Increased Femoral Component Flexion and No Difference in Slope in Robotic- versus Computer-Assisted Total Knee Arthroplasty When Targeting Mechanical Alignment.

Robotic-assisted surgery (RAS) in total knee arthroplasty (TKA) is becoming popular due to better precision, when compared with other instrumentation. Although RAS has been validated in comparison with computer-assisted surgery (CAS), data from clinical settings comparing these two techniques are lacking. This is especially the case for sagittal alignment. Whereas pure mechanical alignment (MA) aims for 0 to 3 degrees of flexion of the femoral component and 3° of posterior slope for the tibial component, adjusted MA (aMA) mostly used with RAS allows for flexing of the femoral component for downsizing and increase of slope for an increase of the flexion gap. In the present study, we compared sagittal alignment after TKA using RAS with aMA and CAS targeting MA, which has been the standard in the center for more than 10 years. We analyzed a prospectively collected database of patients undergoing TKA in a single center. Femoral component flexion and tibial slope were compared for both techniques. In 140 patients, 68 CAS and 72 RAS, we found no difference in tibial slope (p = 0.661), 1° median femoral component flexion (p = 0.023), and no difference in outliers (femur, p = 0.276, tibia, p = 0.289). RAS slightly increases femoral component flexion, but has no influence on tibial slope, when compared with CAS in TKA. If MA is the target, RAS provides no benefit over CAS for achieving the targeted sagittal alignment. LEVEL OF EVIDENCE: Level III retrospective study.

Blood loss after revision knee arthroplasty is 1.38- to 2.17-fold higher than after primary knee arthroplasty: A retrospective analysis of 898 cases.

BACKGROUND: There are a number of factors that influence blood loss during and after primary total knee arthroplasty (TKA) and revision TKA (rTKA). The purpose of this study was to provide a factorial assessment that would aid surgeons in managing expected blood loss in rTKA, when compared to TKA. The first question asked was the blood loss and transfusions between TKA and rTKA and the second question was risk factors for blood loss after rTKA. HYPOTHESIS: Blood loss in any rTKA is higher than in TKA by a factor of 2. PATIENTS AND METHODS: A retrospective single-centre consecutive series of rTKA between 2006 and 2018 was performed. Based on the rTKA types identified in joint registries, 4 rTKA cohorts were created: aseptic minor rTKA, aseptic major rTKA, 1st stage, and 2nd stage septic rTKA. A consecutive TKA cohort from the same study period was used to create a propensity score matched cohort with the aseptic major rTKA cohort. RESULT: A total of 622 rTKA were identified. Aseptic major rTKA had double the median blood loss than TKA. The lowest blood loss was observed in the TKA group followed by aseptic minor rTKA, and the highest in 2nd stage septic rTKA. The median total blood loss was higher in all rTKA by a factor ranging between 1.38 and 2.17. Higher age, female gender, lower preoperative hemoglobin, chronic heart disease and history of myocardial infarction were risk factors for increased blood loss. The type of rTKA performed was not predictive of blood loss in the linear regression analysis. DISCUSSION: Blood loss after rTKA is 1.38 to 2.17-fold higher than after TKA. The blood loss observed in 2nd stage septic rTKA and aseptic major rTKA was the highest. Older female patients, with a low preoperative hemoglobin, were identified to be at the highest risk of blood loss after rTKA. Strategies for further blood loss reductions need to be utilised to the fullest extent for these procedures. LEVEL OF EVIDENCE: III; retrospective prognostic study.

Tegner level is predictive for successful return to sport 2 years after anterior cruciate ligament reconstruction.

PURPOSE: For a successful return to sport (RTS) after an anterior cruciate ligament reconstruction (ACLR), patients are recommended to attend a comprehensive rehabilitation program, followed by an RTS assessment, that is a combination of tests. The purpose of this study was to predict a successful return to sport using the results of the RTS assessment and self-reported questionnaires at minimum 2 years after ACLR. METHODS: A total of 123 consecutive ACLR patients undertook an intensive rehabilitation program followed by a comprehensive RTS assessment that included an established combination of balance and strength tests, the ACL-return to sport after Injury scale (ACL-RSI) questionnaire and a KT1000 laximetry test. Preinjury and expected Tegner and Lysholm were collected at baseline, at RTS and prospectively collected at minimum 2-year follow-up. The patients were asked if they returned to their previous sport and at which level. All variables were included in a regression analysis predicting a successful return to previous sport, return to the same level of sport as well as the Tegner level at 2 years. RESULTS: Sixty-two patients (50%) returned to their previous sport by the 2-year follow-up, without a difference in preinjury Tegner between these two groups (n.s.). Expected preoperative Tegner was the only significant predictor of a successful return to previous sport (p = 0.042; OR 1.300, 95% CI 1.010-1.672). Out of the 62 patients returning to their previous sport, 38 (61%) reported to be on the same or higher level. The only predictive variable for returning to the same level was the higher preinjury Tegner level (p = 0.048; OR 1.522). Multivariate regression analysis of Tegner level at 2 years found younger age to be the only predictive value. From the RTS assessment tests, the ACL-RSI questionnaire and the posterolateral balance test were predictive variables for Tegner at 2-year follow-up, albeit in the univariate regression analysis. CONCLUSIONS: Preoperative Tegner and expected Tegner level collected prior to an ACL reconstruction can aid in the objective prediction of patients' return to sport after 2 years. High-level athletes are more likely to return to their previous sport and to the previous level. Younger patients achieve a higher Tegner level at 2 years. LEVEL OF EVIDENCE: Level III study.

Should Sequential Bilateral Total Knee Arthroplasty Be Limited to Patients Younger than 80? A Two-Arm Propensity Matched Study.

Despite multiple studies, there remains a debate on the safety of bilateral total knee arthroplasty (BTKA) in the average age patient, with a paucity of data on the outcome of BTKA in an elderly population. This study included 89 patients aged 80 years and older undergoing sequential BTKA over 14 years were identified in a prospectively collected database. Two matched comparison groups were created: patients under 80 undergoing sequential BTKA and patients over 80 undergoing unilateral TKA (UTKA). An analysis of complications, mortality, revision, and patient-reported outcome measures was performed. Mean age of the elderly cohorts was similar: 82.6 for BTKA and 82.9 for UTKA. The average age BTKA cohort had a mean age of 69.1. Complication rates were higher in bilateral cohorts, more so in the elderly BTKA cohort. Pulmonary embolism (PE) was observed in bilateral cohorts only. In these patients, history of PE and ischemic heart disease was a strong predictive factor for developing a major complication. There was no difference in revision rates and infection rates between the three cohorts, and no difference in patient survivorship between the two elderly cohorts. Through the combination of low revision and high survivorship rates and comparable clinical outcomes, this article demonstrates that simultaneous BTKA is an appropriate option to consider for an elderly patient, with proper patient selection and perioperative management. The demonstrated risk groups show that emphasis on patient selection should be focused on medical history rather than chronological age.

Predictors of Functional Outcome After Microfracture Treatment of Cartilage Defects of the Knee.

INTRODUCTION: Microfracture (MFx) is a widely used technique in the treatment of articular cartilage defects of the knee. The objective of this study was to determine the prognostic factors of functional outcomes after MFx treatment of knee cartilage defects ≤ 4 cm2. MATERIALS AND METHODS: Forty-eight patients who were to be treated by MFx for knee cartilage defects ≤ 4 cm2 were prospectively included. The mean follow-up was 5.7 years (3.7-9.5). Demographics, sport practiced, time from diagnosis to surgery and associated lesions were collected. The cartilage defect was graded according to the ICRS classification. The MOCART score was calculated from a one-year MRI. The subjective VAS and IKDC scores were collected preoperatively and at the latest follow-up. Prognostic factors were determined using univariate and multivariate regression analyses incorporating pre-, peri- and postoperative clinical and radiological criteria. The dependent variable was defined as the difference between the pre- and post-operative clinical scores (dIKDC and dVAS). RESULTS: The mean size of the cartilage defect was 1.8 cm2 (0.8-4). At the last follow-up, the VAS and IKDC scores were significantly improved compared to the pre-operative period (p<0.01). The average MOCART score on the one-year MRI was 50 (20-70). Three patients (6 %) who demonstrated filling defects on MRI and debilitating pain required surgical re-intervention. The factors that impacted the functional outcome as reflected by the VAS and IKDC scores were age, BMI, time from diagnosis to surgery, size of the lesion and the MOCART score. CONCLUSION: This study demonstrates that MFx is a successful first-line treatment option for small articular cartilage defects (≤ 4 cm2) of the knee and provides good function and pain relief in the mid-term. The predictors of poor functional outcomes were older age, higher BMI, longer time from diagnosis to surgery, larger lesion size and lower MOCART score.

Patients with lateral compartment knee osteoarthritis during arthroscopy are at highest risk of subsequent knee arthroplasty.

BACKGROUND: Arthroscopic treatment of knee osteoarthritis has declined, in part due to concerns with conversion to arthroplasty. Some studies have investigated the demographic predictors for conversion to arthroplasty, few have assessed the risk factors within the knee itself. Our aim was to analyse the demographics and anatomical wear features of a large cohort of patients undergoing knee arthroscopy. METHODS: A retrospective analysis of 1760 cases spanning over 17 years undergoing knee arthroscopy was performed. Patients were 36 years or older at time of the index arthroscopy. Each patient received the International Cartilage Regeneration and Joint Preservation Society (ICRS) grade of all regions as well an estimate of the remaining meniscal percentage. Demographic factors as well as intraoperatively collected data were analysed as predictive variables for subsequent conversion to arthroplasty using a multi-step Cox regression analysis. RESULTS: A total of 102 patients (6.2%) were converted to arthroplasty. Age at arthroscopy (hazard ratio (HR) 1.073; 95% confidence interval (CI) 1.058-1.088) and ICRS grade of the lateral tibial plateau (HR 1.166; 95% CI 1.066-1.276) were statistically significant predicting variables for conversion to arthroplasty. CONCLUSIONS: The results of this study indicate that higher ICRS grade of the lateral tibial plateau at arthroscopy is the most significant predictor for conversion to knee arthroplasty, with a hazard equal to an increase in age. The absence of these factors does not justify arthroscopic treatment of patients with knee osteoarthritis. LEVEL OF EVIDENCE: III.

Anterior knee translation measurements after ACL reconstruction are influenced by the type of laximeter used.

PURPOSE: Laximeters were designed to diagnose an anterior cruciate ligament (ACL) deficient knee, but their use has now focused on providing an objective assessment of the anterior translation (AT) of an intact and ACL-reconstructed knee. In this study we report the introduction and direct comparison of an automated and computerized AT measurement device, GNRB, with the device previously established by the institute and as the current literature standard, the KT1000. METHODS: A prospective data collection was commenced upon introduction of the GNRB. The measurements of AT in each patient were performed by the same investigator with each device using 134 N applied to both knees, giving a side-to-side difference. The investigators were a sport scientist, a biomechanical engineer and a physiotherapist. Increased AT was defined as a difference > 3 mm. RESULTS: Three investigators performed the measurements in 122 patients, 9.8 (± 1.8) months after ACL reconstruction. Mean AT of the healthy knee was 5.7 mm with KT1000 and 4.4 mm with GNRB (p = 0.002). Mean AT of the ACL reconstructed knee was 7.0 mm with the KT1000 and 5.3 mm with the GNRB (p = 0.037). The KT1000 had a higher variance of results than the GNRB (p < 0.001). There were 25 patients with increased AT measured by KT1000 compared with 12 patients using the GNRB (p < 0.016), with only 5 on both devices. CONCLUSIONS: GNRB has better consistency of results when compared to the KT1000. Both devices lack comparability for detecting increased AT, with the KT1000 recording a side-to-side difference of more than 3 mm in twice as many patients as the GNRB. LEVEL OF EVIDENCE: II.

Conventional instruments are more accurate for measuring the depth of the tibial cut than computer-assisted surgery in total knee arthroplasty: a prospective study.

INTRODUCTION: The most commonly used tool for implant positioning are conventional instruments (CI) followed by computer-assisted surgery (CAS). A number of studies have investigated the cutting error of the tibial component when CAS is used, but most of them were focused on the cutting angles. The accuracy of CAS to determine the depth of the cut has not received much attention, even though implications are similar or worse, than with an angle mismatch. MATERIALS AND METHODS: This was an ethics board approved, prospective study of 23 consecutive varus TKAs by a single surgeon. Implant positioning was performed using CAS; however, the depth of the tibial cut was determined with both CAS and CI. Targeted alignment was the mechanical axis and 3° of posterior slope. The planned and the achieved cut, as determined by CAS needed to match. The achieved cut was then measured using a caliper and compared to the depth of the cut as per CAS. Medial and lateral cuts were analyzed separately. Analysis of variance and Bland-Altman plots were used for the comparison. RESULTS: Mean medial navigated cut was 6.3 (± 2.2) mm, mean measured medial cut was 6.6 (± 2.3) mm. Mean lateral navigated cut was 8.9 (± 1.8) mm, mean measured lateral cut was 8.8 (± 1.5) mm. There was a statistical significance for both the medial (p < 0.001) and the lateral (p = 0.004) navigated and measured cuts. CONCLUSIONS: The results of this study suggest that the tibial cut depth, measured by the navigation, does not match the actual bony cuts performed, even if a perfect cut was achieved in both sagittal and coronal plane. Surgeons should be aware of the measurement error in the navigation system and potentially add an additional step for verifying the achieved depth of the cut.

Healthy knee KT1000 measurements of anterior tibial translation have significant variation.

PURPOSE: The most commonly used arthrometer for measuring and reporting anterior tibial translation after anterior cruciate ligament reconstruction is the KT1000. Reports on its consistency and reproducibility vary in the literature, but it remains the "gold standard". The purpose of this study was to assess agreement of KT1000 measurements in a daily clinical setting. METHODS: A retrospective analysis of anterior knee translation in the healthy knee of 770 patients over a 17-year time period was performed. In this cohort, a total of 24 investigators performed 1890 measurement sets at 89 Newtons (N), 134N and at maximum manual force (MMax) level. To assess the inter- and intra-observer agreement, the intraclass-correlation coefficient (ICC) was calculated. The "investigator effect" was a difference between two examiners in the same patient and the "device effect'' a difference within one examiner in the same patient. Minimally important difference (MID) was calculated as 0.5 of the standard deviation. RESULTS: Thirteen investigators were female, performing 1099 measurements and 11 were male, performing 791 measurements. ICC ranged between 0.558 and 0.644. At the MMax level, male investigators had a higher mm reading than female investigators (p < 0.001). Increased experience did not correlate with a higher ICC. MID ranged between 0.85 and 1.65 mm. CONCLUSION: This study investigated the KT1000 arthrometer in a clinical setting with a large number of investigators. This device delivers moderate agreement of results. Both the device and investigator effect are present. The MMax level has shown the lowest agreement and a dependency on the investigator gender. LEVEL OF EVIDENCE: Level III diagnostic study.

The prevalence of a prominent anterior inferior iliac spine.

INTRODUCTION: Impingement of the prominent anterior inferior iliac spine (AIIS) against the femoral neck has recently been described as another type of impingement. The purpose of this study is to provide a distribution of AIIS types using the classification proposed by Hetsroni and thus report on the prevalence of prominent types. MATERIALS AND METHODS: A total of 400 patients were included in the study with an average age 27.3 ± 6.9 years (range 18-40). All patients received a whole-body polytrauma computer tomography (CT) scan in the emergency room (ER) upon arrival. The classification of AIIS proposed by Hetsroni et al., which describes three morphological types, was used. Type II and III were grouped as prominent types. The measurements were performed in all three planes by two examiners. RESULTS: Male to female ratio was 71:29. Type I was observed in 367 (91.7%) patients. Type II was observed in 31 (7.8%) patients and type III was observed in 2 (0.5%) patients, unilaterally. Prominent types were much more prevalent in men (10.5%) than in women (2.6%). The CT assessment demonstrated excellent intra- and interreliability (overall: 0.926, I/II: 0.906, III: 1.000). CONCLUSION: A young population demonstrates a prevalence of a prominent AIIS of 11.5%. Prominent AIIS is more common in men than in women.