Sex-Specific Association of Clinical Parameters and Components of Femoral Bone Quality in Patients Undergoing Total Hip Arthroplasty.

Poor bone quality is a critical factor associated with an increased risk of complications after total hip arthroplasty (THA). However, no consistent recommendations have yet been established for assessing indicators of bone quality preoperatively. Thus, it remains unclear which preoperatively available and readily accessible parameters are most closely associated with femoral bone quality. Here, we obtained femoral neck specimens from 50 patients undergoing THA. Preoperative Dual-energy X-ray absorptiometry (DXA) scans, pelvic radiographs, and laboratory parameters were analyzed. In the obtained specimens, bone microstructure was assessed using micro-CT and histomorphometry. Additionally, matrix mineralization and osteocyte lacunar morphology were evaluated using quantitative backscattered electron imaging. Our analysis revealed that DXA-derived T-scores correlated with trabecular microstructure. Furthermore, radiographic indices and body mass index correlated differentially with aspects of bone quality in women and men. Contrary to previous observations, no correlation was found between serum vitamin D levels and osteoid indices, nor between clinical parameters and matrix mineralization. Age was strongly associated with the number of mineralized osteocyte lacunae, a factor that appeared to be independent of sex. Taken together, our study demonstrates that no single preoperatively available parameter exhibits a strong and consistent association with femoral bone quality. However, DXA remains a reliable preoperative measure for determining the trabecular microstructure of the femoral neck. In clinical practice, surgeons should adopt an individualized approach to preoperative assessments by considering age, sex, BMI, and radiographic indices to enhance their insight into femoral bone quality, particularly when DXA is unavailable.

Areal bone mineral density is not associated with femoral stem subsidence in patients younger than 70 years undergoing total hip arthroplasty.

INTRODUCTION: Femoral stem subsidence is a known complication after uncemented total hip arthroplasty (THA). The purpose of this study was to determine the frequency of osteoporosis and to investigate the relationship between areal bone mineral density (aBMD) and subsidence in a cohort of patients younger than 70 years. METHODS: One hundred consecutive patients (age 60 ± 6 years; 52 female, 48 male) undergoing uncemented THA using a collarless press fit femoral stem were retrospectively reviewed. Dual-energy X-ray absorptiometry (DXA) was performed preoperatively at the proximal femur and lumbar spine, and if not feasible at these sites, at the distal radius. DXA results were compared to a cohort of 100 patients ≥ 70 years scheduled for cemented THA. Age, sex, and body mass index (BMI), canal flare index (CFI), and canal fill ratio (CFR) were assessed. Analysis of stem subsidence and migration was performed on standardized, calibrated radiographs obtained postoperatively and at follow-up. RESULTS: The frequency of osteoporosis was considerably lower in the study cohort compared to patients ≥ 70 years (7% vs. 19%, p = 0.02). Illustrated by the high CFR (mean 96 ± 4%) in the mid-stem region, a sufficient press fit was achieved. After a mean follow-up of 7.4 months, the mean stem subsidence was 0.9 ± 0.9 mm. Only two patients had subsidence greater than 3 mm, one of whom was morbidly obese and the other diagnosed with severe osteoporosis. There were no correlations between any of the parameters (CFI, CFR, age, sex, BMI) and femoral stem subsidence. In addition, aBMD T-scores showed no correlations with subsidence. CONCLUSION: aBMD by DXA does not appear to be associated with stem subsidence in patients younger than 70 years and with adequate press fit.

Bi-planar calibration method for templating of hip joint arthroplasty: phantom study and proof of concept.

PURPOSE: Calibration of radiographs is a critical step in digital templating for hip arthroplasty. Calibration errors of > 1.5% lead to over- or undersizing of the templated implants and may affect logistics and patient safety. Contemporary calibration methods are known to be imprecise with average errors of 6.5% and wide variance. A novel bi-planar radiograph-based calibration method is proposed, and a phantom study was conducted as proof of concept. METHODS: A spherical external calibration marker (ECM) is placed in front of the pubic symphysis of a pelvic bone model at twelve different positions. For each marker position, standard anteroposterior radiographs and four corresponding lateral radiographs with different degrees of rotation (0°-30°) are taken (overall, 60 radiographs). Calibration factors are calculated for an internal calibration marker (ICM) at the centre of the right hip (reference) and the ECM using a novel algorithm. Rotation and marker positions simulate foreseeable use errors and misplacements and aim to test robustness of the method against these errors. RESULTS: ECM calibration factor was 125.9% (range 124.7-127.2), and the mean ICM calibration factor was 126.6% (range 126.2-127.1) ([Formula: see text]). Four images (8.3%) were beyond the 1% error threshold (all with 30° rotation). The mean difference was 0.79% (SD 0.49). CONCLUSION: The bi-planar method precisely predicts the true calibration factor of the hip joint plane under various conditions. In lateral radiographs, rotation of up to 20° did not adversely affect the precision and all images had calibration errors below the threshold for clinical significance.

Outcome of different reconstruction options using allografts in revision total hip arthroplasty for severe acetabular bone loss: a systematic review and meta-analysis.

INTRODUCTION: Several studies have reported good to excellent outcomes of revision total hip arthroplasty (rTHA) using allografts for treating severe acetabular bone defects. However, precise information on the impact of allograft type and reconstruction method is not available. MATERIAL AND METHODS: Systematic literature search was performed in Medline and Web of Science including patients with acetabular bone loss classified according to the Paprosky classification who underwent rTHA involving the use of allografts. Studies with a minimum follow-up of 2 years published between 1990 and 2021 were included. Kendall correlation was applied to determine the relationship between Paprosky grade and allograft type use. Proportion meta-analyses with 95% confidence interval (CI) were performed to summarize the success of various reconstruction options, including allograft type, fixation method, and reconstruction system. RESULTS: Twenty-seven studies met the inclusion criteria encompassing 1561 cases from 1491 patients with an average age of 64 years (range 22-95). The average follow-up period was 7.9 years (range 2-22). Structural bulk and morselized grafts were used in equal proportions for all Paprosky acetabular defect types. Their use increased significantly with the type of acetabular defect (r = 0.69, p = 0.049). The overall success rate ranged from 61.3 to 98.3% with a random effect pooled estimate of 90% [95% CI 87-93]. Trabecular metal augments (93% [76-98]) and shells (97% [84-99]) provided the highest success rates. However, no significant differences between reconstruction systems, allograft types and fixation methods were observed (p > 0.05 for all comparisons). CONCLUSION: Our findings highlight the use of bulk or morselized allograft for massive bone loss independent of Paprosky classification type and indicate similar good mid- to long-term outcomes of the different acetabular reconstruction options using allografts. CLINICAL TRIAL REGISTRATION: PROSPERO: CRD42020223093.

A novel bi-planar calibration method for digital templating in total hip arthroplasty.

In total hip arthroplasty and reconstructive orthopedic surgery, pre-operative digital templating is essential for surgical treatment optimization, risk management, and quality control. Calibration is performed before templating to address magnification effects. Conventional methods including fixed calibration factors, individual marker-based calibration and dual-scale marker methods are not reliable. A novel bi-planar calibration method is described aiming to reduce the error below clinical significance. The bi-planar calibration method requires two conventional orthogonal radiographs and a standard radiopaque marker ball. An algorithm computes the hip plane height parallel to the detector in the antero-posterior radiograph. Foreseeable errors (i.e., patient rotation and misplaced markers or lateral offset) are considered in a correction algorithm. Potential effects of errors are quantified in a standard model. Influence of rotation in lateral radiographs and lateral offset of marker on the calibration factor are quantified. Without correction, patient rotation in the lateral radiograph of 30° results in absolute calibration error of 2.2% with 0 mm offset and 6.5% with 60 mm lateral offset. The error is below the threshold of 1.5% for rotation less than 26° with 0 mm offset and 10° with 60 mm offset. The method is supposed to be reliable in precisely predicting the hip plane and thereby the calibration factor. It may be superior to other methods available. In theory, the method allows correction of clinically relevant rotation of at least 30° and marker displacement without impacting the computed calibration factor.

Dual-scale single marker calibration for digital templating of total hip arthroplasty in standing radiographs: a prospective clinical study.

PURPOSE: Accuracy of calibration of radiographs significantly influences the quality of digital templating for total hip arthroplasty (THA). The standard of care is calibration with external calibration markers (ECM). This method is associated with significant errors. Dual-scale single marker (DSSM) calibration methods may improve accuracy. The present prospective observational study is the first to analyze the application of a DSSM method in standing pelvis radiographs. METHODS: 100 patients with unilateral THA underwent antero-posterior pelvis radiographs with ECM and DSSM. The hip components were used as reference calibration factor (internal calibration factor; ICM). Absolute differences of calibration factors for ECM and DSSM from ICM were calculated. Absolute relative deviations (ARD) were calculated. Subgroup analysis for sex and WHO BMI category was performed. Furthermore, patients reported subjective comfort for each marker using a 10-point scale and choosing the preferred marker. RESULTS: Maximum magnification factor differences from the ICM were 23.3% and 9.5% and mean absolute differences were 12.5% and 2.1% for the ECM and DSSM, respectively. ARD from ICM was significantly lower for DSSM compared to ECM (p < 0.001). Absolute differences increased with BMI category using ECM; calibration by DSSM was consistent in all subgroups. Patients preferred DSSM over ECM (n = 53) or were indifferent (n = 20). Comfort was rated significantly higher for DSSM versus ECM (p < 0.001). CONCLUSION: DSSM method showed superior results in comparison to the ECM method for calibration of digital radiographs. DSSM could be used to improve digital templating in standing radiographs.

Prevalence of osteoporosis and osteopenia in elderly patients scheduled for total knee arthroplasty.

INTRODUCTION: Osteoporosis is a common comorbidity in elderly patients with osteoarthritis (OA) and may increase perioperative complications in orthopedic surgery (e.g., component migration, periprosthetic fractures). As there is no investigation of bone mineral density (BMD) in elderly patients prior to total knee arthroplasty (TKA) in Europe, we investigated this issue with a particular focus on a potential treatment gap. MATERIALS AND METHODS: We assessed the BMD by dual-energy X-ray absorptiometry (DXA) in 109 consecutive elderly patients (age ≥ 70 years) scheduled for TKA. In addition to a detailed assessment of osteoporosis and osteopenia, the influence of clinical risk factors and radiological OA severity on BMD was evaluated using group comparisons and linear regression models. In addition, we analyzed differences in BMD between patients scheduled for TKA vs. total hip arthroplasty (THA). RESULTS: Of the included 109 patients, 19 patients (17.4%) were diagnosed with osteoporosis and 50 (45.9%) with osteopenia. In the osteoporotic patients, a clinically relevant underdiagnosis concomitant with a serious treatment gap was observed in 95.0% of the patients. Body mass index, OA grade, and glucocorticoid use were identified as independent factors associated with BMD. No differences in BMD were found between the patients scheduled for TKA vs. THA. CONCLUSIONS: Considering the high prevalence of osteoporosis and osteopenia in elderly patients, DXA screening should be recommended for patients ≥ 70 years indicated for TKA.

Implications of component size and calibration error on digital templating for total hip arthroplasty. A visual matrix from a simple mathematical model.

OBJECTIVE: Preoperative digital templating is a standard procedure in total hip arthroplasty. Deviations between template size and final implant size may result from inaccurate calibration, templating as well as intraoperative decisions. So far, the explicit effect of calibration errors on templating has not been addressed adequately. MATERIALS AND METHODS: A mathematical simulation of calibration errors up to ± 24% was applied to the templating of acetabular cups (38 to 72 mm diameter). The effect of calibration errors on template component size as deviation from optimal size was calculated. RESULTS: The relationship between calibration error and component size deviation is inverse and linear. Calibration errors have a more pronounced effect on larger component sizes. Calibration errors of 2-6% result in templating errors of up to two component sizes. Common errors of up to 12% may result in templating errors of 3-4 sizes for common implant sizes. A tabular matrix visualizes the effect. CONCLUSION: Calibration errors play a significant role in component size selection during digital templating. Orthopedic surgeons should be aware of this effect and try to identify and address this source of error.

[Cost analysis of inpatient versus outpatient intravenous antibiotic treatment for periprosthetic joint infections : A simulation]. / Kostenanalyse stationärer und ambulanter intravenöser Antibiotikatherapie periprothetischer Gelenkinfektionen : Eine Simulation.

BACKGROUND: Parenteral antibiotic administration in the treatment of periprosthetic joint infections (PJI) often requires inpatient settings. This is associated with significant costs to the healthcare system. OBJECTIVE: The costs of inpatient parenteral antibiotic treatment (IPAT) and simulated costs of outpatient parenteral antibiotic treatment (OPAT) were compared in patients with PJI. Evaluations were carried out from the perspectives of cost bearers (insurances) and healthcare providers (hospitals). MATERIAL AND METHODS: The analysis and simulations were performed for all cases with the ICD-10 diagnosis T84 in the treatment year 2015. RESULTS: The simulated reduction of 159 bed-days in the 12 patients included in the study resulted in a reduction of the total costs of>18,000 € from the perspective of the health insurance. From the perspective of the hospitals the pure proceeds were improved by >22,000 €. The total costs of OPAT were >57,000 € for the health insurance. For hospitals the difference of policlinic proceeds and costs of OPAT showed a loss of >1500 €. CONCLUSION: For hospitals the OPAT is overall financially advantageous. Further advantages due to opportunity costs seem to be interesting. For cost bearers OPAT is associated with an additional financial expenditure, particularly due to costs of outpatient medication. The private sector should be considered due to the assumed additional burden as well as the assumed patient comfort.

Anterior cruciate ligament intactness in osteoarthritic patients indicated for total knee arthroplasty: a systematic literature review and meta-analysis.

Bi-cruciate retaining total knee arthroplasty (BCR TKA) is thought to result in more natural knee kinematics compared to conventional TKA designs. This may lead to a reduction in dissatisfied patients after TKA. An intact anterior cruciate ligament (ACL) is a prerequisite for implantation of a BCR TKA but the frequency of an intact ACL in patients indicated for TKA is not well known. The objective of this systematic literature review was to determine the presence of an intact ACL in patients undergoing TKA by intraoperative macroscopic or MRI assessment. A systematic literature review was conducted using PubMed™ and EMBASE™ in June 2020. The ACL of patients with knee osteoarthritis (OA) undergoing TKA was classified as present (including intact and degenerated) vs. absent, and as intact vs. not fully intact. Proportional meta-analyses were performed. 2840 articles were identified and screened. 135 full texts were analyzed and 18 studies met the inclusion criteria for subsequent qualitative and quantitative meta-analysis. Analysis of the status of the ACL when assessed intraoperatively during TKA showed that the ligament was present in 79.4% of patients (CI: 73.5-84.3%), from 14 studies with 2067 cases studied. The ACL was determined to be intact in 55.0% of patients (CI: 45.3-64.4%), from 14 studies with 1916 cases. Preoperative ACL assessment using MRI (2 studies) revealed it was present in 82.9% of 193 cases (CI: 76.9-87.6%), and intact in 56.8% of 176 cases (CI: 8.2-94.7%). This systematic literature review shows that the ACL is macroscopically intact in more than half of patients with knee OA undergoing TKA, based on intraoperative assessment of the ligament. The results suggest BCR TKA may be considered as an alternative to traditional TKA in a large number of TKA patients. More high-quality studies are needed to better understand the functional status of the ACL in TKA patients.Level of evidence III.

Bi-cruciate retaining total knee arthroplasty: a systematic literature review of clinical outcomes.

Total knee arthroplasty (TKA) has been shown to have good long-term outcomes and survivorship. Nonetheless, dissatisfied patients are frequently reported in the literature. Bi-cruciate retaining total knee prostheses (BCR TKA) were designed to address the demand for more kinematically functional implants that better reconstruct natural knee kinematics. In BCR TKA, the anterior cruciate ligament (ACL) is preserved. Improved patient-reported outcomes and satisfaction levels are expected. This review aimed to summarize indications for and clinical outcomes of BCR TKA. A systematic literature review on BCR TKA was performed. 24 articles were included for data analysis. Indications covered osteoarthritis, inflammatory arthritis and others. The degree of deformity was often but not always limited to minor axial deformity and contractures: maximum acceptable varus/valgus deformity reached 10°-30° and flexion contractures of 15°-65°. ACL intactness was macroscopically examined intraoperatively in nine studies and clinically tested in ten studies (e.g., Lachmann Test, drawer-test). Objective and patient-reported outcome scores were reported for follow-up periods of up to 22 years. Survival rates varied significantly. For first generation implants, 22-year survival reached 82% while a second generation design was associated with 13.5% revision rate at 18 months. Reasons for varying outcomes were not clear and may be attributed to the implant itself, surgical techniques and patient specific variables including changed expectations and functional demand. The literature has not shown clear indications and guidelines for the use of BCR implants. The promising results of first generation BCR TKA designs may be optimized through improved implant designs in the future. Further studies are advocated to provide the necessary evidence of second generation BCR TKA designs.

Intra-individual variance of bilateral femoro-tibial leg rotation: a CT study of 105 healthy subjects.

PURPOSE: In cases of suspected rotational deformity of the lower limb, in particular in post-traumatic malalignment following closed nailing, there is a lack of adequate reference values. Available publications on leg rotation have either small sample sizes or do not include bilateral or whole leg rotation of healthy legs. This study aimed to determine side-specific reference values of lower limb rotation in a large healthy sample. This may be helpful in acute clinical settings as well as for medical expert opinion. METHODS: 226 consecutive bilateral lower limb computed tomography (CT) angiographies were screened. 105 patients (210 legs) were included (40 females, 65 males, mean age 67 ± 12 years). Bilateral axial femoral and tibial rotation alignment were independently measured and overall leg rotation was computed by two methods. Distributions, sex, and side differences were analyzed. RESULTS: Two-sided paired t tests showed significant differences between right and left for all measurements. The left side showed a more pronounced mean anteversion in the femur of 2.2° (p = 0.002) and the right side higher mean external rotation in the tibia of 2.8° (p < 0.001). Overall leg rotation showed 5.1° more mean external rotation on the right side (p < 0.001) with both methods. Absolute side-to-side whole leg rotation difference was 9.5°. Absolute differences between both methods were 3.3°. The variance was high. 23 femora were retroverted, 1 tibia internally rotated, and 9 legs were overall internally rotated. No variables differed between female and male subjects except for femoral version (right p = 0.003 and left p = 0.002). Correlation coefficients were high (rho 0.550-0.934, all p < 0.001). CONCLUSION: There is a significant prevalence of side-to-side asymmetry in femoro-tibial torsion. Although side-to-side differences are not extraordinary, comparative axial femoro-tibial rotation alignment should always be interpreted with caution. LEVEL OF EVIDENCE: Diagnostic, retrospective cohort study, level III.

Indications for bi-cruciate retaining total knee replacement: An international survey of 346 knee surgeons.

There is limited evidence on total knee arthroplasty (TKA) that retains the anterior and the posterior cruciate ligaments. Bi-cruciate retaining (BCR) TKA is considered to show improved clinical function and kinematics. This survey aimed to (1) identify interest in and acceptance of BCR TKA surgery and (2) to capture the range of indications for BCR in the opinion of practicing knee surgeons. 346 surgeons with experience in TKA surgery completed a bi-lingual online survey. Demographics, arthroplasty experience as well as acceptance of and indications for BCR TKA were collected. 53 surgeons were experienced in BCR TKA and 225 would consider implanting it. A mean of 19.5% of TKA patients were considered eligible for BCR TKA. 56.3% were thought to have intact ACL at the time of TKA surgery. Surgeons were not likely to perform BCR TKA in patients with inflammatory arthritis, aged over 80, BMI above 34.9 kg/m2, a varus or valgus deformity of more than 10° and flexion contractures of more than 10°. There is strong interest among orthopedic surgeons to perform BCR TKA and the percentage of potentially eligible patients is high. Significant joint deformity is a limitation of BCR TKA, while age and high BMI are less relevant. BCR TKA experienced surgeons are less restrictive.

A novel calibration method for digital templating of total hip arthroplasty: a prospective clinical study of dual scale type single marker calibration in supine radiographs.

BACKGROUND: External calibration markers (ECM) are the standard of care for digital templating in joint replacements. Spherical mono markers are known to be unreliable. Fixed calibration factors (FCF) can reduce the overall error by placement of markers, but do not address individual patient anatomy. Dual scale calibration marker (DSCM) methods were developed to improve precision of calibration but require two markers. This prospective observational study is the first to analyse the application of a dual scale type single marker (DSSM) method in supine radiographs. METHODS: One hundred patients with unilateral total hip arthroplasty (THA) underwent anterior-posterior pelvis X-ray with ECM and DSSM. The femoral THA head components were used as internal reference (ICM). An empirical fixed calibration factor (FCF; 120%) was used as comparator. Absolute differences of ICM and both ECM and DSSM were calculated. Absolute relative deviations (ARD) were calculated. RESULTS: Mean absolute calibration factor differences of ECM, FCF and DSSM from ICM were 0.105 (0.002-0.182), 0.016 (0.082-0.013) and 0.011 (0.056-0.009), respectively. ARD differences between ECM and DSSM as well as FCF and DSSM were significant (p < 0.001). CONCLUSION: The DSSM method showed superior results over ECM and FCF to predict the optimal calibration factor in supine radiographs. The novel DSSM method could be used to improve digital templating in supine radiographs without need for additional markers.

Publication rate of abstracts presented at the Congress of the European Federation of National Associations of Orthopaedics and Traumatology (EFORT).

BACKGROUND: The publication rate of presented abstracts is an important parameter to assess the scientific quality of medical congresses. It has been investigated for many congresses in orthopaedics and traumatology, but until now, it has not been studied for the congress of the European Federation of National Associations of Orthopaedics and Traumatology (EFORT). The aims of this study were to determine: (1) the publication rate of the EFORT congress, (2) factors that favour publication of abstracts presented at the EFORT congress, (3) the consistency between the congress abstract and publication in relation to authorship. HYPOTHESIS: There are factors that favour publication of abstracts presented at the EFORT congress and there is a high consistency between the congress abstract and publication in relation to authorship. MATERIALS AND METHODS: All 1624 abstracts presented at the EFORT congress in 2011 were included in this study, to allow a 5-year period for publication after the congress. The characteristics of the abstracts presented were studied and the publication rate in peer-reviewed journals was determined using a Medline search. RESULTS: The publication rate for studies presented at the 2011 EFORT congress was 42% (677/1624 abstracts), with a mean of 16 months (-56 to 60 months) between congress and publication. The mean impact factor of the publications was 1.8 (0-7.6). A significantly higher publication rate was found for: oral presentations (52%; 322/617) versus posters (35%; 355/1007) (p<0.01), experimental studies (53%; 110/208) versus clinical studies (40%; 507/1254) (p<0.01), and studies with higher levels of evidence of I or II (59%; 144/244) versus studies with lower levels of evidence of III or IV (36%; 362/1005) (p<0.01). A new author was added in 59% (403/677) of the publications. DISCUSSION: Factors that favour publication of abstracts presented at the EFORT congress are oral presentation, experimental study, and a study with a higher level of evidence of I or II. It is common that a new author is added in the publication. Nevertheless, a high percentage of congress abstracts (58%; 947/1624) remains unpublished. LEVEL OF EVIDENCE: IV, retrospective study.

Cost-analysis of inpatient and outpatient parenteral antimicrobial therapy in orthopaedics: A systematic literature review.

BACKGROUND: Increasing numbers of total joint arthroplasties and consecutive revision surgery are associated with the risk of periprosthetic joint infections (PPJI). Treatment of PPJI is complex and associated with immense socio-economic burden. One treatment aspect is parenteral antiinfective therapy, which usually requires an inpatient setting [Inpatient parenteral antibiotic therapy (IPAT)]. An alternative is outpatient parenteral treatment [Outpatient parenteral antibiotic therapy (OPAT)]. To conduct a health economic cost-benefit analysis of OPAT, a detailed cost analysis of IPAT and OPAT is required. So far, there is a lack of knowledge on the health economic effects of IPAT and OPAT for PPJI. AIM: To review an economic comparison of IPAT and OPAT. METHODS: A systematic literature review was performed through Medline following the PRISMA guidelines. RESULTS: Of 619 identified studies, 174 included information of interest and 21 studies were included for quantitative analysis of OPAT and IPAT costs. Except for one study, all showed relevant cost savings for OPAT compared to IPAT. Costs for IPAT were between 1.10 to 17.34 times higher than those for OPAT. CONCLUSION: There are only few reports on OPAT for PPJI. Detailed analyses to support economic or clinical guidelines are therefore limited. There is good clinical evidence supporting economic benefits of OPAT, but more high quality studies are needed for PPJI.

Risk factors for secondary displacement in conservatively treated isolated greater tuberosity fractures: An analysis of 82 cases.

INTRODUCTION: The optimal treatment of isolated fractures of the greater tuberosity is an important topic of current surgical research. While non-displaced fractures are amenable to conservative treatment, displacement of the fragment can result in rotator cuff malfunction and impingement. For the present study, risk factors predicting secondary fragment displacement were analyzed. HYPOTHESIS: Certain risk factors determine a higher risk of secondary displacement in patients with greater tuberosity fractures. PATIENTS AND METHODS: All patients diagnosed with a fracture of the greater tuberosity and initially treated non-surgically at our Level I trauma center between January 2008 and July 2015 were included in this retrospective analysis. Patients were grouped into: no secondary displacement (group 1) and secondary displacement at follow-up (group 2). The following risk factors were analyzed: age, gender, side of fracture, initial displacement, fragment/head ratio, fragment shape, dislocation, concomitant fractures and concomitant fractures to the same extremity. RESULTS: 82 patients (42 male, 40 female) were eligible for further analyses. Median follow-up was 8.0±39.5 days. Patients with secondary displacement (group 2) were significantly older (group 1: 51.7±15.5, group 2: 68.3±14.3; p<0.001) and had significantly more shoulder dislocations (p=0.024), whereas gender (p=0.299), side of fracture (p=0.189) and fragment/head ratio (p=0.660) showed no significant different distribution between both groups. Finally, split-type fractures increased the risk of secondary displacement. DISCUSSION: The present study identified age older than 65 years to be an important risk factor for secondary displacement in the conservative management of fractures of the greater tuberosity. Furthermore, fracture type and shoulder dislocations are factors associated with an increased relative risk for secondary displacement. LEVEL OF PROOF: III, Retrospective comparative study.

Correction to: Does increased femoral antetorsion predispose to cartilage lesions of the patellofemoral joint?

Unfortunately, the following reference was not included in the original publication of the article.

Influence of calibration on digital templating of hip arthroplasty.

INTRODUCTION: Digital templating for total joint replacement is the current standard. For image calibration, external calibration markers (ECM) are used. However, there are concerns regarding the precision of the method. This study aimed to identify the direct influence of calibration errors on digital templating. PATIENTS AND METHODS: A retrospective analysis of 100 post-operative radiographs with unilateral total hip arthroplasty was performed. The magnification factor of the ECM and of the internal prosthetic femoral head (ICM) as a reference value was calculated for each radiograph. Two blinded observers performed templating of the contralateral hip using a randomized list for all radiographs and both markers. The component size templated by the ECM magnification was compared to the reference by the ICM magnification. RESULTS: Mean magnification factors of ICM and ECM differed significantly (p = 0.006). The absolute difference was 5.2% (range 0.0-23.3%, SD 4.8%). Templating of the acetabular or the femoral component showed no significant differences (p = 0.120, p = 0.599). Differences of more than one size were found in 26% of the acetabular components and 14% of the femoral components and differences over two sizes in 10% respectively 3%. Correlation coefficients for magnification error and size differences of acetabular components were - 0.645 (p < 0.001) and for the femoral component - 0.607 (p < 0.001). INTERPRETATION: The calibration error of external calibration markers in digital templating for hip replacement influences component sizes significantly. Thus, correct positioning of ECM is of utmost importance.

Femoral stem subsidence in cementless total hip arthroplasty: a retrospective single-centre study.

PURPOSE AND HYPOTHESIS: Subsidence is a known reason for early failure of total hip arthroplasty (THA). In particular, cementless THA might be vulnerable to migration. The present study analysed femoral stem subsidence after primary cementless THA. Prosthetic and anatomical risk factors for early femoral stem subsidence were evaluated. METHODS: Two hundred thirty-one consecutive patients who underwent primary cementless THA in a single centre were retrospectively analysed. Post-operative results were evaluated in consideration of prosthetic and anatomical properties in correlation with subsidence on standing pelvic anteroposterior radiographs. Stem type and design, demographic data, BMI, canal flare index (CFI) and canal fill ratio (CFR) were evaluated. RESULTS: The subsidence rate was significantly higher in collarless femoral stems [3.1 mm (SD 2.8 mm) vs. 1.9 mm (SD 1.5 mm); p = 0.013] while the anatomical type of the proximal femur as described by the canal flare index did not influenced subsidence (p = 0.050). Also, the canal fill ratio showed no significant correlation with subsidence at any level. CONCLUSIONS: In the present study, stem subsidence was significantly higher in the collarless group compared to collared stems. No anatomical parameter (CFI and CFR) could be identified as risk factor for subsidence. Neither age nor BMI influenced subsidence in this cohort. Still, subgroup analysis indicated a sex-dependent role of BMI. Prospective studies of large cohorts should address the problem of subsidence in the future. LEVEL OF EVIDENCE: Retrospective therapeutic study, Level IV.