The purpose of this study was to evaluate the effect on movement under load of different techniques of reat-tachment of the humeral tuberosities following 4-part proximal humeral fracture. Biomechanical test sawbones were used. 4-part fracture was simulated and a cemented Neer3 prosthesis inserted. Three different techniques of reattachment of the tuberosities were used – 1)tuberosities attached to the shaft, and to each other through the lateral fins in the prosthesis with one cerclage suture through the anterior hole in the prosthesis, 2)as 1 without cerclage suture, and 3)tuberosities attached to the prosthesis and to the shaft. All methods used a number 5 ethibond suture. Both tuberosities and the shaft had multiple markers attached. Two Digital cameras formed an orthogonal photogrammetric system allowing all segments to be tracked in a 3-D axis system. Humeri were incrementally loaded in abduction using an Instron machine, to a minimum 1200N, and sequential photographs taken. Photographic data was analysed to give 3-D linear and angular motions of all segments with respect to the anatomically relevant humeral axis, allowing intertuberosity and tuberosity-shaft displacement to be measured. Techniques 1 and 2 were the most stable constructs with technique 3 allowing greater separation of fragments and angular movement. True intertuberosity separation at the midpoint of the tuberosities was significantly greater using technique 3 (p< 0.05). The cerclage suture used in technique 2 added no further stability to the fixation. In conclusion, our model suggests that the most effective and simplest technique of reattachment involves suturing the tuberosities to each other as well as to the shaft of the humerus. The cerclage suture appears to add little to the fixation in abduction, although the literature would suggest it may have a role in resisting rotatory movements.

Introduction and Aims: The purpose of this study was to evaluate the effect on movement under load of different techniques of reattachment of the humeral tuberosities following four-part proximal humeral fracture.

Method: Biomechanical test sawbones were used. Four-part fracture was simulated and a cemented Neer3 prosthesis inserted. Three different techniques of reattachment of the tuberosities were used: 1) tuberosities attached to the shaft, and to each other through the lateral fins in the prosthesis with one cerclage suture through the anterior hole in the prosthesis; 2) as one without cerclage suture; 3) tuberosities attached to the prosthesis and to the shaft. All methods used a number five ethibond suture. Both tuberosities and the shaft had multiple markers attached. Two digital cameras formed an orthogonal photogrammetric system, allowing all segments to be tracked in a 3-D axis system. Humeri were incrementally loaded in abduction using an Instron machine, to a minimum 1200N, and sequential photographs taken. Photographic data was analysed to give 3-D linear and angular motions of all segments with respect to the anatomically relevant humeral axis, allowing intertuberosity and tuberosity-shaft displacement to be measured.

Results: Techniques one and two were the most stable constructs with technique three, allowing greater separation of fragments and angular movement. True inter-tuberosity separation at the midpoint of the tuberosities was significantly greater using technique three (p< 0.05). The cerclage suture used in technique two added no further stability to the fixation.

Conclusion: Our model suggests that the most effective and simplest technique of reattachment involves suturing the tuberosities to each other, as well as to the shaft of the humerus. The cerclage suture appears to add little to the fixation in abduction, although the literature would suggest it may have a role in resisting rotatory movements.

The purpose of this study was to evaluate the effect on movement under load of different techniques of reattachment of the humeral tuberosities following 4-part proximal humeral fracture.

Biomechanical test sawbones were used. 4-part fracture was simulated and a cemented Neer3 prosthesis inserted. Three different techniques of reattachment of the tuberosities were used – 1)tuberosities attached to the shaft, and to each other through the lateral fins in the prosthesis with one cerclage suture through the anterior hole in the prosthesis, 2)as 1 without cerclage suture, and 3)tuberosities attached to the prosthesis and to the shaft. All methods used a number 5 ethibond suture. Both tuberosities and the shaft had multiple markers attached. Two Digital cameras formed an orthogonal photogrammetric system allowing all segments to be tracked in a 3-D axis system. Humeri were incrementally loaded in abduction using an Instron machine, to a minimum 1200N, and sequential photographs taken. Photographic data was analysed to give 3-D linear and angular motions of all segments with respect to the anatomically relevant humeral axis, allowing intertuberosity and tuberosity-shaft displacement to be measured.

Techniques 1 and 2 were the most stable constructs with technique 3 allowing greater separation of fragments and angular movement. True intertuberosity separation at the midpoint of the tuberosities was significantly greater using technique 3 (p< 0.05). The cerclage suture used in technique 2 added no further stability to the fixation.

In conclusion, our model suggests that the most effective and simplest technique of reattachment involves suturing the tuberosities to each other as well as to the shaft of the humerus. The cerclage suture appears to add little to the fixation in abduction, although the literature would suggest it may have a role in resisting rotatory movements.