The management of bone loss in revision total knee replacement

In vitro and in vivo evaluation of the osseointegration capacity of a polycarbonate-urethane zirconium-oxide composite material for application in a focal knee resurfacing implant

Currently available focal knee resurfacing implants (FKRIs) are fully or partially composed of metals, which show a large disparity in elastic modulus relative to bone and cartilage tissue. Although titanium is known for its excellent osseointegration, the application in FKRIs can lead to potential stress-shielding and metal implants can cause degeneration of the opposing articulating cartilage due to the high resulting contact stresses. Furthermore, metal implants do not allow for follow-up using magnetic resonance imaging (MRI).To overcome the drawbacks of using metal based FKRIs, a biomimetic and MRI compatible bi-layered non-resorbable thermoplastic polycarbonate-urethane (PCU)-based FKRI was developed. The objective of this preclinical study was to evaluate the mechanical properties, biocompatibility and osteoconduction of a novel Bionate® 75D - zirconium oxide (B75D-ZrO2) composite material in vitro and the osseointegration of a B75D-ZrO2 composite stem PCU implant in a caprine animal model. The tensile strength and elastic modulus of the B75D-ZrO2 composite were characterized through in vitro mechanical tests under ambient and physiological conditions. In vitro biocompatibility and osteoconductivity were evaluated by exposing human mesenchymal stem cells to the B75D-ZrO2 composite and culturing the cells under osteogenic conditions. Cell activity and mineralization were assessed and compared to Bionate® 75D (B75D) and titanium disks. The in vivo osseointegration of implants containing a B75D-ZrO2 stem was compared to implants with a B75D stem and titanium stem in a caprine large animal model. After a follow-up of 6 months, bone histomorphometry was performed to assess the bone-to-implant contact area (BIC). Mechanical testing showed that the B75D-ZrO2 composite material possesses an elastic modulus in the range of the elastic modulus reported for trabecular bone. The B75D-ZrO2 composite material facilitated cell mediated mineralization to a comparable extent as titanium. A significantly higher bone-to-implant contact (BIC) score was observed in the B75D-ZrO2 implants compared to the B75D implants. The BIC of B75D-ZrO2 implants was not significantly different compared to titanium implants. A biocompatible B75D-ZrO2 composite approximating the elastic modulus of trabecular bone was developed by compounding B75D with zirconium oxide. In vivo evaluation showed an significant increase of osseointegration for B75D-ZrO2 composite stem implants compared to B75D polymer stem PCU implants. The osseointegration of B75D-ZrO2 composite stem PCU implants was not significantly different in comparison to analogous titanium stem metal implants.

Biomechanical evaluation of screw and cement placement strategies for treating medial uncontained tibial defects in total knee arthroplasty: A finite element analysis

Total knee arthroplasty faces challenges in the management of medial uncontained tibial defects, affecting prosthesis stability and implant survival. The use of screws and bone cement is a preferred approach; however, optimal screw insertion techniques lack consensus in the existing literature. The present study aimed to address this gap by exploring optimal screw and cement placement strategies, focusing on their biomechanical implications. The present study conducted a finite element analysis using a knee prosthesis model with a defined uncontained tibial defect. Various parameters were systematically adjusted, including the number of screws (1, 2 or 3 screws), screw lengths (10, 18, 30 or 40 mm), lateral-medial screw positions (2, 4 or 6 mm laterally) and abduction rotation angles (0, 5, 10 or 15 degrees). These adjustments were made to evaluate their specific and combined impacts on the vertical displacement and abduction angles of the tibial tray. The results revealed that incorporating three-screw reinforcement markedly reduced vertical displacement, while the single screw in the middle position exhibited superior performance in preventing the deformation of abduction angles compared to scenarios with two screws at anterior and posterior positions without a middle screw. Longer screws and smaller abduction angles contributed to decreased movement of the tibial component. Furthermore, the lateral adjustment of the screw position led to an increase in vertical displacement values, reaching ~1.5% when shifted 6 mm laterally. On the whole, the finite element analysis in the present study suggests that, for the treatment of medial uncontained tibial defects, three-screw reinforcement is advantageous for larger defects. Longer screws and a smaller abduction angle are deemed favorable. Moreover, the results underscore the superiority of medial screw placement over lateral placement. It is imperative to note that further clinical validation is essential to corroborate the biomechanical implications observed herein.

Autogenous structural bone graft reconstruction of ≥ 10-mm-deep uncontained medial proximal tibial defects in primary total knee arthroplasty

BACKGROUND

Management of uncontained medial proximal tibial defects during primary total knee arthroplasty (TKA) can be challenging, especially for defects ≥ 10 mm in depth. This study sought to assess the outcomes of autogenous structural bone grafts to address these defects.

MATERIALS AND METHODS

In this prospective study, patients with uncontained medial proximal tibial defects ≥ 10 mm in depth undergoing TKA were managed by autogenous structural bone grafts fixed by screws and were followed up for at least 36 months. Patients were followed-up clinically with Knee Society Score (KSS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Additionally, radiological follow-up was done to assess bone graft union and implant stability.

RESULTS

The study included 48 patients with a mean age of 69.2 ± 4.5 years. The mean body mass index (BMI) was 31.4 ± 3.7 kg/m2. The mean defect depth was 17 ± 3.6 mm. With a mean follow-up period of 52.2 ± 12.3 months, the median KSS improved significantly from 30 preoperatively to 89, P < 0.001. The median WOMAC score reduced significantly from 85 preoperatively to 30.5, P < 0.001. The mean ROM increased significantly from 73 ± 12.4 preoperatively to 124 ± 8.4 degrees, P < 0.001. The mean graft union time was 4.9 ± 1 months. No significant complications were reported.

CONCLUSIONS

Autogenous bone graft reconstruction is a safe and effective method of addressing uncontained medial proximal tibial defects in primary TKA.

LEVEL OF EVIDENCE

Level IV.

Using acoustic feedback and analyses for removal of bone cement during revision knee replacement surgeries

PURPOSE

The purpose of this study was to analyze the scraping sounds generated during revision knee replacement surgeries to discriminate between the inner cortical bone and the cement, with the goal of minimizing bone removal and increasing the structural integrity of the revision.

METHODS

We prepared seven porcine femurs by partially filling them with bone cement, and recorded scraping sounds produced by a surgical scraping tool. We used a hierarchical machine learning approach to first detect a contact and then classify it as either bone or cement. This approach was based on a Support Vector Machine learning algorithm that was fed with temporal and spectral features of the sounds. A Leave-One-Bone-Out validation method was used to assess the performance of the proposed method.

RESULTS

The average recall for the noncontact, bone, and cement classes was 98%, 75%, and 72%, respectively. The corresponding precision for the respective classes was 99%, 67%, and 61%.

CONCLUSION

The scraping sound that is generated during revision replacement surgeries carries significant information about the material that is being scraped. Such information can be extracted using a supervised machine learning algorithm. The scraping sound produced during revision replacement procedures can potentially be used to enhance cement removal during knee revision surgery. Future work will assess whether such monitoring can increase the structural integrity of the revision.

How metal augments, polyethylene thickness and stem length affect tibial baseplate load transfer in revision total knee arthroplasty

BACKGROUND

It is unclear howmetal augments,polyethylene (PE) liner thickness, and length of cemented stemcontribute to load transferwhen reconstructing uncontained tibial metaphyseal bone loss of Anderson Orthopedic Research Institute (AORI) Type II defects during revision total knee arthroplasty (rTKA).The aimof this study is to understand the impact of these three variableson load transfer through the tibial baseplate. For a fixed defect depth, we hypothesized that there is a particular combination of liner and augment thickness and stem length that minimizes bone stress, reducing the risk of aseptic loosening.

METHODS

We conducted a finite element analysis (FEA) to model stresses at the bone-cement interface with different iterations of metal augments, PE liner thicknesses andfully-cemented stems lengths.

RESULTS

For a 20 mm tibial defect, constructs with thicker metal augments and thinner polyethylene liners were superior. Constructswith a fully cemented stem further reduced bone stress on the tibial plateau. Bone stress was lowest when a 100 mm fully-cemented stem was used, while stems between 30 mm - 80 mm produced similar results.

CONCLUSIONS

When addressing a tibial bone defect of AORI Type II in rTKA, our FEA model demonstrates that surgeons should opt to use the thickest metal augments in combination with afully-cemented stem with an added length of at least 30 mm, which allows for surgical flexibility together with the most stable construct.Our study is notably limited by lack of modeling of knee joint moments, which are important when considering micromotion, bone-implant interface and stem effectiveness.

Cementless Porous-Coated Metaphyseal Sleeves Used for Bone Defects in Revision Total Knee Arthroplasty: Short- to Mid-Term Outcomes

OBJECTIVES

While many studies have presented excellent short-term outcomes of the metaphyseal sleeves used in revision total knee arthroplasty (TKA), currently published mid-term results remain limited and some controversial issues remain unresolved. The purpose of this study was to investigate clinical and radiographic mid-term outcomes of the sleeves for the management of metaphyseal bone defects in revision TKAs.

METHODS

From 2015 to 2019, 44 patients (45 knees) who were operated with cementless porous-coated metaphyseal sleeve in revision TKA were included in this study. Bone defects were assessed according to Anderson Orthopaedic Research Institute Classification. On the tibial side, there were 37 type II and six type III, and with regards to the femur, 15 were type II, and four were type III. Through reviewing electronic records, data were collected, including baseline demographics, operative details, information of prothesis, and complications. Clinical and radiographic evaluations were performed, including Knee Society Scores (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), range of motion (ROM), the radiolucent line, level of joint line, and implant survival rate. Statistical analysis was performed by paired t-test for clinical and radiographic indexes.

RESULTS

The mean follow-up time was 4.4 ± 1.4 years. During surgery, sleeve-related fractures were encountered in four (8.9%) knees, including incomplete tibial fracture of lateral cortex in one knee and of medial cortex in two knees, and longitudinal femoral metaphyseal fracture in one knee. Unions were achieved in all cases at the final follow-up. Significant improvements in KSS and WOMAC scores were found at the final follow-up, respectively, from 83.8 ± 29.1 to 152.9 ± 31.0 (t = -12.146, p < 0.001) and from 148.4 ± 42.3 to 88.1 ± 52.5 (t = 6.025, p < 0.001). The mean ROM improved from 88.7 ± 31.9° to 113.7 ± 13.7° (t = -5.370, p < 0.001). A 75 mm length of cementless stem was used in all patients and only one patient was identified as tibial end-of-stem pain. No sleeve-related revision occurred, and one patient was diagnosed with early postoperative infection and was treated with irrigation and debridement, polyethylene liner exchange, and appropriate antibiotic treatment. The overall implant survival was 97.8% with the endpoint reoperation and 100% with the endpoint revision. Osseointegration at the bone-sleeve interface was found in all patients and no loosening happened. Satisfactory alignment between 3° varus and 3° valgus was achieved in all but not in three patients.

CONCLUSION

The use of metaphyseal sleeves in the treatment of bone defects in rTKAs can provide stable fixation and significantly improve the clinical scores at the midterm follow-up. In addition, the rare occurrence of end-of-stem pain suggests routine use of cementless stems. Although there are chances of intraoperative fractures, it has no negative effect on outcome when managed properly.

Biomechanical Effects of Stemmed Total Knee Arthroplasty on the Human Femur: A CT-Data Based Study

End-of-stem pain of the femur is a common problem in revision total knee arthroplasty (TKA). It may be caused by a problematic interaction between stem and bone, but the exact biomechanical correlate is still unknown. The aim of this prospective study was to find out how the stem is positioned in the medullary canal, how the femoral geometry changes due to implantation, and whether the results are influenced by the diameter of the trial. We implanted 16 rotating hinge knee implants into 16 fresh-frozen human femora using the hybrid fixation technique and comparing two reaming protocols. We created 3-dimensional models of the specimens before and after implantation using CT-scans and calculated the differences. The main contact between stem and bone was found at the proximal 30 mm of the stem, especially anterior. We observed two different contact patterns of stem and bone. The cortical thickness was reduced especially at the anterior tip of the stem with a maximum reduction of 1405 ± 501 μm in the standard group and 980 ± 447 μm in the small_trial group, which is a relative reduction of 34 ± 14% (standard group) and 26 ± 14% (small_trial group). The bone experienced a deformation to posterior and lateral. We conclude that the tip of the stem is an important biomechanical region. Different contact patterns between stem and bone as well as the reduction in cortical thickness at the tip of the stem may play a role in the development of end-of-stem pain.

Tibial metaphyseal cones combined with short stems perform as well as long stems in revision total knee arthroplasty

Backgrounds

There is uncertainty around optimal tibial stem length in revision total knee arthroplasty (rTKA) utilizing a tibial trabecular metal (TM) cone. The purpose of this study was to compare: (1) functional outcomes, (2) radiographic outcomes and (3) implant survivorship in rTKA utilizing TM cones combined with either short stems (SS) or long stems (LS) at minimum 2 years follow‐up.

Methods

In this retrospective, multi‐centre study, patients undergoing rTKA utilizing a TM cone between 2008 and 2019 were included. Patients were divided into: SS group (no diaphyseal engagement), and LS group (diaphyseal engagement). All relevant clinical charts and post‐operative radiographs were examined. Oxford Knee Score (OKS) and EuroQol‐5D (EQ‐5D‐5L) data were collected at most recent follow‐up.

Results

In total, 44 patients were included: 18 in the SS group and 26 in the LS group. The mean time of follow‐up was 4.0 years. Failure free survival was 94.4% for the SS group and 92.3% for the LS group. All failures were for prosthetic joint infections managed with debridement, antibiotics, and implant retention. At most recent follow‐up, 3 patients demonstrated radiographic signs of lucency (1 SS 2 LS, P = 1) and the mean OKS were 37 ± 4 and 36 ± 6 (P = 0.73) in the SS and LS groups, respectively.

Conclusion

Tibial SS combined with TM cones performed as well as LS in rTKA at minimum 2 years follow‐up. A tibial SS in combination with a TM cone is a reliable technique to achieve stable and durable fixation in rTKA.

Reoperações e resultados radiográficos de médio prazo do uso de cone de metal trabecular de tântalo nas artroplastias do joelho

Objetivo O manejo da perda óssea representa um grande desafio em cirurgias de revisão de artroplastia do joelho (rATJ) e em artroplastias totais do joelho (ATJ) primárias complexas. O objetivo do presente estudo foi avaliar os resultados em médio prazo (seguimento mínimo de 5 anos) das reconstruções de joelho nas quais cones de metal trabecular (MT) de tântalo foram utilizados para tratamento de defeitos ósseos tipos 2 e 3, de acordo com a classificação proposta pela Anderson Orthopaedic Research Institute (AORI).

Métodos Feita análise retrospectiva dos prontuários dos pacientes operados entre julho de 2008 e novembro de 2014, coletando-se os seguintes dados: idade, gênero, lateralidade, índice de massa corporal, etiologia da artrose, comorbidade, classificação AORI da falha óssea, causa da revisão da artroplastia total do joelho, reinternações, reoperações, complicações peri- e pós-operatórias, ocorrência de osteointegração radiográfica e manutenção da função de suporte do MT.

Resultados Foram avaliados 11 pacientes com tempo médio de seguimento de 7,28 anos (desvio padrão [DP] = 1,88; variação = 5,12–10 anos), sendo que 1 paciente foi submetido a artroplastia primária, 6 a artroplastia de revisão e 4 a segunda revisão de artroplastia (re-revisão). Três pacientes necessitaram de quatro reoperações devido a complicações com a ferida operatória, a lesão do mecanismo extensor e a soltura do componente femoral. Sinais de osteointegração dos cones trabeculados foram observados em todos os pacientes. Não observamos migração do cone de MT ou dos componentes protéticos.

Conclusão Os cones metafisários de tântalo foram capazes de prover suporte estrutural eficiente aos implantes protéticos com sinais radiográficos de osteointegração em médio prazo.

Tibial Stem Extension versus Standard Configuration in Total Knee Arthroplasty: A Biomechanical Assessment According to Bone Properties

Background and Objectives: This study’s purpose was to examine the benefit of using a tibial extension in the primary operation of total knee arthroplasty (TKA). This is important because it is not a common practice to use the extension in a primary TKA, a standard configuration offering sufficient stability and good long-term survivorship. The following question arises: which situation requires the use of a standard configuration implant (without a stem) and which situation requires using the extension? Materials and Methods: The opportunity to use the tibial extension in the primary TKA was analyzed in correlation to the tibial bone structural properties. Using finite elements (FEs), the virtual model of the tibial bone was connected to that of the prosthetic implant, with and without a stem, and its behavior was analyzed during static and dynamic stresses, both in the situation in which the bone had normal physical properties, as well as in the case in which the bone had diminished physical properties. Results: The maximum stress and displacement values in the static compression regime show that adding a stem is only beneficial to structurally altered bone. Compression fatigue was reduced to almost half in the case of altered bone when adding a stem. Dynamic compression showed slightly better results with the tibial stem in both healthy and degraded bone. Conclusions: It was concluded that, if the bone is healthy and has good structural properties, it is not necessary to use the tibial extension in the primary operation; and if the bone has diminished physical properties, it is necessary to use the tibial extension at the primary operation, enhancing the stability, fixation, and implant lifespan.

Mid-term results of complex primary total knee arthroplasty using a rotating-hinge implant

BACKGROUND

The indications and outcomes of semi- or fully-constrained knee implants in primary total knee arthroplasty (TKA) are still controversially discussed. The present study aims to evaluate the mid-term results and complications of a modular/non-modular rotating-hinge implant in complex primary TKA.

METHODS

Eighty-two patients (86 knees) following primary TKA were retrospectively evaluated with a mean follow-up of 63 months. The functional outcome was assessed using the American Knee Society Score (AKSS) and the Oxford Knee Score (OKS). A Visual Analog Scale (VAS) was used to determine pain levels. Implant survival and reoperation rateswere estimated using competing risk analysis. Cox regression analysis wasperformed to evaluate the influence of modularity on implant survival.

RESULTS

The survival rate with the endpoint implant revision was 90% (95 %CI:83-98%) and the survival rate with the endpoint all reoperations was 84% (95 %CI:75-94%) at 7 years. The AKSS improved significantly from 24 (SD 14.9, range:0-69) preoperatively to 83 (SD 14.3, range:57-100) postoperatively (p < 0.001); functional AKSS improved significantly from 27 (SD 24.3, range:0-100) to 46 (SD: 32.9, range 0-100) (p = 0.003), and OKS from 19 (SD: 8.3, range:5-43) to 29 (SD: 10.7, range:6-48), respectively (p < 0.0001). VAS decreased significantly from 8 (SD: 2.6, range:0-10) preoperatively to 3 (SD: 2.9, range:0-9) postoperatively (p < 0.0001). There was no significant influence of modularity on revision rates comparing modular to non-modular implants (p = 0.072).

CONCLUSIONS

The present rotating-hinge implant provides substantial improvement in function and reduction of pain with good implant survival in the mid-term. Modularity was not associated with higher rates of revision.

[Bone defect management in revision knee arthroplasty]

BACKGROUND

In 2019, 124,677 primary total knee arthroplasties and 14,462 revision TKA were performed in Germany. This corresponds to a percentage of 11.6%. According to the EPRD, the probability of further revision surgery after the first exchange operation is around 15%.

REASONS

The most common reason for revision surgery is still aseptic loosening with 23.9%. One possible cause could be the difficult fixation of revision total knee arthroplasty. If the bone quality is insufficient, cement-free or cemented diaphyseal anchoring of the prosthesis is often not sufficient to ensure adequate fixation. As a rule, defect management and fixation of the implant are based on the defect situation and the quality of the bone. Therefore, revision total knee arthroplasties based on the fixation principle of Jones et al. should be sufficiently fixed in at least 2 zones.

TECHNIQUES

There are various techniques for stable anchoring of revision implants. In addition to cemented or cementless stem anchoring, bone allografts, wedges and blocks and, in recent years, cones and sleeves have become increasingly popular. In the present work, the various options for a stable anchoring of revision implants are presented and evaluated. In addition, the clinical and radiological outcome of cones vs. sleeves in bone defect management in revision knee arthroplasty will be compared.

Comparative Evaluation of Two Glass Polyalkenoate Cements: An In Vivo Pilot Study Using a Sheep Model

Poly(methyl methacrylate) (PMMA) is used to manage bone loss in revision total knee arthroplasty (rTKA). However, the application of PMMA has been associated with complications such as volumetric shrinkage, necrosis, wear debris, and loosening. Glass polyalkenoate cements (GPCs) have potential bone cementation applications. Unlike PMMA, GPC does not undergo volumetric shrinkage, adheres chemically to bone, and does not undergo an exothermic setting reaction. In this study, two different compositions of GPCs (GPCA and GPCB), based on the patented glass system SiO₂-CaO-SrO-P₂O₅-Ta₂O₅, were investigated. Working and setting times, pH, ion release, compressive strength, and cytotoxicity of each composition were assessed, and based on the results of these tests, three sets of samples from GPCA were implanted into the distal femur and proximal tibia of three sheep (alongside PMMA as control). Clinical CT scans and micro-CT images obtained at 0, 6, and 12 weeks revealed the varied radiological responses of sheep bone to GPCA. One GPCA sample (implanted in the sheep for 12 weeks) was characterized with no bone resorption. Furthermore, a continuous bone-cement interface was observed in the CT images of this sample. The other implanted GPCA showed a thin radiolucent border at six weeks, indicating some bone resorption occurred. The third sample showed extensive bone resorption at both six and 12 weeks. Possible speculative factors that might be involved in the varied response can be: excessive Zn²⁺ ion release, low pH, mixing variability, and difficulty in inserting the samples into different parts of the sheep bone.

Aseptic Loosening of Porous Metaphyseal Sleeves and Tantalum Cones in Revision Total Knee Arthroplasty: A Systematic Review

Bone loss often complicates revision total knee arthroplasty (TKA). Management of metaphyseal defects varies, with no clearly superior technique. Two commonly utilized options for metaphyseal defect management include porous-coated metaphyseal sleeves and tantalum cones. A systematic review was conducted according to the international Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We combined search terms "Total knee arthroplasty" AND/OR "Sleeve," "Cone" as either keywords or medical subject heading (MeSH) terms in multiple databases according to PRISMA recommendations. All retrieved articles were reviewed and assessed using defined inclusion and exclusion criteria. A total of 27 studies (12 sleeves and 15 cones) of revision TKAs were included. In the 12 studies on sleeve implantation in revision TKAs, 1,617 sleeves were implanted in 1,133 revision TKAs in 1,025 patients. The overall rate of reoperation was 110/1,133 (9.7%) and the total rate of aseptic loosening per sleeve was 13/1,617 (0.8%). In the 15 studies on tantalum cone implantation in revision TKAs, 701 cones were implanted into 620 revision TKAs in 612 patients. The overall rate of reoperation was 116/620 (18.7%), and the overall rate of aseptic loosening per cone was 12/701 (1.7%). Rates of aseptic loosening of the two implants were found to be similar, while the rate of reoperation was nearly double in revision TKAs utilizing tantalum cones. Variability in the selected studies and the likely multifactorial nature of failure do not allow for any definitive conclusions to be made. This review elucidates the necessity for additional literature examining revision TKA implants.

Comparative Biomechanical In Vitro Study of Different Modular Total Knee Arthroplasty Revision Stems With Bone Defects

BACKGROUND

The aim of this study is to investigate the effects of different stem lengths and types including cones on primary stability in revision total knee arthroplasty with different femoral bone defects and fixation methods in order to maximize bone preservation. It is hypothesized that longer stems provide little additional mechanical stability.

METHODS

Thirty-five human femurs were investigated. A distal bone defect, Anderson Orthopedic Research Institute classification (s. 33) type-F2a, was created in group 1-3 and type-F3 in group 4-6. A cemented, rotating hinge femoral component was combined with different stems (100 and 160 mm total or hybrid cemented cones, or a 100-mm custom-made anatomical cone stem). The femora were loaded according to in vivo loading during gait. Relative movements were measured to investigate primary stability. Pull-out testing was used to obtain a parameter for the primary stability of the construct.

RESULTS

Relative movements were small and similar in all groups (<40 μm). For small defect, the pull-out forces of cemented long (4583 N) and short stems (4650 N) were similar and about twice as high as those of uncemented stems (2221 N). For large defects, short cemented stems with cones showed the highest pull-out forces (5500 N). Long uncemented stems (3324 N) and anatomical cone stems (3990 N) showed similar pull-out forces.

CONCLUSION

All tested stems showed small relative movements. Long cemented stems show no advantages to short cemented stems in small bone defects. The use of cones or an anatomical cone stem with hybrid cementation seems to offer good stability even for larger bone defects. The use of a short cemented stem (with or without cone) may be a suitable choice with a high potential for bone preservation in total knee arthroplasty revision with respective bone defects.

Provision of revision knee surgery and calculation of the effect of a network service reconfiguration: An analysis from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man

BACKGROUND

Revision knee replacement (KR) is technically challenging, expensive, and outcomes can be poor. It is well established that increasing surgeon and unit volumes results in improved outcomes and cost-effectiveness for complex procedures. The aim of this study was to 1) describe the current provision of revision KR in England, Wales and Northern Ireland at the individual surgeon and unit level and 2) investigate the effect on workload of case distribution in a network model.

METHODS

Current practice was mapped using NJR summary statistics containing all revision KR procedures performed over a three-year period (2016-2018). Units were identified as revision centres based on threshold volumes. Units undertaking <20 revisions per year were classified as Primary Arthroplasty Units (PAUs) in calculations on the effect of workload centralisation.

RESULTS

Revision KR was performed by 1353 surgeons at 232 NHS sites. The majority of surgeons and units were low-volume; >1000 surgeons performed <7 and 125 sites performed <20 procedures per year. Reallocation of work from these 125 PAUs (1235 cases, 21% of total workload) to a network model with even redistribution of cases between centres undertaking revision surgery would result in an additional average annual case increase of 11 per unit per year (range six to 14).

CONCLUSIONS

Revision KR workload re-allocation would lift all revision centres above a 30 per year threshold and would appear to be a manageable increase in workload for specialist revision KR centres. Case complexity and local referral agreements will significantly affect the real increase in workload; these factors were not incorporated here.

Bone Defects in Revision Total Knee Arthroplasty

The increase in the number of revision total knee arthroplasty surgeries has been observed in recent years, worldwide, for several causes. In the United States, a 601% increase in the number of total knee arthroplasties, between 2005 and 2030, is estimated. Among the enormous challenges of this complex surgery, the adequate treatment of bone defects is essential to obtain satisfactory and lasting results. The adequate treatment of bone defects aims to build a stable and lasting support platform for the implantation of the definitive prosthetic components and, if possible, with the reconstruction of bone stock. Concomitantly, it allows the correct alignment of the prosthetic and limb components, as well as restoring the height of the joint interline and, thus, restoring the tension of soft parts and load distribution to the host bone, generating a joint reconstruction with good function, stable, and painless. There are several options for the management of these bone defects, among them: bone cement with or without reinforcement with screws, modular metallic augmentations, impacted bone graft, structural homologous graft and, more recently, metal metaphyseal cones, and metaphyseal sleeves. The objective of the present article was to gather classic information and innovations about the main aspects related to the treatment of bone defects during revision surgeries for total knee arthroplasty.

The Role of Poly(Methyl Methacrylate) in Management of Bone Loss and Infection in Revision Total Knee Arthroplasty: A Review

Poly(methyl methacrylate) (PMMA) is widely used in joint arthroplasty to secure an implant to the host bone. Complications including fracture, bone loss and infection might cause failure of total knee arthroplasty (TKA), resulting in the need for revision total knee arthroplasty (rTKA). The goals of this paper are: (1) to identify the most common complications, outside of sepsis, arising from the application of PMMA following rTKA, (2) to discuss the current applications and drawbacks of employing PMMA in managing bone loss, (3) to review the role of PMMA in addressing bone infection following complications in rTKA. Papers published between 1970 to 2018 have been considered through searching in Springer, Google Scholar, IEEE Xplore, Engineering village, PubMed and weblinks. This review considers the use of PMMA as both a bone void filler and as a spacer material in two-stage revision. To manage bone loss, PMMA is widely used to fill peripheral bone defects whose depth is less than 5 mm and covers less than 50% of the bone surface. Treatment of bone infections with PMMA is mainly for two-stage rTKA where antibiotic-loaded PMMA is inserted as a spacer. This review also shows that using antibiotic-loaded PMMA might cause complications such as toxicity to surrounding tissue, incomplete antibiotic agent release from the PMMA, roughness and bacterial colonization on the surface of PMMA. Although PMMA is the only commercial bone cement used in rTKA, there are concerns associated with using PMMA following rTKA. More research and clinical studies are needed to address these complications.

Metaphyseal Sleeves in Revision Total Knee Arthroplasty Provide Reliable Fixation and Excellent Medium to Long-Term Implant Survivorship

BACKGROUND

Addressing bone loss and securing implant fixation can be challenging in revision total knee arthroplasty (TKA). We present the results of a large series of revision TKAs using a metaphyseal sleeve.

METHODS

We retrospectively analyzed 319 revision TKAs with the use of a metaphyseal sleeve that had been followed up for at least 2 years, using a prospectively collected database. The mean follow-up was 91 months, and 73 patients were followed up for more than 10 years.

RESULTS

Implant survivorship was 99.1% at 3 years, 98.7% at 5 years, and 97.8% at 10 years. No metaphyseal sleeve was revised for aseptic loosening. Final radiographic review showed that there were radiolucent lines present in 2.8% of tibial sleeves and 2.7% of femoral sleeves; none of these had progressed and none were revised. About 3.7% of tibial sleeves subsided more than 1 mm compared with the immediate postoperative X-ray but all stabilized and none were revised.

CONCLUSION

Use of a metaphyseal sleeve in revision TKA is associated with excellent survivorship and radiographic outcome in the medium to long term.

Osteointegrative Sleeves for Metaphyseal Defect Augmentation in Revision Total Knee Arthroplasty: Clinical and Radiological 5-Year Follow-Up

BACKGROUND

Cementless metaphyseal implant fixation of revision total knee arthroplasty has encouraging early results. We analyzed midterm results and implant survival of osteointegrative augments in Anderson Orthopedic Research Institute (AORI) type 2a, 2b, and 3 defects. Reasons for implant failure were explored and the potential for anatomic joint line reconstruction evaluated.

METHODS

Sixty-seven consecutive patients (68 revision total knee arthroplasties) received cementless metaphyseal sleeves between 2011 and 2014. The mean follow-up was 5.0 years, mean age was 68.5 years, and mean body mass index was 31.4 kg/m². The clinical and radiographic results were determined using established scoring systems. Additionally, the survival rate was calculated and reasons for failure were analyzed.

RESULTS

In 2 patients (4.3%), sleeves had to be removed early postoperatively for deep infection after second-stage reimplantation. With continuously functioning remaining implants, the aseptic survival rate was 93.6%. Cleared up for initial technical issues due to poor bone quality, it is as high as 98%. The scores remained to be significantly improved by 64.8 points (Western Ontario and McMaster Universities Osteoarthritis Index) and 25.8 points (Knee Society score) (P < .001). In 10 patients (29.4%), diaphyseal radiolucencies were observed without suspicion of loosening. The mean joint line was noted to be 0.36 mm lower to the anatomic level.

CONCLUSION

At a mean follow-up of 5.0 years, cementless osteointegrative sleeves for metaphyseal fixation in AORI 2a, AORI 2b, and AORI 3 defects yielded continuous implant fixation even in cases with preceding revisions. The cleared up aseptic survival rate was 98% at 5 years. The modular sleeve design allowed joint line reconstruction near the anatomic level.

Influence of stems and metaphyseal sleeve on primary stability of cementless revision tibial trays used to reconstruct AORI IIB defects

Metaphyseal augments, such as sleeves, have been introduced to augment the fixation of revision total knee replacement (rTKR) components, and can be used with or without a stem. The effect of sleeve size in combination with stems on the primary stability and load transfer of a rTKR implant in AORI type IIB defects where the defect involves both condyles are poorly understood. The aim of this study was to examine the primary stability of revision tibial tray augmented with a sleeve in an AORI type IIB defect which involves both condyles with loss of cortical and cancellous bone. Finite element models were generated from computed tomography (CT) scans of nine individuals. All the bones used in the study had an AORI type IIB defect. The cohort included eight females (mean weight: 64 kg, height: 1.6 m). Material properties were sampled from CT data and assigned to the FE model. Joint contact forces for level gait, stair descent, and squat were applied. Stemless sleeved implants under various loading conditions were shown to have adequate primary stability in all AORI type IIB defects investigated. Adding a stem only marginally improved the primary stability of the implant but reduced the strain in the metaphysis compared to stemless implants. Once good initial mechanical stability was established with a sleeve, there was no benefit, in terms of primary stability or bone strains, from increasing sleeve size. This study suggests that metaphyseal sleeves, without a stem, can provide the required primary stability required by a rTKR tibial implant, to reconstruct an AORI type IIB defect. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

[Short-term effectiveness of revision total knee arthroplasty with porous-coated metaphyseal Sleeve and MBT implant]

Objective

To evaluate short-term effectiveness of revision total knee arthroplasty (TKA) with porous-coated metaphyseal Sleeve and MBT implant.

Methods

A clinical data of 23 patients (24 knees) who underwent revision TKA by using porous-coated metaphyseal Sleeve combined with MBT implant between March 2015 and April 2017 was retrospectively analyzed. There were 8 males (8 knees) and 15 females (16 knees). The age ranged from 48 to 85 years (mean, 65.4 years). The cause of revision TKA included infection in 14 knees, aseptic loosening in 8 knees, instability in 1 knee, and stiff knee in 1 knee. Bone defects were classified according to the Anderson Orthopaedic Research Institute (AORI) bone defect classification. The femoral defect was rated as type ⅡA in 5 knees, type ⅡB in 17 knees, and type Ⅲ in 2 knees; the tibial defect was rated as type ⅡA in 2 knees, type ⅡB in 20 knees, and type Ⅲ in 2 knees. The mean time between primary TKA and revision TKA was 30.6 months (range, 6-86 months). The preoperative range of motion (ROM) was (56.0±24.9)°. The preoperative Hospital for Special Surgery (HSS) total score was 41.9±14.2; and the pain and function scores were 8.5±5.2 and 33.4±13.5, respectively.

Results

All patients were followed up 12-39 months (mean, 25.6 months). The mean operation time was 2.2 hours (range, 1.6-2.9 hours). The mean intraoperative blood loss was 580 mL (range, 400-1 000 mL). There were 2 knees (8.3%) of intraoperative fracture associated with Sleeve insertion and 1 knee (4.2%) of acute postoperative infection at 25 days after revision TKA. All incisions healed by first intention. No deep venous thrombosis of lower extremity occurred. X-ray film showed that all implants were stable. At last follow-up, slight discomfort after exercise occurred in 4 knees (16.7%); end-of-stem pain in the tibia occurred in 1 knee (4.2%). The ROM was (114.6±5.1)°, which had significant improvement compared with the preoperative result ( t=11.698， P=0.000). The HSS total score (89.0±10.9), pain score (26.9±6.6), and function score (62.1±5.8) also had significant improvement compared with the preoperative results ( t=15.616, P=0.000; t=12.522, P=0.000; t=10.076, P=0.000).

Conclusion

The porous-coated metaphyseal Sleeve combined with MBT implant in revision TKA has a significant improvement in short-term effectiveness and no signs of implant loosening.

Can tibial tantalum cones eventually eliminate the adjuvant use of metallic augments for AORI type 2B/3 metaphyseal defects??-A novel surgical technique and case series

BACKGROUND

For extensive metaphyseal defects, the use of tantalum cones is usually combined with adjuvant stems which may be cemented/cementless and metallic bone augments for additional stability. A Tibial baseplate-Cone construct with proud tibial cones and without metallic augments has been described for AORI type 2B/3 tibial defects.

METHODS

A case series analysis of 6 patients with AORI type 3 defects treated with unstepped proud Tantalum tibial metaphyseal cones without metallic wedges/full width augments. A follow-up analysis done with clinico-radiographic interpretation.

RESULTS

100% osteointegration noted in final radiographs of all patients at an average follow-up of 4.1 years. Preoperative average ROM/KSS of 75/49 improved to postoperative ROM/KSS of 104/79. Outcomes were interpreted as excellent in 50% of cases and good in the remaining 50%.

CONCLUSION

The "Tibial base plate-cone without augments (BCCA)"type of a construct may offer a valid long term advantage over the Tibial base plate-Augment-Cone combination in massive tibial bone defects. Simply building up the tantalum cone to the native joint line position by increasing cone height can exclude use of augments or wedges.

Reduced tibial strain-shielding with extraosseous total knee arthroplasty revision system

•

A novel extracortical support system for revision of failed knee prostheses.

•

Shown to reduce metaphyseal stress-shielding versus intramedullary stem fixation.

•

Reduces bone loss and enables bone grafting of defects after implant loosening.

•

Enables use of conventional prosthesis in a revision scenario.

Background

Revision total knee arthroplasty (RTKA) has poorer results than primary total knee arthroplasty (TKA), and the prostheses are invasive and cause strain-shielding of the bones near the knee. This paper describes an RTKA system with extracortical fixation. It was hypothesised that this would reduce strain-shielding compared with intramedullary fixation.

Methods

Twelve replica tibiae were prepared for full-field optical surface strain analysis. They were either left intact, implanted with RTKA components with cemented intramedullary fixation stems, or implanted with a novel design with a tibial tray subframe supported by two extracortical fixation plates and screw fixation. They were loaded to simulate peak walking and stair climbing loads and the surface strains were measured using digital image correlation. The measurements were validated with strain gauge rosettes.

Results

Compared to the intact bone model, extracortical fixation reduced surface strain-shielding by half versus intramedullary fixation. For all load cases and bone regions examined, the extracortical implant shielded 8–27% of bone strain, whereas the intramedullary component shielded 37–56%.

Conclusions

The new fixation design, which offers less bone destruction than conventional RTKA, also reduced strain-shielding. Clinically, this design may allow greater rebuilding of bone loss, and should increase long-term fixation.

Biomechanical Analysis of Augments in Revision Total Knee Arthroplasty

Augments are a common solution for treating bone loss in revision total knee arthroplasty and industry is providing to surgeons several options, in terms of material, thickness and shapes. Actually, while the choice of the shape and the thickness is mainly dictated by the bone defect, no proper guidelines are currently available to select the optimal material for a specific clinical situation. Nevertheless, different materials could induce different bone responses and, later, potentially compromise implant stability and performances. Therefore, in this study, a biomechanical analysis is performed by means of finite element modelling about existing features for augment designs. Based upon a review of available products at present, the following augments features were analyzed: position (distal/proximal and posterior), thickness (5, 10 and 15 mm) and material (bone cement, porous and solid metal). For all analyzed configurations, bone stresses were investigated in different regions and compared among all configurations and the control model for which no augments were used. Results show that the use of any kind of augment usually induces a change in bone stresses, especially in the region close to the bone cut. The porous metal presents result very close to cement ones; thus it could be considered as a good alternative for defects of any size. Solid metal has the least satisfying results inducing the highest changes in bone stress. The results of this study demonstrate that material stiffness of the augment should be as close as possible to bone properties for allowing the best implant performances.

Revision total knee arthroplasty with porous-coated metaphyseal sleeves provides radiographic ingrowth and stable fixation

PURPOSE

Porous-coated metaphyseal sleeves are designed to fill bone defects and facilitate osseointegration when bone loss in encountered during revision total knee arthroplasty (TKA). The purpose of this study is to evaluate short-term results of porous-coated metaphyseal sleeves with regards to implant fixation and clinical outcomes.

METHODS

A retrospective review was conducted on 50 patients (79 sleeves-49 tibial and 30 femoral) who had a press-fit metaphyseal sleeve with revision TKA. Tibial and femoral bone loss was classified according to the Anderson Orthopaedic Research Institute (AORI) bone defect classification. Post-operative complications of infection, revision surgery, and dislocation were assessed. Follow-up radiographs were evaluated for signs of loosening using the criteria developed by the Knee Society. The median follow-up was 58.8 months (range 25.8-93.0 months).

RESULTS

The bone loss classifications were 1 type 1, 30 type 2a, 2 type 2b, and 17 type 3, and with regards to the femur, 5 were type 1, 8 type 2a, 31 type 2b, and 6 type 3. At final follow-up, 41/45 (91.1%) tibial and 28/29 (96.6%) femoral sleeves showed radiographic evidence of ingrowth. Of these 69 patients, all showed radiographic evidence of bony ingrowth. Three sleeves were revised for infection and two for loosening. The re-operation rate for loosening was 5/74 (6.8%) and for any reason was 14/74 (18.9%).

CONCLUSIONS

Modular porous-coated press fit metaphyseal sleeves fill defects and provide evidence of radiographic ingrowth. Short-term stable fixation can be achieved with sleeves, which is helpful as more patients undergo revision total knee arthroplasty with greater bone loss. Longer duration studies are needed to ascertain the survival rate of these implants.

LEVEL OF EVIDENCE

IV.

Acetabular wedge augments for uncontained tibial plateau defects in revision total knee arthroplasty

Tibial bone loss is a common scenario encountered during revision total knee arthroplasty. Reconstructive options depend on the amount and location of bone loss, but few good solutions exist to address large, uncontained tibial defects where cortical support is lost in the metadiaphyseal region. We describe a novel technique using acetabular augments to buttress a revision tibial component and recreate a hemiplateau during tibial revision total knee arthroplasty. In selected scenarios, this construct can create a biomechanically friendlier surface onto which to support the tibial tray and a less expensive option when compared to traditional stacked augments or cones.

Level of Evidence

IV–Case series.

Using a patterned microtexture to reduce polyethylene wear in metal-on-polyethylene prosthetic bearing couples

The longevity of metal-on-polyethylene prosthetic hip joint bearings, in which a CoCrMo femoral head articulates with a polyethylene liner, is often limited by polyethylene wear and osteolysis caused by polyethylene wear particles. Current approaches to reduce polyethylene wear include improving the mechanical properties of the polyethylene liner, and/or manufacturing ultra-smooth articulating surfaces. In contrast, this experimental work shows that adding a patterned microtexture of concave "dimples" to a polished CoCrMo surface significantly reduces polyethylene wear by promoting the formation of an elastohydrodynamic lubricant film, which reduces contact between the CoCrMo and polyethylene bearing surfaces. Using a gravimetric method to measure polyethylene pin wear during pin-on-disc experiments, it was demonstrated that microtextured CoCrMo caused reduced polyethylene wear compared to polished CoCrMo surfaces. Wear was quantified for different polyethylene materials currently used in commercial prosthetic hip joint bearings, and for several microtexture geometries. It was also documented by correlating polyethylene wear with surface topography measurements that the patterned microtexture reduced contact between the articulating bearing surfaces.

Full Cementation in Revision Total Knee Arthroplasty Using a Constrained Condylar Knee Prosthesis with an Average 7-Year Follow-up

Purpose

To evaluate clinical and radiological outcome of the full cementation technique in revision total knee arthroplasty (TKA) using a constrained condylar knee (CCK) prosthesis.

Materials and Methods

Between January 2008 and March 2012, 18 cases (16 patients) of fully cemented revision TKA were performed using a CCK prosthesis. Fifteen cases of aseptic loosening (13 patients) and 3 cases of infection were included. There were 2 males and 14 females with a mean age of 76.7 years at the time of surgery, and the average follow-up was 81 months. Clinically, the pain score, function score and Hospital for Special Surgery (HSS) score were evaluated. Radiologically, loosening, radiolucent lines and migration of implant were evaluated.

Results

Preoperatively, the pain score, function score and HSS score were 50.3, 24.4 and 61.8 points, respectively. At the latest follow-up, the scores were improved to 84.8, 63.6 and 85.6 points, respectively (p<0.05). Loosening or migration of implant was not observed in any cases. Radiolucent lines were observed in 5 cases underneath the tibial component without progression during the follow-up.

Conclusions

The full cementation technique in revision TKA using a CCK showed excellent clinical results. Although radiolucent lines were observed in 27.8% underneath the tibial component, there was no progression to loosening or instability.

Use of autogenous onlay bone graft for uncontained tibial bone defects in primary total knee arthroplasty

Background

The use of autogenous bone graft is a well–known technique for reconstruction of tibial bone defects in primary total knee arthroplasty (TKA). In cases where the size of the bone graft is inappropriate, the stability of bone graft fixation and subsequent bone graft to host bone incorporation may be compromised. We describe a simple and reliable technique of reconstruction in a proximal tibia bone defect at the time of primary TKA by using autogenous onlay bone graft (AOBG).

Methods

Records were reviewed of 19 patients (mean age, 72 years) who underwent primary TKA using AOBG without the additional allogenous bone or metal augments, between August 2013 and August 2014.

Results

Mean Knee Society score (KSS) in the 22 knees was significantly higher postoperatively than preoperatively (92 ± 4 vs. 30 ± 7, P < 0.001). The mean range of motion (ROM) in the 22 knees, which was 106 ± 12° preoperatively, improved to 112 ± 10° at last follow-up, but this this difference was not significant (P = 0.32). No migration of implants and presence of radiolucent lines at the bone cement-prosthesis interface were observed. Furthermore, the serial radiographs of 19 patients had a mean time of 3.2 months (range, 2.7–4.4 months) for solid union with cross trabeculation between the proximal tibial bone and graft.

Conclusions

This simple AOBG supplement technique may biologically promote graft to host bone healing by enhancing fixation stability without the additional fixatives and assist the surgeon in managing the varying nature of uncontained bone defects.

Trial registration

Trial registration number: KCT0002328, May 15, 2017.

Biomechanical evaluation of tibial bone adaptation after revision total knee arthroplasty: A comparison of different implant systems

The best methods to manage tibial bone defects following total knee arthroplasty remain under debate. Different fixation systems exist to help surgeons reconstruct knee osseous bone loss (such as tantalum cones, cement, modular metal augments, autografts, allografts and porous metaphyseal sleeves) However, the effects of the various solutions on the long-term outcome remain unknown. In the present work, a bone remodeling mathematical model was used to predict bone remodeling after total knee arthroplasty (TKA) revision. Five different types of prostheses were analyzed: one with a straight stem; two with offset stems, with and without supplements; and two with sleeves, with and without stems. Alterations in tibia bone density distribution and implant Von Mises stresses were quantified.

In all cases, the bone density decreased in the proximal epiphysis and medullary channels, and an increase in bone density was predicted in the diaphysis and around stem tips. The highest bone resorption was predicted for the offset prosthesis without the supplement, and the highest bone formation was computed for the straight stem. The highest Von Mises stress was obtained for the straight tibial stem, and the lowest was observed for the stemless metaphyseal sleeves prosthesis.

The computational model predicted different behaviors among the five systems. We were able to demonstrate the importance of choosing an adequate revision system and that in silico models may help surgeons choose patient-specific treatments.

Comparative assessment of different reconstructive techniques of distal femur in revision total knee arthroplasty

PURPOSE

Bone loss is often encountered in revision total knee arthroplasty. In particular, when the cortex of distal femur is breached, the surgical decision on the reconstructive options to be taken is challenging due to the variety of defects and the lack of data from clinical or experimental studies that can support it. The aim of the present work was to test the hypothesis that for an identical defect and bone condition, each reconstructive technique option has a dissimilar stress and stability behaviour, which may be related to differing longevity of the revision procedure.

METHODS

Triaxial strain gauges and video extensometer were used to measure distal cortex strains and implant stability in eight reconstructive techniques replicated with synthetic femur under a load of 2030N. To assess the cancellous bone strains, finite element models were developed and validated.

RESULTS

The measured strains showed that the distal cortex is not immune to the different reconstructive techniques, when applied to an identical defect; however, significant differences (P < 0.05) were found only between bone graft and metal augment on the 12-mm larger distal defect. The stem addition improves the stability of all reconstructive techniques; however, significant differences (P = 0.03) were found only on the bone-graft technique.

CONCLUSIONS

Cement-fill and metal-augment techniques, applied to the 4-mm smaller defect, are not associated with different structural behaviour, while for the 12-mm larger defect, the metal-augment and bone-graft techniques presented distinct biomechanical effects. These effects, by themselves, may not be sufficient to be associated with a different longevity of the revision procedure among techniques, when the stem is added to the bone-graft technique. These findings, based on independent scientific understanding and advanced prediction tools, can improve the surgical decision-making process, when the peripheral cortex of the distal femur is breached.

Union, Knee Alignment, and Clinical Outcomes of Patients Treated With Autologous Bone Grafting for Medial Tibial Defects in Primary Total Knee Arthroplasty

Autologous bone grafting is an established method to overcome bone deficiencies in primary total knee arthroplasty (TKA). However, recently, metal augments have been used by many surgeons. Although autologous bone grafting is a common technique, few large studies have described its success in achieving bone union in primary TKA. The goal of this study was to evaluate primary TKA with autologous bone grafting for tibial defects. A total of 68 knees that had undergone arthroplasty with autologous bone grafting with more than 1 year of follow-up were evaluated. Average follow-up was 6.6 years (range, 1.2-14.6 years). The autologous bone grafting procedure attached the proximal portion of the tibial resection from the lateral side to the bone graft on the medial side with 2 screws. The prosthesis, which had a standard and nonrevision stem, was implanted with cement. Bone union was assessed with fluoroscopic radiography with a weight-bearing anteroposterior view. The rate of bone union was 97% (65 knees). Correction of preoperative alignment was achieved and maintained until final follow-up. Postoperative knee angle and knee and function scores showed significant improvement. One infection occurred, but there were no local complications, such as backout of screws or collapse of bone grafts. The authors believe that autologous bone graft within TKA is a relatively simple and effective procedure that provides good bone union. [Orthopedics. 2017; 40(4):e604-e608.].

Challenges in engineering large customized bone constructs

The ability to treat large tissue defects with customized, patient-specific scaffolds is one of the most exciting applications in the tissue engineering field. While an increasing number of modestly sized tissue engineering solutions are making the transition to clinical use, successfully scaling up to large scaffolds with customized geometry is proving to be a considerable challenge. Managing often conflicting requirements of cell placement, structural integrity, and a hydrodynamic environment supportive of cell culture throughout the entire thickness of the scaffold has driven the continued development of many techniques used in the production, culturing, and characterization of these scaffolds. This review explores a range of technologies and methods relevant to the design and manufacture of large, anatomically accurate tissue-engineered scaffolds with a focus on the interaction of manufactured scaffolds with the dynamic tissue culture fluid environment. Biotechnol. Bioeng. 2017;114: 1129-1139. © 2016 Wiley Periodicals, Inc.

No Difference Between Trabecular Metal Cones and Femoral Head Allografts in Revision TKA: Minimum 5-year Followup

BACKGROUND

Encouraging clinical results have been reported with the use of femoral head structural allografts and, more recently, trabecular metal cones for the management of large structural defects of the femur and tibia during revision total knee arthroplasty (TKA). However, to our knowledge, there are no published studies comparing these two techniques.

QUESTIONS/PURPOSES

Compared with bulk allografts, do trabecular metal cones result in (1) better validated outcomes scores; (2) a lower risk of loosening or revision at 5 years; and (3) fewer surgical complications when used for the management of bone loss in revision TKA?

METHODS

Between 2002 and 2008, three surgeons performed 450 TKA revisions, 45 (10%) of which were performed using augmentation of host bone; in those, femoral head allograft was used in 30 (75%) and trabecular metal cones in 15 (25%). From 2002 to 2007, femoral head allografts were used in all patients (28 patients); from 2007 to 2008, trabecular metal augments were used in all patients. There was a period of 1 year (16 knees) in which there was some overlap; during that time, femoral head structural allografts were used in cases in which we were unable to fit the defect or achieve adequate stability with trabecular metal cones. Followup was at a mean of 9 years (range, 5-12 years). No patients were lost to followup. Knee function and quality of life were assessed using the Oxford Knee Score, WOMAC, SF-12, and the UCLA activity score. Radiographs were assessed for signs of loosening. Surgical complications included superficial or deep infections, iatrogenic fractures, symptomatic deep venous thromboses or pulmonary emboli, and blood loss requiring transfusion; these were obtained from our database and from review of patients' charts.

RESULTS

The mean Oxford Knee Score in the allograft and trabecular metal cone groups was 91 (SD 10) and 91 (SD 14), respectively (95% confidence interval [CI], 88-94; p = 0.29). Mean WOMAC scores were 94 (SD 10) and 92 (SD 14), respectively (95% CI, 80-105; p = 0.52) and mean UCLA scores were 6 (SD 1.2) and 6 (SD 1.5), respectively (95% CI, 4-8; p = 0.49). Five- and 10-year survivorship of the allografts was 93% (95% CI, 77-98) and 93% (95% CI, 77-99), respectively. Survivorship at a mean of 5 years in the trabecular metal cones group was 91% (95% CI, 56-98). With the numbers available, there were no differences between the groups in terms of the frequency of surgical complications (3% [one of 30] versus 7% [one of 15]; odds ratio, 0.5; p = 0.632).

CONCLUSIONS

With the numbers available, we found no difference in pain, function, or repeat revision when comparing femoral head allografts and trabecular metal cones for severe bone defects during revision TKA. However, we used allografts for the larger bone defects. Based on these results, we believe that femoral head allografts and trabecular metal cones can both be used for the management of Anderson Orthopaedic Research Institute Types 2 and 3 defects. Future multicenter studies are required with larger numbers, cost analyses, and a longer duration of followup.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Location of the natural knee axis for internal-external tibial rotation

BACKGROUND

Rotating hinge and mobile bearing tray knee replacement designs utilize a single fixed axis for tibial rotation, yet there is little published information regarding the natural internal-external axis (IEA) for tibial rotation. Identifying the IEA should provide an opportunity for reproducing normal knee kinematics and maintaining the balance of forces in the soft tissues that help control rotation of the tibia.

METHODS

The location and orientation of the IEA relative to the tibial plateau were calculated in 46 fresh frozen human cadaveric specimens using an instant center of rotation analysis at fixed knee flexion angles ranging from five degrees to 105°.

RESULTS

IEA location ranged from 4.0 to 4.9mm medial and 1.7 to 5.5mm posterior to the center of the tibial plateau (from 5° to 105° of knee flexion). IEA orientation was reported relative to a reference axis perpendicular to the plane of the tibial plateau. In the frontal plane, the IEA was not significantly different from the reference axis from five degrees to 45° flexion, and 2.0° to 2.7° valgus to the reference axis from 60° to 105° flexion. In the sagittal plane, the IEA was not significantly different from the reference axis from 5° to 15° flexion, and 3.0° to 7.0° extended from the reference axis from 30° to 105° flexion.

CONCLUSIONS

The IEA moves posteriorly with increasing knee flexion on the tibial plateau. Placement of the IEA relative to the tibial plateau for a rotating hinge or mobile bearing tray implant may represent a compromise between design objectives for moderate and deeper knee flexion.

CLINICAL RELEVANCE

This study has relevance for future knee implant designs.

Does a PEEK Femoral TKA Implant Preserve Intact Femoral Surface Strains Compared With CoCr? A Preliminary Laboratory Study

BACKGROUND

Both the material and geometry of a total knee arthroplasty (TKA) component influence the induced periprosthetic bone strain field. Strain, a measure of the local relative deformation in a structure, corresponds to the mechanical stimulus that governs bone remodeling and is therefore a useful in vitro biomechanical measure for assessing the response of bone to new implant designs and materials. A polyetheretherketone (PEEK) femoral implant has the potential to promote bone strains closer to that of natural bone as a result of its low elastic modulus compared with cobalt-chromium (CoCr).

QUESTIONS/PURPOSES

In the present study, we used a Digital Image Correlation (DIC) technique to answer the following question: Does a PEEK TKA femoral component induce a more physiologically normal bone strain distribution than a CoCr component? To achieve this, a DIC test protocol was developed for periprosthetic bone strain assessment using an analog model; the protocol aimed to minimize errors in strain assessment through the selection of appropriate analysis parameters.

METHODS

Three synthetic bone femurs were used in this experiment. One was implanted with a CoCr femoral component and one with a PEEK femoral component. The third (unimplanted) femur was intact and used as the physiological reference (control) model. All models were subjected to standing loads on the corresponding polyethylene (ultrahigh-molecular-weight polyethylene) tibial component, and speckle image data were acquired for surface strain analysis using DIC in six repeat tests. The strain in 16 regions of interest on the lateral surface of each of the implanted bone models was plotted for comparison with the corresponding strains in the intact case. A Wilcoxon signed-rank test was used to test for difference at the 5% significance level.

RESULTS

Surface analog bone strain after CoCr implantation indicated strain shielding (R² = 0.6178 with slope, β = 0.4314) and was lower than the intact case (p = 0.014). The strain after implantation with the PEEK implant deviated less from the intact case (R² = 0.7972 with slope β = 0.939) with no difference (p = 0.231).

CONCLUSIONS

The strain shielding observed with the contemporary CoCr implant, consistent with clinical bone mineral density change data reported by others, may be reduced by using a PEEK implant.

CLINICAL RELEVANCE

This bone analog in vitro study suggests that a PEEK femoral component could transfer more physiologically normal bone strains with a potentially reduced stress shielding effect, which may improve long-term bone preservation. Additional studies including paired cadaver tests are necessary to test the hypothesis further.

Complex Primary Total Knee Replacement (TKR) Using Prophylactic Gastrocnemius Flap and Rotating-Hinge Knee in Post-traumatic, Infective Arthritis of the Knee - A Case Report

INTRODUCTION

Prophylactic gastrocnemius flap with primary rotating hinge knee is technically demanding in a case of neglected post-traumatic, infective arthritis of the knee, with challenges of compromised skin and soft tissues, articular bone defect, limb mal-alignment, gross instability, retained hardware and a contracted extensor mechanism with the patella fixed in the lateral gutter all in combination, is rarely reported. We report such a complex case in this study.

CASE REPORT

We report a 48 year male patient with a history of fracture lateral femoral condyle of right knee due to road traffic accident 10 years back, for which he got operated with open reduction and internal fixation with cancellous screws, which subsequently got infected. Primary procedure undertaken was removal of implants, debridement, placement of antibiotic-cement spacer followed by prophylactic medial gastrocnemius flap and a temporary joint spanning external fixator. Definitive procedure undertaken, after clearance of infection in 12 weeks was conversion to a rotating hinge TKR using a lateral para-patellar arthrotomy & tibial tubercle osteotomy to address the challenges of fixed patella in the lateral gutter and contracted ligamentum patellae. At one year follow up, the knee was painless, stable, with satisfactory range of motion and improved function without any infection or aseptic lysis.

CONCLUSION

Prophylactic Gastrocnemius flap cover along with rotating hinge knee arthroplasty using a lateral para-patellar approach and tibial tubercle osteotomy in a case of neglected post-traumatic, infective arthritis of knee with the complexities of limb mal-alignment, compromised skin and soft tissue, articular bone loss and ligamentous instability is a satisfactory bail out option in such a highly complex joint scenario.

Radiological Stability after Revision of Infected Total Knee Arthroplasty Using Modular Metal Augments

PURPOSE

To evaluate the radiological stability according to the number of modular augments after revision of infected total knee arthroplasty (TKA).

MATERIALS AND METHODS

Between February 2006 and September 2013, 37 patients (39 knees) followed ≥2 years after revision of infected TKA using modular metal augments for bone defects were reviewed retrospectively. We divided the patients into 3 groups according to the number of augments into group A (≤2 augments, 14 knees), group B (3-4 augments, 18 knees), and group C (5≥ augments, 7 knees) and evaluated the width of radiolucent zones around the implant at the last follow-up.

RESULTS

There were 3 Anderson Orthopedic Research Institute type I, 33 type II, and 3 type III bone defects. The mean number of radiolucent zones of group A was 3 and the sum of width averaged 4.4 mm. In group B, the values were 4.8 and 6.2 mm, respectively. In group C, the values were 8.1 and 12.9 mm, respectively. The differences between the three groups were statistically significant.

CONCLUSIONS

In revision TKA with modular metal augmentation caused by infected TKA, increased modularity can result in radiological instability.

Double metal tibial blocks augmentation in total knee arthroplasty

PURPOSE

Severe uncontained tibial bone defects occurring during total knee arthroplasty are challenging, and which treatment method is the best remains unknown. In this study, clinical and radiographic outcomes of double metal blocks augmentation were examined.

METHODS

Between 2004 and 2012, double metal blocks augmentation was carried out in 17 patients with severe asymmetric uncontained tibial bone defects. The first block was attached to the tibial tray with screws, and then the second block was cemented to the first block. Out of 17 patients, 13 (8 primary, 5 revision) were available for final follow-up at a median of 69 months (range 24-99). For clinical assessment, range of motion and Knee Society score were evaluated preoperatively and annually thereafter. At the final follow-up, Western Ontario and McMaster Universities Osteoarthritis Index, Oxford knee, Short Form-36, Lower extremity functional scale, and Lower extremity activity scale scores were evaluated. Radiographic assessment for radiolucent lines at the block-cement-bone interfaces and signs of failure was performed annually using fluoroscopy and standard radiographs.

RESULTS

Range of motion and Knee Society score were significantly improved post-operatively. Other clinical outcomes were favourable. Radiolucent lines were seen on fluoroscopy in three knees, but no sign of failure, such as loosening, collapse, or instability, was observed at the final follow-up.

CONCLUSIONS

Double metal blocks augmentation is a favourable and useful method, which does not cause mechanical failure or protrusion of the prosthetic because of its modularity, to manage severe asymmetric uncontained proximal tibial bone defects >15 mm in total knee arthroplasty.

LEVEL OF EVIDENCE

Case series, Level IV.

The role of offset stems in revision knee arthroplasty

Revision total knee arthroplasty (TKA) represents a technically challenging procedure. The use of an offset stem extension can help in addressing some of the difficulties that can be encountered during surgery and, in particular, anatomical mismatch, malalignment, and gap balancing. Different offset stem extensions are available and can be classified according to four parameters: modularity, location of the offset, direction, and size of the displacement. Offset stem extensions can assist with implant alignment on the metaphysis if there is an offset diaphysis, can avoid medial-lateral or anterior-posterior component overhang, can reduce the incidence of coronal or sagittal malalignment, and can help in balancing the flexion and extension spaces by effectively translating the components. The aim of this study is to give an overview of the currently available evidence regarding the use of offset stem extensions in revision TKA as well as some useful surgical tips.

Surface or full cementation of the tibial component in total knee arthroplasty: a matched-pair analysis of mid- to long-term results

INTRODUCTION

Despite the clinical success of cemented TKA, aseptic loosening of the tibial component remains a potential long-term complication. Considering the constantly growing revision burden, there is a need for clarification regarding controversial views on primary fixation techniques. In this retrospective analysis, surface (SC) or full cementation (FC) of tibial components was compared in a matched-pair and long-term setting.

METHODS

Matching pairs were identified in a patient series from 1989 to 1994. Hence, 25 primary TKA (SC) were compared to 42 TKA (FC). The study population included 34 patients with rheumatoid arthritis. Patients were matched in a 1:1.7 fashion according to age, gender and initial diagnosis. Outcome was assessed by multiple clinical parameters, detailed radiographic evaluation and survivorship analysis.

RESULTS

Clinical follow-up (FU) was at 10.3 years (range 1.5-15.6) for the SC and 12 years (range 0.2-16.2) for the FC group. Survivorship at 10 years was 100 % for the surface cemented trays and 93.3 % (95 % CI 80.5-100) for the fully cemented implants considering aseptic loosening as endpoint (p = 0.3918). Improvement of the AKS Score was greater in the SC group (p = 0.044) and patients in this group were more satisfied (p = 0.013). For any other clinical parameter, no difference could be observed (p > 0.05).

CONCLUSION

Results of this study showed no statistically significant difference regarding long-term survivorship for the two cementing techniques. This finding questions the claimed advantage of full cementation for tibial components. The presented data do not support the concern that surface cementation results in insufficient fixation in patients with rheumatoid arthritis.

[Defect Reconstruction in Total Knee Arthroplasty with wedges and blocks]. [Corrected]

OBJECTIVE

Surgical technique for primary and revision total knee arthroplasty to reconstruct bone defects with metal augments and reproducible positioning of the implant at the right joint line.

INDICATIONS

Primary and revision total knee arthroplasty with bone defects.

CONTRAINDICATIONS

Complete destruction of the metaphysis.

SURGICAL TECHNIQUE

Implantation of revision components performed in three consecutive steps: first, positioning of the tibia component at correct height and rotation; second, determination of the posterior joint line in flexion through the size and correct rotation of the femoral implant; third, determination of the distal joint line by use of positioning of the femoral component. These steps are performed independently from bone defects, which are subsequently reconstructed with metal augments.

POSTOPERATIVE MANAGEMENT

Mobilization with weight bearing and range of motion as tolerated, depending on osseous and soft tissue condition at primary or revision surgery.

RESULTS

In a prospective study, 132 consecutive knee revisions in 76 women and 56 men with an average age of 72.4 years (range 49-93 years) were followed up clinically and radiologically preoperatively and at a mean follow-up of 74 months (range 38-105 months). Clinical results were based on the American Knee Society score. The score was 46.3 (range 31-65) preoperatively and 82.5 (range 61-96) at follow-up. Radiologically 12.1 % of the knees showed lysis around the augment with no clinical signs of loosening. No revisions were performed due to aseptic loosening. The joint line was correctly reconstructed in 84.8 %.

Strategies for Revision Total Ankle Replacement

As the frequency of primary total ankle replacement (TAR) continues to build, revision will become more commonplace. At present there are no “standard principles” associated with revision TAR. What is clear is that the current approaches are technically complex, fraught with complications and no one approach represents the only answer. Exchange of TAR metallic components to the same system standard or dedicated revision components are viable options with limited occurrence of complications. Explantation and conversion to custom-design long stemmed components has limited availability. Explantation and conversion to another TAR system is high-risk and has strong potential for complications. The use of metal reinforced polymethylmethacrylate cement augmentation of failed TAR systems and tibio-talo-calcaneal arthrodesis should be reserved for very select situations where other options are not possible. There is a real need for long-term survivorship following revision TAR and future efforts ought to be directed in this area.

Bone mineral density of the femur in autopsy retrieved total knee arthroplasties

Bone mineral density (BMD), as measured by DEXA, can vary depending on bone rotation and fat content of soft tissues. We performed DEXA measurements, under controlled positioning, on 24 autopsy-retrieved femora from patients who had fully functional and asymptomatic successful TKA to determine periprosthetic BMD changes and compared results to 24 normal cadaveric femora. In TKA specimens, BMD was affected by gender, preoperative diagnosis, and zone under analysis. The lowest mean BMD was in the anterior femoral condylar zone. Males had higher mean BMD at all zones while patients with preoperative diagnosis of osteoarthritis had higher BMD in the posterior condylar zone. The mean BMD in the anterior femoral condylar zone in TKA specimens was significantly lower than in normal specimens without arthroplasties, most likely due to stress shielding.