Varus Forces Research Articles

Varus Alignment Leads to Increased Forces in the Anterior Cruciate Ligament

Background Varus thrust of the knee is a dynamic increase of an often preexisting varus angle and it is suspected to be a major reason for failure of anterior cruciate ligament reconstructions. However, it is not known if a direct relationship exists between varus thrust and forces in the anterior cruciate ligament. Hypothesis Forces in the anterior cruciate ligament increase with increasing varus alignment, and consequently an anterior cruciate ligament deficiency in a varus-aligned leg leads to more lateral tibiofemoral joint opening. Study Design Controlled laboratory study. Methods Six human cadaver legs were axially loaded with 3 different weightbearing lines—a neutral weightbearing line, a weightbearing line that passes through the middle of the medial tibial plateau (50% varus), and a line passing the edge of the medial tibial plateau (100% varus)—that were used to create a varus moment. The resulting lateral tibiofemoral joint opening and corresponding anterior cruciate ligament tension were measured. The tests were repeated with and without the anterior cruciate ligament in place. Results In the neutral aligned legs, there was no apparent lateral joint opening, and no anterior cruciate ligament tension change was noted. The lateral joint opening increased when the weightbearing line increased from 0% to 50% to 100%. The lateral joint opening was significantly higher in 10° of knee flexion compared with knee extension. In the 100% varus weightbearing line, the anterior cruciate ligament tension was significantly higher (53.9 N) compared with neutral (31 N) or the 50% weightbearing line (37.9 N). A thrust could only be observed in the 100% weightbearing line tests. In the absence of an anterior cruciate ligament, there was more lateral joint opening, although this was only significant in the 100% weightbearing line. Conclusion There is a direct relationship between varus alignment and anterior cruciate ligament tension. In the absence of an anterior cruciate ligament, the amount of lateral opening tends to increase. With increasing lateral opening, a thrust can sometimes be experimentally observed. Clinical Relevance A varus alignment in an anterior cruciate ligament—deficient knee does not necessarily lead to a varus thrust and therefore does not always need operative varus alignment correction. However, in an unstable anterior cruciate ligament—deficient knee with a varus thrust, it might be safer to perform a high valgus tibial osteotomy to minimize the risk of an anterior cruciate ligament reconstruction failure.

Reliability of Navigated Knee Stability Examination

Background Clinical examination remains empirical and may be confusing in the setting of rotatory knee instabilities. Computerized navigation systems provide the ability to visualize and quantify coupled knee motions during knee stability examination. Hypothesis An image-free navigation system can reliably register and collect multiplanar knee kinematics during knee stability examination. Study Design Controlled laboratory study. Methods Coupled knee motions were determined by a robotic/UFS testing system and by an image-free navigation system in 6 cadaveric knees that were subjected to (1) isolated varus stress and (2) combined varus and external rotation force at 0°, 30°, and 60°. This protocol was performed in intact knees and after complete sectioning of the posterolateral corner (lateral collateral ligament, popliteus tendon, and popliteofibular ligament). The correlation between data from the surgical navigation system and the robotic positional sensor was assessed using the intraclass correlation coefficient. The 3-dimensional motion paths of the intact and sectioned knees were assessed qualitatively using the navigation display system. Results Intraclass correlation coefficients between the robotic sensor and the navigation system for varus and external rotation at 0°, 30°, and 60° were all statistically significant at P < .01. The overall intraclass correlation coefficient for all tests was 0.9976 (P < .0001). Real-time visualization of the coupled motions was possible with the navigation system. Post hoc analysis of the knee motion paths during loading distinguished distinct rotatory patterns. Conclusion Surgical navigation is a precise intraoperative tool to quantify knee stability examination and may help delineate pathologic multiplanar or coupled knee motions, particularly in the setting of complex rotatory instability patterns. Repeatability of load application during clinical stability testing remains problematic. Clinical Relevance Surgical navigation may refine the diagnostic evaluation of knee instability.

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Introduction: The elbow is the second most commonly dislocated joint in the body. Forty-nine percent of these are complex dislocations (ie, associated with a fracture). There are classic patterns for elbow injuries. Previous experiments have attempted to recreate these injury patterns using external forces. There is a common belief that elbow dislocations are caused by an axial force accompanied by flexion and an additional varus, valgus, or rotation force that leads to posterior dislocation with injury to either the medial or lateral structures. The elbow must flex to at least 20 degrees to unlock the olecranon before a dislocation can occur. The hypothesis of this study was that elbow injury patterns are influenced both by forearm orientation and the compressive interaction of joint surfaces in the fully extended elbow. Therefore, the objective of this study was to investigate the joint kinematics and injury pattern of the elbow that resulted from an axial load to failure with the forearm in either pronation or supination. Methods: Fourteen upper extremities were resected through the distal 1/3 humerus. Soft tissues were removed, leaving only the joint capsule, ligaments, interosseous membrane, and muscular insertions of the brachialis, supinator, and triceps. The valgus angle of the specimens was determined using markers and digital photos in supination, pronation, and neutral. A custom apparatus was used that allowed free rotation of the ulna, radius, and humerus about a fixed wrist. A compressive load was applied with a material tester (Instron 4411, Canton, MA) at a rate of two millimeters per second until failure occurred. Force and displacement data were collected. An optoelectronic, three-dimensional camera system (Optotrak 3020; Northern Digital Inc, Canada) was used to measure kinematic data for the distal humerus, proximal radius, and proximal ulna. Following failure, the elbow was carefully inspected and photographed to document all fractures and disrupted tissues. Results: Of the fourteen specimens, seven elbows failed in pronation and seven elbows failed in supination. In pronation, 6/7 elbows had a terrible triad type elbow injury with fracture of the radial head and coronoid with posterior dislocation. In supination, 6/7 elbows dislocated without coronoid or radial head fractures. Four out of fourteen elbows had damage to the lateral structures and ten out of fourteen had injury to the medial structures. In each case, damage to either the medial or lateral structures correlated with internal or external rotation of the ulna as compared to the humerus. Load to failure of the extended elbow in pronation most commonly led to a terrible triad (fracture of radial head and coronoid with posterior dislocation). In supination, independent rotation of the ulna and humerus enabled the elbow to dislocate without a fracture of the radial head or coronoid. No additional forces were necessary to allow the ulna to rotate out of the olecranon fossa. Post failure dissection revealed injury to the medial or lateral structures. The documented structural injuries correlated with the calculated rotations of the humerus and ulna relative to each other. When the ulna rotated externally relative to the humerus, the lateral structures were damaged. When the ulna rotated internally relative to the humerus, there was damage to the medial structures. The post failure dissection demonstrated rotation laxity at the elbow after reduction. Conclusions: During axial compression of the extended elbow, the ulna hinges either medially or laterally and allows the elbow to dislocate. The ligaments on the contralateral side are either torn or attenuated. In our study, the medial structures were more commonly disrupted. The terrible triad injury pattern can be produced with the elbow pronated in full extension. If noted, the author indicates something of value received. The codes are identified as follows: a, research or institutional support; b, miscellaneous funding; c, royalties; d, stock options; e, consultant or employee. *The Food and Drug Administration has not cleared the drug and/or medical device for the use described in this presentation (ie, the drug or medical device is being discussed for an “off-label” use). If noted, the author indicates something of value received. The codes are identified as follows: a, research or institutional support; b, miscellaneous funding; c, royalties; d, stock options; e, consultant or employee. *The Food and Drug Administration has not cleared the drug and/or medical device for the use described in this presentation (ie, the drug or medical device is being discussed for an “off-label” use).

MRI of Knee Joint Injury

Most knee injuries are the result of rotational, varus, valgus, hyperextension, or translational forces or a combination of these. The pattern of abnormalities seen on magnetic resonance imaging depends on the mechanism of trauma and the position of the joint at the time of injury. Knee injuries can be classified under two broad categories of direct and indirect injuries.

Arthroscopic Visualization of the Posterior Horn of the Medial Meniscus

We present a method of visualizing the posterior horn of the medial meniscus through the anterolateral portal that has not been previously described in the literature. It allows easy visualization and instrumentation of the posterior horn, an area that commonly has pathology that can be difficult to identify and treat. The technique involves allowing the knee to flex to 60° to 90° over the side of the bed and applying a varus force to the tibia, opening up the posteromedial part of the joint. It does not require any valgus force and therefore minimizes the risk of injury to the medial collateral ligament.

Gait-analytical studies in patients treated by valgus tibial head osteotomy

So far, the use of imaging methods has been the only way of evaluating unicompartmental gonarthritis caused by malalignment of lower extremity axes and the results of operative correction. Unfortunately, radiological visualization does not give any information about the actual loads on the joint, i.e.the forces and moments acting on it under dynamic conditions. These can be determined by means of gait-analytical measurements. The authors explain how the anomalous loading that occurs in the knee joint in the case of varus gonarthritis can be calculated and assessed. The mean maximum varus moment of knee joints in a group of patients with varus deformity was 0.74 Nm\kg, which was significantly higher than that in a control group (0.63 Nm\kg). Even after correction of the axes, increased maximum moments--some of them independent of the angle of the knee and of the correction angle--were observed in 30% of the cases investigated. These cases were found to be characterized by a predisposition to revarization. Knee joints in which the preoperative varus moment was significantly high or there was a tendency to under-correction were especially likely to show these features. For these reasons, valgus tibial head osteotomies should generally be performed with slight overcorrection. If the preoperative gait analysis has already confirmed that significantly increased varus forces are in play, a definite overcorrection to about 5 degrees beyond the physiological angle should be the aim.

Injuries to the posterolateral aspect of the knee accompanied by compression fracture of the anterior part of the medial tibial plateau

We present 12 cases of patients with injury to the posterolateral aspect of the knee accompanied by a compression fracture of the anterior part of the medial tibial plateau. There were 11 male patients and 1 female patient with an average age of 26 years (range, 17 to 44 years). There were 4 cases of posterolateral rotatory instability and 8 cases of straight lateral instability of the knee. The size of the compression fracture was classified into 2 types, small (8 cases) and large (4 cases). Although the mechanism of injury was considered to be hyperextension and varus force, the pattern of cruciate ligament injuries varied from case to case. The following 3 questions should be considered to determine which cruciate ligament is damaged: (1) Was the ipsilateral foot fixed to the ground? (2) Was forward inertia involved? (3) Was there a direct blow to the anteromedial aspect of the tibia or to the femur? Accompanied fractures of the medial tibial plateau were considered to have been compressed by the medial femoral condyle. The size of the accompanying compression fracture varied; 7 of 8 cases with a small-type fracture had posterior cruciate ligament injuries and 3 of 4 cases with a large-type fracture had anterior cruciate ligament injuries. The size of the fracture is determined by which point of the medial tibial plateau touched the medial femoral condyle. We propose that a compression fracture of the anterior part of the medial tibial plateau indicates a coexistent posterolateral aspect injury, and that especially a small compression fracture strongly suggests an accompanying posterior cruciate ligament injury, as well.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 17, No 6 (July-August), 2001: pp 642–647

Elbow load during pushup at various forearm rotations

Objective. Elbow joint loading was evaluated during pushup exercises at various forearm rotations. Design. Subjects were asked to perform pushup in various forearm rotations: neutral, 90° internal rotation, and 90° external rotation. Background. Training with pushup exercise is good for the muscles and joints of the upper extremities. However, excessive shear forces on the elbow might lead to injuries to either normal trainees or to handicapped people, especially for those who rely on elbow prosthesis. Methods. The kinematics and kinetics of the elbow joint were investigated under various forearm rotations. Results. The loading biomechanics of the elbow joint differed with various forearm rotations. It was noted that greater posterior and varus forces of the elbow are encountered with internal rotation of the hand position and, consequently, full forearm pronation. Conclusions. Pushup with hands in internally rotated position should be prevented so as to avoid excessive shear forces or moments. Relevance Knowledge of elbow kinematics and kinetics may be helpful in preventing injuries by reducing the elbow shear force with changes of forearm rotation.

Tension Band Fixation for Unstable Two-Part Humeral Fractures in Patients with Osteopenic Bone (Parachute Technique)

Tension Band Fixation for Unstable Two-Part Humeral Fractures in Patients with Osteopenic Bone (Parachute Technique)

Medial Collateral Ligament Reconstruction

Medial Collateral Ligament Reconstruction

The effects of grade III posterolateral knee complex injuries on anterior cruciate ligament graft force. A biomechanical analysis.

To determine if untreated grade III injuries of the posterolateral structures contribute to increased force on an anterior cruciate ligament graft, we measured the force in the graft in cadaveric knees during joint loading after reconstruction with otherwise intact structures and in the same reconstructed knees after selected cutting of specific posterolateral knee structures. Tests were first performed on the knee with the posterolateral structures intact and then after sequential sectioning of the fibular collateral ligament, popliteofibular ligament, and popliteus tendon. The graft force was significantly higher after fibular collateral ligament transection during varus loading at both 0 degree and 30 degrees of knee flexion than it was for the same loading of the joint with intact posterolateral structures. In addition, coupled loading of varus and internal rotation moments at 0 degree and 30 degrees of flexion further increased graft force beyond that with varus force alone. The increase in graft force remained significant with additional sequential cutting of the popliteofibular ligament and popliteus tendon. We believe this study supports the clinical observation that untreated grade III posterolateral structure injuries contribute to anterior cruciate ligament graft failure by allowing higher forces to stress the graft.

The popliteofibular ligament

We designed an experimental study to prove the existence of the popliteofibular ligament (PFL) and to define its role in providing static stability of the knee. We also examined the contribution of the lateral collateral ligament (LCL). We found this ligament to be present in all eight human cadaver knees examined. These specimens were mounted on a specially designed rig and subjected to posterior, varus and external rotational forces. We used the technique of selective sectioning of ligaments and measured the displacement with a constant force applied, before and after its division. We recorded the displacement in primary posterior translation, coupled external rotation, primary varus angulation and primary external rotation. Statistical analysis using the standard error of the mean by plotting 95% confidence intervals, was used to evaluate the results. The PFL had a significant role in preventing excessive posterior translation and varus angulation, and in restricting excessive primary and coupled external rotation. Isolated section of the belly of popliteus did not cause significant posterolateral instability of the knee. The LCL was also seen to act as a primary restraint against varus angulation and secondary restraint against external rotation and posterior displacement. Our findings showed that in knees with isolated disruption of the PFL stability was restored when it was reconstructed. However in knees in which the LCL was also disrupted, isolated reconstruction of the PFL did not restore stability.

The popliteofibular ligament. An anatomical study of the posterolateral corner of the knee.

We designed an experimental study to prove the existence of the popliteofibular ligament (PFL) and to define its role in providing static stability of the knee. We also examined the contribution of the lateral collateral ligament (LCL). We found this ligament to be present in all eight human cadaver knees examined. These specimens were mounted on a specially designed rig and subjected to posterior, varus and external rotational forces. We used the technique of selective sectioning of ligaments and measured the displacement with a constant force applied, before and after its division. We recorded the displacement in primary posterior translation, coupled external rotation, primary varus angulation and primary external rotation. Statistical analysis using the standard error of the mean by plotting 95% confidence intervals, was used to evaluate the results. The PFL had a significant role in preventing excessive posterior translation and varus angulation, and in restricting excessive primary and coupled external rotation. Isolated section of the belly of popliteus did not cause significant posterolateral instability of the knee. The LCL was also seen to act as a primary restraint against varus angulation and secondary restraint against external rotation and posterior displacement. Our findings showed that in knees with isolated disruption of the PFL stability was restored when it was reconstructed. However in knees in which the LCL was also disrupted, isolated reconstruction of the PFL did not restore stability.

Elbow joint kinematics after excision of the radial head

The contribution of the radial head to elbow joint kinematics was studied in 7 osteoligamentous elbow preparations. During unloaded flexion and extension, radial head excision induced a maximum varus displacement of 1.6° with 20° of joint flexion and a maximum external rotation of 3.2° at 110° of flexion. With application of a 0.75-Nm load, radial head excision induced a maximum laxity of 3.3° at 20° of flexion in forced varus and a maximum laxity of 8.9° at 10° of flexion in forced external rotation. No laxity was observed in forced valgus or internal rotation. The results were independent of the rotation of the forearm. This study indicates that the radial head acts as stabilizer to the elbow joint in forced varus and in forced external rotation. The results suggest that fractures of the radial head cannot be treated by simple excision without altering the basic kinematics of the elbow joint.

Hyperextension trauma to the elbow joint induced through the distal ulna or the distal radius: pathoanatomy and kinematics. An experimental study of the ligament injuries.

Loads applied to the forearm result in hyperextension of the elbow. The pathomechanics of hyperextension trauma with load applied to the distal radius and ulna were studied in 10 macroscopically normal cadaver elbow joint specimens to reveal patterns of injury with radial traction (n = 5) compared to ulnar traction (n = 5). The mean age of the donors was 60.8 years (range 33-74). Kinematic testing was performed in an experimental 3D-kinematic loading apparatus. The extension range of motion increased by 20.9 degrees +/- 2.9 degrees after joint loading. Hyperextension loads induced joint laxity during flexion of less than 60 degrees. In both groups, the changes were significant in joint flexion during forced valgus and external rotation, but were not significant in flexion during forced varus and internal rotation. In both groups, the same four lesions were produced: 1) Anterior capsule rupture, 2) L-formed rupture of the origin of the pronator muscle with elongation of the anterior bundle of the medial collateral ligament, 3) partial rupture of the lateral collateral ligament and 4) small cartilage damage to the posterior or anteromedial edge of the ulna. In conclusion, hyperextension trauma to the elbow joint induced through the distal ulna or the distal radius produced the same pattern of injury as reported in hyperextension of the elbow with traction to the forearm when free rotation of the radius relative to the ulna was allowed.

Hyperextension of the elbow joint: Pathoanatomy and kinematics of ligament injuries

According to an epidemiologic study (Scand J Med Sci 1996;6:297–302) the mechanism of “handball goalie's elbow” may be forced hyperextension. The pathomechanics of hyperextension were studied in nine macroscopically normal male cadaver elbow joints. The mean age of the donors was 43.2 years (range 25 to 61 years). Kinematic tests were performed with an experimental three-dimensional kinematic loading apparatus. Hyperextension loads induced joint laxity during flexion of less than 50°. The kinematic changes were significant in joint flexion during forced valgus and external and internal axial rotation, but were not significant in flexion during forced varus. No instability was found with flexion beyond 90°. The hyperextension loads produced four lesions: (1) anterior capsule rupture; (2) L-shaped rupture of the pronator/flexor origin with elongation of the anterior part of the medial collateral ligament; (3) occasional incomplete rupture of the lateral collateral ligament; and (4) small fragments of cartilage near the posterior edge of the ulna in one of the specimens. One or more of these lesions may be responsible for the symptoms in “handball goalie's elbow.”

Combined hyperextension and supination of the elbow joint induces lateral ligament lesions. An experimental study of the pathoanatomy and kinematics in elbow ligament injuries.

An epidemiological study suggested that the injury mechanism of 'handball goalie's elbow' may be hyperextension. The pathomechanics of hyperextension combined with supination was studied in ten macroscopically normal, male, cadaveric elbow joint specimens. The age of the donors was 28.8 years (range 18-45 years). Extension loading of the elbow was performed in an experimental three-dimensional (3D)-kinematic loading apparatus. The degree of extension increased by 16.7 degrees +/- 8.7 degrees after loading. Hyperextension loads induced significant joint laxity in joint flexion (< 50 degrees) during forced valgus, external and internal rotation, respectively, but not during forced varus. The hyperextension trauma produced three lesions: (1) anterior capsule rupture, (2) avulsion of the proximal insertion of both the medial and the lateral collateral ligaments, and (3) occasional single rupture of the lateral collateral ligament. The lesions indicate that combined hyperextension and supination represent a possible mechanism leading to 'handball goalie's elbow'.

KNEE INJURY - BASEBALL 830

HISTORY: A 23 year old minor league baseball player collides with a team mate while attempting to field a fly ball. While the player is unsure of the mechanism, he believes his right knee was bent when he collided with the other player. Further, he believes the leg was off the ground, and he remembers no twisting motion during the injury. At the end of the play, he fell on his back with the knee bent in flexion. This could not be described any further. He was able to extend the leg, and no clicking or popping was noted. Evaluation by the trainer showed point tenderness along both the medial and lateral joint line. Laxity of the lateral collateral and anterior cruciate ligaments. Over the last 3 days, swelling has occurred despite icing and immobilization of the knee. The pain has localized to the lateral joint line, femoral condyle and tibial condyle. Player is still reluctant to bear weight with out the immobilizer. PHYSICAL EXAMINATION: Right knee is swollen with ballottable patella, but no discoloration. There is point tenderness along the lateral collateral ligament, as well as the lateral joint line. Range of motion showed extension to zero with recurvatum of about 10 degrees on the left knee. Flexion was to 90 degrees on the right side. Muscle strength was 4+ out of 5 for flexion and extension. Laxity of the right knee noted with varus force. Lachman's, and anterior drawer tests. These test did increase pain. Unable to evaluate McMurray test due to swelling. Slight patella laxity with no apprehension or pain, and normal tracking. Neurovascualar was intact. DIFFERENTIAL DIAGNOSIS- Lateral Collateral Sprain, 2nd to 3rd degree. Possible Anterior Cruciate Ligament Sprain, 2nd to 3rd degree. Possible lateral meniscus tear. TESTS AND RESULTS- Right knee X-ray: normal knee without fracture, dislocation, or avulsion fractures. Right knee MRJ: joint effusion, intact PCL, intact MCL, normal appearing menisci, tear of ACL, LCL, and Tensor Fascia Lata. FINAL DIAGNOSIS- LCL 3rd degree sprain ACL 3rd degree sprain Torn Tensor Fascia Lata TREATMENT- Patient under went arthroscopic evaluation and repair of torn structures. This was followed by aggressive rehabilitation.

Kinematics of the lateral ligamentous constraints of the elbow joint.

Thirty osteoligamentous elbow joint specimens were included in a study of the lateral collateral ligament complex (LCLC). The morphologic characteristics of the LCLC were examined, and then three-dimensional kinematic measurements were undertaken after selective ligament dissections were performed. Isolated sectioning of the annular ligament (AL) or the lateral ulnar collateral ligament (LUCL) induced only minor laxity to the elbow joint with a maximum of 2.2 degrees and 4.4 degrees during forced varus and external rotation (supination), respectively. Transsection of the lateral collateral ligament (LCL) caused a maximal laxity of 15.4 degrees and 22.8 degrees during forced varus and external rotation (supination), respectively. Combined ligament dissections showed that total transection of the LCLC at the ulnar or the humeral insertion was important for joint laxity. Total transection of the LCLC at the humeral or the ulnar insertion induced a maximal laxity of 24.5 degrees and 37 degrees during forced varus and external rotation (supination), respectively. This study suggests the AL and the LUCL are of minor importance as constraints when cut separately, whereas the LCL is a significant preventer of elbow joint laxity. The LCLC was observed to be a complex structure of ligamentous fibers rather than discreet bands. The LCLC forms a ligamentous constraint between the lateral humeral epicondyle and the ulna, stabilizing the elbow joint and forming a base for radial head stability and rotation.

Lateral collateral ligament of the elbow joint: anatomy and kinematics.

The structure and kinematics of the lateral collateral ligament of the elbow joint were investigated in 10 cadaveric specimens. The lateral collateral ligament was observed to be a distinct part of the lateral collateral ligament complex. It contains posterior fibers that pass through the annular ligament and insert on the ulna. Three-dimensional kinematic measurements in different forearm rotations showed that joint puncture induced a 1 degree joint laxity significant in forced varus from 30 degrees to 80 degrees of flexion and in forced external rotation from 30 degrees to 120 degrees of flexion. Division of the posterolateral capsule caused no further laxity. Cutting the lateral collateral ligament induced a maximum laxity of 11.8 degrees at 110 degrees of flexion in forced varus and a maximum laxity of 20.6 degrees at 110 degrees of flexion in forced external rotation. The corresponding maximal posterior radial head translation was observed at 80 degrees to 100 degrees of flexion and was 5.7 mm in forced varus and 8.1 mm in forced external rotation. This study suggests the lateral collateral ligament to be an important stabilizer of the humeroulnar joint and the radial head in forced varus and external rotation. The humeroulnar stability is independent of forearm rotation.