The amount of blood loss in a primary cemented total knee arthroplasty (TKA) seems to vary in different reported studies. We carried out a prospective study to determine the factors affecting the peri-operative blood loss, hidden blood loss and blood transfusion requirements in a primary cemented total knee arthroplasty. The factors analysed were gender, diagnosis, tourniquet time and body mass index (BMI). We included a total of 66 consecutive patients who underwent primary TKA by a single surgeon (A.M). There was significantly more peri-operative blood loss in male patients than in females (p=0.001, Student's t test). The patients with rheumatoid arthritis did not show any statistical difference in peri-operative blood loss compared with that in patients with osteoarthritis. The tourniquet time and the surgical time showed a positive correlation with peri-operative blood loss. The BMI did not show any correlation with peri-operative blood loss. The incidence of blood transfusion was significantly higher in patients with rheumatoid knees as their pre-operative haemoglobin value was low. The amount of hidden blood loss in our series was 38%. We concluded that gender and tourniquet time plays a role in blood loss in TKA, but diagnosis (advanced osteoarthritis [OA] or rheumatoid arthritis (RA) does not. The blood transfusion depends on both pre-operative haemoglobin value and intra-operative blood loss. The post-operative transfusion trigger can be brought to 8.0 g% in a haemodynamically stable patient.

Background The weightbearing axis of the limb goes from the pelvis to the ground and includes the hindfoot. However, the influence of hindfoot alignment on mechanical axis and overall limb alignment after TKA is unclear. Questions/purposes We therefore addressed the following questions: (1) Does hindfoot alignment change after TKA for knee osteoarthritis? (2) What factors influence hindfoot alignment after TKA? (3) Does deviation of the mechanical axis from the center of the knee vary when the hindfoot is considered (ground mechanical axis) as compared with when it is not (conventional mechanical axis) after TKA? Patients and Methods We prospectively reviewed the radiographs of 125 patients who underwent 165 TKAs. We evaluated the preoperative and postoperative hipknee-ankle (HKA) angle, conventional mechanical axis deviation, ground mechanical axis (mechanical axis which included the hindfoot) deviation, and tibiocalcaneal angle. Results The preoperative hindfoot valgus alignment decreased after TKA. Preoperative hindfoot alignment was the only factor that influenced hindfoot alignment after TKA. The conventional mechanical axis showed less deviation from the center of the knee when compared with ground mechanical axis which showed lateral deviation after TKA. Despite limb alignment being restored to within 3°of neutral of the conventional mechanical axis after TKA, 29% of limbs had a postoperative ground mechanical axis deviation of 10 mm or greater. Conclusions Accurate restoration of limb alignment after TKA may be associated with persistent hindfoot valgus alignment with the ground mechanical axis passing lateral to the center of the knee. This could have implications on long-term survival of the implant owing to possible excessive loading laterally and needs further investigation.

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