Prosthetic joint infection (PJI) is a complex disease that causes significant damage to the peri-implant tissue. Developing an animal model that is clinically relevant in depicting this disease process is an important step towards developing novel successful therapies. In this study, we have performed a thorough histologic analysis of peri-implant tissue harvested post Staphylococcus aureus (S. aureus) infection of a cemented 3D-printed titanium hip implant in rats.

Sprague-Dawley rats underwent left hip cemented 3D-printed titanium hemiarthroplasty via posterior approach under general anesthesia. Four surgeries were performed for the control group and another four for the infected group. The hip joint was inoculated with 5×10⁹ CFU/mL of S. aureus Xen36 prior to capsule closure. The animals were scarified 3 weeks after infection. The femur was harvested and underwent micro-CT and histologic analysis. Hematoxylin and eosin (H&E), as well as Masson's trichrome (MT) stains were performed. Immunohistochemistry (IHC) using rabbit antibody for S. aureus was also used to localize bacterial presence within femur and acetabulum tissue .

The histologic analysis revealed strong resemblance to tissue changes in the clinical setting of chronic PJI. IHC demonstrated the extent of bacterial spread within the peri-implant tissue away from the site of infection. The H&E and MT stains showed 5 main features in infected bone: 1) increased PMNs, 2) fibrovascular inflammation, 3) bone necrosis, and 4) increased osteoclasts 5) fibrosis of muscular tissue and cartilage. Micro CT data showed significantly more osteolysis present around the infected prosthesis compared to control (surgery with no infection).

This is the first clinically relevant PJI animal model with detailed histologic analysis that strongly resembles the clinical tissue pathology of chronic PJI. This model can provide a better understanding of how various PJI therapies can halt or reverse peri-implant tissue damage caused by infection.

Two knee arthroplasty implants with very different design principles were previously available in our region. Kinemax is PCL retaining with a fixed bearing and cemented components. LCS is PCL sacrificing, fully uncemented and incorporates a rotating bearing. The aim of this study was to compare the outcome of these two radically different knee designs.

Between 1994 and 2004, 300 consecutive patients were recruited and underwent a knee replacement performed by the senior author. Each patient was randomised via sealed envelopes to receive either LCS or Kinemax implants. All patients were followed up by an audit nurse and patient satisfaction and Knee Society Scores (KSSs) were recorded.

By 2012, 135 patients had complete data at a minimum of 10-years of follow-up. The remaining 165 had either died before 10-year review or had not reached the 10-year mark. No patient was lost to follow-up. There were 69 patients in the Kinemax group and 68 in the LCS group. The pre-operative demographics were not significantly different between the two groups.

At 10-years of follow-up, each implant design demonstrated significant improvements in the KSS (p=0.001 kinemax, p=0.001 LCS) over pre-operative values. No significant difference could be identified between the two designs at 10 years. There were only two revisions in the whole study population and both were for kinemax implants at less than five years post-operatively.

In conclusion, there was no statistically significant difference in outcome between the two radically different knee designs at ten years with both designs performing equally well.

Introduction

Recent studies have indicated that healthy and willing patients above 80 years have similar outcomes as younger patients following arthroplasty. We wished to investigate the outcomes in a cohort of patients above 80 years who underwent medial unicompartment knee replacement (UKA).

Introduction

Despite being from different manufacturers, Exeter stem and Ogee cup are commonly used together as cemented ‘cross breed’ combination in United Kingdom. The purpose of this study was to evaluate the long-term outcome of this combination.

Background: To our knowledge, a prospective randomised study comparing blood loss in cemented and uncemented total knee replacement has not been performed.

Method: From 1994 to 2004, 205 consecutive patients (78 men and 128 women) undergoing total knee replacement were randomised to one of the two groups, one using a cemented Kinnimax prosthesis and the other an uncemented LCS knee prosthesis. In 96.1% of the patients the procedures were performed for osteoarthritis whilst 3.9 % for RA. All patients had their haemoglobin and heamatocrit recorded preoperatively and postoperatively. The patient’s height, weight and body mass index were recorded preoperatively. The red blood cell (RBC) volume loss were measured by an indirect method which involved calculations using height, weight and pre op and post op heamatocrit.

Results: The mean red cell volume loss in uncemented knees (0.46lts) was significantly greater than the loss in cemented knees (0.39lts) p = 0.015. There was no statistically significant difference in relation to preoperative deformity, approach or ASA grade.

Conclusion: Our study concludes that the uncemented knees loose more blood compared to cemented knees. There have been smaller studies looking at this, but we believe this to be the largest and most comprehensive to date.

Background: To our knowledge, a prospective randomised study comparing blood loss between cemented and uncemented total knee replacement has not been performed.

Method: From 1994 to 2004, 205 consecutive patients (78 men and 128 women) undergoing total knee replacement was randomised to one of the two groups, cemented Kinnimax or uncemented LCS knees. 96.1 % of the procedures were performed for osteoarthritis whilst 3.9 % for RA. All patients had haemoglobin and heamatocrit recorded preoperatively and postoperatively. Each patients height, weight and body mass index were recorded preoperatively. The red blood cell (RBC) volume loss was measured using an indirect method which involved calculations using height, weight and pre op and post op haematocrit. The mean post operative RBC volume in cemented knees was 1.32lts whilst that of uncemented knees was 1.38lts; p value – 0.202.

Results: The mean red cell volume loss in cemented knees was 0.39lts and that of uncemented knees was 0.45lts, p value 0.015 which was statistically significant. There was no statistically significant difference in relation to preoperative deformity, approach or ASA grade. There was statistically significant increase in tourniquet time in cemented knees.

Conclusion: Our study concludes that the uncemented knees loose more blood compared to cemented knees. There have been smaller studies looking at this, but we believe this to be the largest and most comprehensive to date.