[Preoperative planning and reconstruction in primary total hip arthroplasty with and without modular necks].

STUDY AIM

Preoperative planning is regarded as an important requirement for successful implantation of a hip replacement. One of the crucial aspects of planning is the restoration of the normal anatomy of the hip as this increases the chances for good clinical function and reduces wear debris. Various systems for restoration of the hip are available including stem systems with different stem sizes and offsets and so-called modular stem systems which have the additional possibility of adjusting the neck length and angle. The aim of this study was to investigate to what extent a good postoperative outcome can be achieved using a modular and a non-modular stem system in comparison with preoperative planning. Furthermore, the study assessed the difference between preoperative planning carried out by a senior surgeon and by an assistant surgeon.

METHOD

Standard preoperative and postoperative digitalised radiographs with an anteroposterior view of the pelvis centred over the pubic symphysis were made. Preoperative planning aimed for exact reconstruction of offset and equal leg length. Preoperative planning and evaluation of the postoperative outcome were performed by digitalised image-analysing software. The symptom-free contralateral hip served as reference for anatomic reconstruction.

RESULTS

The postoperative results confirmed the preoperative planning. The preoperative planning was successfully implemented with both systems. Postoperatively, we observed a slightly reduced offset (Group 1: 3.6 mm, Group 2: 3.54 mm) and an increase in leg length of less than 5 mm in both groups. There was no significant difference between the preoperative planning carried out by the senior surgeon and the assistant surgeon.

CONCLUSION

Implementation of preoperative planning with both the modular and the non-modular system was very satisfactory. It was irrelevant if the planning was carried out by a senior surgeon or by an assistant surgeon in the first year of training.