Charnley low-friction arthroplasty in teenage patients: the ultimate challenge.

Increasing follow-up identifies the outcome in younger patients who have undergone total hip replacement (THR) and reveals the true potential for survival of the prosthesis. We identified 28 patients (39 THRs) who had undergone cemented Charnley low friction arthroplasty between 1969 and 2001. Their mean age at operation was 17.9 years (12 to 19) and the maximum follow-up was 34 years. Two patients (4 THRs) were lost to follow-up, 13 (16 THRs) were revised at a mean period of 19.1 years (8 to 34) and 13 (19 THRs) continue to attend regular follow-up at a mean of 12.6 years (2.3 to 29). In this surviving group one acetabular component was radiologically loose and all femoral components were secure. In all the patients the diameter of the femoral head was 22.225 mm with Charnley femoral components used in 29 hips and C-stem femoral components in ten. In young patients who require THR the acetabular bone stock is generally a limiting factor for the size of the component. Excellent long-term results can be obtained with a cemented polyethylene acetabular component and a femoral head of small diameter.

Cement mantle stress under retroversion torque at heel-strike.

The paper presents a theory of fixation failure and loosening in cemented total hip prostheses and proceeds to investigate this using an experimentally validated finite element model and two prosthesis types, namely the Charnley and the C-Stem. The study investigates the effects of retroversion torque occurring at heel-strike in combination with a loss of proximal cement/bone support and distal implant/cement support with a good distal cement/bone interface. A 3D finite element model was validated by comparison of femoral surface strains with those measured in an in vitro experimental simulation using an implanted Sawbone femur loaded in the heel-strike position and including a simplified representation of muscle forces. Results showed that the heel-strike position applies a high retroversion torque to the femoral stem that when combined with proximal debonding of the cement/bone interface and distal debonding of the implant/cement interface increases the strain transfer to the cement that may ultimately lead to the breakdown of the cement mantle leading on to osteolysis and loosening of the prostheses. Experimental fatigue testing of the implanted Charnley stem in a Sawbone femur produced cracks within the cement mantle that were located in positions of maximum stress supporting the finite element analysis results and theory of failure.

Periprosthetic femoral fractures treated with a modular distally cemented stem.

PURPOSE: To assess the treatment outcome of revision hip arthroplasty for Vancouver type B3 periprosthetic femoral fractures using a modular distally cemented stem. METHODS: 22 men and 14 women (37 hips) aged 66 to 79 (mean, 70) years underwent revision hip arthroplasty for Vancouver type B3 periprosthetic femoral fractures. The indication for surgery was periprosthetic fracture with stem loosening and loss of proximal bone stock. The patients were referred from other hospitals after previous surgeries had failed: 8 with 3 previous surgeries, 19 with 2, and 9 with one. Using a transtrochanteric approach, the existing prosthesis was removed and a modular proximal femoral replacement stem was inserted, bypassing the area of proximal femoral fracture and bone loss. The stem was distally cemented. Patients were immobilised within 48 hours of surgery. RESULTS: Patients were followed up for a mean of 14 (range, 8-18) years. The mean Harris hip score improved from 29 (range, 5-40) to 78 (range, 56-88); 24 patients attained excellent or good scores (>80), 10 attained fair, and 2 attained poor scores. The mean healing time was 7 (range, 6-14) months; there was no non-union. Improvement in proximal bone stock was noted on serial radiographs. None of the stems had cement fracture or migration, requiring revision. Two (5%) of the patients had dislocations. CONCLUSION: Vancouver type B3 periprosthetic femoral fractures can be successfully treated with a distally cemented modular proximal femoral replacement prosthesis.

Does salvage and tranexamic acid reduce the need for blood transfusion in revision hip surgery?

We carried out a retrospective case-control study in 80 patients who underwent a revision total hip replacement. Group A (40 patients) received tranexamic acid and intra-operative cell salvage. Group B (40 patients) was a matched control group and did not receive this management. Each group was divided into four subgroups: revision of both components, revision of both components with bone grafting, revision of the acetabular component with or without bone graft, and revision of the femoral component with or without bone graft. In group A the total number of units transfused was 52, compared with 139 in group B, representing a reduction in blood usage of 62.5%. The mean amount of blood transfused from cell salvage in each group was 858 ml (113 to 2100), 477 ml (0 to 2680), 228 ml (75 to 315) and 464 ml (120 to 1125), respectively. There was a significant difference in the amount of blood returned between the groups (p < 0.0001). In group A, 22 patients needed transfusion and in group B, 37 (p < 0.0001). A cost analysis calculation showed a total revenue saving of pounds sterling 70 000 and a potential saving throughout our facility of pounds sterling 318 288 per year. Our results show that a significant reduction in blood transfusion can be made using combined cell salvage and tranexamic acid in revision surgery of the hip.

Determination of the trabecular bone direction from digitised radiographs.

There is increasing evidence for monitoring the bone trabecular structure to explain, in part, the mechanical properties of bone. Despite the emergence of Computed Tomography, a radiograph is the standard format as it is cheap and used for assessing implant performance. Furthermore, various image-processing techniques developed to assess the trabecular structure from radiographs have regained interest owing to improvements in imaging equipment. This study assessed the precision and accuracy of the Co-occurrence and Run-length matrix, Spatial-frequency and Minkowski-fractal techniques to infer the trabecular direction from radiographs. Ten clinical images of femoral neck regions were obtained from digitised pelvic radiographs and subsequently analysed. These data were also used to generate synthetic images where the trabecular thickness, separation and directions were controlled in order to calculate the accuracy of the techniques. Additionally, a Laplacian noise was added in order to infer the precision of the techniques. All methods assessed the trabecular direction with a high degree of accuracy in these synthetic images including a single direction and no noise. However, only the Spatial-frequency and Co-occurrence matrix methods performed well on the clinical and heavily corrupted synthetic images. This demonstrated the possibility of inferring a linear trabecular direction in clinical conditions.

[Management of femoral neck fractures at the Liestal canton hospital]. / Die Versorgung von Schenkelhalsfrakturen am Kantonsspital Liestal.

The mode of treatment for femoral neck fractures at the Kantonsspital Liestal depends on age primarily. Patients over 70 years of age are treated with a unipolar endoprosthesis. Screws are being used in cases of medial femoral neck fractures, DHS in cases of lateral fractures. Total hip arthroplasty is only indicated in patients with evident osteoarthritis. 78 femoral neck fractures were seen in a 3-year-period. 50 endoprostheses were used in 49 patients. The mean age at time of surgery was 80 years. 70% of the patients have died at a mean survival time of 2 1/4 years. 13 out of a total of 14 surviving patients were investigated. The follow-up of 10 surviving patients reveals radiographically a mild protrusion in one case only. Clinically all 13 surviving patients are not compromised by the endoprosthesis after 5 years. We consider the implantation of a unipolar endoprosthesis in patients with femoral neck fractures at age over 70 years the treatment of choice. There is an acceptably low risk for protrusion as a late complication in regard to a reduced life expectancy.