title: Percutaneously assisted total hip (PATH) and Supercapsular percutaneously assisted total hip (SuperPATH) arthroplasty: learning curves and early outcomes.
abstract: BACKGROUND
  A new family of micro-posterior approaches, percutaneously assisted total hip (PATH), SuperCapsular (SuperCap) and Supercapsular percutaneously assisted total hip (SuperPATH) allow preservation of the short external rotators. This study assesses early outcomes and learning curves of the PATH and SuperPATH approaches.
  
  
  METHODS
  Early outcomes of the first consecutive 49 PATH and 50 SuperPATH cases performed by a non-developer surgeon were evaluated. Analysis of variance (ANOVA) was used to compare age, body mass index (BMI), and pre-operative hemoglobin. Gender was compared using a Chi-square test. Clinical outcomes were compared using a nonparametric Wilcoxon test or a Chi-square test. Learning curves were assessed using operative time as a surrogate. Acetabular cup abduction and anteversion were compared using the first post-operative radiograph and a modified protractor.
  
  
  RESULTS
  Both cohorts were similar with respect to diagnosis, gender, and BMI. Mean operative time in minutes was recorded for the PATH (114.5±17.5) and SuperPATH (101.7±18.3) cohorts (P value =0.0002). PATH operative time reached a plateau by case 40, but SuperPATH operative time continued to decrease by case 50. Transfusion rates were low in the PATH (4%) and SuperPATH (6%) cohorts. Mean length of stay (LOS) in days for the SuperPATH and PATH cohorts were 2.2 and 3.0, respectively (P value <0.0001). Complication rates were low in the SuperPATH (4.0%) and PATH (4.1%) cohorts. Acetabular cups in the SuperPATH cohort (anteversion: 23.5°±8.2°, abduction: 39.0°±8.4°) were significantly more anteverted (P value <0.0001) and less abducted (P value <0.05) than in the PATH cohort (anteversion: 13.1°±7.1°; abduction: 42.9°±7.6°).
  
  
  CONCLUSIONS
  Early results demonstrate that the PATH and SuperPATH approaches can be adopted with minimal complications and outcomes consistent with innovator outcomes, even during the learning curve. The SuperPATH technique was associated with shorter operative time that continued to decrease, suggesting that proficiency continues to decrease beyond the first 50 cases. In this author's experience, acetabular cups implanted using the SuperPATH technique were more anteverted than those implanted using the PATH technique. Greater use of the transverse acetabular ligament to guide cup alignment reduced this effect.
authors.affiliation: The Ottawa Hospital-Civic Campus, Ottawa, Ontario K1Y 4E9, Canada.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Rasuli
authors.affiliation: The Ottawa Hospital-Civic Campus, Ottawa, Ontario K1Y 4E9, Canada.
authors.forename: Wade
authors.initials: W
authors.lastname: Gofton
keywords: Supercapsular percutaneously assisted total hip (SuperPATH); Total hip arthroplasty (THA); learning curve; minimally invasive; percutaneously assisted total hip (PATH)