ORIGINAL ARTICLE
Predictors of iatrogenic lateral wall fractures while treating intertrochanteric fracture femur with the dynamic hip screw system in Indian patients
Deepak Joshi •Anoop C.Dhamangaonkar •
Sunil Ramawat •Arvind B.Goregaonkar
Received:30June 2014/Accepted:27October 2014/Published online:23November 2014ÓSpringer-Verlag France 2014
Abstract
Background The integrity of the lateral wall has been reported to be an important factor determining fracture stability in an intertrochanteric fracture.Iatrogenic the lateral wall fracture (ILWF)has been reported while reaming for the lag screw and the barrel of the dynamic hip screw (DHS).This study aimed to identify the predictors of iatrogenic lateral wall fractures (ILWF)while using the DHS,which will help to improve the pre-operative plan-ning and avoid their incidence.
Materials and methods A total of 120adult patients with intertrochanteric fracture femur treated with the DHS were included in this prospective series.Pre-operatively,the parameters noted were the demographic data,quality of bone using Singh’s index,fracture classification using AO/OTA and modified Evan’s system.The incidence of ILWF was recorded immediately after the fixation with the DHS.The two with ILWF and other without ILWF,were compared.
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Results The mean age of 46females and 74men in the study was 61years.Among 120patients,87(72.5%)patients had a posterior sag that had to be corrected while passing the guide wire and while reaming the neck of femur.The incidence of ILWF was 23.33%.The incidence of osteoporosis in patients with unstable fracture was 66.67%.1.7%patients with a stable AO/OTA A1fracture had ILWF,as compared to 50%of patients with type A2.2and type A2.3who sustained an ILWF (p \0.0001).None of the patients with a 2-part fracture on modified Evan’s classification had ILWF,while 53.84%with a 4-part fracture had ILWF (p \0.01).
Conclusion There is a high risk of ILWF using the DHS in unstable intertrochanteric fractures (AO type A2.2and A2.3or 4-part fracture patterns).Level of evidence IV (case series).
Keywords Iatrogenic ÁLateral wall ÁReaming ÁUnstable ÁIntertrochanteric
Introduction
Dynamic hip screw (DHS)has been the workhorse for intertrochanteric hip fracture fixation.But the utility of the DHS,as being the universal solution for all intertrochan-teric fractures,has been questioned.Traditionally,the medial and the posteromedial fracture fragments determine the stability of the intertrochanteric hip fracture.The integrity of lateral wall of proximal femur has now been recog
nised as an independent factor for fracture stability by providing rotational stability,preventing excessive col-lapse,preventing excess medialisation of the shaft,decreasing the reoperation rate and providing a better functional outcome [1].When the lateral wall is fractured,
D.Joshi ÁA.C.Dhamangaonkar (&)ÁA.B.Goregaonkar Department of Orthopaedics,Lokmanya Tilak Municipal Medical College and General Hospital,Sion,Mumbai 400022,India e-mail:anoopd_7@yahoo D.Joshi
e-mail:deepak7joshi7@gmail A.B.Goregaonkar
e-mail:abgortho@hotmail
A.C.Dhamangaonkar
2/28,Madhavi Soc.,Mogal Lane,Matunga (W),Mumbai 400016,India
S.Ramawat
Warringal Medical Centre,Melbourne,VIC,Australia e-mail:sunilramawat@gmail
Eur J Orthop Surg Traumatol (2015)25:677–682DOI 10.1007/s00590-014-1566-1
there is no lateral buttress to prevent the collapse of the proximal fragment leading to an uncontrolled collapse (Fig.1).Thus,the fracture of this delicate structure will convert an intertrochanteric fracture into a subtrochanteric fracture equivalent (Fig.2).This study aims to analyse the factors that would help predict the risk of an iatrogenic lateral wall fracture (ILWF)while treating intertrochanteric fracture femur with the DHS in Indian patients.
Materials and methods
This is a prospective case series from June 2011to May 2013.One hundred and thirty-one adult patients with intertrochanteric hip fractures were enrolled in this study.All the patients were treated at the authors’institution by one of the two senior orthopaedic surgeons who were familiar with the DHS fixation technique.The demographic data of all patients along with the Singh’s index and AO/OTA,and modified Evan’s classification of intertrochan-teric fractures was recorded at presentation.Among 131patients,11were excluded as they had pre-op lateral wall fracture and were classified as reverse oblique fractures.One hundred and twenty patients with intertrochanteric fractures were operated with DHS.All surgeries were performed under regional or general anaesthesia on a fracture table after a closed reduction of the fracture under an image intensifier (IITV)control.Iatrogenic fracture of the lateral wall was identified intra-operatively on the operating tab
le while reaming for the barrel of the lag screw.This was also confirmed on a post-operative
radiograph.The post-operative radiograph showed a frac-tured and proximally migrated greater trochanter,at the site of drilling for the barrel of the lag screw (Fig.3).All post-operative radiographs were analysed by an independent reviewer,another orthopaedic surgeon.Patients with an ILWF (Group 1)were identified from those without (Group 2).These two groups were analysed on basis of age (\65and [65years),sex,degree of osteoporosis (Singh’s index \3),pre-operative involvement of the lesser tro-chanter and that of the greater trochanter.Chi-square test was used to analyse the data using OpenEpi,version-2statistical software with 80%power and 5%significance.To understand the morphometry of proximal femoral region in Indian population,we measured the following dimensions in a pilot study.We measured the circumfer-ence of the cadaveric femoral shaft at 2cm below the vastus ridge,the proportion of the circumference contrib-uted by the lesser trochanter along with the posteromedial fragment.
Results
Forty-six women and 74men,with a mean age of 61(23–84)years,were included in the study.Among 120patients,87(72.5%)patients had a posterior sag that had to be corrected while passing the guide
wire and while reaming the neck of femur.Twenty-eight out of 120patients (23.33%)sustained an ILWF.23.52%(16out of 68)patients younger than 65years sustained ILWF and 23.07%(12out of 58)patients with an age more
than
Fig.1Lateral wall fracture converts a intertrochanteric fracture into a subtrochanteric equivalent
65years had ILWF (p =0.954).21.62%(16out of 74)males had ILWF as compared to 26.00%(12out of 46)females with ILWF (p =0.574).32.75%(19out of 58)patients with a Singh’s index B 3had ILWF as compared to 14.51%(9out of 62)patients with a Singh’s index [3who had ILWF (p =0.018).When a similar analysis was per-formed only on patients with an unstable intertrochanteric fracture,50%(16out of 32)patients with osteoporosis (with a Singh’s index B 3)had ILWF (p =0.941).The incidence of osteoporosis in patients with unstable fracture was 66.67%(32out of 48),and that in patients with a stable IT fracture was 36.11%(26out of 72).43%(24out
of 53)patients with a fractured lesser trochanter pre-operatively had ILWF as compared to 6%(4out of 67)patients with an intact lesser trochanter pre-operatively (p \0.01).When the data were analysed on the basis of AO/OTA classification,1/59(1.7%)patients with A1fracture sustained ILWF as compared to 24out of 48(50%)of patients with type A2.2and type A2.3who sustained ILWF (p \0.0001)(Table 1).None among the 47patients with a 2-part fracture on modified Evan’s classification sustained ILWF,while 21out of 39(53.84%)with a 4-part fracture had ILWF (p \0.01)(Table 2).Our pilot study was aimed to estimate the loss of cortical circumference in case of intertrochanteric fractures which could increase the risk of ILWF in smaller Indian femora.Among the ten cadaveric proximal fe
murs we analysed,the average circumference of the femur at 2cm below the vastus ridge (entry point of the DHS reamer)was 11.59cm (10.5–12.5cm),and the average sectoral cir-cumferential length of only the lesser trochanter
was
Fig.2Iatrogenic lateral wall fracture created after
reaming
Fig.3Separation of greater trochanter and proximal migration
Table 1Incidence of lateral wall fracture based on AO/OTA classification Classification ILWF (yes)ILWF (no)Percentage of ILWF A1.10110/11(0.00%)A1.21361/34(2.78%)A1.30100/10(0.00%)A11581/59(1.7%)A2.13113/14(21.42%)A2.2
lamento131313/26(50.00%)A2.3
111111/22(50.00%)A2.2and A2.3242424/48(50.0%)
Total
28
92
3.78cm(32.61%of the total circumference)while the average circumferential length of the lesser trochanter along with the posteromedial fragment was 6.22cm (53.67%of the total circumference).T
he diameter of the hole made by triple reamer was3cm(25.89%of the circumference),and thus,when the unstable intertrochan-teric fracture is compromised by53.67%,the lateral wall fracture is very likely.
Discussion
ILWF wasfirst reported by Gotfried[1].An intact lateral wall is fractured at the drilling site of a DHSfixation device in an unstable intertrochanteric hip fracture.The structural integrity of lateral wall support was thought to be essential for the successful treatment of unstable intertrochanteric fractures of the femur[2,3].
A major disadvantage of the DHS plates is the fact that the lateral cortex of the femur is breached by the sheer breadth of the reamer.This site of reaming is biomechan-ically important and is highly strained[4].This often leads to complications such as fracture of the greater trochanter leading to loss of stability.
According to Palm et al.[5],3%(5)of168patients with an intact lateral femoral wall post-operatively after a fixation with DHS system underwent a reoperation within 6months,whereas22%(10)of forty-six patients with a iatrogenic fractured lateral wall were reoperated.In their study,stable IT fractures(A
O31A1)had1.10%(1/84) incidence of ILWF while the unstable fractures(AO31 A2.2and A2.3)had a32%(31/97)incidence of ILWF. They recommended treating simple intertrochanteric frac-tures(A1–A2.1)with a sliding hip screw and treating more complex intertrochanteric fractures(A2.2–A3)with an intramedullary nail.Similarly,Joshua Langford et al.found high incidence of29.8%of lateral wall fracture in unstable IT fractures as classified by AO/OTA and modified Evan’s classifications[6].The incidence of ILWF in2-part frac-ture was7%,3-part fractures was23%and4-part frac-tures was50%after being treated with the DHS.They advised using percutaneous compression plate(PCCP)for unstable intertrochanteric fractures.
Our results showed that there was a significant risk (43.38%)of ILWF with a fractured and displaced lesser trochanter.Patients with AO classification31A2.2and31 A2.3had50%risk of an ILWF.Similarly,4-part IT fractures as per the modified Evan’s classification had a 53.84%risk of an ILWF.Both these susceptible fracture patterns had a fractured lesser trochanter as common denominator(Fig.4).Patients with a stable IT fracture as per AO/OTA or modified Evan’s classification had a neg-ligible incidence of ILWF(0–1.70%).All these patients had an intact or undisplaced fracture of the lesser tro-chanter and an intact calcar.
Our study suggested an association between osteoporo-sis and the incidence of ILWF.But we do sta
te that this association could be due to the fact that patients with osteoporosis were more likely to have an unstable inter-trochanteric fracture.This result was similar to a study by Gun et al.where the Singh’s index was not proved to be a significant factor predicting an ILWF[2].
Gotfried also implicated the large size of the reamer for DHS as being the culprit for the occurrence of ILWF[1].We strongly believe that use of a large reamer in thin and oste-oporotic bones was probably an important cause of ILWF.
In unstable IT fractures(with a large posteromedial void),especially among small-sized Indian femurs,only 40–50%of the bony circumference is intact for reaming at the entry point.The size of the drill hole created by triple reamer is2–3cm.In a small-sized femur,this accounts to drilling a3-cm hole in a weakened femur which has only 4.5–6cm bone left after an unstable intertrochanteric fracture as compared to drilling a3-cm hole in a bone with 10cm of bony circumference in a stable intertrochanteric fracture(Fig.5).We believe that the loss of the calcar support in IT fractures removes a very strong reinforce-ment that renders the lateral wall fragile,and this combined with a loss of bone circumference in an intertrochanteric fracture makes ILWF even more likely.
The posterior sag in an unstable intertrochanteric hip fracture could also be a contributory factor for l
小糊涂神歌词ateral wall fracture[6].If posterior sag goes uncorrected,the guide pin for the sliding hip screw would not be collinear with the shaft of the femur and the femoral neck.With this uncor-rected sag and non-collinear reaming of the thin lateral wall with the large triple reamer,often produces an audible crack of the lateral wall being shattered.It is also important to remember that posterior sag occurs more commonly in unstable intertrochanteric fractures which further increases the chance of ILWF.
李兆会个人资料The incidence of ILWF was higher in our study as compared to other studies by Palm et al.and Joshua Langford et al.[5,6].This difference could be due to the small size of femur in Indian patients with no provision for smaller or customised implants for our patients.Siwach
光良童话钢琴谱Classification ILWF(yes)ILWF(no)Total
2Part0470/47(0%)
3Part7277/34(20.58%) 4Part211821/39(53.84%) Total2892
Fig.4Analysis of ILWF.a ,b Unstable intertrochanteric fracture with a displaced lesser trochanter,c three-dimensional computerised tomography reconstruction of the lateral wall configuration in the unstable intertrochanteric fracture,d posterior wall fracture line seen
after erasing septum,e reamer separated from posterior void by only by a small bridge of bone,f delicate Anterior bone bridge also burst out,even after gentle
reaming
Fig.5Comparison of available circumference of the lateral wall for reaming in different IT patterns,a Circumference of the normal proximal femora at the site of reaming for the DHS lag screw,b available bone circumference for reaming in an unstable intertro-chanteric femur fracture,c available bone circumference for reaming in a stable intertrochanteric femur fracture
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