Aims. While mechanical alignment (MA) is the traditional technique in total knee arthroplasty (TKA), its potential for altering constitutional alignment remains poorly understood. This study aimed to quantify unintentional changes to constitutional coronal alignment and joint line obliquity (JLO) resulting from MA. Methods. A retrospective cohort study was undertaken of 700 primary MA TKAs (643 patients) performed between 2014 and 2017. Lateral distal femoral and medial proximal tibial angles were measured pre- and postoperatively to calculate the arithmetic hip-knee-ankle angle (aHKA), JLO, and Coronal Plane Alignment of the Knee (CPAK) phenotypes. The primary outcome was the magnitude and direction of aHKA, JLO, and CPAK alterations. Results. The mean aHKA and JLO increased by 0.1° (SD 3.4°) and 5.8° (SD 3.5°), respectively, from pre- to postoperatively. The most common phenotypes shifted from 76.3% CPAK Types I, II, or III (apex distal JLO) preoperatively to 85.0% IV, V, or VI (apex horizontal JLO) postoperatively. The proportion of knees with apex proximal JLO increased from 0.7% preoperatively to 11.1% postoperatively. Among all MA TKAs, 60.0% (420 knees) were changed from their constitutional alignments into CPAK Type V, while 40.0% (280 knees) either remained in constitutional Type V (5.0%, 35 knees) or were unintentionally aligned into other CPAK types (35.0%; 245 knees). Conclusion. Fixed MA targets in TKA lead to substantial changes from constitutional alignment, primarily a significant increase in JLO. These findings enhance our understanding of alignment alterations resulting from both unintended changes to knee phenotypes and surgical resection imprecision. Cite this article: Bone Jt Open 2024;5(2):109–116

Aims. The extensive variation in axial rotation of tibial components can lead to coronal plane malalignment. We analyzed the change in coronal alignment induced by tray malrotation. Methods. We constructed a computer model of knee arthroplasty and used a virtual cutting guide to cut the tibia at 90° to the coronal plane. The virtual guide was rotated axially (15° medial to 15° lateral) and with posterior slopes (0° to 7°). To assess the effect of axial malrotation, we measured the coronal plane alignment of a tibial tray that was axially rotated (25° internal to 15° external), as viewed on a standard anteroposterior (AP) radiograph. Results. Axial rotation of the cutting guide induced a varus-valgus malalignment up to 1.8° (for 15° of axial rotation combined with 7° of posterior slope). Axial malrotation of tibial tray induced a substantially higher risk of coronal plane malalignment ranging from 1.9° valgus with 15° external rotation, to over 3° varus with 25° of internal rotation. Coronal alignment of the tibial cut changed by 0.07° per degree of axial rotation and 0.22° per degree of posterior slope (linear regression, R. 2. > 0.99). Conclusion. While the effect of axial malalignment has been studied, the impact on coronal alignment is not known. Our results indicate that the direction of the cutting guide and malalignment in axial rotation alter coronal plane alignment and can increase the incidence of outliers. Cite this article: Bone Joint J 2020;102-B(6 Supple A):43–48

Introduction. Malalignment of total knee arthroplasty components may affect implant function and lead to decreased survival, regardless of preferred alignment philosophy – neural mechanical axis restoration or kinematic alignment. A common technique is to set coronal alignment prior to adjusting slope. If the guide is not maintained in a neutral position, adjustment of the slope may alter coronal alignment. Different implant systems recommend varying degrees of slope for ideal function of the implant, from 0–7°. The purpose of this study was to quantify the change in coronal alignment with increasing posterior tibial slope comparing two methods of jig fixation. Methods. Prospective consecutive series of 100 patients undergoing total knee arthroplasty using computer navigation. First cohort of 50 patients had extramedullary cutting jig secured distally with ankle clamp and proximally with one pin and a second cohort of 50 patients with the jig secured distally with ankle clamp and proximally with two pins. The change in coronal alignment was recorded with each degree of increasing posterior slope from 0–7° using computer navigation. Mean coronal alignment and change in coronal alignment was compared between the two cohorts. Results. Utilizing one pin to secure the jig, all osteotomies drifted into increased varus with an average coronal alignment of 2.38° varus (range 0.5–4.5°varus) at 7° posterior slope with an average change of 0.34° in coronal alignment per degree increase of posterior slope. Utilizing two pins to secure the jig showed a propensity to drift into valgus with an average coronal alignment of 0.22° valgus (range 1.0° varus − 1.5° valgus) at 7° posterior slope with an average change of 0.04° in coronal alignment per degree increase of posterior slope. The observed changes in coronal alignment between the two cohorts of patients were significantly different at all recorded levels of posterior slope. Conclusion. In this study, when one pin is utilized to secure the jig increasing posterior slope resulted in varus alignment with 12.0% of patients having greater than a 3 degree increase in varus at 7 degrees posterior slope compared to zero subjects in the group where the jig was secured with two pins. In the single pin group patients started to fall outside of the ±3° safe zone for coronal alignment at 4° of posterior slope. There were no patients in the two-pin cohort that fell outside of the ±3° safe zone for coronal alignment. Excessive varus alignment may result in decreased survivorship when using extramedullary jig attached distally with ankle clamp distally and proximally with one pin. Use of more than one pin and computer navigation are beneficial to prevent deviation from desired coronal alignment in systems with increased posterior slope. Verification of tibial cut intra-op is critical, especially if using one pin fixation with extramedullary jig. The observed relationship may help to explain why alignment of TKA is more accurate with computer navigation and new mid-term studies are demonstrating superior survivorship and outcomes in patients who underwent total knee arthroplasty with computer navigation, in certain cohorts of patients especially < 65 years

Introduction. Patellofemoral arthroplasty (PFA) can give excellent results in well-selected patients. Axial alignment has been extensively studied in this type of surgery. However because there is no distal femoral cut, coronal alignment in PFA is less well known. The position of the patellofemoral component decides the varus or valgus alignment of the implant. Hypothesis. Coronal alignment in PFA (PFJ-Gender, Zimmer, Warsaw, US) is determined by the anterior condylar anatomy and features an important variance influencing coronal alignment. Materials and methods. Coronal alignment was measured in 57 PFAs on full leg weight bearing radiographs as the lateral distal femoral angle compared to the mechanical axis (mLDFA). In a first group of patients the anterior condylar anatomy was followed and in a second group the PFA was aligned to the Whiteside's line. Results. In the group following the condylar anatomy the mean (SD) mLDFA was 100° (9°) compared to the group where the Whiteside's line was followed, which presented a mean (SD) mLDFA was 89° (3°). Patellofemoral tracking evaluated on a Merchant view was better in the second group. Discussion. Literature shows that accurate patellofemoral alignment is 1° of valgus from the mechanical axis. Following the anterior condylar anatomy doesn't allow to recreate accurate frontal alignment with a PFA. This can be obtained by following Whiteside's line as a substitute for finding the mechanical axis. Conclusion. Whiteside's line is not only an accurate landmark for axial alignment but also for coronal alignment in PFA aligning the implant with the mechanical axis

The emergence of patient specific instrumentation has seen an expansion from simple radiographs to plan total knee arthroplasty (TKA) with modern systems using computed tomography (CT) or magnetic resonance imaging scans. Concerns have emerged regarding accuracy of these non-weight bearing modalities to assess true mechanical axis. The aim of our study was to compare coronal alignment on full length standing AP imaging generated by the EOS acquisition system with the CT coronal scout image. Eligible patients underwent unilateral or bilateral primary TKA for osteoarthritis under the care of investigating surgeon between 2017 and 2022, with both EOS X-Ray Imaging Acquisition System and CT scans performed preoperatively. Coronal mechanical alignment was measured on the supine coronal scout CT scan and the standing HKA EOS. Pre-operative lower limb coronal alignment was assessed on 96 knees prior to TKA on the supine coronal scout CT scan and the standing HKA EOS. There were 56 males (56%), and 44 right knees (44%). The mean age was 68 years (range 53-90). The mean coronal alignment was 4.7 degrees (SD 5.3) on CT scan and 4.6 degrees (SD 6.2) on EOS (p=0.70). There was a strong positive correlation of coronal alignment on CT scan and EOS (pearson. 0.927, p=0.001). The mean difference between EOS and CT scan was 0.9 degrees (SD 2.4). Less than 3 degrees variation between measures was observed in 87% of knees. On linear regression for every 1° varus increase in CT HKA alignment, the EOS HKA alignment increased by 0.93° in varus orientation. The model explained 86% of the variability. CT demonstrates excellent reliability for assessing coronal lower limb alignment compared to EOS in osteoarthritic knees. This supports the routine use of CT to plan TKA without further weight bearing imaging in routine cases

Abstract. Introduction. Long term survivorship in Total Knee Arthroplasty is significantly dependent on prosthesis alignment. The aim of this study was to determine, compare and analyse the coronal alignment of the tibial component of a single implant system using 3 different techniques. Method. Retrospective study of cases from a prospectively collected database. Radiological assessment included measurement of the coronal alignment of tibial components of total knee arthroplasties, and its deviation from the mechanical axis. A comparison study of intramedullary, extramedullary and tibial crest alignment methods was performed. Results. 66 consecutive patients (3 groups of 22 each). Mean BMI was 26. The mean angle of deviation from the mechanical axis was significantly lesser (p< 0.05) in the Tibial crest alignment group patients compared to the other 2 groups. Moreover, the number of outliers (+/-3 degrees) were 2 and 4 in the intra and extramedullary group, whereas there were none in the tibial crest group. The inter and intraclass correlation coefficient was 0.8 and 0.9 respectively. Conclusion. The Tibial Crest Alignment Technique is an effective technique to produce consistent results to achieve optimal coronal alignment of the tibial component in TKA, even in patients with high BMI. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Accurate evaluation of lower limb coronal alignment is essential for effective pre-operative planning of knee arthroplasty. Weightbearing hip-knee-ankle (HKA) radiographs are considered the gold standard. Mako SmartRobotics uses CT-based navigation to provide intra-operative data on lower limb coronal alignment during robotic assisted knee arthroplasty. This study aimed to compare the correlation between the two methods in assessing coronal plane alignment. Patients undergoing Mako partial (PKA) or total knee arthroplasty (TKA) were identified from our hospital database. The hospital PACS system was used to measure pre-operative coronal plane alignment on HKA radiographs. This data was correlated to the intraoperative deformity assessment during Mako PKA and TKA surgery. 443 consecutive Mako knee arthroplasties were performed between November 2019 and December 2021. Weightbearing HKA radiographs were done in 56% of cases. Data for intraoperative coronal plane alignment was available for 414 patients. 378 knees were aligned in varus, and 36 in valgus. Mean varus deformity was 7.46° (SD 3.89) on HKA vs 7.13° (SD 3.56) on Mako intraoperative assessment, with a moderate correlation (R= 0.50, p<0.0001). Intraoperative varus deformity of 0-4° correlated to HKA measured varus (within 3°) in 60% of cases, compared to 28% for 5-9°, 17% for 10-14°, and in no cases with >15° deformity. Mean valgus deformity was 6.44° (SD 4.68) on HKA vs 4.75° (SD 3.79) for Mako, with poor correlation (R=0.18, p=0.38). In this series, the correlation between weightbearing HKA radiographs and intraoperative alignment assessment using Mako SmartRobotics appears to be poor, with greater deformities having poorer correlation

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

Introduction and Aims. Sensor technology is seeing increased utility in joint arthroplasty, guiding surgeons in assessing the soft tissue envelope intra-operatively (OrthoSensor, FL, USA). Meanwhile, surgical navigation systems are also transforming, with the recent introduction of inertial measurement unit (IMU) based systems no longer requiring optical trackers and infrared camera systems in the operating room (i.e. OrthAlign, CA, USA). Both approaches have now been combined by embedding an IMU into an intercompartmental load sensor. As a result, the alignment of the tibial varus/valgus cut is now measured concurrently with the mediolateral tibiofemoral contact load magnitudes and locations. The wireless sensor is geometrically identical to the tibial insert trial and is placed on the tibial cutting plane after completing the proximal tibial cut. Subsequently, the knee is moved through a simple calibration maneuver, rotating the tibia around the heel. As a result, the sensor provides a direct assessment of the obtained tibial varus/valgus alignment. This study presents the validation of this measurement. Method. In an in-vitro setting, sensor-based alignment measurements were repeated for several simulated conditions. First, the tibia was cut in near-neutral alignment as guided by a traditional, marker-based surgical navigation system (Stryker, MI, USA). Subsequently, the sensor was inserted and a minimum of five repeated sensor measurements were performed. Following these measurements, a 3D printed shim was inserted between the sensor and the tibial cutting plane, introducing an additional 2 or 4 degrees of varus or valgus, with the measurements then being repeated. Again, for each condition, a minimum of five sensor measurements were performed. Following completion of the tests, a computed tomography (CT) scan of the tibia was obtained and reconstructed using open source software (3DSlicer). Results. By identifying anatomic landmarks on the 3D reconstructed tibia and fibula, the actual tibial coronal alignment of 0.43° valgus was obtained (Figure 1a), in close agreement with the one degree valgus alignment reported by the optical navigation system. Both reference values match well with the 1.16° valgus (SD: 0.91°) calculated by the IMU- based sensor system. When introducing the shims, the sensor consistently predicts the relative angular changes, with a maximum relative difference between the expected and measured condition of 1.29°. For each condition, the standard deviation remained small, with values ranging from 0.27° to 0.60° based on at least five repeated measures (Figure 1b). Conclusion. In conclusion, this paper demonstrates that sensor technology can be used to evaluate tibial coronal alignment, with an accuracy in line with available 3D measurement systems. The authors recognize however the need for further validation, currently being undertaken

Coronal alignment is an important factor in long-term survival of TKA. Many implant systems are available and most aim to produce a posterior slope on the tibial component to reproduce the 7. 0. seen in the normal tibia. We hypothesized that resecting the tibial plateau with a posterior slope can introduce error in coronal plane alignment in TKA. We used a standard saw-bones model in conjunction with a computer navigation system that is available for use in TKA (Stryker Orthopaedics). The normal protocol for preliminary referencing was followed; care was taken to identify tibial landmarks (tibial plateau reference point, true sagittal plane and transmalleolar axis). We then used a standard extramedullary alignment jig (Scorpio TKR System, Stryker Orthopaedics) with cutting blocks designed to give 0, 3, 5 and 7 degrees of posterior slope and varied the position of the alignment jig. Variations included:. Medial rotation of the cutting block,. Medialisation of the plateau reference point,. Mediolateral translation of the distal jig, and. External rotation of the distal jig. In all experiments, there was a greater deviation from ideal coronal alignment as the slope on the tibial cut was increased. The greatest influence was with external rotation of the distal part of the jig, which produced 3. 0. of varus at only 15. 0. of external rotation with a 7. 0. slope. Medialisation of the proximal reference point worsened this to 4.5. 0. of varus. We have quantified the degree of coronal malalignment that can occur for different posterior slopes during tibial resection for TKA. We recommend either using a minimal slope or navigation to ensure correct implant positioning. Correspondence should be addressed to Major M Butler RAMC, Princess Elizabeth Orthopaedic Centre, Royal Devon and Exeter Hospital, Exeter, Devon

Background: Coronal alignment is important in long-term survival of TKA. Many systems are available; most aim to produce a posterior slope on the tibial component in order to reproduce the 7. 0. seen in the normal tibia. Some are designed to produce a bone cut with 7. 0. of slope whereas others combine the slope of the bone cut with an in-built slope on the polyethylene insert. We have investigated the theory that resecting the tibial plateau with a posterior slope can introduce error in coronal plane alignment in TKA. Methods: We used a standard saw-bones model in conjunction with a computer navigation system that is available for use in TKA (Stryker Orthopaedics). The normal protocol for preliminary referencing was followed; care was taken to identify tibial landmarks (tibial plateau reference point, true sagittal plane and transmalleolar axis). We then used a standard extra-medullary alignment jig (Scorpio TKR System, Stryker Orthopaedics) with cutting blocks designed to give 0, 3, 5 and 7 degrees of posterior slope and varied the position of the alignment jig. Variations included:. Medial rotation of the cutting block. Medialisation of the plateau reference point. Medio-lateral translation of the distal jig 4. External rotation of the distal jig. Results: In all experiments, there was a greater deviation from ideal coronal alignment as the slope on the tibial cut was increased. The greatest influence was from external rotation of the distal part of the jig which produced 3. 0. of varus at only 15. 0. of external rotation with a 7. 0. slope. Medialisation of the proximal reference point worsened this to 4.5. 0. of varus. Conclusions: We have quantified the degree of coronal malalignment that can occur for different posterior slopes during tibial resection for TKA. We recommend either using a minimal slope or navigation to ensure correct implant positioning

Maquet's line passes from the centre of the femoral head to the centre of the body of the talus. The distance of this line from the centre of the knee on a long-leg radiograph provides the most accurate measure of coronal alignment. Malalignment causes abnormal forces which may lead to loosening after knee replacement. We report a series of 115 Denham knee replacements performed between 1976 and 1981 using the earliest design of components, inserted with intramedullary guide rods. Patients were assessed clinically and long-leg standing radiographs were taken before operation, soon after surgery and up to 12 years later. In two-thirds of the knees (68%) Maquet's line passed through the middle third of the prosthesis on postoperative films and the incidence of subsequent loosening was 3%. When Maquet's line was medial or lateral to this, an error of approximately +/- 3 degrees, the incidence of loosening at a median period of eight years was 24%. This difference is highly significant (p = 0.001). Accurate coronal alignment appears to be an important factor in prevention of loosening. Means of improving the accuracy of alignment and of measuring it on long-leg radiographs are discussed

Introduction. The hip-knee-ankle (HKA) angle between the mechanical axis of the femur (FM) and the mechanical axis of the tibia (TM) is the standard parameter to assess the coronal alignment of the lower extremity. TM is the line between the center of the tibial spines notch (Point T) and the center of the tibial plafond. However, this theory is based on the premise that TM coincides the anatomical axis of the tibia (TA). Fig.1a shows typical varus knee with medial shift of the tibial articular surface. In this case, TM does not coincide TA. Fig. 2 demonstrates the error of HKA angle when Point T locates medial to TA. Fig.2a shows normal alignment. Fig.2b shows varus alignment. Fig. 2c shows the tibia with medial shift of the tibial articular surface. The tibia has 7 degrees varus articular inclination in Fig.2b and 2c. However, HKA angle is 0 degree in Fig.2c. HKA angle underestimates varus deformity in knees with medial shift of the tibial articular surface. However, the degree of medial shift of the tibial articular surface is obscure. In this study, detailed anatomical configuration of the proximal tibia was evaluated. The effect of the value of HKA angle on the coronal alignment in TKA was then discussed. Methods. This study consists of 117 knees. On the AP view radiograph of the tibia, three distance and two angle parameters were measured. Those were tibial articular surface width, distance between medial edge of the tibial articular surface and Point T, distance from TA to Point T. Angle between TM and TA, and the varus inclination angle of the tibial articular surface relative to the perpendicular line to TA. Results. The mean width of the tibial articular surface was 87.8mm. The mean distance between Point T and medial edge of the articular surface was 43.6mm. Point T located at the center of the tibial articular surface. The mean distance from TA to Point T was 5.6mm. The mean angle between TM and TA was 1.0 degrees. The inclination angle of the tibial articular surface was 8.2 degrees. Discussion. The results clearly showed that varus knees had medial shift of the tibial articular surface. In such knees, the ankle shifts laterally relative to the Point T and HKA angle underestimates the varus deformity. The value of HKA angle also influences the evaluation of the coronal alignment of the lower extremity in TKA (Fig. 3). When the tibial tray is set based on the tibial articular surface width in order to cover the cut surface of the tibia, HKA angle shows the alignment as valgus when the tibial tray is set perpendicular to TA (Fig. 3a). In order to obtain zero degree of HKA angle, the tibial tray should be set perpendicular to TM. This alignment is varus (Fig. 3b). Reduction osteotomy is one procedure to match the value of HKA angle and the true alignment (Fig. 3c). In this technique, HKA angle is zero degree, and TM and TA coincide. For figures, please contact authors directly.

Introduction. Intraoperative assessment of coronal alignment is important when performing corrective osteotomies around the knee and ankle, limb lengthening and trauma surgery. The Joint Angle Tool (JAT) provides surgeons with information about the anatomic and mechanical axes intraoperatively based on true anteroposterior radiographs. Aim: Presentation of the JAT, a low-cost goniometer for intraoperative assessment of the lower limb alignment. Materials and Methods. The JAT consists of pre-printed joint orientation angles of the anatomic and mechanical axis including normal variations on a plastic sheet. It is placed on the screen of the image intensifier after obtaining a true anterior-posterior image. The pre-printed joint orientation angles can intraoperatively assist the surgeons in achieving the pre-planned axis correction. Here, its feasibility is demonstrated in four cases. Results. Here, we present the intraoperative use of JAT in four cases:. 77 mm femoral bone transport due to non-union utilizing a bone transport nail,. distal femoral osteotomy correcting coronal and torsional malalignment using a retrograde intramedullary trauma nail,. proximal / high tibial open wedge osteotomy with an intramedullary implant correcting varus malalignment in a hypophosphatemic rickets patient, and. a supramalleolar, closing wedge osteotomy realigning the anatomic axis with a plate and screws. Conclusions. The JAT is a modified goniometer which allows intraoperative assessment of the mechanical and anatomic axis. JAT is applicable throughout the entire surgical procedure irrespective of the method of internal fixation and may provide additional reassurance of correct alignment. The JAT consists of a plastic sheet with printed joint orientation angles and their normal variation. JAT is freely available from . profeedback.dk/JAT/JAT.pdf. for use and modification according to Creative Commons license (CC BY-SA 4.0)

Introduction Component malalignment may result in failure in total knee arthroplasty (TKA). Knee navigation systems assist surgeons with intra-operative component positioning in TKA. We report on the effect of one system on the post-operative mechanical axis of the limb and coronal alignment of femoral and tibial components in TKA. Methods In a prospective study of 47 total knee replacements we compared 24 cases using conventional techniques to 23 cases using the Stryker Knee Navigation System. Patient groups were matched for sex, weight and age. Postoperative antero-posterior radiographs of the whole leg were used to determine the mechanical axis of the limb and coronal position of the femoral and tibial components. Results The mean post-operative mechanical axis of the limb in the navigated group was 1.3° varus (range 7° varus to 3.5° valgus, SD=2.6). In the control group the mean mechanical axis was 0.8° varus (range 9.5° varus to 10° valgus, SD=4.4). There was no significant difference in the mean mechanical axis between the groups (p=0.6). There was no significant difference in mean coronal alignment of the femoral (p=0.99) or tibial components, (p=0.98). The 95% confidence interval for the mechanical axis was narrower for the navigated group (2.4° varus to 0.2° varus) than for the control group (2.6° varus to 1.1° valgus). Using Levene’s test (not dependant on normal distribution) the variances for the mechanical axis of the limb, and the coronal alignment of the femoral and tibial components are all significantly less in the navigated than non-navigated groups (p=0.05, 0.001 and 0.004 respectively). Conclusions This study showed no difference in the overall mean alignment of navigated versus non-navigated knees. However, a significant decrease in the variance of alignment seen with navigation means we are seeing fewer outlying results that may lead to a decrease in mechanical failure in TKA. In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source

Abstract. Introduction. Controversy exists regarding the optimal tibial coronal alignment in total knee arthroplasty. Many believe navigation or robotics are required to set kinematic alignments or to ensure they remain within ‘safe’ limits e.g. maximum 5° varus on the tibia. Given most navigation or robotic systems require the surgeon to identify the ankle malleoli, this study aimed to radiographically analyse standardly used intra-operative landmarks around the ankle, assessing their value in achieving kinematic alignment / setting safety boundaries. Materials and Methods. Long leg alignment radiographs were analysed independently by two orthopaedic surgeons at two time points, eight weeks apart. Angles were measured between the long axis of the tibia (TB) and: 1. lateral malleolus (TB-LM), 2. lateral border of the talus (TB-LT) and 3. medial aspect of the medial malleolus (TB-MM). Intra- and inter-rater reliabilities were assessed. Results. One hundred and sixty-seven radiographs in 119 patients were analysed; mean age 71.6 years. Mean angles (95% CI) were: TB-LM 4.8° (4.7°- 4.8°), TB-LT 2.6° (2.5° - 2.6°) and TB-MM 4.2° (4.1° - 4.2°). Interrater reliability was good for TB-LM (ICC = 0.72) and TB-MM (ICC=0.67), and fair for TB-LT (ICC= 0.50). Intra-rater reliability was excellent for all measures (ICC >0.85). Conclusion. There are consistent angles between tibial alignment and ankle landmarks. Using these landmarks, with standard instrumentation and alignment checks, allows surgeons to define safe limits, e.g. maximum 4.8° tibial varus if aligned to the tip of the lateral malleolus or set a 2.5° varus cut, without the need for added technology

The aim of this study was to evaluate the rotational axis of the tibia and the association of its axis to tibial coronal alignment after TKR. TKRs were performed using navigated mobile bearing system (40 knees), conventional mobile bearing (48 knees) and conventional fixed bearing (40 knees) and preoperative and postoperative CT scans were assessed using 3D image reconstruction-analysis program. The tibial AP axis which was defined as the line connecting the middle of the PCL and the medial edge of the patellar tendon attachment was measured relative to the AP axis of distal femur preoperatively and postoperatively, as well as the coronal angle of the tibia and posterior slope. The tibial coronal alignments in navigation, postoperative plain radiograph and CT were compared. The AP axis of the tibia was in 2.10° internally rotated position relative to the AP axis of the femur preoperatively and 3.54° postoperatively (range, 19.5° internal rotation to 16.8° external rotation). The coronal angle of the tibia was 0.46° varus on plain radiograph, 0.72° varus on CT, 0.37° valgus in navigation (p=0.005). Posterior slope was 2.53° on plain radiograph and 0.67° in navigation (p< 0.001). There was no correlation between postoperative rotational position of the tibia relative to the femur and the difference in the tibial coronal angle between navigation data and CT. The proposed anteroposterior axis of the tibia centered between 0 to 5 degrees internally rotated position relative to the femur but showed wide range of deviation. The rotation angle of the tibial cutting in navigated TKR did not influence on the postoperative measurement discrepancy between navigation and CT

Introduction. While implant designs and surgical techniques have improved in total knee arthroplasty (TKA), approximately 20% of patients remain dissatisfied. The purpose of this study was to determine if reproduction of anatomic preoperative measurements correlated to improved clinical outcomes in TKA. Methods. We retrospectively reviewed95 patients (106 knees) who underwent a TKA between 2012 −2013 with a minimum of one year follow-up. All patients had a pre and post-operative SF-12 and WOMAC scores. Pre and 6 week post-operative radiographs were reviewed to compare restoration of coronal plane alignment, maintenance of joint line obliquity, and maintenance of tibial varus. Coronal alignment was defined as the angle formed between the mechanical axis of the femur and the the tibia. Joint line obliquity was defined as the angle between the mechanical axis of the limb and the line which best parallels the joint space at the knee. Tibial varus was compared between the preoperative proximal lateral tibial angle and the angle formed by the mechanical axis of the tibia and tibial component postoperatively. Results. In 106 patients, postoperative coronal alignment, maintenance of tibia varus, or restoration of joint line obliquity did not correlate to improved outcomes. Patients with residual varus coronal alignment of more than 2° had increased pain and total WOMAC scores (p=0.013 and p = 0.036). Patients who had under-correction of the native tibial angle, had an increase in overall WOMAC score (p=0.007) with increased pain (p=0.012), stiffness (p=0.038), and function (p = 0.001). Furthermore, over-correction of tibial angle resulted in increased WOMAC functional scores (p=0.019), but was not significant to the overall WOMAC. Conclusions. In this study, restoration of a patient's native tibial varus correlated to improved WOMAC scores at 1 year postoperatively. Undercorrection of varus resulted in worse total WOMAC scores whereas overcorrection resulted in worse WOMAC functional scores

Aim. Computer assisted total knee arthroplasty may have advantages over conventional surgery with respect to component positioning. Femoral component mal-rotation has been shown to be associated with poor outcomes, and may be related to posterior referencing jigs. We aimed to determine the variation between the transepicondylar axis (TEA) and posterior condylar axis (PCA) in a series of knees undergoing navigated total knee arthroplasty (TKA), and to determine the correlation between final intra-operative and post-operative coronal alignment. Method. A review of 184 consecutive patients undergoing primary TKA between June 2007 and August 2010, using Precision navigation and Triathlon implants (Stryker). The difference between the TEA and PCA was measured as was the initial and final coronal alignment. A standing four foot alignment radiograph was obtained 6 weeks after surgery to determine the weight-bearing mechanical axis. Results. The mean difference between the TEA and PCA was 3.94 degrees (−2.80 to 11.59) and median difference was 3.6 degrees. Females and valgus knees had a greater variation. The mean intra-operative alignment was 0.75 degrees (−3 to 6, SD 1.9) and the mean radiographic alignment was 1.24 degrees (−6.5 to 6.5, SD 1.6). The intra-operative and radiographic alignment showed correlation (coefficient 0.43). There was poor correlation between pre-operative deformity and degree of difference between intra-operative and radiographic alignment (coefficient −0.1). Conclusion. There is a wide variation in the difference between the TEA and PCA, and there is not a good relationship with coronal alignment. Although most valgus knees had a bigger difference, such a difference was also seen in many varus knees. This should alert the surgeon when using posterior referencing jigs when determining the femoral component size and rotation. There was reasonable correlation between the final intra-operative mechanical alignment and the weight-bearing alignment as determined by a standing radiograph

A technical goal in total knee arthroplasty is the production of a neutral coronal plane mechanical axis. Errors may produce large mechanical axis deviations precipitating early implant failure. This study sought to test if measured distal femoral resection produced more accurate and consistent coronal alignment than arbitrarily set distal femoral resection. Data from a cohort of 255 consecutive unselected primary total knee arthroplasties undertaken by the senior author (PM) was collected prospectively and independently assessed. In the first 167 cases distal femoral resection was arbitrarily set to 5 degrees of valgus. In the remaining 88 cases the distal femoral resection angle was determined on a preoperative long leg standing AP radiograph. Postoperative coronal alignment was measured on long leg standing AP radiograph in all cases. The measured distal femoral valgus angle was between 4 and 7 degrees. An equal number measured either 5 or 6 degrees and accounted for 85% of the total number. Statistically insignificant improvements in mean axis and standard deviation were observed in the measured group: mean axis deviation −0.31 vs −0.51: p=0.17 (independent samples t test) and standard deviation 0.91 vs 1.09: p=0.055 (Levene test). Acceptable coronal alignment in total knee arthroplasty can reliably be obtained with conventional instrumentation. Improvement in standard deviation with measured distal femoral valgus angle approaches statistical significance