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    Modular Junction Fracture of a Revision Femoral Stem

    A 60-yearold male patient presents with thigh pain and an inability to ambulate 2 years following a revision total hip arthroplasty with a modular tapered fluted titanium stem. What are the best treatment options for his reconstruction?

    Authors

    John P. Prodoehl, BS, and P. Maxwell Courtney, MD

    Introduction

    Tapered fluted titanium stems have become increasingly common in revision total hip arthroplasty (THA). Many surgeons prefer these implants over fully-porous coated cylindrical stems for ease of use and potentially reduced rates of subsidence in cases with substantial femoral bone loss (Paprosky IIIB) where there is less than 4 cm of cortical fit. [1]

    Modular stems provide versatility and flexibility, allowing surgeons to make intraoperative component adjustments for leg length and offset. Several studies show excellent results with modern modular stem designs, including subsidence and mid-term survivorship rates comparable to those of monoblock stems. [2-5]

    The use of modular designs can be of some concern, however, as biomechanical weakness at the modular junction may result in catastrophic implant failure. This has been reported in a few studies. [6,7] Femoral component fracture is a rare complication of monoblock and modular stems in revision THA. Risk factors include: [8,9]

    • Higher activity level
    • Increased body mass index (BMI)
    • Small stem diameter
    • Lack of proximal bony support

    In this case report, we describe the management of a patient with a modular junction fracture of a revision femoral stem, including how to remove the implant and what options are available for reconstruction.

    Case Presentation

    A 60-year-old male patient presents from an outside facility after feeling his right hip “pop” when flexing forward at the waist.

    The patient had undergone a right THA 4 years prior and a subsequent revision THA for a periprosthetic fracture 2 years later. A modular femoral stem (Arcos, Zimmer Biomet; Warsaw, Indiana) was used in the revision. The current implants include a 50 mm, size A cone proximal body with a 16 x 190 mm stem.

    He had been doing well after his revision, with no antecedent hip pain. The patient works as a carpenter, is an avid golfer, and had been ambulating up to 4 miles per day. Immediately after this incident, he was in significant pain and had marked difficulty with weight-bearing.

    His past medical history is significant only for hypertension and asthma.

    Physical Exam

    • Height: 6 feet, 0 inches; weight: 280 pounds; body mass index: 38 kg/m2
    • Well-healed posterior incision
    • 2-cm limb-length discrepancy, right shorter than left
    • Swelling at right lateral proximal thigh
    • Pain with any range of motion of the operative hip
    • Normal distal right lower extremity motor and sensory exam
    • Palpable pedal pulses

    Laboratory Tests

    • C-reactive protein: 0.6 mg/dL
    • Erythrocyte sedimentation rate: 17 mm/hr
    • No growth from intraoperative cultures

    Imaging

    Figure 1. Preoperative radiograph (left) and intraoperative clinical photo demonstrate a fracture at the modular junction of a revision femoral stem.

    Figure 2. Postoperative radiographs demonstrate a cementless proximal femoral replacement and a revision multihole acetabular component with a modular dual mobility bearing.

    Diagnosis

    • Fracture of a revision femoral stem at the modular junction

    Treatment

    We carefully discussed all risks, benefits, and alternatives of the surgical procedure with the patient. He wanted to proceed with revision arthroplasty of his right hip. There were several considerations for the management of this patient, the most challenging of which was implant removal.

    Procedure

    • Using the posterolateral approach, we accessed and identified the fractured 50 mm, size A cone proximal body. It had likely been inadequate for proximal bony support in this patient, although we did not have preoperative radiographs available for review. There was no ability to use a threaded inserter, as the stem-body junction was fractured.
    • We removed the fractured proximal body easily and attempted to preserve the greater trochanter in a single soft tissue sleeve with the abductors and vastus lateralis to help with stability postoperatively.
    • Based on preoperative templating, we resected an additional 5 cm of femur and used a metal cutting burr to cut the stem approximately 2 cm from its distal tip. This left enough cortical scratch fit (minimum needed is 4 cm) for reconstruction.
    • We used several pencil-tip burrs and trephines to ream over and finally remove the stem.
    • No revision stem would have provided adequate proximal support – and might have even failed by the same mechanism – so we elected to use a megaprosthesis. Given the patient’s age and activity level, we chose cementless fixation for the proximal femoral replacement.
    • We reamed to 17 mm for a 150 mm stem (OSS stem, Zimmer Biomet; Warsaw, Indiana) and then impacted into place the stem with the body, ensuring appropriate anteversion.
    • The hip was still unstable, given the version on the existing shell. We removed the acetabular component with explant osteotomes and minimal bone loss, reamed up to 64, and impacted a new acetabular component into place with more anteversion.
    • Because the patient had undergone prior revision, we chose to use a modular dual-mobility bearing to minimize the risk of instability.

    Postoperative Follow-up

    Postoperatively, the patient was allowed to bear weight as tolerated, with posterior hip precautions for 6 weeks. At 3 months, he was back to work with no assistive device, and at 6 months, he was doing well with no pain.

    Surgical Pearls

    • Modular tapered revision stems can fail at the stem-body junction with catastrophic consequences.
    • If using a modular stem in revision THA, ensure that there is enough bony support proximally to minimize the risk of junction failure, especially in patients who are younger, active, and have a higher BMI.
    • Have several metal cutting burrs and 2 sets of trephines available to aid in implant removal of a fractured stem.
    • Since patients with a fractured modular stem junction are usually younger and more active, cementless fixation for a proximal femoral replacement is a good bone-preserving option for reconstruction.

    Author Information

    John P. Prodoehl, BS, is a medical student at Thomas Jefferson University, Sidney Kimmell School of Medicine, in Philadelphia, Pennsylvania. P. Maxwell Courtney, MD, is from The Rothman Institute at Thomas Jefferson University Hospital, Philadelphia, Pennsylvania. Dr. Courtney is also the Adult Reconstruction Section Editor of Rothman Institute Grand Rounds on ICJR.net.

    Disclosures: Mr. Prodoehl has no disclosures relevant to this article. Dr. Courtney has disclosed that he is a paid consultant for DePuy Synthes, Hip Innovation Technology, Stryker, and Zimmer Biomet; that he has stock or stock options in Parvizi Surgical Innovation; and that he is paid presenter or speaker for Smith & Nephew.

    References

    1. Bougherara H, Zdero R, Shah S, et al. A biomechanical assessment of modular and monoblock revision hip implants using FE analysis and strain gage measurements. J Orthop Surg Res. 2010 May 12;5:34. doi: 10.1186/1749-799X-5-34.
    2. Clair A, Gabor J, Patel K, Friedlander S, Deshmukh A, Schwarzkopf R. Subsidence following revision total hip arthroplasty using modular and monolithic components. J Arthroplasty. 2020 Jun;35(6S):S299-S303. doi: 10.1016/j.arth.2020.03.008. Epub 2020 Mar 12.
    3. Moriarty P, Sheridan GA, Wong L, Guerin S, Gul R, Harty JA. Bicortical contact predicts subsidence of modular tapered stems in revision total hip arthroplasty. J Arthroplasty. 2020 Aug;35(8):2195-2199. doi: 10.1016/j.arth.2020.03.047. Epub 2020 Apr 1.
    4. Parry JA, Hernandez NM, Berry DJ, Abdel MP, Yuan BJ. Risk factors for subsidence of modular fluted tapered stems used during revision total hip arthroplasty for periprosthetic hip fractures. J Arthroplasty. 2018 Sep;33(9):2967-2970. doi: 10.1016/j.arth.2018.05.006. Epub 2018 May 9.
    5. Yacovelli S, Ottaway J, Banerjee S, Courtney PM. Modern revision femoral stem designs have no difference in rates of subsidence. J Arthroplasty. 2021;36(1):268-73.
    6. Konan S, Garbuz DS, Masri BA, Duncan CP. Modular tapered titanium stems in revision arthroplasty of the hip: the risk and causes of stem fracture. Bone Joint J. 2016;98-b(1 Suppl A):50-3. doi: 10.1302/0301-620X.98B1.36442.
    7. Kop AM, Keogh C, Swarts E. Proximal component modularity in THA–at what cost? An implant retrieval study. Clin Orthop Relat Res. 2012;470(7):1885-94. doi: 10.1007/s11999-011-2155-9.
    8. Lakstein D, Eliaz N, Levi O. Fracture of cementless femoral stems at the mid-stem junction in modular revision hip arthroplasty systems. J Bone Joint Surg Am. 2011 Jan 5;93(1):57-65. doi: 10.2106/JBJS.I.01589.
    9. Azzam KA, Austin MS, Sharkey PF. Early failure of a nonmodular titanium femoral stem after primary hip arthroplasty. J Arthroplasty2010 Feb;25(2):333.e1-5. doi: 10.1016/j.arth.2008.11.104. Epub 2009 Jan 15.