Summary

A meta-analysis was performed to compare rate of SSI after application of chlorhexidine vs. iodine in total joint arthroplasty. Chlorhexidine had significantly lower odds of SSI.

Soft tissue balance and alignment have long been known to play an essential role in the long-term success of primary total knee arthroplasty (TKA). Until recently balance was confirmed based on intra-operative feel and experience. In this study we analyzed short-term outcomes of cruciate retaining TKA (CR-TKA) performed with a smart tibial trial device (STT), which provides real-time, intra-operative compartmental load and rotational congruency readings, to a comparable cohort of patients receiving conventional TKA where the same surgeon balanced the compartments based on feel and experience.

Seventy patients received CR-TKA with STT and were matched to one-hundred and eighty non-STT consecutive controls using the same anesthesia, surgical approach, and post-operative rehabilitation and pain management protocol. Both groups were evaluated preoperatively and then post-operatively at three months and one year using Short Form 12 (SF12) and the Western Ontario and McMaster University Osteoarthritis Index (WOMAC) questionnaires. T-tests were used to compare average scores within each cohort, as well as between the two cohorts, for each time interval.

The average age and BMI for the STT cohort were 70.9 ± 9.2 years and 29.8 ± 6.1 kg/m². Operation length was seen to be 12.0 minutes greater for the STT cohort compared to the conventional cohort (p = 0.0012). The average difference in pressure between medial and lateral compartments was 8.30, 11.49, and 8.65 lbs at 10°, 45°, and 90° respectively. Only 10 cases had a difference greater than 15 lbs between compartments. At 3 months, the STT cohort had significantly higher average function scores on the WOMAC (p=0.046) and higher change from baseline pain scores on the WOMAC (p=0.0016). When scores were stratified into the top 50% and the bottom 50% and the coronal balance was compared, SF12 pain scores and WOMAC function scores at 1 year in the top 50% had greater coronal balance indicated by pressure differences ≤ 15 lbs (p<0.002)

Given the results of this case-control study, we conclude that STT can indeed help the surgeon balance compartmental loads and femoral-tibial rotational congruency and lead to improved short-term physical and functional outcomes in primary CR-TKA.

Traditional medial soft tissue release for balancing of the varus knee in total knee arthroplasty can lead to an inconsistent reduction in medial tension. The purpose of this study is to establish whether sequential needle puncturing of the medial collateral ligament (MCL) can be a safe and predictable method for medial release.

Total knee prostheses were implanted in 14 cadaveric specimens by a single surgeon. Medial tension was measured in flexion and extension by a pressure sensor with implants in place, and calipers after removal of implants and gap distraction under constant tension. Measurements were performed after each of 5 sets of 5 punctures of the MCL with an 18-gauge needle and following 5 transverse perforations with an 11-blade. A consistent valgus force was applied after each set of MCL punctures with a pneumatic cylinder. Pearson's correlation was used to compare pressure sensor measurement with gap distance measurement under tension. The pressure as detected by the sensor after each set of 5 punctures was analyzed by a repeated measures two-way ANOVA and a Tukey multiple comparisons test to determine a significant decreases between puncture sets.

The pressure sensor device correlated more closely with systematic tissue release (r=0.59 for % change from baseline) than did measurements of gap increase under tension (r= −0.22). All knees had ≤5mm of medial opening with up to 25 needle punctures. Two knees had <5mm of medial opening in flexion after blade perforation. The mean pressure decreases in 90 degrees flexion, mid-flexion and extension were 11.2, 9.4 and 9.9 lbs respectively after 5 needle punctures and 8.1, 11.5 and 9.6 lbs between 5 and 15. Significant pressure decreases were seen after 5 and 10 needle punctures and again after blade perforation (p<0.05)

Needle puncture of the deep and superficial MCL leads to a significant and reliable decrease in medial tension over the first 15, with diminishing effect up to 25 punctures. This method may be employed when up to 20 lbs reduction in medial pressure is desired. Blade perforation after needle puncture should be approached with caution.