Metaphyseal Fixation Using Highly Porous Cones in Revision Total Knee Arthroplasty: Minimum Two Year Follow Up Study

Promising short-term outcomes of free-hand burring technique to implant second-generation metaphyseal cone in Asian knees - a case series

BACKGROUND

The second-generation metaphyseal cone was useful in managing bone defects in revision knee arthroplasty. However, due to the anatomical constraints in Asian osteometry, the authors utilized a novel free-hand burring technique instead of cannulated reaming for bone preparation. We reported the short-term outcomes of our surgical techniques specific to Asian osteometry.

METHODS

We conducted a case series by consecutively recruiting 13 female and 12 male patients (involving 25 knees), with a mean age of 71 years (range, 54-88 years). The patients underwent revision total knee arthroplasty during the period from April 2017 to June 2022. Twenty-three tibial cones and 4 femoral cones using free-hand burring technique were implanted. The mean follow-up duration was 51 months (range 18-80 months). Due to the relatively small bone size and meta-diaphyseal center mismatch in the Asian knees, the free-hand burring technique instead of the cannulated reaming technique was adopted in preparing for cone implantation. The clinical outcomes were knee ranges of motion, the Knee Society Knee scores (KSS), end-of-stem pain, infection, and the need for revision surgery. The radiological outcomes included osteointegration, fracture, and loosening.

RESULTS

Mean knee range of motion improved from 83 degrees (range 0°-120°) preoperatively to 106 degrees (range 60°-125°) postoperatively (P < 0.001). Mean KSS improved significantly from 29 (range 0-70) to 69 (range 5-100) (P < 0.001). All cones were osteointegrated. One case had transient end-of-stem pain, two developed intraoperative minor femoral fractures and one suffered from recurrent infection that did not require cone revision. Cone revision-free survivorship was 100%. There was no aseptic loosening.

CONCLUSIONS

The second-generation cone implanted with free-hand burring bone preparation yielded promising short-term outcomes in Asian knees.

Comparison of Novel 3D-printed Stepped Porous Metal Cones and Metaphyseal Sleeves for Reconstruction of Severe Knee Bone Defects: Short-term Clinical Outcomes

OBJECTIVE

Both porous metal cones and metaphyseal sleeves are excellent implants for reconstructing severe bone defects in the knee joint, but they both exhibit design limitations. The porous metal cone, especially, has significant room for improvement in its shape design. The existing porous metal cones often feature a conical external surface with a relatively small taper, potentially compromising both rotational and axial stability. To improve both axial and rotational stability in porous metal cones, we developed a 3D-printed stepped porous metal cone. This study aimed to assess the short-term clinical outcome of the 3D-printed stepped porous metal cone and to compare it with the clinical outcome of patients who underwent revision total knee arthroplasty (rTKA) with the metaphyseal sleeves during the same period.

METHOD

Patients who underwent total knee arthroplasty revision with metaphyseal bone defect reconstruction from 2019 to 2021 were retrospectively analyzed. A total of 61 patients were enrolled in the study, including 15 patients using 3D-printed stepped porous metal cones and 46 patients using metaphyseal metal sleeves. Thirty patients using metaphyseal sleeves were screened by propensity score matching method and compared with those using stepped cones. Analysis included the American Knee Society Score, the Hospital for Special Surgery knee score, the Western Ontario and McMaster Universities Arthritis index, the Short Form 12 (SF-12) health survey, and radiographic assessment with a mean follow-up of 28.5 ± 8.3 months. To conduct comparative analyses, unpaired Student's t-tests were employed for continuous variables, while categorical variables were analyzed using the appropriate Fisher exact or chi-squared test.

RESULTS

In this study, the survival rates of both the stepped cone and metaphyseal sleeve were 100%. There was no statistically significant difference in postoperative knee function scores between the two groups (p > 0.05). However, patients in the cone group had significantly higher mental component summary scores on the SF-12 scale (p < 0.05) and higher increases in mean postoperative physical component summary scores than patients in the sleeve group (p < 0.05). In addition, patients in the cone group experienced fewer intraoperative and postoperative complications compared to the sleeve group.

CONCLUSION

The 3D-printed stepped porous metal cone can effectively reconstruct bone defects in complex rTKA and provide satisfactory early clinical and radiographic results. The 3D-printed stepped cone provides a more stable structure similar to the sleeve while maintaining the original benefits of the cone making it a promising choice for rTKA.

Tips and Tricks to Save You During Revision Total Knee Arthroplasty

The number of revision total knee arthroplasties (TKAs) performed annually continues to rise. This article is a summary of a symposium on revision TKAs presented at the 2023 American Association of Hip and Knee Surgeons annual meeting. It will provide an overview of the surgical tips and tricks for exposure and component removal, use of metaphyseal fixation and stems to manage bone loss and optimize fixation, constraint in TKA, as well as how to manage extensor mechanism disruptions with a synthetic mesh reconstruction. LEVEL OF EVIDENCE: V.

Short-term Comparison of Survivorship and Functional Outcomes for Metaphyseal Cones with Short and Long Stems in Revision Total Knee Arthroplasty

Printed porous titanium metaphyseal cones have become a mainstay for managing bone loss in revision total knee arthroplasty (rTKA). A short or long stem is routinely used when implanting a cone to augment fixation and offload stresses. This retrospective analysis compared the short-term survivorships and functional outcomes for use of a short or long stem with a metaphyseal cone.A total of 179 cases using metaphyseal cones and stems with median follow-up of 1.95 years (interquartile range, 1.00-2.14) were compared based on stem type. There were 55 cases with long stem(s) and 124 cases with short stem(s). Cases with both long and short stems were excluded. Demographics, Kaplan-Meier survivorships, and preoperative and 1-year postoperative patient-reported outcome measures (PROMs; 2011 Knee Society Score [KSS] objective knee score, function, and satisfaction scores; EuroQol five-dimension scale; and Short Form Survey Physical Component Summary and Mental Component Summary scores) were compared using t-tests with a significance level of α = 0.05. There were no significant differences in body mass index (mean ± standard deviation) or sex (men [%]) between the short and long stem cohorts (32.3 ± 5.3, 36.3% and 31.5 ± 5.5, 38.2%, respectively; p > 0.05). Patients who had short stems were younger (65.9 ± 8.8 vs. 69.0 ± 9.4, p = 0.0323).Revision-free survivorship for the femoral or tibial component was 100% for long stems and 98.2% for short stems at 1 and 2 years, respectively (log-rank p = 0.6330). The two revisions in the short group were for infection, thus the survivorship for aseptic loosening was 100% at 2 years for both cohorts. There were no significant differences in preoperative or postoperative PROMs.This study demonstrated that highly porous printed metaphyseal cones provided rTKA with excellent early survivorship and similar PROMs whether a short or long stem was used. Additional studies will be needed to discern longer term differences.

A novel quantitative grading system for implant fixation in revision total knee arthroplasty

Aims

Obtaining solid implant fixation is crucial in revision total knee arthroplasty (rTKA) to avoid aseptic loosening, a major reason for re-revision. This study aims to validate a novel grading system that quantifies implant fixation across three anatomical zones (epiphysis, metaphysis, diaphysis).

Methods

Based on pre-, intra-, and postoperative assessments, the novel grading system allocates a quantitative score (0, 0.5, or 1 point) for the quality of fixation achieved in each anatomical zone. The criteria used by the algorithm to assign the score include the bone quality, the size of the bone defect, and the type of fixation used. A consecutive cohort of 245 patients undergoing rTKA from 2012 to 2018 were evaluated using the current novel scoring system and followed prospectively. In addition, 100 first-time revision cases were assessed radiologically from the original cohort and graded by three observers to evaluate the intra- and inter-rater reliability of the novel radiological grading system.

Results

At a mean follow-up of 90 months (64 to 130), only two out of 245 cases failed due to aseptic loosening. Intraoperative grading yielded mean scores of 1.87 (95% confidence interval (CI) 1.82 to 1.92) for the femur and 1.96 (95% CI 1.92 to 2.0) for the tibia. Only 3.7% of femoral and 1.7% of tibial reconstructions fell below the 1.5-point threshold, which included the two cases of aseptic loosening. Interobserver reliability for postoperative radiological grading was 0.97 for the femur and 0.85 for the tibia.

Conclusion

A minimum score of 1.5 points for each skeletal segment appears to be a reasonable cut-off to define sufficient fixation in rTKA. There were no revisions for aseptic loosening at mid-term follow-up when this fixation threshold was achieved or exceeded. When assessing first-time revisions, this novel grading system has shown excellent intra- and interobserver reliability.

Metaphyseal Fixation Using Cones and Sleeves for Severe Proximal Tibial Bone Loss

BACKGROUND

Tibial bone defects are commonly encountered in revision total knee arthroplasty (rTKA) and can be managed with metaphyseal cones or sleeves. Few studies have directly compared tibial cones and sleeves in rTKA, and none have limited this comparison to the most severe tibial defects. The purpose of this study was to evaluate and compare the outcomes of metaphyseal cones and sleeves for tibial reconstruction in rTKA regarding implant fixation and clinical outcomes.

METHODS

A retrospective review was conducted on patients undergoing rTKA in which metaphyseal cones or sleeves were utilized for addressing metaphyseal bone loss (34 cones and 18 sleeves). Tibial bone loss was classified according to the Anderson Orthopaedic Research Institute bone defect classification, with types 2B and 3 being included. Patient-reported outcomes and postoperative complications were collected, and a radiographic evaluation of osseointegration or loosening was performed.

RESULTS

There were 52 knees included (34 cones, 18 sleeves), with a median follow-up of 41.0 months. All-cause implant survival was 100% at 2 years and 96% (95% confidence interval: 76 to 99%) at 4 years, with 98% of tibial components demonstrating osseointegration at the final follow-up. During follow-up, there were a total 11 revisions, of which 1 sleeve was revised secondary to implant loosening. Tibial sleeves had a higher risk of revision compared to tibial cones (P < .01), and sleeves fixed with a hybrid technique were more likely to need revision than cones fixed by the same method (P = .01).

CONCLUSIONS

Porous metaphyseal tibial cones and tibial metaphyseal sleeves both performed well at a 41-month median follow-up with no difference in aseptic survivorship between the 2 constructs. Both demonstrate high rates of osseointegration, low rates of aseptic failure, and significant improvement in Knee Society Scores in patients with severe tibial defects in rTKA.

Metaphyseal cones combined with diaphyseal impaction grafting provide good outcomes and survival in a complex revision total knee arthroplasty: a matched comparative analysis

PURPOSE

To compare clinical and radiological outcomes, implant survivorship at a minimum of 1-year follow-up using metaphyseal trabecular cones with or without impaction grafting in a complex revision TKA.

METHODS

A retrospective comparative matched analysis was performed and 15 patients who underwent revision surgery using the combination of porous trabecular metaphyseal cone and diaphyseal impaction grafting (MC-IBG) were matched with a group of 13 patients who also underwent revision surgery using metaphyseal cone (MC) without impaction grafting. All included patients presented severe bone defect (AORI 2,3) and a rotating-hinge prosthesis were implanted.

RESULTS

Both groups were comparable regarding the baseline demographic and clinical data. Patients had previously undergone a mean of 4 (range, 2-12) and 3 (range, 2-5) previous procedures in the MC-IBG and MC groups, respectively. The indications for revision were aseptic loosening in 11 (73.3%) and 11 (84.6%) patients; prosthetic joint infection in 4 (26.7%) and 2 (15.4%) in the MC-IBG and MC groups, respectively. There was no significant difference in the mean postoperative Knee Society Score between the study groups (p = 0.806). Overall, 4 patients had further revision. Two patients were revised in the MC-IBG group, one patient for aseptic loosening and the second one after 2 episodes of instability. Two patients in the MC group presented prosthetic joint infection and underwent a two-stage reimplantation. No significant difference was observed between the study groups at comparison (p = 0.92).

CONCLUSION

Trabecular metal cones with diaphyseal impaction grafting provide an alternative technique in a complex revision TKA surgery with early clinical and radiographic success.

Fostering Excellence in Knee Arthroplasty: Developing Optimal Patient Care Pathways and Inspiring Knowledge Transfer of Advanced Surgical Techniques

Osteoarthritis of the knee is common. Early sports trauma or cartilage defects are risk factors for osteoarthritis. If conservative treatment fails, partial or total joint replacement is often performed. A joint replacement aims to restore physiological biomechanics and the quality of life of affected patients. Total knee arthroplasty is one of the most performed surgeries in musculoskeletal medicine. Several developments have taken place over the last decades that have truly altered the way we look at knee arthroplasty today. Some of the fascinating aspects will be presented and discussed in the present narrative review.

Custom-Made Metaphyseal Sleeves in "Beyond" AORI III Defects for Revision Knee Arthroplasty-Proof of Concept and Short-Term Results of a New Technique

BACKGROUND

While off-the-shelf cones and sleeves yield good results in AORI type 2 and 3 defects in revision knee surgery, massive longitudinal defects may require a proximal tibia replacement. To achieve the best anatomical as well as biomechanical reconstruction and preserve the tibial tuberosity, we developed custom-made metaphyseal sleeves (CMSs) to reconstruct massive defects with a hinge knee replacement.

METHODS

Between 2019 and 2022, 10 patients were treated in a single-center study. The indication for revision was aseptic loosening in five cases and periprosthetic joint infection in five cases. The mean number of previous revisions after the index operations was 7 (SD: 2; 4-12). A postoperative analysis was conducted to evaluate the functional outcome as well as the osteointegrative potential.

RESULTS

Implantation of the CMS in rTKA was carried out in all cases, with a mean operation time of 155 ± 48 (108-256) min. During the follow-up of 23 ± 7 (7-31) months, no CMS was revised and revisions due to other causes were conducted in five cases. Early radiographic evidence of osseointegration was recorded using a validated method. The postoperative OKS showed a significant increase (p < 0.001), with a mean score of 24 (SD: 4; range: 14-31).

CONCLUSION

Custom-made metaphyseal sleeves show acceptable results in extreme cases. As custom-made components become more and more common, this treatment algorithm presents a viable alternative in complex rTKA.

Metaphyseal cones and sleeves are similar in improving short- and mid-term outcomes in Total Knee Arthroplasty revisions

PURPOSE

The purpose of this systematic review and metanalysis was to assess clinical and radiological outcomes of metaphyseal sleeves and cones and to identify their possible advantages and disadvantages.

METHODS

A comprehensive search from the inception of the databases to March 2021 was performed on Medline, Scopus, CINAHL, Cochrane, Embase, Ovid, and Google scholar databases. Coleman Methodology Score was used for quality assessment. Author, year of publication, type of study, level of evidence, sample size, number of patients, number of knees treated, mean age, gender, mean follow-up, clinical outcomes, complications, the reason for revision and, type of prosthesis were extracted for analysis. Clinical studies providing data about patient's outcomes after the primary and Total Knee Arthroplasty revision with the usage of sleeves or cones and a minimum of 2 years of follow-up were included.

RESULTS

The literature search and cross-referencing resulted in a total of 93 articles, but only 30 articles were appropriate for the systematic review. Comparable clinical results were reported between cones and sleeves. The meta-analysis showed a greater incidence of intraoperative fractures in patients treated with sleeves (1.6%, [95% CI 0.7; 3.4] in cones and 4.6%, [95% CI 3.3; 6.4] in sleeves, p = 0.01), while the risk of postoperative fractures (4.3%, [95% CI 2.7; 7] in cones and 2.1%, [95% CI 1.2; 3.5] in sleeves, p = 0.04) and infections (8.5%, [95% CI 6; 12] in cones and 3.7%, [95% CI 2.1; 7.3] in sleeves, p = 0.03) was higher with cones.

CONCLUSION

A higher incidence of intraoperative fracture was reported in patients treated with sleeves, while a higher rate of postoperative fractures and infections was described in patients treated with cones. Nonetheless, complications were reported in both groups.

LEVEL OF EVIDENCE

III.

Novel metaphyseal porous titanium cones allow favorable outcomes in revision total knee arthroplasty

INTRODUCTION

Loosening and migration are common modes of aseptic failure following complex revision total knee arthroplasty (rTKA). Metaphyseal cones allow surgeons to negotiate the loss of femoral and tibial bone stock while obtaining stable bony fixation. This study examines the mid-term functional and radiographic outcomes in patients undergoing rTKA utilizing a novel metaphyseal cone system with stems of variable length and fixation methods.

METHODS

This two-center retrospective study examined all patients who underwent rTKA with a novel porous, titanium tibial or femoral cone in combination with a stem of variable length and fixation who had a minimum follow-up of 2-years. Outcome analysis was separated into tibial and femoral cones as well as the stem fixation method (hybrid vs. fully cemented).

RESULTS

Overall, 123 patients who received 156 cone implants were included (74 [60.2%] tibial only, 16 [13.0%] femoral only, and 33 [26.8%] simultaneous tibial and femoral) with a mean follow-up of 2.76 ± 0.66 years. At 2-years of follow-up the total cohort demonstrated 94.3% freedom from all-cause re-revisions, 97.6% freedom from aseptic re-revisions, and 99.4% of radiographic cone osteointegration. All-cause revision rates did not differ between stem fixation techniques in both the tibial and femoral cone groups.

CONCLUSION

The use of a novel porous titanium femoral and tibial metaphyseal cones combined with stems in patients with moderate to severe bone defects undergoing complex revision total knee arthroplasty confers excellent results independent of stem fixation technique.

LEVEL OF EVIDENCE

IV, case series.

Standardized Fixation Zones and Cone Assessments for Revision Total Knee Arthroplasty Using Deep Learning

BACKGROUND

Achieving adequate implant fixation is critical to optimize survivorship and postoperative outcomes after revision total knee arthroplasty (rTKA). Three anatomical zones (ie, epiphysis, metaphysis, and diaphysis) have been proposed to assess fixation, but are not well-defined. The purpose of the study was to develop a deep learning workflow capable of automatically delineating rTKA zones and cone placements in a standardized way on postoperative radiographs.

METHODS

A total of 235 patients who underwent rTKA were randomly partitioned (6:2:2 training, validation, and testing split), and a U-Net segmentation workflow was developed to delineate rTKA fixation zones and assess revision cone placement on anteroposterior radiographs. Algorithm performance for zone delineation and cone placement were compared against ground truths from a fellowship-trained arthroplasty surgeon using the dice segmentation coefficient and accuracy metrics.

RESULTS

On the testing cohort, the algorithm defined zones in 98% of images (8 seconds/image) using anatomical landmarks. The dice segmentation coefficient between the model and surgeon was 0.89 ± 0.08 (interquartile range [IQR]:0.88-0.94) for femoral zones, 0.91 ± 0.08 (IQR: 0.91-0.95) for tibial zones, and 0.90 ± 0.05 (IQR:0.88-0.94) for all zones. Cone identification and zonal cone placement accuracy were 98% and 96%, respectively, for the femur and 96% and 89%, respectively, for the tibia.

CONCLUSION

A deep learning algorithm was developed to automatically delineate revision zones and cone placements on postoperative rTKA radiographs in an objective, standardized manner. The performance of the algorithm was validated against a trained surgeon, suggesting that the algorithm demonstrated excellent predictive capabilities in accordance with relevant anatomical landmarks used by arthroplasty surgeons in practice.

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.

Tantalum Cones for Severe Bone Defects in Revision Knee Arthroplasty: A Minimum 10-Year Follow-Up

BACKGROUND

Two-to 6-year results of reconstruction of severe bone defects in revision total knee arthroplasty (TKA) with highly porous tantalum cones have been encouraging, but 10-year follow-up is lacking. The purpose of this study was to determine the minimum 10-year results of tantalum cones in revision TKA.

METHODS

From 2005 to 2010, 30 consecutive patients (30 knees) underwent revision TKA with the use of cones. All patients were followed clinically and radiographically for a minimum of 10 years. A total of 42 cones (25 tibial and 17 femoral) were used to reconstruct massive bone defects classified as Anderson Orthopaedic Research Institute Types 2A (10), 2B (12), and 3 (19). The mean age of the patients was 73 years (range, 55 to 84) at the time of revision. The indication for the revision included aseptic loosening (15 patients) and second-stage reimplantation for deep infection (15 patients). Six patients were lost to follow-up.

RESULTS

In total, 6 cones had to be revised. Minimum 10-year cone survivorship for any reason was 81% (25 of 31 cones). With cone revision for aseptic loosening as the end point, survivorship was 96% (30 of 31). No evidence of loosening or migration of any implant was noted on the most recent radiographs.

CONCLUSION

Metaphyseal fixation with tantalum cones in revision TKA demonstrated excellent survivorship and fixation at a minimum follow-up of 10 years. This type of metaphyseal reconstruction can be a durable option for revision TKA in patients who have massive bone defects.

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.

Does the use of 3D-printed cones give a chance to postpone the use of megaprostheses in patients with large bone defects in the knee joint?

Revision procedures and the resulting bone loss are a big challenge for orthopedic surgeons. Therefore, we checked what functional outcomes that 3D-printed cone augments can offer to patients with bone defects (Anderson Orthopedic Research Institute [AORI] classification type 2B and 3) in the knee and whether the use of cones can delay the necessity to use a megaprotheses. Data from 64 patients (M = 22; W = 42) who underwent total knee arthroplasty (TKA) revision were included in the analysis. The Knee Society Clinical Rating System (KSS) and the range of motion in the knee joint were used for the functional assessment. The mean follow-up was 28 months (range: 18–44 months). The survival rate for aseptic loosening at follow-up was 100%. Infection occurred in two (3.1%) patients. The mean KSS score increased from 12.75 points preoperatively to 66.56 postoperatively (p < 0.001). The mean range of motion in the knee changed from 61.15° preoperatively to 115.93° postoperatively (p < 0.001). 3D-printed cone augments seem to be a good solution for patients requiring a TKA revision procedure. When used in patients with bone defects classified as 2B and 3 (AORI), they can be a good alternative, delaying the need for megaprotheses.

Short-Term Survivorship of 3D-Printed Titanium Metaphyseal Cones in Revision Total Knee Arthroplasty: A Systematic Review

Background

Several studies have evaluated the outcomes of tantalum cones in revision knee arthroplasty with moderate-to-severe metaphyseal bone defects. However, recent innovations have led to the development of 3-D printed titanium cones to better adapt to host bone, there remains no consensus on their overall performance.

Objective

We therefore performed a systematic review of the literature to examine short-term survivorship and complication rates of their usage in revision TKAs.

Methods

A systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A comprehensive search of PubMed, MEDLINE, EMBASE, and the Cochrane Database of Systematic Reviews was conducted for English articles using various combinations of keywords.

Results

In all, 7 articles met the inclusion criteria. A total of 687 cones were implanted in 557 revision TKAs. The all-cause revision-free survivorship of the implants was 95.3% (26 revisions), and of the cones was 95.5% (31 cones revised) at mean 24 months follow-up. The cones revision-free survivorship from aseptic loosening was 99.7%. The overall complication rate was 19.7% with infection as the most common complications observed and the most frequent reason for revision with an incidence of 10.4% and 4.1%, respectively. Overall, functional outcomes improved as documented by postoperative knee scores.

Conclusion

3-D printed metal cones represent a reliable option in metaphyseal bone defects reconstruction that provides high fixation, good short-term survivorship, and complications rates in line with similar devices. In addition, they are associated with lower intraoperative complications, and higher survivorship from aseptic loosening.

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.

Revision Total Knee Arthroplasty With a Rotating-Hinge Prosthesis Mated to a Well-Fixed Femoral Sleeve

BACKGROUND

Some knee systems have the unique capability to mate a new hinged femoral component to a well-fixed metaphyseal sleeve from a prior revision. We compared survivorship, radiographs, and clinical outcomes of a rotating-hinge total knee arthroplasty mated to a new metaphyseal sleeve vs a well-fixed sleeve.

METHODS

Sixty patients with an S-ROM Noiles (DePuy Synthes, Warsaw, IN) rotating-hinge total knee arthroplasty implanted from 1998 to 2019 were retrospectively reviewed. Nine patients (15%) had the femoral component mated to a well-fixed sleeve and 51 patients (85%) had a new sleeve. Mean age was 68 years, 68% were female, and mean body mass index was 33 kg/m². The incidences of re-revision and reoperation were calculated, Knee Society Scores were measured, and radiographs were reviewed. Mean follow-up was 5 years.

RESULTS

There were 2 re-revisions (22%) in patients with a well-fixed sleeve: 1 for infection and 1 for aseptic loosening of the femur and tibia. There were no unique failures including the taper junction. Nine patients (18%) with a new sleeve were re-revised: 7 for infection and 2 for tibial aseptic loosening. The mean Knee Society Score for all patients improved from 39 to 73. Radiographically, all components were well fixed except for one loose femur in a patient with a new sleeve.

CONCLUSION

Mating an S-ROM femur to a well-fixed sleeve from a prior revision is a safe, simple, and durable option in the short term that prevents morbidity associated with removal of a well-fixed sleeve. No new modes of failure were observed.

LEVEL OF EVIDENCE

IV (retrospective), Therapeutic.

The Cost-Effectiveness of Tibial Metaphyseal Cones in Revision Total Knee Arthroplasty

BACKGROUND

The purpose of this study is to evaluate the cost-effectiveness of tibial cones in revision total knee arthroplasty.

METHODS

A Markov model was used for cost-effectiveness analysis. The average cone price was obtained from Orthopedic Network News. The average cone aseptic loosening rate was determined by literature review. Hospitalization costs and baseline re-revision rates were calculated using the PearlDiver Database.

RESULTS

The maximum cost-effective cone price varied from $3514 at age 40 to $648 at age 90, compared to the current average selling price of $4201. Cones became cost-effective with baseline aseptic loosening rates of 0.89% annually at age 40 to 4.38% annually at age 90, compared to the current average baseline loosening rate of 0.76% annually.

CONCLUSION

For the average patient, tibial cones are not cost-effective, but may become so at lower prices, in younger patients, or in patients at substantially increased risk of aseptic loosening.

Comparison of Different Strategies in Revision Arthroplasty of the Knee with Severe Bone Loss: A Systematic Review and Meta-Analysis of Clinical Outcomes

BACKGROUND

In revision total knee arthroplasty large bone lesions can jeopardize correct implant orientation and fixation. Different strategies have been proposed to tackle this issue. The purpose of this review and meta-analysis is to evaluate the midterm clinical and survivorship results of porous cones and porous-coated sleeves compared to morselized and structural grafts.

METHODS

We performed a systematic review of the literature on the different strategies targeting moderate to large metaphyseal bone defects. The literature was evaluated for methodological quality. We analyzed results on survivorship using logistic regression correcting for follow-up time and number of knees. We compared these results using forest plots for early and midterm follow-up. Clinical outcome was evaluated by comparing standardized mean difference of patient-related outcome measures.

RESULTS

A total of 77 articles analyzing 4,391 knees were included. The logistic regression curve showed a nonsignificant odds ratio (OR) at 10 years of 0.91 (95% confidence interval [CI] 0.699-1.192, P = .49) for failure comparing all porous implants with all grafting procedures. The available clinical reports show a bigger standardized mean difference increase for tantalum cones (OR 3.04, 95% CI 1.71-4.37) than for porous sleeves (OR 1.72, 95% CI 0.88-2.57).

CONCLUSION

Our analysis shows that the size and quality of the literature on metaphyseal bone defects is progressively improving. Porous implants are effective in tackling metaphyseal bone defects showing good survivorship outcome at midterm follow-up. In younger patients with less constrained prosthetic implants, surgeons might still consider the use of grafts without risking worse outcomes.

Survivorship of Metaphyseal Cones and Sleeves in Revision Total Knee Arthroplasty

BACKGROUND

Bone loss remains an anticipated challenge in revision total knee arthroplasty (rTKA). Recent efforts to enhance rTKA fixation and stability have focused on metaphyseal implants, namely cones and sleeves. We sought to compare cone and sleeve implant survivorship in rTKA.

METHODS

One hundred eighty patients who underwent rTKA with metaphyseal implants from 2005 to 2018 were retrospectively reviewed. A total of 83 cones (22 femoral, 62 tibial) and 121 sleeves (58 femoral, 63 tibial) were identified. The mean age at the time of surgery was 72 years (range 43-97). Intraoperative Anderson Orthopaedic Research Institute bone loss classifications included the following: type 2A (25), type 2B (98), and type 3 (81). Mean follow-up was 41 months.

RESULTS

Revision-free survival for cones was 91.3% vs 92.2% for sleeves (P = .29). Twelve knees (4 cones, 8 sleeves) underwent irrigation, debridement, and polyethylene exchange with metaphyseal implant retention for acute postoperative periprosthetic joint infection (PJI). Development of chronic PJI warranted removal of 7 cones (8.4%), 6 of which were initially placed as part of a 2-stage revision TKA. Eight sleeves (6.6%) were removed for PJI, with all initially placed during a second stage reimplantation. In the absence of infection, survival was 100% and 99.1% for cones and sleeves, respectively. One sleeve was revised for periprosthetic fracture.

CONCLUSION

Metaphyseal cones and sleeves offer equally durable survivorship in revision TKA. PJI was the most common mode of implant failure in this series. Importantly, no cases of cone or sleeve aseptic loosening were observed.

Use of Cementless Metaphyseal Fixation in Revision Total Knee Arthroplasty in the United States

BACKGROUND

Fixation options for revision total knee arthroplasty (rTKA) have expanded and now include cementless metaphyseal fixation. The utilization rates of these implants in the United States are not well known. The purpose of this study was to analyze trends in cementless metaphyseal fixation for rTKA within the American Joint Replacement Registry (AJRR).

METHODS

The AJRR was queried for the years 2015-2019 to identify all rTKA with implant data. Trends in the use of cementless sleeves, metaphyseal cones, and any cementless metaphyseal fixation (sleeves + cones) were examined over the study period using logistic regression analysis.

RESULTS

Twenty thousand two hundred and eighty rTKA were analyzed. Cementless metaphyseal fixation was used in 16% of rTKA and significantly increased over the study period (14% to 19%, P < .0001). Cementless metaphyseal fixation was more frequently utilized during revision for aseptic loosening than other diagnoses (OR 1.014, 95% CI 1.001-1.027). Cementless sleeve utilization decreased over time (11% to 9%, P = .004), driven by decreased use on the femur (4% to 2%, P < .0001). The use of cones increased significantly over time (3% to 9%, P < .0001), driven by increased use on the tibia (2% to 9%, P < .0001). Cones were 22 times more likely to be utilized on the tibia relative to the femur (P < .0001) and were more likely to be used in revisions for infection (OR 1.103, 95% CI 1.089-1.117) and aseptic loosening (OR 1.764, 95% CI 1.728-1.800).

CONCLUSION

Cementless metaphyseal fixation has grown in popularity yet, still comprised only 16% of rTKA over a 5-year period. Most of the increase was due to the utilization of tibial metaphyseal cones.

Revision TKA with a distal femoral replacement is at high risk of reinfection after two-stage exchange for periprosthetic knee joint infection

PURPOSE

Megaprosthetic distal femoral reconstruction (DFR) is a limb-salvage procedure to address bone loss following two-stage revision for periprosthetic knee joint infection (PJI). The purpose of this study was to analyze the survival of DFR compared to hinged total knee arthroplasty (TKA). It was hypothesized that DFR was associated with a poorer survival.

METHODS

In this retrospective single-center study, 97 subjects who underwent two-stage revision of chronic knee PJI were included. Among these, 41 were DFR. The diagnosis of PJI was established using the Musculoskeletal Infection Society (MSIS) criteria. Implant survival was calculated using Kaplan-Meier method and compared with the log-rank test as well as multivariate Cox regression at a minimum follow-up period of 24 months.

RESULTS

The median follow-up period was 59 (interquartile range (IQR) 45-78) months. Overall, 24% (23/97) of patients required revision surgery for infection. The infection-free survival of rotating hinge revision TKA was 93% (95% Confidence Interval (CI) 86-100%) at five years compared to 50% (95% CI 34-66%) for DFR. In multivariate analysis, the risk factors for reinfection were DFR reconstruction (HR 4.7 (95% CI 1-22), p = 0.048), length of megaprosthesis (HR 1.006 (95% CI 1.001-1.012), p = 0.032) and higher BMI (HR 1.066, 95% CI 1.018-1.116), p = 0.007). 10% (4/41) of patients undergoing DFR underwent amputation to treat recurrent infection.

CONCLUSION

Megaprosthetic DFR as part of a two-stage exchange for PJI is a salvage treatment that has a high risk for reinfection compared to non-megaprosthetic TKA. Patients must therefore be counseled accordingly.

LEVEL OF EVIDENCE

Retrospective observational study, Level IV.

A prospective study on outcome of patient-specific cones in revision knee arthroplasty

BACKGROUND

Cones are known to be good substitutes for metaphyseal and diaphyseal bone loss during revision total knee arthroplasty (RTKA). Often the off-the-shelf cones do not fit to the individual patient's anatomy. New 3D-printing additive technologies allow to develop patient-specific cones. The aim of this prospective study was to describe their outcome.

METHODS

From 2017 until 2020, 35 patient-specific titanium cones (15 femoral and 20 tibial) were implanted during 31 RTKAs (45% varus-valgus constrained implants and 55% rotating hinges). Clinical outcome was evaluated using KSS, WOMAC and FJS-12 scoring systems at 12 and 24 months. No patients were lost for follow-up.

RESULTS

In all cases, there were no technical difficulties in adapting the cones to both the host bone and the revision implant. By the time of performing data analysis (January 2021), none of the 31 patients needed revision surgery for any reason. At 12 months of follow-up, the mean values of scores for knee function improved significantly from baseline (p < 0.01): KSS-103.00 (min 100-max 111, SD 5.35), WOMAC-16.5 (min 9-max 24, SD 6.45), FJS-12-61.60 (min 52-max 76, SD 9.20). At 24 months, the trend towards improvement of functional results continued but did not reached statistical significance comparing to 12 months: KSS was 105.92 (min 95-max 155, SD 16.18), WOMAC-14.07 (min 0-max 42, SD 12.42), FJS-12-83.78 (min 65-max 97, SD 09.64). Radiographic signs of osteointegration were detected within the first 6 month after surgery in all cases. Loosening of femoral or tibial components as well as peri-prosthetic infection was not observed in any of the patients during the follow-up.

CONCLUSION

The original additive technology for designing and producing patient-specific metaphyseal and diaphyseal cones with different porosity zones for extensive femoral and tibial bone defects in RTKA is precise and clinically effective solution, at least in the short term. It could be a valid alternative to "off-the-shelf" cones or sleeves as well as structural allografts and even mega-prosthesis, but a longer follow-up period is required to assess its medium- and long-term reliability.

Zonal Fixation in Revision TKA: The Key Is Metaphyseal Fixation

As the volume of primary total knee arthroplasties continues to rise, so will the volume of revision arthroplasties. Bone loss is commonly encountered in revision surgery and must be managed appropriately to optimize outcomes. The concept of zonal fixation highlights the importance of attaining secure fixation within each of the three major osseous zones: the epiphysis, the metaphysis, and the diaphysis. While each zone is important, the metaphysis carries particular significance. The development of new implants such as metaphyseal cones and sleeves has greatly expanded the orthopedic surgeon's armamentarium to allow for solid metaphyseal fixation in virtually every case.

The Use of Metaphyseal Cones and Sleeves in Revision Total Knee Arthroplasty

The burden of revision total knee arthroplasty (rTKA) is expected to increase with the rise in the number of TKA procedures being performed yearly. Management of bone loss during rTKA is challenging and necessitates appropriate surgical planning. Metaphyseal cones and sleeves have emerged as an increasing popular option for addressing metaphyseal femoral and tibial bone loss when performing rTKA. Understanding what cones and sleeves are commercially available and when to use them are critical parts of preoperative evaluation and planning. The purpose of this comprehensive review was to present different design philosophies, types of manufacturing, clinical outcomes, and the versatility and interchangeability of varying cones and sleeves with different TKA revision systems.

Bilateral Primary Total Knee Arthroplasty and Reconstruction of the Medial Tibial Plateau by an Asymmetric Cone in a Patient with Charcot Arthropathy

Charcot arthropathy of the knee is an extremely rare orthopedic disease that is very challenging for the treating physician and is associated with many complications, especially if it is occurring on both knees. Meanwhile, in the advanced stage, despite many potential complications, TKA is recognized as the gold standard. However, destruction of the medial tibial plateau is typical for the disease, which makes a stable anchorage of the prosthesis much more difficult. Therefore, we present a case in which sufficient primary stability could be achieved with an asymmetrical second-generation tibial cone with an anatomical design and implantation instruments adapted to the bony anatomy in the presence of severe tibial destruction on both sides. In the two-year follow-up, the patient showed good mobility and stability on both sides. In advanced Charcot arthropathy of the knee, the use of asymmetric tibial cones appears to be an appropriate solution for secure fixation and stability of the implant.

3D-printed titanium metaphyseal cones in revision total knee arthroplasty with cemented and cementless stems

AIMS

Porous metaphyseal cones can be used for fixation in revision total knee arthroplasty (rTKA) and complex TKAs. This metaphyseal fixation has led to some surgeons using shorter cemented stems instead of diaphyseal engaging cementless stems with a potential benefit of ease of obtaining proper alignment without being beholden to the diaphysis. The purpose of this study was to evaluate short term clinical and radiographic outcomes of a series of TKA cases performed using 3D-printed metaphyseal cones.

METHODS

A retrospective review of 86 rTKAs and nine complex primary TKAs, with an average age of 63.2 years (SD 8.2) and BMI of 34.0 kg/m² (SD 8.7), in which metaphyseal cones were used for both femoral and tibial fixation were compared for their knee alignment based on the type of stem used. Overall, 22 knees had cementless stems on both sides, 52 had cemented stems on both sides, and 15 had mixed stems. Postoperative long-standing radiographs were evaluated for coronal and sagittal plane alignment. Adjusted logistic regression models were run to assess malalignment hip-knee-ankle (HKA) alignment beyond ± 3° and sagittal alignment of the tibial and femoral components ± 3° by stem type.

RESULTS

No patients had a revision of a cone due to aseptic loosening; however, two had revision surgery due to infection. In all, 26 (27%) patients had HKA malalignment; nine (9.5%) patients had sagittal plane malalignment, five (5.6%) of the tibia, and four (10.8%) of the femur. After adjusting for age, sex, and BMI, there was a significantly increased risk for malalignment when a cone was used and both the femur and tibia had cementless compared to cemented stems (odds ratio 3.19, 95% confidence interval 1.01 to 10.05).

CONCLUSION

Porous 3D-printed cones provide excellent metaphyseal fixation. However, these central cones make the use of offset couplers difficult and may generate malalignment with cementless stems. We found 3.19-times higher odds of malalignment in our TKAs performed with metaphyseal cones and both femoral and tibial cementless stems. Cite this article: Bone Joint J 2021;103-B(6 Supple A):150-157.

Mid-term results of tibial cones : reasonable survivorship but increased failure in those with significant bone loss and prior infection

AIMS

Tibial cones are often utilized in revision total knee arthroplasty (TKA) with metaphyseal defects. Because there are few studies evaluating mid-term outcomes with a sufficient cohort, the purpose of this study was to evaluate tibial cone survival and complications in revision TKAs with tibial cones at minimum follow-up of five years.

METHODS

A retrospective review was completed from September 2006 to March 2015, evaluating 67 revision TKAs (64 patients) that received one specific porous tibial cone during revision TKA. The final cohort was composed of 62 knees (59 patients) with five years of clinical follow-up or reoperation. The mean clinical follow-up of the TKAs with minimum five-year clinical follow-up was 7.6 years (5.0 to 13.3). Survivorship analysis was performed with the endpoints of tibial cone revision for aseptic loosening, tibial cone revision for any reason, and reoperation. We also evaluated periprosthetic joint infection (PJI), risk factors for failure, and performed a radiological review.

RESULTS

The rate of cone revision for aseptic loosening was 6.5%, with an eight-year survival of 95%. Significant bone loss (Anderson Orthopaedic Research Institute grade 3) was associated with cone revision for aseptic loosening (p = 0.002). The rate of cone revision for any reason was 17.7%, with an eight-year survival of 84%. Sixteen percent of knees developed PJI following revision. A pre-revision diagnosis of reimplantation as part of a two-stage exchange protocol for infection was associated with both PJI (p < 0.001) and tibial cone revision (p = 0.001).

CONCLUSION

Mid-term results of tibial cones showed a survivorship free of cone revision for aseptic loosening of 95%. Patients with significant bone loss were more likely to have re-revision for tibial cone failure. Infection was common, and patients receiving cones at reimplantation were more likely to develop PJI and undergo cone revision. Cite this article: Bone Joint J 2021;103-B(6 Supple A):158-164.

Mid-Term Clinical Outcomes and Survivorship of a Second-Generation Modular Revision Knee System

INTRODUCTION

Revision knee systems have adapted to the challenges of revision knee arthroplasty with offset stems, augments, cones, and various levels of constraint. The purpose of this study is to review the mid-term outcomes of a second-generation modular knee revision system.

MATERIALS AND METHODS

A retrospective review was conducted from 2011 through 2014 on all patients who underwent knee arthroplasty with the Vanguard® 360 revision knee system (Zimmer Biomet, Warsaw, Indiana). Patients were included in the study if they were eligible for five-year minimum follow up and had signed a general research consent. The initial query revealed 253 patients (267 knees) that met inclusion criteria. Complications assessed were manipulation under anesthesia (MUA) and revision of any component. Statistical analysis using paired t-test was performed to evaluate changes in clinical outcomes and Kaplan-Meier survival analysis.

RESULTS

Mean follow up was 6.6 years. The Vanguard® 360 knee system was used in four (1.5%) primary total knee arthroplasties (TKAs), 66 (24.7%) second-stage reimplantation TKAs after infection, and 197 (73.8%) aseptic revisions. There were significant improvements in knee range of motion and Knee Society Scores (all p<0.05). Manipulations under anesthesia were performed in 17 knees (6.4%). A total of 41 knees (15.4%) failed for any cause and required re-revision surgery. Of these, 11 (4.1%) failed due to aseptic loosening. Kaplan-Meier analysis revealed overall survival to endpoint of aseptic loosening to be 96.4% (95% CI: ±1.2%) at five years and 95.2% (95% CI: ±1.4%) at 9.5 years. When comparing survivorship in patients who underwent initial revision for aseptic indications compared with those whose underwent revision for second-stage reimplantation after infection, Kaplan-Meier survival to endpoint of revision for any cause at 9.5 years was higher for patients with aseptic than septic indication for TKA (87.0% [95% CI: ±2.4%] vs. 75.3% [95% CI: ±5.4%], p=0.0156).

CONCLUSION

The findings of this study demonstrate greater than 95% aseptic survivorship with the use of the Vanguard® revision knee system at mid-term follow up.

Reconstruction of Proximal Metaphyseal Femoral Defects Using Trabecular Metal Augments in Revision Total Hip Arthroplasty

Porous tantalum augments are widely used in revision total hip arthroplasty for the reconstruction of severe bone defects. Here, we present the first 3 cases who underwent femoral revision arthroplasty using standard distal femoral and proximal tibial porous tantalum cones to reconstruct severe bone loss in the proximal femur. Cones were inserted press fit, followed by implantation of a cemented revision stem in all cases. After a mean follow-up period of 15.8 months, all patients showed an improved Harris-Hip-Score and no radiological signs of subsidence or loosening. Porous tantalum cones may be an option in the reconstruction of severe femoral defects in revision total hip arthroplasty. The shape of the tantalum cones should be optimized for the use in the proximal femur.

Preliminary clinical results of coated porous tibia cones in septic and aseptic revision knee arthroplasty

PURPOSE

To analyze the first results of calcium-phosphate-coated porous tibia cones.

METHODS

Patients treated with TrabecuLink^®-CaP Cones were retrospectively recruited from January 2016 to December 2017. These custom-made cones were produced using titanium alloy Ti-6Al-4 V (Tilastan^®) and using additive manufacturing with a special calcium-phosphate coating (HX^®-coating). Clinical outcome was evaluated using Oxford Knee Score. For radiological evaluation of the implants, patients sent us outpatient taken radiographs. A minimum follow-up of one year was required. Lastly, we analyzed postoperative complications and revision rates.

RESULTS

52 patients with revision knee arthroplasty (RKA) were recruited for final analysis, of whom, we had 17 septic RKAs (33%) and 35 aseptic cases of RKA (67%). The bone defects were grouped into 17 AORI Type 2A (32.7%), 14 Type 2B (26.9%) and 21 Type 3 (40.4%). After a mean follow-up of 22 months (13.2-34.8; SD = ± 10), we had 4 surgical revisions (7.7%), 2 septic and 2 aseptic cases. The mean Oxford Knee Score was 28.6 points (8-47; SD = ± 10). 22 of 28 radiographs (78.6%) showed regular positioning of the cones and TKAs at a mean follow-up of 16.8 months (13.2-34.8; SD = ± 6). Three patients (10.7%) showed slight radiolucencies in the bone-cement interfaces and 3 patients (10.7%) had beginning heterotopic ossifications.

CONCLUSIONS

This study shows the initial clinical results of calcium-phosphate-coated tibia cones showing a good functional outcome. Further research should focus on long-term clinical and radiological follow-up.

Trabecular Metal Cones Combined With Short Cemented Stem Allow Favorable Outcomes in Aseptic Revision Total Knee Arthroplasty

BACKGROUND

The purpose of this study was to compare the functional outcomes and implant survivorship at a minimum of 5 years of follow-up of several reconstruction techniques with or without metaphyseal cone and stems of variable length.

METHODS

A retrospective comparative matched analysis was performed from 2 prospectively collected databases. Only patients who underwent revision total knee arthroplasty procedures for aseptic causes using a single design of rotating hinge knee with a minimum of 5 years of follow-up were analyzed. Patients were separated into 3 groups: trabecular metal (TM) cones + short cemented stems (TM + short stem [SS]), TM cones + long uncemented stems (TM + long stem [LS]), and no cone (NC) + long uncemented stems (NC + LS). A matching process based on age (±5 years) was realized.

RESULTS

About 99 patients were included; 33 in the TM + SS group, 33 in the TM + LS group, and 33 in the NC + LS group. The mean time of follow-up was 9.3 years. A significant difference of the improvement of subscale pain, symptom, activities of daily living, quality of life of the Knee Injury and Osteoarthritis Outcome score and knee, function of the Knee Society Score was observed in favor of TM + SS group compared with the 2 other groups. At 8 years of survivorship, the components free of revision for any cause were 90.9% for the TM + SS group, 84.9% for the TM + LS group, and 90.6% for the NC + LS group.

CONCLUSION

The use of a short cemented tibial stem combined with a TM cone in revision total knee arthroplasty offers identical survival rate with better functional outcome compared with the use of a long uncemented stem associated with TM cones or metallic augments at a minimum of 5 years of follow-up.

A systematic review of preclinical in vivo testing of 3D printed porous Ti6Al4V for orthopedic applications, part I: Animal models and bone ingrowth outcome measures

For Ti6Al4V orthopedic and spinal implants, osseointegration is often achieved using complex porous geometries created via additive manufacturing (AM). While AM porous titanium (pTi) has shown clinical success, concerns regarding metallic implants have spurred interest in alternative AM biomaterials for osseointegration. Insights regarding the evaluation of these new materials may be supported by better understanding the role of preclinical testing for AM pTi. We therefore asked: (a) What animal models have been most commonly used to evaluate AM porous Ti6Al4V for orthopedic bone ingrowth; (b) What were the primary reported quantitative outcome measures for these models; and (c) What were the bone ingrowth outcomes associated with the most frequently used models? We performed a systematic literature search and identified 58 articles meeting our inclusion criteria. We found that AM pTi was evaluated most often using rabbit and sheep femoral condyle defect (FCD) models. Additional ingrowth models including transcortical and segmental defects, spinal fusions, and calvarial defects were also used with various animals based on the study goals. Quantitative outcome measures determined via histomorphometry including ''bone ingrowth'' (range: 3.92-53.4% for rabbit/sheep FCD) and bone-implant contact (range: 9.9-59.7% for rabbit/sheep FCD) were the most common. Studies also used 3D imaging to report outcomes such as bone volume fraction (BV/TV, range: 4.4-61.1% for rabbit/sheep FCD), and push-out testing for outcomes such as maximum removal force (range: 46.6-3092 N for rabbit/sheep FCD). Though there were many commonalities among the study methods, we also found significant heterogeneity in the outcome terms and definitions. The considerable diversity in testing and reporting may no longer be necessary considering the reported success of AM pTi across all model types and the ample literature supporting the rabbit and sheep as suitable small and large animal models, respectively. Ultimately, more standardized animal models and reporting of bone ingrowth for porous AM materials will be useful for future studies.

Medium term clinical outcomes of tibial cones in revision knee arthroplasty

INTRODUCTION

Trabecular metal cones are a relatively new option for reconstruction of major bone defects during revision total knee arthroplasty (TKA). The purpose of the present study was to retrospectively assess medium-term results for tibial cones in revision TKA with a severe proximal tibial bone defect. We hypothesized that revision TKA patients with bone defects treated with trabecular metal cones have excellent medium-term clinical and radiological results.

PATIENTS AND METHODS

A single-center retrospective review included all consecutive cases of tibial revision using trabecular metal cones. All patients with a minimum 2-year follow-up were included in the study. There were no exclusion criteria. The primary endpoint was tibial cone survivorship. The secondary endpoints were revision TKA all-cause survivorship, patient-reported outcome measures with a Knee injury and Osteoarthritis Outcome Score (KOOS), SF 12, and radiographic analysis.

RESULTS

Five of the 57 patients alive at last follow-up (8.77%) had undergone revision (4 for infection and 1 for instability). Complications comprised four cases (7.02%) of infection, 2 cases (3.51%) of tibial and femoral implant aseptic loosening that did not require revision surgery, 1 of which (1.75%) with associated patellar loosening, and 1 case (1.75%) of instability. Kaplan-Meier estimates showed 100% 5-year survivorship with tibial cone revision for aseptic loosening and 93.44% (95% CI 83.47-97.49%) for all-cause revision.

DISCUSSION

The present study of cones used for tibial revision supports shows excellent results; however, longer and larger follow-up is needed to better assess results in revision TKA.

LEVEL OF EVIDENCE

4, retrospective study.

Additive manufacturing of porous titanium metaphyseal components: Early osseointegration and implant stability in revision knee arthroplasty

AIMS

Metaphyseal cones and sleeves are components used in revision knee arthroplasty to ensure load transfer, encourage bone on-growth and prevent stress shielding. Additive manufacturing of titanium alloy implants is a novel technique with limited clinical outcome reports in the literature. The aim of this study was to determine radiographic evidence of osseointegration and early results of a single manufacturer porous titanium metaphyseal components in the proximal tibia.

METHODS

We retrospectively reviewed the prospectively collected database of two institutions. Patients who underwent revision knee arthroplasty using porous titanium components by a single manufacturer were identified. Immediate post-operative and latest follow-up radiographs were independently analysed by 2 reviewers to determine metaphyseal bone contact and level of osseointegration in relevant Knee Society Radiographic Evaluation and Scoring System zones.

RESULTS

22 patients (15 males; 7 females) with a mean age of 71 (49-92) years were included. The mean follow-up period was 14 months (2-44 months). Cones were used in 16 patients and sleeves in 6. Interobserver reliability assessment showed substantial agreement (weighted Kappa 0.71, (95% CI: 0.60, 0.81). There was significant correlation between the bone contact in the immediate postop radiograph and osseointegration at final follow-up (kendall's tau-b: 0.698, p < 0.001). Infection free prosthetic joint survival was 20/22 at final follow-up.

CONCLUSION

Porous titanium metaphyseal components produced with additive manufacturing provided excellent osseointegration and no early clinical failures. Partial or complete contact of the cone with native bone in the immediate postoperative radiograph resulted in osseointegration in all cases.

[Revision Total Knee Arthroplasty]

In addition to periprosthetic infections (PJI), the reconstruction of bony defects is the major challenge of revision total knee arthroplasty (TKA). Infection should be ruled out in all cases prior to operation. Revision TKA requires intensive planning with regard to the needed augmentation possibilities and the stems to be used. The sole biological reconstruction of major defects (AORI II and III) shows high failure rates. Large defects must be augmented by metal (wedges/sleeves/cones). The concept of zonal anchorage (3-zone model) with a stable anchorage in 2 out of 3 zones as close to the joint as possible is currently the standard. According to the model, metaphysis (zone 2) is an increasingly important factor for long-term stable anchoring. The use of cones or sleeves seems to significantly improve the results of revision TKA. The anchorage in zone 3 via stems is still mandatory. Cemented metaphysary anchoring and cement-free diaphysary anchoring stems are available, whereby no clear recommendation for a principle can be given.

Excellent two-year survivorship of 3D-printed metaphyseal cones in revision total knee arthroplasty

AIMS

Metaphyseal fixation during revision total knee arthroplasty (TKA) is important, but potentially difficult when using historical designs of cone. Material and manufacturing innovations have improved the size and shape of the cones which are available, and simplified the required bone preparation. In a large series, we assessed the implant survivorship, radiological results, and clinical outcomes of new porous 3D-printed titanium metaphyseal cones featuring a reamer-based system.

METHODS

We reviewed 142 revision TKAs in 139 patients using 202 cones (134 tibial, 68 femoral) which were undertaken between 2015 and 2016. A total of 60 involved tibial and femoral cones. Most cones (149 of 202; 74%) were used for Type 2B or 3 bone loss. The mean age of the patients was 66 years (44 to 88), and 76 (55 %) were female. The mean body mass index (BMI) was 34 kg/m² (18 to 60). The patients had a mean of 2.4 (1 to 8) previous operations on the knee, and 68 (48%) had a history of prosthetic infection. The mean follow-up was 2.4 years (2 to 3.6).

RESULTS

Survivorship free of cone revision for aseptic loosening was 100% and survivorship free of any cone revision was 98%. Survivorships free of any revision and any reoperation were 90% and 83%, respectively. Five cones were revised: three for infection, one for periprosthetic fracture, and one for aseptic tibial loosening. Radiologically, three unrevised femoral cones appeared loose in the presence of hinged implants, while the remaining cones appeared stable. All cases of cone loosening occurred in patients with Type 2B or 3 defects. The mean Knee Society score (KSS) improved significantly from 50 (0 to 94) preoperatively to 87 (72 to 94) (p < 0.001). Three intraoperative fractures with cone impaction (two femoral, one tibial) healed uneventfully.

CONCLUSION

Novel 3D-printed titanium cones, with a reamer-based system, yielded excellent early survivorship and few complications in patients with severe bone loss undergoing difficult revision TKA. The diversity of cone options, relative ease of preparation, and outcomes rivalling those of previous designs of cone support their continued use. Cite this article: Bone Joint J 2020;102-B(6 Supple A):107-115.

Antimicrobial properties of antibiotic-loaded implants

AIMS

The aim of this study was to compare the ability of tantalum, 3D porous titanium, antibiotic-loaded bone cement, and smooth titanium alloy to inhibit staphylococci in an in vitro environment, based on the evaluation of the zone of inhibition (ZOI). The hypothesis was that there would be no significant difference in the inhibition of methicillin-sensitive or methicillin-resistant Staphylococcus aureus (MSSA/MRSA) between the two groups.

METHODS

A total of 30 beads made of three different materials (tantalum/3D porous titanium and smooth titanium alloy) were bathed for one hour in a solution of 1 g vancomycin in 20 ml of sterile water for injection (bath concentration: 50 mg/mL). Ten 1 cm³ cylinders of antibiotic-loaded cement were also created by mixing standard surgical cement with 1 g of vancomycin in standardized sterile moulds. The cylinders were then placed on agar plates inoculated with MSSA and MRSA. The ZOIs were measured each day and the cylinders were transferred onto a new inoculated plate.

RESULTS

For MSSA and MRSA, no inhibitory effect was found in the control group, and antibiotic-loaded smooth titanium alloy beads showed a short inhibitory effect until day 2. For MSSA, both tantalum and 3D porous titanium beads showed significantly larger mean ZOIs than cement beads (all p < 0.01) each day until day 7 for tantalum and until day 3 for 3D porous titanium. After six days, antibiotic-loaded cement had significantly larger mean ZOIs than the 3D porous titanium (p = 0.027), but no significant difference was found with tantalum (p = 0.082). For MRSA, both tantalum and 3D porous titanium beads had significantly larger mean ZOIs than antibiotic-loaded cement each day until day 6 for tantalum (all p < 0.01) and until day 3 for 3D porous titanium (all p < 0.04). Antibiotic-loaded cement had significantly larger mean ZOIs than tantalum and 3D porous titanium from day 7 to 9 (all p < 0.042).

CONCLUSION

These results show that porous metal implants can deliver local antibiotics over slightly varying time frames based on in vitro analysis. Cite this article: Bone Joint J 2020;102-B(6 Supple A):158-162.

A finite element analysis of tibial tritanium cones without stems in varying bone defects

BACKGROUND

In the UK around 10% of hip and knee arthroplasties are revision operations. At revision total knee arthroplasty (rTKA), bone loss management is critical to achieving a stable bone-implant construct. Though tritanium cones have been used to manage bone defects in rTKA, their biomechanical performance with varying defects remains unknown.

METHODS

Uncontained tibial bone defects at four anatomic locations, with varying depths and widths (Type T2A and T2B) were investigated computationally in a composite tibia which was subjected to four loading scenarios. The ability of the tritanium cone to replace the tibial bone defect was examined using the outcome measures of bone strain distribution and interface micromotions.

RESULTS

It was found that anterior and lateral defects do not significantly alter the strain distribution compared with intact bone. For medial defects, strain distribution is sensitive to defect width; while strain distributions for posterior defects are associated with defect width and depth. In general, micromotions at the bone-implant interface are small and are primarily influenced by defect depth.

CONCLUSIONS

Our models show that the cone is an acceptable choice for bone defect management in rTKA. Since all observed micromotions were small, successful osteointegration would be expected in all types of uncontained defects considered in this study. Tritanium cones safely accommodate uncontained tibial defects up to 10 mm deep and extending up to 9 mm from the centre of the cone. Medial and posteriorly based defects managed with symmetric cones display the greatest bone strains and asymmetric cones may be useful in this context.

Outcomes of a technique combining diaphyseal impaction grafting and metaphyseal cones for severe bone loss in revision total knee arthroplasty

Aims

Metaphyseal cones with cemented stems are frequently used in revision total knee arthroplasty (TKA). However, if the diaphysis has been previously violated, the resultant sclerotic canal can impair cemented stem fixation, which is vital for bone ingrowth into the cone, and long-term fixation. We report the outcomes of our solution to this problem, in which impaction grafting and a cemented stem in the diaphysis is combined with an uncemented metaphyseal cone, for revision TKA in patients with severely compromised bone.

Methods

A metaphyseal cone was combined with diaphyseal impaction grafting and cemented stems for 35 revision TKAs. There were two patients with follow-up of less than two years who were excluded, leaving 33 procedures in 32 patients in the study. The mean age of the patients at the time of revision TKA was 67 years (32 to 87); 20 (60%) were male. Patients had undergone a mean of four (1 to 13) previous knee arthroplasty procedures. The indications for revision were aseptic loosening (80%) and two-stage reimplantation for prosthetic joint infection (PJI; 20%). The mean follow-up was four years (2 to 11).

Results

Survival free from revision of the cone/impaction grafting construct due to aseptic loosening was 100% at five years. Survival free from any revision of the construct and free from any reoperation were 92% and 73% at five years, respectively. A total of six patients (six TKAs, 17%) required a further revision, four for infection or wound issues, and two for periprosthetic fracture. Radiologically, one unrevised TKA had evidence of loosening which was asymptomatic. In all unrevised TKAs the impacted diaphyseal bone graft appeared to be incorporated radiologically.

Conclusion

When presented with a sclerotic diaphysis and substantial metaphyseal bone loss, this technique combining diaphyseal impaction grafting with a metaphyseal cone provided near universal success in relation to implant fixation. Moreover, radiographs revealed incorporation of the bone graft and biological fixation of the cone. While long-term follow-up will be important, this technique provides an excellent option for the management of complex revision TKAs. Cite this article: Bone Joint J 2020;102-B(6 Supple A):116–122.

Metaphyseal cones in revision total knee arthroplasty: The role of stems

Aims

Metaphyseal tritanium cones can be used to manage the tibial bone loss commonly encountered at revision total knee arthroplasty (rTKA). Tibial stems provide additional fixation and are generally used in combination with cones. The aim of this study was to examine the role of the stems in the overall stability of tibial implants when metaphyseal cones are used for rTKA.

Methods

This computational study investigates whether stems are required to augment metaphyseal cones at rTKA. Three cemented stem scenarios (no stem, 50 mm stem, and 100 mm stem) were investigated with 10 mm-deep uncontained posterior and medial tibial defects using four loading scenarios designed to mimic activities of daily living.

Results

Small micromotions (mean < 12 µm) were found to occur at the bone-implant interface for all loading cases with or without a stem. Stem inclusion was associated with lower micromotion, however these reductions were too small to have any clinical significance. Peak interface micromotion, even when the cone is used without a stem, was too small to effect osseointegration. The maximum difference occurred with stair descent loading. Stress concentrations in the bone occurred around the inferior aspect of each implant, with the largest occurring at the end of the long stem; these may lead to end-of-stem pain. Stem use is also found to result in stress shielding in the bone along the stem.

Conclusion

When a metaphyseal cone is used at rTKA to manage uncontained posterior or medial defects of up to 10 mm depth, stem use may not be necessary.

Cite this article:Bone Joint Res. 2020;9(4):162–172.

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.

A review of materials for managing bone loss in revision total knee arthroplasty

In 2014-2015, 61,421 total knee arthroplasties (TKAs) were performed in Canada; an increase of about 20% over 2000-2001. Revision total knee arthroplasties (rTKAs) accounted for 6.8% of TKAs performed between 2014 and 2015, and this is estimated to grow another 12% by 2025. rTKAs are typically more complicated than primary TKAs due to the significant loss of femoral and tibial bone stock. The escalating demand and limitations associated with total knee arthroplasty and their revision drives the development of novel treatments. A variety of materials have been utilized to facilitate regeneration of healthy bone around the site of a knee arthroplasty. The selection of these materials is based on the bone defect size and includes bone grafts, graft substitutes and cements. However, all these materials have certain disadvantages such as blood loss, disease transmission (bone grafts), inflammatory response, insufficient mechanical properties (bone graft substitutes) thermal necrosis and stress shielding (bone cement). Recently, the use of metal augments for large bone defects has attracted attention, however they can undergo fretting, corrosion, and stress shielding. All things considered, this review indicates the necessity of developing augments that have structural integrities and biodegradation rates similar to that of human bone. Therefore, the future of bone loss management may lie in fabricating novel bioactive glass augments as they can promote bone healing and implant stability and can degrade with time.