To reduce the incidence of total hip revisions, there have been continuous efforts to enhance prosthetic materials and designs to optimize implant survival. A primary implant with a constrained acetabular component is often used to minimize the risk of dislocations even though this approach has some drawbacks as reported in the literature. To address these concerns, this study aimed to assess the survivorship and dislocation rate of a semi-retentive cemented acetabular cup when used as a primary implant. The specific cemented cup that we studied was not present in any study that we consulted, so to fill this gap, we conducted a retrospective examination of 527 cemented hip prostheses that utilized the semi-retentive cup between the years 2005 and 2012. We employed Cox multiple regression models for our statistical analysis. The revision due to dislocation occurred in 12.8% of all cases, with a lower incidence of 5% (14 cases) in age groups >70 years than in age groups <70 years (14%-32 cases) (p < 0.001). The survival rates of the semi-retentive cemented acetabular cup were 98.6% (520 cases) at 5 years and 92.2% (487 cases) at 10 years. The survival rates were significantly lower in women than men, with 1.9% (7 cases) toward 0% at 5 years and 8.1% (30 cases) toward 5% (7 cases) at 10 years (p = 0.002). The difference in failure rates between age groups over 70 years (2.3%-10 cases) and age groups under 70 years (11.5%-34 cases) was also statistically significant (p < 0.001). Our study indicates that the semi-constrained design may cause frequent damage to the polyethylene liner due to impingement and wear, which are the primary factors for failure. Also, this implant has a similar risk of revision due to dislocation as reported in studies and may be beneficial as a primary implant in elderly patients with low-demanding lifestyles, muscular insufficiency, and low compliance regarding hip prosthetic behavior, without a major effect on survivorship.

UNASSIGNED: Prosthetic instability is one of the most common short-term complications following reverse total shoulder arthroplasty (RTSA). Numerous strategies exist to attempt to mitigate this complication, including utilization of constrained polyethylene humeral liners. A concern of constrained humeral liners is that they may come at the expense of restricted rotational range of motion (ROM). The purpose of the present study is to compare range of ROM and patient-reported outcomes (PROs), and satisfaction among matched cohorts using constrained vs. unconstrained liners after RTSA.
UNASSIGNED: A multicenter shoulder arthroplasty registry was retrospectively reviewed to identify patients with two-year clinical follow-up after RTSA with constrained liners used at the surgeon\'s discretion. All patients had the same inlay humeral prosthesis with a 135° neck shaft angle. This study cohort was matched 1:2 to control patients who underwent RTSA with standard liners based on age, sex, total glenoid-sided lateralization, glenosphere diameter, and surgery performed on the dominant arm. Improvement in PROs and ROM was compared between groups.
UNASSIGNED: Twenty-two patients were identified who underwent RTSA with a constrained humeral liner; these were compared to 44 matched patients with standard liners. The groups were found to have no notable differences in demographics, baseline PROs and ROM. At two years postoperatively, both cohorts demonstrated improvements in all PROs without statistically significant differences between the two groups. There were no differences between groups in improvement in any ROM measure, including forward flexion (constrained: 54°, standard: 57°, P = .771), external rotation at the side (constrained: 42°, standard: 41°, P = .906) or internal rotation at 90° of abduction (constrained: 24°, standard: 20°, P = .587).
UNASSIGNED: For an inlay humeral prosthesis with a 135° neck shaft angle, utilization of a constrained liner for RTSA demonstrates no significant difference in ROM or PROs compared to a well-matched cohort of patients who underwent RTSA with a standard polyethylene humeral liner. These are reassuring data for using constrained liners when there is intraoperative concern for prosthetic instability.

The constrained orthogonal Procrustes problem is the least-squares problem that calls for a rotation matrix that optimally aligns two matrices of the same order. Over past decades, the algorithm of choice for solving this problem has been the Kabsch-Umeyama algorithm, which is effectively no more than the computation of the singular value decomposition of a particular matrix. Its justification, as presented separately by Kabsch and Umeyama, is not totally algebraic since it is based on solving the minimization problem via Lagrange multipliers. In order to provide a more transparent alternative, it is the main purpose of this paper to present a purely algebraic justification of the algorithm through the exclusive use of simple concepts from linear algebra. For the sake of completeness, a proof is also included of the well known and widely used fact that the orientation-preserving rigid motion problem, i.e., the least-squares problem that calls for an orientation-preserving rigid motion that optimally aligns two corresponding sets of points in d-dimensional Euclidean space, reduces to the constrained orthogonal Procrustes problem.

Q-space trajectory imaging (QTI) enables the estimation of useful scalar measures indicative of the local tissue structure. This is accomplished by employing generalized gradient waveforms for diffusion sensitization alongside a diffusion tensor distribution (DTD) model. The first two moments of the underlying DTD are made available by acquisitions at low diffusion sensitivity (b-values). Here, we show that three independent conditions have to be fulfilled by the mean and covariance tensors associated with distributions of symmetric positive semidefinite tensors. We introduce an estimation framework utilizing semi-definite programming (SDP) to guarantee that these conditions are met. Applying the framework on simulated signal profiles for diffusion tensors distributed according to non-central Wishart distributions demonstrates the improved noise resilience of QTI+ over the commonly employed estimation methods. Our findings on a human brain data set also reveal pronounced improvements, especially so for acquisition protocols featuring few number of volumes. Our method\'s robustness to noise is expected to not only improve the accuracy of the estimates, but also enable a meaningful interpretation of contrast in the derived scalar maps. The technique\'s performance on shorter acquisitions could make it feasible in routine clinical practice.

Motion capture systems are used in the analysis and interpretation of athlete movement patterns for a variety of reasons, but data integrity remains critical regardless. The extent to which marker location or constraining degrees of freedom (DOF) in the biomechanical model impacts on this integrity lacks consensus. Ten elite academy footballers performed bilateral overhead squats using a marker-based motion capture system. Kinematic data were calculated using four different marker sets with 3DOF and 6DOF configurations for the three joint rotations of the right knee. Root mean squared error differences between marker sets ranged in the sagittal plane between 1.02 and 4.19 degrees to larger values in the frontal (1.30-6.39 degrees) and transverse planes (1.33 and 7.97 degrees). The cross-correlation function of the knee kinematic time series for all eight marker-sets ranged from excellent for sagittal plane motion (>0.99) but reduced for both coronal and transverse planes (<0.9). Two-way ANOVA repeated measures calculated at peak knee flexion revealed significant differences between marker sets for frontal and transverse planes (p < 0.05). Pairwise comparisons showed significant differences between some marker sets. Marker location and constraining DOF while measuring relatively large ranges of motion in this population are important considerations for data integrity.

Concerns exist about the survival and complication rates of highly constrained total knee arthroplasty (TKA) prostheses. The aims of this study were to determine if there were differences between the revision and complication rates of fully stabilized (FSTKA) and hinged (HTKA) TKA, when used in both primary and revision procedures.
Survivorship of all highly constrained TKA prostheses implanted over a 17 year period were analysed by the Australian Orthopaedic Association National Joint Replacement Registry. The primary outcome measure was time to first revision using Kaplan Meier estimates of survivorship.
In the primary setting, the cumulative percent revision at 11 years was higher for HTKA than for FSTKA prostheses (P = 0.014). However, this finding was only significant for patient >75 years. In the revision setting, there were no differences in the revision rates for either category of prosthesis for any age group. For the indication of periarticular/periprosthetic fracture, HTKA resulted in a lower revision rate than FSTKA in both primary and revision cohorts. There were no differences in the rates of revision for infection and aseptic loosening for either prosthesis type in primary or revision settings. The revision risk for periprosthetic fracture was higher after HTKA prostheses.
Both FSTKA and HTKA prostheses provide similar outcomes in primary and revision procedures except for the setting of periarticular/periprosthetic fracture, where a HTKA should be used. In elderly patients, a FSTKA prosthesis is recommended as the risk of periprosthetic fracture is higher with a HTKA.

Recurrent instability remains a common cause of failure after revision total hip arthroplasty (THA). Dual mobility (DM) cups and designs with constrained acetabular liners (CAL) have both been developed to help overcome this challenge. The aim of this report is to compare safety and efficacy outcomes of both designs based on the literature. A comprehensive literature review including published evidence on the results of DM and CAL in revision THA was performed and summarized. Available literature focusing on overall survival, dislocation, loosening, intra-prosthetic dislocation (IPD), and functional outcomes were analysed. Forty-six reports including an evaluation of 5,617 total hips were evaluated were included in the review. The included studies were divided into two distinct groups based on implantation approach: i) CAL (n=15) and ii) DM (n=31). The DM group had higher overall survival rates (94.7% vs. 81.0%), lower dislocation rates (2.6% vs. 11.0%), and lower acetabular loosening rates (1.0% vs. 2.0%) compared to the CAL group. IPDs were reported in 6 studies (mean rate, 0.6%). No differences in functional outcomes were identified due to incomplete reports. Our observations reveal that designs with CAL have poorer outcomes as compared to DM cups in revision THA. Currently, the use of DM seems more appropriate since they offer lower rates of dislocations, loosening and re-revisions in the short- and mid-term. Concerns regarding the potential of increased wear in a younger, high-demand population require additional data and evaluation by long-term studies for the DM design.

OBJECTIVE: There has been an increase in the use of unlinked constrained condylar knee (CCK) prostheses in primary total knee arthroplasty (TKA) for cases with significant deformities that cannot be adequately balanced in flexion and extension. However, the literature on its outcomes is limited. The goal of this study is to evaluate whether there are any clinic or radiographic outcome differences for a primary, non-stemmed, unlinked constrained TKA as compared to a control group of posterior-stabilized (PS) TKA using the same implant design.
METHODS: Clinical and radiographic outcome measures for 404 cemented, non-stemmed, primary TKAs performed by two surgeons at the same institution were retrospectively reviewed. All patients underwent primary, non-stemmed components; 241 used CCK inserts and 163 used PS inserts. Preoperative deformity, knee society scores (KSS), range-of-motion (ROM), radiographic data and revision rates were compared between the CCK and PS groups.
RESULTS: Both groups had comparable demographics and preoperative ROM and KSS. At similar mean follow-up times (6.1 ± 1.0 years for the CCK group and 6.3 ± 1.2 years for the PS group), no significant difference was found in ROM, KSS or radiographic outcomes. Revision rates were higher for the CCK group (2%) as compared to the HF-PS (0.6%) group (n.s).
CONCLUSIONS: The particular design of cemented, primary, non-stemmed, unlinked CCK-TKA examined in this study provided similar clinical and radiographic outcomes to that of PS-TKA at midterm follow-up.
METHODS: III.

BACKGROUND: Total knee arthroplasty (TKA) is a successful operation for osteoarthrosis. Typically, the knee can be balanced using posterior stabilized or cruciate retaining implants. However, in patients with severe deformity or ligamentous laxity, this cannot be obtained, and more constrained devices are needed. Semi-constrained implants, such as the Total Condylar III (TCIII) provide increased coronal stability. Outcomes in young (<60 years old) patients, following a primary semi-constrained TKA are not well reported in the literature. The purpose of this study was to evaluate patient reported outcomes, functional recovery, and implant survival in this population.
METHODS: We performed a retrospective review of 21 patients, under the age of 60 years, that underwent primary semi-constrained TKA. Patient demographics, postoperative outcomes, patient satisfaction scores, and implant loosening were reported.
RESULTS: At an average follow-up of 66 months, Knee Society Scores (KSS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores were 94.7 and 15.7, respectively. No difference in patient reported outcomes between 1 year and final follow-up were observed. Patient demographics such as age, BMI, and gender had no effect on functional outcomes. No cases of aseptic loosening were observed. Implant survivorship, patient satisfaction, and excellent or good results were reported in 100%, 85.7%, and 92%, respectively.
CONCLUSIONS: In young patients, in which the knee cannot be effectively balanced with standard releases, the use of a semi-constrained TKA as a primary implant lead to positive patient reported outcomes and no evidence of loosening at mid-term follow-up.

BACKGROUND: Dislocation of the knee after primary total knee arthroplasty is rare in a posterior stabilized knee and extremely rare in a constrained total knee arthroplasty. Constrained total knee prostheses are used for severe knee deformities and to provide stable and mobile knees.
METHODS: In this case, we describe a dislocation of a primary constrained total knee arthroplasty using the Genesis II (Smith & Nephew, Memphis Tennessee, USA) prosthesis. Without any significant trauma, the constrained insert dislocated fifteen months after surgery and revision surgery with a bigger insert was needed. Surgical error may have been the cause of dislocation, but we were unable to establish a clear reason behind this dislocation.
CONCLUSIONS: Knee dislocation after TKA is rare but easily overlooked and can lead to serious complications and permanent disability. This system should provide stable and mobile knees to correct collateral ligament laxity.
CONCLUSIONS: Here, we report the first case, to our knowledge, of dislocation with a constrained prosthesis without any history of trauma.