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.

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.

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.

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.

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.

The Utilization of Metal Augments Allows Better Biomechanical Reconstruction of the Hip in Revision Total Hip Arthroplasty With Severe Acetabular Defects: A Comparative Study.

BACKGROUND: Reconstructing the normal hip biomechanics is important for a successful revision total hip arthroplasty (THA). Little is known about whether using metal augments in revision THA is biomechanically superior to traditional techniques. METHODS: A retrospective review was conducted on 74 consecutive THAs revised using metal augments with a cementless hemispherical cup and 77 consecutive THAs revised using the jumbo cup, all with a minimum 2-year follow-up. Biomechanical parameters were measured before and immediately after the revision. Radiological and clinical outcomes at follow-ups were also evaluated. RESULTS: The metal augment group had a reconstructed center of rotation (COR) that was 6.5 mm closer to the anatomic COR in height (P < .001), had 3.6 m smaller cup size (P < .001), and had 5.7 mm less head-cup difference (P < .001). Moreover, there was a reconstructed COR that was much closer to the anatomic COR (vertical distance: 1.8 vs 14.1 mm, P < .001; horizontal distance: -2.1 vs 7.9 mm, P = .013), had 4.1 mm greater femoral offset (P = .006), and had 8 mm less leg length discrepancy (P = .035) in the subgroup of Paprosky type III bone defects when compared to the jumbo cup group. All cup-augment constructs were radiologically stable with a higher mean postoperative Harris Hip Score (P = .012). One jumbo cup was radiologically unstable. CONCLUSION: In revision THA, utilizing metal augments helps to restore the COR position more precisely, avoid using a larger cup, reduce head-cup difference, rebuild femoral offset, and decrease leg length discrepancy, particularly with Paprosky type III bone defects. Moreover, it provides satisfactory radiological and clinical outcomes in the short term.

Accuracy of Digital Tomosynthesis With Metal Artifact Reduction for Detecting Osteointegration in Cementless Hip Arthroplasty.

BACKGROUND: Cementless hip arthroplasty is increasingly gaining popularity worldwide. Radiologic identification of osteointegration is key to confirming biologic fixation. We conducted the study reported here to determine the sensitivity and specificity of digital tomosynthesis with metal artifact reduction (TMAR), radiography, and conventional computed tomography in detecting osteointegration in cementless hip arthroplasty. METHODS: We prospectively included data for 24 patients who underwent revision hip arthroplasty in our hospital, with 13 femoral and 14 acetabular cementless components retrieved that contained solid evidence of biologic fixation. All patients underwent 3 examinations before surgery, and evidence of osteointegration on retrieved prostheses was used as the reference standard. Seven orthopedic surgeons evaluated these images independently using uniform criteria. RESULTS: On the femoral side, the sensitivity and specificity of detecting osteointegration were 73.8% ± 4.6% and 94.3% ± 1.5%, respectively, for TMAR; 50.4% ± 5.3% and 87.8% ± 2.1%, respectively, for radiography; and 36.4% ± 5.1% and 90.9% ± 1.9%, respectively, for CT. On the cup side, the corresponding values were 60.2% ± 8.3% and 86.4% ± 5.7%, respectively, for TMAR; 45.9% ± 8.5% and 66.4% ± 7.8%, respectively, for radiography; and 45.1% ± 8.5% and 73.5% ± 7.3%, respectively, by computed tomography. CONCLUSION: TMAR significantly improved the accuracy osteointegration detection in cementless hip arthroplasty (P < .017).

Location of the Common Peroneal Nerve in Valgus Knees-Is the Reported Safe Zone for Well-Aligned Knees Applicable?

BACKGROUND: Lateral soft-tissue release can jeopardize the common peroneal nerve (CPN) in total knee arthroplasty for valgus knees. Previous studies reporting safe zones to protect the CPN were based on well-aligned knees. We conducted this study to compare the localization of the CPN in well-aligned knees and in valgus knees. METHODS: We conducted a consecutive 3-dimensional radiographic study on magnetic resonance images of 58 well-aligned knees and 39 valgus knees. We measured the distance between the CPN and the tibia, as well as the mediolateral, anteroposterior, and angular location of the CPN. We compared the results between well-aligned knees and valgus knees. RESULTS: We found that there is an increased distance between the CPN and the tibia at the level of the tibial cut, but not at the joint line in valgus knees. It is safer to release the posterolateral capsule at the tibial side than at the level above this. The angular location and the mediolateral or anteroposterior location of the CPN in valgus knees are similar to those of well-aligned knees. CONCLUSION: The location of the CPN in valgus knees is similar to that in well-aligned knees. The previously reported safe zone in well-aligned knees is applicable in valgus knees to protect the CPN.

Digital tomosynthesis with metal artifact reduction for assessing cementless hip arthroplasty: a diagnostic cohort study of 48 patients.

OBJECTIVES: For postoperative imaging assessment of cementless hip arthroplasty, radiography and computed tomography (CT) were restricted by overlapping structures and metal artifacts, respectively. A new tomosynthesis with metal artifact reduction (TMAR) is introduced by using metal extraction and ordered subset-expectation maximization (OS-EM) reconstruction. This study investigated the effectiveness of TMAR in assessing fixation stability of cementless hip arthroplasty components. MATERIALS AND METHODS: We prospectively included 48 consecutive patients scheduled for revision hip arthroplasty in our hospital, with 41 femoral and 35 acetabular cementless components available for evaluation. All patients took the three examinations of radiography, CT, and TMAR preoperatively, with intraoperative mechanical tests, and absence or presence of osteointegration on retrieved prosthesis as reference standards. Three senior surgeons and four junior surgeons evaluated these images independently with uniform criteria. RESULTS: For TMAR, 82 % diagnoses on the femoral side and 84 % diagnoses on the acetabular side were accurate. The corresponding values were 44 and 67 % for radiography, and 39 % and 74 % for CT. Senior surgeons had significantly higher accuracy than junior surgeons by radiography (p < 0.05), but not by TMAR or CT. CONCLUSIONS: By minimizing metal artifacts in the bone-implant interface and clearly depicting peri-implant trabecular structures, the TMAR technique improved the diagnostic accuracy of assessing fixation stability of cementless hip arthroplasty, and shortened the learning curve of less experienced surgeons. LEVEL OF EVIDENCE: Level II, diagnostic cohort study.

Chinese patients' satisfaction with total hip arthroplasty: what is important and dissatisfactory?

Through validated self-administered questionnaires, we conducted a retrospective investigation in 818 patients (1009 hips) who underwent primary THA, to collect data on overall satisfaction plus satisfaction and importance rating for 16 specific functions and issues. Overall, 8.1% patients were dissatisfied with the surgery. The top 3 important items are pain relief, squatting, and walking. The top 3 dissatisfactory items are jogging, squatting, and rising after squatting. The strongest risk factors for dissatisfaction with walking were pain (6.1×), muscle weakness(3.7×), and LLD (3.3×). The strongest risk factors for dissatisfaction with squatting were low postoperative HHS ROM (3.7×) and muscle weakness (2.6×). For Chinese patients, ROM, muscle strength and LLD are very important.

Robotic-assisted differential total knee arthroplasty with patient-specific implants: surgical techniques and preliminary results.

OBJECTIVE: In total knee arthroplasty (TKA), achieving soft-tissue balance while retaining acceptable lower limb alignment is sometimes difficult and may lead to patient dissatisfaction. Theoretically, patient-specific implants can bring great benefits, while the lack of precise surgical tools may hinder the improvement of outcomes. The objective of this study was to illustrate surgical techniques and evaluate kinematics and early clinical outcomes of robotic-assisted TKA using patient-specific implants. METHODS: Based on preoperative CT scan, femoral and tibial components were 3D printed. Medial and lateral tibial liners were separate with different thicknesses, posterior slopes and conformity. TiRobot Recon Robot was used for surgery, and was armed with smart tools that quantify gap, force and femoral-tibial track. We collected data on demographics, intraoperative gap balance and femoral-tibial motion. In the follow-up, we evaluated the range of motion, Visual Analogue Scale (VAS), forgotten joint score (FJS), Knee injury and Osteoarthritis Outcome Score, Joint Replacement (KOOS, JR) score. Radiological data were also harvested. RESULTS: Fifteen patients (17 knees) were enrolled with a mean age of 64.6 ± 6.4 (53-76) years. In 5 knees, we used symmetric tibial liners, the rest were asymmetric. After surgery, the average alignment was 1.6 ± 2.0 (-3-5) degrees varus. The average follow-up lasted 6.7 ± 4.2 (1-14) months. The mean visual analogue scale was 0.8 ± 0.7 (0-2), FJS was 62.4 ± 25.3 (0-87), KOOS was 86.5 ± 9.4 (57-97). 11 patients were "very satisfied", 3 were "satisfied" with the result, and one patient was neutral due to restricted extension and unsatisfactory rehabilitation at five months' follow-up. CONCLUSIONS: With patient-specific implants and robotics, TKA could be performed by a mathematical way, which was dubbed a "differential" TKA. Intraoperative kinematics was excellent in terms of gap-force balancing and femoral-tibial relative motion. Preliminary clinical outcomes were overall satisfactory.

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.

Leg-length discrepancy after revision hip arthroplasty: are modular stems superior?

We retrospectively reviewed data for 79 consecutive patients who underwent revision hip arthroplasty using cementless femoral stems at our center between September 2008 and November 2010. Two cohorts were included, one using MP (modular) femoral stems and the other using Wagner (monoblock) femoral stems. We assessed leg-length discrepancy (LLD) before and after revision and compared the occurrence of leg-length inequality between the 2 cohorts. We found that the incidence of LLD was high in revision hip arthroplasty and that leg shortening was more common than lengthening. Both acetabular and femoral sides contributed to postoperative LLD. Appropriate placement of the femoral components was most critical in adjusting LLD. We also found that compared with monoblock stems, modular stems made adjustment of postoperative leg length easier.

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.

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.

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.

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.

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.

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.