Background: To our knowledge, no previous studies have compared periprosthetic bone remodeling around monoblock versus modular tapered fluted titanium stems with different stem length and thickness. Methods: A retrospective comparative study was performed on 139 consecutive total hip arthroplasties (THAs) revised with a tapered fluted modular titanium stem and 114 consecutive THAs revised with a tapered fluted monoblock titanium stem. The latest follow-up radiographs were compared with immediate postoperative radiographs to assess bone restoration in residual osteolytic areas, femoral stress-shielding, spot-welds, and radiolucent lines. Diameter and medullary canal filling of the 2 stems were measured. Results: More patients in the monoblock group demonstrated osseous restoration than in the modular group (p = 0.009), and the modular stem exerted more severe stress-shielding on the femur (p < 0.001). Stem tip spot-welds developed in 88.5% of modular stems compared with 47.4% of the monoblock stems (p < 0.001). Spot-welds developed in 38.8% of modular stems at the modular junction. Partial or circumferential radiolucent lines were observed at the proximal segment of 30.9% of modular stems, compared with 14.0% of monoblock stems (p = 0.002). Conclusions: Compared with the longer and thinner monoblock stems, modular stems had less proximal osseous restoration in residual osteolytic areas and more severe femoral stress-shielding, stem tip spot-welds, and radiolucent lines around the stems, which were stiffer and had a shorter distal section. The stem diameter and stiffness (which were influenced by stem length, curvature, and modularity) determined bone remodeling patterns. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

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.

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.

Aims: This study aimed to report the surgical techniques and early clinical results of robotic arm-assisted acetabular reconstruction in revision total hip arthroplasty (THA).Methods: Between October 2019 and May 2021, we used the Mako robotic system to perform 62 revision THAs at our hospital. This study included 54 patients who underwent robotic arm-assisted revision THA for acetabular reconstruction. Surgical techniques using the robotic system to reconstruct the acetabulum, including preoperative planning, intraoperative registration, and the accuracy of different registration methods, are reported. The accuracy between the target acetabular component orientation and final orientation was evaluated. The latest follow-up Harris Hip Score (HHS) and radiographs were analyzed.Results: Among the 54 hips included, four types of intraoperative registration methods with different surfaces were developed and registered 65 times. The overall success rate of the registration process was 98.5%. The mean accuracy of successful registration was 0.38 mm (0.2 to 0.5). The median difference between the target and final acetabular component orientations assessed by Mako was 1.0° (-2.0° to 0.0°) for inclination and 0.0° (-1.0° to 1.0°) for anteversion. Four hips were classified as outliers for acetabular component orientation. The reconstructed centres of rotation (CORs) were slightly lower than the anatomical CORs by a mean 4.72 mm (SD 4.71), and shifted laterally by 3.92 mm (SD 4.62) on postoperative radiographs. The median HHS improved significantly from 46.0 (IQR 33.0 to 58.3) preoperatively to 89.0 (IQR 78.3 to 93.0) postoperatively (p < 0.001). The overall satisfaction rate was 86.0% (n = 50). There were no radiological failures at the latest follow-up.Conclusion: Robotic arm-assisted revision THA provides valuable information for the analysis of bone defects to guide reconstructive strategies. Robotic arm-assisted reaming and acetabular component or augment positioning facilitates accurate component position and orientation. The radiological and preliminary clinical results of this cohort were satisfactory.Cite this article: Bone Joint J 2025;107-B(4):404–412.

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.

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.