The Result of In Situ Pinning for Valgus Impacted Femoral Neck Fractures of Patients over 70 Years Old

Abstract

Purpose

We aimed to evaluate the outcome of fixation with cannulated screws for valgus impacted femoral neck fractures in patients over 70 years of age.

Materials and Methods

We reviewed the outcome in 33 patients older than 70 years with valgus impacted femoral neck fractures who were treated with cannulated screws fixation from May 2007 to December 2010. These patients were followed for at least a year. We assessed the fixation failure rate, body mass index (BMI), bone mineral density (BMD) of proximal femur, distance between screw tip and joint, number of screws and time from fracture to operation.

Results

We identified six patients (18.2%) with failure. Two patients with subtrochanteric fractures through the screw insertion site and another patient with osteonecrosis were excluded from the fixation failure group. No difference was found in age, BMI, BMD of proximal femur, distance between screw tip and joint, number of screws and time from fracture to operation between failure and non-failure groups.

Conclusion

The failure rate of cannualted screw fixation for valgus impacted femoral neck fractures in the elderly patients was not low. Risk of failure should be considered in the management of these patients and accurate assessment for fracture type should be performed using computed tomogram and clinical evaluation.

INTRODUCTION

Femoral neck fractures with marked displacement in the elderly patients are primarily treated with arthroplasty as opposed to internal fixation, for its comparatively better improvement in pain, functional recovery of hip, reoperation, satisfaction of patients, quality of life and economical burdens^{1,2,3,4,5,6,7)}. In contrast, the valgus impacted Garden type I femoral neck fracture is often treated with internal fixation using screws^8,9). Recently, there is an increase in the rate of femoral neck fractures thanks to the increased life expectancy. Internal fixation has been widely used to treat valgus impacted femoral neck fractures. Although the prognosis of these fractures are favorable, the complication rate in elderly patients is not low¹⁰⁾ and frequency of reoperation is higher than arthroplasty^11,12). In this study, we investigated clinical outcomes of fixation with cannulated screws for valgus impacted femoral neck fractures in the elderly patients.

MATERIALS AND METHODS

We studied 33 patients with valgus impacted femoral neck fractures who were over 70 years of age and were treated with cannulated screw fixation from May 2007 to December 2010. These patients were followed at least for one year. Twelve male and 21 female patients were included with an average age of 77 years old (70-100 years). Valgus impacted fracture was diagnosed only with plain films. The fracture was not managed with reduction. A guide wire for cannulated screws was non-invasively inserted with the aid of image intensifier. Upon acquisition of an acceptable position for the guide wire, limited incision was made for introduction of screws and the internal fixation was completed with 3-4 cannulated screws. Six patients received three screws for internal fixation, half of whom failed to achieve internal fixation. Use of three screws was limited to patients under 75 years old and older patients had all received four screws. Patients were allowed to put body weight on the repaired fracture at the earliest feasible time, which was 3.5 days on average. Postoperative radiographic examinations were done at 2, 4, 8, and 12 weeks after surgery. Failure of internal fixation was defined by the fulfillment of one these conditions³⁾: dislocation (>1 cm) of the fracture site, penetration of cannulated screws into the joint via the femoral head, more than 2 cm backward displacement of the cannulated screws and change in the angle (>5%) between screws that necessitates total hip replacement. We identified the patients with internal fixation failure (defined as the internal fixation failure group) and compared their age, bone mineral density (BMD) of proximal femur, numbers of cannulated screws, distance between screw tip and joint, time from fracture to operation (i.e., internal fixation) and body mass index (BMI) with patients achieving successful bone union (defined as the bone union group). Independent t-test and logistic regression were used for statistical analysis and a P-values less than 0.05 were considered statistically significant (Fig. 1).

Fig. 1.

Eighty two year-old female patient with valgus impacted right femoral neck fracture. (A) Preoperative plain film shows valgus impacted neck fracture in the right femur. (B) In situ internal fixation with 4 cannulated screws. (C) Six weeks after the operation, fixation failure occurred.

RESULTS

Failure of internal fixation was identified in six patients (18.2%) out of the 33 studied patients. Two other patients had subtrochanteric fractures through the screw insertion site and another patient had post-traumatic femoral head necrosis, who were not included in the internal fixation failure group. The failure of internal fixation could be identified as early as three weeks after the surgery and in all cases within eight weeks (average: 4 weeks). Secondary falling accidents after surgery was the cause of subtrochanteric fractures through the screw insertion site in the two identified patients (Fig. 2).

Fig. 2.

Seventy two-year-old female patient with valgus impacted right femoral neck fracture. (A) Preoperative plain film shows valgus impacted neck fracture in the left femur. (B) In situ internal fixation with 4 cannulated screws. (C) Four weeks after the operation, subtrochanteric fracture through the pin insertion site occurred after slip down.

There was no difference between the age of the patients in the internal fixation failure group (average: 78 years, range: 70-92 years) and bone union group (78 years, 70-100 years). The numbers of cannulated screws were also not different (3.8 screws in both groups). No difference was seen in the distance between the screw tip and the joint (7.3 mm and 8.1 mm for internal fixation failure group and bone union group, respectively; P=0.43) and the elapsed time from fracture to operation (3.3 days and 3.9 days for internal fixation failure group and bone union group, respectively; P=0.357). Lastly, there was no statistically significant difference between the BMI and BMD of proximal femur of the two groups (BMI of 19.5 and 20.3 for internal fixation failure group and bone union group, respectively; Table 1).

Table 1.

Average Bone Mineral Densities of Proximal Femur

DISCUSSION

Valgus impacted femoral neck fractures are characterized by no additional displacement and a relatively stable impaction; hence, internal fixation with screws is considered as the primary treatment option^8,9). Due to the paucity of earlier studies on valgus impacted femoral neck fractures and their clinical outcomes, we reviewed reports on cases of femoral neck fractures without displacement. Gjertsen et al.¹²⁾ compared therapeutic results of arthroplasty, internal fixation for displaced femoral neck fractures and internal fixation of femoral neck fractures without displacement. The frequency of reoperation was found to be lowest in the arthroplasty, followed by the internal fixation of femoral neck fractures without displacement and displaced femoral neck fractures, showing that the clinical outcomes of internal fixation for femoral neck fractures without displacement are not favorable compared to those of arthroplasty. Similarly, Parker et al.¹³⁾ reported that arthroplasty for displaced femoral neck fractures had longer operation time and hospitalization days and higher complication rates, while re-hospitalization and reoperation rates were significantly lower compared to the internal fixation. Furthermore, Sikand et al.¹¹⁾ questioned internal fixation as the first treatment option of femoral neck fractures without displacement because no significant difference in prognosis was found between arthroplasty and internal fixation.

In a previous study on the failure rate of fixation in femoral neck fractures without displacement, Chiu and Lo¹⁴⁾ enrolled a total of 250 patients over 59 years of age and found 6%, 3.6%, and 7.2% of non-union, failure of fixation and femoral head necrosis, respectively. In another study on 375 patients, Conn and Parker¹⁵⁾ reported 7.7% of reoperation due to femoral head necrosis and non-union. Lee et al.¹⁶⁾ enrolled 182 patients with an average age of 67 year and found 10.4% of poor outcomes after 102 months of follow-up. Rogmark et al.¹⁷⁾ followed 224 patients for up to 32 months and reported 15% reoperation and 11% fixation failure. In the study conducted by Clement et al.¹⁰⁾ 162 patients older than 65 years were followed for at least a year and the fixation failure was shown to be 17.3%. Taken together, it seems reasonable to consider that based on previous studies, femoral neck fractures without dislplacement tend to result in poorer clinical outcomes in comparison to internal fixation. When it comes to the timing for weight bearing, Lee et al.¹⁶⁾ and Clement et al.¹⁰⁾ had the policy of allowance as soon as patients were able to do so, while the internal fixation failure was found between 4 weeks and 3 months postoperatively with an average of 5 weeks.

Our patients were older than those described in above investigations. Six patients in our study had failed fixation (18%) and two others had subtrochanteric fractures through the screw insertion site, which makes a 24% reoperation rate. It has been shown that age^14,15), degree of osteoporosis¹⁶⁾, posterior tilt on lateral radiographs^10,15) and walking ability of the patient before surgery¹⁵⁾ are significant prognostic factors of internal fixation failure, but we did not find a significant difference in age and BMD of proximal femur between the internal fixation failure and bone union groups. The degree of posterior tilt, however, was not investigated in our study. It warrants further analysis of preoperative computed tomography in valgus impacted femoral neck fractures to determine properties of fractures and prognosis of retro-displacement after internal fixation, which is also previously addressed by Melvin et al.¹⁸⁾.

Although age and osteoporosis are reportedly key factors of failure, no significant difference was found between our patient groups. BMI of patients was not a significant predictor in our study. Karaeminogullari et al.¹⁹⁾ suggested that favorable prognosis might be expected in surgical treatments within 12 hours from injury, yet we did not find a significant effect of time elapsed from injury to surgery. It has been shown that²⁰⁾ changes at cellular levels begin within 6 hours after injury but necrosis of bone cells progresses slowly over a period of 2 to 3 days; therefore, magnitude of external force and fracture conditions might be more influential in prognosis than time-to-operation.

Given the speculations that the degree of osteoporosis in the elderly patients might significantly affect fixation with screws, we compared the number of cannulated screws and the distance between screws and joint. Unexpectedly, no significant difference between the two groups was found. A number of previous studies have shown that internal fixation with sliding hip screw and plate results in excellent outcomes despite a number of disadvantages such as larger incision, longer hospitalization and blood loss^21,22,23). In a similar context, arthroplasty is argued as the primary therapeutic option given the frequency of reoperation, patients' satisfaction and treatment outcomes despite of risk of deteriorated general condition^{24,25,26,27,28)}. Our study was not designed to compare arthroplasty over internal fixation (with known advantageous such as minimal incision in patients) primarily for the general condition of the elderly patients. It is important to understand the fracture conditions and possible complications to address both merits and demerits of a therapeutic approach for patients and their caregivers.

Secondary falling accidents were the cause of subtrochanteric fractures through the screw insertion site in two patients. Both patients had four cannulated screws. In order to prevent subtrochanteric fractures through the screw insertion site, relevant principles for insertion of cannulated screws should be followed. More specifically, the three cannulated screws should be inserted in form of an inverted triangle in patients with displacement and the distance between screws should be kept at least 4 mm. The lowest screw should not be inserted below the lesser trochanter and the angle between screws are recommended to be kept less than 10°²⁰⁾.

Clinically, patients with typical valgus impacted femoral neck fractures may not have pain, could walk with limping and have limited joint movability²⁰⁾. In our study, patients were retrospectively analyzed with simple anterior-posterior projected images without including all presenting clinical symptoms at the time of injury. We could have included patients with serious displacement in sagittal plane, at least in part, which is one of limitations of our study.

CONCLUSION

The failure rate of internal fixation with cannualted screws for valgus impacted femoral neck fractures was not low in the elderly patients. Therefore, it is important to address any potential inherent risk of a respective therapeutic approach for patients and their caregivers. It is also important to accurately assess the fracture through computed tomogram and clinical evaluation.