Topographical analysis of the femoral components of ex vivo total knee replacements.

With greater numbers of primary knee replacements now performed in younger patients there is a demand for improved performance. Surface roughness of the femoral component has been proposed as a causative mechanism for premature prosthesis failure. Nineteen retrieved total knee replacements were analysed using a non-contacting profilometer to measure the femoral component surface roughness. The Hood technique was used to analyse the wear and surface damage of the matching ultra-high molecular weight polyethylene (UHMWPE) tibial components. All femoral components were shown to be up to 11× rougher after their time in vivo while 95 % showed a change in skewness, further indicating wear. This increase in roughness occurred relatively soon after implantation (within 1 year) and remained unchanged thereafter. Mostly, this roughness was more apparent on the lateral condyle than the medial. This increased femoral surface roughness likely led to damage of the UHMWPE tibial component and increased Hood scores.

Synovectomy during total knee arthroplasty: a pilot single-centre randomised controlled trial.

BACKGROUND: Total knee arthroplasty (TKA) is an effective procedure for late-stage osteoarthritis (OA) of the knee; however, up to 20% of patients remain dissatisfied. In some patients, this may be due to residual inflammation of the synovium. Our aim was to perform the first randomised controlled trial (RCT) of synovectomy during TKA for patients with macroscopically inflamed synovium. The main objectives were to assess recruitment rates, protocol adherence and outcomes relating to safety such as haemoglobin decrease and adverse events. We also collected data on patient-reported outcomes. METHODS: We performed a single-centre pilot RCT. Patients with a macroscopically inflamed synovium were randomised to receive synovectomy versus a control group that did not undergo synovectomy. We determined feasibility by measuring patient enrolment, completeness of follow-up, and safety via haemoglobin decrease and documentation of adverse events. RESULTS: We screened 360 patients with 260 deemed ineligible or could not be recruited. From the 100 eligible patients, 54 were enrolled and 40 progressed through to randomisation. All made it to the 12-month follow-up, indicating good protocol adherence. There were no major differences in adverse events or haemoglobin decrease demonstrating acceptable safety. Outcomes relating to satisfaction were reliably obtained. CONCLUSIONS: Patients with macroscopically inflamed synovium of the knee who are due to undergo TKA can be reliably recruited to a randomised trial and synovectomy can be performed safely. A large number is needed to be screened to identify eligible participants, and therefore, a multi-centre trial would be required to assess whether routine synovectomy would improve outcomes in these patients. TRIAL REGISTRATION: ISRCTN, ISRCTN31010214. Registered 6 October 2016-retrospectively registered.

A comparative surface topographical analysis of explanted total knee replacement prostheses: Oxidised zirconium vs cobalt chromium femoral components.

It has been proposed that an increased surface roughness of the femoral components of Total Knee Replacements (TKRs) may be a contributing factor to the accelerated wear of the polyethylene (PE) bearing and ultimately prosthesis failure. Oxidised Zirconium was introduced to the orthopaedic market in an attempt to reduce PE wear associated failures and increase the longevity of the prosthesis. In this study, non-contacting profilometry was used to measure the surface roughness of the femoral components of 6 retrieved TKRs (3 Oxidised Zirconium (OxZr) and 3 Cobalt Chromium alloy (CoCr) femoral components) and 2 as-manufactured femoral components (1 OxZr and 1 CoCr). A semi-quantitative method was used to analyse the damage on the retrieved PE components. The Sa values for the retrieved OxZr femoral components (Sa = 0.093 µm ± 0.014) and for the retrieved CoCr femoral components (Sa = 0.065 µm ± 0.005) were significantly greater (p < .05) than the roughness values for the as-manufactured femoral components (OxZr Sa = 0.061 µm ± 0.004 and CoCr Sa = 0.042 µm ± 0.003). No significant difference was seen between the surface roughness parameters of the retrieved OxZr and retrieved CoCr femoral components. There was no difference between the PE component damage scores for the retrieved OxZr TKRs compared to the retrieved CoCr TKRs. These results agree with other studies that both OxZr and CoCr femoral components roughen during time in vivo but the lack of difference between the surface roughness measurements of the two materials is in contrast to previous topographical reports. Further analysis of retrieved OxZr TKRs is recommended so that a fuller appreciation of their benefits and limitations be obtained.

Anterior knee symptoms after S-ROM hinge implantation.

PURPOSE: To evaluate the performance of a canal filling hinge device for complex knee arthroplasty. METHODS: Thirty-seven (4 primary hinge implantation and 33 revision cases) patients who had undergone arthroplasty with the S-ROM third generation hinge device for a combination of massive bone loss or ligamentous insufficiency were prospectively examined with a minimum of 5-year follow-up. Median age at surgery was 72 years (range: 43 to 87 years). Principal indications included aseptic loosening or massive osteolysis (24 cases), infection (8 cases) and periprosthetic fracture (4 cases). All patients exhibited either grade 2 (N = 12) or grade 3 (N = 25) AORI bone loss or a grade 3 medial ligament deficiency. RESULTS: One patient experienced implant failure (71 months), and one patient suffered late deep infection (36 months). Mean WOMAC score improved from 27 to 62. Four patients required patellar resurfacing for persistent pain. The 5-year survivorship was 86%. CONCLUSIONS: While the S-ROM device may offer satisfactory medium term outcome for complex end stage knee disease, we report a high rate of debilitating anterior knee symptoms.

Distal femoral resection at knee replacement - the effect of varying entry point and rotation on prosthesis position.

Malalignment may contribute to early prosthesis failure through point loading and premature polyethylene wear. Femoral resection requires for distal planar resection contingent upon correct rotation and coronal alignment. Using a standard model, we have examined the influence of differing femoral entry points and rotations upon final femoral component positioning. A graphical method and navigation system independently quantified the individual and combined impact of these variables, in 3 planes. Nine permutations were assessed with reference to neutral rotation and a central entry point. The graphical results were corroborated by the navigation analyses. We found that external rotation and a superolateral entry point introduced the greatest error in final component positioning. We have identified a safe envelope for femoral rod positioning and recommend that the rotational alignment is determined before distal bone resection.