# Outpatient Total Knee Arthroplasty: A Meta-Analysis
## 4 Discussion  
According to the main findings of the present study, inpatient TKA in selected patients demonstrated greater rate of revision, mortality, and DVT compared to the outpatient procedure. Similarity was found in OKS, readmission and infection rates. Outpatient TKA has recently gained popularity and current evidence is controversial. In 2005, [PERSON] et al. [30] firstly found a greater rate of early readmissions for pain in the  
Figure 3: Forest plots of the comparisons. outpatient compared to inpatient TKA group on 50 procedures. The same authors in 2009 found greater rates of complication for outpatient compared to the inpatient procedure on 111 patients [31]. [PERSON] et al. [32] compared 4391 outpatient versus 128,951 inpatient TKAs from an insurance database. They found a greater risk of complications in the outpatient TKA: infections, DVT, component failure, and stiffness were the most common events [32]. [PERSON] et al. [27], investigating 1200 procedures, in addition to a greater complication rate, to find a greater rate of patients requiring blood transfusions. This finding could be explained by the increased activity of outpatient TKA when support at home is not adequate [33]. Outpatient TKA reported similar knee society score (KSS) and pain level to the inpatient procedure in a clinical setting involving 128 procedures (64 procedures each group) [1]. The clinical relevance of the OKS is questionable. Indeed, only two studies were included in the analyses [20; 29]. Moreover, the final effect did not overcome the minimally clinically important difference (MCID) of the OKS, which is approximately 5 to 6/100 [34; 35; 36; 37]. Moreover, with an overall number of 60 patients, they involved a small sample size [20; 29]. The comparison of the OKS demonstrated narrow estimated effects, and CI overlapping the no-effect threshold. Thus, the reliability of this endpoint is limited, and no solid conclusion can be inferred. The increased incidence of complications is concerning. For a satisfactory implementation to outpatient TKA, preventing complications, such as DVT and pain management, is pivotal. The increased rate of DVT has been reported by previous investigations [27; 38]. This may result from limited patient's compliance with postoperative DVT prophylaxis regimens, or perioperative use of tranexamic acid. Indeed, tranexamic acid, although it significantly reduces blood transfusion by 39%, is considered an independent risk factor for DVT [38; 39; 40]. [PERSON] et al. [26] analyzed 71,795 patients from the US Medicare database. At 2-year follow-up, outpatient TKA resulted in a greater rate of revision (2.1%) compared to inpatient procedure (1.9%) [26]. The most common causes for revision were infections, aseptic loosening, implant failures, dislocations, and mechanical complications [26]. [PERSON] et al. [1] reported 3% (2 of 64 procedures) of revisions in outpatient TKA (one genu recuratum deformity, one tibial plateau fracture), and 3% (2 of 64 procedures) revisions for inpatient TKA (two infections). [PERSON] et al. [17] observed no revisions within 90 days. A statistically significant greater rate of mortality in patients undergoing outpatient TKA has been detected. This comparison included three studies, with an overall 1198 patients in the outpatient TKA and 152,589 patients in the inpatient group [18; 26; 28]. The most commonly causes of death were pulmonary diseases and cardiac failure [41]. [PERSON] et al. [18] showed no difference in within 30 day mortality between outpatient and inpatient on 46,103 patients from the US Medicare database. On the contrary, [PERSON] et al. [28] analyzed data from the National Surgical Quality Improvement Program of the American College of Surgeons, demonstrating that outpatient had the highest rates of mortality, from infections, cardiac failure, thrombosis, and pulmonary embolism on 36,249 procedures. [PERSON] et al. [26] found a greater revision, readmission, and mortality risk for the outpatient and short stay TKA groups.