority of one technique they recommended avoidance of unnecessary modularity in patients that have lesser degrees of femoral bone loss. Where Do We Need To Go? The addition of patient satisfaction, function, and quality of life scores would be an important topic to address in future studies comparing these two techniques. This is illustrated in a similar retrospective single-center study that compared tapered modular body implants to extensively porous coated implants for femoral revision [2]. In that study, all patients were retrospectively administered WOMAC, SF-12, Oxford-12, UCLA activity score, and satisfaction scores. Richards and colleagues found that the tapered fluted modular body stems had better patient scores that supported the authors’ recommendation for these stems. Studies about our reconstructive techniques should measure and present patient-reported outcomes whenever possible; without those, an important angle in the value equation—the patient's perspective—cannot be inferred. How Do We Get There? As researchers, we should look for funding to perform prospective randomized trials. Specialty societies might be able to fund studies of this type. One of the main expenses of a prospective randomized study is the cost and time it takes to complete enrollment. This topic may be easier than some to investigate in the context of a randomized trial because a number of important elements already are in place: The implants are approved for use, most revision hip surgeons are facile with both approaches, and the patterns of bone loss that we are most interested in here (namely, mild to moderate bone loss) are common. The fact that the study by Huddleston and colleagues could not determine superiority of one implant over the other illustrates the need for a prospective randomized trial and provides much of the data for the power analysis, which is needed to design such a study. Although the current study has a lower level of evidence, it was the first to ask an important question regarding modular body stems: Should surgeons continue to use these components for milder femoral bone loss when nonmodular body stems are proven to be effective for these defects? Future researchers inspired by the current study—and “empowered” by it, as it were—now can design a study that will be able to answer the question more definitively.

Distal Airway Stem Cells are Essential for Lung Regeneration.

Distal Airway Stem Cells are Essential for Lung Regeneration.

Brassinazole resistant 1 (BZR1)-dependent brassinosteroid signalling pathway leads to ectopic activation of quiescent cell division and suppresses columella stem cell differentiation.

Previous publications have shown that BRI1 EMS suppressor 1 (BES1), a positive regulator of the brassinosteroid (BR) signalling pathway, enhances cell divisions in the quiescent centre (QC) and stimulates columella stem cell differentiation. Here, it is demonstrated that BZR1, a BES1 homologue, also promotes cell divisions in the QC, but it suppresses columella stem cell differentiation, opposite to the action of BES1. In addition, BR and its BZR1-mediated signalling pathway are shown to alter the expression/subcellular distribution of pin-formed (PINs), which may result in changes in auxin movement. BR promotes intense nuclear accumulation of BZR1 in the root tip area, and the binding of BZR1 to the promoters of several root development-regulating genes, modulating their expression in the root stem cell niche area. These BZR1-mediated signalling cascades may account for both the ectopic activation of QC cell divisions as well as the suppression of the columella stem cell differentiation. They could also inhibit auxin-dependent distal stem cell differentiation by antagonizing the auxin/WOX5-dependent pathway. In conclusion, BZR1-/BES1-mediated BR signalling pathways show differential effects on the maintenance of root apical meristem activities: they stimulate ectopic QC division while they show opposite effects on the differentiation of distal columella stem cells in a BR concentration- and BZR1-/BES1-dependent manner.

Management of femoral bone loss in revision total hip arthroplasty.

Femoral bone loss is frequently encountered during revision total hip arthroplasty. The quality and quantity of remaining bone helps determine the best method for reconstruction. Extensively porous-coated cylindrical stems or titanium fluted tapered devices that achieve fixation in the diaphysis have both demonstrated excellent long-term survivorship. Titanium fluted tapered stems with a modular proximal body allow for more accurate leg length, offset, and version adjustments independent of the distal stem which may optimise hip biomechanics. Intraoperative fractures are more common with cylindrical stems and subsidence with tapered stems, particularly monoblock designs and in both dislocation continues to be one of the most common postoperative complications. In salvage situations in which an ectatic femoral canal is unable to support an uncemented device, impaction bone grafting, allograft-prosthetic composite, or a segmental proximal femoral replacement may be required.

Highly specific gene silencing in a monocot species by artificial microRNAs derived from chimeric miRNA precursors.

SummaryArtificial microRNAs (amiRNAs) are used for selective gene silencing in plants. However, current methods to produce amiRNA constructs for silencing transcripts in monocot species are not suitable for simple, cost‐effective and large‐scale synthesis. Here, a series of expression vectors based on Oryza sativa MIR390 (OsMIR390) precursor was developed for high‐throughput cloning and high expression of amiRNAs in monocots. Four different amiRNA sequences designed to target specifically endogenous genes and expressed from OsMIR390‐based vectors were validated in transgenic Brachypodium distachyon plants. Surprisingly, amiRNAs accumulated to higher levels and were processed more accurately when expressed from chimeric OsMIR390‐based precursors that include distal stem–loop sequences from Arabidopsis thaliana MIR390a (AtMIR390a). In all cases, transgenic plants displayed the predicted phenotypes induced by target gene repression, and accumulated high levels of amiRNAs and low levels of the corresponding target transcripts. Genome‐wide transcriptome profiling combined with 5′‐RLM‐RACE analysis in transgenic plants confirmed that amiRNAs were highly specific.

Total hip replacement (THR) in non union of subtrochanteric fractures of the femur using distal fitting uncemented long stem

Total hip replacement (THR) in non union of subtrochanteric fractures of the femur using distal fitting uncemented long stem

Plant development. Genetic control of distal stem cell fate within root and embryonic meristems.

The root meristem consists of populations of distal and proximal stem cells and an organizing center known as the quiescent center. During embryogenesis, initiation of the root meristem occurs when an asymmetric cell division of the hypophysis forms the distal stem cells and quiescent center. We have identified NO TRANSMITTING TRACT (NTT) and two closely related paralogs as being required for the initiation of the root meristem. All three genes are expressed in the hypophysis, and their expression is dependent on the auxin-signaling pathway. Expression of these genes is necessary for distal stem cell fate within the root meristem, whereas misexpression is sufficient to transform other stem cell populations to a distal stem cell fate in both the embryo and mature roots.

Retrograde Totally Endovascular Recanalization of Occluded Mesenteric Arteries Through the Pancreaticoduodenal Arcade

Introduction Failed antegrade endovascular recanalization of occluded mesenteric arteries has traditionally been dealt with by open mesenteric bypass or by hybrid solutions. This article describes a totally endovascular retrograde approach for recanalization of occluded mesenteric arteries through the pancreaticoduodenal arcade. Surgical technique A femoral or brachial approach is used to gain access to the patent visceral artery. A micro-catheter is advanced in a retrograde fashion into the distal main stem of the occluded artery through the gastroduodenal artery and inferior pancreaticoduodenal arcade. A combination of .014″ and .018″ wires is used to cross the occlusion in a retrograde fashion and to land into the aortic lumen. The guide wire is then snared through the brachial access, establishing a through and through wire. A micro-catheter is then advanced on the through and through wire across the occlusion from the brachial access. The distal occluded artery is then catheterized by advancing a second wire parallel to the through and through wire. The remaining procedure is performed as a standard antegrade approach. Discussion The totally endovascular retrograde approach through collaterals can be helpful for the recanalization of mesenteric artery occlusions. This technically complex procedure should be reserved for cases in which the traditional antegrade approach has failed.

TCT-225 Dedicated Bifurcation BiOSS® Stent In The Treatment Of Distal Left Main Stem Stenosis – International Registry

TCT-225 Dedicated Bifurcation BiOSS® Stent In The Treatment Of Distal Left Main Stem Stenosis – International Registry

Activity and Loading Influence the Predicted Bone Remodeling Around Cemented Hip Replacements

Periprosthetic bone remodeling is frequently observed after total hip replacement. Reduced bone density increases the implant and bone fracture risk, and a gross loss of bone density challenges fixation in subsequent revision surgery. Computational approaches allow bone remodeling to be predicted in agreement with the general clinical observations of proximal resorption and distal hypertrophy. However, these models do not reproduce other clinically observed bone density trends, including faster stabilizing mid-stem density losses, and loss-recovery trends around the distal stem. These may resemble trends in postoperative joint loading and activity, during recovery and rehabilitation, but the established remodeling prediction approach is often used with identical pre- and postoperative load and activity assumptions. Therefore, this study aimed to evaluate the influence of pre- to postoperative changes in activity and loading upon the predicted progression of remodeling. A strain-adaptive finite element model of a femur implanted with a cemented Charnley stem was generated, to predict 60 months of periprosthetic remodeling. A control set of model input data assumed identical pre- and postoperative loading and activity, and was compared to the results obtained from another set of inputs with three varying activity and load profiles. These represented activity changes during rehabilitation for weak, intermediate and strong recoveries, and pre- to postoperative joint force changes due to hip center translation and the use of walking aids. Predicted temporal bone density change trends were analyzed, and absolute bone density changes and the time to homeostasis were inspected, alongside virtual X-rays. The predicted periprosthetic bone density changes obtained using modified loading inputs demonstrated closer agreement with clinical measurements than the control. The modified inputs also predicted the clinically observed temporal density change trends, but still under-estimated density loss during the first three postoperative months. This suggests that other mechanobiological factors have an influence, including the repair of surgical micro-fractures, thermal damage and vascular interruption. This study demonstrates the importance of accounting for pre- to postoperative changes in joint loading and patient activity when predicting periprosthetic bone remodeling. The study's main weakness is the use of an individual patient model; computational expense is a limitation of all previously reported iterative remodeling analysis studies. However, this model showed sufficient computational efficiency for application in probabilistic analysis, and is an easily implemented modification of a well-established technique.

WOX5–IAA17 Feedback Circuit-Mediated Cellular Auxin Response Is Crucial for the Patterning of Root Stem Cell Niches in Arabidopsis

In plants, the patterning of stem cell-enriched meristems requires a graded auxin response maximum that emerges from the concerted action of polar auxin transport, auxin biosynthesis, auxin metabolism, and cellular auxin response machinery. However, mechanisms underlying this auxin response maximum-mediated root stem cell maintenance are not fully understood. Here, we present unexpected evidence that WUSCHEL-RELATED HOMEOBOX 5 (WOX5) transcription factor modulates expression of auxin biosynthetic genes in the quiescent center (QC) of the root and thus provides a robust mechanism for the maintenance of auxin response maximum in the root tip. This WOX5 action is balanced through the activity of indole-3-acetic acid 17 (IAA17) auxin response repressor. Our combined genetic, cell biology, and computational modeling studies revealed a previously uncharacterized feedback loop linking WOX5-mediated auxin production to IAA17-dependent repression of auxin responses. This WOX5-IAA17 feedback circuit further assures the maintenance of auxin response maximum in the root tip and thereby contributes to the maintenance of distal stem cell (DSC) populations. Our experimental studies and in silico computer simulations both demonstrate that the WOX5-IAA17 feedback circuit is essential for the maintenance of auxin gradient in the root tip and the auxin-mediated root DSC differentiation.

Diagnosis of Premature Senescence of Cotton Using SPAD Value

Field experiments were conducted in 2011 on an experimental farm at the Cotton Research Insti-tute, Chinese Academy of Agricultural Sciences, Anyang, China. We conducted experiments with a “SPAD-502” meter to quickly measure the relative value of chlorophyll content in the leaf blades of field cotton. Our goal was to seek a suitable leaf on a cotton plant to diagnose senescence status of crop plants at later stages of growth. We began by studying the dynamic change rule of the dis-tal-most four leaves of the cotton plant during the entire growth period with two early-maturing cultivars (CCRI 36, CCRI 50) and two mid-maturing cultivars (CCRI 41, SCRC 28). We also examined the effect of different nitrogen and potassium fertilizer rates on SPAD values of the leaves of SCRC 28. Our results suggest that SPAD values of the 1st distal stem leaves from two early cultivars can act as good indicators of senescence status in the plants, if they are measured between 10 d before the boll-opening stage and 10 d after boll opening stage. Differences of SPAD values of the 3rd distal stem leaves of two mid-maturing cultivars measured between about 15 d before the boll opening stage and 15 d after the boll opening stage can also be used to measure senescence status in these cotton cultivars. The conclusion can be used for cotton producer to manage N fertilizer better at later growth stage.

Modular Femoral Tapered Revision Stems in Total Hip Arthroplasty

Background: Modular component options can assist the surgeon in addressing complex femoral reconstructions in total hip arthroplasty by allowing for customization of version control and proximal to distal sizing. We review the early clinical results of a single modular femoral revision system that offers 3 proximal body types, 5 distal stem geometries, and a wide range of offset, sizing and auxiliary options.Methods: A query of our practice’s arthroplasty registry revealed 60 patients (61 hips) who signed an IRB-approved general research consent allowing retrospective review, and underwent total hip arthroplasty performed with the modular femoral revision system between December 2009 and April 2012. There were 35 men (58%) and 25 women (42%). Mean age was 65.1 years (range, 35-94) and BMI was 31.3 kg.m2 (range, 14-53). Procedures were complex primary in 1 hip, conversion in 6 (10%), revision in 32 (53%), and two-staged exchange for infection in 22 (33%). Two-thirds of procedures included complete acetabular revision (n=40), while 31% (19) involved liner change only and 2 were isolated femoral revisions.Results: At an average follow-up of 1.5 years (maximum: 3.7 years) there have been no revisions or failures of the femoral component. Average Harris hip scores (0 to 100 possible) improved from 44.2 preoperatively to 66.0 at most recent evaluation, while the pain component (0 to 44 possible) improved from 15.8 to 31.2. Complications requiring surgical intervention included intraoperative periprosthetic femur fracture in one patient returned to the operating suite same day for open reduction internal fixation, which further required incision and debridement for superficial infection at 1 year postoperative; and two patients with dislocation and fracture of the greater trochanter treated with open reduction, revision of the head and liner, and application of cerclage cables, one of which required removal of a migrated claw 10 months later followed 2 weeks subsequently with incision and debridement for a non-healing wound. Postoperative radiographs were available for review for 59 THA in 58 patients. Analysis of the femoral component revealed satisfactory findings in 50 hips (85%) while 9 had radiographic changes that included bone deficit, osteolysis, or radiolucency in one or more zones.Conclusions: The early results of this modular femoral revision system are promising for the treatment of the deficient femur in complex primary and revision total hip arthroplasty. Patients with radiographic changes are advised to return for regular clinical and radiographic follow-up. Survival of the modular femoral component in this series was 100% at mean follow-up of 1.5 years and up to 3.7 years. While HHS clinical and pain scores were somewhat low at most recent evaluation, they were significantly improved over preoperative levels.

Long-term Results and Bone Remodeling After THA With a Short, Metaphyseal-fitting Anatomic Cementless Stem

Long-term results of standard total hip arthroplasty (THA) in young patients were not optimal. There are a number of reported disadvantages to longer cementless stems in THA including thigh pain and proximal stress shielding. However, it is unknown whether a short, metaphyseal-fitting anatomic stem without diaphyseal fixation, which represents a possible alternative, will maintain fixation over the longer term. We therefore evaluated long-term (1) clinical results using validated scoring instruments; (2) osseointegration and bone remodeling; (3) complications; and (4) rates of revision and osteolysis in patients younger than 65years who underwent THA with a short, metaphyseal-fitting anatomic cementless stem. We reviewed 500 patients (630 hips) younger than 65years (mean age at surgery, 52.7years) who underwent THA with the Immediate Postoperative Stability stem (IPS; DePuy, Leeds, UK) by one surgeon (Y-HK) from January 1995 to March 2002. Demographic data, Harris hip score, WOMAC score, UCLA activity score, and radiographic data were recorded. All patients underwent dual-energy x-ray absorptiometry scanning of the acetabulum and proximal femur at 2weeks after the operation and at final followup to determine stress shielding. Thigh pain was specifically investigated and scored by patients on a visual analog scale. Other complications were recorded. We determined component survival rates at 15years using revision and aseptic loosening as end points. Minimum followup was 11years (mean, 15.8years; range, 11-18years). The clinical and functional results improved significantly for the Harris hip score, WOMAC, and UCLA activity scores (p<0.001). At latest followup, mean Harris hip, WOMAC, and UCLA activity scores were 94 (range, 71-100), 15 (range, 5-29), and 7.9 (range, 6-9) points, respectively. All hips had osseous integration of the acetabular and femoral components. No patients had thigh pain. Four hips (0.6%) had deep infection and four (0.6%) had a recurrent dislocation. No patients had Grade 3 stress shielding. Fifteen-year survival rates were 98.7% (95% confidence interval [CI], 0.95-1.00) for the acetabular component and 99.4% (95% CI, 0.97-1.00) for the femoral component with revision as the end point and 100% (95% CI, 0.98-1.00) for both components with aseptic loosening as the end point. The short, metaphyseal-fitting anatomic cementless femoral stem provided stable fixation without relying on diaphyseal fixation in younger patients, suggesting metaphyseal fitting alone is sufficient in young patients who have good bone quality. Because we observed no thigh pain and little stress shielding in our patients, modifying the distal stem design as is done with this implant might be advantageous, but this would need to be determined in future comparative studies. Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

TCT-406 Dedicated Bifurcation Stent BiOSS in the Treatment of Distal Left Main Stem Stenosis - Polish and Bulgarian Registry

TCT-406 Dedicated Bifurcation Stent BiOSS in the Treatment of Distal Left Main Stem Stenosis - Polish and Bulgarian Registry

Transfemoral Approach at Revision Hip Arthroplasty

Results of 41 revision hip arthroplasties (41 interventions) via transfemoral approach were analyzed. That approach was used in stem fracture — 12 (29.26%) cases, cement removal — 20 (48.78%) cases and removal of partially ingrown cementless stem — 9 (21.95%) cases. Techniques of window, oblique, longitudinal oblique osteotomy and resection of greater trochanter were applied. As compared with standard revision intervention the duration of operation was about 40 minutes longer (159 min versus 125 min) and blood loss increased almost for 1 liter (2240 ml versus 1510 ml). Intraoperative complications were registered in 5 (12.20%) patients including 1 case of transverse femur fracture at oblique osteotomy (2.44%), 1 case of femur fracture at window osteotomy (2.44%), 2 cases of greater trochanter fracture (4.88%), 1 case of femoral cortical perforation by the cutter at distal stem fragment removal (2.44%). Excellent and good results were obtained in 30 (73.17%) patients. Indications to every type of transfemoral approach are presented.

Successful primary PCI to distal left main stem bifurcation through a TAVI

Introduction: Trans-catheter Aortic Valve Implantation (TAVI) for symptomatic aortic stenosis (SAS) for high surgical risk patient is increasing and Percutaneous coronary intervention (PCI) in such group of patients when presenting with future acute coronary syndromes are a challenge. We present a case demonstrating the importance of anticipation, preparation for a PCI and the need for a good understanding of the TAVI prosthesis to be able to deal with the challenges during PCI. Case report description: A 64 year old female with Scleroderma and TAVI 15 months ago was admitted to the ED with Chest pain. ECG was consistent with STEMI and she was transferred immediately to cardiac cathlab for Primary PCI. She underwent successful Primary PCI to distal LMS bifurcation lesion and we faced many challenges during and after PCI. We present the case to discuss the precautions that need to be taken before considering PCI in these subsets and to share some important points that we learnt from this case. ![Figure][1] Figure 1. Chanelling JL4 GC through TAVI Discussion: Chronic inflammatory disease is in itself an independent risk factor for coronary artery disease. Long term pharmacotherapy in these patients remains a challenge as no clear guidelines exist. Primary PCI in a TAVI patient poses a huge challenge but is feasible. A good understanding of the commonly used TAVI therapy devices and the techniques used when these devices are implanted in relation to coronaries is important for all interventional cardiologists undertaking Primary PCI. Implications to clinical practice: 1. Always start with an aortogram in these subsets. 2. PCI in patients with previous CoreValve® Revalving® system is safe and feasible. 3. Aggressive management of the disease process in chronic inflammatory condition is important to prevent the progression of atherosclerosis. [1]: pending:yes

Stem micromotion after femoral impaction grafting using irradiated allograft bone: A time zero in vitro study

BackgroundA gamma irradiation dose of 15kGy has been shown to adequately sterilise allograft bone, commonly used in femoral impaction bone grafting to treat bone loss at revision hip replacement, without significantly affecting its mechanical properties. The objective of this study was to evaluate whether use of 15kGy irradiated bone affects the initial mechanical stability of the femoral stem prosthesis, as determined by micromotion in a comprehensive testing apparatus, in a clinically relevant time zero in vitro model of revision hip replacement. MethodsMorselised ovine bone was nonirradiated (control), or irradiated at 15kGy or 60kGy. For each dose, six ovine femurs were implanted with a cemented polished taper stem following femoral impaction bone grafting. Using testing apparatus that reproduces stem loading, stems were cyclically loaded and triaxial micromotion of the stem relative to the bone was measured at the proximal and distal stem regions using non-contact laser transducers and linear variable differential transformers. FindingsThere were no significant differences in proximal or distal stem micromotion between groups for all directions (p≤0.80), apart for significantly greater distal stem medial–lateral micromotion in the 60kGy group compared to the 15kGy group (P=0.03), and near-significance in the anterior–posterior direction (P=0.08, power=0.85). InterpretationUsing a clinically relevant model and loading apparatus, irradiation of bone at 15kGy does not affect initial femoral stem stability following femoral impaction bone grafting.

Follow-Up Results of 10–12 Years After Total Hip Arthroplasty Using Cementless Tapered Stem — Frequency of Severe Stress Shielding With Synergy Stem in Japanese Patients

Synergy stems are tapered stems featuring a proximal porous coating, grid blasting below the proximal third to the distal end. This study included 41 patients (50 hips) who underwent total hip arthroplasty with follow-ups for 10 years or more. No stem reimplantations were performed. Spot welds were observed in the distal stem in Gruen zones 3 and 5 in 35 and 32 hips, respectively. First-degree stress shielding occurred in 8 hips; 2nd-degree, 20 hips; 3rd-degree, 13 hips; and 4th-degree, 9 hips. Because of bone fixation to the distal grit-blasted section of the stem, severe stress shielding was observed in nearly half of the cases. Multiple regression analysis of stress shielding determinants revealed a correlation between stem size and short patient height, showing the cause of stress shielding to be a mismatch in size between the stem and the femoral bone.