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Radiographic and Computed Tomography Analysis of Cemented Pegged Polyethylene Glenoid Components in Total Shoulder Replacement
Edward H. Yian, MD1; Clément M.L. Werner, MD2; Richard W. Nyffeler, MD2; Christian W. Pfirrmann, MD2; Arun Ramappa, MD2; Atul Sukthankar, MD2; Christian Gerber, MD2
1 Southern California Permanente Medical Group, 3401 South Harbor Boulevard, Santa Ava, CA 92704
2 Department of Orthopaedic Surgery, University of Zurich, Balgrist, Forchstrasse 340, 8008 Zurich, Switzerland. E-mail address for C. Gerber: christian.gerber@balgrist.ch
View Disclosures and Other Information
In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from the ResOrtho Foundation, Zurich, Switzerland. In addition, one or more of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity (Zimmer, Inc.). Also, a commercial entity (Zimmer, Inc.) paid or directed, or agreed to pay or direct, benefits to a research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
Investigation performed at the Department of Orthopaedic Surgery, University of Zurich, Balgrist, Zurich, Switzerland

The Journal of Bone and Joint Surgery, Incorporated
J Bone Joint Surg Am, 2005 Sep 01;87(9):1928-1936. doi: 10.2106/JBJS.D.02675
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Abstract

Background: Glenoid loosening continues to be the primary reason for failure of total shoulder arthroplasty. The purpose of this study was to evaluate, with use of a sensitive and reproducible imaging method, the radiographic and clinical results of total shoulder replacement with a pegged, cemented polyethylene glenoid implant.

Methods: Forty-three patients (forty-seven shoulders) underwent a total shoulder replacement with a cemented polyethylene glenoid component with four threaded pegs. The patients were examined clinically, with fluoroscopically guided radiographs, and with computed tomography at an average of forty months. In addition to conventional scoring of radiographic lucency, an 18-point scoring system was used to quantify cement-peg lucencies in six zones of the back surface of the glenoid component as seen on computed tomography scans.

Results: On the average, the absolute Constant score improved from 39 points preoperatively to 70 points at the time of follow-up (p = 0.0001) and the pain score improved from 5 to 13 points (p = 0.001). The mean active anterior elevation improved by 34° (p = 0.001) and the mean abduction, by 46° (p = 0.006). Two patients had symptomatic glenoid loosening requiring revision. Twenty-one of the forty-seven shoulders had radiographic lucency around the glenoid pegs, and nine had progression of the lucency by at least two grades. Computed tomography detected lucencies, primarily at the bone-cement interface, in thirty-six shoulders. The scores for the lucencies seen on the computed tomography scans were associated with the radiographic lucency scores (p < 0.001), pain scores (p = 0.04), and abduction strength (p = 0.02). Computed tomography was more sensitive than radiography with regard to identifying the number of pegs associated with lucency and the size of the lucencies. The overall reproducibility of the scoring based on the computed tomography was higher than that of the radiographic scoring.

Conclusions: Computed tomography provided a more sensitive and reproducible tool for the assessment of loosening of pegged glenoid components than did fluoroscopically guided conventional radiography. Further improvement in implant design and fixation technique appears to be necessary for long-term success of cemented glenoid components.

Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

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    Accreditation Statement
    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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    Thomas M. Gregory
    Posted on January 21, 2011
    Spect-CT: A Useful Tool in the Decision-Making for Glenoid Implant Revision After TSA
    Consultant, Imperial College, London, United Kingdom

    To the Editor:

    We read with interest the article published in 2005 by Yian et al. entitled, “Radiographic and Computed Tomography Analysis of Cemented Pegged Polyethylene Glenoid Components in Total Shoulder Replacement” (2005;87:1928-36). Yian et al. demonstrated that, compared to plane X-rays, computed tomography provided a more sensitive and reproducible tool for assessment of lucencies around the glenoid component. However, they acknowledged that visualization of the glenoid fixation was severely blurred by artefacts caused by the metallic humeral head. A further disadvantage of computed tomography is the need for repeated scans if attempting to demonstrate the existence of active biologic processes, i.e. aseptic glenoid loosening. In the shoulder such repeated scans necessarily causes increased radiation exposure of sensitive organs such as breast, lungs and thyroid.

    Combining computed tomography slices co-registered with tomographic images from a conventional bone scan (Tc99m HDP/ Oxidronate), namely using Tc99m HDP Bone SPECT-CT, could improve the detection of glenoid aseptic loosening without the need for possibly concerning radiation doses and may provide and important new tool in the decision making to revise the glenoid implant. We chose to test the possible value of this methodology in a patient with a suspected loose glenoid.

    The patient was 63 years old when she presented to our clinic. The indication for her primary total shoulder procedure was advanced osteoarthritis. The initial procedure was performed in 1999 in another center. No information on the rotator cuff status or on the evolution of the radiolucent line on plane radiograph were available. The initial outcome was reported by the patient as excellent, with a gradual deterioration over time. The patient presented to our clinic at ten years following the index procedure with persistent and severe pain. Active movement was restricted to 90° of forward flexion and 70° of abduction. On plane X-rays, we noticed a complete radiolucent line around the glenoid component with upward migration of the humeral head (Figure 1). An ultrasound scan confirmed the integrity of the cuff. The analysis of the interface and feasibility of revision of this component was assessed by a CT-scan. The scan demonstrated a wide radiolucent line at the bone cement interface of the glenoid (Figure 2). Subsequently, a Bone SPECT/CT (GE Infinia Hawkeye 4) was performed to assess for a potentially active process around the implant. The images revealed avid tracer uptake that localised to the radiolucent zone on the CT-scan (Figure 3). Because of these observations, the diagnosis of progressive aseptic glenoid loosening was considered highly likely and it was decided to revise the glenoid. At revision surgery, the glenoid component was found to be loose and worn with granuloma formation.


    Fig 1. Plane X-rays.


    Fig 2. CT-scan with patient in lateral decubitus and the arm elevated: Sagittal, Coronal and Axial views of the glenoid implant and fixation.


    Fig 3. Spect-CT demonstrating avid tracer uptake around the glenoid implant fixation.

    Bone SPECT-CT finds more and more applications in musculo-skeletal pathology (1). Increased tracer uptake demonstrates active bone turn-over. According to previous use of bone scanning in knee or hip arthroplasty, increased uptake can be visualized for up to 2 years after joint replacement, due to bone remodelling (2). After 2 years, active process around glenoid fixation is very likely to be pathological (2) (aseptic or septic loosening), especially when associated with radiolucent zone on CT-scan. Conversely, CT evidence for lucency or cavities around the implant without increased tracer uptake are probably not of pathological origin.

    In conclusion, beside the use of conventional CT-scan, Tc99m HDP-Bone SPECT-CT is an helpful tool to detect glenoid aseptic loosening of shoulder prosthesis and subsequently to aid in the decision to perform revision surgery. This application of SPECT-CT has not been reported previously.

    References

    1. Scharf S. SPECT/CT imaging in general orthopedic practice. Semin Nucl Med. 2009;39:293-307.

    2. Rosenthall L. Hip and knee prostheses: evaluation of the natural history of periprosthetic bone changes. Semin Nucl Med. 1997;27:346-54.

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