Modular augmentation in revision total knee arthroplasty

Bone defect classifications in revision total knee arthroplasty, their reliability and utility: a systematic review

BACKGROUND

There are various classification systems described in the literature for managing bone defects in revision knee arthroplasty (RTKA). We analysed the reliability and usefulness of these classification systems.

QUESTIONS/PURPOSES

(1) To review and critique the various classification systems proposed for bone loss in RTKA. (2) Among all the proposed classifications which one is the most commonly used by surgeons to report their results. (3) What is the reliability of various bone defect classification systems for RTKA. In this review, we have assessed the studies validating those classifications with a detailed description of the limitations and the proposed modifications.

METHODS

This systematic review was conducted following PRISMA guidelines. Pubmed/Medline, CINAHL, EMBASE, Scopus, Cochrane databases and Web of Science databases were searched using multiple search terms and MeSH terms where possible. Studies meeting inclusion criteria were assessed for statistical parameters of reliability of a classification system.

RESULTS

We found 16 classification systems for bone defects in RTKA. Six studies were found evaluating a classification system with reporting their reliability parameters. Fifty-four studies were found which classified bone loss using AORI classification in their series. AORI classification is most commonly reported for classifying bone defects. Type T2B and F2B are the most common bone defects in RTKA. The average kappa value for AORI classification for femoral bone loss was 0.38 (0.27-0.50) and 0.76 (0.63-1) for tibial bone loss assessment.

CONCLUSION

None of the available classification systems is reliably established in determining the bone loss and treatment plans in RTKA. Among all, AORI classification is the most widely used system in clinical practice. The reliability of AORI Classification is fair for femoral bone loss and substantial for tibial bone loss.

Periprosthetic knee infection: treatment options

Infection is one of the most catastrophic complication following total knee arthroplasty (TKA) and represents the second most common cause of TKA failure. Treatment of a patient with periprosthetic joint infection (PJI) could require often costly and prolonged hospital stays, weeks or months of antibiotic therapy, and multiple surgical procedures. The best management is still highly debating, whereas many treatment options are available. These include suppressive antibiotics, arthroscopic irrigation and debridement, open debridement with insert exchange, single-stage reimplantation and two-stage reimplantation. The choice of the treatment depends on many variables, including integrity of implant, timing of the infection, host factors (age, health, immunologic status), virulence of the infecting organism and wishes of the patient. The aim of this review is to provide a comprehensive understaning of the different options for knee PJIs.

Radiographic and clinical analysis of a Porous-coated metaphyseal cone for revision total Knee arthroplasty

BACKGROUND

The aim of this study was to evaluate the radiographic and clinical outcomes of a recently introduced metaphyseal cone system for revision TKA.

METHODS

73 revision TKAs in 72 patients were retrospectively reviewed. All patients had a minimum of 2-year clinical follow-up (mean 34.1 months; range 24.0 to 50.3 months). 114 Metaphyseal cones (64 tibial and 50 femoral) of a single manufacturer were implanted. The most common indications for revision were aseptic loosening (56.9%), second stage reimplantation for periprosthetic joint infection (PJI; 26.4%), and instability (12.5%). All femoral and tibial stems were press-fit cementless stems.

RESULTS

Ten of 72 patients underwent re-revision: six for infection (8.3%), two for instability (2.8%), one (1.4%) for patellar tendon rupture and one (1.4%) for femoral component loosening (a cone was not utilized at index revision). Two patients had loose cones (one with an isolated tibial cone and one with both femoral and tibial cones) associated with loose implants but declined re-revision. Aseptic survivorship of our patient cohort free from any re-revision surgery was 95.9% at 2 years (95% CI 87.4-98.7%) and 96.5% of cones demonstrated radiographic evidence of osseointegration. At 2-years, the Knee Society Score (KSS) improved from a mean of 17.2 points preoperatively to 57.8 points (p <.0001).

CONCLUSIONS

Porous-coated metaphyseal cones from this manufacturer demonstrate excellent aseptic survivorship and radiographic evidence of osseointegration similar to prior designs when used with cementless stems.

Usefulness of Trabecular Metal Cones in Revision Total Knee Arthroplasty in a Korean Population: A Case Series

Purpose

The purpose of this study was to assess the medium-term results of trabecular metal cones for the reconstruction of large bone defects in revision TKA.

Methods

Thirteen patients who had undergone revision TKA using trabecular metal cones for femoral and/or tibial large bone defects were identified. We included patients who had a minimum of three years follow-up in the study. We evaluated their functional outcomes, implant survivorship, radiological findings, and complications.

Results

At a mean follow-up of 6.9 years (range of 3.5–9.4 years), all trabecular metal cones and implants were well fixed and did not exhibit any radiographic evidence of migration or loosening. At the final follow-up, the mean Knee Society knee scores had improved from 37.2 to 78.1 (p < 0.05), and function scores had improved from 35.5 to 77.5 points (p < 0.05). One intraoperative fracture in the distal femur occurred in an 85-year-old woman during impaction of a single trabecular metal cone. The fracture was successfully affixed to the femoral cone and bone three months postoperatively.

Conclusion

The present study of trabecular metal cones demonstrates excellent clinical outcomes and survivorship in revision TKA during medium-term follow-up periods. However, longer-term follow-up studies are needed to further investigate these implants in revision TKA. Additionally, the necessity of metal cones in revision procedures should be carefully considered depending on patient needs and economic capabilities.

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.

Management of bone loss in revision total knee arthroplasty: therapeutic options and results

The treatment of small to moderate size defects in revision total knee arthroplasty (rTKA) has yielded good results with various techniques (cement and screws, small metal augments, impaction bone grafting and modular stems). However, the treatment of severe defects remains problematic.

Severe defects have typically been treated with large allograft and metaphyseal sleeves. The use of structural allograft has decreased in recent years due to increased long-term failure rates and the introduction of highly porous metal augments (cones and sleeves).

A systematic review of level IV evidence studies on the outcomes of rTKA metaphyseal sleeves found a 4% rate of septic revision, and a rate of septic loosening of the sleeves of 0.35%. Aseptic re-revision was required in 3% of the cases. The rate of aseptic loosening of the sleeves was 0.7%, and the rate of intraoperative fracture was 3.1%. The mean follow-up was 3.7 years.

Another systematic review of tantalum cones and sleeves found a reoperation rate of 9.7% and a 0.8% rate of aseptic loosening per sleeve. For cones, the reoperation rate was 18.7%, and the rate of aseptic loosening per cone was 1.7%.

The reported survival of metal sleeves was 99.1% at three years, 98.7% at five years and 97.8% at 10 years. The reported survival free of cone revision for aseptic loosening was 100%, and survival free of any cone revision was 98%. Survival free of any revision or reoperation was 90% and 83%, respectively.

Cite this article: EFORT Open Rev 2021;6:1073-1086. DOI: 10.1302/2058-5241.6.210007

Design of Porous Metal Block Augmentation to Treat Tibial Bone Defects in Total Knee Arthroplasty Based on Topology Optimization

Metal block augmentation, which is used for the treatment of tibial bone defects in total knee arthroplasty, with high stiffness will cause significant alteration in stress distribution, and its solid structure is not suitable for osseointegration. This study aimed to design a porous block to reduce weight, promote bone ingrowth, and improve its biomechanical performance. The metal block augmentation technique was applied to finite element models of tibial bone defects. Minimum compliance topology optimization subject to volume fraction combined with the porous architecture was adopted to redesign the block. Biomechanical changes compared with the original block were analyzed by finite element analysis. The stress distribution of the block and proximal tibia was recorded. The strain energy density of the proximal tibia was obtained. The newly designed block realized 40% weight reduction. The maximum stress in the optimized block decreased by 11.6% when compared with the solid one. The maximum stress of the proximal tibia in the optimized group increased by 18.6%. The stress of the anterior, medial, and posterior parts of the proximal medial tibia in the optimized group was significantly greater than that in the original group (all p < 0.05). The optimized block could effectively improve the biomechanical performance between the block and the bone. The presented method might provide a reference for the design of customized three-dimensional printed prostheses.

Tibial tray cementation is not necessary for knee revision with titanium metaphyseal sleeves: a mid-term prospective study in AORI 2B defects

PURPOSE

Metaphyseal fixation with porous titanium sleeves in revision knee surgery provides mechanical support to the implant, promotes biological fixation, and has shown satisfactory short- and mid-term results. Cement is commonly used to fix the tibial tray to the epiphyseal area. The objective of this study is to determine whether cement should be used to achieve fixation of the tibial tray with the hypothesis that metaphyseal sleeves would provide enough axial and rotational stability making cementation unnecessary.

MATERIAL AND METHODS

Prospective study of 60 patients undergoing knee replacement surgery with metaphyseal sleeves in type 2B defects in femur and tibia. Patients were divided into two groups according to the use of cement on the tibial component. Analysis included the American Knee Society Score (KSS) knee and functional scales, the Western Ontario and McMaster Universities (WOMAC) index, the Short Form 12 (SF-12) health survey, and radiographic assessment with a maximum follow-up of 5 years.

RESULTS

No statistically significant differences were found between the two groups in any of the parameters assessed.

CONCLUSION

Metaphyseal sleeves showed a 100% survivorship at five years of followup. There were no differences in clinical and radiographic outcomes at five years of follow-up depending on whether or not cement was used for tibial platform fixation. Cementation of the tibial tray would therefore not be required to achieve satisfactory mid-term results.

LEVEL OF EVIDENCE

Level II: prospective cohort study. Therapeutic.

Midterm Outcomes of Tantalum Metal Cones for Severe Bone Loss in Complex Primary and Revision Total Knee Arthroplasty

Background

Managing severe periarticular bone loss poses a major challenge in complex primary and revision total knee arthroplasty (TKA). Impaction bone graft, structural allografts, metal augments, and mega prosthesis are some of the methods used to address major bone loss. Tantalum metal (TM) Cones (Zimmer, Warsaw, IN) were introduced as an alternative to address this cohort of patients. The advantages of these cones include excellent biocompatibility, high porosity with osteoconductive potential, and a modulus of elasticity between cortical and cancellous bone. In addition, it is bioactive and offers an intrinsically high friction fit.

Methods

A cohort of 62 patients with severe distal femoral and proximal tibial bone loss were operated for primary and revision TKA between January 2007 and December 2014 and followed up for a mean period of 108.5 months (range: 60-156 months). Preoperative and postoperative range of motion and Knee Society score were documented. Postoperatively long leg X-rays were performed at each follow-up visit to determine osteointegration, evidence of loosening, and migration.

Results

The range of motion and Knee Society score improved considerably from preoperative a value of 63.9 ± 13.9° and 52 ± 14.9 to 102.1 ± 9.9° and 76.1 ± 10.03, respectively, at the final follow-up visit in the primary cohort and 52.14 ± 13.3° and 38.1 ± 9.1 to 92 ± 8° and 68.5 ± 4.3, respectively, in the revision cohort. Serial radiographs demonstrated complete osteointegration of the TM cones at the final follow-up.

Conclusions

Our study demonstrates excellent midterm survivorship of TM cones with predictable osteointegration and good outcomes (clinical and radiological) in treatment of severe femoral and tibial metaphyseal bone defects in complex primary and revision TKAs.

Use of porous custom-made cones for meta-diaphyseal bone defects reconstruction in knee revision surgery: a clinical and biomechanical analysis

INTRODUCTION

Although the practice of metaphyseal reconstruction has obtained successful clinical and radiological results in revision total knee surgery, off-the-shelf devices aren't an effective solution for all patients as they do not cover the full range of clinical possibilities. For this reason, during severe knee revisions, custom-made porous titanium cementless metaphyseal cones are nowadays employed as alternative to traditional surgeries. The aim of this study is to understand the benefits gained by the use of the custom-made cones against the performance of more traditional techniques, such as the use of cemented or cementless stems. Thus, a retrospective study on eleven patients and a biomechanical finite element analysis (FEA) was developed, based upon three clinical cases of the clinical analyzed cohort.

MATERIALS AND METHODS

Eleven patients underwent staged total knee arthroplasty revision with the use of 16 custom-made cones to correct severe femoral and tibial meta-diaphyseal bone defects. Clinical scores and range of movement were observed during the follow-up period (mean follow-up 26 ± 9.4 months). Reason for surgery was periprosthetic joint infection (PJI) in eight patients and post-traumatic osteomyelitis in the other three patients. Three patients previously affected by PJI were selected among the eleven patients of the clinical population. For those patients, bone geometries and implants during surgery were replicated in silico and analyzed during different daily activities. For the same patients, as alternative solution for surgery, the use of cemented or cementless stems was also simulated by FEA. Stress patterns in different region of interest and risk of fracture in the bone were calculated and compared.

RESULTS

No loosening, component migration, or mismatches between preoperative planning and intraoperative findings were clinically registered. Biomechanical results demonstrated that the use of custom-made cones induces a more homogeneously distributed bone stress than the other two techniques that concentrate the stress in spotted regions. The risk of fracture is comparable between the use of custom-made cones and cemented technique, while press-fit configurations increase the risk of fracture (more than 35%).

CONCLUSIONS

Based upon the clinical evidence and the findings after the FEAs, the practice of porous custom-made metaphyseal cones in severe revisions of knee arthroplasties is showing promising biomechanical results. The homogeneous stresses distributions and the lower bone stress gradient could justify a reduction of bone fractures and the risk of implant loosening which could be the explanation to the successful clinical outcomes.

Biomechanical comparison between metal block and cement-screw techniques for the treatment of tibial bone defects in total knee arthroplasty based on finite element analysis

BACKGROUND

Managing bone defects is a critical aspect of total knee arthroplasty. In this study, we compared the metal block and cement-screw techniques for the treatment of Anderson Orthopaedic Research Institute type 2A tibial bone defects from the biomechanical standpoint.

METHOD

The metal block and cement-screw techniques were applied to finite element models of 5- and 10-mm tibial bone defects. Biomechanical compatibility was evaluated based on the stress distributions of the proximal tibia and tibial tray. The displacement of the tibial tray and maximum relative micromotion between the tibial stem and tibia were analyzed to assess the stability of the implant.

RESULTS

The maximum stress in both the proximal tibia and tibial tray was greater with the cement-screw technique than with the metal block technique. The stress of the proximal lateral tibia with the cement-screw technique was significantly larger than with the metal block technique (p < 0.05). For the 5-mm bone defect, the maximum relative micromotion was lower than the critical value of 150 μm. For the 10-mm defect, the maximum relative micromotion was 128 μm with the metal block technique and 155 μm with the cement-screw technique, with the latter exceeding the critical value.

CONCLUSIONS

The cement-screw technique showed superior biomechanical compatibility to the metal block technique and is more suitable for 5-mm bone defects. However, as it may reduce the fixation strength in 10-mm bone defects, the metal block technique is more appropriate in this case.

Porous metal cones: gold standard for massive bone loss in complex revision knee arthroplasty? A systematic review of current literature

INTRODUCTION

Revision knee arthroplasty is increasing, and in that case, bone loss management is still a challenging problem. In the last years, the body of literature and interest surrounding porous metal cones has grown, but few systematic evaluations of the existing evidence have been performed. The aim of our systematic review is to collect and critically analyze the available evidence about metal cones in revision knee arthroplasty especially focusing our attention on indications, results, complications, and infection rate of these promising orthopaedic devices.

MATERIALS AND METHODS

We performed a systematic review of the available English literature, considering the outcomes and the complications of tantalum cones. The combinations of keyword were "porous metal cones", "knee revision", "bone loss", "knee arthroplasty", "periprosthetic joint infection", and "outcome".

RESULTS

From the starting 312 papers available, 20 manuscripts were finally included. Only one included study has a control group. The main indication for metal cones is type IIb and III defects according AORI classification. Most of the papers show good clinical and radiological outcomes with low rate of complications.

CONCLUSION

The examined studies provide encouraging clinical and radiological short-to-mid-term outcomes. Clinical studies have shown a low rate of aseptic loosening, intraoperative fractures, infection rate and a lower failure rate than the previous treatment methods. Higher quality papers are needed to draw definitive conclusions about porous metal cones.

Mid-term results for metaphyseal sleeves in revision knee surgery

PURPOSE

Metaphyseal titanium sleeves have been used to provide cementless fixation in challenging bone defects in revision knee arthroplasty. The aim of this study was to evaluate the mid-term results of radiological and clinical outcomes, for metaphyseal sleeves in type 1B and 2 defects of tibia and femur under the hypothesis that they would provide stable and prolonged fixation.

METHODS

One hundred and thirty-four patients were included in a prospective study to evaluate the outcomes of knee revision with sleeves, together with stems and varus-valgus constrained mobile bearing prosthesis. Median follow-up was 71.5 months (range 36-107). Analysis included American Knee Society Score (KSS), Western Ontario and Mcmaster Universities Osteoarthritis Index (WOMAC), SF12 Health Survey and radiographic assessment.

RESULTS

All clinical scores improved significantly in all patients during the follow-up. The median of Knee KSS increased from 33 to 78 and functional KSS from 30 to 80. The median of WOMAC pain index changed from 12 to 4; pre-operative median of WOMAC stiffness and WOMAC function score improved from 5 to 2 and from 45 to 14, respectively. The median of physical SF12 varied from 27 to 44, while mental SF-12 from 43 to 54. Radiological evaluation showed optimal osseous integration in all patients, and neither implant migration nor progressive radiolucency around components was observed. Complications included three cases of end-of-stem pain at tibial side and two revisions due to septic loosening in the first post-operative year. No aseptic loosening was reported.

CONCLUSION

The use of metaphyseal sleeves, in combination with uncemented stems and varus-valgus constrained components with rotating platform, has shown excellent mid-term results allowing osseous ingrowth with no evidence of osteolysis or displacement. This is a promising option for better implant fixation in revision TKA.

LEVEL OF EVIDENCE

Case series with no comparison group, Level IV.

Management of metaphyseal bone loss in revision knee arthroplasty

Background and aim of the work: Revision total knee arthroplasty (TKA) is usually made more complex by the presence of bone defects, which may be caused by periprosthethic infection, polyethylene wear, implant loosening or fractures. The main aim of the present work is to review the available literature to understand the current options to manage with the bone loss during knee revisions. Methods: Available English literature for bone defects in revision TKAs has been evaluated looking at treatment options and their results in terms of clinical and radiological outcomes and failure rates. Results: Anderson Orthopaedic Research Institute (AORI) classification is the most frequently used because it helps in the choice of the most suitable treatment. Several options are available in the management of metaphyseal bone loss in revision knee arthroplasty. For small and contained defects (AORI type 1) cement with or without screws and auto- or allograft morcellized bone are available. In uncontained but mild defects (AORI type 2A) metal augments should be use while large and uncontained defects (AORI type 2B and 3) are best addressed with structural allograft or metal filling devices (cones and sleeves). Stemmed components, either cemented or cementless, are recommended to reduce the strain at the interface implant-host. Conclusions: The treatment of bone defects in revision TKAs has evolved during the last years providing different options with good results at a short/medium term follow up. With the increasing revision burden, further scientific evidence is requested to identify the best approach for each patient. Long-term clinical outcome as well as implant survival after revision TKA are still sub-optimal and depend upon many factors including cause for revision, surgical approach, type of implants used and various patient factors. (www.actabiomedica.it)

Management of metaphyseal bone loss in revision knee arthroplasty

BACKGROUND AND AIM OF THE WORK

Revision total knee arthroplasty (TKA) is usually made more complex by the presence of bone defects, which may be caused by periprosthethic infection, polyethylene wear, implant loosening or fractures. The main aim of the present work is to review the available literature to understand the current options to manage with the bone loss during knee revisions.

METHODS

Available English literature for bone defects in revision TKAs has been evaluated looking at treatment options and their results in terms of clinical and radiological outcomes and failure rates.

RESULTS

Anderson Orthopaedic Research Institute (AORI) classification is the most frequently used because it helps in the choice of the most suitable treatment. Several options are available in the management of metaphyseal bone loss in revision knee arthroplasty. For small and contained defects (AORI type 1) cement with or without screws and auto- or allograft morcellized bone are available. In uncontained but mild defects (AORI type 2A) metal augments should be use while large and uncontained defects (AORI type 2B and 3) are best addressed with structural allograft or metal filling devices (cones and sleeves). Stemmed components, either cemented or cementless, are recommended to reduce the strain at the interface implant-host.

CONCLUSIONS

The treatment of bone defects in revision TKAs has evolved during the last years providing different options with good results at a short/medium term follow up. With the increasing revision burden, further scientific evidence is requested to identify the best approach for each patient. Long-term clinical outcome as well as implant survival after revision TKA are still sub-optimal and depend upon many factors including cause for revision, surgical approach, type of implants used and various patient factors.

Prosthetic knee infection by resistant bacteria: the worst-case scenario

PURPOSE

The aim of the present paper was to determine (1) the incidence of failure (defined as the persistence or the recurrence of the infection), (2) the incidence of prosthesis (or even limb) loss (defined as the final need for an arthrodesis, resection arthroplasty or amputation) and (3) what factors could influence the failure in patients treated with a two-stage reimplantation for periprosthetic knee infections caused by resistant bacteria.

METHODS

The authors retrospectively reviewed 29 total knee arthroplasties infected by resistant bacteria in 29 patients who underwent a two-stage revision. Between the stages, intravenous-targeted antibiotics were administered for a median period of 8 (range 6-12) weeks. Median follow-up was 10 (range 7-14) years.

RESULTS

The authors found that failure occurred in 5 of 29 patients (17.2 %). When methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci (MR-CoNS) were involved, failure rate was 10 % (2 of 20). When vancomycin-resistant enterococcus (VRE), multidrug-resistant (MDR) Acinetobacter baumannii and MDR Pseudomonas aeruginosa were involved, the failure rate was 33.3 % (3 of 9). Of those five patients, two underwent amputations, one chronic suppressive antibiotic therapy, one arthrodesis and one resection arthroplasty; among them, three lost the limb (10.3 % of the overall group). Timing of reimplantation and patient comorbidities did not significantly influence the failure.

CONCLUSIONS

Two-stage protocol resulted in a viable option for patients with infections by some resistant organisms (MRSA and MR-CoNS). However, when highly resistant organisms were involved (VRE, MDR Acinetobacter Baumannii and MDR Pseudomonas aeruginosa), the failure rate was much higher. In all cases of failure of the two-stage reimplantation, prosthesis (or even limb) loss occurred. Consequently, patients should be counselled that when highly resistant bacteria are involved, two-stage reimplantation could not be successful, with high final risk of prosthesis (or even limb) loss.

LEVEL OF EVIDENCE

Retrospective case series, Level IV.

Articulated spacer provides long-term knee improvement after two-stage reimplantation

PURPOSE

The purpose of this study was to determine the long-term outcome in patients who underwent two-stage reimplantation with an articulated spacer following a chronic periprosthetic knee infection. The hypothesis was that the use of an articulated spacer provides significant improvement of clinical results and knee functionality through a long follow-up period, and therefore a durable revision TKA.

METHODS

Forty-six consecutive patients (46 knees) who underwent two-stage reimplantation with an articulated spacer for a chronic periprosthetic knee infection were retrospectively analysed. An articulated cement spacer, moulded in surgery room, was implanted in all cases. Patients were followed for a median period of 12 (range 6-16) years, and no patients were lost to follow-up. Patients were assessed preoperatively and postoperatively through the IKS knee and function scores and ROM.

RESULTS

Two-stage reimplantation was successful in controlling the infection in 91.3 % of patients. In the 42 patients with a successful two-stage revision, the median IKS knee and function scores were 36 (range 16-56) points and 25 (range 15-35) points, respectively, before the operation, and 76 (range 52-94) points and 70 (range 55-90) points (p < 0.001) at the last follow-up. The median ROM increased from 80 (range 60-110) degrees preoperatively to 115 (range 100-128) degrees (p < 0.01) at the last follow-up.

CONCLUSIONS

Two-stage septic revision with an articulated cement spacer provided a significant long-term improvement of preoperative clinical and functional knee scores and therefore a durable revision TKA.

LEVEL OF EVIDENCE

Retrospective case series, Level IV.

The management of bone loss in revision total knee arthroplasty: rebuild, reinforce, and augment

The treatment of bone loss in revision total knee arthroplasty has evolved over the past decade. While the management of small to moderate sized defects has demonstrated good results with a variety of traditional techniques (cement and screws, small metal augments, impaction bone grafting or modular stems), the treatment of severe defects continues to be problematic. The use of a structural allograft has declined in recent years due to an increased failure rate with long-term follow-up and with the introduction of highly porous metal augments that emphasise biological metaphyseal fixation. Recently published mid-term results on the use of tantalum cones in patients with severe bone loss has reaffirmed the success of this treatment strategy.

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.

Metaphyseal bone loss in revision knee arthroplasty

The etiology of bone loss encountered during revision total knee arthroplasty (TKA) is often multifactorial and can include stress shielding, osteolysis, osteonecrosis, infection, mechanical loss due to a grossly loose implant, and iatrogenic loss at the time of implant resection. Selection of the reconstructive technique(s) to manage bone deficiency is determined by the location and magnitude of bone loss, ligament integrity, surgeon experience, and patient factors including the potential for additional revision, functional demand, and comorbidities. Smaller, contained defects are reliably managed with bone graft, cement augmented with screw fixation, or modular augments. Large metaphyseal defects require more extensive reconstruction such as impaction bone grafting with or without mesh augmentation, prosthetic augmentation, use of bulk structural allografts, or use of metaphyseal cones or sleeves. While each technique has advantages and disadvantages, the most optimal method for reconstruction of large metaphyseal bone defects during revision TKA is not clearly established.

Treatment of severe bone defects during revision total knee arthroplasty with structural allografts and porous metal cones-a systematic review

Aseptic loosening and focal osteolysis are the most common reasons for knee arthroplasty failure. The best treatment remains unclear. We reviewed the literature on the treatment of revision knee arthroplasty using bony structural allografts (476 cases) and porous metal cones (223 cases) to determine if a difference in the revision failure rates was discernable. The failure rates were compared using a logistic regression model with adjustment for discrepancies in FU time and number of grafts used (femoral, tibial, or both). In this analysis, the porous implant shows a significantly decreased loosening rate in AORI 2 and 3 defects. The overall failure rate was also substantially lower in the porous metal group than the structural allograft group; little difference in the infection rates was noted.

Outcome of revision total knee arthroplasty with the use of trabecular metal cone for reconstruction of severe bone loss at the proximal tibia

BACKGROUND

The relative effectiveness of different methods for reconstructing large bone loss at the proximal tibia in revision total knee arthroplasty (rTKA) has not been established. The aim of this study was to evaluate the clinical and radiological outcome after the use of trabecular metal technology (TMT) cones for the reconstruction of tibial bone loss at the time of rTKA.

METHODS

Thirty-six patients had rTKA with the use of a TMT Cone. Bone loss was classified according to the AORI classification and 25% of the patients suffered from T3 AORI defects and 75% of the patients from T2 AORI defects. Implants used were from the NexGen series. At follow-up, radiographs were evaluated according to the Knee Society Roentgenographic Scoring System. Knee and function score was calculated using the Knee Society Clinical Rating System. Average follow-up time was 47 months (range 3-84 months).

RESULTS

Clinical and radiological follow-up data were available in 30 patients and missing in six patients: two died and four patients had re-revision (reinfection (n=2), aseptic loosening (n=1), and knee hyperextension (n=1)). Knee- and function scores (follow-up 43 months (range 12-84 months)) improved from 42 to 77 points (p<0.0005) and 19 to 63 points (p<0.0005) respectively. Twenty-seven patients (follow-up 44 months (range 12-72 months)) showed no signs of radiological loosening of rTKA components.

CONCLUSION

Based on our study, it was concluded that the use of TMT Cones provided an effective treatment in terms of surgical efficacy, clinical results and radiological results and was evidently at least as effective as the other options reviewed in the literature.

LEVEL OF EVIDENCE

IV.

Low-grade periprosthetic knee infection: diagnosis and management

Diagnosis and management of low-grade periprosthetic knee infection are still controversial and debatable. The diagnosis of low-grade infection after total knee arthroplasty is often complex, as clinical symptomatology and diagnostic studies are highly conflicting and knees often exhibit well-fixed components. Although the criterion standard for staged reimplantation is interim placement of an antibiotic-loaded spacer, less-invasive surgical procedures have been advocated for managing infections caused by low-virulence bacteria. Debridement with polyethylene exchange and single-stage reimplantation could offer advantages, such as fewer surgeries, reduced potential for intraoperative complications, and lower direct social costs. The aim of this narrative review was to analyze the literature to evaluate the effectiveness of different surgical procedures in managing low-grade periprosthetic knee infections. Additionally, the most reliable investigations for diagnosing total knee infection caused by low-virulence bacteria were reviewed.

Level of evidence Level V.

Metal block augmentation for bone defects of the medial tibia during primary total knee arthroplasty

Background

Stable and well-aligned placement of tibial components during primary total knee arthroplasty is challenging in patients with bone defects. Although rectangular block-shaped augmentations are widely used to reduce the shearing force between the tibial tray and bone compared with wedge-shaped augmentations, the clinical result remains unclear. This study aimed to evaluate the outcome of primary total knee arthroplasty with metal block augmentation.

Methods

We retrospectively reviewed the 3- to 6-year follow-up results of 33 knees that underwent total knee arthroplasty with metal block augmentation (metal-augmented group) for bone defects of the medial tibia and 132 varus knees without bone defects as the control group. All surgeries were performed using posterior-stabilized cemented prostheses in both groups. Cemented stems were routinely augmented when the metal block was used.

Results

There were no differences in implant survival rates (100% in metal-augmented and 99.2% in control) or knee function scores (82 points in metal-augmented and 84 points in control) between the two groups at the final follow-up examination (P = 0.60 and P = 0.09, respectively). No subsidence or loosening of the tibial tray was observed. Of 33 metal-augmented total knee arthroplasties, a nonprogressive radiolucent line beneath the metal was detected in 10 knees (30.3%), and rounding of the medial edge of the tibia was observed in 17 knees (51.5%).

Conclusions

The clinical results of total knee arthroplasty with metal augmentation were not inferior to those in patients without bone defects. However, radiolucent lines were observed in 30.3%.

Three-year follow up utilizing tantal cones in revision total knee arthroplasty

There still is no consensus on the treatment of choice in revision knee arthroplasty associated with severe femoral and/or tibial bone loss. A total of 44 patients underwent revision knee arthroplasty procedures using porous tantalum cones (TM cones) to reconstruct tibial and/or femoral bone defects. At latest follow up after 37 months (32-48), 38 patients remained in the study. Tibial and femoral bone loss was categorized according to the AORI-Classification. The average preoperative KSS improved from 34 (range, 6-90) to 63 points (range, 7-90 points). The VAS improved from 7.5 to 4.8. Two patients required a re-revision due to aseptic loosening. There was no correlation between the different types of knee prosthesis implanted. Our study shows favourable clinical and radiological outcomes using TM cones in managing significant bone loss in revision total knee surgery.

Constraint choice in revision knee arthroplasty

PURPOSE

Along with the increase in primary total knee arthroplasty, there has been an increase in the number of revisions. The aim of this study was to propose a selection algorithm for the knee revision constraint according to the state of ligaments and to the bone defects Anderson Orthopaedic Research Institute Classification [AORI] classification. The hypothesis was that this algorithm would facilitate the appropriate choice of prosthesis constraint, thus providing stable components and a good long-term survivorship of the knee revisions.

METHODS

Sixty consecutive revision knee arthroplasties in 57 patients were prospectively evaluated. Prostheses implanted at revision included postero-stabilised, condylar constrained and rotating hinged, relative to the state of the ligaments and of the bone loss around the knee. The median follow-up was nine years (range, 4-12).

RESULTS

The median IKS knee and function scores and HSS score were 41 (15-62), 21.5 (12-43) and 34 (23-65) points, respectively, before the operation, and 81 (48-97), 79 (56-92) and 83.5 (62-98) points (p < 0.001) at the latest follow-up evaluation. The median ROM increased from 74° (29-110°) preoperatively to 121° (98-132°) (p < 0.01) at the final follow-up. Re-revision was necessary in five (8.3%) patients.

CONCLUSIONS

A selection algorithm for the revision implant constraint based on the state of ligaments and the bone loss AORI classification could provide stable knee reconstructions and long-term success of knee revisions.