Effect of body mass index on limb alignment after total knee arthroplasty.

Prior studies have reported increased failure rates in obese patients with postoperative limb mal-alignment. This study was undertaken to determine if a relationship exists between postoperative limb alignment and BMI in patients undergoing primary TKA performed with mechanical instruments. An IRB-approved retrospective review of 196 knees was undertaken. Limb alignment was determined on full-length, standing, hip-to-ankle x-rays, preoperatively and postoperatively. The effects of gender, side, preoperative mechanical alignment and BMI on postoperative alignment were analyzed via multivariate regression analysis. Both preoperative mechanical limb alignment (P<0.001) and BMI (P=0.009) had a significant effect on postoperative limb alignment following TKA performed with mechanical instruments.

Jeannette Wilkins Award: Can locally delivered gadolinium be visualized on MRI? A pilot study.

BACKGROUND: Management of orthopaedic infections relies on débridement and local delivery of antimicrobials; however, the distribution and concentration of locally delivered antimicrobials in postdébridement surgical sites is unknown. Gadolinium-DTPA (Gd-DTPA) has been proposed as an imaging surrogate for antimicrobials because it is similar in size and diffusion coefficient to gentamicin. QUESTIONS/PURPOSES: Is in vivo distribution of locally delivered Gd-DTPA (1) visible on MRI; (2) reliably visualized by different observers; (3) affected by the anatomic delivery site; and (4) affected by the in vitro release rate from the delivery vehicle? METHODS: Twenty-four local delivery depots were imaged in nine rabbits using two anatomic sites (intramedullary canal, quadriceps) with Gd-DTPA in intermediate-porosity polymethylmethacrylate (PMMA) or high-porosity PMMA; six of the nine rabbits also had Gd-DTPA delivered in collagen at a third site (hamstring). A total of 45,000 fat-suppressed T1-weighted RARE scans were acquired using a 7-T Bruker Biospec MRI: nine rabbits, 2-mm slices over 10 cm, four TR values, 25 time periods (pre, every 15 minutes for 6 hours). T1 maps were constructed at every time period. Gd-DTPA distribution was observed qualitatively on the T1 maps. Interobserver reliability was determined. RESULTS: Locally delivered Gd-DTPA was visible. Interobserver agreement was excellent. Intramuscular delivery followed intermuscular planes; intramedullary delivery was contained within the canal by bone. Distribution from collagen decreased after 1 hour but from PMMA increased over 6 hours. CONCLUSIONS: Locally delivered Gd-DTPA can be visualized on MRI; distribution is affected by anatomical location and delivery vehicle. CLINICAL RELEVANCE: Contrast-based imaging using locally delivered Gd-DTPA may be useful as an antibiotic surrogate to determine antibiotic distribution in surgical sites.

A two-stage retention débridement protocol for acute periprosthetic joint infections.

BACKGROUND: Due to the historically poor infection control rates with débridement and component retention for acute periprosthetic infections we developed a new approach for treating acute periprosthetic total joint infections: initial débridement with prosthesis retention and placement of antibiotic-impregnated cement beads followed by a second débridement within 7 days, at which time the beads are removed and new modular parts inserted. Intravenous antibiotics were used for 6 weeks followed by oral antibiotics. Depending on the clinical situation, antibiotics are discontinued or in selected patients continued indefinitely. QUESTIONS/PURPOSES: We determined the ability of this two-stage débridement to control infection. METHODS: We retrospectively reviewed the charts of 20 patients who underwent this technique; 2 had postoperative and 18 had hematogenous infections. The primary outcome measure was the infection control. The minimum followup was 1 year (mean, 3.5 years; range, 1.2-7.5 years). RESULTS: Two of the 20 patients had persistent infection. There were no failures in the acute postoperative group (0 of 2) and two of 18 in the acute hematogenous group. Of the 18 patients without evidence of persistent infection, 10 were no longer on antibiotics at the most recent followup and eight were treated with long-term antibiotics due to compromised host status. CONCLUSIONS: The control of infection in 18 of 20 patients using this technique compares favorably with historical success rates, which range from 24% to 100%. Further research is required to analyze the individual contribution of débridement technique, the use of serial débridements, local depot antibiotics, and combination antibiotic therapy on short-term infection control rates and the long-term persistent control of periprosthetic infection. LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of level of evidence.