Introduction: Dual-energy x-ray absorptiometry (DEXA) measurement is a valuable and accurate method of assessing periprosthetic bone loss around femoral stems.

Method: The cohort was 21 patients who underwent total hip arthroplasties with double-threaded, cone-shaped, modular, femoral stems and who already had a prosthetic contralateral hip. The contralateral hip arthroplasties were Autophur fully porous coated, Exeter cemented and Charnley cemented stems. DEXA measurements were performed in the anteroposterior femoral plane using a Lunar DPXL densitometer and analysed using the Lunar Orthopaedic Software Package, Version 1.7, designed for periprosthetic measurements. The initial measurement was performed between two and four weeks after the surgery as a baseline and then repeated after three, six, 12 and 24 months. The DEXA scan results were analysed comparing the bone density of the double-threaded cone-shaped modular femoral stem side with the contralateral side in a longitudinal study.

Results: The contralateral hip bone quality remained fairly constant in keeping with the maturity of the hip arthroplasties. The insertion of the double-threaded cone-shaped modular femoral stem caused the expected initial bone loss in Gruen zones one and seven due to proximal stress-shielding. Only minor bone loss occurred distally, reflecting good fixation and load transfer of the prosthesis.

Introduction: Pre-operative templates for total knee arthroplasty are routinely provided by the manufacturers. These often provide a representation of the required size of prosthesis and of the bone cuts. A common deficiency is that the actual cuts made by the jigs are angulated to allow for factors such as distal femoral angulation and back-slope on the tibia. The templates that were provided do not take into account this built in angulation and can lead to bone cuts which appear different to the cuts determined by the template. This factor is taken into account by the surgeon intra-operatively but leaves a situation where estimation is replacing pre-operative planning.

Method and Results: New universal templates have been produced as an adjunct those provided to take into account this angulation. A mathematical proof of the exact difference between various angle templates and right-angle templates yield significant variation in thickness of bone cuts. Using an average of 80mm width of the femur, a difference of 7.0mm in bone cuts is obtained with a five degree template compared with a right-angle template. A tibial anterior-posterior distance of 50mm yields a 2.62mm difference in bone cuts with a back slope of three degrees when compared with that predicted by a right-angle template.

Conclusions: The use of right-angle templates in total knee arthroplasty for sizing should be supplemented with angled templates to allow an accurate assessment of bone cuts to be made.