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    Using the Cement-Within-Cement Technique for Humeral Fixation in Revision RSA

    Editor’s note: Research papers intended for presentation at the canceled annual meeting of the American Academy of Orthopaedic Surgeons are now available online at the AAOS Virtual Education Experience. We’ll be highlighting a few of the more interesting papers throughout the summer.

    Surgeons who perform total hip arthroplasty know that in revision procedures, the cement-within-cement technique is an acceptable option for femoral stem fixation when removing the cement would result in significant femoral bone loss.

    Is this technique a viable option for other joint replacement procedures?

    A study from the Florida Orthopaedic Institute (FOI) and the Foundation for Orthopaedic Research and Education (FORE) in Tampa suggests that the answer is yes: In revision reverse shoulder arthroplasty (RSA), the cement-within-cement technique was found to provide stable fixation for the humeral component and allow for improved range of motion in the affected shoulder.

    With this technique, the new humeral component is cemented into the existing cement mantle. by either of 2 methods:

    • Implanting the largest-diameter stem possible into the retained cement mantle while adding the least amount of cement possible for stem fixation
    • Implanting the smallest-diameter stem possible into the retained cement mantle while adding the maximum amount of cement possible for stem fixation

    The dilemma: The literature provides little guidance on which method is optimum for minimizing the risk of humeral component loosening.

    With the goal of bringing some clarity to the issue, the researchers from FOI and FORE retrospectively identified 98 patients who had undergone revision RSA with the cement-within-cement technique at FOI between 2004 and 2016. They hypothesized that within this cohort, they would find that reducing the incidence of humeral loosening would be associated with the combination of downsizing the diameter of the humeral stem and a greater increase in the amount of added cement.

    They used standard anteroposterior view radiographs to preoperatively and postoperatively measure the total area of the cement mantle and the total area of the humeral stem, both in square millimeters, for all 98 patients (Figure 1). With these measurements, they calculated the filling ratio, defined at the area of the stem to the combined areas of stem and cement.

      

    Figure 1. Radiographic assessment of the cement mantle and humeral stem diameter in patients whose humeral component loosened after revision reverse shoulder arthroplasty (left) and in those whose humeral component did not loosen (right).

    The results were used to further stratify the patients into 2 groups: Those who had developed humeral loosening after revision RSA (n=8) and those who had not develop humeral loosening (n=90). Humeral loosening occurred an average of 3.9 years after the revision procedure (range, 0.6-8.9 years). Data on clinical outcomes were available for 57 patients, none of whom had experienced humeral loosening or undergone a second revision surgery.

    Statistical analysis of cement amount, humeral stem size, and filling ratio showed the following:

    Group 1, Humeral Loosening

    • Cement: Average area of cement preoperatively: 8521 +/- 4355 mm2; average area of cement postoperatively: 9332 +/- 3135 mm2; preoperative-to-postoperative difference in area of cement: 811 +/- 4014 mm2 of added cement (not statistically significant, P=0.484)
    • Stem: Preoperative area of stem: 12353 +/- 8262 mm2; postoperative area of stem: 6102 +/- 1261 mm2; preoperative-to-postoperative stem area: decrease of 6251 mm2 (P=0.025)
    • Filling ratio: Preoperative: 0.59 +/- 0.12; postoperative: 0.41 +/- 0.10; preoperative-to-postoperative difference: decrease of 0.18 +/- 0.11 (statistically significant, P=0.017)

    Group 2, No Humeral Loosening

    • Cement: Average area of cement preoperatively: 8748 +/- 7633 mm2; average area of cement postoperatively: 13129 +/- 12522 mm2; preoperative-to-postoperative difference in area of cement: 4380 +/- 12701 mm2 of added cement (statistically significant, P< 0.0001)
    • Stem size: Preoperative area of stem: 15519 +/- 14384 mm2; postoperative stem area: 8175 +/- 6188 mm2; preoperative-to-postoperative stem area: decrease of 7343 mm2 (statistically significant, P<0.0001)
    • Filling ratio: Preoperative: 0.65 +/- 0.15; postoperative 0.41 +/- 0.08; preoperative-to-postoperative difference: decrease of 0.24 +/- 0.16 (statistically significant, P< 0.0001)

    This statistical analysis proved the researchers’ hypothesis: The humeral stem was downsized in both groups, but the amount of cement used was greater in the non-loosening group compared with the humeral loosening group.

    In addition, as mentioned, clinical outcomes were available for 57 patients who had not experienced humeral loosening. These patients were followed for a mean of 54 months (range, 21 to 156 months). They reported statistically significant improvement in their preoperative-to-postoperative American Shoulder and Elbow Surgeons (P< 0.0001) and Simple Shoulder Test (P< 0.0001) scores, as well as a high rate of satisfaction with the procedure. Improvements in range of motion – forward flexion, shoulder abduction, shoulder internal rotation, and shoulder external rotation – were also recorded.

    The study authors said the clinical findings indicate that using the cement-within-cement technique in revision RSA “is effective in improving functional outcome scores and shoulder range of motion.

    ”With regard to the actual technique, they suggest that surgeons “maximize the added cement volume during reimplantation, including adequately reaming the retained intramedullary cement mantle, and implanting a smaller humeral stem than the previous component.

    “Application of these surgical techniques may lessen the chance of humeral stem loosening requiring additional revision.”

    Source

    Gorman RA 2nd, Christmas KN, Simon P, Hess AV 2nd, Brewley EE Jr., Mighell MA, Frankle MA. Optimizing humeral stem fixation in revision reverse shoulder arthroplasty with the cement-within-cement technique. J Shoulder Elbow Surg. 2020 Jul;29(7S):S9-S16. doi: 10.1016/j.jse.2020.01.094. Epub 2020 Apr 29.

    Gorman RA 2nd, Christmas KN, Simon P, Hess AV 2nd, Brewley EE Jr., Mighell MA, Frankle MA. Optimizing Humeral Stem Fixation in Revision Reverse Shoulder Arthroplasty with the Cement-within-Cement Technique. Poster P0304. AAOS Virtual Education Experience.

    Note: This is the first in a series of studies on the cement-within-cement technique in revision RSA. A biomechanical study is currently being reviewed for publication.