Alessandro Feliciangeli

In vivo kinematics and kinetics of a bi-cruciate substituting total knee arthroplasty: A combined fluoroscopic and gait analysis study

After total knee arthroplasty, changes in articular surface geometry, soft tissue treatment, and component alignment can alter normal lower limb function. The guided motion bi‐cruciate substituting prosthesis was designed specifically to restore physiological knee joint motion. We determined whether this design could in vivo normal kinematics and kinetics, not only at the replaced knee, but also throughout both lower limbs. Sixteen patients (4 male, 12 female, mean age of 68.2 years with a range from 58 to 79 years) with primary knee osteoarthritis were implanted with the bi‐cruciate substituting prosthesis. At 6‐month follow‐up, knee joint kinematics was assessed by video‐fluoroscopy during stair‐climbing, chair‐rising/sitting, and step‐up/down. Lower limb overall function was also assessed on the same day by standard gait analysis with simultaneous electromyography during level walking. By video‐fluoroscopy, mean anteroposterior translations between femoral and tibial components during the three motor tasks were 9.7 ± 3.0, 10 ± 2.6, and 6.9 ± 3.5 mm on the medial compartment, and 14.3 ± 3.5, 18.5 ± 3.0, and 13.9 ± 3.8 mm on the lateral compartment, respectively. Axial rotation ranged from 5.6° to 26.2°. Gait analysis revealed restoration of nearly normal walking patterns in most patients. This rare combination of measurements, i.e., accurate rotation‐translation at the replaced knee and complete locomotion patterns at both lower limb joints, suggested that bi‐cruciate substituting arthroplasty can restore physiological knee motion and normal overall function.

In‐Vivo knee kinematics in rotationally unconstrained total knee arthroplasty

Total knee replacement designs claim characteristic kinematic performance that is rarely assessed in patients. In the present study, in vivo kinematics of a new prosthesis design was measured during activities of daily living. This design is posterior stabilized for which spine–cam interaction coordinates free axial rotation throughout the flexion–extension arc by means of a single radius of curvature for the femoral condyles in the sagittal and frontal planes. Fifteen knees were implanted with this prosthesis, and 3D video‐fluoroscopic analysis was performed at 6‐month follow‐up for three motor tasks. The average range of flexion was 70.1° (range: 60.1–80.2°) during stair‐climbing, 74.7° (64.6–84.8°) during chair‐rising, and 64.1° (52.9–74.3°) during step‐up. The corresponding average rotation on the tibial base‐plate of the lines between the medial and lateral contact points was 9.4° (4.0–22.4°), 11.4° (4.6–22.7°), and 11.3° (5.1–18.0°), respectively. The pivot point for these lines was found mostly in the central area of the base‐plate. Nearly physiological range of axial rotation can be achieved at the replaced knee during activities of daily living.

Geometrical changes of knee ligaments and patellar tendon during passive flexion.

Patterns of fibre elongation and orientation for the cruciate and collateral ligaments of the human knee joint and for the patellar tendon have not yet been established in three-dimensions. These patterns are essential for understanding thoroughly the contribution of these soft tissues to joint function and of value in surgical treatments for a more conscious assessment of the knee status. Measurements from 10 normal cadaver knees are here reported using an accurate surgical navigation system and consistent anatomical references, over a large flexion arc, and according to current recommended conventions. The contours of relevant sub-bundles were digitised over the corresponding origins and insertions on the bones. Representative fibres were calculated as the straight line segments joining the centroids of these attachment areas. The most isometric fibre was also taken as that whose attachment points were at the minimum change in length over the flexion arc. Changes in length and orientation of these fibres were reported versus the flexion angle. A good general repeatability of intra- and inter-specimens was found. Isometric fibres were found in the locations reported in the literature. During knee flexion, ligament sub-bundles slacken in the anterior cruciate ligament, and in the medial and lateral collateral ligaments, whereas they tighten in the posterior cruciate ligament. In each cruciate ligament the two compounding sub-bundles have different extents for the change in fibre length, and also bend differently from each other on both tibial planes. In the collateral ligaments and patellar tendon all fibres bend posteriorly. Patellar tendon underwent complex changes in length and orientation, on both the tibial sagittal and frontal planes. For the first time thorough and consistent patterns of geometrical changes are provided for the main knee ligaments and tendons after careful fibre mapping.

Three-dimensional motion analysis of the human knee joint: comparison between intra- and post-operative measurements

PurposeTo compare intra-operative knee joint kinematic measurements immediately after total knee replacement with those of the same patients post-operatively at 6-month follow-up.MethodsFifteen patients who underwent total knee arthroplasty were analysed retrospectively. Eight were implanted with one prosthesis design and seven with another. The intra-operative measurements were performed by using a standard knee navigation system. This provided accurate three-dimensional positions and orientations for the femur and tibia by corresponding trackers pinned into the bones. At 6-month follow-up, the patients were analysed by standard three-dimensional video-fluoroscopy of the replaced knee during stair climbing, chair rising and step-up. Relevant three-dimensional positions and orientations were obtained by an iterative shape-matching procedure between the silhouette contours and the CAD-model projections. A number of traditional kinematic parameters were calculated from both measurements to represent the joint motion.ResultsGood post-operative replication of the intra-operative measurements was observed for most of the variables analysed. The statistical analysis also supported the good consistency between the intra- and post-operative measurements.ConclusionsIntra-operative kinematic measurements, accessible by a surgical navigation system, are predictive of the following motion performance of the replaced knees as experienced in typical activities of daily living.Level of evidencePrognostic studies—investigating natural history and evaluating the effect of a patient characteristic, Level II.

Patellar Tracking in Computer-Assisted Surgery

It is well known that the human knee is a complex structure that joins the thigh with the shank and, because of the presence of three bones that articulate within this anatomical plexus, it consists of two joints, the lemoral (TFJ) and the patello-femoral joint (PFJ), the latter being the smaller of the two. Regardless of its size and sesamoid development, the patella plays two crucial roles within the knee: the transmission of tensile forces generated by all heads of the quadriceps to the patellar tendon and the tibia, and the increase of the lever arm of the extensor muscles during TFJ flexion-extension, i.e. ultimately the increase of the efficacy of the whole extensor mechanism of the knee [18, 25, 50, 53, 55]. The motion of the patella relative to the distal femur is generally called either PFJ kinematics or patellar tracking, and the important biomechanical functions cited above are successfully achieved only when this motion occurs correctly [18, 50, 53]. Patellar tracking is a full six-degree-of-freedom motion, i.e. the patellar bone is not constrained in its motion. This motion can be described as translation and rotation along and about, respectively, predefined axes [15, 18, 26, 60]. Among all kinematics variables, only a few are generally considered of clinical importance, and these are PFJ flexion, rotation and tilt, these being assessed on the knee sagittal, coronal and transverse plane, respectively, and patella translation along the medio-lateral axis of the distal femur. All references, both on the patella and the femur, have variable definitions [60].

La cinematica femoro-rotulea nell’artroplastica di ginocchio navigata

Despite a large percentage of total knee arthroplasty failures in disorders at the patellofemoral joint, current navigation systems do not track the patella. A new navigated technique has been developed recently, which includes a novel instrumentation. The aim of this study is to report an early experience of intra-operative patellar motion assessment.