| Objective: Femoral neck fracture often occurs in the elderly. Given that the elderly often have medical comorbidities, cannulated screws fixation is regarded as the most common treatment currently for the advantages such as easy to conduct, minimally invasive and less blood loss. But incidence of femoral neck shortening is high. In this study, the elderly patients with femoral neck fracture treated with cannulated screws in oblique and non oblique configurations were involved to analyze the incidence of femoral neck shortening and its risk factors, further, to explore the measurement method of femoral neck shortening and its effect on hip functional outcomes.Methods: Totally 162 elderly femoral neck fracture patients who were treated by cannulated screws fixation from June 2007 to October 2013 including 53 males and 109 females with an average age of 77.54 ± 7.53 years were analyzed retrospectively. According to Garden classification system, 52 cases were Garden type Ⅰand Ⅱ(undisplaced fractures), 110 cases were Garden type Ⅲ and Ⅳ(displaced fracture). The postoperative X-ray and Follow-up X-ray were compared to observe whether the trailing end of screw shaft expose to the outer cortex of the proximal femur. We chose the screw which has longest exposed trailing end to measure the length of the exposed screw shaft as the length of FNS. FNS indexing was according to the ratio of the length of exposed screw shaft and the thickness of screw head: 1 degree FNS:< 1 screw head, 2 degree FNS: 1 ~ 2 screw head, 3 degree FNS: >2 screw head. The incidence and risk factors of femoral neck fracture and the relationship between the length of femoral neck fracture and the femur length decrease and Harris scores of hip functional outcome were analyzed statistically.Results: All the 162 patients obtained follow-up of 10 to 36 months. Femoral neck shortening occurred in 56 cases, the total FNS incidence was 34.6%, including 7 cases for 1 degree, accounting for 4.3%; 18 cases for 2 degrees, accounting for 11.1%; 31 cases for 3 degrees, accounting for 19.1%. The femoral neck shortening rate in oblique fixation group were significantly lower than that in non-oblique fixation group(P<0.05). Low bone mineral density, displaced fracture, dissatisfied reduction, non oblique configuration were found to be significantly correlated with femoral neck shortening(P<0.05). There was significantly positive correlation between the length of Femoral neck shortening and the femur length decrease,and the correlation coefficient r was 0.940(P<0.05). The average Harris score was 77.12±12.95 points,ranging from 32 to 98. Harris score for the shortening group was significantly lower than that for the non-shortening group(t=9.233,P=0.000). There were also significant differences in Harris score related to the three degree of FNS(F=6.088,P=0.004). And there was a decreasing trend of Harris score with the increase in the severity of femoral neck shortening.Conclusion: The incidence of femoral neck shortening after treatment of cannulated screws fixation in the elderly femoral neck fracture patients is high. The bone mineral density, fracture type, reduction quality, screws configuration are risk factors of femoral neck shortening. To some extent, cannulated screws fixation in oblique configuration can reduce the occurrence of femoral neck shortening for the elderly compared with none oblique configuration. The methods of femoral neck shortening measuring and indexing in this study may be intuitive and easy for clinical application. Severe femoral neck shortening can influence the hip function. |
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