Abstract

Introduction

Total hip arthroplasty (THA) is a commonly performed procedure to relieve arthritis or traumatic injury. However, implant failure can occur from implant loosening or crevice corrosion as a result of inadequate seating of the femoral head onto the stem during implantation. There is no consensus—either by manufacturers or by the surgical community—on what head/stem assembly procedure should be used to maximize modular junction stability. Furthermore, the role of “off-axis” loads—loads not aligned with the stem taper axis—during assembly may significantly affect modular junction stability, but has not been sufficiently evaluated.

Wear and corrosion debris generated from total hip replacements (THR) can cause adverse local tissue reactions (ALTR) or osteolysis, often leading to premature implant failure. The tissue response can be best characterized by histopathological analysis, which accurately determines the presence of cell types, but is limited in the characterization of biochemical changes (e.g. protein conformation alteration). Fourier transform infrared micro-spectroscopy imaging (FTIRI) enables rapid analysis of the chemical structure of biological tissue with a high spatial resolution, and minimal additional sample preparation. The data provides the most information through multivariate method carried out by hierarchical clustering analysis (HCA).

It is the goal of this study to demonstrate the beneficial use of this multivariate approach in providing pathologist with biochemical information from cellular and subcellular organization within joint capsule tissue retrieved from THR patients.

Joint capsule tissue from 2 retrieved THRs was studied. Case 1: a metal-on-polyethylene THR, and Case 2: a dual modular metal-on-metal THR. Prior to FTIRI analysis, tissue samples were formalin-fixed paraffin-embedded and 5μm thick microtome sectioned samples were prepared and mounted on BaF₂ discs and deparaffinized. FTIRI data were collected using high-definition transmission mode (pixel size: ∼1.1 μm²). Hyperspectral images were exported to CytoSpec V2.0.06 for processing and reconstruction into pseudo-color maps based on cluster assignments.

Case 1 exhibited a strong presence of lymphocytes and macrophages (Fig. 1a). Since the process of taking second derivatives reduces the half width of the spectral peaks, it increases the sensitivity toward detecting shoulders or second peaks that may not be apparent in the raw spectra (Fig. 1b). Thus, areas occupied by lymphocytes and macrophages can be easily distinguished providing a fast tissue screening method. Here, HCA was able to distinguish macrophages and lymphocytes based on the infrared response, even in areas where both occurred intermixed. (Fig. 1c) The tissue in direct proximity to cells had a slightly altered collagenous structure. Case 1 also exhibited multiple glassy, green particles which can typically observed around THRs that underwent taper corrosion (Fig. 2a). HCA image was able to visualize and distinguish large CrPO₄ particles, embedded within fibrin exudate rich areas, collagenous tissue without inflammatory cells, and a nearby area with a strong macrophage presence and some finer CrPO₄ particles (Fig. 2d). Moreover, this method can not only locate macrophages, but distinguish particle-laden macrophages depending the type of particles within the cells. In Case 2 (Fig. 3a), clustering results (Fig. 3 b&c) are consistent with the fact that different particle types are associated with MoM bearing surface wear (Co rich particles), corrosion of the CoCrMo taper junctions (Cr-oxides and –phosphate), fretting of Ti-alloy dual modular tapers (Ti-oxides, Ti alloy particles), and even suture debris, which all occurred in this case. Although details of debris types are not available, specifications are possible by coupling other techniques.

The results demonstrate that multivariate FTIRI based spectral histopathology is a powerful tool to characterize the chemical structure and foreign body response within periprosthetic tissue, thus providing insights into the biological impact of different types of implant debris.

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Introduction

Little is known about the relationship between head-neck corrosion and its effect on periprosthetic tissues and distant organs in the majority of patients hosting apparently well-functioning devices. We studied the degree and type of taper damage and the histopathologic response in periprosthetic tissue and distant organs.

Introduction: The most appropriate protocol for biopsying musculoskeletal tumours is controversial. Some authors advocate the use of CT-guided core biopsy. At the Royal Prince Alfred Hospital, Sydney, Australia, initial biopsies of most musculoskeletal tumours involve a surgeon-led operative core biopsy technique with frozen section evaluation. The latter is used to determine whether diagnostic tissue has been obtained and, if possible, to establish a definitive diagnosis.

Aims: To determine the accuracy and cost effectiveness of a surgeon-led biopsy protocol for biopsying musculoskeletal tumours.

Methods: A retrospective audit of biopsies of musculoskeletal tumours performed in the bone and soft tissue sarcoma unit at the Royal Prince Alfred Hospital over a two year period was performed.

Results: One hundred and four patients had biopsies performed under the protocol. There were no non-diagnostic biopsies and one minor error resulting in no change in the patient’s management. There was no requirement to re-biopsy any of the patients. A surgeon-led operative core biopsy with frozen section evaluation was 38% more costly than a CT-guided core biopsy (AU$1804 versus AU$1308).

Conclusions: Surgeon-led biopsy with intra-operative frozen section evaluation is effective and accurate and, despite being labour intensive, the reduction in the need for repeat biopsies justifies its use. Whilst the technique is approximately 38% more costly, there is no requirement for re-biopsy and anxiety associated with the need for this is allayed.

Aim: To clinically and radiologically review our first 50 cases of treatment of malignant bone tumours by extra-corporeal irradiation (ECI) and re-implantation and review the world literature’s other 100 such cases.

Methods: We have treated 50 patients with bony malignancy by en bloc resection, ECI with 50Gy and reimplantation of the bone segment as a method of limb salvage. Mean survivor follow-up is 38 months (12–92).

Results: 42 patients remain alive without disease. 4 recurrences occurred. Functional results were generally good: Mankin grades 17 excellent, 13 good, 9 fair, 3 failures; MSTS mean 77 (20–100); TESS mean 81 (40–100). Solid bony union was the norm, however bone resorption was seen in some cases.

Discussion: The dose of radiation is theoretically lethal to all cells and produces a dead autogenous bone graft of perfect fit. ECI is a useful technique of limb salvage where there is a reasonable residual bone stock. It allows effective re-attachment of muscle tendons, and produces a lasting biological reconstruction. The risk from the re-implanted bone of both local recurrence and of late radiotherapy induced malignancy should be nil.

We have treated 50 patients with bony malignancy by en bloc resection, extracorporeal irradiation (ECI) with 50Gy and re-implantation of the bone segment as a method of limb salvage. Mean survivor follow-up is 38 months (12–92). 42 patients remain alive without disease. 4 recurrences occurred. Functional results were generally good: Mankin grades 17 excellent, 13 good, 9 fair, 3 failures; MSTS mean 77 (20–100); TESS mean 81 (40–100). Solid bony union was the norm, however bone resorption was seen in some cases. The dose of radiation is theoretically lethal to all cells and produces a dead autogenous bone graft of perfect fit. ECI is a useful technique of limb salvage where there is a reasonable residual bone stock. It allows effective re-attachment of muscle tendons, and produces a lasting biological reconstruction. The risk from the re-implanted bone of both local recurrence and of late radiotherapy induced malignancy should be nil.