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Orthopaedic Proceedings
Vol. 88-B, Issue SUPP_III | Pages 391 - 391
1 Oct 2006
Lakdawala A Todo S Scott G
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Introduction: Aseptic loosening due to polyethylene wear is a mode of failure in knee arthroplasty. No study has evaluated the roughness of the articulating surface of retrieved femoral components & its role in creation of polyethylene wear. AIM The aim of our study was to investigate the in-vivo changes in the surface roughness of retrieved femoral components. Our hypothesis was that the surface finish of the femoral components, articulating with the polyethylene inserts deteriorated in accordance with the duration of implantation.

Materials and Methods: 22 femoral components, all Freeman-Samuelson prostheses, were retrieved from 18 male and 4 female patients at revision knee surgery. The mean age at revision was 68.4 years and the mean period of implantation was 55.64 months. 18 implants were retrieved for aseptic loosening and 4 for infection. Firstly, the surfaces of femoral components & polyethylene inserts were visually inspected for modes of damage in the articulating areas. The surface finish measurements were performed with a contact stylus profilometer with a 2-mm-radius stylus tip and a cut-off length of 0.8mm. The surface roughness was characterised by measuring Ra(mm), which is the arithmetic mean of the absolute values of the measured height deviations taken within the evaluation area and measured from the main line or surface. Both condyles were examined as separate areas articulating with the tibial components from 0° to 60° and 61° to 120° of knee flexion. Surface roughness (Ra) measurements from the sides of the patellar groove at the top of the femoral flange, which do not articulate either with the patella or tibia, were taken as control. The Ewald method of assessing the orientation of the components was applied to derive the coronal angle of the knee (CAK).

Results: The mean CAK was 7.2° ± 1°. Dull edged parallel scratching and burnishing were the main modes of damage identified on the surface in the articulating areas. Visual analysis of polyethylene inserts failed to identify embedded Polymethyl-methacrylate debris or any other damage, which matched the location of the altered surface finish of the femoral components. The mean Ra values recorded were: Control: Mean-0.0230 mm, SD- 0.00821. Medial Femoral condyle (0° – 60°) – 0.0225 mm, SD – 0.00797, P=0.832 Medial Femoral Condyle (61° – 120°) – 0.0244 mm, SD – 0.00532, P= 0.189 Lateral Femoral condyle (0° – 60°) – 0.0263 mm, SD – 0.00694, P= 0.078 Lateral Femoral Condyle (61° – 120°) – 0.0253 mm, SD – 0.00758, P= 0.286 No statistically significant difference was seen in the mean roughness (Ra) of the articulating areas when compared to that of the control (P< 0.05).

Conclusion: This study showed that the surface finish of these implants did not deteriorate during the period of implantation. On this basis we believe that a well-aligned and well-fixed femoral component, without any accumulated wear debris beneath it, does not require mandatory exchange if the revision is carried out for isolated failure of the tibial prosthesis even if the femoral component has fine scratching or burnishing on its surface.


Orthopaedic Proceedings
Vol. 88-B, Issue SUPP_I | Pages 96 - 96
1 Mar 2006
Lakdawala A Todo S Scott G
Full Access

Aim: The aim of our study was to investigate the in-vivo changes in the surface roughness of retrieved femoral components.

Our hypothesis was that the surface finish of the femoral components deteriorated in accordance with the duration of implantation

Materials and method: 22 femoral components (all Freeman-Samuelson prostheses) were retrieved from 18 male and 4 female patients at revision knee surgery. The mean age at revision was 68.4 years and the mean period of implantation was 55.64 months. 18 implants were retrieved for aseptic loosening and 4 for infection. The surfaces of femoral components & polyethylene inserts were inspected for modes of damage in the articulating areas. The surface finish measurements were performed with a stylus profilometer. The surface roughness was characterised by measuring Ra (micron-meter), which is the mean of the measured height deviations within the evaluation area. The articulating surface on both condyles was examined seperately. Ra measurements from the sides of the patellar groove at the top of the femoral flange, which do not articulate either with the patella or tibia, were taken as control. The Ewald method of assessing the orientation of the components was applied to derive the coronal angle of the knee (CAK)

Results: The mean CAK was 7.2° ± 1°. Parallel scratching and burnishing were the main modes of damage on the surface in the articulating areas. Inspection of polyethylene inserts failed to find embedded Polymethyl-methacrylate debris or any other damage, which matched the location of the altered surface finish of the femoral components.

The mean Ra values were:

Control: Mean-0.0230 mm, SD- 0.00821.

Medial Femoral condyle (0 – 60) = 0.0225 mm, SD – 0.00797

Medial Femoral Condyle (61 – 120) = 0.0244 mm, SD – 0.00532

Lateral Femoral condyle (0 – 60) = 0.0263 mm, SD – 0.00694

Lateral Femoral Condyle (61 – 120) = 0.0253 mm, SD – 0.00758

No statistically significant difference was seen in the mean-Ra of the femoral condyles compared to that of the control (P less than 0.05).

Conclusion: The surface finish of these implants did not deteriorate during the period of implantation. On this basis we believe that a well-aligned and well-fixed femoral component, without any accumulated wear debris beneath it, does not require mandatory exchange if the revision is carried out for isolated failure of the tibial prosthesis.


The Journal of Bone & Joint Surgery British Volume
Vol. 87-B, Issue 6 | Pages 796 - 799
1 Jun 2005
Lakdawala A Todo S Scott G

We investigated the changes in surface roughness of retrieved femoral components in 18 men and four women at revision knee surgery. The mean age at revision was 68.4 years and the mean period of implantation was for 55.6 months. Eighteen implants were retrieved for aseptic loosening and four for infection. The surface changes in the articulating areas were inspected visually and the roughness (Ra) analysed with a profilometer. Parallel scratching and burnishing were the two main forms of damage. The mean Ra measurements in the articulating areas showed no statistically significant difference when compared with those in a control area on either side of the patellar groove at the apex of the femoral flange. This suggests that it is not essential to revise a well-fixed and correctly aligned femoral component where the polished surface has become burnished or bears fine parallel scratches, if the revision is conducted solely for failure of the tibial component.


The Journal of Bone & Joint Surgery British Volume
Vol. 85-B, Issue 3 | Pages 366 - 370
1 Apr 2003
Skinner JA Kroon PO Todo S Scott G

We describe the survival at ten years of 100 femoral components of the Freeman hip prosthesis. It is proximally hydroxyapatite (HA)-coated and was fixed without cement. Radiological assessment identified radiolucent lines (RLLs) and lytic lesions and was used to measure migration.

The criterion of failure was revision or impending revision for aseptic femoral loosening. No femoral components were revised or are awaiting revision for aseptic loosening, giving 100% survival at ten years (95% confidence interval, 95.7 to 100), although 59 were at risk at ten years. Two components were revised for fracture of a ceramic head with damage to the trunnion. Although well fixed in each, for survival analysis we evaluated the hip as if the patient had died.

Twelve acetabular components were revised and at each operation the femoral component was found to be well fixed, was not disturbed and remained in the survival analysis. Three patients were lost to follow-up, and 12 died with well-functioning prostheses. Radiologically, all except one of the components appeared to be well fixed with no RLLs and no lytic lesions at the latest follow-up. The mean vertical migration was 0.4 mm at one year, 0.8 mm at two years and 1.4 mm at ten years. One component had migrated 7.6 mm at ten years (2.1 mm in year 1) and developed RLLs in Gruen zones I and II. The symptoms, however, were only minor and revision was not indicated.

Our study has shown that proximal HA coating gives effective fixation for a femoral component.


The Journal of Bone & Joint Surgery British Volume
Vol. 85-B, Issue 1 | Pages 45 - 51
1 Jan 2003
Skinner JA Todo S Taylor M Wang JS Pinskerova V Scott G

We have compared the survival and radiological outcome at ten years after total hip replacement using two techniques for preparing the femoral canal. The same prosthesis was used throughout and all operations were performed by the same surgical team. In technique 1 the canal was over-reamed by 2 mm and in technique 2 it was reamed to the same size as the prosthesis. Technique 1 was performed on 92 patients and technique 2 on 97 patients.

The survival at ten years was 97.2% (90.6 to 99.2) for technique 1 and 98.8% (92.9 to 99.8) for technique 2. Vertical migration was greater in technique 1 (1.8 mm versus 1.0 mm at five years; p = 0.36). There were significantly more lytic lesions and radiolucent lines at five years (p = 0.0061) with technique 1. We conclude that technique 2 is not worse and may produce better long- term results than current teaching suggests.


The Journal of Bone & Joint Surgery British Volume
Vol. 82-B, Issue 8 | Pages 1199 - 1200
1 Nov 2000
Nakagawa S Kadoya Y Todo S Kobayashi A Sakamoto H Freeman MAR Yamano Y

We studied active flexion from 90° to 133° and passive flexion to 162° using MRI in 20 unloaded knees in Japanese subjects. Flexion over this arc is accompanied by backward movement of the medial femoral condyle of 4.0 mm and by backward movement laterally of 15 mm, i.e., by internal rotation of the tibia. At 162° the lateral femoral condyle lies posterior to the tibia.