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.

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.

Management of soft tissues in patients with periprosthetic joint infection.

BACKGROUND: Appropriate soft tissue management represents a critical step in treating periprosthetic joint infection (PJI). This review discusses relevant guidelines that surgeons should follow in the management of soft tissues in PJI treatment. BODY: It is imperative for arthroplasty surgeons to thoroughly debride and rebuild soft tissue with a good blood supply. Relevant guidelines that surgeons should follow rigorously include preoperative evaluation of soft tissue status and plan-making, adequate surgical area exposure, intraoperative removal of all necrotic and infected soft tissues, adequate coverage of soft tissue defects, timely postoperative assessment and management of soft tissues, wound management and proper rehabilitation. CONCLUSION: Soft tissue management plays a critical role in the treatment of PJI. To improve the infection control rate and postoperative joint function, surgeons should be familiar with these general principles and rigorously practice them in PJI management.

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.

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.

Greater trochanter fixed with a claw plate and cable system in complex primary and revision total hip arthroplasty: long-term follow-up.

BACKGROUND: Maintaining continuity of the greater trochanter and restoring abductor function are of paramount importance in primary and revision total hip arthroplasty. Failure to rigidly fix the greater trochanter can lead to failure. Because of the lack of reports on the clinical results of greater trochanter fixation with a claw plate and cable system, we aimed to analyze the indications for the use of such a system that produces the best clinical results. METHODS: We retrospectively studied 41 consecutive patients who had undergone primary or revision total hip arthroplasty at our institution between January 2004 and December 2014 using a claw plate and cable system to achieve stable fixation of the greater trochanter. RESULTS: The mean follow-up duration was ten years. The median Harris hip score improved from 47 points before surgery to 87 points after surgery (p < 0.01). Significant improvements were observed in the range of motion, hip function, and routine activity. Osseous and fibrous union occurred in all patients, and one patient had severe complications (sciatica). Based on the Beals and Tower classification, 67%, 21%, and 13% of outcomes were considered excellent, good, and poor, respectively. CONCLUSIONS: Our data support the use of a claw plate and cable system for greater trochanter fixation in complex primary and revision hip arthroplasty. The system showed promising results in patients with floating greater trochanters, intertrochanteric fractures requiring extra devices to maintain rotational stability, and extended trochanteric osteotomy fragments with a weakened proximodistal junction. The use of this system should be further investigated and compared to other methods.

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.

Total Hip Arthroplasties for Hartofilakidis Type C1 and C2 High Hip Dislocations Demonstrate Similar Survivorship and Clinical Function at Minimum 10-year Follow-up With Cementless Implants.

BACKGROUND: This study aimed to determine the differences in survivorship, clinical function, and complications among patients who have Hartofilakidis Type C1 or C2 developmental dysplasia of the hips and underwent total hip arthroplasty (THA) with cementless implants. METHODS: This retrospective study identified 84 Hartofilakidis Type C hips that underwent THA between 2002 and 2011 with a minimum 10-year follow-up (mean, 13 years, range, 10 to 19 years). Survivorship, latest Harris Hip Scores and satisfaction levels, radiographic outcomes (eg, implant stability, rate and length of subtrochanteric shortening transverse osteotomy, leg-length discrepancy, cup position, and orientation), as well as complications (eg, dislocation, periprosthetic fracture, periprosthetic joint infection) were compared to analyze the differences between Hartofilakidis C1 and C2 hips. RESULTS: Between C1 and C2 hips, no difference existed in the 15-year cumulative Kaplan-Meier survivorship, with the endpoint defined as any reoperation (93.1 versus 90.8%), aseptic loosening combined with periprosthetic joint infection (93.1 versus 96.2%), or aseptic loosening (94.8 versus 96.2%), latest Harris Hip Score (87.1 versus 86.1%), vertical (6.1 versus 6.0 mm) and horizontal (11.5 versus 10.3 mm) distance to the anatomic center of rotation, postoperative leg length discrepancy (11.2 versus 15.5 mm), dislocation (5.2 versus 11.5%), stem aseptic loosening (6.9 versus 7.7%), periprosthetic fracture (3.4 versus 7.7%), and intraoperative femoral fracture (32.8 versus 23.1%). However, Type C2 hips demonstrated more severe preoperative leg length discrepancy (66.9 versus 42.5 mm) and required a higher percentage of subtrochanteric shortening transverse osteotomies (84.6 versus 36.2%) that were longer (33.7 versus 26.47 mm) than the Type C1 hips. CONCLUSION: With cementless cups positioned near the anatomic acetabular center and cementless stems combined with subtrochanteric shortening transverse osteotomies, THAs for the Hartofilakidis Type C1 and C2 hips demonstrated similar survivorship, clinical function, and complications.

Dexpanthenol attenuates inflammatory damage and apoptosis in kidney and liver tissues of septic mice.

Sepsis is capable of causing systemic infections resulting in multiple organ damage. Dexpanthenol (DXP) has been reported to protect against kidney and liver injury. Therefore, this paper attempts to explore the role of DXP in sepsis-induced kidney and liver injury. A mice model of sepsis was established using the cecal ligation and puncture (CLP) method. The expressions of tumor necrosis factor (TNF)-α, interleukin (IL)-1ß, IL-6 and monocyte chemoattractant protein (MCP)-1 in the serum of mice were measured utilizing enzyme linked immunosorbent assay (ELISA). Additionally, the damage of kidney and liver tissues in CLP-induced mice was determined by their respective commercial kits, western blot, and hematoxylin-eosin (HE) staining kits. The apoptosis of kidney and liver tissues in CLP-induced mice was assessed by means of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and western blot. It was observed that DXP decreased the expressions of TNF-α, IL-1ß, IL-6, and MCP-1 in the serum of CLP-induced mice, attenuated the functional impairment, pathological damage, inflammation, and cell apoptosis of kidney tissue. Meanwhile, DXP decreased the functional impairment of liver in CLP-induced mice, reduced the levels of inflammatory factors and antioxidant enzymes, attenuated liver pathological damage, and decreased cell apoptosis in liver tissues. In conclusion, DXP attenuates inflammatory damage and apoptosis in kidney and liver organs in a sepsis model.

Malposition of components and Femorotibial mechanical Axis changes on pressure distribution in Total knee arthroplasty.

BACKGROUND: To the best of our knowledge, no report has analyzed the postoperative results of poor prosthesis position, particularly when the femoral and tibial components are abnormally positioned relative to neutral lower limb alignment. We aimed to investigate pressure distribution in the knee at different lower limb alignments with diverse positions of femoral and tibial components. METHODS: We established a three-dimensional model of the lower limb using computed tomography and simulated total knee arthroplasty. Tibial and femoral components were changed to 7°, 5°, and 3° of valgus and neutral and 3°, 5°, and 7° of varus positions in the coronal plane. Finite element analysis was performed after applying pressure to simulate weight-bearing, and pressure distribution on the tibial surface was analyzed. We also conducted biomechanical testing using a weight-bearing rig with six cadavers. We measured the pressure at the tibial surface with the position of different components and lower limb alignment. FINDINGS: Peak pressure on the medial or lateral side of the tibia was determined by the mechanical axis. When tibial components are in 3°,5° and 7° of valgus/varus and femoral components are in 3°,5° and 7° of varus/valgus correspondence, no peak pressure was detected with normal alignment, despite malpositioned components. INTERPRETATION: Lower limb alignment is more critical than the position of the component. Medial and lateral tibial compartment pressures were evenly distributed if the alignment was neutral. Malpositioned femoral or tibial components changed the femorotibial mechanical axis, and peak pressure of the proximal tibia was positively related to alignment.

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.

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.

Reliability and validity of commonly used patient-reported outcome measures (PROMs) after medial unicompartmental knee arthroplasty.

INTRODUCTION: Many patient-reported outcome measures (PROMs) have been utilized to assess outcomes after unicompartmental knee arthroplasty (UKA). However, most are not specifically designed for UKA and the measurement properties of these PROMs have never been elucidated in the setting of UKA. This study aimed to evaluate the reliability and validity of commonly used PROMs after UKA, which includes the Oxford knee score (OKS), Knee Society Score (KSS)-function score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Knee Injury and Osteoarthritis Outcome Score (KOOS). HYPOTHESIS: The four commonly used PROMs after UKA are of good reliability and validity, but with different floor/ceiling effect. MATERIAL AND METHODS: Prospectively collected postoperative follow-up PROMs scores of patients after medial UKA cases for osteoarthritis between May 2015 and June 2018 were retrospectively analyzed. All of the PROMs were finished on the same electronic questionnaires. Reliability (internal consistency, test-retest reliability, measurement error), construct validity and floor/ceiling effects were assessed. RESULTS: The whole cohort was composed of 207 cases, with a median age of 62.0 years and a male ratio of 59/207 (28.50%). Internal consistency was high in the OKS, weak in the KSS-function score and with redundancy in the WOMAC and KOOS scores (Cronbach alpha=0.915, 0.610, 0.953, 0.961, respectively). Each of the four PROMs had a high test-retest reliability (all intraclass correlation coefficient (ICC) >0.97). Convergent validity of the four PROMs with the physical component score of the 12-Item Short Form Health Survey (SF-12 PCS) were proven (all r>0.5; p<0.001). While no ceiling effect occurred in the OKS, one was detected in the KSS-function score with 19.81% of patients achieving the best possible score, as well as in the WOMAC sub-score for pain (54.11%) and stiffness (50.72%), in addition to the KOOS sub-score for symptoms (27.54%) and pain (38.16%). DISCUSSION: The four commonly used PROMs after UKA showed good test-retest reliability and construct validity. The OKS is more recommended for its better performance in internal consistency and ceiling effect than the KSS-function score, the WOMAC and KOOS scores. LEVEL OF EVIDENCE: III; Diagnostic study.

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.