Cementless Components Research Articles

Primary elbow arthroplasty: problems and solutions.

Prosthetic replacement of the elbow joint has continued to improve over time. Widespread implantation of certain designs has led to identification a few successful elements of elbow arthroplasty, as well as several opportunities for improvement. Current hot topics in elbow arthroplasty include triceps-preserving exposures, implantation of components with better-expected wear performance, management of the ulnar nerve, prevention of infection, and the development of successful cementless components. Total elbow arthroplasty has the potential to improve pain, function and quality of life for many patients with articular destruction secondary to inflammatory arthropathy or as a consequence of trauma. Continued advances in this field are key to make this operation as reliable and lasting as hip or knee arthroplasty.

Osteocyte physiology and response to fluid shear stress are impaired following exposure to cobalt and chromium: Implications for bone health following joint replacement.

ABSTRACTThe effects of metal ion exposure on osteocytes, the most abundant cell type in bone and responsible for coordinating bone remodeling, remain unclear. However, several studies have previously shown that exposure to cobalt (Co2+) and chromium (Cr3+), at concentrations equivalent to those found clinically, affect osteoblast and osteoclast survival and function. In this study, we tested the hypothesis that metal ions would similarly impair the normal physiology of osteocytes. The survival, dendritic morphology, and response to fluid shear stress of the mature osteocyte‐like cell‐line MLO‐Y4 following exposure to clinically relevant concentrations and combinations of Co and Cr ions were measured in 2D‐culture. Exposure of MLO‐Y4 cells to metal ions reduced cell number, increased dendrites per cell and increased dendrite length. We found that combinations of metal ions had a greater effect than the individual ions alone, and that Co2+ had a predominate effect on changes to cell numbers and dendrites. Combined metal ion exposure blunted the responses of the MLO‐Y4 cells to fluid shear stress, including reducing the intracellular calcium responses and modulation of genes for the osteocyte markers Cx43 and Gp38, and the signaling molecules RANKL and Dkk‐1. Finally, we demonstrated that in the late osteoblasts/early osteocytes cell line MLO‐A5 that Co2+ exposure had no effect on mineralization, but Cr3+ treatment inhibited mineralization in a dose‐dependent manner, without affecting cell viability. Taken together, these data indicate that metal exposure can directly affect osteocyte physiology, with potential implications for bone health including osseointegration of cementless components, and periprosthetic bone remodeling. © 2016 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 35:1716–1723, 2017.

Digital tomosynthesis with metal artifact reduction for assessing cementless hip arthroplasty: a diagnostic cohort study of 48 patients.

For postoperative imaging assessment of cementless hip arthroplasty, radiography and computed tomography (CT) were restricted by overlapping structures and metal artifacts, respectively. A new tomosynthesis with metal artifact reduction (TMAR) is introduced by using metal extraction and ordered subset-expectation maximization (OS-EM) reconstruction. This study investigated the effectiveness of TMAR in assessing fixation stability of cementless hip arthroplasty components. We prospectively included 48 consecutive patients scheduled for revision hip arthroplasty in our hospital, with 41 femoral and 35 acetabular cementless components available for evaluation. All patients took the three examinations of radiography, CT, and TMAR preoperatively, with intraoperative mechanical tests, and absence or presence of osteointegration on retrieved prosthesis as reference standards. Three senior surgeons and four junior surgeons evaluated these images independently with uniform criteria. For TMAR, 82% diagnoses on the femoral side and 84% diagnoses on the acetabular side were accurate. The corresponding values were 44 and 67% for radiography, and 39% and 74% for CT. Senior surgeons had significantly higher accuracy than junior surgeons by radiography (p < 0.05), but not by TMAR or CT. By minimizing metal artifacts in the bone-implant interface and clearly depicting peri-implant trabecular structures, the TMAR technique improved the diagnostic accuracy of assessing fixation stability of cementless hip arthroplasty, and shortened the learning curve of less experienced surgeons. Level II, diagnostic cohort study.

Uncemented Total Hip Replacement After Two Years of Neglected Hip Dislocation With Fracture of Posterior Column and Wall of the Acetabulum

IntroductionPosterior hip dislocation of the hip with acetabular fracture is a challenging problem to treat. Such dislocations are associated with avascular necrosis of the femoral head if neglected. Managing such conditions with total hip replacement (THR) is very difficult because of associated altered anatomy.Case PresentationWe hereby report a two-year neglected hip dislocation with associated acetabular fracture successfully treated with uncemented THR. The patient was successfully treated with uncemented THR and experienced significant improvement in his functional status, with a Harris hip score of 82 at the two-year follow up. Radiologically, there were no radiolucent areas or osteolysis, with good consolidation of the bone graft.ConclusionsA neglected hip dislocation with acetabular fracture can be managed satisfactorily with uncemented THR. Bone reconstruction using chunk grafts and use of cementless components ensures long-term survival and also preserves adequate bone stock for revision, especially in young patients.

Femoral revision with a primary cementless stem

IntroductionThe use of a primary cementless component is a tempting option for revision total hip arthrosplasty (reTHA), however, the results of this type of revision have not been clearly determined. The goal of this retrospective study was to determine: if revision with a primary anatomical cementless femoral stem gives adequate bone fixation; the rate of secondary subsidence or recurrent loosening; the survival rate with this device. HypothesisRevision with a primary anatomical cementless femoral stem results in a low rate of subsidence and recurrent loosening. Materials and methodsThis retrospective series of 43 reTHA performed between 1994 and 2012 included 43 patients, mean age 66 years old (37–90) with a minimum follow-up of 24months. There were grade 1 (n=24) or 2A (n=19) bone defects according to the Paprosky classification. The causes of revision were: aseptic loosening in 27, septic loosening in 6, malposition of the implant in 7 and periprosthetic fractures in 3. Clinical (Postel Merle d’Aubigné [PMA] and Harris scores), and radiological (subsidence) assessment was performed, as well as survival analysis (with a 95% confidence interval). ResultsAll components were changed through posterolateral approach without femorotomy. In four cases de-escalation (use of a primary component for secondary revision of a prior revision component) was performed. There were no perioperative fractures or perforations. After a mean 47months (24–134), the mean PMA score increased from 10 (5–15) to 16 (11–18), and the Harris score from 58 (20–80) to 85 (66–96). Radiological assessment did not show any extensive radiolucencies or secondary subsidence. Only 3 components were placed in a varus position, with no clinical consequences. One patient had subsequent revision for recurrent dislocations. Estimated survival at 80months by Kaplan-Meier analysis was 85% (CI 95%: 64–100%). DiscussionThere are very few studies in the literature (7 series) on this topic, which shows the reluctance of surgeons to use this technique. Placement of a primary femoral stem requires good metaphyseal bone quality for primary stability. Thus, the indication is limited to Paprosky 1 and 2A stages. Revision surgery must be performed by endofemoral approach requiring good preoperative planning, as well as knowledge of the explanted component and a revision component must be available, if necessary, in the operating room. Level of evidenceRetrospective study, level 4.

Impaction grafting for acetabular reconstruction in primary and revision hip arthroplasty

Background Acetabular bone stock loss is a major problem in both primary and revision total hip arthroplasty (THA). The loosening of primary cemented and cementless components of THAs is also accompanied by a loss of bone stock. There are several options for reconstruction of the acetabular defects. In 1979, a biologic method was introduced with tightly impacted cancellous allografts in combination with a cemented polyethylene cup for acetabular reconstruction, to restore acetabular bone stock, to restore normal hip biomechanics, and to allow for further revision if needed. Aim of the work In this study, the results of using morcellized impacted bone graft to reconstruct the deficient acetabulum in 54 hips (49 patients) using either cemented or cementless cups are discussed, with a mean follow-up of 36 (6–96) months. Patients and methods Between May 2002 and April 2010, 54 hips (in 49 patients) with deficient bone stock on the acetabular side had undergone total replacement with acetabular reconstruction using morcellized bone impaction grafting; out of the 54 hips, 34 (63%) were primary THA (17 after fracture of the acetabulum, 12 for protrusio acetabuli, three for rheumatoid arthritis, one for dysplastic hip, and one after tuberculosis arthritis) and 20 hips (37%) were revision THA. There were 21 (43%) women (bilateral in three of them) and 28 (57%) men (bilateral in two of them). Average age was 53 years (range 26–98 years). Out of the 54 hips, 14 (26%) were cementless and 40 (74%) were cemented. Mesh was used in 27 (50%) hips to convert a noncontained defect into a contained defect. Octopus ring was used in one hip, and Muller ring was used in another hip to overcome pelvic discontinuity. Results Fifty-four hips in 49 patients were followed up clinically and radiologically, with a mean follow-up of 36 months. In 46 hips (95.8%), the graft showed radiological signs of union to the host bone and no cup loosening. Cup was loose and revised in two patients (4.2%). One patient had octopus ring and morcellized graft in the first operation, and it was revised using a mesh and morcellized graft 8 years later. The other patient had morcellized graft and Muller ring; this failed after 4 years with cup loosening. It was revised using mesh and morcellized graft. Conclusion Acetabular reconstruction is a demanding procedure and needs preoperative planning and armamentarium. Successful results were obtained using the impaction technique for reconstruction. The aim of bone graft is to restore the normal hip mechanics. The union rate of the impacted graft is relatively satisfactory compared with other grafting methods. Augmentation of the grafting technique by mesh or rings added more stability to the cup component. The use of impaction graft in revisions for infected hip did not increase the risk of reinfection.

Immediate results of treatment periprosthetic femoral fractures after hip replacement

Periprosthetic fractures are one of the most serious complications after hip replacement. Nineteen periprosthetic femoral fractures operated on during the period 2011-2015 were followed-up retrospectively. Periprosthetic fractures were classified according to the Vancouver classification. The functional results were evaluated using Harrison scale. Bone healing and implant stability were evaluated clinically, on plain radiographs and computed tomography. The periprosthetic fractures in all patients occurred in the postoperative period. Time from operation until fracture varied from 2 weeks to 11 years. A wedge-shaped cemented or cementless stems were implanted during the first surgery: Versys ET, Spotorno, CPT (Zimmer, США): cementless fixation was performed in 16 (84,2%) patients, hybrid -in 2 (10,5%) and cemented fixation - in 1 (5,3%) patient. The fractures of greater trochanter were diagnosed in all patients with type A periprosthetic fractures. In type B1 periprosthetic fracture (8 patients) open reduction, cerclage wiring and internal plate osteosynthesis were applied. Loosening stems in 3 patients with type B2 fractures were replaced with Wagner cementless revision component (Wagner SL Revision Stem). Angle-stable plate osteosynthesis and cerclage wiring were also performed. Closed reduction and internal minimal invasive plate osteosynthesis were performed in patients with type C periprosthetic fractures. Bone consolidation was achieved in 18 (94,7%) patients, the average term was 14,3±5,2 weeks. The average Harris hip score in all patients 3 months after treatment was 64,9±16,7 points, and in 12 patients (63,2%) after a year - 86,5±15,9. Femoral periprosthetic fractures require a specialized approach to choosing the treatment tactic depending on the fracture type and quality of bone tissue. It is necessary to evaluate the femoral component stability, especially in differential diagnosis of type B1 and B2 periprosthetic fractures. Computed tomography is one of the necessary methods of diagnosis.

Outcomes of total hip arthroplasty in patients with primary immune thrombocytopenia.

BackgroundImmune thrombocytopenia (ITP) is an immune-mediated acquired disease that is characterized by a decrease in the platelet count and an increased risk of bleeding. There is little information in the literature about the results of major joint replacement surgery in patients with ITP. The aim of this study was to report on the results of total hip arthroplasty (THA) in patients with primary ITP.MethodsWe retrospectively identified 15 THAs performed in 11 patients with primary ITP. The study group was matched (1:2) to a non-ITP control group of 30 THAs in 22 patients. According to the perioperative hematologic evaluation, blood management interventions were performed. All procedures were performed by a single surgeon and all patients received cementless components with ceramic-on-ceramic bearing. Mean duration of follow-up was 7.1 years (range, 2–13).ResultsNo significant differences were found between the two groups with regard to mean operative time, intraoperative blood loss, amount of closed suction drainage, length of hospital stay, and readmission rate. However, the proportion of patients requiring transfusion of packed red blood cells and/or platelet concentrate was higher in the ITP group when compared to the non-ITP group. Mean Harris hip score improved from 49.5 points preoperatively to 93.4 points at the final follow-up and no hips were revised for loosening or osteolysis in the ITP group. No significant differences were found between the two groups with respect to mean postoperative Harris hip scores and complication rates.ConclusionsOur study showed encouraging clinical and radiographic results of THA in patients with ITP without increased risk of adverse events compared to those in patients without ITP. On the basis of these findings, we suggest that modern cementless THA might be a viable treatment for achieving functional improvement in patients with ITP and end-stage hip disease.

Good long-term results following cementless TKA with a titanium plasma coating.

While cemented total knee arthroplasty (TKA) is currently the gold standard for primary osteoarthritis, cementless component fixation has achieved increasingly comparable outcomes due to improvements in both implant designs and surgical technique. Long-term outcomes and survivorship with the TC-Plus cementless, titanium plasma-coated TKA system without patella resurfacing were evaluated. A homogenous population of 171 consecutive patients who received 206 primary TC-Plus TKAs without patella resurfacing over a 19-year period was retrospectively reviewed. Knee Society Clinical Rating System (KSCRS) scores were obtained, and radiographic evaluation was performed after a mean follow-up of 13.2±8.4years. Survivorship analysis was made with endpoints revision for any reason and aseptic loss of biological fixation. One hundred and thirty-six TKAs implanted in 113 patients were available for analysis. Mean KSCRS clinical and functional scores improved significantly versus preoperative values. No radiological loss of biological fixation of femoral and tibial components was observed. Survival with aseptic revision of any component as the endpoint was 95.7% (95% confidence interval (CI) 91.7-97.9%) and 93.6% (95% CI 87.8-96.6%) at 10 and 15years, respectively. Titanium plasma-coated cementless TKA without patella resurfacing showed excellent long-term results, with high 10- and 15-year component survival rates. The clinical and radiological results were comparable to those of other cementless TKAs, providing further evidence for the non-cemented resurfacing of the osteoarthritic knee. IV.

Early Outcomes of Primary Total Hip Arthroplasty for Osteonecrosis of the Femoral Head in Patients with Human Immunodeficiency Virus in China.

Background:Studies have reported that patients with human immunodeficiency virus (HIV) have a high incidence of osteonecrosis of the femoral head (ONFH). Total hip arthroplasty (THA) is an effective management of ONFH. However, little data exist regarding the use of THA for the HIV patients with ONFH in China. This study reviewed the outcomes of HIV-positive patients who underwent THA for ONFH, compared with HIV-negative individuals.Methods:The patients who underwent THA for ONFH from September 2012 to September 2014 in Beijing Ditan Hospital, Capital Medical University were retrospectively studied. Twenty-eight HIV-positive patients and 35 HIV-negative patients underwent 48 THAs and 45 THAs with cementless components, respectively. Medical records and follow-up data were reviewed. Harris Hip Score (HHS) was applied to evaluate the pain and function of the hips before and after THA. Complications such as wound healing, surgical site infection, deep venous thrombosis, pulmonary embolism, sepsis, mortality, and complications from the prosthesis were reviewed. The operation time, blood loss, and hospital stay were compared between the two groups.Results:The mean follow-up period was 19.5 ± 5.8 months (ranging from 6 to 30 months). The mean age of the HIV-positive patients with osteonecrosis at the time of surgery was 35 years old, which was significantly lower than that of the HIV-negative group (42 years old) (P < 0.05). The HIV-positive patients underwent surgery a mean of 2.5 years after their original symptoms, which was significantly shorter than the HIV-negatives’ (mean 4 years) (P < 0.05). Among HIV-positive patients, the prevalence of being male and rate of bilateral procedures were significantly higher than those in the HIV-negative group (P < 0.05). The operation time in HIV-positive patients was significantly longer than that in HIV-negative patients (P < 0.05). There were no significant differences in blood loss or hospital stay between the two groups (P > 0.05). The HHSs of two groups significantly improved after THAs (P < 0.05), without significant difference between two groups. No wound complication, sepsis, mortality, prosthesis complication, and occupational exposure occurred, except for two cases of heterotopic ossification and one case of humeral head necrosis.Conclusions:ONFH is more likely to occur bilaterally in younger HIV-positive males. The development of osteonecrosis seems faster in HIV-positive patients than in HIV-negative patients. This should be cautionary for asymptomatic HIV-positive patients with low viral RNA level and in the primary HIV stage. Despite longer operation times in the HIV-positive patients than in the HIV-negative patients, THA is still a safe and efficient approach to treat ONFH in HIV-positive patients. The incidence of complications is much lower than previously reported. However, the long-term follow-up is needed.

What Are Risk Factors for Intraoperative Humerus Fractures During Revision Reverse Shoulder Arthroplasty and Do They Influence Outcomes?

With the increase in shoulder arthroplasty rates, the number of perioperative complications, such as periprosthetic fractures, continues to be a rise; however, the risk factors and incidence of intraoperative complications, such as fractures, during revision reverse shoulder arthroplasty are not well established. We evaluated patients receiving a reverse shoulder arthroplasty to determine (1) the frequency and characteristics of intraoperative humerus fractures, (2) the risk factors for fracture, (3) the complications associated with treatment of fractures, and (4) clinical and functional outcomes after treatment. Using one institution's total joint registry, we performed a retrospective analysis of medical records of 224 patients (230 shoulders) who underwent revision surgery to reverse shoulder arthroplasty, from 2005 to 2012, for failed total shoulder arthroplasty. Reverse shoulder arthroplasty was used when there was a deficient rotator cuff, prior instability, or deficient glenoid bone stock. Intraoperative periprosthetic humerus fractures occurred in 36 shoulders (16%) (36 patients). The clinical outcome analysis included 29 patients with a minimum 2-year clinical followup (mean followup, 3.1 years; range, 2.0-6.3 years). The control group consisted of 188 patients (194 shoulders), and it was used for risk-factor calculation; whereas only 150 patients (154 shoulders) in the control group had a minimum 2-year followup, and thus only 150 patients (154 shoulders) made up the comparators (controls) for outcome-analysis comparisons. Risk factors were assessed using univariate analysis with odds ratios (OR), whereas implant survival and complications were assessed using the Kaplan-Meier method. Three displaced and 33 nondisplaced fractures occurred during revision reverse total shoulder arthroplasties. Most of the fractures (81%) occurred during component removal of cemented (n = 11) and cementless (n = 25) components. Intraoperative fractures only were treated with stabilization of the prosthetic stem in 28 patients, while adjunctive internal fixation was used in eight patients. Risk of intraoperative periprosthetic fractures was increased by factors including female sex (n =18 women; OR, 2.41; range, 1.11-5.68; p = 0.03); history of instability (n = 27; OR, 2.65; range, 1.18-5.93; p = 0.02); and prior hemiarthroplasty (n = 22; OR, 2.34; range, 1.13-4.84; p = 0.03). There were two postoperative fractures in patients who had an intraoperative fracture and both were treated nonoperatively. Overall, three (8%) revision procedures were performed in patients with intraoperative fractures, with 2- and 5-year survivorship estimates of 94% and 85%, respectively, compared with 89% and 84%, respectively for patients without an intraoperative fracture (p = 0.45). At latest followup, patients experienced good postoperative pain relief, improved shoulder abduction, and good American Shoulder and Elbow Surgeon and Simple Shoulder Test scores. Intraoperative humeral fractures occur in approximately 16% of shoulders undergoing revision surgery. Fractures during revision reverse TSA are not uncommon secondary to the risks of component removal in revision surgery and poor remaining bone stock. The risk seems to be greatest for female patients, patients with instability, and patients who have undergone previous hemiarthroplasties. Intraoperative humeral fractures should be approached in a systematic way to achieve anatomic reduction and stable fixation. When properly stabilized, these fractures appear not to substantially influence overall final outcome. This study provides a foundation for future investigation of methods to reduce the risk for intraoperative humeral fractures attributable to reverse revision TSA. Level III, therapeutic study.

CORR Insights(®): Do Rerevision Rates Differ After First-time Revision of Primary THA With a Cemented and Cementless Femoral Component?

T he lack of consensus regarding the best method of component fixation in primary total hip replacement reflects the complexity of the issue. In addition to method of fixation, multiple factors such as implant characteristics, surgical technique, patient demography and comorbidities affect the outcomes in terms of implant survival, pattern of prosthesis-related complications, and functional outcomes. Although some registry data suggest superior implant survival for cemented fixation [4, 5], other registry data show similar revision rates regardless of method of fixation at primary surgery [7]. Nevertheless, there is an increasing use of cementless fixation in primary total hip replacement worldwide even though support for this approach is not unanimous [4, 5, 8]. Since the pattern of implant failure and structural damage differ depending on primary method of fixation, implant survival after revision surgery could potentially differ for cemented and cementless components. While previous research [3, 6] has focused on different revision techniques, to our knowledge, the role of primary fixation in revision outcomes has not been investigated. Using data on first time revision cases from the Danish Hip Arthroplasty Register [1], the current study by Gromov and colleagues aimed to investigate the association between method of femoral component fixation in the primary total hip replacement and the risk of subsequent rerevision. Gromov and colleagues found that in patients younger than 70 years of age, cementless fixation at the time of index arthroplasty was associated with an increased likelihood of repeat revision surgery, even after controlling for potential confounding variables, This CORR Insights is a commentary on the article ‘‘Do Rerevision Rates Differ After First-time Revision of Primary THA With a Cemented and Cementless Femoral Component?’’ by Gromov and colleagues available at: DOI: 10.1007/s11999-015-42456. The author certifies that he, or any member of his immediate family, has no funding or commercial associations (eg, consultancies, stock ownership, equity interest, patent/ licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request. The opinions expressed are those of the writers, and do not reflect the opinion or policy of CORR or the Association of Bone and Joint Surgeons. This CORR Insights comment refers to the article available at DOI: 10.1007/s11999-0154245-6. O. Rolfson MD, PhD Department of Orthopaedics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden

Validation of a computer-assisted method for measurement of radiographic wear in total hip arthroplasty using all polyethylene cemented acetabular components.

Although cemented all polyethylene (PE) cups have been routinely used in total hip arthroplasty for decades, no computer-assisted method for measurement of radiographic wear has ever been specifically validated for these implants. Using a validated hip phantom model, AP plain hip radiographs were obtained consecutively for eight simulated wear positions. A version of Martell's Hip Analysis Suite software dedicated to all polyethylene sockets was used by three different examiners of varied experience. Bias (mean, standard deviation and 95% confidence interval limit), repeatability (standard deviation and 95% limit) and reproducibility (standard deviation and 95% limit) for two-dimensional wear measurements were assessed, as recommended by the current ASTM guidelines. Using this protocol, the dedicated software showed an overall mean bias of 0.089 ± 0.060 mm (mean ± SD), and 0.118 mm for 95% CI limit. Repeatability (intra examiner) standard deviation and 95% limit were respectively 0.106 mm and 0.292 mm. Reproducibility (inter examiner) standard deviation and 95% limit were respectively 0.112 mm and 0.308 mm. Martell Hip Analysis for all PE cemented cups is a reliable and low-cost instrument in the assessment of wear, despite being less precise than its original version dedicated to cementless components.

Intraoperative periprosthetic hip fractures

Purpose The aim of this work was to study the risk factors, clinical results, particularly the functional outcome, and radiological results for intraoperative periprosthetic fractures (PPFs) around hip arthroplasties through a retrospective analysis. Materials and methods We conducted a retrospective study based on hospital records. Patients with intraoperative PPFs around hip arthroplasties who underwent follow-up for at least 9 months were enrolled in the study. For each patient, preoperative and intraoperative risk factors were analyzed; the functional outcome in terms of the Harris hip score was compared before fracture and at the last follow-up. Results Fifteen cases were enrolled in this study. Six male and nine female patients were included with a mean ± SD age of 57.2 ± 8.5 years. A mean follow-up of 15.2 months was achieved. The average Harris hip score at the last follow-up was 85.7 points. All cases obtained primary bony union. The mean time from surgery to bony union was 8.3 months, ranging 3-12 months. Conclusion Female patients are at a higher risk of intraoperative PPF; in addition, significant femoral deformity and osteopenia are estimated risk factors. Cortical perforations and bone defects along with previously existing osteotomies are the other risk factors. Revision surgeries, cementless components, straight long stem, and vigorous manipulation of the femur are the surgery-related risk factors detected. Component stability is the most important factor for intraoperative decision-making. Extended trochanteric osteotomy is a safe and useful procedure, especially when using long straight stems. In addition, the use of supplementary cerclage fixation of fracture fragments for Vancouver B fractures yields better results.

Early Results of a Modular Cementless Tibial Component for Total Knee Arthroplasty

Cementless components in TKA have been used for almost 3 decades, despite mixed success rates. However, biologic fixation remains attractive, especially for younger patients, because of the potential of unlimited durability. This paper is the first to report results on a modular tibial base plate using trabecular metal as a fixation surface. Twenty-four primary TKAs were evaluated clinical and radiographically at mean 1.9 year followup. Excellent clinical results were obtained. There was no significant subsidence or change in orientation of any component. One component was probably loose radiographically but was insufficiently symptomatic to warrant revision. Five components showed nonprogressive radiolucent lines. One reoperation was performed for stiffness, at which time the components were well fixed. Thus, it would appear that excellent bony fixation can be achieved with a modular cementless tibial component with excellent short-term clinical results.

Early Results of a Modular Cementless Tibial Component for Total Knee Arthroplasty

Cementless components in TKA have been used for almost 3 decades, despite mixed success rates. However, biologic fixation remains attractive, especially for younger patients, because of the potential of unlimited durability. This paper is the first to report results on a modular tibial base plate using trabecular metal as a fixation surface. Twenty-four primary TKAs were evaluated clinical and radiographically at mean 1.9 year followup. Excellent clinical results were obtained. There was no significant subsidence or change in orientation of any component. One component was probably loose radiographically but was insufficiently symptomatic to warrant revision. Five components showed nonprogressive radiolucent lines. One reoperation was performed for stiffness, at which time the components were well fixed. Thus, it would appear that excellent bony fixation can be achieved with a modular cementless tibial component with excellent short-term clinical results.

CORR Insights®: the Mark Coventry Award: Trabecular metal tibial components were durable and reliable in primary total knee arthroplasty: a randomized clinical trial.

CORR Insights®: the Mark Coventry Award: Trabecular metal tibial components were durable and reliable in primary total knee arthroplasty: a randomized clinical trial.

Loosely Implanted Cementless Stems May Become Rotationally Stable After Loading

Experimental studies have suggested that initial micromotion of cementless components may lead to failure of osteointegration. Roentgen stereophotogrammetric analyses have shown durable implant fixation can be achieved long-term even when initial instability exists, as evidenced by subsidence. However improved implant stability as a result of subsidence, before osteointegration, has not been shown biomechanically. We asked whether insertionally loose cementless tapered femoral stems show (1) less rotational stability (more toggle); (2) more subsidence; and (3) reduced ability to resist torsion (lower initial construct stiffness), lower torque at failure, and greater rotation to failure in comparison to well-fixed cementless tapered femoral stems. Ten matched pairs of cadaveric femurs were implanted with well-fixed and loose cementless tapered stems. The loose stem construct was obtained by appropriately broaching the femur but afterwards inserting a stem one size smaller than that broached. Femoral stem rotational stability of implanted femurs was tested by measuring the angular rotation (ie, toggle) required to produce a torque of 2N-m at 0N, 250N, and 500N vertical load in 25° adduction simulating single-legged stance. Subsidence was measured as vertical movement during the toggle tests. Then at 500N initial vertical load, femoral stems were externally rotated to failure. The construct stiffness between 5 and 40N-m was determined to assess ability to resist torsion. The torque and rotation to failure were recorded to compare failure characteristics. Groups were compared using mixed model ANOVA followed by Tukey-Kramer post hoc pairwise comparison for toggle and subsidence tests and by Student's paired t-tests for stiffness, torque at failure, and rotation to failure tests. Loose tapered cementless stems were less stable (ie, more toggle) than well-fixed at 0N of load (p<0.0001), but no difference was detectable in toggle between loose and well-fixed stems at 250N (p=0.7019) and 500N (p=0.9970). Loose tapered cementless stems showed significant subsidence at 250N (p<0.0001) and 500N (p<0.0001), which was not found in the well-fixed stems at 250N (p=0.8813) and 500N (p=0.1621). Torsional stiffness was lower for loose stems as compared with well-fixed stems (p=0.0033). No difference in torque at failure (p=0.7568) or rotation to failure (p=0.2629) was detected between loose and well-fixed stems. In this study, we observed that insertionally loose cementless stems have the ability to subside and become rotationally stable with loading. They did not exhibit a lower torque or rotation to failure in comparison to well-fixed stems when under simulated single-legged stance. Secondary rotational stabilization may prevent insertionally loose tapered stems from producing a stress pattern that predisposes to early postoperative periprosthetic fracture around loose cemented stems.

Stable fixation of the IBP humeral component implanted without cement in total elbow replacement

We determined the short-term clinical outcome and migration within the bone of the humeral cementless component of the Instrumented Bone Preserving (IBP) total elbow replacement in a series of 16 patients. There were four men and 12 women with a mean age at operation of 63 years (40 to 81). Migration was calculated using radiostereometric analysis. There were no intra-operative complications and no revisions. At two-year follow-up, all patients showed a significant reduction in pain and functional improvement of the elbow (both p < 0.001). Although ten components (63%) showed movement or micromovement during the first six weeks, 14 (88%) were stable at one year post-operatively. Translation was primarily found in the proximal direction (median 0.3 mm (interquartile range (IQR) -0.09 to 0.8); the major rotational movement was an anterior tilt (median 0.7° (IQR 0.4° to 1.6°)). One malaligned component continued to migrate during the second year, and one component could not be followed beyond three months because migration had caused the markers to break off the prosthesis. This study shows promising early results for the cementless humeral component of the IBP total elbow replacement. All patients had a good clinical outcome, and most components stabilised within six months of the operation.

Finite element analysis of retroacetabular osteolytic defects following total hip replacement

Periprosthetic osteolysis in the retroacetabular region with cancellous bone loss is a recognized phenomenon in the long-term follow-up of total hip replacement. The effects on load transfer in the presence of defects are less well known. A finite element model incorporating a retroacetabular defect behind a cementless component was validated against a 4th generation sawbone pelvis. Computational predictions of surface strain and von Mises stresses were closely correlated to experimental findings. The presence of a cancellous defect increased von Mises stress in the cortical bone of the medial wall of the pelvis. At a load of 600N this was under the predicted failure stress for cortical bone. Increases in the cup size relative to the acetabulum caused increased stress in the cortical bone of the lateral wall of the pelvis, adjacent to the acetabulum. We are confident that our modeling approach can be applied to patient specific defects to predict pelvis stress with large loads and a range of activities.