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.     

Metallic radial head arthroplasty improves valgus stability of the elbow

The stabilizing influence of radial head arthroplasty was studied in eight medial collateral ligament deficient anatomic specimen elbows. An elbow testing apparatus, which used computer controlled pneumatic actuators to apply tendon loading, was used to simulate active elbow flexion. The motion pathways of the elbow were measured using an electromagnetic tracking device, with the forearm in supination and pronation. As a measure of stability, the maximum varus to valgus laxity over the range of elbow flexion was determined from the difference between varus and valgus gravity loaded motion pathways. After transection of the medial collateral ligament, the radial head was excised and replaced with either a silicone or one of three metallic radial head prostheses. Medial collateral ligament transection caused a significant increase in the maximum varus to valgus laxity to 18.0 degrees +/- 3.2 degrees. After radial head excision, this laxity increased to 35.6 degrees +/- 10.3 degrees. The silicone implant conferred no increase in elbow stability, with a maximum varus to valgus laxity of 32.5 degrees +/- 15.5 degrees. All three metallic implants improved the valgus stability of the medial collateral ligament deficient elbow, providing stability similar to the intact radial head. The use of silicone arthroplasty to replace the radial head in the medial collateral ligament deficient elbow must be questioned. Metallic radial head arthroplasty provides improved valgus stability, approaching that of an intact radial head.     

Ligamentous stabilizers against posterolateral rotatory instability of the elbow.

BACKGROUND: The lateral ulnar collateral ligament, the entire lateral collateral ligament complex, and the overlying extensor muscles have all been suggested as key stabilizers against posterolateral rotatory instability of the elbow. The purpose of this investigation was to determine whether either an intact radial collateral ligament alone or an intact lateral ulnar collateral ligament alone is sufficient to prevent posterolateral rotatory instability when the annular ligament is intact. METHODS: Sequential sectioning of the radial collateral and lateral ulnar collateral ligaments was performed in twelve fresh-frozen cadaveric upper extremities. At each stage of the sectioning protocol, a pivot shift test was performed with the arm in a vertical position. Passive elbow flexion was performed with the forearm maintained in either pronation or supination and the arm in the varus and valgus gravity-loaded orientations. An electromagnetic tracking device was used to quantify the internal-external rotation and varus-valgus angulation of the ulna with respect to the humerus. RESULTS: Compared with the intact elbow, no differences in the magnitude of internal-external rotation or maximum varus-valgus laxity of the ulna were detected with only the radial collateral or lateral ulnar collateral ligament intact (p > 0.05). However, once the entire lateral collateral ligament was transected, significant increases in internal-external rotation (p = 0.0007) and maximum varus-valgus laxity (p < 0.0001) were measured. None of the pivot shift tests had a clinically positive result until the entire lateral collateral ligament was sectioned. CONCLUSIONS: This study suggests that, when the annular ligament is intact, either the radial collateral ligament or the lateral ulnar collateral ligament can be transected without inducing posterolateral rotatory instability of the elbow.     

Single-strand reconstruction of the lateral ulnar collateral ligament restores varus and posterolateral rotatory stability of the elbow

Because of a lack of biomechanical studies of lateral elbow ligament reconstruction in the literature, the initial stability afforded by 3 different techniques of lateral ulnar collateral ligament reconstruction was evaluated in 8 cadaveric elbows. The arm was mounted in a testing apparatus, and passive flexion was performed with the arm in varus and valgus orientations. A pivot shift test was performed with the arm in the vertical orientation. An electromagnetic tracking device was used to quantify motion pathways. After intact testing, each specimen underwent sectioning of the radial collateral and lateral ulnar collateral ligaments from the lateral epicondyle. Reconstruction of the lateral ulnar collateral ligament was performed in a randomized sequence, consisting of proximal single-strand, distal single-strand, and double-strand tendon grafts. Division of the radial collateral and lateral ulnar collateral ligaments from the lateral epicondyle caused a significant decrease in rotational stability when the pivot shift test was being performed (P <.0001). Varus-valgus stability also decreased after transection of the radial collateral and lateral ulnar collateral ligaments (P <.0001). Reconstruction of the lateral ulnar collateral ligament restored elbow stability to that of the intact state. There was no significant difference in stability between the single- and double-strand repair techniques (P >.05). This study demonstrates that both single- and double-strand reconstructions restore varus and posterolateral elbow stability and may be considered appropriate reconstructive procedures in patients with symptomatic insufficiency of the lateral ligaments of the elbow.     

Contribution of monoblock and bipolar radial head prostheses to valgus stability of the elbow.

BACKGROUND: The purpose of this study was to evaluate the stabilizing effect of radial head replacement in cadaver elbows with a deficient medial collateral ligament. METHODS: Passive elbow flexion with the forearm in neutral rotation and in 80 degrees of pronation and supination was performed under valgus and varus loads (1) in intact elbows, (2) after a surgical approach (lateral epicondylar osteotomy of the distal part of the humerus), (3) after release of the anterior bundle of the medial collateral ligament, (4) after release of the anterior bundle of the medial collateral ligament and resection of the radial head, and (5) after subsequent replacement of the radial head with each of three different types of radial head prostheses (a Wright monoblock titanium implant, a KPS bipolar Vitallium [cobalt-chromium]-polyethylene implant, and a Judet bipolar Vitallium-polyethylene-Vitallium implant) in the same cadaver elbow. Total valgus elbow laxity was quantified with use of an electromagnetic tracking device. RESULTS: The mean valgus laxity changed significantly (p < 0.001) as a factor of constraint alteration. The greatest laxity was observed after release of the medial collateral ligament together with resection of the radial head (11.1 degrees +/- 5.6 degrees). Less laxity was seen following release of the medial collateral ligament alone (6.8 degrees +/- 3.4 degrees), and the least laxity was seen in the intact state (3.4 degrees +/- 1.6 degrees). Forearm rotation had a significant effect (p = 0.003) on valgus laxity throughout the range of flexion. The laxity was always greater in pronation than it was in neutral rotation or in supination. The mean valgus laxity values for the elbows with a deficient medial collateral ligament and an implant were significantly greater than those for the medial collateral ligament-deficient elbows before radial head resection (p < 0.05). The implants all performed similarly except in neutral forearm rotation, in which the elbow laxity associated with the Judet implant was significantly greater than that associated with the other two implants. CONCLUSIONS AND CLINICAL RELEVANCE: This study showed that a bipolar radial head prosthesis can be as effective as a solid monoblock prosthesis in restoring valgus stability in a medial collateral ligament-deficient elbow. However, none of the prostheses functioned as well as the native radial head, suggesting that open reduction and internal fixation to restore radial head anatomy is preferable to replacement when possible.     

Lateral collateral ligament deficiency of the elbow joint: A modeling approach

A computational model capable of predicting the effects of lateral collateral ligament deficiency of the elbow joint would be a valuable tool for surgical planning and prediction of the long‐term consequences of ligament deficiency. The purpose of this study was to simulate lateral collateral ligament deficiency during passive flexion using a computational multibody elbow joint model and investigate the effects of ligament insufficiency on the kinematics, ligament loads, and articular contact characteristics (area, pressure). The elbow was placed initially at approximately 20° of flexion and a 345 mm vertical downward motion profile was applied over 40 s to the humerus head. The vertical displacement induced flexion from the initial position to a maximum flexion angle of 135°. The study included simulations for intact, radial collateral ligament deficient, lateral ulnar collateral ligament deficient, and combined radial and lateral ulnar collateral ligament deficient elbow. For each condition, relative bone kinematics, contact pressure, contact area, and intact ligament forces were predicted. Intact and isolated radial collateral ligament deficient elbow simulations were almost identical for all observed outcomes. Minor differences in kinematics, contact area and pressure were observed for the isolated lateral ulnar collateral ligament deficient elbow compared to the intact elbow, but no elbow dislocation was detected. However, sectioning both ligaments together induced substantial differences in kinematics, contact area, and contact pressure, and caused complete dislocation of the elbow joint. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1645–1655, 2016.     

The stability of the elbow following excision of the radial head and transection of the annular ligament. An experimental study

The stabilizing role of the lateral ligament complex and the radial head were investigated in ten osteoligamentous elbow preparations. The annular ligament was the prime stabilizer of the lateral aspect of the elbow. Transection of the annular ligament caused maximal varus and external rotatory instability of 13.7 degrees and 32.8 degrees respectively, with an elbow flexion about 70 degrees. Isolated excision of the radial head caused slight varus and external rotatory instability of 4.8 degrees and 10.4 degrees respectively, with an elbow flexion about 40 degrees. The lateral collateral ligament had only a minor stabilizing function of the elbow. The stability of the elbow after excision of the radial head may be improved by proper preservation of the annular ligament.     

The effect of radial head fracture size on elbow kinematics and stability.

This study determined the effect of radial head fracture size and ligament injury on elbow kinematics. Eight cadaveric upper extremities were studied in an in vitro elbow simulator. Testing was performed with ligaments intact, with the medial collateral (MCL) or lateral collateral (LCL) ligament detached, and with both the MCL and LCL detached. Thirty degree wedges were sequentially removed from the anterolateral radial head up to 120 degrees . Valgus angulation and external rotation of the ulna relative to the humerus were determined for passive motion, active motion, and pivot shift testing with the arm in a vertical (dependent) orientation. Maximum varus-valgus laxity was calculated from measurements of varus and valgus angulation with the arm in horizontal gravity-loaded positions. No effect of increasing radial head fracture size was observed on valgus angulation during passive and active motion in the dependent position. In supination, external rotation increased with increasing fracture size during passive motion with LCL deficiency and both MCL and LCL deficiency. With intact ligaments, maximum varus-valgus laxity increased with increasing radial head fracture size. With ligament disruption, elbows were grossly unstable, and no effect of increasing radial head fracture size occurred. During pivot shift testing, performed with the ligaments intact, subtle instability was noted after resection of one-third of the radial head. In this in vitro biomechanical study, small subtle effects of radial head fracture size on elbow kinematics and stability were seen in both the ligament intact and ligament deficient elbows. These data suggest that fixation of displaced radial head fractures less than or equal to one-third of the articular diameter may have some biomechanical advantages; however, clinical correlation is required.     

The stability of the elbow following excision of the radial head and transection of the annular ligament

Summary The stabilizing role of the lateral ligament complex and the radial head were investigated in ten osteoligamentous elbow preparations. The annular ligament was the prime stabilizer of the lateral aspect of the elbow. Transection of the annular ligament caused maximal varus and external rotatory instability of 13.7° and 32.8° respectively, with an elbow flexion about 70°. Isolated excision of the radial head caused slight varus and external rotatory instability of 4.8° and 10.4° respectively, with an elbow flexion about 40°. The lateral collateral ligament had only a minor stabilizing function of the elbow. The stability of the elbow after excision of the radial head may be improved by proper preservation of the annular ligament.     

Effects of elbow flexion and forearm rotation on valgus laxity of the elbow

BACKGROUND: Clinical evaluation of valgus elbow laxity is difficult. The optimum position of elbow flexion and forearm rotation with which to identify valgus laxity in a patient with an injury of the ulnar collateral ligament of the elbow has not been determined. The purpose of the present study was to determine the effect of forearm rotation and elbow flexion on valgus elbow laxity. METHODS: Twelve intact cadaveric upper extremities were studied with a custom elbow-testing device. Laxity was measured with the forearm in pronation, supination, and neutral rotation at 30 degrees, 50 degrees, and 70 degrees of elbow flexion with use of 2 Nm of valgus torque. Testing was conducted with the ulnar collateral ligament intact, with the joint vented, after cutting of the anterior half (six specimens) or posterior half (six specimens) of the anterior oblique ligament of the ulnar collateral ligament, and after complete sectioning of the anterior oblique ligament. Laxity was measured in degrees of valgus angulation in different positions of elbow flexion and forearm rotation. RESULTS: There were no significant differences in valgus laxity with respect to elbow flexion within each condition. Overall, for both groups of specimens (i.e., specimens in which the anterior or posterior half of the anterior oblique ligament was cut), neutral forearm rotation resulted in greater valgus laxity than pronation or supination did (p < 0.05). Transection of the anterior half of the anterior oblique ligament did not significantly increase valgus laxity; however, transection of the posterior half resulted in increased valgus laxity in some positions. Full transection of the anterior oblique ligament significantly increased valgus laxity in all positions (p < 0.05). CONCLUSIONS: The results of this in vitro cadaveric study demonstrated that forearm rotation had a significant effect on varus-valgus laxity. Laxity was always greatest in neutral forearm rotation throughout the ranges of elbow flexion and the various surgical conditions. CLINICAL RELEVANCE: The information obtained from the present study suggests that forearm rotation affects varus-valgus elbow laxity. Additional investigation is warranted to determine if forearm rotation should be considered in the evaluation and treatment of ulnar collateral ligament injuries of the elbow joint.     

冠突前内侧面骨折与外侧副韧带损伤的治疗

目的探讨冠突前内侧骨折后,外侧副韧带是否需要全部修复。 方法选自2012年7月至2016年7月天津医院共收治的19例冠突前内侧骨折患者,排除1例合并桡骨远端骨折患者,1例既往关节炎患者。术前行影像学检查,包括肘关节正侧位X线片、CT检查,以明确损伤类型。根据O’Driscoll分型2-1型4例,2-2型9例,2-3型4例。所有患者均采用肘关节内侧入路（尺侧腕屈肌入路）,固定冠突骨折后,给予内翻应力试验,如为阳性,修复外侧副韧带;如为阴性,不修复。采用Mayo肘关节功能评分（mayo elbow performance score,MEPS）、上肢功能障碍评分（disability of arm shoulder and hand,DASH）、视觉模拟评分法（visual analogue scale/score,VAS）对肘关节功能进行评价。 结果冠突骨折固定后,内翻试验阳性患者13例,给予外侧副韧带修补术,阴性患者4例,未给予外侧副韧带修补。所有患者均获得满意的肘关节评分,MEPS平均97.6分,DASH平均4.13分,VAS平均0.4分;关节炎Broberg-Morrey标准I度5例。 结论在冠突前内侧骨折的治疗中,冠突固定后的内翻试验对于判断肘关节稳定性至关重要,外侧副韧带修复与否取决于内翻应力试验。     

The effect of medial collateral ligament repair tension on elbow joint kinematics and stability

PURPOSE: Medial collateral ligament (MCL) repair is commonly performed for the management of acute or subacute instability after elbow dislocations and fracture-dislocations. The effectiveness of transosseous repair of the MCL, as is typically performed clinically, in restoring the normal kinematics and stability of the elbow is of interest as is the effect of MCL tensioning on the initial stability of the elbow. The purpose of this study was to determine whether suture repair of the MCL is able to restore the normal kinematics and stability of the elbow and to determine the optimal initial MCL repair tension. METHODS: Six cadaveric upper extremities were mounted in an upper limb joint simulator. Simulated active and passive elbow flexion was generated while the kinematics were measured with the arm in the dependent and the valgus gravity-loaded orientations. After testing the intact elbow, the MCL was released at its humeral attachment and repaired using a transosseous suture technique at three different repair tensions: 20, 40, and 60 N. RESULTS: Medial collateral ligament repair using a transosseous suture technique restored the kinematics and stability of the MCL-deficient elbow. Motion pathways were affected by the magnitude of initial MCL tension. For all arm orientations and forearm positions, the 20-N and 40-N repairs were not statistically different from each other or from the intact MCL. The 60-N repairs, however, were often statistically different than the other groups, suggesting an overtightening that tended to pull the ulna into a varus position-especially in the midrange of flexion. CONCLUSIONS: These data suggest that MCL repair using transosseous sutures provide adequate joint stability to permit early motion. There is a broad range of acceptable tensions for MCL repair, which is a favorable, clinically relevant finding. Clinical studies are needed to validate these in vitro results.     

Elbow subluxation and dislocation. A spectrum of instability.

After sequential releases of the ligaments and capsules of 13 fresh autopsy specimen elbows, external rotation and valgus moments with axial forces resulted in posterior dislocations in 12 of the 13 with the anterior medical collateral ligament (AMCL) intact. Kinematic displacements measured with a three-dimensional electromagnetic tracking device showed that dislocation involved posterolateral rotation of 34 degrees-50 degrees and 5 degrees-23 degrees valgus at about 80 degrees flexion. Dislocation is the final of three sequential stages of elbow instability resulting from posterolateral rotation, with soft-tissue disruption progressing from lateral to medial. In each stage, the pathoanatomy correlated with the pattern and degree of instability. Testing for valgus stability of the elbow during simulated active flexion revealed no significant increase (-0.3 degrees-2.4 degrees) in valgus laxity after reduction compared with the intact specimens (p greater than 0.05, beta = 0.1, delta = 2.5 degrees). In no case did the digitized AMCL origin-to-insertion distance increase beyond normal during the dislocation (p less than 0.01). The mechanism of dislocation during a fall on the outstretched hand would involve the body "rotating internally" on the elbow, which experiences an external rotation/valgus moment as it flexes. Posterior dislocations should therefore be reduced in supination. If valgus stability in pronation is demonstrated, the AMCL can be assumed to be intact, and rehabilitation in a hinged cast-brace with the elbow in full pronation can be commenced immediately.     

Effectiveness of the lateral unilateral dynamic external fixator after elbow ligament injury

BACKGROUND: The optimum management of ligamentous injuries of the elbow is not known. Use of dynamic external fixators has been advocated to stabilize the joint while maintaining motion, but there are no published data to corroborate their efficacy. The purpose of this study was to test the hypothesis that a laterally applied unilateral dynamic external fixator is capable of stabilizing and restoring normal kinematics to elbows with varying degrees of soft-tissue injury. METHODS: Six fresh-frozen cadaveric upper extremities, from donors who were an average of seventy-six years of age at the time of death, were tested in a custom apparatus with an electromagnetic tracking device to analyze the kinematic behavior. Testing began with an injury of either the lateral or the medial collateral ligament, which was followed by a second test with an injury to the ligament on the contralateral side of the joint. In each test, the varus-valgus displacement and the forearm rotatory displacement were measured through the arc of elbow flexion under three loading conditions (hand weight alone, hand weight plus 3.5 N, and hand weight plus 7 N). After each test (with each injury), a unilateral external fixator was applied from the lateral aspect of the elbow, and the same measurements were conducted under the three loading conditions across the elbow joint. RESULTS: With varus stress testing, both after injury of the medial collateral ligament alone and after injury of the lateral collateral ligament and extensor mass alone, the laterally applied unilateral dynamic external fixator was capable of maintaining the displacements within the laxity envelope of an uninjured elbow. With valgus stress testing, after either lateral or medial ligamentous injury, the fixator was unable to maintain displacements within the normal laxity envelope when a 7-N load was applied to the elbow. When both medial and lateral injuries were present, the lateral fixator maintained varus displacement within normal limits, but valgus displacement was consistently maintained within normal limits only when no additional load was applied to the forearm. CONCLUSIONS: A lateral dynamic elbow external fixator is capable of maintaining varus displacements within normal limits in the presence of medial and lateral collateral ligament injuries and with a 7-N load added to the limb. However, valgus displacement is only consistently maintained within normal limits if no additional displacement force is added to the weight of the hand and forearm. The maintenance of valgus displacement is more sensitive to additional load and specifically to the extent of medial soft-tissue injury.     

Rehabilitation of the Medial- and Lateral Collateral Ligament-deficient Elbow: An In Vitro Biomechanical Study

DesignIn vitro biomechanical research using an elbow motion simulator.IntroductionThe optimal rehabilitation of elbow dislocations with medial collateral ligament (MCL) and lateral collateral ligament (LCL) injuries has not been defined.PurposeTo determine a safe rehabilitation protocol for elbow dislocations with MCL and LCL injuries.MethodsEight cadaveric elbows underwent simulated active and passive motions with the arm in multiple orientations. Varus–valgus angulation and internal–external rotation of the ulna relative to the humerus were quantified for the intact joint and with injured MCL and LCL.ResultsActive motion with injured MCL and LCL in the horizontal and vertical orientations resulted in kinematics similar to the intact elbow, whereas passive motion resulted in significant kinematic alterations. Marked elbow instability was noted in the varus and valgus orientations using both active and passive motion.ConclusionsElbows with MCL and LCL injuries should be rehabilitated using active motion in the horizontal or vertical orientations.Level of EvidenceBasic science research.     

尺骨鹰嘴部分切除对肘关节稳定性影响的研究

目的探讨尺骨鹰嘴尖部截骨短缩对肘关节稳定性的影响。方法取10具20侧男性新鲜上肢标本，随机分为四组，每组5侧标本，即尺骨鹰嘴完整组、截骨3mm组、截骨6mm组、截骨9mm组，截骨在尺骨鹰嘴尖部。每组分别在肘关节屈曲30°、60°、90°、120°时，前臂加1．96Nm力矩的情况下，测量外翻位肘外翻角度和内侧副韧带前束长度及内翻位肘内翻角度和桡侧尺副韧带长度。结果尺骨鹰嘴尖部截骨时，于同一肘关节屈曲位，随着尺骨鹰嘴尖部截骨量增大，肘关节内侧副韧带前束的长度逐渐变长，外翻角逐渐增大，当截骨量大于3mm上述变化差异显著，有统计学意义（P〈0．05）。结论尺骨鹰嘴尖部截骨量超过3mm时，肘关节出现不稳定。因此临床上当尺骨鹰嘴尖部严重粉碎性骨折片不超过3mm时，可予以手术切除，对肘关节稳定性影响不大，否则应给予修复重建。而对于尺骨鹰嘴尖部后内侧骨赘，建议仅切除骨赘或切除范围不超过正常鹰嘴尖部3mm。     

Biomechanical evaluation of the elbow using roentgen stereophotogrammetric analysis

The medial collateral ligament complex is the primary constraint of the elbow to valgus forces and is composed of the anterior bundle, the posterior bundle, and a transverse part. Total and partial ruptures have been described. Clinical and radiologic examinations of medial or valgus instability of the elbow are difficult. The effect of different stages of medial collateral ligament ruptures on ulnohumeral movement in cadavers was determined to rationalize the use of physical and radiologic examinations in different stages of valgus instability in vivo. Using roentgen stereophotogrammetric analysis, motion is determined between the humerus and ulna under valgus load and between the humerus and radius during maximal pronation of the forearm after various dimensions of medial collateral ligament lesions. The increase in distance between the humerus and ulna under a 15 N valgus load varied from 2.7 mm to 9.8 mm. The increase in distance between the humerus and proximal radius with the forearm in pronation in an intact specimen and after transsection of the anterior medial collateral ligament and posterior medial collateral ligament in the anterior direction was 9.7 mm. These results suggest that detection of partial ruptures with clinical and radiologic examinations is difficult. Anterior movement of the radial head can be used as an additional parameter of valgus instability.     

Stabilizers of capitellocondylar total elbow arthroplasty

The contribution of the medial and lateral collateral ligaments (MCL, LCL) and muscle forces to the kinematics and stability of the capitellocondylar total elbow arthroplasty was investigated in six fresh cadaveric elbows. The three-dimensional orientation of the ulna relative to the humerus was monitored with the use of an electromagnetic tracking device in neutral, valgus, and varus stress positions with (1) the ligaments intact, (2) LCL insufficiency obtained by osteotomizing the lateral epicondyle, (3) partial MCL insufficiency obtained by sectioning either the anterior or posterior bundle of the MCL, and (4) complete MCL insufficiency. Simulated muscle forces were applied as follows: (1) no load, (2) 1 kg each to the biceps and the brachialis and 2 kg to the triceps, and (3) 2 kg to the biceps and the brachialis and 4 kg to the triceps. The laxity was defined as the difference in valgus/varus orientation of the ulna in the valgus and varus stress positions. The laxity at 40°, 75°, and 110° elbow flexion was analyzed. The greatest laxity occurred with LCL insufficiency (40.7° ± 11.6°, average at three flexion angles) followed by that with MCL insufficiency (15.7° ± 9.9°), both of which were significantly larger than laxity with the intact ligaments (5.6° ± 2.5°). The laxity with the anterior bundle sectioned (12.0° ± 8.1°) was significantly greater than with the posterior bundle sectioned (3.3° ± 3.6°); thus the contribution of anterior bundle to stability was four times that of posterior bundle. Stabilizing effect of muscle loading was small in elbows with intact ligaments, whereas it was large with LCL or MCL insufficiency. Based on these data, we can see that the integrity of both the MCL and LCL is essential to maintain stability of this total elbow, the anterior bundle is a more important stabilizer than the posterior bundle, and the collateral ligaments seem to be the primary stabilizer and the musculature seems to be the secondary stabilizer. Careful implantation technique to preserve the collateral ligaments is required to obtain postoperative stability of this arthroplasty. Otherwise, routine exposure of the MCL and repair or reinforcement of the MCL, if deficient, may need to be considered during surgery.     

Elbow joint stability in relation to forced external rotation: An experimental study of the osseous constraint

The objective of this study was to evaluate the osseous constraint related to forced forearm external rotation as the initial stage in a posterior elbow dislocation. Six joint specimens without soft tissues were examined in a joint analysis system developed for simulation of dislocation. The osseous stability, expressed as the maximal torque needed for pathologic external forearm rotation, increased from varus to valgus stress (P =.0001) and from 10 degrees to 90 degrees of elbow flexion (P =.012) and also tended to increase from forearm supination to pronation. The work of pathologic external forearm rotation until the point of maximal torque decreased from a maximum in full extension to a minimum at 30 degrees of elbow flexion (P =.03). The elbow in a slightly flexed position, varus stress, and forearm external rotation trauma might be the important biomechanical factors in the posterior elbow dislocation, and they might serve as guidelines during clinical investigation for posterolateral instability.     

Role of collateral ligaments in the GSB-linked total elbow prosthesis.

The GSB III elbow prosthesis is a loose-hinged type of elbow implant. The introduction of such hinged elbow arthroplasty expanded the indications for elbow replacement to patients with more deficient bone and ligaments. The purpose of this study was to compare the kinematics and stability of the GSB III elbow prosthesis with that of the normal elbow and to investigate the role of the collateral ligaments in the kinematics and the stability of the GSB III total elbow prosthesis in an in vitro model. The results could show a semiconstrained kinematic pattern of the GSB III implant. The mean laxity for varus/valgus stress of the implant without collateral ligament support was significantly greater for all flexion angles when compared with intact elbows (mean, 12.7 degrees versus 5.4 degrees ) and with elbows treated with a standard implantation technique (mean, 9.5 degrees ). The release of the collateral ligaments increased the already observed varus shift after standard implantation of a GSB III elbow prosthesis. The laxity measured without collateral ligaments during loaded movement reached the maximum varus/valgus laxity of the GSB III prosthesis of 12 degrees degrees. The study confirms the role of the collateral ligaments in stabilizing the GSB III elbow prosthesis. Missing collateral ligaments may overload the implant-cement-bone interface and may be one factor contributing to early aseptic loosening of this device.