A Comprehensive Evaluation of Lateral Unicompartmental Knee Arthroplasty Short to Mid-Term Survivorship, and the Effect of Patient and Implant Characteristics: An Analysis of Data From the Dutch Arthroplasty Register.

BACKGROUND: The rarity of lateral unicompartmental knee arthroplasty (UKA) results in a lack of large cohort studies and understanding. The aim of this study is to comprehensively evaluate survivorship of lateral UKA with registry data and compare this to medial UKA. METHODS: Lateral (n = 537) and medial UKAs (n = 19,295) in 2007-2017 were selected from the Dutch Arthroplasty Register. Survival analyses were performed with revision for any reason as primary endpoint. Adjustments were made for patient and implant characteristics. Stratified analyses according to patient and implant characteristics were performed. Reasons and type of revision were grouped according to laterality and bearing design. RESULTS: The 5-year revision rate was 12.9% for lateral UKA and 9.3% for medial UKA. Multivariable regression analyses showed no significant increased risk for revision for lateral UKA (hazard ratio 0.87, 95% confidence interval 0.66-1.15). Stratified analyses showed that the effect of patient characteristics on revision was comparable between lateral and medial UKA; however, the use of mobile-bearing design for lateral UKA was associated with increased revision rate. Progression of osteoarthritis was the main reason for revision on both sides accompanied by tibia component loosening for medial UKA. Reasons and type of revision varied depending on bearing design. CONCLUSION: Similar survivorship of lateral and medial UKA was reported. Specifically, there is a notable risk for revision when using mobile-bearing designs for lateral UKA. Failure modes and type of revision depends on laterality and bearing design. These findings emphasize that surgical challenges related to anatomy and kinematics of the lateral and medial knee compartment need to be considered.

Bearing design influences short- to mid-term survivorship, but not functional outcomes following lateral unicompartmental knee arthroplasty: a systematic review.

PURPOSE: To determine survivorship and functional outcomes of fixed and mobile-bearing designs in lateral unicompartmental knee arthroplasties (UKA). METHODS: Medline, EMBASE and Cochrane databases were searched. Annual revision rate and functional outcomes were assessed for both fixed and mobile-bearing designs. RESULTS: A total of 28 studies, of which 19 fixed-bearing and 9 mobile-bearing, representing 2265 lateral UKAs were included for survivorship and functional outcome analyses. The mean follow-up of fixed and mobile-bearing studies was 7.5 and 3.9 years, respectively. Annual revision rate of fixed-bearing designs was 0.94 (95% CI 0.66-1.33) compared to 2.16 (95% CI 1.54-3.04) for mobile-bearing. A subgroup analysis of the domed shaped mobile-bearing design noted an annual revision rate of 1.81 (95% CI 0.98-3.34). Good-to-excellent functional outcomes were observed following fixed and mobile-bearing lateral UKAs; no significant differences were found. CONCLUSION: Mobile-bearing lateral UKAs have a higher rate of revision compared to fixed-bearing lateral UKAs with regard to short- to mid-term survivorship; however, the clinical outcomes are similar. Despite the introduction of the domed shaped mobile-bearing design, findings of this study suggest fixed-bearing implant design is preferable in the setting of isolated lateral osteoarthritis (OA). This systematic review was based on low to moderate evidence, therefore, future registry data are needed to confirm these findings. However, this study included a large number of patients, and could provide information regarding risk of revision and functional outcomes of mobile and fixed-bearing type lateral UKA. LEVEL OF EVIDENCE: IV.

Distal Femoral Rotation is not Associated With Preoperative Proximal Tibial Varus Angle in Patients With Isolated Medial Compartment Osteoarthritis.

BACKGROUND: Prior studies have found that greater proximal tibial varus was associated with increased external femoral rotation at time of total knee arthroplasty. These works suggest that measuring the tibial plateau-tibial shaft (TPTS) angle on preoperative weight-bearing long leg radiographs could predict significant variations in the posterior condylar angle. METHODS: A minimum of 68 patients were needed to reach 80% power. Patients were included if they had primary medial compartment osteoarthritis and excluded if they had a valgus mechanical axis. The clinical posterior condylar angle (cPCA) was defined as the angle between the anatomic transepicondylar axis and posterior condylar line. Correlation analyses were performed to test for any relationship between the TPTS and cPCA. Two patient groups were created based on TPTS angle: TPTS ≤4° (mild varus) and TPTS >4° (moderate varus). Mechanical axis and rotational measurements were compared between the groups using independent t-tests. RESULTS: The mean mechanical axis and TPTS angle were 6.9° and 4.8° of varus, respectively. The mean cPCA was 5.0° (standard deviation [SD], 1.4°; range, 2.4°-7.9°). No correlation was found between the TPTS angle and cPCA (P = .15). The mean cPCA in the mild varus group (n = 28 patients) was 5.2° (SD, 1.5°; range, 2.7°-7.9°), and the mean cPCA in the moderate varus group (n = 45 patients) was 4.4° (SD, 1.7°; range, 0.6°-7.5°). These groups were not statistically significantly different from each other (P = .62). CONCLUSION: The present study does not support the conclusions of previous works and suggests that the amount of distal femoral rotation cannot be predicted by tibial varus alignment measured on preoperative long leg radiographs. Consequently, we believe that proximal tibial varus should not be used to preoperatively predict external rotation of the femoral component in patients with isolated medial compartment osteoarthritis.

Larger range of motion and increased return to activity, but higher revision rates following unicompartmental versus total knee arthroplasty in patients under 65: a systematic review.

PURPOSE: Due to the lack of comparative studies, a systematic review was conducted to determine revision rates of unicompartmental and total knee arthroplasty (UKA and TKA), and compare functional outcomes, range of motion and activity scores in patients less than 65 years of age. METHODS: A literature search was performed using PubMed, Embase, and Cochrane systems since 2000. 27 UKA and 33 TKA studies were identified and included. Annual revision rate (ARR), functional outcomes, and return to activity were assessed for both types of arthroplasty using independent t tests. RESULTS: Four level I studies, 12 level II, 16 level III, and 29 level IV were included, which reported on outcomes in 2224 UKAs and 4737 TKAs. UKA studies reported 183 revisions, yielding an ARR of 1.00 and extrapolated 10-year survivorship of 90.0%. TKA studies reported 324 TKA revisions, resulting in an ARR of 0.53 and extrapolated 10-year survivorship of 94.7%. Functional outcomes scores following UKA and TKA were equivalent, however, following UKA larger ROM (125° versus 114°, p = 0.004) and higher UCLA scores were observed compared to TKA (6.9 versus 6.0, n.s.). CONCLUSION: These results show that good-to-excellent outcomes can be achieved following UKA and TKA in patients less than 65 years of age. A higher ARR was noted following UKA compared to TKA. However, improved functional outcomes, ROM and return to activity were found after UKA than TKA in this young population. Comparative studies are needed to confirm these findings and assess factors contributing to failure at the younger patient population. Outcomes of UKA and TKA in patients younger than 65 years are both satisfying, and therefore, both procedures are not contraindicated at younger age. UKA has several important advantages over TKA in this young and frequently more active population. LEVEL OF EVIDENCE: IV.

Midterm Survivorship and Patient Satisfaction of Robotic-Arm-Assisted Medial Unicompartmental Knee Arthroplasty: A Multicenter Study.

BACKGROUND: Studies have showed improved accuracy of lower leg alignment, precise component position, and soft-tissue balance with robotic-assisted unicompartmental knee arthroplasty (UKA). No studies, however, have assessed the effect on midterm survivorship. Therefore, the purpose of this prospective, multicenter study was to determine midtem survivorship, modes of failure, and satisfaction of robotic-assisted medial UKA. METHODS: A total of 473 consecutive patients (528 knees) underwent robotic-arm-assisted medial UKA surgery at 4 separate institutions between March 2009 and December 2011. All patients received a fixed-bearing, metal-backed onlay tibial component. Each patient was contacted at minimum 5-year follow-up and asked a series of questions to determine survival and satisfaction. Kaplan-Meier method was used to determine survivorship. RESULTS: Data were collected for 384 patients (432 knees) with a mean follow-up of 5.7 years (5.0-7.7). The follow-up rate was 81.2%. In total, 13 revisions were performed, of which 11 knees were converted to total knee arthroplasty and in 2 cases 1 UKA component was revised, resulting in 97% survivorship. The mean time to revision was 2.27 years. The most common failure mode was aseptic loosening (7/13). Fourteen reoperations were reported. Of all unrevised patients, 91% was either very satisfied or satisfied with their knee function. CONCLUSION: Robotic-arm-assisted medial UKA showed high survivorship and satisfaction at midterm follow-up in this prospective, multicenter study. However, in spite of the robotic technique, early fixation failure remains the primary cause for revision with cemented implants. Comparative studies are necessary to confirm these findings and compare to conventional implanted UKA and total knee arthroplasty.

Predicting the Feasibility of Correcting Mechanical Axis in Large Varus Deformities With Unicompartmental Knee Arthroplasty.

BACKGROUND: Due to disappointing historical outcomes of unicompartmental knee arthroplasty (UKA), Kozinn and Scott proposed strict selection criteria, including preoperative varus alignment of ≤15°, to improve the outcomes of UKA. No studies to date, however, have assessed the feasibility of correcting large preoperative varus deformities with UKA surgery. The study goals were therefore to (1) assess to what extent patients with large varus deformities could be corrected and (2) determine radiographic parameters to predict sufficient correction. METHODS: In 200 consecutive robotic-arm assisted medial UKA patients with large preoperative varus deformities (≥7°), the mechanical axis angle (MAA) and joint line convergence angle (JLCA) were measured on hip-knee-ankle radiographs. It was assessed what number of patients were corrected to optimal (≤4°) and acceptable (5°-7°) alignment, and whether the feasibility of this correction could be predicted using an estimated MAA (eMAA, preoperative MAA-JLCA) using regression analyses. RESULTS: Mean preoperative MAA was 10° of varus (range, 7°-18°), JLCA was 5° (1°-12°), postoperative MAA was 4° of varus (-3° to 8°), and correction was 6° (1°-14°). Postoperative optimal alignment was achieved in 62% and acceptable alignment in 36%. The eMAA was a significant predictor for optimal postoperative alignment, when corrected for age and gender (P < .001). CONCLUSION: Patients with large preoperative varus deformities (7°-18°) could be considered candidates for medial UKA, as 98% was corrected to optimal or acceptable alignment, although cautious approach is needed in deformities >15°. Furthermore, it was noted that the feasibility of achieving optimal alignment could be predicted using the preoperative MAA, JLCA, and age.

Regional Femoral and Tibial Radiolucency in Cemented Unicompartmental Knee Arthroplasty and the Relationship to Functional Outcomes.

BACKGROUND: Femoral and tibial radiolucent lines (RLL) after unicompartmental knee arthroplasty (UKA) can be categorized in physiological and pathological radiolucencies. Although physiological tibial radiolucency is assessed extensively in literature, studies reporting femoral radiolucency are lacking. Therefore, a retrospective study was performed to assess physiological femoral RLL and its relationship to short-term functional outcomes. METHODS: A total of 352 patients were included who underwent robotic-assisted medial UKA surgery and received a fixed-bearing metal-backed cemented medial UKA. Radiographic follow-up consisted of standard anteroposterior and lateral radiographs. Functional outcomes, using the Western Ontario and McMaster Universities Arthritis Index questionnaire, of patients with RLL were compared with a matched cohort, based on gender, age, and body mass index. RESULTS: In this cohort, 101 patients (28.8%) had physiological regional radiolucency around the femoral (10.3%) and/or tibial (25.3%) components, of which 6.8% concerned both components. Tibial RLL were more frequently seen compared with femoral RLL (P < .001). Our data suggest that the time of onset of femoral radiolucency develops later (1.36 years) than tibial radiolucency (1.00 years, P = .02). No difference in short-term functional outcomes was found between the RLL group and the matched cohort group without radiolucency. CONCLUSION: This study acknowledges that tibial and femoral physiological radiolucencies may develop after cemented medial UKA. Furthermore, this was the first study showing that physiological femoral RLL occur later than tibial RLL. Prospective studies with longer follow-up and larger numbers are necessary to compare radiolucency in different UKA designs and the relationship to outcomes.

Validity and Reliability of the Achillometer(®): An Ankle Dorsiflexion Measurement Device.

Limited ankle dorsiflexion is closely related to important foot and ankle pathologies. Various measurement devices and methods have been examined, but these have demonstrated limited validity and reliability. The purpose of the present study was to assess the validity and intra- and interobserver reliability of the Achillometer(®). A total of 22 consecutive subjects with ankle or foot pathologies and 39 healthy participants were included. All participants were measured using the goniometer and the Achillometer(®), a portable device used to assess ankle dorsiflexion in the weightbearing position with knee in extension. The intraclass correlation coefficient, standard error of the mean, and minimal detectable change were determined. The goniometer and Achillometer(®) revealed high intraobserver reliability coefficients with an intraclass correlation coefficient of 0.88 (standard error of the mean 1.49, minimal detectable change 4.12) and 0.85 (standard error of the mean 1.57, minimal detectable change 4.34), respectively. The interobserver reliability of both measurement techniques ranged from 0.63 to 0.67. The Achillometer(®) showed a strong correlation with the goniometer for both observers. In conclusion, the Achillometer(®) is a valid measurement device to assess ankle dorsiflexion range of motion in the weightbearing position with an extended knee in a heterogeneous population. The device has good intraobserver and moderate interobserver reliability and measurement properties comparable to those of the goniometer.

Ten-Year Survivorship and Patient Satisfaction Following Robotic-Arm-Assisted Medial Unicompartmental Knee Arthroplasty: A Prospective Multicenter Study.

BACKGROUND: Robotic-arm-assisted unicompartmental knee arthroplasty (UKA) has been shown to result in high short- and mid-term survivorship. However, it is not known whether these outcomes are maintained at long-term follow-up. This study aimed to evaluate long-term implant survivorship, modes of failure, and patient satisfaction following robotic-arm-assisted medial UKA. METHODS: A prospective multicenter study of 474 consecutive patients (531 knees) undergoing robotic-arm-assisted medial UKA was conducted. A cemented, fixed-bearing system with a metal-backed onlay tibial implant was used in all cases. Patients were contacted at 10-year follow-up to determine implant survivorship and satisfaction. Survival was analyzed using Kaplan-Meier models. RESULTS: Data were analyzed for 366 patients (411 knees) with a mean follow-up of 10.2 ± 0.4 years. A total of 29 revisions were reported, corresponding to a 10-year survivorship of 91.7% (95% confidence interval, 88.8% to 94.6%). Of all revisions, 26 UKAs were revised to total knee arthroplasty. Unexplained pain and aseptic loosening were the most commonly reported modes of failure, accounting for 38% and 35% of revisions, respectively. Of patients without revision, 91% were either satisfied or very satisfied with their overall knee function. CONCLUSIONS: This prospective multicenter study found high 10-year survivorship and patient satisfaction following robotic-arm-assisted medial UKA. Pain and fixation failure remained common causes for revision following cemented fixed-bearing medial UKA, despite the use of a robotic-arm-assisted technique. Prospective comparative studies are needed to assess the clinical value of robotic assistance over conventional techniques in UKA. LEVEL OF EVIDENCE: Prognostic Level II . See Instructions for Authors for a complete description of levels of evidence.

Selective pathological examination following hip arthroplasty: A retrospective cohort study.

BACKGROUND: Pathological examination of the femoral head after hip arthroplasty is often performed routinely. The cost-effectiveness of the examination with regard to identifying clinically relevant diagnoses has been a point of discussion. To date, recommendations on performing pathological examination based on patient characteristics, disease history or radiographic findings are scarce. The aim of this study was to gain insight in when to select a patient for pathological examination of the femoral head by means of the following research questions: "How many clinically relevant diagnoses does selective pathological examination identify?" "Which factors contribute to selection of the femoral head for conducting pathological examination?" "What are the costs of selective pathological examination for identifying clinically relevant diagnoses?" HYPOTHESIS: Selective pathological examination of the femoral head results in higher ratios of identified clinically relevant diagnoses against substantially lower costs. METHODS: A retrospective cohort study was performed over the period of 2010-2015. All pathological reports were collected from our hospital and screened for resected femoral heads after primary total hip arthroplasty (THA) or primary hemiarthroplasty (HA). The coherence between preoperative diagnosis and postoperative pathological diagnosis was defined as concordant, discrepant or discordant. The aim was to perform logistic regression analysis. RESULTS: In total, 164 patients were included of 3998 hip arthroplasties performed during the study period with a mean age of 74±12.3 years including 54 (33%) male and 110 (67%) female of whom 112 (68%) underwent THA and 52 (32%) HA. A discrepancy in diagnosis was found in nine patients (6%) and discordance in three patients (2%). The most frequently reported reasons to perform pathological examination were malignancy in medical history n=86 (53%), avascular necrosis n=22 (13%), bone abnormality perioperatively n=19 (11%) and pathological fracture n=13 (8%). The factors that identified the unexpected clinically relevant diagnoses were pathological fracture (3 cases out of 13), bone abnormality perioperatively (2 out of 19), abnormalities on preoperative radiographs (1 out of 9) and to a lesser extent malignancy in history (2 out of 86). With costs of pathological examination of approximately €163 per femoral head, performed in 164 patients, the total costs of pathological examination resulted in €26,732. The cost per discrepant case (n=9) was €2970 and the cost per discordant case (n=3) was €8910. CONCLUSION: Selective pathological examination of the femoral head following hip arthroplasty results in higher ratios of discrepant and discordant cases against substantially lower costs. Factors that identify clinically relevant diagnoses are pathological fracture, perioperative bone abnormality, abnormalities on preoperative radiographs and to a lesser extent malignancy in history. LEVEL OF EVIDENCE: III; retrospective cohort study.

Vascularity of the early post-natal human distal femoral chondroepiphysis: Quantitative MRI analysis.

Purpose: Injury to or abnormality of developing distal femoral chondroepiphysis blood supply has been implicated in osteochondritis dissecans development. Progressive decrease in epiphyseal cartilage blood supply occurs in normal development; however, based on animal studies, it is hypothesized that there is greater decrease in regions more prone to osteochondritis dissecans lesions. We aimed to quantify differential regional perfusion of the immature distal femoral chondroepiphysis. We hypothesized there is decreased perfusion in the lateral aspect of the medial femoral condyle, the classic osteochondritis dissecans lesion location. Methods: Five fresh-frozen human cadaveric knees (0-6 months old) were utilized. The superficial femoral artery was cannulated proximally and contrast-enhanced magnetic resonance imaging performed using a previously reported protocol for quantifying osseous and soft tissue perfusion. Regions of interest were defined, and signal enhancement changes between pre- and post-contrast images, normalized to background muscle, were compared. Results: When comparing average normalized post-contrast signal enhancement of whole condyles, as well as distal, posterior, and inner (toward the notch) aspects of the medial and lateral condyles, no significant perfusion differences between condyles were found. In the medial condyle, no significant perfusion difference was found between the medial and lateral aspects. Conclusion: We quantified immature distal femoral chondroepiphysis regional vascularity in the early post-natal knee. In specimens aged 0-6 months, no distinct watershed region was detected. Despite possible limitations, given small sample size, as well as resolution of magnetic resonance imaging and analysis, our results suggest the hypothesized vascular abnormality predisposing osteochondritis dissecans either does not occur universally or occurs after this developmental age.

Assessment of malreduction standards for the syndesmosis in bilateral CT scans of uninjured ankles.

AIMS: Malreduction of the syndesmosis has been reported in up to 52% of patients after fixation of ankle fractures. Multiple radiological parameters are used to define malreduction; there has been limited investigation of the accuracy of these measurements in differentiating malreduction from inherent anatomical asymmetry. The purpose of this study was to identify the prevalence of positive malreduction standards within the syndesmosis of native, uninjured ankles. METHODS: Three observers reviewed 213 bilateral lower limb CT scans of uninjured ankles. Multiple measurements were recorded on the axial CT 1 cm above the plafond: anterior syndesmotic distance; posterior syndesmotic distance; central syndesmotic distance; fibular rotation; and sagittal fibular translation. Previously studied malreduction standards were evaluated on bilateral CT, including differences in: anterior, central and posterior syndesmotic distance; mean syndesmotic distance; fibular rotation; sagittal translational distance; and syndesmotic area. Unilateral CT was used to compare the anterior to posterior syndesmotic distances. RESULTS: A difference of anterior to posterior syndesmotic distance > 2 mm was observed in 89% of ankles (n = 190) on unilateral CT assessment. Using bilateral CT, we found that 35% (n = 75) of normal ankles would be considered malreduced by current malreduction parameters. In 50 patients (23%), only one parameter was anomalous, 18 patients (8%) had two positive parameters and seven patients (3%) had three. Difference in fibular rotation had the lowest false positive rate of all parameters at 6%, whereas posterior syndesmotic distance difference had the highest at 15%. CONCLUSION: In this study, 35% of native, uninjured syndesmoses (n = 75) would be classified as malreduced by current diagnostic standards on bilateral CT and 89% had an asymmetric incisura on unilateral CT (n = 190). Current radiological parameters are insufficient to differentiate mild inherent anatomical asymmetry from malreduction of the syndesmosis. Cite this article: Bone Joint J 2021;103-B(1):178-183.

The Accuracy and Clinical Success of Robotic-Assisted Total Knee Arthroplasty.

Background: Robotic-assisted total knee arthroplasty (rTKA) has emerged as a patient-specific customizable tool that enables 3-dimensional preoperative planning, intraoperative adjustment, robotic-assisted bone preparation, and soft-tissue protection. Haptic rTKA may enhance component positioning, but only a few small studies have examined patient satisfaction and clinical outcomes after haptic rTKA. Purpose: In patients who underwent haptic rTKA, we sought to evaluate (1) the discrepancy in alignment between the executed surgical plan and implanted alignment in the coronal and sagittal planes 1 year postoperatively and (2) patient-reported outcomes 2 years postoperatively. Methods: From a prospectively collected database, we reviewed 105 patients who underwent haptic rTKA from August 2016 to May 2017. Two fellowship-trained arthroplasty surgeons independently reviewed hip-to-ankle standing biplanar radiographs to measure overall limb alignment and individual tibial and femoral component alignment relative to the mechanical axis and compared this to the executed surgical plan. Patient-reported outcomes were collected preoperatively and at 2 years postoperatively using the Lower Activity Extremity Score (LEAS), Knee Injury and Osteoarthritis Outcome Score Junior (KOOS Jr.), and Numeric Pain Rating Scale (NPRS). Results: Mean patient age was 62.4 years, and mean body mass index was 30.6 kg/m2. Interobserver reliability was significant with a κ of 0.89. Absolute mean deviations in postoperative coronal alignment compared to intraoperative alignment were 0.625° ± 0.70° and 0.45° ± 0.50° for the tibia and femur, respectively. Absolute mean deviations in postoperative tibial sagittal alignment were 0.47° ± 0.76°. Overall mechanical alignment was 0.97° ± 1.79°. Outcomes in LEAS, KOOS Jr., and NPRS changed from 8 to 10, 78 to 88.3, and 8 to 1, respectively. Conclusions: Haptic rTKA demonstrated high reliability and accuracy (less than 1°) of tibial coronal, femoral coronal, and tibial sagittal component alignment postoperatively compared to the surgical plan. Patient-reported outcomes improved, as well. A more rigorous study on long-term outcomes is warranted.

Quantitative assessment of the vascularity of the skeletally immature patella: a cadaveric study using MRI.

PURPOSE: While predominant blood supply to the adult patella enters inferomedially, little is known about skeletally immature patellar perfusion. Improved knowledge of immature patella vascularity can further understanding of osteochondritis dissecans, dorsal defects of the patella and bipartite patella, and help ensure safe surgical approaches. We hypothesized that the immature patella would exhibit more uniform blood flow. The study purpose was to quantify immature patella regional perfusion in comparison with adults. METHODS: Ten cadaveric knees were utilized (five immature, five mature). The superficial femoral artery was cannulated proximally. Signal enhancement increases were compared from pre- to post-contrast MRI to assess relative arterial contributions to patella regions (quadrants, anterior/posterior, superior/inferior, medial/lateral, and outer/inner). RESULTS: Quantitative-MRI analysis revealed similar distribution of enhancement between the immature and mature patella. The inferior pole exhibited significantly higher arterial contribution versus superior pole in both immature and mature groups (p = 0.009; both groups), while the inferomedial quadrant had the highest arterial contribution of all quadrants in both groups. The superolateral quadrant demonstrated the lowest arterial contribution in the immature group and second lowest in the adult group. The patella outer periphery had significantly greater arterial contribution than the inner central region in both immature (p = 0.009) and mature (p = 0.009) groups. CONCLUSION: Distribution of arterial contributions between the immature and mature patella was similar. Our results highlight the importance of inferior and inferomedial blood supply in both immature and mature patellas. These findings have implications for paediatric and adult patients; surgical damage to inferior patellar vessels should be avoided to prevent associated complications.

Mid-term survivorship and patient-reported outcomes of robotic-arm assisted partial knee arthroplasty.

AIMS: 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. METHODS: 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. RESULTS: 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. Cite this article: Bone Joint J 2020;102-B(1):108-116.

Pre-operative Static Anterior Tibial Translation Assessed on MRI Does Not Influence Return to Sport or Satisfaction After Anterior Cruciate Ligament Reconstruction.

BACKGROUND: It has been suggested that the degree of anterior tibial translation (ATT) as measured passively on imaging studies (static ATT) after an anterior cruciate ligament (ACL) injury may influence outcomes after ACL reconstruction. However, there is a lack of evidence supporting these suggestions. QUESTIONS/PURPOSES: The purpose of this retrospective prognostic study was to assess the predictive value of pre-operative static ATT in knees with ACL injury on return to sport and in satisfaction after ACL reconstruction. Our hypothesis was that greater static ATT would be associated with lower rates of return to sport and lower levels of satisfaction. METHODS: Patients treated with ACL reconstruction were identified from an institutional registry and assigned to one of three groups according to their ACL injury type: acute ACL injury, chronic ACL injury, and failed ACL reconstruction. ATT in each knee compartment was measured using magnetic resonance imaging, and a retrospective telephone questionnaire was used to investigate post-ACL reconstruction return to sport and subjects' satisfaction. RESULTS: One hundred thirty patients (52 acute with ACL injury, 29 with chronic ACL injury, and 49 with failed ACL reconstruction) completed the questionnaire, with a mean follow-up of 5.67 years. Ninety-seven patients (74.6%) returned to their primary sport, of whom 63 (65%) returned to the same level of sport. The mean time to return to sport was 10.1 months (range, 2 to 24 months). Overall, 113 patients (87%) were either very satisfied or satisfied with their outcomes. No difference in medial or lateral ATT was found between patients who returned to sport and those who did not. The failed-ACL reconstruction group had significantly lower rates of return to sport than did acutely and chronically injured patients (60.4% versus 88.5% and 75.9%, respectively). CONCLUSION: The degree of pre-operative ATT in an ACL-deficient knee was not correlated with return to sport or satisfaction after ACL reconstruction. In this study cohort, only failed-ACL reconstruction patients undergoing revision ACL reconstruction were significantly less likely to return to their main sport. They were also less likely to return to sport at their pre-operative level, if they did return to sport.

What is the impact of patellofemoral joint degeneration and malalignment on patient-reported outcomes after lateral unicompartmental knee arthroplasty?

AIMS: It remains controversial whether patellofemoral joint pathology is a contraindication to lateral unicompartmental knee arthroplasty (UKA). This study aimed to evaluate the effect of preoperative radiological degenerative changes and alignment on patient-reported outcome scores (PROMs) after lateral UKA. Secondarily, the influence of lateral UKA on the alignment of the patellofemoral joint was studied. METHODS: A consecutive series of patients who underwent robotic arm-assisted fixed-bearing lateral UKA with at least two-year follow-up were retrospectively reviewed. Radiological evaluation was conducted to obtain a Kellgren Lawrence (KL) grade, an Altman score, and alignment measurements for each knee. Postoperative PROMs were assessed using the Kujala (Anterior Knee Pain Scale) score, Knee Injury and Osteoarthritis Outcome Score Joint Replacement (KOOS JR), and satisfaction levels. RESULTS: A total of 140 knees (130 patients) were identified for analysis. At mean 4.1 years (2.0 to 8.5) follow-up, good to excellent Kujala scores were reported. The presence of mild to moderate preoperative patellofemoral joint osteoarthritis had no impact on these scores (KL grade 0 vs 1 to 3, p = 0.203; grade 0 to 1 vs 2 to 3, p = 0.674). Comparable scores were reported by patients with osteoarthritis (Altman score of ≥ 2) evident on either the medial or lateral patellofemoral joint facet (medial, p = 0.600 and lateral, p = 0.950). Patients with abnormal patellar congruence and tilt angles (≥ 17° and ≥ 14°, respectively) reported good to excellent Kujala scores. Furthermore, lateral UKA resulted in improvements to patellofemoral alignment. CONCLUSION: This is the first study demonstrating that mild to moderate preoperative radiological degenerative changes and malalignment of the patellofemoral joint are not associated with poor patient-reported outcomes at mid-term follow-up after lateral fixed-bearing UKA. Our data suggest that this may be explained by realignment of the patella and thereby redistribution of loads across the patellofemoral joint. Cite this article: Bone Joint J 2020;102-B(6):727-735.

Satisfaction with return to sports after unicompartmental knee arthroplasty and what type of sports are patients doing.

PURPOSE: The present study provides insight into patient satisfaction with return to sports after unicompartmental knee arthroplasty (UKA) and to what type of activities patients return. This is important because indications for UKA have expanded and younger and more active patients undergo surgery currently. METHODS: Patients who received a UKA were contacted between 12 and 24 months' post-surgery, receiving a questionnaire to evaluate postoperative satisfaction with return to sports, level of return, type of activities performed pre- and postoperatively, and (activity) outcome scores (NRS, UCLA, HAAS). Descriptive statistical analysis focused on the influence of patients' sex and age, and a regression model was fitted to assess the predictors for high satisfaction postoperatively. RESULTS: One hundred and sixty-four patients (179 UKAs) with a mean age of 62.3 years responded at an average follow-up of 20.2 months. Preoperatively, 132 patients (81%) participated in sports, which increased to 147 patients (90%) after UKA. Analyzing outcomes for each knee individually, satisfaction with return to sports was recorded in 83% (149/179). Return to a higher or similar level was reported in 85.4% of the cases (117/137). Most common sports after UKA were cycling (45%), swimming (38%), and stationary cycling (27%). Overall, 93.9% of patients were able to return to low impact sports, 63.9% to intermediate and 32.7% to high impact sports. Regarding activity scores, preoperative NRS score improved from 6.40 ±â€¯2.10 to 1.33 ±â€¯1.73 postoperatively (p < .001). The mean preoperative UCLA score improved from 5.93 ±â€¯2.19 to 6.78 ±â€¯1.92 (p < .001) and HAAS score from 9.13 ±â€¯3.55 to 11.08 ±â€¯2.83 postoperatively (p < .001). Regression analyses showed that male sex, preoperative UCLA score and sports participation predicted high activity scores postoperatively. CONCLUSION: The vast majority of patients undergoing medial UKA returned to sports postoperatively, of which over 80% was satisfied with their restoration of sports ability. Male patients, patients aged ≥70, and patients who participated in low-impact sports preoperatively achieved the highest satisfaction rates. Regarding type of sports, male patients and patients aged ≤55 were most likely to return to high and intermediate impact sports. This study may offer valuable information to help manage patients' expectations regarding their ability to return to sports based on demographics and type of preoperative sporting activities. LEVEL OF EVIDENCE: Case series; Level of evidence IV.

The Influence of Preoperative Radiographic Patellofemoral Degenerative Changes and Malalignment on Patellofemoral-Specific Outcome Scores Following Fixed-Bearing Medial Unicompartmental Knee Arthroplasty.

BACKGROUND: There is controversy as to whether the presence of degenerative changes and malalignment of the patellofemoral joint is a contraindication to medial unicompartmental knee arthroplasty. Therefore, the aim of the present study was to examine the influence of preoperative radiographic patellofemoral joint osteoarthritis and alignment on intermediate-term knee and patellofemoral joint-specific patient-reported outcomes following fixed-bearing medial unicompartmental knee arthroplasty. METHODS: We performed a retrospective review of the records on a consecutive series of patients who had undergone robotic arm-assisted fixed-bearing onlay medial unicompartmental knee arthroplasty and had a minimum duration of follow-up of 2 years. All records were collected from a single surgeon's arthroplasty registry. Patients with severe bone loss or grooving of the lateral patellar facet were excluded. Radiographic assessment was performed with use of the Kellgren-Lawrence and Altman classification systems as well as with patellofemoral joint alignment measurements. The latest follow-up consisted of a patient-reported questionnaire, including the Kujala (Anterior Knee Pain Scale) score, the Knee Injury and Osteoarthritis Outcome Score (KOOS), Junior (JR), and satisfaction levels. RESULTS: A total of 536 patients (639 knees) were included. After a mean duration of follow-up (and standard deviation) of 4.3 ± 1.6 years (range, 2.0 to 9.2 years), good-to-excellent Kujala scores were reported independent of the presence of patellofemoral joint osteoarthritis preoperatively (Kellgren-Lawrence grade 0 compared with ≥1, p = 0.82; grade ≤1 compared with ≥2, p = 0.84). Similar findings were found when osteoarthritis was present in either the medial or lateral side of the patellofemoral joint as defined by an Altman score of ≥2 (medial, p = 0.81; lateral, p = 0.90). KOOS scores and satisfaction also were not affected by degenerative patellofemoral joint changes. Furthermore, neither the patellar tilt angle nor the congruence angle influenced patient-reported outcomes. CONCLUSIONS: Preoperative radiographic mild to moderate patellofemoral joint degeneration (Kellgren-Lawrence grades 1 through 3) and/or malalignment did not compromise intermediate-term knee and patellofemoral joint-specific patient-reported outcomes in patients managed with fixed-bearing medial unicompartmental knee arthroplasty. On the basis of the results of the present study, we believe that neither mild to moderate patellofemoral degeneration nor abnormal patellar tilt or congruence should be considered a contraindication to fixed-bearing medial unicompartmental knee arthroplasty. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Outcomes of Presumed Aseptic Long-Bone Nonunions With Positive Intraoperative Cultures Through a Single-Stage Surgical Protocol.

OBJECTIVE: To evaluate the outcomes of a single-stage surgical protocol to treat a presumed aseptic long-bone nonunion with positive intraoperative cultures obtained at the time of surgery. DESIGN: Retrospective comparative series. SETTING: Orthopaedic specialty hospital. PATIENTS AND METHODS: We retrospectively identified 77 patients with long-bone nonunions thought to be aseptic preoperatively, which grew bacteria from cultures obtained at the time of index nonunion surgery. INTERVENTION: Fifty (65%) patients underwent open debridement of the nonunion site followed by surgical stabilization through plates and screws. Twenty-seven (35%) patients underwent exchange nailing with canal reamings used for cultures. MAIN OUTCOME MEASUREMENT: Rate of radiographic union, time to clinical and radiographic union, nonunion rate after index nonunion surgery, and final union rate after revision procedures. RESULTS: Osseous union after the index nonunion surgery was achieved in 84% of the patients (65 of 77). Time to clinical union was 6.3 months (range, 1-24 months), and time to radiographic union was 7.4 months (range, 2-24 months). Eighteen percent (14 of 77 patients) did not heal after the index nonunion surgery and required additional surgeries. The final union rate after revision surgery was 99% (76 of 77 patients). CONCLUSIONS: Eighty-four percent of presumed aseptic nonunions of long-bone fractures with positive intraoperative cultures fully healed after a single-stage surgical protocol and long-term antibiotic when appropriate. When patients are diagnosed with a subclinical infected nonunion, they should be counseled about the higher likelihood of reoperation, but in most cases can expect excellent union rates after 1 additional surgery. LEVEL OF EVIDENCE: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.