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Patient-specific TKA implants decreased postoperative blood loss, length of stay
Patient-specific implants used during total knee arthroplasty decreased estimated blood loss by 44.72mL, length of stay by 0.39 days and range of motion by 3.90°, however no significant differences were observed between surgical and tourniquet time for patients with these or conventional implants .
In the retrospective consecutive series study, researchers reviewed charts of 621 patients with a mean age 63.19 years. All patients underwent total knee arthroplasty (TKA); 307 of those patients received patient-specific implants (PSIs) compared 314 patients who received conventional implants. The charts for patients in the two groups were divided between two surgeons: Surgeon A — PSIs and conventional implants and Surgeon B — PSIs and conventional implants.
Researchers used linear regression analyses to measure preoperative and 1-year postoperative outcomes in regard to surgical time (Surgeon A), tourniquet time (Surgeon B), estimated blood loss, hospital length of stay and range of motion differences.
Findings showed the overall estimated blood loss was 290.6 mL with mean blood loss of 261.97 mL for the PSI group and 311.31 mL for the conventional implant group. Estimated blood loss for implant types was statistically significantly different.
Surgical time overall for Surgeon A was 99.53 minutes. Mean surgical time was 99.92 minutes for the PSI group and 99.16 minutes for the conventional group. Mean tourniquet time for Surgeon B overall was 72.43 minutes with tourniquet time of 72.47 minutes for PSIs and 72.41 for conventional implants. Implant type used, surgical time and tourniquet time were not significantly different, according to the findings. ‒ by Monica Jaramillo
Disclosures: Schwarzkopf reports he is a board or committee member of the American Academy of Orthopaedic Surgeons, a member of the editorial or governing board for Arthroplasty Today, and has stock or stock options in Gauss Surgical and Pristine. He reports he is a paid consultant for Intellijoint and Smith & Nephew, a part of the editorial or governing board for Journal of Arthroplasty and receives research support from Pricaria.
Perspective
Back to TopThe study by Schwarzkopf and colleagues is a retrospective analysis where conventional total knee arthroplasty (TKA) instruments and implants are compared to a cohort of custom TKAs performed with both patient-specific instruments (PSIs) and custom implants (Conformis). It is important to distinguish what is being compared in this study compared to prior publications on PSIs. Most previous studies evaluated the use of PSIs, where custom cutting guides were manufactured to perform the bone cuts, but standard off-the-shelf implants were used. In this study, similar PSIs were used, but then a custom implant manufactured specifically for that patient was implanted.
This study has a retrospective cohort design with two groups of consecutive patients, the conventional implants from 2008 to 2010 were compared with the custom implants used from 2011 to 2013. This type of chronological study design may invalidate several of the outcome parameters evaluated because of the evolving nature of the perioperative management of the joint replacement patient. The length of stay nationwide has seen a gradual, yet steady drop in duration from year to year. This is likely due to the evolving perioperative management of these patients, along with the organization and comfort required to send the patients home earlier. To attribute this drop in length of stay in any way to the implant seems implausible.
Furthermore, the data showing a decrease in estimated blood loss (EBL) are not only clinically insignificant, but may have factors that bias these data. Many hospitals implemented blood management strategies, such as the use of tranexamic acid, regional anesthesia and intraoperative hypotension, all of which are known to decrease blood loss. While not reported, one of these factors may have been associated with the result seen in this study. I would also use caution in using EBL as the measure of actual blood loss; it is generally inaccurate (especially in TKA, where a tourniquet may be used). A preferable measure would be to calculate the actual blood loss (using pre- and postoperative hematocrit, height, weight and gender) or to report the transfusion rates between the groups. Unfortunately, none of these data were included in the analysis.
The only clinical data that were included in this article comparing the two groups was range of motion. From preop to postop, patients implanted with a custom total knee lost 3.44° of motion compared with a gain of 1.54° for patients implanted with standard implants. While I agree this finding requires further study, I am concerned about a nearly 5° loss of arc of motion using custom compared to standard implants. This finding would be clinically significant in my own practice.
Further study on custom knee implants is required to validate the increased difficulty of their use (i.e., preoperative imaging and cost). It is imperative the study design be optimized (prospective, randomized), so the results can be trusted.