Three dimensional kinematics of the knee joint

The study deals with 3 d-Kinematics and stability patterns according to a knee joint testing machine. During flexion the lateral femoral condyle displays near extension pure rolling, near flexion pure gliding, on the medial side this ratio is vice versa. 41 knee joint specimen provided internal-external transverse rotation during there whole range of motion. Additional varus rotation and medial translation occurred. In osteoarthritis the movement patterns were completely changed.     

Kinematics of the patella in deep flexion. Analysis with magnetic resonance imaging

BACKGROUND: Little information is available on the kinematics of the normal knee in deep flexion. The purpose of this study was to use magnetic resonance imaging to analyze the patellofemoral articulation in deep flexion. METHODS: Axial scans were made of the patellofemoral joint of twenty healthy Japanese volunteers with the knee in approximately 90 degrees of flexion, in maximum active flexion (mean [and standard deviation], 140 degrees +/- 10 degrees ), and in maximum passive flexion (mean, 156 degrees +/- 5 degrees ). A fat-suppressed, three-dimensional, fast low-angle shot sequence was used to visualize the articular cartilage. The patellofemoral contact area was determined on sequential images and was reconstructed three-dimensionally. RESULTS: At 90 degrees of flexion, the contact area on the patella was continuous over the medial and lateral facets in fourteen knees and was located in the proximal half of the articular surface. At maximum active and passive flexion, the odd facet engaged in fifteen and eighteen knees, respectively. At maximum passive flexion, the contact area of the lateral facet moved distally and decreased significantly (p = 0.0002). From 90 degrees of flexion to maximum active flexion, the mean total contact area remained constant (3.43 +/- 0.70 and 3.62 +/- 0.72 cm (2), respectively); it then decreased significantly in maximum passive flexion (2.96 +/- 0.78 cm (2), p = 0.04). CONCLUSIONS: The contact area on the patella was divided into two parts (the odd and lateral facets) and moved distally in deep knee flexion. The size of the contact area on the lateral facet significantly decreased in maximum passive flexion.     

Influence of preload magnitudes and orientation angles on the cervical biomechanics: a finite element study

OBJECTIVE: Although a number of in vivo, in vitro, and finite element studies have attempted to delineate the natural biomechanics, injury mechanisms, and surgical techniques of the cervical spine, none has explored the influence of various preload magnitudes and orientations on the biomechanical responses. METHODS: A nonlinear three-dimensional finite element model of the lower cervical spine (C5-C6) was used for this study. The model was tested under four preload magnitudes and three orientations. For every preload, magnitude, and orientation, pure moments of 1.8 Nm were applied to the superior surface of the moving vertebra (C5) in flexion, extension, lateral bending, and torsion. The resulting rotational motions were obtained and compared against literature data. RESULTS: The predicted biomechanical responses under the same loading directions varied, depending on the preload magnitudes and orientations. With flexion and extension, increasing the preload magnitudes and varying the C5-C6 orientation in the sagittal plane changed the rotational motions by 1% and 18%, respectively. Under normal orientation and with increasing preload magnitudes, flexion and extension increased, whereas lateral bending and torsion decreased. These changes were found to be influenced by several spinal components: posterior facets, passive ligaments, and stiffening of the intervertebral disc. The predicted responses under the direction of loading varied significantly, depending on the preload magnitudes and orientations. Under fixed preload magnitudes and varying the three types of orientations, rotational motions were not affected under flexion but changed under extension, lateral bending, and axial rotations. Under normal orientation and increasing preload magnitudes, biomechanical responses under flexion and extension increased, whereas lateral bending and torsion decreased. Changes in the predicted responses were found to be influenced by several spinal components: posterior facets, passive ligaments, and stiffening of the intervertebral disc. CONCLUSION: The findings of the current study were important for the further understanding of the cervical biomechanics during in vitro testing.     

Muscle forces and pronation stabilize the lateral ligament deficient elbow.

The influence of muscle activity and forearm position on the stability of the lateral collateral ligament deficient elbow was investigated in vitro, using a custom testing apparatus to simulate active and passive elbow flexion. Rotation of the ulna relative to the humerus was measured before and after sectioning of the joint capsule, and the radial and lateral ulnar collateral ligaments from the lateral epicondyle. Gross instability was present after lateral collateral ligament transection during passive elbow flexion with the arm in the varus orientation. In the vertical orientation during passive elbow flexion, stability of the lateral collateral ligament deficient elbow was similar to the intact elbow with the forearm held in pronation, but not similar to the intact elbow when maintained in supination. This instability with the forearm supinated was reduced significantly when simulated active flexion was done. The stabilizing effect of muscle activity suggests physical therapy of the lateral collateral ligament deficient elbow should focus on active rather than passive mobilization, while avoiding shoulder abduction to minimize varus elbow stress. Passive mobilization should be done with the forearm maintained in pronation.     

Biomechanical comparison of transfacet screws to lateral mass screw-rod constructs in the lower cervical spine

Purpose

Transfacet screws have been used as an alternative posterior fixation in the cervical spine. There is lack of spinal stability of the transfacet screws either as stand-along constructs or combined with anterior plate. This study was designed to evaluate spinal stability of transfacet screws following posterior ligamentous injury and combined with anterior plate, respectively, and compare transfacet screws to lateral mass screw-rod constructs.

Methods

Flexibility tests were conducted on eight cadaveric specimens in an intact and injury, and instrumented with the transfacet screw fixation and lateral mass screw-rod construct at C5–C7 levels either after section of the posterior ligamentous complex or combined with an anterior plate and a mesh cage for C6 corpectomy reconstruction. A pure moment of ±2.0 Nm was applied to the specimen in flexion–extension, lateral bending, and axial rotation. Ranges of motion (ROM) were calculated for the C5–C7 segment.

Results

ROM with the transfacet screws was 22 % of intact in flexion–extension, 9 % in lateral bending and 11 % in axial rotation, while ROM with the lateral mass screw-rod construct was 9 % in flexion–extension, 8 % in lateral bending and 22 % in axial rotation. The only significant difference between two constructs was seen in flexion–extension (5.8 ± 4.2° vs. 2.4 ± 1.2°, P = 0.002). When combined with an anterior plate and mesh cage, the transfacet screw fixation reduced ROM to 3.0° in flexion–extension, 1.2° in lateral bending, and 1.1° in axial rotation, which was similar to the lateral mass screw-rod construct.

Conclusions

This study identified the transfacet screw fixation, as stand-alone posterior fixation, was equivalent to the lateral mass screw-rod constructs in axial rotation and lateral bending except in flexion–extension. When combined with an anterior plate, the transfacet screw fixation was similar to the lateral mass screw-rod construct in motion constraint. The results suggested the transfacet screw fixation a biomechanically effective way as supplementation of anterior fixation.

     

Lateral soft‐tissue structures contribute to cruciate‐retaining total knee arthroplasty stability

Little information is available to surgeons regarding how the lateral structures prevent instability in the replaced knee. The aim of this study was to quantify the lateral soft‐tissue contributions to stability following cruciate‐retaining total knee arthroplasty (CR TKA). Nine cadaveric knees were tested in a robotic system at full extension, 30°, 60°, and 90° flexion angles. In both native and CR implanted states, ±90 N anterior–posterior force, ±8 Nm varus–valgus, and ±5 Nm internal–external torque were applied. The anterolateral structures (ALS, including the iliotibial band), the lateral collateral ligament (LCL), the popliteus tendon complex (Pop T), and the posterior cruciate ligament (PCL) were transected and their relative contributions to stabilizing the applied loads were quantified. The LCL was found to be the primary restraint to varus laxity (an average 56% across all flexion angles), and was significant in internal–external rotational stability (28% and 26%, respectively) and anterior drawer (16%). The ALS restrained 25% of internal rotation, while the PCL was significant in posterior drawer only at 60° and 90° flexion. The Pop T was not found to be significant in any tests. Therefore, the LCL was confirmed as the major lateral structure in CR TKA stability throughout the arc of flexion and deficiency could present a complex rotational laxity that cannot be overcome by the other passive lateral structures or the PCL. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1902–1909, 2017.

     

Functional radiographic diagnosis of the cervical spine: flexion/extension

The cervical spines of 59 adults were examined by means of functional roentgenograms. They were divided into two groups consisting of 28 healthy adults and 31 patients who had sustained soft tissue injury to the cervical spine and who were complaining of neck pain. Roentgenographic lateral views were taken in active flexion and extension as well as in passive maximal flexion and extension. Measurements using the techniques of Penning and Buetti-Bauml were made by three observers independently. There was a highly significant difference between the active and passive segmental ranges of motion in healthy adults. Based on the normal values obtained in this study, 19 hypermobile segments could be diagnosed during the active examination, while 31 hypermobile segments were found during the passive examination. In addition, the active examination found 60 hypomobile segments, while the passive examination showed only 43 hypomobile segments. The Penning Method of measurement was found to be more reliable than that of Buetti-Bauml. If possible, the functional roentgenogram examination of the cervical spine in the sagittal plane should be performed by including passive movement and the range of motion should be compared with the normal values obtained by passive examination.     

Fixed‐bearing medial unicompartmental knee arthroplasty restores neither the medial pivoting behavior nor the ligament forces of the intact knee in passive flexion

Medial unicompartmental knee arthroplasty (UKA) is an accepted treatment for isolated medial osteoarthritis. However, using an improper thickness for the tibial component may contribute to early failure of the prosthesis or disease progression in the unreplaced lateral compartment. Little is known of the effect of insert thickness on both knee kinematics and ligament forces. Therefore, a computational model of the tibiofemoral joint was used to determine how non‐conforming, fixed bearing medial UKA affects tibiofemoral kinematics, and tension in the medial collateral ligament (MCL) and the anterior cruciate ligament (ACL) during passive knee flexion. Fixed bearing medial UKA could not maintain the medial pivoting that occurred in the intact knee from 0° to 30° of passive flexion. Abnormal anterior–posterior (AP) translations of the femoral condyles relative to the tibia delayed coupled internal tibial rotation, which occurred in the intact knee from 0° to 30° of flexion, but occurred from 30° to 90° of flexion following UKA. Increasing or decreasing tibial insert thickness following medial UKA also failed to restore the medial pivoting behavior of the intact knee despite modulating MCL and ACL forces. Reduced AP constraint in non‐conforming medial UKA relative to the intact knee leads to abnormal condylar translations regardless of insert thickness even with intact cruciate and collateral ligaments. This finding suggests that the conformity of the medial compartment as driven by the medial meniscus and articular morphology plays an important role in controlling AP condylar translations in the intact tibiofemoral joint during passive flexion. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1868–1875, 2018.

     

The Intact Posterior Cruciate Ligament Not Only Controls Posterior Displacement but Also Maintains the Flexion Gap

Background

The PCL is a strong stabilizer of the knee and provides posterior stability to the tibia. However, sagittal alignment of the PCL with the knee at 90° flexion suggests the PCL might play a role not only in posterior stabilization but also in maintaining the flexion gap.

Questions/purposes

We determined whether the intact PCL helps maintain the flexion gap.

Methods

We examined axial radiographs and gravity sag views of 17 patients with chronic isolated unilateral PCL injury. The flexion gap was defined as the mean value of the medial and lateral distances between the femoral and tibial bones on the axial radiograph. Increase in the flexion gap and posterior laxity were determined by comparing the patients’ injured and contralateral uninjured knees.

Results

The flexion gap of PCL injured knees (median, 7.5 mm; range, 5.3–11.5 mm; medial median, 6.2 mm; medial range, 3.7–8.3 mm; lateral median, 7.9 mm; lateral range, 5.3–11.5 mm) was larger than that seen in uninjured knees (median, 5.0 mm; range, 4.0–7.6 mm; medial median, 4.6 mm; medial range 3.4–7.1 mm; lateral median, 5.6; lateral range, 4.5–11.2 mm). The increment in the medial distance was similar to that in the lateral distance. Posterior laxity of injured knees was 9.1 (median); 5.4 to 15.2 (range) mm greater than that of uninjured knees. We found no correlation between posterior laxity and the flexion gap increment.

Conclusions

Our data suggest the intact PCL controls posterior displacement and maintains the flexion gap.     

Lateral band release for post-traumatic extension contracture of the proximal interphalangeal joint

Summary In the patient with scarring of just the central band and lateral bands, there is a loss of active and passive flexion of the proximal interphalangeal (PIP) joint because the lateral bands have lost their normal volar shift. Surgical freeing of the lateral bands from the central band using parallel incisions may be required to allow full flexion of the PIP joint. This study reports on 10 patients with post-traumatic extension contracture of the PIP joint treated by lateral band release. All operations were successful, with an average gain in range of motion of 47.5°. This technique is simple, quick, and can be performed effectively on an out-patient basis.     

Influence of intra-operative parameters on postoperative early recovery of active knee flexion in posterior-stabilized total knee arthroplasty

Purpose

Active knee flexion is more important for daily activities than passive knee flexion. The hypothesis is that the intra-operative parameters such as osteotomized bone thickness and soft tissue balance affect the postoperative active flexion angle in total knee arthroplasty (TKA). Therefore, we evaluate the influence of intra-operative parameters on postoperative early recovery of active flexion after posterior-stabilized (PS) TKA.

Methods

The subjects were 45 osteoarthritic knees undergoing primary PS TKA with anterior-reference technique. Intra-operative soft tissue balance was measured using an offset type tensor, and each osteotomized bone thickness was also measured. Pre- and postoperative active knee flexion angles were measured using lateral radiographs. Liner regression analysis was used to determine the influence of these intra-operative parameters on postoperative active flexion angles or recovery of active flexion angles.

Results

Pre-operative flexion angle was positively correlated with postoperative flexion angle (R?=?0.52, P?=?0.0002). Postoperative flexion angle was negatively correlated with the osteotomized bone thickness of femoral medial posterior condyle (R?=??0.37, P?=?0.012), and femoral lateral posterior condyle (R?=??0.36, P?=?0.015). Recovery of flexion angle was slightly negatively correlated with gap difference calculated by subtracting joint gap at extension from that at flexion between osteotomized surfaces (R?=??0.30, P?=?0.046).

Conclusions

The osteotomized bone thickness of the femoral posterior condyle is a significant independent factor of postoperative flexion angles. This indicates that the restoration of the posterior condyle offset may lead to larger postoperative active flexion angles in PS TKA.     

Tibiofemoral movement 3: full flexion in the living knee studied by MRI

We studied active flexion from 90 degrees to 133 degrees and passive flexion to 162 degrees using MRI in 20 unloaded knees in Japanese subjects. Flexion over this arc is accompanied by backward movement of the medial femoral condyle of 4.0 mm and by backward movement laterally of 15 mm, i.e., by internal rotation of the tibia. At 162 degrees the lateral femoral condyle lies posterior to the tibia.     

A mechanism of lateral flexion distraction injury of the spine

Flexion distraction fractures or Chance fractures are well described in the literature. We present an unusual pattern of injury of a pure lateral flexion distraction fracture of the T12 vertebra with no posterior element disruption following a blow to the right torso to a passenger in a road traffic accident. The diagnosis was made intra-operatively as the potential for this injury pattern following the described mechanism was not initially recognised. We suggest that this type of injury be suspected in any patient where a fulcrum has acted at any point around the torso.     

Functional anatomy of the ligaments of the elbow

Dissections of 10 fresh cadaver specimens revealed an important insertion of the posterior portion of the lateral collateral ligament to the ulna at the crista supinatoris. The humeral origin of the medial ligament attachments was found to lie posterior to the axis of elbow flexion; in this position a cam effect is created so that ligament tension varies with elbow flexion. The three-dimensional distance between the origin and the insertion of the anterior portion of the medial collateral ligament was found to increase slightly from extension to approximately 60 degrees of flexion; thereafter, it remained nearly constant. The distance of the posterior portion increased by about 9 mm from 60 degrees to 120 degrees of flexion. The flexion axis was shown to pass through the origin of the lateral collateral ligament, so the length of this structure was not changed during elbow flexion.     

Variability and repeatability of the flexion axis at the ulnohumeral joint.

Previous investigations have implemented screw displacement axes (SDAs) to define the elbow flexion axis for proper positioning of dynamic external fixators and endoprostheses. However, results across studies vary, which may be attributed to forearm position (pronation-supination) during elbow motion, or the mode of loading (active/passive) employed to generate flexion. Therefore, the aim of this study was to determine the influence of the flexion mode employed and forearm position on individual variation and repeatability of SDAs throughout elbow flexion. With the forearm pronated, the location of the average SDA was similar whether elbow flexion was generated actively or passively. In contrast, with the forearm supinated, the average SDA was 2.4 degrees and 1.4 degrees more valgus (p<0.001) and internally rotated (p<0.001), respectively, and positioned 1.6 and 0.8 mm further proximally (p=0.002) and anteriorly (p=0.005) relative to the capitellum, respectively, during active compared to passive flexion. During active flexion, the location of the average SDA was independent of forearm position. Conversely, during passive flexion, the average SDA angle was 3.4 degrees and 1.0 degrees more valgus (p<0.001) and internally rotated (p=0.009), respectively, and 1.7 and 0.7 mm more proximal (p<0.001) and anterior (p=0.001) relative to the capitellum, respectively, with the forearm held pronated rather than supinated. SDAs calculated throughout flexion deviated from the average SDA in both orientation and position, demonstrating that elbow flexion behaves similar to a loose hinge joint. These factors suggest that to encompass the location of all SDAs throughout flexion, and therefore properly mimic normal elbow joint motion, an endoprosthesis should be modeled similar to a "loose" rather than "pure" hinge joint. This would allow for dependencies of SDA angulation on forearm position and muscle activation, and slight freedom of movement to account for variances in SDA location. These factors should also be considered during soft-tissue reconstructions.     

Strain in the anteromedial bundle of the anterior cruciate ligament under combination loading.

Strain within the anteromedial bundle (AMB) of the anterior cruciate ligament (ACL) was measured in 13 human knee specimens in order to determine the combination of external loads most likely to cause injury. Using a load application system that allowed 5 df with the flexion angle being fixed, pure loads of anterior/posterior force, medial/lateral force, varus/valgus torque, and internal/external axial torque were applied at three flexion angles: 0 degrees, 15 degrees, 30 degrees. Combined loads were applied in pairs at two flexion angles: 0 degrees and 30 degrees. Liquid mercury strain gauges were used to measure strain in the ACL. Anterior tibial force was the primary determinant of strain in the anteromedial bundle. This strain was significantly larger at 30 degrees flexion than at 0 degrees. The strain sensitivity of the AMB to medial force was approximately one-half that to pure anterior force. The effect of anterior and medial forces was additive when applied in combination. Neither pure axial torque nor pure varus/valgus torque was observed to strain significantly the AMB at any of the flexion angles investigated. However, valgus torque in combination with anterior force resulted in a significantly larger strain than pure anterior force. Internal axial torque in combination with anterior force also resulted in a larger strain than pure anterior force.     

Rehabilitation of the medial collateral ligament-deficient elbow: an in vitro biomechanical study

The purpose of this study was to determine the relative contribution of muscle activity and the effect of forearm position on the stability of the medial collateral ligament (MCL)-deficient elbow. Simulated active and passive elbow flexion with the forearm in both supination and pronation was performed using a custom elbow testing apparatus. Testing was first performed on intact specimens, then on MCL-deficient specimens. Elbow instability was quantified using an electromagnetic tracking device by measuring internal-external rotation and varus-valgus laxity of the ulna relative to the humerus. Compared with the intact elbow, transection of the MCL, with the arm in a vertical orientation, caused a significant increase in internal-external rotation during passive elbow flexion with the forearm in pronation, but forearm supination reduced this instability. Overall, following MCL transection the elbow was more stable with the forearm in supination than pronation during passive flexion. In the pronated forearm position simulated active flexion also reduced the instability detected during passive flexion, with the arm in a varus and valgus gravity-loaded orientation. The maximum varus-valgus laxity was significantly increased with MCL transection regardless of forearm position during passive flexion. We concluded that active mobilization of the elbow with the arm in vertical orientation during rehabilitation is safe in the setting of an MCL-deficient elbow with the forearm in a fully supinated and pronated position. Splinting and passive mobilization of the MCL-deficient elbow with the forearm in supination should minimize instability and valgus elbow stresses should be avoided throughout the rehabilitation period.     

Effect of short-distance spondylodesis of the thoracolumbar transition on neighboring facet joints. A biomechanical study

This study was performed to investigate the range of motion and the forces on the facet joints that are neighboured to spondylodesis on thoracolumbar spine. We used a special spine testing device for a continuous application of pure moments in each direction. For measuring the ranges of motion we used a magnetic tracking device for measuring forces on facet joints we chose a direct measuring system of quartz crystal and prepared for investigation of the spine. The biomechanical testing was done on 18 human spinal specimen. We investigated the range of motion and the forces on facet joints in T11/12 and L2/3 segment with a maximal loading of 8 Nm in each direction (flexion, extension, lateral bending and rotation). This was done before and after double level dorsal instrumentation T12-L2 with an internal fixateur. Statistical analysis was performed using the paired t-test and the Wilcoxon test (p < 0.05). After double level instrumentation there were significant larger ranges of motion in flexion and extension and significant larger forces on facet joints in left lateral bending in the T11/12 segment. No significant differences were found in the L2/3 segment. Our findings could be an indication for changing in joints loading. This could be an explanation for early degenerative changes in spinal segments adjacent to spondylodesis. The results confirm the demand of short segment instrumentation and early remove of implants to keep influence as low as possible.     

Unicompartmental arthroplasty of the knee. Cadaver study of the importance of the anterior cruciate ligament

The tibiofemoral articulation on horizontal and 10 degrees tilted tibial components was examined radiographically in 20 cadaver knees after lateral arthroplasty, and after cutting the anterior cruciate ligament in 10 knees with medial and 10 with lateral arthroplasty. Articulation took place more posteriorly on the horizontal components at any degree of flexion examined; a correlation was found between the operation-induced change in the inclination of the lateral tibial plateau and the point of articulation. Based on the regression equations, the expected point of articulation on an arbitrarily chosen component placement could be calculated for any degree of flexion provided the preoperative inclination was known. Cutting the anterior cruciate ligament caused articulation to move posteriorly on the tibial component at both medial and lateral arthroplasty. We concluded that it was possible to estimate the tilt of the tibial component that was required to avoid marginal articulations when the preoperative slope of the tibial plateau was known. Absence of the anterior cruciate ligament seems to contraindicate unicompartmental arthroplasty.     

Unicompartmental arthroplasty of the knee: Cadaver study of the importance of the anterior cruciate ligament

The tibiofemoral articulation on horizontal and 10° tilted tibial components was examined radiographically in 20 cadaver knees after lateral arthroplasty, and after cutting the anterior cruciate ligament in 10 knees with medial and 10 with lateral arthroplasty. Articulation took place more posteriorly on the horizontal components at any degree of flexion examined; a correlation was found between the operation-induced change in the inclination of the lateral tibial plateau and the point of articulation. Based on the regression equations, the expected point of articulation on an arbitrarily chosen component placement could be calculated for any degree of flexion provided the preoperative inclination was known. Cutting the anterior cruciate ligament caused articulation to move posteriorly on the tibial component at both medial and lateral arthroplasty. We concluded that it was possible to estimate the tilt of the tibial component that was required to avoid marginal articulations when the preoperative slope of the tibial plateau was known. Absence of the anterior cruciate ligament seems to contraindicate unicornpartmental arthroplasty.