Early cartilage lesion and 5-year incident joint surgery in knee osteoarthritis patients: a retrospective cohort study.

OBJECTIVE: to investigate the association between cartilage lesion-related features observed in knee osteoarthritis (OA) patients' first MRI examination and incident knee surgery within 5 years. Additionally, to assess the predictive value of these features for the incident knee surgery. METHODS: We identified patients diagnosed with knee OA and treated at our institution between January 2015 and January 2018, and retrieved their baseline clinical data and first MRI examination films from the information system. Next, we proceeded to determine joint space narrowing grade, cartilage lesion size grade, cartilage full-thickness loss grade and cartilage lesion sum score for the medial and lateral compartments, respectively. Generalized linear regression models examined the association of these features with 5-year incident knee surgery. Positive and negative predictive values (PPVs and NPVs) were determined referring to 5-year incident knee surgery. RESULTS: Totally, 878 participants (knees) were found eligible to form the study population. Within the 5 years, surgery was performed on 61 knees. None of the cartilage-related features had been found significantly associated with incident surgery. The results were similar for medial and lateral compartments. The PPVs were low for all the features. CONCLUSIONS: Among symptomatic clinically diagnosed OA knees, cartilage lesions observed in the first MRI examinations were not found to be associated with the occurrence of joint surgery within a 5-year period. All these cartilage-related features appear to have no additional value in predicting 5-year incident joint surgery.

Massage for rehabilitation after total knee arthroplasty: a systematic review and meta-analysis of randomized controlled trials.

OBJECTIVE: This study aimed to evaluate the effectiveness of massage for postoperative rehabilitation after total knee arthroplasty (TKA). DATA SOURCES: The PubMed, Web of Science, EMBASE, Cochrane Library, and China National Knowledge Infrastructure (CNKI) databases were systematically searched from inception to May 2024. STUDY SELECTION: Any randomized controlled trials on the use of massage for postoperative TKA rehabilitation were included. DATA EXTRACTION: A meta-analysis of outcomes, including postoperative pain, knee range of motion (ROM), postoperative D-dimer levels, and length of hospital stay, was performed. The Cochrane Risk of Bias Assessment Tool was used to assess the risk of bias, and the data for each included study were extracted independently by two researchers. DATA SYNTHESIS: Eleven randomized controlled clinical trials with 940 subjects were included. The results showed that compared with the control group, the massage group experienced more significant pain relief on the 7th, 14th and 21st days after the operation. Moreover, the improvement in knee ROM was more pronounced on postoperative days 7 and 14. In addition, the massage group reported fewer adverse events. However, there was no statistically significant difference in the reduction in postoperative D-dimer levels between the patients and controls. Subgroup analysis revealed that massage shortened the length of hospital stay for postoperative patients in China but not significantly for patients in other regions. Nevertheless, the heterogeneity of the studies was large. CONCLUSIONS: Increased massage treatment was more effective at alleviating pain and improving knee ROM in early post-TKA patients. However, massage did not perform better in reducing D-dimer levels in patients after TKA. Based on the current evidence, massage can be used as an adjunctive treatment for rehabilitation after TKA.

Increased Risk of New-Onset Rheumatoid Arthritis Among Osteoarthritis Patients Received Total Knee Arthroplasty: a global federated health network analysis.

Background: Complications of total knee arthroplasty (TKA) had been widely discussed. However, whether TKA influence risk of rheumatoid arthritis (RA) in osteoarthritis patients remained uncertain. We intend to evaluate the risk of RA in osteoarthritis patients underwent TKA. Methods: In this retrospective cohort study, data was retrieved from the US collaborative networks in TriNetX research network. Within the study period between 2005 and 2017, osteoarthritis patients underwent TKA were enrolled as case cohort whereas osteoarthritis patients never underwent TKA were enrolled as control cohort. Covariates were matched via propensity score matching. Risk of RA in TKA patients were valuated under various follow-up time and sensitivity models. Results: Under 1-year, 3-year and 5-year of follow-up, TKA patients were associated with significantly elevated risk of RA, especially under 1-year follow-up (HR=1.74; 95% CI, 1.39-2.18). Subgroup analysis demonstrated a significant increase in the risk of RA following TKA in the female subgroup (HR=1.42; 95% CI, 1.24-1.63), the subgroup aged 18-64 years (HR=1.48; 95% CI, 1.11-1.97), and the subgroup aged greater than 65 years old (HR=1.38; 95% CI, 1.21-1.58) based on 5-year follow-up. Conclusion: Clinicians should be concerned about uncharted association between TKA and RA reported our current study. Additional prospective studies and in-depth mechanistic inquiries were warranted to determine the causation.

Health-related quality of life after total knee arthroplasty and unicompartmental knee arthroplasty for unicompartmental osteoarthritis: A systematic review and meta-analysis.

BACKGROUND: While previous research has demonstrated potential advantages of unicompartmental knee arthroplasty (UKA) over total knee arthroplasty (TKA), particularly in terms of clinical outcomes such as function and pain relief, the specific impact on health-related quality of life (HRQOL) remains unclear. This systematic review and meta-analysis aim to address this gap by comparing HRQOL outcomes between UKA and TKA, providing valuable insights for clinical decision-making. METHODS: We conducted a literature search in the PubMed, Embase, Cochrane Controlled Register of Trials (CENTRAL), and Web of Science databases up to July 15, 2023. Eligible studies assessed HRQOL using EQ-5D, SF-36, or SF-12 and were assessed for methodological quality using the Newcastle-Ottawa Scale (NOS). RESULTS: Seven eligible studies were included, comprising a total of 64,585 patients with 35,809 undergoing TKA and 28,776 undergoing UKA. Patient age ranged from 52.0 to 67.7 years with an average BMI ranging from 27.2 to 31.0 kg/m2. Follow-up periods ranged from 6 months to 10 years. Five studies (63,829 patients) that evaluated HRQOL using EQ-5D showed significantly better outcomes for UKA compared to TKA (MD -0.04, 95% CI -0.05 to -0.02). Two studies (756 patients) that evaluated HRQOL using SF-36 showed no significant difference between TKA and UKA. Five studies (63,286 patients) that evaluated functional outcomes using Oxford Knee Score (OKS) showed significantly better functional scores for UKA compared to TKA (MD -1.29, 95% CI -1.86 to -0.72). Four studies (24,570 patients) that reported patient satisfaction showed no statistically significant difference between TKA and UKA (MD 0.97, 95% CI 0.90 to 1.05). Further subgroup analysis did not affect the conclusions. CONCLUSIONS: Our meta-analysis suggests that UKA is associated with better HRQOL and knee function, as well as similar patient satisfaction, compared to TKA for patients with unicompartmental osteoarthritis.

Total knee arthroplasty following lateral closing-wedge high tibial osteotomy versus primary total knee arthroplasty: a propensity score matching study.

BACKGROUND: The disparity in patient-reported outcomes between total knee arthroplasty (TKA) following high tibial osteotomy (HTO) and primary TKA has yet to be fully comprehended. This study aims to compare the patient-reported outcomes, radiological parameters and complication rates between TKA following HTO and primary TKA. METHODS: Sixty-five patients who underwent TKA following lateral closing-wedge HTO were compared to a matched group of primary TKA at postoperative 6-months and 1-year. Between-group confounders of age, gender, smoking status, Body Mass index, preoperative Numeric Rating Scale (NRS) pain in rest, Knee injury and Osteoarthritis Outcome Score-Physical function Shortform (KOOS-PS), EuroQol five-dimensional (EQ-5D) overall health score, and Oxford Knee Score (OKS) were balanced by propensity score matching. Patient-reported outcome measures were NRS pain in rest, KOOS-PS, EQ-5D overall health score, and OKS. Radiological parameters were femorotibial angle, medial proximal tibial angle, anatomical lateral distal femoral angle, posterior tibial slope, and patellar height assessed by Insall-Salvati ratio. The complication rates of TKA were compared between the two groups. The HTO survival time, the choice of staple removal before or during TKA in patients who underwent TKA following HTO patients, and the rate of patellar resurfacing were assessed. The p value < 0.0125 indicates statistical significance after Bonferroni correction. RESULTS: After propensity score matching, no significant between-group differences in the patient-reported outcome measures, radiographical parameters and complication rates were found (p > 0.0125). In the TKA following HTO group, with an average HTO survival time of 8.7 years, staples were removed before TKA in 46 patients (71%) and during TKA in 19 patients, and 11 cases (17%) had patella resurfacing. In the primary TKA group, 15 cases (23%) had patella resurfacing. CONCLUSION: The short-term assessment of TKA following HTO indicates outcomes similar to primary TKA. A previous HTO does not impact the early results of subsequent TKA, suggesting that the previous HTO has minimal influence on TKA outcomes. LEVEL OF EVIDENCE: III, cohort study.

Implementation of outpatient hip and knee arthroplasty in a multicenter public healthcare setting.

BACKGROUND AND PURPOSE: Length of hospital stay after hip and knee arthroplasty is about 1 day in Denmark with few patients discharged on the day of surgery. Hence, a protocol for multicenter implementation of discharge on day of surgery has been instituted. We aimed to describe the implementation of outpatient hip and knee arthroplasty in a multicenter public healthcare setting. METHODS: We performed a prospective multicenter study from 7 public hospitals across Denmark. Patients were screened using well-defined in- and exclusion criteria and were discharged on day of surgery when fulfilling functional discharge criteria. The study period was from September 2022 to February 2023 with variable start of implementation. Data from the same centers in a 6-month period before the COVID pandemic from July 2019 to December 2019 was used for baseline control. RESULTS: Of 2,756 primary hip and knee arthroplasties, 37% (95% confidence interval [CI] 35-39) were eligible (range 21-50% in centers) and 52% (range 24-62%) of these were discharged on day of surgery. 21% (CI 20-23) of all patients (eligible and non-eligible) were discharged on day of surgery with a range of 10-31% within centers. This was an additional 15% (CI 13-17, P < 0.001) compared with patients discharged in the control period (6% in 2019). CONCLUSION: We found it possible to perform outpatient hip and knee replacement in 21% of patients in a public healthcare setting, probably to be increased with further center experience.

Unicompartmental knee arthroplasty combined with posterior cruciate ligament reconstruction: a case report.

BACKGROUND: In this study, we present the unique case of a patient with knee osteoarthritis (OA) of the medial compartment and posterior cruciate ligament (PCL) deficiency who underwent simultaneous medial unicompartmental knee arthroplasty (UKA) and PCL reconstruction. CASE PRESENTATION: A 49-year-old male patient presented with a 1-year history of pain and instability in the left knee. The patient had previously experienced a trauma-related injury to the PCL of the left knee that was left untreated. Imaging and physical examination confirmed the presence of left medial knee OA along with PCL rupture. To address these issues, the patient underwent UKA combined with PCL reconstruction. The patient's Lysholm score was 47 before surgery and 81 three months after surgery, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score was 29 before surgery and 18 three months after surgery, and the International Knee Documentation Committee (IKDC) subjective score was 56.3 before surgery and 74.7 three months after surgery. Six months after surgery, the patient's gait returned to normal, and he was able to jog. CONCLUSION: This case report presents the first instance of UKA combined with PCL reconstruction and introduces a novel treatment approach for patients suffering from medial knee OA and ligament injury.

Survivorship and Outcomes of Robotic Arm-Assisted Medial Unicompartmental Knee Arthroplasty at a Minimum of 5-Year Follow-Up.

PURPOSE: This study aimed to evaluate implant survivor-ship, complications, and re-operation rates following robotic arm-assisted unicompartmental knee arthroplasty (UKA) at mid-term follow-up. METHODS: Patient satisfaction, clinical outcome, and knee alignment restoration were evaluated. All patients undergo-ing robotic arm-assisted medial UKA during a 2-year period were prospectively enrolled. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, varus-valgus deformity, and knee range of motion were studied pre- and postoperatively. Revisions and surgery-related complications were recorded. RESULTS: Eighty-five patients were included in the study (mean age: 71.2 years). The mean follow-up was 74.7 months. One conversion to total knee arthroplasty was performed due to periprosthetic fracture 4.5 years after initial surgery result-ing in a survivorship rate of 98.8%. Overall satisfaction was excellent; 97.7% of patients were satisfied or very satisfied, while none was dissatisfied or very dissatisfied. WOMAC score in total, as well as in each component, exhibited sig-nificant improvement postoperatively. Additionally, knee alignment in the coronal plane as well as flexion contracture were significantly improved following the procedure. CONCLUSIONS: The outcomes of the present cohort revealed that precise prosthesis implantation through the robotic arm-assisted system in UKA provided excellent overall satisfac-tion rates and clinical outcomes at mid-term follow-up.

Osteosarcoma After Total Knee Arthroplasty: A Case Report.

CASE: A 79-year-old woman presented with a periprosthetic fracture 8 years after a total knee arthroplasty (TKA). Radiographs demonstrated tibial implant loosening with severe osteolysis. A high-grade osteosarcoma around the prosthesis was diagnosed, and a supracondylar femoral amputation was performed. After 2 years, no complications have occurred. CONCLUSIONS: A malignant tumor around a TKA is extremely rare. Surgeons should remain vigilant with patients who present with rapidly progressive or very aggressive implant loosening with osteolysis. Owing to its complexity and potentially devastating prognosis, treatment should be guided by a specialist multidisciplinary team. Complex limb salvage procedures or amputation is usually required.

Risk of conversion to total knee arthroplasty after surgically treated tibial plateau fractures: an observational cohort study of 439 patients.

BACKGROUND AND PURPOSE: We aimed to assess joint failure rate, i.e., subsequent conversion to TKA after surgical treatment of a tibial plateau fracture (TPF). Secondary aims were to explore the association between joint failure and fracture type, and to determine the risk of failure associated with inadequate joint surface reduction. METHODS: We included all patients ≥ 18 years of age with a surgically treated TPF, treated at Uppsala University Hospital between 2002 and 2015. All fractures were classified according to the Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Traumatology Association (AO/OTA) classification. Postoperative radiographs were evaluated to determine the quality of joint surface inadequate reduction, defined as an articular step-off ≥ 2 mm. The study cohort was linked with the Swedish Arthroplasty Register (SAR) for information on subsequent total knee arthroplasty (TKA). RESULTS: 439 patients (57% women) with a mean age of 55 years (SD 17) were included. According to the AO/OTA classification, the fracture distribution was B1: 4.8%, B2: 10%, B3: 47%, C1: 12%, C2: 6.4%, and C3: 19%. 23 patients (5.2%) were converted to a TKA within 2 years of initial surgery, and 34 patients (7.7%) had been converted by the end of follow-up (16 years). AO/OTA type B3 and C3 had a 6.8 (95% confidence interval [CI] 1.6-29) times greater risk of joint failure compared with B1-2 and C1-C2 at 2 years' follow-up. Inadequate joint surface reduction led to an 8.4 (CI 3.6-20) times greater risk of conversion to TKA at 2 years' follow-up. CONCLUSION: Overall, 5.2% were converted to a TKA within 2 years. Fracture types AO/OTA B3 and C3 with a comminuted articular surface and inadequate joint surface reduction were strongly associated with joint failure.

Association of Preoperative Subchondral Bone Marrow Oedema with Outcomes after Lateral Unicompartmental Knee Arthroplasty.

OBJECTIVE: To determine whether the presence of preoperative subchondral bone marrow oedema (SBME) is associated with inferior outcomes after lateral unicompartmental knee arthroplasty (LUKA). STUDY DESIGN: Descriptive study. Place and Duration of the Study: Department of Orthopaedic Surgery, Chongqing Orthopaedic Hospital of Traditional Chinese Medicine, Chongqing, China, from January 2019 to June 2022. METHODOLOGY: Data on patients treated with LUKA were obtained from the Medical Registry Database. Two groups were made based on the presence and absence of SBME on preoperative magnetic resonance imaging (MRI). The visual analogue scale (VAS), American Knee Society Scores (AKSS), and rate of patient satisfaction were compared between the two groups. RESULTS: A total of 20 patients treated with LUKA were reviewed. The SBME was present in 9 cases and absent in 11 cases. Patients with SBME had inferior scores at preoperative evaluation and at 1, 3, and 6 months postoperatively. However, there was no significant difference between the groups at the 12-month follow-up. Eight (88.9%) patients with SBME were satisfied with the LUKA surgery versus 9 (81.8%) patients without SBME, showing no significant differences between groups. CONCLUSION: Presence of preoperative SBME is associated with inferior functional outcomes after LUKA within six months of follow-up. KEY WORDS: Bone marrow, Oedema, Knee, Arthroplasty, Outcome, Patient satisfaction.

Finite element analysis of the effect of tibial osteotomy on the stress of polyethylene liner in total knee arthroplasty.

AIM: To explore the effects of tibial osteotomy varus angle combined with posterior tibial slope (PTS) on the stress of polyethylene liner in total knee arthroplasty (TKA) by building finite element model (FEM). METHODS: Established the FEM of standard TKA with tibial osteotomy varus angle 0° to 9° were established and divided into 10 groups. Next, each group was created 10 FEMs with 0° to 9° PTS separately. Calculated the stress on polyethylene liner in each group in Abaqus. Finally, the relevancy between tibial osteotomy angle and polyethylene liner stress was statistically analyzed using multiple regression analysis. RESULTS: As the varus angle increased, the area of maximum stress gradually shifted medially on the polyethylene liner. As the PTS increases, the percentage of surface contact forces on the medial and lateral compartmental of the polyethylene liner gradually converge to the same. When the varus angle is between 0° and 3°, the maximum stress of the medial compartmental surfaces of polyethylene liner rises smoothly with the increase of the PTS. When the varus angle is between 4° and 9°, as the increase of the PTS, the maximum stress of polyethylene liner rises first and then falls, forming a trough at PTS 5° and then rises again. Compared to the PTS, the varus angle has a large effect on the maximum stress of the polyethylene liner (p < .001). CONCLUSION: When the varus angle is 0° to 3°, PTS 0° is recommended, which will result in a more equalized stress distribution of the polyethylene liner in TKA.

Robot-assisted total knee arthroplasty system provides more precise control of the femoral rotation angle: A retrospective study.

BACKGROUND: Rotational alignment in total knee arthroplasty (TKA) is a crucial technical point that needs attention. We conducted a retrospective study to investigate whether a new robot-assisted TKA (RA-TKA) could improve the accuracy of rotational alignment and whether rotational alignment affects postoperative pain and functional evaluation of the knee. METHODS: A total of 136 consecutive patients who underwent TKA were included in this study. Half of the patients underwent RA-TKA and the other half underwent conventional TKA (CON-TKA) by the same group of surgeons. Collect the relevant parameters. RESULTS: The postoperative femoral rotation angle (FRA) was -0.72 ± 2.59° in the robot-assisted group and 1.13 ± 2.73° in the conventional group, and were statistically significantly different (p < 0.001). CONCLUSION: This study provides preliminary evidence that the RA-TKA provides more precise control of FRA than CON-TKA, and verifies that tibial rotation angle and combined rotation angle affect postoperative knee pain and functional evaluation.

Orthopaedic surgeons' attitude toward physical activity for people after total hip or knee replacement: Northern vs Southern European country.

BACKGROUND: Regular physical activity (PA) is a key factor of lifestyle behavior enhancing general health and fitness, especially in people after total hip or knee replacement (THR and TKR). Orthopaedic surgeons can play a primary role in advocating the benefits of an active lifestyle. Aim of the study was 1) to assess the attitude of orthopaedic surgeons towards PA for people after THR/TKR and 2) to compare the attitude between a Northern European (the Netherlands) and a Southern European (Italy) country and analyze which factors influence the attitude towards PA. METHODS: A cross-cultural study. An (online) survey was distributed among orthopaedic surgeons in Italy and the Netherlands. Chi-square and Mann-Whitney tests were used to compare surgeons' and clinics' characteristics, and questionnaires' scores, respectively. A linear regression analysis was conducted to assess which surgeon characteristics influence attitude towards PA. RESULTS: A cohort of 159 surgeons (103 Italians and 56 Dutch) was analyzed. The median score of overall orthopaedic surgeons' attitude towards PA was positive (57 out of 72). Dutch surgeons showed a more positive attitude compared to Italian surgeons (p < 0.01). Main difference was found in the "Physical activity concern" factor, where Italian surgeons showed more concern about the negative effects of PA on the survival of the prosthesis. The regression analyses showed that "Country" and "Type of clinic" were associated with the surgeons' attitude. CONCLUSIONS: Overall, the orthopaedic surgeons' attitude towards PA for people with THR and TKR was positive. However, Dutch surgeons seem to be more positive compared to the Italian. The country of residence was the item that most influenced attitude. Further investigations are needed to untangle specific factors, such as cultural, socioeconomic, or contextual differences within the variable "country" that may influence orthopaedic surgeons' attitudes towards PA.

Metal-backed or all-poly tibial components: which are better for medial unicompartmental knee arthroplasty? A propensity-score-matching retrospective study at the 5-year follow-up.

BACKGROUND: This retrospective medium-term follow-up study compares the outcomes of medial fixed-bearing unicompartmental knee arthroplasty (mUKA) using a cemented metal-backed (MB) or an all-polyethylene (AP) tibial component. MATERIALS AND METHODS: The database of our institution was mined for primary mUKA patients implanted with an MB or an AP tibial component (the MB-UKA and AP-UKA groups, respectively) from 2015 to 2018. We compared patient demographics, patient-reported outcome measures (PROMs), and motion analysis data obtained with the Riablo™ system (CoRehab, Trento, Italy). We conducted propensity-score-matching (PSM) analysis (1:1) using multiple variables. RESULTS: PSM analysis yielded 77 pairs of MB-UKA and AP-UKA patients. At 5 years, the physical component summary (PCS) score was 52.4 ± 8.3 in MB-UKA and 48.2 ± 8.3 in AP-UKA patients (p < 0.001). The Forgotten Joint Score (FJS-12) was 82.9 ± 18.8 in MB-UKAs and 73.4 ± 22.5 in AP-UKAs (p = 0.015). Tibial pain was reported by 7.8% of the MB-UKA and 35.1% of the AP-UKA patients (p < 0.001). Static postural sway was, respectively, 3.9 ± 2.1 cm and 5.4 ± 2.3 (p = 0.0002), and gait symmetry was, respectively, 92.7% ± 3.7 cm and 90.4% ± 5.4 cm (p = 0.006). Patient satisfaction was 9.2 ± 0.8 in the MB-UKA and 8.3 ± 2.0 in the AP-UKA group (p < 0.003). CONCLUSIONS: MB-UKA patients experienced significantly better 5-year static sway and gait symmetry outcomes than AP-UKA patients. Although the PROMs of the two groups overlapped, MB-UKA patients had a lower incidence of tibial pain, better FJS-12 and PCS scores, and were more satisfied.

[Considerable regional differences in patient injuries after primary hip and knee arthroplasty and between orthopedic departments depending on surgical volume]. / Regional skillnad i incidensen av skador efter ledprotesoperation.

Hip and knee arthroplasties are mostly successful procedures; however, patient injuries may occur and should be reported to Löf, the Swedish patient insurance. This study investigated the incidence of patient injuries after primary total hip and knee arthroplasty in the Swedish regions, differences in incidence depending on annual surgical volume, and types of approved injuries. Approved patient injuries were related to the total number of hip and knee arthroplasties registered in the Swedish Arthroplasty Register 2012-2021. The national incidence was 11.4 and 8.1 per 1,000 hip and knee arthroplasties respectively and varied in the regions from 30.4 to 4.9 and 15.4 to 5.4 per 1,000 hip and knee arthroplasties respectively. Orthopedic departments with higher annual volumes of performed arthroplasties had a lower proportion of patient injuries. Infection was the most common patient injury, followed by nerve lesions and mechanical complications. The differences may be due to underreporting and varying quality of care in the regions. A centralization of hip and knee arthroplasties may be beneficial.

Evaluating the cost of robotic-assisted total and unicompartmental knee arthroplasty.

As uptake of robotic-assisted arthroplasty increases there is a need for economic evaluation of the implementation and ongoing costs associated with robotic surgery. The aims of this study were to describe the in-hospital cost of robotic-assisted total knee arthroplasty (RA-TKA) and robotic-assisted unicompartmental knee arthroplasty (RA-UKA) and determine the influence of patient characteristics and surgical outcomes on cost. This prospective cohort study included adult patients (≥ 18 years) undergoing primary unilateral RA-TKA and RA-UKA, at a tertiary hospital in Sydney between April 2017 and June 2021. Patient characteristics, surgical outcomes, and in-hospital cost variables were extracted from hospital medical records. Differences between outcomes for RA-TKA and RA-UKA were compared using independent sample t-tests. Logistic regression was performed to determine drivers of cost. Of the 308 robotic-assisted procedures, 247 were RA-TKA and 61 were RA-UKA. Surgical time, time in the operating room, and length of stay were significantly shorter in RA-UKA (p < 0.001); whereas RA-TKA patients were older (p = 0.002) and more likely to be discharged to in-patient rehabilitation (p = 0.009). Total in-hospital cost was significantly higher for RA-TKA cases (AU$18580.02 vs $13275.38; p < 0.001). Robotic system and maintenance cost per case was AU$3867.00 for TKA and AU$5008.77 for UKA. Patients born overseas and lower volume robotic surgeons were significantly associated with higher total cost of RA-UKA. Increasing age and male gender were significantly associated with higher total cost of RA-TKA. Total cost was significantly higher for RA-TKA than RA-UKA. Robotic system costs for RA-UKA are inflated by the software cost relative to the volume of cases compared with RA-TKA. Cost is an important consideration when evaluating long term benefits of robotic-assisted knee arthroplasty in future studies to provide evidence for the economic sustainability of this practice.

Finite element analysis of the stability of retrograde intramedullary nail and plate-screw combinations for periprosthetic femoral fractures following total knee replacement.

OBJECTIVE: Periprosthetic fractures following total knee replacement are rare but challenging. The goal of the treatment is to achieve the most stable fixation that allows early mobilization. Therefore, the aim of this study was to evaluate the biomechanical results of the use of different fixation systems in the treatment of distal femur periprosthetic fractures with finite element analysis. MATERIALS AND METHODS: A total knee prosthesis was implanted in Sawbone femur models. A transverse fracture line was created in the supracondylar region and was fixed in four different groups. In group 1, fracture line fixation was fixed using retrograde intramedullary nailing. In group 2, fixation was applied using a lateral anatomic distal femoral. In group 3, in addition to the fixation made in group 1, a lateral anatomic distal femoral plate was used. In group 4, in addition to the fixation made in group 2, a 3.5 mm Limited Contact Dynamic Compression Plate (LC-DCP) was applied medially. Computed Tomography (CT) scans were taken of the created models and were converted to three-dimensional models. Axial and rotational loading forces were applied to all the created models. RESULTS: The least deformation with axial loading was observed in the double plate group. Group 3 was determined to be more advantageous against rotational forces. The greatest movement in the fracture line was found in group 2. The application of the medial plate was determined to reduce the tension on the lateral plate and increase stability in the fracture line. CONCLUSIONS: Combining a lateral anatomic plate with intramedullary nailing or a medial plate was seen to be biomechanically more advantageous than using a lateral plate or intramedullary nailing alone in the treatment of distal femoral periprosthetic fractures.