Calcar-guided short-stem total hip arthroplasty in fractures of the femoral neck: a prospective observational study of 68 hips.

INTRODUCTION: The indications for cementless short-stem total hip arthroplasty (THA) have been expanded due to encouraging results. However, no evidence in cases of femoral neck fractures (FNFs) is available. We aimed to prospectively obtain data on the safety and the clinical outcomes of a cementless calcar-guided short stem in patients with FNFs. MATERIALS AND METHODS: We conducted a prospective observational study of 68 patients diagnosed with FNFs who underwent short-stem THA between 2016 and 2019 with a calcar-guided stem. Complications during follow-up leading to revision were documented, and patient reported outcome measurements recorded. Stem migration was analyzed using the Einzel-Bild-Röntgen-Analysis Femoral Component Analysis software. RESULTS: The mean follow-up was 33.8 ± 14.8 months. The patient mortality at last follow-up was 10.6%. Two patients required stem revision, due to periprosthetic fracture and late aseptic loosening, respectively, corresponding to 96.2% stem survival. Survivorship for the endpoint of revision for any reason was 91.1% at 6 years. All revisions occurred in females. The mean Harris Hip Score at the last follow-up was 93.0 ± 8.9. The mean axial migration at last follow-up was 1.90 ± 1.81 mm. No significant influence on migration was found regarding gender, age, weight, and body mass index. CONCLUSIONS: The clinical and radiological findings were satisfying and most patients benefited from the minimally invasive procedure. However, as for conventional THA as well, implant survivorship and mortality were markedly worse compared to results regarding osteoarthritis. Especially in elderly female patients with FNF, cementless short-stem THA is a concern and a cemented THA should be the first choice.

An isoelastic monoblock cup versus a modular metal-back cup: a matched-pair analysis of clinical and radiological results using Einzel-Bild-Röntgen-Analyse software.

INTRODUCTION: Bone preservation and long-term survival are the main challenges in cementless total hip arthroplasty (THA). A good bone stock is especially important for adequate anchorage of the cup in revision cases. However, the optimal acetabular cup design for preserving good bone stock is still unclear. We aimed to compare clinical outcome, radiological alterations, migration, and wear at mid-term for two different cup types. MATERIALS AND METHODS: This retrospective matched-pair study was performed using the data for 98 THA cases treated with a monoblock cup composed of vitamin E-blended highly cross-linked polyethylene (VEPE; monoblock group) or a modular cup composed of a highly cross-linked polyethylene (HXLPE) without an antioxidant (modular group). Clinical results were evaluated using the Harris Hip Score (HHS). The obtained radiographs were analyzed for radiological alterations, migration, and wear using Einzel-Bild-Röntgen-Analyse (EBRA) software. RESULTS: The mean follow-up duration was 73.2 ± 19.2 months (range: 32-108 months) and 60.5 ± 12.2 months (range: 20-84 months) in the monoblock and modular groups, respectively. HHS improved to 95.7 points in the monoblock group and 97.6 points in the modular group, without significant differences (p = 0.425). EBRA measurements were obtained in all cases. Acetabular bone alterations were not detected on radiological assessments. Mean cup migration was 1.67 ± 0.92 mm (range: 0.46-3.94 mm) and 1.24 ± 0.87 mm (range: 0.22-3.62 mm) in the monoblock and modular groups. The mean wear rate was 0.21 ± 0.18 mm (range: 0.00-0.70 mm) and 0.20 ± 0.13 mm (range: 0.00-0.50 mm) in the monoblock and modular groups. Both migration and wear pattern showed no significant differences (p = 0.741 and 0.243). None of the cases required revision surgery, yielding an implant survival rate of 100% in both groups. CONCLUSION: The isoelastic press-fit monoblock VEPE cup and modular metal-back HXLPE cup showed equivalent mid-term wear and cup migration. Long-term studies are required to determine the effects of modularity, isoelasticity, and polyethylene stabilization with vitamin E on cup loosening and survival rates.

Survivorship, complications and patient-reported outcomes in calcar-guided short-stem THA: prospective mid-term multicenter data of the first 879 hips.

INTRODUCTION: Short stems are a bone and soft-tissue preserving alternative to conventional stems. The aim of this multicenter study is to present the mid-term outcomes of a calcar-guided short stem. MATERIALS AND METHODS: This is a prospective case series of the first 879 total hip arthroplasties performed on 782 patients across 5 centers using identical calcar-guided short stems. In a mid-term follow-up (6 years), rates and reasons for complications and revisions were documented. The Harris Hip Score (HHS) was obtained; patients reported pain and satisfaction using a visual analog scale. RESULTS: A total of 43 patients died in the study cohort for non-related reasons; 26 patients (3.0%) required at least 1 revision after the index procedure. The survival rate for endpoint stem revision at mid-term was 98.4%. The main reasons for stem revision were aseptic loosening and early periprosthetic fractures. Sex had no influence on stem survival. Older patients or those with a high body mass index showed increased risk for stem revision during follow-up. Dorr type A morphology revealed a significantly lower risk of stem revision than Dorr type B or C (p = 0.0465). The HHS, satisfaction, and load pain at mid-term were 96.5 (SD 8.0), 9.7 (SD 0.9), and 0.5 (SD 1.9), respectively. CONCLUSIONS: This short stem produced highly satisfactory outcomes at mid-term, with 98.4% implant survival for any cause of stem revision and low complication rates. Long-term results are required to further evaluate these promising mid-term results.

Cementless Short Stems in Total Hip Arthroplasty: Chances and Limits. / Zementfreie Kurzschaftprothesen in der Hüftendoprothetik: Möglichkeiten und Limits.

In recent decades, a large number of cementless short stems have been introduced to the market. The concept aims at saving soft tissue using minimally invasive surgery and at the same time preserving as much bone as possible. In particular, the latest generation of short stems, which are implanted using a calcar-guided round-the-corner technique, are attracting increasing attention. An individualised resection level allows individual stem alignment and thus an ideal reconstruction of the hip anatomy. The early clinical results of short-stem total hip arthroplasty (THA) are promising and have led to an expansion of the indications and limitations for the use of short stems. In particular, the individual positioning in valgus or varus and the resulting individual metaphyseal or metadiaphyseal anchorage offers various possibilities to reconstruct even abnormal joint morphologies. Consequently, short stems are increasingly used in patients with complex anatomical variations or in cases of osteonecrosis of the femoral head. In some various cases, they can also be used in revision or conversion arthroplasty. In some patients, short stems can also be used after femoral neck fracture. Currently, scientific data on those areas of indication of short-stem THA is scarce.

[The challenge of revising a well-fixed curved calcar-guided short stem in total hip arthroplasty: Introduction of a new curved extraction chisel system]. / Herausforderung: Revision eines fest eingewachsenen kurvierten Kurzschaftes in der Hüftendoprothetik : Vorstellung eines neuen, kurvierten Extraktions-Meißel-Systems.

OBJECTIVE: Safe and bone-conserving extraction of a well-fixed curved short stem without the necessity of a transfemoral approach. INDICATIONS: The revision of a well-fixed curved short stem, for example, due to periprosthetic infection or malposition. Meticulous preparation of the cone and the lateral shoulder of the stem. CONTRAINDICATIONS: Correct placement of the chuck not possible. SURGICAL TECHNIQUE: Choice of a standard approach to the hip joint. Luxation. Removal of the implanted head. Preparation of the proximal femur and removal of bone at the stem shoulder. Attachment of the chuck to the cone. Insertion of the "prestarter" chisels through the guided slots of the chuck, starting with the lateral chisel, followed by the ventral and dorsal chisel. The cut must point outwards away from the implant. Repetition of this procedure using the "starter" chisels in the same order. Removal of the chuck. Careful insertion of the "final" chisels in the same order. Trial of a stem extraction using an extraction tool. Optional repetition of the whole procedure. In order to avoid fractures, opening of the medial interface only after preparation laterally, ventrally and dorsally, by careful insertion of the medial chisels in the respective order alongside the calcar. Finally, extraction of the stem. POSTOPERATIVE MANAGEMENT: Postoperative protocol according to the respective revision implants and fixation technique used. RESULTS: The described procedure has proven successful in clinical practice in the three author affiliations in a total of 14 cases. In 3 (21.4%) cases, despite the use of the extraction chisel system, an additional transfemoral approach or fenestration had to be performed to remove the short stem. Primary straight stems were used in over half of the cases (57.8%) as revision implants, whereas in 4 cases (36.4%) a cementless short stem could again be used.

Conversion of failed internal fixation in proximal femur fractures using calcar-guided short-stem total hip arthroplasty.

PURPOSE: Reoperations for secondary osteoarthritis, osteonecrosis, or hardware failure following failed internal fixation after intertrochanteric fracture (ITF) or femoral neck fracture (FNF) are common. An effective salvage treatment often involves complete removal of the hardware followed by total hip arthroplasty (THA). Almost no data are available regarding conversion to short-stem THA. This study aimed to evaluate clinical and radiological outcomes, potential complications, and the survival rate of short-stem THA following revision surgery. METHODS: We investigated 27 patients who underwent conversion THA using a calcar-guided short stem. Patient-reported outcome measurements were obtained, including the Harris hip score, the Western Ontario and McMaster Universities Osteoarthritis Index, as well as pain and satisfaction on the visual analogue scale. Radiological follow-up was also performed. RESULTS: We identified 18 (66.7%) patients diagnosed with FNF and 9 (33.3%) patients with ITF. Clinical and radiological outcomes were satisfactory at the last follow-up (30.56 ± 11.62 months). One patient required early revision surgery due to dislocation and greater trochanter fracture. At the last follow-up, none of the short stems required revision. No other major complications occurred. CONCLUSION: Given the low rate of complications and 100% survival, our findings indicate that short stems for conversion THA due to failed internal fixation may be considered an option in a properly selected patient population. However, it should not be considered a standard procedure and should only be performed by experienced surgeons.

Downsizing in total hip arthroplasty. A short stem as a revision implant.

BACKGROUND: Short stems have constantly gained popularity in primary total hip arthroplasty (THA) over the last decade. Although cementless short stems are not primarily designed to be used as revision implants, there may be certain indications for which downsizing the femoral component in failed conventional THA is potentially advantageous. METHODS: In this single center retrospective case series, six patients who underwent revision using a calcar-guided short stem after failed THA are presented. The mean follow-up was 3.32 years (SD 0.63 years). The health status was evaluated by the EQ-5D-5L score. Patient reported outcome measurements (PROM) were recorded using the Harris hip score (HHS) and The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Pain and satisfaction were assessed using a visual analogue scale (VAS). Radiographic analysis was performed by evaluating osteolysis, stress shielding, alignment and signs of aseptic loosening. Complications were documented. RESULTS: At last follow-up the mean EQ-5D-5L index was 0.851 (SD 0.098). Clinical outcome was excellent (HHS ≥ 90) in 4 patients and moderate (HHS 71 and 79) in 2 patients. The mean WOMAC score was 9.20% (SD 12.61%). Pain and satisfaction on VAS were 1.00 (SD 1.15) and 9.17 (SD 0.37), respectively. No major complications occurred. To date, no further revision surgery was needed. Radiologically, no signs of subsidence, aseptic loosening, stress shielding and fractures were obvious. CONCLUSION: The present case series indicates that in failed conventional THA downsizing may be considered a treatment option, using short stem THA in selected cases.

One-stage bilateral versus unilateral short-stem total hip arthroplasty: A matched-pair analysis of 216 hips.

BACKGROUND: One-stage, bilateral, short-stem total hip arthroplasty (1B-ssTHA) represents an alternative to staged, unilateral, short-stem total hip arthroplasty (U-ssTHA); however, the safety and reliability of 1B-ssTHA remain unknown. The objective of the present study was to compare the functional outcomes, complications, and mortality rates between 1B-ssTHA and U-ssTHA at mid-term. METHODS: A retrospective, matched-pair study was performed, including 216 short stems implanted in 162 patients. Among the study population, 54 patients were treated with 1B-ssTHA. Patients were matched by gender, age, body mass index (BMI), and American Society of Anesthesiologists (ASA) classification. A total of 46 full matches could be accomplished. The mean follow-up time for the 1B-ssTHA group was 61.7 months (standard deviation [SD] 6.2 months), compared with was 63.4 months (SD 8.0 months) for the U-ssTHA group. Mortality, complication, and revision rates were documented. For clinical examinations, the visual analogue scale (VAS) was used to evaluate satisfaction, rest pain, and load pain, and the Harris Hip Score (HHS) was determined. RESULTS: No surgery-related deaths were observed. At mid-term, none of the 1B-ssTHA patients required stem revision. The rate of complications for both groups was low. The mean drop in haemoglobin measured in the 1B-ssTHA group was 4.42 mg/dl, compared with 3.18 mg/dl in the U-ssTHA group. The mean HHS in the 1B-ssTHA group was 98.3 points (SD 2.80), whereas, in the U-ssTHA group, the mean HHS was 97.9 points (SD 3.44) (p = 0.478). Satisfaction rates were significantly higher in the 1B-ssTHA group (p = 0.04) than in the U-ssTHA group, whereas no significant differences were found for pain at rest and pain at load (p = 0.56 and p = 0.26, respectively). CONCLUSION: Our findings indicate that 1B-ssTHA is an effective and beneficial procedure for a select population. Mortality, complications, implant survival, and clinical outcomes were comparable to those for a matched group with unilateral osteoarthritis treated with U-ssTHA. However, an increase in blood loss must be acknowledged for the 1B-ssTHA procedure.

Calcar-guided short-stem total hip arthroplasty: Will it be the future standard? Review and perspectives.

Short stems in total hip arthroplasty (THA) are becoming increasingly popular. In Germany, already 10.4% of all primary THAs are performed using a cementless short stem. The concept of modern, calcar-guided, short stems aims for an individualized reconstruction of the hip anatomy by following the calcar of the femoral neck, a bone- and soft-tissue-sparing implantation technique, and physiological loading. The stem design uses either metaphyseal fixation alone or additional diaphyseal anchoring, depending on the stem alignment and indication. These individualized anchorage types increase the potential indications for the safe use of a short stem. The design features may account for potential advantages of current short stem implants compared with earlier short-stem designs, particularly in cases of reduced bone quality or osteonecrosis of the femoral head and femoral neck fractures. The implantation technique, however, requires distinct knowledge regarding the characteristics of varus and valgus positioning, with the potential for clinical consequences. A learning curve for surgeons new to this technique must be taken into account. Cortical contact with the distal lateral cortex appears to be crucial to provide sufficient primary stability, and the use of intraoperative imaging to identify "undersizing" is highly recommended. Current results of several national registries indicate that calcar-guided short stems are among the most successful implants in terms of mid-term survivorship. However, long-term data remain scarce. This review introduces the characteristics of calcar-guided short-stem THA and summarizes the current evidence.

Future burden of primary and revision hip arthroplasty in Germany: a socio-economic challenge.

INTRODUCTION: Total hip arthroplasty (THA) rates have increased dramatically in the recent decades worldwide, with Germany being one of the leading countries in the prevalence of THA. Simultaneously, a rising number of revision procedures is expected, which will put an enormous economic burden on future health care systems. METHODS: Nationwide data provided by the Federal Statistical Office of Germany were used to quantify primary and revision arthroplasty rates as a function of age and gender. Projections were performed with use of Negative Binomial and Poisson regression models on historical procedure rates in relation to population projections from 2020 to 2060. RESULTS: A 62% increase in the incidence rate of primary THAs is projected until 2060. At the same time, the annual total number of revision procedures is forecast to rise about 40% by the year 2060. The highest numbers of revision arthroplasties were calculated around year 2043. The greatest proportions of revision surgery will be observed in women and in those aged 70 years or older. The revision burden is projected to stabilize around 15% by 2060. CONCLUSIONS: The present projections allow a quantification of the increasing economic burden that (revision) THA will place on the German health care system in the upcoming decades. This study may serve as a model for other countries with similar demographic development as the country-specific approach predicts a substantial increase in the number of these procedures. This highlights the need for appropriate financial and human resource management in the future.

Can hip resurfacing be safely revised with short-stem total hip arthroplasty? A case series of six patients.

BACKGROUND: The usage of short stems in primary total hip arthroplasty (THA) has constantly gained popularity over the last decade, however, to date, short stems are not eligible to be used as revision implants. The aim of this study was to retrospectively evaluate the outcome of revision surgery of failed hip resurfacing arthroplasty (HRA) using short-stem THA. METHODS: In a single center, retrospective analysis, 6 consecutive patients who were treated with a calcar-guided short stem after failure of HRA were evaluated. The mean follow-up was 3.25 years (SD 0.45). Patient reported outcome measurements (PROMs) were recorded using the Harris hip score (HHS) and The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). The health status was evaluated by the EQ-5D-5L score. Pain and satisfaction were obtained using the visual analogue scale (VAS). Radiographic analysis was performed by evaluating osteolysis, stress shielding, alignement and signs of aseptic loosening. Complications were documented. RESULTS: At last follow-up, clinical outcome was excellent (HHS ≥ 90) in 5 patients and good (HHS = 87) in 1 patient. The mean WOMAC score was 5.73% (SD 3.66%). The mean EQ-5D-5L index was 0.914 (SD 0.07). Pain and satisfaction on VAS was 1.83 (SD 5.18) and 8.67 (SD 0.94), respectively. Radiologically, no signs of subsidence, aseptic loosening, stress shielding and fracture were obvious. No major complications occurred. To date, no further revision surgery was needed. CONCLUSIONS: The outcomes of the present case series propose that HRA can be safely revised using short-stem THA in a selected patient group. Clinical and radiological results are encouraging. Based on the present data, short stems may be considered as a revision implant for failed HRA for experienced surgeons.

Biomechanics of a cemented short stem: a comparative in vitro study regarding primary stability and maximum fracture load.

PURPOSE: In total hip arthroplasty, uncemented short stems have been used more and more frequently in recent years. Especially for short and curved femoral implants, bone-preserving and soft tissue-sparing properties are postulated. However, indication is limited to sufficient bone quality. At present, there are no curved short stems available which are based on cemented fixation. METHODS: In this in vitro study, primary stability and maximum fracture load of a newly developed cemented short-stem implant was evaluated in comparison to an already well-established cemented conventional straight stem using six pairs of human cadaver femurs with minor bone quality. Primary stability, including reversible micromotion and irreversible migration, was assessed in a dynamic material-testing machine. Furthermore, a subsequent load-to-failure test revealed the periprosthetic fracture characteristics. RESULTS: Reversible and irreversible micromotions showed no statistical difference between the two investigated stems. All short stems fractured under maximum load according to Vancouver type B3, whereas 4 out of 6 conventional stems suffered a periprosthetic fracture according to Vancouver type C. Mean fracture load of the short stems was 3062 N versus 3160 N for the conventional stems (p = 0.84). CONCLUSION: Primary stability of the cemented short stem was not negatively influenced compared to the cemented conventional stem and no significant difference in fracture load was observed. However, a clear difference in the fracture pattern has been identified.

Secondary Osseous Integration of Cementless Unicompartmental Knee Arthroplasty After Internal Fixation of a Felix Type IIIB Fracture: A Case Report.

CASE: A 76-year-old man presented with periprosthetic tibial plateau fracture (TPF), with a completely loosened tibial component 3 weeks after cementless unicompartmental knee arthroplasty (UKA). Internal fixation by buttress plating was performed, and the tibial component was retained and left in situ primarily as a spacer. Revision was planned after fracture consolidation, but at 3 months, the patient was able to walk without support, without pain, and with full range of motion. At 1 year, he is free of complaints. The initial loosened tibial component reintegrated. CONCLUSION: Internal fixation combined with preserving the loosened tibial component may be a treatment option for TPF involving a cementless UKA.

The concept of a cementless isoelastic monoblock cup made of highly cross-linked polyethylene infused with vitamin E: radiological analyses of migration and wear using EBRA and clinical outcomes at mid-term follow-up.

BACKGROUND: The newest generation of cementless titanium-coated, isoelastic monoblock cup with vitamin E-blended highly cross-linked polyethylene (HXLPE) was introduced to the market in 2009. The aim of the present study was to obtain mid-term follow-up data including migration and wear analyses. METHODS: This prospective study investigated 101 primary total hip arthroplasty (THA) cases in 96 patients treated at a single institution. Patients were allowed full weight-bearing on the first day postoperatively. Harris hip score (HHS) and pain and satisfication on a visual analogue scale (VAS) were assessed at a mean follow-up of 79.0 months. Migration and wear were assessed using Einzel-Bild-Roentgen-Analyse (EBRA) software. Radiological acetabular bone alterations and complications were documented. RESULTS: At mid-term follow-up (mean 79.0 months, range: 51.8-101.7), 81 cases with complete clinical and radiological data were analyzed. Utilisable EBRA measurements were obtained for 42 hips. The mean HHS was 91.1 (range 38.0-100.0), VAS satisfaction was 9.6 (range 6.0-10.0), VAS rest pain was 0.2 (range 0.0-4.0), and VAS load pain was 0.6 (range 0.0-9.0). Mean migration was 0.86 mm (range: 0.0-2.56) at 24 months and 1.34 mm (range: 0.09-3.14) at 5 years, and the mean annual migration rate was 0.22 (range: - 0.24-1.34). The mean total wear was 0.4 mm (range: 0.03-1.0), corresponding to a mean annual wear rate of 0.06 mm per year (range: 0.0-0.17). Radiographic analysis did not reveal any cases of osteolysis, and no revision surgeries had to be performed. CONCLUSIONS: After using vitamin-E blended HXLPE in cementless isoelastic monoblock cups, there were no obvious signs of osteolysis or aseptic loosening occurred. No patients required revision surgery after mid-term follow-up. Cup migration and wear values were well below the benchmarks considered predictive for potential future failure. TRIAL REGISTRATION: The trial registration number on ClinicalTrials.gov : NCT04322916 (retrospectively registered at 26.03.2020).

Trends in Total Hip Arthroplasty in Germany from 2007 to 2016: What Has Changed and Where Are We Now?

BACKGROUND: The number of total hip arthroplasties (THA) is rising in many industrialized nations. At the same time, the evidence regarding different types of prostheses and fixation techniques is constantly evolving. Therefore, this study aimed to analyze changes in THA by these advancements during the last decade. METHODS: A retrospective analysis of data provided by the Federal Statistical Office of Germany from 2007 to 2016 was conducted using codes from the German procedure classification system and associated International Statistical Classification of Diseases and Related Health Problems codes. THA procedures were evaluated according to diagnoses, sex, and age of patients, along with the distribution of different prosthesis types. Additionally, changes in these parameters over time were analyzed. RESULTS: From 2007 to 2016 a total of 2 157 041 primary THA procedures were performed in Germany, with an increase of 14.4% over this period. Overall, cementless standard THA (STHA) was used most frequently (50.0%), followed by hybrid variants (18.8%), hemiarthroplasties (15.9%), cemented standard THA (cSTHA; 9.2%), cementless short-stem THA (ssTHA; 4.8%), and hip resurfacing (HR; 0.9%) techniques. During the study period, the number of cSTHA and HR decreased significantly, whereas the use of STHA and ssTHA rose substantially, with a significantly higher application of these procedures in the elderly population. While osteoarthritis of the hip joint was the main indication for THA, several procedure-specific differences were identified. CONCLUSION: The present data clearly demonstrate an increase in the use of cementless fixation for THA in Germany during the last decade and document a rise in ssTHA in recent years with, in contrast, the use of HR decreasing to a minimum.

The projected volume of primary and revision total knee arthroplasty will place an immense burden on future health care systems over the next 30 years.

PURPOSE: Total knee arthroplasty (TKA) rates have increased substantially in the recent decades worldwide, with Germany being one of the leading countries in the prevalence of TKA. The aim of this study was to provide an overview of treatment changes during the last decade and to project the expected burden of primary and revision TKA (rTKA) for the next 30 years. METHODS: Comprehensive nationwide data from Germany was used to quantify primary and revision TKA rates as a function of age and gender. Projections were performed with use of a Poisson regression models and a combination of exponential smoothing and autoregressive integrated moving average models on historical procedure rates in relation to official population projections from 2020 to 2050. RESULTS: The incidence rate of primary TKAs is projected to increase by around 43% to 299 per 100,000 inhabitants [95% CI 231-368], leading to a projected total number of 225,957 primary TKAs in 2050 (95% CI 178,804-276,442). This increase has been related to a growing number of TKA performed in male patients, with the highest increase modelled in patients between 50 and 65 years of age. At the same time, the annual total number of revision procedures is forecast to increase even more rapidly by almost 90%, accounting for 47,313 (95% CI 15,741-78,885; IR = 62.7 per 100,000, 95% CI 20.8-104.5) procedures by 2050. Those numbers are primarily associated with a rising number of rTKAs secondary to periprosthetic joint infection (PJI). CONCLUSIONS: Using this country- specific forecast approach, a rising number of primary TKA and an even more rapidly growing number of rTKA, especially for PJI, has been projected until 2050, which will inevitably provide a huge challenge for the future health care system. As many other industrialized nations will face similar demographic and procedure-specific developments, these forecasts should be alarming for many health care systems worldwide and emphasize the tremendous need for an appropriate financial and human resource management in the future. LEVEL OF EVIDENCE: Level III, prognostic study, economic and decision analysis.

Primary stability of calcar-guided short-stem total hip arthroplasty in the treatment of osteonecrosis of the femoral head: migration analysis using EBRA-FCA.

INTRODUCTION: Osteonecrosis of the femoral head (ONFH) is a disabling condition that often results in secondary arthritis necessitating total hip arthroplasty (THA). Short-stem THA has constantly gained popularity. It remains controversial, whether ONFH represents a risk factor for failure after the implantation of short stems with pronounced metaphyseal anchorage. The potential spread of the osteonecrotic area and bone marrow edema into the metaphyseal bone might result in compromised stability. Early implant migration is considered predictive of subsequent aseptic loosening. The purpose of this study was a migration analysis of a modern, calcar-guided short-stem implant in patients with ONFH in a mid-term follow-up. MATERIALS AND METHODS: This retrospective analysis investigated the migration pattern of 45 calcar-guided short stems in patients with ONFH, using Einzel-Bild-Roentgen-Analyse Femoral-Component-Analysis (EBRA-FCA). Influencing factors such as ARCO categories, age, gender, body weight and BMI were analyzed. Complications and adverse events were documented. RESULTS: At mid-term [48.1 months (SD 20.7 months)], mean axial migration was 1.56 mm (SD 1.77 mm). Mean migration rate stabilized after 2 years. No influence of ARCO categories, age and BMI was found. A tendency of increased axial migration was observed in male patients and in overweight patients. No revision surgeries had to be performed during follow-up. CONCLUSION: The results indicate a migration pattern comparable to that of primary osteoarthritis patients with slight initial migration under full load followed by subsequent stabilization in the metaphyseal femur. The 100% survival rate at mid-term supports the usage of this short-stem design in patients with ONFH.

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.

Mid-term migration pattern of a calcar-guided short stem: A five-year EBRA-FCA-study.

BACKGROUND: Short-term results of several short-stem designs have indicated early axial migration. Mid- and long-term results for most designs are lacking. The objective of this study was to evaluate the mid-term migration pattern of a calcar-guided short stem five years postoperative. METHODS: Implant migration of 191 calcar-guided short stems was assessed by Ein-Bild-Roentgen-Analysis Femoral-Component- Analysis (EBRA-FCA) 5 years after surgery. Migration pattern of the whole group was analyzed and compared to the migration pattern of implants potentially being "at hazard" with a subsidence of more than 1.5 mm at 2 years postoperatively. Influence of preoperative Dorr types (A vs. B vs. C), age (<70 vs. >70 years), gender (female vs. male), weight (<90 kg vs. >90 kg), BMI (<30 vs. >30) and uni-vs. bilateral procedures on mid-term migration pattern was analyzed. Additionally outcome of varus- and valgus stem alignment was assessed. RESULTS: Mean axial subsidence was 1.5 mm (SD 1.48 mm) at final follow-up. Two years after surgery 73 short stems were classified "at hazard". Of these stems, 69 cases showed secondary stabilisation in the following period, whereas 4 cases presented unstable with more than 1 mm of further subsidence. Stem revision was not required neither in the group of implants with early stabilisation nor the group with pronounced early onset migration. Male gender and heavy-weight patients had a significant higher risk for axial migration, as well as extensive valgus stem alignment, whereas for Dorr type B, compared to A, no statistical difference could be observed. CONCLUSIONS: In most cases, even in the group of stems being "at hazard", settling could be documented. While different Dorr types did not show a statistically significant impact on axial migration, particularly in male and heavy-weight patients the risk of continuous subsidence is increased. In those 4 cases with further migration, undersizing of the stem could be recognized. At present, clinical consequences are still uncertain.