Biomechanical effect of metal augment and bone graft on cup stability for acetabular reconstruction of total hip arthroplasty in hip dysplasia: a finite element analysis

Medium- to long-term clinical efficacy of total hip arthroplasty with structural bone grafting for dysplasia of the hip

BACKGROUND

Patients with dysplasia of the hip (DDH) have different degrees of bone defects above and outside the acetabulum, and anatomically reconstructing the acetabular centre of rotation is difficult in primary total hip arthroplasty (THA).

METHODS

From April 2012 to December 2022, 64 patients (64 hips) with DDH treated with THA with structural bone graft in the superolateral acetabulum were selected. The Oxford hip score(OHS), Barthel index (BI), leg length discrepancy, Wibegr central edge-angle(CE), gluteus medius muscle strength, vertical and horizontal distance of the hip rotation center, coverage rate of the bone graft and complications were used to evaluate the clinical effectiveness of the patients.

RESULTS

All patients were followed up for an average of 7.3±1.9 years. The OHS improved significantly after the operation (P<0.001). The postoperative BI was significantly greater than that before operation (P<0.001). The postoperative leg length discrepancy was significantly lower than that before the operation (P<0.001). Postoperative bedside photography revealed that the height and horizontal distance to the hip rotation center were significantly lower after surgery than before surgery (P<0.001). The postoperative CE was significantly greater than that before surgery (P<0.001). No acetabular component loosening or bone graft resorption was found during the postoperative imaging examination.

CONCLUSIONS

The use of biological acetabular cup combined with structural bone graft in the superolateral acetabulum in THA for DDH can obtain satisfactory medium and long-term clinical and radiological results.

Developing and Validating a Model of Humeral Stem Primary Stability, Intended for In Silico Clinical Trials

In silico clinical trials (ISCT) can contribute to demonstrating a device's performance via credible computational models applied on virtual cohorts. Our purpose was to establish the credibility of a model for assessing the risk of humeral stem loosening in total shoulder arthroplasty, based on a twofold validation scheme involving both benchtop and clinical validation activities, for ISCT applications. A finite element model computing bone-implant micromotion (benchtop model) was quantitatively compared to a bone foam micromotion test (benchtop comparator) to ensure that the physics of the system was captured correctly. The model was expanded to a population-based approach (clinical model) and qualitatively evaluated based on its ability to replicate findings from a published clinical study (clinical comparator), namely that grit-blasted stems are at a significantly higher risk of loosening than porous-coated stems, to ensure that clinical performance of the stem can be predicted appropriately. Model form sensitivities pertaining to surgical variation and implant design were evaluated. The model replicated benchtop micromotion measurements (52.1 ± 4.3 µm), without a significant impact of the press-fit ("Press-fit": 54.0 ± 8.5 µm, "No press-fit": 56.0 ± 12.0 µm). Applied to a virtual population, the grit-blasted stems (227 ± 78µm) experienced significantly larger micromotions than porous-coated stems (162 ± 69µm), in accordance with the findings of the clinical comparator. This work provides a concrete example for evaluating the credibility of an ISCT study. By validating the modeling approach against both benchtop and clinical data, model credibility is established for an ISCT application aiming to enrich clinical data in a regulatory submission.

Functionally graded stem optimizes the fixed and sliding surface coupling mechanism

Whether the optimization of fixed surface and sliding surface coupling mechanism is related to the hierarchical level of functionally graded porous stem is unknown. The functionally graded porous finite element stem models were constructed using tetrahedral microstructure with the porosities of 47-95%. The stress distribution for femoral bone gradually strengthened, the stress shielding was decreased along the increase of hierarchical levels of the stem after implantation. The coupling mechanism of fixed and sliding surfaces can be optimized by the functional gradient porous stem, the performance advantages become more prominent with the increase of hierarchical levels of the structure.

Biomechanical analysis and clinical observation of 3D-printed acetabular prosthesis for the acetabular reconstruction of total hip arthroplasty in Crowe III hip dysplasia

Objective: This study aimed to evaluate the biomechanical effectiveness of 3D-printed integrated acetabular prosthesis (IAP) and modular acetabular prosthesis (MAP) in reconstructing the acetabulum for patients with Crowe III developmental dysplasia of the hip (DDH). The results of this study can provide a theoretical foundation for the treatment of Crowe III DDH in total hip arthroplasty (THA). Methods: Finite element (FE) analysis models were created to reconstruct Crowe III DDH acetabular defects using IAP and MAP. The contact stress and relative micromotion between the acetabular prosthesis and the host bone were analyzed by gradually loading in three increments (210 N, 2100 N, and 4200 N). In addition, five patients with Crowe III DDH who underwent IAP acetabular reconstruction were observed. Results: At the same load, the peak values of IAP contact stress and relative micromotion were lower than those of MAP acetabular reconstruction. Under jogging load, the MAP metal augment's peak stress exceeded porous tantalum yield strength, and the risk of prosthesis fracture was higher. The peak stress in the bone interface in contact with the MAP during walking and jogging was higher than that in the cancellous bone, while that of IAP was higher than that of the cancellous bone only under jogging load, so the risk of MAP cancellous bone failure was greater. Under jogging load, the relative micromotion of the MAP reconstruction acetabular implant was 45.2 μm, which was not conducive to bone growth, while under three different loads, the relative micromotion of the IAP acetabular implant was 1.5-11.2 μm, all <40 μm, which was beneficial to bone growth. Five patients with IAP acetabular reconstruction were followed up for 11.8 ± 3.4 months, and the Harris score of the last follow-up was 85.4 ± 5.5. The imaging results showed good stability of all prostheses with no adverse conditions observed. Conclusion: Compared with acetabular reconstruction with MAP, IAP has a lower risk of loosening and fracture, as well as a better long-term stability. The application of IAP is an ideal acetabular reconstruction method for Crowe III DDH.

Extra-articular Blocking Technique to Resolve Severe Acetabular Bone Defect in Developmental Dysplasia of the Hip

OBJECTIVE

The reconstruction of acetabular bone defect in developmental dysplasia of the hip (DDH) is a great challenge. Although several successful solutions have been raised, their efficacy and reliability have not been fully substantiated. This work aims to present a simple, economic and effective acetabular reconstructive technique to resolve the massive acetabular bone defect in DDH scenario.

METHODS

This is a case series and observational study investigating the effectiveness and safety of extra-articular blocking technique in patients diagnosed as DDH of Crowe type II-III and Hartofilakidis B. Sixteen consecutive patients indicated for extra-articular blocking and treated with total hip arthroplasty were enrolled in this series from January 2019 to August 2020. The outcome measures included the surgical indicators such as acetabular coverage, prosthesis position, operational time, medical cost, and short-term follow-up indicators such as complications profile, patient-reported functional scales, overall recovery after surgery, and radiographic bone integration and remodeling. Their medical documentation and follow-up records were carefully reviewed with ethical approval.

RESULTS

The mean values of postoperative acetabular component inclination and anteversion were 42.3° ± 2.1° and 16.4° ± 1.8°, with an average acetabular coverage of 92.1%. The mean cost reduction for patients treated with this technique compared with those treated with trabecular metal augmentation was 15.3%. The mean time until walking under full-weight bearing decreased by 3.5 weeks compared with patients treated with autologous bone grafting. Within an average observational period of 18 months, the mean improvements in Harris hip score and WOMAC score were 31 and 22 points, respectively, which were identical to those with bone graft and metal augmentation techniques. No complications such as dislocation, acetabular loosening, periprosthetic joint infection, and limb length discrepancy were recorded. No signs of translucent line formation, third-party reaction, and wear-associated osteolysis were identified.

CONCLUSION

The extra-articular blocking can work simply and effectively to address acetabular bone defect in DDH patients of Crowe II-III and Hartofilakidis B, as evidenced by cost-effectiveness and instant weight-bearing advantages, low failure rate, and early osteointegration and remodeling.