Acetabular osteolysis in total hip arthroplasty: prevention and treatment

Implementing Machine Learning approaches for accelerated prediction of bone strain in acetabulum of a hip joint

The Finite Element (FE) methods for biomechanical analysis involving implant design and subject parameters for musculoskeletal applications are extensively reported in literature. Such an approach is manually intensive and computationally expensive with longer simulations times. Although Artificial Intelligence (AI) based approaches are implemented to a limited extent in biomechanics, such approaches to predict bone strain in acetabulum of a hip joint, are hardly explored. In this context, the primary objective of this paper is to evaluate machine learning (ML) models in tandem with high-fidelity FEA data for the accelerated prediction of the biomechanical response in the acetabulum of the human hip joint, during the walking gait. The parameters used in the FEA study included the subject weight, number and distribution of fins on the periphery of the acetabular shell, bone condition and phases of the gait cycle. The biomechanical response has also been evaluated using three different acetabular liners, including pre-clinically validated HDPE-20% HA-20% Al2O3, highly-crosslinked ultrahigh molecular weight polyethylene (HC-UHMWPE) and ZrO2-toughened Al2O3 (ZTA). Such parametric variation in FEA analysis, involving 26 variables and a full factorial design resulted in 10,752 datasets for spatially varying bone strains. The bone condition, as opposed to subject weight, was found to play a statistically significant role in determining the strain response in the periprosthetic bone of the acetabulum. While utilising hyperparameter tuning, K-fold cross validation and statistical learning approaches, a number of ML models were trained on the FEA dataset, and the Random Forest model performed the best with a coefficient of determination (R2) value of 0.99/0.97 and Root Mean Square Error (RMSE) of 0.02/0.01 on the training/test dataset. Taken together, this study establishes the potential of ML approach as a fast surrogate of FEA for implant biomechanics analysis, in less than a minute.

Current Concepts of Using Large Femoral Heads in Total Hip Arthroplasty

Instability and dislocation after total hip arthroplasty are the most common causes of revisions and major complications for failure of inserted prostheses, leading to a reduction in quality of life. Because the use of artificial femoral head sizes smaller than patient's own size is the important cause for dislocation, the use of large femoral head have increased. Femoral head sizes greater than 32 mm offer multiple advantages in physical function and activity levels of patients by improving hip stability, decreasing dislocation rate and increasing range of motion. However, various concerns are encountered including wear debris generation at the trunnion-bore interface and increases in frictional torque and stress over the component-bone interface when using larger head sizes. So, the use of femoral head sizes less than 40 mm is recommended.

Effect of design on the initial stability of press-fit cups in the presence of acetabular rim defects: experimental evaluation of the effect of adding circumferential fins

PURPOSE

This experimental study was undertaken to examine the fixation characteristics of a six-finned acetabular cup in both primary and revision arthroplasty in comparison with two other commonly used cup designs without fins.

METHODS

All three cup designs (Ananova® [Intraplant], Plasmacup® NSC [Aesculap]; Exceed ABT™ [Biomet]) were implanted into validated models of normal and revision acetabula. The defect models were designed to simulate a dorso-cranial rim defect of 90° width and 10 mm in depth (moderate rim defect) and a dorso-cranial rim defect of 130° width and 15 mm in depth (severe rim defect). The fixation strength of the three cup designs was tested by cyclically edge-loading the implanted cups using a mechanical testing machine.

RESULTS

The six-finned Ananova implant exhibited greater resistance to foam-cup interface motion than both the Plasmacup and Exceed ABT implants. The largest average differences were observed in the resistance to ultimate spin-out, with Ananova outperforming Exceed ABT and Plasmacup by 26% and 17% in the moderate and by 36% and 38% in the severe defect models, respectively.

CONCLUSIONS

The six-finned Ananova cup was significantly more resistant to edge loading both in the normal acetabulum and in acetabula with moderate to severe dorso-cranial rim defects than cup designs without fins, indicating that it may cover a wider range of clinical indications than conventional press-fit cups and provide clinicians with the confidence that, in primary and simple revision arthroplasty, adequate fixation strength can be obtained.

Incidence of osteolysis in total knee arthroplasty: comparison between radiographic and retrieval analysis

Detection of polyethylene wear and osteolysis in total knee arthroplasty using radiographs is imprecise. To correlate radiographic findings with retrieved tibial component analysis, we reviewed knee revision cases. A joint registry was used to identify all knee revisions. Radiographic scoring systems were developed. Radiographs were analyzed for osteolysis and implant alignment. Polyethylene liner retrievals were visually and optically graded for surface damage. Statistical analyses that included correlation analysis and Mann-Whitney U test were used. When osteolysis was found, radiographic scores and delamination score were significantly higher (P = .047 and P = .014, respectively). Delamination is a good indicator for polyethylene wear and osteolysis. There is a need to develop in vivo methods to identify polyethylene changes and thereby prevent severe clinical outcomes.

Effect of low-friction ion-treated femoral heads on polyethylene wear rates

Polyethylene wear is a major contributor to osteolysis and subsequent aseptic loosening of prosthetic components in total hip arthroplasty. Use of ion implantation as a surface modification to the metallic bearing component of orthopaedic implants may be an effective means of reducing wear debris at the bearing interface. In July 1991, low friction ion treated femoral heads were introduced. This study evaluates the effect of the low friction ion treated femoral head on polyethylene wear. Fifty-five total hip arthroplasties (53 patients) with low friction ion treated femoral heads followed up a minimum of 3 years were matched with 55 total hip arthroplasties (47 patients) without low friction ion treated femoral heads for the same postoperative period. Socket wear was evaluated radiographically. Case matching and strict inclusion criteria were used to control for known factors influencing polyethylene wear. These criteria included: (1) cases matched for gender and age within 2 years; (2) diagnosis limited to osteoarthritis or avascular necrosis of the femoral head only; (3) femoral head diameter limited to 26 or 28 mm only; (4) hydroxyapatite coated femoral stem of the same design and a metal backed socket of the one of two designs with the same polyethylene insert; and (5) minimum followup of 3 years. The linear wear rate of polyethylene was 0.161 +/- 0.095 mm per year in the group without the low friction ion treated heads and 0.116 +/- 0.101 mm per year in the low friction ion treated group. The volumetric wear rates were 74.5 +/- 44.3 mm3 per year for the group without the low friction ion treated heads and 57.8 +/- 51.1 mm3 per year for the low friction ion treated group. Assuming the sensitivity of these measurements can detect these small differences in wear accurately, these results suggest low friction ion treated prosthetic heads are useful in reducing polyethylene wear at 3-year minimum followup.

Total knee arthroplasty in patients with rheumatoid arthritis. An overview

Total knee arthroplasty in patients with rheumatoid arthritis presents several unique challenges. Patients with rheumatoid arthritis often have additional medical, anesthetic, and global musculoskeletal problems that are not present in the patient with osteoarthritis. In terms of the knee, these patients usually have osteopenia and may present with an array of bone and soft tissue deformities, each of which can impact the initial success and long term durability of a total knee replacement. Despite these potential difficulties, the early and long term results of total knee arthroplasty in patients with rheumatoid arthritis have proven to be excellent.

Three-dimensional polyethylene wear of a press-fit titanium prosthesis. Factors influencing generation of polyethylene debris

Between 1985 and 1990, 108 consecutive Harris-Galante I (Zimmer, Warsaw, IN) total hip arthroplasties were performed by four surgeons at a single hospital. At the time of follow-up evaluation, 80 hips were available for review. The mean rate of linear wear was 0.15 mm/y, mean rate of three-dimensional femoral head displacement was 0.21 mm/y, and mean rate of volumetric wear was 121 mm3/y. Eight hips (10%) in this series had radiologic osteolysis around either the femoral or acetabular component. A significantly greater volumetric wear rate was found in patients who were younger, those with a higher activity level, those who received a 32-mm-diameter femoral head, and those with vertical orientation of their acetabular component. No relationship could be made with patient weight, gender, Harris hip score, or cup diameter.