Aims. Periprosthetic fracture and implant loosening are two of the major reasons for revision surgery of cementless implants. Optimal implant fixation with minimal bone damage is challenging in this procedure. This pilot study investigates whether vibratory implant insertion is gentler compared to consecutive single blows for acetabular component implantation in a surrogate polyurethane (PU) model. Methods. Acetabular components (cups) were implanted into 1 mm nominal under-sized cavities in PU foams (15 and 30 per cubic foot (PCF)) using a vibratory implant insertion device and an automated impaction device for single blows. The impaction force, remaining polar gap, and lever-out moment were measured and compared between the impaction methods. Results. Impaction force was reduced by 89% and 53% for vibratory insertion in 15 and 30 PCF foams, respectively. Both methods positioned the component with polar gaps under 2 mm in 15 PCF foam. However, in 30 PCF foam, the vibratory insertion resulted in a clinically undesirable polar gap of over 2 mm. A higher lever-out moment was achieved with the consecutive single blow insertion by 42% in 15 PCF and 2.7 times higher in 30 PCF foam. Conclusion. Vibratory implant insertion may lower periprosthetic fracture risk by reducing impaction forces, particularly in low-quality bone. Achieving implant seating using vibratory insertion requires adjustment of the nominal press-fit, especially in denser bone. Further preclinical testing on real bone tissue is necessary to assess whether its viscoelasticity in combination with an adjusted press-fit can compensate for the reduced primary stability after vibratory insertion observed in this study. Cite this article: Bone Joint Res 2024;13(6):272–278

There is still little information on the histological characteristics of the acetabular bone tissue after failure of the primary prosthetic component. The purpose of this study is to characterize the viability and quality of the acetabular bone tissue in patients undergoing acetabular revision for aseptic loosening of uncemented components. 19 patients were enrolled: 14 hip revisions and 5 primary total hip arthroplasty. . Samples collecting. : three acetabular bone biopsy of patients were collected at the time of surgery with a 8G diameter needle after reaming. . Histological evaluation. : all samples, after removing the mineral component, were cut longitudinally with a thickness section of 5μm and colored with hematoxylin-eosin dichromic dye. Histological evaluation was done by optical microscopy with 40× magnification. Five bone quality classes were developed by evaluating percentage of aseptic necrosis, percentage of active osteoblasts, presence of osteopenia, presence of osteoclasts, absence of intramedullary hematopoietic component. . Histological evaluation. : the bone quality of cases was significantly poorer than the controls. The differences found were statistically significant between the two groups for percentage of necrosis (p=0.0033), percentage of active osteoblasts (p=0.0071) and presence of osteopenia (p=0.037). Overall bone quality was significantly worse in the study group due reduced viability, overturn of lamellar structures, reduced amount of intramedullary hematopoietic component in respect to the controls; this could result in poor ability of the host bone to interact with the implanted components

Bone marrow stem cells (BMSCs) represent a collection of different cell types exhibiting stem cell characteristics but with notable heterogeneity. Among these, Skeletal Stem Cells (SSCs) represent a distinct matrix subgroup within BMSC and demonstrate a specialized capacity to facilitate bone formation, recruit chondrocytes, and contribute to hematopoiesis. SSCs play a pivotal role in orchestrating the functions of skeletal organs. Local ischemia has a significant impact on cell survival and function. We hypothesize that bone ischemia induces alterations in the differentiation potential of SSCs, consequently influencing changes in bone structure. We mechanically dissected tissue from the necrotic segment in the femoral head and more normal appearing areas from the femoral neck of specimens from 5 patients diagnosed with osteonecrosis of the femoral head (ONFH). These tissues were enzymatically broken down into individual cell suspensions. Utilizing fluorescence-activated cell sorting (FACS) based on specific surface markers indicative of human skeletal stem cells (hSSC), namely CD45- CD235a- CD31- TIE2- Podoplanin (PDPN)+ CD146- CD73+ CD164+, we isolated a distinct cell population. Subsequent in vitro evaluations, focusing on clonogenicity, osteogenesis, and chondrogenesis were conducted to assess the functional prowess of these SSCs. Moreover, we introduced BMP2 at a concentration of 50ng/ml to SSCs extracted from necrotic regions to potentially reinstate their osteogenic capabilities. We effectively isolated SSCs from both Necrotic and Non-necrotic Zones. We observed an augmented clonal formation capacity and chondrogenesis ability of SSCs isolated from the necrotic region, accompanied by a significant decline in osteogenic ability (P＜0.01), an effect not reversible even with the addition of BMP2. Ischemia adversely affects the proliferation and function of SSCs, resulting in a diminished osteogenic capacity and an insensitivity to BMP2, ultimately leading to structural alterations in bone tissue

Background. Structural bone allografts are an established treatment method for long-bone structural defects arising from such conditions as trauma, sarcoma, and osteolysis following total joint replacement. However, the quality of structural bone allografts is difficult to non-destructively assess prior to use. The functional lifetime of structural allografts depend on their ability to resist cyclic loading, which can lead to fracture even at stress levels well below the yield strength. Because allograft bone has limited capacity for remodeling, optimizing allograft selection for bone quality could decrease long-term fracture risk. Raman spectroscopy biomarkers can non-destructively assess the three primary components of bone (collagen, mineral, and water), and may predict the resistance of donor bone allografts to fracture from cyclic loads. The purpose of this study was to prospectively assess the ability of Raman biomarkers to predict number of cycles to fracture (“cyclic fatigue life”) of human allograft cortical bone. Methods. Twenty-one cortical bone specimens were from the mid-diaphysis of human donor bone tissue (bilateral femurs from 4 donors: 63M, 61M, 51F, 48F) obtained from the Musculoskeletal Transplant Foundation. Six Raman biomarkers were analyzed: collagen disorganization, type B carbonate substitution (a surrogate for mineral maturation), matrix mineralization, and 3 water compartments. Specimens underwent cyclic fatigue testing under fully reversed conditions at 35 and 45MPa (physiologically relevant stress levels for structural allografts). Specimens were tested to fracture or to 30 million cycles (“run-out”), simulating 15 years of moderate activity (i.e., 6000 steps per day). Multivariate regression analysis was performed using a tobit model (censored linear regression) for prediction of cyclic fatigue life. Specimens were right-censored at 30 million cycles. Results. All of the 6 biomarkers that were evaluated were independently associated with cyclic fatigue life (p < 0.05). The multivariate model explained 70% of the variance in cyclic fatigue life (R2=0.695, p<0.001,). Increasing disordered collagen (p<0.001) and loosely collagen-bound water compartments (p<0.001) were associated with decreased cyclic fatigue life. Increasing type B carbonate substitution (p<0.001), matrix mineralization (p<0.001), tightly collagen-bound water (p<0.001), and mineral-bound water (p=0.002) were associated with increased cyclic fatigue life. In the predictive model, 42% of variance in cyclic fatigue life was attributable to degree of collagen disorder, all bound water compartments accounted for 6%, and age and sex accounted for 17%. Conclusions. Raman biomarkers of three bone components (collagen, mineral, and water) predict cyclic fatigue life of human cortical bone. Increased baseline collagen disorder was associated with decreased cyclic fatigue life, and was the strongest determinant of cyclic fatigue life. Increased matrix mineralization and mineral maturation were associated with increased cyclic fatigue life. Bound-water compartments of bone contributed minimally to cyclic fatigue life. These results are complementary with prior Raman studies of monotonic testing of bone that reported decreased toughness and strength with increased collagen disorder and increased stiffness with increased bone mineralization and mineral maturation. This model should be prospectively validated. Raman analysis is a promising tool for the non-destructive evaluation of structural bone allograft quality and may be useful as a screening tool for selection of allograft bone. Acknowledgements. Supported by a grant from the Musculoskeletal Transplant Foundation. The Dudley P. Allen Fellowship (JYD), Wilbert J. Austin Professor of Engineering Chair (CMR) and the Leonard Case Jr. Professor of Engineering Chair (OA) are gratefully acknowledged

Aims

The main advantage of 3D-printed, off-the-shelf acetabular implants is the potential to promote enhanced bony fixation due to their controllable porous structure. In this study we investigated the extent of osseointegration in retrieved 3D-printed acetabular implants.

Aims

Aseptic loosening is a leading cause of uncemented arthroplasty failure, often accompanied by fibrotic tissue at the bone-implant interface. A biological target, neutrophil extracellular traps (NETs), was investigated as a crucial connection between the innate immune system’s response to injury, fibrotic tissue development, and proper bone healing. Prevalence of NETs in peri-implant fibrotic tissue from aseptic loosening patients was assessed. A murine model of osseointegration failure was used to test the hypothesis that inhibition (through Pad4^-/- mice that display defects in peptidyl arginine deiminase 4 (PAD4), an essential protein required for NETs) or resolution (via DNase 1 treatment, an enzyme that degrades the cytotoxic DNA matrix) of NETs can prevent osseointegration failure and formation of peri-implant fibrotic tissue.

Aims

Cementless acetabular components rely on press-fit fixation for initial stability. In certain cases, initial stability is more difficult to obtain (such as during revision). No current study evaluates how a surgeon’s impaction technique (mallet mass, mallet velocity, and number of strikes) may affect component fixation. This study seeks to answer the following research questions: 1) how does impaction technique affect a) bone strain generation and deterioration (and hence implant stability) and b) seating in different density bones?; and 2) can an impaction technique be recommended to minimize risk of implant loosening while ensuring seating of the acetabular component?

The femoral head receives blood supply mainly from the deep branch of the medial femoral circumflex artery (MFCA). In previous studies we have performed anatomical dissections of 16 specimens and subsequently visualised the arteries supplying the femoral head in 55 healthy individuals. In this further radiological study we compared the arterial supply of the femoral head in 35 patients (34 men and one woman, mean age 37.1 years (16 to 64)) with a fracture/dislocation of the hip with a historical control group of 55 hips. Using CT angiography, we identified the three main arteries supplying the femoral head: the deep branch and the postero-inferior nutrient artery both arising from the MFCA, and the piriformis branch of the inferior gluteal artery. It was possible to visualise changes in blood flow after fracture/dislocation.

Our results suggest that blood flow is present after reduction of the dislocated hip. The deep branch of the MFCA was patent and contrast-enhanced in 32 patients, and the diameter of this branch was significantly larger in the fracture/dislocation group than in the control group (p = 0.022). In a subgroup of ten patients with avascular necrosis (AVN) of the femoral head, we found a contrast-enhanced deep branch of the MFCA in eight hips. Two patients with no blood flow in any of the three main arteries supplying the femoral head developed AVN.

Cite this article: Bone Joint J 2013;95-B:1453–7.

The aim of this study was to obtain detailed long-term data on the cement-bone interface in patients with cemented stems, implanted using the constrained fixation technique. A total of eight stems were removed together with adjacent bone during post-mortem examinations of patients with well-functioning prostheses. Specimens were cut at four defined levels, contact radiographs were obtained for each level, and slices were prepared for histological analysis. Clinical data, clinical radiographs, contact radiographs and histological samples were examined for signs of loosening and remodelling. The mean radiological follow-up was 9.6 years and all stems were well-fixed, based on clinical and radiological criteria. Contact radiographs revealed an incomplete cement mantle but a complete filling of the medullary canal for all implants. Various amounts of polyethylene particles were evident at the cement-bone interface of seven stems, with no accompanying inflammatory reaction. Cortical atrophy and the formation of an ‘inner cortex’ were confirmed in six of eight stems by contact radiographs and histology, but were only visible on two clinical radiographs.

Our results confirm that a complete cement mantle is not essential for the survival of Müller straight stems into the mid term, and support our hypothesis that no benefit to long-term survival can be expected from modern cementing techniques.

We examined whether a selective cyclooxygenase-2 (COX-2) inhibitor (celecoxib) was as effective as a non-selective inhibitor (ibuprofen) for the prevention of heterotopic ossification following total hip replacement. A total of 250 patients were randomised to receive celecoxib (200 mg b/d) or ibuprofen (400 mg t.d.s) for ten days after surgery. Anteroposterior radiographs of the pelvis were examined for heterotopic ossification three months after surgery. Of the 250 patients, 240 were available for assessment. Heterotopic ossification was more common in the ibuprofen group (none 40.7% (50), Brooker class I 46.3% (57), classes II and III 13.0% (16)) than in the celecoxib group (none 59.0% (69), Brooker class I 35.9% (42), classes II and III 5.1% (6), p = 0.002). Celecoxib was more effective than ibuprofen in preventing heterotopic bone formation after total hip replacement.

Between January 1998 and December 1998, 82 consecutive patients (86 hips) underwent total hip arthroplasty using a trabecular metal monoblock acetabular component. All patients had a clinical and radiological follow-up evaluation at six, 12 and 24 weeks, 12 months, and then annually thereafter. On the initial post-operative radiograph 25 hips had a gap between the outer surface of the component and the acetabular host bed which ranged from 1 to 5 mm. All patients were followed up clinically and radiologically for a mean of 7.3 years (7 to 7.5). The 25 hips with the 1 to 5 mm gaps were studied for component migration at two years using the Einzel-Bild-Roentgen-Analyse (EBRA) digital measurement method. At 24 weeks all the post-operative gaps were filled with bone and no acetabular component had migrated. The radiographic outcome of all 86 components showed no radiolucent lines and no evidence of lysis. No acetabular implant was revised. There were no dislocations or other complications. The bridging of the interface gaps (up to 5 mm) by the trabecular metal monoblock acetabular component indicates the strong osteoconductive, and possibly osteoinductive, properties of trabecular metal.