The assessment of canal flare index and proximal femoral bone density can improve stem selection for peri-prosthetic bone maintenance after total hip arthroplasty.

INTRODUCTION: Bone maintenance after total hip arthroplasty (THA) is important for implant success. This study aimed to investigate the relationship between patient characteristics and periprosthetic bone maintenance after THA for better implant selection. MATERIALS AND METHODS: This retrospective cohort study enrolled 112 consecutive patients who underwent THA using full hydroxyapatite (HA) compaction with short (n = 55) or short-tapered wedge (n = 61) stems. Periprosthetic bone mineral density (BMD) was compared between the two groups after propensity score matching, and the relationship between periprosthetic BMD changes and patient background was analyzed. RESULTS: Both groups showed similar periprosthetic BMD changes after adjusting for patient background using propensity score matching. Canal flare index > 3.7 in patients that underwent THA using tapered-wedge stem (odds ratio (OR), 3.2; 95% confidence interval (CI), 1.3-7.9, p = 0.013) and baseline zone 1 BMD > 0.65 in patients that received with short HA compaction stems (OR, 430.0; 95% CI 1.3-1420, p = 0.040) were associated with proximal periprosthetic bone maintenance after THA. CONCLUSION: Considering their predictive value, canal flare index and zone 1 BMD assessment might be useful strategies for implant selection during THA.

Comparison of femoral bone remodeling after total hip arthroplasty with cementless short-tapered wedge stem and fully hydroxyapatite-coated stem.

INTRODUCTION: We aimed to compare periprosthetic femoral bone remodeling after cementless total hip arthroplasty (THA) using a short-tapered wedge stem and a fully hydroxyapatite (HA)-coated stem. MATERIALS AND METHODS: In this retrospective study, 24 primary cementless THA procedures with short-tapered wedge stem and 24 using a fully HA-coated stem were performed. The follow-up duration was 2 years for both groups. Clinical evaluation was performed using the Merle d'Aubigné and Postel scoring systems. Standardized anteroposterior radiographs of the pelvis and femur were obtained. Dual-energy X-ray absorptiometry was performed, and the bone mineral density (BMD) around the stem was assessed in each Gruen zone at the first postoperative week as a baseline value and at 6 weeks, 3 and 6 months, and 1 and 2 years postoperatively. RESULTS: The mean Merle d'Aubigné and Postel scores improved significantly postoperatively in both groups. None of the hips showed loosening in either group. Spot welds occurred in zones 1, 2, 6, and 7 in the short-tapered wedge group, and in all zones in the fully HA-coated group. Significant BMD loss occurred only in zone 4 in the short-tapered wedge group, and no significant bone loss occurred in any zone in the fully HA-coated stem group; a significant difference between the two groups was observed only in zone 4 at 2 years after THA. CONCLUSIONS: Clinical and radiographical outcomes in both groups were good, and both stems suppressed postoperative BMD loss at 2 years.

Is bone remodelling around fully hydroxyapatite-coated and tapered-wedge stems related to the stem fixation pattern?

PURPOSE: This study aimed to compare bone mineral density (BMD) changes around the femoral component after total hip arthroplasty (THA) in a fully hydroxyapatite-coated stem (CORAIL) and in a tapered-wedge stem (Taperloc complete) and identify predictors of BMD changes. METHODS: This retrospective study compared 43 hips in the CORAIL group and 40 hips in the Taperloc group. The relative changes in BMD at 2 years after THA measured using dual-energy X-ray absorptiometry and the three-dimensional quantified contact states of the stem with the femoral cortical bone were assessed. Predictors of the relative change in the BMD around the proximal part of the stem were examined using multiple regression analysis. RESULTS: The decrease in BMD in Gruen zone 7 was significantly less in the CORAIL group than in the Taperloc group (P = 0.02). In the CORAIL group, the contact area in any zone was not a significant predictor of the relative changes in BMD. The contact area between the Taperloc stem and the femoral cortical bone in zones 2 and 6 was a positive predictor of the relative changes in BMD in zones 1 (P = 0.02 and P = 0.04, respectively) and 2 (P = 0.008 and P = 0.004, respectively). CONCLUSION: The CORAIL stem suppressed the postoperative BMD loss around the stem, irrespective of the contact state. The Taperloc complete stem required contact with the proximal femoral metaphysis to suppress the postoperative BMD loss around the stem.

Neocortex Formation in a Tapered Wedge Stem is Not Indicative of Complications or Worse Outcomes.

BACKGROUND: The formation of sclerotic bone, a neocortex, distally surrounding total hip arthroplasty (THA) stems may commonly be seen on radiographs around proximally porous coated stems but can be confused with loosening. The goal of this study was to determine the prevalence of the neocortex finding and whether it associated with worse outcomes after THA. METHODS: A retrospective review of 825 patients with a single tapered wedge stem was performed. Radiographs at 1-year, as well as final follow-up were reviewed for evidence of sclerotic bone (neocortex) surrounding the stem in all 14 Gruen zones. The final attending radiology read of lucency was also recorded. Patients were grouped by the presence of the neocortex. PROMIS Physical Function scores and complications were compared between neocortex groups. RESULTS: The neocortex group had 558 (68%) patients compared to 267 (32%) in the no neocortex group. The most common Gruen zones for evidence of neocortex were 10 (55%), 11 (52%), and 12 (51%). Seven percent of patients had a finding of lucency on radiology read. There was no difference between groups in terms of dislocations (P = .61), infection (P = .79), fracture rates (P = .54), revision surgery (P = .73), and reoperation for any cause (P = .62). PROMIS PF scores were significantly higher in the neocortex group (P < .0001). CONCLUSION: The presence of a distal neocortex is a common finding on radiographs after THA with this proximally porous-coated tapered wedge stem and does not portend worse outcomes, nor is it a sign of aseptic loosening, increased revision rates, infection, dislocation, or periprosthetic fracture risk.

Hydroxyapatite-coated compaction short stem represents a characteristic pattern of peri-prosthetic bone remodelling after total hip arthroplasty.

PURPOSE: We aimed to investigate the differences in peri-prosthetic bone remodelling between the full hydroxyapatite (HA)-collared compaction short stem and the short tapered-wedge stem. METHODS: This retrospective cohort study enrolled 159 consecutive patients (159 joints) undergoing total hip arthroplasty (THA) using the full HA compaction short (n = 64) and short tapered-wedge (n = 95) stems. Body mass index (BMI), peri-prosthetic bone mineral density (BMD), and clinical factors, including the Japanese Orthopaedic Association score and the University of California Los Angeles (UCLA) activity score were assessed and compared. RESULTS: Stem related complications were seen in three cases. Both groups showed similar peri-prosthetic BMD changes. Peri-prosthetic BMD was almost maintained in the distal femur and Gruen zone 6 with both type of stems, but significant BMD loss was found in zones 1 and 7 in both groups and in zone 2 of the full HA compaction stem group. No significant correlations were found between the proximal femoral BMD changes and the age, BMI, and UCLA score in both the full HA compaction and tapered-wedge stem groups. Femoral bone shape affected the peri-prosthetic BMD changes in the tapered-wedge stem group but not in the full HA compaction group. The stem collar of the full HA compaction stem did not affect peri-prosthetic BMD, but unique bone remodelling in the calcar region was observed in 27.6% cases. A significant difference in the peri-prosthetic BMD changes at Gruen zone 2 was found in patients with or without thigh pain. CONCLUSION: Peri-prosthetic bone remodelling remained unaffected by clinical and radiographic factors after THA with the new short full HA compaction stem. Therefore, this new stem may be useful in a variety of cases.

Difference in tapered wedge stem alignment between supine and lateral position in cementless total hip arthroplasty via modified Watson-Jones anterolateral approach.

BACKGROUND: Whether different body positions during surgery affect postoperative stem alignment in total hip arthroplasty (THA) remains unclear. The purpose of this study was to clarify differences in tapered wedge stem alignment between supine and lateral positions in THA under the modified Watson-Jones anterolateral approach. METHODS: We reviewed 242 consecutive, primary cementless THAs performed with ceramic-on-cross-linked polyethylene via the modified Watson-Jones approach in either supine or lateral positions between 2009 and 2015 (supine group: 113 cases; lateral group: 129 cases). No specific reasons to select supine or lateral positions for the surgery were given during the study period. Computed tomography was performed pre- and postoperatively to measure preoperative femoral anteversion and postoperative stem anteversion, respectively. Stem alignment in coronal and sagittal planes was also evaluated. RESULTS: Mean difference in stem anteversion and femoral anteversion was 8.6 ± 9.4 in the supine position and 13.0 ± 11.4 in the lateral position (p = 0.0013). Although no significant difference was seen between groups for stem alignment in the coronal plane, flexed implantation was more likely in the supine group (46/113, 40.7%) than in the lateral group (20/129, 15.5%). A significant correlation was found between femoral anteversion and stem anteversion in both the supine and lateral groups (r = 0.68, p < 0.0001 and r = 0.52, p < 0.0001, respectively). CONCLUSION: Although stem anteversion was more strongly correlated with femoral anteversion in the supine position than in the lateral position, neutral position in the sagittal plane was more likely to be found with the lateral position than with the supine position. Surgeons can achieve ideal stem positioning by considering these results in the modified Watson-Jones approach in both the supine and lateral positions.

Assessment of Early Biological Fixation of Cementless Tapered-Wedge Stems Using Digital Tomosynthesis.

BACKGROUND: We aimed to compare radiographic and digital tomosynthesis assessments of early biological fixation of a cementless stem in primary total hip arthroplasty and to investigate the factors associated with early biological fixation. METHODS: Seventy-three patients underwent total hip arthroplasty using cementless short tapered-wedge stems. Both radiography and digital tomosynthesis were performed at 6 weeks and 3, 6, 12, and 24 months after surgery. The presence of spot welds (SW) was evaluated at each postoperative period to assess biological fixation between the stem and the femur. The area of contact between the femur and the stem was divided into seven zones based on Gruen's zone classification. RESULTS: All 73 patients had no SW 6 weeks after surgery on radiography and digital tomosynthesis. Three months postoperatively, there was no SW on radiography; however, digital tomosynthesis revealed SW in 31 (42%) patients. Six months postoperatively, radiography showed 22 SW in 18 (24.7%) patients and digital tomosynthesis showed 94 SW in 48 patients (65.8%). CONCLUSION: Digital tomosynthesis detected biological fixation between the stem and femur earlier than radiography; biological fixation may appear within 3 months after surgery.

Outcomes of Cerclage Cabling for Intraoperative Calcar Cracks in Cementless Total Hip Arthroplasty Using Broach-Only, Tapered Wedge Stems.

BACKGROUND: Intraoperative femoral fractures are well-known but often overlooked complications in total hip arthroplasty (THA). We examined outcomes of cerclage cabling for intraoperative calcar cracks in THA with cementless tapered wedge stems. METHODS: In total, 4928 primary THAs were performed using broach-only, tapered wedge stems between January 2007 and November 2017 in a single institution. Of these, we identified 71 intraoperative calcar cracks (69 patients) managed by 2-mm cerclage cables. Clinical outcomes, amount of stem subsidence, and implant survivorship of the calcar crack group (68 THAs) were compared with those of the matched control group (68 THAs) without intraoperative fractures. Multivariate analysis was performed to identify potential risk factors for stem subsidence >3 mm. RESULTS: The mean stem subsidence was greater in the calcar crack group (2.0 vs 1.2 mm, P = .021), whereas revision-free survivorships of THA were similar between groups at 6 years (98.5% vs 98.4%; log-rank, P = .987). In the calcar crack group, a Dorr type C femur and the absence of cabling proximal to the lesser trochanter (LT) were identified as independent risk factors for stem subsidence >3 mm. For the subgroup with 42 calcar cracks managed by a single cable applied proximal to the LT, revision-free survivorship of THA was 100% at 6 years. There was no complete radiolucency to indicate aseptic stem loosening in either group. CONCLUSION: The application of a single cable proximal to the LT of the femur for intraoperative calcar cracks demonstrated 100% revision-free survivorship with lower stem subsidence in THA with tapered wedge stems.

Femoral Stem Survivorship in Dorr Type A Femurs After Total Hip Arthroplasty Using a Cementless Tapered Wedge Stem: A Matched Comparative Study With Type B Femurs.

BACKGROUND: There is a lack of understanding on relationship between the femoral geometry and outcomes of total hip arthroplasty (THA). We investigated clinical and radiographic outcomes of THA using a cementless tapered wedge stem in patients with Dorr type A proximal femoral morphology and compared with those of type B femurs at a minimum follow-up of 5 years. METHODS: We analyzed 1089 hips (876 patients) that underwent THA using an identical cementless tapered wedge stem. We divided all femurs into 3 types (Dorr type A, B, and C). Type A and B femurs were statistically matched with age, gender, body mass index, and diagnosis by using propensity score matching. Clinical, radiographic results, and stem survivorship were compared between the matched 2 groups. RESULTS: A total of 611 femurs (56%) were classified as type A, 427 (39%) as type B, and 51 (5%) as type C. More radiolucent lines around femoral stems were found in type A femurs (7.8%) than in type B femurs (2.5%) (P < .001). Patients with radiolucency showed worse Harris Hip Score (86.2 points) compared with those without radiolucency (93.0 points) (P < .001). The stem survivorship of type A femur (97.8%) was lower than that of type B femur (99.5%) (P = .041). The reasons for femoral revision in type A femurs were periprosthetic fracture (67%), aseptic loosening (22%), and deep infection (11%). CONCLUSIONS: This study showed a higher rate of complications after THAs using a cementless tapered wedge stem in Dorr type A femurs than those performed in type B femurs.

Cementless Tapered-Wedge Stem Length Affects the Risk of Periprosthetic Femoral Fractures in Direct Anterior Total Hip Arthroplasty.

BACKGROUND: Although the popularity of the direct anterior approach for total hip arthroplasty has increased, the femoral procedure in this approach is considered technically challenging, and one of the most frequent complications reported was periprosthetic femoral fractures. The present study aimed to identify factors for predicting the risk of periprosthetic femoral fractures after using stems with a cementless tapered-wedge design through the direct anterior approach. METHODS: We retrospectively assessed the medical records of 686 patients (851 hips) who underwent primary total hip arthroplasty using a single stem with a cementless tapered-wedge design having a short or standard length option. The direct anterior approach on a standard operating table was used for all hips. Multivariate logistic regression analysis was performed to identify the independent predictors of intraoperative and early postoperative periprosthetic fractures. RESULTS: Seventeen periprosthetic femoral fractures (2.0%) were observed, including 10 intraoperative (1.2%) and 7 postoperative (0.8%) fractures. The occurrence rate of fractures using short stems was significantly higher compared with that using standard stems. The multivariate logistic regression analysis revealed that only stem length was significantly associated with periprosthetic fractures. CONCLUSION: Our results indicate that the stem design affects the risk of periprosthetic femoral fractures.

The effect of flexion alignment in total hip arthroplasty with a cementless tapered-wedge femoral stem.

INTRODUCTION: The influence of stem sagittal alignment on clinical outcomes is unclear in total hip arthroplasty (THA). The purpose of this study is to assess the relationship between stem sagittal alignment and clinical and radiographic outcomes using 3D-CT. MATERIALS AND METHODS: We performed 370 consecutive primary THAs between 2009 and 2013. After exclusion, 102 hips in 89 patients using single tapered-wedge stem were included. Mean follow-up was 4.7 years. Stem sagittal alignment was measured using CT, and patients were divided into flexion and neutral alignment groups. Clinical and radiographic outcomes were compared between two groups. Furthermore, we evaluated the anterior femoral offset and initial contact state. RESULTS: There were no significant differences in clinical or radiographic outcomes between two groups. CT data analysis and multiple regression analysis showed flexion alignment increased anterior femoral offset (AFO) and Gruen zone 4 contact area. CONCLUSIONS: There was no significant difference in clinical or radiographic outcomes between flexion and neutral alignment of the tapered-wedge stem at an average of 4.7 years of follow-up. The increase of AFO and distal contact area in flexion alignment could affect the improvement of impingement-free range of flexion and intraoperative fracture.

Reduced Incidence of Intraoperative Femur Fracture With a Second-Generation Tapered Wedge Stem.

BACKGROUND: Intraoperative fractures during total hip arthroplasty (THA) are more common when using cementless stems. The purpose of this study was to investigate the impact of a new shorter second-generation cementless, tapered wedge stem with improved proximal femoral fit in reducing the incidence of intraoperative fracture. METHODS: A retrospective study was conducted on primary THA cases performed at a single institution using a first-generation or second-generation cementless stem from 2006-2016. All intraoperative femur fractures were identified, as well as early 30-day postoperative periprosthetic femur fractures, which could represent nondisplaced intraoperative fractures that were initially missed. Risk for intraoperative femur fracture was analyzed using logistic regression, accounting for demographic covariates and surgeon. RESULTS: Of 6473 primary THA performed with a cementless, tapered wedge stem during the study period, 3126 used a first-generation stem and 3347 used a second-generation stem. The incidence of intraoperative fracture was 1.79% for first-generation stems and 0.24% for second-generation stems, representing a 7.5-fold reduction of risk for fracture. After accounting for covariates, the odds of intraoperative fracture were 0.33 using the second-generation stem relative to the first-generation stem (P = .01). However, there was no significant difference in the odds of early 30-day postoperative fractures using the second-generation stem (odds ratio 0.93, P = .56). CONCLUSION: A new second-generation cementless stem resulted in a 7.5-fold decrease in the incidence of intraoperative femur fracture compared with the preceding stem.

Cementless Tapered Wedge Femoral Stems Decrease Subsidence in Obese Patients Compared to Traditional Fit-and-Fill Stems.

BACKGROUND: Femoral component stability and resistance to subsidence is critical for osseointegration and clinical success in cementless total hip arthroplasty. The purpose of this study was to radiographically evaluate the anatomic fit and subsidence of 2 different proximally tapered, porous-coated modern cementless femoral component designs. METHODS: A retrospective cohort study of 126 consecutive cementless total hip arthroplasties was performed. Traditional fit-and-fill stems were implanted in the first 61 hips with the remaining 65 receiving morphometric tapered wedge stems. Preoperative bone morphology was radiographically assessed by the canal flare index. Canal fill in the coronal plane, subsidence, and the sagittal alignment of stems was measured digitally on immediate and 1-month postoperative radiographs. RESULTS: Demographics and canal flare indices were similar between groups. The percentage of femoral canal fill was greater in the tapered wedge compared to the fit-and-fill stem (P = .001). There was significantly less subsidence in the tapered wedge design (0.3 mm) compared to the fit-and-fill design (1.1 mm) (P = .001). Subsidence significantly increased as body mass index (BMI) increased in the fit-and-fill stems, a finding not observed in the tapered wedge design (P = .013). CONCLUSION: An anatomically designed morphometric tapered wedge femoral stem demonstrated greater axial stability and decreased subsidence with increasing BMI than a traditional fit-and-fill stem. The resistance to subsidence, irrespective of BMI, is likely due to the inherent axial stability of a tapered wedge design and may be the optimal stem design for obese patients.

Total Hip Intraoperative Femur Fracture: Do the Design Enhancements of a Second-Generation Tapered-Wedge Stem Reduce the Incidence?

BACKGROUND: Intraoperative femur fracture (IFF) is a well-known complication in primary uncemented total hip arthroplasty (THA). Variations in implant instrumentation design and operative technique may influence the risk of IFF. This study investigates IFF between a standard uncemented tapered-wedge femoral stem and its second-generation successor with the following design changes: size-specific medial curvature, proportional incremental stem growth, modest reduction in stem length, and distal lateral relief. METHODS: A single experienced surgeon's patient database was retrospectively queried for IFF occurring during primary uncemented THA using a standard tapered-wedge femoral stem system or a second-generation stem. All procedures were performed using soft tissue preserving anatomic capsule repair and posterior approach. The primary outcome measure was IFF. A z-test of proportions was performed to determine significant difference between the 2 stems with respect to IFF. Patient demographics, Dorr classification, and implant characteristics were also examined. RESULTS: Forty-one of 1510 patients (2.72%) who received a standard tapered-wedge femoral stem sustained an IFF, whereas 5 of 800 patients (0.63%) using the second-generation stem incurred an IFF. No other significant associations were found. CONCLUSION: A standard tapered-wedge femoral stem instrumentation system resulted in greater than 4 times higher incidence of IFF than its second-generation successor used for primary uncemented THA. Identifying risk factors for IFF is necessary to facilitate implant system improvements and thus maximize patient outcomes.

Preoperative Planning and Operative Techniques of the Shorter Tapered Stem Compared to the Metaphyseal Fit Stem in Cementless Total Hip Arthroplasty.

BACKGROUND: In order to prevent postoperative dislocation due to prosthetic impingement as a result of total hip arthroplasty (THA), the combined anteversion (CA) theory, which combines the anteversion of the femoral stem and the acetabular socket, has been revised in recent years. Particularly, it is necessary to keep CA within the target zone. METHODS: The aim of this study was to investigate whether postoperative CA can be kept within the target zone while using the operative technique which prepares the socket first in cementless THA, by estimating the anteversion of the metaphyseal fit stem or the shorter, tapered wedge stem using preoperative 3-dimensional computerized planning, and by adjusting the anteversion of the socket using a navigation system that considers CA. One hundred fourteen patients (118 hips) were recruited for the study. RESULTS: Postoperative CA in THA using the metaphyseal fit stem was kept within the target zone for 56 of the 60 hips (93.3%). Using the shorter, tapered wedge stem, 49 of the 58 hips (84.4%) were within the target zone. No postoperative dislocations were observed in any hips. CONCLUSION: We found that the metaphyseal fit stem worked better than the shorter, tapered wedge stem in terms of meeting the planned CA. The shorter, tapered wedge stems were flexible in rotation according to the anatomical configuration of the proximal femur. Therefore, the stem could be placed second with the metaphyseal fit stem, but we recommend placing the stem first with the shorter, tapered wedge stem.

Development and verification of a cementless novel tapered wedge stem for total hip arthroplasty.

Most current tapered wedge hip stems were designed based upon the original Mueller straight stem design introduced in 1977. These stems were designed to have a single medial curvature and grew laterally to accommodate different sizes. In this preclinical study, the design and verification of a tapered wedge stem using computed tomography scans of 556 patients are presented. The computer simulation demonstrated that the novel stem, designed for proximal engagement, allowed for reduced distal fixation, particularly in the 40-60 year male population. Moreover, the physical micromotion testing and finite element analysis demonstrated that the novel stem allowed for reduced micromotion. In summary, preclinical data suggest that the computed tomography based stem design described here may offer enhanced implant fit and reduced micromotion.

Effects of micro-arc oxidation coating on outcomes of a cementless grit-blasted tapered-wedge stem in total hip arthroplasty.

To evaluate the effects of micro-arc oxidation (MAO) coating on the outcomes of a grit-blasted tapered-wedge stem in total hip arthroplasty (THA), we performed a retrospective review of 141 THAs using MAO coated stem for a minimum of 5years and compared them to 219 THAs using the same geometry stem without MAO coating. Harris hip score improved from 43.7 points preoperatively to 93.9 points postoperatively. No hips were revised for aseptic loosening. Complications included one squeaking hip, one iliopsoas tendonitis, and one deep vein thrombosis. Postoperative Harris hip scores, WOMAC scores, UCLA activity scores, stem stabilities, and complication rates did not differ between the groups. After medium-term follow-up, our findings did not support the use of MAO coating on grit-blasted tapered-wedge stem to improve clinical outcomes.

Finite element analysis of mechanical stress in a cementless tapered-wedge short stem in the varus position.

BACKGROUND: In recent years, the use of tapered-wedge short stems has increased due to their ability to preserve bones and tendons. Surgical techniques occasionally result in a varus position of the stem, which is particularly pronounced in short stems. Although the varus position is not clinically problematic, there are reports of an increased incidence of stress shielding and cortical hypertrophy. Thus, we evaluated and examined the acceptable range of varus angles using finite element analysis. METHODS: Patients diagnosed with osteoarthritis of the hip joint who had undergone arthroplasty were selected and classified into three types [champagne-flute (type A), intermediate (type B), and stovepipe (type C)]. Finite element analysis was performed using Mechanical Finder. The model was created using a Taperloc microplasty stem with the varus angle increased by 1° from 0° to 5° from the bone axis and classified into seven zones based on Gruen's zone classification under loading conditions in a one-leg standing position. The volume of interest was set, the mean equivalent stress for each zone was calculated. RESULTS: A significant decrease in stress was observed in zone 2, and increased stress was observed in zones 3 and 4, suggesting the emergence of a distal periosteal reaction, similar to the results of previous studies. In zone 2, there was a significant decrease in stress in all groups at a varus angle ≥ 3°. In zone 3, stress increased from ≥ 3° in type B and ≥ 4° in type C. In zone 4, there was a significant increase in stress at varus angles of ≥ 2° in types A and B and at ≥ 3° in type C. CONCLUSION: In zone 2, the varus angle at which stress shielding above Engh classification grade 3 may appear is expected to be ≥ 3°. Distal cortical hypertrophy may appear in zones 3 and 4; the narrower the medullary cavity shape, the smaller the allowable angle of internal recession, and the wider the medullary cavity shape, the wider the allowable range. Long-term follow-up is required in patients with varus angles > 3°.

Stem Alignment With the Tapered Wedge Cementless Stem "Accolade II" Does Not Affect Bone Mineral Density Over 5 Years After Total Hip Arthroplasty.

Background: This study aimed to investigate the relationship between 3-dimensional (3D) alignment and postoperative bone mineral density (BMD) changes with Accolade II tapered wedge stems, which have a different proximal shape from other tapered wedge stems, up to 5 years after primary total hip arthroplasty. Methods: We retrospectively analyzed the hips of 89 patients who underwent total hip arthroplasty using the second-generation proximally coated cementless stem (Accolade II; Stryker Orthopedics, Mahwah, NJ) at our institution from 2014 to 2018 over a 5-year follow-up. We evaluated the relationship between stem alignment, measured using 3D-templating software, and BMD changes in the 7 Gruen zones and compared the data with those from a former study using other short taper-wedge stems. Results: BMDs in zones 1 and 7 continued to decrease gradually every year after surgery, and BMD in zone 7 showed the largest decrease (21%) from baseline over 5 years. No correlation was found between stem alignment (varus/valgus, flexion/extension, and anteversion/retroversion) and changes in BMD in each zone over 5 years. Conclusions: Our data showed no correlation between 3D stem alignment and changes in BMD in each Gruen zone over 5 years. This suggests that the Accolade II stem may fit better into any shape of the proximal medullary canal because of its unique characteristics.

Stem alignment with short tapered-wedge cementless stems affects bone mineral density continuously for at least 5 years after primary total hip arthroplasty.

AIM: This study aimed to assess the relationship between the three-dimensional (3D) alignment of short tapered-wedge cementless stems and bone mineral density (BMD) changes in patients followed up for 5 years after total hip arthroplasty (THA). METHODS: We retrospectively analysed the hips of 52 patients who underwent THA using short tapered-wedge cementless stems at our institution from 2013 to 2016 with complete 5-year follow-up data. We evaluated the relationship between stem alignment, measured using a 3D-templating software, and BMD changes in the 7 Gruen zones. RESULTS: After 1 year, significant negative correlations between varus insertion and a decrease in BMD in zone 7 and between flexed insertion and decreases in BMD in zones 3 and 4 were noted. After 5 years, significant negative correlations between varus insertion and a decrease in BMD in zone 7 and between flexed insertion and decreases in BMD zones 2, 3, and 4 were observed. With increased amounts of varus/flexion stem alignment, the amount of BMD loss decreased. There was no correlation between anteverted stem insertion and changes in BMD levels. CONCLUSIONS: Our data showed that stem alignment affects BMD based on 5-year follow-up data after surgery. Careful observation is necessary, especially when using short tapered-wedge cementless stems, as stem alignment may affect changes in BMD levels more than 5 years after surgery.