title: Preoperative digital planning versus postoperative outcomes in total hip arthroplasty using a calcar-guided short stem: frequent valgization can be avoided.
abstract: BACKGROUND
  Modern total hip arthroplasty is largely dependent on the successful preservation of hip geometry. Thus, a successful implementation of the preoperative planning is of great importance. The present study evaluates the accuracy of anatomic hip reconstruction predicted by 2D digital planning using a calcar-guided short stem of the newest generation.
  
  
  METHODS
  A calcar-guided short stem was implanted in 109 patients in combination with a cementless cup using the modified anterolateral approach. Preoperative digital planning was performed including implant size, caput-collum-diaphyseal angle, offset, and leg length using mediCAD II software. A coordinate system and individual scale factors were implemented. Postoperative outcome was evaluated accordingly and was compared to the planning.
  
  
  RESULTS
  Intraoperatively used stem sizes were within one unit of the planned stem sizes. The postoperative stem alignment showed a minor and insignificant (p = 0.159) mean valgization of 0.5° (SD 3.79°) compared to the planned caput-collum-diaphyseal angles. Compared to the planning, mean femoral offset gained 2.18 (SD 4.24) mm, while acetabular offset was reduced by 0.78 (SD 4.36) mm during implantation resulting in an increased global offset of 1.40 (SD 5.51) mm (p = 0.0094). Postoperative femoroacetabular height increased by a mean of 5.00 (SD 5.98) mm (p < 0.0001) compared to preoperative measures.
  
  
  CONCLUSIONS
  Two-dimensional digital preoperative planning in calcar-guided short-stem total hip arthroplasty assures a satisfying implementation of the intended anatomy. Valgization, which has been frequently observed in previous short-stem designs, negatively affecting offset, can be avoided. However, surgeons have to be aware of a possible leg lengthening.
authors.affiliation: Department for Orthopaedic Surgery and Traumatology, St. Josefs Hospital Wiesbaden, Beethovenstr. 20, 65189, Wiesbaden, Germany. kkutzner@joho.de.
authors.forename: Karl Philipp
authors.initials: KP
authors.lastname: Kutzner
authors.affiliation: Department for Orthopaedic Surgery and Traumatology, St. Josefs Hospital Wiesbaden, Beethovenstr. 20, 65189, Wiesbaden, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Pfeil
authors.affiliation: Clinic for Traumatology, Hand- and Orthopaedic Surgery, HELIOS Dr. Horst Schmidt Clinics Wiesbaden, Wiesbaden, Germany.
authors.forename: Mark Predrag
authors.initials: MP
authors.lastname: Kovacevic
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D060906:Coxa Valga / Q000209:etiology / Q000517:prevention & control; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D010347:Patient Care Planning; D057234:Preoperative Period; D025321:Surgery, Computer-Assisted; D016896:Treatment Outcome
keywords: Digital planning; Offset; Optimys; Short stem; Stem alignment; Total hip arthroplasty; Valgization