A comparison of two implant systems in restoration of hip geometry in arthroplasty

15-year survivorship of a unique dual-modular femoral stem in primary hip arthroplasty

BACKGROUND

Hip offset, version, and length are interdependent femoral variables which determine stability and leg length. Balancing these competing variables remains a core challenge in hip arthroplasty. The potential benefits of modular femoral stems have been overshadowed by higher rates of failure. The objective of this study was to assess the survivorship of a unique dual-modular femoral stem at an average 15-year follow-up period.

METHODS

The records of all patients with osteoarthritis who underwent primary total hip arthroplasty with this device between 2004-2009 were reviewed. There were no exclusions for BMI or other factors. We examined the data with Kaplan-Meier survival analysis. The primary endpoint for survival was mechanical failure of the modular neck-body junction.

RESULTS

The survivorship of this device in 172 subjects was 100% with none experiencing mechanical failure of the modular junction at an average of 15 years. 60 patients died of causes unrelated to their THA and 9 patients were lost to follow-up. There were three early (≤ 12 months) dislocations (1.7%), and seven total dislocations (4.1%). 16 patients underwent reoperations during the follow-up period, none for any complication of the modular junction. Radiographic results showed well-fixed femoral stems in all cases. There were no leg length discrepancies of greater than 10 mm, and 85% were within 5 mm.

CONCLUSION

There were no mechanical failures of the modular junction in any of the subjects over the average 15-year period, demonstrating that this dual-modular design is not associated with increased failure rates. We achieved a 1.7% early dislocation rate and a 4.1% total dislocation rate without any clinically significant leg length discrepancies.

How to Manage Metallosis: A Retrospective Cohort Analysis after Revision Hip Surgery

BACKGROUND

Adverse local tissue reactions to metal debris are due to a metal-on-metal bearing complication caused by micromotions at modular interfaces that induce corrosion of the protective oxide layer. This process could lead to wear, fretting, and abrasion with the release of metal ions locally and systemically, which may cause adverse local reactions in nearby tissues. The aim of this study is to describe a series of patients with painful local adverse tissue reactions secondary to corrosion at the modular neck-body interface, to document the clinical presentation, diagnostic workup, and surgical findings of our research, and to search for a possible correlation between metallosis and infection.

METHODS

A retrospective study of patients with adverse local tissue reactions due to metal surface corrosion was performed. Blood samples were collected to identify erythrocyte sedimentation rate, C reactive protein, and procalcitonin, and a magnetic resonance imaging protocol was performed.

RESULTS

Serum cobalt and chromium levels of the 43 patients tested were significantly higher on average. However, both erythrocyte sedimentation rate and C-reactive protein were significantly elevated. Magnetic resonance imaging showed adverse reactions to metal debris with large soft tissue masses and surrounding tissue damage.

CONCLUSIONS

Corrosion in hip prosthesis can lead to the release of metal ions and debris locally and systemically, resulting in local soft tissue changes. A "tumor-like" debridement can reduce this complication.

Bimodular femoral stems in primary total hip arthroplasty

INTRODUCTION

This review critically examines the efficacy of dual-modular stems in primary total hip arthroplasty. Given the variability and non-comparability of certain femoral stem designs and stem-neck couplings, with some even being withdrawn from the market, this review offers an in-depth analysis of predominant implant performances.

AREAS COVERED

The paper explores a brief historical summary related to dual-modular stems, including the complications associated with their use, diagnostic tools for evaluation, analysis of both recalled and currently available models, as well as alternative therapeutic options. This information is pertinent for both clinical and research domains.

EXPERT OPINION

While dual-modular systems were initially touted to offer several advantages, the evidence substantiating these benefits has been ambiguous. Further, these systems introduce the risk of alternative complications. In specific cases involving patients with developmental hip dysplasia and certain proximal femoral deformities requiring complex reconstructions, dual-modular systems might be relevant. Nonetheless, the use of long interchangeable necks in patients with a body mass index above 30 kg/m2 is discouraged, and pairing a long varus-oriented neck with an extra-long femoral head should be avoided in all patients.

Femoral Anteversion in Total Hip Arthroplasty: Retrospective Comparison of Short- and Straight-Stem Models Using CT Scans

Data on reconstruction of the femoral anteversion (FA) and the center of rotation after total hip arthroplasty (THA) are rare. We aimed to answer whether a short-stem fixation enables improved anatomical reconstruction of the FA compared to a straight-stem. Methods: One hundred and thirty patients who underwent short- (n = 89, group A, prospective) or straight-stem THA (n = 41, group B, retrospective) were included. CT scans of the hip, knee, and ankle were performed pre- and postoperatively in group A and in group B during the last follow-up. Femoral torsion was determined using three-dimensional models. Results: The mean preoperative FA was 22.4° ± 11.0°, and the mean postoperative FA was 23.4° ± 10.1°. The relative difference was −0.8° ± 8°, and the absolute difference was 6.4° ± 4.9°. Gender analysis revealed significant differences in preoperative FA between female (f) and male (m) patients (28.1° ± 11.2° (f) vs. 18.4° ± 8.3° (m); p > 0.001) as well as in postoperative FA (26.7° ± 23.5° (f) vs. 21.0° ± 9.7° (m); p < 0.007) in group A. Postoperative FA was higher in group A (mean 6.8°; 23.9° ± 10.1° (f) vs. 16.6° ± 8.6° (m); p < 0.001). Conclusions: The study’s findings suggest that short-stem THA leads to improved anatomical FA reconstruction; however, a substantial postoperative gender-related FA difference was detectable, which may warrant consideration by surgeons when determining the final stem anteversion. It should be noted that the impact of the postoperative gender-related FA difference on clinical outcomes is not entirely clear, and further research is warranted to elucidate this relationship.

Dual-Modular Versus Single-Modular Stems for Primary Total Hip Arthroplasty: A Long-Term Survival Analysis

Background and Objectives: Increased revision rate of dual-modular (DM) femoral stems in primary total hip arthroplasty (THA) because of modular-neck breakage and adverse local tissue reactions (ALTRs) to additional junction damage products is well established and some designs have been recalled from the market. However, some long-term studies of specific DM stems did not confirm the inferiority of these stems compared to standard single-modular (SM) stems, and a head-to-head comparison THA is missing. The objectives of this multicentre study were to determine the survivorship and complication rates of a common DM stem design compared to a similar SM stem. Materials and Methods: In a time frame from January 2012 to November 2015, a cohort of 807 patients (882 hips) consecutively underwent primary cementless THAs at two orthopaedic centres. 377 hips were treated with a Zweimüller-type DM stem THA system and 505 hips with a similar SM stem THA system, both including a modern press-fit acetabulum. Kaplan-Meier survivorship and complication rates were compared between both groups in a median follow-up of 9.0 years (maximum, 9.9 years). Results: The 9-year survivorship of the DM stem THA system (92.6%, 95% CI 89.9-95.3) was significantly lower than that of the SM stem THA system (97.0%, 95% CI 95.2-98.8). There were no differences in revision rates for septic loosening, dislocation, and periprosthetic fractures between the two groups. One ceramic inlay and one Ti-alloy modular neck breakage occurred in the DM stem THA system group, but the main reason for revision in this group was aseptic loosening of components. Conclusions: The survivorship of the DM stem THA system was lower than the similar SM stem THA system in a comparable clinical environment with long-term follow-up. Our results confirmed that no rationale for stem modularity exists in primary THAs.

Hip replacement in femoral neck fractures: the role of cementation and its technical difficulties

Hip fractures in elderly patients are an arising problem due to aging of population and still represent a controversial challenge for orthopedic surgeon who should help achieve the best functional recovery in the shortest time. Cementation in hip replacement plays an important role, but it should be carefully planned considering the possible risks. According to the literature, there are still no certainties regarding the superiority of an uncemented implant compared to a cemented one. The purpose of this work is to conduct an overview of the scientific literature that can clarify the advantages and disadvantages of cemented and non-cemented implants from a biological and biomechanical point of view.

Gross Trunnion Failure in the Bipolar Hemiarthroplasty; Raising Concern about Short Trunnion: A Case Report

There have been some reports of gross trunnion failure (GTF) in total hip arthroplasty. Here, we report a case of GTF 19 years after bipolar hemiarthroplasty using a 28-mm head with a 14/16 taper bore. Compared to other GTF reports, the current case had some unusual aspects: bipolar hemiarthroplasty, 28-mm head, relatively late-onset, and no apparent findings of metallosis though a severe one was evident. A Computed tomography scout view provided valuable information in evaluating polyethylene, metal head, and neck inside the bipolar cup. The current report suggests a need for concerned regarding short trunnion length which may be associated with GTF.

Unexpected varus deformity and concomitant metal ion release and MRI findings of modular-neck hip stems: descriptive RSA study in 75 hips with 8 years' follow-up

Background and purpose - Modular-neck hip stems have been identified with corrosion-related problems from the neck-stem junction. We report an ongoing varus deformity of modular-neck hip stems with simultaneous metal ion release observed during a study comparing the migration of modular vs. standard hip stems.Patients and methods - We followed 50 patients with modular and 25 with standard neck stems using radiostereometry (RSA). At 5-year follow-up, we noted a compromised integrity of the modular stem with varus deformity in the neck-stem interface. Changes in head-tip distance as well as whole-blood ion concentration and MRI findings were analyzed. The modular stems were followed further up to 8 years.Results - The head-tip distance decreased continuously by 0.15 mm per year resulting in 1.2 (95% CI 1.0-1.4) mm at 8 years for modular stems, while for the standard stems at 5 years, the decrease was 0.09 (CI 0.0-0.2) mm or 0.02 mm/year. For the modular stems, the reduction in head-tip distance correlated to the increase in whole-blood cobalt concentration at 8 years but not to the MRI grading of tissue reactions. At 5 years, cobalt levels were 4.9 µg/L for modular stems and at 8 years 4.8 µg/L, whereas for standard stems this was 1.0 µg/L. After 8 years, 9 of 72 stems had been revised for different reasons, but only 1 with obvious adverse local tissue reaction (ALTR).Interpretation - We present a surprisingly large progressive deformation at the modular neck-stem junction, but so far without a definite clinical problem. Even the femoral head seems to show slight compression onto the taper over time. A high rate of revisions for the modular type of this stem has raised general concerns, and it has been recalled from the market.

How to proceed with asymptomatic modular dual taper hip stems in the case of acetabular revision

How to proceed with a clinically asymptomatic modular Metha® Ti alloy stem with dual taper CoCr neck adapter in case of acetabular revision? To systematically answer this question the status of research and appropriate diagnostic methods in context to clinically symptomatic and asymptomatic dual taper stem-neck couplings has been evaluated based on a systematic literature review. A retrieval analysis of thirteen Metha® modular dual taper CoCr/Ti alloy hip stems has been performed and a rational decision making model as basis for a clinical recommendation was developed. From our observations we propose that in cases of acetabular revision, that for patients with a serum cobalt level of > 4 µg/L and a Co/Cr ratio > 3.6, the revision of the modular dual taper stem may be considered. Prior to acetabular revision surgery a systematic diagnostic evaluation should be executed, using specific tests such as serum metal (Co, Cr) ion analysis, plain antero-posterior and lateral radiographs and cross-sectional imaging modalities (Metal Artefact Reduction Sequence Magnetic Resonance Imaging). For an asymptomatic Metha® dual taper Ti alloy/CoCr stem-neck coupling at the stage of acetabular revision careful clinical decision making according to the proposed model should be followed and overreliance on any single examination should be avoided, considering the complete individual differential diagnosis and patient situation.

Total hip arthroplasty with modular stem for Crowe I and II developmental dysplasia of the hip

BACKGROUND

The variation of femoral anteversion is not completely consistent with the grade of developmental dysplasia of the hip (DDH), which poses challenges to hip replacement with the non-modular tapered stem. Currently, whether the modular stem should be used in Crowe I and II DDH is still controversial. The aim of this study is to compare the clinical efficacy of the modular stem and the non-modular tapered stem in Crowe I and II DDH patients.

METHODS

We retrospective analyzed the clinical data of 196 patients with unilateral Crowe I and II DDH from January 2015 to January 2017. One hundred patients were operated by an experienced surgeon with the modular stems; the remaining 96 patient was operated by another equivalent surgeon with the non-modular tapered stems. The preoperative basic information, operating time, intraoperative and postoperative complications, postoperative leg length discrepancy (LLD) and offset, Harris hip score (HHS), and forgotten joint score (FJS) in postoperative 2 years were collected and analyzed.

RESULTS

Postoperative LLD (P = 0.010) and FJS (P = 0.001) had significant difference between two groups. Concurrent acceptable LLD and offset were achieved in 87% of patients with the modular stem and in 68% of patients with the non-modular stem (P = 0.001). There was no significant difference in the operating time (P = 0.086), intraoperative complication (P = 0.096), postoperative dislocation rate (P = 0.056), postoperative offset difference (P = 0.108), and Harris score (P = 0.877) between two groups.

CONCLUSIONS

Compared with the non-modular tapered stem, the modular stem was more likely to provide accurate reconstruction and forgotten artificial hip for Crowe I and II DDH patients. We recommend the modular stem as routine choice for these patients.

Diagnosis and Management of Adverse Reactions to Metal Debris

Modern total hip arthroplasty implants have incorporated modularity into their designs, providing the benefits of intraoperative flexibility and the ability to exchange the femoral heads in the future if necessary. However, this feature has unfortunately predisposed patients to the effects of corrosion, potentially resulting in adverse local tissue reactions (ALTR) and even systemic effects. A thorough understanding of the science of corrosion is important for the treating surgeon so that they can understand the underlying pathology, quickly diagnose the condition of ALTR, and risk stratify their patients to determine the best method of treatment. Revision surgery is not always necessary in cases of trunnionosis or ALTR, but the results of revision surgery are generally favorable.

What Factors Are Associated With Neck Fracture in One Commonly Used Bimodular THA Design? A Multicenter, Nationwide Study in Slovenia

BACKGROUND

Femoral stems with bimodular (head-neck as well as neck-body) junctions were designed to help surgeons address patients' hip anatomy individually. However, arthroplasty registers have reported higher revision rates in stems with bimodular junctions than in stems with modularity limited to the head-neck trunnion. However, to our knowledge, no epidemiologic study has identified patient-specific risk factors for modular femoral neck fractures, and some stems using these designs still are produced and marketed.

QUESTIONS/PURPOSES

The purposes of this study were (1) to establish the survival rate free from aseptic loosening of one widely used bimodular THA design; (2) to define the proportion of patients who experienced a fracture of the stem's modular femoral neck; and (3) to determine factors associated with neck fracture.

METHODS

In this retrospective, nationwide, multicenter study, we reviewed 2767 bimodular Profemur® Z stems from four hospitals in Slovenia with a mean followup of 8 years (range, 3 days to 15 years). Between 2002 and 2015, the four participating hospitals performed 26,132 primary THAs; this implant was used in 2767 of them (11%). The general indications for using this implant were primary osteoarthritis (OA) in 2198 (79%) hips and other indications in 569 (21%) hips. We followed patients from the date of the index operation to the date of death, date of revision, or the end of followup on March 1, 2018. We believe that all revisions would be captured in our sample, except for patients who may have emigrated outside the country, but the proportion of people immigrating to Slovenia is higher than the proportion of those emigrating from it; however, no formal accounting for loss to followup is possible in a study of this design. There were 1438 (52%) stems implanted in female and 1329 (48%) in male patients, respectively. A titanium alloy neck was used in 2489 hips (90%) and a cobalt-chromium neck in 278 (10%) hips. The mean body mass index (BMI) at the time of operation was 29 kg/m (SD ± 5 kg/m). We used Kaplan-Meier analysis to establish survival rates, and we performed a chart review to determine the proportion of patients who experienced femoral neck fractures. A binary logistic regression model that controlled for the potential confounding variables of age, sex, BMI, time since implantation, type of bearing, diagnosis, hospital, neck length, and neck material was used to analyze neck fractures.

RESULTS

There were 55 (2%) aseptic stem revisions. Survival rate free from aseptic loosening at 12 years was 97% (95% confidence interval [CI] ± 1%). Fracture of the modular neck occurred in 23 patients (0.83%) with a mean BMI of 29 kg/m (SD ± 4 kg/m.) Twenty patients with neck fractures were males and 19 of 23 fractured necks were long. Time since implantation (odds ratio [OR], 0.55; 95% CI 0.46-0.66; p < 0.001), a long neck (OR, 6.77; 95% CI, 2.1-22.2; p = 0.002), a cobalt-chromium alloy neck (OR, 5.7; 95% CI, 1.6-21.1; p = 0.008), younger age (OR, 0.91; 95% CI, 0.86-0.96; p < 0.001), and male sex (OR, 3.98; 95% CI, 1.04-14.55; p = 0.043) were factors associated with neck fracture.

CONCLUSIONS

The loosening and neck fracture rates of the Profemur® Z stem were lower than in some of previously published series. However, the use of modular femoral necks in primary THA increases the risk for neck fracture, particularly in young male patients with cobalt-chromium long femoral necks. The bimodular stem we analyzed fractured unacceptably often, especially in younger male patients. For most patients, the risks of using this device outweigh the benefits, and several dozen patients had revisions and complications they would not have had if a different stem had been used.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Liner dissociation leading to catastrophic failure of an Oxinium femoral head

Oxinium is an alternative bearing surface designed to emulate the superior wear and scratch properties of ceramic femoral heads in total hip arthroplasty while minimizing the risk for brittle fracturing. However, recent studies have indicated that hip dislocation following total hip arthroplasty may be a risk factor for catastrophic failure of the femoral head. Here, we report on a novel case of a catastrophic Oxinium head and polyethylene liner failure in the absence of previous hip dislocation or trauma and review the probable failure mechanism. This report underscores the need to be vigilant about proper acetabular cup and liner seating, particularly in the setting of Oxinium femoral head use. In the event of Oxinium head failure, metallosis may compromise stabilizing soft tissues including the abductors. Dual-mobility articulation, which was successful in this case, is one option to consider when the risk for chronic redislocation is elevated.

Withdrawn: A Randomized Controlled Trial Comparing Modular and Nonmodular Neck Versions of a Titanium Stem

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Comparative Analysis of the Reconstruction of Individual Hip Anatomy Using 3 Different Cementless Stem Designs in Patients With Primary Hip Osteoarthritis

BACKGROUND

We questioned whether there was a radiographic difference in hip geometry reconstruction and implant fixation between 3 different cementless stem design concepts in patients with primary end-stage hip osteoarthritis.

METHODS

We retrospectively evaluated the preoperative and postoperative radiographs by 2 independent and blinded reviewers in a series of 264 consecutive patients who had received either a straight double-tapered stem with 3 offset options (group A), a straight double-tapered stem with 2 shape options and modular necks (group B), and a bone-preserving curved tapered stem with 4 offset options (group C). The following parameters were assessed: acetabular, femoral and hip offset (HO), center of rotation height, leg length difference (LLD), and the endosteal fit of stem in the proximal femur (canal fill index). Group comparisons were performed using a one-way analysis of variance and subsequent pairwise comparisons (t-test).

RESULTS

Postoperatively, HO could be equally restored with all 3 stem designs (P = .079). The postoperative LLD was smaller in group C compared to group A (0.8 mm [standard deviation, 3.2] vs 2.6 mm [standard deviation, 4.5], P = .002). Best combined reconstruction of HO and LLD could be achieved with the short curved stem by junior and senior surgeons (HO: -2.0 and -2.1 mm; LLD: 1.9 and 0.7 mm, respectively). The proximal and mid-height canal fill indexes were higher in groups B and C compared to group A, indicating a better metaphyseal and diaphyseal fit in the proximal femur (both P < .001).

CONCLUSION

All 3 cementless stem designs allowed for good hip geometry reconstruction. Multiple shape and offset options allowed for a better metaphyseal stem fit and offered minor clinical advantages for leg length reconstruction. Modular necks did not provide reconstructive advantages in patients with primary hip osteoarthritis.

A Single-Center Experience With a Titanium Modular Neck Total Hip Arthroplasty

BACKGROUND

Added modular junction has been associated with implant-related failures. We report our experience with a titanium-titanium modular neck-stem interface to assess complications, possible clinical factors influencing use of neck modularity, and whether modularity reduced the incidence of dislocation.

METHODS

A total of 809 total hip arthroplasties completed between 2005 and 2012 from a prospectively collected database were reviewed. The mean follow-up interval was 5.7 years (3.3-10.3 years). Forty-five percent were male (360 of 809), and 55% were female (449 of 809). All stems were uncemented PROFEMUR TL (titanium, flat-tapered, wedge) or PROFEMUR Z (titanium, rectangular, dual-tapered) with a titanium neck.

RESULTS

Increased modularity (anteverted/retroverted and anteverted/retroverted varus/valgus (anteverted/retroverted + anteverted/retroverted varus/valgus) was used in 39.4% (135 of 343) of cases using the posterior approach compared with 6.8% (20 of 293) of anterior and 23.7% (41 of 173) of lateral approaches. Four males sustained neck fractures at a mean of 95.5 months (69.3-115.6 months) after primary surgery. Overall dislocation rate was 1.1% (9 of 809). The posterior approach had both the highest utilization of increased modularity and the highest dislocation rate (2.3%), of which the most were recurrent. The anterior (0.3%) and lateral (0%) approaches had lower dislocation rates with no recurrences.

CONCLUSION

At a mean 5.7 years, our experience demonstrates a low neck fracture (0.5%) and a low dislocation rate (1.1%). Use of increased modularity may not improve dislocation risk for the posterior approach. Continued surveillance of this group will be necessary to determine long term survivorship of this modular titanium implant.

Is there a role for femoral offset restoration during total hip arthroplasty? A systematic review

Benefits of femoral offset restoration during total hip arthroplasty should be the reduction of bearing surfaces wear, implant loosening and dislocation rates. Modular neck stems ensure offset customization but fretting corrosion and catastrophic failures are well-documented complications. Since clinical evidences are needed to substantiate the effectiveness of femoral offset restoration and promote modular neck choice, we systematically reviewed the literature to ascertain whether femoral offset itself has a proven clinical influence: (1) on bearing surfaces wear, (2) implant loosening, (3) and dislocation rates. A systematic literature screening was conducted to find papers dealing with the influence of femoral offset on wear, dislocation and loosening, including articles with conventional radiographic femoral offset assessment and with comparative design. Observational studies, case reports, instructional course lectures, cadaveric and animal studies as well as biomechanical studies, letters to the editor, surgical techniques or technical notes were all excluded. No limits about publication date were supplied but only papers in English were taken into account. Data were extracted into an anonymous spreadsheet. Offset values, dislocation rates, wear rates, follow-up and surgical approaches were all detailed. Ten manuscripts were finally selected. A statistically significant correlation between femoral offset restoration and the reduction of conventional ultrahigh-molecular-weight polyethylene wear was found in two out of three papers investigating this issue, but no correlations were found between femoral offset and dislocation rates or implant loosening. Femoral offset modification influences ultrahigh-molecular-weight polyethylene liners wear, but no correlation was found with dislocation rates or implant loosening. Advantages on wear can be counterbalanced by the use of hard bearing surfaces or highly cross-linked polyethylene liners, besides the availability of larger femoral heads improving implant stability further reduces the importance of femoral offset restoration by means of modularity. We believe that efforts in restoring femoral offset during total hip arthroplasty do not translate into tangible clinical profits and consequently, we do not advise the routinely usage of modular neck stems in total hip arthroplasty.

LEVEL OF EVIDENCE

level III, systematic review of case-control studies.

Result of Modular Necks in Primary Total Hip Arthroplasty with a Average Follow-up of Four Years

Purpose

This study aimed to investigate the outcomes of modular neck-utilization in primary total hip arthroplasty (THA).

Materials and Methods

Thirty patients (34 hips) who had modular stem THA between April 2011 and January 2013 were evaluated. There were 19 men and 11 women with a mean age of 61.2 years at the time of surgery. There were 20 cases of osteonecrosis of femoral head, 7 cases of osteoarthritis, 6 cases of femur neck fracture, and 1 case of rheumatoid arthritis. No patients presented with anatomical deformity of hip. Patients were operated on using a modified Watson-Jones anterolateral approach. All patients underwent clinical and radiological follow-up at 6 weeks, 3, 6, and 12 months, and every year postoperatively. The mean duration of follow-up was 48.2 months (range, 39 to 59 months).

Results

The average Harris hip score improved from 63.7 to 88.1 at the final follow-up. Radiographically, mean acetabular cup inclination was 45.3°(range, 36°-61°) and anteversion was 21.7°(range, 11°-29°). All were neutral-positioned stems except 5 which were varus-positioned stems. In only 3 cases (8.8%), varus or valgus necks were required. A case of linear femoral fracture occurred intraoperatively and 1 case of dislocation occurred at postoperative 2 weeks. No complications at modular junction were occurred.

Conclusion

Our study shows that the use of modular necks had favorable clinical and radiographic results. This suggests that the use of modular neck in primary THA without anatomical deformity is safe at a follow-up of 39 months.

Gross Trunnion Failure of a Cobalt-Chromium Femoral Head on a Titanium Stem at Midterm Follow-up: A Report of 3 Cases

CASE

Three patients underwent uncomplicated primary total hip arthroplasty with cobalt-chromium femoral heads (36+5 mm) on titanium V40 tapers. At 6 to 9 years of follow-up, severe effects of corrosion at the trunnion were noted in all 3 patients, along with elevated levels of serum cobalt ions and normal levels of serum chromium ions. Gross trunnion failure, apparently caused by corrosion, required femoral stem revision in all of the patients.

CONCLUSION

Decreased neck diameter, longer trunnion length, and large-sized cobalt-chromium heads are possible contributors to early failure after primary total hip arthroplasty due to trunnionosis. Surgeons should be mindful of trunnionosis as a cause of pain and a mechanism of failure following total hip arthroplasty, and serum metal ions should be monitored in these patients.

Trunnionosis: Does Head Size Affect Fretting and Corrosion in Total Hip Arthroplasty?

BACKGROUND

Wear and tribocorrosion at the modular head-neck taper interface may be a cause of failure in metal-on-polyethylene total hip arthroplasty (THA). The present investigation endeavored to elucidate the effect of femoral head diameter on fretting and corrosion in retrieved head-neck tapers.

METHODS

A retrieval analysis of THA prostheses in vivo for a minimum of 1 year was performed. Twenty-three femoral heads of 32-mm diameter were matched with 28-mm heads based on time in vivo and head length (-3 mm to +8 mm). All included implants featured a single taper design from a single manufacturer. Fretting and corrosion damage scoring was performed for each implant under stereomicroscopic visualization.

RESULTS

Head diameter was observed to affect fretting (P = .01), with 32-mm femoral heads exhibiting greater total fretting scores than 28-mm heads. Fretting damage was greatest (P = .01) in the central concentric zone of the femoral head bore tapers, regardless of head diameter, length, or stem offset. No significant effect on total corrosion scores was observed for any head or stem variable. Retrieved implant total corrosion scores were positively correlated (ρ = 0.51, P < .001) with implantation time.

CONCLUSION

Increased femoral head diameter in THA may produce greater fretting damage owing to and increased head-neck moment arm. There is no associated increase in corrosion with 28-mm and 32-mm heads of this taper design. The longer a THA prosthesis is implanted, the greater the risk of damage due to corrosion.

Effects of Cobalt and Chromium Levels Following Modular Hip Stem Total Hip Arthroplasty

Due to the increased number of revision total hip arthroplasties (THAs) to correct pain secondary to fretting from modular hip stems, this study was conducted in an effort to correlate objective findings of serum cobalt (Co) levels, serum chromium (Cr) levels, and/or reactive tissue seen on metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) with a patient's need for revision THA. The study group comprised 66 patients, 18 of whom received MARS MRI. Serum Co levels, serum Cr levels, and standard numeric rating scale for pain were documented for all patients. Statistical analysis was then performed to determine whether there was a correlation between the aforementioned variables and the need for revision THA. Serum Cr levels were higher in patients with positive reactive tissue findings on MARS MRI, although this only approached significance (P=.083). Serum Co levels were higher in those undergoing revision THA, but this also only approached significance (P=.076). Pain scores were significantly different between those undergoing revision and those not (P<.001). It is the opinion of the authors that there is no objective finding in this study that can be used to identify patients who require revision THA secondary to fretting of a modular hip stem prosthesis. Only a patient's stated pain level can assist a surgeon in the decision-making process regarding the need for revision THA secondary to fretting. [Orthopedics.2016; 39(5):288-292.].

Agreement Between Proximal Femoral Geometry and Component Design in Total Hip Arthroplasty: Implications for Implant Choice

BACKGROUND

The present study aimed to analyze the agreement between proximal femoral geometry of adult hips and femoral component design in total hip arthroplasty.

METHODS

Anatomical femoral offset (FOAnat) and the anatomical neck-shaft angle (NSAAnat) of 800 adult hips were measured by computed tomography scans, and anatomical femoral neck height (FHAnat) was calculated. Corresponding best-fit implants of the most common hip system (standard, high offset and varus variant) were identified for each hip. Finally, the precision of the best possible anatomic reconstruction was assessed.

RESULTS

The mean FOAnat was 38.0 mm (range: 19.8-57.9 mm, standard deviation [SD]: 6.4 mm), the mean NSAAnat was 130.8° (range: 107.1°-151.9°; SD: 6.5°), and the mean FHAnat was 32.6 mm (range: 14.4-52.0 mm; SD: 5.5 mm). In 450 (56.3%) hips, the standard variant was identified to be the best-fit implant, followed by the varus (n = 282, 35.3%) and the high offset (n = 68, 8.5%) variants. The mean minimal distance from the best-fit implant was 4.5 mm (range: 0.1-20.2 mm, SD: 3.4 mm). Excellent agreement (distance: <2 mm) between hip anatomy and best-fit implant was found in 203 (25.4%) hips, combined excellent and acceptable agreement (distance: <6 mm) in 569 (71.1%) hips, whereas 213 (28.9%) hips were graded as poor (distance: ≥6 mm).

CONCLUSION

The present study revealed a mismatch between proximal femoral anatomy of a relevant proportion of adult hips and implant geometry of the most common femoral component in total hip arthroplasty.

Eighty-six Percent Failure Rate of a Modular-Neck Femoral Stem Design at 3 to 5 Years: Lessons Learned

BACKGROUND

While innovation drives advancement, it is not immune to failure. Previously, we reported a corrosion-related revision rate of 28% (23 of 81 total hip arthroplasties) among patients who received the Rejuvenate modular-neck stem implant with short-term follow-up. Because we observed a dramatic interval failure rate after our initial report, we undertook this study.

METHODS

We prospectively followed a cohort of patients who had undergone implantation of the Rejuvenate modular-neck stem, as previously reported. At a minimum of 3 years of follow-up (range, 3.0 to 5.5 years), 73 hips in 63 patients (90% of the original group) were available for analysis. The mean serum cobalt and chromium ion levels were obtained preoperatively and postoperatively. Elevated serum cobalt ion levels (>4 μg/L), pain, or abnormal magnetic resonance imaging (MRI) findings were indications for revision surgery. Patient factors and serum metal ion levels were correlated to revision surgery. Additionally, post-revision serum cobalt and chromium ion level trends were assessed.

RESULTS

An 86% clinical failure rate (63 of the 73 hips) was observed at a mean follow-up of 4.2 ± 0.6 years (range, 3.0 to 5.5 years); 57 (78%) of the hips underwent revision at a mean of 3.2 ± 1.0 years (range, 1.0 to 5.5 years), and 6 (8%) of the hips were scheduled for revision. Patients who underwent revision surgery were younger and had greater serum metal ion levels and greater pain compared with patients who did not undergo revision. An elevated serum cobalt ion level was the most important independent factor associated with revision surgery. Cobalt ion levels decreased sharply after revision; however, some patients demonstrated persistent elevation with more gradual decline.

CONCLUSIONS

Emphasizing the reporting of positive results may leave orthopaedic surgeons reticent to publicize negative results; however, the high failure rate of this implant design within 5 years prompted this report. We believe that patients and orthopaedic surgeons should be made aware of this implant's clinical problems and patients should be followed closely. Expedient revision is necessary when failure is identified, to minimize potentially severe tissue damage and metal toxicity.

LEVEL OF EVIDENCE

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

MRI Findings Associated with Recalled Modular Femoral Neck Rejuvenate and ABG Implants

MARS-MRI is suggested for the diagnosis of adverse local tissue reactions (ALTR) in patients with recalled femoral stems with modular necks, but there has been no major study looking at MARS-MRI findings in this population. A retrospective review was performed on 312 patients who received a modular neck hip implant between October 2007 and February 2012. 62% of patients had intra-articular effusions, with 27% containing debris. Extra-capsular effusions were present in 35% of hips. 54% had synovitis and 5.4% had osteolysis. Tendinopathy and tendon disruption was present in the gluteus medius (58%/12%), hamstring (56%/12%), gluteus minimus (38%/7.7%) and iliopsoas (7.1%/4.8%). Abnormal MARS-MRI findings are associated with modular neck femoral components and can suggest underlying ALTR. MARS-MRI abnormalities merit serious consideration in this population.

Serum Metal Ions with a Titanium Modular Neck Total Hip Replacement System

The goal of this study is to evaluate serum levels of chromium (Cr), cobalt (Co), and titanium (Ti) within the first two years following total hip arthroplasty using a Ti modular neck system. Twenty-five patients were randomized to a metal-on-metal (MoM) bearing with an all CoCr shell, and the remaining 25 received a metal-on-polyethylene (MoP) with a Ti shell. Serum levels demonstrated increases for Cr, Co, and Ti at 1 year (P < .001). MoM had similar Ti levels to MoP hips at 1 year (P=0.11) but lower at 2 years (P=0.03). Results suggest that the passive corrosion (i.e., chemical, pitting, and crevice corrosion) of exposed non-articular metal surfaces may be a greater source of ions than the neck-stem or head-neck interfaces.

Taperosis

Tribocorrosion at the head–neck taper interface – so-called ‘taperosis’ – may be a source of metal ions and particulate debris in metal-on-polyethylene total hip arthroplasty (THA).

We examined the effect of femoral head length on fretting and corrosion in retrieved head–neck tapers in vivo for a minimum of two years (mean 8.7 years; 2.6 to 15.9). A total of 56 femoral heads ranging from 28 mm to 3 mm to 28 mm + 8 mm, and 17 femoral stems featuring a single taper design were included in the study. Fretting and corrosion were scored in three horizontally oriented concentric zones of each taper by stereomicroscopy.

Head length was observed to affect fretting (p = 0.03), with 28 mm + 8 mm femoral heads showing greater total fretting scores than all other head lengths. The central zone of the femoral head bore taper was subject to increased fretting damage (p = 0.01), regardless of head length or stem offset. High-offset femoral stems were associated with greater total fretting of the bore taper (p = 0.04).

Increased fretting damage is seen with longer head lengths and high-offset femoral stems, and occurs within a central concentric zone of the femoral head bore taper. Further investigation is required to determine the effect of increased head size, and variations in head–neck taper design.

Cite this article: Bone Joint J 2015; 97-B:911–16.

Reproducing the hip center with a femoral neck-retaining implant

Because of the recent trend for total hip arthroplasty in younger patients, more bone-preserving implants have been designed, based partly on the premise that maintenance of more bone stock would allow revision with standard primary implants. Another possible advantage of an implant that retains the femoral neck is that it may allow anatomical recreation of the center of the femoral head, femoral neck anteversion, anterior tilt, and caput-collum-diaphysis (CCD) angle, as well as femoral offset and leg length, without the use of modular implants. To determine whether the proximal femoral anatomy could be recreated, this study used computed tomography data and 3-dimensional modeling from 10 cadaver hips in 6 whole body specimens. Three femoral neck resection levels were investigated: 2 mm, 5 mm (recommended resection), and 10 mm from the base of the femoral neck. Results showed that the center of the femoral head, femoral neck anteversion, and CCD angle could all be recreated with available implant sizes, without modularity, within 2° and 1 mm on average. The addition of a modular neck provided no advantage in recreation of the hip center or other anatomical parameters. Use of a short metaphyseal femoral neck retaining-type of stem should allow restoration of anatomical parameters without the use of an exchangeable modular femoral neck.

Anatomy of the proximal femur at the time of total hip arthroplasty is a matter of morphotype and etiology but not gender

This study aimed to determine (1) whether: gender, morphotype, or etiology are correlated with the shape of the proximal femur in patients with advanced hip osteoarthritis and (2) is there any clinical predictive factors of potential abnormal anatomy of the hip at the time of total hip arthroplasty (THA)? We reviewed 689 European hips of patients who underwent THA for primary osteoarthritis (OA) or avascular necrosis (AVN), between 2000 and 2005. The patients were stratified according to their (1) Morphotype, (2) Gender, and (3) Etiology for undergoing THA. Two independent observers measured the following four anatomical parameters on preoperative CT-scans: neck shaft angle (NSA) and femoral neck version, femoral offset and lower-limb torsion. Our results showed that both morphotype and etiology, but not gender or body mass index, were correlated with femoral anatomical parameters. Two types of patients were identified as "at risk" for abnormal hip anatomy: (1) AVN-Endomorphic patients (2) OA-Ectomorphic patients. Etiology of the advanced hip osteoarthritis and patients' morphotype may predict the proximal femur anatomy at the time of THA.

Midterm results of a femoral stem with a modular neck design: clinical outcomes and metal ion analysis

Modular neck femoral stems have a higher-than-anticipated rate of failure in registry results, but large single-center cohort studies are lacking. This is a retrospective cohort of 152 hips implanted with a single titanium stem with a modular titanium neck, presenting clinical, radiographic, and metal ion results at a mean 4.5-year follow-up. Five hips were revised during the study period, for an overall Kaplan-Meier survival of 0.894 at 8 years. There was one modular neck fracture (0.66%), but others demonstrated corrosion or adverse tissue reaction. Serum metal levels demonstrated wide variability. Despite good clinical results in the majority of patients, we confirmed an increased rate of femoral revision at mid-term follow-up, and therefore urge caution in the use of this particular stem design.

Adverse clinical outcomes in a primary modular neck/stem system

We report our experience with 215 recalled neck modular stems due to corrosion. Among the 195 hips with 2 years follow-up, 56% had no clinical symptoms, 26% had groin pain (typical of corrosion), and 17% had other symptoms. Cobalt levels were comparable between asymptomatic (3.4 μg/L, range 0.7-7.3 μg/L) and symptomatic patients (4.0 μg/L range 0-13.2 μg/L). Abnormal imaging findings were seen in 46% of symptomatic and 11% of asymptomatic hips (P=0.001). Twenty-six hips (13%) have either undergone revision surgery or have been scheduled. Evidence of corrosion was seen at revision surgery in all patients. Despite modest elevations in serum cobalt levels, abnormal imaging studies were seen in 36%, clinical symptoms were seen in 44%, and revision for corrosion was undertaken or scheduled in 13% of the hips.

Modular necks in primary hip arthroplasty without anatomical deformity: no clear benefit on restoration of hip geometry and dislocation rate. An exploratory study

Modular necks were introduced in total hip arthroplasty (THA) to improve restoration of hip-geometry and reduce dislocation-rates. This presumed advantage was evaluated retrospectively for patients with arthritis in otherwise anatomically normal hips. Restoration of hip-geometry was assessed on preoperative and postoperative calibrated radiographs in 95 consecutive primary THAs with a modular neck design and compared with 95 match controlled THAs with a similar monoblock stem. No significant differences were seen in restoration of body moment arm, leg length and cupangle. Offset restoration revealed a borderline significant difference (P = 0.48) with higher values for the monoblock stem. In both groups 4 dislocations within one year were encountered. In this study modular necks did not reveal a clear benefit in restoring hip geometry and dislocation rate after straightforward THA.

The local effects of metal corrosion in total hip arthroplasty

Corrosion has long been recognized to occur in total hip arthroplasty, but the local effects of this process have only recently become better understood. This article provides an overview of corrosion at modular junctions, and discusses the various etiologic factors for corrosion and the biologic response to metal debris released from this junction. Algorithms are provided for diagnosis and treatment, in accordance with the best available data.

Trunnionosis: A pain in the neck

Metal-on-metal (MoM) hip replacements have proven to be a modern day orthopaedic failure. The early enthusiasm and promise of a hard, durable bearing was quickly quashed following the unanticipated wear rates. The release of metal ions into the blood stream has been shown to lead to surrounding soft tissue complications and early failure. The devastating destruction caused has led to a large number of revision procedures and implant extractions. The resulting research into this field has led to a new area of interest; that of the wear at the trunnion of the prosthesis. It had been previously thought that the metal debris was generated solely from the weight bearing articulation, however with the evolution of modularity to aid surgical options, wear at the trunnion is becoming more apparent. The phenomenon of "trunnionosis" is a rapidly developing area of interest that may contribute to the overall effect of metallosis in MoM replacements but may also lead to the release of metal ions in non MoM hip designs. The aim of this paper is to introduce, explain and summarise the evidence so far in the field of trunnionosis. The evidence for this phenomenon, the type of debris particles generated and a contrast between MoM, non MoM and resurfacing procedures are also presented.

Can hip anatomy be reconstructed with femoral components having only one neck morphology? A study on 466 hips

This extensive radiographic study asks if there is a statistical relationship between the size of the stem that will best fit the femur and the vertical and lateral offsets of the reconstructed acetabular center, what is the distribution of vertical and lateral offsets in this large and if there is a statistical difference among surgeons in the planned location of the reconstructed acetabular center. On 466 radiographs, five surgeons separately templated stem size and acetabular cup location. The vertical and horizontal coordinates of the reconstructed acetabulum center were measured relative to the planned position of the stem. We found a strong correlation between the stem size and the average lateral and vertical offsets. Acetabular reaming associated with the anatomic variability of native femoral necks, leads to a span of 36 mm in lateral offset, and a span of 39 mm in vertical offset. Statistically significant differences were also found in the way surgeons plan acetabular reaming.

Adverse local tissue reaction arising from corrosion at the femoral neck-body junction in a dual-taper stem with a cobalt-chromium modular neck

BACKGROUND

Femoral stems with dual-taper modularity were introduced to allow additional options for hip-center restoration independent of femoral fixation in total hip arthroplasty. Despite the increasing availability and use of these femoral stems, concerns exist about potential complications arising from the modular neck-body junction.

METHODS

This was a multicenter retrospective case series of twelve hips (eleven patients) with adverse local tissue reactions secondary to corrosion at the modular neck-body junction. The cohort included eight women and three men who together had an average age of 60.1 years (range, forty-three to seventy-seven years); all hips were implanted with a titanium-alloy stem and cobalt-chromium-alloy neck. Patients presented with new-onset and increasing pain at a mean of 7.9 months (range, five to thirteen months) following total hip arthroplasty. After serum metal-ion studies and metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) revealed abnormal results, the patients underwent hip revision at a mean of 15.2 months (range, ten to twenty-three months). Tissue specimens were examined by a single histopathologist, and the retrieved implants were studied with use of light and scanning electron microscopy.

RESULTS

Serum metal levels demonstrated greater elevation of cobalt (mean, 6.0 ng/mL) than chromium (mean, 0.6 ng/mL) or titanium (mean, 3.4 ng/mL). MRI with use of MARS demonstrated adverse tissue reactions in eight of nine patients in which it was performed. All hips showed large soft-tissue masses and surrounding tissue damage with visible corrosion at the modular femoral neck-body junction. Available histology demonstrated large areas of tissue necrosis in seven of ten cases, while remaining viable capsular tissue showed a dense lymphocytic infiltrate. Microscopic analysis was consistent with fretting and crevice corrosion at the modular neck-body interface.

CONCLUSIONS

Corrosion at the modular neck-body junction in dual-tapered stems with a modular cobalt-chromium-alloy femoral neck can lead to release of metal ions and debris resulting in local soft-tissue destruction. Adverse local tissue reaction should be considered as a potential cause for new-onset pain in patients with these components, and early revision should be considered given the potentially destructive nature of these reactions. A workup including serologic studies (erythrocyte sedimentation rate and C-reactive protein), serum metal levels, and MARS MRI can be helpful in establishing this diagnosis.

In vivo serum titanium ion levels following modular neck total hip arthroplasty--10 year results in 67 patients

The objective of the present cross-sectional study was to determine in vivo titanium ion levels following cementless total hip arthroplasty (THA) using a modular stem system with different shapes for femoral canal fit and multiple neck options. A consecutive series of 173 patients (190 hips) who underwent cementless modular neck THA and a ceramic on polyethylene bearing with a median follow-up of 9 (7-13) years was evaluated retrospectively. According to a standardized protocol, titanium ion measurements were performed on 67 patients using high-resolution inductively coupled plasma-mass spectrometry. Ion levels were compared to a control group comprising patients with non-modular titanium implants (n=11) and to individuals without implants (n=23). Modular neck THA did not result in elevated titanium ion levels compared to non-modular THA. Compared to individuals without implants, both modular THA and non-modular THA showed elevated titanium ion levels. Absolute titanium ion levels, however, were comparatively low for both implants. The data suggest that the present modular stem system does not result in elevated systemic titanium ion levels in the medium term when compared to non-modular stems. Further longitudinal studies are needed to evaluate the use of systemic titanium ion levels as an objective diagnostic tool to identify THA failure and to monitor patients following revision surgery.

Complex primary total hip arthroplasty

Although total hip arthroplasty is now a classic procedure that is well controlled by orthopedic surgeons, some cases remain complex. Difficulties may be due to co-morbidities: obesity, skin problems, muscular problems, a history of neurological disease or associated morphological bone deformities. Obese patients must be informed of their specific risks and a surgical approach must be used that obtains maximum exposure. Healing of incisions is not a particular problem, but adhesions must be assessed. Neurological diseases may require tenotomy and the use of implants that limit instability. Specific techniques or implants are necessary to respect hip biomechanics (offset, neck-shaft angle) in case of a large lever arm or coxa vara. In case of arthrodesis, before THA can be performed, the risk of infection must be specifically evaluated if the etiology is infection, and the strength of the gluteal muscles must be determined. Congenital hip dysplasia presents three problems: the position and coverage of the cup, placement of a specific or custom made femoral stem, with an osteotomy if necessary, and finally lowering the femoral head into the cup by freeing the soft tissues or a shortening osteotomy. Acetabular dysplasia should not be underestimated in the presence of significant bone defect (BD), and reconstruction with a bone graft can be proposed. Sequelae from acetabular fractures presents a problem of associated BD. Internal fixation hardware is rarely an obstacle but the surgical approach should take this into account. Treatment of acetabular protrusio should restore a normal center of rotation, and prevent recurrent progressive protrusion. The use of bone grafts and reinforcement rings are indispensible. Femoral deformities may be congenital or secondary to trauma or osteotomy. They must be evaluated to restore hip biomechanics that are as close to normal as possible. Fixation of implants should restore anteversion, length and the lever arm. Most problems that can make THA a difficult procedure may be anticipated with proper understanding of the case and thorough preoperative planning.

In vitro testing of the deformation pattern and initial stability of a cementless stem coupled to an experimental femoral head, with increased offset and altered femoral neck angles

The ability to vary femoral offset and neck angles in total hip arthroplasty increases the amount of flexibility in the mechanical reconstruction of the hip joint. The present study investigates the changes in strain pattern and bone–implant micromotion caused by increased femoral offset in combination with retroversion or reduced neck–shaft angle, made possible by a large experimental femoral head. A cementless femoral stem was inserted in 10 human cadaver femurs. Three femoral head configurations were tested: the standard situation, an increased offset combined with retroversion, and increased offset combined with reduced neck–shaft angle. The femurs were loaded in a hip simulator that was able to reproduce the conditions that correspond to one-legged stance and stair climbing. There was a statistically significant increase in strain for the experimental head at several strain gauge rosettes compared to the standard head. The largest significant increase in strain was 14.2 per cent on the anterior side of the femur. The largest mean total point motion was 44 µm in the distal coating area for the configuration with increased femoral offset and retroverted neck axis. The clinical relevance of the changes in strain distribution is uncertain. The femoral stem showed excellent initial stability for all test situations.