Clinical results of total hip arthroplasty assisted by robotic arm in Spain: Preliminary study.

Objectives: Clinical, radiological and functional results of the first Spanish series of patients undergoing total hip arthroplasty assisted by Mako® (Stryker) robotic arm at the Hospital Clínico San Carlos (HCSC) in Madrid.

Material And Methods: Prospective and descriptive study analyzing the first 25 patients who underwent robotic-assisted THA at the HCSC, with a minimum follow-up of 4months. Demographics, imaging studies (Mako® processing, Rx and CT), clinical parameters, functionality (modified Harris) and associated complications were evaluated.

Results: Average age was 67.2years (min 47, max 88), being 56% male population sample. 88% involves primary coxarthrosis, 4% post-traumatic coxarthrosis, 4% secondary avascular necrosis and 4% secondary femoroacetabular impingement. Average surgery time was 116.9min (min 92, max 150). The average time of the first five surgeries was 122.6min, and, regarding the last five interventions, it was 108.2min. Found medical intraoperative complications were four intraoperative markers loss. Average admission time was 4.4days (min 3, max 7), with an average postoperative hemoglobin decrease of 3.08±1.08g/dL, requiring a transfusion in 12% of the cases. Three medical complications have been registered in the meantime of the admission, with a relevant case of a confusional syndrome and a fall, which resulted in a non-displaced AG1 periprosthetic fracture. The analysis of the positioning of registered implants with Mako® system shows 40.55±1.53 acetabular inclination degrees and 12.2±3.6 acetabular anteversion degrees. The postoperative image study carried out on patients, are consistent with Mako® s results, as it shows an acetabular inclination of 41.2±1.7 in Rx, as well as acetabular anteversion of 16±4.6 in CT. Hip length variance ranges depending on preoperative values of 3.91mm (SD: 3.9; min -12, max 3) to 1.29mm (SD: 1.96) after surgery registered with Mako®, with an increase of an average hip length of 5.64mm (SD: 3.35). Rx simple study results show a postoperative difference between both hips of 0.5±3.08mm, which is consistent with Mako® results. Native femoral offset was stable after surgery with a showing difference both pre and post operative of the intervened hip of 0.1mm (SD: 3.7), registered with Mako®. Preoperatory modified Harris punctuation was 41.6±13.3, improving to postoperative values of 74.6±9.7 after four months since the surgery. No complications were registered in immediate postoperative (4month).

Conclusions: Total hip arthroplasty robot-assisted achieves an adequate precision and repeatability of the implant positioning and the postoperative hip dysmetry without showing an increase of associated complications to the technique applied. Surgery time, complications and functional results in a short-time period are similar to conventional techniques applied to great series previously published.