The design features of cemented femoral hip implants

Cemented Stem Design in Total Hip Arthroplasty: Fixation Philosophies, Biomechanics, and an Updated Classification System

There is renewed interest in cemented femoral fixation in total hip arthroplasty in the United States, and to fully appreciate the evolution of cemented femoral stem designs, an understanding of their history and design rationale is essential. To adequately study the outcomes of modern-day designs, a comprehensive classification system is also necessary. The biomechanical principles, failure mechanisms, and clinical outcomes associated with various cemented femoral stems are described in this comprehensive review. In addition, an updated version of an existing classification system is described that incorporates the primary design characteristics which differentiate implants currently in use. In this classification, implants are categorized as taper-slip (Type I), which are subdivided by Anatomic (IA), Double-Taper (IB), and Triple-Taper (IC) with subclassification for Traditional and Line-to-Line implants. Composite beam (Type II) implants are similarly divided into Anatomic (IIA), Straight (IIB), and Wedge (IIC) with subclassification for Polished, Satin, or Roughened finish. This classification system provides a basis for comparing cemented femoral stems, thereby improving our understanding of the effect of design characteristics on survivorship to guide future advancements and improve clinical outcomes.

Characterizing Surface Morphological and Chemical Properties of Commonly Used Orthopedic Implant Materials and Determining Their Clinical Significance

The goal of the study was to compare the surface characteristics of typical implant materials used in orthopedic surgery and traumatology, as these determine their successful biointegration. The morphological and chemical structure of Vortex plate anodized titanium from commercially pure (CP) Grade 2 Titanium (Ti2) is generally used in the following; non-cemented total hip replacement (THR) stem and cup Ti alloy (Ti6Al4V) with titanium plasma spray (TPS) coating; cemented THR stem Stainless steel (SS); total knee replacement (TKR) femoral component CoCrMo alloy (CoCr); cemented acetabular component from highly cross-linked ultrahigh molecular weight polyethylene (HXL); and cementless acetabular liner from ultrahigh molecular weight polyethylene (UHMWPE) (Sanatmetal, Ltd., Eger, Hungary) discs, all of which were examined. Visualization and elemental analysis were carried out by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Surface roughness was determined by atomic force microscopy (AFM) and profilometry. TPS Ti presented the highest Ra value (25 ± 2 μm), followed by CoCr (535 ± 19 nm), Ti2 (227 ± 15 nm) and SS (170 ± 11 nm). The roughness measured in the HXL and UHMWPE surfaces was in the same range, 147 ± 13 nm and 144 ± 15 nm, respectively. EDS confirmed typical elements regarding the investigated prosthesis materials. XPS results supported the EDS results and revealed a high % of Ti4+ on Ti2 and TPS surfaces. The results indicate that the surfaces of prosthesis materials have significantly different features, and a detailed characterization is needed to successfully apply them in orthopedic surgery and traumatology.

Risk factors influencing periprosthetic fracture and mortality in elderly patients following hemiarthroplasty with a cemented collarless polished taper stem for an intracapsular hip fracture

Aims

The aims of this study were to evaluate the incidence of reoperation (all cause and specifically for periprosthetic femoral fracture (PFF)) and mortality, and associated risk factors, following a hemiarthroplasty incorporating a cemented collarless polished taper slip stem (PTS) for management of an intracapsular hip fracture.

Methods

This retrospective study included hip fracture patients aged 50 years and older treated with Exeter (PTS) bipolar hemiarthroplasty between 2019 and 2022. Patient demographics, place of domicile, fracture type, delirium status, American Society of Anesthesiologists (ASA) grade, length of stay, and mortality were collected. Reoperation and mortality were recorded up to a median follow-up of 29.5 months (interquartile range 12 to 51.4). Cox regression was performed to evaluate independent risk factors associated with reoperation and mortality.

Results

The cohort consisted of 1,619 patients with a mean age of 82.2 years (50 to 104), of whom 1,100 (67.9%) were female. In total, 29 patients (1.8%) underwent a reoperation; 12 patients (0.7%) sustained a PFF during the observation period (United Classification System (UCS)-A n = 2; UCS-B n = 5; UCS-C n = 5), of whom ten underwent surgical management. Perioperative delirium was independently associated with the occurrence of PFF (hazard ratio (HR) 5.92; p = 0.013) and surgery for UCS-B PFF (HR 21.7; p = 0.022). Neither all-cause reoperation nor PFF-related surgery was independently associated with mortality (HR 0.66; p = 0.217 and HR 0.38; p = 0.170, respectively). Perioperative delirium, male sex, older age, higher ASA grade, and pre-fracture residential status were independently associated with increased mortality risk following hemiarthroplasty (p < 0.001).

Conclusion

The cumulative incidence of PFF at four years was 1.1% in elderly patients following cemented PTS hemiarthroplasty for a hip fracture. Perioperative delirium was independently associated with a PFF. However, reoperation for PPF was not independently associated with patient mortality after adjusting for patient-specific factors.

Investigation of stair ascending and descending activities on the lifespan of hip implants

Total hip arthroplasty (THA) surgeries among young patients are on the increase, so it is crucial to predict the lifespan of hip implants correctly and produce solutions to improve longevity. Current implants are designed and tested against walking conditions to predict the wear rates. However, it would be reasonable to include the additional effects of other daily life activities on wear rates to predict convergent results to clinical outputs. In this study, 14 participants are recruited to perform stair ascending (AS), descending (DS), and walking activities to obtain kinematic and kinetic data for each cycle using marker based Qualisys motion capture (MOCAP) system. AnyBody Modeling System using the Calibrated Anatomical System Technique (CAST) full body marker set are performed Multibody simulations. The 3D generic musculoskeletal model used in this study is a marker-based full-body motion capture model (AMMR,2.3.1 MoCapModel) consisting of the upper extremity and the Twente Lower Extremity Model (TLEM2). The dynamic wear prediction model detailing the intermittent and overall wear rates for CoCr-on-XLPE bearing couple is developed to investigate the wear mechanism under 3D loading for AS, DS, and walking activities over 5 million cycles (Mc) by using finite element modelling technique. The volumetric wear rates of XLPE liner under AS, DS, and walking activities over 5-Mc are predicted as 27.43, 23.22, and 18.84 mm3/Mc respectively. Additionally, the wear rate was predicted by combining stair activities and gait cycles based on the walk-to-stair ratio. By adding the effect of stair activities, the volumetric wear rate of XLPE is predicted as 22.02 mm3/Mc which is equivalent to 19.41% of walking. In conclusion, in this study, the effect of including other daily life activities is demonstrated and evidence is provided by matching them to the clinical data as opposed to simulator test results of implants under ISO 14242 boundary conditions.

Cemented femoral stem design and postoperative periprosthetic fracture risk following total hip arthroplasty

Polished taper-slip (PTS) cemented stems have an excellent clinical track record and are the most common stem type used in primary total hip arthroplasty (THA) in the UK. Due to low rates of aseptic loosening, they have largely replaced more traditional composite beam (CB) cemented stems. However, there is now emerging evidence from multiple joint registries that PTS stems are associated with higher rates of postoperative periprosthetic femoral fracture (PFF) compared to their CB stem counterparts. The risk of both intraoperative and postoperative PFF remains greater with uncemented stems compared to either of these cemented stem subtypes. PFF continues to be a devastating complication following primary THA and is associated with high complication and mortality rates. Recent efforts have focused on identifying implant-related risk factors for PFF in order to guide preventative strategies, and therefore the purpose of this article is to present the current evidence on the effect of cemented femoral stem design on the risk of PFF.

Is it reasonable to shorten the length of cemented stems? A finite element analysis and biomechanical experiment

Background: Uncemented short stems have been shown to optimize load distribution on the proximal femur, reducing stress shielding and preserving bone mass. However, they may adversely affect the initial stability of the stems. To date, most research conducted on short stems has predominantly centered on uncemented stems, leaving a notable dearth of investigations encompassing cemented stems. Therefore, this study aimed to investigate the length of cemented stems on the transmission of femoral load patterns and assess the initial stability of cemented short stems. Method: A series of finite element models were created by gradient truncation on identical cemented stem. The impact of varying lengths of the cemented stem on both the peak stress of the femur and the stress distribution in the proximal femur (specifically Gruen zones 1 and 7) were assessed. In addition, an experimental biomechanical model for cemented short stem was established, and the initial stability was measured by evaluating the axial irreversible displacement of the stem relative to the cement. Result: The maximum von-Mises stress of the femur was 58.170 MPa. Spearman correlation analysis on the shortened length and von-Mises stress of all nodes in each region showed that the p-values for all regions were less than 0.0001, and the correlation coefficients (r) for each region were 0.092 (Gruen Zone 1) and 0.366 (Gruen Zone 7). The result of the biomechanical experiment showed that the irreversible axial displacement of the stem relative to cement was -870 μm (SD 430 μm). Conclusion: Reducing the length of a cemented stem can effectively enhance the proximal load of the femur without posing additional fracture risk. Moreover, the biomechanical experiment demonstrated favorable initial stabilities of cemented short stems.

Minimum 10-Year Follow-Up of Total Hip Arthroplasty With a Collarless Triple-Tapered Polished Cemented Stem With Line-to-Line Implantation Using a Direct Anterior Approach

BACKGROUND

The Trilliance stem (B. Braun-Aesculap, Tuttlingen, Germany), a novel collarless triple-tapered polished stem, was introduced in 2009. The aim of this study is to evaluate the long-term clinical and radiological results of the Trilliance stem with line-to-line implantation in primary total hip arthroplasty using a direct anterior approach.

METHODS

A consecutive retrospective series of 130 patients (151 hips) who underwent total hip arthroplasty between February 2009 and August 2011 were evaluated for a minimum of 10 years. Of these, 87.4% had a diagnosis of secondary osteoarthritis based on developmental hip dysplasia. Clinical and radiological results, complications were evaluated and survival analysis was performed.

RESULTS

The mean follow-up was 10.7 years (range, 10.0-12.1). Thirteen hips (13 patients, 6.8%) were lost to follow-up. Adequate cementation (Barrack grade A) was achieved in 136 hips (93.8%) 1 week post-operatively. Nearly all (144 hips, 99.3%) had been inserted within the range of 3°. No significant differences were identified between high- (≥30 procedures/year) and low- (<30 procedures/year) volume surgeons. The Kaplan-Meier survival analysis with revision of the femoral component for aseptic loosening, revision of the femoral component for any reason and revision of either component for any reason as the end points, cumulative survivorship was 100.0%, 97.6% (95% confidence interval (CI) 95.4-100.0) and 96.5% (95% CI 93.8-99.3) at 10 years, respectively.

CONCLUSION

The Trilliance stem with line-to-line implantation using a direct anterior approach has an excellent clinical and radiological outcome at a minimum of 10 years' follow-up.

LEVEL OF EVIDENCE

Level IV, Retrospective cohort study.

Femoral Stem Cementation in Primary Total Hip Arthroplasty

➢

Femoral stem cementation has undergone considerable investigation since bone cement was first used in arthroplasty, leading to the evolution of modern femoral stem cementation techniques.

➢

Although there is a worldwide trend toward the use of cementless components, cemented femoral stems have shown superiority in some studies and have clear indications in specific populations.

➢

There is a large evidence base regarding cement properties, preparation, and application techniques that underlie current beliefs and practice, but considerable controversy still exists.

➢

Although the cementing process adds technical complexity to total hip arthroplasty, growing evidence supports its use in certain cohorts. As such, it is critical that orthopaedic surgeons and investigators have a thorough understanding of the fundamentals and evidence underlying modern cementation techniques.

The influence of calcar collar and surface finish in the cemented femoral component on the incidence of postoperative periprosthetic femoral fracture at a minimum of five years after primary total hip arthroplasty

INTRODUCTION

Cemented femoral component design including its mechanical behavior in total hip arthroplasty (THA) has influenced the occurrence of postoperative periprosthetic femoral fracture (PPFF). The main aim of this study was to investigate the influence of the calcar collar and surface finish in the cemented femoral component on the risk of PPFF.

MATERIALS AND METHODS

This retrospective review was undertaken of 1082 primary THAs in 912 patients using cemented femoral components followed for a minimum of five years (mean, 9.4 years; range, 5-24 years). The incidence of PPFF, patients' demographics and surgical details were evaluated. Kaplan-Meier survivorship analysis was performed for four different outcomes: any PPFF, revision of the femoral component for PPFF, aseptic loosening, and for any reason.

RESULTS

The overall incidence of PPFFs was 1.0% (n = 11): 1.4% (n = 10) in the collarless polished (CLP) group, none in the collared polished (CP) group and 0.6% (n = 1) in the collared non-polished (CNP) group (p > 0.05). Kaplan-Meier survival analysis for the femoral component at 12 years with PPFF as the end point was 97.4% (95% confidence interval [CI], 94.9 to 99.8) in the collarless group and 99.7% (95% CI, 99.1 to 100) in the collared group (p = 0.048). With revision of the femoral component for aseptic loosening as the end point, survivorship was 100.0% in the CLP and CP groups, and 98.1% (95% CI, 95.9 to 100) in the CNP group (CLP vs CP, p > 0.999; CLP vs CNP, p = 0.001; CP vs CNP, p = 0.112).

CONCLUSION

This study demonstrated that the calcar collar in the cemented femoral component could play an important role to reduce the incidence of PPFF. The surface finish in the cemented femoral components influenced the incidence of femoral component revision for aseptic loosening over 5-12 years. Surgeons should consider not only the geometry and the mechanical function of the femoral components based on different design philosophies, but also potential complications associated with different designs that may require revision arthroplasty.

Survivorship of the C-Stem total hip replacement using the "French Paradox" technique

BACKGROUND

This study evaluates the survivorship of the C-Stem total hip replacement, using the "French Paradox" method, at medium-term follow-up.

METHODS

321 cemented total hip replacements in 307 patients were performed, using the canal-filling technique for the femoral stem. Survival analysis was performed for all-cause revision. The secondary outcome was aseptic loosening of the stem.

RESULTS

Revision rate for all reasons was 2%. Overall ten-year survival was 95%. There were no revisions for femoral stem aseptic loosening.

CONCLUSION

This is a unique study demonstrating successful outcomes of total hip replacement using the "French Paradox" technique with a triple-tapered stem.

Is the French Paradox cementing philosophy superior to the standard cementing? A randomized controlled radiostereometric trial and comparative analysis

Aims

Highly polished stems with force-closed design have shown satisfactory clinical results despite being related to relatively high early migration. It has been suggested that the minimal thickness of cement mantles surrounding the femoral stem should be 2 mm to 4 mm to avoid aseptic loosening. The line-to-line cementing technique of the femoral stem, designed to achieve stem press-fit, challenges this opinion. We compared the migration of a highly polished stem with force-closed design by standard and line-to-line cementing to investigate whether differences in early migration of the stems occur in a clinical study.

Methods

In this single-blind, randomized controlled, clinical radiostereometric analysis (RSA) study, the migration pattern of the cemented Corail hip stem was compared between line-to-line and standard cementing in 48 arthroplasties. The primary outcome measure was femoral stem migration in terms of rotation and translation around and along with the X-, Y-, and Z- axes measured using model-based RSA at three, 12, and 24 months. A linear mixed-effects model was used for statistical analysis.

Results

Results from mixed model analyses revealed a lower mean retroversion for line-to-line (0.72° (95% confidence interval (CI) 0.38° to 1.07°; p < 0.001), but no significant differences in subsidence between the techniques (-0.15 mm (95% CI -0.53 to 0.227; p = 0.429) at 24 months. Radiolucent lines measuring < 2 mm wide were found in three and five arthroplasties cemented by the standard and line-to-line method, respectively.

Conclusion

The cemented Corail stem with a force-closed design seems to settle earlier and better with the line-to-line cementing method, although for subsidence the difference was not significant. However, the lower rate of migration into retroversion may reduce the wear and cement deformation, contributing to good long-term fixation and implant survival.

Cite this article: Bone Joint J 2022;104-B(1):19–26.

Vancouver B and C periprosthetic fractures around the cemented Exeter Stem: sex is associate with fracture pattern

INTRODUCTION

The aim of this study was to identify factors associated with the level of periprosthetic fracture involving a cemented polished tapered stem: Vancouver B or Vancouver C.

METHODS

A retrospective cohort study of 181 unilateral periprosthetic fractures involving Exeter stems was assessed by three observers (mean age 78.5, range 39-103; mean BMI 27.1, 17-39; 97 (54%) male). Patient demographics, deprivation scores, BMI and time since primary prosthesis were recorded. Femoral diameter, femoral cortical thickness, Dorr classification and distal cement mantle length were measured from calibrated radiographs. Interobserver reliability was calculated using intraclass correlation coefficients (ICCs). Univariate and multivariate analysis was performed to identify associations with Vancouver B or C fractures.

RESULTS

160/181 (88%) Vancouver B and 21/181 (12%) Vancouver C-level fractures occurred at a mean of 5.9 ± 5.4 years (0.2-26.5) following primary surgery. Radiographic measurements demonstrated excellent agreement (ICC > 0.8, p < 0.001). Mortality was significantly higher following Vancouver C compared to B fractures: 90 day 14/160 Vs 5/21 (p = 0.05); 1 year 29/160 Vs 8/21 (p = 0.03). Univariate analysis demonstrated that Vancouver C fractures were associated with female sex, bisphosphonate use, cortical bone thickness, and distal cement mantle length (p < 0.05). On multivariate analysis, only female sex was an independent predictor of Vancouver C-level fractures (R² =0.354, p = 0.005).

CONCLUSION

Most PFFs involving the Exeter stem design are Vancouver B-type fractures and appear to be independent of osteoporosis. In contrast, Vancouver C periprosthetic fractures display typical fragility fracture characteristics and are associated with female sex, thinner femoral cortices, longer distal cement mantles and high mortality.

Femoral Stems With Porous Lattice Structures: A Review

Cementless femoral stems are prone to stress shielding of the femoral bone, which is caused by a mismatch in stiffness between the femoral stem and femur. This can cause bone resorption and resultant loosening of the implant. It is possible to reduce the stress shielding by using a femoral stem with porous structures and lower stiffness. A porous structure also provides a secondary function of allowing bone ingrowth, thus improving the long-term stability of the prosthesis. Furthermore, due to the advent of additive manufacturing (AM) technology, it is possible to fabricate femoral stems with internal porous lattices. Several review articles have discussed porous structures, mainly focusing on the geometric design, mechanical properties and influence on bone ingrowth. However, the safety and effectiveness of porous femoral stems depend not only on the characteristic of porous structure but also on the macro design of the femoral stem; for example, the distribution of the porous structure, the stem geometric shape, the material, and the manufacturing process. This review focuses on porous femoral stems, including the porous structure, macro geometric design of the stem, performance evaluation, research methods used for designing and evaluating the femoral stems, materials and manufacturing techniques. In addition, this review will evaluate whether porous femoral stems can reduce stress shielding and increase bone ingrowth, in addition to analyzing their shortcomings and related risks and providing ideas for potential design improvements.

Atypical periprosthetic femoral fractures of the hip: A PRISMA compliant systematic review

INTRODUCTION

Long-term use of bisphosphonates (BPs) is associated with Atypical Femoral Fracture (AFF). Theoretically, periprosthetic femoral fractures (PFF) should be excluded from the diagnosis of AFF. However, recently several studies reported the occurrence of PPFs around a hip arthroplasty presenting features of an AFF. The present study describes the characteristics of Atypical Periprosthetic Femoral Fracture (APFF) and evaluates the effectiveness of their management through a PRISMA compliant systematic review of the published case reports and series.

MATERIALS AND METHODS

A literature search was performed using "periprosthetic fracture" and "atypical femoral fracture" as keywords. Patients demographics, drug use, clinical and imaging characteristics, stem fixation and classification, management strategies for APFF and patients' outcomes, were also collected.

RESULTS

The present review included and analysed 17 patients from 12 studies. All APFFs occurred in females with a mean age of 75.9 years of age (range 43-87). In 11 patients, APFFs occurred around an uncemented stem, and in 6 around a cemented stem. Ten fractures were incomplete, and 7 complete. Conservative management was effective in 4 of 10 patients with incomplete fracture, while all patients with complete fractures underwent open reduction and internal fixation. A fracture non-union was observed in 5 patients and further surgery was required.

DISCUSSIONS

APFFs share several clinical and imaging characteristics with AFF. An appropriate and early diagnosis may allow to improve the outcome of these fractures, the management of which should be based on the same principles of that of AFFs.

CONCLUSIONS

Considering the low quality of published articles and the heterogeneity of the treatment used, a clear recommendation of the most appropriate treatment cannot be formulated.

Cemented short-stem total hip arthroplasty: Characteristics of line-to-line versus undersized cementing techniques using a validated CT-based finite element analysis

Short stems are becoming increasingly popular in total hip arthroplasty as they preserve the bone stock and simplify the implantation process. Short stems are advised mainly for patients with good bone stock. The clinical use of short stems could be enlarged to patients with poor bone stock if a cemented alternative would be available. Therefore, this study aimed to quantify the mechanical performance of a cemented short stem and to compare the "undersized" cementing strategy (stem one size smaller than the rasp) with the "line-to-line" technique (stem and rasp with identical size). A prototype cemented short stem was implanted in eight pairs of human cadaveric femora using the two cementing strategies. Four pairs were experimentally tested in a single-legged stance condition; stiffness, strength, and bone surface displacements were measured. Subject-specific nonlinear finite element models of all the implanted femora were developed, validated against the experimental data, and used to evaluate the behavior of cemented short stems under physiological loading conditions resembling level walking. The two cementing techniques resulted in nonsignificant differences in stiffness and strength. Strength and stiffness as calculated from finite element were 8.7 ± 16% and 9.9 ± 15.0% higher than experimentally measured. Displacements as calculated from finite element analyses corresponded strongly (R ²  ≥ .97) with those measured by digital image correlation. Stresses during level walking were far below the fatigue limit for bone and bone cement. The present study suggests that cemented short stems are a promising solution in osteoporotic bone, and that the line-to-line and undersized cementing techniques provide similar outcomes.

The Effect of a Distal Centralizer on Cemented Femoral Stems in Arthroplasty Shown on Radiographs and SPECT/CT: A Case Report

CASE

A 70-year-old female patient underwent total hip arthroplasty (HA) using a stem cemented line-to-line without centralizer. Postoperatively, she complained of load-dependent thigh pain. Conventional radiographs identified cortical overload because of a distal cement mantle discontinuity at the level of the stem's tip, confirmed by single-photon emission computed tomography/computed tomography scan (SPECT/CT). After cement-in-cement revision using a stem with centralizer, pain ceased rapidly. The cortical overload disappeared, as confirmed on a following SPECT/CT performed for low back pain.

CONCLUSION

In HA, the stem's tip may cause overload on the bone's cortex if the cement mantle is incomplete. Implanting a stem with centralizer avoids or cures this.

Temporal subsidence patterns of cemented polished taper-slip stems: a systematic review

The literature was reviewed to establish the levels of stem subsidence for both double and triple-tapered implants in order to determine whether there were any differences in subsidence levels with regard to the methods of measurement, the magnitude and rate of subsidence and clinical outcomes.

All studies reporting subsidence of polished taper-slip stems were identified. Patient demographics, implant design, radiological findings, details of surgical technique, methods of measurement and levels of subsidence were collected to investigate which factors were related to increased subsidence.

Following application of inclusion and exclusion criteria, 28 papers of relevance were identified. The studies initially recruited 3090 hips with 2099 being available for radiological analysis at final follow-up. Patient age averaged 68 years (42–70), 60.4% were female and the average body mass index (BMI) was 27.4 kg/m² (24.1–29.2).

Mean subsidence at one, two, five and 10 years was 0.97 mm, 1.07 mm, 1.47 mm and 1.61 mm respectively. Although double-tapered stems subsided more than triple-tapered stems at all time points this was not statistically significant (p > 0.05), nor was the method of measurement used (p > 0.05).

We report the levels of subsidence at which clinical outcomes and survivorship remain excellent, but based on the literature it was not possible to determine a threshold of subsidence beyond which failure was more likely.

There were relatively few studies of triple-tapered stems, but given that there were no statistically significant differences, the levels presented in this review can be applied to both double and triple-tapered designs.

Cite this article: EFORT Open Rev 2021;6:331-342. DOI: 10.1302/2058-5241.6.200086

Cemented hemiarthroplasty for femoral neck fracture patients: collarless, polished tapered stem (CPT) versus anatomic matte stem (Lubinus SP2)

BACKGROUND

Cemented hemiarthroplasty is a well-documented treatment for patients with femoral neck fractures (FNFs). However, there are not many cohort studies comparing different types of hemiarthroplasty (HA).

OBJECTIVE

To compare CPT and Lubinus SP2 HA for FNF patients concerning complications and radiological measurements.

METHODS

From January 1, 2013, CPT was introduced instead of Lubinus SP2 as the new cemented HA due to a regional procurement. Data were retrieved 3 years prior and after the introduction. All patient health records were retrospectively reviewed for types of implant, American Society of Anesthesiologists (ASA) score and duration of admission. All X-ray images were analyzed for radiological measurements concerning offset, stem angulation and cement filling. Mortality and major complications within 1 year were retrieved from patient health records as well as the Danish National Patient Registry. Major complications were defined as dislocations, periprosthetic fractures and revisions.

RESULTS

584 cemented HA were included, 300 CPT and 284 with Lubinus SP2. The mean age (SD) was 82 (8.2) years, and there was no baseline difference between the groups concerning age, sex, ASA score and mortality. There were 8.7% major complications for CPT and 9.2% for Lubinus SP2 (p = 0.836). There were, however, seven periprosthetic fractures in the CPT group and one in the Lubinus SP2 group (p = 0.04). In contrast, there were 20 dislocations in the Lubinus SP2 group and 10 in the CPT group (p = 0.042). There was no statistical difference between the stem angulation and periprosthetic fractures (p = 0.824) or major complications (p = 0.602). The Lubinus SP2 had a mean plus 2.7 mm offset postoperatively (p = 0.001), while the CPT had plus 10.6 mm (p < 0.000). The mean (SD) angle of the stems was 1.39 (1.75) degrees for Lubinus SP2 and 2.46 (1.99) for CPT. There was no difference in cementation (p = 0.308).

CONCLUSION

There was no overall statistical difference between the CPT and Lubinus SP2 stem regarding major complications. However, the CPT had a higher prevalence of periprosthetic fractures, while the Lubinus SP2 had a higher dislocation prevalence. The CPT stem had overcorrection of offset and a higher degree of varus positioning.

A finite element study of fatigue load effects on total hip joint prosthesis

The main goal of this study was to perform a fatigue analysis and compare the results for different materials. A 72 years old patient was chosen and his hip radiographic/CT scan images were used to construct the geometry. We used four different material including Titanium, Titanium alloy, Cobalt-Chrome, and Stainless steel. The material characteristics of these prostheses were extracted from the literature. All models were exported to ANSYS software for mathematical analysis and the Von-Mises criteria, deformations, and the fatigue life were calculated for each material. Our findings showed that titanium prosthesis tolerated the lowest stress (i.e., 591 MPa for static, and 687 MPa for fatigue loading) and highest safety factor (i.e., 1.54). We found out that Titanium material could be used as the most appropriate one for the hip prosthesis due to lower stress concentration and longer life compared to other materials.

Short vs Standard-Length Femoral Stems Cemented According to the "French Paradox": A Matched Paired Prospective Study Using Ein Bild Roentgen Analyze Femoral Component at Two-Year Follow-Up

BACKGROUND

The purpose of this prospective matched paired study is to compare the in vivo migration patterns using Ein Bild Roentgen Analyze femoral component of shortened vs standard-length stems cemented line-to-line in primary total hip arthroplasty (THA) at 2-year follow-up.

METHODS

We prospectively included the first 50 consecutive primary cemented THAs in 50 patients using a 12% shortened stem (AmisK group) of which design was derived from the original Charnley-Kerboull (CK) femoral components. These 50 patients were matched paired to 50 patients from a historical series of patients who underwent primary THAs using standard-length CK stems (CK group) with available long-term results, including Ein Bild Roentgen Analyze femoral component data at 2-year follow-up.

RESULTS

Body mass index was significantly higher (P = .007) in the AmisK vs the CK group. At the 2-year follow-up, the mean subsidence was 0.65 mm (0-1.40) in the AmisK group vs 0.68 mm (0.07-1.43) in the CK group (P = .73). When using a 1.5-mm threshold, none of the stems in either group was considered to have subsided. Femoral cortical thickening in zones 3 and 5 occurred in 6 of the 50 hips (12%) in the AmisK group vs 20 (40%) of the 50 hips in the CK group (P = .003).

CONCLUSION

Our study showed that a shortened highly polished double-tapered stem cemented line-to-line provided similar results including minimal subsidence as its standard-length counterpart, with significantly less distal femoral cortical thickening. However, longer term survival analysis still needs to be determined.

Femoral Stem Cementation in Hip Arthroplasty: The Know-How of a "Lost" Art

PURPOSE OF REVIEW

To describe the (1) indications, (2) preoperative precautions, and (3) stepwise technical details of modern femoral stem cemented fixation.

RECENT FINDINGS

Femoral stem cementation provides excellent implant longevity with a low periprosthetic fracture rate among patients with compromised bone quality or aberrant anatomy. Unfamiliarity with the details of modern cementation techniques among trainees who may lack frequent exposure to cementing femoral stems may preclude them from offering this viable option to suitable patients in later stages of their careers. As such, maximizing benefit from cemented femoral stem fixation among suitable candidates is contingent upon the meticulous use of modern cementation techniques. In addition to proper patient selection, modern cementation techniques emphasize the use of (1) pulsatile lavage of the femoral canal, (2) utilization of epinephrine-soaked swabs, (3) vacuum cement mixing, (4) retrograde cement introduction, (5) cement pressurization, and (6) the use of stem centralizers. Furthermore, identifying and optimizing the preoperative status of at-risk patients with pre-existing cardiopulmonary compromise, in addition to intraoperative vigilance, are essential for mitigating the risk of developing bone cement implantation syndrome. Further research is required to assess the utility of cemented femoral stem fixation among younger patients.

Biomechanical Comparison of Periprosthetic Femoral Fracture Risk in Three Femoral Components in a Sawbone Model

BACKGROUND

The increasing use of orthopedic total hip arthroplasty implants has led to a consequent rise in the incidence of associated periprosthetic fractures (PPFs). Analysis of the National Joint Registry data showed the choice of cemented hip stem influenced the risk of a PPF occurring. However, the effect of implant design in relation to the risk of PPFs has not been investigated.

METHODS

The main objective is to compare the biomechanics of PPFs as a failure of the Exeter V40, CPT, and DePuy C-Stem stems in a composite Sawbone model to identify whether a difference in the risk of fracture exists between them. Twenty-six Sawbones were divided into 3 groups, cemented with the Stryker Exeter, Zimmer CPT, or DePuy C-Stem and then torqued to fracture.

RESULTS

When compared with the Exeter, the CPT- and C-Stem-implanted Sawbone models would sustain PPFs at a statistically significantly lower rotation to failure (20.1° and 26.7° vs 33.6°, P < .01) and torque to failure (124 Nm and 143 Nm vs 174 Nm, P < .01) values. The energy release rate at failure for the Exeter was significantly higher than that for the CPT and C-Stem (61.2 Nm vs 21.8 Nm and 38.6 Nm, P < .01), which led to more comminution.

CONCLUSION

The CPT- and C-Stem-implanted femurs, although fracturing earlier, fractured in a simple pattern with less comminution. The differences in stem design mean higher stress at the critical point of failure in the CPT implanted femur compared with the Exeter and DePuy, which is likely the reason behind the observed increased risk of PPFs with the CPT implant.

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.

Risk Factors for Revision of Polished Taper-Slip Cemented Stems for Periprosthetic Femoral Fracture After Primary Total Hip Replacement: A Registry-Based Cohort Study from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man

BACKGROUND

Total hip replacement (THR) with a cemented polished taper-slip (PTS) femoral stem has excellent long-term results but is associated with a higher postoperative periprosthetic femoral fracture (PFF) risk compared with composite beam stems. This study aimed to identify risk factors associated with PFF revision following THR with PTS stems.

METHODS

In a retrospective cohort study, 299,019 primary THRs using PTS stems from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man (NJR) were included, with a median follow-up of 5.2 years (interquartile range [IQR], 3.1 to 8.2 years). The adjusted hazard ratio (HR) of PFF revision was estimated for each variable using multivariable Cox survival regression analysis.

RESULTS

Of 299,019 THR cases, 1,055 underwent revision for PFF at a median time of 3.1 years (IQR, 1.0 to 6.1 years). The mean age (and standard deviation) was 72 ± 9.7 years, 64.3% (192,365 patients) were female, and 82.6% (247,126 patients) had an American Society of Anesthesiologists (ASA) class of 1 or 2. Variables associated with increased PFF were increasing age (HR, 1.02 per year), intraoperative fracture (HR, 2.57 [95% confidence interval (CI), 1.42 to 4.66]), ovaloid (HR, 1.96 [95% CI, 1.22 to 3.16]) and round cross-sectional shapes (HR, 9.58 [95% CI, 2.29 to 40.12]), increasing stem offset (HR, 1.07 per millimeter), increasing head size (HR, 1.04 per millimeter), THR performed from 2012 to 2016 (HR, 1.45 [95% CI, 1.18 to 1.78]), cobalt-chromium stem material (HR, 6.7 [95% CI, 3.0 to 15.4]), and cobalt-chromium stems with low-viscosity cement (HR, 22.88 [95% CI, 9.90 to 52.85]). Variables associated with a decreased risk of PFF revision were female sex (HR, 0.52 [95% CI, 0.45 to 0.59]), increasing stem length (HR, 0.97 per millimeter), and a ceramic-on-polyethylene bearing (HR, 0.55 [95% CI, 0.36 to 0.85]).

CONCLUSIONS

Increased risk of PFF revision was associated with PTS stems that are short, have high offset, are used with large femoral heads, are made of cobalt-chromium, or have ovaloid or round cross-sectional shapes. Large increases in PFF risk were associated with cobalt-chromium stems used with low-viscosity cement. Further study is required to confirm causation.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Radiographic, Functional, and Oncologic Outcomes of Cemented Modular Proximal Femur Replacement Using the "French Paradox" Technique

BACKGROUND

Endoprostheses are frequently used in the management of tumors involving the proximal femur. Aseptic loosening is a common complication that has been linked to the cementing technique. The "French paradox" is well-known cementing technique in the arthroplasty literature. No previous reports have assessed loosening in proximal femur replacements using this technique. We examined rates of femoral stem aseptic loosening in proximal femur replacements, functional outcomes, complications, and oncologic outcomes.

METHODS

We conducted a retrospective review of 47 patients who underwent proximal femur replacement between 2000 and 2019. Two reviewers evaluated preoperative and postoperative radiographs using the International Society of Limb Salvage scoring system and Barrack criteria for stem loosening. The acetabulum was evaluated according to the criteria of Baker et al. Functional outcomes were assessed using Musculoskeletal Tumor Society (MSTS) score and Toronto Extremity Salvage Score. The mean follow-up was 44 months.

RESULTS

The mean International Society of Limb Salvage scores for the 2 reviewers were 86% ± 6% and 84% ± 6%. The first reviewer graded femoral stem loosening as "possibly loose" in 2 patients, one of whom was graded as possibly loose by the second reviewer. The 2 reviewers found no acetabular erosion in 16 (70%) and 15 (65.4%) patients, respectively. The mean Musculoskeletal Tumor Society score and Toronto Extremity Salvage Score at last follow-up were 61% and 72%, respectively. Twenty complications occurred in 13 patients, and 5 patients experienced local recurrence.

CONCLUSION

Despite complications, we showed favorable femoral component survival rates. Cementing the proximal femur prosthesis with tight canal fit and thin cement mantle is a viable option for the short and medium term.

LEVEL OF EVIDENCE

III.

Comparisons of the surface micromotions of cementless femoral prosthesis in the horizontal and vertical levels: a network analysis of biomechanical studies

BACKGROUND

Numerous quantitatively biomechanical studies measuring the fixation stability of femoral stem using micromotions at the bone-implant interfaces in different directions and levels remain inconclusive. This network meta-analysis performed systematically aims to explore the rank probability of micromotions at the bone-implant interfaces based on biomechanical data from studies published.

METHODS

Two electronic databases, PubMed/MEDLINE and Embase, were utilized to retrieve biomechanical studies providing the data of micromotions at the bone-stem interfaces. After screening and diluting out, the studies that met inclusion criteria will be utilized for statistical analysis. In order to contrast the stability of commonness and differences of the different parts of the femoral stem, the horizontal and vertical comparison of micromotions at the bone-implant interfaces were conducted using the pooled evaluation indexes including the mean difference (MD) and the surface under the cumulative ranking (SUCRA) curve, while inconsistency analysis, sensitivity analysis, subgroup analyses, and publication bias were performed for the stability evaluation of outcomes.

RESULTS

Screening determined that 20 studies involving a total of 249 samples were deemed viable for inclusion in the network meta-analysis. Tip point registered the highest micromotions of 13 measurement points. In the horizontal level, the arrangements of 4 measurement points at the proximal (P1-P4), middle (P5-P8) and distal part of the stem (P9-P12) were P1 = P2 = P3 = P4, P7 > P8 > P6 = P5 and P10 ≥ P12 = P9 = P11, respectively. In the vertical level, the arrangements of 3 measurement points at the anterior, posterior, medial, and lateral directions was P9 > P5 = P1, P10 > P6 > P2, P11 > P7 > P3, and P12 > P8 > P4, respectively.

CONCLUSION

The network meta-analysis seems to reveal that the distal part of the femoral stem is easier to register higher micromotion, and tip point of femoral stem registers the highest micromotions.

Postoperative migration of the anatomical and functional anteversion angle following total hip arthroplasty with a well-fixed cemented femoral component with line-to-line implantation

INTRODUCTION

Little is known about the association between well-fixed polished tapered cemented stems (PTCS) implanted by the line-to-line technique and changes of stem migration, or the change of functional anteversion of the femur after total hip arthroplasty (THA).

MATERIALS AND METHODS

This retrospective study included 422 two-stage bilateral primary THAs performed using PTCS implanted by the line-to-line technique. CT scans were made on both the target side (first postoperative CT) and on the contralateral side (second postoperative CT) 1 week postoperatively. The mean follow-up was 7.8 months. CT data for each scan were transferred to 3D template software (Zed hip, Lexi, Japan). The postoperative changes of anatomical stem anteversion (ASA), functional femoral anteversion (FFA), and stem subsidence were evaluated.

RESULTS

A total of 20 THAs with CT scans were available on 3D template software. The ASA and the FFA had migrated - 0.68° ± 0.62° and - 5.5° ± 9.7°, respectively, over the follow-up period. A significant positive correlation was observed between the change of subsidence and ASA (r² = 0.34, p = 0.007), between the FFA on the second postoperative CT and ASA on the first postoperative CT (r² = 0.26, p = 0.02) and between the FFA on the second postoperative CT and FFA on the first postoperative CT (r² = 0.52, p = 0.0003).

CONCLUSION

This study indicates that the change in axial rotation of a PTCS implanted by the line-to-line technique was less than that reported by other studies and the preoperative external rotation contracture was substantially improved after THA.

Current concepts and outcomes in cemented femoral stem design and cementation techniques: the argument for a new classification system

Cemented implant fixation design principles have evolved since the 1950s, and various femoral stem designs are currently in use to provide a stable construct between the implant-cement and cement-bone interfaces.Cemented stems have classically been classified into two broad categories: taper slip or force closed, and composite beams or shaped closed designs. While these simplifications are acceptable general categories, there are other important surgical details that need to be taken into consideration such as different broaching techniques, cementing techniques and mantle thickness.With the evolution of cemented implants, the introduction of newer implants which have hybrid properties, and the use of different broaching techniques, the classification of a very heterogenous group of implants into simple binary categories becomes increasingly difficult. A more comprehensive classification system would aid in comparison of results and better understanding of the implants' biomechanics.We review these differing stem designs, their respective cementing techniques and geometries. We then propose a simple four-part classification system and summarize the long-term outcomes and international registry data for each respective type of cemented prosthesis. Cite this article: EFORT Open Rev 2020;5:241-252. DOI: 10.1302/2058-5241.5.190034.

Carbon nanotube-based biomaterials for orthopaedic applications

Carbon nanotubes can enhance the functionality of orthopedic applications.

Prospective, comparative study of cemented, smooth-surfaced titanium stems and polish-surfaced, stainless steel stems at a minimum follow-up of 10 years

BACKGROUND

Excellent results have been reported with cemented total hip arthroplasty (THA) using both smooth-surfaced and polished-surfaced stems. However, the superiority of polished-surfaced over smooth-surfaced in cemented THA, or vice versa, is still debated.

MATERIALS AND METHODS

Forty-six smooth-surfaced, triple-tapered, titanium-alloy stem (Group C) and 46 Exeter stems (Group T) have been fixed consecutively at different periods at our institute and prospectively evaluated clinically and radiologically. The area and location demonstrating cortical hypertrophy (CH) was measured in the serial radiograph and compared.

RESULTS

The mean postoperative follow-up period was 12.4 years for group C and 10.8 years for group T. No significant difference of clinical results was found between both groups. CH was observed in 8 hips (18.6%) of group C and in 7 hips (17.1%) of group T (NS). Among the hips in which distribution of CH was observed at the medial side, a significantly low proportion belonged to group C (adjusted standardized residual = - 2.3) and a significantly high proportion belonged to group T (adjusted standardized residual = 2.3). The largest area of CH found in each group was 166.1 mm² in group C and 227.6 mm² in group T (NS). The peak location of CH was 100.4% in group C and 84.3% in group T (p = 0.02).

CONCLUSION

Medium-term results of both stems were excellent. CH was observed medially and proximally in group T and laterally and distally in group C.

Long-term outcome of cemented total hip arthroplasty with the Charnley-type femoral stem made of titanium alloy

BACKGROUND

Total hip arthroplasty is a successful treatment for hip diseases including osteoarthritis, osteonecrosis of the femoral head, and rheumatoid arthritis. Various designs of cemented femoral stems made of stainless steel and titanium alloy have been used. Among them, Charnley-type femoral stems made of stainless steel have often been reported to have good long-term outcome. However, the long-term outcome of the Charnley-type femoral stem made of Ti alloy is yet to be reported. We conducted a retrospective study to assess the long-term outcome of cemented primary total hip arthroplasty with the Charnley-type femoral stem made of Ti alloy.

METHODS

Between October 1988 and February 1997, 341 cemented primary total hip arthroplasties with the Charnley-type femoral stem made of Ti alloy were consecutively performed in our hospital. Among these, 164 patients (211 hips) who underwent this procedure were followed up for more than 12 years, and the surgical hips were analysed clinically and radiologically. The mean follow-up period was 20.6 years. Kaplan-Meier survival analyses were performed to assess femoral component survival. Factors affecting stem revision for aseptic loosening were also investigated using log-rank tests.

RESULTS

In the functional assessment, the preoperative Japanese Orthopaedic Association score significantly improved from 47.2 points preoperatively to 79.0 points at the final follow-up. Eventually, 33 femoral stems were revised, of which 12 were revised for aseptic loosening. In the Kaplan-Meier survival analysis, the 20-year survival rates with stem revision for aseptic loosening and radiological stem loosening at the end points were 95.9% and 97.1%, respectively. Original diagnosis (non-osteoarthritis) was the only significant factor for aseptic loosening of the femoral stem.

CONCLUSIONS

Cemented primary total hip arthroplasty with the Charnley-type femoral stem made of Ti alloy showed excellent outcomes for more than 20 years.

Cementing of the hip arthroplasty stem increases load-to-failure force: a cadaveric study

Background and purpose - To date, there is not a single clinical or mechanical study directly comparing a cemented and a cementless version of the same stem. We investigated the load-to-failure force of a cementless and a cemented version of a double tapered stem. Material and methods - 10 femurs from 5 human cadaveric specimens, mean age 74 years (68-79) were extracted. Bone mineral density (BMD) was measured using peripheral quantitative computed tomography. None of the specimens had a compromised quality (average T value 0.0, -1.0 to 1.4). Each specimen from a pair randomly received a cemented or a cementless version of the same stem. A material testing machine was used for lateral load-to-failure test of up to a maximal load of 5.0 kN. Results - Average load-to-failure of the cemented stem was 2.8 kN (2.3-3.2) and 2.2 kN (1.8-2.8) for the cementless stem (p = 0.002). The cemented version of the stem sustained a higher load than its cementless counterpart in all cases. Failure force was not statistically significantly correlated to BMD (p = 0.07). Interpretation - Implanting a cemented version of the stem increases the load-to-failure force by 25%.

Is cemented revision total hip arthroplasty a reasonable treatment option in an elderly population?

Revision THA is increasingly performed especially in the elderly population. The surgeon’s challenge is to provide a solution that supports immediate full weight-bearing, despite poor bone quality. Shape-closed revision stems facilitate that by combining cement fixation with additional press-fit anchoring. The design tolerates varying cement mantle thickness and inconsistent cancellous bone lining of the femoral canal. Following that philosophy, we present our mid-term results using a long version of a cemented Charnley- Kerboull type stem. From 2010 to 2017, 38 long Charnley-Kerboull revision stems (Centris^®, Mathys European Orthopaedics, Bettlach, Switzerland) were implanted and followed prospectively. Surgery was performed via a Hardinge approach in supine position with a third generation cementing technique. Patients were mobilized using full-weight bearing as early as possible. Survival was determined for stem revision for aseptic loosening and stem and/or cup revision for any reason. 20 stems had a minimum follow-up (f/u) of 2 years and were included for further radiological analysis. Detailed subsidence analysis as an early predictor for later aseptic loosening was performed using EBRA-FCA software. Further, the presence of osteolysis and cement debonding was evaluated. Mean follow- up was 4 years. No patient was lost to f/u.18 died of causes unrelated to THA. Stem survival was 100%. Survival for any re-operation was 82.2% (two early infections, one soft-tissue debridement, one cup exchange for recurrent dislocations). None of the cases revised for septic loosening showed signs of persistent infection at final f/u. EBRA-FCA revealed two oligosymptomatic cases of subsidence of 5mm and 6mm over a course of 2 and 12 months, respectively, with stable implants thereafter. Neither required revision. There was no development of osteolysis or debonding. The stem provides a reliable early fullweight bearing solution for revision THA with excellent mid-term survival in an elderly population. Even in two cases where subsidence was present, mobility was not impaired and re-revision could be avoided.

Vancouver B2 Peri-Prosthetic Fractures in Cemented Femoral Implants can be Treated With Open Reduction and Internal Fixation Alone Without Revision

BACKGROUND

The aim of this study is to assess the outcomes of 52 consecutive Vancouver B2 peri-prosthetic fractures around cemented polished double-tapered stems treated by open reduction and internal fixation in 2 trauma centers in 2 countries.

METHODS

Outcomes included modified Harris Hip Score (mHHS), Harris Pain Score, and return to pre-injury mobility. Fracture healing was assessed; implant subsidence measured and complications including re-operations reported.

RESULTS

No patient was lost to follow-up. Median patient age at operation was 82 years (range 43-98); Harris pain scores showed minimal pain (median 42, range 10-44) at latest follow-up. Median total subsidence at 1 year was 1.1 mm (range 0-5.4), the majority of which occurred within the cement mantle. No subsequent femoral stem revision was required (median 2.9 years, 0-10); however, there were 3 re-operations: 1 re-operation for pre-existing recurrent dislocation involving head liner exchange and 2 for repeat fixation due to metal fatigue. Two additional fractures occurred below the new plating, requiring further plating whilst still retaining the original stems.

CONCLUSION

Anatomical reduction and open reduction and internal fixation of Vancouver B2 peri-prosthetic fractures should be considered as an appropriate treatment solution for frail elderly patients with a peri-prosthetic fracture around cemented polished double-tapered stems.

Five-year prospective subsidence analysis of 100 cemented polished straight stems: A concise clinical and radiological follow-up observation

Early subsidence (>1.5mm) has been shown to be an indicator for later aseptic loosening of cemented hip stems. For the cemented twinSys^® stem we published excellent short-term results at 2 years. Midterm data for this stem are available from national registers (NZL, NL), however in all of these sources, clinical and radiological results are missing. Aim of our study was to analyse mid-term survival and radiological changes around the cemented twinSys^® stem with special emphasis on subsidence using EBRA-FCA. We conducted a prospective clinical and radiological 5- year follow-up study of 100 consecutive hybrid total hip arthroplasties (THA) using a polished, cemented collarless straight stem (twinSys^®, Mathys AG^® Bettlach, Switzerland) with a cementless monobloc pressfit cup (RM pressfit^®, Mathys AG^® Bettlach, Switzerland). Median age at surgery was 79 (69 to 93) years. No patient was lost to follow-up. Survival rates were calculated using the Kaplan-Meier method. Clinical (Harris Hip Score [HHS]) and radiological (cementing quality, alignment, osteolysis, debonding and cortical atrophy) outcomes and an in-depth subsidence analysis using EBRA-FCA were performed. 22 patients died in the course of follow-up unrelated to surgery, 21 stems had an incomplete radiological follow-up. 2 stems were revised, both due to an infection. The survival rate for the stem at 5 years was 98.0% (95% CI 95.3-100%). The survival rate of the stem for revision due to aseptic loosening at 5 years was 100%. The HHS improved from 53 (14-86) points preoperatively to 90 (49-100) points 5 years after surgery. Osteolysis was found in 2 stems without clinical symptoms. In 49 out of 55 patients with a complete radiological follow- up, the EBRA-FCA analysis was possible and showed an average subsidence of 0.66 (95% CI 0.46 to 0.86) mm 5 years after surgery. 10 patients showed a subsidence >1 mm, 5 of which bigger than 1.5 mm. Subsidence was independent from radiological changes and cementing quality. The cemented twinSys^® stem showed excellent clinical and radiological mid-term results at five years' follow-up and seems to be a reliable implant.

Cemented Femoral Component Use in Hip Arthroplasty

Elderly patients undergoing both elective and nonelective hip arthroplasty contribute markedly to health care spending, and the current aging population is likely to require even more resources. Several national joint replacement registries show a lower risk of revision surgery in patients older than 75 years who received cemented femoral components compared with cementless implants for primary total hip arthroplasty. Despite a higher incidence of early periprosthetic femoral fracture, noncemented femoral components are being used with increasing frequency in elderly patients worldwide. Improvements in cementing technique and modifications to cemented stem design over several decades allow surgeons to obtain femoral component fixation in poor-quality bone with a relatively low risk of complications. Achieving durable cemented stem fixation requires the surgeon to understand the basic handling properties of cement, how to prepare the femoral bone, and differences in stem design and surface finish.

Biomechanical behaviour of a French femoral component with thin cement mantle: The 'French paradox' may not be a paradox after all

Objective

Cement thickness of at least 2 mm is generally associated with more favorable results for the femoral component in cemented hip arthroplasty. However, French-designed stems have shown favorable outcomes even with thin cement mantle. The biomechanical behaviors of a French stem, Charnley-Marcel-Kerboull (CMK) and cement were researched in this study.

Methods

Six polished CMK stems were implanted into a composite femur, and one million times dynamic loading tests were performed. Stem subsidence and the compressive force at the bone-cement interface were measured. Tantalum ball (ball) migration in the cement was analyzed by micro CT

Results

The cement thickness of 95 % of the proximal and middle region was less than 2.5 mm. A small amount of stem subsidence was observed even with collar contact. The greatest compressive force was observed at the proximal medial region and significant positive correlation was observed between stem subsidence and compressive force. 9 of 11 balls in the medial region moved to the horizontal direction more than that of the perpendicular direction. The amount of ball movement distance in the perpendicular direction was 59 to 83% of the stem subsidence, which was thought to be slip in the cement of the stem. No cement defect and no cement breakage were seen.

Conclusion

Thin cement in CMK stems produced effective hoop stress without excessive stem and cement subsidence. Polished CMK stem may work like force-closed fixation in short-term experiment.

Cite this article: Y. Numata, A. Kaneuji, L. Kerboull, E. Takahashi, T. Ichiseki, K. Fukui, J. Tsujioka, N. Kawahara. Biomechanical behaviour of a French femoral component with thin cement mantle: The ‘French paradox’ may not be a paradox after all. Bone Joint Res 2018;7:485–493. DOI: 10.1302/2046-3758.77.BJR-2017-0288.R2.

Cement mantle thickness does not influence serum or local gentamicin concentrations in hybrid total hip arthroplasty: a randomised controlled trial

INTRODUCTION

We investigated the in vivo gentamicin elution kinetics of Hi-Fatigue Gentamicin Bone Cement (AAP Biomaterials GmbH) in serum and drain fluid after hybrid hip arthroplasty and the relationship with cement mantle thickness.

METHODS

We compared in a randomised, non-blinded prospective study, the local and systemic gentamicin concentrations in 2 groups. The thin cement mantle group ( n = 16) received a stem implanted line-to-line with the broach, whereas the thick group ( n = 14) had an undersized stem. Gentamicin concentrations were measured in drain fluid and serum at set intervals for 3 days postoperatively.

RESULTS

In both groups, local gentamicin concentrations were similar. After a high initial burst above the minimal inhibitory concentration (thin: 57.2 mg/L (SD 34.4), thick: 54.9 mg/L (SD 19.9), p = 0.823) local gentamicin concentrations declined rapidly. In both groups, serum concentrations never exceeded toxic levels (maximum 1.08 mg/L).

CONCLUSION

In hybrid total hip arthroplasty, Hi-Fatigue Gentamicin Bone Cement resulted in effective and safe gentamicin concentrations. Clinical trial protocol number: PMCI 12/02.

Predictive accuracy of RSA migration thresholds for cemented total hip arthroplasty stem designs

INTRODUCTION

Radiostereometric analysis (RSA) migration thresholds for cemented total hip stems have been established beyond which an unacceptably high risk of revision is likely to occur. These thresholds are subsidence >0.23 mm or >1.2 mm after 2 years. The purpose of this study was to retrospectively examine after long-term follow-up the predictive accuracy of the two thresholds.

METHODS

Data from two previous prospective RSA trials with 2 year follow-up for which minimum 10 year survivorship data was available were used. Thirty-six patients received a Spectron stem, 17 patients received an Exeter stem, and 17 patients received a CPCS stem. Subsidence after 2 years was compared to the migration thresholds, and long-term survivorship and clinical outcome scores were obtained.

RESULTS

At 2 years, the Spectron stem subsided 0.046 ± 0.160 mm, the Exeter stem subsided 1.218 ± 0.320 mm, and the CPCS stem subsided 0.681 ± 0.246 mm ( p < 0.0001). The Spectron stem passed both thresholds, the Exeter stem failed both thresholds, and the CPCS stem passed 1 and failed 1 threshold. At 10 years, survivorship exceeded 90% for all stems.

CONCLUSION

All stems demonstrated strong 10 year survivorship and equivalent clinical outcome scores, but this success would not have been equally predicted across RSA migration thresholds. Although RSA is a useful predictive tool, care should be taken in applying migration thresholds only to those stem designs they are indicated for, with the threshold of 1.2 mm of subsidence at 2 years being most broadly applicable.

SPECT/CT in Postoperative Painful Hip Arthroplasty

Consecutive milestones in hip arthroplasty design and surgical technique have contributed to the successful and cost-effective intervention this procedure has become today in maintaining mobility and quality of life in patients with osteoarthritis, fracture, or other hip conditions. With the increasing prevalence of hip joint replacements, the need for improved diagnostic imaging tools to guide revision surgery has risen in parallel. Over the last few years, promising data have emerged on the potential role of bone SPECT/CT imaging in the assessment of patients with recurrent pain after arthroplasty. This review summarizes the trends in hip arthroplasty surgery (partial vs total arthroplasty; cemented vs cementless arthroplasty; resurfacing arthroplasty) and prosthesis design (bearing materials; stem designs) over the last decade. In particular, the impact on the biomechanics and interpretation of bone SPECT/CT findings is discussed, with emphasis on integrative reporting in the following frequently encountered conditions: lysis/aseptic loosening, septic loosening, heterotopic ossification, periprosthetic fracture, tendinopathies, and adverse local tissue reactions. Based on the available literature data, bone SPECT/CT is increasingly being used as second-line imaging modality when conventional investigations are nondiagnostic. Further outcome research is warranted to examine whether this technique could be used earlier in patient management.

Polished Cemented Femoral Stems Have a Lower Rate of Revision Than Matt Finished Cemented Stems in Total Hip Arthroplasty: An Analysis of 96,315 Cemented Femoral Stems

BACKGROUND

Matt and polished femoral stems have been historically grouped together in registry assessment of the outcome of cemented femoral stems in total hip arthroplasty. This is despite differences in the mode of fixation and biomechanics of loading. The aims of this study are to compare the survivorship of polished tapered stems with matt finished cemented stems.

METHODS

Data on primary total hip arthroplasty undertaken for a diagnosis of osteoarthritis from September 1999 to December 2014 were included from a National Joint Registry. Revision rates of the 2 different types of femoral components were compared.

RESULTS

There were 96,315 cemented femoral stems included, of which 82,972 were polished tapered and 13,343 matt finish. The cumulative percent revision at 14 years of polished stems was 3.6% (3.0-4.2) compared to 4.9% (4.1-5.7) for matt finish stems. Polished tapered stems had a significantly lower revision rate of femoral revision (hazard ratio 0.56, P < .001). This difference is evident in patients aged <75, and becomes apparent in the mid-term and continues to increase with time. Aseptic loosening accounts for 75% of revisions of matt finish stems compared to 20% for polished tapered stems.

CONCLUSION

Although both polished and matt finish stems have excellent early to mid-term results, the long-term survivorship of polished stems is significantly better, with aseptic loosening becoming an issue with matt finish stems. In the future reports of cement fixation for femoral stems may benefit from separate analysis of polished and matt finish.

The impact of canal flare index on leg length discrepancy after total hip arthroplasty

INTRODUCTION

The femoral stem should protrude from femur by an appropriate vertical distance to allow leg length equalization at hip arthroplasty; this distance depends on the size/shape of medullary canal and implant. The relationship between femoral morphology and achievability of leg length restoration is currently unclear. Our aim was to examine the impact of the femoral canal flare index (CFI) on the risk of leg length discrepancy (LLD) after total hip arthroplasty with different femoral stems.

MATERIALS AND METHODS

The study cohort included 126 patients with unilateral primary total hip arthroplasty due to idiopathic osteoarthritis and three different types of implanted femoral stems. The impact of CFI on postoperative LLD was assessed with separate logistic regression model for each implant and covariables of age, gender, body mass index and femoral neck resection level.

RESULTS

Higher CFI was an independent risk factor for postoperative LLD ≥ 5 mm with odds ratio 4.5 (p = 0.03) in 49 stems with cementless metaphyseal fixation Implantcast-EcoFit®, regardless of the femoral neck resection level. CFI had no significant impact on LLD in 30 stems with cementless diaphyseal fixation EndoPlus-Zweymüller® or 47 cemented collared stems Link-SPII®. No significant difference was observed between groups in pre/postoperative WOMAC scores, postoperative radiographic LLD, subjectively reported LLD, insole use or complications after mean 6.8 years of follow-up.

CONCLUSIONS

Higher CFI increases the risk of clinically detectable postoperative LLD in single-wedge femoral stems with cementless metaphyseal fixation. CFI has no significant impact on LLD in femoral stems with cementless diaphyseal fixation or cemented fixation.

Long-term results of revision total hip arthroplasty with a cemented femoral component

INTRODUCTION

In revision total hip arthroplasty (THA), the cancellous bone is normally completely removed out of the femoral canal during stem extraction. This situation is comparable to primary THA following the shape-closed concept, with some authors advocating to remove the metaphyseal cancellous bone to enhance press-fit stability ("French paradox"). The aim of this study was to investigate the long-term outcome, regarding survival and radiological results, of a cemented straight stem when used for revision THA and to compare these results to the results of the same stem in primary THA.

MATERIALS AND METHODS

178 stem revisions performed between 01/1994 and 08/2008 using the Virtec straight stem were included. The cumulative incidence for re-revision was calculated using a competing risk model. Risk factors for re-revision of the stem were analyzed using an absolute risk regression model. Radiographs analyzed for osteolysis, debonding and subsidence had a minimum follow-up of 10 years.

RESULTS

The cumulative incidence for re-revision due to aseptic loosening of the stem was 5.5% (95% CI, 2.9-10.2%) at 10 years. Aseptic loosening was associated with younger age, larger defect size and larger stem size. After a minimum 10-year follow-up, osteolysis was seen in 39 of 80 revision THA. Compared to the results in primary THA, the survival in revision THA with the same implant was inferior.

CONCLUSIONS

Cemented straight stems used for revision THA showed excellent long-term results regarding survivorship and radiological outcome. This stem therefore offers a valuable and cost-effective option in revision THA.

The Exeter Trauma Stem: A radiographic follow-up at minimum of five years post implantation

INTRODUCTION

The Exeter Trauma Stem (ETS) has been recommended by National Institute of Clinical Excellence (NICE) guidelines in the United Kingdom as a proven, cemented stem. A single laboratory study in the literature has raised possible concerns about the polished finish of the ETS and subsequent potential for accelerated loosening although there is little clinical evidence to support or refute this.

METHODS

The aim of this study was to assess clinical outcomes of the ETS at a minimum of five years post implantation. Primary outcomes were radiological loosening at a minimum of five years along with survivorship of the implant. Patient demographics were prospectively collected and followed up.

RESULTS

218 ETS's (in 214 patients) were implanted from June 2002 until August 2008 in a single centre by a wide variety of surgeons of differing grades. Of these, 16 underwent revision surgery for fracture (2), dislocation (3), infection (1) and acetabular erosion (10) but there were no revisions for aseptic loosening of the implant. There were 64.0% (137/214) patients that had died by the time of this study. Of the remaining patients, 90 had radiographs of their hips at a minimum of 5 years with 36 of these at a minimum of 7 years post implantation. None of these had evidence of loosening.

CONCLUSION

The ETS is a robust and suitable stem for implantation in patients with hip fractures. There are no clinical suspicions or increased rates of loosening with the ETS in our study. The concerns about surface finish are not borne out in our clinical study which shows no evidence of loosening at a minimum of five years post operation. It confers many advantages including ease of revision and it should continue to be used as per NICE guidelines.

Quantitating the effect of prosthesis design on femoral remodeling using high-resolution region-free densitometric analysis (DXA-RFA)

Dual energy X-ray absorptiometry (DXA) is the reference standard method used to study bone mineral density (BMD) after total hip arthroplasty (THA). However, the subtle, spatially complex changes in bone mass due to strain-adaptive bone remodeling relevant to different prosthesis designs are not readily resolved using conventional DXA analysis. DXA region free analysis (DXA RFA) is a novel computational image analysis technique that provides a high-resolution quantitation of periprosthetic BMD. Here, we applied the technique to quantitate the magnitude and areal size of periprosthetic BMD changes using scans acquired during two previous randomized clinical trials (2004 to 2009); one comparing three cemented prosthesis design geometries, and the other comparing a hip resurfacing versus a conventional cementless prosthesis. DXA RFA resolved subtle differences in magnitude and area of bone remodeling between prosthesis designs not previously identified in conventional DXA analyses. A mean bone loss of 10.3%, 12.1%, and 11.1% occurred for the three cemented prostheses within a bone area fraction of 14.8%, 14.4%, and 6.2%, mostly within the lesser trochanter (p < 0.001). For the cementless prosthesis, a diffuse pattern of bone loss (-14.3%) was observed at the shaft of femur in a small area fraction of 0.6% versus no significant bone loss for the hip resurfacing prosthesis (p < 0.001). BMD increases were observed consistently at the greater trochanter for all prostheses except the hip-resurfacing prosthesis, where BMD increase was widespread across the metaphysis (p < 0.001). DXA RFA provides high-resolution insights into the effect of prosthesis design on the local strain environment in bone. © 2017 The Authors Journal of Orthopaedic Research published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 35:2203-2210, 2017.

Radiographic evaluation of cementation technique using polished, conical, triple-tapered femoral stem in hip arthroplasty

Objective

To radiographically evaluate the quality of cementation and implantation technique using a polished, triple-tapered femoral stem in total hip arthroplasty (THA).

Method

Retrospective study with radiographic evaluation of 86 hips in 83 patients who underwent to primary THA with the triple-tapered cemented femoral stem C-Stem (DePuy Orthopedics, Warsaw, Indiana). Cases with at least one-year of follow-up were included, and data related to preoperative, immediate postoperative, and late postoperative radiographic evolution were recorded. This study analyzed, among others, the proximal femoral anatomy, the quality of cementation as described by Barrack, and the implant positioning. Cementation was also evaluated and quantified in the Gruen zones with one-year of follow-up.

Results

The mean age was 62.85 years. Proximal femoral anatomical conformation was Dorr type A in 34 (39.53%) cases, type B in 52 (60.46%), and no type C cases were found. Five (5.81%) cases were defined as type A by Barrack's cementation classification system, 46 (56.49%) type B, 27 (31.40%) type C, and eight (9.30%) type D. The greatest cement mantle thickness was observed in zones four (15.53 mm) and 11 (15.64 mm), and the smallest in zone nine (3.51 mm). Positioning in varus was observed in eight (9.3%) cases, valgus in 25 (29%), forward deviation in two (5%), and backward deviation in 55 (63.95%).

Conclusions

The C-Stem femoral system presented satisfactory results related to cementation pattern, positioning, osteolysis, and stress shielding with regard to literature referring to double-tapered or triple-tapered models, demonstrating to be a safe method, with a predictable and reliable cementing pattern.

Periprosthetic femoral fractures and trying to avoid them: what is the contribution of femoral component design to the increased risk of periprosthetic femoral fracture?

AIMS

Periprosthetic femoral fractures (PFF) following total hip arthroplasty (THA) are devastating complications that are associated with functional limitations and increased overall mortality. Although cementless implants have been associated with an increased risk of PFF, the precise contribution of implant geometry and design on the risk of both intra-operative and post-operative PFF remains poorly investigated. A systematic review was performed to aggregate all of the PFF literature with specific attention to the femoral implant used.

PATIENTS AND METHODS

A systematic search strategy of several journal databases and recent proceedings from the American Academy of Orthopaedic Surgeons was performed. Clinical articles were included for analysis if sufficient implant description was provided. All articles were reviewed by two reviewers. A review of fundamental investigations of implant load-to-failure was performed, with the intent of identifying similar conclusions from the clinical and fundamental literature.

RESULTS

In total 596 articles were initially identified, with 34 being eligible for analysis. Aggregate analysis of 1691 PFFs in 342 719 primary THAs revealed a significantly higher number of PFFs with cementless femoral implants (p < 0.001). Single-wedge and double-wedge (fit-and-fill) femoral implants were associated with a threefold increase in PFF rates (p < 0.001) compared with anatomical, fully coated and tapered/rounded stems. Within cemented stems, loaded-taper (Exeter) stems were associated with more PFFs than composite-beam (Charnley) stems (p = 0.004). Review of the fundamental literature revealed very few studies comparing cementless component designs.

CONCLUSION

Very few studies within the PFF literature provide detailed implant information. Cementless implants, specifically those of single-wedge and double-wedge, have the highest PFF rates in the literature, with most investigations recommending against their use in older patients with osteoporotic bone. This review illustrates the need for registries and future PFF studies to record implant name and information for future analysis. Furthermore, future biomechanical investigations comparing modern implants are needed to clarify the precise contribution of implant design to PFF risk. Cite this article: Bone Joint J 2017;99-B(1 Supple A):50-9.

Influence of different sizes of composite femora on the biomechanical behavior of cementless hip prosthesis

BACKGROUND

For the biomechanical evaluation of cementless stems different sizes of composite femurs have been used in the literature. However, the impact of different specimen sizes on test results is unknown.

METHODS

To determine the potential effect of femur size the biomechanical properties of a conventional stem (CLS Spotorno) were examined in 3 different sizes (small, medium and large composite Sawbones®). Primary stability was tested under physiologically adapted dynamic loading conditions measuring 3-dimensional micromotions. For the small composite femur the dynamic load needed to be adapted since fractures occurred when reaching 1700N. Additionally, surface strain distribution was recorded before and after implantation to draw conclusions about the tendency for stress shielding.

FINDINGS

All tested sizes revealed similar micromotions only reaching a significant different level at one measurement point. The highest micromotions were observed at the tip of the stems exceeding the limit for osseous integration of 150μm. Regarding strain distribution the highest strain reduction after implantation was registered in all sizes at the level of the lesser trochanter.

INTERPRETATION

Specimen size seems to be a minor influence factor for biomechanical evaluation of cementless stems. However, the small composite femur is less suitable for biomechanical testing since this size failed under physiological adapted loads. For the CLS Spotorno osseous integration is unlikely at the tip of the stem and the tendency for stress shielding is the highest at the level of the lesser trochanter.