Intra-Operative Digital Radiography Improves Component Positioning during Posterior Approach Total Hip Arthroplasty

Introduction:
Appropriate implant position and size during total hip arthroplasty (THA) are associated with improved patient outcomes and implant survival. Intra-operative digital radiography (IODR) facilitates accurate component placement and sizing. The purpose of this study was to quantify the utility of IODR to experienced arthroplasty surgeons performing THAs at a single institution.

Methods:
From March through September 2020, 100 consecutive primary THAs were performed through the posterolateral or superior approach in the lateral decubitus position by four fellowship trained arthroplasty surgeons. After acetabular component and trial femoral component placement, the surgeon predicted the appropriateness of component size and position, limb length and femoral offset. IODR images were obtained and analyzed using software (Radlink, Inc.) The accuracy of surgeon predictions and frequency of intra-operative changes made after IODR were recorded.

Results:
Surgeons accurately predicted cup abduction within ±3 degrees only 46% of the time and cup anteversion within ±3 degrees only 49% of the time (Figure 1). Surgeons were less accurate in predicting limb length (48%, p=0.014), appropriate femoral stem size (66%, p=0.047), and femoral offset (66%, p=0.089) than predicting femoral stem position (varus/valgus) (78%, p=0.27), appropriate acetabular cup size (99%, p=0.999) and acetabular position (87%, p=0.123) (Table 1). After IODR, implants were repositioned in 91% of cases (Table 2). Limb length was adjusted most commonly (68%), followed by stem size (51%), cup abduction (30%) and anteversion (19%). Final cup abduction and anteversion were improved by IODR guided changes (Figure 1).

Discussion:
IODR identified the need for changes in implant position and size in 91% of THAs, and improved radiographic outcomes even for fellowship trained arthroplasty surgeons. IODR during total hip arthroplasty in the lateral decubitus position is a valuable tool to ensure accurate implant position and size, and restoration of appropriate limb length and offset.