BACKGROUND: The aim of the present study is to analyze the clinical-radiological outcomes of patients undergoing knee prosthesis revision surgery using constrained condylar prosthesis (LCCK; Zimmer-Biomet).
METHODS: Retrospective study of 89 patients operated on between the years 2008 and 2020 with a minimum of 2 years of follow-up. Clinical outcomes were evaluated using the WOMAC Index score and KOOS scales. Radiological results (radiolucent lines, osteolysis, and cortical hypertrophy) were evaluated by two independent observers. Implant survival was analyzed using the Kaplan-Meier method.
RESULTS: At the end of follow-up, a mean WOMAC Index score of 78.67 and KOOS score of 68.8 were obtained. Radiolucent lines (both non-progressive and progressive) were detected in 83.3% of the patients in the sample. Areas of osteolysis > 5 mm around the components were present in 6.75%. Cortical hypertrophy was seen around the femoral stem in 20.3% of cases, around the tibial stem in 20.3% and around both components in 6.76%. No statistically significant relationship was found between the presence of radiolucent lines, osteolysis or cortical hypertrophy with functional results. Implant survival was 88.1% at 13 years.
CONCLUSIONS: The present study shows high survival of LCCK prosthesis in revision surgery. The progressive radiolucencies, were associated with worst clinical outcome.

OBJECTIVE: Due to ageing population, the implantation rate of total knee arthroplasties (TKAs) is continuously growing. Aseptic revisions in primary knee arthroplasty are a major cause of revision. The aim of the following study was to determinate the incidence and reasons of aseptic revisions in constrained and unconstrained TKA, as well as in unicondylar knee arthroplasties (UKAs).
METHODS: Data collection was performed using the German Arthroplasty Registry. Reasons for aseptic revisions were calculated. Incidence and comparison of aseptic revisions were analysed using Kaplan-Meier estimates. A multiple χ2 test with Holm\'s method was used to detect group differences in ligament ruptures.
RESULTS: Overall, 300,998 cases of knee arthroplasty with 254,144 (84.4%) unconstrained TKA, 9993 (3.3%) constrained TKA and 36,861 (12.3%) UKA were analysed. Aseptic revision rate in UKA was significantly increased compared to unconstrained and constrained TKA (p < 0.0001). In constrained TKA, a 2.0% revision rate for aseptic reasons were reported after 1 year, while in unconstrained TKA 1.1% and in UKA, 2.7% of revisions were identified. After 7 years in constrained TKA 3.3%, in unconstrained TKA 2.8%, and in UKA 7.8% sustained aseptic revision. Ligament instability was the leading cause of aseptic revision accounting for 13.7% in unconstrained TKA. In constrained TKA, 2.8% resulted in a revision due to ligament instability. In the UKA, the most frequent cause of revisions was tibial loosening, accounting for 14.6% of cases, while progression of osteoarthritis accounted for 7.9% of revisions. Ligament instability was observed in 14.1% of males compared to 15.9% of females in unconstrained TKA and in 4.6% in both genders in UKA.
CONCLUSIONS: In patients with UKA, aseptic revision rates are significantly higher compared to unconstrained and constrained TKA. Ligament instability was the leading cause of aseptic revision in unconstrained TKA. In UKA, the most frequent cause of revisions was tibial loosening, while progression of osteoarthritis was the second most frequent cause of revisions. Comparable levels of ligament instability were observed in both sexes.
METHODS: Level III, cohort study.

BACKGROUND: Achieving stability in total knee arthroplasty (TKA) is crucial for long-term implant survival. In cases of severe deformity or ligament laxity, constrained implants may be required. Traditionally, increasing constraint involved intramedullary stems. However, there are intermediary alternatives, including employing a constrained polyethylene insert without stems, thereby avoiding complications related to them. The study aims to evaluate our experience with a non-modular constrained (NMC) implant in primary TKA.
METHODS: We conducted a retrospective review of the clinical and radiographic outcomes of 108 non-stemmed primary TKAs performed at our institution between 2013 and 2021 in patients with at least 10° deformity or 10mm ligament laxity. Data included demographics, preoperative and postoperative deformities, clinical outcomes and revision rates.
RESULTS: A total of 103 patients (108 knees) with a mean age of 74 were followed up for a minimum of 2 years. The mean postoperative range of motion was 105°/0°. The median Oxford Knee Score, Knee Society Score and Knee Society Function Score were 43.5, 92 and 90, respectively. 17 knees had varus deformity (mean tibiofemoral angle of 2.7°), and 87 knees had excessive valgus deformity (mean tibiofemoral angle of 15.1°). The remaining 4 knees had a neutral alignment. The mean postoperative tibiofemoral angle was 6.8°. The overall revision rate was 6.5% (7 patients): 3 deep periprosthetic infections, 2 patellar dislocations, 1 stiffness and 1 aseptic loosening.
CONCLUSIONS: Our experience demonstrates favorable mid-term outcomes with the NMC implant, providing a safe alternative to stemmed implants in primary TKA, particularly in cases of severe deformity or ligament laxity.

OBJECTIVE: Periprosthetic joint infection (PJI) is a major cause of revision surgery after total knee arthroplasty (TKA) and unicondylar knee arthroplasty (UKA). Patient- and hospital-related risk factors need to be assessed to prevent PJI. This study identifies influential factors and differences in infection rates between different implant types.
METHODS: Data were obtained from the German Arthroplasty Registry. Septic revisions were calculated using Kaplan-Meier estimates with septic revision surgery as the primary endpoint. Patients with constrained and unconstrained TKA or UKA were analysed using Holm\'s multiple log-rank test and Cox\'s proportional hazards ratio. The 300,998 cases of knee arthroplasty analysed included 254,144 (84.4%) unconstrained TKA, 9993 (3.3%) constrained TKA and 36,861 (12.3%) UKA with a maximum follow-up of 7 years.
RESULTS: At 1 year, the PJI rate was 0.5% for UKA and 2.8% for TKA, whereas at 7 years, the PJI rate was 4.5% for UKA and 0.9% for TKA (p < 0.0001). The PJI rate significantly increased for constrained TKA compared to unconstrained TKA (p < 0.0001). The PJI rate was 2.0% for constrained TKA and 0.8% for unconstrained TKA at 1 year and 3.1% and 1.4% at 7 years. Implantation of a constrained TKA (hazard ratio [HR] = 2.55), male sex (HR = 1.84), increased Elixhauser score (HR = 1.18-1.56) and implant volume of less than 25 UKA per year (HR = 2.15) were identified as risk factors for revision surgery; an Elixhauser score of 0 (HR = 0.80) was found to be a preventive factor.
CONCLUSIONS: Reduced implant volume and constrained knee arthroplasty are associated with a higher risk of PJI. Comorbidities (elevated Elixhauser score), male sex and low UKA implant volume have been identified as risk factors for PJI. Patients who meet these criteria require specific measures to prevent infection. Further research is required on the potential impact of prevention and risk factor modification.
METHODS: Level III.

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.

BACKGROUND: Constrained inserts in total knee arthroplasty (TKA) may offer additional stability, but can this insert type allow unrestricted movements or will the extra conformity cause kinematic conflict with the cam-post mechanism in deeper flexion? The objective of this study was to evaluate the weight-bearing kinematics of both traditional and constrained bicruciate stabilized (BCS) TKA inserts to determine if the rollback induced by the cam-post mechanism will work in unison with the constrained polyethylene insert.
METHODS: This study used previously published 3-dimensional model fitting techniques to compare weight-bearing flexion and femoro-tibial condylar motion patterns for 20 patients who had a traditional insert, 20 patients who had a constrained insert, and 10 previously published nonimplanted knees, all performing a deep knee bend activity while under fluoroscopic surveillance.
RESULTS: The results from this study indicate that subjects having a bicruciate stabilized TKA experienced similar postoperative kinematics for both constrained and unconstrained insert options, comparable to normal knees.
CONCLUSIONS: Subjects in this study having either a constrained or traditional insert experienced progressive rollback of both condyles, with the lateral condyle rolling more posterior than the medial condyle, leading to axial rotation. Although less in magnitude, these results were comparable to the normal knee in pattern, indicating that kinematic conflict did not occur for subjects having a constrained insert.

BACKGROUND: The incidence of hemiarthroplasty dislocation for fracture neck of femurs ranges between 1 and 15% and the one-year mortality is 49- 70%. Revision of hemiarthroplasty to total hip replacement using a constrained liner has shown to improve the morbidity and mortality rates. The aim of the study was to assess whether conversion of dislocated hemiarthroplasty to total hip replacement improve functional and one year mortality.
METHODS: A retrospective analysis of the number of patients who had recurrent dislocations of hemiarthroplasty for fracture neck of femurs were carried out. The data were obtained from NHFD (National Hip Fracture Database) and internal hospital computer systems (Medway, Theatre notes and PACS) between Dec 2008 and Dec 2020. Patient demographics including age, sex, Abbreviated Mental Test Score (AMTS), functional assessment, mortality at one and two years were documented. The risk factors which led to dislocations such as Parkinsons disease, Cerebrovascular accidents, Musculo-neuropathies and Alzheimer`s disease was also noted.
RESULTS: A total of 3994 patients were admitted during the study period of which 1735 (43.4%) patients had hemiarthroplasty. Fifty-six (3.23%) patients had dislocation of hemiarthroplasty. The mean age was 81.4 years (range - 61 to 95). There were 40 (71.4%) females and 16 males (28.6%). The average AMTS score was 5.3. All 56 patients had closed manipulative reduction under anaesthesia within in 12 h of admission. Thirty-one patients (55.4%) went on to have recurrent dislocations of which 18 patients (58.4%) had total hip replacement using captive cup, 6 patients (19.4%) had open reduction,3 patients (9.7%) had excision arthroplasty procedure and four patients (12.5%) had no intervention, Eighteen patients who had total hip replacement with constrained captive for followed up to a minimum of two years (range2- 12 years). There were no intraoperative complications, dislocation or periprosthetic fractures in the follow up period. There was no mortality at the end of two years of follow up in this group, two-year mortality for the patients with alternative management for dislocated hemiarthroplasty was 76.67.
CONCLUSIONS: Treatment of recurrent hemiarthroplasty dislocation by revising to a total hip replacement with a constrained liner gives good functional and mortality outcomes.

BACKGROUND: Unicompartmental knee replacement (UKR) is an effective surgical strategy in patients with isolated medial or lateral compartment osteoarthritis. Study aims were to (1) describe the epidemiology of patients undergoing revision of UKR to a hinge knee replacement (HKR); (2) identify factors influencing time to revision; (3) evaluate HKR survival.
METHODS: An analysis of National Joint Registry data was undertaken, exploring revision of UKR to HKR between 2007 and April 2021. Descriptive analysis of eligible patients and Cox Regression to identify key determinants of time to revision were performed. Failure of HKR post-revision was assessed using survival analysis.
RESULTS: 111 patients underwent revision of UKR to HKR. Median age at revision was 70 years and most common indications were instability (n = 42) and infection (n = 22). The most common implant was a rotating HKR. Significant independent factors associated with earlier revision were periprosthetic fracture (p = 0.03) and malalignment (p = 0.03). Progressive osteoarthritis (p = 0.01) and higher ASA grades (3: p = 0.01, 4: p < 0.01) delayed time to revision; patient sex and age were not significant factors. Ten patients required subsequent re-revision; median age at re-revision was 61 years. HKR revised from UKR had an 89.3% revision-free risk at 5 years. Male sex (p < 0.01) and younger age (p < 0.01) were associated with re-revision.
CONCLUSIONS: Factors associated with time to revision may be used to counsel patients prior to UKR. The survivorship of the HKR of 89.3% at 5 years is concerning and careful consideration should be given when using this level of constraint when revising UKR in younger or male patients.

OBJECTIVE: The purpose of the current study was to determine if differences exist between cruciate-retaining (CR) and posterior-stabilized (PS) implant articulations for total knee arthroplasty (TKA) with regards to early post-operative pain.
METHODS: We retrospectively reviewed patients who underwent primary TKA, with the same TKA implant design, at our institution between January 2018 and July 2021. Patients were stratified based on whether they received a CR or non-constrained PS (PSnC) articulation and propensity score matched in a 1:1 ratio. A sub-analysis matching patient who received a constrained PS implant (PSC) to those undergoing CR TKA and PSnC TKA was also carried out. Opioid dosages were converted to morphine milligram equivalents (MME).
RESULTS: 616 patients after CR TKA were matched 1:1 to 616 patients with a PSnC implant. There were no significant differences between demographic variables. There were no statistically significant differences in opioid usage measured by MME on post-operative day (POD) 0 (p = 0.171), POD1 (p = 0.839), POD2 (p = 0.307), or POD3 (p = 0.138); VAS pain scores (p = 0.175); or 90-day readmission rate for pain (p = 0.654). A sub-analysis of CR versus PSC TKA demonstrated no significant differences in opioid usage on POD0 (p = 0.765), POD1 (p = 0.747), POD2 (p = 0.564), POD3 (p = 0.309); VAS pain scores (p = 0.293); and 90-day readmission rate for pain (p > 0.9).
CONCLUSIONS: Our analysis demonstrated no significant difference in post-operative VAS pain scores and MME usage based on implant. The results suggest that neither the type of articulation or constraint used for primary TKA has a significant impact on immediate post-operative pain and opioid consumption.
METHODS: Retrospective Cohort Study.

As instability continues to be a burden post-total hip arthroplasty (THA), there has been a controversial discussion on the ideal implant choice. We report the outcomes of a modern constrained acetabular liner (CAL) system in primary and revision THA at an average follow-up of 2.4 years.
We performed a retrospective study of all patients undergoing primary and revision hip arthroplasty and being implanted with the modern CAL system from 2013 to 2021. We identified 31 hips, of which 13 underwent primary THA and the remaining 18 underwent revision THA for instability.
Of those implanted with CAL primarily, 3 had concomitant abductor tear repair and gluteus maximus transfer, 5 had Parkinson\'s disease, 2 had inclusion body myositis, 1 had amyotrophic lateral sclerosis, and the remaining two were over 94 years of age. All patients implanted with the CAL had active instability post-primary THA and underwent only liner and head exchange without revision of the acetabular or femoral components. At an average follow-up of 2.4 years (ranging from 9 months to 5 years and 4 months), we had 1 case (3.2%) of dislocation post-CAL implantation. None of the patients undergoing surgery with CAL for active instability had a redislocation.
In conclusion, a CAL provides excellent stability in both primary THA in high-risk individuals and revision THA in cases of active instability. There were no dislocations when using a CAL to treat active instability post-THA.