Alignment In Knee Arthroplasty Research Articles

Robotic functional alignment in knee arthroplasty minimizes impact on ankle alignment: Role of MPTA and LDFA preservation.

Alignment strategies in knee arthroplasty have a profound influence not only on knee biomechanics but also on the biomechanics of adjacent joints, particularly the ankle. Functional alignment (FA) represents a flexible alignment strategy aimed at achieving patient-specific balance. However, predefined boundaries are often applied to ensure mechanical stability, leading to adjustments in the medial proximal tibial angle (MPTA) and lateral distal femoral angle (LDFA) while still respecting the patient's native alignment as much as possible. FA is a patient-specific strategy that seeks to respect the patient's preoperative phenotype or constitutional alignment while achieving a balanced and stable knee. The hypothesis is that FA strategies can protect the ankle from excessive biomechanical stress. A retrospective cohort analysis was conducted on 300 consecutive patients who underwent robotic-assisted knee arthroplasty. Preoperative and 6-month post-operative radiographic evaluations measured key ankle parameters, tibial plafond inclination (TPI), talar inclination (TI) and Talar Tilt (TT). Statistical analyses evaluated the influence of alignment strategies on these parameters, with particular focus on whether MPTA and LDFA crossed the 90° threshold, indicating a shift from varus to valgus or vice versa. FA demonstrated smaller changes in ankle parameters compared to mechanical alignment (MA). In the FA group, mean changes were 1.8° for KTPA (standard deviation [SD] = 1.1°, p = 0.03), 2.4° for TPI (SD = 1.0°, p = 0.04), 2.1° for TI (SD = 1.3°, p = 0.05) and 1.7° for TT (SD = 0.9°, p = 0.04). The MA group showed greater deviations: 3.9° for KTPA (SD = 1.5°, p = 0.01), 5.2° for TPI (SD = 1.2°, p = 0.02), 4.8° for TI (SD = 1.4°, p = 0.03) and 3.6° for TT (SD = 1.1°, p = 0.04). Alterations in LDFA and MPTA exceeding 2° were significantly associated with worsening ankle alignment. Furthermore, FA, with its goal of maintaining Coronal Plane Alignment of the Knee (CPAK) classification, was associated with minimal modifications to ankle angles, suggesting potential biomechanical benefits as reported in the literature. FA was associated with smaller changes in ankle alignment parameters, indicating its ability to better preserve native joint positioning. Future research should focus on longitudinal studies to confirm these benefits and further establish the FA strategy as a standard in knee arthroplasty, particularly its capacity to maintain CPAK classification alignment. Level III.

Knee Arthroplasty in Severe Varus Advanced Knee Osteoarthritis with Proximal Tibia Malunion: a case report

Alignment is crucial for successful knee arthroplasty.1 Tibia malunion will make arthroplasty more challenging. In this case, we present advanced knee osteoarthritis with tibia vara due to malunion that needs corrective osteotomy during knee arthroplasty.Case Presentation:A 70 years old female presented to our office complaining pain in both knees markedly on the left, profoundly felt during walking. She has a history of being hit by motorcycle 15 months ago and left knee was more bent since then. Physical examination of the left knee showed severe varus, mild effusion, tenderness on medial tibial condyle, otherwise normal. Plain radiographs showed advanced bilateral knee osteoarthritis with left proximal tibia malunion. Patient underwent left knee arthroplasty with corrective tibia and fibula osteotomy.Solutions and Outcome:Patient underwent closed wedge tibial osteotomy together with fibula osteotomy followed by knee arthroplasty with posterior-stabilized implant and tibial stem extension in a single surgery. Tibial osteotomy was reinforced using plate and screws. Partial weight bearing was achieved in second postoperative day and discharged on the third day. Patient able to walk with painless left knee after 1 month.Discussion:Severe deformity that causes huge malalignment makes knee arthroplasty difficult. Some methods are available to correct malalignment.1 In this case, the surgeon chose to do closed wedge tibial osteotomy reinforced with plate and screws to correct the proximal tibia malunion. Arthroplasty was done using posterior-stabilized implant and tibial stem extension. Patient shows good result in alignment and function.Conclusion:Correcting the associated deformity is crucial in achieving good alignment in knee arthroplasty. Even in our case of severe genu varus due to proximal tibia malunion, correcting proximal tibia varus deformity prior to knee arthroplasty shows good alignment and function.

Arthroplasty in the Valgus Knee: Comparison and Discussion of Lateral vs Medial Parapatellar Approaches and Implant Selection.

Constrained implants are frequently used for primary total knee arthroplasty (TKA) in patients with moderate and severe genu-valgum (>10˚). This deformity presents corrective challenges for ligament release. The lateral-parapatellar approach has been advocated as an alternative to the traditional medial-parapatellar approach. Claimed advantages include better access for release of tight ligamentous structures, without requirement for release of the medial-collateral ligament.We present our comparative experience of the use of an unconstrained knee-replacement prosthesis inserted by the lateral-parapatellar approach in comparison to a constrained-knee prosthesis inserted via the medial-parapatellar approach.49 primary total knee-replacements in 48 (6 males, 42 females) patients were performed; 32 through a lateral-parapatellar approach (group L) using an unconstrained-prosthesis and 17 through a medial-parapatellar approach more often requiring a constrained-prosthesis (group M). Mean preoperative valgus angle was 18.5 (range 11-34˚). Patient demographics (p=0.7) and valgus correctability were similar between the two groups.There was no significant difference in the mean post-operative valgus angle. This was 4.2˚ (range 1-9.5˚) using the lateral-parapatellar approach and 5.3˚ (range 0.3-10˚), p=0.12, using the medial-parapatellar approach.Transient common peroneal injury occurred in 2 patients, both group L, in the presence of valgus angles of greater than 20˚. To date no joints have been revised, or are unstable.The use of a lateral-parapatellar approach, appropriate soft tissue release, and an unconstrained PCL-preserving implant, yielded in all cases a stable, well aligned knee arthroplasty. This represents a viable alternative to the constrained-prosthesis using a medial-parapatellar approach in patients with moderate and severe genu-valgum.

Isocentric 3-Dimensional C-Arm Imaging of Component Alignments in Total Knee Arthroplasty With Potential Intraoperative and Postoperative Applications

An intraoperative imaging tool for total knee arthroplasty could help avoid poor clinical outcomes related to malalignment. We investigated the feasibility of using isocentric (ISO-C) fluoroscopic imaging for this purpose. Three-dimensional ISO-C and computed tomographic (CT) images were acquired from 6 cadaveric specimens implanted with standard knee arthroplasty components and analyzed to determine rotational alignments. In comparison with standard CT measures, the ISO-C–based measures had overall accuracies (determined as root mean square error) of 0.8° and 1.3° and corresponding SDs of 1.3° and 1.4° for the femoral and tibial components, respectively. With ISO-C imaging, it is possible to measure rotational alignment in knee arthroplasty with accuracy and repeatability comparable with CT. Isocentric imaging has strong potential as an intraoperative tool to accurately align arthroplasty components.

Effect of tibial component varus on wear in total knee arthroplasty

IntroductionMalalignment can result in poor clinical outcomes and increased wear. However, component malalignment can occur even when overall limb mechanical axis is within the normal anatomic range. We studied the effect of component malalignment in the presence of acceptable knee alignment in knee arthroplasty. MethodsSixteen tibial inserts retrieved at revision surgery were laser-mapped to measure wear. Average implantation duration was 7.7years (range, 1 to 13). Early (postprimary) and final (prerevision) radiographs were analyzed for overall alignment (limb, femoral and tibial components) and osteolysis. ResultsThe tibial components were initially aligned in a mean of 1.3±1.7° varus (range, –1.5 to 4.5°), which increased to 3.2±2.9° (range, –2.0 to 8.0°) at the time of revision (p=0.05). Tibial components initially placed in greater than 3° varus were associated with almost twice the volumetric penetration rate. Anatomic knee angles were 5.4±0.9° valgus (range, 4.0 to 7.0°) in the post-primary radiographs and decreased in prerevision radiographs to 3.8±2.6° (range, –1.0 to 7.5°), (p=0.04). DiscussionTibial varus was associated with increased medial compartment wear and total wear, thus affecting osteolysis in addition to local destruction of the bearing surface. Varus malalignment as low as 3° may result in accelerated wear, even if overall limb alignment is nearly ideal. These results indicate that tibial component alignment is an important factor associated with tibial tray subsidence and polyethylene wear even when limb alignment is neutral.

Can CT-based patient-matched instrumentation achieve consistent rotational alignment in knee arthroplasty?

Long-term success of contemporary total knee replacements relies to a large extent on proper implant alignment. This study was undertaken to test whether specimen-matched cutting blocks based on computed axial tomography (CT) scans could provide accurate rotational alignment of the femoral component. CT scans of five fresh frozen full leg cadaver specimens, equipped with infrared reflective markers, were used to produce a specimen-matched femoral cutting block. Using those blocks, the bone cuts were made to implant a bi-compartmental femoral component. Rotational alignment of the components in the horizontal plane was determined using an optical measurement system and compared with all relevant rotational reference axes identified on the CT scans. Average rotational alignment for the bi-compartmental component in the horizontal plane was 1.9° (range 0°-6.3°; standard deviation 2.6°). One specimen that showed the highest deviation from the planned alignment also featured a completely degraded medial articular surface. The CT-based specimen-matched cutting blocks achieved good rotational alignment accuracy except for one specimen with badly damaged cartilage. In such cases, imaging techniques that visualize the cartilage layer might be more suitable to design cutting blocks, as they will provide a better fit and increased surface support.

Intra- and inter-observer variation during femoral jig rotational alignment in knee arthroplasty

Rotational alignment of the femoral prosthesis is important in total knee arthroplasty to improve performance and reduce complications. This study investigates the differences between two popular referencing methods and evaluates the variability of surgeons' techniques (inter-observer) and their reproducibility (intra-observer) of femoral alignment. Eight surgeons each established the femoral rotational alignment on four duplicate sets of six cadaveric femoral bone casts, referencing from the epicondylar axis and from the posterior femoral condyles. These derived axes were compared against a reference Whiteside's line (anteroposterior axis). There was no significant difference between referencing techniques and a tendency to align the femoral component in slight external rotation. Femoral rotational alignment was reproducible by each surgeon. Extensive and significant variation in alignment exists between surgeons, independent of other factors (p < 0.001).

Transepicondylar line and condylar line as parameters for axial alignment in knee arthroplasty

In order to investigate the reliability of the transepicondylar line and the condylar line as indicators for lower limb alignment in knee arthroplasty, the femorotibial angle (FTA), and the angle between the transepicondylar line and the tangential line of tibial plateau (angle ε) and condylar-plateau angle (CPA) were measured in 107 (78 patients) full-length standing X-ray films of lower limbs. The mean FTA was measured to be 178.0±9.3°, the CPA 1.5±8.5° and angle ε −0.8±8.5°. The correlation between FTA and the CPA was analyzed to be significant with a correlation coefficient of 0.63, while another correlation between FTA and angle ε was calculated to be significant with a correlation coefficient of 0.81 at the same time. As a result, the correlation of the latter one was highly significant, having a R 2 value of 0.648 ( P<0.001), while the R 2 of the former was only 0.397 ( P<0.001). In conclusion, the transepicondylar line could be considered as a more reliable indicator for lower limb alignment, which may play an important role in ligament balancing and improvement of the guiding system in knee arthroplasty.