Three-dimensional planning of hip arthroplasty is associated with better visualisation of
anatomical landmarks and enhanced mapping for preoperative implant sizing, which can lead to a
decrease in surgical time and complications. Despite the advantages of hip resurfacing arthroplasty
(HRA), it is considered a technically challenging procedure and associated with inaccurate implant
placement. This study aimed to examine the validity, reliability, and usability of preoperative 3D
Hip Planner software for HRA. Fifty random cases of various hip osteoarthritis severity were
planned twice by two junior trainees using the 3D Hip Planner within a one-month interval. Outcome measures included femoral/cup implant size, stem-shaft angle, and cup inclination angle, and
were assessed by comparing outcomes from 2D and 3D planning. An adapted unified theory of
acceptance and use of technology (UTAUT) survey was used for software usability. Bland–Altman
plots between 3D and 2D planning for stem-shaft and inclination angles showed mean differences
of 0.7 and −0.6, respectively (r = 0.93, p < 0.001). Stem-shaft and inclination angles showed inter-rater
reliability biases of around −2° and 3°, respectively. Chi-square and Pearson’s correlation for femoral
implant size showed a significant association between the two assessors (r = 0.91, p < 0.001). The 3D
test–retest coefficient of repeatability for stem-shaft and inclination angles were around ±2° and ±3°,
respectively, with a strong significant association for femoral implant size (r = 0.98, p < 0.001). Survey
analyses showed that 70–90% agreed that 3D planning improved expectancy in four domains. 3D
hip planner appears to be valid and reliable in preoperative HRA and shows significant potential in
optimising the quality and accuracy of surgical planning.