Mechanical alignment (MA) techniques for total knee arthroplasty (TKA) may introduce significant anatomic modifications, as it is known that few patients have neutral femoral, tibial or overall lower limb mechanical axes. A total of 1000 knee CT-Scans were analyzed from a database of patients undergoing TKA. MA tibial and femoral bone resections were simulated. Femoral rotation was aligned with either the trans-epicondylar axis (TEA) or with 3° of external rotation to the posterior condyles (PC). Medial-lateral (DML) and flexion-extension (DFE) gap differences were calculated. Extension space ML imbalances (3mm) occurred in 25% of varus and 54% of valgus knees and significant imbalances (5mm) were present in up to 8% of varus and 19% of valgus knees. For the flexion space DML, higher imbalance rates were created by the TEA technique (p < 0 .001). In valgus knees, TEA resulted in a DML in flexion of 5 mm in 42%, compared to 7% for PC. In varus knees both techniques performed better. When all the differences between DML and DFE are considered together, using TEA there were 18% of valgus knees and 49% of varus knees with < 3 mm imbalances throughout, and using PC 32% of valgus knees and 64% of varus knees. Significant anatomic modifications with related ML or FE gap imbalances are created using MA for TKA. Using MA techniques, PC creates less imbalances than TEA. Some of these imbalances may not be correctable by the surgeon and may explain post-operative TKA instability. Current imaging technology could predict preoperatively these intrinsic imitations of MA. Other alignment techniques that better reproduce knee anatomies should be explored

INTRODUCTION. Mechanical alignment in TKA introduces significant anatomic modifications for many individuals, which may result in unequal medial-lateral or flexion-extension bone resections. The objective of this study was to calculate bone resection thicknesses and resulting gap sizes, simulating a measured resection mechanical alignment technique for TKA. METHODS. Measured resection mechanical alignment bone resections were simulated on 1000 consecutive lower limb CT-Scans from patients undergoing TKA. Bone resections were simulated to reproduce the following measured resection mechanical alignment surgical technique. The distal femoral and proximal tibial cuts were perpendicular to the mechanical axis, setting the resection depth at 8mm from the most distal femoral condyle and from the most proximal tibial plateau (Figure 1). If the resection of the contralateral side was <0mm, the resection level was increased such that the minimum resection was 0mm. An 8mm resection thickness was based on an implant size of 10mm (bone +2mm of cartilage). Femoral rotation was aligned with either the trans-epicondylar axis or with 3 degrees of external rotation to the posterior condyles. After simulation of the bone cuts, media-lateral gap difference and flexion-extension gaps difference were calculated. The gap sizes were calculated as the sum of the femoral and tibial bone resections, with a target bone resection of 16mm (+ cartilage corresponding to the implant thickness). RESULTS. For both the varus and valgus knees, the created gaps in the medial and lateral compartments were reduced in the vast majority of cases (<16mm). The insufficient lateral condyle resection distalises the lateral joint surface by a mean of 2.1mm for the varus and 4.4mm for the valgus knees. The insufficient medial tibial plateau resection proximalises the medial joint surface by 3.3mm for the varus and 1.2mm for the valgus knees. Medio-lateral gap imbalances in the extension space of more than 2mm) occurred in 25% of varus and 54% of valgus knees and significant imbalances of more than 5mm were present in up to 8% of varus and 19% of valgus knees. Higher medio-lateral gap imbalances in the flexion space were created with trans epicondylar axis versus 3 degrees to the posterior condyles (p<0.001). Using trans epicondylar axis, only 49% of varus and 18% of valgus knees had less than 3mm of imbalance in both media-lateral and flexion-extension gaps together. DISCUSSION AND CONCLUSION. A systematic use of the tested measured resection mechanical alignment technique for TKA leads to many cases with medio-lateral or flexion-extension gap asymmetries. Some medio-lateral imbalances may not be correctable surgically and may results in TKA instability. Other versions of the mechanical alignment technique or other alignment methods that better reproduce knee anatomies should be explored. For any figures or tables, please contact the authors directly

Abstract. Background. Conventional TKR aims for neutral mechanical alignment which may result in a smaller lateral distal femoral condyle resection than the implant thickness. We aim to explore the mismatch between implant thickness and bone resection using 3D planning software used for Patient Specific Instrumentation (PSI) TKR. Methods. This is a retrospective anatomical study from pre-operative MRI 3D models for PSI TKR. Cartilage mapping allowed us to recreate the native anatomy, enabling us to quantify the mismatch between the distal lateral femoral condyle resection and the implant thickness. Results. We modelled 292 knees from PSI TKR performed between 2012 and 2015. There were 225 varus knees and 67 valgus knees, with mean supine hip-knee-angle of 5.6±3.1 degrees and 3.6±4.6 degrees, respectively. In varus knees, the mean cartilage loss from medial and lateral femoral condyle was 2.3±0.7mm and 1.1±0.8mm respectively; the mean overstuffing of the lateral condyle 1.9±2.2mm. In valgus knees, the mean cartilage loss from medial and lateral condyle was 1.4±0.8mm and 1.5±0.9mm respectively; the mean overstuffing of the lateral condyle was 4.1±1.9mm. Conclusions. Neutral alignment TKR often results in overstuffing of the lateral condyle. This may increase the patello-femoral pressure at the lateral facet in flexion. Anterior knee pain may be persistent even after patellar resurfacing due to tight lateral retinacular structures. An alternative method of alignment such as anatomic alignment may minimise this problem

The Coronal Plane Alignment of the Knee (CPAK) is a recent method for classifying knees using the hip-knee-ankle angle and joint line obliquity to assist surgeons in selection of an optimal alignment philosophy in total knee arthroplasty (TKA)1. It is unclear, however, how CPAK classification impacts pre-operative joint balance. Our objective was to characterise joint balance differences between CPAK categories. A retrospective review of TKA's using the OMNIBotics platform and BalanceBot (Corin, UK) using a tibia first workflow was performed. Lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) were landmarked intra-operatively and corrected for wear. Joint gaps were measured under a load of 70–90N after the tibial resection. Resection thicknesses were validated to recreate the pre-tibial resection joint balance. Knees were subdivided into 9 categories as described by MacDessi et al.1 Differences in balance at 10°, 40° and 90° were determined using a one-way 2-tailed ANOVA test with a critical p-value of 0.05. 1124 knees satisfied inclusion criteria. The highest proportion of knees (60.7%) are CPAK I with a varus aHKA and Distal Apex JLO, 79.8% report a Distal Apex JLO and 69.3% report a varus aHKA. Greater medial gaps are observed in varus (I, IV, VII) compared to neutral (II, V, VIII) and valgus knees (III, VI, IX) (p<0.05 in all cases) as well as in the Distal Apex (I, II, III) compared to Neutral groups (IV, V, VI) (p<0.05 in all cases). Comparisons could not be made with the Proximal Apex groups due to low frequency (≤2.5%). Significant differences in joint balance were observed between and within CPAK groups. Although both hip-knee-ankle angle and joint line orientation are associated with joint balance, boney anatomy alone is not sufficient to fully characterize the knee

Management of a knee with valgus deformities has always been considered a major challenge. Total knee arthroplasty requires not only correction of this deformity but also meticulous soft tissue balancing and achievement of a balanced rectangular gap. Bony deformities such as hypoplastic lateral condyle, tibial bone loss, and malaligned/malpositioned patella also need to be addressed. In addition, external rotation of the tibia and adaptive metaphyseal remodeling offers a challenge in obtaining the correct rotational alignment of the components. Various techniques for soft tissue balancing have been described in the literature and use of different implant options reported. These options include use of cruciate retaining, sacrificing, substituting and constrained implants. Purpose. This presentation describes options to correct a severe valgus deformity (severe being defined as a femorotibial angle of greater than 15 degrees) and their long term results. Methods. 34 women (50 knees) and 19 men (28 knees) aged 39 to 84 (mean 74) years with severe valgus knees underwent primary TKA by a senior surgeon. A valgus knee was defined as one having a preoperative valgus alignment greater than 15 degrees on a standing anteroposterior radiograph. The authors recommend a medial approach to correct the deformity, a minimal medial release and a distal femoral valgus resection of angle of 3 degrees. We recommend a sequential release of the lateral structures starting anteriorly from the attachment of ITB to the Gerdy's tubercle and going all the way back to the posterolaetral corner and capsule. Correctability of the deformity is checked sequentially after each release. After adequate posterolateral release, if the tibial tubercle could be rotated past the mid-coronal plate medially in both flexion and extension, it indicated appropriate soft tissue release and balance. Fine tuning in terms of final piecrusting of the ITB and or popliteus was carried out after using the trial components. Valgus secondary to an extra-articular deformity was treated using the criteria of Wen et al. In our study the majority of severe valgus knees (86%) could be treated by using unconstrained (CR, PS) knee options reserving the constrained knee / rotating hinge options only in cases of posterolateral instability secondary to an inadequate large release or in situations with very lax or incompetent MCL. Results. The average follow up was 10 years (range 8 to 14 years). The average HSS knee scores improved from 48 points preoperatively (range 32 to 68 points) to 91 points (range 78 to 95 points) postoperatively. The average postoperative range of motion measured with a goniometer was 110 degrees (range 80 to 135 degrees) which was a significant improvement over the preoperative levels (average 65 degrees). None of the patients were clinically unstable in the medioloateral or anteroposterior plane at the time of final follow up. The average preoperative valgus tibiofemoral alignment was 19.6 degrees (range 15 degrees to 45 degrees). Postoperatively the average tibio-femoral alignment was 5 degrees (range 2 degrees to 7 degrees) of valgus. No patient in the study was revised. Conclusion. Adequate lateral soft tissue release is the key to successful TKA in valgus knees. The choice of implant depends on the severity of the valgus deformity and the extent of soft tissue release needed to obtain a stable knee with balanced flexion and extension gaps. The most minimal constraint needed to achieve stability and balance was used in this study. In our experience the long term results of TKR on severe valgus deformities using minimal constrained knee have been good

Introduction. The deformity in osteoarthritis (OA) of the knee has been evaluated mainly in the frontal plane two dimensional X-ray using femorotibial angle. Although the presence of underlying rotational deformity in the varus knee and coexisting hip abnormality in the valgus knee have been suggested, three dimensional (3D) deformities in the varus and valgus knee were still unknown. We evaluated the 3D deformities of the varus and valgus knee using 3D bone models. Methods. Preoperative computed tomography (CT) scans of twenty seven OA knees (fifteen varus and twelve valgus) undergoing total knee arthroplasty were assessed in this study. CT scans of each patient's femur and tibia, with a 2 mm interval, obtained before surgery. We created the 3D digital model of the femur and tibia using visualization and modeling software developed in our institution. The femoral coordinate system was calculated by the 3D mechanical axis and clinical transepicondylar axis and the tibial coordinate system was calculated by the 3D mechanical axis and Akagi's line. The 3D deformities of the knee were determined by the relative position of the femorotibial coordinate system, and described by the tibial position relative to the femur. The anteversion of the femoral neck were calculated to evaluate the relationship between the valgus knee and hip region. Results. The 3D deformities of the varus knee were 12.1±5.5°varus (5.4 to 22.6°), 6.8±6.3°flexion (1.7 to 21.7°) and 6.5±6.1 °external rotation (−1.2 to 23.2°). The flexion and external rotational deformities were larger in knees with increased varus deformities. The 3D deformities of the valgus knee were 10.2±4.2°valgus (0.6 to 15.0°), 9.5±8.8°flexion (−5.2 to 23.7°) and 2.3±7.3°external rotation (−9.4 to 16.1°). Although there were no tendency about the 3D deformities in the valgus knee, the anteversion of the femoral neck in the valgus knees was 31.9°compared with 10.8°in the varus knees. Conclusion. The varus deformity in OA of the knee is associated with significant flexion and external rotational deformity. In contrast, the valgus deformity has a biomechanical background originating from the anteversion of the femoral neck

Introduction. To evaluate the results of correction of knee deformities based on deformity analysis in Achondroplasia, the commonest skeletal dysplasia as some have concomitant ligamentous deformities. Materials and Methods. Retrospective study from a prospective database (2007–2020) of achondroplasts who underwent growth modulation. Analysis of medical records with objective measurement of mechanical axis radiographs was done (Traumacad). Satisfactory alignment was defined as neutral to slightly varus (0–15 mm MAD) so that the MCL/LCL laxity is not revealed. Results. 23 patients, 41 limbs, 34 bilateral, 6 unilateral underwent multiple growth modulation procedures. 2 had valgus knees. 15 patients underwent proximal fibular epiphysiodesis in addition for LCL laxity with one isolated fibular epiphysiodesis. Mechanical axis deviation (MAD) improved or normalised in 16 patients (70%). 4 patients were still undergoing correction. 4 patients needed further surgery out of which 2 patients were over 13 years when growth modulation was attempted and 2 needed correction of ankle varus. JLCA improved/ normalised in 12 patients (75%) with evidence of indirect LCL tightening and no improvement was seen in 4. The rate of correction was MAD 0.61mm/month, LDFA 0.29°/month and MPTA 0.13°/month; expectedly lower in achondroplasia due to lower growth velocity. Conclusions. This study highlights the pathology, application of growth modulation as per deformity analysis unlike previous studies. Proximal fibular epiphysiodesis improves LCL laxity in a majority of these children and is a simple procedure compared to our published series with indirect LCL tightening with frames

For many years, achieving a neutral coronal Hip-Knee-Ankle angle (HKA) measured on radiographs has been considered a factor of success for total knee arthroplasty (TKA). Lower limb HKA is influenced by the acquisition conditions, and static HKA (sHKA) may not be representative of the dynamic loading that occurs during gait. The primary aim of the study was to see if the sHKA is predictive of the dynamic HKA (dHKA). A secondary aim was to document to what degree the dHKA changes throughout gait. We analysed the 3-D knee kinematics during gait of a cohort of 90 healthy individuals (165 knees) with the KneeKG™ system. dHKA was calculated and compared with sHKA values. Knees were considered “Stable” if the dHKA remained positive or negative – i.e. in valgus or varus – for greater than 95% of the corresponding phase and “Changer” otherwise. Patient characteristics of the Stable and Changer knees were compared to find contributing factors. The dHKA absolute variation during gait was 10.9±5.3° [2 .4° – 28.3°] for the whole cohort. The variation was greater for the varus knees (10.3±4.8° [2.4° – 26.3°]), than for the valgus knees (12.8±6.1° [2.9° – 28.3°], p=0.008). We found a low to moderate correlation (r = 0.266 to 0.553, p < 0 .001) between sHKA and the dHKA values for varus knees and no correlation valgus knees. Twenty two percent (36/165) of the knees demonstrated a switch in the dHKA (Changer). Proportion of Changer knees was 15% for varus sHKA versus 39% for valgus sHKA (p < 0.001). Lower limb radiographic measures of coronal alignment have limited value for predicting dynamic measures of alignment during gait

Alignment of total joint replacement in the valgus knee can be done readily with intramedullary alignment and hand-held instruments. Intramedullary alignment instruments usually are used for the femoral resection. The distal femoral surfaces are resected at a valgus angle of 5 degrees. A medialised entry point is advised because the distal femur curves toward valgus in the valgus knee, and the distal surface of the medial femoral condyle is used as reference for distal femoral resection. In the valgus knee, the anteroposterior axis is especially important as a reliable landmark for rotational alignment of the femoral surface cuts because the posterior femoral condyles are in valgus malalignment, and are unreliable for alignment. Rotational alignment of the distal femoral cutting guide is adjusted to resect the anterior and posterior surfaces perpendicular to the anteroposterior axis of the femur. In the valgus knee this almost always results in much greater resection from the medial than from the lateral condyle. Intramedullary alignment instruments are used to resect the proximal tibial surface perpendicular to its long axis. Like the femoral resection, resection of the proximal tibial surface is based on the height of the intact medial bone surface. After correction of the deformity, ligament adjustment is almost always necessary in the valgus knee. Stability is assessed first in flexion by holding the knee at 90 degrees and maximally internally rotating the extremity to stress the medial side of the knee, then maximally externally rotating the extremity to evaluate the lateral side of the knee. Medial opening greater than 4mm, and lateral opening greater than 5mm, is considered abnormally lax, and a very tight lateral side that does not open at all with varus stress is considered to be abnormally tight. Stability is assessed in full extension by applying varus and valgus stress to the knees. Medial opening greater than 2mm is considered to be abnormally lax, and a very tight lateral side that does not open at all with varus stress is considered to be too tight. Release of tight structures should be done in a conservative manner. In some cases, direct release from bone attachment is best (popliteus tendon); in others, release with pie-crusting technique is safe and effective. In knees that are too tight laterally in flexion, but not in extension, the LCL is released in continuity with the periosteum and synovial attachments to the bone. When this lateral tightness is associated with internal rotational contracture, the popliteus tendon attachment to the femur is also released. The iliotibial band and lateral posterior capsule should not be released in this situation because they provide lateral stability only in extension. The only structures that provide passive stability in flexion are the LCL and the popliteus tendon complex, so knees that are tight laterally in flexion and extension have popliteus tendon or LCL release (or both). Stability is tested after adjusting tibial thickness to restore ligament tightness on the lateral side of the knee. Additional releases are done only as necessary to achieve ligament balance. Any remaining lateral ligament tightness usually occurs in the extended position only, and is addressed by releasing the iliotibial band first, then the lateral posterior capsule, if needed. The iliotibial band is approached subcutaneously and released extrasynovially, leaving its proximal and distal ends attached to the synovial membrane. In knees initially too tight laterally in extension, but not in flexion, the LCL and popliteus tendon are left intact, and the iliotibial band is released. If this does not loosen the knee enough laterally, the lateral posterior capsule is released. The LCL and popliteus tendon rarely, if ever, are released in this type of knee. Finally, the tibial component thickness is adjusted to achieve proper balance between the medial and lateral sides of the knee. Anteroposterior stability and femoral rollback are assessed, and posterior cruciate substitution is done, if necessary, to achieve acceptable posterior stability

Background. Achieving a neutral static Hip-Knee-Ankle angle (sHKA) measured on radiographs has been considered a factor of success for total knee arthroplasty (TKA). However, recent studies have shown that sHKA seems to have no effect on TKA survivorship. sHKA is not representative of the dynamic loading occurring during gait, unlike the dynamic HKA (dHKA). Research question. The primary objective was to see if the sHKA is predictive of the dynamic HKA (dHKA). A secondary objective was to document to what degree the dHKA changes during gait. Methods. We analysed 3D knee kinematics during gait of a cohort of 90 healthy individuals with the KneeKG™ system. dHKA was calculated and compared with sHKA. Knees were considered “Stable” if the dHKA remained in valgus or varus for greater than 95% of the corresponding phase, and “Changer” otherwise. Patient characteristics of the Stable and Changer knees were compared to find associated factors. Results. dHKA absolute variation during gait was 10.9±5.3° for the whole cohort. The variation was less for the varus knees (10.3±4.8°), than for the valgus knees (12.8±6.1°, p=0.008). We found low to moderate correlations (r=0.266 to 0.553, p<0.001) between sHKA and dHKA values for varus knees and no significant correlation for valgus knees. Twenty two percent (36/165) of the knees were considered Changers. The proportion of knees that were Changers was 15% of the varus versus 39% of the valgus (p < 0.001). Significance. Lower limb radiographic measures of coronal alignment have limited value for predicting dynamic measures of alignment during gait

Aims. The aim of this retrospective study was to measure and determine variation in VCA between the two limbs in a patient with windswept deformity on preoperative full-length, standing, hip-to-ankle radiographs. We hypothesised that there will be significant difference in VCA between the two limbs of a patient with arthritic windswept deformity and therefore it is necessary to individualise VCA for each limb preoperatively on full-length radiographs during TKA. Patients and Methods. In this retrospective study, femoral valgus correction angle (VCA) measured on full-length, hip-to-ankle, standing radiographs was compared between the varus and the valgus limbs in 63 patients with windswept deformities who underwent TKA. Results. The mean VCA in varus knees was significantly higher compared to mean VCA in valgus knees (p=0.002). The VCA was <5° in 40% of valgus knees compared to 6% in varus knees (p=0.0001) whereas VCA was 5°–7° in 73% of varus knees compared to 47% in valgus knees (p=0.0003). There was no difference in the percentage of varus or valgus knees with VCA >7° (p=0.18). A difference in VCA of <3° between the two limbs was seen in 63% of patients, a difference of ≥3° between the two limbs was seen in 18% of patients and 19% of patients had no difference in VCA between the two limbs. Conclusion. Significant difference in VCA is present between the varus and the valgus limbs in most patients withwindswept deformity undergoing TKA. Clinical Relevance. It may be necessary to individualise VCA for each limb preoperatively on full-length radiographs in patients with windswept deformities in order to minimize error while performing the distal femoral cut during TKA

Background. Total knee arthroplasty has been performed even for severe valgus knee. All ligaments around knee must be balanced to obtain good clinical results. Especially medial collateral ligament plays a role as a stabilizer. For severe valgus knee, however, deep medial collateral ligament (dMCL) located closely to the articulating tibial surface [Fig. 1] can be damaged by bone resection in standard tibial osteotomy which may leads to progress valgus deformity. Purpose. There are no report of dMCL preserved total knee arthroplasty for sever valgus knee. Thus it was evaluated the clinical outcomes of total knee arthroplasty for severe valgus knees using dMCL preservation technique. Methods. Twenty six knees of 18 osteoarthritis and 8 rheumatoid arthritis with severe valgus deformity (from 10° to 56°) underwent TKA between January 2006 and January 2014 was reviewed retrospectively. All surgeries were conducted by lateral parapatellar approach. Additional four mm resection was conducted on distal femur. Resection level at tibia was one to three mm below the medial joint line to preserve dMCL. GENESIS II PS with high flex insert (Smith and Nephew) was used for 25 knees. One knee with 56° valgus deformity that had no end point of MCL was required Rotating Hinge Prosthesis (Link). Mean follow up time was four years (range one to nine years). Results. Mean Japanese Orthopaedic Association (JOA) score and femorotibial angle was improved from 53°±12.6 to 84°±7.6 and from 159°±9.3 preoperatively to 172.6°±2.3 postoperatively, respectively (both P<0.001). Mean extension range of motion were improved significantly from −14.8°±13.1 to −2.3°±4.7 (P<0.001). Mean flexion range of motion, however were not changed significantly from 115.8°±25.9 to 121.3°±20.8 (P>0.05). No patient had any postoperative complications including deep infection, peroneal palsy, loosening of the implant and pulmonary embolism. Every valgus knee underwent total knee arthroplasty using dMCL preservation technique had static end point of MCL at the last follow up. No progress of the valgus deformity was found and revision surgery for every case in this study. No potential COI to disclose

Introduction. Valgus knee deformity is associated especially with differences in anatomy between medial and lateral femoral condyles. Vertically smaller lateral condyle and more distally located medial condyle cause valgus deformity in extension. The anteroposterior dimensions of both condyles influence the knee axis in flexion. In a „true“ valgus knee there is a mismatch between both condyles in both the vertical and anteroposterior dimensions, the lateral condyle is generally smaller. In a „false“ valgus knee there is no mismatch between anteroposterior dimensions of both condyles, the knee axis changes from valgus into varus with increased degree of flexion and lateral soft tissue structures are that's why not so contracted as in „true“ valgus knee deformity, where the knee stays in valgus deviation during the whole range of motion. The aim of the study was to preoperatively identify and analyse patterns of passive movement of osteoarthritic valgus knees with imageless navigation system to optimise surgical approach and intra-operative tissue handling during subsequent total knee replacement (TKR) surgery. Material and Methods. TKR were prospectively performed in 50 valgus knees. Cases with severe bony destruction and enormous soft tissue laxity were excluded from the study. The kinematic navigation system used was OrthoPilot® (Aesculap, Tuttlingen, Germany). It is designed to produce a numerical output of varus/valgus deviation of the knee against the degree of flexion. Before skin incision for TKR surgery, active markers were attached percutaneusly to the femur and the tibia with bicortical screws to create two ‘rigid bodies’. After the registration process the kinematic analysis was performed by passive movement of the knee. The mechanical axis was recorded at 0°, 30°, 60°, 90°, and 120° of flexion. The valgus deformity persistent through the whole range of motion was called „true“ and the valgus deformity passing into varus with flexion was called „false“. In „true“ valgus knees the lateral approach according to Keblish was used, in „false“ valgus knees we used standard medial parapatellar approach. Results. The pre-operative valgus deformity in extension ranged from 13° to 4° (mean 7,8°). We observed „true“ valgus type deformity during passive range of movement in 34 cases (68 %) and „false“ type of kinematics in 16 cases (32 %). The average value of valgus deviation in extension in „true“ group was 7,9° (range, 13° to 4°) and in „false“ group 7,5° (range, 9° to 6°), without statistically significant difference. In the „true“ valgus deviation group the value of deformity gradually decreased with flexion in all cases. The mean difference between axis deviation in 0° and 120° of flexion was 5,5° (range, 10° to 1°) in this group. In the „false“ valgus group the varus deviation was observed either already in 60° of flexion or in most cases in 90° of flexion. The mean difference between axis deviation in 0° and 120° of flexion in this group was much more significant – 12,0° (range, 14° to 10°) – there was statistically significant difference between both groups. The mean time necessary for data collection before surgery was 6 minutes (range, 4 to 11 minutes); afterwards, tha navigation was used for TKR implantation. No complications were observed regarding to the navigation usage. Subsequently correct soft tissue balance was achieved in all TKRs using this method. Conclusions. Computer navigation assistance can easily and fast help to identify the character of valgus deformity („true“ or „false“) just before skin incision. In „true“ valgus deviation lateral structures (iliotibial band, vastus lateralis tendon, lateral collateral ligament, and the popliteus muscle) are tight and lateral approach according to Keblish may be necessary for appropriate release and soft tissue balancing during TKR surgery. Mostly used standard medial parapatellar approach is always sufficient in „false“ valgus knees. Computer navigation can help surgeon to choose the appropriate parapatellar approach (medial or lateral) just before the surgery without significant time lost

Backgrounds. Most of in vivo kinematic studies of total knee arthroplasty (TKA) have reported on varus knee. TKA for the valgus knee deformity is a surgical challenge. The purposes of the current study are to analyze the in vivo kinematic motion and to compare kinematic patterns between weight-bearing (WB) and non-weight-bearing (NWB) knee flexion in posterior-stabilized (PS) fixed-bearing TKA with pre-operative valgus deformity. Methods. A total of sixteen valgus knees in 12 cases that underwent TKA with Scorpio NRG PS knee prosthesis operated by modified gap balancing technique were evaluated. The mean preoperative femorotibial angle (FTA) was 156°±4.2°. During the surgery, distal femur and proximal tibia was cut perpendicular to the mechanical axis of each bone. After excision of the menisci and cruciate ligaments, balancer (Stryker joint dependent kinematics balancer) was inserted into the gap between both bones for evaluation of extension gap. Lateral release was performed in extension. Iliotibial bundle (ITB) was released from Gerdy tubercle then posterolateral capsule was released at the level of the proximal tibial cut surface. If still unbalanced, pie-crust ITB from inside-out was added at 1 cm above joint line until an even lateral and medial gap had been achieved. Flexion gap balance was obtained predominantly by the bone cut of the posterior femoral condyle. Good postoperative stability in extension and flexion was confirmed by stress roentgenogram and axial radiography of the distal femur. We evaluated the in vivo kinematics of the knee using fluoroscopy and femorotibial translation relative to the tibial tray using a 2-dimentional to 3-dimensional registration technique. Results. The average flexion angle was 111.3°±7.5° in weight-bearing and 114.9°±8.4° in non-weight-bearing. The femoral component demonstrated a mean external rotation of 5.9°±5.8° in weight-bearing and 7.4°±5.2° in non-weight-bearing (Fig.1). In weight-bearing, the femoral component showed medial pivot pattern from 0° to midflexion and a bicondylar rollback pattern from midflexion to full flexion (Fig2). Medial condyle moved similarly in non-weight-bearing condition and in weight-bearing condition. Lateral condyle moved posterior in slightly earlier angle during weight-bearing condition than during non-weight-bearing condition (Fig.3). Discussion. Numerous kinematic analyses of a normal knee have demonstrated greater posterior motion of the lateral femoral condyle relative to the medial condyle, leading to a mean external rotation and a bicondylar rollback motion with progressive knee flexion. A kinematic analysis of valgus knee was reported to show a different kinematic pattern from a physiological knee motion. Many valgus knees showed paradoxical anterior translation from extension to mid-flexion and greater posterior translation in the medial condyle than in the lateral condyle. Kitagawa et al. reported that this non-physiologic pattern wasn't completely restored after TKA using medial pivot knee system. In the present study, we showed kinematic patterns of the TKA performed on the valgus knee to be similar to the normal knee for the first time, even though the magnitude of external rotation was small. Conclusions. We conclude that the medial pivot pattern followed by posterior rollback motion can be obtained in TKA with modified gap balancing technique for the preoperative valgus deformity

Introduction. Valgus deformity in an end stage osteoarthritic knee can be difficult to correct with no clear consensus on case management. Dependent on if the joint can be reduced and the degree of medial laxity or distension, a surgeon must use their discretion on the correct method for adequate lateral releases. Robotic assisted (RA) technology has been shown to have three dimensional (3D) cut accuracy which could assist with addressing these complex cases. The purpose of this work was to determine the number of soft tissue releases and component orientation of valgus cases performed with RA total knee arthroplasty (TKA). Methods. This study was a retrospective chart review of 72 RATKA cases with valgus deformity pre-operatively performed by a single surgeon from July 2016 to December 2017. Initial and final 3D component alignment, knee balancing gaps, component size, and full or partial releases were collected intraoperatively. Post-operatively, radiographs, adverse events, WOMAC total and KOOS Jr scores were collected at 6 months, 1 year and 2 year post-operatively. Results. Pre-operatively, knee deformities ranged from reducible knees with less than 5mm of medial laxity to up to 12° with fixed flexion contracture. All knees were corrected within 2.5 degrees of mechanical neutral. Average femoral component position was 0.26. o. valgus, and 4.07. o. flexion. Average tibial component position was 0.37. o. valgus, and 2.96. o. slope, where all tibial components were placed in a neutral or valgus orientation. Flexion and extension gaps were within 2mm (mean 1mm) for all knees. Medial and lateral gaps were balanced 100% in extension and 93% in flexion. The average flexion gap was 18.3mm and the average extension gap was 18.7mm. For component size prediction, the surgeon achieved their planned within one size on the femur 93.8% and tibia 100% of the time. The surgeon upsized the femur in 6.2% of cases. Soft tissue releases were reported in one of the cases. At latest follow-up, radiographic evidence suggested well seated and well fixed components. Radiographs also indicated the patella components were tracking well within the trochlear groove. No revision and re-operation is reported. Mean WOMAC total scores were improved from 24±8.3 pre-op to 6.6±4.4 2-year post-op (p<0.01). Mean KOOS scores were improved from 46.8±9.7 pre-op to 88.4±13.5 2-year post-op (p<0.01). Discussion. In this retrospective case review, the surgeon was able to balance the knee with bone resections and avoid disturbing the soft tissue envelope in valgus knees with 1–12° of deformity. To achieve this balance, the femoral component was often adjusted in axial and valgus rotations. This allowed the surgeon to open lateral flexion and extension gaps. While this study has several limitations, RATKA for valgus knees should continue to be investigated. For any figures or tables, please contact authors directly

Background. We have performed total knee arthroplasties for valgus and varus in the knees of one person and investigate the clinical characteristics of these patients and the relationship between the kind of deformity and postoperative result. Methods. From March 2002 to February 2010, 25 patients who had simultaneous varus and valgus knee deformities underwent total knee arthroplasties and followed more than 12 months were included. The average age was 66.9 years and the average follow-up period was 61.1 months. Follow-up imaging assessments were taken and clinical outcome were evaluated using HSS score at last follow-up. Results. 11 cases had more pain in varus knee and 8 cases had more pain in valgus knee preoperatively. In 11 cases, degenerative scoliosis were associated with the knee deformity and among the cases, 10 cases had valgus deformities in concave side of scoliosis. In three cases, hip deformities were noted in ipsilateral side of the valgus deformity. One case showed both hip deformities with ankylosing spondylitis. Preoperative mean valgus angle was 11.4 degree and varus angle was 7.5 degree. Postoperative valgus and varus angle improved to 6.3 and −5.7 degree. HSS score improved from 64.3 to 84.7 point in valgus deformities and from 62.1 to 85.1 point in varus deformities. Postoperative patellar clunk syndrome was identified in one valgus knee, but resolved by arthroscopic debridement. And postoperatively, one case showed out-toeing gait caused by equinovarus deformity in varus knee, but resolved by correction of foot deformity. Conclusions. Simultaneous or staged total knee arthroplasties in patients with simultaneous varus with contralateral valgus knee deformities brought satisfactory outcomes with regard to objective orthopedic criteria such as radiographic and clinical results. Concave aspect of scoliosis and hip deformity correlate with valgus knee in statistically. But rheumatoid factor and VDRL do not correlate with valgus deformity. And we found no significant difference between the kind of deformity and postoperative result

In a „true“ valgus knee the lateral femoral condyle is smaller in both the vertical and anteroposterior dimensions and lateral soft tissue structures are contracted. In a „false“ valgus knee there is no mismatch between anteroposterior dimensions of both condyles. The aim of the study was to preoperatively analyse patterns of passive movement of valgus knees with imageless navigation system to optimise surgical approach during subsequent total knee replacement (TKR). TKR were prospectively performed in 50 valgus knees. After the data registration process, the kinematic analysis was performed by passive movement of the knee. The mechanical axis was recorded at 0°, 30°, 60°, 90°, and 120° of flexion. The valgus deformity persistent through the whole range of motion was called „true“ and the valgus deformity passing into varus with flexion was called „false“. The pre-operative valgus deformity in extension ranged from 13° to 4° (mean 7.8°). We observed „true“ valgus type deformity during passive range of movement in 34 cases (68%) and „false“ type of kinematics in 16 cases (32%). The average value of valgus deviation in extension in „true“ group was 7.9° (range 13° to 4°) and in „false“ group 7.5° (range 9° to 6°). The mean difference between axis deviation in 0° to 120° range of flexion was 5.5° (range 10° to 1°) in the „true“ valgus group. In the „false“ valgus group the varus deviation was observed in 90° of flexion in all cases and mean difference between axis deviation in 0° to 120° range of flexion was 12.0° (range 14° to 10°). Computer navigation can easily help to identify the character of valgus deformity („true“ or „false“) just before skin incision. In „true“ valgus deviation lateral approach may be necessary for appropriate soft tissue balancing during TKR surgery

Introduction. The prevalence of reversing of extension coronal deformity during flexion and how that may change the routine algorithm of soft tissue balancing in total knee arthroplasty (TKA) has not been published. We name this phenomenon, the reversing coronal deformity (RCD). We observed 12% (45 patients) of coronal deformities consistently reverse in flexion in the osteoarthritic knees before surgery. We conclude that RCD phenomena need to be addressed in every TKA and collateral ligament release need to be modified or avoided; otherwise postoperative flexion instability may be inevitable. Femoral rotation adjustment with posterior capsule release has to be attempted first in RCD patients. Method. We define RCD as the reversing of a coronal extension deformity of more than 2° while the knee reaches 90°of flexion. That is to say a 2° or more varus knee in extension becomes a 2° or more valgus at 90° of flexion or vice versa. We retrospectively analyzed, in a multicenter study the alignment patterns of 387 (US = 270, UK = 117) consecutive computer navigated TKA subjects (June 2004–May 2008). 364/387 (US = 252, UK = 112) subjects were eligible for analysis (23 subjects had incomplete data: US = 18, UK = 5). The coronal deformity kinematics was observed during the range of motion and the range of medial /lateral deflections were analyzed. Result:. 260/364 subjects had varus knees and 104/364 subjects had valgus knees. 18 subjects (7%) of the varus knees reversed to valgus and 27 subjects (26%) of valgus knees reversed to varus by 90°pre-operatively. Therefore, the total number of arthritic knees that reversed their coronal deformity from extension to 90° flexion was 45 (12.4%). Knee alignment in extension was 0° ± 2° in 99% of patients. 1% (4 subjects) had more than 2°of varus or valgus in extension. Collateral ligament was released in 4/45 RCD patients in which all had flexion instability of more than 10° (medial/lateral at 90°). The other 40 patients had posterior capsule release with or without femoral rotation adjustment to balance the flexion gap. None of them had flexion instability (medial /later gaping was 4° or less). The preoperative mean femoral rotation was 3.05° of external rotation (ER) in varus knees and 1.9° ER in valgus knee. While in RCD varus knees, the mean femoral rotation was 1.5 ° ER and RCD valgus knees 2.5°ER. Discussion and Conclusion. Our observation has shed the light on a new concept in the kinematics of the knee, namely the reversing of the coronal deformity (RCD) during flexion which occurs in 12% of patients undergoing TKA. Basically, a varus knee in extension behaves like a valgus knee in flexion and vice versa. It is crucial to be aware of this phenomenon when attempting to do soft tissue release to balance the gaps in TKA. Otherwise, widening one gap in extension to correct a fixed deformity may result in an unacceptable overcorrection of the same gap in flexion in those knees that manifest the reverse coronal deformity phenomena. Soft tissue balance algorithm was noted to be different in such cases in which early collateral ligament release resulted in flexion instability

Background. Differences of dynamic (extension vs. flexion) coronal alignment in osteoarthritic (OA) knees undergoing primary total knee arthroplasty (TKA) remain poorly studied. Methods. Prospectively collected measurements of dynamic coronal alignment using an imageless computer-navigation system (Stryker©) during primary TKA were analysed. Coronal alignment was represented by the hip-knee-ankle angle and determined at maximal extension and 90° flexion before making any bony cuts or ligamentous releases. Measurements were subgrouped according to coronal alignment in extension as varus (≤-3°), neutral (>−3°, <+3°) or valgus (≥+3°). Results. Of 545 knees (347 females), coronal alignment in extension was 261 (48%) varus, 197 (36%) neutral and 87 (16%) valgus. Varus extension alignment was more common in male vs. female OA knees (64% vs. 39%; p< .0001). Valgus extension alignment was more common in female vs male OA knees (19.5% vs 9.5%; p= .002). In flexion, 174 (66%) of varus OA knees remained varus and 6 (3.3%) evolved to valgus. Extension varus exceeding 10° in 29/261 (11%) varus knees remained flexion varus in 28 (96.5%). Mean (±SD) difference between extension and flexion in varus knees was 1.98° (±4.0°) valgus. Of 87 valgus knees, 44 (50.5%) remained valgus and 4 (4.5%) evolved into varus during flexion. Mean (±SD) difference between extension and flexion in valgus knees was 2.3° (±4.2°) varus. Dynamic coronal alignment was unchanged in 27/545 (4.9%) and alternated between varus and valgus in 10/348 (2.9%) varus or valgus AO knees. Conclusion. Different coronal alignment was observed in >95% of OA knees of which almost 3% alternated between varus and valgus. This insight of a dynamic coronal deformity might contribute to improving ligamentous release during TKA. Further studies including prognostic value and functional outcome are warranted. Level of evidence: Level II

The aim of the study was to investigate rotational behaviour of the arthritic knee before (preimplant) and after (postimplant) total knee replacement (TKR) using (image-free navigation system as a measurement tool which recorded the axial plane alignment between femur and tibia, in addition to the coronal and sagittal alignment as the knee is flexed through the range of motion. The data on the rotation of the arthritic knee was collected after the knee exposure and registration of the lower limb (preimplant data). The position of rotation between the femur and tibia was recorded in 30° flexion, 45°, 60°, 90° and maximum degrees of flexion of the knee. The data was divided into subsets of varus and valgus knees and these were analysed pre and postimplant for their rotational position using SPSS for statistics. The system was used in 117 knees of which 91 had full data set available (43 male 48 female). These included 71 varus knees, 16 valgus knees and 4 neutral knees to start in extension. Preimplant data analysis revealed there is tendency for the arthritic knees to first go in internal rotation in the initial part of flexion to 30 degrees and then the rotation is reversed back. This happens irrespective of the initial starting rotational relationship between femur and tibia in full extension. This happens in both varus as well as valgus arthritic knees. This trend of internal rotation in this initial part of flexion is followed in TKR as well implanted with fixed bearing CR knees irrespective of the preoperative deformity. Also noteworthy was the difference in rotation at 30°, 60° and 90 degrees of flexion between preimplant and postimplant knees (irrespective of varus and valgus groups). When calculated at different points of flexion, there was statistically significant difference in the change of rotation at each point of flexion except 45 degree of flexion. The pre-operative values of change in rotation (internal being positive) at each step from the extended position being 5.4° (SD 4.5°) at 30 ° flexion, 4.7°(5.2°) at 45°, 3.6°(6.1°) at 60°, 3.5°(7.2°) at 90° and 4.2°(8.3°) at maximum flexion. Corresponding post-operative rotations were 2.2°(4.8°), 4.1°(6.4°), 6.6°(7.3°), 9.9°(8.8°) and 7.7°(8.9°). There was also an increase in the total range of rotation that the knee goes through after it has been implanted with prosthesis although it may not happen in every knee. This is statistically significant (p value <0.001) and seems more so in valgus group. The rotational movements and interrelationship of the femur and tibia is a complex issue, especially in the arthritic knees. Preimplant arthritic knee behaved generally similarly to normal knees according to the literature. Normal gait pattern demonstrates that the tibia moved through a 4° to 8° arc of internal rotation relative to the femur. The overall range (10.2° =/−4.2°) of knee rotation in this study greater than 8° might be explained by preimplant data acquired after the knee was approached and therefore releasing knee soft tissue envelop. This study confirmed that during the first 30° both varus and valgus knees moved internally. In our study there is increased range of total rotation postimplant (14° =/−6.8°) which may be explained by the fact that the anterior cruciate ligament is lost in all the TKRs and the posterior cruciate ligament may be dysfunctional as well. Thus the constraints on the knee rotation are decreased postimplant leading to increased rotation. We found some difference between varus and valgus post implant knees in that internal rotation seen in initial 30 degrees of flexion is much more pronounced in valgus knees as compared to varus knees (p value <0.001). This study confirmed knee internal rotation in initial stages of flexion, preimplant in arthritic knees during a passive knee flexion assessment. Varus and valgus knee seemed to behave similarly. This mimics the normal knee rotation. Postimplant knees in TKR behave differently