Introduction. We previously reported a 28% short-term corrosion-related revision rate of recalled Rejuvenate modular stem. The purpose of this study was to assess the mid-term clinical results and survivorship of this implant. Methods. Between June 2009 and July 2012, 73 total hip arthroplasty (THA) in 63 patients with the Rejuvenate modular neck implant were performed by a single surgeon and prospectively followed. Average age was 63.2 ± 12.6 years (28 to 86). Elevated metal ion (= 2 µg/L), pain, or positive MRI findings were indication for revision surgery. Correlation between patient factors with serum metal ion levels and revisions were analyzed. Results. At an average follow-up of 4.2 ± 0.6 years (3.0 to 5.5), 57 hips (48 patients, 78%) were revised at mean of 3.2 ± 1 years (1 to 5.5); and 6 other have been scheduled for surgery. The Kaplan-Meier survivorship was 22 % at 5.5 years. Visible corrosion was seen at the trunion-stem junction in each revision case. 51 of 57 hips undergoing revision (89%), had elevated preoperative serum Co levels, 24 (42%) had elevated preoperative Cr. The average serum Co and Cr ion levels prior to revision surgery were 10 ± 8 µg/L (0.3 to 40) and 2.3 ± 1.5 µg/L (1 to 7.4), respectively. There was a significant correlation between revision surgery and younger age (p=0.0137). 52 hips underwent MRI evaluation, 22 hips (42%) had positive findings correlated to pain (p=0.025): 11 hips demonstrated adverse local soft tissue reactions such as fluid collection, capsular thickening, osteolysis, or synovitis, and 11 hips showed evidence of pseudotumor. Conclusions. At mid-term follow-up, 86% of the Rejuvenated modular neck stems have been revised or awaiting revision. Given these findings, all patients with a Rejuvenate modular neck stem implant should be followed closely and advised of impending failure

Background:. The Rejuvenate modular neck stem (Stryker, Mahwah, NJ) was recently recalled due to corrosion at the neck-stem junction. The purpose of this study was to investigate the rate of corrosion related failures and survivorship of this implant, and analyze the correlation between the implant and patient factors with serum metal ion levels. Material and Methods:. Between June 2009 and July 2012, 123 Rejuvenate stems (97 modular and 26 non-modular) THAs were implanted in 104 patients by a single surgeon via a modified anterolateral approach. Serum Cobalt (Co) and Chromium (Cr) levels (microgram per liter [μg/L]) were obtained in all patients. In cases of elevated serum metal ion levels or symptomatic hip, patients underwent magnetic resonance imaging (MRI) for assessment of osteolysis or adverse local tissue reactions (ALTR). Correlation between implant factors (implant size, head size, head length, offset), patient factors (age, gender, BMI) with serum metal ion levels and revisions were analyzed using logistic regression models. Results:. The mean follow-up was 2.7 ± 0.6 years. The mean Co and Cr levels were 5.4 ± 5.7 μg/L (0.2–31) and 2.1 ± 1.5 μg/L (0.1–4.3), respectively. The differences between the Co and Cr levels in the two groups were statistically significant. 49% of THAs in the modular group had elevated metal ion levels (> 4.0 μg/L). There was a significant correlation between higher metal ion levels, younger age, and higher offset (p < 0.05). Presence of pain and high cobalt levels were significant predictors for revision surgery. The rate of revision at the time of this study was 26%, the majority were in the 2. nd. year after surgery. The Kaplan-Meier survivorship was 75% at the time of this study. Discussion and Conclusions:. The short-term high rate of corrosion related revision with Rejuvenate modular neck stems is extremely alarming. We anticipate more revisions in the near future. Level of Evidence: Level III, Therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence

Modular total hip arthroplasty (MTHA) stems were introduced in order to provide increased intra-operative flexibility for restoring hip biomechanics, improving stability and potentially reducing revision risk. However, the additional interface at the neck-body junction provides another location for corrosion or mechanical failure of the stem. To delineate the mid term revision risk of MTHA stems, we examined data from the Canadian Joint Replacement Registry (CJRR) at the Canadian Institute for Health Information (CIHI). Kinectiv, Profemur and Rejuvenate modular stems were identified from CJRR records submitted between 2004 and 2014. Revision status was determined by examining the discharge abstract database (DAD) also housed by CIHI, which collects information on all revisions, regardless of whether the procedure was submitted to CJRR. A total of 2446 modular stems were identified with a mean follow up of 4.2 years (range 0 to 10). Their usage peaked in 2012 (the first year of mandatory CJRR form submission for BC, ON and MB), and dropped rapidly thereafter. A total of 155 (6.3%) were revised. This consisted of 5/301 Kinectiv (1.7%), 141/2050 ProFemur (6.9%), and 9/96 Rejuvenate (9.4%) stems. As a group, this falls below the National Institute for Clinical Excellence (NICE) guidelines of 95% survival at 10 years. While MTHA stems were introduced to improve outcomes and reduce revision risk, our findings of a 6.3% revision risk at a mean follow up of 4.2 years does not appear to support this

Modularity of femoral components has been widely accepted at the head neck junction, most commonly combining two unlike metals with only sporadic reporting of compatibility issues and corrosion. The development and introduction of a new and improved modular neck junction (Rejuvenate Modular Femoral component, Stryker Orthopedics) provided the option of fine-tuning leg lengths, offset and stability. The surgical technique did indeed provide the desired endpoints, however, the early recognition of problems with the junction causing corrosion and Adverse Local Soft Tissue Reaction (ALTR) and subsequent revision has led to the product being voluntarily withdrawn from the market. My experience as an early user of this stem is described in this manuscript providing a better early recognition and treatment of this potentially very destructive process. Methods. A retrospective review of one hundred and ninety one Rejuvenate Stems that were implanted between January 2010 and January of 2012. However, after March 2011, this stem was only used on those patients who had a rejuvenate stem on the contralateral side. They were all implanted through a mini posterior incision with the first 82 patients receiving a Tritanium cluster hole cup (Stryker Orthopedics) with between two and three screws. The remaining 109 patients had an ADM (Anatomic Dual Mobility, Stryker Orthopedics). All patients were allowed to bear weight as tolerated and were followed up with Xrays at six weeks and one year. Clinical visits were recorded at 2 weeks and 6 months postop. Additional follow up was scheduled every two years following the first annual visit. Results. One hundred and seventy four of the 191 hips were available for review at the one-year follow-up. Fourteen patients have undergone revision of the hip due to increased pain and formation of an avascular pseudo capsule due to corrosion at the neck stem junction. All patients have demonstrated a black flaky residue at the taper junction and all have had a large, tense effusion with a milky colored fluid. A neo caspsule has formed in all patients that appeared avascular and thickened. Seven of the eight tritanium cups in the revision cases were loose and required revision, while none of the ADM cups were loose. One patient has undergone two revisions since the initial cause of failure was not recognized and she subsequently developed pain within three months following placement of a new modular neck at the initial revision. One patient who underwent revision developed a deep infection and is currently on antibiotics but has not cleared the infection as of this writing. Conclusion. There has been catastrophic early failure of a modular femoral component due to corrosion at the neck stem junction during the very early stages of follow up. An intense reaction appears to begin early on, perhaps contributing to failure of bony ingrowth in certain cup designs but not others. Patients who develop early onset of discomfort progress to a poorly functioning hip that presents with pain, swelling and decreased ROM. These patients need to be assessed with serum ion levels, joint aspiration for infection and ion levels if possible. A MRI with MARS technology is useful in identifying joint fluid and neo caspsule expansion. These patients should be advised on the adverse reaction that can develop and revision of the hip should be expeditiously carried out

Introduction. Dual modular femoral stems for total hip arthroplasty were initially introduced to optimize joint biomechanics. These implants have been recalled due to fretting and crevice corrosion at the stem-neck interface, ultimately necessitating revision in a significant number of patients. At our institution we had experience with the Rejuvenate (Stryker, Mahwah, NJ) dual modular stem from 2009 until 2011 before it's recall in 2012. This study identifies complications encountered in patients requiring revision of this prosthesis. Methods. We retrospectively identified all patients who had one particular dual modular stem using our registry database. All patients’ charts and imaging was reviewed using our electronic medical records and digital imaging programs. Patients’ age, gender, revision date, intraoperative and postoperative complications, need for subsequent surgery were identified. Results. 118 femoral stems were implanted in 107 patients (61 male & 46 female) with average follow up of over 3 years. 40 stems (34%) were revised in 36 patients with an average time to revision of 2.7 years. Women had a revision rate of 42% versus 28% in men for an odds ratio of 1.5. Complications were also increased overall with a predilection for women. 7 (15%) of revisions required an extended trochanteric osteotomy (ETO), and 5 (12.5%) had greater trochanter (GT) fractures. The most common complication postoperatively was dislocation in 25% of patients, 7 of which required reoperation. One patient had an infection after revision requiring 2-stage revision. Discussion and Conclusion. Dual modular femoral stems are associated with a high early failure rate due to fretting and crevice corrosion. Women in particular are at higher risk for need for revision and have a higher complication rate during and after revision. A significant number of our patients required an ETO or had a GT fracture intraoperatively. Additionally, adverse local tissue reactions (ALTR) are shown to affect the abductor muscles and joint capsule. These two factors likely contribute to the high dislocation rate after revision. Preoperatively counsel patients on the higher complication rate and revision should be carried out carefully to prevent fracture and maximize stability of the hip

PURPOSE:. Wright Medical has a long history of modular neck hip implants but had fracture issues with the original titanium necks. They subsequently changed to chrome cobalt modular necks. Direct contact between these dissimilar metal parts in the modular femoral component brings into consideration the possibility of similar adverse reactions of metal-on-metal articulations that have been previously described in other designs. METHODS:. A retrospective review of 10 patients with Wright Medical chrome cobalt modular necks who were evaluated with chromium and cobalt metal ion levels as well as Metal Artifact Reduction Sequence (MARS) MRI's was performed. Pseudotumors were classified by MRI based on wall thickness, T1/T2 signal, shape, and location and given a corresponding type of I, II, or III. For each patient, symptoms or lack thereof were recorded, and time since surgery noted. RESULTS:. Of 10 patients tested, 9 were symptomatic, and 1 was asymptomatic. The patient that was asymptomatic at last clinical visit at 14 months post-op while symptomatic patients averaged 18 months since initial surgery before symptoms began. Those with metal-poly articulation had an average cobalt level of 1.6, ceramic-ceramic articulation had level of <1, and metal-on-metal had level of 2.9. Five patients had pseudotumor by MRI (2 type I, 1 type II, and 2 type III pseudotumors). CONCLUSION:. It appears that an unintended consequence of changing from titanium to chrome cobalt modular neck may be occurring secondary to corrosion at neck-stem junction. SIGNIFICANCE: This reaction does not appear to be design-specific as these findings are similar to our findings in Stryker Rejuvenate stems. Surgeons evaluating patients with these and other similar stems should be aware of this complication and consider ion testing and MARS MRI

Introduction. Failure of the neck-stem taper in one particular bi-modular primary hip stem due to corrosion and wear of the neck piece has been reported frequently1, and stems were recalled. A specific pattern of material loss on the CoCr neck-piece taper in the areas of highest stresses on the proximal medial male taper was observed in a retrieval study of 27 revised Rejuvenate implants revised after 3 to 38 month time in situ (Stryker, Kalamazoo, MI, USA) (Figure 1). One neck piece exhibited additionally wear marks at the distal end of the flat male neck taper indicating contact with the female taper of the stem. The purpose of this study was to understand the observed failure scenario of bottoming-out by investigating the stem taper morphologies. Materials and Methods. The geometry of taper contact surfaces was determined using a Coordinate Measurement Machine (BHN 805, Mitutoyo, Japan). An algorithm based on the individual unworn areas of the respective taper surfaces was applied to all retrievals. One retrieval is additionally investigated by infinite focus microscopy (G4, Alicona, Austria) in the main wear areas on the neck piece taper, and the bottom, facing each other inside the junction (surfaces of the distal end of the male and the bottom of the female taper). Results. The bottom of the male neck piece taper showed a prominent patch surrounded by a corrosion area (Figure 2), similar to the pattern observed in the proximal taper articulation medial- proximally and lateral-distally (Figure 1). The bottom of the female titanium stem taper did not show material loss to this extent, but only slight scratches. The proximal male taper of the neck piece showed the usual corrosion pattern, with an elevated patch protruding inside the corrosion cavity (Figure 3, left). Contrarily to observations on other retrievals (Figure 3, right), the height of this patch did not reach the original surface level. The wear depth at the patch of the bottomed out taper was 93µm with wear reaching as deep as 170µm. Discussion. Only one of 27 retrieved neck pieces showed bottoming out. It can be speculated that the other retrievals were revised before this situation could occur. In the assembled situation, the initial space between the bottom faces of the stem taper is expectedly in the order of a few 100µm. During the observed wear process, permanent contact at patches on the neck piece prevents its reseating, until these localized structures give in to mechanical and electrochemical exposure. This end stage of failure only occurring in one explant indicates high clinical risks of the implants during earlier stages of intact patches, that are usually observed in retrievals. The formation of such patches has not been reported before, and might be characteristic for the wear and corrosion mechanism of the employed TMZF-CoCr combination, possibly due to the reduced stiffness of the TMZF Titanium. Acknowledgements. The research received funding from the European Union's Seventh Framework Program (FP7/2007-2013) under grant agreement GA-310477 (LifelongJoints)

Having previously been a proponent of the advantages of the modular neck in total hip arthroplasty, I now take the opposite argument because of corrosion that happens with all taper junctions. The advantage of the modular neck is the “uncoupling” of femoral stem position from the final position of the femoral head. Surgical priorities frequently compete, whether positioning the stem for the best press-fit (for cementless fixation) or the best cement mantle (for cemented fixation), and positioning of the stem for preventing dislocation and improving function. My personal use of the modular neck spanned approximately 4 years from 2003–2008 and encompassed a total of 390 primary and revision cases. Excellent functional results were obtained, but some problems occurred that were associated with the modular neck and with large diameter head metal-metal articulations. The modular neck was designed and studied at the Rizzoli Institute in Bologna, Italy with the conclusion that the strength of construct (titanium alloy neck in the titanium alloy stem) was sufficient and the potential for fretting at the modular junction was small and acceptable. Pre-market testing of the device met and exceeded all FDA suggested benchmarks. The first modular neck fracture in my personal series occurred more than 3 years after implantation, in a large man with a long, varus modular neck. Within a year another fracture of a long, varus modular neck occurred in a heavy man. I now know of 6 modular neck fractures among the 390 cases. We have found evidence of corrosion, some very severe, in modular necks that we have revised (both fractured and intact modular necks). This corrosion is caused by Mechanically Assisted Crevice Corrosion associated with fretting at the modular junction which leads to removal of the titanium oxide “passivation” layer that generally forms on a titanium implant. This exposes more of the substrate metal to oxidation and can create pits that, in the notch-sensitive titanium alloy, can lead to the initiation of fracture. The hydrogen that is created from the corrosion reaction and diffused into the metal can cause “embrittlement” which predisposes it to fracture. We also have seen “hydrogen pneumarthrosis” associated with corrosion of the titanium modular neck in which the corrosion concentrated the hydrogen gas in the femoral stem below the modular neck and suddenly was released into the joint with significant pain. The hydrogen gas is irritating to the joint capsule and the patient presents with intense pain and gas in the joint, a clinical picture that can be confused with infection in the joint with a gas-forming organism. We now know that the condition is self-limiting, but suggests that revision of the modular neck construct would be a reasonable course of action. Recently cobalt chromium modular necks have replaced those made of titanium alloy. Since cobalt-chromium is harder and stiffer, the milieu of the taper junction will be different than that of the titanium-titanium junction, and it has been suggested that this will allow safe and long-term use of the modular neck. The first titanium alloy necks were introduced in the early 1990s and it took until the mid-2000s to recognise problems. Last year the Stryker modular neck used with the Rejuvenate stem was recalled because of significant reaction associated with corrosion at the neck-to-stem junction. Corrosion is inevitable at modular junctions exposed to cyclic loading, especially in the milieu of body fluids. We now know that ALTR occurs in response to taper junction corrosion as well, and the more modular junctions there are in a total hip construct, the more debris and potential reaction likely. Fixed neck stems provide satisfactory long-term fixation and function for patients, so despite a functional advantage to the modular neck, it is “a bridge too far”