Risk factors for cut-out in intertrochanteric fractures treated with proximal femoral nail of double proximal screw design

Abstract

Background

Intertrochanteric femoral fractures (IFF) are often seen in the elderly after a simple fall because of osteoporosis, and treatment is generally provided with proximal femoral nail (PFN). The complication of cut-out, which can develop as a result of PFN treatment of IFF, is a significant cause of morbidity. The aim of this study was to examine the risk factors for cut-out in cases treated with double proximal screw design nail (DPSDN).

Methods

A retrospective examination was made of patients aged> 70 years, who were operated on for IFF using DPSDN between January 2018 and December 2020. A record was made of the potential risk factors of age, gender, osteoporosis level (Singh Osteoporosis Index), fracture classification (AO/OTA classification), reduction quality, tip-apex distance(calTAD), and proximal screw placement values. Using logistic regression analysis, it was attempted to determine predictive factors for cut-out complication in cases operated on with DPSDN.

Results

With 219 cases included in the study, two groups were formed as cut-out and non-cut-out. Reduction quality, calTAD, and proximal screw placement were seen to be risk factors for cut-out. According to the univariate logistic regression analysis, the cut-out risk was 57.917-fold greater in those with “poor” reduction quality compared to those with “good” reduction quality, the risk was 17-fold greater in those with “superior”screw placement compared to “central” placement (p < 0.001), and 9.24-fold greater in those with “anterior” placement compared to “central” placement (p < 0.001). The cutoff value for calTAD for the diagnosis of cut-out was found to be > 25.5 mm (p = 0.026).

Conclusion

The results of this study demonstrated that the most important risk factors in the use of DPSDN are reduction quality, calTAD and proximal screw placement,. It was also concluded that just as in implants designed with a single screw, there is an increased risk when calTAD is > 25 mm.

1. Introduction

The rate of hip fractures seen in the geriatric population is increasing every year. The vast majority of hip fractures are intertrochanteric femur fractures (IFF) and the majority of surgeons currently prefer intramedullary femoral nailing in the treatment of IFF.¹ Despite complications and the need for revision surgery in the early designs of proximal cephalomedullary femoral nails, with the changes made to nail design over time, the use of proximal femoral nailing has become widespread in the treatment of IFF. The new-generation nails have been shown to be superior to the old-generation nails and extramedullar fixation.² With greater use in recent years, the double proximal screw design nails (DPSDN) have been accepted as more successful mechanically than single proximal screw design nails (SPSDN) in the prevention of fixation and rotational failure.³

Cut-out has been reported in up to 16% of proximal femoral nail applications.⁴ Although this rate decreases considerably with newly designed implants, it still continues to be an important cause of morbidity. Although the reasons for this complication are still not fully known, several factors have been held responsible in literature, including age, gender, and tip-apex distance (calTAD).5, 6, 7 There are several studies in literature related to SPSDN in respect of cutout complication, but extremely few studies related to DPSDN. Therefore, the aim of this study was to determine the risk factors for cut-out in patients with IFF treated surgically with double proximal nails.

2. Material- method

Approval for the study was granted by the Clinical Research Ethics Committee of Umraniye Training and Research Hospital (registry no: 00140884877). A retrospective review was made of 534 patients who underwent surgery in our hospital because of IFF between January 2018 and December 2020.

The study included patients aged >70 years, operated on using DPSDN (TST-PROFIN- Proximal Femur Nail) and those operated on using a short nail (220 mm in length, 10–12 mm in diameter). Patients were excluded from the study for the following reasons; surgery was applied using SPSDN (n:98), treatment with plate and screw (n:63), a technique other than closed reduction was applied (n:38), a long nail was used (n:42), a history of hip surgery on the same side (n.5) or the contralateral side (n:4), the presence of neurodegenerative disease (n:3), pathological fracture (n:2), follow-up period of less than 6 months (n:34), and the development of complications other than cut-out (n:26). After the implementation of the exclusion criteria, 219 patients were included in the study, of whom 16 developed cut-out during follow up.

The preoperative and postoperative direct radiographs of all the cases were evaluated from the Picture Archiving and Communication System (PACS) of the hospital. Fracture classification was made on the preoperative radiographs according to the Orthopaedic Trauma Association (OTA) criteria.⁸

The severity of osteoporosis at the time of fracture was assessed using the Singh Osteoporosis Index.⁹ Using the ASA classification system, the patients were grouped as mild (ASA 1,2) or severe (ASA 3–5) according to the status of additional diseases. On the first radiographs taken postoperatively, evaluations were made of reduction quality, calTAD, and proximal screw placement. All the radiographic examinations were made by two experienced orthopaedists separately and the average values were accepted for analysis.

The same antibiotic prophylaxis and low-molecular-weight heparin as DVT prophylaxis were administered to all the patients. Surgery was performed with all the patients in a supine position, reduction obtained with a traction table, and using DPSDN (TST-PROFIN- Proximal Femur Nail). The PROFIN nail has a medial-lateral angle of 6°, the diameter of the proximal part is 16 mm, and it has two 8.5 mm cannulated, self-tapping, spongious cephalomedullary screws. The PROFIN is also available in three different distal diameters (10-11-12 mm) and in two different lengths (220–250 mm).

From the first postoperative day, the patients were mobilised with crutches and weight-bearing was not permitted on the operated side. A similar follow-up and rehabilitation protocol was applied to all the patients. Anterior-posterior (AP) and lateral (LAT) direct radiographs were taken postoperatively and the following examinations were made;

• 1)calTAD was measured as defined for DPSDN by Buyukdogan et al.¹⁰ (Fig. 1)
• 2)The femoral head was separated into 3 equal sections on the anterior-posterior and lateral radiographs as defined by Cleveland et al., and the placement of the proximal screws was determined.¹¹ The mid-point of the two screws was evaluated when determining placement of the screws on the AP radiograph.
• 3)Reduction quality was evaluated as described by Baumgartner and Sembro.^12,13 According to this, successful reduction was accepted as appropriate alignment (head-neck angle of 125°–145° and <20° angulation on the lateral image) and ≤ 4 mm displacement of any fragment in both planes. If both criteria were met, reduction quality was accepted as good, if only one criteria was met, as moderate and if neither, as poor reduction quality.

Fig. 1.

ROC curve for the calTAD variable in diagnosing cut-out.

3. Statistical analysis

Data obtained in the study were analyzed statistically using SPSS vn 22.0 software (SPSS Inc, Chicago, IL, USA). Conformity of quantitative variables to normal distribution was assessed with the Kolmogorov-Smirnov test. To determine differences between independent groups, the Mann Whitney U test was applied. Relationships between qualitative data were examined with the Chi-square test. Potential risk factors for the development of cut-out were examined with univariate logistic regression analysis. Variables found to be significant in the univariate logistic regression analysis were entered into the multivariate logistic regression analysis as independent variables. The variable selection method was determined as forward stepwise (likelihood ratio). The criteria for inclusion and exclusion of the variables to the model were selected as p < 0.05 and p > 0.10, respectively. The odds ratios and 95% confidence intervals related to the logistic regression model were calculated. The cutoff value of calTAD for the diagnosis of cut-out was determined with ROC analysis. Descriptive statistics were stated as mean ± standard deviation values for continuous variables with normal distribution and as median (minimum-maximum) when not showing normal distribution. Categorical variables were stated as number (n) and percentage (%). A value of p < 0.05 was accepted as statistically significant.

4. Results

The patients were examined in two groups of cut-out group (n:16) and no cut-out group (n:203). In the univariate analyses of the patients, no statistically significant difference was determined between the groups with and without cut-out in respect of age (p = 0.444), ASA score (p = 0.846), Singh Index (p = 0.900), and AO fracture type (p = 0.361). When a threshold value of p = 0.01 was taken in the univariate analyses, reduction quality, proximal screw placement AP and LAT, and calTAD measurements were determined to be risk factors for cut-out. The p values of all the data, together with odds ratios and confidence intervals are shown in Table 1.

Table 1.

Findings on Univariate logistic regression analysis.

Variables		Total	Group		p
			No cut-out (n = 203)	Cut-out (n = 16)
Ao Classıfıcatıon					0.361
	Type 1	88 (40.2)	84 (41.4)	4 (25)
	Type 2, (vs Type 1)	107 (48.9)	98 (48.3)	9 (56.3)	0.289
	Type 3, (vs Type 1)	24 (11)	21 (10.3)	3 (18.8)	0.171
Gender	Men	78 (35.6)	75 (36.9)	3 (18.8)
	Women, (vs Men)	141 (64.4)	128 (63.1)	13 (81.3)	0.156
Reductıon Quality					<0.001
	Good	141 (64.4)	139 (68.5)	2 (12.5)
	Moderate, (vs good)	56 (25.6)	52 (25.6)	4 (25)	0.057
	Poor, (vs good)	22 (10)	12 (5.9)	10 (62.5)	<0.001
Proximal Screw Placement (AP)					<0.001
	Central	174 (79.5)	170 (83.7)	4 (25)
	Inferiora, (vs central)	3 (1.4)	3 (1.5)	0 (0)	–
	Superior, (vs central)	42 (19.2)	30 (14.8)	12 (75)	<0.001
Proximal Screw Placement (Lat)					<0.001
	Central	160 (73.1)	154 (75.9)	6 (37.5)
	Anterior, (vs central)	34 (15.5)	25 (12.3)	9 (56.3)	<0.001
	Posterior, (vs central)	25 (11.4)	24 (11.8)	1 (6.3)	0.951
Asa Group	>2		126 (62.1)	9 (56.3)
	≤2, (vs > 2)		77 (37.9)	7 (43.8)	0.646
Age		83.01 ± 6.70	83 (70–105)	81.50 (72–91)	0.350
calTAD		22.02 ± 7.07	20.30 (7.20–40.70)	25.75 (11.20–45.60)	0.026
Singh Osteoporosis Index		4.21 ± 1.69	4 (2–6)	4 (2–6)	0.949

^aOdds ratio for the inferior category was not evaluable since the low number of cases.

According to the univariate logistic regression analysis, which investigated the potential risk factors for cut-out, the cut-out risk was 57.917-fold greater in those with “poor” reduction quality compared to those with “good” reduction quality. Cut-out was observed in 2 of 139 patients with good reduction quality, while cut-out was observed in 10 of 22 patients with poor reduction quality. In the measurements of proximal screw placement (AP), the cut-out risk was 17-fold greater in those with “superior” proximal screw placement compared to “central” placement (p < 0.001). In the LAT proximal screw placement measurements, the cut-out risk was determined to be 9.24-fold greater in those with “anterior” placement compared to “central” placement (p < 0.001). There was no significant difference between posterior screw placement and central screw placement (p = 0.951).

As the variable of “reduction quality”, which was found to be significant in the univariate logistic regression analysis, was very strongly correlated with other variables (p < 0.001), it was not included in the multivariate logistic regression analysis. According to the multivariate logistic regression analysis, the cut-out risk was 11.983-fold higher in those with “superior” placement compared to those with “central” placement, and in those with “anterior” placement, the cut-out risk was 5.067-fold higher than in those with “central” placement (p = 0.009) (Table 2).

Table 2.

Findings on multivariate logistic regression analysis.

	OR	% 95 C.I of OR	p
Proximal Screw Placement (AP) (vs central), Inferiora (vs central), Superior			<0.001
	–	–	–
	11,983	3.460–41.506	<0.001
Proximal Screw Placement (Lat) (vs central), Anterior (vs central), Posterior			0.027
	5.067	1.488–17.256	0.009
	0.993	0.105–9.417	0.995

^aOdds ratio for the inferior category was not evaluable since the low number of cases.

In the Receiver Operating Characteristic (ROC) analysis to determine a cutoff value for calTAD in the diagnosis of cut-out risk, a cutoff value of 25.5 mm was determined with 56.25% sensitivity and 76.85% specificity, and Area Under the Curve (AUC) of 0.661 in ROC analysis (Fig. 2).

Fig. 2.

CalTAD measurement.

5. Discussion

To the best of our knowledge, the current study included the largest number of patients in an investigation of the causes of cut-out in patients treated with double proximal screw only, and the rate of cut-out determined in this study was 7.3% (16/219). Reduction quality, proximal screw placements and calTAD were determined to be risk factors for cut-out complication.

Although it has been biomechanically proven that the mechanical effects such as varus collapse and rotational stability are better with double screw design than single screw design in IFF surgery, similar success has not been reported in preventing complications in clinical follow up.^3,14,15

The first evaluation in respect of cut-out complication in double screw design nails was made by Büyükdoğan et al.¹⁰ and there was reported to be cut-out in 9/87 patients (10.5%). When these patients were examined, it was determined that calTAD, as first described by Baumgartner,¹³ had significant predictive value in repect of cut-out. In that study, mean calTAD was reported to be 19.7 ± 4.8 mm, and although there was a need for re-operation in cases with calTAD <21.7 mm, the number of patients was relatively low. In the current study, mean calTAD was found to be 22.02 ± 7.07 mm, and in the ROC curve analysis applied to be able to determine a threshold value of calTAD for the diagnosis of the development of cut-out, a threshold value of 25.5 mm was determined with AUC calculated as 0.661. As it included more patients than the study by Büyükdoğan et al., the current study can be considered of value. However, there are also similar studies but with a single proximal screw, which claim that high calTAD distance is still the most important parameter for cut-out.^16,17 In contrast to those studies reporting that calTAD is important in respect of preventing cut-out, there are other studies in literature stating that calTAD is of no importance in the prevention of cut-out.^6,18 Goffin et al. reported that femoral head size was important in calTAD adjustment and a value of 25 mm was not a predictive value. The current study results were similar to those which have shown that calTAD should be < 25 mm, and from these results it can be considered that care should be taken to remain <25 mm in DPSDN in respect of cut-out complication.

In a study by Parker,¹⁹ posterior screw placement was said to increase the cut-out risk, whereas Baumgaertner⁵ determined a higher risk with anterior placed screws. There are also studies stating that screw placement does not affect the cut-out risk.⁷ The currently generally accepted view about screw localisation is that localisations other than central or inferior on anterior-posterior radiographs and central on lateral radiographs increase the risk of cut-out. To the best of our knowledge, there has been no previous study that has investigated the effect of screw placement on the cut-out risk in cases operated on with DPSDN. In the multivariate analysis of this study, it was determined that superior and anterior placement significantly increased the risk of cut-out.

Several previous studies have shown that inadequate reduction quality increased the risk of cut-out.^20,21 In a study by Murena et al. using SPSDN, “poor” reduction was determined in 3% of cases with no cut-out and in 38% of cases with cut-out.²² In the study by Büyükdoğan et al., as the only cut-out study with double screws in literature, although it was determined that the risk of cut-out increased when reduction quality was “moderate”, as the number of patients was low, it was stated that the finding of no increase seen in cut-out complication in “poor” reduction could not be taken as reliable.¹⁰ In the current study, “poor” reduction was determined in 5.9% of the group without cut-out and in 62.5% of the group with cut-out. According to the univariate regression analysis, the cut-out risk of those with “poor” reduction quality was 57.917-fold higher than patients with “good reduction quality. Therefore, reduction quality was concluded to be a significant risk factor for the complication of cut-out.

In a study by Morvan et al. of 13 cut-out cases, the risk of cut-out was found to be 13% in males and 3% in females, so as the risk was higher in males, it was reported not to be affected by age and osteoporosis severity.⁷ Tsai et al. reported the risk of cut-out to be approximately 10-fold higher in females in a series of 154 cases, but no correlation was determined with age.²³ Several other studies have claimed that the risk of cut-out is not affected by age, gender, or the presence of osteoporosis.^6,10,22 In the current study of cases aged >70 years, it was seen that age, gender, and Singh Index value did not create a risk for cut-out as a result of treatments using DPSDN. However, as the use of the Singh Index to show osteoporosis is debatable,²⁴ it would not be correct to comment on this point. Furthermore, to be able to reveal the risk in relation to gender, there is a need for further studies with larger patient populations.

This study had some limitations; first of all, the design was retrospective and the number of patients in the cut-out group was much less than in the non-cut-out group. However, to the best of our knowledge, this is the largest study to date of predictive factors of cut-out complication in patients treated with twin-screw nails, and it can be said to be a strength of this study. In addition, the cut-out rate can be seen to be higher compared to current studies. We think that this is due to the lack of attention to criteria such as tip-apex distance, reduction quality, and proximal screw placement during the study period.

In conclusion, there are very cut-out studies in literature made with DPSDN. In this, the largest study to have examined the predictive factors for cut-out complication in a DPSDN model, it was determined that calTAD, proximal screw localisation and reduction quality were significant factors in the determination of cut-out risk. Nevertheless, there remains a need for further studies to be made with this nail design and to examine all the surgeon and patient-related risk factors in more detail in larger patient series.

Contributions of each author

AŞ wrote the article.

ÖA collected the data and reviewed the medical files.

SKÇ and SB revised the article for important intellectual content.

ÖP performed the literature review.

Financial disclosure

This study has received no financial support

Declaration of competing interest

No benefits in any form have been received or will be received from a commercial party related directly or indirectly, financially or otherwise, to the subject of this article.