A practical approach to dealing with bone loss in revision total knee arthroplasty

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.

Classification of Bone Loss With Failed Stemmed Components in Revision Total Knee Arthroplasty

INTRODUCTION

With the increasing number of primary total knee arthroplasties (TKA) being performed annually there is also an expected increase in the number of revision TKA, as well as failed revision TKA with stemmed components. A new classification system based upon the location and degree of bone loss in the tibial and or femoral metaphysis and diaphysis is proposed. Type 1 has no bone loss in the metaphysis and diaphysis; Type 2 has a metaphyseal bone loss. Type 3 defects are subdivided into A and B, depending on the extent of the diaphyseal bone loss. Type 4 has extensive bone loss with an expansion of the diaphyseal cortex.

METHOD

An online survey with digital anteroposterior and lateral radiographs was sent to five arthroplasty surgeons. A total of 55 cases with stemmed femoral and tibial components, considered failures and pending revision, were reviewed. By using the proposed classification system, each femoral and tibial component was scored. Interobserver reliability was determined using the intraclass correlation coefficient for pooled data.

RESULTS

Comparisons between each individual reviewer demonstrated moderate to strong agreement overall for the reviewers using the classification, with an average correlation coefficient of 0.67 (95% CI [0.57 to 0.77]) for all cases, signifying a low variation in the scores of each case. Looking specifically at the femoral components, the ICC was 0.62 (95% CI [0.477 to 0.76]), while the ICC for the tibial components was 0.71 (95% CI [0.58 to 0.83]).

DISCUSSION

This classification, which has demonstrated moderate to strong interobserver reliability, can help surgeons determine the degree of anticipated bone loss and approach these complex cases with a preoperative plan based upon the radiographic images. This classification system will also allow standardized communication among surgeons, categorization of procedures for comparative research, and anticipated prognosis.

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

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

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

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

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

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

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

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.

Osteolysis Complicating Total Knee Arthroplasty

Osteolysis is a process mounted by the host immune system that relies on several variables, including patient-related factors, type of insert material, modes of wear, and implant design. Imaging techniques such as radiography, computed tomography (CT) scans, magnetic resonance imaging (MRI), and tomosynthesis aid in diagnosing osteolysis. Surgical options for the treatment of osteolysis include the insertion of bone grafts, bone cement, and prosthetic augmentation. Although no approved pharmacological therapies for the specific treatment of osteolysis exist, the use of bisphosphonates and statins decreases the risk of osteolysis.

Management of metaphyseal bone loss in revision knee arthroplasty

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

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Evaluating the progression of osteolysis after total knee arthroplasty

Osteolysis around the knee following total knee arthroplasty continues to be a leading cause for revision total knee arthroplasty. Risk factors for periprosthetic knee osteolysis are associated with excessive polyethylene wear and include, but may not be limited to, malalignment of the mechanical axis, early-generation polyethylene sterilization techniques, excessive backside polyethylene wear, metal-backed patellar components, patient age, and an elevated body mass index. The initial diagnosis of osteolysis is frequently discovered on routine surveillance radiographs. The location, size, progressive nature, and associated symptomatology of the defect guides treatment. Surgical indications and timing are predicated on the risk of failure with continued observation. Advanced imaging helps to quantitate the size and location of osteolytic lesions as accurately as possible and aids in preoperative planning. When deciding whether surgery or management with continued radiographic surveillance is indicated, a global assessment of the character and progression of the osteolysis must be weighed with the risk factors associated with the patient.

Bone loss management in total knee revision surgery

PURPOSE

Bone stock reconstruction in TKR surgery is one of the biggest challenges for the surgeon. According to some, authors causes of bone stock loosening are multiple, including stress shielding, osteolysis from wear, septic or aseptic loosening, and bone loss caused by a poorly balanced implant. Moreover, bone loss may be iatrogenic at the time of implant removal, indicating that bone preservation during implant removal is critical.

METHODS

Defect localization and extension affect the surgeon's decisions about the choice of the surgical technique and the type of plant to be taken. Today there are several options available for bone deficiency treatment. The treatment choice is undoubtedly linked to the cause of revision, experience and personal philosophy, but it is necessary to consider also the patient's age, expectations of life, functional requirements and bone quality. Many authors prefer bone stock reconstruction techniques in patients with high bone quality and a better quality of life with more prospects. In patients with lower lease on life and lower bone quality the best bone replacement techniques are of modular systems, wedges, and augments. In cases with septic bone loss, more or less extended, different authors recommend reducing bone grafts in favor of modular prostheses to reduce the risk of graft contamination.

RESULTS

All of these techniques have been shown to be durable in midterm outcomes, but concerns exist for a number of reasons, including disease transmission, resorption, fracture, immune reaction to allograft, the cost of custom prostheses, the inability to modify the construct intraoperatively and the overall technical challenge of applying these techniques.

CONCLUSIONS

The choice between different surgical options depends on bone defect dimension and characteristics but are also patient-related. Reestablishment of well-aligned and stable implants is necessary for successful reconstruction, but this can't be accomplished without a sufficient restoration of an eventual bone loss.

Modular augmentation in revision total knee arthroplasty

PURPOSE

Controversy exists about the real effectiveness of modular augmentation to manage bone defects in revision total knee arthroplasty. The purpose of this study was to determine whether use of modular augmentation to reconstruct severe defects (1) significantly increased overall outcomes, (2) caused radiolucency or osteolysis and (3) affected mid-term survivorship of knee revisions. The hypothesis was that modular augmentation provides a good survivorship of knee revisions.

METHODS

Thirty-eight consecutive revision knee arthroplasties were followed for a median follow-up period of 7 (4.5-9) years. Type 2 and 3 defects were treated with metal augments, tantalum cones and modular cementless stems. Patients were assessed using the IKS knee and function scores and the HSS score.

RESULTS

The median IKS knee and function scores and HSS score were 34 (15-58), 19.5 (13-39) and 30 (24-60) points before the operation, respectively, and 78 (49-97), 76 (58-90) and 80.5 (64-98) points (p < 0.001) at the latest follow-up. The median knee flexion increased from 82° (31°-110°) to 116° (100°-129°) (p < 0.01). Tibial radiolucencies were observed in 2 (5.2 %) cases. Re-revision was necessary in three (7.9 %) patients.

CONCLUSIONS

Modular augmentation may reduce the need for allografting to treat severe bone defects, providing a well-functioning and durable knee joint reconstruction.

Restoration of the distal femur impacts patellar height in revision TKA

BACKGROUND

Restoring patellar height is important in revision TKA for normal knee function and kinematics. Alteration in patellar height after revision TKA is associated with inferior extensor mechanism function.

QUESTIONS/PURPOSES

We determined whether gap balancing with bone preservation and distal femoral augmentation would restore patellar height and patellar height changed in patients undergoing septic and aseptic revision TKA.

PATIENTS AND METHODS

We retrospectively reviewed 76 patients who had revision TKA between 2006 and 2009; 12 had two-stage revisions for infected TKA, and 64 had revision for aseptic failure. We compared preoperative and postoperative radiographs and measured the patellar height using the Insall-Salvati ratio in both groups. We reviewed operative records to determine type of exposure and amount of distal femoral augmentation used to restore the joint line.

RESULTS

Overall mean preoperative and postoperative Insall-Salvati ratios were 1.02 and 1.04, respectively. In the septic group, mean preoperative and postoperative Insall-Salvati ratios were 1.07 and 0.99, respectively. In the aseptic group, mean preoperative and postoperative Insall-Salvati ratios were 1.01 and 1.05, respectively. Overall, nine patients had preoperative patella baja; seven of these had an improvement to normal height. There was little difference in preoperative and postoperative Insall-Salvati ratios in patients with patella alta. Distal augmentation was used in 10 of 12 patients in the septic group and 48 of 64 patients in the aseptic group.

CONCLUSIONS

Surgeons can maintain normal patellar height and improve patella baja by preserving bone stock and using distal femoral augments to restore the distal joint line during revision TKA.

Morselized bone grafting in revision arthroplasty of the knee: a retrospective analysis of 34 reconstructions after 2-9 years

BACKGROUND AND PURPOSE

Loosening of a total knee replacement may lead to loss of bone, requiring biological reconstruction at revision arthroplasty. Good results have been reported from revision arthroplasty of the hip using impaction bone grafting. We report our results of revision total knee arthroplasty using the same technique.

PATIENTS AND METHODS

We retrospectively analyzed 30 patients (involving 34 knees) with a mean age of 63 (34-81) years who, between 1994 and 2002, underwent revision arthroplasty of the knee using hinge or rotational knee prostheses (Link) and impaction bone grafting. The average follow-up was 4 (2-9) years and included a questionnaire, a clinical examination, and standardized radiographs.

RESULTS

25 patients were satisfied with their results. 10 patients reported no impairment in their activities of daily living attributed to their operation and did not need any walking support. In 5 patients, there were no clear radiographic signs of incorporation of the graft but that did not compromise the outcome. 5 other patients had complications due to aseptic loosening of their prostheses with radiographic failure of the graft, leading to a periprosthetic fracture in 2 cases.

INTERPRETATION

Our results with impaction bone grafting in knee revision arthroplasty appear to be similar to those obtained by the same technique in revision hip surgery.

Management of bone loss in revision total knee arthroplasty

Bone deficiencies around the knee can present a substantial challenge during revision total knee arthroplasty. Bone loss occurs from stress shielding, osteolysis, chronic infection, and bone removed during implant extraction. Smaller defects have traditionally been treated with cement filling or allograft bone chips. Larger defects can be reconstructed with bulk allografts or custom prostheses. A hinged prosthesis may be necessary to account for ligamentous insufficiency. In addition to traditional methods of managing bone loss, recent developments include the use of metaphyseal-filling implants made of highly porous metal. These implants can be press-fit into host bone to accommodate large metaphyseal defects. Each revision knee surgery provides unique challenges, requiring proficiency in multiple techniques of bone loss management.

Management of bone loss: augments, cones, offset stems

Trabecular metal augmentation has added new treatment options for severe proximal tibial bone defects in revision knee arthroplasty. Porous tantalum tibial cones provide mechanical support for the tibial component and have the potential for long-term biologic fixation. These cones facilitate restoration of the proximal tibia metaphysis in Type 2 and 3 defects. Ten tantalum tibial cones were press-fit into the prepared cavitary defect of a series of revision knee arthroplasties. Voids between the cone and host bone were filled with morselized grafting material. The core tibial component was cemented into the implanted tibial cone; fixation was enhanced with stem extensions, which were press-fit in four knees and cemented in six knees. Extensions ranged from 75-200 mm with length dependent upon the residual bone quality. Offset stems were used in 3 tibias. At follow-up (average 10 months), radiographic evaluation revealed no evidence of loosening or change in position. Strength, range of motion, and stability were comparable to previously reported series of revision arthroplasties. Trabecular metal cones can help reconstruct large cavitary defects and, along with stem extensions and offset stems, may eliminate the need for extensive bone grafting or structural allograft in revision knee arthroplasty.

LEVEL OF EVIDENCE

Therapeutic study, level V (expert opinion). See the Guidelines for Authors for a complete description of levels of evidence.

The Insall legacy in total knee arthroplasty

John N. Insall was a pioneer in the field of knee surgery. He was a rare individual who accomplished unparalleled levels of success as a surgeon, designer, and teacher. During the past 4 decades, he was instrumental in evolving total knee arthroplasty to its current state of excellence. Insall's impact on orthopaedics is felt by all who have come in contact with him.