Introduction

Historically, the most common indications for re-revision of a total hip arthroplasty (THA) have been aseptic loosening, instability, infection, and peri-prosthetic fracture. As revision implants and techniques have evolved and improved, understanding why contemporary revision THAs fail is important to direct further improvement and innovation. As such, the goals of this study were to determine the implant survivorship of contemporary revision THAs, as well as the most common indications for re-revision.

Introduction

The American Joint Replacement Registry (AJRR) was created to capture total hip (THA) and total knee arthroplasty (TKA) procedural data in order to conduct implant-specific survivorship analyses, produce risk-adjusted patient outcome data, and provide hospitals and surgeons with quality benchmarks. The purpose of this study is to compare early reports from the AJRR to other national registries to identify similarities and differences in surgeon practice and potential topics for future analysis.

Introduction

Manual chart review is labor-intensive and requires specialized knowledge possessed by highly-trained medical professionals. The cost and infrastructure challenges required to implement this is prohibitive for most hospitals. Natural language processing (NLP) tools are distinctive in their ability to extract critical information from raw text in the electronic health records (EHR). As a simple proof-of-concept, for the potential application of this technology, we examined its ability to discriminate between a binary classification (periprosthetic fracture [PPFFx] vs. no PPFFx) followed by a more complex classification of the same problem (Vancouver).

Introduction

There is no literature regarding the risk of a patient developing PJI after primary TKA if the patient has previously experienced PJI of a TKA or THA in another joint. The goal of this study was to compare the risk of PJI of primary TKA in this patient population compared to matched controls.

Metal-on-metal bearings have become popular in the last ten years because of a low wear rate combined with the ability to use large head sizes for conventional total hip arthroplasty (THA) and to facilitate resurfacing hip arthroplasty. Further advantages of metal-metal bearings include the fact that they are not at risk for fracture, and they can be made as modular or non-modular acetabular implants.

It was recognized early that metal-on-metal implants had the potential to increase serum ion levels, and this was demonstrated in a number of studies. The significance of elevated ion levels, however, for most patients has been primarily a theoretical concern of toxicity, carcinogenesis or mutagenicity, and to date very few, if any, systemic problems related to systemic metal ions have been documented with certainty. Nevertheless, most surgeons have avoided use of the implants in patients who are likely to become pregnant, patients with renal disease, or patients with major systemic illnesses which have a high likelihood of leading to renal disease. Furthermore, most have avoided using them in patients with known dermal metal allergies, even though the connection between dermal metal allergies and metal bearings has not been established.

Unexpectedly, an extremely important concern has emerged with metal bearings: the finding of local inflammatory reactions related to metal bearings. These inflammatory reactions can take several forms including pain with a milky effusion, local tissue necrosis, or large fluid collections or pseudotumors. The histology of these different reactions appears to be predominantly lymphocytic in nature and a term for at least some of these reactions has been coined “AVALS”. Whether these local reactions are primarily immunologic in nature or primarily related to dose of local metal ions or debris remains uncertain. While there is much still to be learned, it appears that certain patient populations may be at increased risk for metal reactions, possibly related to implant size (women and smaller patients). It also seems verticallyoriented implants, which create edge loading, increase wear and increase risk of local metal reactions.

Perhaps the most important question is the incidence of local metal reactions, which remains to be defined. To date the problems in most series have been infrequent, less than 1 or 2 percent. However, in a few selected series the incidence has been higher, and when screening has been done for asymptomatic patients with fluid or masses around the joint, the rate has been higher in at least one reported series.

Surgeons may interpret the importance of local metal reactions differently, but certainly ultimately incidence of this problem will have a very major effect on the future of these bearings.

It has become a platitude that total knee arthroplasty (TKA) is an excellent operation, provides good pain relief, and over 90% survivorship at 20 years in many series. While all these points are true, total knee arthroplasty as practiced currently still will not meet the demands of many patients who will desire the procedure in the next ten years. The reasons for this include changing demographics of TKA and the changing demands of TKA candidates. TKA is being performed more frequently in patients under 60, in fact this is the fastest growing group of patients by percent growth. We performed a population-based study of trends utilization of TKA and found increasing TKA utilization in all age groups over time but the greatest increase by percent in the youngest patients. Furthermore, younger patients now no longer tend to be lowactivity patients with inflammatory disease. The percentage of patients with primary osteoarthritis and post traumatic arthritis has increased dramatically. Long-term studies of TKA have shown such durability in part because many of the younger patients were Charnley Class C patients, and because historically most TKA patients were older with an average age of most early series of around 69 years. This means there were far fewer young patients in early TKA series than in early THA series. This is important because material failures occur predominantly in younger patients and durability is a greater concern in younger patients, so one may predict that this younger, more active group will not enjoy the same level of TKA durability reported in the literature unless technology improves.

Total knee arthroplasty patients are more active than one might predict. In a study of 1200 patients surveyed at five years the average UCLA score was 7 out of 10. Younger patients achieved a higher activity level but were in general less satisfied with activity provided by TKA than older patients. This implies there is a need for better designs and surgery to facilitate more normal kinematics, more flexion, and more quadriceps strength. A study by Weiss and Noble (CORR 2002) identified specific activities associated with limitations after knee arthroplasty.

Furthermore, a study by Bourne and associates demonstrated lower satisfaction scores after total knee arthroplasty than hip arthroplasty. Finally, in our study of activity levels after knee arthroplasty we found that 16% of current patients participate in heavy labor or sports not recommended by Knee Society guidelines. These patients tend to be younger and predominantly male. This implies there is a subset of the population already doing things that will challenge the current generation of total knee arthroplasty and more patients want to do these activities and already do so. Therefore, there is a need for improved implant durability and improved knee function after knee arthroplasty. This suggests the methods of fixation may need to evolve to accommodate higher demands, and bearing surfaces definitely need to evolve to accommodate higher demands. Finally, more sophisticated implant kinematics to avoid or compensate for anterior cruciate ligament and posterior collateral ligament deficiency and more sophisticated surgery to optimize implant alignment and soft tissue balancing in the individual patient will be necessary to achieve more normal patient knee kinematic stability, strength and “feel”. Finally, we will need better and more sensitive scoring systems to detect improvements in future TKA surgery and design in the future.