0
    211
    views

    Femoral Revisions: What Are the Options?

    At the ICJR Australia meeting in Sydney, Paul N. Smith, MD, FRACS, reviewed his goals when performing a revision total hip:

    • Achieve an “anatomic” reconstruction
    • Restoration of the hip center of rotation, done largely on the acetabular side
    • Restoration of femoral offset, done on the femoral side
    • Restoration of limb length
    • Achieve a “mechanically sound” construct
    • Good fixation to host bone
    • Ensure a stable reconstruction that does not dislocate

    Dr. Smith emphasized the importance of an anatomic reconstruction. Failure to restore “normal” anatomy in a hip arthroplasty has been associated with a higher rate of dislocation, muscle weakness, limping, leg length discrepancy, and impingement, as well as higher risk of early failure due to the increased load on the joint interphases.

    On the femoral side, the femoral offset is particularly important. Restoration of the femoral offset improves range of motion, abductor strength, and WOMAC function scores. By virtue of joint reaction forces, polyethylene bearing wear is reduced, and range of motion is improved.

    Regarding limb length [1], Dr. Smith said that while it may not be possible to achieve perfect limb length equality, it is important to strive to get as close as possible

    Planning the Femoral Revision

    When planning a revision of the femoral component in a total hip arthroplasty, Dr. Smith finds it helpful to use the 1998 Mallory Classification of bone defects:

    • Type 1: Intact metaphyseal cancellous and cortical bone
    • Type 2: Deficient metaphyseal cancellous bone, intact cortical bone
    • Type 3: Deficient cancellous and cortical bone
      • 3a: Proximal to the lesser trochanter
      • 3b: Distal to the lesser trochanter but proximal to diaphysis
      • 3c: Distal to the diaphysis

    What are the options for the femoral revision, given the goals of revision and the amount of bone loss? Generally speaking, there are cemented and cementless options. The option chosen for a procedure will be determined by:

    • Type of bone defect
    • Age of the patient
    • Techniques with which the surgeon is familiar

    Cemented Revision

    If a cemented revision alone is selected, it is important remember that the strength of the revision depends entirely on the strength of the cement-to-bone interface, which in turn depends on the integrity of the cancellous bone.

    If cementing into a cortical bone tube, the strength of the interface is going to be only about 20% of the strength of cementing into cancellous bone [2].

    An older study by Kershaw [3] showed a 6-times higher failure rate when cementing into poor bone stock versus cementing into normal bone stock. A 2007 study by Howie [4] showed a 98% survivorship at 9 years using a collarless double-taper stem, versus 93% using a standard stem.

    Cement-in-Cement Revision

    For a well-fixed femoral component, Dr. Smith is a proponent of leaving the well-fixed bone cement in place and performing a cement-in-cement revision.

    Removing well-fixed bone cement is technically challenging and time consuming, and it involves risks of fracture or penetration of the femur. As described by Greenwald in 1978 [6], the shear strength of cement-into-cement is 94% of the strength of a single mantle, so why not leave well-fixed cement in place?

    To use cement-in-cement technique, the existing mantle must be well fixed, with no loose cement below the level of the lesser trochanter. This technique is indicated for:

    • Removal of the femoral stem to improve access when revising the acetabular component
    • Exchanging a monoblock stem with a damaged head or a modular stem with a damaged or incompatible taper
    • Altering the version of the femoral component in cases or recurrent instability
    • Altering leg length for discrepancy
    • Replacing the component due to fracture of the stem

    Duncan et al [7] reported no stem loosening and a 92% all-cause revision survival at an 8-year average follow-up using cement-in-cement technique

    Impaction Bone Grafting with Cement

    Another fixation option is impaction bone grafting with cement. A 2009 study by Ornstein et al [8] reviewed Swedish registry results for 1,305 such procedures performed in 1,188 patients with a 5- to 18-year follow-up and found an all-cause revision survivorship at 15 years of 94%.

    The disadvantages of this technique are that it:

    • Is technically demanding and has steep learning curve
    • Takes longer
    • Carries an increased risk of intraoperative fracture

    The advantages of this technique are that it:

    • Is the only way to restore bone stock
    • Deals with the patulous femur
    • May be the best option in young patients

    Uncemented Revision Options

    Dr. Smith considers these options as either modular or non-modular.

    • Modular stems
    • Proximal modularity
    • Mid-stem modularity
    • Non-modular stems
    • Proximally coated (historical)
    • Extensively coated

    Recent research shows the modular stems work quite well, with survival rates of 94% to 95% at 6 to 10 years of follow-up. [9, 10]

    Non-modular extensively coated stems are the current stems of choice for many surgeons. If used in the right circumstances, the results are very good, with 95.9% survivorship at 10 years [11].

    Summary

    Dr. Smith summarized his preferences for which techniques to use:

    • Mallory Type 1: Primary implant
    • Mallory Type 2 and 3a
      • Cemented revision with impaction grafting
      • Uncemented revision with proximal or distal fixing modular or non-modular component
    • Mallory Type 3b
      • Impaction grafting
      • Uncemented revision with distal fixing modular or non-modular component
    • Mallory Type 3c
      • Possibly impaction grafting for a patulous femur
      • Tumor prosthesis or allograft composite

    Dr. Smith’s presentation can be found here.

    References

    1. Anatomic and functional leg-length inequality: A review and recommendation for clinical decision-making. Part I, anatomic leg-length inequality: prevalence, magnitude, effects and clinical significance. Gary A Knutson. Chiropractic & Osteopathy 2005, 13:11
    2. Mechanical strength of the cement–bone interface is greater in shear than in tension. K.A Mann, F.W Werner, D.C Ayers. Journal of Biomechanics. Volume 32, Issue 11, p1251–1254, November 1999
    3. Revision total hip arthroplasty for aseptic failure. A review of 276 cases. Kershaw CJ, Atkins RM, Dodd CA, Bulstrode CJ. J Bone Joint Surg Br. 1991 Jul;73(4):564-8.
    4. Revision total hip replacement using cemented collarless double-taper femoral components. Howie DW, Wimhurst JA, McGee MA, Carbone TA, Badaruddin BS. J Bone Joint Surg Br. 2007 Jul;89(7):879-86.
    5. Points in the technique of recementing in the revision of an implant arthroplasty. Greenwald AS, Narten NC, Wilde AH. J Bone Joint Surg Br. 1978 Feb;60(1):107-10.
    6. Revision of the cemented femoral stem using a cement-in-cement technique: a five- to 15-year review. Duncan WW1, Hubble MJ, Howell JR, Whitehouse SL, Timperley AJ, Gie GA. J Bone Joint Surg Br. 2009 May;91(5):577-82.
    7. Femoral impaction bone grafting with the Exeter stem – the Swedish experience: survivorship analysis of 1305 revisions performed between 1989 and 2002. Ornstein E, Linder L, Ranstam J, Lewold S, Eisler T, Torper M. J Bone Joint Surg Br. 2009 Apr;91(4):441-6.
    8. Clinical and radiographic assessment of a modular cementless ingrowth femoral stem system for revision hip arthroplasty. Walter WL1, Walter WK, Zicat B. J Arthroplasty. 2006 Feb;21(2):172-8.
    9. Revision hip arthroplasty with a modular cementless stem: mid-term follow up. Jibodh SR1, Schwarzkopf R, Anthony SG, Malchau H, Dempsey KE, Estok DM 2nd. J Arthroplasty. 2013 Aug;28(7):1167-72.
    10. Extensively porous-coated stems for femoral revision: a choice for all seasons. Hamilton WG1, Cashen DV, Ho H, Hopper RH Jr, Engh CA. J Arthroplasty. 2007 Jun;22(4 Suppl 1):106-10.