Introduction: Shoulder hemiarthroplasty is an established treatment for complex proximal humeral fractures but the functional results of these hemiarthroplasties in proximal humeral fractures are often poor and unpredictable. The capacity of restoring proximal humeral anatomy in such these complex fractures is of capital importance to obtain proper placement and secure fixation of the tuberosities to the prosthesis. The purpose of this study was to determine the value of the upper edge of the pectoralis major insertion as a landmark to determine proper height and version of hemiarthroplasties implanted for proximal humeral fractures.

Material and Methods: The upper edge of the pectoralis major insertion was referenced with a metallic device in 20 cadaveric humerus. A Computed Tomography study was performed in all the specimens. Total humeral length was recorded in all the specimens. The distance between the upper pectoralis major insertion and the tangent to the humeral head was also recorded. The anatomical neck of the humeral head was determined in the axial plane of the CT scan and a perpendicular line was drawn to represent the posterior fin of the prosthesis. To that image, the CT scan slice showing the upper insertion of the pectoralis major was superimposed and the distance of the metallic reference to the posterior fin of the prosthesis was recorded as it was the angle formed by the line connecting the upper pectoralis major insertion with the center of the anatomical neck diameter and with the posterior fin of the prosthesis.

Qualitative variables are presented in absolute and percentage values. Quantitative variables are presented with mean values and standard deviation.

Results: Mean total humeral length was 32,13 cm. The mean distance from the upper pectoralis major insertion to the tangent to the humeral head was of 5,64. The mean distance from the upper pectoralis major insertion to the tangent to the humeral head represents the 17,55% of the total humeral length. The mean distance of the upper pectoralis major insertion to the posterior fin of the prosthesis was of 1,06 cm. The angle between the upper pectoralis major insertion and the posterior fin of the prosthesis was of 24,65º.

Conclusions: Mean distance from the upper part of the pectoralis major insertion to the top of the humeral head of 5, 6 cm with a 95% confidence interval.

Placement of the prosthesis in the proper retroversion can be achieved by placing the posterior fin 1,06 cm posterior to the upper insertion of the pectoralis major or by placing the posterior fin at 24,65º with respect to the upper insertion line.

Upper insertion of the pectoralis major constitutes a reliable reference to reproduce anatomy in hemiarthroplasties for proximal humeral fractures.

Purpose of study was to determine the value of the upper edge of the pectoralis major (UPM) insertion as landmark to determine proper height and version of hemiarthroplasties implanted for proximal humeral fractures.

UPM insertion was referenced with metallic device in 20 cadaveric humerus. Computed Tomography study was performed in all specimens. Total humeral length and distance between the UPM insertion and the tangent to humeral head was recorded. CT scan slice showing UPM superimposition in humeral head was drawn to determine prosthesis retroversion. Qualitative variables are presented in absolute and percentage values. Quantitative variables are presented with mean values and standard deviation.

Mean total humeral length 32,13 cm. Mean distance from the UPM to the tangent to the humeral head 5,64. Mean distance from UPM insertion to the tangent to the humeral head represents the 17,55 % of total humeral length. Mean distance of UPM insertion to the posterior fin of the prosthesis of 1,06 cm. Angle between UPM insertion and posterior fin of the prosthesis 24,65°.

Mean distance from the UPM insertion to the top of the humeral head of 5, 6 cm with a 95% confidence interval. Placement of the prosthesis in the proper retroversion can be achieved by placing the posterior fin 1,06 cm posterior to the UPM or by placing the posterior fin at 24,65° with respect to the upper insertion line. UPM constitutes a reliable reference to reproduce anatomy in hemiarthroplasties for proximal humeral fractures.

Introduction: The correct position of the knee arthroplasty components is associated with a better result of the prosthesis.

In the tibial component, both intramedullar and extramedullar instrumentations have been used for its fiability, but in the femoral component intramedullar guides are more precise than extramedullar ones.

The use of the intramedullar guide for the femoral component is not always possible, because a significant deformity of the femoral shaft or when a intramedullar device has been implanted in the femur.

We have studied the alineation of the components of computer assisted total knee arthroplasties in a group of patients with femoral deformities or implants.

Material and methods: We have used the surgical navigator Stryker-Howmedica for the implantation of a knee arthroplasty in a group of 10 patients in which a endomedullar femoral guide can not be used for femoral shaft severe deformities (6 cases): Paget disease (1 case), previous femoral osteomyelitis (2 cases) or previous femoral fractures (3 cases), or a shaft device was in the femoral shaft (4 cases): long hip femoral stem (3 cases) or a femoral nail (1 case) .

We have studied the alineation of femoral and tibial components with a whole-leg X-ray and Computer Tomography.

Results: All the femoral and tibial components have been implanted in a good position (90 +/– 2 degrees in the A-P plane and a femorotibial axe 180 +/– 3 degrees. The alineation in the sagital and axial planes have been inside the desired values in all cases also.

Discussion: It is generally accepted than intramedullary guides for the femoral component is the gold standard in arthroplasty of the knee.

In the last years, the development of computer assisted systems has allowed to obtain femoral and tibial cuts referred to the mechanical axes of the bone, without using mechanical guides for the alineation.

In some studies these navigation systems are better than mechanical instruments in terms of alineation of the components in cases without great deformities.

In this study, with some cases with severe femoral shaft deformities or with some intramedullary devices that does not allow the use of intramedullary femoral guides, we think that the indication to use a surgical navigator should be nearly absolute.