An Experienced Surgeon Can Meet or Exceed Robotic Accuracy in Manual Unicompartmental Knee Arthroplasty

Background: Reports in the literature indicate that implant placement is more accurate with robotic-assisted unicompartmental knee arthroplasty (UKA); however, these studies have not always accounted for surgeon experience. The purpose of the present study was to compare the accuracy of tibial component alignment in UKA between an experienced high-volume surgeon and the published data on robotic-assisted surgery.

Methods: The radiographs made before and after 128 consecutive medial UKAs performed manually by a single surgeon using a cemented fixed-bearing implant were reviewed. Native tibial and tibial implant slope and varus alignment of the tibial implant were measured on preoperative and postoperative lateral and anteroposterior radiographs, respectively. The percentages of knees in which the postoperative measurements were within preoperative targets and the root mean square (RMS) error rates between the planned and achieved targets were compared with published robotic-assisted-UKA data.

Results: In the present study, the proportion of manual UKAs in which the tibial component alignment was within the preoperative target was 66% (85 of 128), which exceeded published values in a study comparing robotic (58%) with manual (41%) UKA. The RMS error for tibial component alignment in the present study (1.48°) was less than published RMS error rates for robotic UKAs (range, 1.8° to 5°). Fifty-eight percent (74) of the 128 study UKAs were within the surgeon’s preoperative goal for tibial slope, which was closer to the published value of 80% for robotic UKAs than is the published rate of 22% for manual UKAs. The RMS error for tibial slope in the study UKAs (1.50°) was smaller than the published RMS error rates for tibial slope in robotic UKAs (range, 1.6° to 1.9°).

Conclusions: Accurate implant alignment is important in UKA. In this study, an experienced surgeon achieved or exceeded robotic accuracy of tibial implant alignment in UKA. However, the relationship between implant position and patient outcomes is unknown, and a consensus on ideal surgical targets for optimal implant survivorship has yet to be established.

Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.