Tibia-first, gap-balanced patient-specific alignment restores bony phenotypes and joint line obliquity in a great majority of varus and straight knees and normalises valgus and severe varus deformities.

PURPOSE: The present study focuses on testing the capability of a restricted tibia-first, gap-balanced patient-specific alignment technique (PSA) to restore bony morphology and phenotypes. METHODS: Three-hundred and sixty-seven patients were treated with navigated total knee arthroplasty and tibia-first gap-balanced PSA technique. Boundaries for medial proximal tibial angle were 86°-92°, mechanical lateral distal femoral angle 86°-92°, and hip-knee-ankle angle 175°-183°. Knees were classified by coronal plane alignment of the knee (CPAK), with subsequent analyses comparing pre- and postoperative distributions. Phenotype classification within CPAK groups assessed pre- and postoperative distributions. RESULTS: Preoperatively, the largest CPAK group was type II (30.8%), followed by type I (20.5%) and type V (17.8%). Postoperatively, type II remained the largest group (39%), followed by type V (30%). All groups with varus/valgus deformities (I, III, IV and VI) became smaller. While in straight legs (II, IV), the CPAK was restored in more than 70%-75%, in varus groups (I, IV) in 40%-50% and in valgus (III and VI) in 5%-18%. The joint line obliquity remained the same in the majority of knees (straight >75%; varus 63%-80%; valgus VI 95%), with the exception of CPAK III (40%). The phenotype analysis showed for straight legs a phenotype restoration of 85%, for varus 94% and for valgus 37%. Joint line convergence angle was reduced significantly in all groups from 1.8°-4.3° preoperatively to 0.6°-1.2° postoperatively. CONCLUSION: PSA restores bony phenotypes and joint line obliquity in the majority of straight and varus knees, while most of the valgus and extreme varus knees are normalised. LEVEL OF EVIDENCE: Level III, retrospective cohort study.

Tibia-first, gap-balanced patient-specific alignment technique achieves well-balanced gaps in 90% of cases by rebuilding bony anatomy within boundaries.

PURPOSE: Patient-specific alignment (PSA) technique tries to achieve balanced gaps and simultaneously rebuild the individual bony phenotype. The hypothesis was: PSA technique achieves balanced knees in a high percentage with more anatomical resections than adjusted mechanical alignment (AMA). METHODS: Three hundred sixty-seven patients underwent navigated total knee arthroplasty (TKA) with a tibia-first gap-balanced PSA technique. Resection boundaries for medial proximal tibia angle (MPTA) of 86-92°, mechanical lateral distal femoral angle (mLDFA) of 86-92°, and hip-knee-ankle angle (HKA) of 175-185° were defined. Preoperative and intraoperative parameters of HKA, MPTA, mLDFA, and gap widths were recorded. Depending on the coronal deformity, the patients were divided into three groups: varus HKA < 178°; straight 178-182° and valgus HKA > 182°. The stability was analysed by assessing the difference between medial and lateral extension and flexion gaps as well as between flexion and extension gaps. All PSA measurements were compared with data from a previously published AMA series. RESULTS: PSA achieved balanced gaps in extension, flexion and between flexion/extension in over 90% of cases, being similar to AMA. In PSA, MPTA and mLDFA were restored within 1°, except in extreme varus (MPTA difference 2°) and valgus knees (mLDFA difference 3°). This was caused by the defined boundaries of the alignment technique. This individualised reconstruction led to significantly more anatomical resections of all tibia and femur resections. CONCLUSION: A tibia-first, gap-balanced PSA technique achieves balanced joints in more than 90% of cases. By maintaining preoperative MPTA and mLDFA to a high extent, far more anatomical resections, compared to AMA were performed. Future studies need to be conducted to investigate whether those promising intraoperative results correlate with postoperative patient outcomes and whether patients outside the 5° corridor have higher failure rates. LEVEL OF EVIDENCE: Level III, retrospective cohort study.

Independent of the preoperative coronal deformity, adjusted mechanical alignment leads in a high percentage to non-anatomical tibial and femoral bone cuts.

PURPOSE: The technique of adjusted mechanical alignment (AMA) in total knee arthroplasty (TKA) has been described to achieve alignment and balancing goals in varus knees in a high percentage, albeit at the price of non-anatomical bone cuts. The purpose of this study was to analyze (1) whether AMA achieves similar alignment and balancing results in different types of deformity and (2) whether they can be achieved without altering the native anatomy. METHODS: A series of 1000 patients with hip-knee-ankle (HKA) angles from 165° to 195° were analyzed. All patients were operated using AMA technique. According to the preoperative HKA angle, three groups of knee phenotypes (varus, straight, valgus) were defined. The bone cuts were analyzed for being anatomic (< 2 mm deviation of individual joint surface) or non-anatomic (> 4 mm deviation of individual joint surface). RESULTS: AMA reached the goals for postoperative HKA in over 93% in every group (varus: 636 cases, 94%, straight: 191 cases, 98%, valgus: 123 cases, 98%). In 0° extension, the gaps were balanced in varus knees in 654 cases (96%), in straight knees in 189 cases (97%) and in valgus knees in 117 cases (94%). A balanced flexion gap was found in a similar number of cases (varus: 657 cases, 97%, straight: 191 cases, 98%, valgus: 119 cases, 95%). In the varus group, non-anatomical cuts were performed at the medial tibia (89%) and the lateral posterior femur (59%). The straight group showed similar values and distribution for non-anatomical cuts (medial tibia: 73%; lateral posterior femur 58%). Valgus knees showed a different distribution of values, being non-anatomical at the lateral tibia (74%), distal lateral femur (67%) and posterior lateral femur (43%). CONCLUSION: In all knee phenotypes, the AMA goals were achieved in a high percentage by altering the patients' native anatomy. In varus knees, the alignment was corrected by non-anatomical cuts at the medial tibia, and in valgus knees at the lateral tibia and the lateral distal femur. All phenotypes showed non-anatomical resections on the posterior lateral condyle in approximately 50% of cases. LEVEL OF EVIDENCE: III.

Digital TKA Alignment Training with a New Digital Simulation Tool (Knee-CAT) Improves Process Quality, Efficiency, and Confidence.

Individual alignment techniques have been introduced to restore patients' unique anatomical variations during total knee arthroplasty. The transition from conventional mechanical alignment to individualised approaches, with the assistance of computer and/or robotic technologies, is challenging. The objective of this study was to develop a digital training platform with real patient data to educate and simulate various modern alignment philosophies. The aim was to evaluate the training effect of the tool by measuring the process quality and efficiency, as well as the post-training surgeon's confidence with new alignment philosophies. Based on 1000 data sets, a web-based interactive TKA computer navigation simulator (Knee-CAT) was developed. Quantitative decisions on bone cuts were linked to the extension and flexion gap values. Eleven different alignment workflows were introduced. A fully automatic evaluation system for each workflow, with a comparison function for all workflows, was implemented to increase the learning effect. The results of 40 surgeons with different experience levels using the platform were assessed. Initial data were analysed regarding process quality and efficiency and compared after two training courses. Process quality measured by the percentage of correct decisions was increased by the two training courses from 45% to 87.5%. The main reasons for failure were wrong decisions on the joint line, tibia slope, femoral rotation, and gap balancing. Efficiency was obtained with a reduction in time spent per exercise from 4 min 28 s to 2 min 35 s (42%) after the training courses. All volunteers rated the training tool as helpful or extremely helpful for learning new alignment philosophies. Separating the learning experience from OR performance was mentioned as one of the main advantages. A novel digital simulation tool for the case-based learning of various alignment philosophies in TKA surgery was developed and introduced. The simulation tool, together with the training courses, improved surgeon confidence and their ability to learn new alignment techniques in a stress-free out-of-theatre environment and to become more time efficient in making correct alignment decisions.

Navigated, gap-balanced, adjusted mechanical alignment achieves alignment and balancing goals in a very high percentage but with partially non-anatomical resections.

PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Direct, Cementless, Metaphyseal Fixation in Knee Revision Arthroplasty With Sleeves-Short-Term Results.

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.

Is tartrate-resistant acid phosphatase 5b a potent bio-marker for late stage aseptic implant loosening?

PURPOSE: Aseptic loosening is a serious complication after total joint arthroplasty. Plain radiography, along with clinical signs of prosthesis loosening, is the technique of first choice to evaluate loosening of joint replacements. Nevertheless, radiographical signs of osteolysis may not be apparent until progressed stages of loosening. Thus the search for alternative diagnostic methods is of great importance. The purpose of the present study was to evaluate the potential diagnostic significance of TRAP 5b, Osteocalcin, CrossLaps and Bone ALP for aseptic loosening of total joint replacements. METHODS: Thirty-seven patients (25 women, 12 men, mean age 65 years, age range 54-76 years) treated with revision surgery due to clinically and radiologically confirmed late aseptic prosthesis loosening were examined prospectively. Serum levels of TRAP 5b, Osteocalcin, CrossLaps and Bone ALP were compared with a matched control group (n = 39). RESULTS: We found a significant decrease in TRAP 5B level in patients with aseptic loosening. Bone ALP and Osteocalcin as markers of osteoblast activity, and CrossLaps as another resorption marker did not allow any prediction of bone remodeling in this late phase of loosening. CONCLUSION: In the "late" phase of aseptic joint replacement loosening, no increase of TRAP 5b and therefore no increase of osteoclast number and activity was measurable. Thus, in this situation an anti-osteolytic therapy with a bisphosphonate or denosumab would not gain any further benefit.

A new navigation-based technique for lateral distalizing condylar osteotomy in patients undergoing total knee arthroplasty with fixed valgus deformity.

PURPOSE: In a prospective, consecutive study, a navigation-based technique for calculating the sliding distance of the lateral epicondyle prior to osteotomy in TKA surgery of fixed valgus deformity has been developed, and early results have been evaluated. MATERIALS AND METHODS: Twenty-seven knees with a fixed valgus deformity undergoing TKA received this new treatment. Clinical scores and radiograph evaluation were performed preoperatively and 1-year postoperatively. Static and dynamic kinematic data were obtained from navigation at the beginning and at the end of surgery. RESULTS: The calculated amount of sliding distance varied between 5 and 16 mm. No complications regarding this technique occurred. All clinical scores showed a significant improvement, and radiological evaluation showed a correction of all parameters in 100 % of patients. CONCLUSION: With this navigation-based technique, it is possible to calculate the amount of sliding distance prior to osteotomy and obtain excellent early results. All axes have been corrected completely, and flexion and extension gaps were balanced. No specific complications of this technique have occurred so far. LEVEL OF EVIDENCE: II.