Background

Tourniquets and tranexamic acid (TXA) are commonly used in total knee arthroplasty (TKA), but there is not consensus on how these interventions affect blood transfusion rates and total blood loss. Few studies examine the combined use of both interventions. We compared outcome measures and transfusion rates following TKA, with and without the use of tourniquet and TXA.

Introduction and Aims: Polyethylene wear and associated osteolysis is a major factor limiting arthroplasty longevity. The Duration process has the theoretical advantage of reducing wear. Our aim was to evaluate the wear rate of standard and Duration polyethylene using either metal or zirconia ceramic heads in the Anatomique Benoist Girard II hip system.

Method: Of 510 patients, 258 had appropriate radiographs for wear measurement. There were five bearing-couple groups. Group 1, 73 patients: metal (cobalt chrome) head on standard polyethylene; group 2, 73 patients: metal head on Duration polyethylene; group 3, 21 patients: (HIPed) zirconia ceramic head on standard polyethylene; group 4, 63 patients: HIPed zirconia head on Duration polyethylene; and group 5, 28 patients: non-HIPed zirconia head on standard polyethylene. All patients had 28mm heads. Sequential radiographs – at least one year after surgery and at least two years apart thereafter – were digitally scanned and images were analysed using computer software.

Results: Group 1: metal on standard polyethylene (n=73) – mean linear wear rate of 0.138 mm/yr (range 0.023–0.462 mm/yr). Group 2: metal on Duration polyethylene (n=73) – mean linear wear rate of 0.106 mm/yr (range 0.067–0.405 mm/yr). Group 3: HIPed zirconia heads on standard polyethylene (n=21) – mean linear wear rate of 0.124 mm/yr (range 0.037–0.225 mm/yr). Group 4: HIPed zirconia heads on Duration polyethylene (n=63) – mean linear wear rate of 0.120 mm/yr (range 0.001–0.427 mm/yr). Group 5: non-HIPed zirconia heads on standard polyethylene (n=28) – mean linear wear rate of 0.119 mm/yr (range 0.044–0.0330 mm/yr). Comparison of linear wear rates of standard (group 1) and Duration polyethylene (group 2) bearings with metal heads revealed a difference of statistical significance (p=0.0083), with lower annual wear rates with Duration polyethylene. Further comparison between these two groups revealed a male preponderance in the Duration group (p=0.000001). There was also a statistically significant difference in body weight between these groups, with the Duration group being heavier by a mean of 5.1 kilograms (p=0.05). There was no significant difference in wear rates between standard and Duration polyethylene bearings with HIPed zirconia heads. There was no statistically significant difference in age in our patient groups.

Conclusion: Duration polyethylene has lower linear wear rates when coupled with a cobalt chrome head. This is despite a male preponderance and higher body weight. Wear rates between standard and Duration polyethylene bearings coupled with zirconia heads were not statistically different.

Introduction and Aims: Periprosthetic fracture is a serious complication of increasing incidence in joint replacement. Our aim was to evaluate periprosthetic fracture patterns in our series of 1152 primary hip arthroplasties using a cementless proximally hydroxyapatie coated anatomic stem and to identify risk factors from parameters measured in our assessment of these patients.

Method: All patients with periprosthetic fracture following primary total hip arthroplasty using the Anatomique Benoist Girard I (ABG I) hip system were identified. Parameters studied included time of fracture after surgery, patient age and fracture classification. The pre-operative cortical index in the fracture group was measured and compared with a group matched for age, gender, diagnosis, and body mass index.

1152 ABG I primary hip arthroplasties were performed in 1037 patients from 1991–1997. Osteoarthritis was diagnosed in 93% of cases. The average age was 65 years; there were 536 females and 501 males. Mean follow-up was 79.6 months.

Results: Thirty-two patients, 16 male and 16 female, suffered a periprosthetic fracture. Thirty-one patients were treated for osteoarthritis and one for a femoral neck fracture. We retrieved complete records on 28 patients.

The average age of the fracture group was 73 years, compared to 65 years for the whole series (p< 0.0001). The incidence of periprosthetic fracture increased with age. The relative risk for patients over 70 years for peri-prosthetic fracture is 4.7 greater (95% CI 2.14–10.21).

Distinct fractures patterns were related to time from initial surgery. Four fractures occurred within three months of surgery; these early fractures exhibited a particular pattern. The remaining 24 occurred between four and 114 months after surgery. These late fractures exhibited a different but consistent fracture pattern. Two fractures in the early group were identified immediately post-operatively. All others presented after minor low energy trauma.

The mean cortical index in the fracture group was 47% and in the matched group 51%. If the pre-operative cortical index is below 50%, the risk of periprosthetic fracture is 4.75 greater (odds ratio 4.75 CI 1.5–15.00).

All fractures were adequately classified and managed by guidelines in the Vancouver classification.

Conclusion: This study identified distinct fracture patterns related to time from surgery. Cortical index and age have predictive value in pre-operative assessment of fracture risk: cortical index below 50 and age above 70 are risk factors for periprosthetic fracture and should be considered with other parameters to minimise risk of this complication.

In 13 unloaded living knees we confirmed the findings previously obtained in the unloaded cadaver knee during flexion and external rotation/internal rotation using MRI. In seven loaded living knees with the subjects squatting, the relative tibiofemoral movements were similar to those in the unloaded knee except that the medial femoral condyle tended to move about 4 mm forwards with flexion. Four of the seven loaded knees were studied during flexion in external and internal rotation. As predicted, flexion (squatting) with the tibia in external rotation suppressed the internal rotation of the tibia which had been observed during unloaded flexion.

We present the first study in vivo of meniscal movement in normal knees under load. Using an open MR scanner, allowing imaging in physiological positions in near to real-time, 16 young footballers were scanned moving from full extension to 90° flexion in the sagittal and coronal planes. Excursion of the meniscal horns, radial displacement and meniscal height were measured.

On weight-bearing, the anterior horn of the medial meniscus moves through a mean of 7.1 mm and the posterior horn through 3.9 mm, with 3.6 mm of mediolateral radial displacement. The height of the anterior horn increases by 2.6 mm and that of the posterior horn by 2.0 mm. The anterior horn of the lateral meniscus moves 9.5 mm and the posterior horn 5.6 mm, with 3.7 mm of radial displacement. The height of the anterior horn increases by 4.0 mm, and that of the posterior horn by 2.4 mm. In non-weight-bearing, the anterior horn of the medial meniscus moves 5.4 mm and the posterior horn 3.8 mm, with 3.3 mm of radial displacement. The anterior horn of the lateral meniscus moves 6.3 mm, and the posterior horn 4.0 mm, with 3.4 mm of radial displacement. The most significant differences between weight-bearing and non-weight-bearing were the movement and vertical height of the anterior horn of the lateral meniscus.