Accuracy of cup placement and pelvic motion in total hip arthroplasty in the lateral decubitus position using a new computed tomography-based navigation system with augmented reality technology.

INTRODUCTION: This study aimed to investigate the accuracy of cup position and assess the changes in pelvic tilt during primary total hip arthroplasty (THA) in the lateral decubitus position using a new computed tomography (CT)-based navigation system with augmented reality (AR) technology. MATERIALS AND METHODS: There were 37 cementless THAs performed using a CT-based navigation system with AR technology in the lateral decubitus position and 63 cementless THAs performed using manual implant techniques in the lateral decubitus position in this retrospective study. Postoperative cup radiographic inclination and anteversion were measured using postoperative CT, and the proportion of hips within Lewinnek's safe zone was analyzed and compared between the two groups. The mean absolute values of navigation error were assessed. Intraoperative pelvic tilt angles were also recorded using navigation system. RESULTS: The percentage of cups inside Lewinnek's safe zone was 100% in the navigation group and 35% in the control group (p < 0.001). The mean absolute values of navigation error in inclination and anteversion were 2.9° ± 2.1° and 3.3° ± 2.4°, respectively. The mean abduction angle of the pelvis was 5.1° ± 4.8° after placing the patients in the lateral decubitus position and 4.1° ± 6.0° after cup placement. The mean posterior tilt angle was 6.8° ± 5.1° after placing the patients in the lateral decubitus position and 9.3° ± 5.9° after cup placement. The mean internal rotation angle was 14.8° ± 7.4° after cup placement. There were no correlations between the navigation error in inclination or anteversion and the absolute values of changes of the pelvic tilt angle at any phase. CONCLUSIONS: Although progressive pelvic motion occurred in THA in the lateral decubitus position, especially during cup placement, the CT-based navigation system with AR technology improved cup placement accuracy.

Two- and three-dimensional measurements of leg length change using an accelerometer-based portable navigation system in total hip arthroplasty.

BACKGROUND: The aim of this study was examining the accuracy of accelerometer-based portable navigation systems (HipAlign) when measuring leg length changes using two-dimensional (2D) and three-dimensional (3D) methods. METHODS: Inclusion criteria were patients ≥ 20 years old with symptomatic hip disease who underwent primary total hip arthroplasty (THA) in the supine position using HipAlign between June 2019 and April 2020. The exclusion criteria were patients who underwent THA via a posterior approach. We examined correlations between the leg length change measurement with HipAlign and either 2D or 3D measurement. We performed a multivariate analysis to determine which factors may have influenced the absolute error results. RESULTS: This study included 34 patients. The absolute error in leg length change between the HipAlign and 3D measurement (4.0 mm) was greater than the HipAlign and 2D measurement (1.7 mm). There were positive correlations between leg length change with HipAlign and 2D and 3D measurements. Male patients had larger errors with 2D measurement. No significant factors were identified for 3D measurement. CONCLUSION: HipAlign provided acceptable measurement accuracy for leg length changes.

Long-term results of hemi-resurfacing and metal-on-metal hip resurfacing for osteonecrosis of the femoral head.

PURPOSE: Hemi-resurfacing arthroplasty (Hemi) and metal-on-metal hip resurfacing arthroplasty (HR) were proposed as alternatives to conventional total hip arthroplasty (THA) for patients with osteonecrosis of the femoral head (ONFH). Long-term results were evaluated. METHODS: Twenty-three hips with ONFH were treated, using Hemi in 12 and HR in 11. Mean follow-up was 15 years in the Hemi group and 10 years in the HR group. Long-term outcomes were reviewed retrospectively. RESULTS: In the Hemi group, 8 hips showed acetabular protrusion and were revised to THA. One of the 8 hips showed femoral loosening. In the HR group, pseudotumor was detected in 4 hips (36%), and 1 hip was revised due to symptomatic pseudotumor. No evidence of any femoral or acetabular loosening was seen in the HR group. Ten-year survival rates were 64.2% and 90.9% in the Hemi and HR groups, respectively. Survival rate in the Hemi group dropped to 22.9% at 15 years. CONCLUSIONS: Long-term results of Hemi for patients with ONFH were very poor, and Hemi should not continue to be used. Although HR had a concern of pseudotumor, it could offer attractive indications for 10 years.

High rates of outliers in computer-assisted high tibial osteotomy with excellent mid-term outcomes.

PURPOSE: The primary aim was to evaluate the accuracy of navigation in opening wedge high tibial osteotomy (HTO). The secondary aim was to examine mid-term outcomes after HTO. METHODS: Inclusion criteria were patients with medial compartment knee osteoarthritis who underwent computer-assisted HTOs. Mechanical axis (MA), percentage MA (%MA), and change in posterior tibial slope (ΔPTS) were displayed on the navigation screen. Radiographic examinations included hip-knee-ankle (HKA) angle, medial proximal tibial angle (MPTA), joint line convergence angle (JLCA), and PTS. Preoperative and 5 weeks postoperative standing radiographs of the whole lower extremity and knee were used. Clinical evaluations were performed using American Knee Society knee score and function score both preoperatively and at last follow-up. Radiographic evaluations were performed by orthopedic surgeons. Intraoperative navigation after osteotomy and postoperative standing radiograph were compared. MA (HKA), %MA, and ΔPTS were compared. Outliers were defined as > 3° in MA, > 10% in %MA, and > 10° in ΔPTS. Outlier and non-outlier groups were compared. The rate of conversion to arthroplasty was examined. RESULTS: This study involved 38 patients (44 knees) and last follow-up was at a mean of 5 years (range, 1-9 years). Mean American Knee Society knee score and function score improved significantly from 59 to 69 preoperatively to 95 and 85 at last follow-up, respectively. Absolute values of mean errors for MA, %MA, and ΔPTS were 2.1°, 9.3%, 1.2°, respectively. Outlier rates were 18% in MA, 39% in %MA, and 5% in ΔPTS. No significant factors were found in MA and ΔPTS. In %MA, preoperative JLCA was significantly higher in the outlier group compared to the non-outlier group. No knees underwent conversion to total knee arthroplasty. No differences in outcomes were found between outlier and non-outlier groups. CONCLUSION: Although rates of outlier values in computer-assisted opening wedge HTO were high, mid-term outcomes were excellent. LEVEL OF EVIDENCE: IV.

Predicting outcomes after total knee arthroplasty using intraoperative knee kinematics measured by navigation.

OBJECTIVES: The objective of the study is to evaluate the relationship between clinical results following posterior-stabilized total knee arthroplasty (TKA) and intraoperative kinematic pattern determined from navigation. METHODS: Participants were patients with knee osteoarthritis and varus deformity who underwent primary posterior-stabilized TKA. Preoperative and post-implantation kinematic data were recorded, and all kinematic patterns were divided into two types: medial pivot (MP) or non-MP. Knees with MP and non-MP patterns after implantation were compared in terms of postoperative flexion angle, pain, patient satisfaction, expectations, and activity using the new Knee Society Score 2011 at 1 year postoperatively. RESULTS: This study involved 55 patients (12 men, 43 women) with a mean age of 73.1 years and mean body mass index of 26.5 kg/m2. Preoperative kinematic measurements showed MP in 23 knees and non-MP in 32 knees. After implantation, navigation showed MP in 25 knees and non-MP in 30 knees. No significant differences were found between kinematic patterns preoperatively and after implantation. Postoperative flexion angle, pain, patient satisfaction, expectations, and activity using Knee Society Score 2011 showed no differences between MP and non-MP knees. CONCLUSION: Intraoperative knee kinematics as measured by navigation could not predict postoperative outcomes of TKA.

Accuracy of a novel accelerometer-based navigation (Naviswiss) for total hip arthroplasty in the supine position.

BACKGROUND: This study aimed to determine the accuracy of acetabular cup insertion using a novel accelerometer-based navigation system in total hip arthroplasty (THA). METHODS: A single-surgeon study was conducted in which 62 prospective patients with navigation and 42 retrospective patients without navigation in a supine position were compared. Absolute values for errors of radiographic inclination and anteversion were calculated. Navigation error was also calculated. Factors that affected absolute value of navigation error in cup alignment were determined. RESULTS: In the navigation group, mean absolute errors for radiographic inclination and anteversion were 4.1° and 4.3°, respectively. In the control group, mean absolute errors were 6.6° in inclination (p < 0.01) and 5.9° in anteversion (p = 0.04). Mean absolute values of navigation error were 2.8° in inclination and 2.8°in anteversion. Factors affecting navigation errors were not found. CONCLUSION: This novel accelerometer-based navigation system significantly increased the accuracy of cup placement during THA in the supine position.

Preoperative pain catastrophizing affects pain outcome after total knee arthroplasty.

BACKGROUNDS: Preoperative widespread pain sensitization or pain catastrophizing could be associated with chronic pain after total knee arthroplasty (TKA). The aim of the present study was to examine the association between postoperative pain in patients undergoing TKA and preoperative factors, including patient characteristics and preoperative central sensitization as well as pain catastrophizing. METHODS: Preoperative TKA patients were evaluated using the Central Sensitization Inventory (CSI)-9 and Pain Catastrophizing Scale (PCS). Postoperative knee pain was evaluated using a numerical rating scale (NRS) 6 months after TKA. Statistical analyses were performed to assess the relationship between NRS 6 months after TKA and preoperative factors, including patient characteristics, CSI-9, and PCS. RESULTS: We enrolled 58 consecutive patients with osteoarthritis who underwent TKA. Using cutoff of 14, postoperative NRS was higher in the patients with ≥14 than the patients with <14 in CSI (p = 0.025). Postoperative NRS was higher in the patients with ≥30 than the patients with <30 in PCS (p = 0.043). Preoperative PCS was a significant risk factor of postoperative pain using a multivariate analysis. CONCLUSIONS: Surgeon should recognize preoperative PCS could affect postoperative pain 6 months after TKA.

Accuracy of acetabular cup insertion in an anterolateral supine approach using an accelerometer-based portable navigation system.

The purpose of this study was to determine the accuracy of acetabular cup insertion during total hip arthroplasty (THA) in a supine position using an accelerometer-based portable navigation system. A single-surgeon study was conducted in which 62 prospective patients with navigation and 42 retrospective patients without navigation as historical controls were compared. The patients underwent THA via an anterolateral supine approach. The absolute values of errors of radiographic inclination and anteversion were calculated. The navigation error was also calculated. The factors that affected the absolute values of errors of cup alignment were determined. The mean absolute error of the postoperative CT measurement from the target angle for radiographic inclination was 3.8° in the navigation group and 6.6° in the control group (P < 0.001). The mean absolute error for anteversion was 3.3° in the navigation group and 5.9° in the control group (P < 0.001). The mean absolute values of navigation error were 3.7° ± 2.8° in inclination and 3.0° ± 2.6° in anteversion. Changes in the pelvic tilt angle among preoperative, intraoperative, and postoperative were the significant risk factors for the absolute values of navigation error of anteversion relative to the anterior pelvic plane. Other factors affecting the absolute values of errors in the navigation group were not found for radiographic inclination and anteversion. The portable navigation system significantly improved the accuracy of cup inclination and anteversion. Changes in the pelvic tilt were the risk factors for the error of anteversion relative to the anterior pelvic plane.

The accuracy of acetabular cup placement in primary total hip arthroplasty using an image-free navigation system.

BACKGROUND: Intraoperative navigation systems have been shown to improve the accuracy of acetabular component insertion in total hip arthroplasty (THA). The purpose of this study was to investigate the accuracy of cup orientation in primary THA using an image-free navigation system. METHODS: A total of 107 consecutive cementless THAs using an image-free navigation system were performed from February 2017 to March 2020 (the navigation group). As a control group, 77 retrospective consecutive cases who underwent THAs with manual implant-techniques between February 2012 and April 2017 were included. Postoperative cup radiographic inclination and radiographic anteversion relative to the functional pelvic plane were assessed using a 3D-template system after computed tomography (CT) examination. RESULTS: The mean absolute errors of the postoperative measured angles from the target angles in inclination were 3.4° ± 3.0° in the navigation group and 8.4° ± 6.6° in the control group (p < 0.001). The mean absolute errors in anteversion were 5.1° ± 3.6° in the navigation group and 10.8° ± 6.5° in the control group (p < 0.001). The percentage of cups inside the Lewinnek safe zone was 93% in the navigation group and 44% in the control group (p < 0.001). The mean absolute values of navigation error were 3.3° ± 2.8° in inclination and 5.8° ± 4.9° in anteversion. Among the cases of osteoarthritis, the inclination error was significantly higher in Crowe group 2 to 4 than in Crowe group 1 (5.1° ± 3.5° and 3.0° ± 2.5°, respectively, p < 0.05). The percentage of hips with inclination error over 10° in Crowe group 2 to 4 was significantly higher than in Crowe group 1 (17 and 1%, respectively, p < 0.05). CONCLUSIONS: The image-free navigation system improved the accuracy of cup orientation. The accuracy of cup position was less in Crowe group 2 to 4 than in Crowe group 1.

Accuracy of image-free navigation in intraoperative leg length change from total hip arthroplasty using evaluations from 2D and 3D measurements.

BACKGROUND: Leg length discrepancy is one of the most common problems after total hip arthroplasty (THA). The aim of this study was to investigate the accuracy of image-free navigation in intraoperative leg length change (LLC) using evaluations from anteroposterior radiographs (2D measurement) and 3D bone models using CT data (3D measurement). METHODS: One hundred THAs with cementless cups and stems were performed using an image-free navigation system in our hospital. We evaluated the accuracy of image-free navigation based on LLC from 2D and 3D measurements. Furthermore, we also investigated error in absolute value and correlations between 2D and 3D measurements in LLC. RESULTS: The accuracy of image-free navigation based on 2D measurement was 94% within 5 mm and 76% within 3 mm. The accuracy of image-free navigation based on 3D measurement was 92% within 5 mm and 81% within 3 mm. The error in absolute value in LLC between 2D and 3D measurements was 1.7 ± 1.4 mm (range, 0 to 6 mm). A strong correlation was observed between 2D and 3D measurements in the LLC. CONCLUSIONS: In the present study, good accuracy of image-free navigation in intraoperative LLC was confirmed for both evaluation methods from 2D and 3D measurements. In addition, the error in absolute value in the LLC between 2D and 3D measurements was very small, and we observed a strong correlation between 2D and 3D measurements. Based on these results, evaluation of LLC from radiographs was considered sufficient if radiographs can be taken accurately.

Minimum 10-Year Follow-Up of Cementless Total Hip Arthroplasty With a 32-mm Cobalt-Chromium Head on Highly Cross-Linked Polyethylene and a Tapered, Fiber Metal Proximally Coated Femoral Stem.

BACKGROUND: The clinical and radiographic results of cementless total hip arthroplasty using a 32-mm cobalt-chromium head on remelted highly cross-linked polyethylene (HXLPE) and a tapered, fiber metal proximally coated femoral stem were evaluated at a mean follow-up of 12 years. METHODS: A total of 57 cementless total hip arthroplasties using remelted HXLPE combined with a 32-mm cobalt-chromium head, and a tapered, fiber metal proximally coated femoral stem were performed from October 2004 to December 2006. Clinical evaluation was performed using the Merle d'Aubigné and Postel scoring system. Standardized anteroposterior and lateral radiographs of the pelvis and femur without weight-bearing were analyzed. Radiographic measurements of two-dimensional femoral head penetration into the polyethylene were performed with a computerized method. The steady-state wear rates were measured based on the radiographs from the first year after surgery to the final follow-up. RESULTS: The mean Merle d'Aubigné and Postel score improved significantly from 10.7 points preoperatively to 15.6 postoperatively (P < .001). No osteolysis was found around the implant. Stem fixation in all cases showed stable bone ingrowth. Third-degree stress shielding was found in 46% of all stems. The total head penetration rate was 0.05 mm/y, and the steady-state wear rate was 0.01 mm/y. The Kaplan-Meier survivorship with the end point of revision was 95% (95% confidence interval, 85%-98%) at 12 years. CONCLUSION: A 32-mm cobalt-chromium head on remelted HXLPE demonstrated low wear properties, and a tapered, fiber metal proximally coated femoral stem showed good results at long-term follow-up.

Minimum ten-year results in revision total hip arthroplasty using titanium fully porous long stem.

PURPOSE: The fully porous long stem could be used for diaphyseal locking and achieve bypass fixation in revision total hip arthroplasty (THA). This study evaluated long-term results for fully porous long stems made of titanium alloy in revision THA. METHODS: Between 2003 and 2010, 45 consecutive femoral revisions were performed using fully porous long stems. Thirty-eight hips had complete clinical and radiographic data for a mean of 13.8 years (range, 10-16.7 years). Femoral bone loss was Paprosky type II in 14 hips, type IIIA in 18 hips, and type IIIB in six hips. Clinical results were analyzed using the Merle d'Aubigné and Postel scoring system. Femoral stress shielding was graded. Radiological loosening of the femoral component was evaluated. Kaplan-Meier survival analysis was performed with revision for any reason as the end-point. RESULTS: Mean Merle d'Aubigné and Postel score improved significantly from 10.7 before revision to 14.5 at latest follow-up (p < 0.001). Third-degree stress shielding was found in seven hips, and fourth degree in 11 hips. Radiological femoral loosening occurred in one hip, which was revised. Another hip was revised for stem fracture. Kaplan-Meier cumulative survival rate was 94.7% at both ten and 15 years. CONCLUSION: Although stress shielding is a concern with fully porous stems, this stem was useful in revision THA and provided satisfactory long-term results in hips with Paprosky types II, IIIA, and IIIB.

Use of antibiotic-impregnated hydroxyapatite for infection following total knee arthroplasty.

OBJECTIVES: Antibiotic-impregnated hydroxyapatite (HA) is an emerging drug delivery system for the treatment of periprosthetic joint infection (PJI) of the knee. The aim of this study was to evaluate the clinical results of this treatment in patients with PJI following total knee arthroplasty (TKA). METHODS: Participants comprised 14 consecutive patients with PJI of the knee who were scheduled to undergo two-stage knee revision. In the first stage, all components were removed with thorough debridement, and antibiotic-impregnated HA was inserted in the bone and joint space. In the second stage, revision TKA was performed after the eradication of infection. The mean period from the removal of all components and treatment with antibiotic-impregnated HA to revision TKA was 3.4 months. Clinical and radiographic evaluations were performed after a mean follow-up of 6.1 years following revision TKA. Predictors of reinfection were evaluated. RESULTS: Eleven patients had no recurrent infection, whereas 3 patients showed recurrent infection. Knee Society knee score and function score, as well as flexion angles, improved significantly postoperatively. No knees showed osteolysis or loosening after revision TKA. The present study identified no predictors of reinfection. CONCLUSION: Antibiotic-impregnated HA could be effective in treating knee PJI.

Thirteen-year results of cementless total hip arthroplasty with zirconia heads on highly cross-linked polyethylene.

OBJECTIVES: Zirconia ceramic was introduced for femoral heads because of its mechanical strength and fracture toughness. Highly cross-linked polyethylene has been shown to achieve wear reduction compared to conventional polyethylene. The purpose of this study was to investigate the long-term results of cementless total hip arthroplasty with zirconia femoral heads on highly cross-linked polyethylene. METHODS: Radiographic measurements of two-dimensional femoral head penetration into the polyethylene were performed with a computerized method (PolyWare) in 93 hips at a mean follow-up of 13 years. The steady-state wear rates were measured based on the radiographs from the first year after surgery to the final follow-up. RESULTS: The mean Merle d'Aubigné and Postel score had improved significantly from 10.9 points preoperatively to 15.3 postoperatively (p < 0.001). Osteolysis was not found around the implant, and no zirconia heads had fractures. The total head penetration rate was 0.04 mm/year, and the steady-state wear rate was 0.02 mm/year. Kaplan-Meier survivorship with the endpoint of revision was 97% (95% confidence interval [CI], 92% to 99%) at 10 years. CONCLUSION: Zirconia on highly cross-linked polyethylene demonstrated extremely low wear properties at long-term follow-up.

Comparison of three different anti-Xa assays in major orthopedic surgery patients treated with direct oral anticoagulant.

BACKGROUND: Measurement of edoxaban plasma concentration has been gathering attention in major orthopedic surgery patients receiving edoxaban for the prevention of venous thromboembolism (VTE). METHODS: The anti-Xa activity was measured one hour after edoxaban intake using 3 different assays in 200 patients after major orthopedic surgery. RESULTS: The anti-Xa activities on Day 8 were significantly higher than those on Day 4 and those on Day 4 were significantly higher than those on Day 1. The anti-Xa activities in two assays closely correlated with each other, but the other anti-Xa assay did not correlated with other two assays. The anti-Xa activities as detected in the three Xa assays were significantly higher in the patients without deep vein thrombosis (DVT) than in those with DVT on Day 4. Additionally, there were no significant differences in the anti-Xa activities of assays A, B and C between patients with and without massive bleeding (MB) on Days 1, 4, 8 and 15. CONCLUSION: The results of this study suggest that anti-Xa level could be predictive of the risk of VTE, but not of the risk of massive bleeding.

Comparison of accuracy and early outcomes in robotic total knee arthroplasty using NAVIO and ROSA.

This study aimed to compare the cutting and component placement accuracies and early outcomes after total knee arthroplasty (TKA) between an image-free handheld robotic system (NAVIO) and a radiography-based robotic system (ROSA). This retrospective study included 88 patients (88 knees) who underwent TKA using the NAVIO (40 patients) or ROSA (48 patients) robotic systems. The accuracies of the robotic systems were compared. Clinical scores were evaluated using the Knee Society Score 2011 (KSS 2011) and the forgotten joint score (FJS)-12 at 1 year postoperatively. The femoral sagittal cutting error was smaller in the NAVIO group than in the ROSA group. The other cutting errors were not statistically different in both groups. Implantation errors did not differ between the groups. Regarding the clinical outcomes of the KSS 2011 subscales, the symptoms score was higher in knees operated using ROSA than in those using NAVIO. The other KSS 2011 subscales and the FJS-12 showed no differences between the two groups. In conclusion, the femoral sagittal cutting error was smaller in the NAVIO group than in the ROSA group, and the KSS 2011 symptom score subsection at one year was higher in the knees operated using ROSA than in those using NAVIO.

Comparison between accuracy of augmented reality computed tomography-based and portable augmented reality-based navigation systems for cup insertion in total hip arthroplasty.

Augmented reality (AR) has been used for navigation during total hip arthroplasty (THA). AR computed tomography (CT)-based navigation systems and AR-based portable navigation systems that use smartphones can also be used. This study compared the accuracy of cup insertion during THA using AR-CT-based and portable AR-based navigation systems. Patients with symptomatic hip disease who underwent primary THA in the supine position using both AR CT-based and portable AR-based navigation systems simultaneously between October 2021 and July 2023 were included. The primary outcome of this study was the absolute difference between cup angles in the intraoperative navigation record and those measured on postoperative CT. The secondary outcome was to determine the factors affecting the absolute value of the navigation error in radiographic inclination (RI) and radiographic anteversion (RA) of the cup, including sex, age, body mass index, left or right side, approach, and preoperative pelvic tilt. This study included 94 consecutive patients. There were 11 men and 83 women, with a mean age of 68 years. The mean absolute errors of RI were 2.7° ± 2.0° in the AR CT-based and 3.3° ± 2.4° in the portable AR-based navigation system. The mean absolute errors of RA were 2.5° ± 2.1° in the AR CT-based navigation system and 2.3° ± 2.2° in the portable AR-based navigation system. No significant differences were observed in RI or RA of the cup between the two navigation systems (RI: p = 0.706; RA: p = 0.329). No significant factors affected the absolute value of the navigation errors in RI and RA. In conclusion, there were no differences in the accuracy of cup insertion between the AR CT-based and portable AR-based navigation systems.

Neuropathic pain in patients with osteoarthritis of the hip before and after total hip arthroplasty.

OBJECTIVES: The pain associated with osteoarthritis (OA) was thought to be nociceptive; however, neuropathic pain is also observed. We investigated the relationship between hip OA and neuropathic pain using the PainDETECT questionnaire (PDQ). METHODS: A total of 159 hips of 146 consecutive patients who underwent total hip arthroplasty (THA) with a diagnosis of OA were enrolled in this study. The prevalence of each pain phenotype was evaluated preoperatively and at 6 months postoperatively using the PDQ. Patient characteristics and numerical rating scale (NRS) scores were compared between a group with possible neuropathic pain (NP group) and a group with nociceptive pain (non-NP group). RESULTS: Before THA, neuropathic, unclear, and nociceptive pain was observed in 18, 36, and 105 hips, respectively. The prevalence in the NP group was 54 hips, accounting for approximately one-third of all hips, which decreased significantly to seven hips after THA. A significantly higher NRS score was observed in the NP group, both before and after THA. CONCLUSION: Approximately one-third of the patients with hip OA had neuropathic pain. Therefore, neuropathic pain should be considered when treating patients with hip OA.

Two- and three-dimensional evaluations following handheld robot-assisted total knee arthroplasty.

Robot-assisted total knee arthroplasty (TKA) has proven to be successful in improving the accuracy of component positioning and reducing radiographic outliers. This study aimed to evaluate and compare the alignment of the components using two- and three-dimensional (2D and 3D) measurements following handheld imageless robot-assisted TKA. Seventy consecutive patients underwent primary TKA at our institution using a handheld robot-assisted system. Full-length standing anteroposterior and lateral radiographs were obtained 2 weeks after surgery for assessment of 2D component alignments. Pre- and postoperative computed tomography (CT) images were obtained to assess 3D component alignment. The reference points defined on preoperative CT images were transferred to the postoperative CT images. The absolute errors in the 2D and 3D component alignments from the planned, validated cutting, and validated implantation angles were calculated. Outliers of > ± 3° of femoral and tibial component alignments in the coronal and sagittal planes were also investigated. All absolute errors in the 2D and 3D component alignments were < 1°, except for the planned and validated cutting angles of the femoral sagittal alignment. No outliers were observed in the femoral or tibial component in the coronal plane. Significant differences between the 2D and 3D measurements were observed for the mean absolute value from the planned and validated cutting angles in the femoral sagittal plane and from the validated implantation angle in the tibial coronal plane. The handheld robot-assisted system demonstrated a high accuracy for component alignment using 2D and 3D evaluations.