Feature Article

Retrograde Nailing of a Femoral Supracondyle

Chi-Chuan Wu, MD; Ching-Lung Tai, PhD

  • Orthopedics
  • April 2012 - Volume 35 · Issue 4: e491-e496
  • DOI: 10.3928/01477447-20120327-20
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Abstract

Because standard femoral supracondylar nails have certain disadvantages, they are often replaced by traditional femoral or tibial locked nails. The purpose of this study was to make a biomechanical comparison between both types of traditional locked nails to determine which technique was more suitable for treating unstable femoral supracondylar fractures. Fourteen left Sawbones femurs (Pacific Research Laboratories, Vashon, Washington) were osteotomized in the femoral supracondylar area. One centimeter of the medial cortex in the proximal fragment was obliquely removed to simulate an unstable fracture without shortening. Seven specimens were treated with traditional retrograde dynamic femoral locked nails, and the other 7 with traditional retrograde dynamic tibial locked nails. All specimens were tested with a servohydraulic materials testing machine to compare their relative stability. Static compression, dynamic cyclic compression, and static compression to failure were tested. An extensometer was used to measure the displacement of fragments. Displacement between the fragments increased following the increment in loads in both nails. The load–displacement curve was nearly linear up to 1000 N for both nails. The femoral nail had a greater stiffness compared with the tibial nail at 100 and 200 N (P=.02 and P=.04, respectively) in static compression and at 700 to 1000 N (P=.01 in each case) in dynamic cyclic compression, as well as larger loads in static compression to failure (8663 vs 7547 N, respectively; P<.001). Clinically, a traditional femoral locked nail may be more suitable to replace a standard femoral supracondylar nail in a retrograde fashion to treat an unstable femoral supracondylar fracture.

Dr Wu is from the Department of Orthopedic Surgery, Chang Gung Memorial Hospital, and Dr Tai is from the Graduate Institute of Medical Mechatronics, Department of Mechanical Engineering, Chang Gung University, Taoyuan, Taiwan.

Drs Wu and Tai receive financial support from the National Science Council (NSC 98-2314-B-182A-011), Executive Yuan, Republic of China.

Correspondence should be addressed to: Chi-Chuan Wu, MD, Department of Orthopedic Surgery, Chang Gung Memorial Hospital, 5 Fu-Hsin St, 333, Taoyuan, Taiwan (ccwu@mail.cgu.edu.tw).

Retrograde locked intramedullary nailing is widely used to treat femoral supracondylar fractures.1–4 The advantages of this technique are that it (1) may be used as a closed technique, (2) may be used as a load-sharing device, (3) has a shorter lever arm for bending loads compared with plates, and (4) is not affected by the femoral condylar contour during nail insertion.5–7 A high union rate with a low complication rate has been reported in the literature.8,9

A Green-Seligson-Henry nail was the first standard retrograde locked nail used in the treatment of femoral supracondylar fractures.10 Because of their short length, all locked screws can be accurately inserted with a target device. Therefore, an image intensifier may not always be necessary intraoperatively. However, the short length of a Green-Seligson-Henry nail may create a stress riser in the femoral shaft, which can introduce a femoral shaft stress fracture.11 The end of a retrograde locked nail is recommended to reach the level of the lesser trochanter. Accordingly, insertion of locked screws in the upper end of a retrograde locked nail may require the assistance of an image intensifier. In general, insertion of locked screws in the hip area is technically demanding. In addition, the high cost of a standard supracondylar nail may restrict its wide use.

A traditional femoral or tibial locked nail is usually used to replace a standard supracondylar nail.12,13 To prevent a stress fracture, the end of these nails reaches the level of the lesser trochanter. Clinically, these nails are normally used in a dynamic mode, and locked screws are not inserted in the upper end of the nails. Although a high success rate has been reported,14 such a technique may not be applied in all types of femoral supracondylar fractures. Because traditional femoral or tibial locked nails have different contours, their individual use in the femoral supracondylar region may create a varied biomechanical effect. In the current prospective study, the biomechanical effect between both locked nails was compared. As a result of this comparison, it may be possible to recommend which device is better for the treatment of unstable femoral supracondylar fractures.

Materials and Methods

Fourteen left Sawbones femurs (Model #3306; Pacific Research Laboratories, Vashon, Washington) were evenly divided into 2 groups15–17: 1 for testing traditional femoral locked nails and 1 for testing traditional tibial locked nails. The femur had a length of 45 cm (from the piriformis fossa to the intercondylar notch).

A transverse osteotomy was made 3 cm proximal to the medial femoral condyle on all 14 femurs; then, an oblique osteotomy (1 cm length) was made on the proximal fragment from the superomedial to the inferolateral cortex (Figure 1). Subsequently, 1 cm width of the lateral aspect of the proximal fragment was transversely excised. This procedure created an unstable situation for reduced fragments. After the proximal and distal fragments were reduced, traditional femoral or tibial locked nails (Russell-Taylor locked nails; Smith & Nephew, Memphis, Tennessee) were inserted in a retrograde fashion (reaming to 13 mm and inserting 12-mm locked nails, respectively). One oblique femoral locked screw (diameter, 6.4 mm; length, 80 mm) or 2 transverse tibial locked screws (diameter, 5 mm; length, 50 and 60 mm) were inserted in the femoral condyle and supracondyle. No locked screws were inserted in the upper end of the femur. Thus, all fixations were in the dynamic mode (Figure 2). During the sample preparation, a retrograde femoral nail could be inserted smoothly, but a retrograde tibial nail was blocked due to the angled nail impacting on the hard anterior femoral cortex. Consequently, the osteotomy site was revised to match the tibial nail. This procedure slightly shortened the length of the femur (Figure 2).

Illustration of the testing protocol. A transverse osteotomy was made 3 cm proximal to the medial femoral condyle on all 14 left femurs; then, an oblique osteotomy (1 cm length) was made on the proximal fragment from the superomedial to the inferolateral cortex. Subsequently, 1 cm width of the lateral aspect of the proximal fragment was transversely excised. After the proximal and the distal fragments were reduced, tibial locked nails were inserted in a retrograde fashion. Two transverse tibial locked screws were inserted in the femoral supracondyle. No locked screws were inserted in the upper part of the femur.

Figure 1: Illustration of the testing protocol. A transverse osteotomy was made 3 cm proximal to the medial femoral condyle on all 14 left femurs; then, an oblique osteotomy (1 cm length) was made on the proximal fragment from the superomedial to the inferolateral cortex. Subsequently, 1 cm width of the lateral aspect of the proximal fragment was transversely excised. After the proximal and the distal fragments were reduced, tibial locked nails were inserted in a retrograde fashion. Two transverse tibial locked screws were inserted in the femoral supracondyle. No locked screws were inserted in the upper part of the femur.

After a femoral supracondylar osteotomy with removal of the partial medial cortex was performed, the specimens were treated with a traditional femoral (right) or tibial (left) locked nail in a retrograde fashion.

Figure 2: After a femoral supracondylar osteotomy with removal of the partial medial cortex was performed, the specimens were treated with a traditional femoral (right) or tibial (left) locked nail in a retrograde fashion.

All specimens were mounted in a uniaxial servohydraulic materials testing machine (Bionix 858; MTS Systems Corporation, Minneapolis, Minnesota) to compare the relative stability of the 2 types of locked nails (Figure 3). The distal end of the femoral condyle was potted with low-melting alloy in a 6×10-cm block. The femoral shaft was secured at 7° of adduction in the coronal plane and neutral in the sagittal plane. Thus, the mechanical axis was vertical to the ground. A metal cup that matched the femoral head was used for compression of the femur. An extensometer (MTS Systems Corporation) was placed with a vertical contact on the surface of the femoral shaft between both fragments medially to measure the displacement.

All specimens were tested with a servohydraulic materials testing machine for relative stability. The mechanical axis (from the femoral head to the center of the knee) was vertical to the ground. An extensometer was placed with a vertical contact on the surface of the femoral shaft between both fragments medially to measure the displacement.

Figure 3: All specimens were tested with a servohydraulic materials testing machine for relative stability. The mechanical axis (from the femoral head to the center of the knee) was vertical to the ground. An extensometer was placed with a vertical contact on the surface of the femoral shaft between both fragments medially to measure the displacement.

Static Compression Testing

A preload of 20 N was applied on the femoral head, which minimized the gap between the metal cup and the femoral head. A vertical compressive loading with a 0.5-mm per second increment up to 1000 N was applied directly to the femoral head. The applied load was recorded simultaneously with Testar II software (MTS Systems Corporation). The full range of displacement was set within 20 mm. The data acquisition was 1 data/0.01 mm.

Dynamic Cyclic Compression Testing

Using load control, loads were increased with each 100 N up to 1000 N applied to each construct with 500 cycles at a rate of 2 Hz. After each cycle increment, the reading of the displacement was obtained, and specimens were evaluated for evidence of failure. Failure was defined as pullout of the fixation screws, fracture displacement >2 mm, or permanent implant deformation.

Static Compression-to-failure Testing

Loads were applied until failure for each femur, and the ultimate failure strength was obtained. The static compressive strength of each group was obtained from the average failure strength of the 7 femurs in each group.

All data were compared using a paired Student’s t test. A P value of .05 indicated statistical significance.

Results

All 14 specimens completed all 3 tests. In the static compression test, displacement between both fragments increased following increased loads in both nails. The load–displacement curve was nearly linear up to 1000 N for both nails (Figure 4). The femoral nail had a greater stiffness compared with the tibial nail at 100 and 200 N (P=.02 and P=.04, respectively). However, other comparisons were not statistically significantly different (Table).

Load–displacement curve of the static compression test. A femoral locked nail has a greater stiffness than a tibial locked nail. Statistical significance is noted at 100 and 200 N (P<.05).

Figure 4: Load–displacement curve of the static compression test. A femoral locked nail has a greater stiffness than a tibial locked nail. Statistical significance is noted at 100 and 200 N (P<.05).

Displacement of Fragments Following Increased Compressive Loadsa

Table: Displacement of Fragments Following Increased Compressive Loads

In the dynamic cyclic compression test, displacement between both fragments increased following increased loads in both nails. The load–displacement curve was nearly linear up to 1000 N for both nails (Figure 5). The femoral nail had a greater stiffness compared with the tibial nail at 400, 700, 800, 900, and 1000 N (P=.04, P=.01, P=.01, P=.01, and P=.001, respectively). However, other comparisons were not statistically significantly different (Table).

Load–displacement curve of the dynamic cyclic compression test. A femoral locked nail has a greater stiffness than a tibial locked nail. Statistical significance is noted at 700 to 1000 N (P<.05).

Figure 5: Load–displacement curve of the dynamic cyclic compression test. A femoral locked nail has a greater stiffness than a tibial locked nail. Statistical significance is noted at 700 to 1000 N (P<.05).

In the static compression-to-failure test, the femoral nail failed at 8663±224 N, and the tibial nail failed at 7547±221 N (P<.001) (Table). All specimens failed due to transcervical femoral neck fractures (Figure 6). All shafts and implants were intact.

All static compression-to-failure tests ended with a transcervical femoral neck fracture. All shafts and implants were intact.

Figure 6: All static compression-to-failure tests ended with a transcervical femoral neck fracture. All shafts and implants were intact.

Discussion

Factors that favor fracture healing are minimal gap, adequate stability, and sufficient nutrition supply.18 By using dynamic intramedullary nailing to treat long-bone fractures, the gap between both fragments can be minimized.19,20 With a closed technique or minimized dissection of soft tissues, the periosteal vascularity can be preserved and nutrition supply can be well maintained.10,14 If local stability can be sufficiently provided, fracture healing is normally predictable. The current study biomechanically compared a traditional retrograde femoral locked nail and a traditional retrograde tibial locked nail to identify the more relatively stable device.

The mechanism of a dynamic intramedullary nail to stabilize a long-bone fracture is by way of a 3-point fixation principle.21,22 The axial compressive and rotational stabilities are provided by friction between the nail and the bone.23–25 The friction forces between the nail and the bone decide the degree of stability. Mechanically, the wider the contact area between the nail and the bone, the bigger the friction forces.26 Because the contour of a femoral locked nail is more similar to the femur than to a tibial locked nail, the contact area between the nail and the bone is wider in the former.27,28 Thus, a femoral locked nail should have greater success than a tibial locked nail in stabilizing the femur. Although in the current study the comparison is only statistically significant at 100 and 200 N with the static compression test and 700 to 1000 N with the dynamic cyclic compression test, other comparisons may be statistically significant if the testing specimens are increased.

In the current study, a tibial locked nail did not match snugly to the femur in a retrograde fashion.27 As a result, the fragment surface was revised to reduce the fracture. In such cases, the bone contact between the proximal and distal fragments may not be complete, which may reduce the testing stability. Clinically, a femoral locked nail is more commonly used in treating a femoral supracondylar fracture than a tibial locked nail.12,14 The current study confirmed this was a better choice.

When human beings ambulate, the knee sustains 3 to 5 times the body weight of stresses by axial compression, bending, and torsion.29,30 In the current study, a traditional femoral locked nail showed a better axial compressive and bending stability compared with a traditional tibial locked nail. Clinically, the fracture surface is normally rugged.31 After fracture fragments are reduced and compressed by axial compressive forces, the fracture surface is interlocked, and rotational stability increases. An unlocked intramedullary nail has been successfully used in the treatment of middle shaft noncomminuted long-bone fractures.32

Mechanical testing for fixation stability may use static or dynamic cyclic compression, and each has achieved individual support.33–35 In the current study, static and dynamic cyclic compressions achieved consistent results. A femoral locked nail was superior to a tibial locked nail.

A 12-mm-diameter femoral locked nail has a 6.4-mm proximal diagonal screw, and a 12-mm-diameter tibial locked nail has 2 proximal transverse screws. The biomechanical effect may be affected by these screws due to their close proximity to the fracture site.36 However, in the current study, all specimens sustained transcervical femoral neck fractures when undergoing static compression to failure. The osteotomy site, the nailed sawbone femur, and the nail with screws were completely intact. The femoral neck tolerated >750 kg of static compressive forces before fracturing. Thus, once a dynamic femoral or tibial locked nail is used in a retrograde fashion to treat a femoral supracondylar fracture, an implant failure should be unlikely to occur. In contrast, implant failure is not uncommon when an antegrade locked nail is used to treat a femoral supracondylar fracture.37

Variations exist in estimating numbers of steps in daily activity.38,39 In the current study, 500 cycles were used to test dynamic cyclic compression when compressive forces were increased.40 Clinically, under protected weight bearing, the number of steps may not greatly affect the fixation stability.41,42

A limitation of the current study is the small number of specimens, which may have affected the results of the statistical comparisons.35,39 All data showed that a femoral locked nail had better stability than a tibial locked nail. However, a small number of comparisons showed statistical significance. If the sample sizes were increased, more comparisons may have achieved statistical significance.

Conclusion

Because no previous reports have compared the 2 types of locked nails in treating femoral supracondylar fractures either biomechanically or clinically, the data of the current study cannot be compared with other findings. However, experimentally and theoretically, a femoral locked nail has a better stability than a tibial locked nail. The former should be preferentially considered when a femoral supracondylar fracture with an adequate indication is treated. The latter may be considered when a femoral locked nail is unsuitable for use, such as a short femur without an adequate length of femoral locked nails.

References

  1. Cannada LK, Taghizadeh S, Murali J, Obremskey WT, DeCook C, Bosse MJ. Retrograde intramedullary nailing in treatment of bilateral femur fractures. J Orthop Trauma. 2008; 22(8):530–534. doi:10.1097/BOT.0b013e318183eb48 [CrossRef]
  2. Daglar B, Gungor E, Delialioglu OM, et al. Comparison of knee function after antegrade and retrograde intramedullary nailing for diaphyseal femoral fractures: results of isokinetic evaluation. J Orthop Trauma. 2009; 23(9):640–644. doi:10.1097/BOT.0b013e3181a5ad33 [CrossRef]
  3. Ostrum RF, Maurer JP. Distal third femur fractures treated with retrograde femoral nailing and blocking screws. J Orthop Trauma. 2009; 23(9):681–684. doi:10.1097/BOT.0b013e3181ad61f2 [CrossRef]
  4. Poyanli O, Unay K, Akan K, Guven M, Ozkan K. No evidence of infection after retrograde nailing of supracondylar femur fracture in gunshot wounds. J Trauma. 2010; 68(4):970–974.
  5. Meyer RW, Plaxton NA, Postak PD, Gilmore A, Froimson MI, Greenwald AS. Mechanical comparison of a distal femoral side plate and a retrograde intramedullary nail. J Orthop Trauma. 2000; 14(6):398–404. doi:10.1097/00005131-200008000-00004 [CrossRef]
  6. Chen SH, Yu TC, Chang CH, Lu YC. Biomechanical analysis of retrograde intramedullary nail fixation in distal femoral fractures [published online ahead of print August 21, 2008]. Knee. 2008; 15(5):384–389. doi:10.1016/j.knee.2008.05.010 [CrossRef]
  7. Ricci WM, Gallagher B, Haidukewych GJ. Intramedullary nailing of femoral shaft fractures: current concepts. J Am Acad Orthop Surg. 2009; 17(5):296–305.
  8. Moed BR, Watson JT. Retrograde nailing of the femoral shaft. J Am Acad Orthop Surg. 1999; 7(4):209–216.
  9. El-Kawy S, Ansara S, Moftah A, Shalaby H, Varughese V. Retrograde femoral nailing in elderly patients with supracondylar fracture femur; is it the answer for a clinical problem [published online ahead of print May 9, 2006]?Int Orthop. 2007; 31(1):83–86. doi:10.1007/s00264-006-0137-4 [CrossRef]
  10. Henry SL, Trager S, Green S, Seligson D. Management of supracondylar fractures of the femur with the GSH intramedullary nail: preliminary report. Contemp Orthop. 1991; 22(6):631–640.
  11. Ricci WM. Femur: trauma. In: Vaccaro AR, ed. Orthopedic Knowledge Update 8. Vol 2. Rosemont, IL: American Academy of Orthopedic Surgeons; 2005:425–431.
  12. Gregory P, DiCicco J, Karpik K, DiPasquale T, Herscovici D, Sanders R. Ipsilateral fractures of the femur and tibia: treatment with retrograde femoral nailing and unreamed tibial nailing. J Orthop Trauma. 1996; 10(5):309–316. doi:10.1097/00005131-199607000-00004 [CrossRef]
  13. Frankle M, Cordey J, Sanders RW, Koval K, Perren SM. A biomechanical comparison of the antegrade inserted universal femoral nail with the retrograde inserted universal tibial nail for use in femoral shaft fractures. Injury. 1999; 30(suppl 1):A40–A43. doi:10.1016/S0020-1383(99)00125-4 [CrossRef]
  14. Wu CC. Retrograde dynamic locked nailing for femoral supracondylar nonunions after plating. J Trauma. 2009; 66(1):195–199. doi:10.1097/TA.0b013e3181492f2a [CrossRef]
  15. McKellop H, Ebramzadeh E, Niederer PG, Sarmiento A. Comparison of the stability of press-fit prosthesis femoral stem using a synthetic femur model. J Orthop Res. 1991; 9(2):297–305. doi:10.1002/jor.1100090219 [CrossRef]
  16. Harman MK, Toni A, Cristofolini L, Viceconti M. Initial stability of uncemented hip stems: an in vitro protocol to measure torsional interface motion. Med Eng Phys. 1995; 17(3):163–171. doi:10.1016/1350-4533(95)95705-F [CrossRef]
  17. McNamara BP, Cristofolini L, Toni A, Taylor D. Relationship between bone-prosthesis bonding and load transfer in total hip reconstruction. J Biomech. 1997; 30(6):621–630. doi:10.1016/S0021-9290(97)00003-1 [CrossRef]
  18. Karlström G, Olerud S. Fractures of the tibial shaft; a critical evaluation of treatment alternatives. Clin Orthop Relat Res. 1974; (105):82–111.
  19. Wu CC. The effect of dynamization on slowing the healing of femur shaft fractures after interlocking nailing. J Trauma. 1997; 43(2):263–267. doi:10.1097/00005373-199708000-00010 [CrossRef]
  20. Tigani D, Fravisini M, Stagni C, Pascarella R, Boriani S. Interlocking nail for femoral shaft fractures: is dynamization always necessary [published online ahead of print February 16, 2005]?Int Orthop. 2005; 29(2):101–104. doi:10.1007/s00264-004-0627-1 [CrossRef]
  21. Klemm KW. Interlocking nailing of complex fractures. In: Seligson D, ed. Concepts in Intramedullary Nailing. Orlando, FL: Grune & Stratton; 1985:293–313.
  22. Dagrenat D, Kempf I. Biomechanics of locked intramedullary fixation of fractures. In: Kempf I, Leung KS, eds. Practice of Intramedullary Locked Nails: Scientific Basis and Standard Techniques. Berlin, Germany: Springer; 2002:43–49. doi:10.1007/978-3-642-56330-0_5 [CrossRef]
  23. Perren SM. Physical and biological aspects of fracture healing with special reference to internal fixation. Clin Orthop Relat Res. 1979; (138):175–196.
  24. Donald GD, Pope MH. Design of intramedullary nails. In: Seligson D, ed. Concepts in Intramedullary Nailing. Orlando, FL: Grune & Stratton; 1985:69–90.
  25. Schopfer A, Hearn TC, Malisano L, Powell JN, Kellam JF. Comparison of torsional strength of humeral intramedullary nailing: a cadaveric study. J Orthop Trauma. 1994; 8(5):414–421. doi:10.1097/00005131-199410000-00008 [CrossRef]
  26. Carpick RW, Ogletree DF, Salmeron M. A general equation for fitting contact area and friction vs load measurements. J Colloid Interface Sci. 1999; 211(2):395–400. doi:10.1006/jcis.1998.6027 [CrossRef]
  27. Thakur AJ. The Elements of Fracture Fixation. New York, NY: Churchill Livingstone; 1997.
  28. Gaebler C, Speitling A, Milne EL, Stanzl-Tschegg S, Vécsei V, Latta LL. A new modular testing system for biomechanical evaluation of tibial intramedullary fixation devices. Injury. 2001; 32(9):708–712. doi:10.1016/S0020-1383(01)00044-4 [CrossRef]
  29. Nordin M, Frankel VH. Biomechanics of the knee. In: Nordin M, Frankel VH, eds. Basic Biomechanics of the Musculoskeletal System. Philadelphia, PA: Lea & Febiger; 1989:115–134.
  30. Harrington IJ. Knee joint force in normal and pathological gait. In: Niwa S, Perren SM, Hattori T, eds. Biomechanics in Orthopedics. Tokyo, Japan: Springer-Verlag; 1992:121–146. doi:10.1007/978-4-431-68216-5_7 [CrossRef]
  31. Perren SM. Biomechanics of intramedullary nailing. In: Browner BD, Edwards CC, eds. The Science and Practice of Intramedullary Nailing. Baltimore, MD: Williams & Wilkins; 1989:67–75.
  32. Hooper GJ, Lyon DW. Closed unlocked nailing for comminuted femoral fractures. J Bone Joint Surg Br. 1988; 70(4):619–621.
  33. Kinast C, Frigg R, Perren SM. Biomechanics of the interlocking nail. A study of the proximal interlock. Arch Orthop Trauma Surg. 1990; 109(4):197–204. doi:10.1007/BF00453141 [CrossRef]
  34. Sim E, Schmiedmayer HB, Lugner P. Mechanical factors responsible for the obstruction of the gliding mechanism of a dynamic hip screw for stabilizing pertrochanteric femoral fractures. J Trauma. 2000; 49(6):995–1001. doi:10.1097/00005373-200012000-00003 [CrossRef]
  35. Thakur NA, Crisco JJ, Moore DC, Froehlich JA, Limbird RS, Bliss JM. An improved method for cable grip fixation of the greater trochanter after trochanteric slide osteotomy [published online ahead of print December 5, 2008]. J Arthroplasty. 2010; 25(2):319–324. doi:10.1016/j.arth.2008.10.006 [CrossRef]
  36. Nordin M, Frankel VH. Biomechanics of bone. In: Nordin M, Frankel VH, eds. Basic Biomechanics of the Musculoskeletal System. Philadelphia, PA: Lea & Febiger; 1989:3–29.
  37. Wu CC, Shih CH. Biomechanical analysis of the mechanism of interlocking nail failure. Arch Orthop Trauma Surg. 1992; 111(5):268–272. doi:10.1007/BF00571522 [CrossRef]
  38. Schmalzried TP, Szuszczewicz ES, Northfield MR, et al. Quantitative assessment of walking activity after total hip or knee replacement. J Bone Joint Surg Am. 1998; 80(1):54–59.
  39. Hoenig M, Gao F, Kinder J, Zhang LQ, Collinge C, Merk BR. Extra-articular distal tibial fractures: a mechanical evaluation of 4 different treatment methods. J Orthop Trauma. 2010; 24(1):30–35. doi:10.1097/BOT.0b013e3181c29bc0 [CrossRef]
  40. Wähnert D, Hoffmeier KL, von Oldenburg G, Fröber R, Hofmann GO, Mückley T. Internal fixation of type-C distal femoral fractures in osteoporotic bone. J Bone Joint Surg Am. 2010; 92(6):1442–1452. doi:10.2106/JBJS.H.01722 [CrossRef]
  41. Cheung G, Zalzal P, Bhandari M, Spelt JK, Papini M. Finite element analysis of a femoral retrograde intramedullary nail subject to gait loading. Med Eng Phys. 2004; 26(2):93–108. doi:10.1016/j.medengphy.2003.10.006 [CrossRef]
  42. Youdas JW, Kotajarvi BJ, Padgett DJ, Kaufman KR. Partial weight-bearing gait using conventional assistive devices. Arch Phys Med Rehabil. 2005; 86(3):394–398. doi:10.1016/j.apmr.2004.03.026 [CrossRef]

Displacement of Fragments Following Increased Compressive Loadsa

Load, NStatic Compression, mm
Dynamic Cyclic Compression, mm
Femoral Nail (n=7)Tibial Nail (n=7)PFemoral Nail (n=7)Tibial Nail (n=7)P
1000.013±0.0020.016±0.002.02b0.011±0.0020.011±0.001.48
2000.027±0.0020.030±0.002.04b0.023±0.0020.024±0.001.35
3000.041±0.0030.045±0.004.060.036±0.0030.039±0.002.19
4000.057±0.0050.059±0.004.450.047±0.0030.052±0.002.04b
5000.070±0.0070.073±0.005.340.058±0.0040.062±0.001.07
6000.083±0.0080.087±0.005.270.073±0.0040.074±0.002.63
7000.095±0.0090.099±0.004.310.080±0.0020.085±0.003.01b
8000.106±0.0090.112±0.005.140.091±0.0030.098±0.003.01b
9000.116±0.0110.124±0.004.120.105±0.0040.112±0.003.01b
10000.126±0.0100.135±0.005.070.112±0.0030.127±0.004.001b
Failure load8663±2247547±221<.001b
AUTHORS

Dr Wu is from the Department of Orthopedic Surgery, Chang Gung Memorial Hospital, and Dr Tai is from the Graduate Institute of Medical Mechatronics, Department of Mechanical Engineering, Chang Gung University, Taoyuan, Taiwan.

Drs Wu and Tai receive financial support from the National Science Council (NSC 98-2314-B-182A-011), Executive Yuan, Republic of China.

Correspondence should be addressed to: Chi-Chuan Wu, MD, Department of Orthopedic Surgery, Chang Gung Memorial Hospital, 5 Fu-Hsin St, 333, Taoyuan, Taiwan ().ccwu@mail.cgu.edu.tw

doi: 10.3928/01477447-20120327-20

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