International Orthopaedics (SICOT) (2010) 34:1273–1276

DOI 10.1007/s00264-009-0866-2

ORIGINAL PAPER

Risk factors in cutout of sliding hip screw

in intertrochanteric fractures: an evaluation of 937 patients
Kuang-Kai Hsueh & Chi-Kuang Fang &
Chuan-Mu Chen & Yu-Ping Su & Heng-Fei Wu &
Fang-Yao Chiu

Received: 21 June 2009 / Revised: 20 August 2009 / Accepted: 20 August 2009 / Published online: 26 September 2009
# Springer-Verlag 2009

Abstract The aim of this study was designed to assess the Introduction
risk factors of lag-screw cutout in the treatment of
intertrochanteric fracture with a dynamic hip screw Although many devices can achieve rigid fixation for
(DHS). From 2003 to 2007, 1,150 patients who had acute intertrochanteric fractures, the sliding hip screw system is
unilateral intertrochanteric fractures of the femur were the most commonly used device [16, 19]. The commonest
enrolled to the study. All fractures were managed by mechanical failure of fixation in using the sliding hip screw
closed reduction and internal fixation with 135° DHS system is cutout of the implant from the femoral head [6,
devices. Patient demographics, fracture patterns, reduction 10, 12, 20, 21, 23, 24]. Few papers have addressed the risk
and fixation and perioperative course parameters were all factors of screw cutout in the treatment of intertrochanteric
recorded. The follow-up period was 38 months on average fracture using a sliding hip screw, and the case numbers
(range 16–60 months). Finally, 937 patients were available evaluated were relatively small [2, 3, 13, 21]. The purpose
for evaluation of final results in which we focused on lag- of this study was to evaluate in a larger series the possible
screw cutout. Excluding complications not related to screw risk factors of screw cutout in treatment of intertrochanteric
position, 64 patients (6.8%) with screw cutout were fractures using a sliding hip screw.
encountered, and the remaining 873 patients had uneventful
union, with the average union time of 17.5 weeks
(range15–24 weeks). Upon analysis with logistic regres- Materials and methods
sion, the tip−apex distance (TAD) was shown to be the
most important predictive factor for cutout, followed by Between 2003 and 2007, there were 1,150 consecutive
screw position, fracture pattern, reduction and patient age. patients with acute unilateral non-pathological intertrochan-
In order to decrease the risk of lag-screw cutout, it is teric fractures treated by closed reduction and internal
important to ensure good fracture reduction and to place the fixation with a dynamic hip screw (DHS, AO, 135° angle)
lag screw in either the middle/middle or inferior/middle in our institute. During the operations, all fractures were
position with appropriate TAD. reduced as anatomically as possible and were fixed as
rigidly as possible, and all lag screws were place in the
femoral head, with the tip within 10 mm of the articular
surface of the head. These 1,150 patients were included in
the initial evaluation of this retrospective study. Patients
K.-K. Hsueh : C.-K. Fang : C.-M. Chen : Y.-P. Su : H.-F. Wu :
lost to follow-up (23), failure of union due to other reasons
F.-Y. Chiu (*) such as falling with a periprosthetic fracture (25), and death
Departments of Orthopaedics & Traumatology, before fracture union (165) were excluded in final evaluation.
Taipei Veterans General Hospital, The remaining 937 patients with either uneventful fracture
National Yang-Ming University,
201, Sec 2, Shih-Pai Road,
healing [873, 93.2%; union time 17.5 (15–24) weeks] or screw
Taipei 112 Taiwan, People’s Republic of China cutout [64, 6.8%] were included in the final evaluation. In this
e-mail: fychiu@vghtpe.gov.tw study, we focused on lag-screw cutout. All patients received
1274 International Orthopaedics (SICOT) (2010) 34:1273–1276

Table 1 Variables and differ-

ences in fracture reduction for Variable Cutout group Successfully healed group p value
cases of cutout in comparison
with successfully healed cases Number of patients 64 873 -
Sex (M/F) 34 (53%)/30 (47%) 534 (61%)/339 (39%) 0.204a
Age (≧80/<80) 39 (61%)/25 (39%) 388 (44%)/485 (56%) 0.011a
Age (≧70/<70) 57 (89%)/7 (11%) 677 (78%)/196 (22%) 0.031a
Age (≧60/<60) 63 (98%)/1 (2%) 838 (96%)/35 (4%) 0.326a
ASA 3 (0.9) 3 (0.8) 0.261b
ASA American Society of Anes- BMI 25 (2.1) 25 (2.6) 0.725b
thesiologists, BMI body mass Reduction: good/poor 51 (80%)/13 (20%) 774 (89%)/99 (11%) 0.033a
index, TAD tip−apex distance
a
Fracture pattern (stable/unstable) 25 (39%)/39 (61%) 532 (61%)/341 (39%) 0.001a
Chi-square test
b
TAD (≧25/<25) 53 (83%)/11 (17%) 143 (16%)/729 (84%) <0.001a
Student’s t test

the standard postoperative protocol: (1) Protected weight Results

bearing with a walking stick for three months, and (2) calcium
and vitamin D supplementation. Results of the variables and differences between group 1
The follow-up period was 38 months on average (range and group 2 are presented in Table 1. The differences in
16–60 months). All patients had complete records for sex, age, TAD, reduction pattern, and fracture pattern were
age, body mass index (BMI), American Society of statistically significant between the groups (p<0.05). With
Anesthesiologists (ASA) class rating [1], and pre- logistic regression analysis, the TAD was shown to be the
operative and post-operative standard anterior−posterior most important predictive factor for cutout, followed by
(AP) and lateral radiographs. In radiographic evaluations, screw position, fracture pattern, reduction, and patient age.
we recorded the fracture pattern according to Evans [7], tip The distribution of screw position in the femoral head is
−apex distance (TAD) [2, 3], and reduction quality. shown in Fig. 1 and presented in Table 2. According to the
Reduction was graded on the amount of displacement screw positions, the lowest cutout rate was in cases of the
and neck-shaft alignment on immediate post-operative AP middle/middle screw position (3/134, 2.1%). The statistical
and lateral radiographs, being categorised as good or poor differences of screw cutout rates between cases of middle/
[2, 3, 8]. A good reduction had normal or slightly valgus middle screw position and cases of the other screw
neck-shaft alignment in the AP radiograph, <20° of positions are presented in Table 2. It was found that if the
angulation in the lateral radiograph, and displacement screw was in the superior or posterior position, the cutout
of <4 mm on either view. Otherwise, the reduction was rates were highest.
graded as poor. The femoral head was further divided into The average tip−apex distance in group 1 was 35.5 mm
superior, central, and inferior thirds on the AP radiograph and that in group 2 was 22.1 mm. The distribution of TAD
and into anterior, central, and posterior thirds on the lateral in both groups was shown in Fig. 2.
radiograph. Thus, nine separate zones were created to further
locate the screw position [5, 11]. The above parameters were
compared between patients with screw cutout (group 1) and
patients with uneventful fracture healing (group 2).
All patients were measured for all response variables,
which included demographic variables and important out-
comes. Data were represented as mean and standard
deviation (SD) for continuous response variables or
percentages for discrete variables with respect to the two
groups. Chi-square test was used to compare differences
between the two groups for each discrete variable, and
Student’s t test was used for each continuous variable. The
p value was set before analysis at 0.05 for each test.
Logistic regression analysis was used to investigate
interactions among the independent variables and their
Fig. 1 Distribution of screws by zone: 873 healed and 64 cut out. The
ability to predict screw cutout. Analysis of variance number of healed cases in each zone is represented by the numerator,
(ANOVA) and the post hoc test were used for multivariate and the number of screws that cut out in each zone is represented by
statistical analysis the denominator. Ratio: cutout/healed
International Orthopaedics (SICOT) (2010) 34:1273–1276 1275

Table 2 Distribution of cases with different screw positions in reduction, nonunion and malunion with varus deformity of
different groups and comparisons of cutout rate between screw
the femoral neck, marked shortening of the affected limb,
position with lowest cutout rate (MM) and the other screw positions
or screw cutout [6, 9, 10, 14, 16, 18, 23, 24]. In this study,
Screw Cutout Successfully Comparison of we focused on screw cutout. The incidence was 6.8%,
position group healed group cutout rate which is comparable with other series,. The two main
(case (case number, %) with MM position
number, %) (p value) methods described to quantify lag-screw placement are the
TAD described by Baumgaertner et al. [7, 8] and the ratio
MM 3, 2.1% 134, 97.9% - method described by Parker [18]. A subsequent study has
SM 7, 36.8% 12, 63.2% <0.001a shown that a tip−apex distance of <20 mm improves the
IM 14, 4.1% 322, 95.9% 0.259a results [21]. Our study evaluated a greater number of cutout
MA 1, 7.1% 13, 92.9% 0.272a cases, and our findings were somewhat different to those in
SA 3, 20% 12, 80% 0.001a previous reports.
IA 4, 4.2% 90, 95.8% 0.368a In our study, two screw cutouts were noted in cases with
MP 7, 5% 131, 95% 0.202a TAD <20 mm, and no screw cutout was noted in cases with
SP 5, 33.3% 10, 66.7% <0.001a TAD <15 mm, similar to results in a previous report [21].
IP 20, 13.4% 149, 86.6% 0.001a Thus, we suggest that the TAD should be kept to be less
than 15 mm in avoiding cutout of lag screw. Although our
IM inferior/middle, SM superior/middle, MA middle/anterior, MP results support the hypothesis that TAD is the most
middle/posterior, SA superior/anterior, SP superior/posterior, IA
inferior/anterior, IP inferior/posterior, MM middle/middle
important factor in predicting lag-screw cutout with DHS,
a it is not the only factor. In this study, age, fracture pattern,
Chi-square test
fracture reduction, and screw position were also significant
factors. A significantly higher incidence of lag-screw cutout
There were 11 cases of cutout with TAD<25 mm and
was associated with unstable fracture and older age—
two cases with TAD <20 mm (one with TAD of 16 mm and
factors that cannot be controlled by the surgeon. These
the other with TAD of 18 mm). Eight of these 13 cases had
findings have not been reported in previous studies. As in
good screw position but poor fracture reduction, three had
previous studies [4, 12, 15, 17, 20–22], poor fracture
superior screw position and poor fracture reduction, and
reduction and superior screw position had an increased risk
two had superior screw position and good fracture
of cutout; however, in our study, posterior and not anterior
reduction. The average TAD was related to screw position,
screw position had a higher incidence of lag-screw cutout.
i.e., when the screw was in the superior or posterior
The best lag-screw position found in this study was the
position, the TAD was higher (Table 3).
middle/middle position, a finding different to that reported
by Wu et al. [25] who reported that the best position for the
lag screw was the inferior/middle position. We also found
Discussion
Table 3 Correlations of average tip−apex distance (TAD) and screw
Treating intertrochanteric fractures with a DHS may be positions and comparison of mean TAD between screw position with
associated with various complications, such as loss of lowest TAD (MM) and other screw positions

Screw position Mean TAD Comparison of TAD (mm)

with MM position (p value)

MM 19 -
SM 34.1 0.035a
IM 20.8 0.744a
MA 22.9 0.563a
SA 26.4 0.067a
IA 23.9 0.642a
MP 23.1 0.465a
SP 31.9 0.021a
IP 27.9 0.083a

IM inferior/middle,SM superior/middle, MA middle/anterior, MP

middle/posterior, SA superior/anterior, SP superior/posterior, IA
Fig. 2 Number of cutout and healed cases in different ranges of tip−apex inferior/anterior, IP inferior/posterior, MM middle/middle
a
distance (TAD) Analysis of variance (ANOVA), post hoc test
1276 International Orthopaedics (SICOT) (2010) 34:1273–1276

that screw position had a positive correlation with TAD: if 10. Kyle RF (1994) Fractures of the proximal part of the femur. J
Bone Joint Surg Am 76:924–950
the screw was in the peripheral positions, especially
11. Kyle RF, Gustilo RB, Premer RF (1976) Analysis of six hundred
posterior or superior, then TAD increased. Based on our and twenty-two intertrochanteric hip fractures. A retrospective and
findings, fracture reduction, implant position, and TAD are prospective study. J Bone Joint Surg Am 61:216–221
directly correlated, and these three factors should be 12. Geller JA, Saifi C, Morrison TA, Macaulay W (2009) Tip-apex
distance of intramedullary devices as a predictor of cut-out failure
adequately controlled by surgeons during the operation.
in the treatment of peritrochanteric elderly hip fractures. Int
In conclusion, to decrease the risk of lag-screw cutout, it Orthop. doi:10.1007/s00264-009-0837-7
is important to achieve good fracture reduction and to place 13. Larsson S, Friberg S, Hansson LI (1990) Trochanteric fractures.
the lag screw in middle/middle or inferior/middle position Influence of reduction and implant position on impaction and
complications. Clin Orthop 259:130–139
with appropriate TAD (<15 mm). In aged patients 14. Madsen JE, Naess L, Aune AK, Alho A, Ekeland A, Strømsøe K
(>70 years) and patients with unstable fracture, more (1998) Dynamic hip screw with trochanteric stabilizing plate in
attention must be paid to complications during the follow- the treatment of unstable proximal femoral fractures. A compar-
up. However, the limitations of this study, including the fact ative study with Gamma nail and compression hip screw. J Orthop
Trauma 12:241–248
that it was retrospective, had no preset treatment goals
15. Mainds CC, Newman RJ (1989) Implant failures in patients with
considering reposition and TAD, and there was no evaluation proximal fractures of the femur treated with a sliding screw
of bone mineral density, make a further prospective study device. Injury 20:98–100
necessary for more concrete conclusions. 16. Liu M, Yang Z, Pei F, Huang F, Chen S, Xiang Z (2009) A meta-
analysis of the Gamma nail and dynamic hip screw in treating
peritrochanteric fractures. Int Orthop. doi:10.1007/s00264-009-
0783-4, April Online Published
17. Parker MJ (1992) Cutting-out of the dynamic hip screw related to
References its position. J Bone Joint Surg Br 74:625
18. Nordin S, Zulkifli O, Faisham WI (2001) Mechanical failure of
1. American Society of Anesthesiologists (2009) New classification dynamic Hip Screw (DHS) fixation in intertrochanteric fracture of
of physical status. Anesthesiology 24:111 the femur. Med J Malaysia 56:12–17
2. Baumgaertner MR, Curtin SL, Lindskog DM, Keggi JM (1995) The 19. Parker MJ, Handoll HH (2008) Gamma and other cephalocon-
value of the tip-apex distance in predicting failure of fixation of peri- dylic intramedullary nails versus extramedullary implants for
trochanteric fractures of the hip. J Bone Joint Surg Am 77:1058–1064 extracapsular hip fractures in adults. Cochrane Database Syst Rev
3. Baumgaertner MR, Solberg BD (1997) Awareness of tip-apex 16(3):CD000093
distance reduces failure of fixation of trochanteric fractures of the 20. Parker MJ (1993) Valgus reduction of trochanteric fractures.
hip. J Bone Joint Surg Br 79:969–971 Injury 24:313–316
4. Bonamo JJ, Accettola AB (1982) Treatment of intertrochanteric 21. Pervez H, Parker MJ, Vowler S (2004) Prediction of fixation
fractures with a sliding nail-plate. J Trauma 22:205–215 failure after sliding hip screw fixation. Injury 35:994–998
5. Cleveland M, Bosworth DM, Thompson FR, Wilson HJ Jr, 22. Gundle R, Gargan MF, Simpson AH (1995) How to minimize
Ishizuka T (1959) A ten-year analysis of intertrochanteric failure of fixation of unstable intertrochanteric fractures. Injury
fractures of the femur. J Bone Joint Surg Am 41:1399–1408 26:611–614
6. Davis TR, Sher JL, Horsman A, Simpson M, Porter BB, 23. Saarenpää I, Heikkinen T, Ristiniemi J, Hyvönen P, Leppilahti J,
Checketts RG (1990) Intertrochanteric femoral fractures: mechan- Jalovaara P (2009) Functional comparison of the dynamic hip
ical failures after internal fixation. J Bone Joint Surg Br 72:26–31 screw and the Gamma locking nail in trochanteric hip fractures: a
7. Evans EM (1951) Trochanteric fractures: a review of 110 cases matched-pair study of 268 patients. Int Orthop 33:255–260
treated by nail-plate fixation. J Bone Joint Surg Br 33:192–204 24. Simpson AH, Varty K, Dodd CAF (1989) Sliding hip screw:
8. Garden RS (1961) Low-angle fixation in fractures of the femoral modes of failure. Injury 20:227–231
neck. J Bone Joint Surg Br 43:647–663 25. Wu CC, Shih CH, Lee MY, MS TCL (1996) Biomechanical
9. Kaufer H, Mattews LS, Sonstegard D (1974) Stable fixation of analysis of location of lag screw of a dynamic hip screw in
intertrochanteric fracture. A biomechanical evaluation. J Bone treatment of unstable intertrochanteric fracture. J Trauma 41:699–
Joint Surg Am 56:899–907 702