Dangle Cemented Stem in Revision TKA: Simple & Reliable

Aree Tanavalee.
Professor and Chairman
Department of Orthopaedics
Faculty of Medicine
Chulalongkorn University
Bangkok, Thailand
Email: areetana@hotmail.com

Introduction: Three fixation techniques in revision total knee arthroplasty (TKA), including cemented, cementless and hybrid fixation, have been described in the literature. Currently, hybrid fixation, cementing on prosthetic components with press-fit fixation on the stems, is the most popular technique according to good long-term results without much difficulty if it needs to be removed.We introduce the so-called “dangle cemented stem” fixation in revision TKA. This technique is a modified hybrid fixation that thediameter of the selectedstem is smaller than the intramedullary (IM) canal and the surrounding space between stem and IM canal is partially filled with bone cement. Methods: Forty-fourrevision TKAs performed in 44 patients who had F1-F2 and T1-T2 bone loss according to AORI classification with a minimum 5-year follow-up (FU), and were available for latest evaluation were included. All surgeries were performed by a single surgeon using a single revision TKA system. Three-step revision technique, including creating tibial platform, balancing flexion gap and balancing extension gap, was applied and dangle stems were loosely fixed using bone cement. Both femoral and tibial stem extension were 100-mm in length with variation of diameter.The constraint of polyethylene insert was selected based on the stability of combined mediolateral and anteroposterior planes. Clinical outcomes were evaluated and radiographs with single-limb standing at latest FU were compared to those of 6-week FU which were determined as the baseline postoperative parameter. Results:The average patient’s ages were 73 years with dominant female gender (male: female, 36: 8 knees). Regarding the cause of revision, 31 knees had aseptic loosening, 10 knees had stiffness post TKA, and 3 knees had periprosthetic joint infection. All knees had femoral augmentation, and 35 knees had proximal tibial augmentation. Thirty knees had constrained tibial insert, and 14 knees had semi-constrained tibial insert. At the mean 7-year FU, the average KSS clinical and function scores improved from 28 points to 90 points and 25 points to 85 points, respectively. There were 3 knees (7%) and 6 knees (14%) with non-progressive thinradiolucent line around the femoral and tibial stems, respectively, without implant migration or subsidence.The mean time to detect the radiolucent line was 38 months. There was no reoperation for any reasons. The survivorship for re-revision for any reason was 100%. Discussion:Revision TKA using a dangle stem resulted in a smaller stem than that of measured size, which provided an ease to adjust the optimum

position of both femoral and tibial componentsand less chance to use offset stem. Although bone cementwas used to enhance dangle stem fixation, it was not fully applied thorough the IM canal as described in cemented stem fixation. Therefore, mid-term to long-term implant longevity was somewhat questionable. The present study demonstrated that the dangle cemented stem techniquein patients who had F1-F2 and T1-T2 bone lossprovided a stable construct at a mean 7-year FU without revision related to fixation technique. However, up to 14% of knees developednon-progressive thin radiolucent linesurrounding the stem, further FU should be monitored for long-term implant stability. Conclusion:Mid-term outcomes of revision TKA using dangle cemented stem provided stable construct with an ease for implant positioningand less chance to use offset stemin patients who had F1-F2 and T1-T2 bone loss. However, non-progressive thin radiolucent line surrounding the stem was observed at7% and14% of femoral and tibial sides, respectively. Keywords:Revision total knee arthroplasty, outcomes, dangle stem, cement