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Purpose: The influence of lateral patellofemoral osteoarthritis (PFOA) in medial unicompartmental knee arthroplasty (UKA) is controversial. Our aim was to identify radiographic factors that may lead to progressive PFOA after implantation of a fixed-bearing medial UKA and their impact on patient-reported outcomes (PROMs)., Methods: A retrospective consecutive cohort of patients undergoing medial UKA with a minimum follow-up of 60 months between September 2011 and January 2017 was identified. All UKAs had a fixed-bearing design with cemented femoral and tibial components. PROMs included documentation of the Oxford Knee Score (OKS). The following radiographic parameters were evaluated on conventional radiographs and computer tomography (CT) scans: patella tilt angle, patella congruence angle, Caton-Deschamps index, medial and lateral patellofemoral degeneration (Kellgren-Lawrence Classification (KL)), mechanical anteroposterior axis, femoral torsion, tibial tuberosity to trochlear groove distance (TTTG), anteroposterior translation of the femoral component. A hierarchical multiple regression analysis and partial Pearson correlation analysis (SPSS) were used to evaluate for predictors of progression of lateral PFOA., Results: Forty-nine knees allowed PFOA assessment and had an average follow-up of 62 months (range 60-108). Twenty-three patients did not exhibit any progression of lateral PFOA. Twenty-two progressed with 1 stage, whereas four had progressed 2 stages according to the KL classification. TTTG negatively correlated with progressive lateral PFOA (r =  - 0.436, p = 0.01). Progression of lateral PFOA did not correlate with OKS at last follow-up (p = 0.613)., Conclusion: A decreased TTGT correlated with radiographic progression of lateral PFOA after medial fixed-bearing cemented UKA. PFOA however did not influence PROMs at a minimum of five years postoperatively., (© 2023. The Author(s) under exclusive licence to SICOT aisbl.)

In an aging population, the incidence of severe knee osteoarthritis in very elderly patients increases, leading to functional impairment and loss of independence. Knee replacement could be an effective treatment but is often denied due to fear of increased complication rate with advanced age. The objective of this study was to investigate complication rate, mortality, clinical outcome, and quality-adjusted life years (QALYs) of primary knee replacement in very elderly patients, defined as 83 years or older. Medical records of 85 cases, receiving a primary total (total knee arthroplasty [TKA]) or unicompartmental (unicompartmental knee arthroplasty [UKA]) knee replacement, aged 83 years or older at the time of surgery, were retrospectively reviewed for surgical and medical complications as well as survivorship. Functional outcome was obtained by Oxford Knee Score (OKS) and QALY. At a mean follow-up of 21 months (TKA) and 24 months (UKA), surgical and medical complication rates were 9.7 and 8.1% for TKA and 4.3 and 4.3% for UKA, respectively. One-year survival rate was 98.4% in TKA and 98.8% in UKA, the 5-year survival rate was 83.1 and 86.6%, respectively. OKS improved from 19 to 41 points in TKA and 23 to 40 points in UKA. Mean QALYs were 4.1 years for TKA and 3.9 years for UKA. TKA and UKA are safe and reliable surgical procedures in treating end-stage osteoarthritis in very elderly patients. Patients might benefit from improved pain, function, and quality of life. The mortality rate and overall complication rate were low, although slightly higher than reported in cohorts with younger patients. If the patient is suitable, UKA might be preferred over TKA, as the complication rate was significantly lower. Patients should not be excluded from knee replacement based on their age alone, but careful patient selection, peri- and postoperative optimization, and awareness for complications are quintessential for successful treatment., Competing Interests: None declared., (Thieme. All rights reserved.)

Background: It is unclear whether there is a difference in the incidence of postoperative fever (POF) between hip, knee and shoulder arthroplasty. The influence of a trauma setting has not been investigated., Methods: A retrospective review was performed on 675 joint replacement surgeries (hip, knee, shoulder arthroplasty) in an elective or trauma setting over a 2 year period (2016-2018). Patient demographics and perioperative/postoperative parameters were investigated. The fever curve was characterized. The results and costs of any fever-related diagnostic workup were reviewed., Results: A total of 89 patients (13.2%) experienced a POF ≥ 38.0 °C, only 21 patients (3.1%) a POF ≥ 38.5 °C (of the latter: 4.6% of hip arthroplasties, 0.6% of knee arthroplasties, 0% of shoulder arthroplasties). There was a significantly greater risk (OR 3.88) for POF ≥ 38.5 °C in trauma total hip arthroplasty (THA) compared to elective THA (10.6 vs. 3.0%; p < 0.01). Differences in POF rate between the various joint areas were statistically insignificant when comparing only elective and trauma cases with each other, even though there was a trend for higher rates in hip surgery. Patients experiencing POF ≥ 38.5 °C were more often males (p < 0.01) and had an increased intraoperative blood loss (p = 0.03) and longer hospital stay (p < 0.01). There was only 1/89 POF patients developing an early periprosthetic joint infection. The cost of a positive fever workup (3/27 patients, 11.1%) leading to a new diagnosis and treatment was 2045 US$., Conclusion: POF ≥ 38.5 °C was more frequent in traumatic THA compared to elective THA. A trend of difference between POF rates between the different joint areas was statistically insignificant after separating elective and traumatic cases. The risk of developing an early periprosthetic joint infection was not increased in POF. A fever-related diagnostic workup was rarely helpful in the absence of clinical symptoms., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Introduction: There is a paucity of data regarding hybrid-fixated unicompartmental knee arthroplasty (UKA), and no study directly compared all three available fixation techniques (cementless, cemented, and hybrid). The hypothesis was that hybrid fixation might have a lower incidence of radiolucent lines (RLL) than cemented UKA, with equivalent outcomes to uncemented UKA., Materials and Methods: A total of 104 UKA with a minimal follow-up of 1 year were retrospectively included, of which 40 were cemented, 41 cementless, and 23 hybrid prostheses. The functional outcomes scores included the Oxford Knee (OKS), Subjective Knee (SKS), and Forgotten Joint scores (FJS). RLLs, subsidence, and component positioning were assessed on radiographs., Results: At a mean follow-up of 28 months, the survival rate was 95% for cemented UKA and 100% for the cementless and hybrid UKA (n.s.), respectively. Postoperative FJS (93 vs. 82 points, p = 0.007) and SKS (4.7 vs. 4.1 points, p = 0.001) were better in cementless than cemented UKA, with hybrid-fixated UKA in between the two (90 and 4.4 points, n.s.). Improvement of OKS preoperatively to postoperatively did not differ between the groups (n.s.). RLLs were more frequent in cemented (23%) compared to cementless (5%, p = 0.021) and hybrid UKA (9%, n.s.). With an incidence of 12%, subsidence occurred more commonly in cementless UKA compared to cemented (5%) and hybrid (0%) (n.s.) UKA., Conclusion: Hybrid fixation achieves equivalent results to standard UKA fixation techniques regarding implant survival and functional and radiological outcomes. Therefore, the hybrid fixation technique seems to be a valuable alternative as it combines the advantages of cemented tibial components with those of uncemented femoral components., Level of Evidence: III., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: The purpose of the present study was to compare total (TKA) and unicondylar (UKA) knee arthroplasty for spontaneous osteonecrosis of the knee (SONK), and to investigate potential correlations to radiographic parameters., Methods: All consecutive patients with a magnetic resonance imaging (MRI) proven SONK treated with either TKA or UKA between 2002 and 2018 were analysed. The primary outcomes were postoperative complications and failure rates. Functional assessment included Knee Society Score (KSS), WOMAC Score, and range of motion. A novel three-dimensional measurement method was established to determine the size of the osteonecrotic lesion. All outcome parameters were correlated to the size of the necrotic lesion using Spearman's rank correlation., Results: The two treatment groups (34 TKAs, 37 UKAs) did not differ regarding age, body mass index, and ratio of the volume of the necrotic lesion to the volume of the femoral condyle (n.s.). At a mean follow-up of 6.6 years, patients with UKA had better functional outcomes compared to patients with a TKA (WOMAC Score 1.0 vs. 1.6, p = 0.04; KSS pain 86 vs. 83, n.s), with a similar complication rate. No correlation was found between necrotic lesion size and failure rate (n.s.)., Conclusion: UKA is a valuable treatment option for SONK leading to good functional results and a low failure rate. In case of a surgeon's concern regarding implant anchorage, TKA represents an equivalent solution. The MR-tomographic size of the osteonecrotic lesions seems to have no influence on the results., Level of Evidence: III., (© 2020. European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA).)

Background: Implant malpositioning, low surgical caseload, and improper patient selection have been identified as essential factors, which could negatively affect the longevity of unicompartmental knee arthroplasty (UKA). The aim of the current study was to evaluate the impact of the surgeon's caseload on patient selection, component positioning, as well as component survivorship and functional outcomes following a PSI-UKA., Methods: A total of 125 patient-specific instrumented (PSI) UKA were included. One hundred and two cases were treated by a high-volume surgeon (usage 40%) and 23 cases by a low-volume surgeon (< 10 cases/year, usage 34%). Preoperative UIS, as well as the postoperative clinical and radiologic outcome, were assessed retrospectively., Results: Irrespective of the surgeon's UKA caseload, PSI allowed good accuracy in component positioning (p > 0.05). The high-volume surgeon had a more strict indication for UKA with 89% showing a UIS > 25 (considered a good indication) compared to 70% for the low-volume surgeon (p = 0.016). The low-volume surgeon achieved worse results regarding functional outcome (p < 0.05) and a tendency toward an increased risk for UKA failure (p = 0.11) compared to the high-volume surgeon., Conclusion: Due to potential selection errors, mostly connected to a low UKA-caseload, low-volume UKA surgeons might achieve worse outcomes. Very strict indications for UKA might be recommended in low-volume surgeons to achieve excellent clinical outcomes following a UKA.

Background: Poor implant positioning has been identified as a factor in early failure of unicompartmental knee arthroplasty. The aim of this study was to report the accuracy of component positioning, and midterm clinical, functional and radiological outcomes following patient-specific instrumented (PSI) unicompartmental knee arthroplasty (UKA)., Methods: A total of 115 PSI-UKA were included. The primary outcomes were UKA survival, complication, and failure rates. Tibial implant positioning was determined using plain radiographs. Functional assessment included Oxford Knee Score (OKS), Forgotten Joint Score (FJS), patient satisfaction, and range of motion (ROM)., Results: The survival rate of PSI-UKA was 92% after a mean follow-up of 55 months. The complication and failure rate was 13% and eight percent, respectively. The tibial component was accurately implanted in the desired frontal and sagittal alignment with a minor deviation of 0.3° (SD 1.9°) and 0.4° (SD 2.6°) to the preoperative planning. OKS increased from 24 (SD eight) points to 44 (SD six). FJS was 87 (SD 23) and 89.6% of all patients reported to be satisfied at the final follow-up. Patient satisfaction was negatively correlated with patients' age (p < 0.05)., Conclusion: Excellent accuracy regarding component placement in UKA can be achieved with PSI. However, despite excellent survivorship and clinical outcomes, these data indicate that the PSI system is not superior to conventional UKA implantation methods., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Purpose: It was hypothesized that surgeon's experience as well as bone density play a significant role in achieving accurate cuts with patient-specific instrumentation (PSI). The aim of this study was to compare the accuracy of the tibial cuts in different bone densities made by a highly experienced orthopedic surgeon on one hand and a less experienced orthopedic surgeon on the other., Methods: Tibial models from three different sawbone densities were developed for this study. Each surgeon performed 21 cuts. A coordinate measuring machine was used to analyse the cuts. The K-Cohen test was performed to evaluate the results. The analyzed parameters were guide positioning and deviation from the guide cut to the tibial cut, including varus/valgus angle, the tibial slope, cut height, planarity (mm 2 ), and rugosity (mm)., Results: There was a significant difference in the positioning of the tibial cut guide between the two surgeons for the tibial slope (p < 0.05), while no difference was observed for the varus/valgus angle (n.s.) and the cut height (n.s.). No significant difference in the tibial cut was observed between the surgeons for the tibial slope angle (n.s.), varus/valgus angle (n.s.), planarity (n.s.), and rugosity (n.s.). In the different bone types, no significant difference was observed for the tibial slope (n.s.) and varus/valgus angle (n.s.), while planarity and rugosity showed significant differences (p < 0.05). Our study showed no significant difference in the tibial cuts for the tibial slope, varus/valgus angle, planarity, and rugosity between the two surgeons., Conclusions: In the present study, it could be demonstrated that accuracy of the cuts is ensured by PSI not depending on the surgeon's experience and the bone mineral density. This speaks to its clinical significance: PSI might be suited for less experienced surgeons to reduce outliers in total knee arthroplasty (TKA).

Introduction: Proper patient selection is a crucial factor for the outcome of the unicompartmental knee arthroplasty (UKA). However, there is still not a clear consensus on which patients could benefit the utmost from a UKA. The purpose of this prospective study was to introduce a novel, preoperative, predictive score (Unicompartmental Indication Score, UIS) to aid proper patient selection in UKA., Materials and Methods: A total of 152 patients with an average age of 68 years and a mean follow-up of 27 months were evaluated preoperatively with the UIS and postoperative at every follow-up. Correlation analysis was applied to identify potential relationships between the UIS, functional outcomes, pain relief, patient satisfaction, and range of motion. The ROC analysis was used to identify the best cutoff value of the UIS, which would have predicted an optimal outcome following UKA., Results: The majority of the patients (91%) were satisfied with the operation, with 61% reporting excellent and 30% good satisfaction. The UIS was positively correlated to the postoperative Knee Society Score (KSS) for both pain (r = 0.26, p < 0.001) and function (r = 0.31, p < 0.001). The UIS was also positively correlated to the patient satisfaction (p = 0.46, p < 0.001) and maximum postoperative flexion (r = 0.25, p < 0.001). The ROC analysis provided an ideal cutoff for UIS at 25 points (sensitivity: 75%, sensibility: 93%, area under the curve: 86%). At a mean follow-up of 27 months (range 24-37), we observed three revisions in 152 consecutive UKA with a mean UIS of 27 points (range 20-30)., Conclusions: The newly introduced UIS score might be a reliable preoperative scoring system to predict patients with excellent satisfaction, functional outcome, pain relief and possibly implant survivorship following UKA, and therefore, could help the proper patient selection and decision-making in UKA., Level-Of-Evidence: Prospective study, II.

Purpose: Unicompartmental knee arthroplasty (UKA) has recently regained popularity for the treatment of osteoarthritis of the knee. Numerous authors have cited alignment as an important prognostic factor in the survival of UKA. Limb alignment affects not only the longevity of UKA by influencing wear of polyethylene, but also affects the unreplaced contralateral compartment. Malpositioning of the components may result in unequal wear patterns, thus further leading to early failure and additionally influencing clinical outcome as well. However, there is a lack of techniques to assure a high accuracy of the implant positioning., Methods: In this study, we investigated tibia component alignment of 28 medial UKAs implanted with patient-specific cutting blocks. Three patients were excluded due to bad imaging. Measurements of tibial component alignment from postoperatively computed tomography (CT) scans were compared to respective CT-based preoperative plannings to assess the accuracy of implant positioning., Results: Our results show excellent high accuracy of tibial implant position in tibial varus/valgus (Δ 0.3° ± 1.7°), posterior slope (Δ 1.1° ± 2.6°) and external rotation (Δ 1.5° ± 3.3°)., Conclusion: We conclude that patient-specific cutting blocks improve the accuracy of tibia component positioning in unicompartmental knee arthroplasty., Level of Evidence: Case series with no comparison group, Level IV.

Background: Long-term survival of total knee arthroplasty (TKA) is mainly determined by optimal positioning of the components and prosthesis alignment. Implant positioning can be optimized by computer assisted surgery (CAS). Patient specific cutting blocks (PSCB) seem to have the potential to improve component alignment compared to the conventional technique and to be comparable to CAS., Methods: 113 knees were selected for PSI and included in this study. Pre- and postoperative mechanical axis, represented by the hip-knee-angle (HKA), the proximal tibial angle (PTA), the distal femoral angle (DFA), and the tibial slope (TS) were measured and the deviation from expected ideal values was calculated., Results: With a margin of error of ±3°, success rates were 81.4% for HKA, 92.0% for TPA, and 94.7% for DFA. With the margin of error for alignments extended to ±4°, we obtained a success rate of 92.9% for the HKA, 98.2% for the PTA, and 99.1% for the DFA. The TS showed postoperative results of 2.86±2.02° (mean change 1.76±2.85°)., Conclusion: PSCBs for TKA seem to restore the overall leg alignment. Our data suggest that each individual component can be implanted accurately and the results are comparable to the ones in CAS.

Osteoarthritis of the knee is one of the most common problems in the orthopedic practice and its surgical technique is still challenging. This Mini-Review presents patient specific cutting blocks for the implantation of a total knee arthroplasty.

Asymmetric resection of the patella during total knee arthroplasty (TKA) correlates with anterior knee pain, bony impingement and patellar maltracking. Despite this, there is no consensus regarding the desired landmarks; the cut is often done freehand; and there has been no quantitative comparison of proposed resection planes. The objectives of this study were to: determine the intra- and inter-surgeon repeatability of two radiographic resection definitions (medial-divot, MD, and medial-lateral extents, MLE); calculate two additional definitions from the radiographic patellar circumferences (parallel to the anterior surface, ANT, and perpendicular to the anteroposterior tangent points, PERP); compare the clinical resection line to the previous four definitions before and after introducing the MD method clinically; and identify distinguishing features of patellae with better vs. worse resection angles. We hypothesized that the MD method would improve repeatability both radiographically and clinically, that the different radiographic definitions would produce comparable angles, and that we could identify distinguishing features. For the radiographic study, three surgeons drew lines on 40 preoperative X-rays plus 9 interspersed repetitions of 3 of these X-rays. For the clinical study, we compared the patellar resection angle for 20 patients immediately before and after implementing the new method. Given that the clinical goal is to have equal distances from the resection surface to the anterior surface, we compared all results to the ANT definition as the theoretically ideal definition. Confirming the first hypothesis, intra-surgeon repeatability (10 repetitions of 3 X-rays) and inter-surgeon repeatability (3 surgeons x 40 X-rays) were both significantly better using the new MD method compared to the MLE method (p<0.001). Contrary to the second hypothesis, clinical use of the MD method did not improve resection symmetry. Contrary to the third hypothesis, the PERP definition was significantly different from the other three definitions. In agreement with the fourth hypothesis, female patellae and more deformed patella had significantly greater asymmetry (p<0.001). Given the inherent variability shown in drawing the 'patellar horizon', we encourage researchers to draw the line several times and average the results when comparing tilt or the resection angle to this horizon. Based on the distinguishing characteristics of asymmetrically resurfaced patellae in our series, we recommend that clinicians be particularly careful when resecting laterally deformed patellae and the patellae of female patients.

Unlabelled: The management of the patellar articular surface at the time of primary total knee arthroplasty (TKA) is controversial. We used expected-value decision analysis to determine whether the patella should be resurfaced in TKA, and also whether secondary resurfacing on an unresurfaced patella is worthwhile. Outcome probabilities and utility values were derived from randomized controlled trials only. A decision tree was constructed and fold-back analysis was performed to ascertain the best treatment path. Sensitivity analyses were performed to determine the effect on decision-making of varying outcome probabilities and utilities. Our model showed patellar resurfacing is the best management strategy for the patella at the time of primary TKA. This decision is robust to changes in the specific data: the best path would remain the same as long as the incidence of persistent anterior knee pain (AKP) with resurfacing remains less than 29% (current mean, 12%) or the incidence of AKP after nonresurfacing falls below 12% (current mean, 26%). Delayed (ie, secondary) patellar resurfacing for ongoing patellar pain provides inferior results for the majority of patients., Level of Evidence: Level II, decision analysis. See the Guidelines for Authors for a complete description of levels of evidence.