Loose fit versus press fit stems and risk for surgical reintervention following radial head arthroplasty: A US-based cohort study of 1575 patients.

INTRODUCTION: Radial head arthroplasty (RHA) is performed with increasing frequency for reconstruction of comminuted radial head fractures. Implants can be categorized by stem design, either loose fit or press fit. Currently, the RHA literature does not suggest one implant type is superior to another based on revision and reoperation rates, although most RHA outcome studies have small numbers of patients with few events to detect a difference. This study evaluated the association between stem design and risk of revision and reoperation after RHA. METHODS: 1575 patients aged ≥18 years who underwent primary RHA within a US-based healthcare system were identified (2009-2021). Revision following the index RHA was the primary outcome of interest; ipsilateral reoperation was a secondary outcome. Multivariable Cox proportional hazard regression was used to evaluate the risk of outcomes by loose versus press fit with the adjustment for race/ethnicity, ASA classification, region, surgeon RHA volume, and simultaneous ipsilateral extremity procedures. RESULTS: Of the 1575 RHA, 681 (43.2%) received a loose fit stem. The cumulative revision probability was 2.6% for loose fit and 3.5% for press fit. In adjusted analysis, we did not observe a difference in risk of revision (HR=0.78, 95% CI=0.41-1.46) or reoperation (HR=0.73, 95% CI=0.43-1.25). Additionally, there were no observed differences in risk of revision (HR=0.62, 95% CI=0.28-1.38) or reoperation (HR=0.90, 95% CI=0.48-1.71) in the patient subgroup who underwent additional procedures in the same extremity at the time of RHA. CONCLUSION: In this large multi-center cohort of 1575 primary RHA, we did not observe a difference in risk of revision or reoperation following RHA based upon stem design. The choice between using an implant with a loose or press fit stem may be based more on surgeon familiarity, implant availability and cost, and ease of use.

Humeral stem loosening is not always prosthetic joint infection.

BACKGROUND: Aseptic humeral stem loosening is an uncommon complication of shoulder arthroplasty, and its presence has been considered a highly specific predictor of prosthetic joint infection (PJI). Literature on aseptic humeral stem loosening is sparse. The primary purpose of this study was to determine the rate of aseptic humeral loosening in revision shoulder arthroplasty. Secondarily, we sought to identify predictors of septic and aseptic humeral loosening. METHODS: Our institutional revision shoulder arthroplasty database was reviewed. Inclusion criteria were patients with humeral stem loosening as indicated in the operative report. Patient demographics, index surgery and indication, revision surgery and indication, and operative data were recorded. Charts were manually reviewed, and PJI scores were calculated using the International Consensus Meeting scoring criteria. International Consensus Meeting classifications of PJI "unlikely" and "possible" were considered aseptic, and PJI "probable" and "definite" were considered septic. Statistical analysis was performed to determine associations between the abovementioned variables and aseptic humeral loosening. RESULTS: Forty-six patients with 48 shoulders were included in our analysis. Ten cases (21%) were classified as definite PJI, 13 cases (27%) were classified as probable PJI, 4 cases (8%) were classified as possible PJI, and 21 cases (44%) were classified as PJI unlikely. On analysis of stem design, there were no statistically significant associations with aseptic loosening; although, a lack of proximal porous ingrowth surface trended toward higher rates of aseptic loosening in all patients and in anatomic total shoulder arthroplasty (ATSA) and reverse total shoulder arthroplasty (RTSA) subgroup analyses. In the index RTSA subgroup, aseptic loosening was associated with female sex (P = .005). Seventeen of 39 shoulders (44%) that underwent either index ATSA or RTSA demonstrated concomitant glenoid loosening. The absence of glenoid loosening was associated with aseptic humeral loosening in index ATSA and RTSA (P < .001). CONCLUSION: Fifty-two % of revision shoulder arthroplasty cases with humeral loosening performed at our institution were aseptic. There appear to be distinct demographic and radiographic factors that are more commonly associated with aseptic as opposed to septic humeral loosening. Our data demonstrate that demographic predictors of aseptic loosening of RTSA include female sex. The absence of glenoid component loosening is associated with aseptic humeral loosening and concomitant glenoid loosening is associated with septic humeral loosening. Understanding of these factors can guide the preoperative index of suspicion for PJI in the setting of humeral stem loosening.

Does Femoral Stem Design Influence Periprosthetic Fracture Incidence and Morphology in Total Hip Arthroplasty?

BACKGROUND: As the incidence of total hip arthroplasty (THA) increases, the number of periprosthetic femur fractures (PFF) will also rise. The surgical approach and stem design have been shown to influence the rate of PFF. This study evaluated PFF in cementless THA done through the posterior approach and described how stem design influences intraoperative and early postoperative fracture incidence and morphology. METHODS: A retrospective review of 3,183 primary THAs for osteoarthritis from 2013 to 2021 was performed. Demographics, comorbidities, femoral stem designs, intraoperative and early postoperative PFFs (< 90 days), and aseptic femoral revisions were recorded. Stems were classified as single-wedge taper (Type 1), double-wedge taper (Type 2), or ream and broach (Type 3). There were 1,192 Type 1, 240 Type 2, and 1,726 Type 3 femoral stems. The PFF and aseptic femoral revisions were compared with univariable and multivariable analyses. Cox regression and Kaplan-Meier analyses evaluated survival to femoral revision. RESULTS: In this population, 25 patients (0.8%) had an intraoperative or early postoperative PFF. Patients who had PFFs were older (68 versus 63; P = 0.03) and more likely to be women (76 versus 24%; P = 0.02). Type 2 stems had a significantly higher incidence of all-cause PFFs when compared to Type 1 (3.6 versus 0.7%; P < 0.01) and Type 3 (3.6 versus 0.4%; P < 0.01) stems. Type 2 stems also had a higher incidence of Vancouver B2 PFFs when compared to Type 3 stems (0.8 versus 0.05%; P = 0.04). Stem design was not associated with PFF or all-cause femoral revision. There were no differences in survival to femoral revision. CONCLUSION: Double-wedge taper stems may be associated with increased intraoperative and early postoperative PFFs, including those requiring femoral stem revision. However, there was no statistically significant difference in late PFF, aseptic loosening, or femoral revision.

Risk factors for intraoperative femoral fractures in cementless bipolar hip arthroplasty for femoral neck fracture in multicenter: The TRON group study.

BACKGROUND: Intraoperative femoral fractures are more common in cementless bipolar hip arthroplasty (BHA) for displaced femoral neck fractures than they are in cemented BHA and remain one of the major concerns. This study aimed to investigate the risk factors for intraoperative femoral fractures in cementless BHA. METHODS: The study included 1,392 patients who underwent cementless BHA for displaced femoral neck fractures from January 2015 to December 2019 in 14 hospitals of the Trauma Research Group. They were divided into two groups according to the presence or absence of intraoperative femoral fractures, and factors associated with intraoperative fractures were statistically examined. RESULTS: Forty (2.9 %) intraoperative and 28 (2.0 %) postoperative, totally 68 (4.9 %) femoral fractures occurred. The mean age of the patients, presence of opposite-side proximal femoral fracture, approach, and cementless stem design were significantly different between the two groups (P < 0.05). The logistic regression analysis model showed that a fully HA-coated stem (odds ratio, 4.12; 95 % confidence interval, 1.43-11.9) was an independent factor associated with intraoperative femoral fractures. CONCLUSION: This study investigated the risk factors associated with intraoperative fractures and showed that fully HA-coated stems were an independent factor associated with intraoperative femoral fractures. Surgeons should be cautious in the early stages of introducing fully HA-coated stems.

Biomechanical analysis of different THA cementless femoral stem designs in physiological and osteoporotic bone during static loading conditions.

BACKGROUND: The influence of THA stem design on periprosthetic femoral fractures (PFFs) risk is subject of debate. This study aims to compare the effects of different cementless stem designs on stress-strain distributions in both physiological and osteoporotic femur under various loading conditions. MATERIALS: A biomechanical study using finite-element analysis was conducted. Four models were developed: three with implanted femurs and a native one chosen as control. Each model was analyzed for both healthy and osteoporotic bone. The following stem designs were examined: short anatomical stem with femoral neck preservation, double-wedge stem, and anatomical standard stem. Three loading conditions were assessed: gait, sideways falling, and four-point bending. RESULTS: During gait in physiological bone, the anatomical stem and the short anatomical stem with femoral neck preservation showed stress distribution similar to the native model. The double-wedge stem reduced stress in the proximal area but concentrated it in the meta-diaphysis. In osteoporotic bone, the double-wedge stem design increased average stress by up to 10%. During sideways falling, the double-wedge stem exhibited higher stresses in osteoporotic bone. No significant differences in average stress were found in any of the studied models during four-point bending. CONCLUSION: In physiological bone, anatomical stems demonstrated stress distribution comparable to the native model. The double-wedge stem showed uneven stress distribution, which may contribute to long-term stress shielding. In the case of osteoporotic bone, the double-wedge stem design resulted in a significant increase in average stress during both gait and sideways falling, potentially indicating a higher theoretical risk of PFF.

Aseptic midterm survival rates between different cemented tibial stem designs in hinged total knee arthroplasty: a 6-year evaluation from the German Arthroplasty Registry.

INTRODUCTION: The rate of revision TKA and thus the use of hinged implants (HI) steadily rises. Aseptic loosening lies on the top of the failure patterns. However, no evidence exists until now based on national scale high-caseloads that analyzes the impact of cemented HI stem-design on aseptic survival rates. METHODS: Data on aseptic HI-revisions with full-cemented tibia-stems were conducted from the German Arthroplasty Registry. Cases were divided in primary HI (PHI) and HI used in revision operations (RHI). Endpoint was a new revision following either a PHI or an RHI. The impact of stem conicity (conical vs. cylindrical), diameter (≤ 13 mm vs. > 13 mm), length (≤ 90 mm vs. > 90 mm) and offset on the 6-Year-Cumulative-Aseptic-Revision-Rate (6Y-CARR) was estimated via Kaplan-Meier curve and compared between groups via Log-Rank-Tests. RESULTS: 3953 PHI and 2032 RHI fulfilled inclusion-criteria. Stem conicity had no impact on 6Y-CARR (p = 0.08 and p = 0.8). Diameter > 13 mm hat an impact on PHI (p = 0.05) with lower 6Y-CARR but not on RHI (p = 0.2). Length > 90 mm showed significantly worst 6Y-CARR in PHI (p = 0.0001) but not in RHI (p = 0.3). Offset-stems showed significantly better 6Y-CARR in PHI (p = 0.04), but not in RHI (p = 0.7). CONCLUSION: There was no significant impact of the cemented tibia-stem conicity on 6Y-CARR, neither in PHI nor in RHI. The effect of length, diameter and offset on the 6Y-CARR observed in the PHI, was not detectable in the more complex RHI-cases reflecting its limited clinical relevance by itself in more multifactorial backgrounds. Therefore, results must be interpreted with caution due to considerable system-effects and different utilization-scenarios.

Improved outcomes of older patients with acute and displaced proximal humerus fractures treated with window bone ingrowth fracture-specific stem reverse shoulder arthroplasty.

BACKGROUND: The optimal treatment of displaced proximal humerus fractures (PHFs) in the older people population remains controversial. Reverse shoulder arthroplasty (RSA) is a popular surgical treatment option that provides improved and reproducible results. However, the relevance of fracture-specific stem designs for RSA to improve tuberosity consolidation and shoulder function remains debatable. METHODS: This study included all patients 70 years or older with acute and displaced PHFs primarily treated with RSA at a single institution in Portugal, between January 2010 and December 2019 who participated in a minimum follow-up of 2 years. RESULTS: A total of 112 patients (15 men and 97 women) with a median clinical follow-up of 52 months were included. The mean age at the time of fracture was 78.6 years. All fractures were classified as Neer types 3 and 4 (n = 50 and n = 62, respectively). A window bone ingrowth fracture-specific stem was used for 86 patients, and a conventional humeral stem was used for 26 patients. Regarding the tuberosity fixation technique, 76 tuberosities were attached using technique A (according to Boileau's principles), 36 tuberosities were attached using technique B (not following Boileau's principles) and 11cases were classified as technique C (if fixation was not possible). The overall survival rate during the 2-year follow-up was 88.2%; however, this decreased to 79% at 5 years. Only three patients had complications (two infections and one dislocation) requiring revision surgery. In the multivariable analysis, the tuberosity fixation technique (P = 0.012) and tuberosity anatomical consolidation (P < 0.001) were associated with improved Constant scores (median Constant Score 62.67 (technique A), 55.32 (technique B), 49.70 (technique C). Fracture-specific humeral implants (P = 0.051), the tuberosity fixation technique (P = 0.041), tuberosity anatomical consolidation (P < 0.001), and dementia influenced the achievement of functional mobility (P = 0.014). Tuberosity anatomic consolidation was positively associated with bone ingrowth fracture-specific humeral implants (P < 0.01) and a strong tuberosity fixation technique (P < 0.01). CONCLUSION: RSA is used for complex and displaced fractures of the proximal humerus in older patients. Dementia was negatively correlated with functional outcomes. A window bone ingrowth fracture-specific stem combined with strong tuberosity fixation can yield better clinical and radiological results. LEVEL OF EVIDENCE: Level II; prospective comparative study; treatment study.

Does stem profile have an impact on the failure patterns in revision total knee arthroplasty?

INTRODUCTION: Revision total knee arthroplasty (RTKA) has been increasing continuously. The results of RTKA still remain unsatisfactory. Failure patterns and risk factors in RTKA were thoroughly analyzed, with periprosthetic joint infections (PJI) and aseptic loosening remaining at the forefront of re-revision (ReRTKA) causes. While there is evidence that stem profile impacts the revisability of cemented implants, its association with the modes of RTKA failure is unknown. METHODS: 50 consecutive ReRTKA performed in a single orthopedic center during 2016-2017 were retrospectively analyzed. The cases were stratified according to age, sex, number of preexisting revisions, fixation technique, stem design and causes of re-revision. All explanted implants with conical vs. cylindrical stem profiles were compared. RESULTS: Mean age was 67 ± 11.5, and 54% were females. 72% of the cases had ≥ 3 previous revisions. 88% were full-cemented, 3% hybrid and 9% press-fit stems. 36% of the RTKA had conical, 58% cylindrical and 6% combined stem profiles. 92% of the RTKA components were removed. Removal causes were: PJI (52.2%), aseptic loosening (34.8%), implant malposition (9.8%), painful knee (1.1%) and instability (2.2%). While the overall RTKA failure patterns were equally distributed between conical and cylindrical stems, subgroup analysis of only cemented ReRTKA revealed a higher incidence of aseptic loosening within cylindrical stem profiles (46.7% vs. 25.7%, P = 0.05). CONCLUSION: Stem profile may have an impact on the process of aseptic loosening in cemented non-metaphyseal engaging RTKA, with cylindrical designs tending to worse outcomes than conical designs. Large cohort studies could provide more clarity on current observation.

Impact of stem profile on the revisability and the need for osteotomy in well-fixed cemented revision total knee arthroplasty implants.

INTRODUCTION: While re-revision total knee arthroplasty (ReRTKA) steadily increases, the ease and bone-sparing removal of RTKA implants is gaining more and more in importance. Biomechanical data suggest that cemented conical stems can be removed significantly easier than cylindrical stems. However, no clinical evidence exists supporting this observation. Aim of this study was to compare the revisability and need for osteotomy (OT) between removals of well-fixed cemented conical vs. cylindrical RTKA stems. MATERIALS AND METHODS: 55 removals of well-fixed full-cemented RTKA stems (29 knees) performed between 2016 and 2018 were retrospectively analyzed. Main outcome variables were: bone loss, fractures, osteotomy incidence, surgery duration, early postoperative complications (EPC), hemoglobin drop and blood transfusion. SPSS was used for the statistical analysis. RESULTS: 44.8% were conical, 48.3% cylindrical, and 6.9% combined stem designs. Causes for re-revision were PJI (75.9%), malposition (17.2%) and persistent pain (6.9%). 10 stem removals (18.2%) required an OT (four femoral, six tibial): eight stems (14.5%) had cylindrical and two (3.6%) conical designs (P = 0.041). Fractures were noted solely in removals without OT (11.1% vs. 0%,). There was a tendency to more bone loss in cylindrical stem revisions (53.8% vs. 32%, P = 0.24). A longer overall surgery time was observed in revisions of cylindrical stems (+ 37 min, P = 0.05). There was higher hemoglobin drop and need for blood transfusion in revisions of cylindrical stems or after OT but without reaching statistical significance. The EPC rates were slightly higher in ReRTKA on cylindrical stems (P = 0.28). CONCLUSION: Well-fixed cemented conical stems may be revision friendlier with less demands on OT and shorter overall surgery time than cemented cylindrical stems.

Restoration of hip geometry after total hip arthroplasty: retrospective comparison of two short stems and one straight stem.

BACKGROUND: The preservation or restoration of hip geometry following total hip arthroplasty (THA) is of importance, considering that alterations in the centrum-collum-diaphysis (CCD)-angle, femoral offset (FO), acetabular offset (AO) and total offset (TO) change hip biomechanics. Therefore, the most suitable implant should be used. The aim of this study was to compare the ability of two short-stem-systems and one straight-stem-system to reconstruct hip geometry. METHODS: Two-hundred-fifty-one patients (mean age: 62.0 ± 10.0 years; 51.8% males) undergoing THA with three different stem types were retrospectively included, after excluding 11 patients with missing radiological follow-up. Pre- and postoperative radiographic images (group I, ANA.NOVA Alpha Schaft Proxy®, ImplanTec, 12 options: n = 99; group II, Optimys® Mathys, 24 options: n = 62; group III: Corail®-System, DePuy-Synthes, 76 options: n = 90) were analyzed. Differences in pre- and postoperative hip geometry (i.e. CCD, FO, AO, TO) were compared between groups with one-way-analysis-of-variance (ANOVA), and post-hoc t-tests. RESULTS: The CCD-angle increased by a mean of 8.4° ± 7.2° from pre-to postoperative, with no significant difference between groups (p = 0.097). Significantly larger increases in FO were observed for groups II (4.1 mm ± 7.8 mm) and III (4.9 ± 7.2 mm), in comparison to group I (1.6 ± 6.9 mm; p = 0.006). AO decreased by a mean of 2.2 ± 4.5 mm, with the largest decrease observed in group III (-3.3 ± 5.3 mm), and the smallest for group I (-1.4 ± 3.6 mm; p = 0.011). There was no significant difference in change of TO between groups (p = 0.177). CONCLUSIONS: Reconstruction of hip geometry using a single-version novel short-stem-system is achievable with comparable results to stem-systems offering multiple options.

Does difference in stem design affect accuracy of stem alignment in total hip arthroplasty with a CT-based navigation system?

The efficacy of a computed tomography (CT)-based navigation system to accurately position the stem for intended alignment is unclear. In addition, the influence of stem design on the accuracy of insertion is unknown. We therefore retrospectively compared the accuracy and precision for the intended alignment of two different designs of femoral stem which were implanted with or without the navigation system. Forty-nine total hip arthroplasties (THAs) using a tapered wedge stem and 91 THAs using an anatomic stem were evaluated for the navigation group. Thirty-three THAs using the tapered wedge stem and 15 THAs using the anatomic stem were controls for the non-navigation group. Differences between postoperative measurement and preoperative planning were compared among the groups. In the navigation groups, accuracy (mean absolute difference) and precision (95% limits of agreement) of stem anteversion were 4.3° and ± 10.1° in the tapered wedge stem and 3.1° and ± 6.9° in the anatomic stem. In the non-navigation groups, these were 6.0° and ± 15.2° and 4.8° and ± 12.4°, respectively. The accuracy and precision in the navigation groups were significantly superior to those in the non-navigation group, and those in the anatomic stem group were significantly superior to those in the tapered wedge group. Using the CT-based navigation system, the accuracy and precision for intended stem anteversion were improved. When compared under guidance of navigation system, the accuracy and precision for intended stem anteversion in the anatomic stem were superior to those in the tapered wedge stem.

Modern Revision Femoral Stem Designs Have No Difference in Rates of Subsidence.

BACKGROUND: Both modular and monoblock tapered fluted titanium (TFT) stems have gained popularity over fully porous-coated cylindrical (FPCC) femoral stem designs, but limited data exist comparing subsidence rates following revision total hip arthroplasty (THA). The purpose of this study is to determine differences in subsidence and clinical outcomes among 3 revision femoral stem designs. METHODS: We reviewed a consecutive series of 335 patients who underwent femoral component revision to a cementless modular TFT (n = 225), monoblock TFT (n = 63), or FPCC (n = 47) stem between 2012 and 2019. We evaluated radiographic subsidence rates, re-revision rates, and patient-reported outcomes between the 3 stems. A multivariate regression analysis was performed to determine the independent effect of stem type on the risk of subsidence >5 mm. RESULTS: At an average follow-up of 39 months (range, 12 to 96 months), there were no differences in mean subsidence rates (3.5 vs 2.4 vs 2.1 mm, P = .14), HOOS Jr scores (78 vs 74 vs 64 points, P = .15), or aseptic re-revision rates (4% vs 3% vs 0%, P = .29) between modular TFT, monoblock TFT, and FPCC stems. Although modular TFT stems were more often used in patients with extensive femoral bone loss (Paprosky III and IV), there were no differences in subsidence rates >5 mm among the 3 stems (P > .05) in multivariate analysis. CONCLUSION: Modular TFT, monoblock TFT, and FPCC femoral stem designs all perform well in revision THA with no difference in clinical outcomes or subsidence rates. Surgeons should select the stem which they feel is the most clinically appropriate.

Periprosthetic Femur Fracture Risk: Influenced by Stem Choice, Not Surgical Approach.

BACKGROUND: Periprosthetic femur fracture (PFF) remains a common reason for failure after total hip arthroplasty (THA). For over 10 years, our institution has performed both anterior approach (AA) and posterolateral (PL) approaches for primary THA with multiple stem designs. The aim of this study is to determine the 90-day relative risk of PFF with regard to approach and stem design. METHODS: A retrospective review of our institutional database was performed on all patients undergoing primary THA from 2007 to 2018 using AA or PL approaches. Five surgeons performing 6309 THAs (AA = 4510; PL = 1799) using single-wedge taper (n = 2417) or fit-and-fill (n = 3892) stems were included. PFF occurring within 90 days of the index procedure were analyzed. Differences in PFF rates, fracture location, stem type, and treatment method were assessed. Comparisons were made using a Cox regression analysis. RESULTS: The 90-day revision rate for fracture was 0.3%. Clinically significant fractures requiring cerclage cabling, stem change, revision, or open reduction internal fixation occurred in 0.9% of patients (intraoperative = 37, 0.6%; postoperative = 17, 0.3%). Cox regression found PFF risk was significant for female patients (P = .008), patients older than age 65 (P < .01), single-wedge taper stems (P = .05), and for cases with collarless stems (P = .04). Among PFF cases that required surgical intervention, risk factors were female sex, age older than 65, and body mass index under 25 (P < .05). Collarless stems were 2.6 times more likely to result in PFF than collared stems (P = .04). Single-wedge taper stems were 2.3 times more likely to result in PFF than fit-and-fill stems (P = .05). Approach was not found to be an independent risk factor for PFF (P = .85). CONCLUSION: Our single-center experience demonstrates the risk of periprosthetic fracture within 90 days of surgery is significantly lower with collared stems and fit-and-fill stem designs. Female sex, age over 65, and body mass index below 25 nearly double the PFF risk. Surgical approach did not influence fracture rates.

Risk Factors for Periprosthetic Femur Fracture and Influence of Femoral Fixation Using the Mini-Anterolateral Approach in Primary Total Hip Arthroplasty.

BACKGROUND: The mini-anterolateral (AL) approach for total hip arthroplasty (THA) has gained popularity. In contrast to other approaches, risk factors for periprosthetic femur fractures have not been well established for the AL approach. METHODS: Six hundred eighty-four primary THAs performed using the AL approach were retrospectively reviewed for risk factors associated with perioperative periprosthetic femur fractures within 3 months of surgery. Risk factors evaluated were gender, age, body mass index, laterality, and Dorr ratio of the proximal femur. Cemented stems and collared uncemented stems were compared to uncemented tapered-wedge and meta-diaphyseal stems. A Student's t-test was used for continuous variables, and a chi-squared test was used for categorical variables. RESULTS: Of 684 primary THAs performed, 57 (8.3%) resulted in fracture. Twenty-eight (4.1%) occurred intraoperatively and 29 (4.2%) occurred postoperatively within 90 days. All intraoperative fractures were fixed at the time of surgery and healed uneventfully. Of the postoperative fractures, 15 (2.2%) were amenable to nonoperative management and healed. Fourteen (2.0%) required revision arthroplasty. There was a significantly lower rate of fracture in patients receiving cemented or collared stems (0%, n = 101) than in those receiving tapered-wedge or meta-diaphyseal fitting stems (9.8%, n = 583; P = .0009). Odds of fracture increased with female gender (P = .0063) and increasing Dorr ratio (P = .0003). Analysis showed a trend toward increased risk with older age, but did not achieve statistical significance. Body mass index and laterality showed no statistically significant effect. CONCLUSION: Performing primary THA via the AL approach, 2.0% of patients had a postoperative fracture requiring revision within the first 3 months. With cemented and collared stems, the fracture rate was significantly lower. Surgeons should consider using cemented or collared stems in high-risk patients.

Effect of humeral stem and glenosphere designs on range of motion and muscle length in reverse shoulder arthroplasty.

PURPOSE: To determine how different combinations of humeral stem and glenosphere designs for reverse shoulder arthroplasty (RSA) influence range of motion (ROM) and muscle elongation. METHODS: A computed tomography scan of a non-pathologic shoulder was used to simulate all shoulder motions, and thereby compare the ROM and rotator cuff muscle lengths of the native shoulder versus 30 combinations of humeral components (1 inlay straight stem with 155° inclination and five onlay curved stems with 135°, 145° or 155° inclinations, using concentric, medialized or lateralized trays) and glenospheres (standard, large, lateralized, inferior eccentric and bony increased-offset (BIO-RSA)). RESULTS: Only five of the 30 combinations restored ≥ 50% of the native ROM in all directions: the 145° onlay stem (concentric tray) combined with lateralized or inferior eccentric glenospheres and the 145° stem (lateralized tray) combined with either a large, lateralized or inferior eccentric glenosphere. Lengthening of the supraspinatus and infraspinatus, observed for all configurations, was greatest using onlay stems (7-30%) and BIO-RSA glenospheres (13-31%). Subscapularis lengthening was observed for onlay stems combined with BIO-RSA glenospheres (5-9%), while excessive subscapularis shortening was observed for the inlay stem combined with all glenospheres except the BIO-RSA design (> 15%). CONCLUSIONS: The authors suggest implanting 145° onlay stems, with concentric or lateralized trays, together with lateralized or inferior eccentric glenospheres.

Sagittal profile has a significant impact on the explantability of well-fixed cemented stems in revision knee arthroplasty: a biomechanical comparison study of five established knee implant models.

BACKGROUND: Easy revisability is gaining increasingly in importance. The removal of well-fixed cemented stems is very demanding and is often associated with increased operative morbidity. Implant design may be here a decisive impact factor, and the best way to ascertain it is experimentally. Aim of this study is to assess different cemented stems of established knee revision implants in regard to their removal capability. METHODS: Based on their sagittal profile, five stem extensions from known manufacturers were divided in conical, conical-cylindrical and cylindrical designs. The pedicles were also characterized in respect to their cross section, diameter and surface roughness. The cemented stems were dismounted six times each in a reproducible biomechanical setup. The explantation energy required was determined and statistical analyzed. RESULTS: The conical shaft needed significantly the slightest explantation energy with 19.2 joules (p = 0.004). There was a strong negative linear correlation between conicity proportion and explantation energy of the cemented stems (R2 = 0.983). The removal of the three purely cylindrical shafts-regardless of their differences in diameter, cross-sectional design and surface- was the most demanding (98.3, 105, and 116.7 joules) with only secondary differences between them. CONCLUSION: The longitudinal stem profile may have a primary impact on the explantability of well-fixed cemented shafts with conical designs showing superiority. Cross-sectional profile and surface roughness had here a less decisive influence on the explantability. Surgeons can choose proper implants and removal techniques depending on potential implant-associated revision risks and re-revisions to be expected.

Impact of Femoral Stem Design on Failure After Anterior Approach Total Hip Arthroplasty.

BACKGROUND: An increased rate of complications related to femoral component failure has been described with less invasive total hip arthroplasty (THA). This study evaluated the incidence of femoral complications associated with the direct anterior approach for THA. METHODS: Retrospective review was performed of the initial 1120 consecutive patients who underwent direct anterior THA by 2 surgeons. RESULTS: A total of 899 patients (80.3%) had a 2-year follow-up (range, 2-8 years). Complications within 90 days occurred in 20 patients (1.8%): 10 calcar fractures, 1 greater trochanter fracture, 1 canal perforation, 3 hematomas, 2 dislocations, 2 superficial, and 1 deep infection. Nine patients (1%) underwent revision: 5 for aseptic femoral loosening (0.55%), 1 for periprosthetic joint infection, 1 for dislocation, 1 for hip flexor irritation, and 1 for a damaged polyethylene liner. Of the 5 patients with aseptic femoral loosening, 3 had a short, mediolateral tapered stem, 1 cemented stem, and 1 S-ROM stem placed to bypass a canal perforation. There were no revisions for aseptic loosening in the collared, fully hydroxyapatite (HA)-coated compaction broached or triple tapered proximal fit and fill stem designs (70.6% of all stems). Revision rate for femoral loosening was significantly higher for tapered wedge over HA-coated, compaction broached stems (P < .005). CONCLUSION: Pain and function improved predictably with a 0.55% rate of femoral loosening at 2-year follow-up. Among collared, fully HA-coated and triple taper fit and fill femoral stems, there were no instances of revision for aseptic loosening vs 3 in the short stem, collarless mediolateral tapered group.

Polished, Collarless, Tapered, Cemented Stems for Primary Hip Arthroplasty May Exhibit High Rate of Periprosthetic Fracture at Short-Term Follow-Up.

BACKGROUND: Cemented stems are designed to follow 1 of 2 principles of fixation: composite beams or slide taper. Stems in the latter category have a collarless, polished, tapered (CPT) design and subside into the cement mantle, creating hoop stresses. We compared the rate of periprosthetic fracture (PPF) of stem designed with these 2 principles of fixation. In addition, we examined radiographic factors that may predispose to the development of PPF. METHODS: We retrospectively reviewed all patients who underwent primary THA by a single surgeon using highly polished cemented stems. PPF rates were compared between CPT stems (follow-up, 21 months; standard deviation [SD], 22) and composite beam stems (follow-up, 21.7 months; SD, 26). Demographic data were compared between patients with and without a PPF. Three preoperative radiographic parameters (canal bone ratio [CBR], canal-calcar ratio, and canal flare index), stem alignment, and cement mantle were compared in match-paired patients with and without a PPF (1:34). RESULTS: Seven of 1460 THA patients developed a PPF (0.479%); 4 hips of 185 with a CPT stem (2.2%); and 3 of 1275 hips with a composite beam stem (0.23%; P = .0064). Three of the 4 PPFs in the CPT group and none in the composite beam group were classified as Vancouver B2. The CBR in patients with a PPF was 0.50 (SD, 0.07) and 0.43 (SD, 0.07) in the match cohort of hips without PPF (P = .013). CONCLUSION: CPT stems may be associated with a higher risk of PPF that often require reoperation. An increased CBR may be a risk factor for postoperative PPF.

Cemented conical stems can be removed more easily than cylindrical stems, regardless of cone angle in revision knee arthroplasty.

BACKGROUND: According to literature, more than 30% of revised knee arthroplasties will require at least one re-revision. Practical experience has shown that there are considerable product-specific differences in the explantability of cemented long-stem prostheses. In the registers of successful implants, stem geometry varies considerably between the manufacturers. However, comparative data on explantability of the respective stems are missing. Objective of the present study was to identify a correlation between the geometry of a smooth cemented long stem and the necessary explantation energy required until failure of the implant-cement interface occurs. METHODS: Eight cemented stems with different conical profile angles (0°-3°) were explanted in a reproducible biomechanical setup each six times to evaluate the correlation between the stem design and the required explantation energy. RESULTS: The average explantation energy was highest in the case of the cylindrical stem, at 18.1 ± 3.6 J. At a cone angle of 0.25°, it was just 12.1 ± 2.1 J (p < 0.001) and dropped beyond 0.5° to an average of 5.7 ± 1.8 J (p < 0.001). Between 0.5° and 3°, no significant difference in the required extraction energy was observed. CONCLUSIONS: Whereas smooth conical stems can mostly be removed easily, an early decision in favour of osteotomy or fenestration can be taken in the case of cylindrical cemented stems.

Difference in Postoperative Periprosthetic Bone Mineral Density Changes Between 3 Major Designs of Uncemented Stems: A 3-Year Follow-Up Study.

BACKGROUND: Although few studies have examined the direct effect of stress shielding on clinical outcomes, periprosthetic bone loss due to stress shielding is still an issue of concern, especially when physicians perform uncemented total hip arthroplasty (THA) in younger patients. Differences in femoral stem design may affect the degree of postoperative stress shielding. Therefore, the characteristics of the behavior for stress shielding of each type of femoral stem should be determined. This study compares differences in bone mineral density (BMD) change in the femur after primary THA between 3 major types of uncemented stems. METHODS: Among a total of 89 hips, 26 hips received THA with a fit-and-fill type stem (VerSys Fiber Metal MidCoat; Zimmer, Inc, Warsaw, IN), 32 hips received a tapered rectangular Zweymüller-type stem (SL-Plus; Smith & Nephew Inc, Memphis, TN), and 31 received a tapered wedge-type stem (Accolade TMZF; Stryker Orthopaedics, Mahwah, NJ). BMD measurements were performed with a HOLOGIC Discovery device (Hologic Inc, Waltham, MA). RESULTS: BMD in the medial-proximal femur was maintained for 3 years after THA in the group with the tapered wedge-type stem. BMD in the lateral-proximal femur was maintained for 3 years after THA in the group with the Zweymüller-type stem. There were no significant differences in the Harris Hip Score among the 3 stem groups preoperatively and 1, 2, and 3 years after surgery. CONCLUSION: There are clear differences in postoperative BMD loss of the proximal femur among these 3 commonly used uncemented stems.