Majority of osteoporosis related fractures are treated surgically using metallic fixation devices. Anchorage of fixation devices is sometimes challenging due to poor osteoporotic bone quality that can lead to failure of the fracture fixation.

Using a rat osteoporosis model, we employed neutron tomography and histology to study the biological effects of implant augmentation using an isothermally setting calcium sulphate/hydroxyapatite (CaS/HA) biomaterial with synthetic HA particles as recruiting moiety for systemically administered bisphosphonates. Using an osteoporotic sawbones model, we then provide a standardized method for the delivery of the CaS/HA biomaterial at the bone-implant interface for improved mechanical anchorage of a lag-screw commonly used for hip fracture fixation. As a proof-of-concept, the method was then verified in donated femoral heads and in patients with osteoporosis undergoing hip fracture fixation.

We show that placing HA particles around a stainless-steel screw in-vivo, systemically administered bisphosphonates could be targeted towards the implant, yielding significantly higher peri-implant bone formation compared to un-augmented controls. In the sawbones model, CaS/HA based lag-screw augmentation led to significant increase (up to 4 times) in peak extraction force with CaS/HA performing at par with PMMA. Micro-CT imaging of the CaS/HA augmented lag-screws in cadaver femoral heads verified that the entire length of the lag-screw threads and the surrounding bone was covered with the CaS/HA material. X-ray images from fracture fixation surgery indicated that the CaS/HA material could be applied at the lag-screw-bone interface without exerting any additional pressure or risk of venous vascular leakage.: We present a new method for augmentation of lag-screws in fragile bone. It is envisaged that this methodcould potentially reduce the risk of fracture fixation failure especially when HA seeking “bone active” drugs are used systemically.

Objectives

The aim of this study was to analyze drain fluid, blood, and urine simultaneously to follow the long-term release of vancomycin from a biphasic ceramic carrier in major hip surgery. Our hypothesis was that there would be high local vancomycin concentrations during the first week with safe low systemic trough levels and a complete antibiotic release during the first month.

Aim

In vivo studies have shown a preventive and curative effect of using an injectable vancomycin containing biphasic ceramic in an osteomyelitis model. No clinical long term pharmacokinetic release study has been reported. Inadequate concentration in target tissues results in treatment failure and selection pressure for antibiotic-resistant organisms.

Our hypothesis was that vancomycin in the first week would reach high local concentrations but with low systemic levels.

Aim

The demand for a synthetic bone substitute that can build bone and at the same time kill bacteria is high. The aim of this study was to compare the elution of gentamicin from a new synthetic bone substitute in vitro with the performance in clinical applications.

Objectives

Deep bone and joint infections (DBJI) are directly intertwined with health, demographic change towards an elderly population, and wellbeing.

The elderly human population is more prone to acquire infections, and the consequences such as pain, reduced quality of life, morbidity, absence from work and premature retirement due to disability place significant burdens on already strained healthcare systems and societal budgets.

DBJIs are less responsive to systemic antibiotics because of poor vascular perfusion in necrotic bone, large bone defects and persistent biofilm-based infection. Emerging bacterial resistance poses a major threat and new innovative treatment modalities are urgently needed to curb its current trajectory.

Introduction: Changes of the proximal femur like oste-olysis, stress shielding and osteopenia are frequently observed after total hip arthroplasty (THA). Such find-ings might be considered as risk factors for aseptic loosening and later revision. Cortical thinning is observed of healthy femora too and it is questioned whether the effect of the implant can be discriminated from age-related changes.

Aim of our study was to analyze cortical bone changes in prosthetic hips with time and compare those changes with the contra lateral non operated femur.

Materials and Methods:From 1984–87 165 hips were operated with a cemented Muller straight stem. Regular clinical and radiological follow up was scheduled after 1, 2, 5, 10, 15 years. We included only patients operated for osteoarthritis without revision and complete follow-up of more than 10 years. 37 THA hips in 35 patients remained for inclusion in the study. The mean follow-up was 16±4,6 years. Thickness of cortices was measured medially and laterally in 6 locations according to the 2nd to 6th Gruen zones and mean cortical thinning was calculated. The measurements were taken on standardized anterior-posterior x-rays of the pelvis. All measurements were analyzed with Image Access 4 Software calibrated with the reference to 32 mm femoral head.

10 patients were not operated on the contralateral hip and were measured in standardized manner in the same locations as in THA femurs.

Results: All included patients had pain free hips and did not require revision surgery at the last follow-up. Mean cortical thinning was 0,17±0,15 mm/year and it was mostly expressed in mid part of the stem (Gruen 2 and 6 zones). Most thinning occurred within the first 5 years (0,32±0,34 mm/year), later thinning was slower (0.09±0,37 mm/year). For the group with non operated contralateral hip mean thickness loss in THA hip was 0,2±0,17 mm/year and there was thickness loss of the contralateral femur too (0,03±0,12 mm/year), being much less as compared to the operated side (p< 0.001).

Conclusions: Loss of cortical thickness in THA hip with the Muller straight stem is frequently observed in long term and is not associated to expression of clinical symptoms and subsequent revision surgery. The effect is pronounced in the first postoperative years, mainly being explained by stress shielding. Additionally there is cortical thinning due to ageing, being much less than the influence of the implant. Thinning of the cortical bone must not be interpreted a sign of aseptic loosening.

Background: The role of polyethylene (PE) wear in relation to synovitis and elevated hydrostatic pressure in the loosening process after THA has gained increased attention. The aim of our study was to investigate the correlation between prosthetic head size, PE wear and sonographic capsular distention, reflecting the degree of intracapsular synovitis/synovia/hydrostatic pressure.

Patients and methods: In 2005 we analyzed 60 randomly selected and unrevised OA patients 10 years after surgery with 32 or 28mm femoral heads. We evaluated radiographic signs of loosening, linear and volumetric PE wear. Sonographic examination was performed to measure the “capsular distance”, i.e. the capsular distension, defined as the distance between the metallic echo from the anterior surface of the prosthetic femoral neck, and the echo from the anterior surface of the anterior capsule.

Results: The linear wear was 0.2 mm per year and 0.1 mm per year in the 32 mm and 28 mm head size group respectively (p< 0.001), the volumetric wear was 139 mm3/year and 48 mm3/year (p< 0.001), and the capsular distention was 17 mm and 13 mm respectively (p< 0.001). There was also a significant positive correlation between PE volumetric wear and capsular distension (r=0.63, p< 0.001).

Interpretation: We conclude that 32 mm femoral heads were associated with almost three times higher volumetric wear as compared to 28 mm heads, and increased “capsular distension”, reflecting increased synovitis/synovia/hydrostatic pressure in prosthetic hip.

Introduction. Since the early days of total hip arthroplasty (THA) the choice of the proper diameter of the femoral head has been debated with respect to its effect on wear. The most widely accepted theory explaining aseptic loosening of THA is that of polyethylene particles induced osteolysis. In a previous study concerning 1,660 ScanHip THA’s that were followed for up to 12 years the cumulative revision rate was not found to be dependent on if a 22 mm or a 32 mm head size had been used1. We have reexamined these patients to see whether a longer follow-up time (9–21 years) would disclose an effect of head size on the revision rate.

Patients and Methods. We analyzed the CRR for 1,720 Scan Hip^® Classic I THA implanted in 1,550 patients, with 22 and 32mm heads, performed at Lund University Hospital during 1983 to 1995. Patients with the 3 most common diagnoses were included in the analysis, i.e. osteoarthritis, rheumatoid arthritis and femoral neck fracture. The end-point was defined as revision of any component for aseptic loosening before the end of 2004.

Results. Using the life table method analyzed cumulative revision rate for osteoarthritis, femoral neck fracture and rheumatoid arthritis patients and found that the 32 mm head had higher cumulative revision rate (p=0.04 (Wilcoxon)). Further analysis with Cox regression adjusting for age and sex showed that the 32 mm head had 2.8 times greater risk of revision (CI 1.7–4.6), p< 0.001. For each year increase in age the risk of revision was reduced 0.96 times (CI 0.95 – 0.97), p< 0.001, males had 1.5 times (CI 1.1 – 2.1), p=0.01 greater risk of revision than females.

Discussion. The reason that we did not find any significant difference in cumulative revision rates when followed up to 12 years, depending on head size in previous study (Kesteris et al. 1998) may be the time it takes for wear particles to induce the chain of events, eventually ending up in loosening. However extended follow-up up to 21 years after THA revealed significant differences in cumulative revision rates depending on head size.