Query: Lateral cyst formation after knee arthroplasty

title: Large Soft tissue Mass Formation After Revision Total Knee Arthroplasty: An Unusual Case of Adverse Reaction to Metal Debris and Review of the Literature
abstract: We report about the rare case of a patient who developed large soft tissue mass formations related with revision total knee arthroplasty which was implanted 4 years prior. Owing to suspected periprosthetic joint infection, the prosthesis was removed and the lesions were resected, resulting in severe soft tissue loss and temporary arthrodesis using a poly(methyl methacrylate) spacer. Histological analysis revealed a type VI periprosthetic membrane. The situation was further complicated by wound infection requiring multiple revision surgeries. After discussion and evaluation of the available treatment options, the decision for an above the knee amputation was made. The tissue reaction resulting in these soft tissue lesions is referred to as an "adverse local tissue reaction." Wear induced lesions after total knee arthroplasty, especially of this magnitude, are very rare and difficult to treat.

title: MRI determined preoperative lateral meniscus degeneration is not associated with adverse mid term clinical results after mobile bearing unicompartmental knee arthroplasty.
abstract: One of the conditions constituting surgical indication for medial mobile bearing unicompartmental knee arthroplasty (UKA) is that there is full thickness cartilage in the lateral compartment under valgus stress radiography. However, it is unclear whether medial unicompartmental knee arthroplasty should be performed if there is degeneration of the lateral meniscus on preoperative magnetic resonance imaging (MRI) METHODS The records of 77 patients (77 knees) who underwent Oxford mobile bearing UKA were retrospectively reviewed. Based on the status of the lateral meniscus in each knee using preoperative MRI with Stoller's classification system, the patients were divided into two groups; a normal group and a lateral meniscus degenerated group (grades 1 3) The preoperative personal data and the outcome data three years postoperatively were compared.  The normal group contained 31 knees while the lateral meniscus degenerated group comprised 46 knees. There was no difference in clinical outcome or knee function between the groups at three years after UKA. There was no difference in re operation and revision rate between the groups with no revisions in either group.  It may not be necessary to exclude UKA indications for cases with degenerative findings in the lateral meniscus on preoperative MRI.

title: Lateral subvastus lateralis versus medial parapatellar approach for total knee arthroplasty: A cadaveric biomechanical study.
abstract: The standard of care for total knee arthroplasty (TKA) is a medial parapatellar approach (MPA) We aimed to study a novel lateral subvastus lateralis approach (SLA) which offers the benefit of keeping the extensor mechanism and medial soft tissues intact. To ensure the approach could be used safely in vivo, a biomechanical study was performed to assess whether the joint kinematics would be preserved after performing a TKA.  A biomechanical study was conducted using 14 fresh frozen cadaveric knees, with seven specimens each for the MPA and SLA. After a single radius, cemented cruciate retaining TKA was performed, specimens were tested on a VIVO joint motion simulator to measure and compare anterior/posterior, internal/external, and varus/valgus kinematics and laxity.  There was no significant difference in joint kinematics or laxity between the SLA and MPA groups.  Both the SLA and MPA offer similar knee kinematics and laxity based on a cadaveric model. Although the surgical approach was different, inherently releasing different ligaments, both approaches resulted in a stable knee. This suggests that either approach will enable the surgeon to provide a stable knee, and that the implant itself may contribute a significant portion of the knee's kinematics.

title: Lateral unicompartmental knee arthroplasty is a safe procedure for post traumatic osteoarthritis after lateral tibial plateau fracture: a case control study at 10 year follow up
abstract: Very few studies focus on lateral unicompartmental arthroplasty (LUKA) in the setting of post traumatic osteoarthritis (PTOA) The hypothesis of our study is that LUKA is an effective procedure for isolated lateral PTOA with similar outcomes to non traumatic LUKA. Between 1990 and 2016, eighteen LUKA performed for isolated lateral tibiofemoral osteoarthritis secondary to tibial plateau fracture were retrospectively reviewed (post traumatic group) and matched with a control group of thirty six LUKA performed for non traumatic OA. Clinical (International Knee Score) radiological outcomes and revision rate were compared between the two groups with a minimum follow up of three years. With a mean follow up of 10.1 years, postoperative IKS scores were similar between the two groups (IKS Knee: 89.1 (control) versus 85 (p 0.03) and IKS Function: 85.9 (control) versus 77.9 (n.s. Clinical improvement was greater for the post traumatic group. No difference was observed with regard to revision rate (3/18 (16.7% cases in the post traumatic group and 7/36 (19.4% in the control group, n.s. or polyethylene wear per year between the two groups. The revision free survival rate was 64.8% for the post traumatic group and 58.8% for the control group at 22 year follow up (n.s. LUKA is an effective procedure at long term for patients suffering from isolated lateral PTOA with similar clinical and radiographic results compared to LUKA performed for non traumatic OA and without increased risk of revision or prosthetic wear. IV.

title: Predictors of Satisfactory Outcomes With Fixed Bearing Lateral Unicompartmental Knee Arthroplasty: Up to 7 year Follow Up.
abstract: There is little literature available examining factors that may predict functional recovery after lateral unicompartmental knee arthroplasty (UKA) The purpose of this study was to report short to mid term effectiveness and evaluate predictors of better outcome following lateral UKA.  We retrospectively reviewed 248 patients (260 knees) who underwent lateral UKA from January 2013, with a mean 5 year follow up. The primary outcome measures comprised the Hospital for Special Surgery (HSS) score and patient satisfaction. Multivariate regression analyses were implemented to investigate associations between these factors with a satisfactory outcome. Implant survival was estimated by Kaplan Meier analysis.  Complete follow up was available for 186 patients (198 knees) At last follow up, the HSS scores were changed from 52.1 (range, 38 80) preoperatively to 85.6 (range, 61 98) (P .001) The OKS improved from 22.8 (range, 16 32) preoperatively to 42.7 (range, 30 47) postoperatively (P .01) The 5 year survival was 99.5% The multivariate analysis showed that the following factors tended to obtain a satisfactory outcome: higher proportion of ASA class I (P .001) diagnosis of primary OA (P .007) postoperative limb alignment (P .007) and higher preoperative HSS score (P .019) Patients with valgus 9deg 12deg reported the highest HSS scores among different subgroups (P .001)  Following lateral UKA, postoperative outcomes were satisfactory in patients with lower ASA scores, diagnosis with primary OA, higher preoperative HSS scores and those with postoperative valgus alignment. It is important to understand these correlations to help appropriate patient selection to obtain optimal function after lateral UKA.

title: Preoperative Condition of the Patellofemoral Joint Does Not Negatively Impact Surgical Outcomes of Lateral Unicompartmental Knee Arthroplasty in the Short Term.
abstract: The relationship between patellofemoral joint (PFJ) degeneration and clinical outcomes following lateral unicompartmental knee arthroplasty (UKA) has not been well described thus far. This study aimed to investigate the relationship between the preoperative PFJ condition and postoperative outcomes and the changes in lower limb and PFJ alignment after lateral UKA. This was a retrospective study including 54 patients (mean age 72.9 years) who underwent lateral UKA for isolated lateral knee osteoarthritis at our institution between March 2013 and January 2019. The Oxford Knee Score (OKS) the Knee Society Score Knee (KSSK) and Knee Society Score Function (KSSF) the degree of degeneration, tilting angle and lateral shift of the PFJ, and the hip knee ankle angle (HKA) were evaluated pre and postoperatively. The average follow up period was 2.8 (range 1 6.1) years. There was a significant improvement in the OKS, KSSK, and KSSF after lateral UKA. Preoperative degeneration of the PFJ did not correlate with the recovery of clinical scores. The degeneration, tilting angle, and lateral shift of the PFJ did not significantly progress following lateral UKA. The HKA was improved after lateral UKA, and there was no correlation between the HKA change and PFJ condition. Postoperative severe valgus knee alignment was associated with a greater tilting angle. Preoperative degeneration of the PFJ did not have a negative impact on postoperative outcomes, and no short term changes in the degeneration, tilting angle, and lateral shift of the PFJ were observed. Correction of knee joint alignment did not have a negative impact on the condition of the PFJ.

title: Low Degree Tibial Slope Angle Prevents Component Overhang by Enlarging the Lateral Plateau Surface Area in Total Knee Arthroplasty.
abstract: This study aimed to investigate whether overhang or underhang around the tibial component that occurs during the placement of tibial baseplates was affected by different slope angles of the tibial plateau and determine the changes in the lateral and medial plateau diameters while changing the slope angle in total knee arthroplasty. Three dimensional tibia models were reconstructed using the computed tomography scans of 120 tibial dry bones. Tibial plateau slope cuts were performed with 9, 7, 5, 3, and 0 degrees of slope angles 2 mm below the subchondral bone in the deepest point of the medial plateau. Total, lateral, and medial tibial plateau areas and overhang/underhang rates were measured at each cut level. Digital implantations of the asymmetric and symmetric tibial baseplates were made on the tibial plateau with each slope angles. Following the implantations, the slope angle that prevents overhang or underhang at the bone border and the slope angle that has more surface area was identified. A significant increase was noted in the total tibial surface area, lateral plateau surface area, and lateral anteroposterior distance, whereas the slope cut angles were changed from 9 to 0 degrees in both gender groups. It was found that the amount of posteromedial underhang and posterolateral overhang increased in both the asymmetric and symmetric tibial baseplates when the slope angle was changed from 0 to 9 degrees. Although the mediolateral diameter did not change after the proximal tibia cuts at different slope angles, the surface area and anteroposterior diameter of the lateral plateau could change, leading to increased lateral plateau area. Although prosthesis designs are highly compatible with the tibial surface area, it should be noted that the component overhangs, especially beyond the posterolateral edge, it can be prevented by changing the slope cut angle in males and females.

title: Lateral and patellofemoral compartment osteoarthritis progression after medial unicompartmental knee arthroplasty: A five to 10 year follow up study.
abstract: The purpose of the study was to evaluate lateral and patellofemoral osteoarthritis (OA) progression after medial unicompartmental knee arthroplasty (UKA) and identify factors affecting the progression that were not identified previously.  We evaluated 146 patients who underwent medial UKA between 2009 and 2014. Kellgren Lawrence grading of lateral and patellofemoral OA was performed on preoperative and final follow up knee radiographs. Radiographic and clinical characteristics, SF 36, and Oxford knee scores were compared between the OA progressed and non progressed groups. Risk factors for lateral and patellofemoral OA progression were evaluated.  The lateral OA progressed and non progressed groups significantly differed in side, preoperative flexion contracture, preoperative joint line convergence angle, postoperative tibiofemoral angle, insert size, revision status (P 0.05) and the patellofemoral OA progressed and non progressed groups significantly differed in age, pre and postoperative flexion contracture, postoperative tibiofemoral angle and pre and postoperative patellofemoral OA grade (P 0.05) At the final follow up, Visual Analogue Scale, Oxford Knee Scores, and SF 36 sub scores were significantly better in the lateral OA non progressed group (P 0.001) Dominant leg (odds ratio (OR) 2.759) insert size >4, OR: 2.219) revision status OR: 6.692) and postoperative tibiofemoral angle >5.5deg, OR: 1.177) were independent risk factors for lateral OA progression, whereas age >60 years, OR: 3.222) preoperative patellofemoral OA grade >1, OR: 2.085) and postoperative flexion contracture >10deg, OR: 1.919) were those for patellofemoral OA progression.  Mild radiographic progression of 1 KL grade is frequently seen five to 10 years after medial UKA. Postoperative outcomes are significantly affected by lateral compartment OA progression but not by patellofemoral OA progression.

title: Sports activity and patient related outcomes after fixed bearing lateral unicompartmental knee arthroplasty.
abstract: Unicompartmental osteoarthrosis increasingly affects younger patients who have high expectations concerning their postoperative level of activity. However, there is no available data on the activity level after fixed bearing lateral unicompartmentalkneearthroplasty (UKA) The aim of this study was to report sports activity after fixed bearing lateral UKA with a minimum two year follow up.  Nineteen patients were surveyed to determine their sporting activities at a mean follow up of 4.6 years (range 2.0 9.7 years) after fixed bearing lateral UKA. We also assessed the Knee Injury and Osteoarthritis Outcome Score Joint Replacement (KOOS JR) Score and the University of California, Los Angeles activity scale (UCLA scale) at baseline and latest follow up.  Before the onset of the first symptoms, 15 of 19 patients were active in at least one sport compared with 13 of 19 patients after surgery. Eighty six per cent of the patients returned to activity. Within 6 months, 68% returned to their activities after surgery. The mean postoperative UCLA score was 6.4 1.3) Half of the patients reached a high activity level (UCLA 7) Most common activities after surgery were long walks, biking and hiking. High impact activities showed a significant decrease.  Eighty six per cent of the patients were able to return to regular recreational and sporting activities. In general, a shift from high impact to low impact activities was observed. There was no difference in the number of disciplines performed. Overall, the session length and frequency remained unchanged. However, male patients and younger patients participated in sports less frequently compared with preoperative levels.

title: Mid term survivorship and patient reported outcomes of robotic arm assisted partial knee arthroplasty.
abstract: Limited evidence is available on mid term outcomes of robotic arm assisted (RA) partial knee arthroplasty (PKA) Therefore, the purpose of this study was to evaluate mid term survivorship, modes of failure, and patient reported outcomes of RA PKA.  A retrospective review of patients who underwent RA PKA between June 2007 and August 2016 was performed. Patients received a fixed bearing medial or lateral unicompartmental knee arthroplasty (UKA) patellofemoral arthroplasty (PFA) or bicompartmental knee arthroplasty (BiKA; PFA plus medial UKA) All patients completed a questionnaire regarding revision surgery, reoperations, and level of satisfaction. Knee Injury and Osteoarthritis Outcome Scores (KOOS) were assessed using the KOOS for Joint Replacement Junior survey.  Mean follow up was 4.7 years (2.0 to 10.8) Five year survivorship of medial UKA (n 802) lateral UKA (n 171) and PFA/BiKA (n 35/10) was 97.8% 97.7% and 93.3% respectively. Component loosening and progression of osteoarthritis (OA) were the most common reasons for revision. Mean KOOS scores after medial UKA, lateral UKA, and PFA/BiKA were 84.3 (SD 15.9) 85.6 (SD 14.3) and 78.2 (SD 14.2) respectively. The vast majority of the patients reported high satisfaction levels after RA PKA. Subgroup analyses suggested tibial component design, body mass index (BMI) and age affects RA PKA outcomes. Five year survivorship was 98.4% (95% confidence interval (CI) 97.2 to 99.5) for onlay medial UKA (n 742) and 99.1% (95% CI 97.9 to 100) for onlay medial UKA in patients with a BMI 30 kg/m2 (n 479) CONCLUSION This large single surgeon study showed high mid term survivorship, satisfaction levels, and functional outcomes in RA UKA using metal backed tibial onlay components. In addition, favourable results were reported in RA PFA and BiKA.