Origin of the medial ulnar collateral ligament on the pediatric elbow

Purpose

Surgical reconstruction of the adult anterior bundle of the medial ulnar collateral elbow ligament (UCL) is a common and established treatment that yields satisfactory results. Children sustain these injuries less frequently, and surgical intervention is complicated by the juxtaposed medial epicondyle apophysis. The purpose of this study was to identify the anatomical origin of the pediatric UCL and determine if this location changes with elbow maturity.

Methods

A retrospective analysis of children with an elbow MRI between 2009 and 2012 was performed. Ninety children (68 boys, 22 girls), mean age 12.8 years (range 6–18), were grouped by age (<11, 11–13, and >13) and gender. Measurements of UCL width and UCL midpoint distance from medial epicondyle apophysis were recorded on coronal T1 images utilizing digital PACS software.

Results

Across all groups, boys had a wider UCL than girls (4.05 ± 0.16 mm vs 3.72 ± 0.20 mm, p = 0.03); however, there was no difference in the anatomical origin of the UCL relative to the medial epicondyle apophysis between gender (p = 0.52), between gender age-matched groups, or within gender age-matched groups. Yet, the anatomic origin of the UCL always remained medial to the cartilaginous interface of the apophysis with the osseous distal humerus and was centered approximately 3 mm medial to the lateral edge of the apophysis.

Conclusion

Regardless of age or gender, the humeral origin for the medial ulnar collateral ligament is medial to the interface between the medial epicondyle apophysis and distal humerus, which has surgical implications for anatomic reconstruction in children.     

Avulsion fracture of the supinator crest of the proximal ulna in the context of elbow joint injuries

Purpose

While performing CT examinations of the elbow, we frequently observed a previously undescribed fracture fragment of the supinator crest of the ulna. According to the anatomy of the lateral collateral ligament complex, this fracture might be an avulsion fracture of the annular ligament and/or the lateral ulnar collateral ligament. The aim of this study was to further characterize these fragments and document their associated injuries.

Methods

Retrospective evaluation of CT scans of the elbow was performed. Conventional X-ray and CT diagnoses were used to systematically document any associated injuries.

Results

A total of 152 CT scans were evaluated. The fragment in question was discovered in 17 patients (11.2 %). The average age of the patients was 40 years (±14.9; 9–71 years). The fragment size varied between a few millimetres and 2.4 cm. Multifragmented fractures were observed. In 82.3 % of the cases, associated radial head fractures were diagnosed. In 29.4 %, a coronoid process fracture was present. Distal humerus fractures were found in 23.5 %. Instability in the medial collateral ligament and an Osborne-Cotterill lesion were found in 11.8 % of the patients, respectively.

Conclusions

In a significant percentage of the population, a previously undescribed fracture fragment of the supinator crest of the ulna could be detected. The most frequently occurring associated injuries were fractures of the radial head, the coronoid process, and the distal humerus. The aetiology of these lesions is unknown; however, bony avulsion of the annular or the lateral ulnar collateral ligament seems to be the most likely cause. If this fragment is to be diagnosed by CT, the possibility of lateral or posterolateral instability should be considered.     

The olecranon osteotomy provides better outcome than the triceps-lifting approach for the treatment of distal humerus fractures

Introduction

Intra-articular distal humeral fractures can be approached in a variety of ways. The purpose of this study is to evaluate and compare the functional outcomes of two approaches: approach with olecranon osteotomy and triceps-lifting approach for the treatment of intra-articular distal humeral fractures.

Methods

This study shows a consecutive series of 54 intra-articular distal humeral fractures of 54 patients who were treated with open reduction and internal fixation with anatomic plating. Lateral plating was performed in 10 (45.5 %) patients, and medial and lateral parallel plating was performed in 12 (54.5 %) patients in olecranon osteotomy group, while lateral plating was performed in 8 (25 %) patients, and medial and lateral parallel plating was performed in 24 (75 %) patients in triceps-lifting group.

Results

Mean follow-up was 38.3 months for olecranon osteotomy group and 41.4 months for triceps-lifting group. Functional outcomes according to MAYO elbow score and extension-flexion motion arc values were significantly better in olecranon osteotomy group (p < 0.05).

Conclusion

Approach with olecranon osteotomy provided better functional outcomes than triceps-lifting approach. Additionally, intra-articular distal humerus fractures can be safely treated with olecranon osteotomy which provides more control over the elbow joint and better visualisation and allows early postoperative rehabilitation.

Level of evidence

IV.     

Open reduction and bi-columnar internal fixation of intra-articular distal humerus fractures through a combined medial and lateral approach

Purpose

The aim of this retrospective study was to investigate the suitability of bi-columnar internal fixation through a combined medial and lateral approach for the treatment of intra-articular distal humerus fractures.

Methods

Nineteen cases of intra-articular distal humerus fractures were treated with open reduction and bi-columnar internal fixation through a combined medial and lateral approach. The reduction in the articular surface and functional recovery of the affected elbows was assessed at an average follow-up of 15.8 ± 7.9 (7–43) months.

Results

The gap in the main articular fragments was less than 1 mm in 16 cases, while a gap of more than 1 mm and less than 2 mm was identified in 2 cases and of 3.7 mm in one case. All the fractures were united. At the latest follow-up, the mean flexion–extension of the elbows was 113.4° ± 20.7°, while the pronation–supination of the forearms was 158.3° ± 8.5°, and the mean Mayo Elbow Performance Index was 93.7 ± 9.1 points, leading to 13 excellent outcomes, and 6 with good results.

Conclusions

Intra-articular fractures of the distal humerus can be effectively treated by open reduction and internal fixation through a combined medial and lateral approach at the elbow.     

Instabilitätsrelevante Anatomie des Ellenbogens

Background

Detailed knowledge of elbow anatomy is crucial for diagnosis and therapy of instabilities around the elbow joint.

Discussion

Several anatomical structures stabilize the elbow joint. Due to its high congruency, the ulnohumeral joint protects the joint especially against varus as well as valgus stress and distraction particularly in full extension. The radiohumeral joint and proximal radioulnar joint are secondary stabilizers against valgus stress. The primary stabilizer against valgus stress is the medial collateral ligament which can be divided into an anterior and a posterior bundle. The lateral collateral ligament consists of the radial collateral ligament, the lateral ulnar collateral ligament and the annular ligament. The lateral collateral ligament in its entirety stabilizes the elbow against varus forces and posterolateral rotatory instability.

Conclusion

In addition, muscles spanning over the elbow joint are dynamic and static stabilizers via joint compression forces of the muscles and the orientation of muscle fibers that resemble those of the collateral ligaments.

     

Safe Zone for Superolateral Entry Pin Into the Distal Humerus in Children: An MRI Analysis

Background

The radial nerve is at risk for iatrogenic injury during placement of pins, screws, or wires around the distal humerus. Unlike adults, detailed anatomic information about the relationship of the nerve to the distal humerus is lacking in children.

Question/purposes

This study evaluates the relationship of the radial nerve to the distal humerus in a pediatric population on conventional MRI and proposes an anatomic safe zone using easily identifiable bony landmarks on an AP elbow radiograph.

Methods

To determine the course of the radial nerve at the lateral distal humerus, we reviewed 23 elbow radiographs and MRIs of 22 children (mean age, 9 ± 4 years; range, 3–12 years) obtained as part of their workup for various elbow conditions. We described a technique using distance ratios calculated as a percentage of the patient’s own transepicondylar distance, defined as the distance measured between the apices of the medial and lateral epicondyles, on the AP elbow radiograph and the midcoronal MR image. The cross-reference tool on a Picture Archiving and Communication System was then used to identify axial MR image at the level where the transepicondylar distance was measured. On this axial image, a line was drawn connecting the medial and lateral epicondyles (the transepicondylar axis) and its midpoint was determined. The radial nerve angle was measured by a line from the radial nerve to the midpoint of the transepicondylar axis and a line along the lateral half of the transepicondylar axis. On this axial slice, the closest distance from the nerve to the underlying cortex of the distal humerus was measured. To further localize the nerve along the distal humerus, predetermined percentages of the transepicondylar distance were projected proximally from the level of the transepicondylar axis along the longitudinal axis of the humerus on the midcoronal MR image. At these designated heights, the corresponding axial MR image was identified using the cross-reference tool and the nerve was mapped in a similar fashion. We then proposed a simpler method using a best-fit line drawn along the lateral supracondylar ridge on the AP radiograph to define the safe zone for lateral pin entry.

Results

On axial MR images, the radial nerve was located in the anterolateral quadrant with a mean radial nerve angle of 54° (range, 35°–87) at 0% transepicondylar distance (23 MRIs), 41° (range, 24°–63°) at 50% transepicondylar distance (23 MRIs), and ≥ 10° at 75% transepicondylar distance (on the 13 MRIs that extended this far cephalad). The mean closest distance between the radial nerve and the underlying humeral cortex was 10 mm (range, 3–26 mm) at 0% transepicondylar distance and 7 mm (3–16 mm) at 50% transepicondylar distance. On the AP elbow radiograph, the height of the lateral supracondylar ridge, determined by a best-fit line drawn along the lateral cortex of the ridge, diverged from the most proximal extent of the ridge at a point located at 60% transepicondylar distance (range, 51%–76%). At the corresponding location on the axial MR image, the nerve was located anterolaterally with a mean radial nerve angle of 39° (range, 15°–61°) and a mean distance of 6 mm (range, 2–10 mm) from the underlying humerus.

Conclusions

Our data suggest that percutaneous direct lateral entry Kirschner wires and half-pins can be safely inserted in the distal humerus in children along the transepicondylar axis, either at or slightly posterior to the lateral supracondylar ridge, when placed caudal to the point located where the lateral supracondylar ridge line diverges from the proximal extent of the supracondylar ridge on AP elbow radiograph.     

AO extra-articular distal humerus locking plate: extended spectrum of usage in intra-articular distal fractures with metaphyseal extension—our experience with 20 cases

Background

LCP extra-articular plate designed by AO has been used in extra-articular fractures of the distal humerus, mal-unions, and nonunions of the distal humerus. They provide anatomically shaped and angular stable fixation system for extra-articular fractures of the distal humerus. We extended the usage spectrum of this plate to the extra-articular with intra-articular distal humerus fractures and compared it with the standard orthogonal locking plate fixation.

Methods

We included 22 consecutive distal humerus intra-articular fractures with metaphyseal and diaphyseal extension into the study. Each case underwent osteosynthesis with LCP extra-articular plate fixation and augmented the intra-articular fragments with 4.0 mm partially threaded cancellous screws. The cost, surgical time, VAS, Modified Mayo Clinic Performance Index for elbow, and postoperative complications were recorded. The radiological union and postoperative elbow range of motion were assessed at 6 weeks, 6, and 12 months of follow-up. Twenty cases completed the scheduled follow-up. The results were compared with retrospective data of 20 cases from our institute where similar fractures were treated with standard orthogonal LCP distal humerus plate (LCPDHP).

Results

The radiological union rates and the range of motion at 6 weeks, 6, and 12 months in both the groups were comparable and did not vary significantly (p > 0.05). The cost and operative time with the LCP extra-articular plates were significantly less (p < 0.05) when compared to the group LCPDHP.

Conclusion

The usage spectrum of extra-articular distal humerus locking plate can be extended to intra-articular fractures. It provides good results and significantly reduces the cost and operative time.     

Current concepts of elbow-joint disorders and their treatment

Background

Recently, many studies have emphasized the importance of the comprehension of detailed functional anatomy and biomechanics of the elbow and its significant contribution in facilitating good functional outcomes of conservative and surgical treatment in the field of elbow disorders.

Methods

The most common disease of elbow disorders and their treatment was reviewed.

Results

Lateral epicondylitis of the elbow, is defined as a microscopic tear of extensor carpi radialis brevis tendon, and microscopic findings show immature reparative tissue (angiofibroblastic hyperplasia). The patient needs coordinated rehabilitation, range-of motion-exercise, stretching, and bracing in the second phase. Ninety-five percent of patients with lateral epicondylitis heal spontaneously or conservatively. The medial collateral ligament injury of the elbow is most common in the overhead-throwing athlete. Jobe’s procedure, the original reconstruction technique, and its modifications in bone-tunnel creation, allow a tendon graft to be wound in a figure-eight configuration through the tunnels. Further modification of Jobe’s procedure in bone-tunnel configuration reduced the total number of tunnels and facilitates easier graft tensioning. Outcomes with these reconstruction techniques have proven effective in returning high-level throwing athletes back to their sport. Arthroscopic surgery for the elbow in the throwing athlete has evolved and has proven successful results. Arthroscopic treatment includes debridement of posteromedial synovitis, loose-body removal, and excision of the olecranon spur. Posteromedial elbow impingement is also a source of disability in the overhead-throwing athlete. Twenty-five percent of these patients require a medial collateral ligament reconstruction after removal of a posteromedial bony spur. Linked and unlinked total elbow arthroplasty are successful treatment procedures for patients with rheumatoid arthritis, posttraumatic osteoarthritis, and elderly patients with comminuted distal humeral fractures and the salvage of distal humeral nonunion. Proper selection and implantation of prostheses are also important to achieve good functional outcome and longevity.

Conclusion

The success of treatment of elbow disorders depends greatly on surgical design and technique, both of which require comprehensive knowledge of detailed anatomy and biomechanics of the elbow.     

Biomechanical consequences of a posterior root tear of the lateral meniscus: stabilizing effect of the meniscofemoral ligament

Purpose

The purpose of this study was to evaluate the effects of different types of lateral meniscus root tears in terms of tibiofemoral contact stress.

Methods

Ten porcine knees each underwent five different testing conditions with the menisci intact, a simulated lateral posterior root tear with and without cutting the meniscofemoral ligament and with an artificial tear of the posterior root of the medial meniscus. Biomechanical testing was performed at 30° of flexion with an axial load of 100 N. A pressure sensor (st Sensor Type S2042, Novel, Munich) was used to measure the tibiofemoral contact area and the tibiofemoral contact pressure. Data were analyzed to assess the differences in contact area and tibiofemoral peak contact pressure among the five meniscal conditions.

Results

There was no significant difference in mean contact pressure between the state with the menisci intact and an isolated posterior root tear of the lateral meniscus. In case of a root tear and a tear of the meniscofemoral ligament, the contact area decreased in comparison with the intact state of the menisci. After additional cutting of the meniscofemoral ligament, the tibiofemoral contact pressure was significantly higher in comparison with the intact state and the avulsion injury. In the medial compartment, joint compression forces were significantly increased in comparison with the intact state after cutting the posterior root of the medial meniscus (P < 0.05).

Conclusions

The consequence of a medial meniscus root tear is well known and was verified by this analysis. The results of the present study show that the biomechanical consequences of a lateral meniscus root tear depend on the state of the meniscofemoral ligament. An increase in tibiofemoral contact pressure is only to be expected in combined injuries of the meniscus root and the meniscofemoral ligaments.

Clinical relevance

Posterior lateral meniscus root tear might have a better prognosis in terms of the development of osteoarthritis when the meniscofemoral ligament is intact.     

Weichteilmanagement bei der Varusgonarthrose

Background

Knees with severe varus deformities and contractures of the medial and lateral collateral ligaments and the posterior capsule require special soft tissue management to gain a stable knee over the full range of movement. The introduction of navigation systems into knee surgery has now made precise measurement of the leg axis and gap size possible.

Methods

Ten knee joints received a computer-assisted total knee replacement (Ci^® navigation system DePuy^® I-Orthopaedics^®, Munich). The change of the leg axis and the size of the mediolateral gaps were measured and documented when performing a standardized medial ligament release sequence.

Results

We found a significant effect after each release step regarding the change of the leg axis as well as the gap width (p<0.001). The highest effect was seen for the 6-cm capsule release in extension and the release of the medial collateral ligament in 90° flexion.

Conclusion

Implementation of computer-assisted navigation facilitates visualization and quantification of the effect of the sequential medial soft tissue release in total knee arthroplasty.     

Distal-third diaphyseal fractures of the humerus: choice of approach and surgical treatment

Purpose

Distal-third diaphyseal fractures of the humerus are often hard to treat due to location and pattern of the fractures, radial nerve injury, and quality of bone and age of patients. The aim of this retrospective study is to propose the best approach and the best surgical technique according to the pattern of extra-articular fracture of the distal humerus.

Methods

We have treated 37 fractures of the distal humerus between January 2010 and July 2015 classified according to the AO classification. There were 2 open fractures. We treated all fractures with open reduction and internal fixation with plates and screws. In 20 cases, we performed a posterior midline triceps-splitting approach, with patients in prone decubitus position; in 2 cases, the triceps-splitting approach with the patients in supine decubitus position; in 3 cases, the olecranon osteotomy approach in prone decubitus position; and in 12 cases, the lateral approach in supine decubitus position.

Results

Thirty cases had a medium follow-up of 6 months. We observe 2 post-operative radial nerve palsies healed in 5 months and 2 cases of non-union. The average time to union of remaining cases was 16 weeks (range 12–24). Elbow motility was complete in 25 cases, in 4 cases there was an extension loss of 5°, and in one case there was an extension loss of 10°.

Conclusions

The use of plates allows an anatomical fracture reduction, a better control of alignment of humerus and, with a rigid fixation, an early elbow mobilization. The best approach and the best surgical technique depend on the pattern of the fracture of distal humerus.

     

Primärer endoprothetischer Ellbogengelenkersatz bei komplexen intraartikulären distalen Humerusfrakturen

Introduction

Open reduction and internal fixation of multifragmentary intra-articular fractures of the distal humerus often do not provide satisfactory results in elderly patients with osteoporosis.

Method

From December 2001 to January 2008 a total elbow arthroplasty (Coonrad-Morrey, Zimmer, USA) was performed on 12 patients (average age 81±9  ears) who presented with a type C distal humeral fracture. The mean time of follow-up with clinical and radiological assessment was 28±17 months.

Results

The Mayo score showed a good functional result with an average of 81±9 out of 100. DASH and SECEC scores showed a fair result with respect to elbow function (43±8 and 68±7 points, respectively). The average range of motion of all patients was 120-33-0°. Heterotopic ossifications were found by X-ray examination in 4 cases and asymptomatic radiolucent lines in 4 cases.

Conclusion

Primary total elbow arthroplasty for complex intra-articular distal humerus fractures in elderly patients has good functional results and is an alternative to osteosynthesis.     

The “lateral gutter drive-through” sign revisited: a cadaveric study exploring its real mechanism based on the individual posterolateral structure of knee joints

Background

Although the validity of the “lateral gutter drive-through” (LGDT) test has been proved to offer high sensitivity and specificity in diagnosing the posterolateral rotational instability of knee joints, the real mechanism on how the injury pattern of individual posterolateral knee structure triggers the positive LGDT sign still remains unknown.

Hypothesis

A certain amount of popliteus tendon (POP-T) laxity resulted from specific injury patterns of individual posterolateral knee structure or some degree of medial structural injury will lead to positive LGDT sign.

Study design

Controlled laboratory study.

Methods

Seven non-paired intact cadaveric knees were divided into four groups and tested under unique sequential sectioning sequences including: (1) distal POP-T and popliteofibular ligament (PFL) (n = 2); (2) PFL and distal POP-T (n = 3); (3) lateral collateral ligament (LCL), distal POP-T and PFL (n = 1); (4) superficial medial collateral ligament (sMCL), deep MCL, posterior oblique ligament (POL), anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) (n = 1). The LGDT tests and the measurements of external tibial rotational angle (ETRA) were first performed on all the intact knees and then at each time point when an additional structure was sectioned. Results of each LGDT test and the absolute value of increased ETRA compared with the intact knee were recorded. Each knee was tested at 30° of flexion. A navigation system was used to measure motion changes of the tibia with respect to the femur.

Results

Initially, the LGDT tests all showed negative on each of the intact knee. Isolated sectioning of the distal POP-T, PFL or the LCL produced increased but insignificant ETRA with the LGDT tests still negative. However, simultaneous sectioning of the distal POP-T and PFL produced significantly increased ETRA with the LGDT tests changed to positive. In addition, for the knee with medial structural injuries, the LGDT test could also be positive only when the posteromedial structures (sMCL, deep MCL, POL) and the cruciate ligaments (ACL and PCL) were all sectioned.

Conclusion

In this cadaveric sequential sectioning study, the LGDT test showed positive merely at the following two situations: (1) the distal POP-T and PFL were both sectioned; (2) the posteromedial structures (sMCL, deep MCL and POL) and the cruciate ligaments (ACL and PCL) were all sectioned.

Clinical relevance

Accuracy of the LGDT test in diagnosing acute or chronic posterolateral corner (PLC) injuries will improve with the information in this study. It was the combined POP-T and PFL injuries that finally led to a positive LGDT sign. However, one should be cautious to use the LGDT test in diagnosing the PLC injuries when posteromedial structures and cruciate ligaments were all involved.     

Anatomical transosseous fixation of the deep and superficial fibers of the radioulnar ligaments

Introduction

The triangular fibrocartilage complex is in conjunction with the interosseous membrane the most important stabilizer of the distal radioulnar joint. Lesions of the triangular fibrocartilage complex may cause instability of the distal radioulnar joint with serious consequences. Therefore, the goal is to reconstruct and provide stability to prevent further harm.

Surgical technique

Based on the anatomical configuration of the radioulnar ligaments, we present a technique which addresses both the deep and the superficial fibers of the radioulnar ligaments. This surgical procedure can be performed either openly or arthroscopically assisted. Two osseous 2-mm tunnels starting from the ulnar neck to the foveal surface are created. A nonabsorbable suture is passed through the tunnels and the triangular fibrocartilage using a 20-gauge venipuncture needle in order to attach the deep fibers. Then a third osseous tunnel starting from the lateral base of the styloid process to the medial aspect is created. The suture is passed through this tunnel and through the triangular fibrocartilage and around the styloid process palmarily using the same needle as before in order to anchor the superficial fibers anatomically. After reducing the ulna head the sutures are tightened.

Conclusion

This technique is quite simple and addresses the anatomical configuration of the radioulnar ligaments.     

Triangular Fixation Technique for Bicolumn Restoration in Treatment of Distal Humerus Intercondylar Fracture

Background

Distal humerus intercondylar fractures are intra-articular and comminuted fractures involving soft tissue injury. As distal humerus is triangle-shaped, parallel plating coupled with articular fixation would be suitable for bicolumn restoration in treatment of distal humerus intercondylar fracture.

Methods

This study included 38 patients (15 males and 23 females) who underwent olecranon osteotomy, open reduction and internal fixation with the triangle-shaped cannulated screw and parallel locking plates (triangular fixation technique). Functional results were assessed with the visual analog scale (VAS) scores, Mayo elbow performance (MEP) scores and Disabilities of the Arm, Shoulder and Hand (DASH) questionnaires. Anteroposterior and lateral elbow radiographs were assessed for reduction, alignment, fracture union, posttraumatic arthrosis, and heterotopic ossification, and computed tomography (CT) scans were used to obtain more accurate measurements of articular discrepancy.

Results

All fractures healed primarily with no loss of reduction. The mean VAS, MEP, and DASH scores of the affected elbow were not significantly different from those of the unaffected elbow (p = 0.140, p = 0.090, and p = 0.262, respectively). The mean degree of flexion was significantly lower in the affected elbow than in the unaffected elbow, but was still considered as functional (p = 0.001, > 100° in 33 of 38 patients). Two cases of articular step-offs (> 2 mm) were seen on follow-up CT scans, but not significantly higher in the affected elbow than in the unaffected elbow (p = 0.657). Binary logistic regression analysis revealed that only Association for Osteosynthesis (AO) type C3 fractures correlated with good/excellent functional outcome (p = 0.012). Complications occurred in 12 of the 38 patients, and the overall reoperation rate for complications was 10.5% (4 of 38 patients).

Conclusions

Triangular fixation technique for bicolumn restoration was an effective and reliable method in treatment of distal humerus intercondylar fracture. This technique maintained articular congruency and restored both medial and lateral columns, resulting in good elbow function.     

Surgical exposures of the distal humeral fractures: An anatomical study of theanterior, posterior, medial and lateral approaches

Purpose

Exposure of the articular surface is the key to the successful treatment of intra-articular fractures of distal humerus. Anterior, posterior olecranon osteotomy as well as medial and lateral approaches are the four main approaches to the elbow. The aim of this study was to compare the exposure of distal articular surfaces of these surgical approaches.

Biomechanischer Vergleich von zwei winkelstabilen, anatomisch angepassten Plattensystemen am distalen Humerus

Background

The clinical strategy for the surgical treatment of complex distal humerus fractures changed rapidly during recent years due to new implant designs. The modern reconstruction plates offer anatomical predesigned plates with mono- or polyaxial locking screws. For good functional outcome after complex fractures, early rehabilitation is crucial. The aim of the current study was the comparison of two different plate systems regarding their biomechanical properties.

Material and methods

Two plate systems were investigated. The Locking Compression Plate (LCP, Synthes, Umkirch, Germany) with a 90° configuration of the plates (i.e., medial – dorsolateral) System and the Congruent Elbow Plates (CEP, Acumed, Hillsboro, OR/USA) System with a 180° configuration of the plates (medial – lateral). As a fracture model, an AO C 2.3-fracture on an artificial bone (4^th Generation Sawbones) was simulated. The load to failure, system rigidity, and the median fatigue limit were determined. The tests were conducted under 75° flexion and 5° extension.

Results

In static tests, the load to failure for the LCP system was reached at values of 581 N in flexion and 325 N in extension. The CEP system failed at values of 1192 N in flexion and 1320 N in extension. The stiffness of the CEP system was 70–80% higher compared to the LCP system. Median fatigue limit was reached at dynamic loads of 196 N (LCP) and 787 N (CEP). Failure of the osteosynthesis was observed for the CEP technique at the screw-bone interface, whereas for the LCP system the screw-plate interface was the weakest.

Conclusions

The results of this study indicate a higher biomechanical stability for the CEP system. One aspect is the parallel configuration of the plates, offering a higher geometric moment of inertia. Another advantage is the higher stability of the screw-plate fastening and the stronger profile of the plates compared to the LCP system. From the biomechanical point of view, the CEP system appears to be the choice for osteosynthesis, thus, allowing the immediate postoperative rehabilitation of patients with comminuted distal humerus fractures.     

„Impingement“ der posterolateralen Humerusplatte

Background

Double-plate osteosynthesis has to be considered the gold standard for treating complex distal humeral fractures in adults. Impingement of the posterolateral plate with the olecranon or the radial head in extension of the elbow joint is a possible complication after double-plate osteosynthesis with a 90° configuration, especially after olecranon osteotomy.

Objectives

The goal of this study was to analyze the positioning of the posterolateral humeral plate in order to define guidance values for intraoperative application.

Methods

The positioning of the posterolateral humeral plate in relation to the olecranon in full extension of the elbow joint was analyzed in 71 dissected upper extremities of cadavers. Values on the cadavers were measured under image-intensifier control (distal olecranon impingement line) that can be reproduced intraoperatively.

Results

The average distance between the distal edge of the plate and junction of cartilage and bone at the capitulum humeri was 4.8 mm (SD?±?1.2 mm). The average distances from the medial border of the plate to the lateral border of the olecranon fossa and to the lateral epicondyle were 2.5 mm (SD?±?0.9 mm) and 22.7 mm (SD?±?2.4 mm), respectively. The distal olecranon impingement line averaged 5.2 mm (SD?±?1.5 mm) on the left and 7.2 mm (SD?±?1.4 mm) on the right side of cadavers.

Conclusions

The measured values offer landmarks for correct positioning of the posterolateral humeral plate. The distance between the lateral border of the olecranon fossa and the medial edge of the posterolateral plate as well as the proximal end of the distal olecranon impingement line should be respected in order to avoid impingement. If possible, the posterolateral plate should be placed at least 4.3 mm lateral to the radial edge of the olecranon fossa so that impingement can be successfully avoided.     

Radial Head Reconstruction in Elbow Fracture-Dislocation: Monopolar or Bipolar Prosthesis?

Background

Monopolar and bipolar radial head prosthetic arthroplasties have been used successfully to treat elbow fracture-dislocation with unsalvageable radial head fractures. The relative stability of these two designs in different clinical situations is a topic of ongoing investigation.

Questions/purposes

We tested the effects of monopolar and bipolar fixed-neck prosthetic radial head implants on improvement in elbow coronal and axial plane laxity in a terrible triad biomechanical model that accounted for lateral collateral ligament integrity and the presence of a transverse coronoid fracture.

Methods

Kinematic data were collected on six fresh-frozen cadaveric upper extremities tested with passive motion throughout the flexion arc. Varus and valgus gravity stress were applied with the wrist in neutral position. A lateral collateral ligament reconstruction was simulated. We assessed instability after radial head resection and reconstruction with either a monopolar or bipolar implant in the presence of a transversely fractured (Regan and Morrey Type 2) or fixed coronoid process.

Results

With collateral ligament integrity, no difference was detected, with the numbers available, in valgus laxity between implants under valgus stress (p = 1.0). Laxity improvement with each prosthesis was higher when the coronoid was fractured (mean ± SD: monopolar: 7.4° ± 1.6°, p < 0.001; bipolar: 6.4° ± 1.6°, p = 0.003) than when it was fixed (monopolar: 4.0° ± 1.6°, p = 0.02; bipolar: 4.2° ± 1.6°, p = 0.01). With the numbers available, there was no difference in external rotation laxity between implants under valgus stress (p = 1.0). The greatest stabilizing effect of the prostheses occurred when the coronoid was fractured (monopolar: 3.3° ± 1.2°, p = 0.15; bipolar: 3.3° ± 1.2°, p = 0.17). Radial head arthroplasty offered no substantial stability under varus stress for varus or internal rotation laxity.

Conclusions

In our terrible triad cadaveric model, coronoid fixation was effective in improving varus laxity with a monopolar or bipolar prosthesis in place. Also, both types of prostheses were effective in improving valgus and external rotation laxity to the elbow, regardless of coronoid status. With collateral ligaments reconstructed, no large kinematic differences were noted between implants regardless of the varus-valgus position or whether the coronoid was fractured or fixed.

Clinical Relevance

The data from our cadaveric model support the use of either implant type in terrible triad injuries if the collateral ligaments are intact or reconstructed.     

Increased pin diameter improves torsional stability in supracondylar humerus fractures: an experimental study

Background

Pediatric supracondylar humerus fractures are the most common elbow fractures seen in children, and account for 16 % of all pediatric fractures. Closed reduction and percutaneous pin fixation is the current treatment technique of choice for displaced supracondylar fractures of the distal humerus in children. The purpose of this study was to determine whether pin diameter affects the torsional strength of supracondylar humerus fractures treated by closed reduction and pin fixation.

Methods

Pediatric sawbone humeri simulating a Gartland type III fracture were utilized. Four different pin configurations were compared. Specimens were subjected to a torsional load producing internal rotation of the distal fragment. The stability provided by 1.25- and 1.6-mm pins was compared.

Results

The amount of torque required to produce 15° and 25° of rotation was greater using larger diameter pins in all models tested. The two lateral and one medial large pin (1.6 mm) configuration required the highest amount of torque to produce both 15° and 25° of rotation.

Conclusions

In a synthetic pediatric humerus model of supracondylar humerus fractures, larger diameter pins (1.6 mm) provided increased stability compared with small diameter pins (1.25 mm). Fixation using larger diameter pins created a stronger construct and improved the strength of fixation.