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Navigated, gap-balanced adjusted mechanical alignment (AMA) including a 0° varus tibial cut and modification of angles and resections of the femoral cuts to obtain optimal balance accepting minor axis deviations. Objectives of this study were (1) to analyse to what extent AMA achieves the goals for leg alignment and gap balance, and (2) in what percentage non-anatomical cuts are needed to achieve these goals.Out of 1000 total knee arthroplasties (TKA) all varus knees (hip-knee-ankle (HKA) angle 178°; n = 680) were included. All surgeries were performed as computer assisted surgery (CAS) in AMA technique. CAS data at the end of surgery were analysed with respect to HKA and gap-sizes. All bone cuts were quantified. Depending on the amount of deformity, a subgroup analysis was performed. It was analysed whether the amount of deformity influences the non-anatomical cuts by correlation analysis.AMA reached the goals for postoperative HKA (3° corridor) in 636 cases (93.5%). While extension and flexion gap balance were achieved in more than 653 cases (96%), flexion and extension gap size were equalled in 615 knees (90.4%). The resections of the lateral tibia plateau and distal and posterior medial femoral condyle were anatomical (Tibia: 7.0 ± 1.7 mm; medial condyle distal: 7.8 ± 1.4 mm; medial posterior: 8.2 ± 1.8 mm). The number of non-anatomical resections for those cuts were low; 67 (9.9%); 24 (3.5%); 32 (4.7%). For the medial tibia plateau and the lateral posterior condyle, the cuts were non-anatomical in a high percentage of cases; Tibia: 606 (89.1%), lateral posterior condyle: 398 (58.5%). Moderate but significant correlations were found between resection differences and amount of deformity (medio-lateral: tibia: 0.399; distal femur: 0.310; posterior femur: 0.167). No correlations were found between resection differences and gap values.AMA reaches the intended target for HKA and gap balance in over 612 (90%) of cases and maintains the medial femoral condyle anatomically. Non-anatomical tibial resection causes increased external rotation of the femoral component and by that non-anatomical cut of the posterior lateral condyle. Nonanatomical resections of AMA might be one reason for the persisting high rate of unsatisfied patients after TKA. Anatomical and individual alignment philosophies might help to reduce this rate of dissatisfaction.

Metaphyseal sleeves have shown an improved fixation in Revision Total Knee Arthroplasty (R-TKA) leading to a reduced aspetic loosening rate compared to other stem based fixation options. In the majority of these studies sleeve have been used with stems. Due to that is was not clear how much of this improved fixation could be rated to the sleeve and how much to the additional sleeves. In this review article we analysed the results of sleeve-only obtained in in-vitro or in-vivo studies. In Vitro models showed independent of the set-up a dominant fixation of the sleeve, an additional stem was not adding a lot to the overall fixation. Undersized additional stems showed an increased micromotion and the stem tip, while distal engaging stems showed a proximal stress shielding effect. Very interestingly an increased BMI had not a significant effect on primary fixation of the sleeve. Reduced bone quality on the other hand had and this effect was increased in cases with an increased BMI. In vivo results of sleeve-only patients showed comparable good results to sleeve and stem constructs. In particular on the femoral side the use of an additional stem is required only in a few scenarios. It has to be stated that the numbers of sleeves-only in rotating hinges is too low, to give any recommendation for this high constraint implants. Majority of cases was done with PS and VVC constraint. So far no in vivo data exist on the limitations of sleeve-only in patients with reduced bone quality and increased body weight. In conclusion we can state, that Sleeve-only is an option for R-TKA. In majority of cases the aspetic loosening rate is as low as with additional stems. The borderlines in terms of constraint, bone quality and body weight need to be investigated in future in vivo studies. The in vitro results look so far encouraging.

The purpose of this study was to investigate the dynamic gap widths of valgus knees in extension and flexion to evaluate the influence of deformity on gap differences and to find out whether different ligamentous subtypes in valgus knees exist.Dynamic gap widths of 1000 consecutive total knee arthroplasty (TKA) patients were measured at different flexion angles by applying a computer-assisted surgery (CAS) technique. 198 knees showed a valgus deformity and were assessed regarding its degree of fulfillment of the following criteria of valgus knee: 1. Medial extension gap greater than lateral; 2. Medial flexion gap greater than lateral; 3. Flexion gap greater than extension gap. A single-factor ANOVA subgroup analysis was performed, based on the amount of deformity. The effect of other patient factors (age, gender, weight) on gap differences was investigated.The medial extension gap (3.7 ± 2.2 mm) was significantly (p 0.01) larger than the lateral extension gap (1.1 ± 2.9 mm). The amount of deformity correlated highly with gap difference in extension (rValgus knees show large variability in terms of gap widths. The extent of deformity correlates highly with gap difference in extension, but not in other flexion angles. Vast majority of valgus knees were valgus in extension only. Because of this variability, it should be aimed for an individualized balancing technique based on intraoperative gap sizes.Level III.

We cannot deny that technology has become an important part of our daily life, not only in automobiles, houses or cellphones but also in hospitals. In the OR, in particular for knee arthroplasty, image free navigation has proven to reduce the number of outliers and by that the revision rate in younger patients. Over the last years robotics has again been introduced into the operation theatres. However, in their present version they add time and costs, but only minimal benefits to the procedure. Therefore, future robots should be faster and instrumentation free. Beside those more economical aspects, the goal of this digital technology must be an improvement in clinical outcome. To achieve that, additional steps for analyzing the pre-, and intra-OP quantitative data is key. With the use of artificial intelligence and/or machine learning a data based algorithm will probably be developed, which helps the surgeon to integrate all parameters into his individual cutting and releasing plan for each patient. Digital data therefore, might become the key to enable the surgeon to treat patients more individual and by that hopefully deliver better outcome.

Background Various options exist for implant fixation in revision total knee arthroplasty. One of it is direct cementless metaphyseal sleeve fixation with stems, which has shown excellent short-term and midterm results. Stemless fixation of sleeves is another fixation option for the treatment of specific bone defects; however, so far no data in larger series exist. The objective of this study was, therefore, to analyze the midterm (3-6.5 years) results of stemless sleeve fixation in a larger revision total knee arthroplasty series. Methods In this prospective study, 85 patients with 109 stemless sleeves have been assessed with a mean follow-up of 58.2 (36-78) months. An exclusion criterion was uncontained type II and type III defects. Analysis included clinical and radiographic assessment. Results The results showed a survival rate of sleeves in 96% of the tibia (27/28) and 100% of the femur (81/81). This results in an overall survival rate of sleeves of 99% (108/109). So far, 10 patients (11.8%) underwent rerevision during the follow-up period. The main reason for failure was infection (4/85; 4.7%). Range of motion, Oxford Knee Score, Knee Society Score, and Functional Score improved significantly. Mechanical leg alignment was within the 3° corridor in all patients. Conclusions In cases with type I and contained type II defects, sleeves without stems are a promising option, with a survival rate of sleeves of 99% after 5 years. Also, the clinical improvement and reconstruction of leg alignment showed excellent results. In uncontained defects and type III defects, however, we do recommend using stems for additional fixation in the diaphysis. Although the midterm results are very promising, long-term data are needed.

To achieve a higher level of satisfaction in patients having undergone Total Knee Arthroplasty (TKA), a more personalized approach has been discussed recently. It can be assumed that a more profound knowledge of bony morphology and ligamentous situation would be beneficial. While CT/MRI can give 3D information on bone morphology, the understanding of the ligamentous situation in different flexion angles is still incomplete. In this study, the dynamic gap widths of a large number of varus knees were assessed in various flexion angles, to find out whether all varus knees behave similar or have more individual soft tissue patterns. Additionally, it was investigated whether the amount of varus deformity or other patient factors have an effect on joint gap widths. A series of 1000 consecutive TKA patients, including their CAS data and patient records were analyzed. Joint gap widths in multiple flexion angles (0°, 30°, 60°, 90°) were measured in mm and differences between the joint gaps were compared. A “standard” varus knee was defined as follows: (1) Lateral extension gap greater than medial, (2) lateral flexion gap greater than medial, and (3) flexion gap greater than extension gap. The percentage of fulfillment was tested for each and all criteria. To measure the influence of varus deformity on gap width difference, three subgroups were formed based on the deformity. Data were analyzed at 0°, 30°, 60° and 90° flexion. The effect of patient factors (gender, BMI, age) on gap sizes was tested by performing subgroup analyses. Only 444 of 680 (65%) patients met all three varus knee criteria. The lateral extension gap (4.1 mm) was significantly larger than the medial extension gap (0.6 mm) in 657 (97%) patients and the gap difference highly correlated with the amount of varus deformity (r2 = 0.62). In all flexion positions, however, no correlation between gap differences and varus deformity existed. Women had significantly larger extension and flexion gaps. Age and BMI showed no significant effect on gap widths. Varus knees show a large inter-individual variability regarding gap widths and gap differences. The amount of varus deformity correlates highly with the medio-lateral gap difference in extension, but not in any flexion angle. As varus knees are not all alike, a uniform surgical technique will not treat all varus knees adequately and the individual gap sizes need to be analyzed and addressed accordingly with an individualized balancing technique. Which final balancing goal should be achieved needs to be analyzed in future studies. Level III.

Due to the compromised bone situation revision implants need extended fixation options in order to achieve good long-term survival. Over decades this has been achieved with stems, either cemented or uncemented. In the last decade additional fixation options in terms of cementless metaphyseal sleeves or metaphyseal cones have been introduced and widely accepted. Revision of such implants is challenging, in particular if those porous coated parts are well integrated. Therefore, partial revision leaving the well-fixed parts in place can be an option if the indication is allowing it. This can help to preserve bone. In this study we show 2 cases with metaphyseal sleeves, in which we demonstrate when and how revision can be performed leaving sleeves in place. Meticulous pre-Op analysis of the failure mechanism is mandatory to find those few cases in which a partial revision can be recommended. In our cases, it was one patient with persistent tibia stem pain and another patient with secondary instability. In both cases implant fixation was not the problem, and therefore leaving the well-fixed sleeves in place was considered. Before final decision was made, specific information on implants sizes and constraint are needed. In our tibial revision stem thickness was less than 14 mm decision, in this situation the stem can be removed through the sleeve, leaving the sleeve in place. The technique how to do it, is shown in this study. In the second case a traumatic MCL rupture was leading to a secondary instability, needing a revision from a VVC constraint to a rotating hinge. Again, pre-Op analysis and the surgical technique of femoral component removal are described. In the great majority of cases a full revision with complete implant removal is required. In a few cases a partial revision with maintenance of implant parts can be considered but only after careful analysis of the failure mode. Even if the failure mode allows a partial revision specific implant information need to be obtained to clarify whether it is really possible. If it is possible, a specific surgical technique is recommended and described in this study.

Clinical outcome of TKA remains unsatisfactory in 20% of the cases. Navigation has added accuracy in terms of alignment, but has improved clinical outcome only in small series with gap-balanced techniques. Reason for that could be that conventional gap balanced TKA determines gaps in extension and 90° of flexion only. Furthermore, measurement is only static. Therefore, the accuracy of a new dynamic navigation software which allows gap assessment throughout the entire range of motion was tested. The purpose of this study was to investigate the accuracy and reliability of dynamic gap testing during gap-balanced TKA. In two different centres, a total of 65 TKA procedures were performed in a tibia-first, gap-balanced technique using a new CAS software. At the same and at different time points of surgery, two different surgeons performed gap measurement to provide inter-observer reliability data and repeated gap measurement to provide intra-observer reliability data. These gap measurements were performed throughout the entire ROM under dynamic stress testing to detect maximum gap values. CAS surgery was able to produce correct coronal alignment in 96.4% of the cases (within 3° mechanical alignment). Both inter-observer and intra-observer reliabilities were excellent for gap values throughout the entire ROM. Inter-observer bias of deviation 0.05; 95% limits of agreement of − 2.1 to + 2.21 mm. Intra-observer bias of deviation 0.09; 95% limits of agreement of − 2.27 to + 2.44 mm. This new CAS software in combination with the presented dynamic gap measurement provides accurate gap values and therefore facilitates balancing TKA. This technique works reproducibly for different surgeons and has proven robustness also for repeated measurements of any surgeon in this study.

Background Different methods exist for deformity correction and ligament balancing in total knee arthroplasty (TKA) of valgus knees, the sliding osteotomy being one of them. The objective of the current study was to analyze the clinical and radiological short-term and mid-term results of this technique in a larger series. Methods Between June 2007 and May 2014, 98 patients were treated with 98 TKAs and a simultaneous sliding osteotomy. All of them had a Grade 2 fixed valgus deformity (between 10° and 20°). All patients received a mobile-bearing, non-constrained (CR) implant. After prospective inclusion (T1), patients were clinically assessed after one (T2) and 4.5 years (± 2.1 years) (T3), and radiological and Oxford Knee Score (OKS), Knee Society Knee Score (KSS) and the Knee Society Function Score (KSF) were obtained. Results All knees were corrected to a mechanical leg alignment within three degrees. Significant improvement of all scores could be measured at T2 and T3. Seven revisions needed to be performed; three of them were procedure-related. In two of them, a problem of capsular closure occurred, while in one the slided epicondyle dislocated after three months. All other revisions were performed because of non-procedure-related problems (e.g. infection). Conclusions Sliding osteotomy of the lateral condyle is a successful option for the treatment of Grade 2 fixed valgus deformity. Due to this technique, higher constraint could be avoided. The results stayed constant over time. The procedure-related complications need to be kept in mind. Long-term results still need to be awaited.

Different options for implant fixation in revision TKA exist. Small series have been published on direct cementless fixation with sleeves. The objective of this study was to analyze the short- and mid-term results of sleeve-fixation in a large revision TKA series. In this prospective study 121 patients with 193 sleeves (119 tibial and 74 femoral) were included. Mean follow-up was 3.6 years (2-6.1 years). Analysis included clinical and radiographic assessment. ROM, KSS and Functional Score improved significantly. Fourteen patients (11.4%) underwent operative re-revision during the follow-up period. Direct cementless fixation in the metaphysis by sleeves is a promising option for implant fixation in revision TKA, both on the tibial and femoral side.