Biomechanical comparison of 3 possible fixation strategies to resist femoral neck shortening after fracture

Risk factors of neck re-shortening after reduction and fixation in patients with valgus-impacted femoral neck fractures

BACKGROUND

To analyze the risk factors of neck re-shortening after reduction and fixation in patients with valgus-impacted femoral neck fractures.

MATERIAL AND METHODS

Analysis of the clinical data of 46 cases with valgus-impacted femoral neck fractures treated by one surgeon in our hospital from January 2020 and December 2023. The collected clinical data includes: patient's gender, age, body mass index (BMI) and American Society of Anesthesiologists (ASA) classification, fracture side, Cause of injury, time from injury to surgery, Pauwels angle, valgus angle, posterior tilt, Hounsfield units of femoral neck from CT scan, surgical time, internal fixation method, blood loss in operation. SPSS 26.0 software (univariate analysis and Logistic regression analysis) was used to simulate a decision analysis and find risk factors.

RESULTS

17 of 46 patients who were included in the study developed neck re-shortening after surgery, with an incidence rate of 37.0%. Univariate analysis showed that there were significant differences in age(P = 0.004), valgus angle(P < 0.001), femoral neck CT HU value(P < 0.001). Logistic regression analysis showed that age > 53.5 years (OR 4.821, 95% CI: 1.248-18.624), initial valgus angle was > 17.6° (OR 2.417, 95% CI: 1.567-3.727), and femoral neck CT HU ≤ 92.5(OR 15.500, 95% CI: 4.057-59.222) were risk factors of postoperative neck re-shortening(P < 0.05).

CONCLUSION

Age, valgus angle, femoral neck CT HU value may be risk factors of neck re-shortening after surgery. For patients with high risk factors, in situ fixation may be a choice, but for young patient with good bone quantity, fixation after reduction is a better choice, which may be beneficial for reconstruction normal hip function.

Difference of Neck Shortening in Femoral Neck Fracture between Femoral Neck System and Multiple Cannulated Cancellous Screws: Single Center, Prospective Randomized Controlled Trial

Purpose

Fracture union after osteosynthesis of a fracture neck femur (FNF) occurs by compression of the fracture ends and potential neck shortening. Selection of an implant for fixation of a femoral fracture of the neck can be challenging when making management decisions. Femoral neck shortening after internal fixation of FNFs using a femoral neck system (FNS) or multiple cannulated cancellous screws (MCS) was compared.

Materials and Methods

This prospective interventional single-blinded randomized controlled trial was conducted at a university teaching hospital. Sixty patients undergoing internal fixation for management of sub-capital or trans-cervical FNFs were randomized and assigned, to one of the two groups-the test group (FNS group) and the control group (MCS group). Primary outcome was determined by measuring the difference in 1-year shortening of the femoral neck on radiographs between FNS and MCS. The secondary objective was to determine the correlation between neck shortening with patient reported outcome measures (PROMs) at the end of the final follow-up.

Results

At the final follow-up, shortening of the femoral neck was 3.77±1.87 mm in the FNS group, significantly lower compared with the MCS group, 6.53±1.59 mm.

Conclusion

Significantly less shortening of the femoral neck was observed in the FNS group compared with the MCS group. No statistically significant difference in PROMs was observed at 1-year follow-up. The findings of the study suggest that FNS can be regarded as a suitable alternative for internal fixation in young adults (<60 years) with trans-cervical and subcapital FNFs.

Femoral neck shortening as a sequela of internal fixation for femoral neck fractures and its effect on the coronal alignment of the limb: a pilot study

INTRODUCTION

Femoral neck shortening is a common phenomenon following osteosynthesis for femoral neck fractures, which was shown to have a negative effect on hip function. There is paucity of literature on the effect of shortening on the ipsilateral limb mechanical axis and knee coronal alignment. We hypothesized that postoperative femoral neck shortening can alter the limb's mechanical axis into valgus.

METHODS

Of 583 patients screened, 13 patients with severe neck shortening (< 10 mm) following femoral neck fracture fixation, were found eligible and agreed to participate. A full-length lower limb radiographs were obtained and radiographic parameters (offset, neck-shaft angle, HKA, mLPFA, mDLFA, mMPTFA, MAD, MAD-r) as well as functional scores were obtained.

RESULTS

Statistically significant differences in mechanical axis deviation ratio (MAD-r) were found between the ipsilateral and the contralateral extremities (0.41 ± 0.16 versus 0.55 ± 0.11, p = 0.03). A correlation between femoral neck length differences and MAD was not statistically significant although a tendency towards lateral deviation of the mechanical axis was noted (r = - 0.5, p = 0.077). A negative correlation was found between a greater difference in the femoral neck length and the SF12 score, both in the physical and the mental parts (r = - 0.69, p = 0.008; r = - 0.58, p = 0.035, respectively).

CONCLUSION

We found a more lateralized mechanical axis in limbs that demonstrated post-operative ipsilateral femoral neck severe shortening. These findings may provide a possible explanation and rationale for knee pain and perhaps for the development of knee osteoarthritis as a sequalae of femoral neck shortening. Further investigation and larger cohort, long-term studies are needed to further explore this hypothesis.

Comparison between headless cannulated screws and partially threaded screws in femoral neck fracture treatment: a retrospective cohort study

The choices of the treatments for femoral neck fractures (FNF) remain controversial. The purpose of this study is to evaluate the prognoses of the variable pitch fully threaded headless cannulated screws (HCS) in the fixation of femoral neck fractures and to compare them with those of partially threaded cannulated screws (PCS). Between 1st January 2012 and 31st December 2016, there were 89 patients with the main diagnose of FNF who accepted the treatment of closed reduction cannulated screw fixation in Peking University People’s Hospital. 34 cases of PCS and 23 cases of HCS met the criterion. The characteristics, prognoses and the imaging changes of all cases were described and the differences between the two groups were compared. Statistical analyses were performed using SPSS version 23.0 (SPSS Inc., USA). Mann–Whitney U test, Analysis of Variance and Chi-square test were used. Statistical significance was defined as P value (two sided) less than 0.05. There was no significant difference in the general characteristics, fracture classifications and reduction quality between the two groups. HCS group had a significant lower angle decrease rate (30.4% vs. 58.8%, P = 0.035), femoral neck shortening rate (26.1% vs. 52.9%, P = 0.044) and screw back-sliding rate (21.7% vs. 50.0%, P = 0.032), but a higher screw cut-out rate (21.7% vs. 0.0%, P = 0.008). In non-displacement fracture subgroup, HCS had significant higher Harris Score (92 vs. 90, P = 0.048). Compared with PCS, HCS had a lower screw back-sliding rate, femoral shortening rate, angle decrease rate and similar function score, but would result in more screw cut-outs in displaced FNF. As a conclusion, HCS should not be used in displaced FNF due to its higher screw cut-out rate, and its potential advantage in non-displaced FNF needs to be further proved. Further qualified investigations with a larger scale of patients and longer follow-up are needed in the future.

Analysis on risk factors for neck shortening after internal fixation for Pauwels II femoral neck fracture in young patients

Background

Femoral neck shortening can occur in young patients receiving internal fixation for Pauwels type II femoral neck fracture. The risk factors for neck shortening, which can affect hip function, are not clear. This study aimed to retrospectively identify risk factors for neck shortening after internal fixation with parallel partially threaded cannulated cancellous screws (FPTCS) for Pauwels type II femoral neck fracture in relatively young patients.

Methods

Clinical data from 122 cases with Pauwels type II femoral neck fracture from February 2014 to February 2019 were reviewed and analyzed, and causes of neck shortening were statistically analyzed. And the Chi-squared test or Fisher’s exact test was used to compare indicators. Multivariate analysis was conducted with non-conditional logistic regression analysis.

Results

Statistically significant differences were found in age, sex, BMD, BMI, fracture type, posterior medial cortex comminution, and reduction quality between patients with femoral neck shortening and those without femoral neck shortening. Logistic regression analysis showed that fracture type, posterior medial cortex comminution, and reduction quality were the main risk factors for neck shortening.

Conclusion

Fracture type, posterior medial cortex comminution, and reduction quality can be used as important reference indexes to predict the possibility of neck shortening after internal fixation with FPTCS for Pauwels type II femoral neck fracture in young patients. BMD and BMI may be also risk factors.

Comparison of early complications between the use of a cannulated screw locking plate and multiple cancellous screws in the treatment of displaced intracapsular hip fractures in young adults: a randomized controlled clinical trial

Background

The incidence of early postoperative complications of displaced intracapsular hip fractures is high. The purpose of this study was to compare the early postoperative complications and assess the incidence of femoral neck shortening on using a newly designed proximal femoral cannulated screw locking plate (CSLP) versus multiple cancellous screws (MCS) in the treatment of displaced intracapsular hip fractures in young adults.

Methods

Sixty-eight young adult patients with displaced intracapsular hip fractures were randomly assigned to either the CSLP group or the MCS group and treated routinely by internal fixation with either the CSLP or the MCS. Harris Hip Score, nonunion, failure of fixation, overall complications, and femoral neck shortening were recorded and compared.

Results

Two patients (5.88%) in the CSLP group and eight (23.53%) in the MCS group had postoperative nonunion (P < 0.05). There was one case (2.94%) of fixation failure in the CSLP group and three cases (8.82%) in the MCS group (P > 0.05). Three patients (8.82%) in the CSLP group and 11 (32.35%) in the MCS group had overall complications (P < 0.05). Mean femoral neck shortening was 5.10 mm in the vertical plane and 5.11 mm in the horizontal plane in the CSLP group and 11.14 mm in the vertical plane and 10.51 mm in the horizontal plane in the MCS group. Severe femoral neck shortening (≥ 10 mm) did not occur in either the vertical or the horizontal plane in any patient of the CSLP group but occurred in 10 patients (28.57%) in the vertical plane and in 8 (22.86%) patients in the horizontal plane in the MCS group.

Conclusions

Compared with MCS, the use of CSLP in the treatment of displaced intracapsular hip fractures in young adults can reduce the rates of postoperative nonunion and overall complications and minimize femoral neck shortening.

Trial registration

ChiCTR1800016032. Registered 8 May 2018. Retrospectively registered.

Use of fully threaded cannulated screws decreases femoral neck shortening after fixation of femoral neck fractures

BACKGROUND

Femoral neck fractures (FNF) are becoming increasingly common as population ages. Nondisplaced fractures are commonly treated by cancellous, parallel placed, partially threaded cannulated screws (PTS). This allows controlled fracture impaction. However, sliding implants can lead to femoral neck shortening (FNS) that has been shown to be correlated with reduced quality of life and impaired gait pattern. Recently, in our institution we have changed the fixation of FNF to fully threaded screws (FTS) with or without an additional partially threaded screw in order to minimize this phenomenon. The aim of this study was to compare the FNS in patients treated with FTS as compared with our historical controls treated with PTS.

PATIENTS AND METHODS

Between 2014 and 2016, 38 patients with FNF were treated with FTS. Out of the 38, 24 were available for radiographic follow-up. 41 patients treated previously with PTS were available as a control group. Radiographic analysis was performed to assess the FNF in three vectors: Horizontal (X), Vertical (Y) and overall (Z) according to the neck-shaft angle.

RESULTS

Time for admission to surgery was longer in the PTS group (p = 0.04). Patient demographics and major complication rates were similar in the two patient groups. Average FNS in the X axis was significantly smaller in the FTS group than in the PTS group (2.8 ± 3.6 vs 7.6 ± 4.2 mm, p < 0.01) as well as the Y axis (1.2 ± 2.6 vs 4.9 ± 4.2 mm, p < 0.01) and thus also decreased overall Z shortening (2.3 ± 3.5 vs 6.23 ± 4.5 mm, p < 0.01). There was a tendency towards a more valgus reduction in the PTS (137° vs 134°, p = 0.08). There was a significantly smaller number of FTS patients with moderate (5-10 mm) or severe (> 10 mm) FNS. Screw pull-out > 5 mm occurred in 17/41 patients in the PTS but none in the FTS group (p < 0.01).

CONCLUSION

This study proves that use of FTS improves the radiographic results following FNF fixation using cannulated screws.

Vertically Oriented Femoral Neck Fractures: A Biomechanical Comparison of 3 Fixation Constructs

OBJECTIVES

To compare the static and dynamic mechanical properties of a modified crossed cannulated screw (CS) configuration, the inverted triangle (IT) cannulated screw configuration, and a compression hip screw (CHS) with derotation screw in Pauwels type III femoral neck fractures.

METHODS

Thirty synthetic femora were divided into 3 groups, and vertical femoral neck osteotomies were made. Ten osteotomized femora were fixed with a CS configuration, 10 were fixed with 3 parallel screws in an IT configuration, and the remaining 10 osteotomized femora were fixed with a CHS construct. All groups were tested using a cyclic (up to 15,000 load cycles) axial loading protocol, and survivors were statically loaded to failure. Cycles to failure, load to failure, and stiffness were calculated. The Kaplan-Meier method was used to estimate survival functions and were compared among fixation methods. The relationship between construct structural properties (maximum load and stiffness) and treatment were assessed using general linear modeling.

RESULTS

All CHS fixation constructs survived the 15,000 cycle loading protocol. They endured longer (P = 0.034) than the CS fixation constructs (mean failure 13,332 cycles), but were not different from IT fixation constructs (mean failure 13,592 cycles). Maximum loads to failure for CS (3870 N) and IT (3756 N) fixation constructs were not different, but were less (P < 0.0001) than the maximum loads to failure for the CHS fixation constructs (5654 N). These findings parallel the results of the axial stiffness measurements: CS fixation constructs (663.01 N/mm) were not stiffer than IT fixation constructs (620.0 N/mm), but were less (P = 0.0005) than the axial stiffness of the CHS fixation constructs (1241.86 N/mm).

CONCLUSIONS

The biomechanical performance of the CHS fixation method was superior to both the CS fixation method and the IT fixation method using a synthetic femoral model and this test protocol. Biomechanical performance of the latter 2 groups was indistinguishable. We recommend the use of CHS with the derotational screw construct for Pauwels III femoral neck fractures whenever possible.

Incidence of and Factors Influencing Femoral Neck Shortening in Elderly Patients After Fracture Fixation with Multiple Cancellous Screws

BACKGROUND To study the incidence of and factors influencing "neck shortening" in elderly patients treated for femoral neck fractures using multiple cancellous screws. MATERIAL AND METHODS Of the 197 femoral neck fracture cases treated via closed reduction and cancellous screws fixation from January 2006 to February 2010, 110 were followed up. Patient age, gender, operative time, implantation method, reduction quality, fracture type, bone mineral density, loading time, length of hospital stay, and Harris hip score 12 months after operation were recorded. The patients were divided into two groups (shortening and non-shortening) based on their X-ray performance during follow-up. The healing rates and Harris hip scores of the two groups were compared, and the influencing factors of femoral neck shortening were analyzed. RESULTS Of the 110 cases followed up, 94.5% (104/110) were healed and neck shortening occurred in 41.8% (46/110) within 12.5 months (mean) after treatment. The Harris hip score of the shortening group was lower than that of the non-shortening group (78±17 vs. 86±23, p=0.048). The fracture healing rates of the two groups were not significantly different (p=0.068). The factors influencing neck shortening were significantly correlated with bone mineral density, patient age, gender, and type of fracture. CONCLUSIONS The incidence of neck shortening in elderly patients treated for femoral neck fracture using cancellous screws was high. Bone mineral density, patient age, gender, and type of fracture were the influencing factors of neck shortening.

Mechanical analysis of femoral neck fracture fixation in synthetic bone

OBJECTIVE:

To analyze statistically results obtained between biomechanical assays on fixation of femoral neck fracture type Pauwels III, on synthetic bone, using 7.5 mm non parallel cannulated screws and control group.

METHODS:

Ten synthetic bones from a national brand were used. Test group: fixation of 70^(o) tilt femoral neck osteotomy was performed using three 7.5 mm non parallel cannulated screws. We analyzed the resistance of this fixation with 5 mm of displacement, and rotational deviation (phase 1) and with 10 mm offset (phase 2). Control group: the models were tested in their integrity until the femoral neck fracture occurred.

RESULTS:

the values of the test group in phase 1, in sample 1-5 had a mean of 517N and SD = 96N. Rotational deviations showed a mean of 3.79° e SD = 2. 03°. In phase 2, mean was 649N and SD = 94N. The values of the maximum load in the control group were: 1544N, 1110N, 1359N, 1194N, 1437N; respectively. Statistical analysis between the groups showed a statistically significant lower value in the test group.

CONCLUSION:

the analysis of mechanical resistance between the groups has determined statistically significant value for the test group.

Level of Evidence III, Case-control Study.