Quantification of soft tissue artifacts using CT registration and subject-specific multibody modeling.

The potential use of gait analysis for quantitative preoperative planning in total hip arthroplasty (THA) has previously been demonstrated. However, the joint kinematic data measured through this process tend to be unreliable for surgical planning due to distortions caused by soft tissue artifacts (STAs). In this study, we developed a novel motion capture framework by combining computed tomography (CT)-based postural calibration and subject-specific multibody dynamics modeling to prevent the effect of STAs in measuring hip kinematics. Three subjects with femoroacetabular impingement syndrome were recruited, and CT data for each patient were collected by attaching marker clusters near the hip. A subject-specific multibody hip joint model was developed based on reconstructed CT data. Spring-dashpot network calculations were performed to minimize the distance between the anatomical landmark and its corresponding infrared reflective marker. The STAs of the thigh was described as six degrees of freedom viscoelastic bushing elements, and their parameter values were identified via smooth orthogonal decomposition. Least squares optimization was used to modify the pelvic rotations to compensate for the rigid components of STAs. The results showed that CT-assisted motion tracking enabled the successful identification of STA influences in gait and squat positions. Furthermore, STA effects were found to alter maximal pelvis tilt and hip rotations during a squat. Compared to other techniques, such as dual fluoroscopic imaging, the adopted framework does not require additional medical imaging for patients undergoing robot-assisted THA surgery and is thus a practical way of evaluating hip joint kinematics for preoperative surgical planning.

Using novel porous metal pillars for tibial bone defects in primary total knee arthroplasty.

BACKGROUND: The optimal method to treat tibial bone defects during primary total knee arthroplasty (TKA) is still unclear. A novel technique of porous metal pillar augmentation has been applied recently. This study aimed to assess the short-term outcomes of primary TKA with the use of novel porous metal pillars for tibial bone defects. METHODS: A total of 24 cases (22 patients) of primary TKA between January 2019 and December 2020 using porous metal pillars for tibial bone defects were reviewed. Clinical results were evaluated using the Knee Society knee score (KSKS) and function score (KSFS), the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and range of motion (ROM). Hip-knee-ankle angle (HKAA), femorotibial angle (FTA), and radiolucent lines were assessed radiologically. RESULTS: The median follow-up period was 36.0 months (interquartile range: 31-37 months). The KSKS, KSFS, WOMAC score, and ROM improved significantly at the final follow-up assessment compared with the preoperative evaluation. Both of the HKAA and FTA were corrected after surgery. Only one knee had a nonprogressive radiolucent line at the bone-cement interface. No radiolucent lines were detected around the pillar in any of the cases. There were no cases of prosthesis loosening and revision. CONCLUSIONS: The use of novel porous metal pillars yielded satisfactory clinical outcomes and reliable radiological evidence of fixation in this study with a minimum 2-year follow-up. Porous metal pillar augmentation can be considered as a valuable and easy-to-use method for the management of tibial bone defects in primary TKA.

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.

[Midterm follow-up outcomes of total hip arthroplasty in treatment for patients with juvenile-onset ankylosing spondylitis].

Objective: To assess the midterm follow-up outcomes of total hip arthroplasty (THA) for the treatment of patients with juvenile-onset ankylosing spondylitis (JAS). Methods: The clinical data of 81 patients (127 hips) with JAS (age≤16 years, JAS group) and 267 patients (391 hips) with adult onset ankylosing spondylitis (AAS) (age>16 years, AAS group) between January 2004 and March 2018 were retrospectively analysed. The baseline demographics, clinical, radiographic, and laboratory parameters were collected. Before operation and at last follow-up, the overall disease activity [Bath ankylosing spondylitis disease activity index (BASDAI)] and function status [Bath ankylosing spondylitis functional index (BASFI)], hip subjective score [Harris hip score (HHS)] and objective score [12-item short form health survey (SF-12), including physical component score (PCS) and mental component score (MCS)], and patient satisfaction for THA were reviewed. The major orthopedic complications, including periprosthetic infection, dislocation, periprosthetic fractures, and poor incision healing, were also recorded during the follow-up period. Results: The comparison of preoperative baseline parameters showed that the body mass, body mass index, age of onset, age of surgery, disease duration, and the proportion of combined smoking history in the JAS group were significantly lower than those in the AAS group ( P<0.05), the proportion of bilateral surgeries, proportion of uveitis, proportion of combined family history, C-reactive protein, albumin, and preoperative BASFI were significantly higher than those in the AAS group ( P<0.05). Both groups were followed up. The follow-up time in the JAS group was 29-199 months, with an average of 113 months; in the AAS group was 35-199 months, with an average of 98 months. Incisions in both groups healed by first intention. During the follow-up period, there were 1 case of periprosthetic fracture, 1 case of dislocation, and 1 case of ceramic fragmentation in the JAS group, 1 case of periprosthetic infection and 6 cases of periprosthetic fracture in the AAS group. There was no significant difference in the incidence of complications between the two groups ( P>0.05). At last follow-up, the BASDAI, BASFI, SF-12 MCS, SF-12 PCS, and HHS score of the two groups were significantly improved when compared with those before operation ( P<0.05); but there was no significan difference in the difference of the above parameters before and after operation and the patient satisfaction between the two groups ( P>0.05). Conclusion: The midterm follow-up outcomes of THA for the treatment of JAS patients were reliable. A low age at disease onset did not exert a significant negative effect on THA reconstruction for the treatment of ankylosing spondylitis.