Long waiting times and a growing demand on services for joint replacement surgery (JRS) prompted the Victorian Department of Human Services to fund a University of Melbourne/Melbourne Health partnership to develop and implement an osteoarthritis (OA) hip and knee service delivery and prioritisation system for those who may require JRS.

The service delivery model consists of a multidisciplinary team providing, comprehensive early assessment, evidence-based interventions, including support for patient self-management, continuity of care processes, and prioritisation for both surgical assessment and JRS. Prioritisation occurs via clinical assessment and the Hip and Knee Multi-Attribute Prioritisation Tool (MAPT), a patient, clinician, or proxy-administered 11-item questionnaire, resulting in a 100-point scale ranking of need for surgery. The Hip and Knee MAPT was developed using intensive consultation with surgeons, state-of-the-art clinimetrics and with input from patients, hospital management groups. Ninety-six surgeons contributed to the developing the final scoring system.

Over 4000 patients per year are entering the system across 14 hospitals in Victoria. Under the supervision of the orthopaedics unit, musculoskeletal coordinator (MSC), typically an experienced physiotherapist or nurse, as part of the multidisciplinary team, undertakes early comprehensive assessment, referral and prioritisation of patients with hip or knee OA referred to orthopaedic outpatient clinics. In addition, the MSC coordinates the monitoring and management of patients on the orthopaedic surgery waiting list. The processes enable patients who are most needy (via higher MAPT score and clinical assessment) to be fast-tracked to orthopaedic surgery; conversely those patients with lower scores receive prompt conservative management.

Time to first assessment and waiting times to see a surgeon for many patients have reduced from 12+ months to weeks. Patients seen by surgeons are more likely to be ready for surgery and have had more comprehensive non-operative optimisation. Patients placed on the surgical waiting list receive quarterly reassessments and evidence of deterioration is used as a basis for fast-tracking to surgery.

The OWL system is a whole of system(tm) approach informed by patients needs and surgeons needs. Clinicians have developed confidence in the clinical relevance of the MAPT scores. Uptake of the OWL model of care has been very high because it facilitates better care and better patient outcomes.

We have demonstrated that erythromycin (EM) inhibits wear debris-induced macrophage activation and osteo-clastogenesis (both in vitro and in vivo) through targeting NF-κB signalling. Our clinical trial further verified that oral EM can be efficiently delivered to periprosthetic tissue and improve local inflammation. The purpose of this study was to assess the efficacy of periprosthetic EM delivery in a rat osteolysis model.

The PA coated titanium (Ti) pin (Stryker) was loaded with EM (8 μl = 2.8 mg/pin). Drug release assay showed around 25% of loaded EM was remained in the PA layer 24 hours after loading. Rats were divided into three groups:

saline control (n=5);

Uncoated Ti pins were pressfit inserted into right tibia following the injection 200 μl of either UHMWPE particles (5 mg/ml) or saline (control). The revision surgeries were performed 6 weeks after the first surgery. The previous implanted pins were replaced with new Ti pins either with or without EM coating. Rats were then sacrificed one month after “revision surgery”, and the knee joint samples were collected for μCT and histology analysis.

μCT analysis showed that the value of bone volume (bv/tv) in the group treated with EM (0.26 ± 0.07) was significantly higher than the group untreated (0.14 ± 0.04), while there was no significant difference between EM treated group and the saline control group (0.15 ± 0.11). The parameters of cancellous bone structure all pointed a trend of better structure in EM treated group than other two groups. However, this difference did not reach statistical significance. Histology analysis (H& E staining) demonstrated that in the saline control the tibia retained a smooth endocortical surface with a prominent periprosthetic membrane. In the EM-treated group, endocortical erosion was reduced and the peri-prosthetic tissue appeared thinner than uncoated pins.

The overall cellularity of periprosthetic membranes from the EM-treated group was decreased compared to the untreated group. Analysis of membrane thickness revealed a significantly thinner membrane in EM-treated group compared with untreated group and saline control (p< 0.05).

The results of this study seem to indicate that an EM coated Ti pin provided a sufficient drug source to effectively treat wear debris-induced periprosthetic inflammation and osteolysis.

The purpose of this study was to evaluate trabecular bone response, at fifty-two week follow-up, to four different synthetic graft materials (CaSO4 and CaSO4 – HA/TCP composites) as compared to autograft in a canine defect model. The group with the highest HA/ TCP proportion had the greatest amount of residual graft material and total mineralized material. Increasing the proportion of HA/TCP reduces the rate of dissolution, and appears to have little effect on bone formation at long term follow-up. This study further suggests that a range of composites could be created to match the spectrum of resorption rates demanded by clinical applications.

The purpose of this study was to evaluate trabecular bone response to four synthetic graft materials (CaSO4 and CaSO4 – HA/TCP composites) as compared to autograft in a canine defect model, at long term follow-up.

Both 85% CaSO4 – 15% HA/TCP and 65% CaSO4 – 15% HA/TCP showed bone formation similar to autograft. The group with the highest proportion of HA/TCP lasted longer than the other formulations. The results suggest that increased HA/TCP proportions reduce the rates of dissolution, without compromising bone formation in the current model.

Results suggests that a range of composites could be created to match the spectrum of resorption rates demanded by clinical applications.

In this REB-approved RCT, bilateral humeral and femoral cylindrical defects were filled with one of four types of pellets with varying proportions of CaSO4 – HA/TCP, autograft bone, or left unfilled. After sacrifice at six, twelve, twenty-six or fifty-two weeks, defect sites were evaluated histologically for tissue and inflammatory response, area fractions of residual graft material, and bone ingrowth in the defects.

The area of the defect occupied by residual graft material in the group with the highest percentage of HA/TCP was greater than in other composite groups (p< 0.0001). This group contained the greatest amount of total mineralized material (graft material + bone) (p< 0.03. The extent of new bone formation increased from twelve to twenty-six weeks (p< 0.0001). Both 85% CaSO4 – 15% HA/TCP and 65% CaSO4 – 15% HA/TCP showed bone formation similar to autograft.

Funding: Research grant from Stryker Howmedica, Matwah, NJ.

The purpose of this study was to evaluate trabecular bone response to four different synthetic graft materials (CaSO₄ and CaSO₄ – HA/TCP composites) as compared to autograft in a canine defect model. The group with the highest HA/TCP proportion (and the lowest CaSO4 proportion) had the greatest amount of residual graft material and total mineralized material (p< 0.05). Increasing the proportion of HA/TCP reduces the rate of dissolution, and appears to have little effect on bone formation. This study suggests that a range of composites could be created to match the spectrum of resorption rates demanded by clinical applications.

Calcium sulfates and phosphates have become popular clinically for use as bone graft substitutes, however, their in-vivo performance has not been well characterized. The purpose of this study was to evaluate trabecular bone response to four synthetic graft materials (CaSO₄ and CaSO₄ – HA/TCP composites) as compared to autograft in a canine defect model.

Both 100% CaSO₄ and the 3 CaSO₄– HA/TCP formulations showed good bone formation. The group with the highest proportion of HA/TCP lasted longer than the other formulations, suggesting increased HA/TCP proportions reduce the rates of dissolution, without compromising bone formation in the current model.

Results suggests that a range of composites could be created to match the spectrum of resorption rates demanded by clinical applications.

In this REB-approved RCT, bilateral humeral and femoral cylindrical defects were filled with one of four types of pellets with varying proportions of CaSO₄ – HA/TCP, autograft bone, or left unfilled. After sacrifice at six or twelve weeks, defect sites were evaluated histologically for tissue and inflammatory response, area fractions of residual graft material, and bone ingrowth in the defects.

The area of the defect occupied by residual graft material in the group with the highest percentage of HA/TCP was greater than in other composite groups (p< 0.0006). At twelve weeks, this group contained more total mineralized material (graft material + bone) (p< 0.005). The extent of new bone formation was not different among the composite groups at either time-point, but all showed more bone formation than the empty defect.

Funding: This study was funded by a research grant from Stryker Howmedica, Matwah, NJ.

Introduction and Aims: Titanium foam implants simulate the trabecular structure of bone to maximise porous space for bone ingrowth. Plasma-sprayed hydroxyapatite coatings work well on non-porous substrates but do not coat the inner surfaces of open-porous substrates. Chemical deposition is an attractive alternative that produces consistent coats on porous surfaces.

Method: Titanium foam cylinders (5mm diameter by 25mm length) were implanted bilaterally in 40 rabbit femurs. Twenty implants were coated with 20 microns of hydroxyapatite (T-HA) by electrochemical deposition while 20 implants had no hydroxyapatite coat (T). Osseointegration was measured at six and 12 weeks by automated computerised histomorphometry of scanning electron microscopy images of sections taken through the implant at two levels: diaphyseal and metaphyseal. Bone ingrowth was quantified in the pores and was also measured up to 1mm beyond the surface of the implant to determine the pattern of bone growth.

Results: For the T-HA surface, bone ingrowth increased from 35.0 ±8.5 % at six weeks to 41.5 ± 7.4 % at 12 weeks (p < 0.05). For the T surface, bone growth was 14.1 ± 8.8% at six weeks and 11.4 ± 4.2 % at 12 weeks. At both time points mean bone ingrowth was significantly different between hydroxyapatite-coated and non-hydroxyapatite-coated implants, (p< 0.01). No significant differences were noted between the diaphyseal and metaphyseal bone response.

Conclusion: For the T-HA surface, bone ingrowth increased from 35.0 ±8.5 % at six weeks to 41.5 ± 7.4 % at 12 weeks (p < 0.05). For the T surface, bone growth was 14.1 ± 8.8% at six weeks and 11.4 ± 4.2 % at 12 weeks. At both time points mean bone ingrowth was significantly different between hydroxyapatite-coated and non-hydroxyapatite-coated implants, (p< 0.01). No significant differences were noted between the diaphyseal and metaphyseal bone response.

Introduction and Aims: Calcium sulfates and phosphates have become popular as bone graft substitutes, however, their in-vivo performance has not been well characterised. The purpose of this study was to evaluate trabecular bone response to four synthetic graft materials (CaSO4 and CaSO4 – HA/TCP composites) as compared to autograft in a canine defect model.

Method: In this REB-approved RCT, bilateral humeral and femoral cylindrical defects were filled with one of four types of pellets with varying proportions of CaSO4 – HA/TCP, autograft bone, or left unfilled. After sacrifice at six or 12 weeks, defect sites were evaluated histologically for tissue and inflammatory response, area fractions of residual graft material, and bone ingrowth in the defects.

Results: The area of the defect occupied by residual graft material in the group with the highest percentage of HA/TCP was greater than in other composite groups (p< 0.0006). At 12 weeks, this group contained more total mineralised material (graft material + bone) (p< 0.005). The extent of new bone formation was not different among the composite groups at either time-point, but all showed more bone formation than the empty defect. Both 100% CaSO4 and the 3 CaSO4 – HA/TCP formulations showed good bone formation.

Conclusion: The group with the highest proportion of HA/TCP lasted longest, suggesting increased HA/TCP proportions reduce the rates of dissolution, without compromising bone formation in this model. Results suggest that a range of composites could be created to match the spectrum of resorption rates demanded by clinical applications.