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CT based measurement of anatomical dimensions of femur and its relevance in nail designs for proximal femoral fractures
Journal Pre-proof CT based measurement of anatomical dimensions of femur and its relevance in nail designs for proximal femoral fractures. Mahesh Kulkarni, Monappa Naik A, Chethan B. Shetty, Samir M. Paruthikunnan, Sharath K. Rao PII:
S0972-978X(19)30620-8
DOI:
https://doi.org/10.1016/j.jor.2019.12.002
Reference:
JOR 909
To appear in:
Journal of Orthopaedics
Received Date: 26 September 2019 Accepted Date: 8 December 2019
Please cite this article as: Kulkarni M, Naik A M, Shetty CB, Paruthikunnan SM, Rao SK, CT based measurement of anatomical dimensions of femur and its relevance in nail designs for proximal femoral fractures., Journal of Orthopaedics, https://doi.org/10.1016/j.jor.2019.12.002. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier B.V. on behalf of Professor P K Surendran Memorial Education Foundation.
Title: CT based measurement of anatomical dimensions of femur and its relevance in nail designs for proximal femoral fractures. Authors: Mahesh Kulkarni1, Monappa Naik A2, Chethan B Shetty3, Samir M Paruthikunnan4, Sharath K Rao5 1Assistant Professor, Department of Orthopedics 2 Associate Professor, Department of Orthopedics. Corresponding Author:
ORCID: 0000-0003-3147-050X ORCID: 0000-0002-8107-0873
Email ID [email protected] Contact Number: +919448484894
3 Senior Resident, Department of Orthopedics
ORCID: 0000-0003-4459-6099
Kasturba Medical College, Manipal Academy of Higher Education, Manipal, Karnataka, India. 4 Assistant Professor, Department of Radiology 5 Professor, Department of Orthopedics
ORCID: 0000-0002-6013-2537
Kasturba Medical College, Manipal Academy of Higher Education, Manipal, Karnataka, India. Conflict of interest: There was no internal/external source of funding for this study and authors also declare no conflict of interest regarding submission and publication of this manuscript.
CT based measurement of anatomical dimensions of femur and its relevance in nail designs for proximal femoral fractures. Author contribution: MN Aroor: Protocol development, Manuscript editing. MS Kulkarni: Data Analysis, Manuscript Editing. CB Shetty: Data management, Data analysis, Manuscript writing. SM Paruthikunnan: Data management, Data analysis. SK Rao: Protocol development, Manuscript editing.
TITLE: CT based measurement of anatomical dimensions of femur and its relevance in nail designs for proximal femoral fractures. Abstract: Introduction: The purpose of this study was to obtain computed tomography (CT) based measurements of femoral dimensions in adults, to identify its relevance with intramedullary nails used in the management of proximal femur fractures and to suggest a best fitting implant dimensions to our population. To best of our knowledge our study would be first to compile different CT based dimension in single study. Methods: In our retrospective study of 50 femurs, CT based femoral dimensions measured in standardized cuts and compared with previous studies and commonly available proximal femur intramedullary devices. Results: 68.4 was the mean age in our study, neck shaft angle (NSA) was 127.2±5.20, anteversion 11.2±7.40, endosteal isthmus diameter was 11.9±1.7 mm, anterior radius of curvature (ROC) was 116.8±20 mm, horizontal femoral offset 37.5±4.6 mm, medio-lateral angle 7.8±1.60, with good inter and intra observer correlation. Femoral length and neck width was positively correlated to head diameter, horizontal femoral offset with medio-lateral (ML) angle. One of the 50 femur studied had the parameters in the range of available implant and could match appropriately Conclusion: CT based dimensions in our population is different from other population. Based on this study, a design modification of nails used in present day management of proximal femur fractures has been recommended. 1
Keywords: Femoral dimension, Neck shaft angle, Proximal femur fractures, CT, Implant mismatch, Anteversion, Intramedullary nail.
2
CT based measurement of anatomical dimensions of femur and its relevance in nail designs for proximal femoral fractures. 1. Introduction: Incidence of pertrochanteric fractures are on the rise in most of the developed and developing countries. Low velocity injuries in growing elderly population and high velocity injuries in the younger population due to increase in motor vehicle accidents are the main reasons.1 For most of these fractures cephalomedullary nailing has become the treatment of choice over extramedullary devices due to the cited advantages of intramedullary fixation, decreased lever arm, decreased blood loss, stable construct, load sharing nature of the construct and small incision.2 Restoring the anatomical alignment and stable fixation are the key to successful outcome. Many investigators have noted the mismatch between the designed implant and prosthesis which are commercially available with that of the femur geometry.3–6 Mismatch between the profile of the implant and proximal femur anatomy will lead to the difficulty in maintaining the fracture reduction and hence subsequent malalignment which will result in complications and suboptimal outcome.3,4,7–9 There are no studies in the literature which have described the mismatch between the proximal femur morphology using the clinically relevant CT scan and available implants for the fixation of pertrochanteric fractures in the elderly population. The purpose of this study is to obtain CT based measurements and to study the femoral dimensions in adults, to identify its relevance with nails used in management of proximal femur fractures. In this study we hypothesized that commonly used nailing systems will have the wide options which can cater the need of the best fit implant for the native morphology of the injured proximal femur. It is normally expected that the implant manufacturers would have evaluated
3
morphological and anatomical characteristic of the bone and would have manufactured the implants as per the requirement. 2. Materials and Methods: In this retrospective study we identified consecutive 50 skeletally matured patients with per trochanteric fractures who were having the full length CT images of the unaffected femur which was taken as a part of the evaluation of the fracture. Patients with history of previous surgery or with bony deformity of the unaffected side were excluded. Ethical committee approval for the study was obtained (IEC No. 633/2016). Femoral dimensions were measured by two independent observers with following parameters. All CT were imaged under standard specifications using Philips brilliance 64 slice MDCT with slice thickness – 0.9 mm, slice increment – 0.45 mm, Kv – 140, mAs/slice – 300, pitch – 0.484, rotation time – 0.75 sec, collimation 64X0.625, matrix – 768 pixels and measured using software Phillips Intellispace portal V 4.0.2. All the measurements were calculated in oblique standardized cuts.10–12 [Fig 1] Supero-inferior (SI) Head diameter, SI Neck width, Neck shaft angle, Head diameter AP, Neck width AP, Femoral offset, Medio-lateral angle, Anteversion, Isthmus diameter, Isthmus distance, Femur shaft length and Anterior radius of curvature of femur are the femoral dimensions measured from the standard cuts. Details are available in the annexure I and II. 3. Statistical Analysis: Descriptive statistics were used for describing the demographic details. Independent ‘t’ test was used to compare the means between the male and female groups. Pearson correlation was used to find the correlation between the femoral dimensions. Spearman correlation and unpaired 2 tailed 4
t test was used to analyze statistical significance between age and femoral dimensions. Concordance between the examiners were calculated (intra and inter observer variability) and assessed using interclass correlation coefficient (ICC). 4. Results: We analysed 50 femur CTs with mean age being 68.42±13.68 yrs of which majority were males 29/50 [Fig 2]. We found reasonably good interclass correlation coefficient ICC 0.92 to 0.96 in all the measurements and in ROC, ICC was 0.83 suggesting good agreement between intra and inter observer measurements. Our typical patient had SI head diameter of 43.8±3.59mm, SI neck width of 24.76±3.47mm, neck shaft angle of 127.22 ±5.22 º anteversion of 10.08±9.57 and femoral length of 419.53±28.50 mm. Table 1: Table showing various mean values of femur morphology and influence of Gender Mean
Male
Female
P
Age( Yr)
68.42±13.68
65.38±14.58
72.62±11.37
0.122
Head Diameter AP(mm)
43.48±3.34
45.54±2.28
40.63±2.30
0.000*
Head Diameter SI(mm)
43.8±3.59
45.94±2.65
40.84±2.46
0.000*
Neck width AP (mm)
22.93±4.17
23.45±4.34
22.20±3.90
0.302
Neck width SI (mm)
24.76±3.47
26.50±2.81
22.36±2.84
0.000*
Anteversion (º)
10.08±9.57
7.81±9.97
13.21±8.22
0.048*
Isthmus (mm)
11.85±1.70
11.87±1.93
11.80±1.37
0.882
Isthmus Distance (mm)
171.53±25.12
176.18±26.69
165.11±21.78
0.125
Femoral length (mm)
419.53±28.50
433.09±28.23
400.80±15.46
0.000*
Anterior Radius of curvature (cm)
116.77±19.99
119.49±17.68
113.02±22.73
0.263
5
Neck shaft angle(º)
127.22±5.22
128.27±5.39
125.76±4.72
0.095
Femoral Offset(mm)
37.32±5.91
37.45±4.57
37.13±7.49
0.852
Lateral angle(º)
7.76±1.60
8.07±1.70
7.33±1.38
0.108
* ‘P’ value < 0.05 There was significant difference in the measurements of femur head, neck, femoral anteversion and femur length parameters between male and female patients (Table 1). There was a significant correlation was found between the various parameters as shown in Table 2. Table 2: List of the various femur Morphological parameters correlation. Correlations
Correlation
P value
coefficient (r) Head Diameter SI vs AP
0.921
0.000**
Neck width SI vs Head Diameter AP
0.692
0.000**
Neck width SI vs Head Diameter SI
0.595
0.000**
Isthmus vs Neck width AP
-0.330
0.019*
Isthmus distance vs Head Diameter AP
0.303
0.032*
Isthmus distance vs Head Diameter SI
0.397
0.004**
Isthmus distance vs Isthmus
0.485
0.000**
Femoral Length vs Femoral head AP
0.652
0.000**
Femoral Length vs Femoral head SI
0.726
0.000**
Femoral Length vs Neck width SI
0.517
0.000**
Femoral Length vs Isthmus
0.325
0.021*
6
Femoral Length vs Isthmus Distance
0.532
0.000*
Neck shaft angle vs Neck width AP
0.374
0.008*
Neck shaft angle vs Isthmus
-0.330
0.019*
Neck shaft angle vs Isthmus distance
-0.309
0.029*
Femoral Offset vs Neck width AP
0.461
0.00**
Lateral angle Vs Anteversion
-0.316
0.025*
* ‘P’ value < 0.05 ** ‘P’ value < 0.001 We compared our results with published western, eastern and with Indian studies (Table 3). Table 3: Comparison of Femur morphological features of various other population Study
Neck shaft
Population Angle (º)
Anteversion Isthmus(mm) Ant
Femur
Head
ROC(cm) Length(mm) Diameter
(º)
in mm Chinese &
125.6±6 to
11.4±7.7 to
South east
134±4.4
19.8±9.3
Indian &
123±4.3
8.7±6.6 to
South Asia
to126.8±5.8 13.6±7.9
9.6
112±23.4
NA
40.8±3.4 to 44.35
Asia 9±1.9
NA
418.8 to
41.7±3.1
436.5
to 45.4±3.7
Our study
127.2±5.2
11.2±7.4
11.9±1.7
7
116.8±20
419±28.5
43.5 ±
3.3, 43.8 ± 3.6 Western
122.9±7.6
countries
to
13.1±8
13.1±2.1 to
112 to
378.6±23.2
14.1±2.8
120±40
to
134.2±5.2
NA
409.8±28,2
We also compared and contrasted our measurements with commonly available and used 3 intramedullary devices (Table 4). We mainly focused on best fit based on Neck shaft angle, anteversion and additionally with ROC measurements. We found 1/50 femur was having morphological parameters in the range of available fixation devices. Table 4: Best fit analysis of the available nails with the femur morphology and our recommended nailing option. Parameters
Nail A, B &
Best fit
overall
C
Our
Best fit
Overall
120 º -140 º
48(96%)
45(90%)
-10 º TO 30 º
47(94%)
100-140
40(80%)
recommendati on
Neck shaft
125 º to135 º
30(60%)
3(6%)
angle Anteversion 10 & 15 Roc
127.5 , 140,
(cm)
152.5
3(6%) 16(32%)
1(2%)
5. Discussion: 8
36(72%)
Due to the increase in the geriatric population and motor vehicle accidents pertrochanteric fractures are on the rise worldwide. Many implant manufacturers are offering the devices for these fractures which have limited options in different sizes which are expected to fit in most of the femurs. Variations in the femur morphometry has been noted by many investigators which varies with age, gender, race, ethnicity and regional customs like sitting cross legged or squatting. 6,12–15 This heterogeneity in the morphometric parameters of the femur should be considered in the designing of suitable implants. Many investigators have evaluated the morphology of proximal femur with respect to the prosthetic replacement. 6,14 Mismatch of the implants with the bony anatomy lead to loss of reduction, penetration of the nail, mismatch between the locking hole and aiming device, screw cut through, delayed union, malunion, nonunion, failure of the implants and increased morbidity. 2,7,8,16,17 We wanted to evaluate the morphological features of the femur primarily and evaluation of the suitability of the available implants for the described femur morphology was the secondary objective of this study. Major chunk of our study population belonged to elderly population which is due to the inclusion criteria as pertrochanteric fractures are common in this age group. And hence it can be considered as representative of elderly population. Due to imprecise positioning problems Radiographs are not reliable for accurate measurements. 6,13 CT studies are preferred in the morphological evaluation which can also give valuable information about the nature of the fracture and articular surfaces. In our series male femurs had bigger heads, broader neck and longer femoral length when compared to females. 18 Females had significantly more anteverted femoral neck.11 [Fig 3] Males and females had almost similar isthmus, anterior radius of curvature, neck shaft angle, femoral offset and lateral angle (Table 1). On analyzing the parameters on the age distribution we didn’t 9
find any significant changes across age group in our study. This could be attributed to the fact that we didn’t have many cases from the younger age group in our population which could have given the insight regarding variation in the morphology due to age. 6,11,13,19 On comparing with Chinese/ south east Asian populations our study group had lesser neck shaft angle, anteversion. But isthmus diameter and head diameter were similar. 6,11,14,15 On comparing with the western population our study group had lesser neck shaft angle, smaller isthmus and similar anteversion and femur length. 4,10,13,18,20. Our morphological parameters are in concurrence with the studies from Indian and south Asian subcontinent.1,5,21,22,22 One parameter which didn’t differ among the populations was anterior Radius of curvature which was fairly similar in all the populations. Also we didn’t observe any significant changes due to age, gender and sidedness on ROC which are partially in line with other studies.3,4,20 One interesting finding what we observed in our series was lateral angle was inversely correlating with the anteversion [Fig 4]. We also observed that Neck shaft angle was directly correlated with neck width but inversely correlated with the isthmus [Fig 5]. Which can explain the increase in the pertrochanteric fractures in persons with higher NSA as neck will be stronger in these patients and less likely to fail.23,24 We collected the information regarding the sizes of the available implants from the manufacturer’s website. As varying options for the length of the nails were available, isthmus could be reamed appropriately and lateral angle slightly different from the mean. We didn’t consider femoral length, isthmus diameter and lateral angle for the best fit measurement. Of all the other parameters neck shaft angle and anteversion cannot be adjusted and were fixed or having very less options. NSA and anteversion are important because mismatch in these parameters will lead to the loss of reduction and fixation in suboptimal way which may 10
jeopardize the outcome. Jiang et al have shown that in total a gap of 25mm and Riehl et al have shown that an angulation of >10º in either coronal or sagittal plane will have bad outcome.11,25 Only one of the 50 proximal femur which were analysed was having the parameters which could result in proper fit with the available implants. When ROC was excluded it increased to 3 femurs which could have had proper fit. Availability of the implant system which offer varied options as suggested with NSA, anteversion and ROC in nails could have increased the overall fit to 72%. If we exclude the ROC mismatch which can be adjusted by using thinner, shorter nail or by reaming to some extent, up to 90% of the femurs will accommodate the proper fitting of such nail.7,8 (Table 4). Bicer et al in their study using cadaveric bones and light scanning method to assess the measurements also had the similar findings of mismatch of nails and the native femur morphological parameters.9 Hence we recommend having nails with wider options available in neck shaft angle and anteversion. We also suggest CT evaluation to include the opposite whole femur which can give the valuable information regarding the morphological features of the native bone. Strengths of this study are uniformity in the sample population which represent one of the most common fracture patterns treated routinely in the clinical setting. Evaluation of the femur morphology which was done by CT which is easily available and gives better clinically relevant accurate information when compared to plain radiographs. Limitations of this study is that it does not represent the entire adult population but a subset of it. Our sample size is only 50. A study with larger study group would have been preferred. In this study we didn’t evaluate the functional outcome of the fracture treated with cephalomedullary nailing which could have given final verdict regarding the fixation of the fracture using mismatched implant. A randomised control study with large number of cases comparing the 11
regular implants and properly fitting implants in pertrochanteric fracture management would give the ideal verdict. Having implants with multiple options in NSA, Anteversion, ROC, femoral length and diameter will lead to the requirement of the huge inventory and logistical nightmare. We suggest development of the newer intramedullary devices having the intrinsic mechanism or to have modular options to adjust the NSA and anteversion to accommodate the variations seen commonly in proximal femur. 6. Conclusion: There is a wide variation of the anatomical measures with respect to neck shaft angle (NSA) and anteversion in proximal femur anatomy. This needs to be addressed during selection of the implants with appropriate angles to fix the fracture in anatomical position. This probably can be achieved by having modular proximal femur implants.
Funding: Nil Conflict of interest: There was no external source of funding for this study and no conflicts of interest regarding submission and publication of this manuscript.
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Refererences: 1.
Pathrot D, Ul Haq R, Aggarwal A, Nagar M, Bhatt S. Assessment of the geometry of proximal femur for short cephalomedullary nail placement: An observational study in dry femora and living subjects. Indian J Orthop. 2016;50(3):269.
2.
Shukla S, Johnston P, Ahmad MA, Wynn-Jones H, Patel AD, Walton NP. Outcome of traumatic subtrochanteric femoral fractures fixed using cephalo-medullary nails. Injury. 2007 Nov;38(11):1286–93.
3.
Harma A, Germen B, Karakas HM, Elmali N, Inan M. The comparison of femoral curves and curves of contemporary intramedullary nails. Surg Radiol Anat. 2005 Dec;27(6):502–6.
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Egol KA, Chang EY, Cvitkovic J, Kummer FJ, Koval KJ. Mismatch of Current Intramedullary Nails With the Anterior Bow of the Femur: J Orthop Trauma. 2004 Aug;18(7):410–5.
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Siwach R, Dahiya S. Anthropometric study of proximal femur geometry and its clinical application. INDIAN J Orthop. 2003;37(4):5.
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Maruyama M, Feinberg JR, Capello WN, D???Antonio JA. Morphologic Features of the Acetabulum and Femur: Anteversion Angle and Implant Positioning. Clin Orthop. 2001 Dec;393:52–65.
7.
Kleweno C, Morgan J, Redshaw J, Harris M, Rodriguez E, Zurakowski D, et al. Short Versus Long Cephalomedullary Nails for the Treatment of Intertrochanteric Hip Fractures in Patients Older than 65 Years: J Orthop Trauma. 2014 Jul;28(7):391–7.
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8.
Baldwin PC, Lavender RC, Sanders R, Koval KJ. Controversies in Intramedullary Fixation for Intertrochanteric Hip Fractures: J Orthop Trauma. 2016 Dec;30(12):635–41.
9.
Biçer ÖS. How anatomic are intramedullary femoral nails? A cadaveric study. ACTA Orthop Traumatol Turc [Internet]. 2016 [cited 2018 Aug 23]; Available from: http://www.aott.org.tr/index.php/aott/article/view/3215/4051
10. Dimitriou D, Tsai T-Y, Yue B, Rubash HE, Kwon Y-M, Li G. Side-to-side variation in normal femoral morphology: 3D CT analysis of 122 femurs. Orthop Traumatol Surg Res. 2016 Feb;102(1):91–7. 11. Jiang N, Peng L, Al-Qwbani M, Xie G-P, Yang Q-M, Chai Y, et al. Femoral Version, Neck-Shaft Angle, and Acetabular Anteversion in Chinese Han Population: A Retrospective Analysis of 466 Healthy Adults. Medicine (Baltimore). 2015 May;94(21):e891. 12. Gulan G, Matovinovi D, Nemec B, Rubini D, Ravli J. Femoral Neck Anteversion: Values, Development, Measurement, Common Problems. Coll Antropol. 2000;7. 13. Boese CK, Jostmeier J, Oppermann J, Dargel J, Chang D-H, Eysel P, et al. The neck shaft angle: CT reference values of 800 adult hips. Skeletal Radiol. 2016 Apr;45(4):455–63. 14. Khang G, Choi K, Kim C-S, Yang JS, Bae T-S. A Study of Korean Femoral Geometry: Clin Orthop. 2003 Jan;406:116–22.
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15. Mahaisavariya B, Sitthiseripratip K, Tongdee T, Bohez ELJ, Vander Sloten J, Oris P. Morphological study of the proximal femur: a new method of geometrical assessment using 3-dimensional reverse engineering. Med Eng Phys. 2002 Nov;24(9):617–22. 16. Tyagi V, Yang JH, Oh KJ. A computed tomography-based analysis of proximal femoral geometry for lateral impingement with two types of proximal femoral nail anterotation in subtrochanteric fractures. Injury. 2010 Aug;41(8):857–61. 17. Brunner A, Jöckel JA, Babst R. The PFNA Proximal Femur Nail in Treatment of Unstable Proximal Femur Fractures-3 Cases of Postoperative Perforation of the Helical Blade Into the Hip Joint. J Orthop Trauma. 2008 Dec;22(10):731. 18. de Farias THS, Borges VQ, de Souza ES, Miki N, Abdala F. Radiographic study on the anatomical characteristics of the proximal femur in Brazilian adults. Rev Bras Ortop Engl Ed. 2015 Jan;50(1):16–21. 19. Noble PC, Box GG, Kamaric E, Fink MJ, Alexander JW, Tullos HS. The effect of aging on the shape of the proximal femur. Clin Orthop. 1995 Jul;(316):31–44. 20. Maratt J, Schilling PL, Holcombe S, Dougherty R, Murphy R, Wang SC, et al. Variation in the Femoral Bow: A Novel High-Throughput Analysis of 3922 Femurs on Cross-Sectional Imaging. J Orthop Trauma. 2014 Jan;28(1):6–9. 21. Lakhwani OP. Correlation of Trochanter-Shaft Angle in Selection of Entry Site in Antegrade Intramedullary Femoral Nail. ISRN Orthop. 2012;2012:1–5.
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22. Rawal B, Malhotra R, Ribeiro R, Bhatnagar N. Anthropometric measurements to design best-fit femoral stem for the Indian population. Indian J Orthop. 2012;46(1):46. 23. Gnudi S, Sitta E, Pignotti E. Prediction of incident hip fracture by femoral neck bone mineral density and neck–shaft angle: a 5-year longitudinal study in post-menopausal females. Br J Radiol. 2012 Aug 1;85(1016):e467–73. 24. Im GI, Lim MJ. Proximal hip geometry and hip fracture risk assessment in a Korean population. Osteoporos Int. 2011 Mar 1;22(3):803–7. 25. Riehl JT, Koval KJ, Langford JR, Munro MW, Kupiszewski SJ, Haidukewych GJ. Intramedullary nailing of subtrochanteric fractures does malreduction matter? Bull NYU Hosp Jt Dis. 2014;72(2):159–159.
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Annexure I: Standard Cuts •
Standard cut 1: Oblique coronal plane going through head and neck bisecting head and neck into two equal halves. Head diameter superio-inferior, neck width superio-inferior, Neck Shaft Angle (NSA) were calculated in this cut.
•
Standard cut 2: Oblique axial plane going through head and neck bisecting head and neck into two equal halves which is perpendicular to cut 1. AP Head diameter, AP neck width were calculated using cut 2.
•
Standard cut 3: A cut in the oblique coronal section which divides head equally into two halves and also passes through tip of greater trochanter. Femoral offset and mediolateral angle (ML angle) was calculated in this cut.
•
Standard cut 4: Anteversion was calculated using superimposed images of condyle and neck axis along long axis of femur with condylar axis being a plane perpendicular to the long axis of femur shaft sliced at perfect roman arch of condyles, with neck axis being a plane cutting long axis perpendicular and bisecting equally at neck along with inferior part of head.
•
Standard cut 5 Axial cut perpendicular to femoral axis was used for measuring isthmus and distance of isthmus from greater trochanter (GT).
•
Standard cut 6 is an oblique sagittal cut with both highest point of greater trochanter and center of intercondylar groove, femoral shaft length and anterior radius of curvature was calculated using this sagittal cut.
Annexure II: Femoral dimensions from these standard cuts were measured as follows
17
Supero-inferior (SI) Head diameter: In standard cut 1, area of a largest best fit circle on the head drawn touching at least 3 point at 11, 3, 5 o’clock position on femoral head was calculated by software and diameter was calculated from mathematical formula for area. SI Neck width: In standard cut 1, smallest endosteal width in perpendicular to the neck axis. Neck shaft angle: In standard cut 1, the angle between femoral shaft axis and neck axis. Neck axis is a line passing through center of best fit femoral head circle indicating center of femoral head and dividing neck into two equal halves. Femoral axis is the line passing through center of two circles touching outer cortices of medial and lateral femoral border at lesser trochanter and 5 cm below lesser trochanter13. Head diameter AP: In standard cut 2, area of a largest best fit circle on the head drawn touching at least 3 point at 11, 3, 5 o’clock position on femoral head was calculated by software and diameter was calculated from mathematical formula for area.. Neck width AP: In standard cut 2, smallest endosteal width in perpendicular to the neck axis. Femoral offset: It is a distance between long axis of femur and a line parallel to axis and passing through center of femoral head in standard cut 3. Medio-lateral angle: Angle formed by line joining the highest point of greater trochanter with axis of shaft at 5cm distal to lesser trochanter, it is actually an angle formed by the implant shaft which is along long axis of femur due to lateral greater trochanter entry point
18
Anteversion: Angular difference between axis of femoral neck over condylar axis, in standard cut 4 condylar and neck axis is overlapped and angulation between these axis is measured on lateral side12. Isthmus diameter: this represents the smallest diameter of femoral shaft, standard cut 5 which is passing perpendicular to femoral shaft axis measured for every 0.9mm cut, the smallest endosteal width was considered. Isthmus distance: Distance of isthmus from tip of greater trochanter. Femur shaft length: In standard cut 6, distance measurement done from tip of greater trochanter tip to the lowest point of intercondylar groove. Anterior radius of curvature of femur: a best fit circle along anterior cortex of femoral shaft which is forming a part of circumference was drawn, whose diameter and hence radius is calculated.
19
Table 1: Table showing various mean values of femur morphology and influence of Gender Mean
Male
Female
P
Age( Yr)
68.42±13.68
65.38±14.58
72.62±11.37
0.122
Head Diameter AP(mm)
43.48±3.34
45.54±2.28
40.63±2.30
0.000*
Head Diameter SI(mm)
43.8±3.59
45.94±2.65
40.84±2.46
0.000*
Neck width AP (mm)
22.93±4.17
23.45±4.34
22.20±3.90
0.302
Neck width SI (mm)
24.76±3.47
26.50±2.81
22.36±2.84
0.000*
Anteversion (º)
10.08±9.57
7.81±9.97
13.21±8.22
0.048*
Isthmus (mm)
11.85±1.70
11.87±1.93
11.80±1.37
0.882
Isthmus Distance (mm)
171.53±25.12
176.18±26.69
165.11±21.78
0.125
Femoral length (mm)
419.53±28.50
433.09±28.23
400.80±15.46
0.000*
Anterior Radius of curvature (cm)
116.77±19.99
119.49±17.68
113.02±22.73
0.263
Neck shaft angle(º)
127.22±5.22
128.27±5.39
125.76±4.72
0.095
Femoral Offset(mm)
37.32±5.91
37.45±4.57
37.13±7.49
0.852
Lateral angle(º)
7.76±1.60
8.07±1.70
7.33±1.38
0.108
* ‘P’ value < 0.05
1
Table 2: List of the various femur Morphological parameters correlation. Correlations
Correlation coefficient (r) 0.921
0.000**
Neck width SI vs Head Diameter AP
0.692
0.000**
Neck width SI vs Head Diameter SI
0.595
0.000**
Isthmus vs Neck width AP
-0.330
0.019*
Isthmus distance vs Head Diameter AP
0.303
0.032*
Isthmus distance vs Head Diameter SI
0.397
0.004**
Isthmus distance vs Isthmus
0.485
0.000**
Femoral Length vs Femoral head AP
0.652
0.000**
Femoral Length vs Femoral head SI
0.726
0.000**
Femoral Length vs Neck width SI
0.517
0.000**
Femoral Length vs Isthmus
0.325
0.021*
Femoral Length vs Isthmus Distance
0.532
0.000*
Neck shaft angle vs Neck width AP
0.374
0.008*
Neck shaft angle vs Isthmus
-0.330
0.019*
Neck shaft angle vs Isthmus distance
-0.309
0.029*
Femoral Offset vs Neck width AP
0.461
0.00**
Lateral angle Vs Anteversion
-0.316
0.025*
Head Diameter SI vs AP
* ‘P’ value < 0.05 ** ‘P’ value < 0.001
1
P value
Table 3: Comparison of Femur morphological features of various other population Study
Neck shaft
Anteversio
Isthmus(m
Ant
Femur
Head
Populatio
Angle (º)
n
m)
ROC(cm)
Length(mm
Diamete
)
r in mm
NA
40.8±3.4
n
(º)
Chinese &
125.6±6 to
11.4±7.7 to
South east
134±4.4
19.8±9.3
123±4.3
8.7±6.6 to
9.6
112±23.4
to 44.35
Asia Indian &
South Asia to126.8±5.
9±1.9
NA
13.6±7.9
418.8 to
41.7±3.1
436.5
to
8 Our study
127.2±5.2
45.4±3.7 11.2±7.4
11.9±1.7
116.8±20
419±28.5
43.5 ± 3.3, 43.8 ± 3.6
Western
122.9±7.6
countries
to
13.1±8
13.1±2.1 to
112 to
378.6±23.2
14.1±2.8
120±40
to
134.2±5.2
409.8±28,2
1
NA
Table 4: Best fit analysis of the available nails with the femur morphology and our recommended nailing option. Parameters
Nail A, B &
Best fit
overall Our
C Neck shaft
125 to135
Best fit
Overall
45(90%)
recommendation 30(60%) 3(6%)
120 º -140 º
48(96%)
3(6%)
-10 º TO 30 º
47(94%)
16(32%) 1(2%)
100-140
40(80%)
angle Anteversion 10 & 15 Roc
127.5, 140,
(cm)
152.5
1
36(72%)
S0972-978X(19)30620-8
DOI:
https://doi.org/10.1016/j.jor.2019.12.002
Reference:
JOR 909
To appear in:
Journal of Orthopaedics
Received Date: 26 September 2019 Accepted Date: 8 December 2019
Please cite this article as: Kulkarni M, Naik A M, Shetty CB, Paruthikunnan SM, Rao SK, CT based measurement of anatomical dimensions of femur and its relevance in nail designs for proximal femoral fractures., Journal of Orthopaedics, https://doi.org/10.1016/j.jor.2019.12.002. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier B.V. on behalf of Professor P K Surendran Memorial Education Foundation.
Title: CT based measurement of anatomical dimensions of femur and its relevance in nail designs for proximal femoral fractures. Authors: Mahesh Kulkarni1, Monappa Naik A2, Chethan B Shetty3, Samir M Paruthikunnan4, Sharath K Rao5 1Assistant Professor, Department of Orthopedics 2 Associate Professor, Department of Orthopedics. Corresponding Author:
ORCID: 0000-0003-3147-050X ORCID: 0000-0002-8107-0873
Email ID [email protected] Contact Number: +919448484894
3 Senior Resident, Department of Orthopedics
ORCID: 0000-0003-4459-6099
Kasturba Medical College, Manipal Academy of Higher Education, Manipal, Karnataka, India. 4 Assistant Professor, Department of Radiology 5 Professor, Department of Orthopedics
ORCID: 0000-0002-6013-2537
Kasturba Medical College, Manipal Academy of Higher Education, Manipal, Karnataka, India. Conflict of interest: There was no internal/external source of funding for this study and authors also declare no conflict of interest regarding submission and publication of this manuscript.
CT based measurement of anatomical dimensions of femur and its relevance in nail designs for proximal femoral fractures. Author contribution: MN Aroor: Protocol development, Manuscript editing. MS Kulkarni: Data Analysis, Manuscript Editing. CB Shetty: Data management, Data analysis, Manuscript writing. SM Paruthikunnan: Data management, Data analysis. SK Rao: Protocol development, Manuscript editing.
TITLE: CT based measurement of anatomical dimensions of femur and its relevance in nail designs for proximal femoral fractures. Abstract: Introduction: The purpose of this study was to obtain computed tomography (CT) based measurements of femoral dimensions in adults, to identify its relevance with intramedullary nails used in the management of proximal femur fractures and to suggest a best fitting implant dimensions to our population. To best of our knowledge our study would be first to compile different CT based dimension in single study. Methods: In our retrospective study of 50 femurs, CT based femoral dimensions measured in standardized cuts and compared with previous studies and commonly available proximal femur intramedullary devices. Results: 68.4 was the mean age in our study, neck shaft angle (NSA) was 127.2±5.20, anteversion 11.2±7.40, endosteal isthmus diameter was 11.9±1.7 mm, anterior radius of curvature (ROC) was 116.8±20 mm, horizontal femoral offset 37.5±4.6 mm, medio-lateral angle 7.8±1.60, with good inter and intra observer correlation. Femoral length and neck width was positively correlated to head diameter, horizontal femoral offset with medio-lateral (ML) angle. One of the 50 femur studied had the parameters in the range of available implant and could match appropriately Conclusion: CT based dimensions in our population is different from other population. Based on this study, a design modification of nails used in present day management of proximal femur fractures has been recommended. 1
Keywords: Femoral dimension, Neck shaft angle, Proximal femur fractures, CT, Implant mismatch, Anteversion, Intramedullary nail.
2
CT based measurement of anatomical dimensions of femur and its relevance in nail designs for proximal femoral fractures. 1. Introduction: Incidence of pertrochanteric fractures are on the rise in most of the developed and developing countries. Low velocity injuries in growing elderly population and high velocity injuries in the younger population due to increase in motor vehicle accidents are the main reasons.1 For most of these fractures cephalomedullary nailing has become the treatment of choice over extramedullary devices due to the cited advantages of intramedullary fixation, decreased lever arm, decreased blood loss, stable construct, load sharing nature of the construct and small incision.2 Restoring the anatomical alignment and stable fixation are the key to successful outcome. Many investigators have noted the mismatch between the designed implant and prosthesis which are commercially available with that of the femur geometry.3–6 Mismatch between the profile of the implant and proximal femur anatomy will lead to the difficulty in maintaining the fracture reduction and hence subsequent malalignment which will result in complications and suboptimal outcome.3,4,7–9 There are no studies in the literature which have described the mismatch between the proximal femur morphology using the clinically relevant CT scan and available implants for the fixation of pertrochanteric fractures in the elderly population. The purpose of this study is to obtain CT based measurements and to study the femoral dimensions in adults, to identify its relevance with nails used in management of proximal femur fractures. In this study we hypothesized that commonly used nailing systems will have the wide options which can cater the need of the best fit implant for the native morphology of the injured proximal femur. It is normally expected that the implant manufacturers would have evaluated
3
morphological and anatomical characteristic of the bone and would have manufactured the implants as per the requirement. 2. Materials and Methods: In this retrospective study we identified consecutive 50 skeletally matured patients with per trochanteric fractures who were having the full length CT images of the unaffected femur which was taken as a part of the evaluation of the fracture. Patients with history of previous surgery or with bony deformity of the unaffected side were excluded. Ethical committee approval for the study was obtained (IEC No. 633/2016). Femoral dimensions were measured by two independent observers with following parameters. All CT were imaged under standard specifications using Philips brilliance 64 slice MDCT with slice thickness – 0.9 mm, slice increment – 0.45 mm, Kv – 140, mAs/slice – 300, pitch – 0.484, rotation time – 0.75 sec, collimation 64X0.625, matrix – 768 pixels and measured using software Phillips Intellispace portal V 4.0.2. All the measurements were calculated in oblique standardized cuts.10–12 [Fig 1] Supero-inferior (SI) Head diameter, SI Neck width, Neck shaft angle, Head diameter AP, Neck width AP, Femoral offset, Medio-lateral angle, Anteversion, Isthmus diameter, Isthmus distance, Femur shaft length and Anterior radius of curvature of femur are the femoral dimensions measured from the standard cuts. Details are available in the annexure I and II. 3. Statistical Analysis: Descriptive statistics were used for describing the demographic details. Independent ‘t’ test was used to compare the means between the male and female groups. Pearson correlation was used to find the correlation between the femoral dimensions. Spearman correlation and unpaired 2 tailed 4
t test was used to analyze statistical significance between age and femoral dimensions. Concordance between the examiners were calculated (intra and inter observer variability) and assessed using interclass correlation coefficient (ICC). 4. Results: We analysed 50 femur CTs with mean age being 68.42±13.68 yrs of which majority were males 29/50 [Fig 2]. We found reasonably good interclass correlation coefficient ICC 0.92 to 0.96 in all the measurements and in ROC, ICC was 0.83 suggesting good agreement between intra and inter observer measurements. Our typical patient had SI head diameter of 43.8±3.59mm, SI neck width of 24.76±3.47mm, neck shaft angle of 127.22 ±5.22 º anteversion of 10.08±9.57 and femoral length of 419.53±28.50 mm. Table 1: Table showing various mean values of femur morphology and influence of Gender Mean
Male
Female
P
Age( Yr)
68.42±13.68
65.38±14.58
72.62±11.37
0.122
Head Diameter AP(mm)
43.48±3.34
45.54±2.28
40.63±2.30
0.000*
Head Diameter SI(mm)
43.8±3.59
45.94±2.65
40.84±2.46
0.000*
Neck width AP (mm)
22.93±4.17
23.45±4.34
22.20±3.90
0.302
Neck width SI (mm)
24.76±3.47
26.50±2.81
22.36±2.84
0.000*
Anteversion (º)
10.08±9.57
7.81±9.97
13.21±8.22
0.048*
Isthmus (mm)
11.85±1.70
11.87±1.93
11.80±1.37
0.882
Isthmus Distance (mm)
171.53±25.12
176.18±26.69
165.11±21.78
0.125
Femoral length (mm)
419.53±28.50
433.09±28.23
400.80±15.46
0.000*
Anterior Radius of curvature (cm)
116.77±19.99
119.49±17.68
113.02±22.73
0.263
5
Neck shaft angle(º)
127.22±5.22
128.27±5.39
125.76±4.72
0.095
Femoral Offset(mm)
37.32±5.91
37.45±4.57
37.13±7.49
0.852
Lateral angle(º)
7.76±1.60
8.07±1.70
7.33±1.38
0.108
* ‘P’ value < 0.05 There was significant difference in the measurements of femur head, neck, femoral anteversion and femur length parameters between male and female patients (Table 1). There was a significant correlation was found between the various parameters as shown in Table 2. Table 2: List of the various femur Morphological parameters correlation. Correlations
Correlation
P value
coefficient (r) Head Diameter SI vs AP
0.921
0.000**
Neck width SI vs Head Diameter AP
0.692
0.000**
Neck width SI vs Head Diameter SI
0.595
0.000**
Isthmus vs Neck width AP
-0.330
0.019*
Isthmus distance vs Head Diameter AP
0.303
0.032*
Isthmus distance vs Head Diameter SI
0.397
0.004**
Isthmus distance vs Isthmus
0.485
0.000**
Femoral Length vs Femoral head AP
0.652
0.000**
Femoral Length vs Femoral head SI
0.726
0.000**
Femoral Length vs Neck width SI
0.517
0.000**
Femoral Length vs Isthmus
0.325
0.021*
6
Femoral Length vs Isthmus Distance
0.532
0.000*
Neck shaft angle vs Neck width AP
0.374
0.008*
Neck shaft angle vs Isthmus
-0.330
0.019*
Neck shaft angle vs Isthmus distance
-0.309
0.029*
Femoral Offset vs Neck width AP
0.461
0.00**
Lateral angle Vs Anteversion
-0.316
0.025*
* ‘P’ value < 0.05 ** ‘P’ value < 0.001 We compared our results with published western, eastern and with Indian studies (Table 3). Table 3: Comparison of Femur morphological features of various other population Study
Neck shaft
Population Angle (º)
Anteversion Isthmus(mm) Ant
Femur
Head
ROC(cm) Length(mm) Diameter
(º)
in mm Chinese &
125.6±6 to
11.4±7.7 to
South east
134±4.4
19.8±9.3
Indian &
123±4.3
8.7±6.6 to
South Asia
to126.8±5.8 13.6±7.9
9.6
112±23.4
NA
40.8±3.4 to 44.35
Asia 9±1.9
NA
418.8 to
41.7±3.1
436.5
to 45.4±3.7
Our study
127.2±5.2
11.2±7.4
11.9±1.7
7
116.8±20
419±28.5
43.5 ±
3.3, 43.8 ± 3.6 Western
122.9±7.6
countries
to
13.1±8
13.1±2.1 to
112 to
378.6±23.2
14.1±2.8
120±40
to
134.2±5.2
NA
409.8±28,2
We also compared and contrasted our measurements with commonly available and used 3 intramedullary devices (Table 4). We mainly focused on best fit based on Neck shaft angle, anteversion and additionally with ROC measurements. We found 1/50 femur was having morphological parameters in the range of available fixation devices. Table 4: Best fit analysis of the available nails with the femur morphology and our recommended nailing option. Parameters
Nail A, B &
Best fit
overall
C
Our
Best fit
Overall
120 º -140 º
48(96%)
45(90%)
-10 º TO 30 º
47(94%)
100-140
40(80%)
recommendati on
Neck shaft
125 º to135 º
30(60%)
3(6%)
angle Anteversion 10 & 15 Roc
127.5 , 140,
(cm)
152.5
3(6%) 16(32%)
1(2%)
5. Discussion: 8
36(72%)
Due to the increase in the geriatric population and motor vehicle accidents pertrochanteric fractures are on the rise worldwide. Many implant manufacturers are offering the devices for these fractures which have limited options in different sizes which are expected to fit in most of the femurs. Variations in the femur morphometry has been noted by many investigators which varies with age, gender, race, ethnicity and regional customs like sitting cross legged or squatting. 6,12–15 This heterogeneity in the morphometric parameters of the femur should be considered in the designing of suitable implants. Many investigators have evaluated the morphology of proximal femur with respect to the prosthetic replacement. 6,14 Mismatch of the implants with the bony anatomy lead to loss of reduction, penetration of the nail, mismatch between the locking hole and aiming device, screw cut through, delayed union, malunion, nonunion, failure of the implants and increased morbidity. 2,7,8,16,17 We wanted to evaluate the morphological features of the femur primarily and evaluation of the suitability of the available implants for the described femur morphology was the secondary objective of this study. Major chunk of our study population belonged to elderly population which is due to the inclusion criteria as pertrochanteric fractures are common in this age group. And hence it can be considered as representative of elderly population. Due to imprecise positioning problems Radiographs are not reliable for accurate measurements. 6,13 CT studies are preferred in the morphological evaluation which can also give valuable information about the nature of the fracture and articular surfaces. In our series male femurs had bigger heads, broader neck and longer femoral length when compared to females. 18 Females had significantly more anteverted femoral neck.11 [Fig 3] Males and females had almost similar isthmus, anterior radius of curvature, neck shaft angle, femoral offset and lateral angle (Table 1). On analyzing the parameters on the age distribution we didn’t 9
find any significant changes across age group in our study. This could be attributed to the fact that we didn’t have many cases from the younger age group in our population which could have given the insight regarding variation in the morphology due to age. 6,11,13,19 On comparing with Chinese/ south east Asian populations our study group had lesser neck shaft angle, anteversion. But isthmus diameter and head diameter were similar. 6,11,14,15 On comparing with the western population our study group had lesser neck shaft angle, smaller isthmus and similar anteversion and femur length. 4,10,13,18,20. Our morphological parameters are in concurrence with the studies from Indian and south Asian subcontinent.1,5,21,22,22 One parameter which didn’t differ among the populations was anterior Radius of curvature which was fairly similar in all the populations. Also we didn’t observe any significant changes due to age, gender and sidedness on ROC which are partially in line with other studies.3,4,20 One interesting finding what we observed in our series was lateral angle was inversely correlating with the anteversion [Fig 4]. We also observed that Neck shaft angle was directly correlated with neck width but inversely correlated with the isthmus [Fig 5]. Which can explain the increase in the pertrochanteric fractures in persons with higher NSA as neck will be stronger in these patients and less likely to fail.23,24 We collected the information regarding the sizes of the available implants from the manufacturer’s website. As varying options for the length of the nails were available, isthmus could be reamed appropriately and lateral angle slightly different from the mean. We didn’t consider femoral length, isthmus diameter and lateral angle for the best fit measurement. Of all the other parameters neck shaft angle and anteversion cannot be adjusted and were fixed or having very less options. NSA and anteversion are important because mismatch in these parameters will lead to the loss of reduction and fixation in suboptimal way which may 10
jeopardize the outcome. Jiang et al have shown that in total a gap of 25mm and Riehl et al have shown that an angulation of >10º in either coronal or sagittal plane will have bad outcome.11,25 Only one of the 50 proximal femur which were analysed was having the parameters which could result in proper fit with the available implants. When ROC was excluded it increased to 3 femurs which could have had proper fit. Availability of the implant system which offer varied options as suggested with NSA, anteversion and ROC in nails could have increased the overall fit to 72%. If we exclude the ROC mismatch which can be adjusted by using thinner, shorter nail or by reaming to some extent, up to 90% of the femurs will accommodate the proper fitting of such nail.7,8 (Table 4). Bicer et al in their study using cadaveric bones and light scanning method to assess the measurements also had the similar findings of mismatch of nails and the native femur morphological parameters.9 Hence we recommend having nails with wider options available in neck shaft angle and anteversion. We also suggest CT evaluation to include the opposite whole femur which can give the valuable information regarding the morphological features of the native bone. Strengths of this study are uniformity in the sample population which represent one of the most common fracture patterns treated routinely in the clinical setting. Evaluation of the femur morphology which was done by CT which is easily available and gives better clinically relevant accurate information when compared to plain radiographs. Limitations of this study is that it does not represent the entire adult population but a subset of it. Our sample size is only 50. A study with larger study group would have been preferred. In this study we didn’t evaluate the functional outcome of the fracture treated with cephalomedullary nailing which could have given final verdict regarding the fixation of the fracture using mismatched implant. A randomised control study with large number of cases comparing the 11
regular implants and properly fitting implants in pertrochanteric fracture management would give the ideal verdict. Having implants with multiple options in NSA, Anteversion, ROC, femoral length and diameter will lead to the requirement of the huge inventory and logistical nightmare. We suggest development of the newer intramedullary devices having the intrinsic mechanism or to have modular options to adjust the NSA and anteversion to accommodate the variations seen commonly in proximal femur. 6. Conclusion: There is a wide variation of the anatomical measures with respect to neck shaft angle (NSA) and anteversion in proximal femur anatomy. This needs to be addressed during selection of the implants with appropriate angles to fix the fracture in anatomical position. This probably can be achieved by having modular proximal femur implants.
Funding: Nil Conflict of interest: There was no external source of funding for this study and no conflicts of interest regarding submission and publication of this manuscript.
12
Refererences: 1.
Pathrot D, Ul Haq R, Aggarwal A, Nagar M, Bhatt S. Assessment of the geometry of proximal femur for short cephalomedullary nail placement: An observational study in dry femora and living subjects. Indian J Orthop. 2016;50(3):269.
2.
Shukla S, Johnston P, Ahmad MA, Wynn-Jones H, Patel AD, Walton NP. Outcome of traumatic subtrochanteric femoral fractures fixed using cephalo-medullary nails. Injury. 2007 Nov;38(11):1286–93.
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Harma A, Germen B, Karakas HM, Elmali N, Inan M. The comparison of femoral curves and curves of contemporary intramedullary nails. Surg Radiol Anat. 2005 Dec;27(6):502–6.
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Egol KA, Chang EY, Cvitkovic J, Kummer FJ, Koval KJ. Mismatch of Current Intramedullary Nails With the Anterior Bow of the Femur: J Orthop Trauma. 2004 Aug;18(7):410–5.
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Siwach R, Dahiya S. Anthropometric study of proximal femur geometry and its clinical application. INDIAN J Orthop. 2003;37(4):5.
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Maruyama M, Feinberg JR, Capello WN, D???Antonio JA. Morphologic Features of the Acetabulum and Femur: Anteversion Angle and Implant Positioning. Clin Orthop. 2001 Dec;393:52–65.
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Kleweno C, Morgan J, Redshaw J, Harris M, Rodriguez E, Zurakowski D, et al. Short Versus Long Cephalomedullary Nails for the Treatment of Intertrochanteric Hip Fractures in Patients Older than 65 Years: J Orthop Trauma. 2014 Jul;28(7):391–7.
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Baldwin PC, Lavender RC, Sanders R, Koval KJ. Controversies in Intramedullary Fixation for Intertrochanteric Hip Fractures: J Orthop Trauma. 2016 Dec;30(12):635–41.
9.
Biçer ÖS. How anatomic are intramedullary femoral nails? A cadaveric study. ACTA Orthop Traumatol Turc [Internet]. 2016 [cited 2018 Aug 23]; Available from: http://www.aott.org.tr/index.php/aott/article/view/3215/4051
10. Dimitriou D, Tsai T-Y, Yue B, Rubash HE, Kwon Y-M, Li G. Side-to-side variation in normal femoral morphology: 3D CT analysis of 122 femurs. Orthop Traumatol Surg Res. 2016 Feb;102(1):91–7. 11. Jiang N, Peng L, Al-Qwbani M, Xie G-P, Yang Q-M, Chai Y, et al. Femoral Version, Neck-Shaft Angle, and Acetabular Anteversion in Chinese Han Population: A Retrospective Analysis of 466 Healthy Adults. Medicine (Baltimore). 2015 May;94(21):e891. 12. Gulan G, Matovinovi D, Nemec B, Rubini D, Ravli J. Femoral Neck Anteversion: Values, Development, Measurement, Common Problems. Coll Antropol. 2000;7. 13. Boese CK, Jostmeier J, Oppermann J, Dargel J, Chang D-H, Eysel P, et al. The neck shaft angle: CT reference values of 800 adult hips. Skeletal Radiol. 2016 Apr;45(4):455–63. 14. Khang G, Choi K, Kim C-S, Yang JS, Bae T-S. A Study of Korean Femoral Geometry: Clin Orthop. 2003 Jan;406:116–22.
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15. Mahaisavariya B, Sitthiseripratip K, Tongdee T, Bohez ELJ, Vander Sloten J, Oris P. Morphological study of the proximal femur: a new method of geometrical assessment using 3-dimensional reverse engineering. Med Eng Phys. 2002 Nov;24(9):617–22. 16. Tyagi V, Yang JH, Oh KJ. A computed tomography-based analysis of proximal femoral geometry for lateral impingement with two types of proximal femoral nail anterotation in subtrochanteric fractures. Injury. 2010 Aug;41(8):857–61. 17. Brunner A, Jöckel JA, Babst R. The PFNA Proximal Femur Nail in Treatment of Unstable Proximal Femur Fractures-3 Cases of Postoperative Perforation of the Helical Blade Into the Hip Joint. J Orthop Trauma. 2008 Dec;22(10):731. 18. de Farias THS, Borges VQ, de Souza ES, Miki N, Abdala F. Radiographic study on the anatomical characteristics of the proximal femur in Brazilian adults. Rev Bras Ortop Engl Ed. 2015 Jan;50(1):16–21. 19. Noble PC, Box GG, Kamaric E, Fink MJ, Alexander JW, Tullos HS. The effect of aging on the shape of the proximal femur. Clin Orthop. 1995 Jul;(316):31–44. 20. Maratt J, Schilling PL, Holcombe S, Dougherty R, Murphy R, Wang SC, et al. Variation in the Femoral Bow: A Novel High-Throughput Analysis of 3922 Femurs on Cross-Sectional Imaging. J Orthop Trauma. 2014 Jan;28(1):6–9. 21. Lakhwani OP. Correlation of Trochanter-Shaft Angle in Selection of Entry Site in Antegrade Intramedullary Femoral Nail. ISRN Orthop. 2012;2012:1–5.
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22. Rawal B, Malhotra R, Ribeiro R, Bhatnagar N. Anthropometric measurements to design best-fit femoral stem for the Indian population. Indian J Orthop. 2012;46(1):46. 23. Gnudi S, Sitta E, Pignotti E. Prediction of incident hip fracture by femoral neck bone mineral density and neck–shaft angle: a 5-year longitudinal study in post-menopausal females. Br J Radiol. 2012 Aug 1;85(1016):e467–73. 24. Im GI, Lim MJ. Proximal hip geometry and hip fracture risk assessment in a Korean population. Osteoporos Int. 2011 Mar 1;22(3):803–7. 25. Riehl JT, Koval KJ, Langford JR, Munro MW, Kupiszewski SJ, Haidukewych GJ. Intramedullary nailing of subtrochanteric fractures does malreduction matter? Bull NYU Hosp Jt Dis. 2014;72(2):159–159.
16
Annexure I: Standard Cuts •
Standard cut 1: Oblique coronal plane going through head and neck bisecting head and neck into two equal halves. Head diameter superio-inferior, neck width superio-inferior, Neck Shaft Angle (NSA) were calculated in this cut.
•
Standard cut 2: Oblique axial plane going through head and neck bisecting head and neck into two equal halves which is perpendicular to cut 1. AP Head diameter, AP neck width were calculated using cut 2.
•
Standard cut 3: A cut in the oblique coronal section which divides head equally into two halves and also passes through tip of greater trochanter. Femoral offset and mediolateral angle (ML angle) was calculated in this cut.
•
Standard cut 4: Anteversion was calculated using superimposed images of condyle and neck axis along long axis of femur with condylar axis being a plane perpendicular to the long axis of femur shaft sliced at perfect roman arch of condyles, with neck axis being a plane cutting long axis perpendicular and bisecting equally at neck along with inferior part of head.
•
Standard cut 5 Axial cut perpendicular to femoral axis was used for measuring isthmus and distance of isthmus from greater trochanter (GT).
•
Standard cut 6 is an oblique sagittal cut with both highest point of greater trochanter and center of intercondylar groove, femoral shaft length and anterior radius of curvature was calculated using this sagittal cut.
Annexure II: Femoral dimensions from these standard cuts were measured as follows
17
Supero-inferior (SI) Head diameter: In standard cut 1, area of a largest best fit circle on the head drawn touching at least 3 point at 11, 3, 5 o’clock position on femoral head was calculated by software and diameter was calculated from mathematical formula for area. SI Neck width: In standard cut 1, smallest endosteal width in perpendicular to the neck axis. Neck shaft angle: In standard cut 1, the angle between femoral shaft axis and neck axis. Neck axis is a line passing through center of best fit femoral head circle indicating center of femoral head and dividing neck into two equal halves. Femoral axis is the line passing through center of two circles touching outer cortices of medial and lateral femoral border at lesser trochanter and 5 cm below lesser trochanter13. Head diameter AP: In standard cut 2, area of a largest best fit circle on the head drawn touching at least 3 point at 11, 3, 5 o’clock position on femoral head was calculated by software and diameter was calculated from mathematical formula for area.. Neck width AP: In standard cut 2, smallest endosteal width in perpendicular to the neck axis. Femoral offset: It is a distance between long axis of femur and a line parallel to axis and passing through center of femoral head in standard cut 3. Medio-lateral angle: Angle formed by line joining the highest point of greater trochanter with axis of shaft at 5cm distal to lesser trochanter, it is actually an angle formed by the implant shaft which is along long axis of femur due to lateral greater trochanter entry point
18
Anteversion: Angular difference between axis of femoral neck over condylar axis, in standard cut 4 condylar and neck axis is overlapped and angulation between these axis is measured on lateral side12. Isthmus diameter: this represents the smallest diameter of femoral shaft, standard cut 5 which is passing perpendicular to femoral shaft axis measured for every 0.9mm cut, the smallest endosteal width was considered. Isthmus distance: Distance of isthmus from tip of greater trochanter. Femur shaft length: In standard cut 6, distance measurement done from tip of greater trochanter tip to the lowest point of intercondylar groove. Anterior radius of curvature of femur: a best fit circle along anterior cortex of femoral shaft which is forming a part of circumference was drawn, whose diameter and hence radius is calculated.
19
Table 1: Table showing various mean values of femur morphology and influence of Gender Mean
Male
Female
P
Age( Yr)
68.42±13.68
65.38±14.58
72.62±11.37
0.122
Head Diameter AP(mm)
43.48±3.34
45.54±2.28
40.63±2.30
0.000*
Head Diameter SI(mm)
43.8±3.59
45.94±2.65
40.84±2.46
0.000*
Neck width AP (mm)
22.93±4.17
23.45±4.34
22.20±3.90
0.302
Neck width SI (mm)
24.76±3.47
26.50±2.81
22.36±2.84
0.000*
Anteversion (º)
10.08±9.57
7.81±9.97
13.21±8.22
0.048*
Isthmus (mm)
11.85±1.70
11.87±1.93
11.80±1.37
0.882
Isthmus Distance (mm)
171.53±25.12
176.18±26.69
165.11±21.78
0.125
Femoral length (mm)
419.53±28.50
433.09±28.23
400.80±15.46
0.000*
Anterior Radius of curvature (cm)
116.77±19.99
119.49±17.68
113.02±22.73
0.263
Neck shaft angle(º)
127.22±5.22
128.27±5.39
125.76±4.72
0.095
Femoral Offset(mm)
37.32±5.91
37.45±4.57
37.13±7.49
0.852
Lateral angle(º)
7.76±1.60
8.07±1.70
7.33±1.38
0.108
* ‘P’ value < 0.05
1
Table 2: List of the various femur Morphological parameters correlation. Correlations
Correlation coefficient (r) 0.921
0.000**
Neck width SI vs Head Diameter AP
0.692
0.000**
Neck width SI vs Head Diameter SI
0.595
0.000**
Isthmus vs Neck width AP
-0.330
0.019*
Isthmus distance vs Head Diameter AP
0.303
0.032*
Isthmus distance vs Head Diameter SI
0.397
0.004**
Isthmus distance vs Isthmus
0.485
0.000**
Femoral Length vs Femoral head AP
0.652
0.000**
Femoral Length vs Femoral head SI
0.726
0.000**
Femoral Length vs Neck width SI
0.517
0.000**
Femoral Length vs Isthmus
0.325
0.021*
Femoral Length vs Isthmus Distance
0.532
0.000*
Neck shaft angle vs Neck width AP
0.374
0.008*
Neck shaft angle vs Isthmus
-0.330
0.019*
Neck shaft angle vs Isthmus distance
-0.309
0.029*
Femoral Offset vs Neck width AP
0.461
0.00**
Lateral angle Vs Anteversion
-0.316
0.025*
Head Diameter SI vs AP
* ‘P’ value < 0.05 ** ‘P’ value < 0.001
1
P value
Table 3: Comparison of Femur morphological features of various other population Study
Neck shaft
Anteversio
Isthmus(m
Ant
Femur
Head
Populatio
Angle (º)
n
m)
ROC(cm)
Length(mm
Diamete
)
r in mm
NA
40.8±3.4
n
(º)
Chinese &
125.6±6 to
11.4±7.7 to
South east
134±4.4
19.8±9.3
123±4.3
8.7±6.6 to
9.6
112±23.4
to 44.35
Asia Indian &
South Asia to126.8±5.
9±1.9
NA
13.6±7.9
418.8 to
41.7±3.1
436.5
to
8 Our study
127.2±5.2
45.4±3.7 11.2±7.4
11.9±1.7
116.8±20
419±28.5
43.5 ± 3.3, 43.8 ± 3.6
Western
122.9±7.6
countries
to
13.1±8
13.1±2.1 to
112 to
378.6±23.2
14.1±2.8
120±40
to
134.2±5.2
409.8±28,2
1
NA
Table 4: Best fit analysis of the available nails with the femur morphology and our recommended nailing option. Parameters
Nail A, B &
Best fit
overall Our
C Neck shaft
125 to135
Best fit
Overall
45(90%)
recommendation 30(60%) 3(6%)
120 º -140 º
48(96%)
3(6%)
-10 º TO 30 º
47(94%)
16(32%) 1(2%)
100-140
40(80%)
angle Anteversion 10 & 15 Roc
127.5, 140,
(cm)
152.5
1
36(72%)