An EM-Tracked Approach for Calibrating the 3D Pose of Flexible Endoscopes.

Flexible endoscopes are ideal instruments for visualizing and diagnosing the inner surfaces of organs via a minimally invasive incision. Calibrating a flexible endoscope is a troublesome yet inevitable process in image-based tools tracking. Aiming to simplify the calibration process, we propose an electromagnetic (EM)-tracked calibration approach that does not require any predefined poses of the EM sensor. A three-stage calibration protocol was presented in an extensor. First, the orientation of the endoscope tube was derived by conducting a circular rotation of the endoscope around its axis utilizing a pair of tightly bearing stands. Second, the 3D position of the endoscope tip was acquired by having the tip come into contact with a flat plane. Third, the pose model of the bending section was derived and transformed into the local coordinate system of the EM sensor attached to the endoscope handle. To assess the accuracy of the proposed calibration approach, two experiments were designed and performed. Experimental results indicate accuracies of 0.09 ± 0.06 deg and 0.03 ± 0.19 deg in the estimation of the endoscope tube orientation and 0.52 ± 0.29, 0.33 ± 0.11, and 0.29 ± 0.17 mm in the x, y, and z estimations of the endoscope tip position, respectively. The proposed approach is accurate and easy to operate, does not require the employment of custom calibration markers, and can be used not only in surgical training systems but also in the endoscopic-based tools tracking.

Variety of femoral anteversion and its measurement in cementless total hip arthroplasty: Does robotic technology improve accuracy?

BACKGROUND: High-performance total hip arthroplasty (THA) depends on the accurate position of components. However, femoral anteversion is variable, and current studies only used traditional instruments to evaluate it, such as protractor and spirit level with limited cases. This study aimed to identify the variability in the measured femoral native anteversion and intraoperative stem anteversion under different measurement methods, including intraoperative robotic method. We hypothesized that robotic technology was more accurate than traditional instruments for femoral anteversion evaluation. METHODS: This study included 117 hips of patients who underwent robotic-assisted THA between November 2019 and March 2021. Preoperative native femoral anteversion was measured using a robotic system. Intraoperative femoral stem anteversion was evaluated visually, and then measured with a goniometer and a robotic system, respectively. Variability in the measured femoral native anteversion and intraoperative femoral stem anteversion was calculated and compared. Intraclass correlation coefficient (ICC) and Pearson correlation analysis were used to assess the consistency and correlation of anteversion of different measurements and postoperative CT-measured stem anteversion, respectively. RESULTS: The result of measurement for preoperative native femoral anteversion was more variable than the intraoperative robotic-measured stem anteversion. Intraoperative robotic-measured stem version showed the highest correlation with postoperative CT measurement of stem version (r = 0.806, P < 0.001), while intraoperative surgeon estimation had the lowest correlation coefficient (r = 0.281, P = 0.025). As for the consistency with postoperative CT measurement of femoral stem anteversion, the intraoperative robotic-measured femoral stem version also had the highest value (ICC = 0.892, P < 0.001). CONCLUSION: Native femoral anteversion was variable preoperatively. Using cementless stems, anteversion was also highly variable. Robotic assessment for stem anteversion during surgery was more consistent with the final position than the preoperative assessment and conventional intraoperative estimation.

Using sequential bone cutting to titrate soft tissue balance in total knee arthroplasty effectively minimizes soft tissue release.

BACKGROUND: Achieving soft tissue balance while maintaining limb alignment within acceptable boundaries is crucial for successful total knee arthroplasty (TKA). We proposed a sequential bone cutting (SBC) technique to titrate the soft tissue balance in robot-assisted TKA to achieve the desired balance with minimum soft tissue release. METHODS: In total, 106 robot-assisted TKAs using the SBC technique were included. The preoperative hip-knee-ankle angle (HKA) was < 10° in 76 and ≥ 10° in 30 knees. The gaps were initially balanced with the help of the pre-resection balancing provided by the robotic system. Soft tissue balance and alignment were quantitatively measured after the initial bone cutting and final bone cutting. Additional adjustments (bone recuts and soft tissue releases) required to address soft tissue imbalance after initial bone cutting were recorded. The frequencies of soft tissue releases, soft tissue balance, and resultant alignment ≤ 3° were compared between non-severe (HKA < 10°) and severe deformity (HKA ≥ 10°) groups. RESULTS: Soft tissue balance was achieved in 45 knees (42.5%) after initial bone cutting and in 93 knees (87.7%) after final balancing. The postoperative alignment was within 3° from neutral in 87 knees (82.1%) and 3-5° in 17 knees (16.0%). For unbalanced knees (n = 61) after initial bone cutting, soft tissue release was avoided by SBC in 37 knees (60.7%) and was deemed necessary in 24 knees (39.3%). Soft tissue release was more likely to be avoided in the non-severe deformity cohort (86.8% [33 of 38]) than in the severe deformity cohort (17.4% [4 of 23]; p < 0.001). The non-severe deformity cohort showed a significantly higher rate of resultant alignment ≤ 3° from neutral than the severe deformity cohort (90.8% vs. 60.0%; p < 0.001). CONCLUSION: Pre-resection balancing is inappropriate to ensure soft tissue balance. The SBC technique is effective in minimizing soft tissue release while maintaining overall alignment within acceptable boundaries.

ArthroNavi framework: stereo endoscope-guided instrument localization for arthroscopic minimally invasive surgeries.

Significance: As an example of a minimally invasive arthroscopic surgical procedure, arthroscopic osteochondral autograft transplantation (OAT) is a common option for repairing focal cartilage defects in the knee joints. Arthroscopic OAT offers considerable benefits to patients, such as less post-operative pain and shorter hospital stays. However, performing OAT arthroscopically is an extremely demanding task because the osteochondral graft harvester must remain perpendicular to the cartilage surface to avoid differences in angulation. Aim: We present a practical ArthroNavi framework for instrument pose localization by combining a self-developed stereo endoscopy with electromagnetic computation, which equips surgeons with surgical navigation assistance that eases the operational constraints of arthroscopic OAT surgery. Approach: A prototype of a stereo endoscope specifically fit for a texture-less scene is introduced extensively. Then, the proposed framework employs the semi-global matching algorithm integrating the matching cubes method for real-time processing of the 3D point cloud. To address issues regarding initialization and occlusion, a displaying method based on patient tracking coordinates is proposed for intra-operative robust navigation. A geometrical constraint method that utilizes the 3D point cloud is used to compute a pose for the instrument. Finally, a hemisphere tabulation method is presented for pose accuracy evaluation. Results: Experimental results show that our endoscope achieves 3D shape measurement with an accuracy of <730 µm. The mean error of pose localization is 15.4 deg (range of 10.3 deg to 21.3 deg; standard deviation of 3.08 deg) in our ArthroNavi method, which is within the same order of magnitude as that achieved by experienced surgeons using a freehand technique. Conclusions: The effectiveness of the proposed ArthroNavi has been validated on a phantom femur. The potential contribution of this framework may provide a new computer-aided option for arthroscopic OAT surgery.

Hemisphere Tabulation Method: An Ingenious Approach for Pose Evaluation of Instruments Using the Electromagnetic-Based Stereo Imaging Method.

Drilling of a bone surface often occurs in clinical orthopaedic surgery. The position and orientation of the instrument are the most important factors in this process. Theoretically, some mechanical components may assist in orienting an instrument to certain bone shapes, such as the knee joint and caput femoris. However, the mechanical assisting component does not seem to work in some confined spaces where the bone shape is a free-form surface. In this paper, we propose an ingenious hemisphere tabulation method (HTM) for assessing the pose accuracy of an instrument. The acquisition and assessment of HTM is conducted based on an electromagnetic-based stereo imaging method using a custom-made optical measurement unit, and the operation steps of HTM are described in detail. Experimental results based on 50 tests show that the HTM can identify ideal poses and the evaluated pose of an instrument location on a hemisphere model. The mean error of pose localisation is 7.24 deg, with a range of 1.35 to 15.84 and a standard of 3.66 deg, which is more accurate than our previous method.

Medial wall reconstruction using metal disc augments in revision total hip arthroplasty.

PURPOSE: Medial acetabular bone defects are frequently encountered in revision total hip arthroplasty (THA), but few studies have focused on their reconstruction. This study aimed to report the radiographic and clinical results after medial acetabular wall reconstruction using metal disc augments in revision THA. METHODS: Forty consecutive revision THA cases using metal disc augments for medial acetabular wall reconstruction were identified. Post-operative cup orientation, the centre of rotation (COR), stability of acetabular components and peri-augments osseointegration were measured. The pre-operative and post-operative Harris Hip Score (HHS) and Western Ontario and McMaster Universities Arthritis Index (WOMAC) were compared. RESULTS: The mean post-operative inclination and anteversion were 41.88 ± 6.70° and 16.73 ± 5.35°, respectively. The median vertical and lateral distance between the reconstructed CORs and the anatomic CORs were -3.45 mm (interquartile range [IQR]: -11.30 mm, -0.02 mm) and 3.18 mm (IQR: -0.03 mm, 6.99 mm). Thirty-eight cases completed the minimum two year clinical follow-up, whereas 31 had a minimum two year radiographic follow-up. Acetabular components were radiographically stable with bone ingrowth in 30 cases (30/31, 96.8%) while one case was classified as radiographic failure. Osseointegration around disc augments was observed in 25 of 31 cases (80.6%). The median HHS improved from 33.50 (IQR: 27.50-40.25) pre-operatively to 90.00 (IQR: 86.50-96.25) (p < 0.001), whereas the median WOMAC significantly improved from 38.02 (IQR: 29.17-46.09) to 85.94 (IQR: 79.43-93.75) (p < 0.001). CONCLUSION: In revision THA with severe medial acetabular bone defect, disc augments could provide favorable cup position and stability, peri-augments osseointegration, with satisfactory clinical scores.

Robotic-assisted revision total joint arthroplasty: a state-of-the-art scoping review.

Background: During the past decades, robotic-assisted technology has experienced an incredible advancement in the field of total joint arthroplasty (TJA), which demonstrated promise in improving the accuracy and precision of implantation and alignment in both primary total hip arthroplasty (THA) and total knee arthroplasty (TKA). However, revision TJA remains a technically challenging procedure with issues of large-scale bone defects and damage to nearby anatomical structures. Thus, surgeons are trying to harness the abilities of robotic-assisted technology for revision TJA surgery. Methods: PubMed, Embase, Cochrane Library, and Google Scholar were comprehensively searched to identify relevant publications that reported the application of robotic-assisted technology in revision TJA. Results: Overall, ten studies reported the use of the robotic system in revision TJA, including active (ROBODOC) and semi-active (MAKO and NAVIO) systems. One clinical case reported conversion from hip fusion to THA, and three studies reported revision from primary THA to revision THA. Moreover, four studies reported that robotic-assisted technology is helpful in revising unicompartmental knee arthroplasty (UKA) to TKA, and two case reports converted primary TKA to revision TKA. In this study, we present the latest evolvements, applications, and technical obstacles of robotic-assisted technology in the revision of TJA and the current state-of-the-art. Conclusion: Current available evidence suggests that robotic-assisted technology may help surgeons to reproducibly perform preoperative plans and accurately achieve operative targets during revision TJA. However, concerns remain regarding preoperative metal artifacts, registration techniques, closed software platforms, further bone loss after implant removal, and whether robotic-assisted surgery will improve implant positioning and long-term survivorship.

Effect of blood lipids and lipid-lowering therapies on osteoarthritis risk: A Mendelian randomization study.

Background: We aimed to investigate the effects of blood lipids and lipid-lowering agents on osteoarthritis (OA) risk. Materials and methods: We performed Mendelian randomization (MR) analyses to estimate the causal effect of blood low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglyceride (TG) levels on knee and hip OA. Single nucleotide polymorphisms (SNPs) were selected from large genome-wide association studies (GWASs) of individuals of European ancestry as genetic instruments for blood lipid levels. The associations of selected genetic instruments with knee and hip OA were estimated in a recent GWAS of the UK Biobank and arcOGEN datasets. Univariate and multivariate MR analyses were performed to detect and adjust for potential pleiotropy. Furthermore, genetic instruments in HMGCR, NPC1L1, and PCSK9 regions were used to mimic LDL-C-lowering effects of statin, ezetimibe, and evolocumab, respectively. Results: Genetically determined LDL-C increments led to reduced risks of both knee OA (OR = 0.91 per 1-SD increment, 95% CI: 0.86-0.95, P = 6.3 × 10-5) and hip OA (OR = 0.92, 95% CI: 0.85-0.99, P = 0.027). Multivariate MR analysis proved that the effect was independent of HDL-C, TG, and body mass index. TG increment was associated with reduced risks of hip OA in the univariate MR analysis; however, this was not supported by the multivariate MR analysis. Genetically proxied LDL-C-lowering effects of statins are related to increased risks of knee OA but not hip OA. Conclusions: The findings suggested that LDL-C increments have independent protective effects on both knee and hip OA. LDL-C-lowering effects of statins may increase the risk of knee OA.

Assessing component orientation of total hip arthroplasty using the low-dose bi-planar radiographs.

BACKGROUND: Three-dimensional computed tomography (3D CT) reconstruction is the reference standard for measuring component orientation. However, functional cup orientation in standing position is preferable compared with supine position. The low-dose bi-planar radiographs can be used to analyze standing cup component orientation. We aimed to assess the validity and reliability of the component orientation using the low-dose bi-planar radiographs compared with the 3D CT reconstruction, and explore the differences between the functional cup orientation in standing radiographs and supine CT scans. METHODS: A retrospective study, including 44 patients (50 hips) with total hip arthroplasty (THA), was conducted. CT scans were taken 1 week after surgery and the low-dose bi-planar radiographs were taken in the follow-up 6 weeks later. Component orientation measurement was performed using the anterior pelvic plane and the radiographic coronal plane as reference, respectively. RESULTS: The study showed no significant difference in cup anteversion (p = 0.160), cup inclination (p = 0.486), and stem anteversion (p = 0.219) measured by the low-dose bi-planar radiographs and 3D reconstruction. The differences calculated by the Bland-Altman analysis ranged from - 0.4° to 0.6° for the three measured angles. However, the mean absolute error was 4.76 ± 1.07° for functional anteversion (p = 0.035) and 4.02 ± 1.08° for functional inclination (p = 0.030) measured by the bi-planar radiographs and supine CT scans. CONCLUSIONS: The low-dose bi-planar radiographs are the same reliable and accurate as 3D CT reconstruction to assess post-THA patients' component orientation, while providing more valuable functional component orientation than supine CT scans.

Which serum markers predict the success of reimplantation after periprosthetic joint infection?

PURPOSE: In clinical practice, serum C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) levels are routinely used to screen for periprosthetic joint infection (PJI), but the effectiveness of predicting the success of reimplantation is variable. This study aimed to evaluate the diagnostic effectiveness of serum CRP, ESR, plasma D-dimer, and fibrinogen values in groups achieving treatment success or failure for PJI. METHODS: A total of 119 PJI cases between January 2012 and January 2017 were identified and included in this study. The most recent serum CRP, ESR, plasma D-dimer, and fibrinogen values obtained prior to performing second-stage revision or spacer exchange were collected for analysis. Treatment failure was defined as having been unable to undergo reimplantation due to clinically persistent infection or reinfection after reimplantation. RESULTS: All these tests showed significantly lower values in the treatment success group than in the treatment failure group. The optimal cutoff serum CRP, ESR, plasma D-dimer, and fibrinogen levels for predicting the success of reimplantation were 9.4 mg/L, 29 mm/h, 1740 ng/mL, and 365.6 mg/dL, respectively. All tests had the same sensitivity (72.7%) except for ESR (63.6%), while their specificities were 92.6%, 88.0%, 72.3%, and 83.2%, respectively. Plasma fibrinogen had the highest AUC value of 0.831 [95% confidence interval (CI), 0.685 to 0.978], followed by serum CRP (0.829) and ESR (0.795); plasma D-dimer had the lowest AUC value of 0.716 (95% CI, 0.573 to 0.859). CONCLUSION: Plasma CRP and fibrinogen are good tests for predicting reimplantation success after two-stage revision procedures for patients with PJI.

Symptom duration is associated with failure of periprosthetic joint infection treated with debridement, antibiotics and implant retention.

Background: Debridement, antibiotics, and implant retention (DAIR) is an alternative treatment strategy for periprosthetic joint infection (PJI). However, no consensus exists regarding which patient population(s) may be most suitable for DAIR. This study aims to investigate the overall infection control rate and explore the prognostic factors associated with acute, hematogenous, and chronic PJIs treated with DAIR. Methods: We retrospectively reviewed the included patients who were diagnosed with PJI and underwent DAIR at two institutions from 2009 to 2018 (n = 104). We collected the clinical data, including demographics, preoperative laboratory tests, Charlson Comorbidity Index, surgical information, and culture organism results. Treatment success was defined according to the criteria reported by Diaz-Ledezma. All patients were followed for at least one year unless failure preceded that time point. A multivariable analysis was utilized to identify prognostic factors associated with treatment, and a Kaplan-Meier survival analysis was used to depict the infection control rate. Results: The overall treatment success rate in the current cohort of patients was 67.3% at a median 38.6 (interquartile range: 23.5, 90.7) months follow-up. Patients with a duration of infectious symptoms of more than ten days were more likely to fail (P = 0.035, hazard ratio 8.492, 95% confidence interval 1.159-62.212). There was no difference among acute, hematogenous, and chronic infections in terms of failure rate (P = 0.161). Conclusions: DAIR is a reasonable treatment option for PJI, and its use in the setting of chronic infection does not appear to be a contraindication. Performing DAIR within ten days of the presentation of symptoms had a higher rate of treatment success.

Extended Ischiopubic Fixation Using Porous Metal Augments in Cementless Acetabular Reconstruction during Revision Total Hip Arthroplasty.

OBJECTIVES: The aims of this study were to introduce the definition, indication, and surgical technique of extended ischiopubic fixation (EIF) and to investigate the early clinical, radiographic results and complications of hips revised with EIF. METHODS: Patients who underwent revision THA utilizing the technique of EIF which was defined as securing the porous metal augment >5 mm deep into the ischium and/or pubic ramus to gain adequate mechanical support and fresh host bone for bony ingrowth in a single institution from February 2015 to February 2020 were retrospectively reviewed. After applying the inclusion and exclusion criteria, a total of 30 hips (28 patients) were eligible for the study and were enrolled. Four patients were lost to follow-up postoperatively. The data of the remaining 24 patients (26 hips) were analyzed. The patients' clinical results were assessed using of the Harris Hip Score and any complications including postoperative periprosthetic joint infection, intraoperative fracture, postoperative periprosthetic fracture, dislocation, nerve palsy, hematoma or wound complication were documented. The radiographic results were assessed with the construct stability, the position of the center of rotation, and cup orientation. RESULTS: The median age of these 25 patients was 62.00 (interquartile: 54.25-68.25) years, with a median body mass index (BMI) of 22.60 kg/m2 (interquartile: 21.49-25.12 kg/m2 ). A total of 12 (48%) patients were female. At a median duration of follow-up of 49.16 months, 20 (80%) patients rated their satisfaction level as "very satisfied," five (20%) were "satisfied." The median HHS improved from 36.00 (interquartile range: 31.25-49.75) preoperatively to 81.00 (interquartile range: 74.75-88.25) at the most recent follow-up (p < 0.001). No complications such as periprosthetic joint infection, intraoperative fracture, periprosthetic fracture, dislocation, nerve palsy, hematoma, or wound complication were identified. All constructs were considered to have obtained stable fixation. The median vertical and horizontal distance between the latest postoperative centers of rotation to the anatomic center of rotation improved from 13.62 and 8.68 mm preoperatively to 4.42 and 4.19 mm at final follow-up (p < 0.001). CONCLUSIONS: Early follow-up of patients reconstructed with porous metal augments using the EIF technique demonstrated satisfactory clinical results with no particular complications, stable fixation, and restoration of the center of rotation.

Predictors of a forgotten joint after medial fixed-bearing unicompartmental knee arthroplasty.

BACKGROUND: A forgotten joint is considered the ultimate goal of joint replacement. We aim to explore the predictive factors of a forgotten joint after fixed-bearing unicompartmental knee arthroplasty (UKA). METHODS: This retrospective cohort study used prospectively collected data from 302 cases of medial-compartment UKA with a minimum of 2-year follow-up. The primary outcome was the achievement of a forgotten joint after UKA, according to the Forgotten Joint Score (FJS-12) at the last follow-up. Patients with FJS-12 > 84 were considered to have forgotten UKA. Univariate and multivariate logistic regression analyses were conducted with preoperative patient characteristics and surgery-related factors as potential predictors. RESULTS: Of patients, 94 (31.1%) achieved a forgotten joint post-surgery. Multivariate logistic regression analysis revealed that preoperative hip-knee-ankle angle (HKAA), anatomic lateral distal femoral angle (aLDFA), and postoperative HKAA and HKAA changes were independent predictors of a forgotten joint. The probability of achieving a forgotten joint increased by 29% (OR = 1.29, 95% CI: 1.12-1.51) with a 1° increase in aLDFA. Preoperative HKAA, postoperative HKAA, HKAA changes (ΔHKAA), and outcomes exhibited a non-linear relationship. The probability of achieving a forgotten joint was the highest with preoperative HKAA > 172.0°, postoperative HKAA of 176.0-178.5°, and ΔHKAA < 5.5°. CONCLUSION: To achieve the forgotten joint state, the ideal HKAA range after medial fixed-bearing UKA is 176.0-178.5° and ΔHKAA should be <5.5°. Patients with smaller preoperative aLDFA and HKAA have a lower probability of achieving a forgotten joint after UKA.

Patient-perceived knee enlargement after total knee arthroplasty: prevalence, risk factors, and association with functional outcomes and radiological analysis.

PURPOSE: In clinical practice, many patients complained that their knees became larger after total knee arthroplasty (TKA), yet no studies have described this phenomenon. We named this as "patient-perceived enlargement of knee" (PPEK). This study aimed to investigate the prevalence of PPEK after TKA; assess the association between PPEK and demographics, surgical options, or component size; assess the influence of PPEK on patient satisfaction and functional outcomes; and determine whether there was radiological difference between patients with or without PPEK. METHODS: We reviewed patients that underwent unilateral primary TKA between May 2018 and April 2019. We investigated the prevalence of PPEK and acquired functional scores and satisfaction. Patients were divided into two groups according to whether they complained of PPEK. In radiological evaluation, we measured anterior and posterior condyle offset (ACO and PCO) of the femur, tibial coverage lines, tibial overhanging lines, and femoral overhanging lines. RESULTS: A total of 389 patients were enrolled and 101 patients felt their knee became "larger" after TKA. Patients with PPEK had significantly shorter height and lower weight, yet component size distribution showed no statistical difference. Patients with PPEK had significantly lower functional scores and satisfaction. Patients with PPEK had significantly larger ACO, shorter postoperative PCO, more ACO increase, and less anterior underhang of the tibia. CONCLUSION: PPEK is common in TKA patients, especially in individuals with smaller height and weight. PPEK is associated with poor satisfaction and lower functional scores. In radiology, post-operative ACO, PCO, and anterior underhang of the tibial component were correlated with PPEK.

Better PROMs and higher return-to-sport rate after modular bicompartmental knee arthroplasty than after total knee arthroplasty for medial and patellofemoral compartment osteoarthritis.

Background: Theoretical advantages of bicompartmental knee arthroplasty (BKA) over total knee arthroplasty (TKA) for bicompartmental (medial combined with patellofemoral) osteoarthritis (OA) are still unclear. This study aimed to compare patient-reported outcome measures (PROMs) and return-to-sport (RTS) rate between modular BKA and TKA in early follow-up. Methods: Twenty-five consecutive modular BKA cases with a minimum 2-year follow-up were matched with 50 TKA cases at 1:2 ratio. Demographic data and preoperative functional scores, including the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Knee Society Scores (KSSs), were analyzed to ensure comparability. Postoperative WOMAC score, KSS, range of motion (ROM), Forgotten Joint Score-12 (FJS-12), and RTS rates were compared. Operative time and blood loss were also analyzed. Results: Significant differences in the WOMAC-function (median 97.1 vs. 89.7, p < 0.001) and KSS-function (median 90.0 vs. 80.0, p = 0.003) scores were identified between the BKA and TKA groups. ROM was significantly greater in the BKA group than in the TKA group (median 125.0° vs. 120.0°, p = 0.004), in addition to the FJS-12 (median 89.6 vs. 53.1, p < 0.001). The overall RTS rate was significantly higher in the BKA group than in the TKA group (71.6% vs. 56.5%, p = 0.039). Operative time was significantly longer in the BKA group than in the TKA group (median 105.0 vs. 67.5 min, p < 0.001), but blood loss was similar (median 557.6 vs. 450.7 ml, p = 0.334). Conclusion: Modular BKA demonstrated better functional recovery, better joint perception, and higher RTS rate than TKA; thus, modular BKA can be a good alternative for bicompartmental OA.

Correlation between tibial valgus deformity and aspect ratio of resected tibial surface in female Chinese patients undergoing total knee arthroplasty.

Background: Morphology of the resected tibial surface is the reference for tibial component design, selection, and implantation in total knee arthroplasty (TKA). This comparative study sought to answer whether valgus deformity of the tibia would affect the morphology of the resected tibial surface in TKA. Methods: Thirty-one female Chinese patients with valgus tibias were retrospectively and consecutively identified from a single-center registration database. Thirty-one patients with well-aligned tibias were matched in terms of gender, height, and weight. Weight-bearing full-length radiographs and computed tomography images of the whole lower limb were obtained for every case. Tibial resection was mimicked perpendicular to the mechanical axis of the tibia in the frontal plane with 3° of posterior slope and a cut level individualized by the actual intraoperative cut. On the resected surface, mediolateral dimension (MLD), medial anteroposterior dimensions (mAPD), and lateral anteroposterior dimensions (lAPD) were measured, and aspect ratios (AR) were calculated. We compared the AR between the two groups. Results: The aspect ratio of resected tibial surface positively correlated with tibial valgus alignment. Patients with valgus tibias had significantly smaller AR (MLD/mAPD) for the medial plateau (1.50 ± 0.06 vs. 1.54 ± 0.07, P = 0.032). However, the AR for the lateral plateau was similar between the two groups (1.63 ± 0.08 vs. 1.65 ± 0.07, P = 0.328). Conclusion: This difference in morphology of resected tibial surface between valgus and well-aligned tibias should be considered in tibial component design, as well as in the selection and placement of TKA implants for knees with valgus tibias.

Different Deformity Origins and Morphological Features in Subtypes of Valgus Knees: A Radiological Classification System.

OBJECTIVE: To analyze the deformity origins and distribution among valgus knees to individualize their morphological features. METHODS: Radiographic images of 105 valgus knees were analyzed. Long-film radiographs and computed tomography were collected for every knee. A malalignment test was performed on standing long-film radiographs. The hip-knee-ankle angle (HKA), the anatomical lateral distal femoral angle (aLDFA), and the anatomical medial proximal tibial angle (aMPTA) were measured on long-film radiographs. The distal condylar angle and posterior condylar angle on distal femur were further measured on computed tomography scans. The tibial bone varus angle was measured on long-film radiographs as well. All the valgus knees were sorted into different subtypes according to the origins of bony deformity, and the prevalence of each subtype was reported. Finally, to examine the inter-observer reproducibility of this classification system, two observers measured the deformities and did the classification for all the 105 knees independently and then the intraclass correlation coefficient (ICC) was calculated. RESULTS: Among the 105 knees, 48 knees (45.7%) had apparent deformity from the tibial plateau, and 62 knees (59.0%) had apparent deformity from the supracondylar region of the femur. Eighteen knees (17.1%) had distal condylar angle >7°, among which 11 knees had posterior condylar angle >3° simultaneously. Valgus knees had five subtypes of bone deformity origins-the supracondylar part of the femur, the distal aspect of the lateral femoral condyle, both distal and posterior aspects of the lateral femoral condyle, the tibial plateau, or the metaphyseal segment of the tibia. A valgus knee could be labeled as only one subtype, or a combination of two or more subtypes. Labeling 105 knees with origin of the most severe deformity, the prevalence of each subtype was 40.0%, 5.7%, 9.5%, 28.6%, and 16.2%, respectively. The intra-observer and inter-observer ICC of this classification system was 0.992 and 0.976, respectively. CONCLUSIONS: Valgus knees can be classified into different subtypes according to deformity origins. This radiological classification system has satisfactory reproducibility. It helps surgeons better individualize morphological features of valgus knees.

[Early effectiveness of robot-assisted total hip arthroplasty via direct superior approach].

OBJECTIVE: To evaluate the early effectiveness of the robot-assisted total hip arthroplasty (THA) via direct superior approach (DSA). METHODS: Between March 2021 and April 2021, 11 patients (11 hips) were treated with a robot-assisted THA via DSA. There were 7 males and 4 females, with an average age of 55 years (range, 26-73 years). There were 5 patients of osteoarthritis secondary to hip dysplasia and 6 patients of osteonecrosis of femoral head. Preoperative hip Harris score was 55.8±6.3. The operation time, volume of blood loss, length of incision, postoperative blood transfusion and hospital stay, and the incidence of surgical complications were recorded. The visual analogue scale (VAS) score and Harris score were used to evaluate hip joint pain and function. The leg length discrepancy (LLD) was measured on the X-ray films. The inclination angle and anteversion angle of the acetabular component were also measured, and the difference between the planned and actual values were compared. RESULTS: One THA was performed via conventional posterolateral approach finally because of poor exposure. The rest of 10 THAs were performed with assistance of robotic arm via DSA. The average operation time was 89 minutes (range, 65-120 minutes); the average length of incision was 10.5 cm (range, 9-13 cm); and the average blood loss was 400 mL (range, 110-740 mL). One patient was given a blood transfusion for 2 unit. All incisions healed by first intention and no neurovascular injury, deep vein thrombosis, or fracture occurred. The length of hospital stay after operation was 2-6 days (mean, 4.4 days). The duration of follow-up was 1-3 months (mean, 2.1 months). The VAS score was 0 in 9 patients and 2 in 1 patient at the day of discharge. At last follow-up, the hip Harris score was 84.9±6.7, showing significant difference when compared with that before operation ( t=-8.717, P=0.000). The inclination and anteversion angles were (37.4±2.0)° and (17.1±4.5)°, respectively, and there was no significant difference when compared with the planned values [(38.2±1.6)°, (16.6±3.7)°] ( t=1.809, P=0.104; t=-1.103, P=0.299). The LLD ranged from -2 to 4 mm. No complication such as dislocation, aseptic loosening, or periprosthetic joint infection occurred. CONCLUSION: The robot-assisted THA via DSA has encouraged early effectiveness.

A Novel Endosteal Reconstruction of the Femur from Distal Femoral Remnant Using 3D-Printed Titanium Rings: A Two-Case Report.

CASE: Femur reconstruction with only the distal femoral remnant is challenging because of poor bone volume required for stem fixation. Although proximal femoral replacement, total femur replacement, allograft prosthesis composite, and custom porous tantalum implants are options, hybrid fixation enhanced by endosteal reconstruction with three-dimensional (3D)-printed porous titanium rings to reconstruct the femur without supporting isthmus has not been described. We report 2 cases with satisfactory 34- and 22-month follow-up results of hybrid fixation enhanced by endosteal reconstruction with 3D-printed porous titanium rings. CONCLUSION: This novel method provides a solution to revise loosened femoral endoprosthesis with only distal femoral remnant.

Does robotic assisted technology improve the accuracy of acetabular component positioning in patients with DDH?

BACKGROUND: Accurate positioning of the acetabular component is key in performing total hip arthroplasty (THA). However, reconstruction of the acetabulum in the setting of developmental dysplasia of the hip (DDH) is a challenge. Robotic assisted THA has the potential to improve the accuracy of implantation of the acetabular cup in cases with DDH. The purpose of this study was to assess whether robotic technology improves the accuracy of acetabular component positioning in patients with DDH. MATERIAL AND METHODS: We included 59 THAs using robotic assisted technology from June 2019 to January 2020 as the study group. These were compared to conventional THAs without robotic technology after control for age, gender, body mass index (BMI), Crowe type and operation date. Radiographic measurements were taken by 2 blinded orthopaedic residents. The percentage of hips within the Lewinnek and Collanan safe zones were calculated, along with acetabular rotation centers for the "target zone." Surgical time and perioperative bleeding were also compared between both groups. RESULTS: One patient suffered dislocation in conventional group while no dislocation occurred in robotic group. The acetabular components of the robotic assisted group had more cases located within the Lewinnek (p = 0.013) and Collanan (p = 0.008) safe zones than conventional group (94.9% vs 79.7% and 74.6% vs 50.8%). There were 7 cases in conventional group and 4 cases in robotic group that had more lateral or more superior rotational centers of THA, but did not reach statistical significance (p = 0.342). No statistical difference was detected between groups with regards to blood loss (p = 0.098) and surgical time (p = 0.602). CONCLUSION: Robot assisted technology can assist surgeons with implanting acetabular cups more in Lewinnek and Callanan safe zone than conventional techniques without additional blood loss and surgical time. LEVEL OF EVIDENCE: Therapeutic Level Ⅲ.