Differences in Survival Rates between Different Patterns of Unstable Pertrochanteric Femoral Fractures

doi:10.4236/ojo.2013.36049

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Open Journal of Orthopedics, 2013, 3, 261-268

http://dx.doi.org/10.4236/ojo.2013.36049 Published Online October 2013 (http://www.scirp.org/journal/ojo)

261

Differences in Survival Rates between Different Patterns of

Unstable Pertrochanteric Femoral Fractures*

Amir Herman1,2#, Yair Landau1, Alexander Hazanov3, Tal Segev4,5, Ran Thein1, Nachshon Shazar1

1Department of Orthopedic Surgery, Chaim Sheba Medical Center, Tel-Hashomer, Israel; 2Talpiot Medical Leadership Program,

Chaim Sheba Medical Center, Tel-Hashomer, Israel; 3Department of Anesthesiology, Chaim Sheba Medical Center, Tel-Hashomer,

Israel; 4Department of Vascular Surgery, Chaim Sheba Medical Center, Tel-Hashomer, Israel; 5Sackler Faculty of Medicine, Tel

Aviv University, Tel Aviv, Israel.

Email: #[email protected]

Received August 6th, 2013; revised September 6th, 2013; accepted September 21st, 2013

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

ABSTRACT

Background: Unstable pertrochanter femur fractures are common in orthopedic practice. They pose a surgical chal-

lenge in both reduction and fixation. The fixation devices used are based on hip intramedullary nailing with femur head

lag screw or blade. The aim of this paper is to compare different types of unstable pertrochanter fractures. Materials &

Methods: We retrospectively reviewed 386 unstable pertrochanter femur fractures surgically treated in our hospital

from 2000 to 2009. These included 62 (16.1%) unstable pertrochanter fractures with fractured lesser trochanter

(31.A2-2, 31.A2-3); 63 (16.3%) reverse oblique fractures (31.A3-1), 51 (13.2%) transverse fractures (31.A3-2), 145

(37.6%) comminuted fractures (31.A3-3) and 65 (16.8%) subtrochanter fractures. We compared survival rates between

fracture types. The clinical characteristics, surgery immediate outcome (e.g., tip apex distance, reduction quality), and

long term results, i.e., complications were also compared between fracture types. Results: Survival analysis showed

that the fracture types can be grouped into low and high risk fracture types. The former group included, reverse oblique

and comminuted fractures. Lesser trochanter, transverse and subtrochanter fractures were included in the high risk

group. The survival estimates for five years were 64.6% and 49.3% for the low and high risk fracture types, respectively

(p value = 0.008). Multivariate survival analysis showed that the hazard ratio for the high risk fracture group was 1.9

(95% CI = 1.37 - 2.67). No differences were found between unstable pertrochanter femur fractures with regards to

clinical and epidemiology characteristics. Optimal tip apex distance (TAD) of less than 25 mm was found in 66.7%,

57.1% and 66.7% of lesser trochanter, reverse oblique and sutrochanter fractures, respectively. TAD of less than 25 mm

was found in 81.2% of both transverse and comminuted fractures (p value = 0.032). No statistically significant differ-

ence was found between fracture types, in regards to complication or revision rates. Conclusions: Survival rates were

higher in patients suffering from reverse oblique or comminuted pertrochanteric fractures. No differences were found

between fracture types, in regards to clinical and other outcome parameters.

Keywords: Intertrochanteric Fractures; Survival; Fracture Classification

1. Introduction

Pertrochanteric fractures are among the most widely

treated orthopedic injuries. Their annual incidence is ex-

pected to reach 500,000 by 2040, in the US alone [1].

About half of this is estimated to be unstable factures [2].

The AO/OTA classification system divides pertrochan-

teric fractures into several groups: simple pertrochanteric

(31.A1), pertrochanteric with lesser trochanter fracture

(31.A2) and complex pertrochanteric fractures (31.A3)

[3]. Each of these three groups is further divided into

three groups, consisting of a total of nine different fracture

patterns. These patterns are commonly divided into stable

pertrochanteric fractures (31.A1 fracture group and 31.A2-

1 subtype) and unstable pertrochanteric fractures (31.A2-

2 and 31.A2-3 subtypes and 31.A3 fracture group) [4-6].

Fixation devices available for pertrochanteric fractures

vary from intra-medullary devices and extra-medullary

plate both with femur head screw. The extra-medullary

*Conflict of interest statement: No benefit in any form has been or will

e received from a commercial party related directly or indirectly to the

subject of this manuscript.

#Corresponding author.

Differences in Survival Rates between Different Patterns of Unstable Pertrochanteric Femoral Fractures

262

device was shown to have fewer complications in stable

pertrochanteric fractures. Patients with unstable pertro-

chanteric fractures were shown to benefit from intrame-

dullary fixation devices such as the Cephalomedullary

nail, Gamma nail, Y nail among other [5,7-20].

Subtrochanteric fractures are defined as fractures with-

in the immediate 5 cm distal to the lesser trochanter. As

opposed to femur shaft fractures, these fractures require

fixation of the femoral head-neck-shaft complex. Frac-

tures of the subtrochanteric region often are fixed by in-

tramedulary proximal femur fixation devices. As such

these factures can be included as part of the unstable per-

subtrochanteric fracture patterns [21].

Several authors described their experience of different

unstable pertrochanteric fractures. These include a recent

review by Lundy focusing on subtrochanteric fractures

and a description of open reduction in treating subtro-

chanteric fractures [2]. Other authors focused on reverse

oblique or transverse fracture types [6]. We are unaware

of any work comparing the survival among different sub-

types of unstable pertrochanteric fractures.

In this report we compare between the different pat-

terns of unstable per-subtrochanteric fractures. We com-

pare the survival rates, epidemiology, reduction achieved,

screw placement, complications and revision rates be-

tween the different fracture types.

2. Patients & Methods

The study presented is a retrospective study based on na-

tional mortality registry and our hospital admission and

outpatient-clinic files. The study was approved by our

institute’s internal review board (IRB) ethics committee.

Since this is a retrospective study, patients’ informed con-

sent was not required by the IRB.

Between 2000 and 2009, 386 unstable pertrochanteric

fractures were operated in our institute. These consisted

of 62 (16.1%) pertrochanteric fractures in which the les-

ser trochanter was fractured and the fracture was defined

as unstable (31.A2-2 and 31.A2-3). There were 63 (16.3%)

reverse oblique fractures (31.A3-1), 51 (13.2%) transver-

es pertrochanteric fractures (31.A3-2) and 145 (37.6%)

of comminuted fractures (31.A3-3). Subtrochanteric frac-

tures included 65 (16.8%) fractures.

The Fractures had been fixed by means of the Targon

proximal femur (Targon PF) device (Aesculap, Tuttlin-

gen, Germany) or with the antirotation trochanteric nail-

ing system (ATN) device (dePuy, Warsaw, IN, USA).

Both of which are double screw intramedullary fixation

devices. All surgeries were performed in accordance to

standard surgery technique and the manufacturer’s rec-

ommendations.

The radiology computerized achieve was used for clas-

sification of fractures according to the OTA/AO classifi-

cation system [3]. Patterns were classified by two inde-

pendent researchers (A.O and Y.L). The senior author

(N.S) was consulted whenever consensus was not rea-

ched. Radiology measurements were performed includ-

ing the tip apex distance and placement of the center of

the lag screw within the head-neck interface “Safe-zone”

(defined as the second quarter from the bottom) [22].

Acceptable reduction was considered as translation of

less than 20 mm in any plane as measured by the medial

cortex in anterior-posterior radiography view or anterior

cortex on axial radiography view.

Statistical analysis was performed by an experienced

biostatistician (A.H.). Data analysis was conducted using

SPSS© 16 (SPSS©, Chicago, IL). Categorical data are

presented as frequency count (percent of available data).

Comparisons of categorical variables between fracture

types were performed using either the chi-square test or

the Fisher’s exact test. The latter was used when expec-

ted count in any cell was less or equal five. Continuous

variables are presented as mean (±standard deviation).

Comparisons of continuous variables among fracture pat-

terns were performed using the Kruskal-Wallis test. Com-

parisons of paired data, mainly the increase in mobility

aids before and one year after surgery, were performed

using the Wilcoxon rank sign test. Survival data are pre-

sented using the Kaplan-Meier survival curves. Kaplan-

Meier survival estimates were used for one and five years

survival along with 95% confidence interval (95% CI).

Comparisons between survival curves were done by the

log-rank test.

Data were extracted by reviewing of the patients’ ad-

mission and out-patients clinic electronic files. Compli-

cations, comorbidities, use of walking aids and recovery

parameters were extracted from the hospital records. The

national mortality registry was consulted for mortality

status and date. Patients that were not registered as de-

ceased were considered as censured at the date of the in-

quiry.

Multivariate survival analysis was performed with the

Cox proportional hazards model. The independent co-

variates in the model were fracture group (according to

high or low risk fracture type), ASA score and Age group

—up to 60 years old (46 pts, 11.9%), 60 - 80 years old (158

pts, 40.7%), above 80 year old (182 pts, 47.1%). Results

are reported as hazard ratios and their 95% confidence in-

tervals. Hazard ratio should be interpreted as relative risk,

so that hazard ratio above one means excessive risk.

Data were not available for all patients in all variables

measured. The numbers of patients used for analysis of

each variable are given within the summary tables. In each

analysis frequencies and percents were calculated from

available data. For example, for epidemiologic and clini-

cal presentation parameters, percents were calculated from

Differences in Survival Rates between Different Patterns of Unstable Pertrochanteric Femoral Fractures

263

the entire patients’ population. Complications and revi-

sion rates are calculated from a subset of patients which

included patients that either had a complication or com-

pleted at least one year of follow-up and showed signs of

union on X-ray radiography.

3. Results

Between 2000 and 2009, 386 unstable pertrochanteric

fractures were operated in our institute. These included

95 (24.6%) fractures in men and 291 (75.4%) fractures in

women. Mean age at surgery was 76.16 years (±15.2).

Mean American society of anesthesiologists (ASA) score

was 2.75 (±0.61), where 124 patients (32.2%) and 225

patients (58.4%) had ASA scores of 2 and 3, respectively.

Patients with transverse fractures (31.A3-2) had higher

ASA scores (p value = 0.026). Mechanism of injury was

low energy fall in 175 fractures (87.1%). Initial treatment

at the emergency ward included skeletal traction in 145

fractures (71.8%). Skeletal traction was performed more

often in reverse oblique, comminuted or subtrochanter frac-

tures. This difference was found to be statistically signi-

ficant (p value = 0.001) Epidemiological and clinical data

according to fracture types are presented in Table 1.

Of the 386 fractures treated, 254 fractures (65.8%)

were treated by the Targon PF © device, while 132 frac-

tures (34.3%) were fixed using the ATN © device. No

statistically significant difference was found between the

fracture types. The nail length was found to be longer

(300 mm - 340 mm) in fixation of subtrochanteric and

comminuted fractures (Table 2).

Immediate surgical outcome varied between fracture

types. Tip Apex Distance (TAD) was found to be below

25 mm in about 81% of comminuted and transverse frac-

Table 1. Demographic and clinical characteristics (Total = 386 patients).

Fractured Lesser

Trochanter

(A2.2 & A2.3) N = 62

Reverse Oblique

(A3.1) N = 63

Transverse

(A3.2) N = 51

Comminuted

(A3.3) N = 145

Subtrochanteric

N = 65 P value

Gender

Male

Female

20 (32.3%)

42 (67.7%)

11 (17.5%)

52 (82.5%)

9 (17.6%)

42 (82.4%)

35 (24.1%)

110 (75.9%)

20 (30%)

45 (69.2%)

0.173

Age 78.9 (±12.5) 79.0 (±9.8) 77.5 (±14.2) 75.8 (±14.8) 70.4 (±21.1) 0.243

Side

Left

Right

32 (51.6%)

30 (48.4%)

32 (50.8%)

31 (49.2%)

29 (56.9%)

22 (43.1%)

78 (53.8%)

67 (46.2%)

34 (52.3%)

31 (47.7%)

0.971

ASA score 2.69 (±0.64) 2.78 (±0.60) 3.00 (±0.566) 2.68 (±0.61) 2.72 (±0.50) 0.026

Above one year follow-up 26 (41.9%) 26 (41.3%) 19 (37.3%) 72 (49.7%) 22 (34.4%) 0.253

Skeletal traction (N = 202) 3 (7%) 11 (40.7%) 5 (17.9%) 25 (32.9%) 13 (46.4%) 0.001

Diabetes Mellitus (N = 201) 10 (23.8%) 4 (14.8%) 5 (17.9%) 19 (25.0%) 5 (17.9%) 0.764

Mechanism of injury

(N = 202)

Low energy (fall)

High energy

37 (86%)

6 (14%)

25 (92.6%)

2 (7.4%)

24 (85.7%)

4 (14.3%)

68 (89.5%)

8 (10.5%)

21 (77.8%)

6 (22.2%)

0.327

Table 2. Surgery and post operative outcome parameters.

Fractured Lesser

Trochanter

(A2.2 & A2.3) N = 62

Reverse Oblique

(A3.1) N = 63

Transverse

(A3.2) N = 51

Comminuted

(A3.3) N = 145

Subtrochanteric

N = 65 P value

IM Nail Type

Targon PF

AT N

34 (53.9%)

29 (46.1%)

49 (77.8%)

14 (22.2%)

28 (54.9%)

23 (45.1%)

96 (66.2%)

49 (33.8%)

47 (73.4%)

17 (26.6%)

0.13

Nail length

Standard (200 - 240 mm)

Long (300 - 340 mm)

56 (90.3%)

6 (9.7%)

58 (92.1%)

5 (7.9%)

48 (94.1%)

3 (5.9%)

109 (75.2%)

36 (24.8%)

12 (19.0%)

51 (81.0%)

0.0001

Tip Apex distance ≤ 25 mm

(N = 235) 28 (66.7%) 24 (57.1%) 29 (81.2%) 69 (81.2%) 20 (66.7%) 0.032

Lag screw within “safe-zone”

(N = 378) 53 (85.5%) 50 (80.6%) 42 (87.5%) 120 (84.5%) 49 (76.6%) 0.506

Reduction not achieved (N = 383) 6 (9.8%) 17 (27.0%) 10 (19.6%) 35 (24.1%) 12 (19.0%) 0.134

Mobility points change from pre to

1 year post surgery (N = 60) 1.66 (±1.23) 1.77 (±1.30) 2.14 (±1.06) 1.90 (±1.33) 0.75 (±1.35) 0.174

Walking 1 year after surgery

(N = 77) 72% - 93.5% 15 (100%) 8 (88.9%) 11 (100%) 25 (89.3%) 13 (92.9%) 0.566

Differences in Survival Rates between Different Patterns of Unstable Pertrochanteric Femoral Fractures

264

tures. The TAD was below 25 mm in only 57% - 66% of

lesser trochanter, reveres oblique and subtrochanteric

fractures. This difference was found to be statistically

significant (p value = 0.032). However, 76% to 87% of

the lag screws were placed within the head-neck inter-

face “safe-zone”. This difference was not found to be sta-

tistically significant (p value = 0.506). Reduction was not

achieved in 7.6% patients. No statistically significant dif-

ference was found between fracture types (p value =

0.386).

Seventy two patients (93.5%) walked of 77 patients

whose mobility status was recorded one year after sur-

gery. Mobility aids used as recorded by the Parker score

increased by a mean of 1.6 points (±1.3) one year after

surgery. Sixty nine percent of the patients used a walking

frame one year after surgery (Figure 1). No statistically

significant difference was found in regards to mobility

status between fracture types (Table 2).

One hundred and ninety one patients had either at least

one year of follow-up with documented fracture union or

any complication. Common complications included 14

(7.3%) fractures that had cutout, 10 fractures (5.2%) that

had hardware failure and 7 fractures fixed with internal

rotation above 30 degrees. Less common complications

included deep wound infection, secondary loss of reduc-

tion, and fractures non-unions, with rates of 5 (2.6%), 5

(2.6%) and 3 (1.6%) fractures, respectively. No statisti-

cally significant difference was found between fracture

types (Table 3).

Thirty two patients (16.8%) of the aforementioned 191

patients had revision surgery. Common revision types

included 14 (7.3%) hardware removals, 7 (3.7%) arthro-

Figure 1. Walking aids score: where no aids, one aid, two aids, walking frame and wheel chair received a score of 1 - 5 in an

ascending order. Mean increase in ambulation score from preoperative to 1 year after surgery was 1.63 points (±1.32). This

difference was found to be statistically significant (p value = 0.0001). No statistically significant difference was found between

fracture patterns.

Table 3. Complications.

Total N = 191

Fractured Lesser

Trochanter (A2.2

& A2.3) N = 34

Reverse Oblique

(A3.1) N = 31

Transverse (A3.2)

N = 23

Comminuted

(A3.3) N = 78

Subtrochanteric

N = 25

value

Cut out—14 pts (7.3%) 3 (8.8%) 2 (6.5%) 4 (17.4%) 5 (6.4%) --- 0.232

Hardware failure—10 pts

(5.2%) 4 (11.7%) 2 (6.5%) --- 4 (5.2%) --- 0.278

Nonunion—3 pts (1.6%) 1 (2.9%) --- 1 (4.3%) --- 1 (4.0%) 0.16

Deep wound infection

—5 pts (2.6%) --- --- --- 4 (5.1%) 1 (4.0%) 0.508

Secondary loss of

reduction 5 pts (2.6%) 1 (2.9%) 1 (3.2%) --- 1 (1.3%) 1 (4.0%) 0.674

Internal rotation—7 pts

(3.7%) 3 (8.8%) 2 (6.5%) --- 1 (1.3%) 1 (4.0%) 0.172

Other—3 pts (1.5%) 1 (2.9%) --- --- 1 (1.3%) 1 (4.0%) 0.564

Total complications—47

pts (24.6%) 13 (38.2%) 7 (22.6%) 5 (21.7%) 16 (20.5%) 6 (24.0%) 0.369

Table 3 includes surgical complications and revision surgery. Other complications include one patient with pain that required revision, 1 patient with fracture at

the lower end of the fixation device, and one patient with superior placement of the fixation device that required revision. No cases of deep vein thrombosis

were reported.

Differences in Survival Rates between Different Patterns of Unstable Pertrochanteric Femoral Fractures 265

plasties and 5 (2.6%) rotational corrections. No statisti-

cally significant difference was found between fracture

types (Table 4).

One year and five years survival of the entire cohort

were 79.6% (95% CI of 75.1% - 84.2%) and 48.9% (95%

CI of 42.3% - 56.4%), respectively. Comparing survival

between specific inter-trochanteric fractures, no statisti-

cally significant difference was found (p value = 0.07,

Table 5). The fractures were grouped into high and low

risk fracture types, according to survival. The low risk

fracture types included reverse oblique fractures (31.A3-

1) and comminuted fractures (31.A3-3). High risk frac-

ture types included lesser trochanter unstable fractures

(31.A2-2 and 31.A2-3), transverse fractures (31.A3-2)

and subtrochanteric fractures (32 either A, B or C). One

year and five years survival for the low risk fracture

types were 86% (95% CI 81.4% - 90.8%) and 64.6%

(95% CI 57.4% - 72.6%), respectively. One year and five

years survival for the high risk fracture types were 76.4%

(95% CI, 70.4% - 82.9%) and 49.3% (95% CI, 41.0% -

59.2%). This difference was found to be statistically sig-

nificant (p value = 0.008, Figure 2).

Multivariate analysis by the Proportional hazards mo-

del showed that the high risk fracture group was asso-

ciated with higher mortality risk. Setting the low risk

fracture group to have hazard ratio of one (as baseline)

the hazard ratio for the high risk fracture group was 1.9

(95% CI = 1.37 - 2.67). This difference was found to be

statistically significant (p value = 0.0001). The hazard

rate associated with age 60 - 80 was 17.7 (95% CI = 4.3 -

73.1). The hazard rate associated with age above 80 years

old was 19.6 (95% CI = 4.7 - 80.7). The hazard rate as-

sociated with each point of the ASA score was 1.152

(95% CI = 0.88 - 1.5). This was not found to be statisti-

cally significant (p value = 0.29).

4. Discussion

In this manuscript, it was shown that survival rates dif-

fered between different types of unstable pertrochanteric

fractures. These fractures could be divided into low and

high risk fracture types. The low risk group includes: re-

verse oblique and comminuted fractures. The high risk

fracture types include: lesser trochanter, transverse and

subtrochanteric fractures. No difference in clinical or epi-

demiologic characteristics was found in order to explain

the difference in survival. No difference was found in

complication and revision rates that could also elucidate

the survival difference.

In previous works, other authors focused mainly on

Table 4. Revisions.

Total N = 191 pts

Fractured Lesser

Trochanter

(A2.2 & A2.3) N = 34

Reverse Oblique

(A3.1) N = 31

Transverse

(A3.2) N = 23

Comminuted

(A3.3) N = 78

Subtrochanteric

N = 25 P value

Total Hip replacement

—3 pts (1.6%) 2 (5.9%) --- 1 (4.3%) --- --- 0.086

Hemiarthroplasty—4

pts (2.1%) --- --- --- 4 (5.1%) --- 0.441

Exchange nail—4 pts

(2.1%) --- --- 1 (4.3%) 2 (2.6%) 1 (4.0%) 0.533

Hardware removal—11

pts (5.7%) 3 (8.8%) 3 (9.4%) 1 (4.3%) 4 (5.1%) --- 0.552

Nail removal and

plating—3 pts (1.6%) --- --- 2 (8.7%) --- 1 (4.0%) 0.018

Rotation correction—5

pts (2.6%) 2 (5.9%) 1 (3.2%) --- 1 (1.3%) 1 (4.0%) 0.455

Soft tissue revision due

to infection 1 pt (0.5%) --- --- --- 1 (1.3%) --- 1.00

Total revisions—32 pts

(16.8%) 7 (20.6%) 4 (12.9%) 5 (21.7%) 12 (15.4%) 4 (16.0%) 0.876

Table 5. Survival estimates (95% confidence intervals).

Total = 386 patients

Fractured Lesser

Trochanter

(A2.2 & A2.3) N = 62

Reverse Oblique (A3.1)

N = 63

Transverse (A3.2)

N = 51

Comminuted (A3.3)

N = 145 Subtrochanteric N = 65

Six months 95.2% (90% - 100%) 93.5% (87.6% - 99.9%)88.2% (79.8% - 97.5%)91% (86.5% - 95.8%) 80% (70.8% - 90.3%)

One year 77.4% (67.6% - 88.5%) 90.3% (83.3% - 98%)74.5% (63.4% - 87.5%)84.1% (78.4% - 90.3%) 76.9% (67.3% - 87.9%)

Five years 55.7% (42% - 73.9%) 63.2% (50.9% - 78.4%)37.9% (22.8% - 62.8%)64.5% (56% - 74.3%) 50.5% (38.5% - 66.3%)

P value for survival curves comparing all the fracture types = 0.07.

Differences in Survival Rates between Different Patterns of Unstable Pertrochanteric Femoral Fractures

266

(a) (b)

Figure 2. Kaplan-Meier survival curves. Low risk fracture types include AO types A3.1 (reverse oblique), A3.3 (Commin-

uted). High risk fracture type include AO types A2 (lesser trochaner fracture), A3.2 (transverse), and subtrochanteric frac-

tures. The difference in survival was found to be statistically significant (p value = 0.008). (a) Kaplan Meier survival curves

after fixation—by fracture type. (b) Kaplan Meier survival curves after fixation—by risk group.

describing series of specific unstable fractures, without

comparing between them. Reported complications of un-

stable pertrochanteric fractures fixation included cutouts

(4% - 20%), femoral shaft fractures (0% - 10%) and no-

nunions (1% - 2%) [4]. Subtrochanteric fracture fixation

had shown similar results [21,23]. These complication

rates are comparable to the rates presented in this study.

In our work, no statistically significant difference was

found between fracture types in reviewing postoperative

complications.

Some authors studied factors influencing the mortality

of patients after internal fixation of pertrochanteric frac-

tures. Forte et al. have examined the ninety day mortality

in patients treated by internal fixation of pertrochanteric

fracture. They have shown that patients treated at a low

volume versus high volume institutes had mortality rates

for ninety days of 24.4% and 12.9%, respectively [24].

These survival rates are comparable to the survival pre-

sented in this study. Donegan et al. has shown that higher

ASA was associated with higher in hospital mortality

rates. This was due to higher medical complications in

patients with higher ASA scores [25]. In our study no cli-

nically significant difference in ASA score was found be-

tween fracture types.

We found the lack of successful reduction in 7.6% of

patients, with no statistically significant difference among

fracture types. This result does not indicate as to the dif-

ficulty in achieving reduction, only the final results. This

finding is especially important since the reduction quality

is considered by many to be one of the major criteria in

preventing further complications [26-28]. The TAD was

found to differ between fracture types. This did not in-

fluence the failure rates between fracture types. This fin-

ding is in contradiction to other authors who have shown

that TAD above 25 was associated with higher rates of

cutouts [26,29].

Recently, we reported a new radiographic measure for

correcting lag screw position. Using polar to Cartesian co-

ordinates transformation, we were able to devise a femur

head-neck interface “safe zone” for the center of the lag

screw. In short, this safe zone is the second quarter (from

the bottom) of the head-neck interface line. In this data-

set 76% to 87% of the lag screws were found within the

head-neck “safe-zone”. This parameter did not differ

among fracture types. This finding can explain why there

were no differences in the rates of cutout between dif-

ferent fracture patterns.

The main drawback of the article is the fact that it is

retrospective. As such, some data were not available,

either not accessible or it was not recorded to begin with.

However, the retrospective nature of the analysis enabled

us to include maximum patients in our study. Further, the

main result of the study, namely survival rates, was ex-

tracted from the national databases which are independ-

ent from the study design.

We believe that our results offer some new conclu-

sions regarding unstable pertrochanteric fractures. We

found that unstable pertrochanteric fractures are similar

in demographics and surgery outcome. Also their com-

plications and revision rates are similar. However, these

fractures differ in survival of patients after surgery.

5. Acknowledgements

This study was funded by the Talpiot medical leadership

program of the Chaim Sheba, Tel-Hashomer, Hospital.

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Differences in Survival Rates between Different Patterns of Unstable Pertrochanteric Femoral Fractures 267

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