Management of metaphyseal bone loss in revision knee arthroplasty

Dorsal cortex line is more reliable than transepicondylar axis for rotation in revision total knee arthroplasty with severe bone loss

Aims

The transepicondylar axis is a well-established reference for the determination of femoral component rotation in total knee arthroplasty (TKA). However, when severe bone loss is present in the femoral condyles, rotational alignment can be more complicated. There is a lack of validated landmarks in the supracondylar region of the distal femur. Therefore, the aim of this study was to analyze the correlation between the surgical transepicondylar axis (sTEA) and the suggested dorsal cortex line (DCL) in the coronal plane and the inter- and intraobserver reliability of its CT scan measurement.

Methods

A total of 75 randomly selected CT scans were measured by three experienced surgeons independently. The DCL was defined in the coronal plane as a tangent to the dorsal femoral cortex located 75 mm above the joint line in the frontal plane. The difference between sTEA and DCL was calculated. Descriptive statistics and angulation correlations were generated for the sTEA and DCL, as well as for the distribution of measurement error for intra- and inter-rater reliability.

Results

The external rotation of the DCL to the sTEA was a mean of 9.47° (SD 3.06°), and a median of 9.2° (IQR 7.45° to 11.60°), with a minimum value of 1.7° and maximum of 16.3°. The measurements of the DCL demonstrated very good to excellent test-retest and inter-rater reliability coefficients (intraclass correlation coefficient 0.80 to 0.99).

Conclusion

This study reveals a correlation between the sTEA and the DCL. Overall, 10° of external rotation of the dorsal femoral cortical bone to the sTEA may serve as a reliable landmark for initial position of the femoral component. Surgeons should be aware that there are outliers in this study in up to 17% of the measurements, which potentially could result in deviations of femoral component rotation.

Prevalence and clinical impact of radiographic sclerotic lines adjacent to cementless tibial stems in revision total knee arthroplasty: a long-term follow-up study

Intramedullary stem extensions are typically added to the femoral and tibial components during revision total knee arthroplasty (TKA) to augment fixation of the components and improve survivorship. A commonly used option includes hybrid fixation with cement at the interface between the component and the host bone combined with cementless diaphyseal fitting stems. Radiographic sclerotic lines may appear with these constructs over time, and it is unclear if this finding has implications relative to implant survivorship. The purpose of this study was to quantify the prevalence of sclerotic lines at the bone-implant interface and assess the impact of progressive sclerotic lines on revision for aseptic loosening.

METHODS

A retrospective chart review of a consecutive series of patients who underwent revision TKA at a single tertiary care institution between January 2001 and December 2009 was performed. Data were collected regarding patient demographics, stem size, types of implants, and complications. Radiological reports and radiographs were evaluated for sclerotic lines, propagation, and their location around the tibial stem. Aseptic loosening rates were compared between patients with and without sclerotic lines.

RESULTS

One hundred and fifty-three patients with at least 15 years of follow-up were identified. The mean follow-up was 16.5 ± 4.12 years (range 15-23). Overall, 19 patients required re-revision surgery. Survivorship free of failure due to aseptic loosening was 94.8% (95% CI 76.4-98) at 15 years, with three patients requiring re-revision surgery for aseptic loosening. Twelve (7.8%) patients were found to have sclerotic lines surrounding the tibial stem, all under 2 mm in width. Two (1%) patients with sclerotic lines required re-revision surgery, one patient due to infection and one due to aseptic loosening. There was no significant difference in rates of aseptic loosening in patients with or without sclerotic lines.

CONCLUSION

Radiographic sclerotic lines around revision TKA stems-measuring less than 2mm wide, nonprogressive, and located at the lateral-distal aspect of the stem-were identified in fewer than 8% of cases and did not correlate with re-revision surgery.

Safety and effectiveness of intraosseous regional prophylactic antibiotics in total knee arthroplasty: a systematic review and meta-analysis

BACKGROUND

Intraosseous regional administration (IORA) as a widely applicable and clinically valuable route of administration has gained significant attention in the context of total knee arthroplasty (TKA) for the prophylactic administration of antibiotics. However, there is still controversy regarding its effectiveness and safety. The latest meta-analysis reports that the use of IORA for antibiotics in TKA is as safe and effective as IV administration in preventing prosthetic joint infection (PJI), but they did not separate the statistics for primary TKA and revision TKA, which may be inappropriate. There is currently a lack of evidence specifically comparing the outcomes of prophylactic antibiotic administration via IORA or IV route in primary/revision TKA, respectively, and new research evidence has emerged.

PURPOSES

In this study, we conducted a systematic review and meta-analysis with the primary objective of comparing the local drug tissue concentration and the incidence of PJI between preoperative IORA and intravenous (IV) administration of prophylactic antibiotics in TKA. Additionally, the occurrence of complications between the two administration routes was also compared.

PATIENTS AND METHODS

This meta-analysis was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement (PRISMA) guidelines. Retrospective cohort studies and prospective randomized controlled trials that utilized intraosseous local drug delivery for prophylactic antibiotics in knee arthroplasty were included. English literature from PubMed, Embase, and Cochrane Library databases was searched from the inception of each database until December 2023. Two researchers independently screened the literature, assessed the quality, and extracted data according to the inclusion criteria. The primary outcomes were local antibiotic tissue concentration and postoperative PJI incidence, while the secondary outcome was the occurrence of postoperative complications. Statistical analysis was performed using Review Manager 5.3 software.

RESULTS

This study included 7 prospective randomized controlled trials and 5 retrospective cohort studies. A total of 4091 patients participated in the 12 included studies, with 1,801 cases receiving IORA and 2,290 cases in the control group. In terms of local drug tissue concentration, intraosseous infusion (IO) 500 mg vancomycin significantly increased the drug concentration in the periarticular adipose tissue (SMD: 1.36; 95% CI: 0.87-1.84; P < 0.001; I2 = 0%) and bone tissue (SMD: 0.94; 95% CI: 0.49-1.40; P < 0.001; I2 = 0%) compared to IV 1 g vancomycin. Regarding the incidence of postoperative PJI after primary TKA, IO 500 mg vancomycin was more effective in reducing the occurrence of PJI compared to IV 1 g vancomycin (OR: 0.19; 95% CI: 0.06-0.59; P < 0.001; I2 = 36%). Finally, no significant differences were found between the two groups in terms of postoperative pulmonary embolism (PE) (OR: 1.72; 95% CI: 0.22-13.69; P = 0.59; I2 = 0%) and vancomycin-related complications (OR: 0.54; 95% CI: 0.25-1.19; P = 0.44; I2 = 0%).

CONCLUSIONS

Preoperative prophylactic antibiotic administration via IORA in TKA significantly increases local drug tissue concentration without significantly increasing systemic drug-related complications compared to traditional IV administration. In primary TKA, low-dose vancomycin via IORA is more effective in reducing the incidence of PJI compared to traditional IV regimens. However, its effectiveness remains controversial in high-risk populations for PJI, such as obese, diabetic, and renal insufficiency patients, as well as in revision TKA.

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

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

A comparison between 3D printed models and standard 2D planning in the use of metal block augments in revision knee arthroplasty

OBJECTIVES

The study focused on the ability to predict the need and size of femoral and tibial augmentation using standard two-dimensional (2D) templates and models created with three-dimensional (3D) printing in surgical planning.

PATIENTS AND METHODS

This observational cohort study included 28 consecutive patients (22 females, 6 males; mean age: 71±7.3 years; range, 54 to 82 years) with periprosthetic joint infection recruited between March 2021 and September 2023 undergoing revision total knee arthroplasty revision (TKA). Standard planning was made using calibrated X-ray images. The 3D planning started with computed tomography scans to generate a 3D template of the distal femur and proximal tibia. The model was exported to a 3D printer to produce a patient-specific phantom. The surgery was then simulated on the 3D phantom using revision knee arthroplasty instrumentation to evaluate the appropriate augmentation to use until a correct alignment was obtained.

RESULTS

Three-dimensional planning predicted the need for femoral and tibial augments in 22 (78.6%) cases at both the tibial and femoral components, while 2D planning correctly predicted the need for augmentation in 17 (60.7%) for the tibial side and 18 (64.3%) for the femoral side. The Cohen's kappa demonstrated a significant agreement between the 3D planning for the femoral metal block and the intraoperative requirement (kappa=0.553), whereas 2D planning showed only nonsignificant poor agreement (kappa=0.083). In contrast, the agreement between 2D or 3D preoperative planning for tibial augment and the intraoperative requirement was nonsignificant (kappa=0.130 and kappa=0.158, respectively). On the femoral side, 2D planning showed only a fair nonsignificant correlation (r=0.35, p=0.069), whereas 3D planning exhibited substantial agreement with the actual thickness of the implanted augment (r=0.65, p<0.001). On the tibial side, 3D and 2D planning showed substantial agreement with the actual size of implanted augments (3D planning, r=0.73, p<0.001; 2D planning, r=0.69, p<0.001).

CONCLUSION

Prediction based on 3D computed tomography segmentation showed significant agreement with the intraoperative need for augmentations in revision TKA. The results suggest that planning with 3D printed models represents a stronger aid in this kind of surgery rather than standard 2D planning, providing greater accuracy in the prediction of the required augmentation in revision TKA.

Clinical outcome and survival rate of condylar constrained knee prosthesis in revision total knee arthroplasty: an average nine point six year follow-up

PURPOSE

Condylar constrained knee prostheses (CCK) are increasingly used in revision total knee arthroplasty (rTKA), but the clinical effectiveness and long-term survival remain a debate. The purpose of this study is to report the long-term clinical and radiographic outcome, implant survival rate, and surgical safety of revision total knee arthroplasty with condylar constrained knee prosthesis.

METHODS

A retrospective cohort study was performed on patients undergoing rTKA with CCK. The cases who received rTKA with CCK from January 2005 to January 2022 were selected. The duration of operation, the estimated perioperative blood loss, and the intraoperative blood transfusion rate were recorded to evaluate surgical safety. The pain visual analog scale (VAS), range of motion (ROM), the Hospital for Special Surgery (HSS) score, the Knee Society Score (KSS), the Western Ontario and McMaster University Osteoarthritis Index (WOMAC), and the Oxford knee score (OKS) was recorded to assess clinical outcome. Standard anteroposterior, lateral, skyline and long-standing AP radiographs of the lower limbs were conducted to assess radiographic outcome. Implant survival was analyzed by Kaplan-Meier survival estimates.

RESULTS

Fifty-five cases were followed up for an average of 9.6 years (1-18 years), including 16 males and 38 females, with an average age of 66 and an average BMI of 26.9 kg/m2. The  main reasons for revision were periprosthetic infection (32 knees, 58.2%) and aseptic loosening (13 knees, 23.6%). The duration of operation was 149 ± 56.2 min. The perioperative blood loss was 973.6 ± 421.6 ml. At the last follow-up, VAS (8.0 ± 1.1 to 1.3 ± 1.4), ROM (82.7° ± 26.1° to 108.4° ± 11.8°), HSS (45.0 ± 10.4 to 85.3 ± 8.6), KSKS (38.4 ± 12.1 to 88.5 ± 12.0), KSFS (19.6 ± 12.9 to 68.8 ± 15.1), WOMAC (67.9 ± 12.5 to 14.4 ± 9.5), and OKS (9.9 ± 4.2 to 41.6 ± 7.7) were significantly improved (P < 0.001). A total of five complications were observed, all of which were periprosthetic infection. Non-progressive radiolucent lines were observed in 26 knees (47.3%). The 10-year survival rate for no operation was 96.0%. The ten year survival rate for no revision was 98.0%.

CONCLUSION

The use of CCK prosthesis for rTKA can achieve good long-term efficacy and prosthesis survival.

The First Stage of Knee Revision Arthroplasty in Periprosthetic Infection with Replacement of a Large Defect Double Cementing Method: A Case Report

Aim

Large bone defects in patients with chronic deep periprosthetic knee infection is a major problem. It is widely accepted that bone defects filling with polymethylmethacrylate (PMMA) cement could be used only in selected cases of small bone defects (up to 5 mm) and less than 50% of articular surface due to multiple reasons: risk of thermal bone damage, inadequate cement pressurization and bone cement shrinkage, etc. Staged cementing for preventing bone heating and over negative effects of cementing on a thick layer of bone cement has limited support in the literature.

Case Presentation

We present the case of 4.5 years follow up after temporary-permanent spacer implantation in a 63-year-old male with chronic deep knee PJI and tibial AORI type 3 bone defect reconstructed via double cementing method.

Results

Method of double (staged) cementing used for reconstruction of epiphyseal tibial bone defect in a patient with fistula form of knee PJI shows excellent clinical results at 4.5 years follow up.

Medial Femoral Condyle Cyst in Severe Varus Knee Osteoarthritis: A Finding Prior to Primary Total Knee Arthroplasty

Knee osteoarthritis (OA) often results in subchondral bone cysts (SBCs), which were initially identified as a concentric arrangement of trabeculae surrounding an enlarged marrow space on plain radiographs. Although the Anderson Orthopedic Research Institute (AORI) classification is commonly used, it lacks quantitative measures and is based on radiographs, which can underestimate the actual bone defect. There is a need for a more comprehensive classification system to achieve accurate preoperative planning for bone defect management. A 74-year-old male presented, complaining of bilateral knee pain that began seven years ago. Non-operative management failed to relieve his symptoms despite his ideal BMI of 23.6. Initial radiographs revealed severe bilateral OA (Kellgren and Lawrence grade 4) with a suspected cyst occupying the medial femoral condyle. A CT scan of the right knee confirmed the presence of a cyst in the medial femoral condyle. The authors believe that patients with severe knee OA (Kellgren and Lawrence grade 3 or 4) should not simply be treated as having a sequel of knee arthritis. Instead, a CT scan should be conducted to confirm the size and extent of any cyst.

Revision of total knee arthroplasty with press-fit condylar SIGMA TC3-mobile bearing system and porous metaphyseal sleeves in type AORI type II and III bone defects. A long-term follow-up study

BACKGROUND AND AIM

Revision total knee arthroplasty(rTKA) is a challenging and expensive treatment for orthopedic surgeons who have to deal with poor bone quality and bone loss. This study aims to retrospectively evaluate the clinical and radiological results of patients undergoing rTKA and porous metaphyseal sleeves in AORI type II and III bone defects.

METHODS

We conducted a retrospective series of continuous patients treated for mechanical failure of TKA. All patients with aseptic loosening of TKR underwent revision arthroplasty. We included only patients with AORI type IIa/b and III bone defects. The Septic revision or other grades of bone defect or patients lost at follow-up or with less than 2 years follow-up were excluded. We evaluated knee function with Oxford Knee Score (OKS) pain with Visual Analogue Scale (VAS) and range of motion (flex-ext), while radiological evaluation was performed to evaluate any sign of loosening.

RESULTS

The mean preoperative OKS was 13.85 +/- 5.39 (range 5 -22), and it improved to 33.89 +/- 3.98 (range 20 - 40) (p<0.00001). The mean preoperative VAS was 7.77 +/- 1.33 (range 5 - 9), and it improved to 1.89 +/- 0.92 (range 0 - 4) (p<0.00001). ROM improved from 62.23° +/- 13.71° (range 40° - 90°) to 100.53° +/- 6.93° (range 90° - 120°) (p<0.00001). No signs of loosening or implant migration were reported.

CONCLUSIONS

Metaphyseal sleeves made knee revision in large bone defects reliable and effective with good results. Good implant stability was reached in all the cases treated with metaphyseal sleeves.

Application strategy of finite element analysis in artificial knee arthroplasty

Artificial knee arthroplasty, as the most effective method for the treatment of end-stage joint diseases such as knee osteoarthritis and rheumatoid arthritis, is widely used in the field of joint surgery. At present, Finite element analysis (FEA) has been widely used in artificial knee replacement biomechanical research. This review presents the current hotspots for the application of FEA in the field of artificial knee replacement by reviewing the existing research literature and, by comparison, summarizes guidance and recommendations for artificial knee replacement surgery. We believe that lower contact stress can produce less wear and complications when components move against each other, in the process of total knee arthroplasty (TKA), mobile-bearing prostheses reduce the contact surface stress of the tibial-femoral joint compared with fixed-bearing prostheses, thus reducing the wear of the polyethylene insert. Compared with mechanical alignment, kinematic alignment reduces the maximum stress and maximum strain of the femoral component and polyethylene insert in TKA, and the lower stress reduces the wear of the joint contact surface and prolongs the life of the prosthesis. In the unicompartmental knee arthroplasty (UKA), the femoral and tibial components of mobile-bearing prostheses have better conformity, which can reduce the wear of the components, while local stress concentration caused by excessive overconformity of fixed-bearing prostheses should be avoided in UKA to prevent accelerated wear of the components, the mobile-bearing prosthesis maintained in the coronal position from 4° varus to 4° valgus and the fixed-bearing prosthesis implanted in the neutral position (0°) are recommended. In revision total knee arthroplasty (RTKA), the stem implant design should maintain the best balance between preserving bone and reducing stress around the prosthesis after implantation. Compared with cemented stems, cementless press-fit femoral stems show higher fretting, for tibial plateau bone defects, porous metal blocks are more effective in stress dispersion. Finally, compared with traditional mechanical research methods, FEA methods can yield relatively accurate simulations, which could compensate for the deficiencies of traditional mechanics in knee joint research. Thus, FEA has great potential for applications in the field of medicine.

Mechanical Distribution and New Bone Regeneration After Implanting 3D Printed Prostheses for Repairing Metaphyseal Bone Defects: A Finite Element Analysis and Prospective Clinical Study

Critical metaphyseal bone defects caused by nonunion and osteomyelitis are intractable to repair in clinical practice owing to the rigorous demanding of structure and performance. Compared with traditional treatment methods, 3D printing of customized porous titanium alloy prostheses offer feasible and safe opportunities in repairing such bone defects. Yet, so far, no standard guidelines for optimal 3D printed prostheses design and fixation mode have been proposed to further promote prosthesis stability as well as ensure the continuous growth of new bone. In this study, we used a finite element analysis (FEA) to explore the biomechanical distribution and observed new bone regeneration in clinical practice after implanting 3D printed prostheses for repairing metaphyseal bone defects. The results reflected that different fixation modes could result in diverse prosthesis mechanical conductions. If an intramedullary (IM) nail was applied, the stress mainly conducted equally along the nail instead of bone and prosthesis structure. While the stress would transfer more to the lateral bone and prosthesis’s body when the printed wing and screws are selected to accomplish fixation. All these fixation modes could guarantee the initial and long-term stability of the implanted prosthesis, but new bone regenerated with varying degrees under special biomechanical environments. The fixation mode of IM nail was more conducive to new bone regeneration and remodeling, which conformed to the Wolff’s law. Nevertheless, when the prosthesis was fixed by screws alone, no dense new callus could be observed. This fixation mode was optional for defects extremely close to the articular surface. In conclusion, our innovative study could provide valuable references for the fixation mode selection of 3D printed prosthesis to repair metaphyseal bone defect.

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.

Metaphyseal Sleeve Failure in Revision Total Knee Arthroplasty

Introduction

A significant percentage of patients require re-revision surgery regardless of the demonstrated durable short- and mid-term clinical results using metaphyseal sleeves in revision total knee arthroplasty (TKA). The aim of this study was to identify the association between sleeve alignment and contact zones, with loosening in patients with revision TKA.

Materials & Methods

Of a series of 103 patients who underwent revision TKA, at a mean follow-up of eight years, six patients were re-revised for tibial loosening. These patients were compared with 19 unrevised control subjects in a 1:3 ratio. We calculated and compared the cumulative number of contact zones between the porous-coated part of the sleeve and bone on immediate postoperative X-rays between re-revised and unrevised patients. The main hypothesis was that neutral positioning and absolute circumferential contact between trabecular metaphyseal bone and porous-coated part of the sleeve would lead to a better outcome.

Results

The use of a conservative (nonparametric) approach indeed revealed better circumferential contact between trabecular metaphyseal bone and porous-coated part of the sleeve among the survivors, i.e., survivors: median (interquartile range [IQR]): 3 (2-4); failures: 3 (1-3), p = 0.003 (Mann-Whitney [MW] test). The difference was borderline significant for coronal alignment, i.e., survivors: median (IQR): −1 (−4 to 2); failures: 0 (−1 to 3), p = 0.0569 (MW test).

Conclusion

A circumferential bony contact of the metaphyseal sleeve would lead to better survival of the revision implant, whereas the degree of varus fixation did not seem to influence the longevity of the implant.

[Bone defect management in revision knee arthroplasty]

BACKGROUND

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

REASONS

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

TECHNIQUES

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

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.

Mid-term clinical and radiographic outcomes of porous-coated metaphyseal sleeves used in revision total knee arthroplasty

Background

The management of bone defects remains one of the major challenges surgeons are faced with in revision total knee arthroplasty (RTKA). Large and uncontained bone defects are traditionally managed with metaphyseal sleeves that facilitate osseointegration and have reported construct stability. While many studies have presented excellent short-term outcomes using metaphyseal sleeves, less is known on their performance in the longer term. The purpose of this study was to present our mid-term results of the metaphyseal sleeves used in patients undergoing RTKA.

Materials and methods

Between January 2007 and January 2015, 30 patients underwent RTKA with the use of a CCKMB prosthesis combined with an osteointegrative sleeve. The main indications for RTKA were instability in 40% of the cases (n = 12), aseptic loosening in 30% (n = 9), infection in 26.7% (n = 8), and “other” in 3.3% (n = 1). The minimal follow-up time was 5 years and the mean follow-up time was 82.4 months (SD = 22.6). Clinical outcomes were assessed by Knee Society scores (KSS), range of motion and rate of re-operation.

Results

The mean Knee Society score increased significantly from 72.1 preoperatively to 90.0 postoperatively (p < 0.001). The cumulative incidence of re-operation in our study was 13.3% (n = 4). Our study reported no cases of aseptic loosening or mobile-bearing spin-out. Knee flexion to 90° and more was impossible in seven cases (23.3%) preoperatively and in one case (3.3%) postoperatively.

Conclusion

Porous-coated metaphyseal sleeves demonstrated excellent rates of survivorship and radiographic ingrowth in the mid-term setting. However, further studies are required to assess their outcomes in the long-term.

[Distal femur replacement in extensive defects of the distal femur in revision arthroplasty]

OBJECTIVE

Use of distal femur replacement implants in advanced bone defects after multiple bone-damaging revision surgery on the knee joint.

INDICATIONS

Advanced femoral bone defects (AORI IIb and III defects) in revision arthroplasty of the knee joint.

CONTRAINDICATIONS

Persistent or current joint infection, general infection, defect and/or nonreconstructable insufficient extensor apparatus.

SURGICAL TECHNIQUE

Standard access including existing skin scars, arthrotomy, removal of cement spacer if necessary and removal of multiple tissue samples; preparation of tibia first to define the joint line, then preparation of the femur. Determining the resection height of the remaining femur corresponding to the preoperative planning. Gradual drilling using flexible medullary drills and then preparation by femoral rasps. Two stem systems are available for coupling to the distal femur (MUTARS). First there is the standard MUTARS stem (available lengths of 90, 120 and 160 mm); if longer shafts are required, so-called revision shaft (RS) stems are necessary (stems available in 150, 200 and 250 mm). In case of extensive femoral defects extension sleeves in different lengths can be used to reconstruct the femur. After preparation the implant position and the joint line height is checked.

POSTOPERATIVE MANAGEMENT

Full weight bearing, in case of existing bony defects possibly partial load of a maximum of 10 kg für 6 weeks; regular wound control; limitation of the degree of flexion only with weakened or reconstructed extensor apparatus.

RESULTS

Between February 2015 and August 2018, a total of 34 distal femurs were implanted. In 19 patients, the implantation was performed after septic and aseptic loosening of a knee prosthesis. All patients had an intraoperative AORI III defect of the femur. Of the 19 patients who underwent a distal femur implantation, 7 had to be revised due to a persistent infection; 4 of these 7 patients had to be revised several times and, finally, had a conversion to a knee arthrodesis. One patient had to undergo a revision with a stem change due to a secondary aseptic loosening of the cemented stem. The mean follow-up period was 11.2 months (range 4-29 months). The follow-up included clinical examination, KSS (Knee Society Score) and X‑ray analysis. A significant improvement in range of motion from 65 ± 16° to 83 ± 14° (p < 0.01) was noted. The KSS improved significantly from 69 ± 9 points preoperatively to 115 ± 15 points postoperatively. Four patients complained of persistent symptoms during exercise after 9 months; femoral shaft pain was denied by all patients. After about 11 months, an implant survival rate of 73.7% was observed in the patient collective.

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

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