Every month, JBJS publishes a review of the most pertinent and impactful studies published in the orthopaedic literature during the previous year in one of 13 subspecialties. Click here for a collection of all OrthoBuzz subspecialty summaries. This month, Michael J. Taunton, MD, author of the January 16, 2019 “What’s New in Adult Reconstructive Knee Surgery,” selected the five most compelling findings from among the more than 100 noteworthy studies summarized in the article.
Cementless vs Cemented TKA Fixation
—A matched case-control study of 400 primary total knee arthroplasties (TKAs) found that cementless TKAs had a 0.5% rate of aseptic loosening over a mean follow-up of 2.5 years, while cemented TKAs had an aseptic loosening rate of 2.5%.1
TKA Component Size in Obese Patients
—Among 35 revision-TKA patients with a varus collapse of the tibia, 29 weighed >200 lbs. Fehring et al. found that patients with implants at the small end of the range of the manufacturer’s tibial size offering and with >5° of preoperative varus were at increased risk of tibial-component failure.2
—A retrospective multivariate analysis of >4,300 patients who underwent outpatient TKA and >128,900 patients who underwent inpatient TKA found that, within 1 year, those who had outpatient procedures were more likely to experience a tibial and/or femoral component revision due to a noninfectious cause, irrigation and debridement, explantation of the prosthesis, and stiffness requiring manipulation under anesthesia.
—In a randomized trial of patients undergoing TKA, one group received 15 mg/kg of systemic intravenous vancomycin, and a second group received intraosseous regional administration of 500 mg vancomycin into the tibia. Mean tissue concentrations of the antibiotic were 34.4 mg/g in the intraosseous group and 6.1 mg/g in the intravenous group, suggesting that intraosseous administration provides a significantly higher tissue concentration of that antibiotic. 3
TKA Anesthesia Protocol
—A retrospective review of 156 consecutive patients who underwent primary TKA found that procedures performed with mepivacaine spinal anesthesia led to fewer episodes of urinary catheterization and shorter mean length of stay compared with procedures performed with bupivacaine spinal anesthesia.4
- Miller AJ, Stimac JD, Smith LS, Feher AW, Yakkanti MR, Malkani AL. Results of cemented vs cementless primary total knee arthroplasty using the same implant design. J Arthroplasty.2018 Apr;33(4):1089-93. Epub 2017 Dec
- Fehring TK, Fehring KA, Anderson LA, Otero JE, Springer BD. Catastrophic varus collapse of the tibia in obese total knee arthroplasty. J Arthroplasty.2017 May;32(5):1625-9. Epub 2017 Jan 30.
- Chin SJ, Moore GA, Zhang M, Clarke HD, Spangehl MJ, Young SW. The AAHKS Clinical Research Award: intraosseous regional prophylaxis provides higher tissue concentrations in high BMI patients in total knee arthroplasty: a randomized trial. J Arthroplasty.2018 Jul;33(7S):S13-8. Epub 2018 Mar 15.
- Mahan MC, Jildeh TR, Tenbrunsel TN, Davis JJ. Mepivacaine spinal anesthesia facilitates rapid recovery in total knee arthroplasty compared to bupivacaine. J Arthroplasty.2018 Jun;33(6):1699-704. Epub 2018 Jan 16.
One key question for orthopaedic surgeons regarding revision total knee arthroplasty (TKA) is how best to affix femoral and tibial stems. The August 17, 2016 edition of the Journal of Bone & Joint Surgery contains findings from a Level I randomized trial by Heesterbeek et al . that addresses this clinical conundrum.
Thirty-two patients with Type-I or II bone defects who needed a revision TKA received the same basic implant, with the femoral components and tibial baseplates being cemented in all cases. However, in half the patients the femoral and tibial stems were cemented, and in the other half the stems were press-fit (so-called hybrid fixation).
Measuring micromotion with radiostereometric analysis (RSA) at baseline, 6 weeks, and 3, 6, 12, and 24 months, the authors found no significant between-group differences in component migration. Similarly, at the 2-year follow-up, there were no significant between-group differences in clinical scores, including KOOS and visual analog ratings of pain and satisfaction.
The authors expressed concern about what they deemed the “relatively high” number of components in both groups that migrated > 1 mm (translation) or > 1° (rotation), and they are continuing to follow all these patients to determine whether clinically relevant component loosening eventually ensues.