Modular Stem Research Articles

Midterm outcomes of titanium modular femoral necks in total hip arthroplasty.

Modular femoral necks present surgical and biomechanical advantages in total hip arthroplasty (THA), but their benefits remain controversial due to risks of corrosion and fracture at the additional junction. This study aimed to report 10-year survival and clinical outcomes of a titanium femoral stem with a titanium modular neck in consecutive series. The authors reviewed the records of 97 patients (99 THAs) using uncemented modular stem and ceramic-on-ceramic acetabular components. Patients were evaluated at minimum follow-up of 5 years using the Harris Hip Score (HHS) and Postel Merle-D'Aubigné score (PMA). Survival was calculated using the Kaplan-Meier (KM) method with any reoperation or revision as endpoint. From the original cohort, 14 patients died, 6 were lost to follow-up, and 5 had revision operations with exchange of the femoral stem. The KM survival at 10 years was 94.2% (CI, 86.5-97.5). Clinical assessment was performed on 67 of the 72 patients (69 of the 74 hips) presently living with their original THA components. At mean follow-up of 9.4±1.0 years (median, 10; range, 5-11), the HHS was 93.6±8.2 and the PMA score 17.0±1.6. The X-rays revealed no signs of adverse reactions or bone loss. The uncemented titanium hip stem with modular titanium neck provided a satisfactory 10-year survival and clinical outcomes. Neck modularity enabled restoration of patient-specific femoral offset and limb length thanks to five possible neck configurations, though greater follow up is required to confirm the long-term benefits and safety of this design concept.

The 16-Year Evolution of Proximal Modular Stem Design – Eliminating Failure of Modular Junction

Background: The complexity of hip reconstruction has been and continues to be a perplexing problem with restoring leg length, femoral offset, joint stability and overall hip implant fixation. These were contributing factors that lead to the development of a novel proximal femoral component design “Apex Modular Stem” (Omni, Raynham, MA). The basic stem geometry features a straight stem with a metaphyseal fit and fill cone, a medial triangle and a modular neck junction that allows for version and offset adjustment.In recent years, there has been great concern with the use of modularity in total hip arthroplasty. The goals of this study are (1) to identify complications with the use of a proximal modular design and (2) demonstrated factors that have eliminated those complications.Methods: This is a retrospective study of a single surgeon series (Design A and Design B) of using the same cementless stem and proximal modular neck body (Apex Modular Stem and Omni Mod Hip Stem) from 2000 to 2016 totaling 2,125 stems. 483 stems were the Design A and 1,642 stems, were of the Design B style.Results: Design A, 483 stems were implanted between 2000 and 2004. 31 alignment pins sheared resulting in a revision rate of 6.4%. Design B, 1,642 stems have been implanted between 2004 and 2016 all by the same surgeon, with no failures of the modular junction.Conclusion: All implant devices entail a multitude of risks and benefits. The Apex Modular Stem (Design A), provided excellent fixation, minimal risk of modular junction corrosion, and simple control of anteversion and femoral offset. The limitation was found to be the risk of the alignment pin shearing (6.4%). The pin was enlarged to make it 225% stronger in torsional resistance, and in a subsequent series of over 1,600 femoral stems in a single surgeon series, there were no pin failures over a 12 year duration.

Inferior Radiographic and Functional Outcomes With Modular Stem in Metal-on-Metal Total Hip Arthroplasty

BackgroundData on the association between stem type and metal-on-metal (MoM) total hip arthroplasty (THA) performance are limited. The aim of this study is to investigate the effect of stem type on the prevalence of osteolysis and radiolucency, blood metal ion levels, and functional outcomes in patients with Articular Surface Replacement THA (ASR XL), a type of MoM THA. MethodsWe analyzed 539 unilateral MoM THAs coupled with Summit (48%), Corail (35%), or S-ROM (17%) hip stems at a mean follow-up of 6.4 years. Fifty-four percent of the patients were male, and the mean age was 60 years. We studied radiographs, patient-reported outcome measures, and ion levels. ResultsPatients with S-ROM hip stems were 3.8 times more likely to have osteolysis (P = .003) and 7.6 times more likely to have radiolucency (P < .001) than those treated with Summit hip stems. In addition, patients treated with S-ROM hip stems scored worse than those with Summit hip stems in 4 of the 5 patient-reported outcome measures: Harris Hip Score, Visual Analog Scale pain, University of California at Los Angeles activity, and EQ-5D index. All these differences were statistically significant and ranged from 5% to 10%, which is clinically significant. ConclusionPatients with S-ROM hip stems had inferior functional and radiographic results compared to patients with Summit hip stems. Retrieval studies on large diameter head MoM THA and close follow-up of these patients with hip stems are needed to understand the mechanism causing the differences in outcomes between these stem types.

Modular Femoral Stems in Revision Total Hip Arthroplasty

Revision total hip arthroplasty presents some of the most difficult challenges in reconstructive surgery. With the success of nonmodular stems, the use of modularity to address complex revisions has been questioned. Multiple studies highlight the success of these stems; they allow for improved reconstruction options when addressing concerns for bone quality, leg length discrepancy, and stability. The increased modularity allows opportunities for improvement but can also lead to an increased number of challenges. This article highlights the important aspects when considering the use of a modular femoral stem.

Optimizing Mechanical Alignment With Modular Stems in Revision TKA

BackgroundAlthough mechanical alignment is critical for optimal function and long-term implant durability, the role of modular stems in achieving ideal alignment is unclear. MethodsWe identified 319 revision total knee arthroplasty from 2003-2013, for which stem length, stem diameter, and stem fixation method were recorded prospectively. Three-dimensional canal-filling ratio, the product of canal-filling ratio at the stem tip in both the anteroposterior and lateral planes, and alignment were measured radiographically. ResultsIdeal alignment of the femur was considered to be 95° in the anteroposterior (AP) plane and from 1° of extension to 4° of flexion in the lateral plane, and ideal tibial alignment was considered to be 90° in the AP plane. Even after accounting for difference in stem size and canal-fill, ideal AP alignment was more reliably achieved with press-fit stems. ConclusionFurthermore, increased engagement of the diaphysis and its anatomical axis with canal-filling stems facilitates accurate alignment.

Clinical results in early and mid term of using the S-ROM femoral stem in revision

To investigate and the clinical effect of S-ROM modular stem in femur reconstruction in hip revision arthroplasty. From January 2008 to January 2016, 21 patients received revision hip arthroplasties using S-ROM stems. There were 5 males and 16 females with an average of 48.33 years old(range, 29 to 73 years old). There were 13 cases caused by aseptic loosening, 4 cases by infection, 2 cases by nonunion of sub-tuberosity osteotomy, 1 case for repeated dislocation, 1 case for traumatic great trochanter fracture. Primary THA reasons:12 cases for DDH(9 cases for Crowe IV), 5 cases for femoral neck fracture, 2 cases for necrosis of femoral head, 2 cases for proximal femoral deformity caused by early infection. The femur bone defects included Paprosky II in 11 cases, IIIa in 9, and IIIb in 1. Harris hip score , pain score and hip flexion were recorded before and after operation. The subjective satisfaction was recorded at the last follow-up. The operation time and blood loss were 189 min(125 to 290 min) and 867 ml (200 to 2 000 ml). At the final followup, the pain score improved from (17.14±9.56) points preoperatively to (41.71±2.03) points (t=11.42, P=0.00). The function score improved from (24.01±11.02) points preoperatively to (49.95±5.38) points (t=9.73, P=0.00). Harris hip score improved from (41.15±14.81) points preoperatively to(91.67±5.83) points(t=15.33, P=0.00). The degree of hip flexion increased from (93.10±27.27) points preoperatively to (121.90±16.62) points at the last follow-up (t=4.59, P=0.00). The mean subjective satisfaction was 9.48(10 points system), 14 of which were completely satisfactory. The last follow-up hip X-ray showed 21 cases of bone ingrowth, and other femoral stem without loosening or sinking sign significantly. There were 5 cases with bone anchor syndrome around proximal femoral cuff. There were 5 cases of proximal femur fracture, 3 cases of lesser trochanter fracture, 2 cases of greater trochanter fracture intra-operatively. Due to femoral canal stenosis, there were 4 cases of pre-tied wire at lesser trochanter to prevent fractures. There was 1 case of traumatic femoral fracture around stems with a distal oblique fracture, open reduction and locking plate fixation was performed. Other patients had no nerve stretch injury, dislocation, infection and lower limb deep vein thrombosis and other complications at the final follow-up. S-ROM prosthesis has satisfactory results in hip revision arthroplasty with Paprosky II and III femoral defects. Especially for patients with Crowe IV DDH and other proximal femoral deformities, it is possible to adapt to the medullary cavity morphology. Excellent initial stability, less complications and long-term biological fixation can be achieved with S-ROM in femur revision.

Long-Term Results of Cementless Total Hip Arthroplasty Using a Modular Stem in Patients with Femoral Head Osteonecrosis

Patients with femoral head osteonecrosis are younger and more active than those with osteoarthritis of the hip. More than 10-year results of total hip arthroplasty (THA) using modular cementless stem in osteonecrotic patients have not yet been reported. We determined clinical and radiologic results of cementless modular stem in a consecutive series of patients with femoral head osteonecrosis a minimum follow-up of 10 years. We retrospectively reviewed 48 patients (58 hips) who underwent THA for femoral head osteonecrosis with a cementless modular femoral stem. Metal-on-metal articulation was used in 32 hips and ceramic-on-ceramic articulation in 26. There were 26 men and 22 women with a mean age of 52 years at the time of the operation. These patients were followed for 10 to 15 years. All of the acetabular cups and femoral stems had radiographic evidence of bone ingrown stability at the final follow-up. Three hips were revised due to infection. There were no revisions for ceramic fracture or adverse reaction to metal debris. The survival rate was 94.8% (95% confidence interval: 89.8–100%). However, 12 patients (12 hips, 21%) suffered thigh pain. In six patients (six hips), the pain disappeared within 1 to 2 years, whereas the pain persisted until the final follow-up in the remaining six patients. As of 10 to 15 year, radiologic results and survival of THA using a modular femoral stem were good in patients with osteonecrosis. However, the incidence of thigh pain remains a matter of concern.

Excellent Mid-Term Results of a New Polished Tapered Modular Cemented Stem: A Study of 113 Hip Replacements with Minimum 5-Year Follow-Up

BackgroundThis prospective cohort study reports the medium-term clinical and radiographic results of 113 hips treated with a hybrid total hip replacement (THR) with a new cemented tapered cobalt-chrome (Co-Cr) stem with a titanium (Ti) modular neck (ProfemurXm®).MethodBetween October 2008 and December 2010 we performed 115 consecutive hybrid THR with the ProfemurXm® in 105 patients.ResultsSurvivorship of the implant (stem and modular neck) at a mean of 6.5 years (min 5-max 8) was 100% with the endpoint revision for any reason. No implant was at risk for revision or showed signs of loosening. The mean Harris Hip Score was 89/100, mean Oxford Hip Score was 43/48, mean WOMAC was 91/100. No patient had thigh pain, no patient reported squeaking. There were no dislocations in this cohort. No implant showed development of radiolucent lines (RLL), either at the stem-cement or cement-bone interface. No hip showed osteolysis or calcar resorption. The mean femoral subsidence of the stem within the cement mantel was 0.31 mm (range 0-0.6 mm) after 6.5 years. With the use of this modular stem, 93% of hips showed no measurable leg length difference after THR, and leg length could be restored within a 5-mm limit in 99% of hips.ConclusionsThe mid-term results of this new polished stem were excellent, without adverse effects from the use of modularity.

Chemical and Microstructural Characterization of Modular Femoral Stems Manufactured in ISO 5832-9 Stainless Steel

The aim of this study is to evaluate and compare the chemical composition and microstructure of two femoral stems manufactured in ISO 5832-9 austenitic stainless steel by different manufacturers. Both the femoral stems under study are used in Brazil. Chemical analyses of the elements were performed by glow discharge optical emission spectrometry. The microstructure of the stems was characterized by optical and scanning electron microscopy and x-ray diffraction. Vickers hardness measurements were also taken. Both stems exhibited small amounts of Z-phase dispersed in the austenitic matrix and had similar grain sizes of austenite. The hardness was 46% higher in one stem, which was attributed mainly to the higher nitrogen content of this stem. The results also showed that small variances, although still within the requirements of the standard, produce differences of the Z-phase, grain size, and hardness of the steels. The control of these characteristics has clinical relevance because it has a direct influence on fatigue and corrosion resistance.

Comment on: Modular titanium alloy neck failure in total hip replacement

To the Editor of the SICOT-J Orthopaedic Journal, I am writing to you as I would like to kindly express some considerations on the case-report of Dr. Marco Ceretti on “Modular titanium alloy neck failure in total hip replacement” published in your on-line journal last April (M. Ceretti and F. Falez SICOT J 2016, 2, 20). The Authors report on “a case of a repetitive modular femoral neck prosthesis fracture”; they had initially revised a broken modular Metha stem with a MODULUS stem, neck 135° long, head 36 medium in a 43-year-old woman with body mass index (BMI) 38.6 kg/m2 (weight 110 kg, height 170 cm); both stems presented modular necks in titanium alloy. The MODULUS stem was then revised with a Wagner monoblock uncemented titanium stem following the fracture at the neck-stem junction. This article reports a clinical case but it does not include any laboratory evidence in terms of fracture analysis to support the Authors’ conclusions and to elucidate the mechanisms of failure. No retrieval analysis on the two stems seems to have been in fact carried out, such as standard macroscopic inspection and observations, standard corrosion testing, micro analysis of the implant alloy, light microscopy, Scanning Electron Microscopy (SEM) and patient’s blood sample to check the release of metal ions. Besides, several publications nowadays report comparative analysis of cobalt-chromium and titanium modular femoral necks, showing that the first material present “improved resistance against fretting” with “lower incidence of surface micromotions” (e.g. [1, 2]). Nevertheless, the fracture of these two modular necks should be attributable to an error of indication and not to a failure of the devices themselves, meant to be used in patients with lower BMI. The surgical technique of the MODULUS stem reports: “Complications or failures of the total hip replacement may occur in heavy and highly active patients and high offset combinations. The surgeon should perform a careful evaluation of the patient’s clinical condition and level of physical activity before performing hip replacement. Patients who are overweight and/or have high activity levels may not be candidates for hip replacement with modular stems. Alternative devices, such as monoblock hip stems, should be used, when possible, in these patients.” The available literature sources clearly support these indications on the use of modular stems in the current clinical practice: “Among patients treated with the titanium alloy neck adapter, a combination of different parameters was identified as risk factors of implant failure. The parameters are intraoperative particle contamination of the cone connection, excessive loading due to a patient weight above 100 kg or high activity level, and male gender. In addition, the risk for failure rises with CCD angles of the cone adapter of 135° and smaller.” “Contamination with cortical bone particles in the interface was found to be the main influence factor on the fatigue behaviour of the titanium alloy neck adapter.” [1] “Various circumstances such as large femoral head with a long varus neck, corrosion, patients’ BMI, and activity level may participate in creating the necessary environment for fatigue failure of a modular hip replacement implant.” [3] Furthermore, I would like to take this opportunity to kindly bring to the attention of your Editorial Office that no failures of the MODULUS stem are recorded in some series of publications concerning clinical experience with this medical device, as indicated in the following articles [4–7]. Conflict of interest One of the author is a consultant of Lima Corporate as a Scientific Adviser.

FRETTING CORROSION OF COBALT AND TITANIUM IMPLANT ALLOYS IN SIMULATED BODY FLUIDS

The most important advantage of using modular hip joint endoprostheses is the possibility to adapt the endoprosthesis to the morphology and size of individual patients. However, the additional contact surface is subjected to fretting wear due to mutual micro displacements and the aggressive chemistry of the environment inside the human body (fretting corrosion). Today’s hip endoprostheses are generally composed of a hip stem, a femoral ball head and an acetabular cup (Figure 1). The hip stem is made of stainless steel, CoCrMo or a Ti alloys. The femoral ball head is made of stainless steel, CoCrMo, or a ceramic material. In the case of a modular hip stem, i.e. with a modular neck portion, the materials used are generally CoCrMo and Ti6Al 4V. (The interface between femoral ball head and the acetabular cup is an articulating surface and not the subject of this research project.) In this framework, a comparative study of the fretting corrosion resistance of the three most common metallic material combinations occurring in a modular, the non-articulating connection of total hip joint endoprostheses (CoCrMo-CoCrMo, CoCrMo-Ti6Al4V, and Ti6Al4V-Ti6Al4V) was undertaken. Studies were performed with a tribological tester, working in articulating-reciprocating motion, integrated with a potentiostat equipped with a tri-electrode system. The tribosystem consisted of a fixed stem pressed with a constant force to a plate performing the reciprocating motion of a predetermined frequency and amplitude. The tests were performed in diluted bovine serum at 37°C. Based on the obtained results, it was found that the greatest resistance to corrosion in static conditions was exhibited by the CoCrMo-CoCrMo friction pair, while the lowest ΔE value was obtained by CoCrMo-Ti6Al4V. It also confirmed the existence of a correlation between the intensity of the depassivation process caused by the mechanical destruction of the surface layer and the friction resistance values in the tribological system.

Feasibility of biological acetabular component with high placement technique in hip revision arthroplasty

Objective To investigate the feasibility of biological acetabular component with high placement technique in hip revision arthroplasty. Methods From March 2006 to March 2015, 34 patients (35 hips) underwent hip revision arthroplasty with biological acetabular components with high placement technique. There were 15 males (15 hips) and 19 females (20 hips) with an average of 55 years (range, 26-74 years). There were 22 hips caused by aseptic loosening and 13 hips by infection. The acetabular bone defects included Paprosky IIA in 3 cases, IIB in 4, IIC in 2, IIIA in 17, and IIIB in 9. Modular tapered stems with distal fixation were performed in most femoral sides. The height of hip center was greater than 2.5 cm for all the patients, which were divided into two groups according to the degree of placement: 2.5-3.5 cm for the high placement group, greater than 3.5 cm for the high hip center group. Harris hip score, pain visual analogue score (VAS), leg length difference, gait characteristics were compared between two groups postoperatively and at the final follow-up respectively. The height of hip center and the horizontal distance between hip center and teardrop were measured in the hip X-ray. Radiolucent lines and migrations were also recorded. Results The average operation time and blood loss was 108 min (100-220 min) and 525 ml (300-1 200 ml) in two groups respectively. All the patients were followed up for average 49.2 months (range, 12-116 months). At the final follow-up, the average Harris hip score improved from 36.52±17.17 points preoperatively to 83.46±7.63 (t=18.99, P=0.001). The average VAS score decreased from 8.06±1.24 points preoperatively to 1.91±1.62 postoperatively (t=18.57, P=0.001). The height of hip center was 1.47±0.33 cm preoperatively and 3.85±1.13 cm postoperatively (t=12.15, P=0.001). The horizontal distance was 3.33±0.53 cm pre-operatively and 3.23±0.63 cm post-operatively (t=0.98, P=0.640). At the final follow-up, Trendelenburg sign improved from 25/10 (positive/negative, hips) preoperatively to 7/28 (χ2=18.65, P=0.001). There was 1 case of severe limp, moderate in 1, mild in 8 and other cases had no limp. The leg length discrepancy decreased from 1.84±1.92 cm preoperatively to 0.71±1.57 postoperatively (t=4.24, P=0.001). There were 6 cases of Paprosky IIIb with the use of ultra small cup and extremely high placement. The average Harris hip score improved from 26.65±13.46 points preoperatively to 79.83±10.55 (t=12.33, P=0.001). The average VAS score decreased from 8.50 ± 1.38 points preoperatively to 2.83 ± 2.64 postoperatively (t=4.61, P=0.006). One case had acetabular loosening at 4 years later postoperatively and re-revision surgery was performed. Other patients had no infection, dislocation, periprosthetic fracture or any other complications at the final follow-up. Conclusion Highly placement of biological acetabular component with a distal tapered modular stem can get enough contact with the host bone and achieve optimal clinical outcomes, regardless of the degree of high placement. Particularly, using ultra small cup in extremely high placement shows good effectiveness in simplified operation, and it can be used in many complicated or even impossible acetabular reconstruction. Key words: Arthroplasty, replacement, hip; Reoperation; Acetabulum; Osteolysis; Prosthesis-related infections

Asymptomatic Pseudotumors in Patients with Taper Corrosion of a Dual-Taper Modular Femoral Stem: MARS-MRI and Metal Ion Study.

Modularity in total hip arthroplasty facilitates intraoperative restoration of patient anatomy. Although dual-taper modular total hip arthroplasty offers potential advantages for optimizing the hip center of rotation, it has been associated with modular taper corrosion. This corrosion has led to adverse local tissue reactions (pseudotumors) at the neck-stem junction and elevated metal-ion levels. However, the occurrence of taper-corrosion-related pseudotumors in patients who remain asymptomatic following total hip arthroplasty with a dual-taper modular femoral stem remains largely unknown. The aims of this study were (1) to determine the prevalence of asymptomatic pseudotumors by utilizing metal artifact reduction sequence magnetic resonance imaging (MARS-MRI) and (2) compare serum metal-ion levels between symptomatic and asymptomatic patients with a dual-taper modular stem total hip replacement. We performed a retrospective cross-sectional study of 97 consecutive patients who had been treated with a dual-taper modular femoral stem total hip arthroplasty. Eighty-three patients were stratified into symptomatic and asymptomatic groups and evaluated with MARS-MRI, measurement of serum metal-ion levels, and the University of California at Los Angeles (UCLA) functional hip score. The prevalence of pseudotumors as determined with MARS-MRI was 15% in our asymptomatic patients and 36% in the overall cohort. The median serum cobalt level and cobalt/chromium ratio were significantly higher in patients with a pseudotumor than in those without a pseudotumor (8.0 versus 2.0 μg/L [p = 0.004] and 10.3 versus 2.4 μg/L [p = 0.012], respectively). However, there was no significant difference in the serum cobalt level or cobalt/chromium ratio between symptomatic patients with a pseudotumor and asymptomatic patients with a pseudotumor (7.6 versus 6.2 μg/L [p = 0.37] and 8.3 versus 10.6 μg/L [p = 0.46], respectively). The UCLA scores of asymptomatic patients with a pseudotumor were similar to those of patients without a pseudotumor (6.7 versus 6.6). The prevalence of asymptomatic taper-corrosion-related pseudotumors on MARS-MRI in this study demonstrated that the absence of symptoms does not exclude the presence of adverse local tissue reactions. Elevated cobalt levels and cobalt/chromium ratios were associated with the presence of pseudotumors in asymptomatic and symptomatic patients. Cross-sectional imaging such as MARS-MRI is indicated for patients with elevated metal-ion levels. A longitudinal study is required to determine whether asymptomatic patients with taper-corrosion-related pseudotumors will develop symptoms with time. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

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

PurposeThis study aimed to investigate the outcomes of modular neck-utilization in primary total hip arthroplasty (THA).Materials and MethodsThirty 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).ResultsThe 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.ConclusionOur 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.

GUIDING PRINCIPLES AND PEARLS IN A STEPWISE SURGICAL TECHNIQUE OF REVISION TOTAL KNEE ARTHROPLASTY.

The authors aim at reviewing the guiding principles in revision total knee arthroplasty according to a stepwise procedure. Strict preoperative planning is of paramount importance for this surgery. Thorough clinical history and physical exam, the assessment of limb deformity and knee range of motion as well as knee stability in flexion, extension and mid-flexion are crucial. Blood exam, standardized radiographic views, and CT scan are powerful tools for etiologic diagnosis of total knee arthroplasty failure. Templating is unique and mandatory to provide the surgeon with the critical data concerning the valgus position of the femoral component, the AP size of the femoral component, and the optimal position of the joint line; these three parameters are determinant for the final clinical outcome. A stepwise surgical technique with close adherence to the guiding principles of revision knee arthroplasty should be adopted from skin incision to closure. Femoral and tibia components with modular stem are ideally set at their optimal position as predetermined by templating. Any residual implant-bone gap is filled with metallic augment or bone graft. Finally, repositioning of the patella on a symmetrical bone cut presents a great value for a successful procedure.

CORR Insights®: No Difference between Trabecular Metal Cones and Femoral Head Allograft in Revision TKA: Minimum 5-year Followup.

Where Are We Now? A substantial increase in the volume of primary TKA in conjunction with increases in patient lifespan has resulted in an increased need for revision TKA. An analysis of revision TKA volume in Medicare beneficiaries showed revision volume increased 105.9% from 1991 to 2010 [2]. There is some degree of bone loss associated with each revision procedure because of initial bone resection at the time of primary TKA, osteolysis from wear debris or other causes, and bone loss associated with component removal. Minor bone defects (Anderson Orthopaedic Research Institute [AORI] Types 1 and 2 [4]) are usually managed simply with cancellous cavitary bone grafting, bone cement with or without screws, or peripheral metal augments. Larger defects (AORI Types 2B and 3 [2]) make it more difficult to achieve durable implant fixation because of the loss of bone support. Historically, structural allografts have been used to reconstruct these defects, with 91% demonstrating satisfactory function in a report of 46 subjects at a mean followup duration of 97 months [5], although problems with nonunion, late graft collapse, and the potential for disease transmission have been identified [1]. These problems have resulted in the development of metaphyseal sleeves and trabecular metal cones to enhance long-term fixation [3, 6, 7]. Short-term results with these devices have been favorable but have analyzed only a single method of defect management rather than comparative studies of multiple techniques. The current report is the first to compare different techniques (structural allograft versus trabecular metal cones). The authors observed no differences in pain relief, function, or repeat revision TKA rates between patients treated with the two approaches. Where Do We Need To Go? Numerous questions remain regarding management of large bone defects in revision TKA. Will the findings of this small study, which includes a combined total of only 45 patients (30 femoral had allografts versus 15 trabecular metal cones), be confirmed in larger and more diverse revision TKA populations? Will the clinical results remain similar with longer followup duration since some reports of use of structural allografts have demonstrated failure due to graft resorption at followup intervals longer than 10 years? Should a revision TKA utilizing either of these techniques fail, what are the results of a repeat revision procedure? Does one technique result in a simpler or more complex re-revision procedure? For example, will use of a structural allograft provide restored bone stock for future revisions? Should infection occur, does an incorporated structural allograft or trabecular metal cone require total removal? How difficult is removal of a well-fixed trabecular metal cone and what are the technical tips for safe removal? Does removal of a well-fixed trabecular metal cone result in a substantial amount of retained third-body metallic debris particulate that may accelerate polyethylene wear in repeat revision procedures? Allografts can be sterilized using multiple methods; to what degree are there clinically important tradeoffs among these approaches? Will irradiation of frozen grafts to reduce disease transmission result in unacceptable reductions in mechanical strength compared to fresh-frozen allografts? Lastly, is use of modular stem extensions necessary for all revision TKA operations utilizing one or both of the techniques studied in the current evaluation? If so, how long should the stems be? Are short cemented stem extensions adequate or will longer stem extensions engaging diaphyseal bone prove more durable? How Do We Get There? Randomized comparative analyses of the two techniques with followup duration of a minimum of 10 years are necessary. While difficult to accomplish, a multicenter effort would likely be required to create a case volume adequate to draw firm conclusions. In such a study, it would be beneficial to include a third technique of using porous coated metaphyseal sleeves [3] as these are commonly used for Types 2B and 3 [2] bone defects. All Type 2B and 3 bone defects [4] are not the same. Some have more loss of cortical rim support than others. The amount of bone loss using the AORI bone defect classification [4] is variable. A more-critical evaluation of defect size and shape is necessary to better discern whether structural bone allografts or trabecular metal cones are superior in the management of specific bone defect geometries. Of course, bone defects also occur on the femur; are results different when dealing with femoral versus tibial defects? For example, Type 3 femoral defects have the potential for loss of collateral ligament support; does this influence which approach might be better? These questions and others call for larger, longer-term, randomized and likely multicenter studies. To accomplish this, economic support from national organizations such as the Knee Society and the American Association of Hip and Knee Surgeons would be helpful as their memberships contain leaders in TKA with competent databases necessary to provide the required meaningful data.

Fracture at the Modular Junction of a Cementless Revision Hip System: A Case Report.

Multiple cases of modular femoral component failure involving fatigue at the modular stem junction have been reported following revision total hip arthroplasty. In the present report, we describe what we believe to be the first case of catastrophic failure involving the Biomet Arcos revision system. The failure involved a young patient with an elevated body mass index and proximal bone deficiency. The possibility of this failure mechanism must be weighed against the potential advantages of modular cementless stems when planning for complex hip arthroplasty, especially in the young, active patient.

Fretting Induced Fracture Damage in a Ti6Al4V Total Hip Prosthesis

Abstract Within the body, hip implants are subjected both to mechanical and corrosive effects. In narrow crevices such as in the moving surfaces of modular femoral stems, even in the case of proven materials, complex interactions occur between mechanically and corrosively induced material damage, which can strongly influence the service reliability of the implant itself. After almost a year in service, the modular femoral stem presented in this article, fractured. The stem, which had been implanted into a somewhat less than active patient, fractured possibly as a result of defective implantation and diagnosed loosening, causing fretting and corrosion which eventually resulted in the fatigue fracture of the modular hip stem. The failure analysis presented, carried out as part of an IMWF student research project at the MPA University of Stuttgart, was initiated to investigate the damage found at a number of different levels and using various different investigatory techniques in order to determine the cause of the failure and to suggest guidelines to aid in the investigation of other similar failures.

Not all cementless stems are created equal: A selection algorithm

Patients, and their femurs, come in all shapes, sizes, and types. Fortunately, so do cementless femoral stems. Each surgeon should have a “go to” cementless femoral component that can address over 90% of cases. A simple approach is to separately consider (A) the part inside the bone and (B) the part outside the bone. The inner-cortical geometry (Dorr type) and bone density influence stem size (the part inside the bone) and influence femoral canal preparation. Femoral deformity or old hardware can occasionally necessitate the use of a short stem or a modular stem. Restoration of limb length and offset is a function of the neck angle and length (the part outside the bone). Undersizing of cementless stems increases the risk of aseptic loosening while restoration of limb length and offset favorably affects patient satisfaction and function.

Utility of Serum Inflammatory and Synovial Fluid Counts in the Diagnosis of Infection in Taper Corrosion of Dual Taper Modular Stems

BackgroundAn accurate diagnosis of periprosthetic joint infection (PJI) is critical as treatment of the infected total hip arthroplasty differs from aseptic failure. The clinical presentation of PJI may mimic symptoms of taper corrosion. Our aim was to evaluate the utility of serum inflammatory markers and synovial fluid white blood cell (WBC)/differential counts in diagnosis of PJI in failed dual taper total hip arthroplasty due to taper corrosion. MethodsWe retrospectively reviewed 62 dual taper modular stem patients who underwent revision surgery for symptomatic adverse local tissue reaction due to taper corrosion. All patients had preoperative hip synovial aspirations, serum inflammatory markers, metal ion levels, and intraoperative cultures. Using Musculoskeletal Infection Society PJI criteria, we divided the cohort into infected and noninfected groups. Receiver-operating characteristic curves were constructed to determine the relationship and optimal cutoff values for erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and synovial fluid counts. ResultsInfection group had significantly higher mean ESR (P = .002), CRP (P = .01), synovial fluid WBC (P < .001), and neutrophil percentage (P = .02). Cobalt levels were significantly elevated in noninfection group (P = .02). Using receiver-operating characteristic curve analysis, the most ideal tests for diagnosis of PJI were synovial fluid WBC (area under the curve = 86%, optimal cutoff 730 WBC/uL) and neutrophil percentage (area under the curve = 83%, optimal cutoff 65%). ESR and CRP thresholds of 22 mm/h and 3 mg/L demonstrated 57% sensitivity and 95% specificity and 29% sensitivity and 93% specificity for detection of PJI, respectively. ConclusionOur study suggests that ESR and CRP are useful in excluding PJI in dual taper modular implants with corrosion, whereas both synovial WBC count and neutrophil percentage are useful markers for diagnosing infection.