Closed reduction and internal fixation of femoral neck fractures has traditionally been associated with a high risk of treatment failure. In our material, the proportion of internal fixation failure was low compared to other studies, with reported incidences varying between 8 – 24 % and 35 – 62 % for undisplaced and displaced fractures, respectively (8) – (11). These inconsistencies may in part be explained by our study’s retrospective design. Only a minority of the patients were followed up after three months, and consequently, instances of treatment failure may not have been disclosed. Some patients were probably treated at other hospitals without their treatment being registered in our material. If the patients had been followed prospectively, the number of registered cases of failed internal fixations would probably have been higher. However, there is little reason to believe that the distribution of unrecorded cases was so skewed as to significantly affect the comparisons of treatment failure between the different patient groups.
We found no significant association between the risk of treatment failure and the quality of the fracture reduction in patients with undisplaced fractures. This was not unexpected, since the reduction scores were more uniform and the risk of internal fixation failure was considerably lower compared to displaced fractures. Moreover, a large proportion of undisplaced fractures are impacted and have a high degree of inherent stability. These impacted fractures have a good prognosis and should be stabilised without attempts to reduce the fracture. With regard to to displaced fractures, we found a higher risk of treatment failure in patients whose fractures were poorly reduced. These findings are consistent with earlier studies (8, 12, 13).
A number of attempts have been made to establish radiological criteria that have prognostic significance for the outcome in patients treated with closed reduction and internal fixation of femoral neck fractures (14) – (17). The emphasis has primarily been on pre-operative factors, and inter-observer reliability has varied between 0.20 – 0.58 (18) – (20). In our material we achieved a kappa value of 0.50 for the reduction criteria, which is acceptable by comparison.
We did not observe that placement of the hip pins significantly influenced the risk of failure of the internal fixation, and the criteria we chose might simply not affect treatment results. However, the number of patients may have been too small to reveal any slight differences, and our criteria did not take into account potentially important factors such as support in the posterior cortex of the femoral neck and perforation of the femoral head. Furthermore, the X-ray images were not standardised with respect to hip rotation. We also found that our criteria lacked precision, and the kappa value for inter-observer reliability was lower than the criteria for assessing fracture reduction. There was a tendency for patients awarded a lower score for placement of the hip pins to have a higher proportion of failed internal fixations, but these differences were not statistically significant. This is in contrast to some studies that have found that placement of the screws or pins is of significance for the prognosis (21, 22).
When we looked at delay of surgical treatment and its influence on the outcome, we found a significantly higher risk of non-union for patients treated more than 48 hours after injury. This is possibly the result of the blood supply to the femoral head being better maintained by prompt reduction and stabilisation. According to our material, closed reduction and internal fixation should therefore be performed within 48 hours, as a short time between injury and surgery has also been shown to reduce the risk of perioperative complications (23) – (26). However, it is important to emphasise that we did not take into consideration other factors that may be of significance, such as comorbidity, dementia and function level. These are factors that possibly have a skewed distribution between patients treated before and after 48 hours. Nor have we examined whether there is a linear or proportional relationship between the risk of failure of the internal fixation and the time elapsed between injury and surgery, a relationship for which earlier work has provided evidence (27).
Closed reduction and internal fixation entails a longer period of rehabilitation and a higher risk of re-operation than arthroplasty. This raises the question of whether poorer function and inadequate mobilisation of patients with failed internal fixation lead to higher mortality. However, we did not observe differences in mortality in patients who had poorer reduction results or in patients who were treated surgically more than 48 hours after injury. This may indicate that there are other factors of considerably greater importance. Lower mortality in patients with failure of internal fixation is probably due to the fact that some patients died before treatment failed, but it may also imply inadequate follow-up of the weakest patients. Moreover, the healthiest patients may expose their internal fixations to higher loads and strains. Even though higher risk of treatment failure did not result in increased mortality in our material, the patients’ quality of life depends largely on relief from pain and good functional results. This again stresses the need for close, thorough follow-up of a vulnerable patient group who, in our experience, make few demands on the health services.