Dislocation of hip arthroplasty in patients with femoral neck fractures

Treatment of displaced fractures of the femoral neck with a hemiarthroplasty (HA) or a total hip arthroplasty (THA) today constitutes standard procedures with a good and predictable outcome with regard to the need for revision surgery, hip function and the health-related quality of life (HRQoL). However, dislocation of the prosthesis remains a substantial clinical problem in this patient group and the dislocation rate is considerably higher than what can be expected following a THA in patients with osteoarthritis. There are several reported risk factors for prosthetic dislocations of which the influence of the surgical approach in patients with femoral neck fractures is still controversial. Moreover, little is known about the effect of the dislocation on the patients HRQoL. In order to prevent dislocation of the hip arthroplasty information on the direction of the dislocation is important for accurate implant positioning and for optimising the postoperative regimens. However, specific studies regarding this topic are missing for patients with fractures of the femoral neck.

In Study I, a prospective cohort study on 739 hips treated with HA due to a femoral neck fracture, factors influencing the risk of prosthetic dislocation were analysed. In a 2-10 year follow-up the posterolateral approach was associated with a significantly increased risk for dislocation of the prosthesis compared to the anterolateral approach. The patients age, gender, the indication for surgery, the surgeon s experience or the type of HA did not affect the dislocation rate.

In Study II, another prospective cohort study with a 1 11 year follow-up of 713 hips treated with THA due to a femoral neck fracture, factors influencing the risk of prosthetic dislocation were analysed. Compared to the anterolateral approach, the posterolateral approach was associated with a significantly increased risk for dislocation of the prosthesis. The patients age, gender, the indication for surgery, the surgeon s experience or the size of the femoral head did not affect the dislocation rate.

In Study III, a multicentre prospective cohort study on 319 patients treated with a primary HA or THA due to a femoral neck fracture, dislocation of the prosthesis had a significant negative effect on the HRQoL during the first year after the surgery. A recurrent dislocation of the arthroplasty seems to result in a persistent deterioration in the HRQoL, while patients with a single dislocation appear to experience only a temporary deterioration.

In Study IV a study on 74 patients with a primary dislocation of an HA or a THA within one year after surgery due to a femoral neck fracture, the surgical approach significantly influenced the direction of dislocation in patients treated with HA, while no such correlation was found after THA. This suggests that the surgical approach is only one of several factors affecting the direction of dislocation after THA. Our results imply that the position of the acetabular component might be one important factor.

The major conclusions of this thesis are that a prosthesis dislocation has a negative influence on the health-related quality of life and, in order to reduce the overall dislocation rate after both HA and THA in patients with femoral neck fractures, an anterolateral surgical approach should be used instead of a posterolateral one.

List of scientific papers

I. Enocson A, Tidermark J, Tornkvist H, Lapidus LJ (2008). Dislocation of hemiarthroplasty after femoral neck fracture: better outcome after the anterolateral approach in a prospective cohort study on 739 consecutive hips. Acta Orthop. 79(2): 211-7.
https://pubmed.ncbi.nlm.nih.gov/18484246

II. Enocson A, Hedbeck CJ, Tidermark J, Pettersson H, Ponzer S, Lapidus LJ (2009). Dislocation of total hip replacement in patients with fractures of the femoral neck. Acta Orthop. 80(2): 184-9.
https://pubmed.ncbi.nlm.nih.gov/19404800

III. Enocson A, Pettersson H, Ponzer S, Törnkvist H, Dalén N, Tidermark J (2009). Quality of life after dislocation of hip arthroplasty: a prospective cohort study on 319 patients with femoral neck fractures with a one-year follow-up. Qual Life Res. 18: 1177-1184.
https://pubmed.ncbi.nlm.nih.gov/19714486

IV. Enocson A, Lapidus G, Törnkvist H, Tidermark J, Lapidus LJ (2009). The influence of the surgical approach on the direction of hip arthroplasty dislocation. A study on patients with femoral neck fractures. [Submitted]