- Email: [email protected]
Tip to apex distance in femoral intertrochanteric fractures: a systematic review
J Orthop Sci (2013) 18:592–598 DOI 10.1007/s00776-013-0402-5
ORIGINAL ARTICLE
Tip to apex distance in femoral intertrochanteric fractures: a systematic review Jorge Rubio-Avila • Kim Madden • Nicole Simunovic • Mohit Bhandari
Received: 19 February 2013 / Accepted: 12 April 2013 / Published online: 2 May 2013 Ó The Japanese Orthopaedic Association 2013
Abstract Background Hip fractures are associated with high morbidity, mortality, and cost. Implants used for hip fracture fixation can fail for many reasons including lag screw cutout. Tip–apex distance (TAD) is indicative of the position and depth of a screw in the femoral head and has been shown to be associated with cut-out failure. We conducted a systematic review of the published literature to quantify the association between TAD and cut-out failure for patients undergoing hip fracture fixation surgery. Methods We performed a search of the Medline, Embase, and Cochrane databases. We performed abstract and full text reviews independently and in duplicate. We used a random effects model to combine, in duplicate, the incidence of cut-out for patients who had TAD \25 mm and TAD [25 mm. We also combined mean TAD values for patients who had cut-out failure and those who did not. Results Seventeen studies were eligible for this review, four of which were included in combined analysis of dichotomous outcomes and seven in combined analysis of continuous outcomes. Patients with TAD [25 mm had a significantly greater risk of cut-out than patients with TAD J. Rubio-Avila Clı´nica Medica, Sur. Av. Carnero # 5432 Fraccionamiento Arboledas, C.P. 45070, Zapopan, Jalisco, Mexico K. Madden N. Simunovic M. Bhandari (&) Department of Clinical Epidemiology and Biostatistics, McMaster University, 293 Wellington Street North, Suite 110, Hamilton, ON L8L 8E7, Canada e-mail: [email protected] K. Madden N. Simunovic M. Bhandari Division of Orthopaedic Surgery, Department of Surgery, McMaster University, 293 Wellington Street North, Suite 110, Hamilton, ON L8L 8E7, Canada
123
\25 mm (RR = 12.71). Patients who experienced implant cut-out had significantly higher TAD scores than those who did not (mean difference = 6.54 mm). Conclusion Tip–apex distance is an important concept in relation to cut-out failure of hip fracture fixation surgery. Surgeons should understand and apply the concept of TAD to improve outcomes for their patients.
Introduction There is a strong association between the incidence of proximal femoral fractures and high morbidity [1]. Intertrochanteric fractures have been described as one of the most common fractures among the elderly, and the number is likely to increase substantially over the next several decades [2]. Johnell [3] estimated the annual number of deaths globally from hip fractures was 730,000, with most (67 %) affecting women. In the United States, in 2007 alone, the Centers for Disease Control reported over 280,000 seniors admitted to hospitals for treatment of hip fractures [4]. The lifetime cost attributed to each hip fracture has been estimated to be over $80,000, with over 50 % of these expenses occurring in the year after injury, because of nursing, rehabilitation, and homecare facilities [5]. The economic costs and physical suffering associated with this type of injury are not only immense, but are likely to increase without implementation of preventive measures [6]. Surgical methods using implants are regularly used to treat patients presenting with hip fractures in health-care settings. A variety of different implants are used to treat hip fractures, for example plates, sliding mechanisms, screws, and nails [7]. Mechanical failure after screw implantation is commonly attributed to cut-out of the lag screw through
Tip to apex distance in femoral intertrochanteric fractures
the femoral head [8]. Cut-out failures may be averted by precise placement of the screw in the femoral head [8]. One method used to assist accurate measurement of screw position is calculation of the tip–apex distance (TAD) on anteroposterior and lateral radiographs. Specifically, this value is the sum of the distance from the apex of the femoral head to the top of the lag screw and is indicative of both the position and depth of a screw in the femoral head [9]. A TAD greater than 25 mm has been shown to be important in lag screw cut-out, a complication associated with high morbidity and mortality [10]. When the TAD is greater than 36 mm the probability of cut-out is greater than 30 %, and a TAD greater than 45 mm can lead to cutout 60 % of the time [11, 12]. Parmar et al. [10] reintroduced the concept of TAD to surgeons with the intention of improving the accuracy and quality of surgical technique. Accordingly, a large improvement was observed in TAD measurements on prospective radiographs compared with retrospective radiographs illustrating implant placement during hip fracture fixation. The authors concluded that introducing the concept of TAD to surgeons has a significant effect on the position of lag screw placement and on the incidence of cut-out complications. Although this information seems to be based on sound practical and theoretical rationale, the evidence for the association between TAD and cut-out failure has never been formally assessed in a systematic review and metaanalysis. Consequently, this systematic review was conducted to determine the extent to which TAD affects the incidence of cut-out for patients undergoing surgery for hip fracture fixation. This systematic summary enables clarification and elaboration of the importance of TAD in cutout failure because it provides the most complete evidence currently available about the relationship between TAD and cut-out failure.
Methods We conducted a systematic review of how TAD affects the incidence of cut-out in hip fracture fixation surgery. Efforts were made to include all published studies that compared the incidence of cut-out for patients with TAD [25 mm versus TAD \25 mm or that compared mean TAD for patients with cut-out failure versus those without cut-out failure. We performed an electronic search of the Medline, Embase, and Cochrane databases in November 2012. We identified articles in English that met three eligibility criteria: 1 the study was published in November 2012 or before; 2 the target population consisted of adults with hip fractures requiring surgical fixation; and
593
3
an objective of the study was to determine the relationship between TAD and cut-out failure.
We included all level I, II, and III evidence studies that met the inclusion criteria. We excluded case series studies, letters, comments, case reports, and guidelines. We used the search strategy: (‘‘hip fracture’’ OR ‘‘intertrochanteric fracture’’ OR ‘‘trochanteric fracture’’ OR ‘‘femur neck fracture’’) AND (‘‘tip apex distance’’ OR ‘‘tip–apex’’ OR ‘‘tip to apex distance’’ OR ‘‘TAD’’). Additional strategies used to identify studies included consultation with experts and a review of reference lists from articles that fulfilled our eligibility criteria. Assessment of study eligibility Two authors (JRA and KM) reviewed all titles for possible inclusion. Studies were excluded only if both reviewers agreed to exclude them on the basis of review title. Three of the authors (JRA, KM, and NS) independently assessed all identified abstracts and full texts for inclusion. Disagreements were resolved by discussion to achieve consensus. A senior reviewer (MB) was also available to resolve disagreements. We used the kappa statistic to determine level of reviewer agreement for study inclusion. Assessment of methodological quality Because randomly assigning patients to experience high TAD or low TAD is unethical, we knew the most common designs of included studies would be case–control and cohort, so we were able to choose an appropriate quality assessment tool in advance. Two reviewers, one with methodological expertise (KM) and one with content expertise (JRA) graded the methodological quality of each included study by use of questions from the Newcastle– Ottawa Quality Assessment Scale (NOS) for cohort and case–controls studies independently and in duplicate. Before data extraction, we determined that a score of 1–3 on the NOS is low quality, 4–6 is moderate quality and 7–9 is high quality. Data extraction and analysis One reviewer (JRA) extracted study characteristics on the basis of a pre-designed data extraction form. We extracted the incidence of cut-out for patients with TAD of greater than 25 mm versus those for patients with TAD of less than 25 mm (dichotomous data). We also extracted mean TAD for patients who had cut-out failure versus those who did not (continuous data). The two outcomes were extracted independently in duplicate by two of the reviewers (KM and JRA) to increase reliability. We also performed
123
594
J. Rubio-Avila et al.
subgroup analysis of the association between implant type (intramedullary devices versus extramedullary devices) and TAD. We analyzed study characteristics by using descriptive statistics and combined the primary outcomes by use of the DerSimonian–Laird random-effects model [13] implemented by Review Manager Version 5. We used the I2 statistic to formally assess heterogeneity.
the other studies were conducted in Australia, Turkey, Spain, Israel, the Netherlands, Taiwan, and China. Eleven of the included studies were case–control studies and six were cohort studies. We judged six studies to be of high methodological quality and eleven studies to be of moderate quality. A total of 4,910 patients were included in this systematic review. Most of the patients included were female and over the age of 65.
Results
Incidence of cut-out by TAD
Study identification
We were able to extract enough data on this outcome from four studies [9, 11, 14, 15]. Figure 2 shows the incidence of cut-out for each study by whether the patient had TAD \25 mm or TAD[25 mm. On the basis of these data, the relative risk was 12.71 (95 % CI: 2.41–67.12; p = 0.003). Heterogeneity of the data was fairly high (I2 = 65 %) because of the different implants and population characteristics.
Our literature search identified 57 potentially relevant citations, of which 27 were considered for inclusion after abstract review (Fig. 1). Ten of these 27 studies were excluded after full text review. A total of seventeen studies were therefore included in this review. We were able to combine results for four studies for the dichotomous outcome (high TAD versus low TAD group) and seven studies for the continuous outcome (mean TAD for cut-out versus no cut-out group). Inter-rater agreement was good for fulltext inclusion (j = 0.611; 95 % CI: 0.305–0.917). Absolute agreement was 81 %. Study characteristics Details of the selected studies are shown in Table 1. Many studies were conducted in the US (5/17, 29 %) and the UK (3/17, 18 %). Two studies were conducted in Germany and Fig. 1 Flow chart of study process
123
Mean TAD for patients who had cut-out failure vs. patients who did not have cut-out failure We were able to extract enough data on this outcome from seven studies [9, 16–21]. Figure 3 shows the mean TAD for patients who had cut-out failure versus patients who did not have cut-out failure. On the basis of these data, the mean difference was 6.54 (95 % CI: 2.37–10.72; p = 0.002). Heterogeneity of the data was high (I2 = 82 %) and may be related to different implants and population characteristics.
Tip to apex distance in femoral intertrochanteric fractures
595
Table 1 Included study characteristics Ref.
Location
Type of implant
Number of patients
% Female patients
Mean age (years)
Quality
Andruszkow et al. [17]
Germany
Dynamic hip screw; Gamma nail
235
70.2
80.8 ± 11.0
High
Baumgaertner and Solberg [8]
USA
Fixed-angle DHS and either a sideplate or an IM nail
311 (316 fractures)
NR
Study group: 81 Control group: 77
High
Baumgaertner [9]
USA
Dynamic hip screw
193 (198 fractures)
73
78
Moderate
Brammar et al. [23]
UK
Dynamic hip screw; Medoff plates; SHS and stabilizing plate Gamma nail (Stryker/S&N) Targon nail PF
101
80
77.3
Moderate
De Bruijn et al. [16]
Netherlands
Dynamic hip screw; Gamma nail
215
78
Geller et al. [14]
USA
2nd and 3rd generation gamma nail (Stryker)
82
84.1
Gu¨ven et al. [11]
Turkey
65
32.3
78.0 ± 14.9
Moderate
78 ± 12
Moderate
Long trochanteric fixation nail (Synthes) Dynamic hip screw
TAD \25 mm 63.14 ± 16.76
Moderate
TAD [25 mm 56.12 ± 16.6 Herman et al. [19]
Israel
Targon PF (Aesculap)
227
77
Antirotation trochanteric nail (dePuy)
Cut-out group: 78.2 (SD 14.9)
High
No failure group: 75.3 (SD 15.74) Holt et al. [25]
UK
IM Hip Screw (S&N)
158
74
Proximal femur nail (Synthes)
IMHS: 77.3
High
PFN: 80.4
Hsueh et al. [15]
China
Dynamic hip screw
937
39.4
Inglis and Jaarsma [24] Kyle et al. [21]
Australia
IM Hip screw (Smith and Nephew)
26
84.6
USA
Dynamic hip screw
20
35
65
Moderate
Lenich et al. [7]
Germany
Proximal femoral nail (Synthes)
322
Cut-out group: 78.8
81
Moderate
Gleitnagel (S&N) Trochanteric fixation nail (Synthes)
Spain
Gamma nail 2nd gen.
81.9
Moderate Moderate
Control group: 81.3
Proximal femur nail antirotation (Synthes) Lobo-Escolar et al. [20]
NR
1231
Trochanteric nail (Stryker) Subtrochanteric nail (Zimmer)
Cut-out group: 78.8 Control group: 81.3
Pervez et al. [22]
UK
Dynamic hip screw
100
78
SchmidtRohlfing et al. [18]
USA
PCCP implant
96
72
Wu and Tai [26]
Taiwan
Sliding compression screw
591
NR
Cut-out group: 81.1 ± 7.9
High
Control group: 83.6 ± 6.5
81 80 ± 10
NR
Moderate High
Moderate
NR not reported
123
596
Study or Subgroup Baumgaertner 1995 Geller 2010 Guven 2010 Hsueh 2010
J. Rubio-Avila et al. TAD >25mm TAD <25mm Events Total Events Total Weight 19 7 3 53
Total (95% CI)
78 23 51 196
0 0 1 11
19.0% 18.7% 23.9% 38.4%
59.73 [3.66, 975.23] 41.88 [2.48, 705.69] 0.82 [0.09, 7.32] 18.19 [9.69, 34.16]
940 100.0%
12.71 [2.41, 67.12]
120 66 14 740
348
Risk Ratio M-H, Random, 95% CI Year
Total events 82 12 Heterogeneity: Tau² = 1.77; Chi² = 8.65, df = 3 (P = 0.03); I² = 65% Test for overall effect: Z = 2.99 (P = 0.003)
Risk Ratio M-H, Random, 95% CI
1995 2010 2010 2010
1 10 0.01 0.1 100 Favours TAD >25mm Favours TAD
Fig. 2 Incidence of cut-out by high TAD or low TAD
Study or Subgroup
Cut-out No cut-out SD Total Weight SD Total Mean Mean
Baumgaertner 1995 Kyle 2005 Lobo-Escolar 2010 Schmidt-Rohlfing 2012 Andruszkow 2012 DeBruijn 2012 Herman 2012
5 38 7 26 32.2 11.4 18 47 26.99 6.09 25.9 8.6 24 6.5
24 13.5 16 7 30 5 23.8 8.5 33 10 33 5 8 19.65 7.76 21.3 6.1 16 20.3 6.5 15 98
Total (95% CI)
Mean Difference IV, Random, 95% CI Year
182 15 315 91 227 199 207
17.3% 12.4% 16.3% 5.1% 15.9% 16.0% 17.0%
14.00 [10.86, 17.14] -4.00 [-11.08, 3.08] 8.40 [4.40, 12.40] 14.00 [-1.91, 29.91] 7.34 [3.00, 11.68] 4.60 [0.30, 8.90] 3.70 [0.29, 7.11]
1236
100.0%
6.54 [2.37, 10.72]
Mean Difference IV, Random, 95% CI
1995 2005 2010 2012 2012 2012 2012
Heterogeneity: Tau² = 23.61; Chi² = 33.97, df = 6 (P < 0.00001); I² = 82% Test for overall effect: Z = 3.07 (P = 0.002)
-20 -10 0 20 10 Favours Cut-out Favours No cut-out
Fig. 3 Mean TAD for cut-out group versus no cut-out group
Study or Subgroup 1.3.1 IM devices Lobo-Escolar 2010 Herman 2012 Subtotal (95% CI)
Cut-out No cut-out Mean SD Total Mean SD Total Weight 32.2 11.4 24 6.5
33 15 48
23.8 20.3
8.5 6.5
315 207 522
Mean Difference IV, Random, 95% CI Year
32.8% 34.5% 67.2%
8.40 [4.40, 12.40] 2010 3.70 [0.29, 7.11] 2012 5.93 [1.33, 10.53]
23.7% 9.0% 32.8%
-4.00 [-11.08, 3.08] 2005 14.00 [-1.91, 29.91] 2012 3.53 [-13.87, 20.94]
Mean Difference IV, Random, 95% CI
Heterogeneity: Tau² = 7.45; Chi² = 3.07, df = 1 (P = 0.08); I² = 67% Test for overall effect: Z = 2.53 (P = 0.01) 1.3.2 EM devices Kyle 2005 Schmidt-Rohlfing 2012 Subtotal (95% CI)
26 47
7 18
5 5 10
30 33
7 10
15 91 106
Heterogeneity: Tau² = 122.52; Chi² = 4.10, df = 1 (P = 0.04); I² = 76% Test for overall effect: Z = 0.40 (P = 0.69) Total (95% CI)
58
628 100.0%
Heterogeneity: Tau² = 19.24; Chi² = 10.72, df = 3 (P = 0.01); I² = 72% Test for overall effect: Z = 1.57 (P = 0.12) Test for subgroup differences: Chi² = 0.07, df = 1 (P = 0.79), I² = 0%
4.34 [-1.09, 9.77] -20 -10 10 20 0 Favours Cut-out Favours No cut-out
Fig. 4 Subgroup analysis of implant type (IM versus EM)
For the seven included studies that did not have sufficient data to combine incidence of cut-out or continuous data, all seven studies agreed TAD is an accurate predictor of incidence of cut-out [7, 8, 22–26]. Subgroup analysis: intramedullary versus extramedullary devices We had enough information to perform subgroup analysis of implant type (IM compared to EM devices) and its effect
123
on mean TAD for patients who had cut-out failure versus those who did not. We included two studies in the IM group and two studies in the EM group. The mean difference between IM devices was 5.93 mm (95 % CI: 1.33–10.53; p = 0.01). The mean difference was not significant for EM devices (3.53 mm, 95 % CI: -13.87 to 20.94; p = 0.69) (Fig. 4). This result should be interpreted with caution because the sample size of EM devices compared with IM devices was small, resulting in increased variance around the point estimate.
Tip to apex distance in femoral intertrochanteric fractures
Discussion In this systematic review we assessed the effect of TAD on incidence of cut-out in hip fracture fixation surgery. Our findings confirm that TAD values [25 mm result in a significantly greater risk of cut-out than lower values, but, on the basis of subgroup analysis, this effect is not significant when looking at extramedullary implants alone. Fracture fixation devices for hip fractures may fail for many reasons, including patient-related factors, fracture type, bone quality, and implant design [27–29]. Baumgaertner et al. [9] sought to explain screw placement (one of the factors associated with implant failure) by developing a quantitative measure that predicts outcomes, specifically cut-out. Our review shows that TAD is important in cut-out failure. The concept of TAD is important because it enables the surgeon to quickly assess one aspect of the quality of hip fracture fixation surgery. Parmar and Kumar [10] found that surgeons who understood the concept of TAD were able to place implants for fixation of extracapsular femoral fractures more accurately than other surgeons. Understanding the concept of TAD can assist surgeons in properly placing implants, potentially leading to better outcomes for patients. This systematic review demonstrates the importance of TAD in cut-out failure, but there are very few data on such functional outcomes as pain and reduced function in relation to TAD. Only one study included in this review evaluated the effects of TAD on functional outcomes. The study found no association between TAD and cut-out and no association between TAD and functional scores [11]. Theoretically, because high TAD is associated with increased risk of cut-out failure, it should also be associated with poorer functional outcomes, increased pain, increased risk of non-union, and increased need for reoperation. Future studies should focus on patient-important outcomes related to high TAD and on making recommendations about when surgeons should perform revision surgery to correct high TAD. Our study has several strengths. We conducted a comprehensive search of the literature and reviewed, in duplicate, all abstracts and full texts for inclusion. We extracted primary outcome data from eligible studies independently and in duplicate to ensure accuracy, and the included studies were usually of moderate to high quality. Despite these strengths, our study is limited by large heterogeneity (I2 = 65 % for dichotomous data and 82 % for continuous data) which may be partially explained by implant type (IM compared to EM devices). The studies included had different population characteristics and involved a variety of different surgeons, with differing skills, and several different types of implant; these are likely to have contributed to the variations. Another limitation is that in some studies
597
patients who had cut-out failure were significantly more likely to be over the age of 80 and to have an unstable fracture compared with patients with no cut-out failure, potentially confounding the results [15]. An important limitation in TAD research is the inability to conduct randomized controlled trials, because assigning patients to high TAD or low TAD groups would be infeasible and unethical. Although we were unable to include level I evidence studies (randomized controlled trials) in this meta-analysis, we were still able to include level II and III evidence (cohort and case–control) studies, which is the best available evidence in these circumstances. Despite the limitations, our combined data show that the risk of cut-out is closely associated with higher TAD, but this effect is not statistically significant when considering extramedullary devices only. Because TAD is an important concept in relation to cut-out failure of hip fracture fixation surgery, surgeons should understand and apply the concept of TAD to improve outcomes for their patients. Acknowledgments The authors would like to acknowledge Alice Chen and Sahaana Rangarajan for their assistance with administrative tasks. Conflict of interest of interest.
The authors declare that they have no conflict
References 1. Keene G, Parker M, Pryor G. Mortality and morbidity after hip fractures. BMJ. 1993;307:1248–50. 2. Brandt SE, Lefever S, Janzing HMJ, Broos PLO, Pilot P, Houben BJ. Percutaneous compression plating (PCCP) versus the dynamic hip screw for pertrochanteric hip fractures: preliminary results. Injury. 2002;33:413–8. 3. Johnell O, Kanis JA. An estimate of the worldwide prevalence, mortality and disability associated with hip fracture. Osteoporos Int. 2004;15:897–902 (Epub 2004). 4. Centers for Disease Control and Prevention. Hip Fractures Among Older Adults [Internet]. Atlanta (GA): USA.gov; [2010; cited 2010]. http://www.cdc.gov/homeandrecreationalsafety/ falls/adulthipfx.html. 5. Braithwaite R, Col N, Wong J. Estimating hip fracture morbidity, mortality, and costs. J Am Geriatr Soc. 2003;51:364–70. 6. Autier P, Haentjens J, Bentin J, Baillon JM, Grivegnee AR, Closon MC, Boonen S. Costs induced by hip fractures: a prospective controlled study in Belgium. Osteoporos Int. 2000;11: 373–80. 7. Lenich A, Vester H, Nerlich M, Mayr E, Sto¨ckle U, Fu¨chtmeier B. Clinical comparison of the second and third generation of intramedullary devices for trochanteric fractures of the hip— blade vs screw. Injury. 2010;41:1292–6. 8. Baumgaertner MR, Solberg BD. Awareness of tip–apex distance reduces failure of fixation of trochanteric fractures of the hip. JBJS. 1997;79:969–71. 9. Baumgaertner MR, Curtin SL, Lindskog DM, Keggi JM. The value of the tip–apex distance in predicting failure of fixation of peritrochanteric fractures of the hip. J Bone Joint Surg Am. 1995;77:1058–64.
123
598 10. Parmar V, Kumar A. The importance of surgical education in the accuracy of implant placement during hip fracture fixation. J Orthop Traumatol. 2009;10:59–61. 11. Gu¨ven M, Yavuz U, Kadiog˘lu B, Akman B, Kilinc¸og˘lu V, Unay K, Altintas¸ F. Importance of screw position in intertrochanteric femoral fractures treated by dynamic hip screw. Orthop Traumatol Surg Res. 2010;96:21–7. 12. Stern R, Lu¨bbeke A, Suva D, Miozzari H, Hoffmeyer P. Prospective randomised study comparing screw versus helical blade in the treatment of low-energy trochanteric fractures. Int Orthop. 2011;35:1855–61 (Epub 2011). 13. DerSimonian R, Laird N. Meta-analysis in clinical trials. Control Clin Trials. 1986;7:177–88. 14. Geller JA, Saifi C, Morrison TA, Macaulay W. Tip–apex distance of intramedullary devices as a predictor of cut-out failure in the treatment of peritrochanteric elderly hip fractures. Int Orthop. 2010;34:719–22. 15. Hsueh KK, Fang CK, Chen CM, Su YP, Wu HF, Chiu FY. Risk factors in cutout of sliding hip screw in intertrochanteric fractures: an evaluation of 937 patients. Int Orthop. 2010;34:1273–6 (Epub 2009). 16. De Bruijn K, den Hartog D, Tuinebreijer W, Roukema G. Reliability of Predictors for Screw Cut-out in Intertrochanteric Hip Fractures. J Bone Joint Surg Am. 2012;94:1266–72. 17. Andruszkow H, Frink M, Fro¨mke C, Matityahu A, Zeckey C, Mommsen P, Suntardjo S, Krettek C, Hildebrand F. Tip apex distance, hip screw placement, and neck shaft angle as potential risk factors for cut-out failure of hip screws after surgical treatment of intertrochanteric fractures. Int Orthop. 2012;36:2347–54. doi:10.1007/s00264-012-1636-0 (Epub 2012). 18. Schmidt-Rohlfing B, Heussen N, Knobe M, Pfeifer R, Kaneshige JR, Pape HC. Re-operation rate after internal fixation of intertrochanteric femur fractures with the Percutaneous Compression Plate (PCCP): what are the risk factors? J Orthop Trauma. 2012 (Epub ahead of print).
123
J. Rubio-Avila et al. 19. Herman A, Landau Y, Gutman G, Ougortsin V, Chechick A, Shazar N. Radiological evaluation of intertrochanteric fracture fixation by the proximal femoral nail. Injury. 2012;43:856–63 (Epub 2011). 20. Lobo-Escolar A, Joven E, Iglesias D, Herrera A. Predictive factors for cutting-out in femoral intramedullary nailing. Injury. 2010;41:1312–6 (Epub 2010). 21. Kyle RF, Ellis TJ, Templeman DC. Surgical treatment of intertrochanteric hip fractures with associated femoral neck fractures using a sliding hip screw. J Orthop Trauma. 2005;19:1–4. 22. Pervez H, Parker MJ, Vowler S. Prediction of fixation failure after sliding hip screw fixation. Injury. 2004;35:994–8. 23. Brammar TJ, Kendrew J, Khan RJ, Parker MJ. Reverse obliquity and transverse fractures of the trochanteric region of the femur; a review of 101 cases. Injury. 2005;36:851–7 (Epub 2005). 24. Inglis MRB, Jaarsma RL. Intramedullary hip screw fixation of reverse oblique and transverse trochanteric femur fractures. Eur J Orthop Surg Traumatol. 2008;18:323–6. 25. Holt G, Nunag P, Duncan K, Gregori A. Outcome after short intramedullary nail fixation of unstable proximal femoral fractures. Acta Orthop Belg. 2010;76:347–55. 26. Wu CC, Tai CL. Effect of lag-screw positions on modes of fixation failure in elderly patients with unstable intertrochanteric fractures of the femur. J Orthop Surg (Hong Kong). 2010;18:158–65. 27. Heineman DJ, van Buijtenen JM, Heuff G, Derksen EJ, Po RG. Intra-abdominal migration of a lag screw in gamma nailing: report of a case. J Orthop Trauma. 2010;24:e119–22. 28. Frank MA, Yoon RS, Yalamanchili P, Choung EW, Liporace FA. Forward progression of the helical blade into the pelvis after repair with the trochanter fixation nail (TFN). J Orthop Trauma. 2011;25:e100–3. 29. Lenich A, Bachmeier S, Dendorfer S, Mayr E, Nerlich M, Fu¨chtmeier B. Development of a test system to analyze different hip fracture osteosyntheses under simulated walking. Biomed Tech (Berl). 2012;57:113–9. doi:10.1515/bmt-2011-0999.
ORIGINAL ARTICLE
Tip to apex distance in femoral intertrochanteric fractures: a systematic review Jorge Rubio-Avila • Kim Madden • Nicole Simunovic • Mohit Bhandari
Received: 19 February 2013 / Accepted: 12 April 2013 / Published online: 2 May 2013 Ó The Japanese Orthopaedic Association 2013
Abstract Background Hip fractures are associated with high morbidity, mortality, and cost. Implants used for hip fracture fixation can fail for many reasons including lag screw cutout. Tip–apex distance (TAD) is indicative of the position and depth of a screw in the femoral head and has been shown to be associated with cut-out failure. We conducted a systematic review of the published literature to quantify the association between TAD and cut-out failure for patients undergoing hip fracture fixation surgery. Methods We performed a search of the Medline, Embase, and Cochrane databases. We performed abstract and full text reviews independently and in duplicate. We used a random effects model to combine, in duplicate, the incidence of cut-out for patients who had TAD \25 mm and TAD [25 mm. We also combined mean TAD values for patients who had cut-out failure and those who did not. Results Seventeen studies were eligible for this review, four of which were included in combined analysis of dichotomous outcomes and seven in combined analysis of continuous outcomes. Patients with TAD [25 mm had a significantly greater risk of cut-out than patients with TAD J. Rubio-Avila Clı´nica Medica, Sur. Av. Carnero # 5432 Fraccionamiento Arboledas, C.P. 45070, Zapopan, Jalisco, Mexico K. Madden N. Simunovic M. Bhandari (&) Department of Clinical Epidemiology and Biostatistics, McMaster University, 293 Wellington Street North, Suite 110, Hamilton, ON L8L 8E7, Canada e-mail: [email protected] K. Madden N. Simunovic M. Bhandari Division of Orthopaedic Surgery, Department of Surgery, McMaster University, 293 Wellington Street North, Suite 110, Hamilton, ON L8L 8E7, Canada
123
\25 mm (RR = 12.71). Patients who experienced implant cut-out had significantly higher TAD scores than those who did not (mean difference = 6.54 mm). Conclusion Tip–apex distance is an important concept in relation to cut-out failure of hip fracture fixation surgery. Surgeons should understand and apply the concept of TAD to improve outcomes for their patients.
Introduction There is a strong association between the incidence of proximal femoral fractures and high morbidity [1]. Intertrochanteric fractures have been described as one of the most common fractures among the elderly, and the number is likely to increase substantially over the next several decades [2]. Johnell [3] estimated the annual number of deaths globally from hip fractures was 730,000, with most (67 %) affecting women. In the United States, in 2007 alone, the Centers for Disease Control reported over 280,000 seniors admitted to hospitals for treatment of hip fractures [4]. The lifetime cost attributed to each hip fracture has been estimated to be over $80,000, with over 50 % of these expenses occurring in the year after injury, because of nursing, rehabilitation, and homecare facilities [5]. The economic costs and physical suffering associated with this type of injury are not only immense, but are likely to increase without implementation of preventive measures [6]. Surgical methods using implants are regularly used to treat patients presenting with hip fractures in health-care settings. A variety of different implants are used to treat hip fractures, for example plates, sliding mechanisms, screws, and nails [7]. Mechanical failure after screw implantation is commonly attributed to cut-out of the lag screw through
Tip to apex distance in femoral intertrochanteric fractures
the femoral head [8]. Cut-out failures may be averted by precise placement of the screw in the femoral head [8]. One method used to assist accurate measurement of screw position is calculation of the tip–apex distance (TAD) on anteroposterior and lateral radiographs. Specifically, this value is the sum of the distance from the apex of the femoral head to the top of the lag screw and is indicative of both the position and depth of a screw in the femoral head [9]. A TAD greater than 25 mm has been shown to be important in lag screw cut-out, a complication associated with high morbidity and mortality [10]. When the TAD is greater than 36 mm the probability of cut-out is greater than 30 %, and a TAD greater than 45 mm can lead to cutout 60 % of the time [11, 12]. Parmar et al. [10] reintroduced the concept of TAD to surgeons with the intention of improving the accuracy and quality of surgical technique. Accordingly, a large improvement was observed in TAD measurements on prospective radiographs compared with retrospective radiographs illustrating implant placement during hip fracture fixation. The authors concluded that introducing the concept of TAD to surgeons has a significant effect on the position of lag screw placement and on the incidence of cut-out complications. Although this information seems to be based on sound practical and theoretical rationale, the evidence for the association between TAD and cut-out failure has never been formally assessed in a systematic review and metaanalysis. Consequently, this systematic review was conducted to determine the extent to which TAD affects the incidence of cut-out for patients undergoing surgery for hip fracture fixation. This systematic summary enables clarification and elaboration of the importance of TAD in cutout failure because it provides the most complete evidence currently available about the relationship between TAD and cut-out failure.
Methods We conducted a systematic review of how TAD affects the incidence of cut-out in hip fracture fixation surgery. Efforts were made to include all published studies that compared the incidence of cut-out for patients with TAD [25 mm versus TAD \25 mm or that compared mean TAD for patients with cut-out failure versus those without cut-out failure. We performed an electronic search of the Medline, Embase, and Cochrane databases in November 2012. We identified articles in English that met three eligibility criteria: 1 the study was published in November 2012 or before; 2 the target population consisted of adults with hip fractures requiring surgical fixation; and
593
3
an objective of the study was to determine the relationship between TAD and cut-out failure.
We included all level I, II, and III evidence studies that met the inclusion criteria. We excluded case series studies, letters, comments, case reports, and guidelines. We used the search strategy: (‘‘hip fracture’’ OR ‘‘intertrochanteric fracture’’ OR ‘‘trochanteric fracture’’ OR ‘‘femur neck fracture’’) AND (‘‘tip apex distance’’ OR ‘‘tip–apex’’ OR ‘‘tip to apex distance’’ OR ‘‘TAD’’). Additional strategies used to identify studies included consultation with experts and a review of reference lists from articles that fulfilled our eligibility criteria. Assessment of study eligibility Two authors (JRA and KM) reviewed all titles for possible inclusion. Studies were excluded only if both reviewers agreed to exclude them on the basis of review title. Three of the authors (JRA, KM, and NS) independently assessed all identified abstracts and full texts for inclusion. Disagreements were resolved by discussion to achieve consensus. A senior reviewer (MB) was also available to resolve disagreements. We used the kappa statistic to determine level of reviewer agreement for study inclusion. Assessment of methodological quality Because randomly assigning patients to experience high TAD or low TAD is unethical, we knew the most common designs of included studies would be case–control and cohort, so we were able to choose an appropriate quality assessment tool in advance. Two reviewers, one with methodological expertise (KM) and one with content expertise (JRA) graded the methodological quality of each included study by use of questions from the Newcastle– Ottawa Quality Assessment Scale (NOS) for cohort and case–controls studies independently and in duplicate. Before data extraction, we determined that a score of 1–3 on the NOS is low quality, 4–6 is moderate quality and 7–9 is high quality. Data extraction and analysis One reviewer (JRA) extracted study characteristics on the basis of a pre-designed data extraction form. We extracted the incidence of cut-out for patients with TAD of greater than 25 mm versus those for patients with TAD of less than 25 mm (dichotomous data). We also extracted mean TAD for patients who had cut-out failure versus those who did not (continuous data). The two outcomes were extracted independently in duplicate by two of the reviewers (KM and JRA) to increase reliability. We also performed
123
594
J. Rubio-Avila et al.
subgroup analysis of the association between implant type (intramedullary devices versus extramedullary devices) and TAD. We analyzed study characteristics by using descriptive statistics and combined the primary outcomes by use of the DerSimonian–Laird random-effects model [13] implemented by Review Manager Version 5. We used the I2 statistic to formally assess heterogeneity.
the other studies were conducted in Australia, Turkey, Spain, Israel, the Netherlands, Taiwan, and China. Eleven of the included studies were case–control studies and six were cohort studies. We judged six studies to be of high methodological quality and eleven studies to be of moderate quality. A total of 4,910 patients were included in this systematic review. Most of the patients included were female and over the age of 65.
Results
Incidence of cut-out by TAD
Study identification
We were able to extract enough data on this outcome from four studies [9, 11, 14, 15]. Figure 2 shows the incidence of cut-out for each study by whether the patient had TAD \25 mm or TAD[25 mm. On the basis of these data, the relative risk was 12.71 (95 % CI: 2.41–67.12; p = 0.003). Heterogeneity of the data was fairly high (I2 = 65 %) because of the different implants and population characteristics.
Our literature search identified 57 potentially relevant citations, of which 27 were considered for inclusion after abstract review (Fig. 1). Ten of these 27 studies were excluded after full text review. A total of seventeen studies were therefore included in this review. We were able to combine results for four studies for the dichotomous outcome (high TAD versus low TAD group) and seven studies for the continuous outcome (mean TAD for cut-out versus no cut-out group). Inter-rater agreement was good for fulltext inclusion (j = 0.611; 95 % CI: 0.305–0.917). Absolute agreement was 81 %. Study characteristics Details of the selected studies are shown in Table 1. Many studies were conducted in the US (5/17, 29 %) and the UK (3/17, 18 %). Two studies were conducted in Germany and Fig. 1 Flow chart of study process
123
Mean TAD for patients who had cut-out failure vs. patients who did not have cut-out failure We were able to extract enough data on this outcome from seven studies [9, 16–21]. Figure 3 shows the mean TAD for patients who had cut-out failure versus patients who did not have cut-out failure. On the basis of these data, the mean difference was 6.54 (95 % CI: 2.37–10.72; p = 0.002). Heterogeneity of the data was high (I2 = 82 %) and may be related to different implants and population characteristics.
Tip to apex distance in femoral intertrochanteric fractures
595
Table 1 Included study characteristics Ref.
Location
Type of implant
Number of patients
% Female patients
Mean age (years)
Quality
Andruszkow et al. [17]
Germany
Dynamic hip screw; Gamma nail
235
70.2
80.8 ± 11.0
High
Baumgaertner and Solberg [8]
USA
Fixed-angle DHS and either a sideplate or an IM nail
311 (316 fractures)
NR
Study group: 81 Control group: 77
High
Baumgaertner [9]
USA
Dynamic hip screw
193 (198 fractures)
73
78
Moderate
Brammar et al. [23]
UK
Dynamic hip screw; Medoff plates; SHS and stabilizing plate Gamma nail (Stryker/S&N) Targon nail PF
101
80
77.3
Moderate
De Bruijn et al. [16]
Netherlands
Dynamic hip screw; Gamma nail
215
78
Geller et al. [14]
USA
2nd and 3rd generation gamma nail (Stryker)
82
84.1
Gu¨ven et al. [11]
Turkey
65
32.3
78.0 ± 14.9
Moderate
78 ± 12
Moderate
Long trochanteric fixation nail (Synthes) Dynamic hip screw
TAD \25 mm 63.14 ± 16.76
Moderate
TAD [25 mm 56.12 ± 16.6 Herman et al. [19]
Israel
Targon PF (Aesculap)
227
77
Antirotation trochanteric nail (dePuy)
Cut-out group: 78.2 (SD 14.9)
High
No failure group: 75.3 (SD 15.74) Holt et al. [25]
UK
IM Hip Screw (S&N)
158
74
Proximal femur nail (Synthes)
IMHS: 77.3
High
PFN: 80.4
Hsueh et al. [15]
China
Dynamic hip screw
937
39.4
Inglis and Jaarsma [24] Kyle et al. [21]
Australia
IM Hip screw (Smith and Nephew)
26
84.6
USA
Dynamic hip screw
20
35
65
Moderate
Lenich et al. [7]
Germany
Proximal femoral nail (Synthes)
322
Cut-out group: 78.8
81
Moderate
Gleitnagel (S&N) Trochanteric fixation nail (Synthes)
Spain
Gamma nail 2nd gen.
81.9
Moderate Moderate
Control group: 81.3
Proximal femur nail antirotation (Synthes) Lobo-Escolar et al. [20]
NR
1231
Trochanteric nail (Stryker) Subtrochanteric nail (Zimmer)
Cut-out group: 78.8 Control group: 81.3
Pervez et al. [22]
UK
Dynamic hip screw
100
78
SchmidtRohlfing et al. [18]
USA
PCCP implant
96
72
Wu and Tai [26]
Taiwan
Sliding compression screw
591
NR
Cut-out group: 81.1 ± 7.9
High
Control group: 83.6 ± 6.5
81 80 ± 10
NR
Moderate High
Moderate
NR not reported
123
596
Study or Subgroup Baumgaertner 1995 Geller 2010 Guven 2010 Hsueh 2010
J. Rubio-Avila et al. TAD >25mm TAD <25mm Events Total Events Total Weight 19 7 3 53
Total (95% CI)
78 23 51 196
0 0 1 11
19.0% 18.7% 23.9% 38.4%
59.73 [3.66, 975.23] 41.88 [2.48, 705.69] 0.82 [0.09, 7.32] 18.19 [9.69, 34.16]
940 100.0%
12.71 [2.41, 67.12]
120 66 14 740
348
Risk Ratio M-H, Random, 95% CI Year
Total events 82 12 Heterogeneity: Tau² = 1.77; Chi² = 8.65, df = 3 (P = 0.03); I² = 65% Test for overall effect: Z = 2.99 (P = 0.003)
Risk Ratio M-H, Random, 95% CI
1995 2010 2010 2010
1 10 0.01 0.1 100 Favours TAD >25mm Favours TAD
Fig. 2 Incidence of cut-out by high TAD or low TAD
Study or Subgroup
Cut-out No cut-out SD Total Weight SD Total Mean Mean
Baumgaertner 1995 Kyle 2005 Lobo-Escolar 2010 Schmidt-Rohlfing 2012 Andruszkow 2012 DeBruijn 2012 Herman 2012
5 38 7 26 32.2 11.4 18 47 26.99 6.09 25.9 8.6 24 6.5
24 13.5 16 7 30 5 23.8 8.5 33 10 33 5 8 19.65 7.76 21.3 6.1 16 20.3 6.5 15 98
Total (95% CI)
Mean Difference IV, Random, 95% CI Year
182 15 315 91 227 199 207
17.3% 12.4% 16.3% 5.1% 15.9% 16.0% 17.0%
14.00 [10.86, 17.14] -4.00 [-11.08, 3.08] 8.40 [4.40, 12.40] 14.00 [-1.91, 29.91] 7.34 [3.00, 11.68] 4.60 [0.30, 8.90] 3.70 [0.29, 7.11]
1236
100.0%
6.54 [2.37, 10.72]
Mean Difference IV, Random, 95% CI
1995 2005 2010 2012 2012 2012 2012
Heterogeneity: Tau² = 23.61; Chi² = 33.97, df = 6 (P < 0.00001); I² = 82% Test for overall effect: Z = 3.07 (P = 0.002)
-20 -10 0 20 10 Favours Cut-out Favours No cut-out
Fig. 3 Mean TAD for cut-out group versus no cut-out group
Study or Subgroup 1.3.1 IM devices Lobo-Escolar 2010 Herman 2012 Subtotal (95% CI)
Cut-out No cut-out Mean SD Total Mean SD Total Weight 32.2 11.4 24 6.5
33 15 48
23.8 20.3
8.5 6.5
315 207 522
Mean Difference IV, Random, 95% CI Year
32.8% 34.5% 67.2%
8.40 [4.40, 12.40] 2010 3.70 [0.29, 7.11] 2012 5.93 [1.33, 10.53]
23.7% 9.0% 32.8%
-4.00 [-11.08, 3.08] 2005 14.00 [-1.91, 29.91] 2012 3.53 [-13.87, 20.94]
Mean Difference IV, Random, 95% CI
Heterogeneity: Tau² = 7.45; Chi² = 3.07, df = 1 (P = 0.08); I² = 67% Test for overall effect: Z = 2.53 (P = 0.01) 1.3.2 EM devices Kyle 2005 Schmidt-Rohlfing 2012 Subtotal (95% CI)
26 47
7 18
5 5 10
30 33
7 10
15 91 106
Heterogeneity: Tau² = 122.52; Chi² = 4.10, df = 1 (P = 0.04); I² = 76% Test for overall effect: Z = 0.40 (P = 0.69) Total (95% CI)
58
628 100.0%
Heterogeneity: Tau² = 19.24; Chi² = 10.72, df = 3 (P = 0.01); I² = 72% Test for overall effect: Z = 1.57 (P = 0.12) Test for subgroup differences: Chi² = 0.07, df = 1 (P = 0.79), I² = 0%
4.34 [-1.09, 9.77] -20 -10 10 20 0 Favours Cut-out Favours No cut-out
Fig. 4 Subgroup analysis of implant type (IM versus EM)
For the seven included studies that did not have sufficient data to combine incidence of cut-out or continuous data, all seven studies agreed TAD is an accurate predictor of incidence of cut-out [7, 8, 22–26]. Subgroup analysis: intramedullary versus extramedullary devices We had enough information to perform subgroup analysis of implant type (IM compared to EM devices) and its effect
123
on mean TAD for patients who had cut-out failure versus those who did not. We included two studies in the IM group and two studies in the EM group. The mean difference between IM devices was 5.93 mm (95 % CI: 1.33–10.53; p = 0.01). The mean difference was not significant for EM devices (3.53 mm, 95 % CI: -13.87 to 20.94; p = 0.69) (Fig. 4). This result should be interpreted with caution because the sample size of EM devices compared with IM devices was small, resulting in increased variance around the point estimate.
Tip to apex distance in femoral intertrochanteric fractures
Discussion In this systematic review we assessed the effect of TAD on incidence of cut-out in hip fracture fixation surgery. Our findings confirm that TAD values [25 mm result in a significantly greater risk of cut-out than lower values, but, on the basis of subgroup analysis, this effect is not significant when looking at extramedullary implants alone. Fracture fixation devices for hip fractures may fail for many reasons, including patient-related factors, fracture type, bone quality, and implant design [27–29]. Baumgaertner et al. [9] sought to explain screw placement (one of the factors associated with implant failure) by developing a quantitative measure that predicts outcomes, specifically cut-out. Our review shows that TAD is important in cut-out failure. The concept of TAD is important because it enables the surgeon to quickly assess one aspect of the quality of hip fracture fixation surgery. Parmar and Kumar [10] found that surgeons who understood the concept of TAD were able to place implants for fixation of extracapsular femoral fractures more accurately than other surgeons. Understanding the concept of TAD can assist surgeons in properly placing implants, potentially leading to better outcomes for patients. This systematic review demonstrates the importance of TAD in cut-out failure, but there are very few data on such functional outcomes as pain and reduced function in relation to TAD. Only one study included in this review evaluated the effects of TAD on functional outcomes. The study found no association between TAD and cut-out and no association between TAD and functional scores [11]. Theoretically, because high TAD is associated with increased risk of cut-out failure, it should also be associated with poorer functional outcomes, increased pain, increased risk of non-union, and increased need for reoperation. Future studies should focus on patient-important outcomes related to high TAD and on making recommendations about when surgeons should perform revision surgery to correct high TAD. Our study has several strengths. We conducted a comprehensive search of the literature and reviewed, in duplicate, all abstracts and full texts for inclusion. We extracted primary outcome data from eligible studies independently and in duplicate to ensure accuracy, and the included studies were usually of moderate to high quality. Despite these strengths, our study is limited by large heterogeneity (I2 = 65 % for dichotomous data and 82 % for continuous data) which may be partially explained by implant type (IM compared to EM devices). The studies included had different population characteristics and involved a variety of different surgeons, with differing skills, and several different types of implant; these are likely to have contributed to the variations. Another limitation is that in some studies
597
patients who had cut-out failure were significantly more likely to be over the age of 80 and to have an unstable fracture compared with patients with no cut-out failure, potentially confounding the results [15]. An important limitation in TAD research is the inability to conduct randomized controlled trials, because assigning patients to high TAD or low TAD groups would be infeasible and unethical. Although we were unable to include level I evidence studies (randomized controlled trials) in this meta-analysis, we were still able to include level II and III evidence (cohort and case–control) studies, which is the best available evidence in these circumstances. Despite the limitations, our combined data show that the risk of cut-out is closely associated with higher TAD, but this effect is not statistically significant when considering extramedullary devices only. Because TAD is an important concept in relation to cut-out failure of hip fracture fixation surgery, surgeons should understand and apply the concept of TAD to improve outcomes for their patients. Acknowledgments The authors would like to acknowledge Alice Chen and Sahaana Rangarajan for their assistance with administrative tasks. Conflict of interest of interest.
The authors declare that they have no conflict
References 1. Keene G, Parker M, Pryor G. Mortality and morbidity after hip fractures. BMJ. 1993;307:1248–50. 2. Brandt SE, Lefever S, Janzing HMJ, Broos PLO, Pilot P, Houben BJ. Percutaneous compression plating (PCCP) versus the dynamic hip screw for pertrochanteric hip fractures: preliminary results. Injury. 2002;33:413–8. 3. Johnell O, Kanis JA. An estimate of the worldwide prevalence, mortality and disability associated with hip fracture. Osteoporos Int. 2004;15:897–902 (Epub 2004). 4. Centers for Disease Control and Prevention. Hip Fractures Among Older Adults [Internet]. Atlanta (GA): USA.gov; [2010; cited 2010]. http://www.cdc.gov/homeandrecreationalsafety/ falls/adulthipfx.html. 5. Braithwaite R, Col N, Wong J. Estimating hip fracture morbidity, mortality, and costs. J Am Geriatr Soc. 2003;51:364–70. 6. Autier P, Haentjens J, Bentin J, Baillon JM, Grivegnee AR, Closon MC, Boonen S. Costs induced by hip fractures: a prospective controlled study in Belgium. Osteoporos Int. 2000;11: 373–80. 7. Lenich A, Vester H, Nerlich M, Mayr E, Sto¨ckle U, Fu¨chtmeier B. Clinical comparison of the second and third generation of intramedullary devices for trochanteric fractures of the hip— blade vs screw. Injury. 2010;41:1292–6. 8. Baumgaertner MR, Solberg BD. Awareness of tip–apex distance reduces failure of fixation of trochanteric fractures of the hip. JBJS. 1997;79:969–71. 9. Baumgaertner MR, Curtin SL, Lindskog DM, Keggi JM. The value of the tip–apex distance in predicting failure of fixation of peritrochanteric fractures of the hip. J Bone Joint Surg Am. 1995;77:1058–64.
123
598 10. Parmar V, Kumar A. The importance of surgical education in the accuracy of implant placement during hip fracture fixation. J Orthop Traumatol. 2009;10:59–61. 11. Gu¨ven M, Yavuz U, Kadiog˘lu B, Akman B, Kilinc¸og˘lu V, Unay K, Altintas¸ F. Importance of screw position in intertrochanteric femoral fractures treated by dynamic hip screw. Orthop Traumatol Surg Res. 2010;96:21–7. 12. Stern R, Lu¨bbeke A, Suva D, Miozzari H, Hoffmeyer P. Prospective randomised study comparing screw versus helical blade in the treatment of low-energy trochanteric fractures. Int Orthop. 2011;35:1855–61 (Epub 2011). 13. DerSimonian R, Laird N. Meta-analysis in clinical trials. Control Clin Trials. 1986;7:177–88. 14. Geller JA, Saifi C, Morrison TA, Macaulay W. Tip–apex distance of intramedullary devices as a predictor of cut-out failure in the treatment of peritrochanteric elderly hip fractures. Int Orthop. 2010;34:719–22. 15. Hsueh KK, Fang CK, Chen CM, Su YP, Wu HF, Chiu FY. Risk factors in cutout of sliding hip screw in intertrochanteric fractures: an evaluation of 937 patients. Int Orthop. 2010;34:1273–6 (Epub 2009). 16. De Bruijn K, den Hartog D, Tuinebreijer W, Roukema G. Reliability of Predictors for Screw Cut-out in Intertrochanteric Hip Fractures. J Bone Joint Surg Am. 2012;94:1266–72. 17. Andruszkow H, Frink M, Fro¨mke C, Matityahu A, Zeckey C, Mommsen P, Suntardjo S, Krettek C, Hildebrand F. Tip apex distance, hip screw placement, and neck shaft angle as potential risk factors for cut-out failure of hip screws after surgical treatment of intertrochanteric fractures. Int Orthop. 2012;36:2347–54. doi:10.1007/s00264-012-1636-0 (Epub 2012). 18. Schmidt-Rohlfing B, Heussen N, Knobe M, Pfeifer R, Kaneshige JR, Pape HC. Re-operation rate after internal fixation of intertrochanteric femur fractures with the Percutaneous Compression Plate (PCCP): what are the risk factors? J Orthop Trauma. 2012 (Epub ahead of print).
123
J. Rubio-Avila et al. 19. Herman A, Landau Y, Gutman G, Ougortsin V, Chechick A, Shazar N. Radiological evaluation of intertrochanteric fracture fixation by the proximal femoral nail. Injury. 2012;43:856–63 (Epub 2011). 20. Lobo-Escolar A, Joven E, Iglesias D, Herrera A. Predictive factors for cutting-out in femoral intramedullary nailing. Injury. 2010;41:1312–6 (Epub 2010). 21. Kyle RF, Ellis TJ, Templeman DC. Surgical treatment of intertrochanteric hip fractures with associated femoral neck fractures using a sliding hip screw. J Orthop Trauma. 2005;19:1–4. 22. Pervez H, Parker MJ, Vowler S. Prediction of fixation failure after sliding hip screw fixation. Injury. 2004;35:994–8. 23. Brammar TJ, Kendrew J, Khan RJ, Parker MJ. Reverse obliquity and transverse fractures of the trochanteric region of the femur; a review of 101 cases. Injury. 2005;36:851–7 (Epub 2005). 24. Inglis MRB, Jaarsma RL. Intramedullary hip screw fixation of reverse oblique and transverse trochanteric femur fractures. Eur J Orthop Surg Traumatol. 2008;18:323–6. 25. Holt G, Nunag P, Duncan K, Gregori A. Outcome after short intramedullary nail fixation of unstable proximal femoral fractures. Acta Orthop Belg. 2010;76:347–55. 26. Wu CC, Tai CL. Effect of lag-screw positions on modes of fixation failure in elderly patients with unstable intertrochanteric fractures of the femur. J Orthop Surg (Hong Kong). 2010;18:158–65. 27. Heineman DJ, van Buijtenen JM, Heuff G, Derksen EJ, Po RG. Intra-abdominal migration of a lag screw in gamma nailing: report of a case. J Orthop Trauma. 2010;24:e119–22. 28. Frank MA, Yoon RS, Yalamanchili P, Choung EW, Liporace FA. Forward progression of the helical blade into the pelvis after repair with the trochanter fixation nail (TFN). J Orthop Trauma. 2011;25:e100–3. 29. Lenich A, Bachmeier S, Dendorfer S, Mayr E, Nerlich M, Fu¨chtmeier B. Development of a test system to analyze different hip fracture osteosyntheses under simulated walking. Biomed Tech (Berl). 2012;57:113–9. doi:10.1515/bmt-2011-0999.