The use of imageless navigation to quantify cutting error in total knee arthroplasty

Purpose Navigated total knee arthroplasty (TKA) improves implant alignment by providing feedback on resection parameters based on femoral and tibial cutting guide positions. However, saw blade thickness, deflection, and cutting guide motion may lead to final bone cuts differing from planned resections, potentially contributing to suboptimal component alignment. We used an imageless navigation device to intraoperatively quantify the magnitude of error between planned and actual resections, hypothesizing final bone cuts will differ from planned alignment. Materials and methods A retrospective study including 60 consecutive patients undergoing primary TKA using a novel imageless navigation device was conducted. Device measurements of resection parameters were obtained via attachment of optical trackers to femoral and tibial cutting guides prior to resection. Following resection, optical trackers were placed directly on the bone cut surface and measurements were recorded. Cutting guide and bone resection measurements of both femoral and tibial varus/valgus, femoral flexion, tibial slope angles, and both femoral and tibial medial and lateral resection depths were compared using a Student's t-test. Results Femoral cutting guide position differed from the actual cut by an average 0.6 ± 0.5° (p = 0.85) in the varus/valgus angle and 1.0 ± 1.0° (p = 0.003) in the flexion/extension angle. The difference between planned and actual cut measurements for medial and lateral femoral resection depth was 1.1 ± 1.1 mm (p = 0.32) and 1.2 ± 1.0 mm (p = 0.067), respectively. Planned cut measurements based on tibial guide position differed from the actual cut by an average of 0.9 ± 0.8° (p = 0.63) in the varus/valgus angle and 1.1 ± 1.0° (p = 0.95) in slope angle. Measurement of medial and lateral tibial resection depth differed by an average of 0.1 ± 1.8 mm (p = 0.78) and 0.2 ± 2.1 mm (p = 0.85), respectively. Conclusions Significant discrepancies between planned and actual femoral bone resection were demonstrated for flexion/extension angle, likely the result of cutting error. Our data highlights the importance of cut verification postresection to confirm planned resections are achieved, and suggests imageless navigation may be a source of feedback that would allow surgeons to intraoperatively adjust resections to achieve optimal implant alignment.

Imageless robotic-assisted revision arthroplasty from UKA to TKA

Background and objective It is evident from the national joint registries that numbers of revision knee arthroplasty operations are rising. The aim of this article is to introduce a new robotic-assisted approach in UKA to TKA revision arthroplasty and investigate the alignment accuracy, implant component use and surgery time and to compare it to primary robotic-assisted TKA arthroplasty. Methods This retrospective, case-control study included patients undergoing image-less robotic-assisted revision arthroplasty from UKA to TKA (n = 20) and patients undergoing image-less robotic-assisted primary TKA (control group, n = 20) from 11/2018 to 07/2020. The control group was matched based on the BMI and natural alignment. Comparison of groups was based on postoperative alignment, outlier rate, tibial insert size, lateral bone resection depth, incision-to-wound closure time. All surgeries were performed by a single senior surgeon using the same bi-cruciate stabilizing TKA system. Statistical analysis consisted of parametric t‑testing and Fisher’s exact test with a level of significance of p < 0.05. Results The two groups showed no differences in mean BMI, natural alignment (p > 0.05) and mean overall limb alignment. No outlier was found for OLA and slope analysis. The smallest insert size (9 mm) was used in 70% of the cases in the revision group (n = 14) and in 90% of the cases in the primary group (n = 18, p = 0.24), distal femoral and tibial resection depth showed no statistical difference (p > 0.05). The incision to wound closure time was longer in the revision group but showed no significant difference. Conclusion Image-less robotic-assisted revision arthroplasty from UKA to TKA showed a comparable surgery time, and alignment accuracy in comparison to primary robotic-assisted TKA. Comparable bone preservation and subsequent tibial insert size use was observed for both groups.

Proposal of a New Reference Point to Determine the Tibial Resection Depth during Total Knee Arthroplasty for Valgus Knees

The tibial resection depth during total knee arthroplasty for valgus knees has been variously described and not been standardized yet. Accordingly, it has been proposed in this article, that the sulcus between the medial and lateral intercondylar tibial tubercles can be used as a reference point for the tibial resection depth. The resection can be performed 8 to 9 mm distal to the sulcus.

No Correlation Between Depth of Acetabuloplasty or Postoperative Lateral Center-Edge Angle on Midterm Outcomes of Hip Arthroscopy With Acetabuloplasty and Labral Repair

Background: The treatment of pincer deformity in hip arthroscopy remains controversial, with some authors advocating that over resection may risk early joint deterioration. The role of acetabular resection depth and postoperative acetabular morphology on postoperative outcomes has yet to be defined. Purpose/Hypothesis: This study measures the influence of acetabular resection depth and postoperative lateral center-edge angle (LCEA) on minimum 5-year patient-reported outcomes (PROs), revision rates, and conversion to total hip arthroplasty using a single surgeon’s prospective database. We hypothesized that patients with acetabular resections >10°, as measured by LCEA, or patients with postoperative LCEA outside the normal range of 25° to 35° would have lower PROs, higher revision rates, and higher conversion to total hip arthroplasty at midterm follow-up. Study Design: Cohort study; Level of evidence, 2. Methods: A total of 192 patients who underwent primary hip arthroscopy with acetabuloplasty and labral repair by a single surgeon with a minimum 5-year follow-up met the inclusion criteria. Preoperative and postoperative LCEAs were measured on supine anteroposterior radiographs, and patients were divided into cohorts based on LCEA and acetabular resection depth. Cohorts for postoperative LCEA were <20° (dysplasia), 20° to 25° (borderline dysplasia), 25° to 35° (normal), and >35° (borderline overcoverage). Cohorts for acetabular resection depth were <5°, 5° to 10°, and >10° difference from preoperative to postoperative LCEA. Outcome measures included the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), 12-Item Short Form Health Survey, modified Harris Hip Score, Hip Outcome Score, satisfaction scores, revision rates, and conversion to arthroplasty rates. Results: Patients significantly improved in all outcome score measures at final follow-up. There were no statistically significant differences in PRO scores or conversion to total hip arthroplasty between any cohorts in the postoperative LCEA group. There were more revisions in the 25° to 35° cohort than the other cohorts ( P = .02). The 5-10° resection depth cohort demonstrated a higher postoperative WOMAC score ( P = .03), but otherwise no statistically significant differences were seen between resection depth cohorts in the remaining postoperative outcomes scores, revision rates, or conversion to total hip arthroplasty rates. Conclusion: Patients with postoperative LCEA values outside the normal reference range and with large resections perform similar to those with normal postoperative LCEA values and smaller resections at a minimum 5-year follow-up.

Total Knee Arthroplasty with CAOS Augmentation

This study sought to evaluate the efficiency, usage, and accuracy of a novel technology that augments mechanical instrumentation with intraoperative CAOS guidance. Technical reports on 411 primary TKA cases performed using the technology were reviewed. The results demonstrated high surgical efficiency (time) and resection accuracy (alignment and resection depth). Furthermore, it was observed that one fifth of the time, the surgeons placed the cutting block that deviated more than &gt;2°/mm from the ideal position in the coronal plane. Substantial adjustments were found to be required (on average ~10 °/mm per case) to correct the initial placement of the cutting block. The CAOS augmentation minimized the error in cutting block placement and assisted in achieving high accuracy in bony resections. The findings revealed the prevalence of clinical error with manual conventional bony preparation that can be addressed with efficiency and accuracy by adding CAOS augmentation to the mechanical instrumentation.